BACKGROUND AND PURPOSE: Hypoxic preconditioning (PC) confers robust neuroprotection against neonatal hypoxic-ischemic brain injury (H-I), yet the underlying mechanism is poorly understood. In the adult brain, neuronal survival after ischemia is associated with the activation of the phosphatidylinositol 3-kinase (PI3-K)/Akt signaling pathway. Suppression of inflammation is a newly identified direct consequence of PI3-K/Akt signaling. We therefore investigated whether PI3-K/Akt suppresses inflammation and contributes to PC-induced neuroprotection. METHODS: Postnatal day 7 rats were exposed for 3 hours to either ambient air or 8% oxygen, which induces hypoxic PC. H-I was produced 24 hours later by unilateral carotid artery ligation followed by 2.5 hours of hypoxia. Animals were euthanized 0 to 24 hours later for detecting Akt and glycogen synthetase kinase-3beta phosphorylation (p-Akt, p-GSK-3beta), 24 hours later for assessing cytokine expression and inflammatory markers, and 7 days later for measuring brain tissue loss. In addition, LY294002 was injected intracerebroventricularly to inhibit PI3-K/Akt. RESULTS: Brains with H-I without PC showed delayed but sustained reduction in p-Akt. PC restored the levels of p-Akt and the Akt substrate GSK-3beta, reduced proinflammatory markers (NF-kappaB, COX-2, CD68, myeloperoxidase, and microglial activation), and markedly ameliorated H-I-induced brain tissue loss. Inhibition of PI3-K/Akt using LY294002 attenuated PC neuroprotection and promoted the expression of NF-kappaB, COX-2, and CD68. Proteomic microarray analysis revealed that PC inhibited expression of proinflammatory cytokines induced by H-I or a dose of lipopolysaccharide that resulted in minimal tissue damage. CONCLUSIONS: Suppression of inflammatory responses may contribute to PC neuroprotection against neonatal H-I brain injury. This effect is mediated in part via upregulating PI3-K/Akt activity.
BACKGROUND AND PURPOSE: Hypoxic preconditioning (PC) confers robust neuroprotection against neonatal hypoxic-ischemic brain injury (H-I), yet the underlying mechanism is poorly understood. In the adult brain, neuronal survival after ischemia is associated with the activation of the phosphatidylinositol 3-kinase (PI3-K)/Akt signaling pathway. Suppression of inflammation is a newly identified direct consequence of PI3-K/Akt signaling. We therefore investigated whether PI3-K/Akt suppresses inflammation and contributes to PC-induced neuroprotection. METHODS: Postnatal day 7 rats were exposed for 3 hours to either ambient air or 8% oxygen, which induces hypoxic PC. H-I was produced 24 hours later by unilateral carotid artery ligation followed by 2.5 hours of hypoxia. Animals were euthanized 0 to 24 hours later for detecting Akt and glycogen synthetase kinase-3beta phosphorylation (p-Akt, p-GSK-3beta), 24 hours later for assessing cytokine expression and inflammatory markers, and 7 days later for measuring brain tissue loss. In addition, LY294002 was injected intracerebroventricularly to inhibit PI3-K/Akt. RESULTS: Brains with H-I without PC showed delayed but sustained reduction in p-Akt. PC restored the levels of p-Akt and the Akt substrate GSK-3beta, reduced proinflammatory markers (NF-kappaB, COX-2, CD68, myeloperoxidase, and microglial activation), and markedly ameliorated H-I-induced brain tissue loss. Inhibition of PI3-K/Akt using LY294002 attenuated PC neuroprotection and promoted the expression of NF-kappaB, COX-2, and CD68. Proteomic microarray analysis revealed that PC inhibited expression of proinflammatory cytokines induced by H-I or a dose of lipopolysaccharide that resulted in minimal tissue damage. CONCLUSIONS: Suppression of inflammatory responses may contribute to PC neuroprotection against neonatal H-I brain injury. This effect is mediated in part via upregulating PI3-K/Akt activity.
Authors: Ying H Shen; Lin Zhang; Pingping Ren; Mary T Nguyen; Sili Zou; Darrell Wu; Xing Li Wang; Joseph S Coselli; Scott A LeMaire Journal: Circ Res Date: 2012-12-18 Impact factor: 17.367
Authors: Lisa C Hoyte; Keith J Brooks; Simon Nagel; Asim Akhtar; Ruoli Chen; Sylvie Mardiguian; Martina A McAteer; Daniel C Anthony; Robin P Choudhury; Alastair M Buchan; Nicola R Sibson Journal: J Cereb Blood Flow Metab Date: 2010-01-20 Impact factor: 6.200