For these reasons, the diazeniumdiolate compound technical support NOC 12, with a half life of 327 minutes was used for exogenous NO production to further investigate the conditions in which NO is cytotoxic to chondrocytes. A primary basis for the use of diazenium diolates is that many of them decompose spontaneously in aqueous media to release the critical bioregulatory species. The main advantages of these compounds are known rates of NO generation, NO generation rates Inhibitors,Modulators,Libraries covering a wide range, spontaneity of NO generation and tenable generation of NO redox forms. The precise role of NO in the induction of chondrocyte death is repeatedly debated. Treatment with classical NO donors consistently induces apoptosis in cultured chon drocytes, whereas the production of high levels of endogenous NO by the over expression of the iNOS gene in transfected chondrocytes has not been found to cause cell death.

This discrepancy might be the result of using chemical NO donors, which not only generate reactive nitrogen species but also produce var ious secondary reactions depending on the cellular milieu with in vitro experiments. Also, an anti apoptotic role has been addressed in several review articles. Specifically, del Carlo and collaborators Inhibitors,Modulators,Libraries showed that compounds that only release NO, such as the diazenium diolates NOC 5 and NOC 12, do not cause chondrocyte cell death and can even be protective under certain con ditions of oxidative stress. It is likely that persistent spontaneous release of NO is necessary for the protective effect and that peroxynitrite and cyanide contribute to the cytotoxic effect of NO donors.

Chondrocyte cell death from NO occurs under conditions Inhibitors,Modulators,Libraries where other reactive oxygen species are also generated. Chondrocyte death does not correlate with the amount of NO released by NO donors. Similar to other authors, our results showed that SNP is the least potent in terms of producing exogenous NO in chondrocyte Inhibitors,Modulators,Libraries cul ture, Inhibitors,Modulators,Libraries although it is the most potent inducer of chondro cyte death. The amount of NO produced by NOC 12 was 10 fold higher than the NO produced by SNP, but the level of cell death induced was not as profound as that produced by SNP. As previously shown in our laboratory, SNP was able to induce formation of apoptotic bodies, which are produced from cells undergoing cell death by apoptosis. However, we observed that NOC 12 increased the hypodiploid nuclei number without forma tion of apoptotic bodies, which is probably related kinase inhibitor Lenalidomide to another type of programmed cell death. Recently it has been proposed that autophagy is another type of pro grammed cell death than happens in the human articular cartilage as well.