Hydrogen sulfide as a potential biomarker of asthma

Hydrogen sulfide (H2S), a gas characterized by the odor of rotten eggs, is produced by many cells in the airways and lungs, and may regulate physiologic and pathophysiologic processes. It plays a role in cellular signaling, and represents the third gasotransmitter after nitric oxide and carbon monoxide. Endogenous and exogenous H2S have anti-inflammatory and anti-proliferative effects, with inhibitory effects in models of lung inflammation and fibrosis. Under certain conditions, H2S may also be proinflammatory. It is generally a vasodilator and relaxant of airway and vascular smooth muscle cells. It acts as a reducing agent, being able to scavenge superoxide and peroxynitrite. H2S is detectable in serum and in sputum supernatants with raised levels observed in asthmatics. The sputum levels correlated inversely with lung function. H2S may play a role in the pathogenesis of asthma.