Metallothionein isoform 2A expression is inducible and protects against ROS-mediated cell death in rotenone-treated HeLa cells

Abstract

The role of MT (metallothionein) gene expression was investigated in rotenone-treated HeLa cells to induce a deficiency of NADH:ubiquinone oxidoreductase (complex I). Complex I deficiency leads to a diversity of cellular consequences, including production of ROS (reactive oxygen species) and apoptosis. HeLa cells were titrated with rotenone, resulting in dose-dependent decrease in complex I activity and elevated ROS production at activities lower than 33%. Expression of MT2A (MT isoform 2A), but not MT1A or MT1B RNA, was significantly inducible by rotenone (up to 7-fold), t-BHP (t-butyl hydroperoxide; 5-fold) and CdCl2 (50-fold), but not ZnCl2. Myxothiazol treatment did not elevate either ROS or MT2A levels, which supports a ROS-related mechanism for rotenone-induced MT2A expression. To evaluate the role of MT2A expression, MT2A and MT1B were overexpressed in HeLa cells and treated with rotenone. Compared with control and MT1B-overexpressing cells, ROS production was significantly lower and cell viability higher in MT2A-overexpressing HeLa cells when ROS production was enhanced by treatment with t-BHP. Mitochondrial membrane potential was noticeably less reduced in both MT-overexpressing cell lines. MT2A overexpression in rotenone-treated cells also significantly reduced or delayed apoptosis induction, as measured by caspase 3/7 activity and cytosolic nucleosome enrichment. We conclude that MT2A offers significant protection against the main death-causing consequences of rotenone-induced complex I deficiency in HeLa cells. Our results are in support of the protective role against oxidative stress ascribed to MTs and provide evidence that MT2A expression may be a beneficial downstream adaptive response in complex I-deficient cells.

Expression of Metallothionein in Oral Cancer

“…Nonetheless, the results of the in vitro experiments are in accordance with the results of the epidemiological studies conducted on Taiwan population, showing an enhanced incidence of OSCC development in patients with simultaneous areca quid and cigarette consumption (Ko et al, 1995, Lin et al, 2011. Moreover, this results also underlie the results of studies showing upregulated expression in response to reactive oxygen species (Iqbal et al, 2003;Reinecke et al, 2006). As areca nuts contain also high amounts of copper ions, high MT-1/2 expression in OSCC originating from areca nut chewers may be partially explained by its interaction with this metal ion.…”

Reactive oxygen species contribute to oridonin-induced apoptosis and autophagy in human cervical carcinoma HeLa cells

“…However, oxidative stress, a condition characterized by the dramatic increase in ROS levels and the disruption of the antioxidant balance, results in oxidative damage to cellular structures, signal transduction changes and cell death [13] . In addition, many studies have reported that ROS induce apoptosis in various cancer cells [14][15][16] . The mitochondrial membrane potential and the expression of Bcl-2 family proteins, which have been closely linked to mitochondrial-mediated apoptosis, were also reported to be affected by ROS [17] .…”

Differential Glucocorticoid Receptor-mediated Transcription Mechanisms

“…For MT2A, this may be due to the relatively high level of basal expression of the gene (Ref. 29 and data not shown). In addition, studies have shown that RNAPII can be localized to promoters of low expressing genes prior to gene activation, and these genes are poised for activation by environmental cues (30 -34).…”