Period circadian clock 3 is crucial for regulation of IL-22-producing type 3 innate lymphoid cells by flavonoids from Shen Ling Bai Zhu San to alleviate colitis

Type 3 Innate lymphoid cells (ILC3s) functions bear complex response during Inflammatory bowel diseases (IBD). Here, our study first analyzed the main pharmacological components in Shen Ling Bai Zhu San n-butanol extracts (S-Nb), and then explored whether S-Nb administrated immune response of ILC3s, and how it regulates ILC3s. Shen Ling Bai Zhu San (SLBZS) or S-Nb were administrated for 7 days to analyze the frequency of ILC3s and their produced cytokine. Using siRNA technology to knock down the expression of period circadian clock 2 (Per2) and period circadian clock 3 (Per3) and Anti-IL-22 antibody was supplied to mice, then detecting the moderator effect of S-Nb on colitis. The most class of S-Nb is flavonoids, with a content of approximately 48%. Oral administration of S-Nb enhanced the production of NCR⁺ILC3s and IL-22 produced by ILC3s, but did not alter IL-17A. Surprisingly, knocking down the expression of Per3 instead of Per2 inhibited the modulation effect of S-Nb on colitis and reduced IL-22 production, whether originating from NCR⁺ILC3s or NCR^-ILC3s. After neutralizing the expression of IL-22 in mice, S-Nb was deprived of ability to alleviate colitis. The reason why S-Nb alleviates colitis is by enhancing the expression of Per3 via flavonoids, which in turn promotes the secretion of IL-22⁺ILC3s in intestine.