Intracellular Calcium Concentration (intracellular + calcium_concentration)

Distribution by Scientific Domains
Distribution within Medical Sciences


Selected Abstracts


Functional protease-activated receptors in the dorsal motor nucleus of the vagus

NEUROGASTROENTEROLOGY & MOTILITY, Issue 4 2010
H. Wang
Abstract Background, Protease-activated receptors (PARs), a family member of G-protein coupled receptors, are present and functionally active in a wide variety of cells. The object of this study was to demonstrate the presence and function of PAR-1 and PAR-2 in the dorsal motor nucleus of the vagus (DMV). Methods, DMNV neurons were isolated from neonatal rat brainstems using micro-dissection and enzymatic digestion. Neurons were cultured in Neurobasal medium A containing 2% B27 supplement. Intracellular calcium concentration ([Ca2 + ]i) was measured using fura-2 based microspectrometry. Expression of PARs was detected by RT-PCR and immunofluorescent staining. Key Result, Thrombin and PAR-1 agonist peptide activate PAR-1 with a maximum change in [Ca2 + ]i expressed as ,F/F0 of 229 14% and 137 7%, respectively. Trypsin and PAR-2 agonist peptide activate PAR-2 with a maximum ,F/F0 change of 258 12% and 242 10%, respectively. Inhibition of phospholipase C (PLC) by U73312 (1 ,m) decreased the maximal change in ,F/F0 induced by PAR-1 activation from 140 17% to 21 3%, while the PAR-2-mediated maximal change in ,F/F0 decreased from 185 21% to 19 6%. Blockade of IP3 receptor with 2APB inhibited the maximal change in ,F/F0 due to PAR-1 and PAR-2 activation by 72 13% and 71 20% respectively. PAR-1 immnuoreactivity was present in DMV neurons. Increase in transcripts for PAR-1 and PAR-2 were detected in DMV tissues derived from IBD rats relative to control animals. Conclusions & Inferences, Our results indicate that PAR-1 and PAR-2 are present in the DMV neurons, and their activation leads to increases in intracellular calcium via signal transduction mechanism that involves activation of PLC and the production of IP3. [source]


Pre-activation of retinoid signaling facilitates neuronal differentiation of mesenchymal stem cells

DEVELOPMENT GROWTH & DIFFERENTIATION, Issue 5 2010
Yang Bi
Mesenchymal stem cells (MSCs) can differentiate into neurons in an appropriate cellular environment. Retinoid signaling pathway is required in neural development. However, the effect and mechanism through retinoid signaling regulates neuronal differentiation of MSCs are still poorly understood. Here, we report that all-trans-retinoic acid (ATRA) pre-induction improved neuronal differentiation of rat MSCs. We found that, when MSCs were exposed to different concentrations of ATRA (0.01,100 ,mol/L) for 24 h and then cultured with modified neuronal induction medium (MNM), 1 ,mol/L ATRA pre-induction significantly improved neuronal differentiation efficiency and neural-cell survival. Compared with MNM alone induced neural-like cells, ATRA/MNM induced cells expressed higher levels of Nestin, neuron specific enolase (NSE), microtubule-associated protein-2 (MAP-2), but lower levels of CD68, glial fibrillary acidic protein (GFAP), and glial cell line-derived neurotrophic factor(GDNF), also exhibited higher resting membrane potential and intracellular calcium concentration, supporting that ATRA pre-induction promotes maturation and function of derived neurons but not neuroglia cells from MSCs. Endogenous retinoid X receptors (RXR) RXR, and RXR, (and to a lesser extent, RXR,) were weakly expressed in MSCs. But the expression of RAR, and RAR, was readily detectable, whereas RAR, was undetectable. However, at 24 h after ATRA treatment, the expression of RAR,, not RAR, or RAR,, increased significantly. We further found the subnuclear redistribution of RAR, in differentiated neurons, suggesting that RAR, may function as a major mediator of retinoid signaling during neuronal differentiation from MSCs. ATRA treatment upregulated the expression of Vimentin and Stra13, while it downregulated the expression of Brachyury in MSCs. Thus, our results demonstrate that pre-activation of retinoid signaling by ATRA facilitates neuronal differentiation of MSCs. [source]


Hypotonic stress influence the membrane potential and alter the proliferation of keratinocytes in vitro

EXPERIMENTAL DERMATOLOGY, Issue 4 2007
Mnika Gnczi
Abstract:, Keratinocyte proliferation and differentiation is strongly influenced by mechanical forces. We investigated the effect of osmotic changes in the development of HaCaT cells in culture using intracellular calcium measurements, electrophysiological recordings and molecular biology techniques. The application of hypotonic stress (174 mOsmol/l) caused a sustained hyperpolarization of HaCaT cells from a resting potential of ,27 4 to ,51 9 mV. This change was partially reversible. The surface membrane channels involved in the hyperpolarization were identified as chloride channels due to the lack of response in the absence of the anion. Cells responded with an elevation of intracellular calcium concentration to hypotonic stress, which critically depended on external calcium. The presence of phorbol-12-myristate-13-acetate in the culture medium for 12 h augmented the subsequent response to hypotonic stress. A sudden switch from iso- to hypotonic solution increased cell proliferation and suppressed the production of involucrin, filaggrin and transglutaminase, markers of keratinocyte differentiation. It is concluded that sudden mechanical forces increase the proliferation of keratinocytes through alterations in their membrane potential and intracellular calcium concentration. These changes together with additional modifications in channel expression and intracellular signalling mechanisms could underlie the increased proliferation of keratinocytes in hyperproliferative skin diseases. [source]


NMDA receptors influence the intracellular calcium concen-tration and the expression of differentiation markers in HaCaT cells

EXPERIMENTAL DERMATOLOGY, Issue 9 2004
M. Fischer
Ionotropic glutamate receptors (ligand-gated, ion-channel proteins) of the N -methyl- d -aspartate (NMDA) receptor type could enable a transmembranous calcium influx from the extracellular space. Though ionotropic glutamate receptors are predominantly neuronal receptors, they are also expressed in non-neuronal tissues like keratinocytes. Therefore, investigations were performed to study the function of NMDA receptors in HaCaT cells. The intracellular calcium concentration of HaCaT cells was studied under the influence of the selective receptor agonist NMDA and the selective NMDA antagonist MK-801. The proliferation of HaCaT cells was investigated using the crystal-violet method. Furthermore, the expression of Cytokeratin 10 and Filaggrin was examined in HaCaT cells after blocking NMDA receptors with MK-801. Using NMDA, there was a significant increase in the number of HaCaT cells showing elevated intracellular calcium concentration, at a dose between 25 m and 1 mm (up to 84.6% of cells). The NMDA-associated calcium influx could be significantly suppressed by prior application of MK-801. There was no influence of NMDA on the proliferation of HaCaT cells. There was also no cytotoxic effect of NMDA (up to 1 mm). The expression of Cytokeratin 10 and Filaggrin could be suppressed by blocking NMDA receptors with MK-801. The investigations show that glutamate receptors of the NMDA-type play a role in the differentiation of HaCaT cells by regulating their intracellular calcium concentration. [source]


Inhibition of carbachol-evoked oscillatory currents by the NO donor sodium nitroprusside in guinea-pig ileal myocytes

EXPERIMENTAL PHYSIOLOGY, Issue 4 2005
Seung-Soo Chung
The effect of sodium nitroprusside (SNP) on carbachol (CCh)-evoked inward cationic current (Icat) oscillations in guinea-pig ileal longitudinal myocytes was investigated using the whole-cell patch-clamp technique and permeabilized longitudinal muscle strips. SNP (10 ,m) completely inhibited Icat oscillations evoked by 1 ,m CCh. 1H-(1,2,4) Oxadiazole [4,3-a] quinoxaline-1-one (ODQ; 1 ,m) almost completely prevented the inhibitory effect of SNP on Icat oscillations. 8-Bromo-guanosine 3,,5,-cyclic monophosphate (8-Br-cGMP; 30 ,m) in the pipette solution completely abolished Icat oscillations. However, a pipette solution containing Rp-8-Br-cGMP (30 ,m) almost completely abolished the inhibitory effect of SNP on Icat oscillations. When the intracellular calcium concentration ([Ca2+]i) was held at a resting level using BAPTA (10 mm) and Ca2+ (4.6 ,m) in the pipette solution, CCh (1 ,m) evoked only the sustained component of Icat without any oscillations and SNP did not affect the current. A high concentration of inositol 1,4,5-trisphosphate (IP3; 30 ,m) in the patch pipette solutions significantly reduced the inhibitory effect of SNP (10 ,m) on Icat oscillations. SNP significantly inhibited the Ca2+ release evoked by either CCh or IP3 but not by caffeine in permeabilized preparations of longitudinal muscle strips. These results suggest that the inhibitory effects of SNP on Icat oscillations are mediated, in part, by functional modulation of the IP3 receptor, and not by the inhibition of cationic channels themselves or by muscarinic receptors in the plasma membrane. This inhibition seems to be mediated by an increased cGMP concentration in a protein kinase G-dependent manner. [source]


Calcium and polyamine regulated calcium-sensing receptors in cardiac tissues

FEBS JOURNAL, Issue 12 2003
Rui Wang
Activation of a calcium-sensing receptor (Ca-SR) leads to increased intracellular calcium concentration and altered cellular activities. The expression of Ca-SR has been identified in both nonexcitable and excitable cells, including neurons and smooth muscle cells. Whether Ca-SR was expressed and functioning in cardiac myocytes remained unclear. In the present study, the transcripts of Ca-SR were identified in rat heart tissues using RT-PCR that was further confirmed by sequence analysis. Ca-SR proteins were detected in rat ventricular and atrial tissues as well as in isolated cardiac myocytes. Anti-(Ca-SR) Ig did not detect any specific bands after preadsorption with standard Ca-SR antigens. An immunohistochemistry study revealed the presence of Ca-SR in rat cardiac as well as other tissues. An increase in extracellular calcium or gadolinium induced a concentration-dependent sustained increase in [Ca2+]i in isolated ventricular myocytes from adult rats. Spermine (1,10 mm) also increased [Ca2+]i. Pre-treatment of cardiac myocytes with thapsigargin or U73122 abolished the extracellular calcium, gadolinium or spermine-induced increase in [Ca2+]i. The blockade of Na+/Ca2+ exchanger or voltage-dependent calcium channels did not alter the extracellular calcium-induced increase in [Ca2+]i. Finally, extracellular calcium, gadolinium and spermine all increased intracellular inositol 1,4,5-triphosphate (IP3) levels. Our results demonstrated that Ca-SR was expressed in cardiac tissue and cardiomyocytes and its function was regulated by extracellular calcium and spermine. [source]


Effects of prolactin on intracellular calcium concentration and cell proliferation in human glioma cells

GLIA, Issue 3 2002
Thomas Ducret
Abstract Prolactin (PRL) has several physiological effects on peripheral tissues and the brain. This hormone acts via its membrane receptor (PRL-R) to induce cell differentiation or proliferation. Using reverse transcription,polymerase chain reaction (RT-PCR) combined with Southern blot analysis, we detected PRL-R transcripts in a human glioma cell line (U87-MG) and in primary cultured human glioblastoma cells. These transcripts were deleted or not in their extracellular domains. We examined the effects of PRL on intracellular free Ca2+ concentration ([Ca2+]i) in these cells in order to improve our understanding of the PRL transduction mechanism, which is still poorly documented. [Ca2+]i was measured by microspectrofluorimetry using indo-1 as the Ca2+ fluorescent probe. Spatiotemporal aspects of PRL-induced Ca2+ signals were investigated using high-speed fluo-3 confocal imaging. We found that physiological concentrations (0.4,4 nM) of PRL-stimulated Ca2+ entry and intracellular Ca2+ mobilization via a tyrosine kinase,dependent mechanism. The two types of Ca2+ responses observed were distinguishable by their kinetics: one showing a slow (type I) and the other a fast (type II) increase in [Ca2+]i. The amplitude of PRL-induced Ca2+ increases may be sufficient to provoke several physiological responses, such as stimulating proliferation. Furthermore, PRL induced a dose-dependent increase in [3H]thymidine incorporation levels and in cellular growth and survival, detected by the MTT method. These data indicate that PRL induced mitogenesis of human glioma cells. GLIA 38:200,214, 2002. 2002 Wiley-Liss, Inc. [source]


Prostaglandins in rainbow trout (Oncorhynchus mykiss Walbaum, 1792) sperm biology , searching for answers

JOURNAL OF APPLIED ICHTHYOLOGY, Issue 4 2008
R. K. Kowalski
Summary The purpose of this study was to determine the concentrations of prostaglandins E2 and F2, (PGE2 and PGF2,) in the blood, testis and seminal plasma of mature male rainbow trout and in the ovarian fluid to assess the effects of these prostaglandins on sperm motility parameters when present in activation media. Also prolonged incubation with prostaglandins on sperm motility and calcium influx were studied. The profile of PGE2 and PGF2, differed in concentration between blood, testicular supernatant and seminal plasma. PGE2 was predominant in the blood sample (0.29 ng ml,1) and testicular supernatant (3.1 ng ml,1) whereas their level in seminal plasma was lower than PGF2, (0.23 ng ml,1). The concentrations of PGF2, in blood, testis and seminal plasma were 0.04, 0.99, 1.3 ng ml,1, respectively. In the ovarian fluid the concentrations of both prostaglandins were higher than in the male reproductive tract. Adding both prostaglandins to activation buffer (at concentrations 15 and 70 ng ml,1) had no effect on any CASA parameters. Calcium influx related to rainbow trout sperm incubations with PGE2, and PGF2, was not detected. After 24 h incubation of sperm in artificial seminal plasma solution without and with prostaglandins all sperm samples increased their motility potential and intracellular calcium concentration. Therefore, this effect was not related to the presence of prostaglandins. In summary PGE2, and PGF2, were present in the rainbow trout male reproductive tract, and their profile varies from that of blood, testis and seminal plasma. The specific role of both prostaglandins in salmonid sperm biology remains unclear. [source]


Prostaglandin F2, inhibits adipocyte differentiation via a G,q-Calcium-Calcineurin-Dependent signaling pathway

JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 1 2007
Li Liu
Abstract Prostaglandin F2, (PGF2,) is a potent physiological inhibitor of adipocyte differentiation, however the specific signaling pathways and molecular mechanisms involved in mediating its anti-adipogenic effects are not well understood. In the current study, we now provide evidence that PGF2, inhibits adipocyte differentiation via a signaling pathway that requires heterotrimeric G-protein G,q subunits, the elevation of the intracellular calcium concentration ([Ca2+]i), and the activation of the Ca2+/calmodulin-regulated serine/threonine phosphatase calcineurin. We show that while this pathway acts to inhibit an early step in the adipogenic cascade, it does not interfere with the initial mitotic clonal expansion phase of adipogenesis, nor does it affect either the expression, DNA binding activity or differentiation-induced phosphorylation of the early transcription factor C/EBP,. Instead, we find that PGF2, inhibits adipocyte differentiation via a calcineurin-dependent mechanism that acts to prevent the expression of the critical pro-adipogenic transcription factors PPAR, and C/EBP,. Furthermore, we demonstrate that the inhibitory effects of PGF2, on both the expression of PPAR, and C/EBP, and subsequent adipogenesis can be attenuated by treatment of preadipocytes with the histone deacetylase (HDAC) inhibitor trichostatin A. Taken together, these results indicate that PGF2, inhibits adipocyte differentiation via a G,q-Ca2+ -calcineurin-dependent signaling pathway that acts to block expression of PPAR, and C/EBP, by a mechanism that appears to involves an HDAC-sensitive step. J. Cell. Biochem. 100: 161,173, 2007. 2006 Wiley-Liss, Inc. [source]


Annulus cells release ATP in response to vibratory loading in vitro

JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 4 2003
Satoru Yamazaki
Abstract Mechanical forces regulate the developmental path and phenotype of a variety of tissues and cultured cells. Vibratory loading as a mechanical stimulus occurs in connective tissues due to energy returned from ground reaction forces, as well as a mechanical input from use of motorized tools and vehicles. Structures in the spine may be particularly at risk when exposed to destructive vibratory stimuli. Cells from many tissues respond to mechanical stimuli, such as fluid flow, by increasing intracellular calcium concentration ([Ca2+]ic) and releasing adenosine 5,-triphosphate (ATP), extracellularly, as a mediator to activate signaling pathways. Therefore, we examined whether ATP is released from rabbit (rAN) and human (hAN) intervertebral disc annulus cells in response to vibratory loading. ATP release from annulus cells by vibratory stimulation as well as in control cells was quantitated using a firefly luciferin-luciferase assay. Cultured hAN and rAN cells had a basal level of extracellular ATP ([ATP]ec) in the range of 1,1.5 nM. Vibratory loading of hAN cells stimulated ATP release, reaching a net maximum [ATP] within 10 min of continuous vibration, and shortly thereafter, [ATP] declined and returned to below baseline level. [ATP] in the supernatant fluid of hAN cells was significantly reduced compared to the control level when the cells received vibration for longer than 15 min. In rAN cells, [ATP] was increased in response to vibratory loading, attaining a level significantly greater than that of the control after 30 min of continuous vibration. Results of the current study show that resting annulus cells secrete ATP and maintain a basal [ATP]ec. Annulus cells may use this nucleotide as a signaling messenger in an autocrine/paracrine fashion in response to vibratory loading. Rapid degradation of ATP to ADP may alternatively modulate cellular responses. It is hypothesized that exposure to repetitive, complex vibration regimens may activate signaling pathways that regulate matrix destruction in the disc. As in tendon cells, ATP may block subsequent responses to load and modulate the vibration response. Rabbit annulus cells were used as a readily obtainable source of cells in development of an animal model for testing effects of vibration on the disc. Human cells obtained from discarded surgical specimens were used to correlate responses of animal to human cells. 2003 Wiley-Liss, Inc. [source]


Role of calcium and ROS in cell death induced by polyunsaturated fatty acids in murine thymocytes

JOURNAL OF CELLULAR PHYSIOLOGY, Issue 3 2010
Aparna Prasad
We investigated the mechanisms whereby omega-3 and -6 polyunsaturated fatty acids (PUFAs) cause cell death of mouse thymocytes using flow cytometry, focusing on the respective roles of intracellular calcium concentration, [Ca2+]i and reactive oxygen species (ROS). We applied the C-22, 20, and 18 carbon omega-3 (DHA, EPA, ALA) and omega-6 (DTA, ARA, and LNA) fatty acids to isolated thymocytes and monitored cell death using the DNA-binding dye, propidium iodide. When applied at 20,M concentration, omega-3 fatty acids killed thymocytes over a period of 1,h with a potency of DHA,>,EPA,>,ALA. The omega-6 PUFAs were more potent. The C18 omega-6 fatty acid, LNA, was the most potent, followed by DHA and ARA. Cell death was always accompanied by an increase in the levels of [Ca2+]i and ROS. Both increases were in proportion to the potency of the PUFAs in inducing cell death. Removing extracellular calcium did not prevent the elevation in [Ca2+]i nor cell death. However, the intracellular calcium chelator, BAPTA, almost totally reduced both the elevation in [Ca2+]i and cell death, while vitamin E reduced the elevation in ROS and cell death. BAPTA also prevented the elevation in ROS, but vitamin E did not prevent the elevation in [Ca2+]i. Thapsigargin, which depletes endoplasmic reticulum calcium, blocked the elevation in [Ca2+]i, but CCCP, a mitochondrial calcium uptake inhibitor, did not. These results suggest that the six PUFAs we studied kill thymocytes by causing release of calcium from endoplasmic reticulum, which causes release of ROS from mitochondria which leads to cell death. J. Cell. Physiol. 225: 829,836, 2010. 2010 Wiley-Liss, Inc. [source]


A preliminary examination of the role of NFAT 3 in human skin, cultured keratocytes and dermal fibroblasts

JOURNAL OF CUTANEOUS PATHOLOGY, Issue 9 2010
Wael I. Al-Daraji
Background: Ciclosporin A (CsA) is widely utilized for the treatment of inflammatory skin diseases such as psoriasis. The therapeutic effects of CsA are thought to be mediated via its immunosuppressive action on infiltrating lymphocytes in skin lesions. CsA and tacrolimus block T cell activation by inhibiting the phosphatase calcineurin and preventing translocation from the cytoplasm to the nucleus of the transcription factor Nuclear Factor of Activated T cells (NFAT). Methods: RT-PCR and Western Analysis were used to investigate the presence of NFAT-3 mRNA and protein in human keratocytes. Tissue culture of human keratocytes and immunostaining of cells on coverslips and confocal microscopy were used to assess the degree of nuclear localisation of NFAT-3 in cultured cells. Keratome biopsies were taken from patients with psoriasis (lesional and non-lesional skin) and normal skin and immunohistochemistry was used to assess the NFAT-3 localisation in these biopsies using a well characterized anti-NFAT-3 antibody. Results: The NFAT-3 mRNA and protein expression was demonstrated using RT-PCR and Western blotting. The expression of NFAT-3 in human keratocytes and response to different agonists provides perhaps a unique opportunity to examine the regulation, subcellular localization and kinetics of translocation of different NFATs in primary cultured human cells. As with NFAT 1, NFAT 2 and recently NFAT 5, differentiation-promoting agents that increase intracellular calcium concentration induced nuclear translocation of NFAT-3 in cultured keratocytes but with different kinetics. Conclusion: These data provide the first evidence of that NFAT-3 is expressed in normal skin, psoriasis and that NFAT-3 functionally active in human keratocytes and that nuclear translocation of NFAT-3 in human skin cells has different kinetics than NFAT 1 suggesting that NFAT-3 may play an important role in regulation of keratocytes proliferation and differentiation at a different stage. Inhibition of this pathway in human epidermal keratocytes many account, in part for the therapeutic effects of CsA and tacrolimus in skin disorders such as psoriasis. Al-Daraji WI. A preliminary examination of the role of NFAT 3 in human skin, cultured keratocytes and dermal fibroblasts. [source]


Neuropeptide Y inhibits [Ca2+]i changes in rat retinal neurons through NPY Y1, Y4, and Y5 receptors

JOURNAL OF NEUROCHEMISTRY, Issue 5 2009
Ana Rita lvaro
Abstract Neuropeptide Y (NPY) and NPY receptors are widely distributed in the CNS, including the retina, but the role of NPY in the retina is largely unknown. The aim of this study was to investigate whether NPY modulates intracellular calcium concentration ([Ca2+]i) changes in retinal neurons and identify the NPY receptors involved. As NPY decreased the [Ca2+]i amplitudes evoked by 30 mM KCl in only 50% of neurons analyzed, we divided them in two populations: NPY-non-responsive neurons (,2/,1 , 0.80) and NPY-responsive neurons (,2/,1 < 0.80), being the ,2/,1 the ratio between the amplitude of [Ca2+]i increase evoked by the second (,2) and the first (,1) stimuli of KCl. The NPY Y1/Y5, Y4, and Y5 receptor agonists (100 nM), but not the Y2 receptor agonist (300 nM), inhibited the [Ca2+]i increase induced by KCl. In addition, the inhibitory effect of NPY on evoked-[Ca2+]i changes was reduced in the presence of the Y1 or the Y5 receptor antagonists. In conclusion, NPY inhibits KCl-evoked [Ca2+]i increase in retinal neurons through the activation of NPY Y1, Y4, and Y5 receptors. This effect may be viewed as a potential neuroprotective mechanism of NPY against retinal neurodegeneration. [source]


Fluorescence spectroscopic analysis of circulating platelet activation during coronary angioplasty

LASERS IN SURGERY AND MEDICINE, Issue 5 2001
Alexander Christov PhD
Abstract Background and Objective Platelet activation during percutaneous transluminal coronary angioplasty (PTCA) initiates thrombus formation and plaque regrowth at sites of arterial injury, limiting procedure efficacy. We have developed a simple assay for circulating platelet activation based on fluorescence analysis of membrane fluidity and intracellular calcium concentration and light scattering analysis of platelet aggregation. Study Design/Materials and Methods Platelet activation state was measured in 45 patients undergoing angioplasty, before and after treatment with platelet inhibitors. Results PTCA alone produced a decrease in pyrene dimer formation (P0.0083) and an increase in light scattering at 650 nm (P0.0128). Treatment with ADP and GPIIb/IIIa receptor antagonists reduced PTCA induced changes in pyrene dimer formation. An unexpected decrease in pyrene dimer formation (P0.05) was detected when the GPIIb/IIIa receptor antagonist was given together with an ADP receptor antagonist. Conclusions 1) Analysis of membrane fluidity provides a sensitive marker for platelet activation state. 2) Reduced membrane fluidity after combined platelet inhibitor treatments suggests reduced antiplatelet efficacy. Lasers Surg. Med. 39:414,426, 2001. 2001 Wiley-Liss, Inc. [source]


Calcium signalling in bacteria

MOLECULAR MICROBIOLOGY, Issue 2 2004
Delfina C. Dominguez
Summary Whereas the importance of calcium as a cell regulator is well established in eukaryotes, the role of calcium in prokaryotes is still elusive. Over the past few years, there has been an increased interest in the role of calcium in bacteria. It has been demonstrated that as in eukaryotic organisms, the intracellular calcium concentration in prokaryotes is tightly regulated ranging from 100 to 300 nM. It has been found that calcium ions are involved in the maintenance of cell structure, motility, transport and cell differentiation processes such as sporulation, heterocyst formation and fruiting body development. In addition, a number of calcium-binding proteins have been isolated in several prokaryotic organisms. The characterization of these proteins and the identification of other factors suggest the possibility that calcium signal transduction exists in bacteria. This review presents recent developments of calcium in bacteria as it relates to signal transduction. [source]


Phospholipase C-mediated calcium signalling is required for fungal development and pathogenicity in Magnaporthe oryzae

MOLECULAR PLANT PATHOLOGY, Issue 3 2009
HEE-SOOL RHO
SUMMARY Calcium signalling has profound implications in the fungal infection of plants and animals, during which a series of physiological and morphological transitions are required. In this article, using a model fungal pathogen, Magnaporthe oryzae, we demonstrate that the regulation of the intracellular calcium concentration ([Ca2+]int) is essential for fungal development and pathogenesis. Imaging of [Ca2+]int showed that infection-specific morphogenesis is highly correlated with the spatiotemporal regulation of calcium flux. Deletion of the fungal phospholipase C gene (M. oryzae phospholipase C 1, MoPLC1) suppressed calcium flux, resulting in a fungus defective in developmental steps, including appressorium formation and pathogenicity. Surprisingly, the PLC-,1 gene of mouse was able to functionally substitute for MoPLC1 by restoring the calcium flux, suggesting the evolutionary conservation of the phospholipase C-mediated regulation of calcium flux. Our results reveal that MoPLC1 is a conserved modulator of calcium flux that is essential for the regulation of key steps in fungal development and pathogenesis. [source]


Anti-thrombotic effect of milrinone is caused by inhibition of calcium release from the dense tubular system in human platelets,

ACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 1 2003
N. Hiramatsu
Aim: Milrinone, a phosphodiesterase III inhibitor, exerts positive inotropic effects which induce an increase in the intracellular calcium concentration by raising the cyclic adenosine monophosphate level in cardiac muscle. Milrinone was also reported to inhibit platelet aggregation, however, its mechanism remains unknown. Therefore, we investigated the effects of milrinone on intracellular calcium mobilization when platelets were activated. Methods: Washed platelets, obtained from six healthy volunteers, were preincubated with milrinone (0.9 M) for 1 min and then exposed to 0.015 i ml,1 thrombin for 5 min. The effect of milrinone on changes in the intracellular calcium level using a fluorescent dye, fura-2, was also observed. Calcium mobilizations via plasma membrane calcium channels and the dense tubular system were assessed differentially. Results: Milrinone (0.9 M) significantly suppressed the aggregation ratios at 5 min compared with those in controls (865%) to 758%. The increase in the intracellular calcium concentration was also significantly suppressed (controls, 915293 nM vs. 405240 nM) when stimulated by thrombin. Milrinone also significantly inhibited the release of calcium from the dense tubular system (controls, 284111 nM vs. 15851 nM). Calcium influx through the plasma membrane was suppressed by milrinone 2.4 M. Conclusion: Milrinone (0.9 M) inhibited thrombin-induced platelet aggregation. This inhibitory effect was mainly mediated by suppressing calcium release from the dense tubular system. [source]


The effects of low level laser irradiation on osteoblastic cells

ORTHODONTICS & CRANIOFACIAL RESEARCH, Issue 1 2001
A. R. Coombe
Low level laser therapy has been used in treating many conditions with reports of multiple clinical effects including promotion of healing of both hard and soft tissue lesions. Low level laser therapy as a treatment modality remains controversial, however. The effects of wavelength, beam type, energy output, energy level, energy intensity, and exposure regime of low level laser therapy remain unexplained. Moreover, no specific therapeutic window for dosimetry and mechanism of action has been determined at the level of individual cell types. The aim of this study was to investigate the effects of low level laser irradiation on the human osteosarcoma cell line, SAOS-2. The cells were irradiated as a single or daily dose for up to 10 days with a GaAlAs continuous wave diode laser (830 nm, net output of 90 mW, energy levels of 0.3, 0.5, 1, 2, and 4 Joules). Cell viability was not affected by laser irradiation, with the viability being greater than 90% for all experimental groups. Cellular proliferation or activation was not found to be significantly affected by any of the energy levels and varying exposure regimes investigated. Low level laser irradiation did result in a heat shock response at an energy level of 2 J. No significant early or late effects of laser irradiation on protein expression and alkaline phosphatase activity were found. Investigation of intracellular calcium concentration revealed a tendency of a transient positive change after irradiation. Low level laser irradiation was unable to stimulate the osteosarcoma cells utilised for this research at a gross cell population level. The heat shock response and increased intracellular calcium indicate that the cells do respond to low level laser irradiation. Further research is required, utilising different cell and animal models, to more specifically determine the effects of low level laser irradiation at a cellular level. These effects should be more thoroughly investigated before low level laser therapy can be considered as a potential accelerator stimulus for orthodontic tooth movement. [source]


AMPA-sst2 somatostatin receptor interaction in rat hypothalamus requires activation of nmda and/or metabotropic glutamate receptors and depends on intracellular calcium

THE JOURNAL OF PHYSIOLOGY, Issue 1 2003
Stphane Peineau
Modulation of glutamatergic transmission by neuropeptides is an essential aspect of neuronal network activity. Activation of the hypothalamic somatostatin sst2 receptor subtype by octreotide decreases AMPA glutamate responses, indicating a central link between a neurohormonal and neuromodulatory peptide and the main hypothalamic fast excitatory neurotransmitter. In mediobasal hypothalamic slices, sst2 activation inhibits the AMPA component of glutamatergic synaptic responses but is ineffective when AMPA currents are pharmacologically isolated. In mediobasal hypothalamic cultures, the decrease of AMPA currents induced by octreotide requires a concomitant activation of sst2 receptors with either NMDA and/or metabotropic glutamate receptors. This modulation depends on changes in intracellular calcium concentration induced by calcium flux through NMDA receptors or calcium release from intracellular stores following metabotropic glutamate receptor activation. These results highlight an unusual regulatory mechanism in which the simultaneous activation of at least three different types of receptor is necessary to allow somatostatin-induced modulation of fast synaptic glutamatergic transmission in the hypothalamus. [source]


Origin and propagation of spontaneous excitation in smooth muscle of the guinea-pig urinary bladder

THE JOURNAL OF PHYSIOLOGY, Issue 2 2001
Hikaru Hashitani
1The origin and propagation of waves of spontaneous excitation in bundles of smooth muscle of the guinea-pig bladder were examined using intracellular recording techniques and visualization of the changes in the intracellular calcium concentration ([Ca2+]i). 2Bladder smooth muscle cells exhibited spontaneous transient increases in [Ca2+]i which originated along a boundary of each smooth muscle bundle and then spread to the other boundary with a conduction velocity of 2.0 mm s,1. 3Spontaneous increases in [Ca2+]i were always preceded by action potentials. Nifedipine (10 ,M) abolished increases in both [Ca2+]i and action potentials. Caffeine (10 mM), ryanodine (50 ,M) and cyclopiazonic acid (10 ,M) reduced the amplitude of the associated increases in [Ca2+]i without preventing the generation of action potentials. 4Spontaneous action potentials had conduction velocities of 40 mm s,1 in the axial direction and 1.3 mm s,1 in the transverse direction. The electrical length constants of the bundles of muscle were 425 ,m in the axial direction and 12.5 ,m in the transverse direction. 5Neurobiotin, injected into an impaled smooth muscle cell, spread more readily to neighbouring cells located in the axial direction than those located in the transverse direction. The spread of neurobiotin was inhibited by 18,-glycyrrhetinic acid (18,-GA, 40 ,M), a gap junction blocker. 6Immunohistochemistry for Connexin 43 showed abundant punctate staining on the smooth muscle cell membranes. 7These results suggested that spontaneous action potentials and associated calcium waves occur almost simultaneously along the boundary of bladder smooth muscle bundles and then propagate to the other boundary probably through gap junctions. [source]


Pharmacological characterization of a Bombyx mori ,-adrenergic-like octopamine receptor stably expressed in a mammalian cell line

ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY (ELECTRONIC), Issue 2 2010
Jia Huang
Abstract Series of agonists and antagonists were examined for their actions on a Bombyx mori,-adrenergic-like octopamine receptor (OAR) stably expressed in HEK-293 cells. The rank order of potency of the agonists was clonidine>naphazoline>tolazoline in Ca2+ mobilization assays, and that of the antagonists was chlorpromazine>yohimbine. These findings suggest that the B. mori OAR is more closely related to the class-1 OAR in the intact tissue than to the other classes. N,-(4-Chloro- o -tolyl)- N -methylformamidine (DMCDM) and 2-(2,6-diethylphenylimino)imidazolidine (NC-5) elevated the intracellular calcium concentration ([Ca2+]i) with EC50s of 92.8,M and 15.2,nM, respectively. DMCDM and NC-5 led to increases in intracellular cAMP concentration ([cAMP]i) with EC50s of 234,nM and 125,nM, respectively. The difference in DMCDM potencies between the cAMP and Ca2+ assays might be due to "functional selectivity." The Ca2+ and cAMP assay results for DMCDM suggest that the elevation of [cAMP]i, but not that of [Ca2+]i, might account for the insecticidal effect of formamidine insecticides. 2009 Wiley Periodicals, Inc. [source]


Tumor necrosis factor , and interleukin-1, modulate calcium and nitric oxide signaling in mechanically stimulated osteocytes

ARTHRITIS & RHEUMATISM, Issue 11 2009
A. D. Bakker
Objective Inflammatory diseases often coincide with reduced bone mass. Mechanoresponsive osteocytes regulate bone mass by maintaining the balance between bone formation and resorption. Despite its biologic significance, the effect of inflammation on osteocyte mechanoresponsiveness is not understood. To fill this gap, we investigated whether the inflammatory cytokines tumor necrosis factor , (TNF,) and interleukin-1, (IL-1,) modulate the osteocyte response to mechanical loading. Methods MLO-Y4 osteocytes were incubated with TNF, (0.5,30 ng/ml) or IL-1, (0.1,10 ng/ml) for 30 minutes or 24 hours, or with calcium inhibitors for 30 minutes. Cells were subjected to mechanical loading by pulsatile fluid flow (mean amplitude 0.7 0.3 Pa, 5 Hz), and the response was quantified by measuring nitric oxide (NO) production using Griess reagent and by measuring intracellular calcium concentration ([Ca2+]i) using Fluo-4/AM. Focal adhesions and filamentous actin (F-actin) were visualized by immunostaining, and apoptosis was quantified by measuring caspase 3/7 activity. Cell-generated tractions were quantified using traction force microscopy, and cytoskeletal stiffness was quantified using optical magnetic twisting cytometry. Results Pulsatile fluid flow increased [Ca2+]i within seconds (in 13% of cells) and NO production within 5 minutes (4.7-fold). TNF, and IL-1, inhibited these responses. Calcium inhibitors decreased pulsatile fluid flow,induced NO production. TNF, and IL-1, affected cytoskeletal stiffness, likely because 24 hours of incubation with TNF, and IL-1, decreased the amount of F-actin. Incubation with IL-1, for 24 hours stimulated osteocyte apoptosis. Conclusion Our results suggest that TNF, and IL-1, inhibit mechanical loading,induced NO production by osteocytes via abrogation of pulsatile fluid flow,stimulated [Ca2+]i, and that IL-1, stimulates osteocyte apoptosis. Since both NO and osteocyte apoptosis affect osteoclasts, these findings provide a mechanism by which inflammatory cytokines might contribute to bone loss and consequently affect bone mass in rheumatoid arthritis. [source]


Relation Between Echinocytosis and Erythrocyte Calcium Content in Hemodialyzed Uremic Patients

ARTIFICIAL ORGANS, Issue 6 2001
B. Agroyannis
Abstract: A rise in intracellular calcium concentration in erythrocytes has multiple effects on these cells. The purpose of this study was to determine the changes of calcium content in red blood cells (RBCs) and of echinocyte percentages in uremic patients during hemodialysis sessions. In 30 uremic patients under hemodialysis, the calcium content of RBCs and echinocyte percentages were determined in 3 blood samples collected at 0 min hemodialysis (prehemodialysis), 45 min hemodialysis, and 240 min hemodialysis (end hemodialysis) for a 4 h hemodialysis session. Calcium content of RBCs and echinocytes were also determined in 22 normal subjects (controls). The findings of the present study were that the mean values (SD) of calcium content of RBCs in patients at 0 min hemodialysis, 45 min hemodialysis, and 240 min hemodialysis were 2.00 1.0, 2.66 0.87, and 1.62 0.66 ,g/ml respectively and 0.65 0.07 ,g/ml in controls. These values show that the calcium content of RBCs in uremic patients at 0 min hemodialysis, 45 min hemodialysis, and 240 hemodialysis was significantly higher than in controls (p < 0.0001), and that RBC calcium content at 45 min hemodialysis was significantly higher in comparison to that at 0 min hemodialysis (p < 0.001) and to that at 240 min hemodialysis (p < 0.0001), while that at 240 min hemodialysis was significantly lower than at 0 min hemodialysis (p < 0.05). The mean values (SD) of echinocyte percentages in patients at 0 min hemodialysis, 45 min hemodialysis, and 240 hemodialysis were 11.93 6.18, 17.23 4.1, and 7.96 5.67% respectively, and in controls ranged from 0 to 1%. The values in uremic patients show a transient increase of echinocyte percentages at 45 min hemodialysis, which is significant in comparison to that at 0 min hemodialysis (p < 0.001) and to that at 240 min hemodialysis (p < 0.0001). Echinocyte percentages at 240 min hemodialysis were significantly lower to those at 0 min hemodialysis (p < 0.001). Correlation between calcium content of erythrocytes and echinocyte percentages shows a significantly positive relationship at 45 min hemodialysis (r = 0.368, p < 0.05) but no significant relationship at 0 min hemodialysis and 240 min hemodialysis. In conclusion, uremic patients under hemodialysis present with high calcium content in erythrocytes and abnormal erythrocytes like echinocytes. A rapid and transient increase of erythrocyte calcium is also accompanied by transient elevation of echinocytes in the first hour of hemodialysis (45 min hemodialysis), which returns after hemodialysis to lower than prehemodialysis levels. [source]


Noncompetitive antagonism of BIBN4096BS on CGRP-induced responses in human subcutaneous arteries

BRITISH JOURNAL OF PHARMACOLOGY, Issue 8 2004
Majid Sheykhzade
We investigated the antagonistic effect of 1-piperidinecarboxamide, N -[2-[[5amino-l-[[4-(4-pyridinyl)-l-piperazinyl]carbonyl]pentyl]amino]-1-[(3,5-dibromo-4-hydroxyphenyl)methyl]-2-oxoethyl]-4-(1,4-dihydro-2-oxo-3(2H)-quinazolinyl) (BIBN4096BS) on the calcitonin gene-related peptide (CGRP)-induced responses by using isometric myograph and FURA-2 technique in human subcutaneous arteries removed in association with abdominal surgery. BIBN4096BS, at the concentration of 1 pM, had no significant effect on the CGRP-induced relaxation in these vessels. At the concentration of 10 pM, BIBN4096BS had a competitive antagonistic-like behaviour characterized by parallel rightward shift in the log CGRP concentration-tension curve with no depression of the Emax. At the higher concentrations (0.1 and 1 nM), BIBN4096BS had a concentration-dependent noncompetitive antagonistic effect on the CGRP-induced responses. The efficacy and potency of CGRP was significantly greater in the smaller (lumen diameter ,200 ,m) human subcutaneous arteries compared to the larger ones. The apparent agonist equilibrium dissociation constant, KA, for CGRP1 receptors in the human subcutaneous arteries was approximately 1 nM. Analysis of the relationship between receptor occupancy and response to CGRP indicates that the receptor reserve is relatively small. Using reverse transcriptase-polymerase chain reaction (RT-PCR), the presence of mRNA sequences encoding the calcitonin receptor-like receptor, receptor activity modifying protein (RAMP1, RAMP2, RAMP3) and receptor component protein were demonstrated in human subcutaneous arteries, indicating the presence of CGRP1 -like receptor and the necessary component for the receptor activation. In conclusion, the inhibitory action of BIBN4096BS at the low concentration (10 pM) on the CGRP-tension curve (but not intracellular calcium concentration ([Ca2+]i) resembles what is seen with a reversible competitive antagonist. However, at the higher concentrations (0.1 and 1 nM), BIBN4096BS acts as a selective noncompetitive inhibitor at CGRP1 receptors in human subcutaneous arteries. British Journal of Pharmacology (2004) 143, 1066,1073. doi:10.1038/sj.bjp.0705967 [source]


Involvement of thioredoxin-binding protein 2 in the antitumor activity of CD437

CANCER SCIENCE, Issue 12 2008
Saori Matsuoka
The present authors previously reported that a synthetic retinoid, CD437, induces endoplasmic reticulum stress-mediated apoptosis in ovarian adenocarcinoma cells in spite of no response to natural retinoids. However, the precise mechanism of its proapoptotic action has not been fully determined. The present study herein demonstrates that apoptosis induction of ovarian adenocarcinoma SKOV3 cells by CD437 involves the upregulation of thioredoxin-binding protein 2 (TBP2) by a mechanism that is dependent on the intracellular calcium concentration. TBP2 is known to bind to and suppress thioredoxin (TRX) activity whereas TRX has an anti-apoptotic effect by inhibiting apoptosis signal-regulating kinase 1 (ASK1). The activation of ASK1 and its downstream molecule, c-Jun N-terminal kinase, was observed after induction of TBP2 by CD437. Interestingly, CD437 induced the association of TBP2 with TRX and, in turn, facilitated the dissociation of ASK1 from TRX. Moreover, blockade of TBP2 induction by small interfering RNA (siRNA) significantly attenuated the cytotoxic effect of CD437. These results suggest that TBP2 plays a critical role in the mechanism by which CD437 exerts proapoptotic action against SKOV3 cells. (Cancer Sci 2008; 99: 2485,2490) [source]


Small-Molecule Inhibitors of Store-Operated Calcium Entry

CHEMMEDCHEM, Issue 5 2009
Zachary
Abstract Molecules that inhibit store-operated calcium entry (SOCE) are potentially useful immunomodulating agents. The identification of proteins involved in this pathway may further enable the identification of selective inhibitors. Herein we document some examples of the small-molecule inhibitors of SOCE that have been reported to date. We also describe methods that were used to characterize the mechanism of action of these inhibitors. Controlled variation in intracellular calcium concentration is a key component of the immune response signaling pathway in lymphocytes. Store-operated calcium entry (SOCE) in these cells provides a prolonged increase in cytoplasmic Ca2+ concentrations and ultimately leads to the production of pro-inflammatory cytokines. Molecules that inhibit SOCE could therefore be useful immunomodulating agents for the treatment of rheumatoid arthritis, psoriasis, inflammatory bowel disease, and other conditions. Although the presence of the SOCE signaling pathway in lymphocytes and other cells involved in the immune response has been known for many years, key proteins involved in SOCE were identified only recently. The identification of these proteins may further enable the identification of agents that inhibit SOCE without affecting other cellular processes. This contribution documents representative examples of the small-molecule inhibitors of SOCE that have been reported to date. Where possible, methods that were used to characterize the mechanism of action of the inhibitors are also described. [source]


Granulocyte function in patients with L-ferritin iron-responsive element (IRE) 39C,T-positive hereditary hyperferritinaemia,cataract syndrome

EUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 10 2004
R. Fritsche-Polanz
Abstract Background, Hereditary hyperferritinaemia,cataract syndrome (HHCS) is an autosomal dominant trait associated with mutations in the iron responsive element (IRE) of the ferritin light-chain (L-ferritin) gene. Patients typically show elevated serum ferritin concentrations without iron overload and a bilateral cataract. Hyperferritinaemia can be associated with granulocyte dysfunction in patients with thalassemia beta and in haemodialysis patients. The effect of increased L-ferritin levels on granulocyte function in patients with HHCS is unknown. Material and methods, We examined glucose uptake, oxidative burst, chemotaxis, phagocytosis, apoptosis and intracellular calcium concentrations in polymorphonuclear leucocytes (PMNLs) of five affected members of a family with HHCS and in five healthy individuals matched for age and gender. Results, Mutation testing revealed a 39C,T transition in IRE in all five patients with HHCS. Serum ferritin levels of patients ranged between 907 and 2030 g L,1, respectively. In comparison with healthy individuals, PMNLs of patients with HHCS showed a significant increase in PMA-mediated stimulation of the oxidative burst, as well as a significantly higher stimulation of glucose uptake but no difference with respect to chemotaxis, phagocytosis, apoptosis and intracellular calcium concentrations. Conclusion, In summary, our study suggests that hyperferritinaemia in patients with IRE 39C,T-positive HHCS is associated with activation of PMNLs but not with disturbance of fundamental PMNL function. [source]


Neuronal representation of odourants in the olfactory bulb of Xenopus laevis tadpoles

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2003
Dirk Czesnik
Abstract When an odourant enters the nose, olfactory receptor neurons (ORNs) convey information about it to the olfactory bulb (OB), where this information is processed and where the first central representations of the odourant are generated. In this paper we show how odourants are represented by ensembles of OB neurons, in particular mitral cells (MCs) which are the output neurons of the OB. We were able to demonstrate for the first time that the intracellular calcium concentrations ([Ca2+]i) in the somata of these neurons undergo specific changes and that different stimuli are represented by different neuronal [Ca2+]i patterns. The similarity of patterns was assessed by cross-correlation analysis. We further show that noradrenaline (NA), which is reported to be involved in olfactory memory formation and to modulate synaptic transmission at dendrodendritic synapses in the OB, profoundly changes the representation of odourants at the level of MCs. [source]


Cyclosporin A prevents calpain activation despite increased intracellular calcium concentrations, as well as translocation of apoptosis-inducing factor, cytochrome c and caspase-3 activation in neurons exposed to transient hypoglycemia

JOURNAL OF NEUROCHEMISTRY, Issue 6 2003
Michel Ferrand-Drake
Abstract Blockade of mitochondrial permeability transition protects against hypoglycemic brain damage. To study the mechanisms downstream from mitochondria that may cause neuronal death, we investigated the effects of cyclosporin A on subcellular localization of apoptosis-inducing factor and cytochrome c, activation of the cysteine proteases calpain and caspase-3, as well as its effect on brain extracellular calcium concentrations. Redistribution of cytochrome c occurred at 30 min of iso-electricity, whereas translocation of apoptosis-inducing factor to nuclei occurred at 30 min of recovery following 30 min of iso-electricity. Active caspase-3 and calpain-induced fodrin breakdown products were barely detectable in the dentate gyrus and CA1 region of the hippocampus of rat brain exposed to 30 or 60 min of insulin-induced hypoglycemia. However, 30 min or 3 h after recovery of blood glucose levels, fodrin breakdown products and active caspase-3 markedly increased, concomitant with a twofold increase in caspase-3-like enzymatic activity. When rats were treated with neuroprotective doses of cyclosporin A, but not with FK 506, the redistribution of apoptosis-inducing factor and cytochrome c was reduced and fodrin breakdown products and active caspase-3 immuno-reactivity was diminished whereas the extracellular calcium concentration was unaffected. We conclude that hypoglycemia leads to mitochondrial permeability transition which, upon recovery of energy metabolism, mediates the activation of caspase-3 and calpains, promoting cell death. [source]


Areca nut extracts-activated secretion of leukotriene B4, and phosphorylation of p38 mitogen-activated protein kinase and elevated intracellular calcium concentrations in human polymorphonuclear leukocytes

JOURNAL OF PERIODONTAL RESEARCH, Issue 5 2007
S.-L. Hung
Background and Objective:, Polymorphonuclear leukocytes are the major source of leukotriene B4, which is synthesized via the 5-lipoxygenase pathway. Activation of the 5-lipoxygenase pathway is regulated by intracellular calcium and the phosphorylation of p38 mitogen-activated protein kinase (MAPK). The impact of areca nut extracts on the biosynthesis of leukotriene B4 by human polymorphonuclear leukocytes was evaluated, and some of the possible mechanisms underlying the responses were examined. Material and Methods:, Polymorphonuclear leukocytes were treated with various concentrations of areca nut extracts. The concentrations of leukotriene B4 released into the supernatants were evaluated using enzyme immunoassay. The phosphorylation of p38 MAPK was monitored using immunoblotting, and the cytosolic calcium kinetics were assessed fluorometrically using Fura-2. Results:, Exposure of polymorphonuclear leukocytes to areca nut extracts led to a dose-dependent increase in the production of leukotriene B4, with levels peaking at 30 min and decreasing thereafter. Areca nut extracts enhanced the phosphorylation of p38 MAPK, an enzyme known to activate 5-lipoxygenase. Incubation with areca nut extracts also resulted in a rapid elevation of intracellular calcium concentrations in polymorphonuclear leukocytes. The induction of leukotriene B4 by areca nut extracts was suppressed with the p38 MAPK inhibitor, SB203580, or with the intracellular calcium chelator, BAPTA-AM. Conclusion:, The interaction of areca nut extracts with polymorphonuclear leukocytes activated the arachidonic acid metabolic cascade. Incubation of polymorphonuclear leukocytes with areca nut extracts resulted in the activation of intracellular events, such as phosphorylation of p38 MAPK and Ca2+ mobilization, involved in the release of pro-inflammatory lipid mediators. The results of this study emphasize the potential importance of polymorphonuclear leukocytes as a source of leukotriene B4, which may modulate the inflammatory response in areca chewers. [source]