Vitamin D, an Immunomodulator for Eosinophils in Asthma and Allergy

Abstract

Epidemiological studies correlate vitamin D deficiency with asthma severity. Calcitriol modulates receptor and cytokine expression from various leukocytes in an anti-inflammatory manner. Despite eosinophil activity during mucosal inflammation, knowledge on the direct effect of calcitriol on this granulocyte is very limited. We propose that calcitriol exerts direct effects on eosinophil biology by modulating its programmed cell death pathways and other functions. Purified peripheral blood eosinophils from atopic donors were incubated with calcitriol (10nM) for up to 14 days with and without IL-5. We observed that calcitriol significantly reduced eosinophil necrosis and cytolytic release of EPX in media when co-incubated with IL-5. The addition of calcitriol also significantly decreased CRTh2 and CCR10 expression on eosinophils. Eosinophil cytotoxic mediator release into mucosal tissues, resulting from necrotic cytolysis, as well as eosinophil recruitment to lungs are major contributors to airway inflammation in allergic asthma. Hence, the reduction of mucosal inflammation achieved by decreasing eosinophil necrosis and recruitment unveil new anti-inflammatory mechanisms for calcitriol in the context of airway inflammation.