Connexin43 hemichannels contribute to cadmium-induced oxidative stress and cell injury

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 Cd ²⁺-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⁺. Cd ²⁺ 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. Cd ²⁺ 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 Cd ²⁺-initiated cytotoxicity, possibly through hemichannel-mediated effects on intracellular oxidative status.