title: MAPK signaling drives inflammation in LPS-stimulated cardiomyocytes: the route of crosstalk to G-protein-coupled receptors.
abstract: Profound cardiovascular dysfunction is an important cause of mortality from septic shock. The molecular underpinnings of cardiac dysfunction during the inflammatory surge of early sepsis are not fully understood. MAPKs are important signal transducers mediating inflammation whereas G-protein signaling pathways modulate the cardiac response to stress. Using H9c2 cardiomyocytes, we investigated the interaction of MAPK and G-protein signaling in a sepsis model to test the hypothesis that the cardiomyocyte inflammatory response is controlled by MAPKs via G-protein-mediated events. We found that LPS stimulated proinflammatory cytokine production was markedly exacerbated by siRNA knockdown of the MAPK negative regulator Mkp-1. Cytokine production was blunted when cells were treated with p38 inhibitor. Two important cellular signaling molecules typically regulated by G-protein-coupled receptors, cAMP and PKC activity, were also stimulated by LPS and inflammatory cytokines TNF-α and IL-6, through a process regulated by Mkp-1 and p38. Interestingly, neutralizing antibodies against Gα(s) and Gα(q) blocked the increase in cellular cAMP and PKC activation, respectively, in response to inflammatory stimuli, indicating a critical role of G-protein coupled receptors in this process. LPS stimulation increased COX-2 in H9c2 cells, which also express prostaglandin receptors. Blockade of G-protein-coupled EP4 prostaglandin receptor by AH 23848 prevented LPS-induced cAMP increase. These data implicate MAPKs and G-proteins in the cardiomyocyte inflammatory response to LPS as well as crosstalk via COX-2-generated PGE(2). These data add to our understanding of the pathogenesis of septic shock and have the potential to guide the selection of future therapeutics.
authors.affiliation: Department of Pediatrics, The Ohio State University College of Medicine, Columbus, OH, USA. warren.frazier@nationwidechildrens.org
authors.forename: W Joshua
authors.initials: WJ
authors.lastname: Frazier
authors.forename: Jianjing
authors.initials: J
authors.lastname: Xue
authors.forename: Wendy A
authors.initials: WA
authors.lastname: Luce
authors.forename: Yusen
authors.initials: Y
authors.lastname: Liu
mesh_terms: D000818:Animals; D057134:Antibodies, Neutralizing / Q000494:pharmacology; D001713:Biphenyl Compounds / Q000494:pharmacology; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism; D054638:Dual Specificity Phosphatase 1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D007249:Inflammation / Q000378:metabolism; D015850:Interleukin-6 / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology*; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D011458:Prostaglandins E / Q000378:metabolism; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D043562:Receptors, G-Protein-Coupled / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
chemical_list: D057134:Antibodies, Neutralizing; D001713:Biphenyl Compounds; D015850:Interleukin-6; D008070:Lipopolysaccharides; D011458:Prostaglandins E; D047428:Protein Kinase Inhibitors; D034741:RNA, Small Interfering; D043562:Receptors, G-Protein-Coupled; D014409:Tumor Necrosis Factor-alpha; C046926:AH 23848; D000242:Cyclic AMP; D051546:Cyclooxygenase 2; D011493:Protein Kinase C; D048051:p38 Mitogen-Activated Protein Kinases; D054638:Dual Specificity Phosphatase 1; C517021:Dusp1 protein, rat