Inhibition of Calcium/Calmodulin-Dependent Protein Kinase Kinase β and Calcium/Calmodulin-Dependent Protein Kinase IV Is Detrimental in Cerebral Ischemia

Abstract

Background and Purpose— Elevation of intracellular calcium was traditionally thought to be detrimental in stroke pathology. However, clinical trials testing treatments that block calcium signaling have failed to improve outcomes in ischemic stroke. Emerging data suggest that calcium may also trigger endogenous protective pathways after stroke. Calcium/calmodulin-dependent protein kinase kinase (CaMKK) is a major kinase activated by rising intracellular calcium. Compelling evidence has suggested that CaMKK and its downstream kinase CaMK IV are critical in neuronal survival when cells are under ischemic stress. We examined the functional role of CaMKK/CaMK IV signaling in stroke. Methods— We used a middle cerebral artery occlusion model in mice. Results— Our data demonstrated that pharmacological and genetic inhibition of CaMKK aggravated stroke injury. Additionally, deletion of CaMKK β, one of the 2 CaMKK isoforms, reduced CaMK IV activation, and CaMK IV deletion in mice worsened stroke outcome. Finally, CaMKK β or CaMK IV knockout mice had exacerbated blood–brain barrier disruption evidenced by increased hemorrhagic transformation and activation of matrix metalloproteinase. We observed transcriptional inactivation including reduced levels of histone deacetylase 4 phosphorylation in mice with CaMKK β or CaMK IV deletion after stroke. Conclusions— Our data have established that the CaMKK/CaMK IV pathway is a key endogenous protective mechanism in ischemia. Our results suggest that this pathway serves as an important regulator of blood–brain barrier integrity and transcriptional activation of neuroprotective molecules in stroke.