No significant expression of CYP2E1 in rat liver stellate cells

Expression of type I collagen in response to Isoniazid exposure is indirect and is facilitated by collateral induction of cytochrome P450 2E1: An in-vitro study

We wanted to investigate whether Isoniazid (INH) can directly stimulate activation of hepatic stellate cells (HSCs) and enhance production of collagen. Treatment of human hepatic stellate cell line LX2 with or without 5μM INH for 24 to 72 hours was performed to look into content of cytochrome P450 2E1 (CYP2E1), activity of NADPH oxidase (NOX) and intracellular oxidative stress. Protein level as well as mRNA expression of alpha smooth muscle actin (α-SMA) and collagen1A1 (COL1A1) were assessed by western blot and real time PCR. In some experiments pyrazole (PY) was pre-treated to LX2 cells to induce CYP2E1 prior to INH treatment. CYP2E1 level as well as NOX activity was gradually increased with INH treatment in LX2 cells till 72 hours. Following 72 hours of INH exposure, intracellular glutathione (GSH) level was found to be reduced compared to control (p<0.01) and showed expression of α-SMA, indicating activation of HSC. We could not found any change in collagen expression in this experimental study. Pyrazole (PY) pre-treatment to LX2 cells caused significant increase in cellular CYP2E1 content associated with increase of NOX, intracellular reactive oxygen species (ROS), and expression of α-SMA and collagen1 after INH exposure. CYP2E1 is present in insignificant amount in HSCs and INH treatment could not induce collagen expression, although altered cellular oxidant levels was observed. But in LX2 cells when CYP2E1 was over-expressed by PY, INH administration provokes oxidative stress mediated stellate cells activation along with collagen type I expression.

Pathobiology of alcoholic pancreatitis

This paper provides a summary of the effects of alcohol abuse on the pathobiologic responses that occur during acute and chronic pancreatitis considering both the human disease and animal/tissue models. The effects are multiple and include ones on cell death leading to necrosis; on inflammation resulting in a sensitized response to pancreatic stress; and fibrosis through effects of ethanol on pancreatic stellate cells and the plasminogen system. Although the effects of alcohol are multiple and complex, it is likely that a combination of a few key effects on these pathobiologic responses drive the increased sensitivity of the pancreas to acute pancreatitis with pancreatic stress and the promotion of chronic pancreatitis with pancreatic injury occurring during acute pancreatitis.

Study on the in vitro and in vivo activation of rat hepatic stellate cells by Raman spectroscopy

The feasibility of a novel and efficient diagnostic method for liver fibrosis using Raman spectroscopy is studied. Confocal Raman spectroscopy (CRS) is utilized to monitor the molecular changes of hepatic stellate cells (HSCs) in vitro as well as in vivo activation. In vitro activation was induced by growth in uncoated plastic plates, while the in vivo activation is induced by a single intraperitoneal injection of carbon tetrachloride (CCl(4)). The biochemical changes of HSCs during activation such as the loss of retinoid, the increase of alpha-helical protein, and the increased production of extracellular matrix proteins are observed by CRS. A user-friendly autoclassifying system is also developed to classify Raman spectra of liver injury tissues with a 90% accuracy rate. Raman spectroscopy combined with a fiber optical probe could be potentially accomplished for in vivo detection, which can lead to a novel and efficient diagnosis for liver fibrosis.

Effects of ethanol and acetaldehyde on reactive oxygen species production in rat hepatic stellate cells

BACKGROUND

Alcoholism is a common cause of cirrhosis. Hepatic stellate cells are the main source of collagen that ultimately leads to hepatic fibrosis and cirrhosis. Reactive oxygen species (ROS) enhance stellate cell activation and stimulate fibrogenesis. In this study, the acute effects of ethanol (ET) and acetaldehyde (AC) were determined on the production of ROS in isolated rat hepatic stellate cells.

METHODS

Rat stellate cells were isolated in situ by perfusion of the portal vein and cultured. Hydrogen peroxide (H(2)O(2)) was determined by luminol-derived chemiluminescence (CL), while superoxide anion (O(2*-)) production was assessed by the fluorescent probe hydroethidine.

RESULTS

AC increased the formation of H(2)O(2) and O(2*-), and these effects were first detectable at AC concentrations of 5 and 10 microM, respectively, reaching a maximum at 50 to 75 microM. Reduction of glutathione (GSH) synthesis by 1-buthionine sulfoximide (BSO) or by GSH conjugation with dimethylmaleate (DEM) further enhanced the effects of AC on H(2)O(2) and O(2*-) formation, while N-acetylcysteine (NAC) decreased H(2)O(2) and eliminated the enhanced generation of O(2*-) caused by AC. Raloxifene, which inhibits O(2*-) production by NAD(P)H oxidase, reduced the effects of AC on H(2)O(2) and O(2*-) production. ET increased H(2)O(2) or O(2*-) only in the presence of BSO or DEM.

CONCLUSION

This study shows that concentrations of AC, which occur in vivo after the ingestion of alcoholic beverages, result in the formation of ROS in rat hepatic stellate cells. The increases in ROS are known to activate stellate cells promoting fibrogenesis.

Pharmacokinetics of ethanol: a review of the methodology

This paper reviews current concepts on tools for studying the pharmacokinetics of alcohol. It has been known that ethanol metabolism occurs mainly in the liver via alcohol dehydrogenase and an accessory microsomal pathway. The contribution of each pathway has been examined by administration of metabolic inhibitors. The role of gastric alcohol dehydrogenase in the first-pass effects of ethanol has been speculative and may be relatively low. Some pharmacokinetic approaches with mathematical models have elucidated the role of gastric alcohol dehydorgenase, hepatic alcohol dehydrogenase and cytochrome P450 2E1 in ethanol elimination. The scale-up of ethanol elimination kinetics has enabled extrapolation from animal models to human kinetics. The clarification of the pharmacokinetics of ethanol is very important for estimating the effects of ethanol on biological events.

Use of cultured cells in assessing ethanol toxicity and ethanol-related metabolism

This article represents the proceedings of a symposium at the 2000 ISBRA Meeting in Yokohama, Japan. The chairs were Terrence M. Donohue, Jr, and Dahn L. Clemens. The presentations were (1) Characterization of single and double recombinant hepatoma cells that express ethanol-metabolizing enzymes, by Terrence M. Donohue, Jr; (2) Inhibition of cell growth by ethanol metabolism, by Dahn L. Clemens; (3) Use of transfected HeLa cells to study the genesis of alcoholic fatty liver, by Andrea Galli and David Crabb; (4) CYP2E1-mediated oxidative stress induces COL1A2 mRNA in hepatic stellate cells and in a coculture system of HepG2 and stellate cells, by Natalia Nieto; (5) Transforming growth factor-alpha secreted from ethanol-exposed hepatocytes contributes to development of alcoholic hepatic fibrosis, by Junji Kato; and (6) Effect of ethanol on Fas-dependent caspase-3 activation and apoptosis in CD4+ T cells, by Shirish S. Barve.

Use of cultured cells in assessing ethanol toxicity and ethanol-related metabolism

This article represents the proceedings of a symposium at the 2000 ISBRA Meeting in Yokohama, Japan. The chairs were Terrence M. Donohue, Jr, and Dahn L. Clemens. The presentations were (1) Characterization of single and double recombinant hepatoma cells that express ethanol-metabolizing enzymes, by Terrence M. Donohue, Jr; (2) Inhibition of cell growth by ethanol metabolism, by Dahn L. Clemens; (3) Use of transfected HeLa cells to study the genesis of alcoholic fatty liver, by Andrea Galli and David Crabb; (4) CYP2E1-mediated oxidative stress induces COL1A2 mRNA in hepatic stellate cells and in a coculture system of HepG2 and stellate cells, by Natalia Nieto; (5) Transforming growth factor-alpha secreted from ethanol-exposed hepatocytes contributes to development of alcoholic hepatic fibrosis, by Junji Kato; and (6) Effect of ethanol on Fas-dependent caspase-3 activation and apoptosis in CD4+ T cells, by Shirish S. Barve.

Ethanol and arachidonic acid increase alpha 2(I) collagen expression in rat hepatic stellate cells overexpressing cytochrome P450 2E1. Role of H2O2 and cyclooxygenase-2

The ability of ethanol and arachidonic acid (AA), as inducers of oxidative stress and key factors in alcoholic liver disease, to up-regulate alpha 2 collagen type I (COL1A2) gene expression was studied in a hepatic stellate cell line overexpressing the ethanol-inducible cytochrome P450 2E1 (CYP2E1) (E5 cells). A time- and dose-dependent induction in COL1A2 mRNA by ethanol or AA was observed that was prevented by diallylsulfide, a CYP2E1 inhibitor. Nuclear run-on experiments showed transcriptional activation of the COL1A2 gene by ethanol and AA. Catalase abrogated the increase in COL1A2 mRNA suggesting an H(2)O(2)-dependent mechanism. Cyclooxygenase-2 (COX-2) levels and production of prostaglandin E(2) upon addition of AA were elevated in the E5 cells. Incubation with NS-398, a COX-2 inhibitor, blocked the effect of AA, but not of ethanol, on COL1A2 expression suggesting that CYP2E1 activates COX-2 expression, and the oxidation of AA by COX-2 is responsible for the increase in COL1A2. Activity of a reporter construct driven by -378 base pairs of the proximal promoter region of the COL1A2 gene increased in E5 but not control cells and was further increased by ethanol or AA. These experiments link CYP2E1-dependent oxidative stress to induction of COX-2 and the actions of ethanol and AA on activation of collagen gene expression in hepatic stellate cells.

CYP2E1-mediated oxidative stress induces collagen type I expression in rat hepatic stellate cells

Hepatic stellate cells (HSCs) are a major source of extracellular matrix, which, during fibrogenesis, undergo a process of "activation" characterized by increased proliferation and collagen synthesis. Oxidative stress can stimulate HSC proliferation and collagen synthesis in vitro. Cytochrome P4502E1 (CYP2E1) is an effective producer of reactive oxygen species. To study how intracellular oxidative stress modulates alpha 2 collagen type I (COL1A2) gene induction, a rat HSC line (HSC-T6) was transfected with human CYP2E1 complementary DNA in the sense and antisense orientation and with empty vector, and stable cell lines were generated. The cells expressing CYP2E1 displayed elevated production of reactive oxygen species and showed a 4-fold increase in COL1A2 messenger RNA (mRNA) levels; expression of this mRNA among different clones appeared to correlate with the level of CYP2E1. COL1A2 expression was decreased by vitamin E treatment or transfection with manganese superoxide dismutase, and was further increased after treatment with L-buthionine sulfoximine (BSO) to lower GSH levels. Thus, CYP2E1-dependent oxidative stress plays a major role in the elevation of COL1A2 mRNA levels in this system. Nuclear run-on assay showed a 3-and-a-half-fold increase in COL1A2 transcription in the cells expressing CYP2E1; stabilization of COL1A2 mRNA was also observed. These results indicate that under oxidative stress conditions, COL1A2 mRNA expression is regulated both transcriptionally and through mRNA stabilization. The CYP2E1-expressing HSC appear to be a valuable model for the sustained generation of reactive oxygen species and may allow the elucidation of signaling pathways responsible for oxidant stress-mediated collagen gene induction.