Endoplasmic Reticulum stress induces hepatic stellate cell apoptosis and contributes to fibrosis resolution.

BACKGROUND: Survival of hepatic stellate cells (HSCs) is a hallmark of liver fibrosis, while the induction of HSC apoptosis may induce recovery. Activated HSC are resistant to many pro-apoptotic stimuli. To this issue, the role of Endoplasmic Reticulum (ER) stress in promoting apoptosis of HSCs and consequently fibrosis resolution is still debated. AIM: To evaluate the potential ER stress-mediated apoptosis of HSCs and fibrosis resolution METHODS: HSCs were incubated with the ER stress agonists, tunicamycin or thapsigargin. In vivo, HSC were isolated from normal, bile duct-ligated (BDL) and bile duct-diverted (BDD) rats. RESULTS: In activated HSC, the specific inhibitor of ER stress-induced apoptosis, calpastatin, is significantly increased vs. quiescent HSCs. Calpain is conversely reduced in activated HSCs. This pattern of protein expression provides HSCs resistance to the ER stress signals of apoptosis (apoptosis-resistant phenotype). However, both tunicamycin and thapsigargin are able to induce apoptosis in HSCs in vitro, completely reversing the calpain/calpastatin pattern expression. Furthermore, in vivo, the fibrosis resolution observed in rat livers subjected to bile duct ligation (BDL) and subsequent bile duct diversion (BDD), leads to fibrosis resolution through a mechanism of HSCs apoptosis, potentially associated with ER stress: in fact, BDD rat liver shows an increased number of apoptotic HSCs associated with reduced calapstatin and increased calpain protein expression, leading to an apoptosis-sensible phenotype. CONCLUSIONS: ER stress sensitizes HSC to apoptosis both in vitro and in vivo. Thus, ER stress represents a key target to trigger cell death in activated HSC and promotes fibrosis resolution

Lipid Peroxidation and Paraoxonase-1 Activity in Celiac Disease

Paraoxonase-1 (PON1) plays an antioxidant and anti-inflammatory role. Aim of the study was to investigate the alteration of paraoxonase-1 activity in celiac disease (CD), an intestinal disorder characterized by toxic injury exerted by gluten peptides. Activities of PON1, levels of biochemical markers of lipid peroxidation and total antioxidant capacity were evaluated in serum obtained from 27 celiac patients (11 at diagnosis, 16 treated with gluten free diet) and 25 healthy subjects. Moreover, the serum susceptibility of Cu2+-induced lipid peroxidation was investigated in controls and patients. The results showed a lower PON1 activity in serum of both groups of celiac patients with respect to control subjects. PON1 activity in CD was related with markers of disease severity and was negatively correlated with the levels of lipid hydroperoxide and with the susceptibility of serum to lipid peroxidation induced in vitro by metal ions. The alteration of PON1 activity and markers of lipid peroxidation realized at lower extent in patients who were on a gluten-free diet

Lipid Peroxidation and Paraoxonase-1 Activity in Celiac Disease

Paraoxonase-1 (PON1) plays an antioxidant and anti-inflammatory role. Aim of the study was to investigate the alteration of paraoxonase-1 activity in celiac disease (CD), an intestinal disorder characterized by toxic injury exerted by gluten peptides. Activities of PON1, levels of biochemical markers of lipid peroxidation and total antioxidant capacity were evaluated in serum obtained from 27 celiac patients (11 at diagnosis, 16 treated with gluten free diet) and 25 healthy subjects. Moreover, the serum susceptibility of Cu(2+)-induced lipid peroxidation was investigated in controls and patients. The results showed a lower PON1 activity in serum of both groups of celiac patients with respect to control subjects. PON1 activity in CD was related with markers of disease severity and was negatively correlated with the levels of lipid hydroperoxide and with the susceptibility of serum to lipid peroxidation induced in vitro by metal ions. The alteration of PON1 activity and markers of lipid peroxidation realized at lower extent in patients who were on a gluten-free diet

A Model of Insulin Resistance and Nonalcoholic Steatohepatitis in Rats : Role of Peroxisome Proliferator-Activated Receptor-α and n-3 Polyunsaturated Fatty Acid Treatment on Liver Injury

Insulin resistance induces nonalcoholic fatty liver disease and nonalcoholic steatohepatitis (NASH). We used a high-fat, high-calorie solid diet (HFD) to create a model of insulin resistance and NASH in nongenetically modified rats and to study the relationship between visceral adipose tissue and liver. Obesity and insulin resistance occurred in HFD rats, accompanied by a progressive increase in visceral adipose tissue tumor necrosis factor (TNF)-α mRNA and in circulating free fatty acids. HFD also decreased adiponectin mRNA and peroxisome proliferator-activated receptor (PPAR)-α expression in the visceral adipose tissue and the liver, respectively, and induced hepatic insulin resistance through TNF-α-mediated c-Jun N-terminal kinase (JNK)-dependent insulin receptor substrate-1(Ser307) phosphorylation. These modifications lead to hepatic steatosis accompanied by oxidative stress phenomena, necroinflammation, and hepatocyte apoptosis at 4 weeks and by pericentral fibrosis at 6 months. Supplementation of n-3 polyunsaturated fatty acid, a PPARα ligand, to HFD-treated animals restored hepatic adiponectin and PPARα expression, reduced TNF-α hepatic levels, and ameliorated fatty liver and the degree of liver injury. Thus, our model mimics the most common features of NASH in humans and provides an ideal tool to study the role of individual pathogenetic events (as for PPARα down-regulation) and to define any future experimental therapy, such as n-3 polyunsaturated fatty acid, which ameliorated the degree of liver injury

HCC Development Is Associated to Peripheral Insulin Resistance in a Mouse Model of NASH

NAFLD is the most common liver disease worldwide but it is the potential evolution to NASH and eventually to hepatocellular carcinoma (HCC), even in the absence of cirrhosis, that makes NAFLD of such clinical importance. Aim: we aimed to create a mouse model reproducing the pathological spectrum of NAFLD and to investigate the role of possible co-factors in promoting HCC. Methods: mice were treated with a choline-deficient L-amino-acid-defined-diet (CDAA) or its control (CSAA diet) and subjected to a low-dose i.p. injection of CCl4 or vehicle. Insulin resistance was measured by the euglycemic-hyperinsulinemic clamp method. Steatosis, fibrosis and HCC were evaluated by histological and molecular analysis. Results: CDAA-treated mice showed peripheral insulin resistance at 1 month. At 1-3 months, extensive steatosis and fibrosis were observed in CDAA and CDAA+CCl4 groups. At 6 months, equal increase in steatosis and fibrosis was observed between the two groups, together with the appearance of tumor. At 9 months of treatment, the 100% of CDAA+CCl4 treated mice revealed tumor versus 40% of CDAA mice. Insulin-like Growth Factor-2 (IGF-2) and Osteopontin (SPP-1) were increased in CDAA mice versus CSAA. Furthermore, Immunostaining for p-AKT, p-c-Myc and Glypican-3 revealed increased positivity in the tumors. Conclusions: the CDAA model promotes the development of HCC from NAFLD-NASH in the presence of insulin resistance but in the absence of cirrhosis. Since this condition is increasingly recognized in humans, our study provides a model that may help understanding mechanisms of carcinogenesis in NAFLD