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Myofibroblast-specific YY1 promotes liver fibrosis.

ABSTRACT: Liver fibrosis is a common consequence of various chronic hepatitis and liver injuries. The myofibroblasts, through the accumulation of extracellular matrix (ECM) proteins, are closely associated with the progression of liver fibrosis. However, the molecular mechanisms underlying transcriptional regulation of fibrogenic genes and ECM proteins in myofibroblasts remain largely unknown. Using tamoxifen inducible myofibroblast-specific Cre-expressing mouse lines with selective deletion of the transcription factor Yin Yang 1 (YY1), here we show that YY1 deletion in myofibroblasts mitigates carbon tetrachloride-induced liver fibrosis. This protective effect of YY1 ablation on liver fibrosis was accompanied with reduced expression of profibrogenic genes and ECM proteins, including TNF-?, TGF-?, PDGF, IL-6, ?-SMA and Col1?1 in liver tissues from YY1 mutant mice. Moreover, using the human hepatic stellate cell (HSC) line LX-2, we found that knockdown of YY1 in myofibroblasts by siRNA treatment diminished myofibroblast proliferation, ?-SMA expression, and collagen deposition. Collectively, our findings reveal a specific role of YY1 in hepatic myofibroblasts and suggest a new therapeutic strategy for hepatic fibrosis-associated liver diseases.

SUBMITTER: Liu H

PROVIDER: S-EPMC7134377 | biostudies-literature | 2019 Jun

REPOSITORIES: biostudies-literature

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Myofibroblast-specific YY1 promotes liver fibrosis.

Liu Huan H Zhang Shuya S Xu Suowen S Koroleva Marina M Small Eric M EM Jin Zheng Gen ZG

Biochemical and biophysical research communications 20190510 3

Liver fibrosis is a common consequence of various chronic hepatitis and liver injuries. The myofibroblasts, through the accumulation of extracellular matrix (ECM) proteins, are closely associated with the progression of liver fibrosis. However, the molecular mechanisms underlying transcriptional regulation of fibrogenic genes and ECM proteins in myofibroblasts remain largely unknown. Using tamoxifen inducible myofibroblast-specific Cre-expressing mouse lines with selective deletion of the transc ...[more]

PMID: 31084931

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Project description:Background and aimsHuman transmembrane 6 superfamily 2 (TM6SF2) variant rs58542926 is associated with NAFLD and HCC. However, conflicting reports in germline Tm6sf2 knockout mice suggest no change or decreased very low density lipoprotein (VLDL) secretion and either unchanged or increased hepatic steatosis, with no increased fibrosis. We generated liver-specific Tm6Sf2 knockout mice (Tm6 LKO) to study VLDL secretion and the impact on development and progression of NAFLD.Approach and resultsTwo independent lines of Tm6 LKO mice exhibited spontaneous hepatic steatosis. Targeted lipidomic analyses showed increased triglyceride species whose distribution and abundance phenocopied findings in mice with liver-specific deletion of microsomal triglyceride transfer protein. The VLDL triglyceride secretion was reduced with small, underlipidated particles and unchanged or increased apolipoprotein B. Liver-specific adeno-associated viral, serotype 8 (AAV8) rescue using either wild-type or mutant E167K-Tm6 reduced hepatic steatosis and improved VLDL secretion. The Tm6 LKO mice fed a high milk-fat diet for 3 weeks exhibited increased steatosis and fibrosis, and those phenotypes were further exacerbated when mice were fed fibrogenic, high fat/fructose diets for 20 weeks. In two models of HCC, either neonatal mice injected with streptozotocin (NASH/STAM) and high-fat fed or with diethylnitrosamine injection plus fibrogenic diet feeding, Tm6 LKO mice exhibited increased steatosis, greater tumor burden, and increased tumor area versus Tm6 flox controls. Additionally, diethylnitrosamine-injected and fibrogenic diet-fed Tm6 LKO mice administered wild-type Tm6 or E167K-mutant Tm6 AAV8 revealed significant tumor attenuation, with tumor burden inversely correlated with Tm6 protein levels.ConclusionsLiver-specific Tm6sf2 deletion impairs VLDL secretion, promoting hepatic steatosis, fibrosis, and accelerated development of HCC, which was mitigated with AAV8- mediated rescue.

Project description:A hallmark of chronic liver injury is fibrosis, with accumulation of extracellular matrix orchestrated by activated hepatic stellate cells (HSCs). Glucocorticoids limit HSC activation in vitro, and tissue glucocorticoid levels are amplified by 11beta-hydroxysteroid dehydrogenase-1 (11βHSD1). Although 11βHSD1 inhibitors have been developed for type 2 diabetes mellitus and improve diet-induced fatty liver in various mouse models, effects on the progression and/or resolution of liver injury and consequent fibrosis have not been characterized. We have used the reversible carbon tetrachloride-induced model of hepatocyte injury and liver fibrosis to show that in two models of genetic 11βHSD1 deficiency (global, Hsd11b1-/- , and hepatic myofibroblast-specific, Hsd11b1fl/fl /Pdgfrb-cre) 11βHSD1 pharmacological inhibition in vivo exacerbates hepatic myofibroblast activation and liver fibrosis. In contrast, liver injury and fibrosis in hepatocyte-specific Hsd11b1fl/fl /albumin-cre mice did not differ from that of controls, ruling out 11βHSD1 deficiency in hepatocytes as the cause of the increased fibrosis. In primary HSC culture, glucocorticoids inhibited expression of the key profibrotic genes Acta2 and Col1α1, an effect attenuated by the 11βHSD1 inhibitor [4-(2-chlorophenyl-4-fluoro-1-piperidinyl][5-(1H-pyrazol-4-yl)-3-thienyl]-methanone. HSCs from Hsd11b1-/- and Hsd11b1fl/fl /Pdgfrb-cre mice expressed higher levels of Acta2 and Col1α1 and were correspondingly more potently activated. In vivo [4-(2-chlorophenyl-4-fluoro-1-piperidinyl][5-(1H-pyrazol-4-yl)-3-thienyl]-methanone administration prior to chemical injury recapitulated findings in Hsd11b1-/- mice, including greater fibrosis.Conclusion11βHSD1 deficiency enhances myofibroblast activation and promotes initial fibrosis following chemical liver injury; hence, the effects of 11βHSD1 inhibitors on liver injury and repair are likely to be context-dependent and deserve careful scrutiny as these compounds are developed for chronic diseases including metabolic syndrome and dementia. (Hepatology 2018;67:2167-2181).

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Myofibroblast-specific YY1 promotes liver fibrosis.

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Myofibroblast-specific YY1 promotes liver fibrosis.

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