Aristolochic acid I promotes renal tubulointerstitial fibrosis by up-regulating expression of indoleamine 2,3-dioxygenase-1 (IDO1)

Aristolochic acid I (AAI) is strongly nephrotoxic and can cause "Aristolochic acid nephropathy (AAN)". Aristolochic acid nephropathy is characterized by extensive renal interstitial fibrosis. However, the exact mechanism by which it occurs has not been fully elucidated. lt has been reported that indoleamine 2,3-dioxygenase-1 (IDO1) promotes renal fibrosis in renal disorders, but it is unclear how IDO1 functions in AAI-induced kidney fibrosis. In this work, we systematically examined the role of IDO1 in AAI-induced renal tubulointerstitial fibrosis. The results showed that AAI induced upregulation of IDO1 expression in renal tubular epithelial cells and mouse kidney. Inhibition of IDO1 expression reduced the levels of fibrosis-associated markers α-SMA, COL-I and FN and ameliorated renal tubular epithelial cell fibrosis. It also improved renal function, reduced collagen deposition, and ameliorated interstitial fibrosis in mice. Moreover, we discovered that inhibition of IDO1 decreased the expression of the apoptotic protein BAX, raised the expression of BCL-2 protein, and reduced apoptosis. The above studies suggest that IDO1 is a target of action in renal tubulointerstitial fibrosis caused by AAI, and inhibition of IDO1 may be a viable approach for the therapy of AAI-induced renal tubulointerstitial fibrosis.