Nitric oxide from both exogenous and endogenous sources activates mitochondria‐dependent events and induces insults to human chondrocytes

Abstract

During inflammation, overproduction of nitric oxide (NO) can damage chondrocytes. In this study, we separately evaluated the toxic effects of exogenous and endogenous NO on human chondrocytes and their possible mechanisms. Human chondrocytes were exposed to sodium nitroprusside (SNP), an NO donor, or a combination of lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma) as the exogenous and endogenous sources of NO, respectively. Administration of SNP or a combination of LPS and IFN-gamma in human chondrocytes increased cellular NO levels but decreased cell viability. Exposure to exogenous or endogenous NO significantly induced apoptosis of human chondrocytes. When treated with exogenous or endogenous NO, the mitochondrial membrane potential time-dependently decreased. Exposure to exogenous or endogenous NO significantly enhanced cellular reactive oxygen species (ROS) and cytochrome c (Cyt c) levels. Administration of exogenous or endogenous NO increased caspase-3 activity and consequently induced DNA fragmentation. Suppression of caspase-3 activation by Z-DEVD-FMK decreased NO-induced DNA fragmentation and cell apoptosis. Similar to SNP, exposure of human chondrocytes to S-nitrosoglutathione (GSNO), another NO donor, caused significant increases in Cyt c levels, caspase-3 activity, and DNA fragmentation, and induced cell apoptosis. Pretreatment with N-monomethyl arginine (NMMA), an inhibitor of NO synthase, significantly decreased cellular NO levels, and lowered endogenous NO-induced alterations in cellular Cyt c amounts, caspase-3 activity, DNA fragmentation, and cell apoptosis. Results of this study show that NO from exogenous and endogenous sources can induce apoptotic insults to human chondrocytes via a mitochondria-dependent mechanism.

Saponin-rich fraction from Clematis chinensis Osbeck roots protects rabbit chondrocytes against nitric oxide-induced apoptosis via preventing mitochondria impairment and caspase-3 activation

“…The p53 protein transcriptionally regulates expression and translocation of Bax, a proapoptotic member of Bcl-2 family. Bax is then redistributed from the cytosol to the mitochondria, where it causes a decline in mitochondrial membrane pontential, followed by cytochrome c release and caspase activation (Kim et al 2002b;Wu et al 2007), Fig. 4 Effect of SFC on caspase-3 activity in SNP-treated chondrocytes.…”

Both endoplasmic reticulum and mitochondria are involved in disc cell apoptosis and intervertebral disc degeneration in rats

“…The reasons for using sodium nitroprusside as apoptosis inducer in our in vitro experiments are as follows. First, super-physiological concentrations of nitric oxide not only results in DNA damage followed by depletion of the mitochondria (Wu et al 2007) but also activate ER stress (Gotoh and Mori 2006), and apoptotic cell death occurs eventually. Second, there is evidence showing that sodium nitroprusside can induce apoptosis of cultured human disc cells (Kohyama et al 2000).…”

Cytoskeleton Interruption in Human Hepatoma HepG2 Cells Induced by Ketamine Occurs Possibly through Suppression of Calcium Mobilization and Mitochondrial Function

“…To avoid drug interaction, when HepG2 cells were exposed to ketamine, the culture medium did not contain serum and antibiotics. Levels of ␥-glutamyltranspeptidase and lactate dehydrogenase in the culture medium were measured to evaluate the cytotoxicity of ketamine to HepG2 cells as described previously (Wu et al, 2007).…”