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bioRxiv · 10.1101/2023.08.14.552900

TGF-β1 inhibits cholesterol metabolism in hepatocytes to facilitate cell death, EMT and signals for HSC activation.

Wang, S.·Link, F.·Han, M.·Liebe, R.·Yao, Y.·Hammad, S.·Dropmann, A.·Chaudhary, R.·Asimakopoulos, A.·Krizanac, M.·Weiskirchen, R.·Henis, Y. I.·Ehrlich, M.·Ebert, M.·Dooley, S.
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Abstract

Background and Aims: Transforming growth factor-{beta}1 (TGF-{beta}1) plays important roles in chronic liver diseases, including metabolic dysfunction-associated steatotic liver disease (MASLD). MASLD involves various biological processes including dysfunctional cholesterol metabolism and contributes to progression to metabolic dysfunction-associated steatohepatitis (MASH) and hepatocellular carcinoma (HCC). However, the reciprocal regulation of TGF-{beta}1 signaling and cholesterol metabolism in MASLD is yet unknown. Methods: Changes in transcription of genes associated with cholesterol metabolism were assessed by RNA-Seq of murine hepatocyte cell line (AML12) and mouse primary hepatocytes (MPH) treated with TGF-{beta}1. Functional assays were performed on AML12 cells (untreated, TGF-{beta}1 treated, or subjected to cholesterol enrichment (CE) or depletion (CD)), and on mice injected with adeno-associated virus 8 (AAV8)-Control/TGF-{beta}1. Results: TGF-{beta}1 inhibited mRNA expression of several cholesterol metabolism regulatory genes, including rate-limiting enzymes of cholesterol biosynthesis in AML12 cells, MPHs, and AAV8-TGF-{beta}1-treated mice. Total cholesterol levels and lipid droplet accumulation in AML12 cells and liver tissue were also reduced upon TGF-{beta}1 treatment. Smad2/3 phosphorylation following 2 h TGF-{beta}1 treatment persisted after CE or CD and was mildly increased following CD, while TGF-{beta}1-mediated AKT phosphorylation (30 min) was inhibited by CE. Furthermore, CE protected AML12 cells from several effects mediated by 72 h incubation with TGF-{beta}1, including EMT, actin polymerization, and apoptosis. CD mimicked the outcome of long term TGF- {beta}1 administration, an effect that was blocked by an inhibitor of the type I TGF-{beta} receptor. Additionally, the supernatant of CE- or CD-treated AML12 cells inhibited or promoted, respectively, the activation of LX-2 hepatic stellate cells. Conclusions: TGF-{beta}1 inhibits cholesterol metabolism while cholesterol attenuates TGF-{beta}1 downstream effects in hepatocytes.

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Wang, S., Link, F., Han, M., Liebe, R., Yao, Y., Hammad, S., Dropmann, A., Chaudhary, R., Asimakopoulos, A., Krizanac, M., Weiskirchen, R., Henis, Y. I., Ehrlich, M., Ebert, M., Dooley, S.. 2023-08-15. TGF-β1 inhibits cholesterol metabolism in hepatocytes to facilitate cell death, EMT and signals for HSC activation.. https://doi.org/10.1101/2023.08.14.552900

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