Text Box: PAFText Box: PUFA




Text Box:  Tlr4Text Box: PKG



Text Box:  PAFR 5/5/2007/-20




 Pediatr Res. 2007 Apr;61(4):427-32.Click here to read  Links

Polyunsaturated Fatty Acid supplementation alters proinflammatory gene expression and reduces the incidence of necrotizing enterocolitis in a neonatal rat model.

     Lu J, Jilling T, Li D, Caplan MS.

Although supplementation of preterm formula with polyunsaturated fatty acids (PUFA) has been shown to reduce the incidence of necrotizing enterocolitis (NEC) in animal models and clinical trials, the mechanisms remain elusive. We hypothesized that the protective effect of PUFA on NEC may be due to the ability of PUFA to suppress Toll-like receptor (TLR) 4 and platelet-activating factor receptor (PAFR) gene expression (molecules that are important in the pathogenesis of NEC) in epithelial cells. To investigate the efficacy of different PUFA preparations on NEC in a neonatal rat model, we compared the incidence of NEC among the four PUFA supplemented groups-A: arachidonic acid and docosahexaenoic acid (AA+DHA), B: egg phospholipids (EP), C: DHA, and D: control without PUFA. PUFA supplementation reduced the incidence of NEC and inhibited intestinal PAFR and TLR4 gene expression compared with the controls. To validate the in vivo observations, IEC-6 cells were exposed to PAF after pretreatment with AA or DHA. Both AA and DHA supplementation blocked PAF-induced TLR4 and PAFR mRNA expression in these enterocytes. These results suggest that PUFA modulates gene expression of key factors involved in experimental NEC pathogenesis. These effects might in part explain the protective effect of PUFA on neonatal NEC. ABBREVIATIONS::

PMID: 17515866 [PubMed - in process]

Proteins. 2007 Apr 1;67(1):41-52.Click here to read  Links

Understanding the regulation mechanisms of PAF receptor by agonists and antagonists: molecular modeling and molecular dynamics simulation studies.

     Gui C, Zhu W, Chen G, Luo X, Liew OW, Puah CM, Chen K, Jiang H.

Drug Discovery and Design Centre, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, People's Republic of China.

Platelet-activating factor receptor (PAFR) is a member of G-protein coupled receptor (GPCR) superfamily. Understanding the regulation mechanisms of PAFR by its agonists and antagonists at the atomic level is essential for designing PAFR antagonists as drug candidates for treating PAF-mediated diseases. In this study, a 3D model of PAFR was constructed by a hierarchical approach integrating homology modeling, molecular docking and molecular dynamics (MD) simulations. Based on the 3D model, regulation mechanisms of PAFR by agonists and antagonists were investigated via three 8-ns MD simulations on the systems of apo-PAFR, PAFR-PAF and PAFR-GB. The simulations revealed that binding of PAF to PAFR triggers the straightening process of the kinked helix VI, leading to its activated state. In contrast, binding of GB to PAFR locks PAFR in its inactive state. (c) 2007 Wiley-Liss, Inc.

PMID: 17243151 [PubMed - indexed for MEDLINE

J Pharmacol Exp Ther. 2007 Feb;320(2):728-37. Epub 2006 Nov 3.Click here to read  Links

Platelet-activating factor modulates activity of cyclic nucleotides in fetal ovine pulmonary vascular smooth muscle.

     Ibe BO, Ameer A, Portugal AM, Renteria L, Raj JU.

Division of Neonatology, Department of Pediatrics, Los Angeles Biomedical Research Institute, Torrance, CA 90502, USA. ibe@labiomed.org

At birth, release of endogenous vasodilators such as nitric oxide and prostacyclin facilitate pulmonary vasodilation via the cyclic nucleotides, cGMP and cAMP. Interaction of cyclic nucleotides and platelet-activating factor (PAF)-mediated responses in pulmonary vascular smooth muscle is not known. We studied the effects of cGMP and cAMP on PAF-mediated responses in ovine fetal intrapulmonary venous smooth muscle cells. Studies were done in hypoxia or normoxia with buffer with 8-Br-cGMP (BGMP) and 8-Br-cAMP (BAMP), as well as cGMP-dependent protein kinase (PKG) and cAMP-dependent protein kinase (PKA) inhibitors. All groups were treated with 1 nM PAF and incubated for 30 min for the binding assay or 20 min for measurement of inositol 1,4,5-phosphate (IP(3)) production. BGMP and BAMP decreased PAF binding in normoxia by 63 and 14%, respectively. Incubations with the PKG inhibitor Rp-8-(4-chlorophenylthio)-guanosine-3',5'-cyclic monophosphorothioate sodium and the PKA inhibitor Rp-adenosine-3',5'-cyclic monophosphorothioate abrogated the inhibitory effects of BGMP and BAMP. PAF-stimulated IP(3) production was 8565 +/- 314 dpm/10(6) cells in hypoxia and 5418 +/- 118 dpm/10(6) cells in normoxia, a 40% decrease. BGMP attenuated PAF-stimulated IP(3) production by 67 and 37% in hypoxia and normoxia, respectively; the value for BAMP was 44% under both conditions. Pretreatment with PKG or PKA inhibitor abrogated BGMP and BAMP inhibition of IP(3) release. PAF receptor (PAFr) protein expression decreased in normoxia, but pretreatment with 10 nM PAF up-regulated PAFr expression. Pretreatment with PAF decreased expression and activities of PKG or PKA proteins in normoxia and hypoxia. Our data demonstrate the existence of cGMP/cAMP-PAF cross-talk in pulmonary vascular smooth muscle cells, which may be one mechanism by which PAFr-mediated vasoconstriction is down-regulated at birth.

PMID: 17085546 [PubMed - indexed for MEDLINE













































Differential Regulation of CD40-Mediated TNF Receptor-Associated Factor Degradation in B Lymphocytes.

Moore CR, Bishop GA.

Interdisciplinary Graduate Program in Immunology.

Engagement of CD40 on murine B cells by its ligand CD154 induces the binding of TNFR-associated factors (TRAFs) 1, 2, 3, and 6, followed by the rapid degradation of TRAFs 2 and 3. TRAF degradation occurs in response to signaling by other TNFR superfamily members, and is likely to be a normal regulatory component of signaling by this receptor family. In this study, we found that receptor-induced TRAF degradation limits TRAF2-dependent CD40 signals to murine B cells. However, TRAFs 1 and 6 are not degraded in response to CD40 engagement, despite their association with CD40. To better understand the mechanisms underlying differential TRAF degradation, mixed protein domain TRAF chimeras were analyzed in murine B cells. Chimeras containing the TRAF2 zinc (Zn) domains induced effective degradation, if attached to a TRAF domain that binds to the PXQXT motif of CD40. However, the Zn domains of TRAF3 and TRAF6 could not induce degradation in response to CD40, regardless of the TRAF domains to which they were attached. Our data indicate that TRAF2 serves as the master regulator of TRAF degradation in response to CD40 signaling, and this function is dependent upon both the TRAF Zn domains and receptor binding position.

PMID: 16148124 [PubMed - in process]



B Cell Maturation Antigen, the Receptor for a Proliferation-Inducing Ligand and B Cell-Activating Factor of the TNF Family, Induces Antigen Presentation in B Cells.

Yang M, Hase H, Legarda-Addison D, Varughese L, Seed B, Ting AT.

Immunobiology Center, Mount Sinai School of Medicine, New York, NY 10029.

B cell maturation Ag (BCMA), a member of the TNFR superfamily expressed on B cells, binds to a proliferation-inducing ligand (APRIL) and B cell-activating factor of the TNF family (BAFF) but the specific B cell responses regulated by BCMA remain unclear. This study demonstrates that ligation of A20 B cells transfected with BCMA induces the expression of CD40, CD80/B7-1, CD86/B7-2, MHC class II, and CD54/ICAM-1, which subsequently enhances the presentation of OVA peptide Ag to DO11.10 T cells. BCMA expression in murine splenic B cells can be induced with IL-4 and IL-6, allowing subsequent treatment with APRIL or agonist anti-BCMA to similarly induce Ag presentation. A comparative analysis of hybrid receptors of TNFR2 fused to the cytoplasmic domains of APRIL/BAFF receptors found that only BCMA, but not transmembrane activator and calcium-modulator and cyclophilin ligand interactor or BAFF-R, is capable of activating Ag presentation. Although all three receptors can trigger NF-kappaB signaling, only BCMA activates the JNK pathway conferring on BCMA the specific ability to activate this Ag presentation response.

PMID: 16116167 [PubMed - in process]






ICAM-1 gene expression in endothelial cells: Effects on the inhibition of STAT3 phosphorylation.
Resveratrol suppresses IL-6-induced
Wung BS, Hsu MC, Wu CC, Hsieh CW.

Department of Applied Microbiology, National Chiayi University, Chiayi, Taiwan.

Resveratrol, a polyphenolic phytoaxelin present in red wine, has been suggested to protect against atherosclerosis and cardiovascular disease because of its antioxidant effects. Intercellular adhesion molecule (ICAM-1), induced by cytokines, has been hypothesized to play a role in the early events during atherosclerosis. In this study we tested the effects of resveratrol upon both IL-6-induced ICAM-1 gene expression and its underlying signaling pathways in endothelial cells (ECs). Resveratrol was found to inhibit both TNFalpha- and IL-6-induced ICAM-1 gene expression at the promoter, transcriptional and protein levels. Resveratrol also abrogates the tyr705 phosphorylation of STAT3 in IL-6-treated ECs, in a dose- and time-dependent manner. Although quercetin had similar effects, resveratrol showed higher inhibitory properties following 2-4 h pretreatments. Resveratrol has been shown to induce the activity of endothelial nitric oxide synthase (eNOS) and increase NO production. Consistent with this, the treatment of ECs with a NO donor (SNAP) reduces IL-6-induced STAT3 phosphorylation. Conversely, exposure of ECs to a NOS inhibitor reversed the effects of resveratrol upon IL-6-induced STAT3 phosphorylation. Furthermore, ECs transfected with constitutively active Rac1 (RacV12) showed increases in ICAM-1 promoter activity, intracellular reactive oxygen species (ROS) levels and STAT3 phosphorylation, and these increases were attenuated by resveratrol treatment. In summary, we demonstrate for the first time that resveratrol inhibits IL-6-induced ICAM-1 gene expression, in part, by interfering with Rac-mediated pathways via the attenuation of STAT3 phosphorylation. This study therefore provides important new insights that may contribute to the proposed beneficial effects of resveratrol in endothelial responses to cytokines during inflammation.

PMID: 16150460 [PubMed - as supplied by publisher]