tDCS confers neuroprotection by regulating LAT1-isoleucine-CBFB-PTEN
signaling after rat cerebral ischemia-reperfusion injury
Abstract
Background and Purpose: Isoleucine is a branched-chain amino acid
serving as an essential nutrient resource and metabolic. However, its
role in cerebral ischemic stroke remains unknown. Experimental Approach:
Middle cerebral artery occlusion (MCAO) was used to mimic in vivo model
of stroke. Oxygen-glucose deprivation insult (OGD) was used to injure
cultured cortical neurons. High-Performance Liquid Chromatography (HPLC)
was used to measure the level of isoleucine. A western blot assay and
immunofluorescent staining were used to measure the level of CBFB and
PTEN. TTC staining was used to measure the infarct size. Cell death and
viability were assessed by LDH and CCK8 assays. DCS was used to
stimulate cortical neurons. tDCS was used to stimulate the cortex. Key
Results: Extraneuronal isoleucine is decreased and intraneuronal
isoleucine is increased after rat cerebral I/R injury. Reducing
intraneuronal isoleucine via inhibition of its transporter, LAT1
promotes neuronal survival whereas supplementing isoleucine aggravates
neuronal damage. Isoleucine downregulates the expression of CBFB, and
that acts upstream of PTEN to mediate isoleucine-induced neuronal damage
after OGD insult. To identify the therapeutic approach that suppresses
the ischemia-induced increase of intraneuronal isoleucine, we tested the
effect of tDCS on isoleucine. Our data suggest that Cathodal tDCS can
reduce cerebral infarct size. And such neuroprotection is mediated
through reducing LAT1-dependent increase of intraneuronal isoleucine.
Conclusions and Implications: This study identifies LAT1- dependent
increase of intraneuronal isoleucine promotes neuronal death after rat
cerebral I/R injury. Our results indicate that tDCS protects against rat
cerebral I/R injury through regulating LAT1-isoleucine-CBFB-PTEN
signaling.