Nitric oxide induces apoptosis in human gingival fibroblast through mitochondria-dependent pathway and JNK activation

AimTo investigate the molecular mechanisms of nitric oxide (NO)-induced cytotoxic effect in human gingival fibroblast (HGF) cells. MethodologyAfter sodium nitroprusside (SNP), as NO donor, was treated to HGF, viability was measured by MTT assay and apoptosis was determined by TUNEL and DNA fragmentation assay. Mitochondrial membrane potential was detected using confocal microscopy, and caspase activity assay was measured by spectrophotometer. Mitogen-activated protein kinases (MAPK) activation, Bax/Bcl-2 ratio and cytochrome c release were analysed by Western blot analyses. Cells were exposed to MAPK inhibitors (U0126, SB203580 and SP600125) before SNP treatment to investigate the effects of MAPK kinases on the NO-induced apoptosis in HGF. Statistical analysis was performed using one-way analysis of variance with the Student-Newman-Keuls post hoc test for multiple group comparison. ResultsApoptosis was significantly increased (P=0.011 and 0.0004, respectively) in the presence of SNP (1 and 3mmolL(-1)) after 12h in HGF. However, 1H-[1,2,4] oxadiatolo [4, 3-a] cluinoxaline-1-one (ODQ), a soluble guanylate cyclase inhibitor, did not block the decrement of cell viability by NO. SNP treatment induced the loss of mitochondrial membrane potential, release of cytochrome c, increased Bax/Bcl-2 ratio and activation of caspases in HGF. Also, SNP treatment increased phosphorylation of MAPKinases and c-Jun N-terminal kinase (JNK) inhibitor (5 and 10molL(-1)) rescued cell viability decreased by SNP in HGF (P=0.024 and 0.0149, respectively). ConclusionNitric oxide induced apoptosis in human gingival fibroblast through the mitochondria-mediated pathway by regulation of Bcl-2 family and JNK activation.