Caspase-Dependent and Caspase-Independent Pathways Are Involved in Cadmium-Induced Apoptosis in Primary Rat Proximal Tubular Cell Culture

• DOI: 10.1371/journal.pone.0166823
• Publication Date: 2016-11-18T13:48:06Z
• Authors: Gang Liu; Hui Zou; Tongwang Luo; Mengfei Long; Jianchun Bian; Xuezhong Liu; Jianhong Gu; Yan Yuan; Ruilong Song; Yi Wang; Jiaqiao Zhu; Zongping Liu
• Keywords: Science; Primary Cell Culture; Apoptosis; Mitochondrial Membrane Transport Proteins; Kidney Tubules, Proximal; Mitochondrial Proteins; 03 medical and health sciences; Animals; Gene Silencing; 0303 health sciences; Endodeoxyribonucleases; Mitochondrial Permeability Transition Pore; Q; R; Cytochromes c; Membrane Proteins; Epithelial Cells; Caspase Inhibitors; Mitochondria; Rats; Oxidative Stress; Caspases; Medicine; Reactive Oxygen Species; Research Article; Cadmium; Signal Transduction

We designed this study to investigate whether cadmium induces caspase-independent apoptosis and to investigate the relationship between the caspase-dependent and caspase-independent apoptotic pathways. Cadmium (1.25-2.5 μM) induced oxidative stress in rat proximal tubular (rPT) cells, as seen in the reactive oxygen species levels; N-acetylcysteine prevented this. Cyclosporin A (CsA) prevented mitochondrial permeability transition pore opening and apoptosis; there was mitochondrial ultrastructural disruption, mitochondrial cytochrome c (cyt c) translocation to the cytoplasm, and subsequent caspase-9 and caspase-3 activation. Z-VAD-FMK prevented caspase-3 activation and apoptosis and decreased BNIP-3 (Bcl-2/adenovirus E1B 19-kDa interacting protein 3) expression levels and apoptosis-inducing factor/endonuclease G (AIF/Endo G) translocation. Simultaneously, cadmium induced prominent BNIP-3 expression in the mitochondria and cytoplasmic AIF/Endo G translocation to the nucleus. BNIP-3 silencing significantly prevented AIF and Endo G translocation and decreased the apoptosis rate, cyt c release, and caspase-9 and caspase-3 activation. These results suggest that BNIP-3 is involved in the caspase-independent apoptotic pathway and is located upstream of AIF/Endo G; both the caspase-dependent and caspase-independent pathways are involved in cadmium-induced rPT cell apoptosis and act synergistically.