Melatonin synthesised in the lungs acts as a barrier against Covid-19 infection. This also prevents the expression of genes that are entry points for the virus, researchers at the University of São Paulo (USP) stated in a study.
The study, published in the journal Melatonin Research, found that melatonin encodes proteins in cells such as resident macrophages in the nose and pulmonary alveoli, and epithelial cells lining the alveoli, to prevent virus entry.
The hormone, therefore, prevents infection of these cells by the virus and inhibits the immune response so that the virus remains in the respiratory tract for a few days. The virus eventually leaves to find another host.
The aim of the study was to understand why some people are not infected or do not manifest symptoms of Covid-19 even when reliably diagnosed as carriers of the virus by RT-PCR.
In addition, it intended to offer the prospect of nasal administration of melatonin, in drops or as a spray, to prevent the disease from developing in pre-symptomatic patients.
“We showed that melatonin produced in the lung acts as a barrier against SARS-CoV-2, preventing the virus from entering the epithelium, activating the immune system and triggering the production of antibodies,” Regina Pekelmann Markus, a professor at USP’s Institute of Biosciences (IB) and principal investigator for the project, told Agência FAPESP.
“This action mechanism by pulmonary melatonin must also involve other respiratory viruses such as influenza,” she added.
For the study, the researchers analysed 455 genes associated with Covid-19 co-morbidities, the interaction between SARS-CoV-2 and human proteins, and viral entry points.
Using RNA sequencing data downloaded from a public database, they quantified the level of expression of the 212 Covid-19 signature genes in 288 samples from healthy human lungs.
The findings of the study suggested that lung melatonin inhibits transcription of the genes that encode proteins for viral entry point cells. Furthermore, the application of melatonin directly into the lungs in the form of drops or spray could block the virus.
However, more research is required to prove that this is indeed the case, however, the researchers noted.