LOX-induced tubulointerstitial fibrosis via the TGF-β/LOX/Snail axis in diabetic mice.

Background: The partial epithelial-mesenchymal transition (EMT) is emerging as a significant mechanism in diabetic nephropathy (DN). LOX is a copper amine oxidase conventionally thought to act by crosslinking collagen. However, the role of LOX in partial EMT and fibrotic progression in diabetic nephropathy has not been investigated experimentally.

Methods: The bulk RNA sequencing and single-nuclei RNA sequencing (snRNA-seq) analysis were explored to find the role of LOX in diabetic nephropathy. We then investigated the partial EMT and the possible signaling pathway of LOX, both in vivo and in vitro by LOX inhibition experiments in diabetic mice and HK-2 cells. Besides, we further assessed kidney fibrosis and renal function.

Results: LOX expression was elevated in kidneys of diabetic mice. Additionally, snRNA-seq results indicated that LOX expression was higher in partial epithelial-mesenchymal transition proximal tubular (PemtPT) epithelial cells. Moreover, we found that increased LOX prompted partial EMT of renal tubular epithelial cells (RTECs) by modulating the transcription factor Snail both in vivo and in vitro. Remarkably, inhibition of LOX effectively mitigated the partial EMT of RTECs in diabetic mice, thereby attenuating kidney fibrosis and enhancing renal function. Additionally, we identified the TGF-β signaling pathway as an upstream regulator of LOX, and inhibiting LOX partially reversed the partial EMT program in HK-2 cells induced by the TGF-β signaling pathway.

Conclusions: Hyperglycemia induces partial EMT of RTECs via the TGF-β/LOX/Snail axis, thereby contributing to diabetic kidney fibrosis. Inhibiting LOX can effectively reverse the partial EMT of RTECs, diminish diabetic kidney fibrosis, and improve renal function.