Vitamin D improves corticosteroid efficacy and attenuates its side-effects in an animal model of asthma

The subacute use of corticosteroids has side-effects such as glucose intolerance, dyslipidemia, anxiety, and depression, which could be halted with vitamin D, which is an immunomodulatory vitamin. Thus, we aimed to study the anti-asthmatic efficacy and side-effects profile of vitamin D, the corticosteroid dexamethasone, and their combination on ovalbumin-induced airway inflammation in rats. For this, 2 different doses of vitamin D (50 IU/kg, daily for 2 weeks, or and 60000 IU/kg, bolus dose, by intraperitoneal injection (i.p.)) were administered in combination with dexamethasone (2.5 mg/kg, i.p., for 2 weeks) prior to challenge with ovalbumin. At the end of the therapy, the asthmatic parameters such as differential white blood cell counts, serum levels of immunoglobulin E, bronchoalveolar lavaged fluid, and interleukin-5, as well as serum levels of nitric oxide were significantly increased after allergen challenges in asthmatic rats as compared with the controls. Such increases were significantly attenuated by monotherapy with vitamin D and with combination therapy of vitamin D and dexamethasone, where the combination therapy was superior to the monotherapy. Dexamethasone-induced hyperglycemia, hyperlipidemia, and behavioral abnormalities in the allergic rats were attenuated with vitamin D. The daily dose was better for controlling serum levels of immunoglobulin E than the bolus dose, whereas the bolus was superior for reducing dexamethasone-induced psychotropic abnormalities. There were no significant changes in other parameters between the daily and the bolus dose. In conclusion, a daily dose of vitamin D in combination with dexamethasone is more efficacious for treating asthma in allergic rats than monotherapy.