Vitamin D deficiency protects against the effects of chronic house dust mite exposure

Introduction: Reduced levels of vitamin D are associated with airway hyperresponsiveness (AHR) and increased markers of asthma severity. We aimed to determine whether vitamin D deficiency exacerbates respiratory outcomes in a chronic mouse model of allergic asthma.

Methods: A physiologically relevant mouse model of vitamin D defi ciency was developed by raising BALB/c mice on vitamin D-defi cient or -replete diets. Offspring from -defi cient and -replete mice of both sexes at 8 weeks of age were intranasally inoculated with house dust mite (HDM) extract (25 μg of protein in 50 μL of saline) or saline as a control 5 days a week for 5 weeks. AHR was assessed by measuring lung function responses to increasing doses of inhaled methacholine 72 h after the last HDM exposure. Bronchoalveolar lavage (BAL) fluid was collected to assess cellular infl ammation and cytokine levels.

Results: Chronic HDM exposure increased baseline airway resistance in female vitamin D-replete mice compared with vitamin D-defi cient mice (p < 0.05). Similarly, HDM exposure increased the maximum response in tissue elastance and the sensitivity of tissue damping to MCh in vitamin D replete male mice compared to deficient male mice (p < 0.05). There were increased eosinophils and transforming growth factor β levels in the BAL of vitamin D-replete HDM-sensitized females (p < 0.05), but not males.

Discussion: Unexpectedly, vitamin D defi ciency protects mice against both the infl ammatory and physiological impairments induced by chronic HDM exposure.