Initiation of caspase-independent death in mouse mesangial cells by Cd2+: involvement of p38 kinase and CaMK-II.
Cadmium (Cd) is a toxic metal with multiple effects on cell signaling and cell death. We studied the effects of Cd(2+) on quiescent mouse mesangial cells in serum-free conditions. Cadmium induces cell death over 6 h through annexin V+ states without or with causing uptake of propidium iodide, termed apoptotic and apoptosis-like death, respectively. Little or no necrosis is observed, and cell death is caspase-independent and associated with nuclear translocation of the apoptosis-inducing factor, AIF. We previously showed that Cd(2+) increased phosphorylation of Erk and CaMK-II, and CaMK-II activation increased cell death in an Erk-independent manner. Here we demonstrate that Cd(2+) increases Jnk and p38 kinase phosphorylation, and inhibition of p38-but not of Jnk-increases cell viability by suppressing apoptosis in preference to apoptosis-like death. Neither p38 kinase nor CaMK-II inhibition protects against a decrease in mitochondrial membrane potential, psi, indicating that kinase-mediated death is either independent of, or involves events downstream of a mitochondrial pathway. However, both the antioxidant N-acetyl cysteine (NAC) and the mitochondrial membrane-stabilizing agent cyclosporine A (CsA) partially preserve psi, suppress activation of p38 kinase, and partially protect the cells from Cd(2+)-induced death. Whereas the effect of CsA is on apoptosis, NAC acts on apoptosis-like death. Inhibition of glutathione synthesis exacerbates a Cd(2+)-dependent increase in cellular peroxides and favors apoptosis-like death over apoptosis. The caspase-independence of these modes of cell death is not due to an absence of this machinery in the mesangial cells: when they are exposed to Cd(2+) for longer periods in the presence of serum, procaspase-3 and PARP are cleaved and caspase inhibition is protective. We conclude that Cd(2+) can kill mesangial cells by multiple pathways, including caspase-dependent and -independent apoptotic and apoptosis-like death. Necrosis is not prominent. Activation of p38 kinase and of CaMK-II by Cd(2+) are associated with caspase-independent apoptosis that is not dependent on mitochondrial destabilization.
Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada.
Ying
Y
Liu
Douglas M
DM
Templeton
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D051033:Apoptosis Inducing Factor / Q000378:metabolism; D019256:Cadmium Chloride / Q000633:toxicity*; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000378:metabolism*; D020169:Caspases / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D016895:Culture Media, Serum-Free; D004305:Dose-Response Relationship, Drug; D005978:Glutathione / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D050527:Mesangial Cells / Q000187:drug effects* / Q000201:enzymology / Q000473:pathology; D051379:Mice; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D013997:Time Factors; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*
D000975:Antioxidants; D051033:Apoptosis Inducing Factor; D016895:Culture Media, Serum-Free; C494830:AIFM1 protein, mouse; D047428:Protein Kinase Inhibitors; D017382:Reactive Oxygen Species; D000255:Adenosine Triphosphate; C499321:Parp1 protein, mouse; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D020169:Caspases; D005978:Glutathione; D019256:Cadmium Chloride