Hepatocyte-specific deletion of thromboxane-prostanoid receptor has protective effects on alcohol-associated liver disease
Authors: Ai Weilun , Casey Carol , Saraswathi Viswanathan 
Published: May 2023

Alcohol-associated liver disease (ALD) is a major health issue worldwide with limited effective treatment options. Thromboxane-prostanoid receptor (TP-R), a G-protein-coupled receptor, is widely expressed in liver. Previous studies reported that an alcohol diet increased levels of TP-R ligands, thromboxane A2 and 8-isoprostane, in mouse liver. However, the role of TP-R signaling in ALD still remains unknown. Here, to test the hypothesis that deleting hepatocyte TP-R ameliorates liver injury caused by an alcohol diet, nine-week female hepatocyte-specific TP-R knock-out mice (KO) and their wild-type (WT) littermate control mice were fed the Lieber-DeCarli control (CONT) or 5% (v/v) ethanol (ET) diet for 4 weeks. Mice were divided into four groups: WT-CONT (n=8), KO-CONT (n=8), WT-ET (n=10), and KO-ET (n=8). Real-time PCR analyses showed that deleting hepatocyte TP-R attenuated alcohol-induced increase in mRNA levels of inflammatory markers including interleukin 6 ( P<0.01) and lipocalin 2 ( P<0.01). In addition, mRNA levels of other inflammatory markers including C-C motif chemokine ligand 2 ( P<0.05) and interleukin 1β ( P<0.01) were increased significantly only in WT-ET mice but not in KO-ET mice compared with controls. Of note, both real-time PCR and immunohistochemistry analyses showed that deleting TP-R in hepatocytes attenuates alcohol-induced increase in the expression of cluster of differentiation 36 (CD36, P<0.05), a fatty acid transport protein. Previous studies documented that chronic alcohol consumption led to hepatic steatosis through promoting CD36-mediated fatty acid uptake. Interestingly, the gas chromatographic analysis of liver lipids revealed a remarkable increase in linoleic acid ( P<0.05) level in liver triglyceride (TG) in WT-ET mice and this effect was blunted in KO-ET group. Additionally, the alcohol diet increased the levels of arachidonic acid ( P<0.01), dihomo-gamma-linoleic acid ( P<0.05), and docosatetraenoic acid ( P<0.05) in liver TG of WT mice, but these fatty acids were not altered by alcohol diet in KO-ET group. Chronic alcohol feeding is known to elicit an oxidative stress in mouse livers though increasing the activity of cytochrome P450 family 2 subfamily E member 1 (CYP2E1). Accordingly, we noted that ablation of hepatocyte TP-R inhibited liver CYP2E1 activity in mice fed an alcohol diet ( P<0.01). Moreover, the alcohol diet increased liver malondialdehyde level in WT mice ( P<0.01) but not in KO mice. These findings suggest that hepatocyte TP-R plays an important role in regulating lipid metabolism and oxidative stress, thereby contributing to the development of AALD. This study was supported by R21 awards from NIH-National Institute on Alcohol Abuse and Alcoholism (R21- AA025445 and R21-AA027367) and a Merit Award from the Department of Veterans Affairs (I01CX002084). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.