Caution – nanotubes
Long carbon nanotubes suspected of the ability to provoke cancer
Daria Spasskaya, N+1
Carbon nanotubes with a length of more than 15 microns, which are used in the production of composite materials, have the same carcinogenicity as asbestos, scientists from the UK have found out. When ingested into the respiratory tract, nanotubes, like asbestos fibers, cause chronic inflammation and over time can contribute to the development of a malignant tumor of the connective tissue membrane of the lungs by a similar molecular mechanism, including suppression of the function of tumor suppressors. The study is published in the journal Current Biology.
Asbestos is a natural fibrous mineral based on silicon, which was previously widely used in industry, including as a building material. In recent years, it has been abandoned in developed countries due to its high toxicity. Chronic inhalation of asbestos dust turned out to be the cause of malignant proliferation of the connective tissue membrane of the lungs (pleura) – mesotheliomas. Studies show that the incidence of mesothelioma in asbestos mine workers reaches 15 percent, and the incubation period of the disease can be decades.
Scientists from the toxicology department of the UK Medical Research Council have shown that the development of mesothelioma by a mechanism similar to asbestos leads to the ingestion of long carbon nanotubes into the lungs. Carbon nanotubes with various parameters are currently used in industry in the production of composite materials, as well as in microelectronics and even in medicine.
The researchers compared the effects of long (more than 15 microns long) and short asbestos fibers, as well as long and short carbon nanotubes, on connective tissue membranes in mice. The particles were injected into the respiratory tract of mice in different concentrations corresponding to acute or mild, but prolonged exposure. The period of administration ranged from a week to 20 months. During the experiment, as well as 20 months after it, the authors of the work evaluated changes in the pulmonary membrane, where particles that are not decomposed in the body move from the lungs.
Scientists have shown that the presence of long asbestos fibers and long nanotubes led over time to the development of chronic inflammation, oxidative DNA damage, and activation of pro-oncogenic signaling pathways in shell cells. By the end of the follow-up, 10 to 25 percent of mice in different groups suffered from mesothelioma, which corresponds to the incidence rate among humans.
It turned out that at the molecular level, the development of mesothelioma is caused by suppression of the expression of the CDKN2A gene as a result of hypermethylation of its regulatory site. In some cases, even deletions in the area of this genetic locus were observed, leading to the loss of gene function. The CDKN2A gene encodes the p16 protein, which regulates the cell cycle and is an important tumor suppressor, that is, a protein whose functions prevent uncontrolled cell division. The loss of p16 protein by pleural cells was observed both when the shell was destroyed by asbestos particles and by long carbon nanotubes. At the same time, short nanotubes did not cause changes in the pleura, apparently due to the timely disposal of small particles by immune cells.
Figure from an article in Current Biology – VM.
The discovery of the molecular mechanism underlying the development of mesothelioma will make it possible to assess the condition of the lungs and pleura by appropriate biomarkers in people at risk – mainly workers of harmful industries.
The scientists emphasize that their findings do not apply to all types of carbon nanotubes, and their main task is to attract the attention of manufacturers and regulators so that they can choose safer versions of nanomaterials. At the same time, appropriate safety measures are already being taken at factories producing nanomaterials.
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