Anti-inflammatory effects of chemically modified tetracyclines by the inhibition of nitric oxide and interleukin-12 synthesis in J774 cell line

Abstract

We investigated the effects of chemically modified tetracyclines (CMTs) on the production of nitric oxide (NO) and on the synthesis of some cytokines: tumour necrosis factor alpha (TNF-α), interleukin(IL)-10 and IL-12 in lipopolysaccharide (LPS)-treated J774 cell line. Furthermore, we studied the ability of these drugs to modify the viability in LPS-stimulated J774 macrophages. CMTs decreased, in a dose-dependent manner, inducible NO synthase (iNOS) activity and, consequently, nitrite formation in J774 cultures. The CMT-induced decrease in NO production is due to the inhibition of enzyme activity rather than to a direct effect on enzyme expression. The absence of the inhibition in mRNA accumulation indicates that the inhibiting activity is mainly post-transcriptional. CMTs were unable to modulate TNF-α and IL-10 synthesis and they were not effective in modifying the transcription of relative mRNA in J774 macrophages. On the contrary, IL-12 mRNA expression was significantly increased by CMT-1 and CMT-8 with LPS activation. Since IL-12 protein secretion was inhibited by CMTs, these compounds interfere in the blocking of post-transcriptional events. The studies on cell viability showed that various CMTs induced a dose-dependent decrease in J774 macrophage viability. The cytotoxic activity was present even though NO production was inhibited by CMTs. These compounds appear to be able to activate apoptosis in a NO-independent way. Altogether, these results indicate that CMTs can exert anti-inflammatory effects by inhibiting NO synthesis, and they are able to modify cell viability by exerting a strong apoptotic activity.