title: The role of endogenous and exogenous ligands for the peroxisome proliferator-activated receptor alpha (PPAR-alpha) in the regulation of inflammation in macrophages.
abstract: The aim of the present study was to evaluate the role of endogenous and exogenous peroxisome proliferator-activated receptor alpha (PPAR-alpha), a nuclear receptor, on the regulation of inflammation in macrophages. To address this question, we have stimulated peritoneal macrophages from PPAR-alpha wild-type mice and PPAR-alpha knockout mice (PPAR-alpha) with 10 microg/mL LPS and 100 U/mL IFN-gamma. We report here that the absence of a functional PPAR-alpha gene in PPAR-alpha knockout mice resulted in a significant augmentation of various inflammatory parameters in peritoneal macrophages. In particular, we have clearly demonstrated that PPAR-alpha gene deletion increases (1) the mitogen-activated protein kinase phosphorylation (extracellular signal-regulated kinase, c-Jun NH2-terminal kinase, and p38), (2) nuclear factor-kappaB activation, (3) IkappaB-alpha degradation, (4) iNOS expression and NO formation, and (5) cyclooxygenase 2 expression and prostaglandin E2 formation caused by LPS/IFN-gamma stimulation. On the contrary, the incubation of peritoneal macrophages from PPAR-alpha wild type with clofibrate (2 mM) at 2 h before the LPS and IFN-gamma stimulation significantly reduced the expression and the release of the proinflammatory mediators. To elucidate whether the protective effects of clofibrate is related to activation of the PPAR-alpha receptor, we also investigated the effect of clofibrate treatment on PPAR-alpha-deficient mice. The absence of the PPAR-alpha receptor significantly abolished the protective effect of the PPAR-alpha agonist against LPS/IFN-gamma-induced macrophage inflammation. In conclusion, our study demonstrates that the endogenous and exogenous PPAR-alpha ligands reduce the degree of macrophage inflammation caused by LPS/IFN-gamma stimulation.
authors.affiliation: Department of Clinical and Experimental Medicine and Pharmacology, School of Medicine, University of Messina Torre Biologica, Policlinico Universitario, Messina, Italy.
authors.forename: Concetta
authors.initials: C
authors.lastname: Crisafulli
authors.forename: Salvatore
authors.initials: S
authors.lastname: Cuzzocrea
mesh_terms: D000818:Animals; D015153:Blotting, Western; D019069:Cell Respiration / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D051546:Cyclooxygenase 2 / Q000378:metabolism; D015232:Dinoprostone / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D007371:Interferon-gamma / Q000494:pharmacology; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D017737:Macrophages, Peritoneal / Q000166:cytology / Q000187:drug effects / Q000276:immunology*; D051379:Mice; D018345:Mice, Knockout; D016328:NF-kappa B / Q000378:metabolism; D047493:PPAR alpha / Q000235:genetics / Q000502:physiology*; D010766:Phosphorylation / Q000187:drug effects; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D008070:Lipopolysaccharides; D016328:NF-kappa B; D047493:PPAR alpha; D007371:Interferon-gamma; D051546:Cyclooxygenase 2; D048049:Extracellular Signal-Regulated MAP Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D015232:Dinoprostone