How SARS-CoV-2 might affect potassium balance via impairing epithelial sodium channels?

Pre-hospital oxygen therapy and saturation variability in COVID-19 patients with and without glucose metabolism disorders: part of the COLOS Study

The COVID-19 pandemic has revealed that viruses can have multiple receptor properties, penetrating various tissues and causing mutations in various genes, thus promoting a range of metabolic disorders. The purpose of this study was to investigate the connection between three factors: diabetic status, pre-hospitalization oxygen therapy, and saturation levels, to the values of morphological, inflammatory, and biochemical parameters in the blood serum of COVID-19 patients. The study group consisted of 2139 patients, 1076 women (50.30%) and 1063 men (49.70%), with an average age of 63.73 ± 15.69 years. The population was divided into three groups based on a three-stage scale, taking into account patients with either type 2 diabetes/prediabetes (473 patients), those who received oxygen therapy before hospitalization, and those with a saturation value of below 95% (cut-off value). Among patients who did not receive pre-hospitalization oxygen therapy, those with diabetes and a SpO2 level < 95% had significantly higher levels of D-dimers, procalcitonin, albumin, lymphocytes, RDW-SD ≥ 47, potassium, creatinine, and troponin T when compared to diabetic patients with a SpO2 level ≥ 95%. Similarly, in the same group of patients without pre-hospitalization oxygen therapy, those without diabetes but with a SpO2 level < 95% showed significantly increased levels of IL-6, CRP, albumin, lymphocytes, RDW-SD ≥ 47, glucose, potassium, sodium, creatinine, and ALT, compared to patients without diabetes and with a SpO2 level ≥ 95%. The findings suggest that lower saturation levels may result in increased potassium and glucose levels in patients who did not receive any oxygen therapy before hospitalization due to COVID-19. It is hypothesized that this may be caused by damage to pancreatic β-cells by SARS-CoV-2, and disturbances in the potassium channel, leading to cell membrane depolarization and insulin secretion.

Aprotinin (I): Understanding the Role of Host Proteases in COVID-19 and the Importance of Pharmacologically Regulating Their Function

Proteases are produced and released in the mucosal cells of the respiratory tract and have important physiological functions, for example, maintaining airway humidification to allow proper gas exchange. The infectious mechanism of severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2), which causes coronavirus disease 2019 (COVID-19), takes advantage of host proteases in two ways: to change the spatial conformation of the spike (S) protein via endoproteolysis (e.g., transmembrane serine protease type 2 (TMPRSS2)) and as a target to anchor to epithelial cells (e.g., angiotensin-converting enzyme 2 (ACE2)). This infectious process leads to an imbalance in the mucosa between the release and action of proteases versus regulation by anti-proteases, which contributes to the exacerbation of the inflammatory and prothrombotic response in COVID-19. In this article, we describe the most important proteases that are affected in COVID-19, and how their overactivation affects the three main physiological systems in which they participate: the complement system and the kinin-kallikrein system (KKS), which both form part of the contact system of innate immunity, and the renin-angiotensin-aldosterone system (RAAS). We aim to elucidate the pathophysiological bases of COVID-19 in the context of the imbalance between the action of proteases and anti-proteases to understand the mechanism of aprotinin action (a panprotease inhibitor). In a second-part review, titled "Aprotinin (II): Inhalational Administration for the Treatment of COVID-19 and Other Viral Conditions", we explain in depth the pharmacodynamics, pharmacokinetics, toxicity, and use of aprotinin as an antiviral drug.

Aprotinin (II): Inhalational Administration for the Treatment of COVID-19 and Other Viral Conditions

Aprotinin is a broad-spectrum inhibitor of human proteases that has been approved for the treatment of bleeding in single coronary artery bypass surgery because of its potent antifibrinolytic actions. Following the outbreak of the COVID-19 pandemic, there was an urgent need to find new antiviral drugs. Aprotinin is a good candidate for therapeutic repositioning as a broad-spectrum antiviral drug and for treating the symptomatic processes that characterise viral respiratory diseases, including COVID-19. This is due to its strong pharmacological ability to inhibit a plethora of host proteases used by respiratory viruses in their infective mechanisms. The proteases allow the cleavage and conformational change of proteins that make up their viral capsid, and thus enable them to anchor themselves by recognition of their target in the epithelial cell. In addition, the activation of these proteases initiates the inflammatory process that triggers the infection. The attraction of the drug is not only its pharmacodynamic characteristics but also the possibility of administration by the inhalation route, avoiding unwanted systemic effects. This, together with the low cost of treatment (≈2 Euro/dose), makes it a good candidate to reach countries with lower economic means. In this article, we will discuss the pharmacodynamic, pharmacokinetic, and toxicological characteristics of aprotinin administered by the inhalation route; analyse the main advances in our knowledge of this medication; and the future directions that should be taken in research in order to reposition this medication in therapeutics.

Association of ACE2 and TMPRSS2 genes variants with disease severity and most important biomarkers in COVID-19 patients in Bosnia and Herzegovina

AIM

To assess the association of single nucleotide polymorphisms (SNPs) in the ACE2 and TMPRSS2 genes with COVID-19 severity and key biomarkers.

METHODS

The study involved 750 COVID-19 patients from Bosnia and Herzegovina, divided into three groups: mild, moderate, and severe cases. Genetic variations within the ACE2 (rs2285666) and TMPRSS2 (rs2070788) genes were examined with real-time polymerase chain reaction. Biochemical markers were determined with standard procedures.

RESULTS

There was a significant difference in the rs2070788 genotype distribution between patients with mild and moderate symptoms, but not between other groups. For the rs2285666 polymorphism, no significant difference in genotype distribution was found. In patients with mild symptoms, carriers of the GG genotype of rs2070788 had significantly higher total bilirubin levels than carriers of the AA genotype. Similarly, carriers of the TT genotype of rs2285666 had significantly higher activated partial thromboplastin time and international normalized ratio, and lower lactate dehydrogenase levels compared with the CC genotype. Among patients with severe symptoms, carriers of the GG genotype showed significantly higher potassium levels than carriers of the AA genotype, while carriers of the TT genotype showed significantly higher erythrocyte count as well as hemoglobin and hematocrit levels compared with the CC genotype.

CONCLUSION

This study highlights the role of genetic factors, particularly SNPs in the ACE2 and TMPRSS2 genes, in determining COVID-19 severity, aiding patient risk assessment and prognosis.

Effect of SARS-CoV-2 S protein on the proteolytic cleavage of the epithelial Na+ channel ENaC

Severe cases of COVID-19 are characterized by development of acute respiratory distress syndrome (ARDS). Water accumulation in the lungs is thought to occur as consequence of an exaggerated inflammatory response. A possible mechanism could involve decreased activity of the epithelial Na+ channel, ENaC, expressed in type II pneumocytes. Reduced transepithelial Na+ reabsorption could contribute to lung edema due to reduced alveolar fluid clearance. This hypothesis is based on the observation of the presence of a novel furin cleavage site in the S protein of SARS-CoV-2 that is identical to the furin cleavage site present in the alpha subunit of ENaC. Proteolytic processing of αENaC by furin-like proteases is essential for channel activity. Thus, competition between S protein and αENaC for furin-mediated cleavage in SARS-CoV-2-infected cells may negatively affect channel activity. Here we present experimental evidence showing that coexpression of the S protein with ENaC in a cellular model reduces channel activity. In addition, we show that bidirectional competition for cleavage by furin-like proteases occurs between 〈ENaC and S protein. In transgenic mice sensitive to lethal SARS-CoV-2, however, a significant decrease in gamma ENaC expression was not observed by immunostaining of lungs infected as shown by SARS-CoV2 nucleoprotein staining.

IgM N-glycosylation correlates with COVID-19 severity and rate of complement deposition

The glycosylation of IgG plays a critical role during human severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, activating immune cells and inducing cytokine production. However, the role of IgM N-glycosylation has not been studied during human acute viral infection. The analysis of IgM N-glycosylation from healthy controls and hospitalized coronavirus disease 2019 (COVID-19) patients reveals increased high-mannose and sialylation that correlates with COVID-19 severity. These trends are confirmed within SARS-CoV-2-specific immunoglobulin N-glycan profiles. Moreover, the degree of total IgM mannosylation and sialylation correlate significantly with markers of disease severity. We link the changes of IgM N-glycosylation with the expression of Golgi glycosyltransferases. Lastly, we observe antigen-specific IgM antibody-dependent complement deposition is elevated in severe COVID-19 patients and modulated by exoglycosidase digestion. Taken together, this work links the IgM N-glycosylation with COVID-19 severity and highlights the need to understand IgM glycosylation and downstream immune function during human disease.

IgM N-glycosylation correlates with COVID-19 severity and rate of complement deposition

The glycosylation of IgG plays a critical role during human SARS-CoV-2, activating immune cells and inducing cytokine production. However, the role of IgM N-glycosylation has not been studied during acute viral infection in humans. In vitro evidence suggests that the glycosylation of IgM inhibits T cell proliferation and alters complement activation rates. The analysis of IgM N-glycosylation from healthy controls and hospitalized COVID-19 patients reveals that mannosylation and sialyation levels associate with COVID-19 severity. Specifically, we find increased di- and tri-sialylated glycans and altered mannose glycans in total serum IgM in severe COVID-19 patients when compared to moderate COVID-19 patients. This is in direct contrast with the decrease of sialic acid found on the serum IgG from the same cohorts. Moreover, the degree of mannosylation and sialylation correlated significantly with markers of disease severity: D-dimer, BUN, creatinine, potassium, and early anti-COVID-19 amounts of IgG, IgA, and IgM. Further, IL-16 and IL-18 cytokines showed similar trends with the amount of mannose and sialic acid present on IgM, implicating these cytokines' potential to impact glycosyltransferase expression during IgM production. When examining PBMC mRNA transcripts, we observe a decrease in the expression of Golgi mannosidases that correlates with the overall reduction in mannose processing we detect in the IgM N-glycosylation profile. Importantly, we found that IgM contains alpha-2,3 linked sialic acids in addition to the previously reported alpha-2,6 linkage. We also report that antigen-specific IgM antibody-dependent complement deposition is elevated in severe COVID-19 patients. Taken together, this work links the immunoglobulin M N-glycosylation with COVID-19 severity and highlights the need to understand the connection between IgM glycosylation and downstream immune function during human disease.

Regulation of Epithelial Sodium Transport by SARS-CoV-2 Is Closely Related with Fibrinolytic System-Associated Proteins

Dyspnea and progressive hypoxemia are the main clinical features of patients with coronavirus disease 2019 (COVID-19), which is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Pulmonary pathology shows diffuse alveolar damage with edema, hemorrhage, and the deposition of fibrinogens in the alveolar space, which are consistent with the Berlin Acute Respiratory Distress Syndrome Criteria. The epithelial sodium channel (ENaC) is a key channel protein in alveolar ion transport and the rate-limiting step for pulmonary edema fluid clearance, the dysregulation of which is associated with acute lung injury/acute respiratory distress syndrome. The main protein of the fibrinolysis system, plasmin, can bind to the furin site of γ-ENaC and induce it to an activation state, facilitating pulmonary fluid reabsorption. Intriguingly, the unique feature of SARS-CoV-2 from other β-coronaviruses is that the spike protein of the former has the same furin site (RRAR) with ENaC, suggesting that a potential competition exists between SARS-CoV-2 and ENaC for the cleavage by plasmin. Extensive pulmonary microthrombosis caused by disorders of the coagulation and fibrinolysis system has also been seen in COVID-19 patients. To some extent, high plasmin (ogen) is a common risk factor for SARS-CoV-2 infection since an increased cleavage by plasmin accelerates virus invasion. This review elaborates on the closely related relationship between SARS-CoV-2 and ENaC for fibrinolysis system-related proteins, aiming to clarify the regulation of ENaC under SARS-CoV-2 infection and provide a novel reference for the treatment of COVID-19 from the view of sodium transport regulation in the lung epithelium.

Biochemical and Anthropometric Nutritional Assessment in Children Infected with COVID-19: A Cross-sectional Study

Background: Severe acute respiratory syndrome has led to a pandemic of coronavirus disease 2019 (COVID-19). Malnutrition either biochemically or anthropometrically is a well-known risk factor for COVID-19 and may be the vice versa Objectives  : To investigate the prevalence of malnutrition in children infected with COVID-19 through evaluating the nutritional biomarkers such as serum electrolytes, serum albumin and hemoglobin together with the anthropometric assessment.  Methods: A cross sectional study that was conducted at ElMatria Teaching Hospital for all children admitted with confirmed COVID-19 over a period of 6 months from 1st February 2021 to the end of July, 2021. Nutritional biochemical evaluation included serum electrolytes particularly   the potassium and other nutritional biomarkers such  as serum albumin and hemoglobin. Nutritional anthropometric evaluation depended on BMI (body mass index), the height/length, weight for length and weight for height..The prevalence of malnutrition esp. hypokalemia was the main outcome. Results: Hypokalemia was present in 21.8% of the study participants . Other nutritional biomarkers were found  as hyponatremia, hypocalcemia , hypophosphatemia, hypomagnesemia were detected in 49.1% , 38.2%,21.8% and 34.5%  of the study subjects respectively. Anthropometric malnutrition was present in most of the enrolled children with COVID-19 in the study (65.5 %  (n= 36) )through which overweight and obese children occupied a greater percentage. Conclusion: Malnutrition either biochemically or anthropometrically could be linked to   COVID-19 in children. COVID-19 could have negative outcomes on the nutritional status such as electrolytes disturbances. Both malnutrition and COVID-19 are considered synergistic associations   Keywords: Malnutrition. COVID-19. Children. Hypokalemia. Obesity

Sudden Cardiac Arrest in a Patient With COVID-19 as a Result of Severe Hyperkalemia After Administration of Succinylcholine Chloride for Reintubation. A Case Report

Background

We present a case study of a man with coronavirus disease 2019 (COVID-19) who developed cardiac arrest as a result of hyperkalemia following administration of chlororsuccinylcholine during endotracheal intubation.

Case Summary

A patient with a severe course of COVID-19, hospitalized in the Intensive Care Unit, underwent reintubation on day 16. The applied scheme was rapid sequence induction and intubation with administration of chlororsuccinylcholine. Immediately after intubation, there was a sudden cardiac arrest due to hyperkalemia (cK + 10.2 meq/L). Treatment was initiated as per guidelines, which resulted in a return to spontaneous circulation after 6 min.

Conclusion

Chlorsucynylcholine may cause life-threatening hyperkalemia. We recommend using rocuronium as a neuromuscular blocking agent in critically ill COVID-19 patients due to its more optimal safety profile.

Transmembrane serine protease 2 (TMPRSS2) proteolytically activates the epithelial sodium channel (ENaC) by cleaving the channel's γ-subunit

The epithelial sodium channel (ENaC) is a heterotrimer consisting of α-, β-, and γ-subunits. Channel activation requires proteolytic release of inhibitory tracts from the extracellular domains of α-ENaC and γ-ENaC; however, the proteases involved in the removal of the γ-inhibitory tract remain unclear. In several epithelial tissues, ENaC is coexpressed with the transmembrane serine protease 2 (TMPRSS2). Here, we explored the effect of human TMPRSS2 on human αβγ-ENaC heterologously expressed in Xenopus laevis oocytes. We found that coexpression of TMPRSS2 stimulated ENaC-mediated whole-cell currents by approximately threefold, likely because of an increase in average channel open probability. Furthermore, TMPRSS2-dependent ENaC stimulation was not observed using a catalytically inactive TMPRSS2 mutant and was associated with fully cleaved γ-ENaC in the intracellular and cell surface protein fractions. This stimulatory effect of TMPRSS2 on ENaC was partially preserved when inhibiting its proteolytic activity at the cell surface using aprotinin but was abolished when the γ-inhibitory tract remained attached to its binding site following introduction of two cysteine residues (S155C–Q426C) to form a disulfide bridge. In addition, computer simulations and site-directed mutagenesis experiments indicated that TMPRSS2 can cleave γ-ENaC at sites both proximal and distal to the γ-inhibitory tract. This suggests a dual role of TMPRSS2 in the proteolytic release of the γ-inhibitory tract. Finally, we demonstrated that TMPRSS2 knockdown in cultured human airway epithelial cells (H441) reduced baseline proteolytic activation of endogenously expressed ENaC. Thus, we conclude that TMPRSS2 is likely to contribute to proteolytic ENaC activation in epithelial tissues in vivo.