镉诱发肝细胞毒性和胞内Ca2+变化及硒的保护作用研究

本文通过研究镉诱发鼠肝细胞毒性和胞内游离Ca2 变化及硒的干预效应,探讨镉致肝细胞损伤机制及硒的保护作用。分离培养新生鼠原代肝细胞,随机分为正常对照组、4个5、25、100和250μmol/LCdCl2组、2个10和20μmol/LNa2SeO3组和8个用10和20μmol/LNa2SeO3分别与5、25、100和250μmol/LCdCl2联合作用组。在实验后第12h检测肝细胞存活及其MDA含量和培养液中LDH活性,激光共聚焦显微镜分析肝细胞内游离Ca2 水平(Ca2 ]i)。结果显示,镉处理的肝细胞存活随镉浓度增加明显下降,硒处理组与对照组差异不明显;硒提高或明显提高镉染毒肝细胞存活。肝细胞培养上清液LDH活性随镉浓度增加而逐渐升高,且100和250μmol/LCdCl2组显著高于对照组,而硒处理组未见明显变化;给予硒的25、100和250μmol/LCdCl2处理组LDH活性下降或明显下降。不同浓度镉均诱发肝细胞MDA含量显著升高,而硒处理组未见类似表现;10和20μmol/LNa2SeO3抑制或显著地降低25、100和250μmol/LCdCl2诱发的MDA的生成。经镉处理的肝细胞Ca2 ]i荧光强度明显高于对照组,且随镉浓度的增加而上升,而给予硒的肝细胞Ca2 ]i荧光强度未见升高,与对照组相近;加入硒的镉染毒肝细胞Ca2 ]i均比各对应浓度的镉处理组有较大幅度地下降,其中给予硒的25μmol/LCdCl2处理组差异显著,且接近对照组的水平。结果提示,镉诱发肝细胞毒性和损伤以及肝细胞Ca2 ]i升高;硒可能通过干预肝损伤细胞脂质过氧化反应,改善和保护肝细胞Ca2 ]i稳态而减轻镉诱发的细胞毒性和损伤过程。

CADMIUM-INDUCED CYTOTOXICITY AND INTRACELLULAR Ca2+ ALTERATION IN HEPATOCYTES AND PROTECTION BY SELENIUM

Cadmium (Cd)-induced cytotoxicity and intracellular Ca2+ alteration (Ca2+]i) in hepatocytes and intervention with selenium (Se) were studied to discuss mechanism of Cd-induced hepatocyte injury and protective effect by Se. Freshly primary culture hepatocytes isolated from neonatal mice were randomly divided into a normal control group, four treatment groups with cadmium chloride (CdCl2,5,25,100,250 micromol/L, respectively), two treatment groups with sodium selenite (Na2SeO3,10,20 micromol/L, respectively), and eight treatment groups with CdCl2 (5,25,100, 250 micromol/L,respectively) of administered Na2SeO3 (10,20 micromol/L, respectively). Hepatocyte viability and its malondialdehyde (MDA) content as well as lactate dehydrogenase (LDH) activity in cultured medium were assayed, and the intracellular free Ca2+ level (Ca2+]i) in hepatocytes was detected with laser scanning confocal microscope (LSCM) at 12 h after treatment. The results showed that hepatocyte viability significantly decreased in Cd-exposed groups with dosages, and had no significant differences in Se-treated groups compared with that of control group. Administration of Se increased or obviously raised the viability in Cd-exposed hepatocytes. We observed a dose-dependent increase of LDH activity and significantly higher values in cultured medium of 100 and 250 micromol/L CdC12 groups compared with that in control group,while Se-treated groups had no significant change. LDH activity of administered Se in 25,100,250 micromol/L CdCl2 groups decreased or significant decreased, respectively. Different dosages of Cd induced significant elevation of MDA concentration in hepatocytes, but administration of Se to hepatocytes is incapable of eliciting the same consequences as Cd. 10 and 20 micromol/L Na2SeO3 inhibited or significantly reduced MDA production in hepatocytes induced by 25,100 and 250 micromol/L CdCl2, respectively. Ca2+]i fluorescence intensity was significantly higher in Cd-exposed hepatocytes than in control cells and showed a dose-dependent manner,however, Ca2+]i level of administered Se in hepatocytes was not enhanced and near to that of control cells. Ca2+]i level of administered Se in Cd-exposed hepatocytes greatly decreased compared with Cd-exposed cells and significantly lower values of administered Se in 25 micromol/L CdCl2-exposed hepatocytes were observed and near to that of control cells. These results suggest that Cd induce cytotoxicity and damage as well as Ca2+]i elevation in hepatocytes. Se can relieve the process of cytotoxicity and damage by intervening lipid peroxidation,improving and protecting Ca2+]i homeostasis in Cd-induced hepatocytes.