Limonin delays the progression of intervertebral disc degeneration in vivo and in vitro: the key role of the MAPK/NF-kappa B and necroptosis pathways

Objectives Limonin has received significant attention due to its multiple biological effects, intervertebral disc degeneration (IDD) is also of interest due to the high prevalence of this disease. In this study, we determined the effects of limonin on IDD and the underlying mechanism of action to find novel ways to treat IDD.Methods An IL-1 beta-induced cell inflammation model and a lumbar instability model inducing IDD were established to assess the progression of IDD with or without limonin treatment. We further evaluated MAPK/NF-kappa B and necroptosis pathways and alterations in the extracellular matrix specific within the disc. Key findings Limonin suppresses inflammation in the nucleus pulposus in vitro by reducing the production of pro-inflammatory markers such as iNOS and COX-2. Limonin reduced the activation of the MAPK/NF-kappa B signalling pathway and the RIP1/RIP3/MLKL necroptosis pathway in the NP cells. Moreover, limonin delays the IDD progression in the lumbar instability model.Conclusions Limonin could potentially delay IDD by inhibiting NP cell necroptosis and modulating peripheral matrix proteins within the intervertebral disc and is a potential pharmacological research direction for the therapy in patients with IDD.