Inhibition of LRRK2 Restores Parkin-Mediated Mitophagy and Suppresses Apoptosis in Intervertebral Disc Degeneration

Background: Apoptosis of nucleus pulposus cells (NPCs) is a major contributor to the pathogenesis of intervertebral disc degeneration (IDD), mitophagy may remove dysfunctional mitochondria to combat apoptosis. Previously, we found that although the expression of Parkin was increased, it is not fully functionalized in mitophagy during IDD. LRRK2 is related to the activity of Parkin in mitophagy. This study aims to elucidate the role of LRRK2 in IDD as well as its mitophagy regulation mechanism. Methods: The expression of LRRK2 in human degenerative NP tissues as well as in oxidative stress induced rat NPCs was detected by western blot. LRRK2 was knocked down in NPCs by lentivirus transfection (LV-shLRRK2); apoptosis and mitophagy were assessed by western blot, TUNEL assay, immunofluorescence staining and mitophagy detection assay in LRRK2 knockdown NPCs under oxidative stress. In puncture induced rat IDD model, X-ray, MRI, hematoxylin-eosin (HE) and Safranin O-Fast green (SO) staining were performed to evaluate the therapeutic effects of LRRK2 inhibition (LV-shLRRK2) on IDD at 4 and 8 weeks post-surgery. Findings: The expression of LRRK2 was increased in degenerative NPCs both in vivo and in vitro. LRRK2 knockdown significantly inhibited oxidative stress-induced mitochondria-dependent apoptosis in NPCs; meanwhile, mitophagy was promoted. However, these effects were abolished by the mitophagy inhibitor 3-MA. Furthermore, LRRK2 inhibition ameliorated IDD in rats. Interpretation: Our study demonstrated that LRRK2 is involved in the pathogenesis of IDD, while knockdown of LRRK2 inhibits oxidative stress induced apoptosis through mitophagy. Thus, inhibition of LRRK2 may be a promising therapeutic strategy for IDD. Funding Statement: This work is supported by grants from National Nature Foundation of China (81871806, 81972094), Zhejiang Public service technology research program / social development (LGF18H060008), Zhejiang Provincial Natural Science Foundation of China (LY17H060010 and LY18H060012), Major scientific and technological project of medical and health in Zhejiang Province (WKJ-ZJ-1527), Zhejiang Provincial Project for Medical and Health Science and Technology (2017KY463). Declaration of Interests: The authors declare no conflict of interest. Ethics Approval Statement: All surgical interventions, treatments and postoperative animal care procedures were performed in strict accordance with the Animal Care and Use Committee of Wenzhou Medical University.