The role of hydrogen sulphide in lung diseases

Hydrogen sulphide (H2S) is a recently discovered gasotransmitter. It is endogenously synthesized by cystathionine β synthetase, cystathionine γ lyase, cysteine aminotransferase, 3-mercaptopyruvate sulphurtransferase and cysteine lyase. Its metabolism leads to the production of sulphate (SO42−), methanthiol, dimethylsulphide and thiocynate. The gas interacts with ion channels, protein kinases and transcription factors. It is also involved in post-translational modification of proteins via S-sulphhydration. Although debate continues as to whether H2S is pro- or anti-inflammatory, its anti-inflammatory properties seem to have beneficial effects in various lung diseases. Serum levels of H2S differ between asthma, chronic obstructive pulmonary disease and pulmonary fibrosis, which makes it difficult for the gas to be used as a biomarker for lung diseases. Apart from exogenous sources of H2S, targets to enhance or inhibit the gas can be found in its synthesis and metabolism pathway. H2S-releasing non-steroidal anti-inflammatory drugs are currently being developed. Further research will aid to determine the precise role of H2S in respiratory diseases.