Elsevier

Brain Research Bulletin

Volume 147, April 2019, Pages 159-164
Brain Research Bulletin

Research report
SUMOylation participates in induction of ischemic tolerance in mice

https://doi.org/10.1016/j.brainresbull.2019.02.012Get rights and content

Highlights

  • First: SUMO conjugated proteins were mapped firstly in vivo ischemic tolerance model.

  • Second: SUMOylation function in vivo IPC may be different with in vitro.

  • Third:SUMOylation was associated with neuronal apoptosis in IPC.

Abstract

A group of proteins, small ubiquitin-like modifier (SUMO) proteins, has been shown to play a major role in rodent cerebral ischemia. Here, we proved that transient global cerebral ischemia induces a marked increase in protein sumo2/3 conjugation levels, we also find that global sumo2/3 conjugation is involved in ischemic tolerance in mice. Mice preconditioned by sublethal ischemia were less vulnerable to severe ischemia than non-preconditioned mice. Five-minute BCCAO precondition decreased the levels of SUMO2/3-conjugated proteins induced by MCAO. These findings suggest that maintenance of a globally decreased SUMO2/3 (and maybe SUMO-2/3) conjugation level as revealed by immunoblot assays is a component of ischemic tolerance.

Introduction

Ischemic Stroke is a principal cause of death and severe, long-term disability (Zhen et al., 2016; Wang et al., 2017). Although there have been recent progress (Doré and Shafique Ahmad, 2015; Emanuele and Balasubramaniam, 2014; Cruz et al., 2011), further development of cytoprotective treatments for acute ischemic stroke remains an unmet need. The elements accounting for ischemic tolerance are not well understood, although in past researches have confirmed many kinds of constructive mediators (Hirayama and Koizumi, 2017; Lehotský et al., 2016; Sisalli et al., 2015).

Sumoylation is a post-translational modification that modifies the interaction of target proteins with protein partners and thereby alters their subcellular localization, activity, and stability (Wilkinson and Henley, 2010; Guo et al., 2013). A number of studies have shown dramatically increased SUMO-conjugation of proteins in the brain of animal models of cerebral ischemia/stroke (Cimarosti et al., 2008a; Yang et al., 2008a, b). This suggests that protein sumoylation may play a role in determining the fate of post-ischemic neurons. In a rodent model of transient middle cerebral artery occlusion (tMCAO), SUMO2/3-conjugated, but not SUMO1-conjugated proteins, were found to be increased in the hippocampus and cerebral cortex (Yang et al., 2008a, b; Zhang et al., 2016). In animals subjected to permanent and transient focal cerebral ischemia, both SUMO1 and SUMO2/3 conjugations were shown to be activated not only in the infarcted striatum but also in the contralateral striatum (Cimarosti et al., 2008a). A blockade of SUMO2/3 translation in primary cortical neurons enhanced vulnerability to the OGD-induced damage, indicating that SUMO2/3 conjugation may be protective to neuronal injury (Datwyler et al., 2011a).

A subthreshold ischemic insult to the brain induces cellular pathways that can reduce cerebral damage caused by subsequent ischemic insults, known as ischemic preconditioning (IPC) (Meller and Simon, 2013). The IPC phenomenon has contributed to the discovery of various neuroprotective mechanisms. A study (Lee et al., 2009a) shows that global SUMOylation is also involved in ischemic tolerance in primary cortical neuronal cultures (from rats and mice) and SHSY5Y human neuroblastoma cells. Cultured cortical neurons preconditioned by sublethal oxygen/glucose deprivation (OGD) were less vulnerable to severe OGD than non-preconditioned neurons. Preconditioned neurons maintained elevated SUMO-1 conjugation levels (and, to a lesser extent those of SUMO-2/3) on western blots in contrast to non-preconditioned cells. Further, cortical neurons and SHSY5Y cells in which transfected SUMO-1 or SUMO-2 were over-expressed showed increased survival after severe OGD. In contrast, cell cultures subjected to depletion of endogenous SUMO-1 protein by RNAi had reduced survival after exposure to this form of in vitro ischemia and an attenuated protective response to preconditioning. But whether the SUMOylation involving in ischemic tolerance in vivo or not is unclear, Our results show that decreased SUMO2/3 (not SUMO1) conjugation level in ischemic preconditioning mice cortex, which is different from the discover In vitro.

Section snippets

Induction of cerebral IPC and cerebral ischemia

All animal procedures were carried out in accordance with the guidelines for the Care and Use of Laboratory Animals of Shanghai Jiao Tong University School of Medicine and approved by the Institutional Animal Care and Use Committee, all the study protocol adhered to the ARRIVE guidelines. 150 mice (n = 150, C57Bl/6 male, aged 7–8 weeks;) were used, and 25 of them were abandoned because of death or model failure.

C57Bl/6 male WT mice obtained from Department of animal science and technology

Five-minute BCCAO had neuroprotection effect on infarct volumes in mice subjected to 30 min MCAO and 72 h reperfusion

To ensure a similar degree of ischemic insult to the brain, cerebral blood flow was measured for each mouse by laser doppler flowmetry during tMCAO (Fig. 1B). We occluded the bilateral common carotid arteries for 5 min and left middle cerebral artery for different time periods (30 m, 1 h and 2 h) as outlined in Fig. 1A then assessed brain damage by TTC staining 3 d later. A 5 min BCCAO period caused no damage, whereas a 30 min, 1 h and 2 h MCAO (not shown) period caused Different levels of

Discussion

Growing evidence has implicated the importance of sumoylation in regulation of cell signaling, protein stability and apoptosis. However, whether and how sumoylation contributes in induction of ischemic tolerance in vivo remain poorly understood. Here, we use a cerebral ischemia preconditioning model as previous described, we found that five-minute BCCAO had neuroprotection in on mice subjected to 30 min MCAO and 72 h reperfusion, including smaller infarct volume, slighter neurological deficits

Author contributions

H.Z. and Y.Y. designed research; H.Z., D.H., J.Z. and Y.X. performed research; H.Z., H.Z., D.H., J.Z. and Y.X. analyzed data; H.Z wrote the manuscript.

Conflict of interest

The authors declare no conflict of interest.

Acknowledgements

This study was supported by grants from the doctoral research startup fund of Tong Ren Hospital Shanghai Jiaotong University School of Medicine.

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