Genetic Suppression of Akt1 Activity Aggravates Cerebral Ischemia/Reperfusion Injury After Deep Hypothermic Low Flow in Transgenic Mice

Abstract

Objective: We investigated the genetic role of the PI3K/Akt signaling pathway in Akt1^+/− mice after cerebral ischemia/reperfusion injury following post-surgery deep hypothermic low flow.

Methods: 3-week-old Akt1^+/− and wild-type C57/B6 mice were randomly and equally divided into sham-surgery and surgery groups. Surgery group mice were subjected to gradual body temperature reduction and bilateral common carotid artery occlusion for 120 min at 18.5±0.5 °C, followed by artery reopening and rewarming. Occlusion was not performed in sham-surgery group animals. Regional cerebral blood flow was determined by laser Doppler flowmetry. Using reverse transcriptase-PCR, apoptotic assays, immunohistology, and Western blot analyses, we determined the apoptotic level of cerebral cells and the expression of Akt signaling pathway components.

Results: Regional cerebral blood flow was decreased by ≥86% during bilateral common carotid artery occlusion. Akt1^+/− mice experienced showed mortality after 24 h of cerebral I/R, and displayed increased numbers of apoptotic cerebral cells and apoptotic protein expression levels. Western analysis revealed Akt1 hypoactivity, which led to less efficient apoptotic signaling pathway inhibition.

Conclusion: Akt1 suppresses the mitochondrial apoptosis signaling pathway, and Akt1 haplo-insufficiency exacerbates cerebral ischemia/reperfusion after deep hypothermic low flow conditions in mice. Akt may be a potential molecular therapeutic target for brain protection during surgery in congenital heart disease patients.

Key words

deep hypothermic low flow (DHLF) - cerebral protection - PI3K/Akt signaling pathway - Akt1mutant mice

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