Circadian gene period1b regulates proinflammatory cytokine expression through NF–κB signalling in zebrafish

Abstract The circadian clock plays a critical role in regulating the immune system. Our previous publication revealed that a mutation in the circadian gene period1b ( per1b ) in zebrafish significantly decreased proinflammatory gene expression, particularly under constant darkness (DD) conditions; however, the underlying mechanisms remain unclear. In this study, using per1b -null mutant zebrafish and a larval tail fin injury model, we observed that the loss of per1b resulted in the downregulation expression of proinflammatory cytokines, such as IL-6 and TNF-α, at protein level. Furthermore, the loss of per1b downregulated ERK phosphorylation and inhibited p65 phosphorylation, leading to reduced NF-κB activation, which could downregulate the expression of proinflammatory cytokines, such as IL-6 and TNF-α, in zebrafish. These results provided insight into the communication between the circadian clock and immune functions.