Abstract 29: Calcium/calmodulin-dependent Protein Kinase Kinase β (CaMKK β) is Neuroprotective in Stroke in Aged Mice

Abstract

Background: CaMKK β is a major kinase activated by elevated levels of intracellular calcium. Our previous data has suggested that CaMKK β is neuroprotective after stroke in young mice as inhibition of this kinase aggravated stroke outcome. As aging is an important determinant of stroke outcomes, here we evaluated the functional role of CaMKK β in stroke in aged mice. Methods: Aged wild type (WT) males received intracerebral injections of lentiviral vectors carrying either CaMKK β (LV-CaMKK β) or GFP (LV-GFP) 7 days before middle cerebral artery occlusion (MCAO, 90 minutes). Acute infarcts and neurological deficits scores were then analyzed at 72 hours post MCAO. In chronic survival studies, aged male CaMKK β knockout (KO) and WT mice were subjected to 60 minutes MCAO. Following stroke, long-term behavioral assessments were continuously performed for 3 weeks in KO and WT mice until the sacrifice for tissue loss assessments. Results: Baseline levels of CaMKK β in aged brain were significantly lower when compared to that in young mice measured by Western Blots (Aged WT 0.66±0.06 vs. Young WT 1.00±0.05, n=3 p/g, p<0.05). Administration of LV-CaMKK β to WT mice increased levels of this protein in brain (LV-CaMKK β 1.65±0.11 vs. LV-GFP control 1.07±0.05, n=3 p/g, p<0.05). Further, LV-CaMKK β treatment reduced infarcts assessed 3 days after stroke (total: LV-CaMKK β 16.76± 3.16% vs. LV-GFP control 26.43±4.30%, n=7 p/g, p<0.05) and neurological deficits [LV-CaMKK β 1(1) vs. LV-GFP 2(1), median (interquartile range), n=7 p/g, p<0.05]. In chronic survival experiments, CaMKK β KO mice showed increased tissue loss in ipsilateral hemispheres measured at 3 weeks after stroke (tissue loss: Aged KO 20.59±1.90% vs. Aged WT 11.89±1.00%, n=6 KO, 7 WT, p<0.05). Additionally, KO mice had worsened functional recovery when compared to WT controls during 3 weeks survival measured by rotarod test, locomotor activity in an open field, and in the novel object recognition test. Conclusions: Our studies demonstrated that CaMKK β is neuroprotective in stroke in the aged. As the elderly population has worse functional recovery after stroke, our data suggested that this protein may be a potential target for reducing long term disability of stroke patients.