In Alzheimer disease, the most common age-related form of dementia, brain blood supply is severely compromised. Cerebrovascular blood clot formation and activation of inflammatory cells represent a major threat to healthy levels of blood flow in the brain. However, how aging and cerebrovascular inflammation are linked is still largely unexplored. Ongoing research as part of our NINDS R35 funding addresses this connection. Formation of blood clots can disrupt brain homeostatic blood flow. Paradoxically, these clots may be promoted by a proximate immunological feedback, such as by immune cell hyperactivation. Understanding the effect of aging on blood clot formation necessitates the ability to monitor the spatial and temporal dynamics of vascular inflammation in real time. Toward this goal, we developed a means to target a microscopic lesion to the wall of a selected microvessel using amplified ultrashort pulsed laser light (Nishimura et al., Nature Methods 2006). This procedure encompasses state-of-the-art in vivo two-photon imaging, including the use of adaptive optics for unprecedented deep imaging (Liu et al Nature Methods 2019), to measure cerebral blood flow and immune cell trafficking in the vicinity of a minimal, laser injury by delivering amplified laser pulses with energies of 1 to 10 J at the site of injury. We are currently the pulsed laser technique to investigate the effect of hyperglycemia on the immediate and early inflammatory response to vascular injury (Shaked et al. SfN abstract 2018). We make use of three mouse models. The first is Streptozotocin (STZ)-induced type 1 diabetes mellitus. The second makes use of leptin-receptor knock-out mice, i.e., obese DB/DB mice; this addresses type 2 diabetes. In both cases we find that diabetes leads to a heightened sensitivity to vascular damage. Alzheimer's disease mice form a third model, so called type 3 diabetes. In a pilot study with 5XFAD mice, which display severe amyloid pathology, we confirm that 5XFAD mice display a heightened glucose intolerance and, in new data, find that cortical vessels in these animals have a significantly heighted response to weak injury. The current amplifier for laser injury is 12 years old, past the end of it's lifetime, and degrading rapidly. Further, it is no loner maintained by the company. I am requesting administrative funds for a replacement, a Coherent Astrella. The funding will be shared by the NIH ($100K request) and the Physical Sciences Division (letter of commitment attached). This funding will allow us to continue our studies, including those related to Alzheimer disease.
The patency of blood vessels may be judged by their response to focal injury; we designed and implemented such a procedure to assess single vessels deep in cortex In conjunction with measures of blood flow and neuroimmunological responses. We find that hypoglycemia in normal and diabetic mice, including vessels compromised by severe amyloid pathology, leads to a heightened sensitivity to vascular damage that can be ameliorated by pharmacological agents. This request for an administrative supplement serves to replace aged and failing equipment that is necessary for the continuation of these and related studies supported by our R35 grant.
