Ceramide induces the death of retina photoreceptors through activation of parthanatos

PRADO SPALM F.H.; VERA MS; DIBO MJ; SIMON M.V.; POLITI L.E.; ROTSTEIN N.P.

MOLECULAR NEUROBIOLOGY

HUMANA PRESS INC

Lugar: Oregon; Año: 2019 vol. 56 p. 4760 - 4777

0893-7648

Ceramide (Cer) has a key role inducing cell death and has been proposed as a messenger in photoreceptor cell death in the retina. Here we explored the pathways induced by C2-acetylsphingosine (C2-Cer), a cell permeable Cer, to elicit photoreceptor death. Treating pure retina neuronal cultures with 10 µM C2-Cer for 6 h selectively induced photoreceptor death, decreasing mitochondrial membrane potential and increasing the formation of reactive oxygen species (ROS). In contrast, amacrine neurons preserved their viability. Noteworthy, the amount of TUNEL-labeled cells and photoreceptors expressing cleaved-caspase 3 remained constant and pretreatment with a pan-caspase inhibitor did not prevent C2-Cer-induced death. C2-Cer provoked polyADP ribosyl polymerase-1 (PARP-1) overactivation. Inhibiting PARP-1 decreased C2-Cer induced photoreceptor death; C2-Cer increased polyADP ribose polymer (PAR) levels and induced the translocation of apoptosis inducing factor (AIF) from mitochondria to photoreceptor nuclei, which was prevented by PARP-1 inhibition. Pretreatment with a calpain and cathepsin inhibitor, and with a calpain inhibitor reduced photoreceptor death whereas selective cathepsin inhibitors granted no protection. Combined pretreatment with a PARP-1 and a calpain inhibitor evidenced the same protection as each inhibitor by itself. Neither autophagy nor necroptosis were involved in C2-Cer-elicited death; no increase in LDH release was observed upon C2-Cer treatment and pretreatment with inhibitors of necroptosis and autophagy did not rescue photoreceptors. These results suggest that C2-Cer induced photoreceptor death by a novel, caspase independent mechanism, involving activation of PARP-1, decline of mitochondrial membrane potential, calpain activation and AIF translocation, all of which are biochemical features of parthanatos.