Paroxetine mediate macrophage polarization by regulating GRK2-EP4-cAMP-pCREB signaling pathway in treating mice with DSS-induced colitis

Abstract Objective and design This study aimed to investigate the role of GRK2 in macrophage polarization of ulcerative colitis and to detect weather paroxetine could alleviate the symptoms of DSS-induced colitis in mice by regulating GRK2 translocation to affect macrophage polarization. Subjects After informed consent, colonic biopsies were obtained from a total of 22 patients with ulcerative colitis group and 22 volunteers who have received colonoscopy as control group. GRK2 heterozygous mice on the C57BL/6J background and WT littermates were used in this study. In vitro experiments were conducted in THP-1 cell. MethodsLamina propria mononuclear cells (LPMCs) were isolated from surgically resected colonic tissue by using enzymatic technique. THP-1 cells were stimulated by PMA (100 ng/ml) for 48 h to differentiate into macrophages (THP-M). Experimental colitis was induced in mice by administrating 3.5% dextran sodium sulfate for consecutive 7 days. Pathological changes in the colon tissues were assessed by hematoxylin and eosin staining. The levels of infammatory factors, including PGE2, cAMP, IL-1β, and IL-10 were determined by enzymelinked immunosorbent assay. The expression levels of GRK2, EP4, and pCREB proteins were measured by Western blot analysis. The mRNA levels of IRF5 and IRF4 weremeasured by real-time quantitative polymerase chain reaction. The levels of CD68, CD86, CD206 and F4/80 were detected by flow cytometric analysis. Results UC patients showed higher PGE2 level and higher M1/M2 ratio than control group patients. In mice, the absence of GRK2 prevented higher disease activity index DAI and higher spleen index. In THP-1, the pIRES-EGFP-GRK2 plasmids transfection enhanced the release of IL-1β and increased the ratio of M1/M2. Paroxetine could influence macrophage polarization by down-regulating EP4/cAMP/pCREB-dependent GRK2 translocation, and alleviated the symptoms in mice with DSS-induced colitis. Conclusion GRK2 mediates the changes of PGE2-EP4-cAMP-pCREB pathway may influence M2 polarization in LPMCs of UC patients. Paroxetine alleviated the symptoms in mice with DSS-induced colitis and maybe a potential target for UC.