Therapeutic targeting of Nrf2/HO-1/NF-κB signaling axis with casticin mitigates intervertebral disc degeneration: in vitro and in vivo investigations.

As a persistent osteoarticular degenerative condition, intervertebral disc deterioration (IDD) has been established as a principal causative element in lumbar spine discomfort development. The present investigation seeks to assess the protective effects of casticin against IDD progression and elucidate associated molecular pathways. The CCK8 kit was used to assess the cytotoxicity of casticin on rat nucleus pulposus cells (NPCs). Western blot assay, qRT-PCR, enzyme-linked immunosorbent assay, reactive oxygen species assay, and immunofluorescence were used to detect the expression levels of inflammatory mediators and ROS production between different groups. The nuclear translocation of NF-κB p65 and expression of Nrf2/HO-1 signal pathway in lipopolysaccharide (LPS)-induced NPCs were detected by confocal microscopy. Moreover, histological analysis was used to evaluate the degree of disc degeneration in rats. Casticin treatment inhibited the production of oxygen free radicals and inflammatory mediators induced by LPS, such as ROS, TNF-α, IL-1β, and PGE2. Not only that, we also found that casticin retained the content of type II collagen and aggrecan in NPCs and inhibited the expression of MMP-13 and ADAMTS-5. Moreover, casticin treatment activated the Nrf2/HO-1 signal axis and inhibited nuclear translocation of NF-κB p65 in LPS-exposed NPCs. Histological analysis found that the treatment of casticin in rat IDD models prevented the loss of notochordal cells and the disordered arrangement of fiber loops. Casticin inhibits LPS-stimulated oxidative stress, inflammatory response, and ECM degradation by activating the Nrf2/HO-1 signaling axis and indirectly blocking the NF-κB pathway.