Tumor necrosis factor (TNF)-alpha is responsible for expressions of several clock genes and affects joint symptoms of rheumatoid arthritis (RA) with diurnal fluctuation. We tried to determine the mechanism involved in over-expression of Bmall, induced by TNF-alpha, in primary cultured rheumatoid synovial cells. Cells were incubated with intra-cellular Ca2+ chelator BAPTA-AM, calcineurin inhibitor FK506 and p300/ CBP (CREB binding protein) inhibitor C646, respectively, or transfected with p300 and CBP small interfering RNA (siRNA) before stimulation with TNF-alpha. Oscillation phase and amplitude of Bmall, transcriptional activator Rora, transcriptional repressor Rev-erba, and histone acetyltransferases (p300 and Cbp) were evaluated by quantitative real-time PCR. As results, TNF-alpha did not influence the oscillation phase of Rev-erba, while enhanced those of Rora, resulting in over-expression of Bmall. When Ca2+ influx was inhibited by BAPTA-AM, TNF-alpha-mediated up-regulation of Rora was cancelled, however, that of Bmall was still apparent. When we further explored another pathway between TNF-alpha and Bmall, TNF-alpha suppressed the expression of Rev-erba in the absence of Ca2+ influx, as well as those of p300 and Cbp genes. Finally, actions of TNF-alpha, in increasing Small Mora and decreasing Rev-erba, were cancelled by C646 treatment or silencing of both p300 and Cbp. In conclusion, we determined a novel role of TNF-alpha in inducing Bmall via dual calcium dependent pathways; Rora was up-regulated in the presence of Ca2+ influx and Rev-erba was down-regulated in the absence of that. Results proposed that inhibition of p3001 CBP could be new therapeutic targets for RA. (C) 2017 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license