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Primary Mediator (primary + mediator)
Selected AbstractsTNF receptor type 1 regulates RANK ligand expression by stromal cells and modulates osteoclastogenesisJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 5 2004Yousef Abu-Amer Abstract TNF, is a major osteoclastogenic cytokine and a primary mediator of inflammatory osteoclastogenesis. We have previously shown that this cytokine directly targets osteoclasts and their precursors and that deletion of its type-1 receptor (TNFr1) lessens osteoclastogenesis and impacts RANK signaling molecules. Osteoclastogenesis is primarily a RANK/RANKL-dependent event and occurs in an environment governed by both hematopoietic and mesenchymal compartments. Thus, we reasoned that TNF/TNFr1 may regulate RANKL and possibly RANK expression by stromal cells and osteoclast precursors (OCPs), respectively. RT-PCR experiments reveal that levels of RANKL mRNA in WT stromal cells are increased following treatment with 1,25-VD3 compared to low levels in TNFr1-null cells. Expression levels of OPG, the RANKL decoy protein, were largely unchanged, thus supporting a RANKL/OPG positive ratio favoring WT cells. RANK protein expression by OCPs was lower in TNFr1-null cells despite only subtle differences in mRNA expression in both cell types. Mix and match experiments of different cell populations from the two mice phenotypes show that WT stromal cells significantly, but not entirely, restore osteoclastogenesis by TNFr1-null OCPs. Similar results were obtained when the latter cells were cultured in the presence of exogenous RANKL. Altogether, these findings indicate that in the absence of TNFr1 both cell compartments are impaired. This was further confirmed by gain of function experiments using TNFr1- null cultures of both cell types at which exogenous TNFr1 cDNA was virally expressed. Thus, restoration of TNFr1 expression in OCPs and stromal cells was sufficient to reinstate osteoclastogenesis and provides direct evidence that TNFr1 integrity is required for optimal RANK-mediated osteoclastogenesis. © 2004 Wiley-Liss, Inc. [source] Diameter of the Cochlear Nerve in Endolymphatic Hydrops: Implications for the Etiology of Hearing Loss in Ménière's Disease,THE LARYNGOSCOPE, Issue 9 2005Cliff A. Megerian MD Abstract Objective/Hypothesis: Endolymphatic hydrops (ELH) is an important histopathological hallmark of Ménière's disease. Experimental data from human temporal bones as well as animal models of the disorder have generally failed to determine the mechanism by which ELH or related pathology causes hearing loss. Hair cell and spiral ganglion cell counts in both human and animal case studies have not, for the most part, shown severe enough deterioration to explain associated severe sensorineural hearing loss. However a limited number of detailed ultrastructural studies have demonstrated significant reductions in dendritic innervation densities, raising the possibility that neurotoxicity plays an important role in the pathology of Ménière's disease (MD) as well as experimental endolymphatic hydrops (ELH). This study tests the hypothesis that neurotoxicity is an important primary mediator of injury to the hydropic ear and is reflected in measurable deterioration of the cochlear nerve in the animal model of ELH. This study also explores the previously presented hypothesis that cochlear injury in ELH is mediated through the actions of nitric oxide (NO) by evaluating whether hearing loss or various measures of cochlear damage can be ameliorated by administration of an agent that limits excess production of NO. Study Design: Part one of the project involves the surgical induction of endolymphatic hydrops and correlation of long term hearing loss with histological parameters of ELH severity as well as cochlear nerve and eighth cranial nerve diameter measurements. In part two, aminoguanidine is administered orally to a separate set of hydropic animals in an attempt to limit cochlear injury presumably mediated by NO. Methods: Guinea pigs are subjected to surgical induction of unilateral endolymphatic hydrops after establishing baseline ABR thresholds at 2, 4, 8, 16, and 32 kHz. Threshold shifts are established prior to sacrifice at 4 to 6 months and temporal bones processed for light microscopy. Measurements of cochlear nerve and eighth cranial nerve maximal diameters as well as average maximal diameters are carried out and correlated to hearing loss and a semi-quantitative measure of hydrops severity. The identical experiments are carried out in animals treated with aminoguanidine, an inhibitor of inducible nitric oxide synthase. Results: The mean maximal diameter (n = 14) of the hydropic cochlear nerve was significantly reduced (432.14 ± 43.18 vs. 479.28 ± 49.22 microns, P = .0025) as compared to the control nerve. This was also seen in measures of the eighth cranial nerve (855.71 ± 108.82 vs. 929 ± 81.53 microns, P = 0.0003). Correlation studies failed to show correlation between hydrops severity and a cochlear nerve deterioration index (r = -0.0614, P = .8348). Similarly, hearing loss severity failed to correlate with cochlear nerve deterioration (r = 0.1300, P = .6577). There was a significant correlation between hearing loss and hydrops severity (r = 0.6148, P = .0193). Aminoguanidine treated animals (n = 5) also sustained nerve deterioration to the same degree as non-treated animals and there appeared to be no protective effect (at the dosage administered) against ELH related hearing loss, hydrops formation, or nerve deterioration. Conclusion: ELH results in significant deterioration of cochlear nerve and eighth cranial nerve maximal diameters in the guinea pig model. These findings are in accord with previous studies which detected ultrastructural evidence of dendritic damage and indicate that neural injury is of sufficient severity to result in light microscopic evidence of cochlear nerve and eighth cranial nerve deterioration. These data support the concept that the principle pathological insult in ELH is a form of neurotoxicity, especially in light of previous studies which indicate relative preservation of hair cells at similar points in time. The lack of correlation between the severity of hydrops and nerve deterioration suggests that nerve deterioration is independent of hydrops severity. [source] Developmental consequences of abnormal folate transport during murine heart morphogenesis ,BIRTH DEFECTS RESEARCH, Issue 7 2004Louisa S. Tang Abstract BACKGROUND Folic acid is essential for the synthesis of nucleotides and methyl transfer reactions. Folic acid,binding protein one (Folbp1) is the primary mediator of folic acid transport into murine cells. Folbp1 knockout mouse embryos die in utero with multiple malformations, including severe congenital heart defects (CHDs). Although maternal folate supplementation is believed to prevent human conotruncal heart defects, its precise role during cardiac morphogenesis remains unclear. In this study, we examined the role of folic acid on the phenotypic expression of heart defects in Folbp1 mice, mindful of the importance of neural crest cells to the formation of the conotruncus. METHODS To determine if the Folbp1 gene participates in the commitment and differentiation of the cardiomyocytes, relative levels of dead and proliferating precursor cells in the heart were examined by flow cytometry, Western blot, and immunohistostaining. RESULTS Our studies revealed that impaired folic acid transport results in extensive apoptosis-mediated cell death, which concentrated in the interventricular septum and truncus arteriosus, thus being anatomically restricted to the two regions of congenital heart defects. Together with a reduced proliferative capacity of the cardiomyocytes, the limited size of the available precursor cell pool may contribute to the observed cardiac defects. Notably, there is a substantial reduction in Pax-3 expression in the region of the presumptive migrating cardiac neural crest, suggesting that this cell population may be the most severely affected by the massive cell death. CONCLUSIONS Our findings demonstrate for the first time a prominent role of the Folbp1 gene in mediating susceptibility to heart defects. Birth Defects Research (Part A), 2004. © 2004 Wiley-Liss, Inc. [source] Endothelial stimulation by small lymphocytic lymphoma correlates with secreted levels of basic fibroblastic growth factorBRITISH JOURNAL OF HAEMATOLOGY, Issue 5 2003Lisa Rimsza Summary. Lymph nodes (LN) involved with small lympho- cytic lymphoma (SLL) reportedly contain increased numbers of microvessels that may constitute a therapeutic target in this disease. We investigated the secretion of the angiogenic growth factor, basic fibroblastic growth factor (bFGF), from primary tissue cultures of 15 LN with SLL and 10 reactive LN. bFGF was detected from the resulting conditioned media (CM) in 13/15 SLL samples (mean 92 ± 30, range 5,420 pg/ml) but was undetectable in CM from all reactive lymph nodes. CM was also used in a 72-h human umbilical vein endothelial cell (HUVEC) proliferation assay. HUVEC proliferation increased in the presence of SLL CM (70 ± 17%, range ,4,194%), proportional to secreted levels of bFGF (R2 = 0·95), and was reversed by depleting bFGF from CM. Previous SLL studies have examined either patient serum samples or paraffin-embedded lymph node tissue sections. This is the first study to examine the secretion of an angiogenic growth factor from primary cultures of lymph node cells. Our results indicate that bFGF is probably the primary mediator responsible for increased angiogenesis in involved nodes. These findings may be pertinent to future investigation into the mechanisms of increased angiogenesis in SLL. [source] Tamoxifen dilates porcine coronary arteries: roles for nitric oxide and ouabain-sensitive mechanismsBRITISH JOURNAL OF PHARMACOLOGY, Issue 6 2006H S Leung Background and purpose: Experiments were designed to determine the mechanism of the relaxation induced by tamoxifen in porcine coronary arteries at the tissue, cellular and molecular levels. Experimental approach: Porcine left circumflex coronary arteries were isolated and isometric tension was measured. [Ca2+]i in native endothelial cells of intact arteries was determined by a calcium fluorescence imaging technique and eNOS ser1177 phosphorylation was assayed by Western blotting. Key results: Tamoxifen induced an endothelium-dependent relaxation that was antagonized by ICI 182,780 and abolished by NG -nitro-L-arginine methyl ester (L-NAME) or 1H-[1,2,4]oxadizolo[4,3-a]quinoxalin-1-one (ODQ). L-Arginine reversed the effect of L-NAME while indomethacin was without effect. Tamoxifen-induced relaxation was attenuated by charybdotoxin (CTX) plus apamin, ouabain or by incubation in a K+ -free solution. Moreover, tamoxifen triggered extracellular Ca2+ -dependent increases in endothelial [Ca2+]i and this effect was abolished by ICI 182,780. Endothelium-independent relaxation to sodium nitroprusside was also inhibited by ouabain or in a K+ -free solution. Furthermore, tamoxifen increased endothelial nitric oxide synthase (eNOS) phosphorylation at Ser-1177 and ICI 182,780 prevented this effect. Conclusions and Implications: The present results suggest that tamoxifen mainly induces endothelium-dependent relaxation and that endothelial nitric oxide (NO) is the primary mediator of this effect. NO-dependent responses may result from elevated [Ca2+]i in endothelial cells; an effect abolished by ICI 182,780. NO activates Na+/K+ -ATPase in vascular smooth muscle, leading to relaxation. These results suggest that tamoxifen is able to modulate eNOS phosphorylation directly. British Journal of Pharmacology (2006) 149, 703,711. doi:10.1038/sj.bjp.0706921 [source] Oxidative Stress as the Leading Cause of Acute Myocardial Infarction in DiabeticsCARDIOVASCULAR THERAPEUTICS, Issue 2 2006Clara Di Filippo ABSTRACT The risk factors, such as hypertension and metabolic syndrome, tend to promote heart pathology. These risk factors can aggravate concomitant heart insults as well. Diabetes mellitus represents one of the most important risk factors for the development of heart pathology. By itself it represents a source of vascular and heart dysfunction through formation of reactive oxygen species (ROS) and can compromise the recovery from cardiovascular diseases. This review focuses on the evidence that cellular oxidative stress is the leading cause of the worst outcome of myocardial infarction (MI) in diabetics. Hyperglycemia is viewed in this article as the primary mediator of a cascade of heart damaging events, starting from ROS formation and leading to myocardial ischemia, inflammation and death of myocytes. This article also provides insights into why diverse therapeutic interventions, which have in common the ability to reduce oxidative stress and inflammation, can impede or delay the onset of complications of myocardial infarction in diabetic patients. [source] The roles of external ethnoguarantors and primary mediators in Cyprus and Northern IrelandCONFLICT RESOLUTION QUARTERLY, Issue 2 2006Sean J. Byrne This article discusses two different types of third-party interveners in the Cyprus and Northern Ireland conflicts. The comparative case study examines the roles of primary mediators who have the power and clout to enforce agreements and regional external ethnoguarantors who have cultural, historical, and political ties to internal allies. [source] Large-scale expression and thermodynamic characterization of a glutamate receptor agonist-binding domainFEBS JOURNAL, Issue 13 2000Dean R. Madden The ionotropic glutamate receptors (GluR) are the primary mediators of excitatory synaptic transmission in the brain. GluR agonist binding has been localized to an extracellular domain whose core is homologous to the bacterial periplasmic binding proteins (PBP). We have established routine, baculovirus-mediated expression of a complete ligand-binding domain construct at the 10-L scale, yielding 10,40 milligrams of purified protein. This construct contains peptides that lie outside the PBP-homologous core and that connect the domain core to the transmembrane domains of the channel and to the N-terminal ,X'-domain. These linker peptides have been implicated in modulating channel physiology. Such extended constructs have proven difficult to express in bacteria, but the protein described here is stable and monomeric. Isothermal titration calorimetry reveals that glutamate binding to the domain involves a substantial heat capacity change and that at physiological temperatures, the reaction is both entropically and enthalpically favorable. [source] Inflammatory processes of prostate tissue microenvironment drive rat prostate carcinogenesis: Preventive effects of celecoxibTHE PROSTATE, Issue 2 2009Narayanan K. Narayanan Abstract BACKGROUND Prostate tissue microenvironment is susceptible to several risk factors including carcinogens, dietary factors, hormones, cytokines and growth factors that could induce chronic inflammation. Because of the difference in the serum levels and the intrinsic ability of monocytes/macrophages to cause harm, the transcriptional responses triggered by inflammatory stimuli must be controlled. Unfortunately, an in-depth association between prostate cancer and potential mediators of inflammation has not been completely investigated. METHODS To determine whether activated macrophage (infiltrating monocytes), iNOS and NF-,B are primary mediators of inflammation, besides COX-2, in prostate carcinogenesis, we examined tissue sections of rat prostate tumor induced by N -methyl- N -nitrosourea (MNU) plus testosterone in a follow-up study. We performed H&E and immunohsitochemical staining of the prostate tissue to detect specific markers of inflammation. RESULTS We report an increase in infiltrating monocyte, iNOS, NF-,Bp65, VEGF and TNF-, at the early and advanced stages of tumor growth in MNU plus testosterone treated rats. Monocyte infiltration was often found in the stromal and perivascular regions of the DL prostate. We conclude for the first time that prostate cancer induced by MNU plus testosterone partly involves mediators of inflammation which could trigger the process of carcinogenesis and cause loss of apoptosis. Selective COX-2 inhibitor celecoxib at a dose of 500 mg/kg/bw administered for 52 weeks reduced infiltrating monocytes, inhibited iNOS, NF-,B p65 expression, induced apoptosis and tumor growth inhibition. CONCLUSION Carcinogen plus testosterone induced prostate carcinogenesis showing activation of macrophage, iNOS and NF-,Bp65 could be prevented by celecoxib or related anti-inflammatory agents. Prostate 69: 133,141, 2009. © 2008 Wiley,Liss, Inc. [source] The effects of heparin and related molecules on vascular permeability and neutrophil accumulation in rabbit skinBRITISH JOURNAL OF PHARMACOLOGY, Issue 2 2002Helen Jones Unfractionated heparin (UH) has been shown to possess a wide range of properties which are potentially anti-inflammatory. Many of these studies, including effects of heparin on adhesion of inflammatory cells to endothelium, have been carried out in vitro. In the present study, we have used radioisotopic techniques to study the effect of UH, and related molecules, on in vivo inflammatory responses (plasma exudation (PE) and PMN accumulation) in rabbit skin induced by cationic proteins, mediators and antigen. Intradermal (i.d.) pretreatment with UH dose-dependently inhibited poly-L-lysine (PLL)-induced responses. The same treatment had no effect on antigen (extract of Alternaria tenuis, AT)-, formyl-methionyl-leucyl-phenylalanine (fMLP)- or leukotriene (LT) B4 -induced responses, although i.d. dextran sulphate (DS) significantly inhibited responses to all of these mediators. High dose (10,000 u kg,1) intravenous UH significantly decreased cutaneous responses to fMLP and LTB4. By comparison, the selectin inhibitor, fucoidin, and DS, were very effective inhibitors of these responses, and of responses to AT and PLL. In contrast to the weak effect in the in vivo studies, UH significantly inhibited in vitro homotypic aggregation of rabbit PMNs, showing that it can modify PMN function. Our data with i.d. UH confirm the important ability of this molecule to interact with and neutralize polycationic peptides in vivo, suggesting that this is a prime role of endogenous heparin. The lack of effect of exogenous heparin on acute inflammatory responses induced by allergen, suggests that cationic proteins are unlikely to be primary mediators of the allergen-induced PE or PMN accumulation. British Journal of Pharmacology (2002) 135, 469,479; doi:10.1038/sj.bjp.0704505 [source] Paths of Effects of Early Childhood Intervention on Educational Attainment and Delinquency: A Confirmatory Analysis of the Chicago Child-Parent CentersCHILD DEVELOPMENT, Issue 5 2004Arthur J. Reynolds This study investigated the contributions of 5 mechanisms to the effects of preschool participation in the Child-Parent Centers for 1,404 low-income children in the Chicago Longitudinal Study. Based on a matched-group design, preschool participation was associated with significantly higher rates of educational attainment and lower rates of juvenile arrest. LISREL analysis revealed that the primary mediators of effects for both outcomes were attendance in high-quality elementary schools and lower mobility (school support hypothesis), literacy skills in kindergarten and avoidance of grade retention (cognitive advantage hypothesis), and parent involvement in school and avoidance of child maltreatment (family support hypothesis). The model accounted for 58% and 79% of the preschool links with school completion and juvenile arrest, respectively. The maintenance early intervention effects are influenced by many alterable factors. [source] | |||||||||||||