Nicorandil abates arthritic perturbations induced by complete Freund's adjuvant in rats via conquering TLR4-MyD88-TRAF6 signaling pathway

Background and purpose: Rheumatoid arthritis (RA) is a chronic, systemic autoimmune inflammatory disease which poses a need to explore effective yet safe pharmacotherapeutic options. The current work aimed to study the therapeutic role of nicorandil in controlling RA. Experimental approach: Complete Freund's adjuvant (CFA)-induced arthritis model was applied by injecting 400 mu L of CFA in the right hind paw at day 0 and day 7. Four groups of rats were used as follows: normal-control (CTRL), CFA-induced arthritis (ART), CFA-induced arthritis treated with diclofenac (DIC) and CFA-induced arthritis treated with nicorandil (NIC). Both NIC and DIC were administered at day 14 for two weeks. Paw volume, knee joint diameter, pain behavior assessment as well as body weight were all periodically recorded throughout the experimental period. Following the sacrifice of animals at day 28, gene expressions of TLR-4, MyD88 and TRAF6 as well as extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), nuclear factor Kappa B (NF-kappa B) were quantified in hind paws tissue. Finally, the serum levels of the inflammatory biomarkers (tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta) and interleukin-6 (IL-6) together with the histopathological examination of sections in the rat hind paw were recorded. Results: Both NIC and DIC proved promising anti-arthritic potential mediated, at least in part through switching off TLR4-MyD88-TRAF6 axis as well as downstream TRAF6 dependent activated MAP kinases and NF-kappa B. Conclusion and implications: Nicorandil, via interfering with TLR4 signaling, sheds light on a potential clinical role of the drug in pursuit for safe and effective regimens for RA.