Inhibition of de novo ceramide biosynthesis affects aging phenotype in an in vitro model of neuronal senescence

Although aging is considered to be an unavoidable event, recent experimental evidence suggests that the process can be counteracted. Intracellular calcium (Cai2+) dyshomeostasis, mitochondrial dysfunction, oxidative stress, and lipid dysregulation are critical factors that contribute to senescence-related processes. Ceramides, a pleiotropic class of sphingolipids, are important mediators of cellular senescence, but their role in neuronal aging is still largely unexplored. In this study, we investigated the effects of L-cycloserine (L-CS), an inhibitor of the de novo ceramide biosynthesis, on the aging phenotype of cortical neurons cultured for 22 days, a setting employed as an in vitro model of senescence. Our findings indicate that, compared to control cultures, 'aged' neurons display dysregulation of [Ca2+]i levels, mitochondrial dysfunction, increased generation of reactive oxygen species (ROS), altered synaptic activity as well as the activation of neuronal death-related molecules. Treatment with L-CS positively affected the senescent phenotype, a result associated with recovery of neuronal [Ca2+]i signaling and reduction of mitochondrial dysfunction and ROS generation. The results suggest that the de novo ceramide biosynthesis represents a critical intermediate in the molecular and functional cascade leading to neuronal senescence and identify ceramide biosynthesis inhibitors as promising pharmacological tools to decrease age-related neuronal dysfunctions.