Hydrogen peroxide inhibits gap junctional intercellular communication in glutathione sufficient but not glutathione deficient cells

Cell to cell communication via gap junctions is essential in themaintenance of the homeostatic balance of multicellular organisms. Aberrantintercellular gap junctional communication (GJIC) has been implicated intumor promotion, neuropathy and teratogenesis. Oxidative stress has alsobeen implicated in similar pathologies such as cancer. We report apotential link between oxidative stress and GJIC. Hydrogen peroxide, aknown tumor promoter, inhibited GJIC in WB-F344 rat liver epithelial cellswith an I50 value of 200 microM. Inhibition of GJIC by H2O2 was reversibleas indicated by the complete recovery of GJIC with the removal of H2O2 viaa change of fresh media. Free radical scavengers, such as t-butyl alcohol,propylgallate, and Trolox, did not prevent the inhibition of GJIC by H2O2,which indicated that the effects of H2O2 on GJIC was probably not aconsequence of aqueous free radical damage. The depletion of intracellularGSH reversed the inhibitory effect of H2O2 on GJIC. The treatment ofglutathione- sufficient cells with H2O2 resulted in thehyperphosphorylation of connexin43, which is the basic subunit of thehexameric gap junction protein, as determined by Western blot analysis.TPA, a well-known tumor promoter, also inhibits GJIC viahyperphosphorylation of GJIC, which is a result of protein kinase-Cactivation. However, H2O2 also induced hyperphosphorylation inGSH-deficient cells that had normal rates of GJIC. Therefore, the mechanismof GJIC inhibition must be different from the TPA-pathway and involves GSH.