Bronchoalveolar Lavage and Plasma Cathelicidin Response to 25-Hydroxy Vitamin D Supplementation: A Pilot Study.

Sanders, Emily C; Burkes, Robert M; Mock, Jason R; Brown, Todd T; Wise, Robert A; Hansel, Nadia N; Liu, Mark C; Drummond, M Bradley

Introduction Cathelicidin is a vitamin D-regulated antimicrobial peptide involved in the innate immune response of the airways. Reduced plasma cathelicidin concentrations are independently associated with worse pulmonary outcomes in current and former smokers. This study aimed to determine whether oral vitamin D supplementation in vitamin D deficient current smokers increases plasma and bronchoalveolar lavage (BAL) cathelicidin levels. Methods Vitamin D deficient (25 hydroxy vitamin D (25OHD) <20 ng/ml) smokers (n=17) underwent collection of plasma and BAL for cathelicidin and 25OHD measurements before and after eight weeks of oral supplementation with 50,000 IU vitamin D3 weekly. Differences between baseline and eight-week levels of cathelicidin and 25OHD in blood and BAL were assessed along with correlations between serum 25OHD, plasma cathelicidin and BAL cathelicidin. Results At baseline, there was no correlation between BAL and plasma cathelicidin. There was a significant increase in 25OHD (median 17.0 to 43.3 ng/mL, p<0.001) after eight weeks of vitamin D supplementation. There was no change in plasma cathelicidin (p=0.86), BAL cathelicidin (p=0.31), or BAL 25OHD (p=0.89). There was no correlation between serum 25OHD and either BAL or plasma cathelicidin post-supplementation. Conclusion Oral vitamin D supplementation, while increasing serum 25OHD levels, does not increase plasma or BAL cathelicidin levels in vitamin D deficient active smokers. The lack of increased BAL cathelicidin may be explained by multiple factors related to dosing, smoking effects or putative mechanisms of engagement. Future studies are needed to determine the effects of vitamin D supplementation on lung and blood functional activity.