What form of nanofibers is responsible for pulmonary fibrosis?

After years of discussion, the use of asbestos was finally banned in France in 1997. Although the health risks have been known since ancient times, its exploitation has continued over the centuries. Accumulation of scientific data in the twentieth century^H The century has clearly proven that inhaling the fibers of this substance causes lung inflammation, fibrosis, and various types of cancer. Despite these results, the French authorities were slow to take appropriate action, causing the “asbestos scandal.” According to a parliamentary report, 35,000 people died in France between 1965 and 1995 due to exposure to asbestos fibres.

Although the harmful effects on human health and the environment caused by asbestos are well documented, the pathogenic mechanism remains to be understood. The chemical composition of asbestos has long been blamed, but another factor also plays a role. Working with chemically inert glass nanofibers, Christian Amator, from the École Normale Supérieure in Paris, and a Chinese team came to shed light on a general mechanism linked to asbestos. Nanoglass fiber engineering, which is similar to the engineering of asbestos fibers and carbon nanotubes.

When these fibers are inhaled and deposited in the lungs, phagocytes go into action to eliminate them through phagocytosis. Normally, the immune system's sentinels eliminate pathogens by absorbing them into a closed intracellular vacuole (phagosome) and breaking them down into small molecules. However, when nanofibers are too long (at least 15 μm), macrophages are unable to completely phagocytose them. When macrophages attack large bacilli, such as anthrax, they can gradually move up the body of the bacillus and digest it entirely.

But glass nanofibers are chemically inert and phagocytosis cannot degrade them: we talk about “frustrated phagocytosis”. In experiments In vivo And in the laboratoryThe researchers then found that because the phagosome is not closed, the immune system cell secretes reactive oxygen and nitrogen compounds that diffuse into the surrounding environment. “To detect these leaks at the phagosomal level, we had to design electrochemical nanosensors with very high sensitivity,” emphasizes Christian Amator. These leaks then cause damage to nearby cells, leading to chronic stress and lung tissue damage. In mice exposed to inert nanofibers, these lesions led to the development of fibrosis.

This finding suggests that nanofiber materials used in the construction sector to replace asbestos could pose the same health risks to those who come into contact with them.