Tetracycline Inhibits Local Inflammation Induced by Cerebral Ischemia via Modulating Autophagy

BACKGROUND: Tetracycline exerts neuroprotection via suppressing the local inflammation induced by cerebral ischemia. However, the underlying mechanism is not completely clear. METHODOLOGY/PRINCIPAL FINDINGS: The mRNA and protein expressions of tumor necrosis factor α and interleukin 6 and the number of activated microglia were measured to detect the inflammatory process in the ischemic hemisphere. The key proteins of nuclear factor kappa B pathway and the binding activity of nuclear factor kappa B were also measured. Two key components of autophagy, Beclin 1 and LC3, were detected by western blotting. Pretreatment with tetracycline inhibited the mRNA and protein expressions of tumor necrosis factor α and interleukin 6 and decreased the numbers of activated and phagocytotic microglia. Tetracycline down regulated the total and phosphorylated expressions of IKK, IκB and p65 (P<0.05). The autophagy inhibitor, 3-methyladenine, inhibited inflammation and activation of nuclear factor kappa B pathway. The levels of Beclin 1 and LC3 were decreased by 3-methyladenine and tetracycline. CONCLUSIONS/SIGNIFICANCE: Our data suggested that pretreatment of tetracycline may inhibit autophagy in the ischemic stroke brain and then suppress the inflammatory process via inhibiting the activation of nuclear factor kappa B pathway.