Inhibition of the TLR/NF-κB Signaling Pathway and Improvement of Autophagy Mediates Neuroprotective Effects of Plumbagin in Parkinson's Disease

A naphthoquinone molecule known as plumbagin (PL), which has a wide range of pharmacological properties including antitumor, antioxidation, anti-inflammation, and neuroprotective effects, is extracted from the roots of the medicinal herb Plumbago zeylanica L. Plumbagin has been studied for its potential to treat Parkinson's disease (PD). However, its effectiveness and mechanism are still unknown. This study intends to evaluate plumbagin's effectiveness against PD in vitro and in vivo. Plumbagin partially repaired the loss of dopaminergic neurons in the nigral substantia nigra and the resulting behavioural impairment caused by MPTP or MPTP/probenecid in mice. Furthermore, plumbagin treatment significantly inhibited the TLR/NF-κB pathways. It reduced the TNF-α, IL-6, and IL-1β mRNA expression in PD mice induced by MPTP or MPTP/probenecid, which was consistent with the findings in the inflammatory model of BV2 cells induced by MPP+ or LPS. In addition, plumbagin treatment enhanced the microtubule-associated protein 1 light chain 3 beta (LC3) LC3-II/LC3-I levels while decreasing the p-mTOR and p62 protein accumulation in PD mice induced by MPTP or MPTP/probenecid, which was similar to the results obtained from the experiments in SH-SY5Y and PC12 cells induced by MPP+. Consequently, our results support the hypothesis that plumbagin, by promoting autophagy and inhibiting the activation of the TLR/NF-κB signaling pathway, is a promising treatment agent for treating Parkinson's disease (PD). However, to confirm plumbagin's anti-PD action more thoroughly, other animal and cell PD models must be used in future studies.