Ursodeoxycholic acid alleviates acute kidney injury via potentiating the AMPK/NRF2 cascade: Dual mechanisms of promoting HINT1-dependent phosphorylation of LKB1 and enhancing LKB1/AMPK interaction.

Acute kidney injury (AKI) induced by the nephrotoxic substance aristolochic acid I (AAI) or ischemia-reperfusion (IR) is closely associated with intrarenal oxidative stress. Although ursodeoxycholic acid (UDCA) alleviates liver injury by activating the nuclear factor erythroid 2-related factor 2 (NRF2) antioxidant pathway, the molecular mechanism through which UDCA potentiates NRF2 is currently unclear. Here, we revealed that UDCA protected against AKI induced by AAI in mice or IR in rats. In human kidney 2 cells (HK2) proximal tubular epithelial cells, UDCA suppressed H2O2-or AAI-induced apoptosis and ferroptosis. Mechanistically, UDCA upregulated the histidine triad nucleotide-binding protein 1 (HINT1) and activated the liver kinase B1 (LKB1)/AMP-activated protein kinase (AMPK)/NRF2 antioxidant cascade in both HK2 cells and damaged animal kidneys. Knockdown of HINT1 expression abrogated the phosphorylation of LKB1 and subsequent activation of the AMPK/NRF2 axis triggered by UDCA. UDCA-mediated protection against H2O2 or AAI was also eliminated. HINT1 promoted the interaction between LKB1 and its upstream activator protein kinase A (PKA), and overexpression of HINT1 reduced AAI-induced AKI in vitro and in mice. Furthermore, UDCA interacted with AMPK protein and enhanced the LKB1/AMPK interaction. The inhibition of AMPK eliminated UDCA-mediated activation of NRF2. In summary, we identified HINT1 as a new positive regulator of LKB1 phosphorylation and suggested that UDCA activates the renal AMPK/NRF2 antioxidant cascade through dual mechanisms: promoting LKB1 phosphorylation by upregulating HINT1 expression and enhancing the LKB1/AMPK interaction through binding to AMPK. These data are conducive to the application of UDCA in clinical intervention for AKI.