Combination of PGE2 Elevated Anti-TNF Therapy In Experimental Colitis via Regulating Treg/Th17 Balance

Background: Anti-TNF therapies have gained great success in treating autoimmune disease. However, the efficacy and safety of high-dose anti-TNF agents are insufficient in clinical cases. An anti-TNF nanobody, V19, and combination therapy with PGE2 were introduced to improve the therapeutic efficacy of anti-TNF agents. Method: Dextran sulfate sodium-induced colitis mice were used to evaluate the therapeutic effect of V19 and combination therapy. Variation of the Treg/Th17 balance was a criterion for comparing therapeutic efficacy with combination therapy and monotherapy.  Findings: V19 expressed in Escherichia coli showed a therapeutic effect on DSS-induced colitis mice by inducing an increase in Treg by upregulating tm-TNF-α and TNFR2 in peripheral blood. However, cell apoptosis (Treg, dendritic cells, and CD8 T cells) was induced in peripheral blood by high doses of V19, accompanied by upregulated tm-TNF-α. Further, Th17 cells in colons of DSS-induced mice were induced by V19, accompanied by the upregulation of IL-6. Combination therapy showed better therapeutic effects than monotherapy. After combination therapy, Th17 cells were significantly decreased in colons, and an in vitro assay demonstrated that PGE2 reduced Th17 cells by downregulating IL-6 in colons via EP4. Although PGE2 showed no influence on cell apoptosis and could not induce Treg generation, it enhanced the ability of V19 to induce Treg by upregulating TNFR2 via EP4 in peripheral blood. Interpretation: This combination therapy has good clinical significance as PGE2 can expand the drug delivery window and enhance the therapeutic effect during anti-TNF clinical treatment.   Funding: This work was supported by grants from the Chinese National Natural Sciences Foundation (81630092, 81773099, 81573338, 81773099) and the National Key R&D Research Program of the Ministry of Science and Technology (2017YFA0506002). Declaration of Interest: None to declare. Ethical Approval: All animal protocols were performed as per the appropriate ethical guidelines of the Nanjing University Animal Care and Use Committee. Female C57BL/6 mice (6–8-week) and TNFR2-/- mice were obtained from the Model Animal Research Center of Nanjing University (Nanjing, China) and housed under germ-free conditions. Animal welfare and experimental procedures were carried out per the Guide for the Care and Use of Laboratory Animals (Ministry of Science and Technology of China, 2006) and our university's related ethical regulations. All animal experiments were approved by the Nanjing University Animal Care and Use Committee (NJU-ACUC) and were performed to minimize suffering and reduce the number of animals used.