Indoleamine 2,3-Dioxygenase (IDO) Regulates Th17/Treg Immunity in Experimental IgA Nephropathy

IgA nephropathy (IgAN) is the most common glomerulonephritis worldwide. Current studies have shown that the Th17/Treg immune balance may be involved in the occurrence of IgAN, but the exact mechanism is still unclear. Indoleamine 2,3-dioxygenase (IDO) is an enzyme that catalyses degradation of tryptophan (Trp) through the kynurenine (Kyn) pathway; it can control inflammation and immune response by inducing Trp starvation. IDO may be a key molecule in regulating the Th17/Treg immune balance. However, it is not clear whether IDO is involved in the IgAN disease occurrence by regulating the Th17/Treg immune balance. In this study, an IgAN mouse model was established. The mice were intraperitoneally inoculated with IDO inhibitor 1-MT or agonist ISS-ODN to observe whether the IDO signalling pathway participates in the occurrence and development of IgAN by regulating the Th17/Treg immune balance. The results showed that IDO inhibitor 1-MT significantly increased renal injury and glomerular IgA accumulation and up-regulated Th17/Treg and Th17-related cytokine expression in IgAN mice, while ISS-ODN significantly decreased renal injury and glomerular IgA accumulation, down-regulated Th17/Treg expression and inhibited Th17-related cytokine expression in IgAN mice. In conclusion, IDO was involved in the occurrence and progress of IgAN by regulating the Th17/ Treg balance.