Sputum and serum hydrogen sulfide (H₂S) as novel biomarker of asthma

Background

Hydrogen sulfide (H₂S) is a gas produced by respiratory cells including smooth muscle cells and may play a role as a gasotransmitter. We determined whether H₂S levels in serum or sputum supernatants could represent a biomaker of asthma.

Methods

We measured H₂S in induced sputum and serum samples of patients with severe and non-severe asthma and of healthy subjects. H₂S concentrations were measured using a sulfide-sensitive electrode.

Results

H₂S levels in induced sputum from severe and non-severe asthmatic patients were significantly higher than those from healthy subjects but there was no difference between the severe and non-severe group. Serum H₂S levels were 10 times higher than in sputum and these were also higher in severe and non-severe asthmatic subjects compared to healthy subjects. There was a positive correlation between sputum and blood H₂S levels (r=0.42, p<0.05). Sputum H₂S levels were negatively correlated with FEV₁ %predicted (r=-0.42, p=0.003), and with reversibility to salbutamol (r= -0.54, p<0.01). There was a correlation between sputum H₂S and sputum neutrophils and macrophages, and a negative correlation between sputum H₂S and Fe_NO levels.

Conclusions

Endogenous H₂S, measured in induced sputum, may be a marker of neutrophilic inflammation and bronchial narrowing.