Inhibition of calcium/calmodulin‐dependent protein kinase kinase (CaMKK) exacerbates impairment of endothelial cell and blood–brain barrier after stroke. (29th November 2018)

• Record Type: Journal Article
• Authors: Sun, Ping; Bu, Fan; Min, Jia‐Wei; Munshi, Yashasvee; Howe, Matthew D.; Liu, Lin; Koellhoffer, Edward C.; Qi, Li; McCullough, Louise D.; Li, Jun
• Is Part Of: European journal of neuroscience. Volume 49:Number 1(2019)
• Page Start: 27
• Page End: 39
• Publication Date: 2018-11-29
• Subjects: blood–brain barrier -- calcium/calmodulin‐dependent protein kinase kinase -- endothelial cells -- sirtuin 1 -- stroke; Nervous system -- Periodicals; 612.8
• DOI: 10.1111/ejn.14223
• Languages: English
• ISSNs: 0953-816X

Abstract

Abstract: Brain microvascular endothelial cells play an essential role in maintaining blood–brain barrier (BBB) integrity, and disruption of the BBB aggravates the ischemic injury. CaMKK (α and β) is a major kinase activated by elevated intracellular calcium. Previously, we demonstrated that inhibition of CaMKK exacerbated outcomes, conversely, overexpression reduced brain injury after stroke in mice. Interestingly, CaMKK has been shown to activate a key endothelial protector, sirtuin 1 (SIRT1). We hypothesized that CaMKK protects brain endothelial cells via SIRT1 activation after stroke. In this study, Oxygen‐Glucose Deprivation (OGD) was performed in human brain microvascular endothelial cells. Stroke was induced by middle cerebral artery occlusion (MCAO) in male mice. Knockdown of CaMKK β using siRNA increased cell death following OGD. Inhibition of CaMKK β by STO‐609 significantly and selectively down‐regulated levels of phosphorylated SIRT1 after OGD. Changes in the downstream targets of SIRT1 were observed following STO‐609 treatment. The effect of STO‐609 on cell viability after OGD was absent, when SIRT1 was concurrently inhibited. We also demonstrated that STO‐609 increased endothelial expression of the pro‐inflammatory proteins ICAM‐1 and VCAM‐1 and inhibition of CaMKK exacerbated OGD‐induced leukocyte‐endothelial adhesion. Finally, intracerebroventricular injection of STO‐609 exacerbated endothelial apoptosis and reduced BBB integrity after 24‐hr reperfusion following MCAO in vivo. Collectively, these results demonstrated that CaMKK inhibition reduced endothelial cell viability, exacerbated inflammatory responses and aggravated BBB impairment after ischemia. CaMKK activation may attenuate ischemic brain injury via protection of the microvascular system and a reduction in the infiltration of pro‐inflammatory factors. Abstract : In brain endothelial cells after stroke, CaMKK β activates SIRT1 by phosphorylation, which subsequently produces anti‐oxidative effect and enhances eNOS signaling. eNOS signaling then produces pleiotropic effects including endothelial cell protection and inhibiting inflammation by reducing VCAM‐1, ICAM‐1, E‐selectins, and leukocytes extravasation. STO‐609 and EX‐527 are pharmacological inhibitors of CaMKK and SIRT1, respectively.