Antioxidant and antiapoptotic activities of idoxifene and estradiol in hepatic fibrosis in rats.

Oxidative stress plays a causative role in the development of hepatic fibrosis and apoptosis. Estradiol (E2) is an antioxidant, and idoxifene is a tissue-specific selective estrogen receptor modulator. We have previously demonstrated that E2 inhibits hepatic fibrosis in a rat model of hepatic fibrosis induced with dimethylnitrosamine (DMN), and suppresses activation of the nuclear factor (NF)-kappaB proinflammatory transcription factor in cultured rat hepatocytes undergoing oxidative stress. This study reports on the antioxidant and antiapoptotic role of idoxifene and E2 in the DMN model of hepatic fibrosis. The DMN model rats were administered with idoxifene or E2, and were examined activity of superoxide dismutase (SOD) and glutathione peroxidase (GPx) and expression of Bcl-2 family proteins in the liver. During the course of hepatofibrogenesis after DMN treatment, serum levels of lactate dehydrogenase (LDH), a biomarker for necrosis, and hepatic levels of malondialdehyde (MDA), an end product of lipid peroxidation, increased rapidly for 3 days. On day 14, serum LDH levels normalized, and hepatic fibrosis developed with increased levels of MDA and collagen and decreased production of SOD and GPx in the liver. Fibrotic liver also showed downregulation of Bcl-2 and Bcl-X(L) expression and upregulation of Bad expression. Idoxifene and E2 suppressed DMN-mediated necrosis, lipid peroxidation, the loss of antioxidant enzyme activity, and proapoptotic status in Bcl-2 family protein expression as well as hepatic fibrosis. These findings indicate that, in addition to their antiinflammatory and antifibrotic action, idoxifene and E2 could enhance antioxidant and antiapoptotic activity in hepatic fibrosis in rats.

Inhibitory effect of a soluble transforming growth factor beta type II receptor on the activation of rat hepatic stellate cells in primary culture.

BACKGROUND/AIMS: Oxidative stress, including the generation of reactive oxygen species (ROS) that acts as a signaling mediator for transforming growth factor (TGF)-beta, plays a key role in hepatic fibrosis. Hepatic stellate cells (HSCs) produce and respond to TGF-beta in an autocrine manner with increased collagen expression. It has previously been reported that the adenovirus-mediated overexpression of a soluble receptor against the extracellular domain of the TGF-beta type II receptor prevents hepatofibrogenesis in vivo, although its inhibitory role and mechanism in HSC activation remains to be elucidated. METHODS: In this study, we report on an examination of the actual role of TGF-beta inhibition on oxidative stress and the activation of cultured rat HSCs, using the adenovirus-mediated soluble TGF-beta type II receptor. RESULTS: This soluble receptor secreted from the adenovirus-infected cells binds to TGF-beta. Infection of HSCs with this adenovirus attenuated intracellular levels of TGF-beta1 mRNA and protein, NADH oxidative activity, ROS generation and lipid peroxidation, and prevented HSC activation. CONCLUSIONS: These findings suggest that this adenovirus-mediated soluble TGF-beta receptor may lead to an interruption of the TGF-beta autocrine loop in activated HSC, in part, by inhibiting oxidative stress.

Idoxifene and estradiol enhance antiapoptotic activity through estrogen receptor-beta in cultured rat hepatocytes.

Oxidative stress plays a causative role in the development of hepatic fibrosis and apoptosis. Estradiol (E2) is an antioxidant, and idoxifene is a tissue-specific selective estrogen-receptor modulator. We have previously demonstrated that E2 inhibits hepatic fibrosis in rat models of hepatic fibrosis and that the actions of E2 are mediated through estrogen receptors (ERs). This study reports on the antiapoptotic role of idoxifene and E2, and the functions of ER subtypes ER-alpha and ER-beta in hepatocytes undergoing oxidative stress. Lipid peroxidation was induced in cultured rat hepatocytes with ferric nitrilotriacetate solution with idoxifene or E2. Oxidative stress-induced early apoptosis was linked to its ability to inhibit not only the expression of Bcl-2 and Bcl-XL but the production of antioxidant enzymes as well and to stimulate Bad expression. Hepatocytes possessed functional ER-beta, but not ER-alpha, to respond directly to idoxifene and E2. Idoxifene and E2 suppressed oxidative stress-induced reactive oxygen species generation and lipid peroxidation, and their antiapoptotic effects on the activation of activator protein-1 and nuclear factor-kappaB, the loss of antioxidant enzyme activity, and Bcl-2 family protein expression in early apoptotic hepatocytes were blocked by the pure ER antagonist ICI 182,780. Our results indicate that idoxifene and E2 could enhance antiapoptotic activity through ER-beta during oxidative damage in hepatocytes.

Interferon-alpha enhances biological defense activities against oxidative stress in cultured rat hepatocytes and hepatic stellate cells.

Oxidative stress has been implicated as a cause of hepatic fibrosis, and hepatic stellate cells (HSCs), which are the most important collagen-producing cell types, have been reported to be activated by lipid peroxidation products. Antioxidant enzymes such as superoxide dismutase (SOD) and glutathione peroxidase (GPx) provide a defense system that plays a critical role in protecting the cell from free radical damage, particularly lipid peroxidation. To elucidate the antioxidant activity of interferon-alpha (IFN-alpha), the effects of IFN-alpha on rat hepatocytes undergoing oxidative stress and HSCs in primary culture as well as isolated rat liver mitochondria were examined. IFN-alpha was observed to dose-dependently increase the immunoreactive protein levels of copper, zinc-and manganese-dependent SOD as well as the enzyme activities of GPx, and decrease the lipid peroxidation product levels and oxidative burst both in stressed hepatocytes and activated HSCs; GPx activities, however, were not detected in the latter cells. IFN-alpha also inhibited HSC activation and lipid peroxidation in liver mitochondria. These findings suggest that IFN-alpha may enhance biological defense activities against oxidative stress and function as a potent fibrosuppressant by protecting hepatocytes and hepatic stellate cells from lipid peroxidation in vivo.