Intermedin protects peritubular capillaries by inhibiting eNOS uncoupling through AMPK/GTPCH-I/BH4 pathway and alleviate CKD following AKI

  • Free Radic Biol Med. 2025 Jul:234:72-85. doi: 10.1016/j.freeradbiomed.2025.04.015.
Hui Lin  1 ,  Juan Pan  1 ,  Junhua Zhang  1 ,  Yuyin He  1 ,  Yuan Ge  1 ,  Dan Niu  2 ,  Weixia Han  2 ,  Xiaoli Han  1 ,  Fan Li  1 ,  Xiaomei Bai  1 ,  Xinyuan Feng  1 ,  Ling Lin  1 ,  Ruihua Shen  1 ,  Xiaole Su  1 ,  Xi Qiao  3
Affiliations
  • 1. Department of Nephrology, Second Hospital of Shanxi Medical University, Taiyuan, People's Republic of China; Shanxi Kidney Disease Institute, Taiyuan, People's Republic of China; Kidney Research Center of Shanxi Medical University, Taiyuan, People's Republic of China.
  • 2. Department of Pathology, Second Hospital of Shanxi Medical University, Taiyuan, People's Republic of China.
  • 3. Department of Nephrology, Second Hospital of Shanxi Medical University, Taiyuan, People's Republic of China; Shanxi Kidney Disease Institute, Taiyuan, People's Republic of China; Kidney Research Center of Shanxi Medical University, Taiyuan, People's Republic of China. Electronic address: [email protected].
PMID: 40228707 DOI: 10.1016/j.freeradbiomed.2025.04.015
Abstract

Background: Even after recovery of kidney function following AKI, progression to CKD may still occur, characterized by a reduction in peritubular capillaries (PTC) and subsequent kidney fibrosis. Reactive Oxygen Species (ROS) from uncoupled eNOS are suspected to damage endothelial cells and cause PTC rarefaction observed in AKI-CKD. Intermedin (IMD) inhibits eNOS uncoupling by activating AMPK, but its impact on AKI-CKD transition remains unclear.

Methods: We utilized IMD-deficient (IMD-/-) mice to explore its effects on AKI-CKD transition, PTC density, endothelial damage, and kidney ROS in a kidney ischemia/reperfusion injury (IRI) model. To elucidate its protective mechanism for PTCs, we subsequently investigated the effects of IMD on endothelial cells and ROS using a hypoxia/reoxygenation (HR) model with human umbilical vein endothelial cells (HUVECs). Finally, we investigated the influence of IMD on AMPK/GTPCH-I/BH4/eNOS to explore its mechanism in alleviating oxidative stress.

Results: Compared with IMD+/+ littermate sham controls, PTC density was significantly reduced in IMD-/- sham mice, with significantly increased oxidative stress. Post-AKI, both IMD+/+ and IMD-/- mice demonstrated substantial declines in kidney function and histology, along with significant fibrosis, PTC reduction, and heightened oxidative stress. Moreover, the severity of kidney damage in IMD-/- mice following AKI was considerably more pronounced than in IMD+/+ mice. HR significantly induced eNOS uncoupling and oxidative stress in HUVECs. Treatment with IMD effectively inhibited eNOS uncoupling and ROS production, achieving levels comparable to the antioxidant N-acetylcysteine. The inhibitory effect of IMD on eNOS uncoupling was abrogated when L-NAME was introduced after HR. HR significantly impaired AMPK activation, which could be reversed by IMD. Additional experiments with inhibitors of GTPCH-I and AMPK, and exogenous BH4, confirmed that IMD protects endothelial cells by activating AMPK/GTPCH-I/BH4, thereby inhibiting eNOS uncoupling and ROS production.

Conclusion: We concluded that IMD inhibits AKI-CKD transition by protecting endothelial cells of PTC via AMPK/GTPCH-I/BH4/eNOS pathway.

Keywords
AMPK; Acute kidney injury; Chronic kidney disease; GTPCH-I; Intermedin; eNOS.
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