Salubrinal attenuates nitric oxide mediated PERK:IRE1α: ATF-6 signaling and DNA damage in neuronal cells

The present study was conducted to investigate the effect of salubrinal on nitric oxide mediated endoplasmic reticulum stress signaling and neuronal apoptosis. Rotenone treatment to neuro2a cells caused significantly decreased cell viability, increased cytotoxicity, augmented nitrite levels, increased nitrotyrosine level and augmented level of key ER stress markers (GRP-78, GADD153 and caspase-12). These augmented levels of ER stress markers could be attenuated with pretreatment of nitric oxide synthase inhibitor-aminoguanidine as well as with salubrinal. The rotenone treatment to neuro2a cells also triggered the ER stress induced up regulation of various signaling factors of unfolded protein response involving pPERK, ATF4, p-IRE1α, XBP-1 and ATF-6. Pretreatment of salubrinal significantly attenuated the activation of transmembrane kinases (PERK and IRE1) and ATF6 and restored the rotenone induced altered level of other UPR related signaling factors. Rotenone induced dephosphorylation of eIF2α was also inhibited with salubrinal treatment. Biochemically rotenone treatment to neuro2a cells caused the reactive oxygen species generation, depleted mitochondrial membrane potential and increased intra cellular calcium level which was attenuated with salubrinal treatment. Rotenone treatment to neuro2a cells also caused neuronal apoptosis, DNA fragmentation and chromatin condensation which were attenuated with salubrinal treatment. In conclusion, the findings suggested that rotenone causes the augmented level of nitric oxide which contributes in ER stress and could be inhibited by both aminoguanidine and/or salubrinal treatment. Further, salubrinal treatment attenuates the nitric oxide induced ER stress axis PERK:IRE1α:ATF-6 and inhibits the DNA damage and neuronal apoptosis.