A Study of the Vascular Basis of Alzheimer’s Disease: The Role of Beta Amyloid (Aβ) Proteins and Saturated Fatty Acids in Endothelial Dysfunction and Inflammation

Abstract

Background: Studies have shown that Alzheimer’s Disease (AD) is strongly associated with the presence of atherosclerosis risk factors, including hyperlipidemia (and associated increased free fatty acids), hypertension and diabetes. We tested the hypotheses that β‐ amyloid proteins (Aβ) or palmitic acid (PA), a saturated fatty acid and known atherosclerotic risk factor, cause impaired function and viability of human umbilical vein endothelial cells (HUVEC), and that together, they exert synergistic effects on HUVEC dysfunction. Methods: HUVEC were exposed for 18‐20 hours to vehicle, Aβ42 (2μM) ± PA (150μM) or PA (150μM) while some HUVEC were exposed to a 4‐hour pre‐treatment with PA (150mM) followed wash and treatment with vehicle ± Aβ42 (2μM) for 18‐20 hours. Outcomes measured included: (1) nitric oxide (NO) and measures of oxidative stress (superoxide) and nitrosative stress (peroxynitrite), (2) inflammatory and associated markers (interleukins (IL)‐6, IL‐8, Reaction for Advanced Glyocolytic End Products (RAGE) 1 and 2, and Matrix Metalloproteinases (MMP‐9) by PCR. Results: HUVECs exposed to either Aβ or PA showed impaired NO production and increased superoxide and peroxynitrite when compared to vehicle control. Co‐treatment with Aβ and PA did not cause a statistically significant change compared to Aβ or PA alone. HUVEC demonstrated variable inflammatory responses following exposure to either Aβ or PA. Treatment with PA resulted in upregulation of RAGE2 gene expression (p<0.003) and trend towards IL‐6 overexpression (p=0.059). Co‐treatment with both Aβ and PA led to an observed increase in inflammatory responses versus control, but the results did not reach statistical significance. Conclusion: Independent exposure of HUVECs to Aβ and PA caused decreased nitric oxide production and increased oxidative and nitrosative stress. HUVECs did not demonstrate Aβ‐ induced endothelial cell inflammation. Co‐treatment with 2μM Aβ and PA 150μM did not result in a synergistic or additive increase in endothelial cell inflammatory responses.