ABSTRACT
Objective:To observe any regulatory effect of a pulsed electromagnetic field (PEMF) on A2A adenosine receptors (A2ARs) in the nucleus pulposus of rats with intervertebral disc degeneration (IDD), and to explore any combination with the A2ARs′ agonist-mediating ROS/PI3K/Akt signaling pathway.Methods:Fifty Sprague-Dawley rats were randomly divided into a control group, an intervertebral disc degeneration group (the model group), an A2AR agonist CGS-21680 treatment group (the agonist group), a PEMF group and a PEMF combined with CGS-21680 treatment group (the observation group). IDD was modeled in all except the rats in the control group. 100μL of CGS-21680 (100μg/kg) was injected into the L 5-6 intervertebral discs of the agonist group, while the PEMF group was given 30 minutes of PEMF intervention daily for 14 days at 1.5mT and 75Hz with a pulse width of 150μs. The observation group was injected with CGS-21680 and then given the same PEMF intervention. Primary nucleus pulposus cells from each group (50ng/mL) were cultured and the expressions of 8-OHDG, SOD, MDA and ROS were detected by immunohistochemistry, immunofluorescence or with an ELISA kit. The A2AR, PI3K, AKT and p-AKT protein levels were detected using western blotting. Results:The nucleus pulposus cells and the annulus fibrosus were obviously wrinkled, necrotic and broken in the model group but the annulus fibrosus was intact and the nucleus pulposus was almost normal in the observation group. Compared with the model group, the levels of SOD and A2AR, PI3K, p-AKT and AKT protein were higher in the agonist, PEMF and observation groups, while the expressions of MDA, ROS and 8-OHDG were weaker. The ROS level in the observation group was significantly lower than that in the agonist and PEMF groups, and the phosphorylation level of p-AKT in the observation group was significantly higher than in the agonist and PEMF groups. The average levels of SOD, A2AR, PI3K, p-AKT and AKT protein in the nucleus pulposus cells of the agonist, PEMF and observation groups were significantly higher than the IL-1β group′s average, while the average levels of MDA, ROS and 8-OHDG were significantly lower. The ROS levels in the observation group were significantly lower than in the agonist and PEMF groups, while the A2AR protein content and p-AKT phosphorylation in the observation group were significantly greater. The average Bax levels in the nucleus pulposus cells of the agonist, PEMF and observation groups were significantly lower than that in the IL-1β group, and the expression of Bcl-2 was significantly increased. There was significantly less apoptosis observed in the observation group than in the agonist and PEMF groups, while the expression of Bcl-2 was significantly higher.Conclusions:PEMF plays an anti-oxidative stress role by up-regulating A2AR activity and reducing ROS generation. Treatment with PEMF and A2AR agonist could further activate the phosphorylation of PI3K/Akt, down-regulate Bax and up-regulate Bcl-2, thus inhibiting the apoptosis of nucleus pulposus cells and alleviating the malignant progression of IDD.