1.
Cr(VI)-induced overactive mitophagy contributes to mitochondrial loss and cytotoxicity in L02 hepatocytes.
Zhang, Y, Bian, H, Ma, Y, Xiao, Y, Xiao, F
The Biochemical journal. 2020;(14):2607-2619
Abstract
Hexavalent chromium [Cr(VI)] has aroused the main interest of environmental health researchers due to its high toxicity. Liver is the main target organ of Cr(VI), and the purpose of this study was to explore whether mitophagy contributes to Cr(VI)-induced hepatotoxicity and to demonstrate the potential mechanisms. Cr(VI) exposure induced mitochondrial loss, energy metabolism disorders and cell apoptosis, which were associated with the occurrence of excessive mitophagy characterized by the increased number of green fluorescent protein-microtubule-associated protein light chain 3 (GFP-LC3) puncta and lysosomal colocalization with mitochondria. In addition, the suppression of mitophagy by autophagy-related 5 (ATG5) siRNA can effectively inhibit Cr(VI)-induced mitochondrial loss and cytotoxicity. In summary, we reached the conclusion that Cr(VI)-induced overactive mitophagy contributes to mitochondrial loss and cytotoxicity in L02 hepatocytes, which will further reveal the possible mechanisms of Cr(VI)-induced hepatotoxicity, and provide a new experimental basis for the study of the health hazard effects of chromium.
2.
Expression of Clusterin suppresses Cr(VI)-induced premature senescence through activation of PI3K/AKT pathway.
Zhang, Y, Zhang, Y, Xiao, Y, Zhong, C, Xiao, F
Ecotoxicology and environmental safety. 2019;:109465
Abstract
Our group found that long-term low-dose exposure to hexavalent chromium [Cr(VI)] in L-02 hepatocytes resulted in premature senescence, which accompanied by the increased expression of Clusterin (CLU), but the functional role of CLU in premature senescence has never been explored. In the present study, the CLU overexpressed or silenced L-02 hepatocytes were established by lentiviral vector transfection. Cell viability assay, cell cycle analysis, western blotting, plate clone formation assay, and confocal microcopy were performed. The results indicated that Cr(VI)-induced premature senescence was associated with phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) pathway inhibition, and high expression of CLU in the senescent cells exerted its functional role of promoting cell proliferation. CLU could complex with eukaryotic translation initiation factor 3 subunit I (EIF3I) and prevent its degradation, leading to the increase of AKT activity in Cr(VI)-exposed senescent hepatocytes. Blockage of the PI3K/AKT pathway with its inhibitor LY294002 eliminated the inhibitory effect of CLU on Cr(VI)-induced premature senescence. We concluded that high expression of CLU suppressed Cr(VI)-induced premature senescence through activation of PI3K/AKT pathway, which will provide the experimental basis for the study of Cr(VI)-induced liver cancer, especially for the elucidation of the mechanism of liver cancer cells escaping from senescence.
3.
The role of STIM1 in the Cr(vi)-induced [Ca2+]i increase and cell injury in L-02 hepatocytes.
Yi, X, Zhang, Y, Zhong, C, Zhong, X, Xiao, F
Metallomics : integrated biometal science. 2016;(12):1273-1282
Abstract
Hexavalent chromium [Cr(vi)] is a potent cytotoxin and carcinogen. In recent years, drinking water contamination with Cr(vi) has become a worldwide problem of significant public health importance, thus much attention has been paid to the investigation of Cr(vi)-induced hepatotoxicity. The concentration of intracellular calcium ions ([Ca2+]i) was found to be increased after Cr(vi) exposure, but the exact underlying mechanisms involved in the Ca2+ homeostasis imbalance remain poorly characterized. In the present study, by utilizing the antagonist of store-operated calcium channels (SOCCs) 2-aminoethoxydiphenyl borate (2-APB), small interfering RNA against stromal interaction molecule 1 (si-STIM1) and antioxidant N-acetylcysteine (NAC), we found that Cr(vi) induces [Ca2+]i increase, cell viability loss and transaminase (AST/ALT) leakage, and that these could be suppressed by both 2-APB and si-STIM1. NAC significantly alleviated Cr(vi)-induced up-regulation of STIM1, phosphorylated-extracellular-signal-regulated kinases 1 and 2 (p-ERK1/2), ERK1/2 and nuclear factor κB (NF-κB). By utilizing the ERK inhibitor U0126 and the NF-κB inhibitor pyrrolidine dithiocarbamate (PDTC), we confirmed that STIM1 can be regulated by ERK and NF-κB. Thus we concluded that STIM1 plays a role in the Cr(vi)-induced [Ca2+]i increase and cell injury. Our current data provide new insights into the mechanisms of STIM1 function in Cr(vi)-induced hepatotoxicity, and may provide experimental clues for the prevention and treatment of liver diseases in the occupational population exposed to Cr(vi).