Oxidative metabolism and Ca2+ handling in isolated brain mitochondria and striatal neurons from R6/2 mice, a model of Huntington's disease

Abstract

Alterations in oxidativemetabolism and defects inmitochondrial Ca2+handling have been implicated in the pathology of Huntington's disease (HD), but existing data are contradictory.We investigated the effect of humanmHtt fragments on oxidativemetabolismand Ca2+handling in isolated brainmitochondria and cultured striatal neurons fromthe R6/2mouse model of HD. Non-synaptic and synapticmitochondria isolated fromthe brains of R6/2mice had similar respiratory rates and Ca2+uptake capacity compared withmitochondria from wild-type (WT)mice. Respiratory activity of cultured striatal neurons measured with Seahorse XF24 flux analyzer revealed unaltered cellular respiration in neurons derived fromR6/2mice compared with neurons fromWT animals. Consistent with the lack of respiratory dysfunction, ATP content of cultured striatal neurons fromR6/2 andWTmice was similar. Mitochondrial Ca2+accumulation was also evaluated in cultured striatal neurons fromR6/2 andWT animals. Our data obtained with striatal neurons derived fromR6/2 andWTmice showthat both glutamate-induced increases in cytosolic Ca2+and subsequent carbonilcyanide p-triflouromethoxyphenylhydrazone-induced increases in cytosolic Ca2+were similar betweenWT and R6/2, suggesting thatmitochondria in neurons derived from both types of animals accumulated comparable amounts of Ca2+. Overall, our data argue against respiratory deficiency and impaired Ca2+handling induced by humanmHtt fragments in both isolated brainmitochondria and cultured striatal neurons fromtransgenic R6/2mice.