Extracellular vesicles and angiotensin-converting enzyme 2 in COVID-19 disease

Extracellular vesicles(EVs)are membranous vesicular structures released from almost all eukaryotic cell types under different physiological or pathological conditions.Growing evidence demonstrates that EVs can serve as mediators of intercellular communication between donor and recipient cells or microorganism-infected and noninfected cells.Coronavirus disease 2019(COVID-19)disease is caused by infection of the severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)of host cells in the respiratory system and various extra-pulmonary tissue/organs,resulting in complications of multiple organ systems.As the cell surface receptor,angiotensin-converting enzyme 2(ACE2)mediates cellular entry of SARS-CoV-2 into the host cells in patients with COVID-19.Recent studies have found that ACE2 can be released with EVs,which have been shown to interfere with the entry of the virus into host cells and thus may be involved in COVID-19 pathophysiology.In addition,ACE2,neprilysin(NEP),and thimet oligopeptidase(TOP)are the key enzymes that regulate angiotensin metabolism by converting angiotensin II or angiotensin I to angiotensin 1-7,the latter of which has protective effects in counterbalancing the harmful effects of angiotensin II in COVID-19 disease.This review summarizes the recent research progress regarding EV-associated ACE2,NEP,and TOP and the perspectives of their potential involvement in the pathophysiology of COVID-19 disease.

Effects of Yinchenhao Decoction on Self-regulation of Renin-angiotensin System by Targeting Angiotensin Converting Enzyme 2 in Bile Duct-ligated Rat Liver

Summary： In order to investigate whether Yinchenhao decoction （YCHD） attenuates hepatic fibro- genesis in the bile duct ligation （BDL） model via recovering and restoring the self-regulation and bal- ance of the renin-angiotensin system （RAS）, 33 specific-pathogen-free （SPF） male Sprague-Dawley rats with common BDL and scission were randomly divided into five groups as follows： G1, the sham group （n=4）; G2, BDL 7-day group （n=5）; G3, BDL＋YCHD 430 mg/mL （n=8）; G4, BDL＋losartan 0.65 mg/mL （ARB group, n=8）; G5, model group （BDL without any treatment, n=8）. YCHD and losartan （10 mL.kgl.day-1） were given by gastric gavage for 16 days following BDL in G3 and G4 groups, respec- tively. The effect of YCHD on liver fibrosis and the detailed molecular mechanisms were assessed by liver function including total bilirubin （TBIL）, direct bilirubin （DBIL）, indirect bilirubin （IDBIL）, alanine aminotransferase （ALT）, and aspartate aminotransferase （AST）. Histological changes were ob-. served by transmission electron microscopy （TEM） and Masson trichrome staining. Western blotting was used to detect the protein expression level of the renin-angiotensin system （RAS） components in- cluding angiotensin converting enzyme （ACE）, angiotensin II type 1 receptor （AT1R）, ACE2, angio- tensin II （Ang II） as well as transforming growth factor 131 （TGF131）. The experimental data were ana- lyzed by principle component analytical method of pattern recognition. The results showed that bio- chemically, serum TBIL, DBIL, IDBIL, ALT and AST levels were markedly increased following BDL as compared with the sham group （P〈0.05）. Serum TBIL, IDBIL and DBIL levels in G3 group were dramatically decreased as compared with G5 and G4 groups （P〈0.05）. Serum AST level in G3 was sig- nificantly lowered than in G5 group （P〈0.05）, but there was no significant difference in ALT among G3, G4 and G5 groups （P〉0.05）. Histologically, livers in G3 group showed less hepatocytes necrosis, less bile duct hyperplasia and less collagen formation than in G4 and G5 groups. The protein expression lev- els of ACE2, ACE, Ang II, AT1R and TGF131 in G2, G3 and G4 groups were significantly higher than in sham group （P〈0.05）, and lower than in G5 group （P〈0.05）. However, the differences among G2, G3 and G4 groups were not significant （P〉0.05）. ACE2 protein expression in G3 group was significantly higher than in G2 group （P〈0.05） and there was no significant difference in comparison with G4 group （P〉0.05）. Moreover, the protein expression of TGF131 in G3 group was significantly lower than in G5 and G4 groups （P〈0.05）. Our findings suggest that the antifibrotic effects of YCHD may be associated with the decreased classical RAS pathway components and TGFI31 downexpression so as to recover and rebuild self-regulation of the RAS by elevating the protein expression of ACE2.

Origin and genomic characteristics of SARS-CoV-2 and its interaction with angiotensin converting enzyme type 2 receptors, focusing on the gastrointestinal tract

The emergence of coronavirus disease-2019 induced by a newly identified bcoronavirus, namely severe acute respiratory syndrome coronavirus 2(SARSCoV-2) has constituted a public health emergency. Even though it was considered a zoonotic disease, the virus has also spread among humans via respiratory secretions. The expression and distribution of angiotensin converting enzyme type 2(ACE2) in various human organs might also show other possible infection routes. High ACE2 ribonucleic acid expression has been identified in the gastrointestinal tract(GI) indicating its importance as a possible infection pathway of SARS-CoV-2. ACE2 induces viral entry into the host and most importantly has been found to be associated with the function of the gut. Its deficiency has been implicated in several pathologies such as colorectal inflammation. The renin-angiotensin system(RAS) is an essential regulatory cascade operating both at a local tissue level and at the systemic or circulatory level. The RAS may be important in the pathogenesis of chronic liver disease and is associated with the up-regulation of ACE2. Thus, the aim of this review is firstly, the analysis of some important general and genome characteristics of SARS-CoV-2 and secondly, and most importantly, to focus on the utility of ACE2 receptors in both SARS-CoV-2 replication and pathogenesis, especially in the GI tract.

Angiotensin-converting enzyme 2 receptors,chronic liver diseases,common medications,and clinical outcomes in coronavirus disease 2019 patients

The severe acute respiratory syndrome coronavirus 2(SARS-CoV-2),the virus responsible for coronavirus disease 2019(COVID-19),enters affected cells through the angiotensin-converting enzyme 2(ACE2)receptor,which is highly expressed in type II alveolar cells,enterocytes,and cholangiocytes.SARS-CoV-2 infection causes fever,dry cough,and breathing difficulty,which can progress to respiratory distress due to interstitial pneumonia,and hepatobiliary injury due to COVID-19 is increasingly recognized.The hepatobiliary injury may be evident at presentation of the disease or develop during the disease progression.The development of more severe clinical outcomes in patients with chronic liver diseases(CLD)with or without cirrhosis infected with SARS-CoV-2 has not been elucidated.Moreover,there is limited data related to common medications that affect the disease severity of COVID-19 patients.Additionally,ACE2 receptor expression of hepatobiliary tissue related to the disease severity also have not been clarified.This review summarized the current situation regarding the clinical outcomes of COVID-19 patients with chronic liver diseases who were treated with common medications.Furthermore,the association between ACE2 receptor expression and disease severity in these patients is discussed.

Circulating angiotensin converting enzyme 2 and COVID-19

The severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)has triggered a widespread outbreak since December 2019.The SARS-CoV-2 infection-related illness has been dubbed the coronavirus disease 2019(COVID-19)by the World Health Organization.Asymptomatic and subclinical infections,a severe hyperinflammatory state,and mortality are all examples of clinical signs.After attaching to the angiotensin converting enzyme 2(ACE2)receptor,the SARSCoV-2 virus can enter cells through membrane fusion and endocytosis.In addition to enabling viruses to cling to target cells,the connection between the spike protein(S-protein)of SARS-CoV-2 and ACE2 may potentially impair the functionality of ACE2.Blood pressure is controlled by ACE2,which catalyzes the hydrolysis of the active vasoconstrictor octapeptide angiotensin(Ang)II to the heptapeptide Ang-(1-7)and free L-Phe.Additionally,Ang I can be broken down by ACE2 into Ang-(1-9)and metabolized into Ang-(1-7).Numerous studies have demonstrated that circulating ACE2(cACE2)and Ang-(1-7)have the ability to restore myocardial damage in a variety of cardiovascular diseases and have antiinflammatory,antioxidant,anti-apoptotic,and anti-cardiomyocyte fibrosis actions.There have been some suggestions for raising ACE2 expression in COVID-19 patients,which might be used as a target for the creation of novel treatment therapies.With regard to this,SARS-CoV-2 is neutralized by soluble recombinant human ACE2(hrsACE2),which binds the viral S-protein and reduces damage to a variety of organs,including the heart,kidneys,and lungs,by lowering Ang II concentrations and enhancing conversion to Ang-(1-7).This review aims to investigate how the presence of SARS-CoV-2 and cACE2 are related.Additionally,there will be discussion of a number of potential therapeutic approaches to tip the ACE/ACE-2 balance in favor of the ACE-2/Ang-(1-7)axis.

Renin-angiotensin system in the pathogenesis of liver fibrosis

Hepatic fibrosis is considered a common response to many chronic hepatic injuries. It is a multifunctional process that involves several cell types, cytokines, chemokines and growth factors leading to a disruption of homeostatic mechanisms that maintain the liver ecosystem. In spite of many studies regarding the development of fibrosis, the understanding of the pathogenesis remains obscure. The hepatic tissue remodeling process is highly complex, resulting from the balance between collagen degradation and synthesis. Among the many mediators that take part in this process, the components of the Renin angiotensin system （RAS） have progressively assumed an important role. Angiotensin （Ang） II acts as a profibrotic mediator and Ang-（1-7）, the newly recognized RAS component, appears to exert a counter-regulatory role in liver tissue. We briefly review the liver fibrosis process and current aspects of the RAS. This review also aims to discuss some experimental evidence regarding the participation of RAS mediators in the pathogenesis of liver fibrosis, focusing on the putative role of the ACE2-Ang-（1-7）- Mas receptor axis.

Relationship between angiotensin-(1-7) and angiotensin Ⅱ correlates with hemodynamic changes in human liver cirrhosis

AIM： To measure circulating angiotensins at different stages of human cirrhosis and to further evaluate a possible relationship between renin angiotensin system （RAS） components and hemodynamic changes. METHODS： Patients were allocated into 4 groups： mild-to-moderate liver disease （MLD）, advanced liver disease （ALD）, patients undergoing liver transplantation, and healthy controls. Blood was collected to determine plasma renin activity （PRA）, angiotensin （Ang） Ⅰ, Ang Ⅱ, and Ang-（1-7） levels using radioimmunoassays. During liver transplantation, hemodynamic parameters were determined and blood was simultaneously obtained from the portal vein and radial artery in order to measure RAS components. RESULTS： PRA and angiotensins were elevated in ALD when compared to MLD and controls （P 〈 0.05）. In contrast, Ang Ⅱ was significantly reduced in MLD. Ang-（1-7）/Ang Ⅱ ratios were increased in MLD when compared to controls and ALD. During transplantation, Ang Ⅱ levels were lower and Ang-（1-7）/Ang Ⅱ ratios were higher in the splanchnic circulation than in the peripheral circulation （0.52 ± 0.08 vs 0.38 ±0.04, P 〈 0.02）, whereas the peripheral circulating Ang Ⅱ/Ang Ⅰ ratio was elevated in comparison to splanchnic levels （0.18 ±0.02 vs 0.13 ±0.02, P 〈 0.04）. Ang-（1-7）/ Ang Ⅱ ratios positively correlated with cardiac output （r = 0.66） and negatively correlated with systemic vascular resistance （r = -0.70）. CONCLUSION： Our findings suggest that the relationship between Ang-（1-7） and Ang Ⅱ may play a role in the hemodynamic changes of human cirrhosis.

Ocular renin-angiotensin system with special reference in the anterior part of the eye

The renin-angiotensin system(RAS) regulates blood pressure(BP) homeostasis, systemic fluid volume and electrolyte balance. The RAS cascade includes over twenty peptidases, close to twenty angiotensin peptides and at least six receptors. Out of these, angiotensin Ⅱ, angiotensin converting enzyme 1 and angiotensin Ⅱ type 1 receptor(AngⅡ-ACE1-AT1R) together with angiotensin(1-7), angiotensin converting enzyme 2 and Mas receptor(Ang(1-7)-ACE2-Mas R) are regarded as the main components of RAS. In addition to circulating RAS, local RA-system exists in various organs. Local RA-systems are regarded as tissue-specific regulatory system accounting for local effects and long term changes in different organs. Many of the central components such as the two main axes of RAS: AngⅡ-ACE1-AT1 R and Ang(1-7)-ACE2-Mas R, have been identified in the human eye. Furthermore, it has been shown that systemic antihypertensive RAS- inhibiting medications lower intraocular pressure(IOP). These findings suggest the crucial role of RAS not only in the regulation of BP but also in the regulation of IOP, and RAS potentially plays a role in the development of glaucoma and antiglaucomatous drugs.

Clinical implications of COVID-19 in patients with metabolicassociated fatty liver disease

People across the world are affected by the"coronavirus disease 2019(COVID-19)",brought on by the"SARS-CoV type-2 coronavirus".Due to its high incidence in individuals with diabetes,metabolic syndrome,and metabolic-associated fatty liver disease(MAFLD),COVID-19 has gained much attention.The metabolic syndrome's hepatic manifestation,MAFLD,carries a significant risk of type-2-diabetes.The link between the above two conditions has also drawn increasing consideration since MAFLD is intricately linked to the obesity epidemic.Independent of the metabolic syndrome,MAFLD may impact the severity of the viral infections,including COVID-19 or may even be a risk factor.An important question is whether the present COVID-19 pandemic has been fueled by the obesity and MAFLD epidemics.Many liver markers are seen elevated in COVID-19.MAFLD patients with associated comorbid conditions like obesity,cardiovascular disease,renal disease,malignancy,hypertension,and old age are prone to develop severe disease.There is an urgent need for more studies to determine the link between the two conditions and whether it might account for racial differences in the mortality and morbidity rates linked to COVID-19.The role of innate and adaptive immunity alterations in MAFLD patients may influence the severity of COVID-19.This review investigates the implications of COVID-19 on liver injury and disease severity and viceversa.We also addressed the severity of COVID-19 in patients with prior MAFLD and its potential implications and therapeutic administration in the clinical setting.

Pathophysiological mechanisms underlying gastrointestinal symptoms in patients with COVID-19

Gastrointestinal(GI)symptoms,such as diarrhea,abdominal pain,vomiting,and anorexia,are frequently observed in patients with coronavirus disease 2019(COVID-19).However,the pathophysiological mechanisms connecting these GI symptoms to severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)infections remain elusive.Previous studies indicate that the entry of SARS-CoV-2 into intestinal cells leads to downregulation of angiotensin converting enzyme 2(ACE2)receptors resulting in impaired barrier function.While intestinal ACE2 functions as a chaperone for the amino acid transporter B0AT1,the B0AT1/ACE2 complex within the intestinal epithelium acts as a regulator of gut microbiota composition and function.Alternations to the B0AT1/ACE2 complex lead to microbial dysbiosis through increased local and systemic immune responses.Previous studies have also suggested that altered serotonin metabolism may be the underlying cause of GI disorders involving diarrhea.The findings of elevated plasma serotonin levels and high fecal calprotectin in COVID-19 patients with diarrhea indicate that the viral infection evokes a systemic inflammatory response that specifically involves the GI.Interestingly,the elevated proinflammatory cytokines correlate with elevated serotonin and fecal calprotectin levels further supporting the evidence of GI inflammation,a hallmark of functional GI disorders.Moreover,the finding that rectal swabs of COVID-19 patients remain positive for SARS-CoV-2 even after the nasopharynx clears the virus,suggests that viral replication and shedding from the GI tract may be more robust than that of the respiratory tract,further indicating fecal-oral transmission as another important route of viral spread.This review summarized the evidence for pathophysiological mechanisms(impaired barrier function,gut inflammation,altered serotonin metabolism and gut microbiota dysbiosis)underlying the GI symptoms in patients with COVID-19.

Cathepsin L, transmembrane peptidase/serine subfamily member 2/4, and other host proteases in COVID-19 pathogenesis – with impact on gastrointestinal tract

Severe acute respiratory syndrome coronavirus-2(SARS-CoV-2)seems to employ two routes of entrance to the host cell;via membrane fusion(with the cells expressing both angiotensin converting enzyme 2(ACE2)and transmembrane peptidase/serine subfamily member 2/4(TMPRSS2/4))or via receptor-mediated endocytosis(to the target cells expressing only ACE2).The second mode is associated with cysteine cathepsins(probably cathepsin L)involvement in the virus spike protein(S protein)proteolytic activation.Also furin might activate the virus S protein enabling it to enter cells.Gastrointestinal tract(GIT)involvement in SARS-CoV-2 infection is evident in a subset of coronavirus disease 2019(COVID-19)patients exhibiting GIT symptoms,such as diarrhea,and presenting viral-shedding in feces.Considering the abundance and co-localization of ACE2 and TMPRSS2 in the lower GIT(especially brush-border enterocytes),these two receptors seem to be mainly involved in SARS-CoV-2 invasion of the digestive tract.Additionally,in vitro studies have demonstrated the virions capability of infection and replication in the human epithelial cells lining GIT.However,also furin and cysteine cathepsins(cathepsin L)might participate in the activation of SARS-CoV-2 spike protein contributing to the virus invasiveness within GIT.Moreover,cathepsin L(due to its involvement in extracellular matrix components degradation and remodeling,the processes enhanced during SARS-CoV-2-induced inflammation)might be responsible for the dysregulation of absorption/digestion functions of GIT,thus adding to the observed in some COVID-19 patients symptoms such as diarrhea.

Liver in the limelight in the corona(COVID-19)time

The novel coronavirus,severe acute respiratory syndrome-corona virus-2(SARSCoV-2),is a topic of great interest currently in the medical field due to the significant morbidity and mortality associated with it.There is immense curiosity about this virus as knowledge about it is limited from pathogenesis,host related factors and the variable effect it has on different patient populations.Though it has claimed fame due to its ability to compromise the respiratory system,it possess the capability to infect other organs as well including the liver.It is important for clinicians to recognize that the virus can result in multi-organ dysfunction as well.Presentation with gastrointestinal symptoms and involvement of the liver can be subtle and can be misdiagnosed.Those with preexisting liver disease may be more susceptible as well as those who are immunosuppressed or have other co-morbidities.This review article provides a brief overview of some of the information that is available so far with regards to how the liver is impacted by the coronavirus.

ACE2/Ang-(1-7) signaling and vascular remodeling

The renin-angiotensin system(RAS)regulates vascular tone and plays a critical role in vascular remodeling,which is the result of a complex interplay of alterations in vascular tone and structure.Inhibition of the RAS has led to important pharmacological tools to prevent and treat vascular diseases such as hypertension,diabetic vasculopathy and atherosclerosis.Angiotensin converting enzyme 2(ACE2)was recently identified as a multifunctional monocarboxypeptidase responsible for the conversion of angiotensin(Ang)II to Ang-(1-7).The ACE2/Ang-(1-7)signaling has been shown to prevent cellular proliferation,pathological hypertrophy,oxidative stress and vascular fibrosis.Thus,the ACE2/Ang-(1-7)signaling is deemed to be beneficial to the cardiovascular system as a negative regulator of the RAS.The addition of the ACE2/Ang-(1-7)signaling to the complexities of the RAS may lead to the development of novel therapeutics for the treatment of hypertension and other vascular diseases.The present review considers recent findings regarding the ACE2/Ang-(1-7)signaling and focuses on its regulatory roles in processes related to proliferation,inflammation,vascular fibrosis and remodeling,providing proof of principle for the potential use of ACE2 as a novel therapy for vascular disorders related to vascular remodeling.

2019 novel-coronavirus: Cardiovascular insights about risk factors, myocardial injury, therapy and clinical implications

From December 31st,2019,a novel highly pathogenic coronavirus,severe acute respiratory syndrome coronavirus 2(SARS-CoV-2),has spread worldwide,reaching at present the dimension of a pandemic.In addition to damaging the lungs,SARS-CoV-2 may also damage the heart and this is corroborated by the evidence that cardiovascular comorbidities are associated with a higher mortality and poor clinical outcomes in patient infected by the virus.During the infection myocardial injury,myocarditis and arrhythmias have also been reported,but the pathophysiological mechanisms of these complications are yet to be understood.Great attention is also being posed on the potential beneficial/harmful role of angiotensin converting enzyme(ACE)inhibitors,as far as the virus binds to ACE2 to infect cells,but evidences lack.Furthermore,SARS-CoV-2 can also affect the aspect of acute coronary syndromes,not only because these two distinct pathological entities share pathogenic aspects(such as the systemic inflammatory state and cytokine release),but also and above all for the consequences that the need to contain the infection has on the management of cardiological urgencies.The aim of this review was therefore to summarize the relationship between the virus and the cardiovascular system.

COVID-19 and Alzheimer’s disease:how one crisis worsens the other

Alzheimer’s disease(AD)has emerged as a key comorbidity of coronavirus disease 2019(COVID-19)caused by severe acute respiratory syndrome coronavirus-2(SARS-CoV-2).The morbidity and mortality of COVID-19 are elevated in AD due to multiple pathological changes in AD patients such as the excessive expression of viral receptor angiotensin converting enzyme 2 and pro-inflammatory molecules,various AD complications including diabetes,lifestyle alterations in AD,and drug-drug interactions.Meanwhile,COVID-19 has also been reported to cause various neurologic symptoms including cognitive impairment that may ultimately result in AD,probably through the invasion of SARS-CoV-2 into the central nervous system,COVID-19-induced inflammation,long-term hospitalization and delirium,and post-COVID-19 syndrome.In addition,the COVID-19 crisis also worsens behavioral symptoms in uninfected AD patients and poses new challenges for AD prevention.In this review,we first introduce the symptoms and pathogenesis of COVID-19 and AD.Next,we provide a comprehensive discussion on the aggravating effects of AD on COVID-19 and the underlying mechanisms from molecular to social levels.We also highlight the influence of COVID-19 on cognitive function,and propose possible routes of viral invasion into the brain and potential mechanisms underlying the COVID-19-induced cognitive impairment.Last,we summarize the negative impacts of COVID-19 pandemic on uninfected AD patients and dementia prevention.

Cytoplasmic domain and enzymatic activity of ACE2 are not required for PI4KB dependent endocytosis entry of SARS-CoV-2 into host cells

The recent COVID-19 pandemic poses a global health emergency.Cellular entry of the causative agent SARS-CoV-2 is mediated by its spike protein interacting with cellular receptor-human angiotensin converting enzyme 2(ACE2).Here,by using lentivirus based pseudotypes bearing spike protein,we demonstrated that entry of SARS-CoV-2 into host cells was dependent on clathrin-mediated endocytosis,and phosphoinositides played essential roles during this process.In addition,we showed that the intracellular domain and the catalytic activity of ACE2 were not required for efficient virus entry.Finally,we showed that the current predominant Delta variant,although with high infectivity and high syncytium formation,also entered cells through clathrin-mediated endocytosis.These results provide new insights into SARS-CoV-2 cellular entry and present proof of principle that targeting viral entry could be an effective way to treat different variant infections.