Upregulation of TCPTP in Macrophages Is Involved in IL‐35 Mediated Attenuation of Experimental Colitis

Abstract

Ulcerative colitis (UC) is a chronic intestinal inflammatory disease with complex etiology. Interleukin‐35 (IL‐35), as a cytokine with immunomodulatory function, has been shown to have therapeutic effects on UC, but its mechanism is not yet clear. Therefore, we constructed Pichia pastoris stably expressing IL‐35 which enables the cytokines to reach the diseased mucosa, and explored whether upregulation of T‐cell protein tyrosine phosphatase (TCPTP) in macrophages is involved in the mechanisms of IL‐35‐mediated attenuation of UC. After the successful construction of engineered bacteria expressing IL‐35, a colitis model was successfully induced by giving BALB/c mice a solution containing 3% dextran sulfate sodium (DSS). Mice were treated with Pichia/IL‐35, empty plasmid‐transformed Pichia (Pichia/0), or PBS by gavage, respectively. The expression of TCPTP in macrophages (RAW264.7, BMDMs) and intestinal tissues after IL‐35 treatment was detected. After administration of Pichia/IL‐35, the mice showed significant improvement in weight loss, bloody stools, and shortened colon. Colon pathology also showed that the inflammatory condition of mice in the Pichia/IL‐35 treatment group was alleviated. Notably, Pichia/IL‐35 treatment not only increases local M2 macrophages but also decreases the expression of inflammatory cytokine IL‐6 in the colon. With Pichia/IL‐35 treatment, the proportion of M1 macrophages, Th17, and Th1 cells in mouse MLNs were markedly decreased, while Tregs were significantly increased. In vitro experiments, IL‐35 significantly promoted the expression of TCPTP in macrophages stimulated with LPS. Similarly, the mice in the Pichia/IL‐35 group also expressed more TCPTP than that of the untreated group and the Pichia/0 group.