PPARγ stimulation promotes mitochondrial biogenesis and prevents glucose deprivation-induced neuronal cell loss

Peroxisome proliferator-activated receptor (PPAR)γ stimulation provides protection in several models of neurological disorders, but the mechanisms underlying these effects remain to be fully elucidated. Here we have studied whether two PPARγ agonists, pioglitazone and rosiglitazone, prevent loss of differentiated SH-SY5Y cells transiently exposed to glucose deprivation (GD). Nanomolar drug concentrations prevented GD-induced cell loss in a concentration- and time-dependent manner. These effects were abolished by malonate, a reversible mitochondrial Complex II inhibitor, while significantly potentiated by pyruvate, thus suggesting that they are related to mitochondrial function. During cell pretreatment, PPARγ agonists promoted biogenesis of functional mitochondria, as indicated by the up-regulation of PPARγ coactivator (PGC)-1α, NRF1, TFAM, cytochrome c oxidase subunit (CO) I and CO IV, and the increased level of mtDNA, while did not significantly change mitochondrial membrane potential. In addition, the analysis of the concentration–response and time-course curves for the protective effects and the up-regulation of mitochondrial biogenesis markers suggests that mitochondrial biogenesis and cell loss prevention are related effects. In conclusion our data indicate that a prolonged PPARγ stimulation, by repeated administration of nanomolar pioglitazone or rosiglitazone concentrations, decreases GD-induced loss of differentiated SH-SY5Y cells. In addition, they suggest that mitochondrial biogenesis may contribute to these effects.