Soluble Protein Oligomers Induce Endoplasmic Reticulum Stress and Exacerbated Vasodilation via Nitric Oxide Release in Resistance Arteries from Male and Female Mice

Abstract

Amyloid b (Ab) protein which gives rise to small, toxic, and soluble Ab oligomers (SPOs) is capable of interfering with synaptic function and integrity, thus memory loss in Alzhemier’s disease (AD). Further their accumulation induces endoplasmic reticulum (ER) stress, leading to cell death in several cardiovascular diseases. Our previous data showed for the first time that in arteries from both male and female mice, SPOs exert their vasoactive effects by inducing ER stress in acute conditions, resulting in pathologically exacerbated endothelium‐dependent vasodilation due to loss of vascular autoregulation, edema formation and chronic, irreversible vascular collapse. ER stress was also confirmed with anti‐KDEL antibody staining, specific for ER resident chaperones Grp78/94 and visualized with multiphoton fluorescent confocal microscopy. Additionally, we showed that ER stress induced further release of SPOs in arteries from female mice, showing a positive feedforward mechanism. Based on these prior research, we hypothetized that SPOs lead to exacerbated and deleterious vasodilation via nitric oxide synthase (NOS) and nicotinamide adenine dinucleotide phosphate oxidase (NADPH oxidase) activation. Mesenteric resistance arteries (MRA) were isolated from male and female C57BL/6J mice (~14 weeks old) (n=4‐7). The arteries were pre‐incubated for 30 minutes in the presence or absence of specific hydrogen peroxide (H2O2) inhibitor, catalase (500u/ml); NOS inhibitor, L‐NAME (100µM); cyclooxygenase (COX) inhibitor, Indomethacin (10µM); NADPH oxidase‐1 (Nox1) inhibitor (10 µM) and Nox 1/4 inhibitor (GKT136901,10μM), followed by incubation with SPOs (0.1 μM) for 45 minutes. Subsequently, concentration response curves to acetylcholine (1 nM‐30 µM) were performed after contraction with phenylephrine (10 µM). No differences were observed in the presence of catalase, indomethacin or GKT136901. However, L‐NAME was able to eliminate the SPOs ability to increase vasodilation in arteries form both male and female mice (Fig 1. A and B, Two‐way ANOVA). We therefore concluded that the mechanism that SPOs use to pathologically exacerbate endothelium‐dependent vasodilation in the resistance arteries is NO dependent, and was observed in arteries from both male and female mice. This could be one of the mechanisms that AD leads to loss of myogenic tone and edema in the microvasculature.