Honokiol alleviates the degeneration of intervertebral disc via suppressing the activation of TXNIP-NLRP3 inflammasome signal pathway.

Intervertebral disc degeneration (IVDD) is a multifactorial disease and responsible for many spine related disorders, causes disability in the workforce and heavy social costs all over the world. Honokiol, a low molecular weight natural product, could penetrate into and distribute in IVDs to achieve therapeutic effect in a rat tail model. Therefore, the present study was undertaken to examine the antiinflammatory, antioxidation and IVD-protective effect of honokiol using nucleus pulposus cells and investigate its mechanisms to provide a new basis for future clinical treatment of IVDD. In the current study, we demonstrated that honokiol inhibits the HO-induced apoptosis (caspase-9, caspase-3, and bax), levels of oxidative stress mediators (ROS, MDA), expression of inflammatory mediators (Interleukin-6, COX-2, and iNOS), major matrix degrading proteases (MMP-3, MMP-13, ADAMTS5, and ADAMTS4) associated with nucleus pulposus degradation. Furthermore, we found nucleus pulposus protective ability of honokiol by up-regulating extra cellular matrix anabolic factors like type II collagen (Col II) and SOX9 in nucleus pulposus. We also found that honokiol suppressed the phosphorylation of NF-kB and JNK, and activation of TXNIP-NLRP3 inflammasome in HO-stimulated nucleus pulposus cells, thereby inhibiting the activation of downstream inflammatory mediators such as Interleukin-1β. Furthermore, honokiol showed a cartilage protective effect in the progression of IVDD in a rat model induced by puncture. Thus, our results demonstrate that honokiol inhibited the HO induced apoptosis, oxidative stress, and inflammatory responses through the depression of TXNIP/NLRP3/caspase-1/ Interleukin - 1β signaling axis and the activation of NF-kB and JNK. Honokiol possess nucleus pulposus protective properties and may be of value in suppressing the pathogenesis of IVDD.