Activation of protein kinase C isozymes protects LLCPK₁ cells from H₂O₂ induced necrotic cell death

Background/Aims: We have previously reported that ischemia/reperfusion injury (IRI) to the kidney leads to induced expression of RACK1 and changes in the level of expression and subcellular distribution of PKC isozymes α, βII and ζ. In order to further define the role of PKC isozymes in IRI we investigated the effect of activation or inhibition of the isozymes on cytotoxicity mediated by H₂O₂ in LLCPK₁ cells. Methods: Cytotoxicity was analyzed by Trypan blue assay and LDH release assay. Translocation of PKC isozymes postinjury in LLCPK1 cells was analyzed by immunostaining and Western blot analysis. Results: Western blot analysis showed that the expression of PKC-α was up-regulated in a triphasic pattern with the initial induction within the first 10 min of injury followed by higher levels of expression at 2 and 24 h postinjury. The expression of PKC-ζ was highly induced within the first 15 min of injury but its expression was down-regulated to that of normal levels by 30 min postinjury. Immunocytochemistry showed that both PKC-α and PKC-ζ translocated to the nucleus and perinuclear region during H₂O₂ treatment. Following injury, PKC-α expression was localized to the nuclear membrane at earlier time points but a translocation to the nucleus occurred at later time points. PKC-ζ translocated to nucleus at 30 minutes post injury and relocated back to the nuclear membrane at later time points. Conclusion: These data suggest that activation of PKC-α and PKC-ζ is involved in the H₂O₂ induced injury of LLCPK1 cells.