Do gene-environment interactions play a role in COVID-19 distribution? The case of Alpha-1 Antitrypsin, air pollution and COVID-19

Shedding light on the cellular mechanisms involved in the combined adverse effects of fine particulate matter and SARS-CoV-2 on human lung cells

Airborne pathogens represent a topic of scientific relevance, especially considering the recent COVID-19 pandemic. Air pollution, and particulate matter (PM) in particular, has been proposed as a possible risk factor for the onset and spread of pathogen-driven respiratory diseases. Regarding SARS-CoV-2 infection, exposure to fine PM (PM2.5, particles with an aerodynamic diameter < 2.5 μm) has been associated with increased incidence of the COVID-19 disease. To provide useful insights into the mechanisms through which PM might be involved in infection, we exposed human lung cells (A549) to PM2.5 and SARS-CoV-2, to evaluate the toxicological properties and the molecular pathways activated when airborne particles are combined with viral particles. Winter PM2.5 was collected in a metropolitan urban area and its physico-chemical composition was analyzed. A549 cells were exposed to SARS-CoV-2 concomitantly or after pre-treatment with PM2.5. Inflammation, oxidative stress and xenobiotic metabolism were the main pathways investigated. Results showed that after 72 h of exposure PM2.5 significantly increased the expression of the angiotensin-converting enzyme 2 (ACE2) receptor, which is one of the keys used by the virus to infect host cells. We also analyzed the endosomal route in the process of internalization, by studying the expression of RAB5 and RAB7. The results show that in cells pre-activated with PM and then exposed to SARS-CoV-2, RAB5 expression is significantly increased. The activation of the inflammatory process was then studied. Our findings show an increase of pro-inflammatory markers (NF-kB and IL-8) in cells pre-activated with PM for 72 h and subsequently exposed to the virus for a further 24 h, further demonstrating that the interaction between PM and SARS-CoV-2 determines the severity of the inflammatory responses in lung epithelial cells. In conclusion, the study provides mechanistic biological evidence of PM contribution to the onset and progression of viral respiratory diseases in exposed populations.

The Inhibition of Serine Proteases by Serpins Is Augmented by Negatively Charged Heparin: A Concise Review of Some Clinically Relevant Interactions

Serine proteases are members of a large family of hydrolytic enzymes in which a particular serine residue in the active site performs an essential role as a nucleophile, which is required for their proteolytic cleavage function. The array of functions performed by serine proteases is vast and includes, among others, the following: (i) the ability to fight infections; (ii) the activation of blood coagulation or blood clot lysis systems; (iii) the activation of digestive enzymes; and (iv) reproduction. Serine protease activity is highly regulated by multiple families of protease inhibitors, known collectively as the SERine Protease INhibitor (SERPIN). The serpins use a conformational change mechanism to inhibit proteases in an irreversible way. The unusual conformational change required for serpin function provides an elegant opportunity for allosteric regulation by the binding of cofactors, of which the most well-studied is heparin. The goal of this review is to discuss some of the clinically relevant serine protease-serpin interactions that may be enhanced by heparin or other negatively charged polysaccharides. The paired serine protease-serpin in the framework of heparin that we review includes the following: thrombin-antithrombin III, plasmin-anti-plasmin, C1 esterase/kallikrein-C1 esterase inhibitor, and furin/TMPRSS2 (serine protease Transmembrane Protease 2)-alpha-1-antitrypsin, with the latter in the context of COVID-19 and prostate cancer.

Alpha-1-antitrypsin antagonizes COVID-19: a review of the epidemiology, molecular mechanisms, and clinical evidence

Alpha-1-antitrypsin (AAT), a serine protease inhibitor (serpin), is increasingly recognized to inhibit SARS-CoV-2 infection and counter many of the pathogenic mechanisms of COVID-19. Herein, we reviewed the epidemiologic evidence, the molecular mechanisms, and the clinical evidence that support this paradigm. As background to our discussion, we first examined the basic mechanism of SARS-CoV-2 infection and contend that despite the availability of vaccines and anti-viral agents, COVID-19 remains problematic due to viral evolution. We next underscored that measures to prevent severe COVID-19 currently exists but teeters on a balance and that current treatment for severe COVID-19 remains grossly suboptimal. We then reviewed the epidemiologic and clinical evidence that AAT deficiency increases risk of COVID-19 infection and of more severe disease, and the experimental evidence that AAT inhibits cell surface transmembrane protease 2 (TMPRSS2) - a host serine protease required for SARS-CoV-2 entry into cells - and that this inhibition may be augmented by heparin. We also elaborated on the panoply of other activities of AAT (and heparin) that could mitigate severity of COVID-19. Finally, we evaluated the available clinical evidence for AAT treatment of COVID-19.

COVID-19 and non-Hodgkin's lymphoma: A common susceptibility pattern?

OBJECTIVE

To explore the link between COVID-19 incidence, socio-economic covariates, and NHL incidence.

DESIGN

Ecological study design.

SETTING

Sardinia, Italy.

PARTICIPANTS

We used official reports on the total cases of COVID-19 in 2020, published data on NHL incidence, and socio-economic indicators by administrative unit, covering the whole regional population.

MAIN OUTCOMES AND MEASURES

We used multivariable regression analysis to explore the association between the natural logarithm (ln) of the 2020 cumulative incidence of COVID-19 and the ln-transformed NHL incidence in 1974-2003, weighing by population size and adjusting by socioeconomic deprivation and other covariates.

RESULTS

The cumulative incidence of COVID-19 increased in relation to past incidence of NHL (p < 0.001), socioeconomic deprivation (p = 0.006), and proportion of elderly residents (p < 0.001) and decreased with urban residency (p = 0.001). Several sensitivity analyses confirmed the finding of an association between COVID-19 and NHL.

CONCLUSION

This ecological study found an ecological association between NHL and COVID-19. If further investigation would confirm our findings, shared susceptibility factors should be investigated among the plausible underlying mechanisms.

Exposure to particulate matter: Direct and indirect role in the COVID-19 pandemic

Knowing the transmission factors and the natural environment that favor the spread of a viral infection is crucial to stop outbreaks and develop effective preventive strategies. This work aims to evaluate the role of Particulate Matter (PM) in the COVID-19 pandemic, focusing especially on that of PM as a vector for SARS-CoV-2. Exposure to PM has been related to new cases and to the clinical severity of people infected by SARS-CoV-2, which can be explained by the oxidative stress and the inflammatory response generated by these particles when entering the respiratory system, as well as by the role of PM in the expression of ACE-2 in respiratory cells in human hosts. In addition, different authors have detected SARS-CoV-2 RNA in PM sampled both in outdoor and indoor environments. The results of various studies lead to the hypothesis that the aerosols emitted by an infected person could be deposited in other suspended particles, sometimes of natural but especially of anthropogenic origin, that form the basal PM. However, the viability of the virus in PM has not yet been demonstrated. Should PM be confirmed as a vector of transmission, prevention strategies ought to be adapted, and PM sampling in outdoor environments could become an indicator of viral load in a specific area.