Inhibition of the Cell Uptake of Delta and Omicron SARS-CoV-2 Pseudoviruses by N-Acetylcysteine Irrespective of the Oxidoreductive Environment.

The binding of SARS-CoV-2 spikes to the cell receptor angiotensin-converting enzyme 2 (ACE2) is a crucial target both in the prevention and in the therapy of COVID-19. We explored the involvement of oxidoreductive mechanisms by investigating the effects of oxidants and antioxidants on virus uptake by ACE2-expressing cells of human origin (ACE2-HEK293). The cell uptake of pseudoviruses carrying the envelope of either Delta or Omicron variants of SARS-CoV-2 was evaluated by means of a cytofluorimetric approach. The thiol N-acetyl-L-cysteine (NAC) inhibited the uptake of both variants in a reproducible and dose-dependent fashion. Ascorbic acid showed modest effects. In contrast, neither hydrogen peroxide (H2O2) nor a system-generating reactive oxygen species (ROS), which play an important role in the intracellular alterations produced by SARS-CoV-2, were able to affect the ability of either Delta or Omicron SARS-CoV-2 pseudoviruses to be internalized into ACE2-expressing cells. In addition, neither H2O2 nor the ROS generating system interfered with the ability of NAC to inhibit that mechanism. Moreover, based on previous studies, a preventive pharmacological approach with NAC would have the advantage of decreasing the risk of developing COVID-19, irrespective of its variants, and at the same time other respiratory viral infections and associated comorbidities.

Growth and decline of the COVID-19 epidemic wave in Italy from March to June 2020.

March 21, 2020 was the ridgeline between the growth of the coronavirus disease 2019 (COVID-19) epidemic wave in Italy and the start of its decline. We analyzed the epidemic patterns from March 1 to June 30. There was a progressive drop of cases from March (104,710) to April (94,888), May (25,705) and June (8110). Likewise, after a slight increase of deaths in April (14,804) compared to March (12,396), a considerable decline occurred in May (5170) and June (1464). Doubling times of cumulative cases grew from 2 to 6 days until March 20 to 2 weeks up to April 5, and thereafter no further doubling occurred until June 30. There was a striking North-South gradient of both cases and deaths. At the end of June, the nine Northern Italian regions or provinces, five central regions, and seven southern regions had contributed to the 81.1%, 12.4%, and 6.5% of the 240,578 national cases, respectively. Lombardy, the most populous region, was by far the most heavily affected one, accounting for the 39.0% of the national cases occurring over the analyzed 4-month period. However, in relative terms, it was preceded by Aosta Valley, the least populous region, less than 1% of the population of both regions having been affected by cases of COVID-19. The curves showing the ratio of daily cumulative cases and deaths to those of the previous day tended to flatten with time by approaching the zero growth but without reaching it, which documents a persisting circulation of severe acute respiratory syndrome coronavirus 2 in the Italian territory.

Epidemiological trends of COVID-19 epidemic in Italy over March 2020: From 1000 to 100 000 cases.

The coronavirus disease 2019 epidemic started in Italy by the end of January 2020 and, after 1 month, it affected 1049 persons. Based on the Italian Ministry of Health data, we reconstructed the daily course of virus-positive cases and deaths over March 2020 for the whole of Italy, 19 regions and 2 provinces. From 29 February to 31 March, there was a 100.9-fold increase in the cumulative number of cases and a 428.6-fold increase in the number of deaths in Italy. When plotted on a semilogarithmic scale, the curves tended to diverge from linearity with 23%, 16%, and 7% average daily increases during the three decades of March. Similarly, the number of deaths decreased from an average daily growth of 19% over the second decade to 10% over the third decade. The correlation coefficients relating the days to cases or deaths over each one of the three decades approached unity. As inferred from the equations of the regression lines relative to the three decades, the doubling times of cases were 3.4, 5.1, and 9.6 days, respectively. The doubling times of deaths over the second and third decades were 4.9 and 7.0 days, respectively. There was a broad geographic variability, with a striking gradient from the North, where 40.8% of cases and 57.9% of deaths occurred in Lombardy, to the South. On the whole, over March there was a trend to epidemic growth decline but the time for the end of the epidemic will depend on a variety of factors and, at present, it is unpredictable.

Rationale for the use of N-acetylcysteine in both prevention and adjuvant therapy of COVID-19.

COVID-19 may cause pneumonia, acute respiratory distress syndrome, cardiovascular alterations, and multiple organ failure, which have been ascribed to a cytokine storm, a systemic inflammatory response, and an attack by the immune system. Moreover, an oxidative stress imbalance has been demonstrated to occur in COVID-19 patients. N- Acetyl-L-cysteine (NAC) is a precursor of reduced glutathione (GSH). Due to its tolerability, this pleiotropic drug has been proposed not only as a mucolytic agent, but also as a preventive/therapeutic agent in a variety of disorders involving GSH depletion and oxidative stress. At very high doses, NAC is also used as an antidote against paracetamol intoxication. Thiols block the angiotensin-converting enzyme 2 thereby hampering penetration of SARS-CoV-2 into cells. Based on a broad range of antioxidant and anti-inflammatory mechanisms, which are herein reviewed, the oral administration of NAC is likely to attenuate the risk of developing COVID-19, as it was previously demonstrated for influenza and influenza-like illnesses. Moreover, high-dose intravenous NAC may be expected to play an adjuvant role in the treatment of severe COVID-19 cases and in the control of its lethal complications, also including pulmonary and cardiovascular adverse events.