Tryptophan Metabolites Analogue, N-(3,4-dimethoxycinnamonyl) Anthranilic Acid, Ameliorates Acute Graft-Versus-Host Disease Through Inhibiting Th1 Responses

Local catabolism of tryptophan (Trp) by indoleamine 2,3-dioxygenase (IDO) is considered an important mechanism of regulating T cell immunity. N-(3,4-dimethoxycinnamonyl) anthranilic acid (3,4-DAA) is an active synthetic anthranilic acid derivative which was proved to be effective to treat type±helper T lymphocytes (Th1) mediated autoimmune diseases such as multiple sclerosis. In this report, we investigated the effects of 3,4-DAA on the acute graft versus host disease (aGVHD) following allogeneic bone marrow transplantation (allo-BMT) and its potential mechanism of action. we established a murine aGVHD model, 3,4-DAA was injected intraperitoneally at 200 mg/kg/day per mouse immediately after allo-BMT or at the onset of aGVHD for 14 consecutive days; the signs of aGVHD and the survival were recorded periodically; the histological changes of target organs were evaluated with hematoxylin-eosin staining; the IDO activity and cytokine levels in plasma were measured by reverse-phase high-performance liquid chromatography (HPLC) and enzyme linked immunosorbent assay (ELISA), respectively. We revealed that administration of 3,4-DAA after allo-BMT significantly reduced the severity and the histological score of aGVHD; The survival for mice receiving 3,4-DAA prophylaxis and treatment were prolonged in comparison to the vehicle control mice. The plasma levels of IFN-γ, TNF-α, IL-12 and IL-2 in 3,4-DAA treatment group were found to be decreased, while the IDO activity, the IL-10, IL-5 and IL-4 levels elevated in these mice. In consistent with the in vivo results, 3,4-DAA also inhibited IFN-γ and IL-2 production of spleen T lymphocytes in vitro. Our findings suggest that 3,4-DAA can diminish the murine experimental aGVHD through inhibition of Th1 response; this property makes it a potential alternative agent for prevention and treatment of GVHD in the clinic.