Roles and mechanisms of SIRT6 on intervertebral disc degeneration

English Keywords:Disc degeneration disease  SIRT6  Oxidative stress  TGFβ-smad1/5 signaling pathway

English Abstract:

  【Abstract】 Objectives: To investigate sirtuin(SIRT)6′s effects and its mechanisms on intervertebral disc degeneration. Methods: 32 C57BL/6 mice were randomly divided into sham group, model group, SIRT6 agonist group, and SIRT6 inhibitor group, with 8 mice in each group. The mice modeled were constructed as intervertebral disc degeneration models by puncture method, and SIRT6 agonist group and SIRT6 inhibitor group of mice were administered intraperitoneally with SIRT6 agonist and SIRT6 inhibitor(20mg/kg) respectively, and the sham group and model group of mice were administered an equal amount of physiological saline into the abdominal cavity for 7d. Imaging observations were performed and intervertebral disc tissues were collected at the end of the intervention, and the percentage of SIRT6 positive intervertebral disc tissues was detected by immunohistochemistry; Hematoxylin-eosin(HE) staining, Masson staining, and toluidine blue staining were used to observe the histopathological changes of intervertebral discs; The contents of MDA, GSH-Px, SOD and ROS in intervertebral disc tissues were detected biochemically; The expressions of SIRT6, transforming growth fator(TGF-β)1, smad1, and smad5 mRNA in intervertebral disc tissues were detected by quantitative real-time polymerase chain reaction(qRT-PCR); The expressions of collagen Ⅱ, collagen X, TGF-β1, smad1, smad5, p-smad1 and p-smad5 protein were detected by Western blot. Results: Imaging observation result after intervention showed that osteophyte formation was found in the model group, but not the sham group, and comparing with the model group, SIRT6 agonist group was inhibited while SIRT6 inhibitor group was more obvious. Comparing with the sham group, the expression of SIRT6 and the contents of GSH-Px and SOD in the intervertebral disc tissue of mice in the model group were significantly lower, while the contents of MDA and ROS and the expression of collagen Ⅱ, collagen X, TGF-β1, smad1, smad5, p-smad1, p-smad5 were significantly higher(P<0.01); Local cartilage endplates of intervertebral disc tissue of the model group reduced, collagen fibers were disorganized and dense, and blurred in morphology. Compared with the model group, the expression of SIRT6 and the contents of GSH-Px and SOD in the intervertebral disc tissues in the SIRT6 agonist group were significantly increased, and the contents of MDA and ROS and the expression of collagen Ⅱ, collagen X, TGF-β1, smad1, smad5, p-smad1, p-smad5 were significantly decreased (P<0.05), while those in the SIRT6 inhibitor group were the opposite. Conclusions: SIRT6 over-expression can effectively regulate oxidative stress and inhibit the TGFβ-smad1/5 signaling pathway, which in turn can slow down intervertebral disc degeneration.