Curcumin alleviates indomethacin-ciprofloxacin combination-induced small intestinal injury in mice by modulating Treg/Th17 balance and synergistically treats severe traumatic infections

Abstract Objective To investigate the effect and underlying mechanisms of curcumin (CUR) on small intestinal injuries associated with severe traumatic infections after combined treatment of ciprofloxacin (CIP) and indomethacin (IND). Methods Adult male C57BL/6 mice (8 weeks old) were randomly divided into (10 animals for survival rate observation, 10 for other indicators) control group, model group [hemorrhage+ fracture+Pseudomonas aeruginosa (PA) infection], IND+CIP treatment group, and IND+ CIP+CUR treatment group. The survival rates within 72 h post-modelling were observed across all groups. At 24 h post-modelling, peripheral blood samples, small intestinal tissues and mesenteric lymph nodes (MLN) were harvested. Small intestinal length, hemorrhagic status, and adhesions were also observed grossly in each group. Bacterial load was determined via dilute plating. HE staining was used to observe histopathological alterations in intestinal tissues across groups. ELISA was employed to measure the contents of inflammatory cytokines, IL-1β, IL-6, IL-10 and TNF-α in the serum and small intestinal homogenate of each group. Liver, renal, and cardiac functions were evaluated by measuring key biochemical indicators. Flow cytometry was applied to measure the percentages of IFN-γ, IL-4, TGF-β, and IL-17 positive cells within CD4+ T cells in the MLN. Real-time quantitative polymerase chain reaction (qPCR) was performed to detect the mRNA expression of forkhead box protein P3 (FOXP3) and retinoic acid receptor-related orphan receptor gamma (RORγ)-t in each group. Results Both the IND+CIP treatment group and the IND+CIP+CUR treatment group significantly improved survival rates in mice with severe traumatic infections (P<0.05). CUR addition reduced bacterial load in the mice (P<0.01). The IND+CIP treatment group exhibited small intestinal injury, which worsened over time, manifested by elevated contents of TNF-α (P<0.01), IL-6 (P<0.05), and IL-1β (P<0.05) and decreased IL-10 (P<0.01) in the small intestine tissues, accompanied with pathological damage in the small intestine. The IND+CIP+CUR treatment group had significantly reversed small intestinal injury, reduced inflammatory factor levels (P<0.01), and restored normal small intestinal structure, showing no significant differences in relevant blood biochemical indicators when compared to the IND+CIP treatment group. The expression of FOXP3 was increased and that of RORγ-t was decreased in CD4+ T cells from the IND+CIP+CUR treatment group than the IND+CIP treatment group (both P<0.01). Conclusion The combination of CUR with IND and CIP can effectively alleviate severe traumatic infections, while antagonize small intestinal damage observed in IND and CIP therapy, with no significant adverse effects on vital organ functions. This mechanism may be related to the balance between regulatory T (Treg) cells and T helper 17 (Th17) cells.