# Exploring the mechanisms underlying quercetin, a key component of Achyranthis Bidentatae Radix, against intervertebral disc degeneration

## TL;DR

This study explores how quercetin, a compound from a traditional herb, protects against disc degeneration by reducing inflammation and cell damage through a specific signaling pathway.

## Contribution

The study identifies a novel mechanism of quercetin in treating intervertebral disc degeneration via the PI3K/Akt/eNOS pathway.

## Key findings

- Quercetin improves NP cell viability and reduces oxidative stress and inflammation in an in vitro model of IDD.
- Quercetin suppresses the PI3K/Akt/eNOS pathway, with NOS3 as a key downstream target, in NP cells.
- In vivo experiments show quercetin reduces disc degeneration in a rat model.

## Abstract

Intervertebral disc degeneration (IDD) is a complex, multifactorial orthopedic disorder. This study aims to investigate the therapeutic effects and underlying mechanisms of quercetin (QUE), a key bioactive component of Achyranthis Bidentatae Radix (ABR), against IDD.

Network pharmacology and RNA sequencing (RNA-seq) were utilized to identify active components and key molecular targets of ABR in IDD treatment. The findings indicated that 30 overlapping hub genes were enriched in pathways associated with hypoxia, collagen biosynthesis, inflammation, apoptosis, angiogenesis, and PI3K-Akt signaling. Network construction, molecular docking, and molecular dynamics (MD) simulation revealed that QUE, a major bioactive component of ABR, exhibits strong binding affinity to NOS3 (eNOS). An in vitro IDD model was established using nucleus pulposus (NP) cells stimulated with interleukin-1β (IL-1β). QUE significantly improved NP cell viability and mitigated IL-1β-induced oxidative stress, extracellular matrix (ECM) degradation, inflammation, apoptosis, and cellular senescence. Additionally, QUE suppressed PI3K, Akt, and eNOS phosphorylation, suggesting its role in modulating IDD progression. Mechanistically, loss-of-function validation confirmed Nos3 as an essential component within this pathway. Functional assessment further demonstrated that QUE significantly reduced IL-1β-induced NO overproduction in NP cells, confirming its regulatory effect on the PI3K/Akt/eNOS pathway. Finally, in vivo, QUE attenuated the degree of IDD in the puncture-induced rat model.

Our results demonstrate that QUE, a key active component of ABR, exerts protective effects on NP cells by alleviating IL-1β-induced oxidative stress, ECM degradation, inflammation, apoptosis, and senescence. These effects may be mediated through the PI3K/Akt/eNOS signaling pathway, with Nos3 serving as an indispensable downstream component. Our findings elucidate a novel mechanism of QUE and provide a pharmacological basis for the therapeutic application of ABR in IDD management.

Flowchart illustrating a multi-step research process for target identification and validation: screening for targets using RNA-seq, functional enrichment analysis (GO and KEGG), network construction (PPI network, compound–target–signaling network), molecular docking verification (molecular docking and dynamics simulation), and experimental assessment with various assays and in vivo experiments, each represented with diagrams, graphs, and labeled sections.