G6PD and asthma: This compound, being both a major signaling molecule and a free radical, has a dual effect: at low levels, it has mainly an airway-muscle-relaxing role, and, at high levels, it activates proinflammatory mechanisms; therefore, in asthma, the effect of NO depletion is complex, and, in severe G6PD, a deficiency may be beneficial as well as adverse.