Finally, we found that HuR and LKB1 (Ser428) levels were highly expressed in activated Acalabrutinib HSCs in human cirrhotic samples. Conclusion: Our results show that HuR is important for the pathogenesis of liver fibrosis development in the cholestatic injury model, for HSC activation, and for the response of activated HSC to PDGF and TGF-β. (HEPATOLOGY 2012;56:1870–1882) Hepatic fibrosis is the common consequence of chronic liver diseases (CLDs), such as viral and autoimmune hepatitis, alcohol consumption, biliary obstruction, and nonalcoholic fatty liver disease.1 Hepatic stellate cells (HSCs) are the major producers of collagen in the damaged liver.2

In healthy liver, Proteases inhibitor HSCs have a quiescent phenotype, accumulating retinoids (i.e., vitamin A) and expressing markers characteristic of adipocytes.3 After continued liver damage, these quiescent HSCs are exposed to apoptotic hepatocytes, reactive oxygen species, as well as inflammatory and profibrogenic factors, and undergo a process of activation to a myofibroblastic phenotype. These activated HSCs increase proliferation and migration, acquire contractility and proinflammatory properties, and express myogenic markers, such as alpha

smooth muscle actin (α-SMA) to become the major collagen type 1 alpha 1 (col1a1)-producing cells.4 In the liver, levels of many messenger RNAs (mRNAs) are regulated in response to fibrosis-inducing injuries.5 RNA-binding proteins (RBPs) can promote rapid spatiotemporal expression of proteins by binding to U- and AU-rich elements (AREs) in mRNAs.6

Human antigen R (HuR), a member of the Hu/Elav family, is a ubiquitously expressed RBP predominantly (>90%) localized in the nucleus of most unstimulated cells. In response to proliferative, stress, apoptotic, differentiation, senescence, inflammatory, and immune stimuli, HuR is exported to the cytoplasm, increasing the half-life and/or 上海皓元 the rate of translation of target mRNAs.6 Several studies have shown that HuR has important functions in hepatocytes, including hepatocyte growth factor–induced hepatocyte proliferation,7 differentiation,8 and apoptosis9 as well as during hepatocyte malignant transformation.8, 10 Also, HuR expression is up-regulated in hepatocellular carcinoma (HCC) tissue, compared to healthy tissues,10 suggesting that it could represent a novel target for liver damage research. The aims of the current work were to study the role of HuR in liver fibrosis and in HSC activation, and examine its role in controlling the functions of two principal mediators of HSC activation, platelet-derived growth factor (PDGF), and transforming growth factor beta (TGF-β).