Role of vitamin D in cystic fibrosis and non-cystic fibrosis bronchiectasis

Abstract

Bronchiectasis is usually classified as cystic fibrosis (CF) related or CF unrelated (non-CF); the latter is not considered an orphan disease any more, even in developed countries. Irrespective of the underlying etiology, bronchiectasis is the result of interaction between host, pathogens, and environment. Vitamin D is known to be involved in a wide spectrum of significant immunomodulatory effects such as down-regulation of pro-inflammatory cytokines and chemokines. Respiratory epithelial cells constitutively express 1α-hydroxylase leading to the local transformation of the inactive 25(OH)-vitamin D to the active 1,25(OH)₂-vitamin D. The latter through its autocrine and paracrine functions up-regulates vitamin D dependent genes with important consequences in the local immunity of lungs. Despite the scarcity of direct evidence on the involvement of vitamin D deficiency states in the development of bronchiectasis in either CF or non-CF patients, it is reasonable to postulate that vitamin D may play some role in the pathogenesis of lung diseases and especially bronchiectasis. The potential contribution of vitamin D deficiency in the process of bronchiectasis is of particular clinical importance, taking into consideration the increasing prevalence of vitamin D deficiency worldwide and the significant morbidity of bronchiectasis. Given the well-established association of vitamin D deficiency with increased inflammation, and the indicative evidence for harmful consequences in lungs, it is intriguing to speculate that the administration of vitamin D supplementation could be a reasonable and cost effective supplementary therapeutic approach for children with non-CF bronchiectasis. Regarding CF patients, maybe in the future as more data become available, we have to re-evaluate our policy on the most appropriate dosage scheme for vitamin D.

Keywords: Vitamin D, Bronchiectasis, Cystic fibrosis, Vitamin D supplementation

Core tip: Vitamin D deficiency seems to be associated with respiratory health. Herein, we present the experimental and epidemiological data that imply a role of vitamin D deficiency in the development of cystic fibrosis (CF) and non-CF bronchiectasis. Numerous experimental data provide insight to the mechanism by which vitamin D modulates immunity, and therefore its deficiency may enhance the susceptibility to infectious diseases and affect the control of inflammation process. Epidemiological data provide evidence for the association of vitamin D deficiency and bronchiectasis, either directly or indirectly, through its relation with the risk for respiratory tract infections. This knowledge is of interest for the pediatrician as vitamin D supplementation may be a future candidate therapeutic option for bronchiectasis.