Troxerutin improves diabetic cognitive dysfunction by inhibiting mitochondrial fission mediated by transient receptor potential melastatin 7/calcineurin/dynamin-related protein 1ser637.

Abstract

Background: Diabetic cognitive dysfunction (DCD) is one of the chronic complications of diabetes, but its mechanism is currently unknown. Studies have shown that mitochondrial fission mediated by calcium overload is an important mechanism of DCD. Blocking calcium overload and restoring calcium homeostasis are key steps in treatment. Transient receptor potential melastatin 7 (TRPM7) is a novel player in causing calcium overload. Our previous studies have shown that genetic silencing of TRPM7 in type 1 diabetic rats leads to significant improvements in cognitive function, but the specific mechanism remains unclear. Troxerutin, extracted from the flowers of Sophora japonica, is one of the derivatives of rutin and has been shown to have neuroprotective effects. However, its association with TRPM7 remains unclear.

Aim: To use animal and cellular models, we investigated whether TRPM7 mediated mitochondrial fission by upregulation of calcineurin (CaN)/dynamin-related protein 1 (Drp1)^ser637 in DCD, and whether Troxerutin improved DCD by inhibiting TRPM7-mediated mitochondrial division.

Methods: In this study, we used db/db mice and hippocampal neuronal cell lines (HT22) treated with high-concentration glucose as our study subjects. We evaluated cognitive function using Morris water maze, novel object recognition tasks, and Nesting tests. We observed mitochondrial morphology using transmission electron microscopy and measured mitochondrial energy metabolism indicators using a spectrophotometer. We also detected mRNA and protein expression of TRPM7, CaN, p-Drp1^ser637, caspase-3, B-cell lymphoma 2 associated X protein, and B-cell lymphoma 2 using quantitative real-time polymerase chain reaction, western blotting, and immunofluorescence.

Results: In the db/db diabetic mice with cognitive dysfunction, as well as in hippocampal neurons exposed to high-concentration glucose, TRPM7 and CaN expression were upregulated, phosphorylated Drp1^ser637 expression was downregulated, and mitochondrial fission was increased. By modulating (inhibiting or overexpressing) TRPM7, it was further validated that TRPM7 activates the CaN/Drp1^ser637 pathway, resulting in an increase in mitochondrial fission and neuronal cell apoptosis. Troxerutin downregulated TRPM7/CaN/Drp1^ser637, reduced mitochondrial fission, and improved DCD.

Conclusion: TRPM7 promotes mitochondrial fission via the CaN/Drp1^ser637 pathway. Troxerutin improves mitochondrial function and reduces neuronal damage by inhibiting this pathway, suggesting TRPM7 as a potential therapeutic target for DCD.