Neuroprotective effect of meglumine cyclic adenylate against ischemia/reperfusion injury via STAT3-Ser727 phosphorylation

Abstract

Objectives: Ischemia/reperfusion can induce neuronal apoptosis in the brain and lead to function deficits. The activation of cyclic adenosine monophosphate (cAMP)-dependent protein kinase (PKA) is neuroprotective against transient cerebral ischemia. The neuroprotective mechanisms of PKA mainly involve the regulation of gene transcription via the PKA/CREB pathway. The present study aims to investigate the neuroprotective effect of meglumine cyclic adenylate, an activator of PKA, under a rat model of global cerebral ischemia/reperfusion and to reveal the underlying mechanism involving signal transducer and activator of transcription 3 (STAT3)-Ser727 phosphorylation and mitochondrion modulation.

Materials and methods: Male Sprague-Dawley rats were subjected to 15 min global cerebral ischemia, and meglumine cyclic adenylate was treated through tail intravenous injection 30 min before ischemia. Cresyl violet staining was used to evaluate neuron injury at 5 d of reperfusion. Western blotting was used to detect p-Ser⁷²⁷-STAT3, total STAT3, cytochrome c (Cyt c) and active caspase-3 in the tissues of hippocampal CA1 region at 6 h of reperfusion. STAT3-S727A was overexpressed in HT22 cells to reveal the significance of STAT3-Ser727 phosphorylation in the neuroprotective effect of meglumine cyclic adenylate.

Results: Pretreatment with meglumine cyclic adenylate not only significantly ameliorated neuron loss in CA1 region after global cerebral ischemia but also enhanced STAT3-Ser727 phosphorylation, increased mitochondrial STAT3, and decreased cytosolic Cyt c and active caspase-3. Overexpression of STAT3-S727A in HT22 cells eliminated meglumine cyclic adenylate-induced increase of p-Ser⁷²⁷-STAT3, mitochondrial STAT3, cytosolic Cyt c and active caspase-3.

Conclusion: Meglumine cyclic adenylate protects neurons against ischemia/reperfusion injury via promoting p-Ser⁷²⁷-STAT3-associated mitochondrion modulation and inhibiting apoptosis pathway.

Keywords: Brain ischemia; Meglumine cyclic adenylate; Mitochondrion; PKA; Phosphorylation; STAT3.