Mild allergic airways responses to an environmental mixture increase cardiovascular risk in rats
Recent epidemiological findings link asthma to adverse cardiovascular responses. Yet, the precise cardiovascular impacts of allergic airways disease alone have been challenging to disentangle from the potential cardiovascular effects caused by asthma medication. The purpose of this study was to determine the impacts of allergic airways disease alone on cardiovascular function in an experimental model. Female Wistar rats were intranasally sensitized and then challenged once per week for five weeks with saline vehicle or a mixture of environmental allergens (ragweed, house dust mite, and aspergillus fumigatus). Ventilatory and cardiovascular function, measured using double chamber plethysmography and implantable blood pressure (BP) telemetry and cardiovascular ultrasound, respectively, were assessed before sensitization and after single and final allergen challenge. Responses to a single 0.5 ppm ozone exposure and to the cardiac arrhythmogenic agent aconitine were also assessed after final challenge. A single allergen challenge in sensitized rats increased tidal volume and specific airways resistance in response to provocation with methacholine and increased bronchoalveolar lavage fluid (BALF) eosinophils, neutrophils, lymphocytes, cytokines interleukin (IL)-4, IL-5, IL-10, IL-1β, tumor necrosis factor-α and keratinocyte chemoattract-growth-related oncogene characteristic of allergic airways responses. Lung responses after final allergen challenge in sensitized rats were diminished although ozone exposure increased BALF IL-6, IL-13, IL-1 β, and interferon-g and modified ventilatory responses only in the allergen group. Final allergen challenge also increased systolic and diastolic BP, stroke volume, cardiac output, sensitivity to aconitine-induced cardiac arrhythmia and cardiac gene expression with lesser effects after a single challenge. These findings demonstrate that allergic airways disease may increase cardiovascular risk in part by altering blood pressure and myocardial function and by causing cardiac electrical instability.