Chronic Unpredictable Stress impairs Relaxation Responses to Acetylcholine in Resistance Arteries from Mice

Background Exposure to chronic stress is considered a major environmental factor that causes vascular aging, giving rise to the development of cardiovascular diseases. The chronic unpredictable stress (CUS) protocol has emerged as a translationally relevant model for studying the pathophysiology of stress exposure in rodents. The CUS protocol relies on heterotypic, unpredictable, and uncontrollable stressors that prevent adaptation and lead to disrupted stress response systems, mimicking the real‐life situation. CUS induces changes in cardiovascular function that are accompanied by the release of inflammatory cytokines. Indeed, previous studies have reported endothelial dysfunction in humans exposed to chronic stress and experimental animal models of chronic unpredictable stress. However, the mechanisms through which CUS induces cardiovascular injury are still unknown and require investigation. Hypothesis This study tests the hypothesis that mice exposed to CUS will have impaired endothelial function. Methods Vascular function using wire myographs was performed on isolated mesenteric resistance arteries (MRAs) from male and female C57BL/6 mice subjected to CUS for 28 days. The arterial rings were kept in physiological salt solution at 37°C, constantly aerated with 95%O 2 /5%CO 2 . Concentration‐response curves to phenylephrine (PE; 10 ‐9 ‐3x10 ‐5 M) were performed in some arterial rings, whereas concentration‐response curves to acetylcholine (ACh; 10 ‐9 – 3x10 ‐5 M) were performed in arterial rings precontracted with phenylephrine (PE 3x10 ‐6 M). Concentration‐response curves were analyzed using non‐linear regression analysis. Data are presented as mean ± S.E.M. Statistical significance set at p<0.05. Data were analyzed with GraphPad Prism 9.2.0. Results In the MRA of both males and females, relaxation responses to ACh were impaired in the animals exposed to CUS when compared to their controls. There were no differences in the contractile responses to PE between controls and mice exposed to CUS. Conclusion Our results show that relaxation responses to acetylcholine are impaired in mesenteric resistance arteries from mice exposed to chronic unpredictable stress. This suggests that exposure to chronic unpredictable stress causes endothelial dysfunction and may have important implications for the role of stress on the development of cardiovascular diseases, particularly, hypertension.