Tetrandrine protects against oxygen-glucose-serum deprivation/reoxygenation-induced injury via PI3K/AKT/NF-κB signaling pathway in rat spinal cord astrocytes

Tetrandrine (TET) is a bis-benzylisoquinoline alkaloid, which is isolated from a Chinese medicinal herb with antioxidant and anti-inflammatory activities. In this study, we investigated the effects of TET on oxygen-glucose-serum deprivation/reoxygenation (OGSD/R)-induced injury in rat spinal cord astrocytes, which mimics hypoxic/ischemic conditions in vivo. MTT and LDH assays indicated that cell viability was distinctly reduced and LDH leakage was elevated after OGSD/R exposure, which were dose-dependently reversed by pretreatment with TET (0.1, 1, 10, 20μM). Western blot analysis showed that OGSD/R exposure resulted in an enhanced expression of Bax and Caspase-3 proteins, and Bcl-2 reduction; whereas these effects were dose-dependently restored by TET pretreatment. TET pretreatment also dose-dependently inhibited the elevated Caspase-3 activity in OGSD/R-treated astrocytes. The oxidative stress status was evaluated using commercial kits, and the results demonstrated that OGSD/R exposure induced obvious oxidative stress, accompanied by elevated levels of reactive oxygen species (ROS) and malondialdehyde (MDA), and reduced superoxide dismutase (SOD) activity, which were dose-dependently restored by TET pretreatment. In addition, TET pretreatment diminished the accumulation of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and interleukin-6 (IL-6) induced by OGSD/R. Moreover, TET pretreatment dose-dependently suppressed Akt phosphorylation and nuclear factor-kappaB (NF-κB) activity augmented by OGSD/R. Similarly, both PI3K inhibitor LY294002 and NF-κB inhibitor PDTC notably attenuated OGSD/R-induced Akt phosphorylation, NF-κB activation, ROS generation, and TNF-α secretion. Taken together, these data demonstrated that TET protected against OGSD/R-induced injury in rat spinal cord astrocytes, which may be attributed to its antioxidant and anti-inflammatory activities via PI3K/AKT/NF-κB signaling pathway.