Potential therapeutic approaches for the early entry of SARS-CoV-2 by interrupting the interaction between the spike protein on SARS-CoV-2 and angiotensin-converting enzyme 2 (ACE2)

An overview on the impact of viral pathogens on Alzheimer's disease

Alzheimer's disease (AD) is the most common type of dementia which affects over than 60 million cases worldwide with higher incidence in low and middle-income countries by 2030. Based on the multifactorial nature of AD different risk factors are linked to the condition considering the brain's β-amyloid plaques (Aβ) and neurofibrillary tangles (NFTs) as its primary hallmarks. Lately, viral photogenes specially after recent SARS-CoV-2 pandemic has gained a lot of attention in promoting the neurodegenerative disorder such as AD based on their capacity to increase the permeability of the blood-brain barrier, dysregulation of immune responses, and the impact on Aβ processing and phosphorylation of tau proteins. Therefore, in this review, we summarized the important association of viral pathogens and their mechanism by which they contribute with AD formation and development. AN OVERVIEW OF THE ROLES OF VIRAL PATHOGENS IN AD: According to this figure, viruses can infect neurons directly by modulating the BBB, transferring from endothelial cells to glial cells and then to neurons, increasing the Aβ deposition, and affecting the tau protein phosphorylation or indirectly through the virus's entrance and pathogenicity that can be accelerated by genetic and epigenetic factors, as well as chronic neuroinflammation caused by activated microglia and astrocytes.

Engineering a NanoBiT biosensor for detecting angiotensin-converting enzyme-2 (hACE2) interaction with SARS-CoV-2 spike protein and screening the inhibitors to block hACE2 and spike interaction

Infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is facilitated by its trimeric surface spike protein, which binds to the human angiotensin-converting enzyme 2 (hACE2) receptor. This critical interaction facilitates viral entry and is a primary target for therapeutic intervention against COVID-19. However, it is difficult to fully optimize viral infection using existing protein-protein interaction methods. Herein, we introduce a nano-luciferase binary technology (NanoBiT)-based pseudoviral sensor designed to stimulate the dynamics of viral infection in both living cells and animals. Infection progression can be dynamically visualized via a rapid increase in luminescence within 3 h using an in vivo imaging system (IVIS). Inhibition of viral infection by baicalein and baicalin was evaluated using a NanoBiT-based pseudoviral sensor. These results indicate that the inhibitory efficacy of baicalein was strengthened by targeting the spike protein, whereas baicalin targeted the hACE2 protein. Additionally, under optimized conditions, baicalein and baicalin provided a synergistic combination to inhibit pseudoviral infection. Live bioluminescence imaging was used to evaluate the in vivo effects of baicalein and baicalin treatment on LgBiT-hACE2 mice infected with the BA.2-SmBiT spike pseudovirus. This innovative bioluminescent system functions as a sensitive and early-stage quantitative viral transduction in vitro and in vivo. This platform provides novel opportunities for studying the molecular biology of animal models.

Relationship between Vitamin D and Immunity in Older People with COVID-19

Vitamin D is a group of lipophilic hormones with pleiotropic actions. It has been traditionally related to bone metabolism, although several studies in the last decade have suggested its role in sarcopenia, cardiovascular and neurological diseases, insulin-resistance and diabetes, malignancies, and autoimmune diseases and infections. In the pandemic era, by considering the response of the different branches of the immune system to SARS-CoV-2 infection, our aims are both to analyse, among the pleiotropic effects of vitamin D, how its strong multimodal modulatory effect on the immune system is able to affect the pathophysiology of COVID-19 disease and to emphasise a possible relationship between the well-known circannual fluctuations in blood levels of this hormone and the epidemiological trend of this infection, particularly in the elderly population. The biologically active form of vitamin D, or calcitriol, can influence both the innate and the adaptive arm of the immune response. Calcifediol levels have been found to be inversely correlated with upper respiratory tract infections in several studies, and this activity seems to be related to its role in the innate immunity. Cathelicidin is one of the main underlying mechanisms since this peptide increases the phagocytic and germicidal activity acting as chemoattractant for neutrophils and monocytes, and representing the first barrier in the respiratory epithelium to pathogenic invasion. Furthermore, vitamin D exerts a predominantly inhibitory action on the adaptive immune response, and it influences either cell-mediated or humoral immunity through suppression of B cells proliferation, immunoglobulins production or plasma cells differentiation. This role is played by promoting the shift from a type 1 to a type 2 immune response. In particular, the suppression of Th1 response is due to the inhibition of T cells proliferation, pro-inflammatory cytokines production (e.g., INF-γ, TNF-α, IL-2, IL-17) and macrophage activation. Finally, T cells also play a fundamental role in viral infectious diseases. CD4 T cells provide support to B cells antibodies production and coordinate the activity of the other immunological cells; moreover, CD8 T lymphocytes remove infected cells and reduce viral load. For all these reasons, calcifediol could have a protective role in the lung damage produced by COVID-19 by both modulating the sensitivity of tissue to angiotensin II and promoting overexpression of ACE-2. Promising results for the potential effectiveness of vitamin D supplementation in reducing the severity of COVID-19 disease was demonstrated in a pilot clinical trial of 76 hospitalised patients with SARS-CoV-2 infection where oral calcifediol administration reduced the need for ICU treatment. These interesting results need to be confirmed in larger studies with available information on vitamin D serum levels.

Functionalized protein microparticles targeting hACE2 as a novel preventive strategy for SARS-CoV-2 infection

The coronavirus disease 2019 (COVID-19) pandemic is caused by severe acute respiratory syndrome coronavirus 2(SARS-CoV-2), resulting in a serious burden on public health and social economy worldwide. SARS-CoV-2 infection is mainly initialized in the nasopharyngeal cavity through the binding of viral spike (S) protein to human angiotensin-converting enzyme 2 (hACE2) receptors which are widely expressed in many human cells. Thus, blockade of the interaction between viral S protein and hACE2 receptor in the primary entry site is a promising prevention strategy for the management of COVID-19. Here we showed protein microparticles (PMPs) decorated with hACE2 could bind and neutralize SARS-CoV-2 S protein-expressing pseudovirus (PSV) and protect host cells from infection in vitro. In the hACE2 transgenic mouse model, administration of intranasal spray with hACE2-decorated PMPs markedly decreased the viral load of SARS-CoV-2 in the lungs though the inflammation was not attenuated significantly. Our results provided evidence for developing functionalized PMPs as a potential strategy for preventing emerging air-borne infectious pathogens, such as SARS-CoV-2 infection.

Targeting SARS-CoV-2 and host cell receptor interactions

Despite the availability of vaccines and therapeutics, continual genetic alterations render the severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) a persistent threat, particularly for the immunocompromised and elderly. Through interactions of its spike (S) protein with different receptors and coreceptors on host cell surfaces, the virus enters the cell either via fusion with the plasma membrane or through endocytosis. Angiotensin-converting enzyme 2 (ACE2) has been identified as a key receptor utilized by SARS-CoV-2 and related human coronaviruses to mediate cell entry in the lung airways. Auxiliary SARS-CoV-2 entry receptors such as ASGPR1, Kremen protein 1, integrins have also been reported. In this review, therapeutic approaches to block SARS-CoV-2 and host cell receptor interactions are discussed.

Ginkgolic acids inhibit SARS-CoV-2 and its variants by blocking the spike protein/ACE2 interplay

Targeting the interaction between the spike protein receptor binding domain (S-RBD) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and angiotensin-converting enzyme 2 (ACE2) is a potential therapeutic strategy for treating coronavirus disease 2019 (COVID-19). However, we still lack small-molecule drug candidates for this target due to the missing knowledge in the hot spots for the protein-protein interaction. Here, we used NanoBiT technology to identify three Ginkgolic acids from an in-house traditional Chinese medicine (TCM) library, and they interfere with the S-RBD/ACE2 interplay. Our pseudovirus assay showed that one of the compounds, Ginkgolic acid C17:1 (GA171), significantly inhibits the entry of original SARS-CoV-2 and its variants into the ACE2-overexpressed HEK293T cells. We investigated and proposed the binding sites of GA171 on S-RBD by combining molecular docking and molecular dynamics simulations. Site-directed mutagenesis and surface plasmon resonance revealed that GA171 specifically binds to the pocket near R403 and Y505, critical residues of S-RBD for S-RBD interacting with ACE2. Thus, we provide structural insights into developing new small-molecule inhibitors and vaccines against the proposed S-RBD binding site.

Small molecules in the treatment of COVID-19

The outbreak of COVID-19 has become a global crisis, and brought severe disruptions to societies and economies. Until now, effective therapeutics against COVID-19 are in high demand. Along with our improved understanding of the structure, function, and pathogenic process of SARS-CoV-2, many small molecules with potential anti-COVID-19 effects have been developed. So far, several antiviral strategies were explored. Besides directly inhibition of viral proteins such as RdRp and Mpro, interference of host enzymes including ACE2 and proteases, and blocking relevant immunoregulatory pathways represented by JAK/STAT, BTK, NF-κB, and NLRP3 pathways, are regarded feasible in drug development. The development of small molecules to treat COVID-19 has been achieved by several strategies, including computer-aided lead compound design and screening, natural product discovery, drug repurposing, and combination therapy. Several small molecules representative by remdesivir and paxlovid have been proved or authorized emergency use in many countries. And many candidates have entered clinical-trial stage. Nevertheless, due to the epidemiological features and variability issues of SARS-CoV-2, it is necessary to continue exploring novel strategies against COVID-19. This review discusses the current findings in the development of small molecules for COVID-19 treatment. Moreover, their detailed mechanism of action, chemical structures, and preclinical and clinical efficacies are discussed.

Resistance profile and mechanism of severe acute respiratory syndrome coronavirus-2 variants to LCB1 inhibitor targeting the spike receptor-binding motif

LCB1 is a 56-mer miniprotein computationally designed to target the spike (S) receptor-binding motif of SARS-CoV-2 with potent in vitro and in vivo inhibitory activities (Cao et al., 2020; Case et al., 2021). However, the rapid emergence and epidemic of viral variants have greatly impacted the effectiveness of S protein-targeting vaccines and antivirals. In this study, we chemically synthesized a peptide-based LCB1 inhibitor and characterized the resistance profile and underlying mechanism of SARS-CoV-2 variants. Among five variants of concern (VOCs), we found that pseudoviruses of Beta, Gamma, and Omicron were highly resistant to the LCB1 inhibition, whereas the pseudoviruses of Alpha and Delta as well as the variant of interest (VOI) Lambda only caused mild resistance. By generating a group of mutant viruses carrying single or combination mutations, we verified that K417N and N501Y substitutions in RBD critically determined the high resistance phenotype of VOCs. Furthermore, a large panel of 85 pseudoviruses with naturally occurring RBD point-mutations were generated and applied to LCB1, which identified that E406Q, K417N, and L455F conferred high-levels of resistance, when Y505W caused a ∼6-fold resistance fold-change. We also showed that the resistance mutations could greatly weaken the binding affinity of LCB1 to RBD and thus attenuated its blocking capacity on the interaction between RBD and the cell receptor ACE2. In conclusion, our data have provided crucial information for understanding the mechanism of SARS-CoV-2 resistance to LCB1 and will guide the design strategy of novel LCB1-based antivirals against divergent VOCs and evolutionary mutants.

Exploring the Spike-hACE 2 Residue-Residue Interaction in Human Coronaviruses SARS-CoV-2, SARS-CoV, and HCoV-NL63

Coronaviruses (CoVs) have been responsible for three major outbreaks since the beginning of the 21st century, and the emergence of the recent COVID-19 pandemic has resulted in considerable efforts to design new therapies against coronaviruses. Thus, it is crucial to understand the structural features of their major proteins related to the virus-host interaction. Several studies have shown that from the seven known CoV human pathogens, three of them use the human Angiotensin-Converting Enzyme 2 (hACE-2) to mediate their host's cell entry: SARS-CoV-2, SARS-CoV, and HCoV-NL63. Therefore, we employed quantum biochemistry techniques within the density function theory (DFT) framework and the molecular fragmentation with conjugate caps (MFCC) approach to analyze the interactions between the hACE-2 and the spike protein-RBD of the three CoVs in order to map the hot-spot residues that form the recognition surface for these complexes and define the similarities and differences in the interaction scenario. The total interaction energy evaluated showed a good agreement with the experimental binding affinity order: SARS-2 > SARS > NL63. A detailed investigation revealed the energetically most relevant regions of hACE-2 and the spike protein for each complex, as well as the key residue-residue interactions. Our results provide valuable information to deeply understand the structural behavior and binding site characteristics that could help to develop antiviral therapeutics that inhibit protein-protein interactions between CoVs S protein and hACE-2.

ADAM and ADAMTS disintegrin and metalloproteinases as major factors and molecular targets in vascular malfunction and disease

A Disintegrin and Metalloproteinase (ADAM) and A Disintegrin and Metalloproteinase with Thrombospondin Motifs (ADAMTS) are two closely related families of proteolytic enzymes. ADAMs are largely membrane-bound enzymes that act as molecular scissors or sheddases of membrane-bound proteins, growth factors, cytokines, receptors and ligands, whereas ADAMTS are mainly secreted enzymes. ADAMs have a pro-domain, and a metalloproteinase, disintegrin, cysteine-rich and transmembrane domain. Similarly, ADAMTS family members have a pro-domain, and a metalloproteinase, disintegrin, and cysteine-rich domain, but instead of a transmembrane domain they have thrombospondin motifs. Most ADAMs and ADAMTS are activated by pro-protein convertases, and can be regulated by G-protein coupled receptor agonists, Ca²⁺ ionophores and protein kinase C. Activated ADAMs and ADAMTS participate in numerous vascular processes including angiogenesis, vascular smooth muscle cell proliferation and migration, vascular cell apoptosis, cell survival, tissue repair, and wound healing. ADAMs and ADAMTS also play a role in vascular malfunction and cardiovascular diseases such as hypertension, atherosclerosis, coronary artery disease, myocardial infarction, heart failure, peripheral artery disease, and vascular aneurysm. Decreased ADAMTS13 is involved in thrombotic thrombocytopenic purpura and microangiopathies. The activity of ADAMs and ADAMTS can be regulated by endogenous tissue inhibitors of metalloproteinases and other synthetic small molecule inhibitors. ADAMs and ADAMTS can be used as diagnostic biomarkers and molecular targets in cardiovascular disease, and modulators of ADAMs and ADAMTS activity may provide potential new approaches for the management of cardiovascular disorders.