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 (Ca) ionophore A23187 (0.1 mmol). PMNs were activated using N‐formyl‐methionyl‐leucyl‐phenylalanine (fMLP) (10 pmol), and the production of superoxide (O‐2) was measured by the spectrophotometric reduction of cytochrome c. Results: Mg2+ reduced activated PMN O‐2 production compared with that for no Mg2+ (1.0 ± 0.1 nmol O‐2/5 ± 105 PMN/min) in both low (‐0.52* ± 0.3 nmol O‐2/5 ± 105 PMN/min) and high (‐0.76* ± 0.3 nmol O‐2/5 ± 105 PMN/min; *p < 0.05) concentrations. The addition of A23187 increased O‐2 production in both the high (0.53* ± 0.02 nmol O‐2/5 ± 105 PMN/min) and the low (1.5* ± 0.6 nmol O‐2/5 ± 105 PMN/ min) Mg2+ groups, with no change in the control group (1.2 ± 0.2 nmol O‐2/105 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.