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Smoking cigarettes increases the risk of serious coronavirus infection by dampening the body’s immune response, a new study suggests.
Laboratory studies of models of airways made from human stem cells show that smoking prevents key molecules in the immune system, called interferons, from working properly.
Interferons are messengers that tell infected cells to make proteins to attack the invading pathogen and are essential in fighting the initial infection.
They also invoke the support of the broader immune system and warn uninfected cells to prepare for the virus.
The study found that smoking prevents this pathway from working properly, leading to a threefold increase in the number of human cells infected with the virus.
This finding runs counter to a growing body of evidence showing that smokers are in fact less likely to catch the coronavirus.
For example, a Mexican study published this summer analyzed data from nearly 90,000 patients and found that smokers were 23% less likely than non-smokers to be diagnosed with Covid-19.
And the team also found that smokers who had been infected were no longer likely to need intensive care, be on a ventilator, or die.
Academics at University College London also reviewed 28 articles and found that the proportion of smokers among hospital patients was “lower than expected.”
One of the studies showed that in the UK the proportion of smokers among patients with COVID-19 was only 5%, a third of the national rate of 14.4%.
A May study found that less than 5% of 441 COVID-19 patients who were due to be admitted to an Italian hospital were smokers.
Scientists have described it as a “very low” number, given that a quarter of the general population is known to be addicted to cigarettes.
Photo microscopic images of models of respiratory tract tissue derived from human stem cells with cell nuclei (blue) and cells infected with SARS-CoV-2 virus (green); tissues exposed to cigarette smoke (right) contained two to three times as many infected cells as unexposed tissues (left)
Smoking increases the risk of serious coronavirus infection by suppressing the immune response. Laboratory studies of airway models made from human stem cells reveal that smoking prevents key molecules in the immune system, called interferons, from working properly (stock)
In the new study, scientists at UCLA used human stem cells from donors to create an airway analogue called an air-liquid interface culture.
Researchers focused on this part of the respiratory system before the lungs, as this is where mucus forms and where most of the cilia live, small hairs designed to help move mucus and trapped infections out of the body. .
Some were not abused, while others were exposed to cigarette smoke for three minutes a day for four days.
They were then both infected with SARS-CoV-2 to see how the virus behaved in both systems.
In the models exposed to the smoke, the researchers say in their article, published in Cell Stem Cell, there were between two and three times as many infected cells.
This graph summarizes how the presence of coronavirus and cigarette smoke affects the human respiratory tract. It shows that more coronavirus infects cells if cells have been exposed to cigarette smoke. It also shows that when interferons are introduced artificially (bottom), there is no infection. This proves that smoke inhibits the interferon pathway and this is why smokers are more at risk of developing severe Covid than non-smokers.
There have been conflicting reports on the impact of smoking on a Covid patient’s prognosis, with some studies finding it reduces risk and others finding it to be the opposite. Now, academics at the University of California, Los Angeles have determined how smoking likely results in a more serious SARS-CoV-2 infection.
At the start of the pandemic, when little was known about SARS-CoV-2, the virus that causes Covid-19, researchers instinctively warned that smokers would be at higher risk due to the fact that the coronavirus targets the respiratory system and smoking. has long been linked to lung cancer, stroke, diabetes and other chronic diseases.
However, studies quickly emerged indicating that smokers were at a reduced risk. Experts struggled to explain how it could be, calling it weird and weird.
Since then, more studies have been published suggesting that smokers may be at increased risk, but scientists have struggled to provide any real data or a mechanism to support this.
In June, German researchers conducted a comprehensive review of the impact of smoking and vaping on coronavirus infection.
Both harden the arteries and increase the risk of developing lung and heart disease – two risk factors for coronaviruses – up to seven times, they found.
They admitted that smoking is more toxic to the body than vaping, but cautioned that vaping should not be seen as a “ healthy alternative. ”
The review – published in the European Heart Journal – did not, however, analyze hospital records of patients with Covid-19.
Meanwhile, French doctors have suggested that nicotine could control the immune system, preventing it from reacting dangerously to infection – a phenomenon that kills many Covid-19 patients.
In June, the World Health Organization said smoking – which impairs lung function – can make people more susceptible to COVID-19.
“If you think of the airways as the high walls that protect a castle, smoking cigarettes is like creating holes in those walls,” says the author of the latest study, Dr. Brigitte Gomperts, of UCLA. .
“Smoking reduces the natural defenses and allows the virus to take hold.”
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