Moderate exercise training under constant light condition amplifies inflammatory signals through disruption of splenic clock mechanism in osteoarthritic animals

Abstract

Physical exercise has been recommended for osteoarthritic(OA) patients, the effects of which depends on exercise protocol. Here, we determined whether the benefits of exercise are influenced by lighting condition in the OA rats. Moderate treadmill exercise(Ex) was performed for 4 weeks at ZT14 under 12:12hr light‐dark(L/D) as well as constant light(LL). Intervention was applied for 30 min on 5 days/week. Splenic Cry1 expression was suppressed in the trained rats under constant light condition, leading to upregulation of proinflammatory cytokines mRNA. Moreover, TNFα level in serum was higher in the LL+Ex group than the L/D+Ex group. Constant light combined with exercise exacerbated primary cartilage lesion through an increase of catabolic molecules as well as a transcriptional suppression of anabolic factors. The level of synovial RANKL protein was elevated in the LL+Ex group, leading to loss of tibial trabeculae. And increased joint diameter was not recovered in the exercise‐trained rats under LL condition. Exercise training under constant lighting condition enhanced activation of catabolic machinery in soleus as well as gastrocnemius muscle. Treatment of proinflammatory cytokines disrupted rhythmic expression of catabolic enzymes in C2C12‐derived myotubes. Taken together, lighting condition might be a considerable environmental factor to obtain exercise‐induced benefits.Support or Funding InformationFunding: NRF‐2015R1C1A2A01055691, NRF‐2017R1A2A2A01067169, KGM4611714This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.