The Endogenous Level Of TIGAR In Brain Is Associated With The Vulnerability Of Neurons To Ischemic Injury

Aim: To investigate the developmental changes of TIGAR protein level in neurons and the correlation of TIGAR expression and vulnerability of neurons to ischemic injury.Methods: The expression of TIGAR in different regions and ages of the mice brains was analyzed with western blot and immunofluorescence. The subcelluar localization of TIGAR in neurons was examined with electron microscopy. TTC(2,3,5-Triphenyltetrazolium chloride) staining was used to evaluate the infarct volume of the mouse brain 24 h after t MCAO. Neurological score and survival rate was used to assess the vulnerability of mice to ischemia insut. The expression level change of TIGAR in cultured neurons from different embryonic day mice after OGD/reperfusion or H2O2 treatment was also analyzed with western blot. The neuronal cells viability was examined with CCK 8. DHE staining was used for ROS production assessment. DNA and mitochondrial insult was analyzed with western blot and immunofluorenscence.Results: In this study, we found that TIGAR was widely expressed in all brain regions with relative high levels in the cortex,olfactory bulb, cerebellum and hippocampus.At cellular level, TIGAR was predominantly localized in the cytoplasm, but was also present in the mitochondria, endoplasmic reticulum(ER). The expression of TIGAR was high in the prenatal day 10-20, declined in the postanal day 1 but slightly recovered in early postnatal days, then remained at the low levels in adulthood. TIGAR expression was increased in response to OGD/reoxygenation insult in cultured primary neurons of different embryonic periods(E 12, E 16, E 20). H2O2 could also induce the expression of TIGAR in the neurons of different embryonic periods. The primary neurons from early embryonic period had a lower death rate under oxidative stress. The expression of TIGAR was also increased in mouse brain after ischemia/reperfusion 4, 8, 12 weeks after birth. The increase in mitochondria localization of TIGAR was found in response to ischemia/reperfusion insult. Four-week-old mice had smaller infarct volume, lower neurological score and death rate after t MCAO compared with the 8-weeks-old and 12-week-old mice. The youngermice and primary neurons had a higher activity of pentose phosphate pathway than the elder ones, while the elder mice and primary neurons had a severer DNA and mitochondrial damage than the younger ones.Conclusions: TIGAR had a higher expression in the early embryonic period and young adult mice and increased after OGD/reoxygenation or t MCAO/reperfusion. These results demonstrate that expression level of TIGAR is correlated to the vulnerability of neurons to ischemic injury, suggesting that TIGAR plays an important role in regulating vulnerability of neurons to ischemic injury.