Paeonol reduces IL-1β induced apoptosis and degeneration by regulating MAPK pathway in nucleus pulposus cells

OBJECTIVES: Our study sought to examine paeonol's effects and possible regulatory mechanism in intervertebral disc degeneration (IDD). METHODS: In human nucleus pulposus (NP) cells, interleukin-1β (IL-1β) was used to construct IDD cell model. Cell viability, senescence, and apoptosis were checked utilizing cell counting kit-8 assay, β-galactosidase staining, and flow cytometry. The related indicators of cell senescence (cyclin dependent kinase inhibitor 2A, p16INK4a), apoptosis [Bcl-2-associated X protein (Bax) and cleaved caspase-3 (C-caspase-3)], inflammation [interleukin-6 (IL-6), inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2)], extracellular matrix (ECM) degradation [(Collagen II, matrix metallopeptidase 13 (MMP13), and a disintegrin and metalloproteinase with thrombospondin motifs 5 (ADAMTS5)], and mitogen-activated protein kinase (MAPK) pathway (p38 and p-p38) were examined by reverse transcription-quantitative polymerase chain reaction, Western blot, or immunofluorescence staining. The possible molecular mechanism of paeonol was explored via network pharmacology analysis. RESULTS: Under IL-1β treatment, paeonol enhanced NP cell viability, inhibited cell senescence and apoptosis, impeded inflammation and ECM degradation. Furthermore, paeonol reduced the levels of p16INK4a, Bax, C-caspase-3, IL-6, iNOS, COX-2, MMP13, and ADAMTS5 and increased Collagen II levels. Network and pharmacology analysis revealed that paeonol was associated with MAPK signaling pathway and there was a binding between paeonol and MAPK14 (also known as p38). The levels of p38 and p-p38 were decreased by paeonol. In addition, paeonol's promotion on NP cell viability and inhibition on NP cell apoptosis, inflammation, and ECM degradation were reversed by p38 overexpression. CONCLUSIONS: Paeonol exerted a protective role on alleviating IDD by attenuating NP cell apoptosis, inflammation, and ECM degradation through the inhibition of MAPK signaling pathway.