Inverse agonist of ERR gamma reduces cannabinoid receptor type 1-mediated induction of fibrinogen synthesis in mice with a high-fat diet-intoxicated liver

Abstract

Upon liver intoxication with malnutrition or high-fat diet feeding, fibrinogen is synthesized by hepatocytes and secreted into the blood in human and mouse. Its primary function is to occlude blood vessels upon damage and thereby stop excessive bleeding. High fibrinogen levels may contribute to the development of pathological thrombosis, which is one mechanism linking fatty liver disease with cardiovascular disease. Our previous results present ERR gamma as key regulator of hepatocytic fibrinogen gene expression in human. In a therapeutic approach, we now tested ERR gamma inverse agonist GSK5182 as regulator of fibrinogen levels in mouse hyperfibrinogenemia caused by diet-induced obesity and in mouse hepatocytes. ACEA, a CB1R agonist, up-regulated transcription of mouse fibrinogen via induction of ERR gamma, whereas knockdown of ERR gamma attenuated the effect of ACEA (10 A mu M) on fibrinogen expression in AML12 mouse hepatocytes. Deletion analyses of the mouse fibrinogen gamma (FGG) gene promoter and ChIP assays revealed binding sites for ERR gamma on the mouse FGG promoter. ACEA or adenovirus ERR gamma injection induced FGA, FGB and FGG mRNA and protein expression in mouse liver, while ERR gamma knockdown with Ad-shERR gamma attenuated ACEA-mediated induction of fibrinogen gene expression. Moreover, mice maintained on a high-fat diet (HFD) expressed higher levels of fibrinogen, whereas cannabinoid receptor type 1 (CB1R)-KO mice fed an HFD had nearly normal fibrinogen levels. Finally, GSK5182 (40 mg/kg) strongly inhibits the ACEA (10 mg/kg) or HFD-mediated induction of fibrinogen level in mice. Taken together, targeting ERR gamma with its inverse agonist GSK5182 represents a promising therapeutic strategy for ameliorating hyperfibrinogenemia.