Purification and characterization of a novel inhibitor of the proliferation of hepatic stellate cells

Sodium ferulate lowers portal pressure in rats with secondary biliary cirrhosis through the RhoA/Rho-kinase signaling pathway: a preliminary study

Cirrhotic rats show higher expression levels of hepatic RhoA and Rho-kinase than normal healthy rats, and the activation of this signaling pathway leads to portal hypertension. Sodium ferulate (SF) has been shown to decrease the production of geranylgeranyl pyrophosphate (GGPP), a substance essential for RhoA activation. In the present study, to investigate the effects of SF on fibrosis, portal hypertension and the RhoA/Rho-kinase pathway, hepatic cirrhosis was induced in rats by bile duct ligation. Liver function and fibrogenesis-related biochemical parameters, the hepatic hydroxyproline content, the pathological characteristics of the liver sections and the levels of hepatic α-smooth muscle actin (α-SMA; by immunohistochemistry) were analyzed to assess effects of SF on hepatic fibrosis. In addition, hepatic RhoA, Rho-kinase and endothelial nitric oxide synthase (eNOS) expression was examined by immunohistochemistry. Apoptosis in the SF-treated and SF + GGPP-treated rat primary hepatic stellate cells (HSCs) and a human stellate cell line (LX-2) was examined by flow cytometry. Intrahepatic resistance and responsiveness to the α1-adrenoceptor agonist, methoxamine, were investigated by in situ liver perfusion. Treatment with SF did not affect fibrosis-related biochemical parameters or the hydroxyproline content; however, SF reduced the histological evidence of fibrosis and hepatocyte damage. The SF-treated rats had a significantly lower expression of α-SMA and Rho-kinase, as well as an increased hepatic eNOS content; however, SF did not affect RhoA expression. The SF-treated HSCs had a significantly increased apoptotic rate compared to the untreated rats. Following the addition of GGPP, the rate apoptotic rate decreased. SF reduced basal intrahepatic resistance and the responsiveness of hepatic vascular smooth muscle to methoxamine. Therefore, our data demonstrate that SF reduces fibrogenesis, decreases portal pressure in cirrhotic rats and inhibits the activation of the RhoA/Rho-kinase signaling pathway.

Zag expression during aging suppresses proliferation after kidney injury

Recovery after acute kidney injury is impaired in the elderly, but mechanistic information regarding why this occurs is limited. In this study, aged mouse kidneys displayed a reduced epithelial proliferative reserve in vivo and in vitro. Microarray analysis identified increased expression of zinc-alpha (2)-glycoprotein (Zag) in aged proximal tubular cells. The addition of recombinant Zag to primary renal epithelial cell cultures decreased proliferation, whereas knockdown of Zag increased proliferation. In vivo, systemic small interference RNA suppressed expression of Zag in the mouse proximal tubule; this increased the rate of epithelial cell proliferation after renal ischemia/reperfusion in aged mice but also increased parenchymal fibrosis. These results demonstrate that increased Zag expression in the aged kidney acts to suppress the proliferative response to injury and introduce Zag as a modifier of the aging phenotype.

Lipolysis is altered in MHC class I zinc-α2-glycoprotein deficient mice

Non-conventional major histocompatibility complex class I molecules are involved in a variety of physiological functions, most at the periphery of the immune system per se. Zinc-alpha(2)-glycoprotein (ZAG), the sole soluble member of this superfamily has been implicated in cachexia, a poorly understood yet life-threatening, severe wasting syndrome. To further ascertain the role of ZAG in lipid metabolism and perhaps the immune system, we inactivated both ZAG alleles by gene targeting in mice. Subjecting these ZAG deficient animals to standard or lipid rich food regimens led to increased body weight in comparison to identically treated wild-type mice. This phenotype appeared to correlate with a significant decrease in adipocytic lipolysis that could not be rescued by several pharmacological agents including beta(3)-adrenoreceptor agonists. Furthermore, in contrast to previously reported data, ZAG was found to be ubiquitously and constitutively expressed, with an especially high level in the mouse liver. No overt immunological phenotype was identified in these animals.

The role of non-parenchymal cells in liver growth

The main non-parenchymal cells of the liver, Kupffer cells, sinusoidal endothelial cells and stellate cells, participate in liver growth with respect to both their own proliferation, and effects on hepatocyte proliferation. In the well-characterised paradigm of 70% partial hepatectomy, they undergo DNA synthesis and cell division 20-24h later than the hepatocyte population. They exert both positive and negative influences on hepatocyte proliferation, including provision of an extracellular matrix-bound reservoir of hepatocyte growth factor that is activated after damage; priming of hepatocytes for DNA synthesis through rapid generation of TNF-alpha and IL-6; and generation of factors at later time points that curb hepatocyte DNA synthesis (IL-1, TGF-beta) and initiate reconstruction and reformation of matrix proteins.