IL6 and rheumatoid arthritis: Inhibit the release of NO, TNF-α, IL-1β and IL-6 in LPS-induced RAW 264.7 cell; attenuate the severity, pathological changes, and release of cytokines (IL-6 and HIF-1α) during rheumatoid arthritis progression by regulating the PI3K/AKT and HIF-1 pathways