Anti-Inflammatory Mechanism of An Alkaloid Rutaecarpine in LTA-Stimulated RAW 264.7 Cells: Pivotal Role on NF-κB and ERK/p38 Signaling Molecules.

Lipoteichoic acid (LTA) is a key cell wall component and virulence factor of Gram-positive bacteria. LTA contributes a major role in infection and it mediates inflammatory responses in the host. Rutaecarpine, an indolopyridoquinazolinone alkaloid isolated from Evodia rutaecarpa, has shown a variety of fascinating biological properties such as anti-thrombotic, anticancer, anti-obesity and thermoregulatory, vasorelaxing activity. It has also potent effects on the cardiovascular and endocrine systems. Herein, we investigated rutaecarpine's (Rut) anti-inflammatory effects in LTA-stimulated RAW macrophage cells. The Western blot and spectrophotometric results revealed that Rut inhibited the production of nitric oxide (NO) and the expression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and interleukin (IL)-1β in the LTA-induced macrophage cells. Successively, our mechanistic studies publicized that Rut inhibited LTA-induced phosphorylation of mitogen-activated protein kinase (MAPK) including the extracellular signal-regulated kinase (ERK), and p38, but not c-Jun NH2-terminal kinase (JNK). In addition, the respective Western blot and confocal image analyses exhibited that Rut reserved nuclear transcription factor kappa-B (NF-κB) by hindering inhibitor of nuclear factor κB-α (IκBα) and NF-κB p65 phosphorylation and p65 nuclear translocation. These results indicate that Rut exhibits its anti-inflammatory effects mainly through attenuating NF-κB and ERK/p38 signaling pathways. Overall, this result suggests that Rut could be a potential therapeutic agent for the treatment of Gram-positive bacteria induced inflammatory diseases.