Magnesium attenuates the neutrophil respiratory burst in adult asthmatic patients

Abstract

Introduction: IV magnesium (Mg2+) has been proposed as an emergent treatment for acute asthma exacerbations. Recent studies have focused on the effects of Mg2+ on bronchial smooth muscle, yet asthma is primarily an inflammatory disease. Objective: To assess the effects of Mg2+ on the neutrophil respiratory burst of adult patients with asthma. Methods: A prospective, blind study of volunteer adult asthmatic patients was performed. The patients' polymorphonuclear neutrophils (PMNs) were isolated, purified, and placed into phosphate-buffered saline with the following test conditions: concentrations of magnesium chloride (MgCl2) added: 0 mmol MgCl2, 1 mmol MgCl2 (low), and 10 mmol MgCl2 (high) both with and without the calcium (Ca2+) ionophore A23187 (0.1 mmol). PMNs were activated using N-formyl- methionyl-leucyl-phenylalanine (fMLP) (10 μmol), and the production of superoxide (O2/-) was measured by the spectrophotometric reduction of cytochrome c. Results: Mg2+ reduced activated PMN O2/- production compared with that for no Mg2+ (1.0 ± 0.1 nmol O2/-/5 x 105 PMN/min) in both low (-0.52* ± 0.3 nmol O2/-/5 x 105 PMN/min) and high (-0.76* ± 0.3 nmol O2/-/5 x 105 PMN/min; *p < 0.05) concentrations. The addition of A23187 increased O2/- production in both the high (0.53* ± 0.02 nmol O2/-/5 x 105 PMN/min) and the low (1.5* ± 0.6 nmol O2/-/5 x 105 PMN/min) Mg2+ groups, with no change in the control group (1.2 ± 0.2 nmol O2/-/105 PMN/min). Conclusions: In clinically relevant concentrations, Mg2+ attenuates the neutrophil respiratory burst in adult asthmatic patients. Mg2+ appears to affect PMNs by interfering with extracellular Ca2+ influx. Mg2+ may have a beneficial anti-inflammatory effect in asthmatic individuals.