A new study that explored the impact of smoking cigarettes on a Covid-infected person revealed that it exacerbates the infection, making it more lethal especially in the airways of the lungs.
The study was led by scientists at the Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research at UCLA. It was published in the journal Cell Stem Cell .
The study also intended to explore new therapeutic strategies to help reduce smokers’ chances of developing severe diseases.
Earlier studies have also stressed that current smokers are at an increased risk of severe infection and death. However, the reasons remain obscure.
To help understand how smoking affects SARS-CoV-2 infection on a cellular and molecular level, Dr. Brigitte Gomperts partnered with co-senior authors Vaithilingaraja Arumugaswami, an associate professor of molecular and medical pharmacology, and Kathrin Plath, a professor of biological chemistry.
The researchers recreated what happens when the airways of a current smoker are infected with Covid-19.
For the study, the team utilised a platform known as an air-liquid interface culture, which is grown from human airway stem cells and closely replicates how the airways behave and function in humans.
The airways, which carry air breathed in from the nose and mouth to the lungs, are the body’s first line of defence against airborne pathogens like viruses, bacteria and smoke.
Gomperts, a professor of pulmonary medicine, said: “Our model replicates the upper part of the airways, which is the first place the virus hits.”
He added: “This is the part that produces mucus to trap viruses, bacteria and toxins and contains cells with finger-like projections that beat that mucus up and out of the body.”
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Mimicked changes
The air-liquid interface cultures used in the study were grown from airway stem cells taken from the lungs of five young, healthy, non-smoking tissue donors. The researchers exposed these airway cultures to cigarette smoke for three minutes per day over four days to replicate the effects of smoking.
“This type of model has been used to study lung diseases for over a decade and has been shown to mimic the changes in the airway that you would see in a person who currently smokes,” said Gomperts.
Next, the group infected the cultures exposed to cigarette smoke — along with identical cultures that had not been exposed — with live SARS-CoV-2 virus and the two groups were compared.
The authors found that in the models exposed to smoke, the cells were infected two-three times more.
Furthermore, interferons in the airways, which play a critical role in the body’s early immune response by triggering infected cells to produce proteins to attack the virus, were reduced by smoking.
“If you think of the airways like the high walls that protect a castle, smoking cigarettes is like creating holes in these walls. Smoking reduces the natural defences and that allows the virus to set in,” Gomperts concluded.
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