title: Carbon monoxide induced PPARγ SUMOylation and UCP2 block inflammatory gene expression in macrophages.
abstract: Carbon monoxide (CO) dampens pro-inflammatory responses in a peroxisome proliferator-activated receptor-γ (PPARγ) and p38 mitogen-activated protein kinase (MAPK) dependent manner. Previously, we demonstrated that CO inhibits lipopolysaccharide (LPS)-induced expression of the proinflammatory early growth response-1 (Egr-1) transcription factor in macrophages via activation of PPARγ. Here, we further characterize the molecular mechanisms by which CO modulates the activity of PPARγ and Egr-1 repression. We demonstrate that CO enhances SUMOylation of PPARγ which we find was attributed to mitochondrial ROS generation. Ectopic expression of a SUMOylation-defective PPARγ-K365R mutant partially abolished CO-mediated suppression of LPS-induced Egr-1 promoter activity. Expression of a PPARγ-K77R mutant did not impair the effect of CO. In addition to PPARγ SUMOylation, CO-activated p38 MAPK was responsible for Egr-1 repression. Blocking both CO-induced PPARγ SUMOylation and p38 activation, completely reversed the effects of CO on inflammatory gene expression. In primary macrophages isolated form C57/BL6 male mice, we identify mitochondrial ROS formation by CO as the upstream trigger for the observed effects on Egr-1 in part through uncoupling protein 2 (UCP2). Macrophages derived from bone marrow isolated from Ucp2 gene Knock-Out C57/BL6 mice (Ucp2(-/-)), produced significantly less ROS with CO exposure versus wild-type macrophages. Moreover, absence of UCP2 resulted in a complete loss of CO mediated Egr-1 repression. Collectively, these results indentify p38 activation, PPARγ-SUMOylation and ROS formation via UCP2 as a cooperative system by which CO impacts the inflammatory response.
authors: Department of Laboratory Medicine, Medical University of Vienna, Vienna, Austria.
authors: Arvand
authors: A
authors: Haschemi
authors: Beek Yoke
authors: BY
authors: Chin
authors: Markus
authors: M
authors: Jeitler
authors: Harald
authors: H
authors: Esterbauer
authors: Oswald
authors: O
authors: Wagner
authors: Martin
authors: M
authors: Bilban
authors: Leo E
authors: LE
authors: Otterbein
mesh_terms: D000818:Animals; D002248:Carbon Monoxide / Q000494:pharmacology*; D051766:Early Growth Response Protein 1 / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D007249:Inflammation / Q000139:chemically induced* / Q000235:genetics; D007473:Ion Channels / Q000502:physiology*; D008264:Macrophages / Q000378:metabolism*; D008297:Male; D051379:Mice; D024101:Mitochondrial Proteins / Q000502:physiology*; D047495:PPAR gamma / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism; D058207:Sumoylation / Q000187:drug effects*; D000071246:Uncoupling Protein 2; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D051766:Early Growth Response Protein 1; D007473:Ion Channels; D024101:Mitochondrial Proteins; D047495:PPAR gamma; D017382:Reactive Oxygen Species; C000604390:Ucp2 protein, mouse; D000071246:Uncoupling Protein 2; D002248:Carbon Monoxide; D048051:p38 Mitogen-Activated Protein Kinases