Mediating of caspase-independent apoptosis by cadmium through the mitochondria-ROS pathway in MRC-5 fibroblasts
✍ Scribed by Chwen-Ming Shih; Wun-Chang Ko; Jui-Sheng Wu; Yau-Huei Wei; Leng-Fang Wang; E-E. Chang; Tsui-Yun Lo; Huey-Hwa Cheng; Chien-Tsu Chen
- Publisher
- John Wiley and Sons
- Year
- 2004
- Tongue
- English
- Weight
- 251 KB
- Volume
- 91
- Category
- Article
- ISSN
- 0730-2312
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✦ Synopsis
Abstract
Cadmium (Cd) is an environmental pollutant of global concern with a 10–30‐year biological half‐life in humans. Accumulating evidence suggests that the lung is one of the major target organs of inhaled Cd compounds. Our previous report demonstrated that 100 μM Cd induces MRC‐5 cells, normal human lung fibroblasts, to undergo caspase‐independent apoptosis mediated by mitochondrial membrane depolarization and translocation of apoptosis‐inducing factor (AIF) from mitochondria into the nucleus. Here, using benzyloxycarbonyl‐Val‐Ala‐Asp‐(ome) fluoromethyl ketone (Z‐VAD.fmk) as a tool, we further demonstrated that Cd could induce caspase‐independent apoptosis at concentrations varied from 25 to 150 μM, which was modulated by reactive oxygen species (ROS) scavengers, such as N‐acetylcysteine (NAC), mannitol, and tiron, indicating that ROS play a crucial role in the apoptogenic activity of Cd. Consistent with this notion, the intracellular hydrogen peroxide (H~2~O~2~) was 2.9‐fold elevated after 3 h of Cd treatment and diminished rapidly within 1 h as detected by flow cytometry with 2′,7′‐dichlorodihydrofluorescein diacetate (DCFH‐DA) staining. Using inhibitors of the mitochondrial electron transport chain (ETC) (oligomycin A and rotenone for complex I and V, respectively) and mitochondrial permeability transition pore (MPTP) (cyclosporin A and aristolochic acid), we coincidently found the ROS production, mitochondrial membrane depolarization, and apoptotic content were almost completely or partially abolished. As revealed by confocal microscopy staining with chloromethyl‐X‐rosamine (CMXRos) and an anti‐AIF antibody, the collapse of mitochondrial membrane potential induced by Cd (3 h‐treatment) was a prelude to the translocation of caspase‐independent pro‐apoptotic factor, AIF, into the nucleus (after 4 h of Cd treatment). In summary, this study demonstrated that, in MRC‐5 fibroblasts, Cd induced caspase‐independent apoptosis through a mitochondria‐ROS pathway. More importantly, we provide several lines of evidence supporting a role of mitochondrial ETC and MPTP in the regulation of caspase‐independent cell death triggered by Cd. © 2003 Wiley‐Liss, Inc.