Ischemic stroke causes a lack of
oxygen and
glucose supply to brain, eventually leads to severe
neurological disorders.
Retinoic acid is a major metabolic product of
vitamin A and has various biological effects. The PI3K-Akt signaling pathway is an important survival pathway in brain. Phosphorylated Akt is important in regulating survival and apoptosis. We examined whether
retinoic acid has
neuroprotective effects in
stroke model by regulating Akt and its downstream
protein, Bad. Moreover, we investigated the relationship between
retinoic acid and Bcl-2 family
protein interactions. Animals were intraperitoneally administered vehicle or
retinoic acid (5 mg/kg) for four days before surgery and
ischemic stroke was induced by
middle cerebral artery occlusion (MCAO) surgery. Neurobehavioral tests were performed 24 h after MCAO and cerebral cortical tissues were collected.
Cresyl violet staining and TUNEL histochemistry were performed, Western blot and immunoprecipitation analysis were performed to elucidate the expression of various
proteins.
Retinoic acid reduced neurological deficits and histopathological changes, decreased the number of TUNEL-positive cells, and alleviated reduction of phospho-PDK1, phospho-Akt, and phospho-Bad expression caused by MCAO damage. Immunoprecipitation analysis showed that MCAO damage reduced the interaction between phospho-Bad and 14-3-3, which was attenuated by
retinoic acid. Furthermore,
retinoic acid mitigated the increase in Bcl-2/Bad and Bcl-xL/Bad binding levels and the reduction in Bcl-2/Bax and Bcl-xL/Bax binding levels caused by MCAO damage.
Retinoic acid alleviated MCAO-induced increase of
caspase-3 and cleaved
caspase-3 expression. We demonstrate that
retinoic acid prevented apoptosis against
cerebral ischemia through phosphorylation of Akt and Bad, maintenance of phospho-Bad and 14-3-3 binding, and regulation of Bcl-2 family
protein interactions. .