In collagen-induced arthritis, endocannabinoids, like anandamide, improves synovial inflammation. In previous studies anandamide decreased TNF-induced IL-6, IL-8 and MMP-3 in synovial fibroblasts (SFs) in a TRPA1-dependent manner. Joint pain and inflammation are driven by pro-inflammatory cytokines like TNF, which is also involved in sensitizing TRP-channels. Therefore, the hypothesis was tested that TNF augments TRPA1 mediated effects in SFs. TRPA1 expression after TNF exposure was analyzed by western blotting and cell based ELISA. Cell proliferation was determined by cell titer blue and cell death was monitored by lactate dehydrogenase (LDH) levels. Calcium flux assays were performed with Fura-2. Exposure of SFs to TNF (10 ng/ml) for 72 h increased TRPA1 protein accompanied by an increase in intracellular calcium following TRPA1 agonist allyl isothiocyanate (AITC). While SFs did not respond to AITC without TNF pretreatment, TNF pre-incubation elicited a robust increase in calcium in response to AITC (10 μ M–500 μ M). This was paralleled by increased LDH indicating cell death in response to TRPA1 activation. Cell proliferation was also modulated by TRPA1 activation. While TNF naive cells demonstrated reduced proliferation in response to 100 μ M AITC, TNF pre-treatment lowered the effective concentration to 12.5 μ M. The observed increase in TRPA1 mediated effects by TNF might explain lack of effects of endocannabinoids on basal cytokine production in SFs. Targeting TRPA1 in inflammation might have therapeutic advantages, since it mainly affects SFs pre-activated by pro-inflammatory cytokines.