title: Lipoapoptosis induced by saturated free fatty acids stimulates monocyte migration: a novel role for Pannexin1 in liver cells.
abstract: Recruitment of monocytes in the liver is a key pathogenic feature of hepatic inflammation in nonalcoholic steatohepatitis (NASH), but the mechanisms involved are poorly understood. Here, we studied migration of human monocytes in response to supernatants obtained from liver cells after inducing lipoapoptosis with saturated free fatty acids (FFA). Lipoapoptotic supernatants stimulated monocyte migration with the magnitude similar to a monocyte chemoattractant protein, CCL2 (MCP-1). Inhibition of c-Jun NH2-terminal kinase (JNK) in liver cells with SP600125 blocked migration of monocytes in a dose-dependent manner, indicating that JNK stimulates release of chemoattractants in lipoapoptosis. Notably, treatment of supernatants with Apyrase to remove ATP potently inhibited migration of THP-1 monocytes and partially blocked migration of primary human monocytes. Inhibition of the CCL2 receptor (CCR2) on THP-1 monocytes with RS102895, a specific CCR2 inhibitor, did not block migration induced by lipoapoptotic supernatants. Consistent with these findings, lipoapoptosis stimulated pathophysiological extracellular ATP (eATP) release that increased supernatant eATP concentration from 5 to ~60 nM. Importantly, inhibition of Panx1 expression in liver cells with short hairpin RNA (shRNA) decreased supernatant eATP concentration and inhibited monocyte migration, indicating that monocyte migration is mediated in part by Panx1-dependent eATP release. Moreover, JNK inhibition decreased supernatant eATP concentration and inhibited Pannexin1 activation, as determined by YoPro-1 uptake in liver cells in a dose-dependent manner. These results suggest that JNK regulates activation of Panx1 channels, and provide evidence that Pannexin1-dependent pathophysiological eATP release in lipoapoptosis is capable of stimulating migration of human monocytes, and may participate in the recruitment of monocytes in chronic liver injury induced by saturated FFA.
authors.affiliation: Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, 75390-8884, USA.
authors.forename: Feng
authors.initials: F
authors.lastname: Xiao
authors.forename: Shar L
authors.initials: SL
authors.lastname: Waldrop
authors.forename: Steve F
authors.initials: SF
authors.lastname: Bronk
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Gores
authors.forename: Laurie S
authors.initials: LS
authors.lastname: Davis
authors.forename: Gordan
authors.initials: G
authors.lastname: Kilic
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002460:Cell Line; D002465:Cell Movement / Q000187:drug effects*; D018932:Chemokine CCL2 / Q000037:antagonists & inhibitors; D017630:Connexins / Q000235:genetics / Q000502:physiology*; D005227:Fatty Acids / Q000494:pharmacology*; D005230:Fatty Acids, Nonesterified / Q000494:pharmacology*; D006801:Humans; D008099:Liver / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D048670:MAP Kinase Kinase 4 / Q000037:antagonists & inhibitors / Q000378:metabolism; D009000:Monocytes / Q000187:drug effects*; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000502:physiology*; D019308:Palmitic Acid / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000096:biosynthesis / Q000235:genetics; D051381:Rats; D054390:Receptors, CCR2 / Q000037:antagonists & inhibitors
chemical_list: C111835:CCL2 protein, human; C515334:CCR2 protein, human; D018932:Chemokine CCL2; D017630:Connexins; D005227:Fatty Acids; D005230:Fatty Acids, Nonesterified; D009419:Nerve Tissue Proteins; C492764:PANX1 protein, human; D034741:RNA, Small Interfering; D054390:Receptors, CCR2; D019308:Palmitic Acid; D000255:Adenosine Triphosphate; D048670:MAP Kinase Kinase 4