Juanbi Tang Attenuates Intervertebral Disc Degeneration by Suppressing p38MAPK/NF‐κB Signaling and Activating Atg5‐Dependent Autophagy to Promote Macrophage M2 Polarization: In Vivo and In Vitro Evidence

Background Intervertebral disc degeneration (IDD) is driven by macrophage‐mediated inflammation involving the p38MAPK/NF‐κB signaling pathway and impaired autophagic flux. Juanbi Tang (JBT), a classical eleven‐herb Chinese formula documented since 1732 CE for the treatment of Bi syndrome (a traditional diagnosis encompassing painful musculoskeletal obstruction conceptually corresponding to degenerative spinal conditions), demonstrates clinical anti‐inflammatory activity; however, its molecular mechanism in IDD remains uncharacterized. Methods JBT chemical composition was characterized by HPLC fingerprinting with osthole as quantitative reference standard (inter‐batch RSD 2.3%) in accordance with the 2020 Chinese Pharmacopoeia, and quality control was extended beyond a single marker constituent by multi‐component fingerprint similarity analysis using the cosine angle and correlation coefficient methods. A male Sprague–Dawley rat annular puncture IDD model (five groups: Sham, IDD, IDD + JBT, IDD + 3‐methyladenine [3‐MA], and IDD + JBT + 3‐MA) was evaluated by MRI, CT, Safranin O–Fast Green, Masson trichrome and hematoxylin and eosin staining. LPS‐stimulated (1 μg/mL) primary rat nucleus pulposus (NP) cells and murine RAW264.7 macrophages — including Atg5‐overexpressing (Atg5‐OE) and knockdown (Atg5‐KD) variants — were used for in vitro mechanistic studies. Endpoints included apoptosis, mitochondrial membrane potential (ΔΨm), reactive oxygen species (ROS), macrophage M1/M2 polarization, ELISA cytokine quantification and Western blot pathway analysis. Results In vivo, JBT significantly improved Pfirrmann grade, disc height index, Safranin O staining intensity, Masson‐stained collagen content and Thompson grade, with concomitant suppression of serum TNF‐α and restoration of IL‐10; all benefits were partially abrogated by 3‐MA co‐administration. JBT suppressed p‐p38MAPK and p‐NF‐κB p65 and restored the COL II/MMP‐13 balance in disc tissue. In NP cells, JBT reduced total apoptosis from 29.1% to 14.5%, restored ΔΨm, attenuated ROS accumulation, reversed the Bax/Bcl‐2 ratio, and activated autophagy (LC3‐II ↑ , p62 ↓ ). In RAW264.7 macrophages, JBT promoted M2 polarization (CD206 + : 28.1% to 49.7%) and suppressed M1 polarization (CD197 + : 52.4% to 18.9%) under LPS stimulation, with concurrent autophagy activation. Western blot analysis across normal, Atg5‐OE and Atg5‐KD macrophages demonstrated that Atg5 expression level bidirectionally modulates p62 clearance and consequent NF‐κB suppression, consistent with the autophagy–p62–NF‐κB regulatory module contributing to JBT's pharmacological activity. Conclusions JBT attenuates IDD through coordinated suppression of macrophage‐driven inflammation and activation of autophagy, providing mechanistic support for its clinical application in musculoskeletal disease.