Green tea activity and iron overload induced molecular fibrogenesis of rat liver

Abstract

Iron overload toxicity was shown to associate with chronic liver diseases which lead to hepatic fibrosis and subsequently the progression to cancer through oxidative stress and apoptotic pathways. Green tea potential activity as chelating, anti-oxidative, or anti-apoptotic mechanisms against metal toxicity was poorly clarified. Here, we are trying to evaluate the anti-oxidant and anti-apoptotic properties of green tea in the regulation of serum hepcidin levels, reduction in iron overloads, and improve of liver fibrosis in iron overloaded experimental rats. Three groups of male adult rats were randomly classified into three groups and treated as follows: control rats, iron treated rats for two months in drinking water followed by either vehicle or green tea extract (AGTE; 100 mg/kg) treatment for 2 more months. Thereafter, we studied the effects of AGTE on iron overload-induced lipid peroxidation, anti-oxidant depletion, liver cell injury and apoptosis. Treatment of iron-overloaded rats with AGTE resulted in marked decreases in iron accumulation within liver, depletion in serum ferritin, and hepcidin levels. Iron-overloaded rats had significant increase in malonyldialdehyde (MDA), a marker of lipid peroxidation and nitric oxide (NO) in liver when compared to control group. Also, significant change in cytochrome c and DNA content as apoptotic markers were reported in iron treated rats. The effects of iron overload on lipid peroxidation, NO levels, cytochrome c and DNA content were significantly reduced by the intervention treatment with AGTE (P < 0.001). Furthermore, the endogenous anti-oxidant capacities/levels (TAC) in liver were also significantly decreased in chronic iron overload and administration of AGTE restored the decrease in the hepatic antioxidant activities/levels. Also, hepatic hepcidin was shown to be significantly correlated with oxidative and apoptotic relating biomarkers as well as an improvement in liver fibrosis of iron treated rats following AGTE treatment. In-vitro analysis showed that, the improvement in iron toxicity of the liver depend mainly on antioxidant and protective ability of green tea polyphenolic compounds especiallyepigallocatechin-3-gallate (EGCG). Our study showed that green tea extract (GTE) ameliorates iron overload induced hepatotoxicity, apoptosis and oxidative stress in rat liver via inhibition of hepatic iron accumulation; improve of liver antioxidant capacity, and down regulation of serum hepcidin as well as reduction in the release of apoptotic relating proteins.

Keywords: Apoptosis; Green tea; Hepcidin; Iron overload; Liver fibrosis; Oxidative stress.

Fig. 1

Effect of aqueous green tea extract (AGTE) on the levels of liver function biomarkers in overload and green tea treated experimental rats. All values represent mean ± SD. ^*P < 0.05; ^**P < 0.01 compared to control; Student’s t-test.

Fig. 2

Potential effects of aqueous green tea extract (AGTE) on iron accumulation, serum ferritin, and hepcidin in experimental rats. [A] Fold change in the level of hepatic iron (μmole/g tissue) in iron overloaded and green tea treated rat livers in relation to control group. [B] Fold change in hepatic hepcidin and ferritin levels of iron overloaded and green tea treated rat livers in relation to control group. All values represent mean ± SD. ^*P < 0.05; ^**P < 0.01 compared to control; Student’s t-test.

Fig. 3

Effect of iron deposition on oxidative stress, NO levels, and apoptotic related biomarkers (DNA, cytochrome C) in livers, and potential effects of aqueous green tea extract (AGTE). [A] Fold change of hepatic malonyldialdehyde (MDA) as a marker of oxidative stress in liver tissues (nmole/g wet tissue). MDA levels significantly increased in livers of iron overloaded rats compared to both control and AGTE treated groups. [B] Fold change in hepatic nitric oxide (NO) (nmole/g wet tissue) in liver. Levels of NO showed significant increase in iron overloaded rats than in control rats, whereas significant reduction in NO levels were reported in iron overloaded rats following green tea treatments (AGTE; 100/kg). [C] Fold change in total antioxidant capacity (TAC; nmol/mM) in hepatic cells of iron overloaded and green tea treated rats in relation to control rats. Significant decrease in TAC activity was reported in iron overloaded rats compared to control and green tea treated rats. [D] Fold change in hepatic DNA content and cytochrome C as markers of apoptosis. Significant decrease in DNA content and increase in cytochrome C in iron overloaded rats compared to control rats, and significantly improved in iron overloaded rats following AGTE treatments. All values represent mean ± SD. ^*P < 0.05; ^**P < 0.01; ^***P < 0.001 compared to control; Student’s t-test.