TIGAR contributes to ischemic tolerance induced by cerebral preconditioning through scavenging of reactive oxygen species and inhibition of apoptosis.

Jun-Hao Zhou,Zheng-Hong Qin,Dan-Dan Song,Yun-Fei Xia,Tong-Tong Zhang,Rui Sheng

doi:10.1038/srep27096

Abstract

Previous study showed that TIGAR (TP53-induced glycolysis and apoptosis regulator) protected ischemic brain injury via enhancing pentose phosphate pathway (PPP) flux and preserving mitochondria function. This study was aimed to study the role of TIGAR in cerebral preconditioning. The ischemic preconditioning (IPC) and isoflurane preconditioning (ISO) models were established in primary cultured cortical neurons and in mice. Both IPC and ISO increased TIGAR expression in cortical neurons. Preconditioning might upregulate TIGAR through SP1 transcription factor. Lentivirus mediated knockdown of TIGAR significantly abolished the ischemic tolerance induced by IPC and ISO. ISO also increased TIGAR in mouse cortex and hippocampus and alleviated subsequent brain ischemia-reperfusion injury, while the ischemic tolerance induced by ISO was eliminated with TIGAR knockdown in mouse brain. ISO increased the production of NADPH and glutathione (GSH), and scavenged reactive oxygen species (ROS), while TIGAR knockdown decreased GSH and NADPH production and increased the level of ROS. Supplementation of ROS scavenger NAC and PPP product NADPH effectively rescue the neuronal injury caused by TIGAR deficiency. Notably, TIGAR knockdown inhibited ISO-induced anti-apoptotic effects in cortical neurons. These results suggest that TIGAR participates in the cerebral preconditioning through reduction of ROS and subsequent cell apoptosis.

Highlights

Neurons are unable to enter glycolysis effectively under stressed conditions, while they may preferentially use glucose through the phosphate pathway (PPP) flux to generate GSH and NADPH and to maintain their antioxidant status[23]
The results showed that TIGAR began to increase 1 h after ischemic preconditioning (IPC) and reached peak at 6 h. (Fig. 1A, P < 0.05, P < 0.001 compared with the control group)
The results showed that LV-shTIGAR abrogated the ischemic tolerance induced by isoflurane preconditioning (ISO) (Fig. 5E, P < 0.001 compared with LV-NC +ISO +oxygen glucose deprivation (OGD)), while supplementation of NAC or NADPH both significantly attenuated the neuronal injury caused by TIGAR knockdown (P < 0.001 compared with LV-shTIGAR +ISO +OGD), indicating that inhibition of PPP flux and reactive oxygen species (ROS) production might contribute to neuronal injury induced by TIGAR knockdown

Summary

Introduction

Neurons are unable to enter glycolysis effectively under stressed conditions, while they may preferentially use glucose through the PPP flux to generate GSH and NADPH and to maintain their antioxidant status[23]. The previous results of our lab showed that TIGAR was rapidly upregulated in neurons in response to ischemia/reperfusion. Overexpression of TIGAR reduced ischemic neuronal injury, whereas TIGAR knockdown aggravated ischemic injury[24]. We hypothesize that TIGAR might be involved in cerebral preconditioning. We established IPC and ISO cerebral preconditioning models in vivo and in vitro. We investigated whether TIGAR is involved in preconditioning- induced ischemic tolerance

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Conclusion