DeRosa, N. | bioRxiv Science

bioRxiv2026

mTOR drives cerebrovascular dysfunction and blood-brain barrier breakdown in a model of Alzheimers disease with cerebral amyloid angiopathy

Cerebral amyloid angiopathy (CAA) is characterized by the deposition of amyloid {beta} fibrils (A{beta}) within walls of the cerebrovasculature and contributes to intracerebral hemorrhage, ischemic stroke, and cognitive dysfunction in patients with Alzheimers disease (AD) and in non-pathological aging. Previous studies have shown that mTOR drives cerebrovascular dysfunction and cognitive impairment observed in AD, vascular cognitive impairment, and normative aging. However, the mechanisms by which mTOR contributes to CAA are unknown. Here, we show that mTOR drives the accumulation of fibrillar vascular A{beta} lesions in the Tg2576 Model of AD with CAA (using equal numbers of female and male mice), which directly impair endothelium-dependent cerebrovascular reactivity. Additionally, we found that blood-brain barrier (BBB) breakdown and remodeling of tight junction proteins, dependent on mTOR, are associated with increased cerebral microhemorrhages. Finally, we show that mTOR contributes to neurovascular uncoupling in Tg2576 AD mice through nNOS dysfunction and inhibition of non-nitric oxide synthase-dependent contributions to neurovascular coupling (NVC). Contextual memory impairments were ameliorated by the mTOR inhibitor rapamycin. Improvements in memory were associated with reduced cerebrovascular A{beta} fibril accumulation, enhanced endothelium-dependent vasodilation, reduced fibrillar A{beta} load, restoration of BBB integrity, attenuation of intracerebral microhemorrhage, and restoration of NVC. These data indicate that mTOR drives vascular accumulation of fibrillar A{beta}, including those associated with brain vasculature, and mediates cerebrovascular dysfunction in a model of AD with CAA. Thus, mTOR inhibitors represent a promising treatment option for patients with CAA and AD.

neuroscience↗

bioRxiv2022

Adenosine A1R/A3R Agonist AST-004 Reduces Brain Infarction in Mouse and Rat Models of Acute Ischemic Stroke

Acute ischemic stroke (AIS) is the second leading cause of death globally. No Food and Drug Administration (FDA) approved therapies exist targeting cerebroprotection following stroke. Our group recently reported significant cerebroprotection with the adenosine A1/A3 receptor agonist, AST-004, in a transient stroke model in non-human primates (NHP) and in a preclinical mouse model of traumatic brain injury (TBI). However, the specific receptor pathway activated was only inferred based on in vitro binding studies. The current study investigated the underlying mechanism of AST-004 cerebroprotection in two independent models of AIS: permanent photothrombotic stroke in mice and transient middle cerebral artery occlusion (MCAO) in rats. AST-004 treatments across a range of doses were cerebroprotective and efficacy could be blocked by A3R antagonism, indicating a mechanism of action that does not require A1R agonism. The high affinity A3R agonist MRS5698 was also cerebroprotective following stroke, but not the A3R agonist Cl-IB-MECA under our experimental conditions. AST-004 efficacy was blocked by the astrocyte specific mitochondrial toxin fluoroacetate, confirming an underlying mechanism of cerebroprotection dependent on astrocyte mitochondrial metabolism. An increase in A3R mRNA levels following stroke suggested an intrinsic cerebroprotective response that was mediated by A3R signaling. Together, these studies confirm certain A3R agonists, such as AST-004, are promising new therapeutics for the treatment of AIS.

neuroscience↗