Abstract
This study aimed to estimate the role of phosphatidylethanolamine binding protein 1 (PEBP1) in cerebral ischemia-reperfusion (I/R) injury and the underlying mechanisms. Middle cerebral artery occlusion/reperfusion (MCAO/R) model in adult male Sprague Dawley rats (250–280 g) were established and cultured neurons were exposed to oxygen-glucose deprivation/reoxygenation (OGD/R) to mimic I/R injury in vitro. Expression vectors encoding wild-type PEBP1 and PEBP1 with Ser153Ala mutation (S153A), PEBP1 specific siRNAs, and human recombinant PEBP1 (rhPEBP1) were administered intracerebroventricularly. Endogenous PEBP1 level and its phosphorylation at Ser153 were increased within penumbra tissue and cultured neurons after I/R, accompanied by decreased interaction between PEBP1 and Raf-1. There was a trend toward increased Raf-1/MEK/ERK/NF-κB signaling pathway and phosphatidylcholine-phospholipase C (PC-PLC) activity after I/R, which was enhanced by wild-type PEBP1overexpression and rhPEBP1 treatment and inhibited by PEBP1 (S153A) overexpression. And PEBP1 (S153A) overexpression increased its interaction with Raf-1, reduced infarct size, neuronal death and inflammation, and improved neurological function after I/R, while wild-type PEBP1overexpression exerted opposite effects, suggesting that phosphorylation at Ser153 may exert as a functional switch of PEBP1 by switching PEBP1 from Raf-1 inhibition to PC-PLC activation following I/R. Compared with PEBP1 knockdown, PEBP1 (S153A) overexpression exerted a better rescue effect on I/R injury, which further proved that PEBP1 may be a good protein gone bad with phosphorylation at S153 as a functional switch following I/R. Collectively, our findings suggest that PEBP1 contributed to neuronal death and inflammation after I/R. Selective inhibition of PEBP1 phosphorylation may be a novel approach to ameliorate I/R injury.
Highlights
Stroke is a devastating disease that can cause cognitive and motor dysfunction, and even acute death, and is becoming the leading cause of mortality and morbidity worldwide (Chen et al, 2014; Wang et al, 2016)
The results demonstrated that, compared with the sham group, both the protein level of phosphatidylethanolamine binding protein 1 (PEBP1) and Phosphorylated PEBP1 (p-PEBP1) in the penumbra tissue reached the highest point at 6 h, and rebounded gradually (Figure 2A)
Consistent with the in vivo data, western blot assay showed that the protein levels of PEBP1 and p-PEBP1 in cultured neurons were significantly increased by oxygen-glucose deprivation/reoxygenation (OGD/R) at 2–12 h and peaked at 6 h (Figure 2B)
Summary
Stroke is a devastating disease that can cause cognitive and motor dysfunction, and even acute death, and is becoming the leading cause of mortality and morbidity worldwide (Chen et al, 2014; Wang et al, 2016). As neuronal death starts as early as 5 min after oxygen deprivation (Radermacher et al, 2012), early recanalization is currently the preferred treatment strategy for ischemic stroke (Radermacher et al, 2012; Imam et al, 2016). Bernier and Jolles (1984) first found and isolated a 23 kDa cytosolic protein from bovine brain. Due to its potential of binding to phospholipid, the protein was named as phosphatidylethanolamine binding protein (PEBP) (Bernier et al, 1986). PEBP1 has been found to have crucial roles in neural development and differentiation (Ojika et al, 1992) and participate in many neurological disorders, including Alzheimer’s disease, depression and nervous system tumors (Danzer, 2012; Amemori et al, 2015)
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