Melatonin activates autophagy via the NF-κB signaling pathway to prevent extracellular matrix degeneration in intervertebral disc

Objective: This study investigated whether melatonin alleviates intervertebral disc degeneration (IVDD) by promoting autophagy through inhibiting the NF-kappa B signaling pathway. Methods: Magnetic resonance imaging (MRI), hematoxylin and eosin (H&E) staining and Safranin-O staining were used to measure disc degeneration in rat needle puncture IVDD models, and melatonin was injected intraperitoneally in the treated group to test its function. The expression of autophagy and extracellular matrix (ECM) degeneration related-markers were measured in the discs using immunohistochemistry. Transmission electron microscopy was used to evaluate the activation of autophagy in human nucleus pulposus (NP) tissues with different degenerated statuses. The expression of autophagy and disc degeneration related-markers were detected in NP cells by Western blot, RT-qPCR, and immunofluorescence analyses. NF-kappa B signaling pathway involvement was studied by lentivirus-mediated knockdown, Western blotting, and immunohistochemistry and immunofluorescence staining. Results: Melatonin prevented IVDD development in vivo and in vitro. Compared to non-degenerated disc tissues, degenerated human NP tissues showed a decrease in the autophagy-specific marker LC3B and the numbers of autophagosomes and autolysosomes, whereas the p62 level was increased; similar results were observed in rat IVDD models, indicating a negative correlation between autophagy and IVDD. Furthermore, both in vivo and in vitro studies found that melatonin application induced autophagy and reduced ECM disc degradation. Melatonin was also shown to regulate autophagy by inhibiting the NF-kappa B signaling pathway in vivo and vitro. Conclusion: This study indicates that melatonin prevents IVDD by promoting autophagy, indicating its possible therapeutic potential for controlling the progression of IVDD. (c) 2020 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.