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

We investigated the effects of chemically modified tetracyclines (CMTs) on the production of nitric oxide (NO) and on the synthesis of some cytokines: turnout necrosis factor alpha (TNF-alpha), interleukin(IL)-10 and IL-12 in lipopolysaccharide (LPS)-treated J774 cell line. Furthermore, we studied t he ability of these drugs to modify the viability in LPS-stimulated J774 ma crophages. CMTs decreased, in a dose-dependent manner, inducible NO synthas e (iNOS) activity and, consequently, nitrite formation in J774 cultures. Th e 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 o f the inhibition in mRNA accumulation indicates that the inhibiting activit y is mainly post-transcriptional. CMTs were unable to modulate TNF-alpha an d IL-10 synthesis and they were not effective in modifying the transcriptio n of relative mRNA in J774 macrophages. On the contrary, IL-12 mRNA express ion was significantly increased by CMT-1 and CMT-8 with LPS activation. Sin ce IL-12 protein secretion was inhibited by CMTs, these compounds interfere in the blocking of post-transcriptional events. The studies on cell viabil ity showed that various CMTs induced a dose-dependent decrease in J774 macr ophage viability. The cytotoxic activity was present even though NO product ion was inhibited by CMTs. These compounds appear to be able to activate ap optosis in aNO-independent way. Altogether, these results indicate that CMT s can exert anti-inflammatory effects by inhibiting NO synthesis. and they are able to modify cell viability by exerting a strong apoptotic activity. (C) 2001 Elsevier Science B.V. All rights reserved.