Vitamin D ‘could enhance asthma control’
medwireNews: In vitro study results show that the active form of vitamin D can reduce the production of the pro-inflammatory cytokine interleukin (IL)-17A in both steroid-resistant and steroid-responsive patients with asthma.
The study authors say their findings suggest that vitamin D could improve disease control in patients with asthma, regardless of their steroid responsiveness.
The researchers, led by Catherine Hawrylowicz from King's College London, UK, analyzed blood cells from 18 patients with steroid-resistant asthma, 10 patients with steroid-sensitive asthma, and 10 healthy controls.
Levels of IL-17A and its coproduct IL-22 were not significantly greater in the cultured T cells of patients with steroid-sensitive asthma than in controls. By contrast, IL-17A levels were seven times greater in patients with steroid-resistant asthma than in controls and five times greater than in steroid-sensitive patients.
As reported in the Journal of Allergy and Clinical Immunology, glucocorticoids did not decrease the production of inflammatory cytokines in either patients or controls. On the contrary, in cultures from healthy controls, the addition of 10-7 mol/L dexamethasone significantly increased the mean percentage of cells expressing IL-17A, resulting in concentration-dependent increases in IL-17A and IL-22 secretion.
Meanwhile, in cultures from patients with asthma, there was a significant increase in the number of cells expressing IL-17A, a nonsignificant trend toward increased IL-17A secretion, and partial inhibition of IL-22 secretion in both steroid-resistant and steroid-sensitive patients.
Also, the addition of 1α,-25-dihydroxyvitamin D3 (1,25[OH]2D3) significantly decreased the mean percentage of cells producing IL-17A and IL-22. In comparison to dexamethasone alone, active vitamin D significantly reduced expression of the cytokines, both alone and in combination with the glucocorticoid.
"These data highlight the capacity of 1,25(OH)2D3 to counteract any detrimental effect or lack of effect of dexamethasone on TH17-associated cytokine synthesis in cell cultures from asthmatic patients," Hawrylowicz and colleagues write.
"Manipulation of vitamin D status for therapeutic benefit in asthmatic patients and patients with other respiratory conditions is currently highly topical," the authors say. Recent research has found that patients with poorly controlled asthma and/or steroid-resistance have reduced vitamin D levels, and 1,25(OH)2D3 has also been linked to airway smooth muscle mass.
"Understanding the various mechanisms through which vitamin D controls respiratory health and steroid responsiveness is central in targeting this pathway therapeutically, and our results provide support for an additional beneficial effect," the authors conclude.
medwireNews (www.medwirenews.com) is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2013
By Kirsty Oswald, medwireNews Reporter