title: Lysophosphatidic acid inhibits bacterial endotoxin-induced pro-inflammatory response: potential anti-inflammatory signaling pathways.
abstract: Previous studies have demonstrated that heterotrimeric guanine nucleotide-binding regulatory (Gi) protein-deficient mice exhibit augmented inflammatory responses to lipopolysaccharide (LPS). These findings suggest that Gi protein agonists will suppress LPS-induced inflammatory gene expression. Lysophosphatidic acid (LPA) activates G protein-coupled receptors leading to Gi protein activation. We hypothesized that LPA will inhibit LPS-induced inflammatory responses through activation of Gi-coupled anti-inflammatory signaling pathways. We examined the anti-inflammatory effect of LPA on LPS responses both in vivo and in vitro in CD-1 mice. The mice were injected intravenously with LPA (10 mg/kg) followed by intraperitoneal injection of LPS (75 mg/kg for survival and 25 mg/kg for other studies). LPA significantly increased the mice survival to endotoxemia (P < 0.05). LPA injection reduced LPS-induced plasma TNF-alpha production (69 +/- 6%, P < 0.05) and myeloperoxidase (MPO) activity in lung (33 +/- 9%, P < 0.05) as compared to vehicle injection. LPS-induced plasma IL-6 was unchanged by LPA. In vitro studies with peritoneal macrophages paralleled results from in vivo studies. LPA (1 and 10 microM) significantly inhibited LPS-induced TNFalpha production (61 +/- 9% and 72 +/- 9%, respectively, P < 0.05) but not IL-6. We further demonstrated that the anti-inflammatory effect of LPA was reversed by ERK 1/2 and phosphatase inhibitors, suggesting that ERK 1/2 pathway and serine/threonine phosphatases are involved. Inhibition of phosphatidylinositol 3 (PI3) kinase signaling pathways also partially reversed the LPA anti-inflammatory response. However, LPA did not alter NFkappaB and peroxisome proliferator-activated receptor gamma (PPARgamma) activation. Inhibitors of PPARgamma did not alter LPA-induced inhibition of LPS signaling. These studies demonstrate that LPA has significant anti-inflammatory activities involving activation of ERK 1/2, serine/threonine phosphatases, and PI3 kinase signaling pathways.
authors.affiliation: Department of Neurosciences, Medical University of South Carolina, Charleston, South Carolina, USA.
authors.forename: Hongkuan
authors.initials: H
authors.lastname: Fan
authors.forename: Basilia
authors.initials: B
authors.lastname: Zingarelli
authors.forename: Vashaunta
authors.initials: V
authors.lastname: Harris
authors.forename: George E
authors.initials: GE
authors.lastname: Tempel
authors.forename: Perry V
authors.initials: PV
authors.lastname: Halushka
authors.forename: James A
authors.initials: JA
authors.lastname: Cook
mesh_terms: D000818:Animals; D019446:Endotoxemia / Q000139:chemically induced / Q000276:immunology* / Q000401:mortality; D004731:Endotoxins / Q000037:antagonists & inhibitors* / Q000276:immunology / Q000494:pharmacology; D007249:Inflammation / Q000139:chemically induced* / Q000276:immunology / Q000378:metabolism; D008070:Lipopolysaccharides / Q000037:antagonists & inhibitors* / Q000276:immunology / Q000494:pharmacology; D008246:Lysophospholipids / Q000494:pharmacology*; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology; D016019:Survival Analysis; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D004731:Endotoxins; D008070:Lipopolysaccharides; D008246:Lysophospholipids; D014409:Tumor Necrosis Factor-alpha; D019869:Phosphatidylinositol 3-Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D010749:Phosphoprotein Phosphatases; C032881:lysophosphatidic acid