Role of PKCδ and Nrf2 expression in liver injury of arsenic poisoning rats induced through coal-burning

Abstract

Objective To observe the expression of Protein Kinase C Delta (PKCδ) and NF-E2-related factor 2(Nrf2) in the liver of arsenic poisoning rats induced by coal-burning, and explore their roles. Methods According to body weight (80-100 g), thirty Wistar rats (half male half female) were divided into five groups of 6 each using random number table method, the control group, and drinking arsenic, low, medium and high arsenic contaminated grain groups. The control group was fed normally for 3 months; drinking arsenic, low, medium and high arsenic contaminated grain groups were fed respectively with 100 mg/L As2O3 solution and different concentrations of arsenic-containing feed (25, 50 and 100 mg/kg). At the end of the experiment period, non-anticoagulant whole blood 2 ml from peripheral vein was collected. Malondialdehyde (MDA) contents, activities of superoxide dismutase 1 (SOD1) and glutathione peroxidase (GPx) were detected. After sacrificing the animals, the liver was separated and then diacylglycerol (DAG) contents, mRNA and protein expressions of PKCδ and Nrf2 were determined, and the correlation was analyzed by Pearson. Results There were significant differences in serum MDA contents, SOD1 and GPx activities among groups (F=26.441, 3.327, 120.645, P < 0.05). The serum MDA contents in arsenic-exposed groups were higher than that of the control group (P < 0.05). However, activities of SOD1 and GPx1 were lower than those in the control group (P < 0.05). There were significant differences in liver DAG contents, Nrf2 mRNA expression levels among groups (F=8.237, 8.656, P < 0.05). DAG contents in the liver tissues of the drinking arsenic, low, medium and high arsenic contaminated grain groups were respectively (2.67 ± 0.25), (2.36 ± 0.19), (2.54 ± 0.22) and (2.69 ± 0.32) μg/L, which were significantly higher than that in the control group [(2.05 ± 0.24) μg/L, P < 0.05]. The expression levels of Nrf2 mRNA in liver tissue were respectively 1.16 ± 0.09, 1.09 ± 1.20, 1.14 ± 0.15 and 1.27 ± 0.16, which were higher than that in the control group (0.94 ± 0.08, P < 0.05). There were significant differences in the expression of pPKCδ protein in the cell membrane and cytoplasm of liver tissue between groups (F=15.925, 6.699, P < 0.05). The protein expression levels of pPKCδ in the cell membrane of liver tissue were 0.49 ± 0.06, 0.33 ± 0.05, 0.37 ± 0.06 and 0.50 ± 0.08, respectively, which were significantly higher than that in the control group (0.28 ± 0.04, P < 0.05). The protein expression levels of pPKCδ in the cytoplasm were 0.38 ± 0.06, 0.31 ± 0.05, 0.35 ± 0.05 and 0.36 ± 0.05, respectively, which were higher than that in the control group(0.24 ± 0.05, P < 0.05). There were significant differences in the expression of Nrf2 and pNrf2 in cytoplasm and nucleus of liver tissues among groups (F=9.024, 9.709, 10.396, 25.532, P < 0.05). The protein expression levels of Nrf2 in the cytoplasm were respectively 0.76 ± 0.09, 0.58 ± 0.07, 0.64 ± 0.09 and 0.73 ± 0.07, which were higher than that of the control group (0.52 ± 0.08, P < 0.05), except the low arsenic contaminated grain group. The protein expression levels of pNrf2 in the cytoplasm were respectively 0.50 ± 0.07, 0.43 ± 0.06, 0.48 ± 0.06 and 0.54 ± 0.07, which were higher than that in the control group (0.32 ± 0.06, P < 0.05). The expression levels of Nrf2 protein in the nucleus were respectively 0.44 ± 0.07, 0.41 ± 0.06, 0.47 ± 0.06 and 0.54 ± 0.09, which were higher than that in the control group (0.30 ± 0.05, P < 0.05). The protein expression levels of pNrf2 in the nucleus were respectively 0.35 ± 0.04, 0.29 ± 0.04, 0.41 ± 0.05 and 0.43 ± 0.06, which were higher than that in the control group (0.20 ± 0.03, P < 0.05). The correlation analysis showed that DAG contents and the protein expression of pPKCδ in the cell membrane and the cytoplasm were positively correlated (r=0.663, 0.604, P < 0.05). Furthermore, the protein expression of pPKCδ in the cell membrane and pNrf2 in the cytoplasm and nucleus were also positively correlated (r=0.642, 0.670, P < 0.05). Conclusions Arsenic could induce oxidative stress liver injury, and upregulate the mRNA and protein expression of Nrf2. Moreover, arsenic could also increase the protein expression of pPKCδ and DAG content, and then promote pPKCδ membrane transposition, phosphorylate Nrf2, and induce its nuclear transposition, which could regulate oxidative stress reaction. Key words: Arsenic poisoning; Coal; Liver injury; Protein kinase Cδ; Nrf2