AbstractBackgroundHyperhomocysteinemia (HHcy), or high levels of homocysteine, is considered a risk factor for vascular disease. Cardiovascular (CV) risk factors, such as HHcy, may lead to exacerbation of cerebral amyloid angiopathy (CAA) due to their detrimental effects on cerebrovascular function. Cerebrovascular function is regulated, in part, by endothelial cells (EC), the most important cellular component of the blood‐brain barrier (BBB). Dysfunctional ECs may lead to deficits in vascular perfusion, clearance, and may eventually result in neuroinflammation, microhemorrhages, and neurodegeneration. EC mitochondria serve as sensors of cellular damage and mediate downstream pathways such as cell death and inflammation. In ECs, mitochondrial dysfunction may lie as the point of convergence of CV risk factors and amyloid β (Aβ)‐induced neurovascular dysfunction. Understanding the mitochondrial deficits elicited by CV risk factors, Aβ, or their combination, may open roads to new therapeutics aimed at preserving mitochondrial function. Indeed, we have previously shown that carbonic anhydrase inhibitors (CAi) reduce amyloid‐induced cell death and mitochondrial dysfunction. Here, we aim to understand the changes occurring in EC mitochondria during Aβ‐ and mixed (Aβ+HHcy)‐ vascular pathologies. In addition, we will assess the therapeutic potential of CAi in such pathologies.MethodHuman brain microvascular ECs were challenged with Aβ, Hcy, or the combination in the presence or absence of CAi. EC barrier properties and changes in mitochondrial function were assessed.ResultThe presence of Aβ or Hcy independently increased BBB permeability, and, when both present, Hcy worsened Aβ‐induced barrier permeability; these effects were prevented by CAi. Preliminary data suggests that the mitochondrial ATP production is impaired in the presence of Aβ40‐E22Q (Dutch mutant) but not in the presence of Hcy. These results may be a reflection of the observed deficits in mitochondrial oxygen consumption rate (OCR).ConclusionThe EC barrier is negatively affected by the presence of Aβ, and Hcy aggravates Aβ‐induced BBB permeability. The presence of Aβ40‐E22Q affects mitochondrial OCR and ATP production, indicative of changes in cellular metabolism and mitochondrial dysfunction. These results suggest a central role of the mitochondria as a mediator of vascular dysfunction in the presence of Aβ.