RUNX3 alleviates mitochondrial dysfunction and tubular damage by inhibiting TLR4/NF-κB signalling pathway in diabetic kidney disease

Abstract

Aim: The impaired function of tubular mitochondria is critical in diabetic kidney disease (DKD) progression. RUNX3 is down-regulated in DKD models. We intend to explore the effects of RUNX3 on mitochondrial dysfunction and renal tubule injury in DKD and related mechanisms.

Methods: The development of diabetes models involved injecting mice with streptozotocin while treating HK-2 cells with high glucose (HG). By using immunohistochemical techniques, the renal localizations of RUNX3 were identified. Levels of adenosine triphosphate (ATP), mitochondrial membrane potential, and biochemical index were detected by appropriate kits. Reactive oxygen species (ROS) generation was assessed with dihydroethidium and MitoSOX Red staining. Apoptosis was assessed by flow cytometry and TUNEL. RUNX3 ubiquitination was measured.

Results: RUNX3 was mainly present in renal tubules. Overexpressing RUNX3 increased Mfn2, Mfn1, ATP levels, and mitochondrial membrane potential, reduced Drp1 and ROS levels and cell apoptosis, as well as Cyt-C release into the cytoplasm. RUNX3 overexpression displayed a reduction in urinary albumin to creatinine ratio, Hemoglobin A1c, serum creatinine, and blood urea nitrogen. Overexpressing TLR4 attenuated the inhibitory effect of RUNX3 overexpression on mitochondrial dysfunction and cell apoptosis. HG promoted RUNX3 ubiquitination and SMURF2 expression. RUNX3 knockdown cancelled the inhibitory effect of SMURF2 on mitochondrial dysfunction and cell apoptosis.

Conclusion: SMURF2 interference inhibits RUNX3 ubiquitination and TLR4/NF-κB signalling pathway, thereby alleviating renal tubule injury.

Keywords: RUNX3; SMURF2; diabetic kidney disease; mitochondrial dysfunction; renal tubular epithelial cells.