ACE2-like carboxypeptidase B38-CAP protects from SARS-CoV-2-induced lung injury

Searching COVID-19 Clinical Research Using Graph Queries: Algorithm Development and Validation

BACKGROUND

Since the beginning of the COVID-19 pandemic, >1 million studies have been collected within the COVID-19 Open Research Dataset, a corpus of manuscripts created to accelerate research against the disease. Their related abstracts hold a wealth of information that remains largely unexplored and difficult to search due to its unstructured nature. Keyword-based search is the standard approach, which allows users to retrieve the documents of a corpus that contain (all or some of) the words in a target list. This type of search, however, does not provide visual support to the task and is not suited to expressing complex queries or compensating for missing specifications.

OBJECTIVE

This study aims to consider small graphs of concepts and exploit them for expressing graph searches over existing COVID-19-related literature, leveraging the increasing use of graphs to represent and query scientific knowledge and providing a user-friendly search and exploration experience.

METHODS

We considered the COVID-19 Open Research Dataset corpus and summarized its content by annotating the publications' abstracts using terms selected from the Unified Medical Language System and the Ontology of Coronavirus Infectious Disease. Then, we built a co-occurrence network that includes all relevant concepts mentioned in the corpus, establishing connections when their mutual information is relevant. A sophisticated graph query engine was built to allow the identification of the best matches of graph queries on the network. It also supports partial matches and suggests potential query completions using shortest paths.

RESULTS

We built a large co-occurrence network, consisting of 128,249 entities and 47,198,965 relationships; the GRAPH-SEARCH interface allows users to explore the network by formulating or adapting graph queries; it produces a bibliography of publications, which are globally ranked; and each publication is further associated with the specific parts of the query that it explains, thereby allowing the user to understand each aspect of the matching.

CONCLUSIONS

Our approach supports the process of query formulation and evidence search upon a large text corpus; it can be reapplied to any scientific domain where documents corpora and curated ontologies are made available.

Disruption of TIGAR-TAK1 alleviates immunopathology in a murine model of sepsis

Macrophage-orchestrated inflammation contributes to multiple diseases including sepsis. However, the underlying mechanisms remain to be defined clearly. Here, we show that macrophage TP53-induced glycolysis and apoptosis regulator (TIGAR) is up-regulated in murine sepsis models. When myeloid Tigar is ablated, sepsis induced by either lipopolysaccharide treatment or cecal ligation puncture in male mice is attenuated via inflammation inhibition. Mechanistic characterizations indicate that TIGAR directly binds to transforming growth factor β-activated kinase (TAK1) and promotes tumor necrosis factor receptor-associated factor 6-mediated ubiquitination and auto-phosphorylation of TAK1, in which residues 152-161 of TIGAR constitute crucial motif independent of its phosphatase activity. Interference with the binding of TIGAR to TAK1 by 5Z-7-oxozeaenol exhibits therapeutic effects in male murine model of sepsis. These findings demonstrate a non-canonical function of macrophage TIGAR in promoting inflammation, and confer a potential therapeutic target for sepsis by disruption of TIGAR-TAK1 interaction.

ACE2: the node connecting the lung cancer and COVID-19

Angiotensin-converting Enzyme 2 (ACE2) collaborates with Angiotensin (Ang) 1-7 and Mas receptors to establish the ACE2-Ang (1-7)-Mas receptor axis. ACE2 impacts lung function and can cause lung injury due to its inflammatory effects. Additionally, ACE2 contributes to pulmonary vasculature dysfunction, resulting in pulmonary hypertension. In addition, ACE2 is a receptor for coronavirus entry into host cells, leading to coronavirus infection. Lung cancer, one of the most common respiratory diseases worldwide, has a high rate of infection. Elevated levels of ACE2 in lung cancer patients, which increase the risk of SARS-CoV-2 infection and severe disease, have been demonstrated in clinical studies and by molecular mechanisms. The association between lung cancer and SARS-CoV-2 is closely linked to ACE2. This review examines the basic pathophysiological role of ACE2 in the lung, the long-term effects of SARS-CoV-2 infection on lung function, the development of pulmonary fibrosis, chronic inflammation in long-term COVID patients, and the clinical research and mechanisms underlying the increased susceptibility of lung cancer patients to the virus. Possible mechanisms of lung cancer in SARS-CoV-2-infected individuals and the potential role of ACE2 in this process are also explored in this review. The role of ACE2 as a therapeutic target in the novel coronavirus infection process is also summarized. This will help to inform prevention and treatment of long-term pulmonary complications in patients.

Liver injury in COVID-19: an insight into pathobiology and roles of risk factors

COVID-19 is a complex disease that can lead to fatal respiratory failure with extrapulmonary complications, either as a direct result of viral invasion in multiple organs or secondary to oxygen supply shortage. Liver is susceptible to many viral pathogens, and due to its versatile functions in the body, it is of great interest to determine how hepatocytes may interact with SARS-CoV-2 in COVID-19 patients. Liver injury is a major cause of death, and SARS-CoV-2 is suspected to contribute significantly to hepatopathy. Owing to the lack of knowledge in this field, further research is required to address these ambiguities. Therefore, we aimed to provide a comprehensive insight into host-virus interactions, underlying mechanisms, and associated risk factors by collecting results from epidemiological analyses and relevant laboratory experiments. Backed by an avalanche of recent studies, our findings support that liver injury is a sequela of severe COVID-19, and certain pre-existing liver conditions can also intensify the morbidity of SARS-CoV-2 infection in synergy. Notably, age, sex, lifestyle, dietary habits, coinfection, and particular drug regimens play a decisive role in the final outcome and prognosis as well. Taken together, our goal was to unravel these complexities concerning the development of novel diagnostic, prophylactic, and therapeutic approaches with a focus on prioritizing high-risk groups.

ACE2 improves endothelial cell function and reduces acute lung injury by downregulating FAK expression

Endothelial cell (EC) barrier dysfunction and increased adhesion of immune inflammatory cells to ECs crucially contribute to acute lung injury (ALI). Angiotensin-converting enzyme 2 (ACE2) is an essential regulator of the renin-angiotensin system (RAS) and exerts characteristic vasodilatory and anti-inflammatory effects. SARS-COV-2 infects the lungs by binding to ACE2, which can lead to dysregulation of ACE2 expression, further leading to ALI with predominantly vascular inflammation and eventually to more severe acute respiratory distress syndrome (ARDS). Therefore, restoration of ACE2 expression represents a valuable therapeutic approach for SARS-COV-2-related ALI/ARDS. In this study, we used polyinosinic-polycytidylic acid (Poly(I:C)), a double-stranded RNA analog, to construct a mouse ALI model that mimics virus infection. After Poly(I:C) exposure, ACE2 was downregulated in mouse lung tissues and in cultured ECs. Treatment with DIZE, an ACE2-activating compound, upregulated ACE2 expression and relieved ALI in mice. DIZE also improved barrier function and reduced the number of THP-1 monocytes adhering to cultured ECs. Focal adhesion kinase (FAK) and phosphorylated FAK (p-FAK) levels were increased in lung tissues of ALI mice as well as in Poly(I:C)-treated ECs in vitro. Both DIZE and the FAK inhibitor PF562271 decreased FAK/p-FAK expression in both ALI models, attenuating ALI severity in vivo and increasing barrier function and reducing monocyte adhesion in cultured ECs. Furthermore, in vivo experiments using ANG 1-7 and the MAS inhibitor A779 corroborated that DIZE-mediated ACE2 activation stimulated the activity of the ANG 1-7/MAS axis, which inhibited FAK/p-FAK expression in the mouse lung. These findings provide further evidence that activation of ACE2 in ECs may be a valuable therapeutic strategy for ALI.

Comparative Pathogenesis of Severe Acute Respiratory Syndrome Coronaviruses

Over the last two decades the world has witnessed the global spread of two genetically related highly pathogenic coronaviruses, severe acute respiratory syndrome coronavirus (SARS-CoV) and SARS-CoV-2. However, the impact of these outbreaks differed significantly with respect to the hospitalizations and fatalities seen worldwide. While many studies have been performed recently on SARS-CoV-2, a comparative pathogenesis analysis with SARS-CoV may further provide critical insights into the mechanisms of disease that drive coronavirus-induced respiratory disease. In this review, we comprehensively describe clinical and experimental observations related to transmission and pathogenesis of SARS-CoV-2 in comparison with SARS-CoV, focusing on human, animal, and in vitro studies. By deciphering the similarities and disparities of SARS-CoV and SARS-CoV-2, in terms of transmission and pathogenesis mechanisms, we offer insights into the divergent characteristics of these two viruses. This information may also be relevant to assessing potential novel introductions of genetically related highly pathogenic coronaviruses.

Intranasal soluble ACE2 improves survival and prevents brain SARS-CoV-2 infection

A soluble ACE2 protein bioengineered for long duration of action and high affinity to SARS-CoV-2 was administered either intranasally (IN) or intraperitoneally (IP) to SARS-CoV-2-inoculated k18hACE2 mice. This decoy protein (ACE2 618-DDC-ABD) was given either IN or IP, pre- and post-inoculation, or IN, IP, or IN + IP but only post-inoculation. Survival by day 5 was 0% in untreated mice, 40% in the IP-pre, and 90% in the IN-pre group. In the IN-pre group, brain histopathology was essentially normal and lung histopathology significantly improved. Consistent with this, brain SARS-CoV-2 titers were undetectable and lung titers reduced in the IN-pre group. When ACE2 618-DDC-ABD was administered only post-inoculation, survival was 30% in the IN + IP, 20% in the IN, and 20% in the IP group. We conclude that ACE2 618-DDC-ABD results in markedly improved survival and provides organ protection when given intranasally as compared with when given either systemically or after viral inoculation, and that lowering brain titers is a critical determinant of survival and organ protection.

Protein structure-based in-silico approaches to drug discovery: Guide to COVID-19 therapeutics

With more than 5 million fatalities and close to 300 million reported cases, COVID-19 is the first documented pandemic due to a coronavirus that continues to be a major health challenge. Despite being rapid, uncontrollable, and highly infectious in its spread, it also created incentives for technology development and redefined public health needs and research agendas to fast-track innovations to be translated. Breakthroughs in computational biology peaked during the pandemic with renewed attention to making all cutting-edge technology deliver agents to combat the disease. The demand to develop effective treatments yielded surprising collaborations from previously segregated fields of science and technology. The long-standing pharmaceutical industry's aversion to repurposing existing drugs due to a lack of exponential financial gain was overrun by the health crisis and pressures created by front-line researchers and providers. Effective vaccine development even at an unprecedented pace took more than a year to develop and commence trials. Now the emergence of variants and waning protections during the booster shots is resulting in breakthrough infections that continue to strain health care systems. As of now, every protein of SARS-CoV-2 has been structurally characterized and related host pathways have been extensively mapped out. The research community has addressed the druggability of a multitude of possible targets. This has been made possible due to existing technology for virtual computer-assisted drug development as well as new tools and technologies such as artificial intelligence to deliver new leads. Here in this article, we are discussing advances in the drug discovery field related to target-based drug discovery and exploring the implications of known target-specific agents on COVID-19 therapeutic management. The current scenario calls for more personalized medicine efforts and stratifying patient populations early on for their need for different combinations of prognosis-specific therapeutics. We intend to highlight target hotspots and their potential agents, with the ultimate goal of using rational design of new therapeutics to not only end this pandemic but also uncover a generalizable platform for use in future pandemics.

A computationally designed ACE2 decoy has broad efficacy against SARS-CoV-2 omicron variants and related viruses in vitro and in vivo

SARS-CoV-2, especially B.1.1.529/omicron and its sublineages, continues to mutate to evade monoclonal antibodies and antibodies elicited by vaccination. Affinity-enhanced soluble ACE2 (sACE2) is an alternative strategy that works by binding the SARS-CoV-2 S protein, acting as a 'decoy' to block the interaction between the S and human ACE2. Using a computational design strategy, we designed an affinity-enhanced ACE2 decoy, FLIF, that exhibited tight binding to SARS-CoV-2 delta and omicron variants. Our computationally calculated absolute binding free energies (ABFE) between sACE2:SARS-CoV-2 S proteins and their variants showed excellent agreement to binding experiments. FLIF displayed robust therapeutic utility against a broad range of SARS-CoV-2 variants and sarbecoviruses, and neutralized omicron BA.5 in vitro and in vivo. Furthermore, we directly compared the in vivo therapeutic efficacy of wild-type ACE2 (non-affinity enhanced ACE2) against FLIF. A few wild-type sACE2 decoys have shown to be effective against early circulating variants such as Wuhan in vivo. Our data suggest that moving forward, affinity-enhanced ACE2 decoys like FLIF may be required to combat evolving SARS-CoV-2 variants. The approach described herein emphasizes how computational methods have become sufficiently accurate for the design of therapeutics against viral protein targets. Affinity-enhanced ACE2 decoys remain highly effective at neutralizing omicron subvariants.

Advances in developing ACE2 derivatives against SARS-CoV-2

Extensive immune evasion of SARS-CoV-2 rendered therapeutic antibodies ineffective in the COVID-19 pandemic. Propagating SARS-CoV-2 variants are characterised by immune evasion capacity through key amino acid mutations, but can still bind human angiotensin-converting enzyme 2 (ACE2) through the spike protein and are, thus, sensitive to ACE2-mimicking decoys as inhibitors. In this Review, we examine advances in the development of ACE2 derivatives from the past 3 years, including the recombinant ACE2 proteins, ACE2-loaded extracellular vesicles, ACE2-mimicking antibodies, and peptide or mini-protein mimetics of ACE2. Several ACE2 derivatives are granted potent neutralisation efficacy against SARS-CoV-2 variants that rival or surpass endogenous antibodies by various auxiliary techniques such as chemical modification and practical recombinant design. The derivatives also represent enhanced production efficiency and improved bioavailability. In addition to these derivatives of ACE2, new effective therapeutics against SARS-CoV-2 variants are expected to be developed.

A specific molecular signature in SARS-CoV-2-infected kidney biopsies

Acute kidney injury is one of the most important complications in patients with COVID-19 and is considered a negative prognostic factor with respect to patient survival. The occurrence of direct infection of the kidney by SARS-CoV-2, and its contribution to the renal deterioration process, remain controversial issues. By studying 32 renal biopsies from patients with COVID-19, we verified that the major pathological feature of COVID-19 is acute tubular injury (ATI). Using single-molecule fluorescence in situ hybridization, we showed that SARS-CoV-2 infected living renal cells and that infection, which paralleled renal angiotensin-converting enzyme 2 expression levels, was associated with increased death. Mechanistically, a transcriptomic analysis uncovered specific molecular signatures in SARS-CoV-2-infected kidneys as compared with healthy kidneys and non-COVID-19 ATI kidneys. On the other hand, we demonstrated that SARS-CoV-2 and hantavirus, 2 RNA viruses, activated different genetic networks despite triggering the same pathological lesions. Finally, we identified X-linked inhibitor of apoptosis-associated factor 1 as a critical target of SARS-CoV-2 infection. In conclusion, this study demonstrated that SARS-CoV-2 can directly infect living renal cells and identified specific druggable molecular targets that can potentially aid in the design of novel therapeutic strategies to preserve renal function in patients with COVID-19.

Angiotensin-converting enzyme 2-at the heart of the COVID-19 pandemic

ACE2 is the indispensable entry receptor for SARS-CoV and SARS-CoV-2. Because of the COVID-19 pandemic, it has become one of the most therapeutically targeted human molecules in biomedicine. ACE2 serves two fundamental physiological roles: as an enzyme, it alters peptide cascade balance; as a chaperone, it controls intestinal amino acid uptake. ACE2's tissue distribution, affected by co-morbidities and sex, explains the broad tropism of coronaviruses and the clinical manifestations of SARS and COVID-19. ACE2-based therapeutics provide a universal strategy to prevent and treat SARS-CoV-2 infections, applicable to all SARS-CoV-2 variants and other emerging zoonotic coronaviruses exploiting ACE2 as their cellular receptor.

Effect of continuing the use of renin-angiotensin system inhibitors on mortality in patients hospitalized for coronavirus disease 2019: a systematic review, meta-analysis, and meta-regression analysis

BACKGROUND

The effect of angiotensin-converting enzyme inhibitors (ACEIs)/angiotensin receptor blockers (ARBs) on mortality was preliminarily explored through the comparison of ACEIs/ARBs with non-ACEIs/ARBs in patients with coronavirus disease 2019 (COVID-19). Reaching a conclusion on whether previous ACEI/ARB treatment should be continued in view of the different ACE2 levels in the comparison groups was not unimpeachable. Therefore, this study aimed to further elucidate the effect of ACEI/ARB continuation on hospital mortality, intensive care unit (ICU) admission, and invasive mechanical ventilation (IMV) in the same patient population.

METHODS

We searched PubMed, the Cochrane Library, Ovid, and Embase for relevant articles published between December 1, 2019 and April 30, 2022. Continuation of ACEI/ARB use after hospitalization due to COVID-19 was considered as an exposure and discontinuation of ACEI/ARB considered as a control. The primary outcome was hospital mortality, and the secondary outcomes included 30-day mortality, rate of ICU admission, IMV, and other clinical outcomes.

RESULTS

Seven observational studies and four randomized controlled trials involving 2823 patients were included. The pooled hospital mortality in the continuation group (13.04%, 158/1212) was significantly lower than that (22.15%, 278/1255) in the discontinuation group (risk ratio [RR] = 0.45; 95% confidence interval [CI], 0.28-0.72; P = 0.001). Continuation of ACEI/ARB use was associated with lower rates of ICU admission (10.5% versus 16.2%, RR = 0.63; 95% CI 0.5-0.79; P < 0.0001) and IMV (8.2% versus 12.5%, RR = 0.62; 95% CI 0.46-0.83, P = 0.001). Nevertheless, the effect was mainly demonstrated in the observational study subgroup (P < 0.05). Continuing ACEI/ARB had no significant effect on 30-day mortality (P = 0.34), acute myocardial infarction (P = 0.08), heart failure (P = 0.82), and acute kidney injury after hospitalization (P = 0.98).

CONCLUSION

Previous ACEI/ARB treatment could be continued since it was associated with lower hospital deaths, ICU admission, and IMV in patients with COVID-19, although the benefits of continuing use were mainly shown in observational studies. More evidence from multicenter RCTs are still needed to increase the robustness of the data. Trial registration PROSPERO (CRD42022341169). Registered 27 June 2022.

The relationship between gut microbiota and COVID-19 progression: new insights into immunopathogenesis and treatment

The coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has posed a global health crisis. Increasing evidence underlines the key role of competent immune responses in resisting SARS-CoV-2 infection and manifests the disastrous consequence of host immune dysregulation. Elucidating the mechanisms responsible for deregulated host immunity in COVID-19 may provide a theoretical basis for further research on new treatment modalities. Gut microbiota comprises trillions of microorganisms colonizing the human gastrointestinal tract and has a vital role in immune homeostasis and the gut-lung crosstalk. Particularly, SARS-CoV-2 infection can lead to the disruption of gut microbiota equilibrium, a condition called gut dysbiosis. Due to its regulatory effect on host immunity, gut microbiota has recently received considerable attention in the field of SARS-CoV-2 immunopathology. Imbalanced gut microbiota can fuel COVID-19 progression through production of bioactive metabolites, intestinal metabolism, enhancement of the cytokine storm, exaggeration of inflammation, regulation of adaptive immunity and other aspects. In this review, we provide an overview of the alterations in gut microbiota in COVID-19 patients, and their effects on individuals' susceptibility to viral infection and COVID-19 progression. Moreover, we summarize currently available data on the critical role of the bidirectional regulation between intestinal microbes and host immunity in SARS-CoV-2-induced pathology, and highlight the immunomodulatory mechanisms of gut microbiota contributing to COVID-19 pathogenesis. In addition, we discuss the therapeutic benefits and future perspectives of microbiota-targeted interventions including faecal microbiota transplantation (FMT), bacteriotherapy and traditional Chinese medicine (TCM) in COVID-19 treatment.

Superiority of intranasal over systemic administration of bioengineered soluble ACE2 for survival and brain protection against SARS-CoV-2 infection

The present study was designed to investigate the effects of a soluble ACE2 protein termed ACE2 618-DDC-ABD, bioengineered to have long duration of action and high binding affinity to SARS-CoV-2, when administered either intranasally (IN) or intraperitoneally (IP) and before or after SARS-CoV-2 inoculation. K18hACE2 mice permissive for SARS-CoV-2 infection were inoculated with 2Ã-10 4 PFU wildtype SARS-CoV-2. In one protocol, ACE2 618-DDC-ABD was given either IN or IP, pre- and post-viral inoculation. In a second protocol, ACE2 618-DDC-ABD was given either IN, IP or IN+IP but only post-viral inoculation. In addition, A549 and Vero E6 cells were used to test neutralization of SARS-CoV-2 variants by ACE2 618-DDC-ABD at different concentrations. Survival by day 5 was 0% in infected untreated mice, and 40% in mice from the ACE2 618-DDC-ABD IP-pre treated group. By contrast, in the IN-pre group survival was 90%, histopathology of brain and kidney was essentially normal and markedly improved in the lungs. When ACE2 618-DDC-ABD was administered only post viral inoculation, survival was 30% in the IN+IP group, 20% in the IN and 0% in the IP group. Brain SARS-CoV-2 titers were high in all groups except for the IN-pre group where titers were undetectable in all mice. In cells permissive for SARS-CoV-2 infection, ACE2 618-DDC-ABD neutralized wildtype SARS-CoV-2 at high concentrations, whereas much lower concentrations neutralized omicron BA. 1. We conclude that ACE2 618-DDC-ABD provides much better survival and organ protection when administered intranasally than when given systemically or after viral inoculation and that lowering brain titers is a critical determinant of survival and organ protection.

SARS-CoV-2 down-regulates ACE2 through lysosomal degradation

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) utilizes its Spike (S) glycoprotein to bind to the angiotensin-converting enzyme 2 (ACE2) receptor for cellular entry. ACE2 is a critical negative regulator of the renin-angiotensin system and plays a protective role in preventing tissue injury. Expression of ACE2 has been shown to decrease upon infection by SARS-CoV. However, whether SARS-CoV-2 down-regulates ACE2 and the underlying mechanism and biological impact of this down-regulation have not been well defined. Here we show that the SARS-CoV-2 infection down-regulates ACE2 in vivo in an animal model, and in cultured cells in vitro, by inducing clathrin- and AP2-dependent endocytosis, leading to its degradation in the lysosome. SARS-CoV-2 S-treated cells and ACE2 knockdown cells exhibit similar alterations in downstream gene expression, with a pattern indicative of activated cytokine signaling that is associated with respiratory distress and inflammatory diseases often observed in COVID-19 patients. Finally, we have identified a soluble ACE2 fragment with a stronger binding to SARS-CoV-2 S that can efficiently block ACE2 down-regulation and viral infection. Thus, our study suggests that ACE2 down-regulation represents an important mechanism underlying SARS-CoV-2-associated pathology, and blocking this process could be a promising therapeutic strategy.

An ACE2 decoy can be administered by inhalation and potently targets omicron variants of SARS-CoV-2

Monoclonal antibodies targeting the SARS-CoV-2 spike (S) neutralize infection and are efficacious for the treatment of COVID-19. However, SARS-CoV-2 variants, notably sublineages of B.1.1.529/omicron, have emerged that escape antibodies in clinical use. As an alternative, soluble decoy receptors based on the host entry receptor ACE2 broadly bind and block S from SARS-CoV-2 variants and related betacoronaviruses. The high-affinity and catalytically active decoy sACE2₂ .v2.4-IgG1 was previously shown to be effective against SARS-CoV-2 variants when administered intravenously. Here, inhalation of aerosolized sACE2₂ .v2.4-IgG1 increased survival and ameliorated lung injury in K18-hACE2 mice inoculated with P.1/gamma virus. Loss of catalytic activity reduced the decoy's therapeutic efficacy, which was further confirmed by intravenous administration, supporting dual mechanisms of action: direct blocking of S and turnover of ACE2 substrates associated with lung injury and inflammation. Furthermore, sACE2₂ .v2.4-IgG1 tightly binds and neutralizes BA.1, BA.2, and BA.4/BA.5 omicron and protects K18-hACE2 mice inoculated with a high dose of BA.1 omicron virus. Overall, the therapeutic potential of sACE2₂ .v2.4-IgG1 is demonstrated by the inhalation route and broad neutralization potency persists against highly divergent SARS-CoV-2 variants.

Molecular mechanisms and roles of pyroptosis in acute lung injury

ABSTRACT

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS), which are characterized by excessive inflammation and accompanied by diffuse injury of alveoli, can result in severe respiratory failures. The morbidity and mortality of patients remain high because the major treatments for ALI/ARDS are mainly supportive due to the lack of effective therapies. Numerous studies have demonstrated that the aggravation of coronavirus disease 2019 (COVID-19) leads to severe pneumonia and even ARDS. Pyroptosis, a biological process identified as a type of programed cell death, is mainly triggered by inflammatory caspase activation and is directly meditated by the gasdermin protein family, as well as being associated with the secretion and release of pro-inflammatory cytokines. Clinical and experimental evidence corroborates that pyroptosis of various cells in the lung, such as immune cells and structural cells, may play an important role in the pathogenesis of "cytokine storms" in ALI/ARDS, including those induced by COVID-19. Here, with a focus on ALI/ARDS and COVID-19, we summarized the recent advances in this field and proposed the theory of an inflammatory cascade in pyroptosis to identify new targets and pave the way for new approaches to treat these diseases.

Ang II (Angiotensin II)-Induced FGFR1 (Fibroblast Growth Factor Receptor 1) Activation in Tubular Epithelial Cells Promotes Hypertensive Kidney Fibrosis and Injury

BACKGROUND

Elevated Ang II (angiotensin II) level leads to a range of conditions, including hypertensive kidney disease. Recent evidences indicate that FGFR1 (fibroblast growth factor receptor 1) signaling may be involved in kidney injuries. In this study, we determined whether Ang II alters FGFR1 signaling to mediate renal dysfunction.

METHODS

Human archival kidney samples from patients with or without hypertension were examined. Multiple genetic and pharmacological approaches were used to investigate FGFR1-mediated signaling in tubular epithelial NRK-52E cells in response to Ang II stimulation. C57BL/6 mice were infused with Ang II for 28 days to develop hypertensive kidney disease. Mice were treated with either adeno-associated virus expressing FGFR1 shRNA or FGFR1 inhibitor AZD4547.

RESULTS

Kidney specimens from subjects with hypertension and mice challenged with Ang II have increased FGFR1 activity in renal epithelial cells. Renal epithelial cells in culture initiate extracellular matrix programming in response to Ang II, through the activation of FGFR1, which is independent of both AT1R (angiotensin II receptor type 1) and AT2R (angiotensin II receptor type 2). The RNA sequencing analysis indicated that disrupting FGFR1 suppresses Ang II-induced fibrogenic responses in epithelial cells. Mechanistically, Ang II-activated FGFR1 leads to STAT3 (signal transducer and activator of transcription 3) activation, which is responsible for fibrogenic factor expression in kidneys. In the mouse model of hypertensive kidney disease, genetic knockdown of FGFR1 or pharmacological inhibition of its activity protected kidneys from dysfunction and fibrosis upon Ang II challenge.

CONCLUSIONS

Our studies uncover a novel mechanism causing renal fibrosis in hypertension and indicate FGFR1 as a potential target to preserve renal function and integrity.

Targeting thromboinflammation in COVID-19 - A narrative review of the potential of C1 inhibitor to prevent disease progression

Coronavirus disease 2019 (COVID-19) caused by SARS-CoV-2 is associated with a clinical spectrum ranging from asymptomatic carriers to critically ill patients with complications including thromboembolic events, myocardial injury, multisystemic inflammatory syndromes and death. Since the beginning of the pandemic several therapeutic options emerged, with a multitude of randomized trials, changing the medical landscape of COVID-19. The effect of various monoclonal antibodies, antiviral, anti-inflammatory and anticoagulation drugs have been studied, and to some extent, implemented into clinical practice. In addition, a multitude of trials improved the understanding of the disease and emerging evidence points towards a significant role of the complement system, kallikrein-kinin, and contact activation system as drivers of disease in severe COVID-19. Despite their involvement in COVID-19, treatments targeting these plasmatic cascades have neither been systematically studied nor introduced into clinical practice, and randomized studies with regards to these treatments are scarce. Given the multiple-action, multiple-target nature of C1 inhibitor (C1-INH), the natural inhibitor of these cascades, this drug may be an interesting candidate to prevent disease progression and combat thromboinflammation in COVID-19. This narrative review will discuss the current evidence with regards to the involvement of these plasmatic cascades as well as endothelial cells in COVID-19. Furthermore, we summarize the evidence of C1-INH in COVID-19 and potential benefits and pitfalls of C1-INH treatment in COVID-19.

ACE2-like enzyme B38-CAP suppresses abdominal sepsis and severe acute lung injury

Angiotensin-converting enzyme 2 (ACE2) is the carboxypeptidase to degrade angiotensin II (Ang II) to angiotensin 1–7 (Ang 1–7) and improves the pathologies of cardiovascular disease and acute respiratory distress syndrome (ARDS)/acute lung injury. B38-CAP is a bacteria-derived ACE2-like carboxypeptidase as potent as human ACE2 and ameliorates hypertension, heart failure and SARS-CoV-2-induced lung injury in mice. Recombinant B38-CAP is prepared with E. coli protein expression system more efficiently than recombinant soluble human ACE2. Here we show therapeutic effects of B38-CAP on abdominal sepsis- or acid aspiration-induced acute lung injury. ACE2 expression was downregulated in the lungs of mice with cecal ligation puncture (CLP)-induced sepsis or acid-induced lung injury thereby leading to upregulation of Ang II levels. Intraperitoneal injection of B38-CAP significantly decreased Ang II levels while upregulated angiotensin 1–7 levels. B38-CAP improved survival rate of the mice under sepsis. B38-CAP suppressed the pathologies of lung inflammation, improved lung dysfunction and downregulated elevated cytokine mRNA levels in the mice with acute lung injury. Thus, systemic treatment with an ACE2-like enzyme might be a potential therapeutic strategy for the patients with severe sepsis or ARDS.

Engineered ACE2-Fc counters murine lethal SARS-CoV-2 infection through direct neutralization and Fc-effector activities

Soluble angiotensin-converting enzyme 2 (ACE2) constitutes an attractive antiviral capable of targeting a wide range of coronaviruses using ACE2 as their receptor. Using structure-guided approaches, we developed a series of bivalent ACE2-Fcs harboring functionally and structurally validated mutations that enhance severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) receptor binding domain recognition by up to ~12-fold and remove angiotensin enzymatic activity. The lead variant M81 potently cross-neutralized SARS-CoV-2 variants of concern (VOCs), including Omicron, at subnanomolar half-maximal inhibitory concentration and was capable of robust Fc-effector functions, including antibody-dependent cellular cytotoxicity, phagocytosis, and complement deposition. When tested in a stringent K18-hACE2 mouse model, Fc-enhanced ACE2-Fc delayed death by 3 to 5 days or effectively resolved lethal SARS-CoV-2 infection in both prophylactic and therapeutic settings via the combined effects of neutralization and Fc-effector functions. These data add to the demonstrated utility of soluble ACE2 as a valuable SARS-CoV-2 antiviral and indicate that Fc-effector functions may constitute an important component of ACE2-Fc therapeutic activity.

Structural insights revealed by crystal structure of B38-CAP, an isoenzyme of carboxypeptidase ACE2, the receptor of SARS-CoV-2

The worldwide pandemic of Coronavirus disease 2019 (COVID-19) is triggered by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and further worsened by the emergence of a variety of SARS-CoV-2 variants. Angiotensin-converting enzyme 2 (ACE2), a carboxypeptidase of M32 family, serves as the receptor of SARS-CoV-2 and key regulator of host renin-angiotensin system (RAS), both of which are mainly mediated via the carboxypeptidase domain of ACE2 (sACE2) or its activity. sACE2 is thus promising in the treatment of COVID-19 but unfortunately weakened by its unstrigent substrate preference and complex interplay with host RAS. B38-CAP, an isoenzyme of ACE2, partically compensates these defects but still encounters the problem related to carboxypeptidase activity and specificity. In this study, we firstly determined the crystal structure of B38-CAP at a resolution of 2.44 Å which exists in dimeric form with the non-crystallographic two-fold axis being in coincidence with the crystallographic two-fold axis. Further structural analysis revealed the structural conservatism feature among M32 family, particularly the catalytic core and moreover lead us to hypothesize that conformational flexibility might play an pivotal role in the catalysis of B38-CAP and ACE2. The work provided here presents key features of the M32 family carboxypeptidase and provides structural basis for further development of B38-CAP-based anti-SARS-CoV-2 drugs.

Angiotensin-converting enzyme 2 (ACE2): Two decades of revelations and re-evaluation

Angiotensin-converting enzyme-2, or ACE2, is primarily a zinc-dependent peptidase and ectoenzyme expressed in numerous cell types and functioning as a counterbalance to ACE in the renin-angiotensin system. It was discovered 21 years ago more than 40 years after the discovery of ACE itself. Its primary physiological activity is believed to be in the conversion of angiotensin II to the vasodilatory angiotensin-(1-7) acting through the Mas receptor. As such it has been implicated in numerous pathological conditions, largely in a protective mode which has led to the search for ACE2 activatory mechanisms. ACE2 has a diverse substrate specificity allowing its participation in multiple peptide pathways. It also regulates aspects of amino acid transport through its homology with a membrane protein, collectrin. It also serves as a viral receptor for the SARS virus, and subsequently SARS-CoV2, driving the current COVID-19 pandemic. ACE2 therefore provides a therapeutic target for the treatment of COVID and understanding the biological events following viral binding can provide insight into the multiple pathologies caused by the virus, particularly inflammatory and vascular. In part this may relate to the ability of ACE2, like ACE, to be shed from the cell membrane. The shed form of ACE2 (sACE2) may be a factor in determining susceptibility to certain COVID pathologies. Hence, for just over 20 years, ACE2 has provided numerous surprises in the field of vasoactive peptides with, no doubt, more to come but it is its central role in COVID pathology that is producing the current intense interest in its biology.

Animal models for studying covid-19, prevention, and therapy: Pathology and disease phenotypes

Translational models have played an important role in the rapid development of safe and effective vaccines and therapeutic agents for the ongoing coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Animal models recapitulating the clinical and underlying pathological manifestations of COVID-19 have been vital for identification and rational design of safe and effective vaccines and therapies. This manuscript provides an overview of commonly used COVID-19 animal models and the pathologic features of SARS-CoV-2 infection in these models in relation to their clinical presentation in humans. Also discussed are considerations for selecting appropriate animal models for infectious diseases such as COVID-19, the host determinants that can influence species-specific susceptibility to SARS-CoV-2, and the pathogenesis of COVID-19. Finally, the limitations of currently available COVID-19 animal models are highlighted.

Inhaled hydrogel-based microspheres for management of COVID-19: A new sweeper biological platform

The cytokine storm caused by SARS-CoV-2 infection threatens the condition of patients, even leading to death. In a recent issue of Matter, Prof. Wenguo Cui and co-workers have prepared lung-sweeper inhaled hydrogel microspheres for intratracheal neutralization of COVID-19 and cytokine storm calming, which could be applied for antiviral tissue regeneration, drug delivery, and disease diagnosis.

An engineered ACE2 decoy receptor can be administered by inhalation and potently targets the BA.1 and BA.2 omicron variants of SARS-CoV-2

Monoclonal antibodies targeting the SARS-CoV-2 spike (S) glycoprotein neutralize infection and are efficacious for the treatment of mild-to-moderate COVID-19. However, SARS-CoV-2 variants have emerged that partially or fully escape monoclonal antibodies in clinical use. Notably, the BA.2 sublineage of B.1.1.529/omicron escapes nearly all monoclonal antibodies currently authorized for therapeutic treatment of COVID-19. Decoy receptors, which are based on soluble forms of the host entry receptor ACE2, are an alternative strategy that broadly bind and block S from SARS-CoV-2 variants and related betacoronaviruses. The high-affinity and catalytically active decoy sACE2₂.v2.4-IgG1 was previously shown to be effective in vivo against SARS-CoV-2 variants when administered intravenously. Here, the inhalation of sACE2₂.v2.4-IgG1 is found to increase survival and ameliorate lung injury in K18-hACE2 transgenic mice inoculated with a lethal dose of the virulent P.1/gamma virus. Loss of catalytic activity reduced the decoy’s therapeutic efficacy supporting dual mechanisms of action: direct blocking of viral S and turnover of ACE2 substrates associated with lung injury and inflammation. Binding of sACE2₂.v2.4-IgG1 remained tight to S of BA.1 omicron, despite BA.1 omicron having extensive mutations, and binding exceeded that of four monoclonal antibodies approved for clinical use. BA.1 pseudovirus and authentic virus were neutralized at picomolar concentrations. Finally, tight binding was maintained against S from the BA.2 omicron sublineage, which differs from S of BA.1 by 26 mutations. Overall, the therapeutic potential of sACE2₂.v2.4-IgG1 is further confirmed by inhalation route and broad neutralization potency persists against increasingly divergent SARS-CoV-2 variants.

Understanding on the possible routes for SARS CoV-2 invasion via ACE2 in the host linked with multiple organs damage

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), accountable for causing the coronavirus diseases 2019 (COVID-19), is already declared as a pandemic disease globally. Like previously reported SARS-CoV strain, the novel SARS-CoV-2 also initiates the viral pathogenesis via docking viral spike-protein with the membranal angiotensin-converting enzyme 2 (ACE2) - a receptor on variety of cells in the human body. Therefore, COVID-19 is broadly characterized as a disease that targets multiple organs, particularly causing acute complications via organ-specific pathogenesis accompanied by destruction of ACE2⁺ cells, including alveolus, cardiac microvasculature, endothelium, and glomerulus. Under such circumstances, the high expression of ACE2 in predisposing individuals associated with anomalous production of the renin-angiotensin system (RAS) may promote enhanced viral load in COVID-19, which comparatively triggers excessive apoptosis. Furthermore, multi-organ injuries were found linked to altered ACE2 expression and inequality between the ACE2/angiotensin-(1-7)/mitochondrial Ang system (MAS) and renin-angiotensin-system (RAS) in COVID-19 patients. However, the exact pathogenesis of multi-organ damage in COVID-19 is still obscure, but several perspectives have been postulated, involving altered ACE2 expression linked with direct/indirect damages by the virus-induced immune responses, such as cytokinin storm. Thus, insights into the invasion of a virus with respect to ACE2 expression site can be helpful to simulate or understand the possible complications in the targeted organ during viral infection. Hence, this review summarizes the multiple organs invasion by SARS CoV-2 linked with ACE2 expression and their consequences, which can be helpful in the management of the COVID-19 pathogenesis under life-threatening conditions.

Significance of Immune Status of SARS-CoV-2 Infected Patients in Determining the Efficacy of Therapeutic Interventions

Coronavirus disease 2019 (COVID-19) is now being investigated for its distinctive patterns in the course of disease development which can be indicated with miscellaneous immune responses in infected individuals. Besides this series of investigations on the pathophysiology of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), significant fundamental immunological and physiological processes are indispensable to address clinical markers of COVID-19 disease and essential to identify or design effective therapeutics. Recent developments in the literature suggest that deficiency of type I interferon (IFN) in serum samples can be used to represent a severe progression of COVID-19 disease and can be used as the basis to develop combined immunotherapeutic strategies. Precise control over inflammatory response is a significant aspect of targeting viral infections. This account presents a brief review of the pathophysiological characteristics of the SARS-CoV-2 virus and the understanding of the immune status of infected patients. We further discuss the immune system’s interaction with the SARS-CoV-2 virus and their subsequent involvement of dysfunctional immune responses during the progression of the disease. Finally, we highlight some of the implications of the different approaches applicable in developing promising therapeutic interventions that redirect immunoregulation and viral infection.

A decoy mutant ACE2 designed to reduce COVID-19

The need for new coronavirus disease 2019 (COVID-19) therapeutic strategies continues, especially as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants emerge. Zhang and colleagues elegantly engineered a mutant angiotensin-converting enzyme 2 (ACE2) that competitively binds SARS-CoV-2 spike protein, reduces viral uptake by human lung cells, and ameliorates SARS-CoV-2-induced lung injury in mice expressing human ACE2.

Angiotensin-Converting Enzyme 2 (ACE2) in the Pathogenesis of ARDS in COVID-19

Seventeen years after the epidemic of SARS coronavirus, a novel coronavirus SARS-CoV-2-emerged resulting in an unprecedented pandemic. Angiotensin-converting enzyme 2 (ACE2) is an essential receptor for cell entry of SARS-CoV-2 as well as the SARS coronavirus. Despite many similarities to SARS coronavirus, SARS-CoV-2 exhibits a higher affinity to ACE2 and shows higher infectivity and transmissibility, resulting in explosive increase of infected people and COVID-19 patients. Emergence of the variants harboring mutations in the receptor-binding domain of the Spike protein has drawn critical attention to the interaction between ACE2 and Spike and the efficacies of vaccines and neutralizing antibodies. ACE2 is a carboxypeptidase which degrades angiotensin II, B1-bradykinin, or apelin, and thereby is a critical regulator of cardiovascular physiology and pathology. In addition, the enzymatic activity of ACE2 is protective against acute respiratory distress syndrome (ARDS) caused by viral and non-viral pneumonias, aspiration, or sepsis. Upon infection, both SARS-CoV-2 and SARS coronaviruses downregulates ACE2 expression, likely associated with the pathogenesis of ARDS. Thus, ACE2 is not only the SARS-CoV-2 receptor but might also play an important role in multiple aspects of COVID-19 pathogenesis and possibly post-COVID-19 syndromes. Soluble forms of recombinant ACE2 are currently utilized as a pan-variant decoy to neutralize SARS-CoV-2 and a supplementation of ACE2 carboxypeptidase activity. Here, we review the role of ACE2 in the pathology of ARDS in COVID-19 and the potential application of recombinant ACE2 protein for treating COVID-19.