IL6 and rheumatoid arthritis: In addition, Engler et al. (91) showed that stimulation of the cultured synovial fibroblasts of OA and RA in human patients with capsaicin (TRPV1 agonist) led to the increased expression of IL-6 mRNA and IL-6 protein, and that IL-6 protein expression could be antagonized with capsazepine (a TRPV1 antagonist).