Nitroalkenes suppress lipopolysaccharide-induced signal transducer and activator of transcription signaling in macrophages: a critical role of mitogen-activated protein kinase phosphatase 1.
Nitration products of unsaturated fatty acids are formed via NO-dependent oxidative reactions and appear to be a new class of endogenous antiinflammatory mediators. Nitroalkene derivatives of nitrated linoleic acid (LNO(2)) and nitrated oleic acid (OA-NO(2)) alleviate inflammatory responses in macrophages, but the underlying mechanisms remain to be fully defined. Herein we report that LNO(2) and OA-NO(2) suppress proinflammatory signal transducer and activator of transcription (STAT) signaling in macrophages. In RAW264.7 cells, a murine macrophage cell line, LNO(2) and OA-NO(2) inhibited the lipopolysaccharide (LPS)-induced STAT1 phosphorylation and the STAT1-dependent transcriptional activity, thereby suppressing expression of its target gene such as iNOS and MCP-1. The nitroalkene-mediated inhibition of STAT1 activity was not affected by 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (a NO scavenger), GW9662 (a peroxisome proliferator-activated receptor-gamma-specific antagonist) or glutathione (an antioxidant), suggesting an underlying mechanism independent of NO, peroxisome proliferator-activated receptor-gamma, or thio-nitralkylation. In contrast, LNO(2) or OA-NO(2) alone up-regulated both mRNA and protein levels of MAPK phosphatase 1 (MKP-1) and strongly augmented the LPS-induced MKP-1 protein expression. Knockdown of MKP-1 by MKP-1 small interfering RNA enhanced the LPS-induced STAT1 phosphorylation, suggesting that MKP-1 acts as a negative regulator for LPS-induced STAT signaling. In addition, the nitroalkene-mediated inhibitory effects on STAT1 phosphorylation, iNOS expression, and MCP-1 secretion were also largely attenuated by the MKP-1 small interfering RNA approach. Taken together, our data demonstrate that nitroalkenes inhibit proinflammatory STAT signaling through inducting MKP-1 in macrophages.
Ichikawa
Tomonaga
T
Cardiovascular Medicine, University of Michigan Medical Center, Ann Arbor, Michigan 48109, USA.
Zhang
Jifeng
J
Chen
Kai
K
Liu
Yusen
Y
Schopfer
Francisco J
FJ
Baker
Paul R S
PR
Freeman
Bruce A
BA
Chen
Yuqing E
YE
Cui
Taixing
T
D000475:Alkenes / Q000494:pharmacology*; D000818:Animals; D002478:Cells, Cultured; D054638:Dual Specificity Phosphatase 1 / Q000378:metabolism / Q000502:physiology*; D007249:Inflammation / Q000378:metabolism; D008041:Linoleic Acids / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008264:Macrophages / Q000187:drug effects* / Q000378:metabolism; D051379:Mice; D009569:Nitric Oxide / Q000378:metabolism; D009574:Nitro Compounds / Q000494:pharmacology; D009829:Oleic Acids / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D050794:STAT1 Transcription Factor / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D013438:Sulfhydryl Compounds / Q000378:metabolism / Q000494:pharmacology
C501856:12-nitro-9,12-octadecadienoic acid; D000475:Alkenes; D008041:Linoleic Acids; D008070:Lipopolysaccharides; D009574:Nitro Compounds; D009829:Oleic Acids; D050794:STAT1 Transcription Factor; C494080:Stat1 protein, mouse; D013438:Sulfhydryl Compounds; D009569:Nitric Oxide; D054638:Dual Specificity Phosphatase 1