Apoptosis induced by NO via phosphorylation of p38 MAPK that stimulates NF-kappaB, p53 and caspase-3 activation in rabbit articular chondrocytes.

Nitric oxide (NO), reported as an important inducer of apoptosis, plays a considerable role in the pathogenetic mechanisms of articular diseases. This research aimed at investigating the role of p38 MAPK signal transduction pathway on apoptosis induced by NO in rabbit articular chondrocytes. In the present study, NO was produced by a novel NO donor NOC-18. Rabbit articular chondrocytes were cultured as monolayer, and the first passage cells were used for the experiments. We detected apoptosis induced by NO using Annexin V-FITC/PI flow cytometry and TUNEL assay. Measurement of caspase-3 has reflected its activity level. Western blotting was performed to show the protein expressions of p38, NF-kappaB, p53 and caspase-3. Furthermore, we examined the inhibitory effects in the NO pathway with p38-specific inhibitor SB203580. Treatment with NOC-18 caused accelerated apoptosis in a concentration dependent manner. This acceleration was able to be reduced when added to SB203580. Besides, the inhibitor could significantly decrease NO-induced p38, NF-kappaB, p53 and caspase-3 protein expressions, as well as caspase-3 intracellular activity (P<0.05). These results suggest that p38 MAPK signal transduction pathway is critical to NO-induced chondrocyte apoptosis, and p38 plays a role by way of stimulating NF-kappaB, p53 and caspase-3 activation.