Production of H2O2 in the Endoplasmic Reticulum Promotes In Vivo Disulfide Bond Formation

Aims: Oxidative protein folding in the luminal compartment of endoplasmic reticulum (ER) is thought to beaccompanied by the generation of H2O2, as side-product of disulfide bond formation. We aimed to examine therole of H2O2 produced in the lumen, which on one hand can lead to redox imbalance and hence can contribute toER stress caused by overproduction of secretory proteins; on the other hand, as an excellent electron acceptor,H2O2 might serve as an additional pro-oxidant in physiological oxidative folding. Results: Stimulation of H2O2production in the hepatic ER resulted in a decrease in microsomal GSH and protein-thiol contents and in a redoxshift of certain luminal oxidoreductases in mice. The oxidative effect, accompanied by moderate signs of ERstress and reversible dilation of ER cisternae, was prevented by concomitant reducing treatment. The imbalancealso affected the redox state of pyridine nucleotides in the ER. Antibody producing cells artificially engineeredwith powerful luminal H2O2 eliminating system showed diminished secretion of mature antibody polymers,while incomplete antibody monomers/dimers were accumulated and/or secreted. Innovation: Evidence areprovided by using in vivo models that hydrogen peroxide can promote disulfide bond formation in the ER.Conclusion: The results indicate that local H2O2 production promotes, while quenching of H2O2 impairs disulfideformation. The contribution of H2O2 to disulfide bond formation previously observed in vitro can be alsoshown in cellular and in vivo systems.