Mice with Scleroderma Protected from Fibrosis by Hydrogen Sulfide, the Rotten Egg Gas

A study showed the effectiveness of hydrogen sulfide in a mouse model of scleroderma, and researchers in China suggest that the compound should be explored as a potential treatment for patients.

The study, “The protective effect of hydrogen sulfide on systemic sclerosis associated skin and lung fibrosis in mice model,” published in the journal Springer Plus, reflects a renewed interest in a molecule that used to be viewed solely as a toxic factor, but is now known to contribute to several processes keeping us healthy.

Hydrogen sulfide is a tiny molecule consisting of only three atoms. Most people know it as the colorless gas with a prominent smell — that of rotten eggs. This is the smell we encounter when biological material is broken down by certain bacteria in places with no oxygen, such as swamps or sewers.

In recent decades, researchers discovered that hydrogen sulfide exists in the body in minute quantities, and behaves as a signaling molecule, just as the gaseous compound nitric oxide exists, too. Studies have suggested that hydrogen sulfide participates in anti-inflammatory and antioxidant activities, also regulating both cell divisions and cell death.

Research has also suggested the molecule might have antifibrotic properties. Studies of heart and kidney fibrosis reported good results when animals were treated with hydrogen sulfide, and a study looking at lung fibrosis suggested that the protective effect might be explained by the fact that the compound prevents oxidative degradation of fat molecules in cells.

The Chinese researchers, with the Second Affiliated Hospital of Soochow University, decided to test the compound in a mouse model of scleroderma. They injected mice with the substance bleomycin under the skin, a common way to trigger fibrosis. Some of the mice were also injected with sodium hydrosulfide, a compound that releases hydrogen sulfide in the body.

Bleomycin-injected mice developed skin and lung fibrosis, with clear signs of inflammation and collagen deposits. Researchers analyzed the progress of their condition at day 7, 28, and 42, and watched the fibrosis get progressively worse, with increased levels of molecules typically found during fibrosis development, and lower blood levels of hydrogen sulfide.

In mice receiving shots of sodium hydrosulfide, the fibrotic changes were less severe, both in the skin and the lungs. The research team tested two doses of sodium hydrosulfide and noted the protective effect in both, but particularly in the mice receiving the higher dose. In these mice, the molecular changes usually accompanying fibrosis were absent.