Major Mediator (major + mediator)

Distribution by Scientific Domains

Selected Abstracts

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

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]

Prospects for therapeutic vaccination with glatiramer acetate for neurodegenerative diseases such as Alzheimer's disease

Michal Schwartz
Abstract Neurodegenerative diseases, whatever their primary causes, are characterized by certain common features, one of which is their self-perpetuating nature. The ongoing progression of the disorder is due to the effects of destructive self-compounds, whose presence in the tissues is an outcome of the early phase of the disease and which gradually destroy remaining functional neurons. Studies in our laboratory have led to the recent formulation of a novel concept of protective autoimmunity as the body's mechanism of defense against these destructive self-compounds. This autoimmune response to central nervous system (CNS) insults is mediated by T-cells and presumably operates by activating and regulating local microglia and infiltrating macrophages (inflammatory response) to carry out their function of clearing destructive material from the tissue at risk. We suggest that a well-controlled autoimmunity counteracts and overcomes the destructive effects of the potentially harmful self-compounds, at the cost of some loss of tissue. An additional risk to the individual is the induction of an autoimmune disease, which is likely to occur if the autoimmune response is malfunctioning. An optimal balance of the various factors will lead to an outcome of maximal benefit at minimal cost to the tissue. A procedure for safely boosting the autoimmune response, by vaccination with a weak self-crossreactive antigen such as glatiramer acetate (also known as Cop-1) was found to protect rats from glutamate toxicity, a major mediator of the spread of damage and a well-known causative factor in neurodegenerative disorders. Cop-1, when administered according to a different regimen, is an FDA-approved drug for the treatment of multiple sclerosis. Different formulations of the same drug can therefore be used to treat two extreme manifestations of chronic degenerative diseases of the CNS. Drug Dev. Res. 56:143,149, 2002. © 2002 Wiley-Liss, Inc. [source]

Vascular endothelial growth factor gene polymorphisms are associated with the risk of developing adenomyosis

Shan Kang
Abstract Vascular endothelial growth factor (VEGF), a major mediator of angiogenesis and vascular permeability, may play a key role in the development of adenomyosis. The aim of this study was to investigate whether these four VEGF polymorphisms (,2578C/A, ,1154G/A, ,460C/T, and +936C/T) were associated with the risk of adenomyosis development. Genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay in 174 adenomyosis patients and 199 frequency-matched control women. There were significant differences between patients and control group in allele frequencies and genotype distributions of the ,2578C/A polymorphisms (P = 0.010 and 0.044, respectively). Compared with the C/C genotype, the A/A + C/A genotype could significantly modify the risk of developing adenomyosis [odds ratio (OR) = 0.64, 95% confidence interval (CI) = 0.42,0.97]. For the ,1154G/A polymorphism, the allele frequencies and genotype distributions in patient group were significant different from those of the controls (P = 0.001 and 0.007, respectively). Compared with the G/G genotype, the A/A + G/A genotype could significantly decrease the risk of developing adenomyosis (OR = 0.51, 95% CI = 0.33,0.80). However, the genotype distributions and allele frequencies of the ,460C/T and +936C/T polymorphisms did not significantly differ between controls and patients (all P value > 0.05). The haplotype analysis suggested that the TGA (VEGF ,460/,1154/,2578) and CGA haplotypes exhibited a significant decrease in the risk of developing adenomyosis compared with the haplotype of TGC (OR = 0.64, 95% CI = 0.41,1.00; OR = 0.44, 95% CI = 0.21,0.93, respectively). The study indicated that the ,2578A or ,1154A allele of VEGF gene could significantly decrease the risk of adenomyosis and might be potentially protective factors for adenomyosis development. Environ. Mol. Mutagen., 2009. © 2009 Wiley-Liss, Inc. [source]

Altered behavioural adaptation in mice with neural corticotrophin-releasing factor overexpression

M. Kasahara
Overproduction of corticotrophin-releasing factor (CRF), the major mediator of the stress response, has been linked to anxiety, depression and addiction. CRF excess results in increased arousal, anxiety and altered cognition in rodents. The ability to adapt to a potentially threatening stimulus is crucial for survival, and impaired adaptation may underlie stress-related psychiatric disorders. Therefore, we examined the effects of chronic transgenic neural CRF overproduction on behavioural adaptation to repeated exposure to a non-home cage environment. We report that CRF transgenic mice show impaired adaptation in locomotor response to the novel open field. In contrast to wild-type (WT) mice, anxiety-related behaviour of CRF transgenic mice does not change during repeated exposure to the same environment over the period of 7 days or at retest 1 week later. We found that locomotor response to novelty correlates significantly with total locomotor activity and activity in the centre at the last day of testing and at retest in WT but not in CRF transgenic mice. Mice were divided into low responders and high responders on the basis of their initial locomotor response to novelty. We found that differences in habituation and re-exposure response are related to individual differences in locomotor response to novelty. In summary, these results show that CRF transgenic mice are fundamentally different from WT in their ability to adapt to an environmental stressor. This may be related to individual differences in stress reactivity. These findings have implications for our understanding of the role of CRF overproduction in behavioural maladaptation and stress-related psychiatric disorders. [source]

Heparin modulates the growth and adherence and augments the growth-inhibitory action of TNF-, on cultured human keratinocytes

Ilkka T. Harvima
Abstract Previous works suggest the involvement of mast cells in the epithelialization of chronic wounds. Since heparin is a major mediator stored in the secretory granules of mast cells, the purpose of this work was to elucidate the function of heparin in epithelialization using in vitro culture models. For this, low- and high-calcium media in monolayer and epithelium cultures of keratinocytes were used. Also, an assay based on keratinocyte adherence onto plastic surface was used as well. Heparin (0.02,200 ,g/ml) inhibited keratinocyte growth in a non-cytotoxic and dose-dependent manner in low- and high-calcium media, Keratinocyte-SFM® and DMEM, in the absence of growth factors and serum. Also, heparin inhibited the growth of keratinocyte epithelium in the presence of 10% fetal calf serum and DMEM. Instead, in the presence of Keratinocyte-SFM and growth factors, heparin at 2 ,g/ml inhibited the growth by 18% but at higher heparin concentrations the inhibition was reversed to baseline. TNF-, is another preformed mediator in mast cell granules and it inhibited keratinocyte growth in monolayer and epithelium cultures. Interestingly, heparin at 2,20 ,g/ml augmented or even potentiated this growth-inhibitory effect of TNF-,. The association of TNF-, with heparin was shown by demonstrating that TNF-, bound tightly to heparin-Sepharose chromatographic material. However, heparin could not augment TNF-,-induced cell cycle arrest at G0/G1 phase or intercellular adhesion molecule-1 expression in keratinocytes. In the cell adherence assay, heparin at 2 ,g/ml inhibited significantly by 12,13% or 33% the adherence of keratinocytes onto the plastic surface coated with fibronectin or collagen, respectively, but this inhibition was reversed back to baseline at 20 or 200 ,g/ml heparin. Also, heparin affected the cell membrane rather than the protein coat on the plastic surface. In conclusion, heparin not only inhibits or modulates keratinocyte growth and adherence but it also binds and potentiates the growth-inhibitory function of TNF-,. © 2004 Wiley-Liss, Inc. [source]

Nitric oxide-induced biphasic mechanism of vascular relaxation via dephosphorylation of CPI-17 and MYPT1

Toshio Kitazawa
Nitric oxide (NO) from endothelium is a major mediator of vasodilatation through cGMP/PKG signals that lead to a decrease in Ca2+ concentration. In addition, NO-mediated signals trigger an increase in myosin light chain phosphatase (MLCP) activity. To evaluate the mechanism of NO-induced relaxation through MLCP deinhibition, we compared time-dependent changes in Ca2+, myosin light chain (MLC) phosphorylation and contraction to changes in phosphorylation levels of CPI-17 at Thr38, RhoA at Ser188, and MYPT1 at Ser695, Thr696 and Thr853 in response to sodium nitroprusside (SNP)-induced relaxation in denuded rabbit femoral artery. During phenylephrine (PE)-induced contraction, SNP reduced CPI-17 phosphorylation to a minimal value within 15 s, in parallel with decreases in Ca2+ and MLC phosphorylation, followed by a reduction of contractile force having a latency period of about 15 s. MYPT1 phosphorylation at Ser695, the PKG-target site, increased concurrently with relaxation. Phosphorylation of RhoA, MYPT1 Thr696 and Thr853 differed significantly at 5 min but not within 1 min of SNP exposure. Inhibition of Ca2+ release delayed SNP-induced relaxation while inhibition of Ca2+ channel, BKCa channel or phosphodiesterase-5 did not. Pretreatment of resting artery with SNP suppressed an increase in Ca2+, contractile force and phosphorylation of MLC, CPI-17, MYPT1 Thr696 and Thr853 at 10 s after PE stimulation, but had no effect on phorbol ester-induced CPI-17 phosphorylation. Together, these results suggest that NO production suppresses Ca2+ release, which causes an inactivation of PKC and rapid CPI-17 dephosphorylation as well as MLCK inactivation, resulting in rapid MLC dephosphorylation and relaxation. [source]

Tie2 receptor tyrosine kinase, a major mediator of tumor necrosis factor ,,induced angiogenesis in rheumatoid arthritis

Laura M. DeBusk
Objective Rheumatoid arthritis (RA) is an inflammatory disease and an angiogenic disease. However, the molecular mechanisms promoting angiogenesis in RA are not clearly identified. Our objective was to study the role of an endothelium-specific receptor tyrosine kinase, Tie2, in angiogenesis of inflammatory arthritis. Methods Expression of Tie2 and its ligand, angiopoietin 1 (Ang1), in human synovium was examined by immunohistochemistry and Western blot. A novel synovium vascular window model was established to study the role of Tie2 in angiogenesis in vivo. Primary cultured endothelial cells and synoviocytes were used to study tumor necrosis factor , (TNF,),induced Tie2 and Ang1 expression. Results Tie2 was implicated in pathologic angiogenesis. We observed that Tie2 and Ang1 were elevated in human RA synovium. Using a novel collagen-induced arthritis synovial window model, we demonstrated that Tie2 signaling regulated arthritis angiogenesis in vivo. We also showed that Tie2 mediated TNF,-induced angiogenesis in a mouse cornea assay. In addition, we observed that TNF, can regulate Tie2 activation in multiple ways that may involve interactions between endothelial cells and synoviocytes. TNF, up-regulates Tie2 in endothelial cells through nuclear factor ,B, and it up-regulates Ang1 in synoviocytes. These findings suggest paracrine regulation of angiogenesis between endothelial cells and synoviocytes. Conclusion This study demonstrates that Tie2 regulates angiogenesis in inflammatory synovium. Tie2 signaling is an important angiogenic mediator that links the proinflammatory cytokine TNF, to pathologic angiogenesis. [source]

Effect of nitric oxide on iron-mediated cytotoxicity in primary cultured renal proximal tubules

Zhao-long Wu
Abstract Nitric oxide (NO) has been proved to be a mediator of hypoxic injury in renal proximal tubules (PT), but its effect on iron-induced cytotoxicity has remained little known. In this study, we observed the relationship between NO production and lactate dehydrogenase (LDH) release in primary proximal tubular epithelia co-incubated with different doses of NTA-Fe and lipopolysaccharide (LPS) alone or in combination. NO production was monitored by NO2 concentration in supernatants based on the Griess reaction; while the semi-quantitative RT-PCR was applied to detect the inducible nitric oxide synthase (iNOS) mRNA level induced by NTA-Fe and LPS together. In addition, experimental groups were subjected to reactive oxygen species (ROS) scavengers to determine the impact of the interaction between NO and ROS on iron-mediated cytotoxicity. After a 12-h co-incubation, we found that NTA-Fe increased both LDH release and 2, production in a dose-dependent manner (P,<,0.001). The level of iNOS mRNA induced by LPS was enhanced by 500 ,m NTA-Fe (P,<,0.01), lower or higher concentrations had no effect. However, the supernatant 2, level in the same group did not change significantly (P,>,0.05) although tubular injury was aggravated (P,<,0.001). The addition of l -arginine increased LDH release from 25.05,±,8.36% in the iron group to 38.67,±,7.67% in iron plus LPS group (P,<,0.05); concomitantly, l -NAME mitigated iron toxicity in LPS-treated PT (P,<,0.05). Hydroxyl scavengers provided complete protection against iron-mediated cytotoxicity (P,<,0.001), but the decrease of 2, production was only significant in the LPS-treated group. In contrast, SOD was partially effective in the LPS group (P,<,0.05) whereas the 2, level in the supernatant was inversely raised (P,<,0.05). GSH had no effect on either iron toxicity or 2, production. Thus, we conclude that NO can exacerbate the cytotoxicity caused by NTA-Fe in cultured proximal tubular epithelia, but NO is not the only factor. NTA-Fe could enhance the upregulation of iNOS transcription induced by LPS in a specific concentration range, and its regulation of NO production might also involve a post-transcription mechanism. The hydroxyl group is the major mediator in our model and the pro-oxidant role of NO is probably due to its ability to promote the Fenton reaction and form both ONOO, and ,OH via its interaction with ROS. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Discovery of Potent Vascular Endothelial Growth Factor Receptor-2 Inhibitors

CHEMMEDCHEM, Issue 1 2010
Athanasios Papakyriakou Dr.
Abstract Substantial evidence over the last decades has implicated uncontrolled angiogenesis with various pathological states, including cancer. Vascular endothelial growth factor (VEGF) plays a critical role in its regulation. Because the tyrosine kinase VEGF receptor-2 (VEGFR-2) is the major mediator of the mitogenic, angiogenic, and permeability-enhancing effects of VEGF, it has become one of the most profound anti-angiogenesis targets. Inspired by the anthranilamide class of VEGFR-2 inhibitors, we performed a computational analysis of some potent representative members, using docking and molecular dynamics calculations. Based on the observations drawn from introducing the effect of the receptor's flexibility in implicit aqueous environment, we designed, synthesized, and characterized several new analogues of related scaffolds with modifications in their steric and electronic characteristics. In,vitro evaluation of these compounds revealed several novel VEGFR-2 inhibitors that are less cytotoxic and more potent than the parent compounds. [source]


ND Vaziri
SUMMARY 1Lead is a common environmental and industrial toxin that can cause a variety of acute and chronic illnesses. For example, chronic exposure to low levels of lead has been shown to raise arterial pressure and promote renal and cardiovascular complications. 2Several mechanisms have been identified by which chronic lead exposure can cause hypertension and cardiovascular disease. In recent years, increasing evidence has emerged pointing to the role of oxidative stress as a major mediator of lead-induced hypertension. 3The present article provides an overview of the published studies on this subject. [source]

Metabolic Syndrome and Cardiovascular Disease: Challenges and Opportunities

Pharm D, Rhonda M. Cooper-DeHoff
Abstract Metabolic syndrome (MetS) has been defined in different ways. However, key components common to most definitions are a constellation of risk factors including abdominal adiposity, impaired fasting glucose, hypertension, and dyslipidemia. A major mediator of MetS appears to be insulin resistance, which relates to the development of the vascular and metabolic dysfunctions that precede overt cardiovascular disease and type 2 diabetes. Evidence suggests that the mechanisms underlying the elevated cardiovascular risk associated with MetS begin with subclinical organ damage. Therapy for MetS targets individual components of the syndrome and includes lifestyle interventions, lipid-modifying therapy, and antihypertensive agents, particularly those that inhibit the renin-angiotensin system. Results of trials of angiotensin-converting enzyme inhibitors and angiotensin receptor blockers have demonstrated reductions in new-onset diabetes and cardiovascular events in a wide range of patients. Clinical trials to investigate further the role of these drugs in the primary prevention of type 2 diabetes in patients with MetS are currently under way. The purpose of this paper is to review the MetS from the perspective of the cardiology workforce with the hope that a better understanding of the links between MetS and cardiovascular disease could lead to improved management of persons at risk. Copyright © 2007 Wiley Periodicals, Inc. [source]

Expression of gp130 and leukaemia inhibitory factor receptor subunits in adult rat sensory neurones: regulation by nerve injury

Natalie J. Gardiner
Abstract Members of the interleukin-6 (IL-6) family of cytokines have been implicated as major mediators of the response of the adult nervous system to injury. The basis for an interaction of IL-6 cytokines with adult sensory neurones has been established by analysing the levels and distribution of the two signal-transducing receptor subunits, glycoprotein 130 (gp130) and leukaemia inhibitory factor receptor (LIFR), in the dorsal root ganglion (DRG) of male adult rats before and following nerve injury. All sensory neurones express gp130-immunoreactivity (IR) in the cytoplasm and on the plasma membrane. Levels of gp130 and its intracellular distribution remained unchanged up to 14 days following sciatic nerve axotomy. LIFR-IR was largely absent from the cytoplasm and plasma membrane of sensory neurones, but confined almost exclusively to the nuclear compartment. However, following axotomy, punctate cytoplasmic LIFR-IR was detected which persisted up to 28 days following axotomy. The expression of cytoplasmic LIFR 2 days post-axotomy was proportionally greater in a subset of small diameter sensory neurones which expressed either the sensory neuropeptide CGRP or the cell surface marker isolectin B4. The coexpression of gp130 and LIFR in the same intracellular compartment following axotomy conveys potential responsiveness of injured sensory neurones to members of the IL-6 family of cytokines. [source]

Plasma levels and skin-eosinophil-expression of vascular endothelial growth factor in patients with chronic urticaria

ALLERGY, Issue 11 2009
A. Tedeschi
Background:, Although chronic urticaria (CU) is often regarded as autoimmune in nature, only less than 50% of sera from CU patients contain histamine-releasing autoantibodies. This suggests that other factors may contribute to its pathogenesis. We evaluated the possible involvement of vascular endothelial growth factor (VEGF), one of the major mediators of vascular permeability, in CU. Methods:, Eighty consecutive adult patients with CU and 53 healthy subjects were studied. VEGF and prothrombin fragment F1+2 were measured by enzyme immunoassays. Autologous plasma skin test (APST) was performed in CU patients and, in six of them, skin biopsy specimens were taken from wheals to evaluate the immunohistochemical expression of VEGF and eosinophil cationic protein (ECP). Results:, Plasma VEGF concentrations were higher in CU patients (8.00 ± 0.90 pmol/l) than in controls (0.54 ± 0.08 pmol/l) (P = 0.0001) and tended to parallel both the severity of CU and to correlate with F1+2 levels. APST was positive in 85.1% of patients. VEGF concentration was significantly higher in APST-positive than in APST-negative patients (P = 0.0003). Immunohistochemically, all specimens from patients with CU showed a strong expression of VEGF (P = 0.002) that colocalized with ECP, a classic eosinophil marker. Conclusions:, VEGF plasma levels are elevated in CU and parallel the disease severity. This supports a possible role of this molecule in CU pathophysiology. Eosinophils are the main cellular source of VEGF in CU lesional skin. [source]