SIRT3-Mediated CypD-K166 Deacetylation Alleviates Neuropathic Pain by Improving Mitochondrial Dysfunction and Inhibiting Oxidative Stress

Numerous studies have shown that mitochondrial dysfunction manifested by increased mitochondrial permeability transition pore (mPTP) opening and Reactive Oxygen Species (ROS) level, and decreased mitochondrial membrane potential (MMP) plays an important role in the development of neuropathic pain. Sirtuin3 (SIRT3), a nicotinamide adenine dinucleotide (NAD⁺)-dependent histone deacetylase, has been shown to inhibit mitochondrial oxidative stress. However, the role of SIRT3 in neuropathic pain is unclear. In this study, we found that the protein and mRNA levels of SIRT3 were significantly downregulated in the spinal cords of spared nerve injury- (SNI-) induced neuropathic pain mice, while overexpression of spinal SIRT3 reversed SNI-induced pain hypersensitivity. Further study showed that SIRT3 overexpression reduced the acetylation level of lysine 166 (K166) on Cyclophilin D (CypD), the regulatory component of the mPTP, inhibited the mPTP opening, decreased ROS and malondialdehyde (MDA) levels, and increased MMP and manganese superoxide dismutase (MnSOD) in SNI mice. Point mutation of K166 to arginine on CypD (CypD-K166R) abrogated SNI-induced mitochondrial dysfunction and neuropathic pain in mice. Moreover, inhibiting mPTP opening by cyclosporin A (CsA) improved mitochondrial function and neuropathic pain in SNI mice. Together, these data show that SIRT3 is necessary to prevent neuropathic pain by deacetylating CypD-K166 and further improving mitochondrial dysfunction. This study may shed light on a potential drug target for the treatment of neuropathic pain.