Regulation of growth and apoptosis of cultured guinea pig gastric mucosal cells by mitogenic oxidase 1

We previously reported that primary cultures of guinea pig gastric pit cells expressed all of the phagocyte NADPH oxidase components (gp91-, p22-, p67-, p47-, and p40-phox) and could spontaneously release superoxide anion (O-2(-)). We demonstrate here that pit cells express a nonphagocyte-specific gp91-phox homolog (Mox1) but not gp91-phox. Inclusion of catalase significantly inhibited [H-3] thymidine uptake during the initial 2 days of culture. Pit cells, matured on day 2, slowly underwent spontaneous apoptosis. Scavenging O-2(-) and related oxidants by superoxide dismutase plus catalase or N-acetyl cysteine (NAC) and inhibiting Mox1 oxidase by diphenylene iodonium activated caspase 3-like proteases and markedly enhanced chromatin condensation and DNA fragmentation. This accelerated apoptosis was completely blocked by a caspase inhibitor, z-Val-Ala-Asp-CH2F. Mox1-derived reactive oxygen intermediates constitutively activated nuclear factor-kappaB, and inhibition of this activity by nuclear factor-kappaB decoy oligodeoxynucleotide accelerated their spontaneous apoptosis. These results suggest that O-2(-) produced by the pit cell Mox1 oxidase may play a crucial role in the regulation of their spontaneous apoptosis as well as cell proliferation.