If nicotine turns out to be useful in treating or preventing COVID-19, we already have access to smoking-cessation products that offer controlled doses of it
In the wake of my Monday column on the paradoxical effects of smoking on COVID-19 risk, I got a short note from Konstantinos Farsalinos, a physician in Greece who was one of the first to spot the strangely low incidence of current smokers in the Chinese patient data. Readers who are especially interested in the issue might like to consult Farsalinos’s overview of the issue, dated Apr. 23. (Unlike much of what we’re all reading, it has undergone peer review.)
The paper offers a frank discussion of the extreme limitations of the Chinese data, which boil down to “Nobody knows how they identified and counted the smokers, or whether their methods for doing that went straight to hell in the middle of a raging epidemic.” But it also pre-dates the new English evidence for a possible protective effect of cigarettes that I discussed in the column.
What might be most useful about Dr. Farsalinos’s paper, for the lay reader, is that it breaks down two of the more likely reasons for the smoker’s paradox, if it really exists. One is that nicotine helps keep the immune system tame. There is prior evidence that nicotine selectively inhibits cytokines (proteins for immunological signalling) that cause inflammation, while leaving alone ones that don’t. When these normally protective inflammatory cytokines get out of control in response to a pathogen, you end up with the so-called “cytokine storm,” thought to be a common cause of death in severe COVID cases.
Another possibility is that nicotine has a beneficial effect on the renin-angiotensin system that is ordinarily in charge of controlling blood pressure. It appears that smoking might “up-regulate” production of the ACE2 enzyme that the SARS-CoV-2 virus uses to infiltrate the body. In principle (as I discussed early last month) this sounds bad, but it could actually be good: in effect, nicotine might be leaving smokers with protective “extra” ACE2.
Colby Cosh – National Post – May 12, 2020.