Role of glutathione in the induction of hemoxygenase-1 enzyme in intestinal epithelial cells

Hemoxygenase-1 (HO-1) enzyme plays a protective role in the mechanism of inflammatory bowel disease. The expression of HO-1 can be induced by a number of agents, e.g. by heavy metals and hem (FePP). The mechanism of HO-1 induction is not fully understood, however, the involvement of glutathione (GSH) is suspected. AIM: We investigated the interaction of GSH with HO-1 expression in a human epithelial cell line (DLD-1). Methods: The expression of HO-1 and the GSH level were determined by Western Blot and by the DTNB method, respectively. Cells were treated with the GSH promoter, N-acetylcisteine (NAC; 10 mM)) or with the NF-kappaB inhibitor, MG 132. Results: Administration of FePP (50 micoM) or cadmium chloride (CdCl2; 10 microM) decreased GSH level within 10min. The maximum effect occurred after 1h, when baseline GSH level (23±0.5 nM/mg protein) reduced by 48% or 54% after FePP or CdCl2 administration, respectively. The expression of HO-1 developed 2h after incubation, when GSH level returned to the baseline value. Concurrent administration of NAC with FePP resulted in 45% decrease in GSH level, and an increase in HO-1 expression in a similar time-dependent manner as we found with FePP or CdCl2 alone. Administration of NAC inhibited FePP-provoked GSH level reduction, and delayed the expression of HO-1 over 4h. Administration of MG-132 (10 microM) did not affect FePP-evoked HO-1 induction. CONCLUSION: The reduction of GSH level following FePP and CdCl2 exposure is suggested to be involved in the induction of HO-1 in the human DLD-1 cell line. The present work was supported by The Hungarian Research Fund (OTKA F 42565).