Involvement of oxidative stress induction in Na(+) toxicity and its relation to the inhibition of a Ca(2+)-dependent but calcineurin-independent mechanism in Saccharomyces cerevisiae

Uridine 5'-hexadecylphosphate (UMPC16) inhibited the growth of Saccharomyces cerevisiae under a hypersaline stress condition with Nasup(+) more strongly than the calcineurin inhibitor cyclosporine A (CsA). Additional Casup(2+) supplementation similarly suppressed the inhibitory activities of UMPC16 and CsA on yeast cell growth in a medium with Nasup(+). UMPC16, but not CsA, accelerated mitochondrial reactive oxygen species (ROS) generation in combination with Nasup(+), suggesting its inhibition of a Ca2sup(+) -dependent but calcineurin-independent mechanism for protection against Nasup(+) toxicity.