Cerebral blood flow (CBF) reductions in Alzheimer’s disease (AD) patients and related mouse models have been recognized for decades, but the underlying mechanisms and resulting consequences on AD pathogenesis remain poorly understood. In APP/PS1 and 5xFAD mice we found that an increased number of cortical capillaries had stalled blood flow as compared to wildtype animals, largely due to neutrophils that adhered in capillary segments and blocked blood flow. Administration of antibodies against the neutrophil marker Ly6G reduced the number of stalled capillaries, leading to an immediate increase in CBF and to rapidly improved performance in spatial and working memory tasks. This study identified a novel cellular mechanism that explains the majority of the CBF reduction seen in two mouse models of AD and demonstrated that improving CBF rapidly improved short-term memory function. Restoring cerebral perfusion by preventing neutrophil adhesion may provide a novel strategy for improving cognition in AD patients.

Obesity is linked to increased risk for and severity of Alzheimer’s disease (AD). Cerebral blood flow (CBF) reductions are an early feature of AD and are also linked to obesity. We recently showed that non-flowing capillaries, caused by adhered neutrophils, contribute to CBF reduction in mouse models of AD. Because obesity could exacerbate the vascular inflammation likely underlying this neutrophil adhesion, we tested links between obesity and AD by feeding APP/PS1 mice a high fat diet (Hfd) and evaluating behavioral, physiological, and pathological changes. We found trends toward poorer memory performance in APP/PS1 mice fed a Hfd, impaired social interactions with either APP/PS1 genotype or a Hfd, and synergistic impairment of sensory-motor function in APP/PS1 mice fed a Hfd. The Hfd led to increases in amyloid-beta monomers and plaques in APP/PS1 mice, as well as increased brain inflammation. These results agree with previous reports showing obesity exacerbates AD-related pathology and symptoms in mice. We used a crowd-sourced, citizen science approach to analyze imaging data to determine the impact of the APP/PS1 genotype and a Hfd on capillary stalling and CBF. Surprisingly, we did not see an increase in the number of non-flowing capillaries or a worsening of the CBF deficit in APP/PS1 mice fed a Hfd as compared to controls, suggesting that capillary stalling is not a mechanistic link between a Hfd and increased severity of AD in mice. Reducing capillary stalling by blocking neutrophil adhesion improved CBF and short-term memory function in APP/PS1 mice, even when fed a Hfd.

Abstract:The existence of cerebral blood flow (CBF) reductions in Alzheimer's disease (AD) patients and related mouse models has been known for decades, but the underlying mechanisms and the resulting impacts on cognitive function and AD pathogenesis remain poorly understood. In the APP/PS1 mouse model of AD we found that an increased number of cortical capillaries had stalled blood flow as compared to wildtype animals, largely due to leukocytes that adhered in capillary segments and blocked blood flow. These capillary stalls were an early feature of disease development, appearing before amyloid deposits.Administration of antibodies against the neutrophil marker Ly6G reduced the number of stalled capillaries, leading to an immediate increase in CBF and to rapidly improved performance in spatial and working memory tasks. Our work has thus identified a cellular mechanism that explains the majority of the CBF reduction seen in a mouse model of AD and has also demonstrated that improving CBF rapidly improved short-term memory function. Restoring cerebral perfusion by preventing the leukocyte adhesion that plugs capillaries may provide a novel strategy for improving cognition in AD patients.

Despite apparent disagreement in the scholarly literature on standards of pediatric decision making, a recognition that similar norms underpin many of the dominant frameworks motivated a June 2022 symposium “Best Interests and Beyond: Standards of Decision Making in Pediatrics” in St Louis, MO. Over the course of this 3-day symposium, 17 expert scholars (see author list) deliberated on the question “In the context of US pediatric care, what moral precepts ought to guide parents and clinicians in medical decision making for children?” The symposium and subsequent discussion generated 6 consensus recommendations for pediatric decision making, constructed with the primary goals of accessibility, teachability, and feasibility for practicing clinicians, parents, and legal guardians. In this article, we summarize these recommendations, including their justification, limitations, and remaining concerns.

Written in response to what he recognizes as the problematic philosophical underpinnings of “orthodox research ethics,” Alex John London’s For the Common Good reimagines what is called for in any effort to create a better system of oversight and regulation in biomedical research. London weaves a common thread — justice — through this historical and critical account of the practice of research ethics and its organization of stakeholders, institutions and regulations. By introducing the idea of “a common good” London reframes the narrative and responsibilities of the research ethics field to demonstrate that scientific research and regard for the rights and welfare of individuals are not mutually exclusive. This impressive monograph encourages its readers to push past the limitations of traditional research ethics to consider the context in which the discipline is embedded. That is, rather than settling for analysis at the level of researchers and research participants alone, London encourages us to expand our inquiry to encompass a wider array of stakeholders who co-labor in the social undertaking of biomedical knowledge production. London accomplishes the difficult task of upstream analysis — turning his attention to the conditions and assumptions which create ethical dilemmas rather than applying a retrospective ethical salve to injuries near-guaranteed by a broken system. As opposed to the limited domain of orthodox research ethics (researchers, participants, and the institutional bodies which regulate interaction between the two) London also considers the role and contributions of affected communities, pharmaceutical firms, philanthropic organizations, and journal editors among others.