Deacetylase SIRT3 alleviates neuropathic pain by improving mitochondrial fission and fusion in spinal dorsal horn neurons

Abstract

Background: The mitochondria contribute to neuropathic pain (NP) by regulating mitochondrial function and cellular redox capacity. Sirtuin3 (SIRT3), an NAD+-dependent deacetylase primarily expressed in the mitochondria, is involved in the regulation of mitochondrial proteins. This study aimed to investigate the effect of SIRT3 within succinate dehydrogenase (SDH) on mitochondrial function and NP in mice with chronic constriction injury (CCI). Methods: Wild-type littermates underwent CCI surgery at 8-10 weeks postnatally. Western-blot and immunofluorescence was applied to detect the changes of SIRT3 protein in SDH after CCI. Lentivirus-SIRT3 and SIRT3-knockout mice (SIRT3-/-) were used to overexpress or knockdown of SIRT3. Mitochondrial fluorescence probe and electron microscope were used to observe the changes of mitochondrial morphology. ROS fluorescent probe dihydroethidium (DHE) and antioxidant enzyme kit were employed to determine the level of oxidative stress in SDH. Results: SIRT3 protein levels were significantly decreased in CCI mice. Overexpression of spinal SIRT3 by intrathecal injection of LV-SIRT3 attenuates pain hypersensitivity in CCI mice. Transgenic SIRT3-knockout mice (SIRT3-/-) show pain allergy in the physiological state. SIRT3 plays a major role in the regulation of mitochondrial fusion protein expression in optic atrophy 1 (OPA1). Ultrastructural analysis showed that CCI and SIRT3-/- mice induced mitochondria with smaller perimeters, areas, and interconnectivity in the SDH. CCI and SIRT3 deletion significantly increased oxidative stress, as evidenced by increased ROS levels and decreased activity of antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) in the SDH. Conclusion: Taken together, these results suggest that SIRT3 attenuates pain hypersensitivity in mice by regulating dynamic changes and oxidative stress in mitochondria.