Resveratrol inhibits IL-1ß-mediated nucleus pulposus cell apoptosis through regulating the PI3K/Akt pathway.

Nucleus pulposus (NP) cell apoptosis is a classical cellular character during intervertebral disc degeneration (IDD). Previous studies have shown that inflammatory cytokine-induced NP cell apoptosis plays an important role in disc degeneration. The present study was aimed to investigate whether resveratrol can suppress IL-1ß-mediated NP cell apoptosis and the potential signal transduction pathway. Experimental rat NP cells were treated with culture medium containing IL-1ß (20 ng/ml) for 7 days. Control NP cells were cultured in the baseline medium. Resveratrol was added along with culture medium to investigate its effects. The inhibitor LY294002 was used to study the role of the PI3K/Akt pathway. NP cell apoptosis was reflected by the caspase-3 activity, cell apoptosis ratio, and expression of apoptosis-related molecules (Bcl-2, Bax, caspase-3, cleaved caspase-3, and cleaved PARP). Compared with the control NP cells, IL-1ß significantly increased caspase-3 activity, NP cell apoptosis ratio and mRNA/protein expression of Bax, caspase-3, cleaved caspase-3 and cleaved PARP, but decreased mRNA expression of Bcl-2. However, resveratrol partly suppressed the effects of IL-1ß on those cell apoptosis-related parameters. Further analysis showed that IL-1ß significantly decreased activity of the PI3K/Akt pathway whereas resveratrol partly increased activity of the PI3K/Akt pathway in NP cells treated with IL-1ß. Additionally, when the inhibitor LY294002 was added along with the resveratrol, its protective effects against IL-1ß-induced NP cell apoptosis were attenuated. In conclusion, resveratrol suppresses IL-1ß-mediated NP cell apoptosis through activating the PI3K/Akt pathway. Resveratrol may be an effective drug to attenuate inflammatory cytokine-induced disc degenerative changes.

Responses of apoptosis and matrix metabolism of annulus fibrosus cells to different magnitudes of mechanical tension in vitro.

BACKGROUND: Annulus fibrosus (AF) is important to confine disc nucleus pulposus (NP) tissue during mechanical load experience. However, the knowledge on AF cell biology under mechanical load is much limited compared with disc NP. OBJECTIVE: The present study aimed to investigate responses of apoptosis and matrix metabolism of AF cells to different magnitudes of mechanical tension in vitro Methods: Rat AF cells were subjected to different magnitudes (5, 10, and 20% elongations at a frequency of 1.0 Hz for 6 h per day) of mechanical tension for 7 days. Control AF cells were cultured without mechanical tension. Cell apoptosis ratio, caspase-3 activity, gene/protein expression of apoptosis-related molecules (Bcl-2, Bax, caspase-3/cleaved caspase-3 and cleaved PARP), matrix macromolecules (aggrecan and collagen I) and matrix metabolism-related enzymes (TIMP-1, TIMP-3, MMP-3, and ADAMTS-4) were analyzed. RESULTS: Compared with 5% tension group and control group, 10 and 20% tension groups significantly increased apoptosis ratio, caspase-3 activity, up-regulated gene/protein expression of Bax, caspase-3/cleaved caspase-3, cleaved PARP, MMP-3, and ADAMTS-4, whereas down-regulated gene/protein expression of Bcl-2, aggrecan, collagen I, TIMP-1, and TIMP-3. No significant difference was found in these parameters apart from Bcl-2 expression between the control group and 5% tension group. CONCLUSION: High mechanical tension promotes AF cell apoptosis and suppresses AF matrix synthesis compared with low mechanical tension. The present study indirectly indicates how mechanical overload induces disc degeneration through affecting AF biology.