Metabolism of angiotensin peptides by angiotensin converting enzyme 2 (ACE2) and analysis of the effect of excess zinc on ACE2 enzymatic activity

Impact of zinc on immunometabolism and its putative role on respiratory diseases

Zinc is the second most abundant trace mineral in the human body and plays a critical role in immune cell function and metabolism. Zinc deficiency impairs immune cell function and is associated with increased susceptibility to respiratory diseases, including pneumonia, influenza, and COVID-19. Zinc homeostasis, maintained by numerous zinc transporters and metal-binding proteins (ie, metallothionein), is essential for coordinating immune cell signaling, gene expression, and enzymatic activities in response to respiratory infections. This article highlights the emerging role of zinc in various aspects of immune function, particularly through its influence on cellular metabolism. Given the significant global burden of respiratory diseases, there is a need to identify effective nutritional interventions that could be readily leveraged to prevent and/or mitigate respiratory disease risk, particularly in older adults who are prone to zinc deficiency. However, the immunometabolic mechanisms underlying zinc's protective effects remain poorly characterized. Future research should focus on elucidating how micronutrients, such as zinc, can support changes in immune cell metabolism in response to infections. Such efforts will help determine how zinc metabolism and zinc intervention strategies may best be leveraged to prevent or mitigate respiratory disease.

Density functional theory and enzyme studies support interactions between angiotensin receptor blockers and angiotensin converting enzyme-2: Relevance to coronavirus 2019

The binding affinities and interactions between eight drug candidates, both commercially available (candesartan; losartan; losartan carboxylic acid; nirmatrelvir; telmisartan) and newly synthesized benzimidazole-N-biphenyltetrazole (ACC519T), benzimidazole bis-N,N'-biphenyltetrazole (ACC519T(2) and 4-butyl-N,N-bis([2-(2H-tetrazol-5-yl)biphenyl-4-yl]) methyl (BV6), and the active site of angiotensin-converting enzyme-2 (ACE2) were evaluated for their potential as inhibitors against SARS-CoV-2 and regulators of ACE2 function through Density Functional Theory methodology and enzyme activity assays, respectively. Notably, telmisartan and ACC519T(2) exhibited pronounced binding affinities, forming strong interactions with ACE2's active center, favorably accepting proton from the guanidinium group of arginine273. The ordering of candidates by binding affinity and reactivity descriptors, emerged as telmisartan > ACC519T(2) > candesartan > ACC519T > losartan carboxylic acid > BV6 > losartan > nirmatrelvir. Proton transfers among the active center amino acids revealed their interconnectedness, highlighting a chain-like proton transfer involving tyrosine, phenylalanine, and histidine. Furthermore, these candidates revealed their potential antiviral abilities by influencing proton transfer within the ACE2 active site. Furthermore, through an in vitro pharmacological assays we determined that candesartan and the BV6 derivative, 4-butyl-N,N0-bis[20-2Htetrazol-5-yl)bipheyl-4-yl]methyl)imidazolium bromide (BV6(K+)2) also contain the capacity to increase ACE2 functional activity. This comprehensive analysis collectively underscores the promise of these compounds as potential therapeutic agents against SARS-CoV-2 by targeting crucial protein interactions.

Pathobiological alterations affecting the distinct clinical courses of pediatric versus adult COVID-19 syndrome

Background/aim

The clinical presentation of pediatric coronavirus disease 2019 (COVID-19) is associated with a milder disease course than the adult COVID-19 syndrome. The disease course of COVID-19 has three clinicobiological phases: initiation, propagation, and complication. This study aimed to assess the pathobiological alterations affecting the distinct clinical courses of COVID-19 in pediatric age groups versus the adult population. We hypothesized that critical biogenomic marker expressions drive the mild clinical presentations of pediatric COVID-19.

Materials and methods

Blood samples were obtained from 72 patients with COVID-19 hospitalized at Ankara City Hospital between March and July 2021. Peripheral blood mononuclear cells were isolated using Ficoll-Paque and density-gradient sedimentation. The groups were compared using a t-test and limma analyses. Mean standardized gene expression levels were used to hierarchically cluster genes employing Euclidean Gene Cluster 3.0. The expression levels of identified genes were determined using reverse transcription-polymerase chain reaction.

Results

This study found that ANPEP gene expression was significantly downregulated in the pediatric group (p < 0.05, FC: 1.57) and IGF2R gene expression was significantly upregulated in the adult group (p < 0.05, FC: 2.98). The study results indicated that the expression of critical biogenomic markers, such as the first-phase (ACE2 and ANPEP) and second-phase (EGFR and IGF2R) receptor genes, was crucial in the genesis of mild clinical presentations of pediatric COVID-19. ANPEP gene expression was lower in pediatric COVID-19.

Conclusion

The interrelationship between the ANPEP and ACE2 genes may prevent the progression of COVID-19 from initiation to the propagating phase in pediatric patients. High IGF2R gene expression could potentially contribute to a protective effect and may be a contributing factor for the mild clinical course observed in pediatric patients.

When the Dust Has Settled: Calculation of Binding Affinities from First Principles for SARS-CoV-2 Variants with Quantitative Accuracy

Accurate determination of binding free energy is pivotal for the study of many biological processes and has been applied in a number of theoretical investigations to compare the affinity of severe acute respiratory syndrome coronavirus 2 variants toward the host cell. Diversity of these variants challenges the development of effective general therapies, their transmissibility relying either on an increased affinity toward their dedicated human receptor, the angiotensin-converting enzyme 2 (ACE2), or on escaping the immune response. Now that robust structural data are available, we have determined with utmost accuracy the standard binding free energy of the receptor-binding domain to the most widespread variants, namely, Alpha, Beta, Delta, and Omicron BA.2, as well as the wild type (WT) in complex either with ACE2 or with antibodies, namely, S2E12 and H11-D4, using a rigorous theoretical framework that combines molecular dynamics and potential-of-mean-force calculations. Our results show that an appropriate starting structure is crucial to ensure appropriate reproduction of the binding affinity, allowing the variants to be compared. They also emphasize the necessity to apply the relevant methodology, bereft of any shortcut, to account for all the contributions to the standard binding free energy. Our estimates of the binding affinities support the view that while the Alpha and Beta variants lean on an increased affinity toward the host cell, the Delta and Omicron BA.2 variants choose immune escape. Moreover, the S2E12 antibody, already known to be active against the WT (Starr et al., 2021; Mlcochova et al., 2021), proved to be equally effective against the Delta variant. In stark contrast, H11-D4 retains a low affinity toward the WT compared to that of ACE2 for the latter. Assuming robust structural information, the methodology employed herein successfully addresses the challenging protein-protein binding problem in the context of coronavirus disease 2019 while offering promising perspectives for predictive studies of ever-emerging variants.

The Effect of Allicin on the Proteome of SARS-CoV-2 Infected Calu-3 Cells

Allicin (diallyl thiosulfinate) is the major thiol-reactive organosulfur compound produced by garlic plants (Allium sativum) upon tissue damage. Allicin exerts its strong antimicrobial activity against bacteria and fungi via S-thioallylation of protein thiols and low molecular weight thiols. Here, we investigated the effect of allicin on SARS-CoV-2 infected Vero E6 and Calu-3 cells. Toxicity tests revealed that Calu-3 cells showed greater allicin tolerance, probably due to >4-fold higher GSH levels compared to the very sensitive Vero E6 cells. Exposure of infected Vero E6 and Calu-3 cells to biocompatible allicin doses led to a ∼60–70% decrease of viral RNA and infectious viral particles. Label-free quantitative proteomics was used to investigate the changes in the Calu-3 proteome after SARS-CoV-2 infection and the effect of allicin on the host-virus proteome. SARS-CoV-2 infection of Calu-3 cells caused a strong induction of the antiviral interferon-stimulated gene (ISG) signature, including several antiviral effectors, such as cGAS, Mx1, IFIT, IFIH, IFI16, IFI44, OAS, and ISG15, pathways of vesicular transport, tight junctions (KIF5A/B/C, OSBPL2, CLTCL1, and ARHGAP17) and ubiquitin modification (UBE2L3/5), as well as reprogramming of host metabolism, transcription and translation. Allicin treatment of infected Calu-3 cells reduced the expression of IFN signaling pathways and ISG effectors and reverted several host pathways to levels of uninfected cells. Allicin further reduced the abundance of the structural viral proteins N, M, S and ORF3 in the host-virus proteome. In conclusion, our data demonstrate the antiviral and immunomodulatory activity of biocompatible doses of allicin in SARS-CoV-2-infected cell cultures. Future drug research should be directed to exploit the thiol-reactivity of allicin derivatives with increased stability and lower human cell toxicity as antiviral lead compounds.

Zinc as a Drug for Wilson's Disease, Non-Alcoholic Liver Disease and COVID-19-Related Liver Injury

Zinc is the second most abundant trace element in the human body, and it plays a fundamental role in human physiology, being an integral component of hundreds of enzymes and transcription factors. The discovery that zinc atoms may compete with copper for their absorption in the gastrointestinal tract let to introduce zinc in the therapy of Wilson's disease, a congenital disorder of copper metabolism characterized by a systemic copper storage. Nowadays, zinc salts are considered one of the best therapeutic approach in patients affected by Wilson's disease. On the basis of the similarities, at histological level, between Wilson's disease and non-alcoholic liver disease, zinc has been successfully introduced in the therapy of non-alcoholic liver disease, with positive effects both on insulin resistance and oxidative stress. Recently, zinc deficiency has been indicated as a possible factor responsible for the susceptibility of elderly patients to undergo infection by SARS-CoV-2, the coronavirus responsible for the COVID-19 pandemic. Here, we present the data correlating zinc deficiency with the insurgence and progression of Covid-19 with low zinc levels associated with severe disease states. Finally, the relevance of zinc supplementation in aged people at risk for SARS-CoV-2 is underlined, with the aim that the zinc-based drug, classically used in the treatment of copper overload, might be recorded as one of the tools reducing the mortality of COVID-19, particularly in elderly people.