Calcium/calmodulin-dependent protein kinase kinase is neuroprotective in stroke in aged mice

Stroke is a devastating neurological disease and the leading cause of long-term disability, particularly in the elderly. Calcium/calmodulin-dependent protein kinase kinase (CaMKK ) is a major kinase activated by elevated levels of intracellular calcium. Our previous findings in young mice have suggested that CaMKK is neuroprotective as KO mice had worse stroke outcomes. Because age is an important determinant of stroke outcome, we evaluated the functional role of CaMKK in stroke in aged mice. We used middle cerebral artery occlusion to induce stroke in aged wild-type (WT) and CaMKK KO male mice. Lentiviral vectors carrying CaMKK (LV-CaMKK ) were used to overexpress CaMKK in the mouse brain. Baseline levels of CaMKK in the aged brain were significantly lower than those in young mice. LV-CaMKK treatment reduced infarcts and neurological deficits assessed 3days after stroke. In chronic survival experiments, CaMKK KO mice showed increased tissue loss in the ipsilateral hemisphere 3weeks after stroke. In addition, KO mice showed poorer functional recovery during the 3-week survival period, as measured by the rotarod test, corner test, locomotor activity assay, and novel object recognition test, compared with WT controls. The loss of blood-brain barrier proteins, inactivation of survival gene expression such as B-cell lymphoma 2 (Bcl-2) and an increase in inflammatory cytokines in the serum were observed after stroke with CaMKK inhibition. We demonstrate that CaMKK is neuroprotective in stroke in aged mice. Therefore, our data suggest that CaMKK may be a potential target for reducing long-term disability after stroke.