Specific Inhibitors of Vacuolar Type H⁺-ATPases Induce Apoptotic Cell Death

Concanamycin A and bafilomycin A₁ are known as strong inhibitors of the vacuolar type H⁺-ATPases in vitro. These inhibitors exhibited cytotoxic effects on twelve cell lines in cell viability assay. On the other hand, the F₁F₀-type H⁺-ATPase inhibitor oligomycin and the E₁E₂-type H⁺-ATPase inhibitor vanadate showed no cytotoxic effect. We show here that concanamycin A and bafilomycin A₁ induce a significant increase in the proportion of fragmented DNA in agarose gel electrophoresis. Flow cytometric cell cycle analysis of WEHI 231 cells stimulated with concanamycin A revealed the increased percentage of apoptotic cells with hypodiploid DNA. These findings indicate that cell death induced by specific inhibitors of vacuolar type H⁺-ATPases occurs through apoptosis.