Paradoxical effects of cigarette smoke and COPD on SARS-CoV-2 infection and disease

Live to die another day: novel insights may explain the pathophysiology behind smoker's paradox in SARS-CoV-2 infection

The severe acute respiratory coronavirus 2 (SARS-CoV-2) infection demonstrates a highly variable and unpredictable course. Several reports have claimed a smoker's paradox in coronavirus disease 2019 (COVID-19), in line with previous suggestions that smoking is associated with better survival after acute myocardial infarction and appears protective in preeclampsia. Several plausible physiological explanations exist accounting for the paradoxical observation of smoking engendering protection against SARS-CoV-2 infection. In this review, we delineate novel mechanisms whereby smoking habits and smokers' genetic polymorphism status affecting various nitric oxide (NO) pathways (endothelial NO synthase, cytochrome P450 (CYP450), erythropoietin receptor (EPOR); β-common receptor (βcR)), along with tobacco smoke modulation of microRNA-155 and aryl-hydrocarbon receptor (AHR) effects, may be important determinators of SARS-CoV-2 infection and COVID-19 course. While transient NO bioavailability increase and beneficial immunoregulatory modulations through the above-mentioned pathways using exogenous, endogenous, genetic and/or therapeutic modalities may have direct and specific, viricidal SARS-CoV-2 effects, employing tobacco smoke inhalation to achieve protection equals self-harm. Tobacco smoking remains the leading cause of death, illness, and impoverishment.

Current tobacco use and COVID-19 diagnoses in a cohort of adult clients of public dental clinics in Sweden

Smoking has been linked with both increased and decreased risk of COVID-19, prompting the hypothesis of a protective role of nicotine in the pathogenesis of the disease. Studies of the association between use of smokeless tobacco and COVID-19 would help refining this hypothesis. We analysed data from 424,386 residents in the Stockholm Region, Sweden, with information on smoking and smokeless tobacco (snus) use prior to the pandemic obtained from dental records. Diagnoses of COVID-19 between February and October 2020 were obtained from health-care registers. We estimated the risk of receiving a diagnosis of COVID-19 for current smokers and for current snus users relative to non-users of tobacco, adjusting for potential confounders (aRR). The aRR of COVID -19 was elevated for current snus users (1.09 ;95%CI = 0.99-1.21 among men and 1.15; 95%CI = 1.00-1.33 among women). The risk for women consuming more than 1 can/day was twice as high as among non-users of tobacco. Current smoking was negatively associated with risk of COVID-19 (aRR = 0.68; 95% CI = 0.61-0.75); including hospital admission (aRR = 0.60; 95% CI = 0.47-0.76) and intensive care (aRR = 0.43; 95% CI = 0.21-0.89). The hypothesis of a protective effect of tobacco nicotine on COVID-19 was not supported by the findings. The negative association between smoking and COVID-19 remains unexplained.

Nicotine patches in patients on mechanical ventilation for severe COVID-19: a randomized, double-blind, placebo-controlled, multicentre trial

Purpose

Epidemiologic studies have documented lower rates of active smokers compared to former or non-smokers in symptomatic patients affected by coronavirus disease 2019 (COVID-19). We assessed the efficacy and safety of nicotine administered by a transdermal patch in critically ill patients with COVID-19 pneumonia.

Methods

In this multicentre, double-blind, placebo-controlled trial conducted in 18 intensive care units in France, we randomly assigned adult patients (non-smokers, non-vapers or who had quit smoking/vaping for at least 12 months) with proven COVID-19 pneumonia receiving invasive mechanical ventilation for up to 72 h to receive transdermal patches containing either nicotine at a daily dose of 14 mg or placebo until 48 h following successful weaning from mechanical ventilation or for a maximum of 30 days, followed by 3-week dose tapering by 3.5 mg per week. Randomization was stratified by centre, non- or former smoker status and Sequential Organ Function Assessment score (< or ≥ 7). The primary outcome was day-28 mortality. Main prespecified secondary outcomes included 60-day mortality, time to successful extubation, days alive and free from mechanical ventilation, renal replacement therapy, vasopressor support or organ failure at day 28.

Results

Between November 6th 2020, and April 2nd 2021, 220 patients were randomized from 18 active recruiting centers. After excluding 2 patients who withdrew consent, 218 patients (152 [70%] men) were included in the analysis: 106 patients to the nicotine group and 112 to the placebo group. Day-28 mortality did not differ between the two groups (30 [28%] of 106 patients in the nicotine group vs 31 [28%] of 112 patients in the placebo group; odds ratio 1.03 [95% confidence interval, CI 0.57–1.87]; p = 0.46). The median number of day-28 ventilator-free days was 0 (IQR 0–14) in the nicotine group and 0 (0–13) in the placebo group (with a difference estimate between the medians of 0 [95% CI -3–7]). Adverse events likely related to nicotine were rare (3%) and similar between the two groups.

Conclusion

In patients having developed severe COVID-19 pneumonia requiring invasive mechanical ventilation, transdermal nicotine did not significantly reduce day-28 mortality. There is no indication to use nicotine in this situation.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00134-022-06721-1.

Renin-angiotensin system blockade on angiotensin-converting enzyme 2 and TMPRSS2 in human type II pneumocytes

AIMS

Angiotensin-converting enzyme (ACE) 2 is the receptor for severe acute respiratory syndrome coronavirus 2 which causes coronavirus disease 2019 (COVID-19). Viral cellular entry requires ACE2 and transmembrane protease serine 2 (TMPRSS2). ACE inhibitors (ACEIs) or angiotensin (Ang) receptor blockers (ARBs) influence ACE2 in animals, though evidence in human lungs is lacking. We investigated ACE2 and TMPRSS2 in type II pneumocytes, the key cells that maintain lung homeostasis, in lung parenchymal of ACEI/ARB-treated subjects compared to untreated control subjects.

MAIN METHODS

Ang II and Ang-(1-7) levels and ACE2 and TMPRSS2 protein expression were measured by radioimmunoassay and immunohistochemistry, respectively.

KEY FINDINGS

We found that the ratio Ang-(1-7)/Ang II, a surrogate marker of ACE2 activity, as well as the amount of ACE2-expressing type II pneumocytes were not different between ACEI/ARB-treated and untreated subjects. ACE2 protein content correlated positively with smoking habit and age. The percentage of TMPRSS2-expressing type II pneumocytes was higher in males than females and in subjects under 60 years of age but it was not different between ACEI/ARB-treated and untreated subjects. However, there was a positive association of TMPRSS2 protein content with age and smoking in ACEI/ARB-treated subjects, with high TMPRSS2 protein levels most evident in ACEI/ARB-treated older adults and smokers.

SIGNIFICANCE

ACEI/ARB treatment influences human lung TMPRSS2 but not ACE2 protein content and this effect is dependent on age and smoking habit. This finding may help explain the increased susceptibility to COVID-19 seen in smokers and older patients with treated cardiovascular-related pathologies.

Involvement of the ACE2/Ang-(1-7)/MasR Axis in Pulmonary Fibrosis: Implications for COVID-19

Pulmonary fibrosis is a chronic, fibrotic lung disease affecting 3 million people worldwide. The ACE2/Ang-(1–7)/MasR axis is of interest in pulmonary fibrosis due to evidence of its anti-fibrotic action. Current scientific evidence supports that inhibition of ACE2 causes enhanced fibrosis. ACE2 is also the primary receptor that facilitates the entry of SARS-CoV-2, the virus responsible for the current COVID-19 pandemic. COVID-19 is associated with a myriad of symptoms ranging from asymptomatic to severe pneumonia and acute respiratory distress syndrome (ARDS) leading to respiratory failure, mechanical ventilation, and often death. One of the potential complications in people who recover from COVID-19 is pulmonary fibrosis. Cigarette smoking is a risk factor for fibrotic lung diseases, including the idiopathic form of this disease (idiopathic pulmonary fibrosis), which has a prevalence of 41% to 83%. Cigarette smoke increases the expression of pulmonary ACE2 and is thought to alter susceptibility to COVID-19. Cannabis is another popular combustible product that shares some similarities with cigarette smoke, however, cannabis contains cannabinoids that may reduce inflammation and/or ACE2 levels. The role of cannabis smoke in the pathogenesis of pulmonary fibrosis remains unknown. This review aimed to characterize the ACE2-Ang-(1–7)-MasR Axis in the context of pulmonary fibrosis with an emphasis on risk factors, including the SARS-CoV-2 virus and exposure to environmental toxicants. In the context of the pandemic, there is a dire need for an understanding of pulmonary fibrotic events. More research is needed to understand the interplay between ACE2, pulmonary fibrosis, and susceptibility to coronavirus infection.

Impact of smoking, COPD and comorbidities on the mortality of COVID-19 patients

The prognosis of the coronavirus disease 2019 (COVID-19) patients is variable and depends on several factors. Current data about the impact of chronic obstructive pulmonary disease (COPD) and smoking on the clinical course of COVID-19 are still controversial. This study evaluated the prevalence and the prognosis of COPD patients and smokers in a cohort of 521 patients admitted to four intermediate Respiratory Intensive Care Units (Puglia, Italy) with respiratory failure due to COVID-19 pneumonia. The prevalence of COPD and current smokers was 14% and 13%, respectively. COPD patients had a higher 30-day all-cause mortality than non-COPD patients. Former smokers compared to never smokers and current smokers had higher 30-day all-cause mortality. COPD patients and former smokers had more comorbidities. This study described the prevalence and the outcomes of COPD patients and smokers in a homogenous cohort of COVID-19 patients. The study showed that the prevalence of COPD and current smokers was not high, suggesting that they were not at increased risk of getting the infection. However, when SARS-CoV-2 infection occurred, COPD patients and former smokers were those with the highest all-cause mortality, which seemed to be mainly related to the presence of comorbidities and not to COPD and smoking itself.