Pharynx mitochondrial [Ca(2+)] dynamics in live C. elegans worms during aging

Progressive decline in mitochondrial function is generally considered one of the hallmarks of aging. We have expressed a Ca(2+) sensor in the mitochondrial matrix of C. elegans pharynx cells and we have measured for the first time mitochondrial [Ca(2+)] ([Ca(2+)](M)) dynamics in the pharynx of live C. elegans worms during aging. Our results show that worms stimulated with serotonin display a pharynx [Ca(2+)](M) oscillatory kinetics that includes both high frequency oscillations (up to about 1Hz) and very prolonged “square-wave” [Ca(2+)](M) increases, indicative of energy depletion of the pharynx cells. Mitochondrial [Ca(2+)] is therefore able to follow “beat-to-beat” the fast oscillations of cytosolic [Ca(2+)]. The fast [Ca(2+)](M) oscillations kept steady frequency values during the whole worm life, from 2 to 12 days old, but the height and width of the peaks was progressively reduced. [Ca(2+)](M) oscillations were also present with similar kinetics in respiratory chain complex I nuo-6 mutant worms, although with smaller height and frequency than in the controls, and larger width. In summary, Ca(2+) fluxes in and out of the mitochondria are relatively well preserved during the C. elegans life, but there is a clear progressive decrease in their magnitude during aging. Moreover, mitochondrial Ca(2+) fluxes were smaller in nuo-6 mutants with respect to the controls at every age and decreased similarly during aging.