Connexin43 Hemichannels Contribute to Cadmium-Induced Oxidative Stress and Cell Injury
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We investigated the potential involvement of connexin hemichannels in cadmium ions (Cd2+)-elicited cell injury. Transfection of LLC-PK1 cells with a wild-type connexin43 (Cx43) sensitized them to Cd2+-elicited cell injury. The cell susceptibility to Cd2+ was increased by depletion of glutathione (GSH) with DL-buthionine-[S,R]- sulfoximine, and decreased by N-acetyl-cysteine or glutathione reduced ethyl ester. Fibroblasts derived from Cx43 wild-type (Cx43+/+) and knockout (Cx43-/-) fetal littermates displayed different susceptibility to Cd2+. Cd2+ induced a higher concentration of reactive oxygen species, a stronger activation c-Jun N-terminal kinase, and significantly more severe cell injury in Cx43+/+ fibroblasts, as compared with Cx43-/- fibroblasts. Cd2+ caused a reduction in intracellular GSH, whereas it elevated extracellular GSH. This effect of Cd2+ was more dramatic in Cx43+/+ than Cx43-/- fibroblasts. Treatment of Cx43+/+ fibroblasts with Cd2+ caused a Cx43 hemichannel-dependent influx of Lucifer Yellow and efflux of ATP. Collectively, our study demonstrates that Cx43 sensitizes cells to Cd2+-initiated cytotoxicity, possibly through hemichannel-mediated effects on intracellular oxidative status.
Antioxidants & Redox Signaling