Inhibitory effect of carbazolequinone derivatives on lipopolysaccharide and interferon-γ-induced nitric oxide production in mouse macrophage RAW264.7 cells

Objectives The aim of this study was to examine the mechanism underlying the inhibitory effect of our synthesized carbazolequinone derivatives on nitric oxide (NO) production in activated macrophages. Methods Lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma)-stimulated RAW264.7 macrophages were treated with carbazolequinone derivatives. The NO and prostaglandin E-2 (PGE(2)) levels in cell culture supernatants fractions were measured by Greiss and ELISA assay, respectively. The expression of inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2) was assessed by the real-time RT-PCR method. Nuclear factor kappa B (NF-kappa B) activation was detected by an NF-kappa B-dependent luciferase reporter assay. Key findings Our synthesized carbazolequinone derivatives (7-methoxy-2- methylcarbazole-1,4-quinone, 6-methoxy-2-methylcarbazole-1,4-quinone and 6-chloro-2-methylcarbazole-1,4-quinone) significantly inhibited LPS/IFN-gamma-induced NO production and iNOS expression in RAW264.7 cells. They also inhibited the LPS/IFN-gamma-mediated induction of COX-2 expression and PGE2 production. In addition, the LPS/IFN-gamma-induced transcription activity of NF-kappa B was attenuated. Using the RAW264.7-tsAM5NE co-culture system, we found that these carbazolequinone derivatives protected neuronally differentiated tsAM5NE cells from NO-induced cell death by inhibiting the production of NO. Conclusions These results suggest that the three carbazolequinone derivatives inhibit LPS/IFN-gamma-induced NO production via iNOS and COX-2 downregulation due to NF-kappa B inhibition. Therefore, these three carbazolequinone derivatives may be useful for developing a new drug against NO-mediated neurodegenerative diseases.