Transient increases in intracellular Ca2+ activate endothelium-dependent vasodilatory pathways. This process is impaired in cerebral amyloid angiopathy, where amyloid- β(1-40) accumulates around blood vessels. In neurons, amyloid- β impairs the Ca2+-permeable N-methyl-D-aspartate receptor (NMDAR), a mediator of endothelium-dependent dilation in arteries. We hypothesized that amyloid- β(1-40) reduces NMDAR-elicited Ca2+ signals in mouse cerebral artery endothelial cells, blunting dilation. Cerebral arteries isolated from 4-5 months-old, male and female cdh5:Gcamp8 mice were used for imaging of unitary Ca2+ influx through NMDAR ( NMDAR sparklets) and intracellular Ca2+ transients. The NMDAR agonist NMDA (10 µmol/L) increased frequency of NMDAR sparklets and intracellular Ca2+ transients in endothelial cells; these effects were prevented by NMDAR antagonists D-AP5 and MK-801. Next, we tested if amyloid- β(1-40) impairs NMDAR-elicited Ca2+ transients. Cerebral arteries incubated with amyloid- β(1-40) (5 µmol/L) exhibited reduced NMDAR sparklets and intracellular Ca2+ transients. Lastly, we observed that NMDA-induced dilation of pial arteries is reduced by acute intraluminal amyloid- β(1-40), as well as in a mouse model of Alzheimer’s disease, the 5x-FAD, linked to downregulation of Grin1 mRNA compared to wild-type littermates. These data suggest that endothelial NMDAR mediate dilation via Ca2+-dependent pathways, a process disrupted by amyloid- β(1-40) and impaired in 5x-FAD mice.

Chronic calorie restriction (CR) results in lengthened lifespan and reduced disease risk. Many previous studies have implemented 30–40% calorie restriction to investigate these benefits. The goal of our study was to investigate the effects of calorie restriction, beginning at 4 months of age, on metabolic and physical changes induced by aging. Male C57BL/6NCrl calorie restricted and ad libitum fed control mice were obtained from the National Institute on Aging (NIA) and studied at 10, 18, 26, and 28 months of age to better understand the metabolic changes that occur in response to CR in middle age and advanced age. Food intake was measured in ad libitum fed controls to assess the true degree of CR (15%) in these mice. We found that 15% CR decreased body mass and liver triglyceride content, improved oral glucose clearance, and increased all limb grip strength in 10- and 18-month-old mice. Glucose clearance in ad libitum fed 26- and 28-month-old mice is enhanced relative to younger mice but was not further improved by CR. CR decreased basal insulin concentrations in all age groups and improved insulin sensitivity and rotarod time to fall in 28-month-old mice. The results of our study demonstrate that even a modest reduction (15%) in caloric intake may improve metabolic and physical health. Thus, moderate calorie restriction may be a dietary intervention to promote healthy aging with improved likelihood for adherence in human populations.

Introduction: Cerebral amyloid angiopathy (CAA), the accumulation of amyloid- β (1-40) (A β ) around cerebral arteries, impairs endothelial function. Endothelium-dependent dilation is a consequence of transient increases in intracellular [Ca 2+ ] in endothelial cells (EC). The Ca 2+ permeable N-methyl-D-aspartate receptor (NMDAR) mediates endothelium-dependent dilation, although if these effects are dependent on Ca 2+ influx and transients, or if they are impaired by A β , remains undetermined. Hypothesis: A β inhibits endothelial NMDAR-mediated Ca 2+ influx and transients in murine pial arteries. Methods: We performed Ca 2+ time-lapse imaging of en face pial arteries from cdh5-GCaMP8 mice to quantify EC Ca 2+ events induced by NMDAR activation. Data are means ± SEM. Results: Elemental Ca 2+ entry through NMDAR, hereon called NMDAR sparklets , was assessed in arteries incubated with EGTA-AM and cyclopiazonic acid (CPA) to inhibit intracellular Ca 2+ transients. NMDA (10 μM) induced an increase in NMDAR sparklets frequency when compared to vehicle, an effect inhibited by the NMDAR antagonist D-APV (in Hz: 0.12±0.01 vs 0.44±0.05 vs 0.21±0.02, vehicle vs NMDA vs NMDA+D-APV, p<0.05). Further, pial arteries exposed to NMDA without EGTA-AM and CPA showed an increase in the frequency of intracellular Ca 2+ transients, also blocked by D-APV (in Hz: 0.24±0.05 vs 0.53±0.10 vs 0.28±0.05, vehicle vs NMDA vs NMDA+D-APV, p<0.05). We then tested the effects of A β on Ca 2+ events in pial artery EC. We observed that 30 minutes exposure to A β (5 μM) caused a significant reduction in NMDAR sparklets (in Hz: 0.62±0.07 vs 0.22±0.03, NMDA vs NMDA + A β , p<0.05) but did not significantly alter intracellular Ca 2+ transients (in Hz: 0.62±0.37 vs 0.27±0.07, NMDA vs NMDA + A β ). Lastly, we performed pressure myography on pial arteries of wild-type and 5x-FAD mice, a model of familial Alzheimer’s disease with rapid amyloid accumulation. 5x-FAD mice displayed impaired vasodilation to NMDA (vasodilation (%): 9.86±0.64 vs 4.22±2.76, wild-type vs 5x-FAD , p<0.05). Conclusion: These preliminary data suggest that A β impairs endothelial NMDAR-associated Ca 2+ influx events in cerebral arteries, which can impair blood flow in CAA patients, thus contributing to cognitive impairment.

Background and Purpose Cerebrovascular dynamics and pathomechanisms that evolve in the minutes and hours following traumatic vascular injury in the brain remain largely unknown. We investigated the pathophysiology evolution in mice within the first 3 hours after closed‐head traumatic brain injury (TBI) and subarachnoid hemorrhage (SAH), two significant traumatic vascular injuries. Methods We took a multimodal imaging approach using photoacoustic imaging, color Doppler ultrasound, and MRI to track injury outcomes using a variety of metrics. Results Brain oxygenation and velocity‐weighted volume of blood flow (VVF) values significantly decreased from baseline to 15 minutes after both TBI and SAH. TBI resulted in 19.2% and 41.0% ipsilateral oxygenation and VVF reductions 15 minutes postinjury, while SAH resulted in 43.9% and 85.0% ipsilateral oxygenation and VVF reduction (p < .001). We found partial recovery of oxygenation from 15 minutes to 3 hours after injury for TBI but not SAH. Hemorrhage, edema, reduced perfusion, and altered diffusivity were evident from MRI scans acquired 90‐150 minutes after injury in both injury models, although the spatial distribution was mostly focal for TBI and diffuse for SAH. Conclusions The results reveal that the cerebral oxygenation deficits immediately following injuries are reversible for TBI and irreversible for SAH. Our findings can inform future studies on mitigating these early responses to improve long‐term recovery.

Endothelium‐dependent dilation of cerebral arteries, a process dependent on transient increases in intracellular calcium, contributes to neurovascular coupling (NVC), which is altered in cerebral amyloid angiopathy (CAA).The N‐methyl‐D‐aspartate receptor (NMDAR), a nonselective cation channel with high Ca2+ permeability, has been shown to mediate endothelium‐dependent dilation in cerebral arteries. NMDAR activity is reduced by amyloid‐β, which accumulates around the cerebral vasculature during CAA. We hypothesized that amyloid‐β impairs NMDAR‐induced Ca2+ transients in endothelial cells of cerebral arteries, which impairs endothelium‐mediated dilation in mice. All animal experiments were approved by the University of Arizona IACUC. Data are means ± SEM, both in male and female mice (no sex differences were observed). Cerebral arteries isolated from mice expressing the genetically‐encoded calcium indicator GCaMP8 in endothelial cells (cdh5:Gcamp8) were prepared en face for time‐lapse imaging of endothelial Ca2+ transients induced by NMDAR activation. In fields of view that displayed Ca2+ transients, we found that the NMDAR agonist NMDA (1 μM) increased the frequency of endothelial Ca2+ transients compared to baseline (0.22 ± 0.06 vs 0.58 ± 0.15 Hz, baseline vs NMDA, n = 10 and 13 fields of view from at least 3 mice, p < 0.05, one way ANOVA). Pre‐incubation (5 minutes) of preparations with the NMDAR antagonist D‐AP5 (10 μM) prevented NMDA induction of endothelial cell Ca2+ transients (frequency: 0.14 ± 0.05, n = 10 fields of view, p < 0.05 vs NMDA, one‐way ANOVA). These data suggest that endothelial NMDAR Ca2+ transients can be stimulated in cerebral arteries via NMDA. We then tested whether the peptide amyloid‐β(1‐42), commonly found in CAA, blunted NMDAR‐elicited Ca2+ transients. Cerebral artery preparations were incubated for 30 minutes with 5 μM amyloid‐β(1‐42), then exposed to NMDA. Our preliminary data suggests that pre‐incubation of preparations with amyloid‐β blunts NMDA‐dependent induction of endothelial cell Ca2+ transients (0.21 ± 0.04, n = 10 fields of view, p < 0.05 vs NMDA, one‐way ANOVA). In order to evaluate the effects of amyloid‐β on dilation of cerebral arterioles, we then performed ex vivo pressure myography experiments with cerebral parenchymal arterioles from a mouse model of familial Alzheimer’s disease without aging (5x‐FAD) or wildtype littermates. Our preliminary results suggest that NMDA‐elicited dilation of parenchymal arterioles may be impaired in 5x‐FAD mice (30 μM NMDA, vasodilation (%): 11.06 ± 0.78 vs 6.21 ± 2.09, wildtype vs 5x‐FAD, n = 3 arterioles from 3 mice, p = 0.067, two‐tailed Student’s t‐test). These preliminary data suggest that NMDA receptors in the cerebrovascular endothelium of wildtype mice mediate arteriolar dilation via an increase in Ca2+ transients. Further, amyloid‐β may impair the activity of endothelial NMDA receptors and thus contribute to neurovascular dysfunction via impaired arteriolar dilation in individuals with CAA. Support or Funding Information National...