Circulating angiotensin-converting enzyme 2 activity in patients with chronic kidney disease without previous history of cardiovascular disease

Soluble ACE2 correlates with severe COVID-19 and can impair antibody responses

Identifying immune modulators that impact neutralizing antibody responses against severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) is of great relevance. We postulated that high serum concentrations of soluble angiotensin-converting enzyme 2 (sACE2) might mask the spike and interfere with antibody maturation toward the SARS-CoV-2-receptor-binding motif (RBM). We tested 717 longitudinal samples from 295 COVID-19 patients and showed a 2- to 10-fold increase of enzymatically active sACE2 (a-sACE2), with up to 1 μg/mL total sACE2 in moderate and severe patients. Fifty percent of COVID-19 sera inhibited ACE2 activity, in contrast to 1.3% of healthy donors and 4% of non-COVID-19 pneumonia patients. A mild inverse correlation of a-sACE2 with RBM-directed serum antibodies was observed. In silico, we show that sACE2 concentrations measured in COVID-19 sera can disrupt germinal center formation and inhibit timely production of high-affinity antibodies. We suggest that sACE2 is a biomarker for COVID-19 and that soluble receptors may contribute to immune suppression informing vaccine design.

Antihypertensive treatment of end-stage renal disease patients on hemodialysis does not alter circulating ACE and ACE2 activity and angiotensin peptides

Cardiovascular diseases (CVD) are the main causes of death in hemodialysis patients, representing a public health challenge. We investigated the effect of different antihypertensive treatments on circulating levels of renin-angiotensin system (RAS) components in end-stage renal disease (ESRD) patients on hemodialysis. ESRD patients were grouped following the prescribed antihypertensive drugs: ß-blocker, ß-blocker+ACEi and ß-blocker+AT1R blocker. ESDR patients under no antihypertensive drug treatment were used as controls. Blood samples were collected before hemodialysis sessions. Enzymatic activities of the angiotensin-converting enzymes ACE and ACE2 were measured through fluorescence assays and plasma concentrations of the peptides Angiotensin II (Ang II) and Angiotensin-(1-7) [Ang-(1-7)] were quantified using mass spectrometry (LC-MS/MS). ACE activity was decreased only in the ß-blocker+ACEi group compared to the ß-blocker+AT1R, while ACE2 activity did not change according to the antihypertensive treatment. Both Ang II and Ang-(1-7) levels also did not change according to the antihypertensive treatment. We concluded that the treatment of ESRD patients on hemodialysis with different antihypertensive drugs do not alter the circulating levels of RAS components.

Targeting SARS-CoV-2 entry processes: The promising potential and future of host-targeted small-molecule inhibitors

The COVID-19 pandemic, caused by SARS-CoV-2, has had a huge impact on global health. To respond to rapidly mutating viruses and to prepare for the next pandemic, there is an urgent need to develop small molecule therapies that target critical stages of the SARS-CoV-2 life cycle. Inhibiting the entry process of the virus can effectively control viral infection and play a role in prevention and treatment. Host factors involved in this process, such as ACE2, TMPRSS2, ADAM17, furin, PIKfyve, TPC2, CTSL, AAK1, V-ATPase, HSPG, and NRP1, have been found to be potentially good targets with stability. Through further exploration of the cell entry process of SARS-CoV-2, small-molecule drugs targeting these host factors have been developed. This review focuses on the structural functions of potential host cell targets during the entry of SARS-CoV-2 into host cells. The research progress, chemical structure, structure-activity relationship, and clinical value of small-molecule inhibitors against COVID-19 are reviewed to provide a reference for the development of small-molecule drugs against COVID-19.

Circulating ACE2 level and zinc/albumin ratio as potential biomarkers for a precision medicine approach to COVID-19

Highly mutable influenza is successfully countered based on individual susceptibility and similar precision-like medicine approach should be effective against SARS-COV-2. Among predictive markers to bring precision medicine to COVID-19, circulating ACE2 has potential features being upregulated in both severe COVID-19 and predisposing comorbidities. Spike SARS-CoVs were shown to induce ADAM17-mediated shedding of enzymatic active ACE2, thus accounting for its increased activity that has also been suggested to induce positive feedback loops leading to COVID-19-like manifestations. For this reason, pre-existing ACE2 activity and inhibition of ACE2/ADAM17 zinc-metalloproteases through zinc chelating agents have been proposed to predict COVID-19 outcome before infection and to protect from COVID-19, respectively. Since most diagnostic laboratories are not equipped for enzymatic activity determination, other potential predictive markers of disease progression exploitable by diagnostic laboratories were explored. Concentrations of circulating albumin, zinc, ACE2 protein and its activity were investigated in healthy, diabetic (COVID-19-susceptible) and SARS-CoV-2-negative COVID-19 individuals. ACE2 both protein levels and activity significantly increased in COVID-19 and diabetic patients. Abnormal high levels of ACE2 characterised a subgroup (16-19%) of diabetics, while COVID-19 patients were characterised by significantly higher zinc/albumin ratios, pointing to a relative increase of albumin-unbound zinc species, such as free zinc ones. Data on circulating ACE2 levels are in line with the hypothesis that they can drive susceptibility to COVID-19 and elevated zinc/albumin ratios support the therapeutic use of zinc chelating inhibitors of ACE2/ADAM17 zinc-metalloproteases in a targeted therapy for COVID-19.

Prognostic value of elevated plasma angiotensin-converting enzyme 2 in cardiometabolic diseases: A review

Angiotensin-converting enzyme 2, as an internal anti regulator of the renin-angiotensin hormone cascade reaction, plays a protective role in vasodilation, inhibition of fibrosis, and initiation of anti-inflammatory and antioxidative stress by degrading angiotensin II and generating angiotensin (1-7). Multiple studies have shown that plasma angiotensin-converting enzyme 2 activity is low in healthy populations without significant cardiometabolic disease, and elevated plasma angiotensin-converting enzyme 2 levels can be used as a novel biomarker of abnormal myocardial structure and/or adverse events in cardiometabolic diseases. This article aims to elaborate the determinants of plasma angiotensin-converting enzyme 2 concentration, the relevance between angiotensin-converting enzyme 2 and cardiometabolic disease risk markers, and its relative importance compared with known cardiovascular disease risk factors. Confronted with the known cardiovascular risk factors, plasma angiotensin-converting enzyme 2 (ACE2) concentration uniformly emerged as a firm predictor of abnormal myocardial structure and/or adverse events in cardiometabolic diseases and may improve the risk prediction of cardiometabolic diseases when combined with other conventional risk factors. Cardiovascular disease is the leading cause of death worldwide, while the renin-angiotensin system is the main hormone cascade system involved in the pathophysiology of cardiovascular disease. A multi-ancestry global cohort study from the general population by Narula et al revealed that plasma ACE2 concentration was strongly associated with cardiometabolic disease and might be an easily measurable indicator of renin-angiotensin system disorder. The association between this atypical hormone disorder marker and cardiometabolic disease is isolated from conventional cardiac risk factors and brain natriuretic peptide, suggesting that a clearer comprehending of the changes in plasma ACE2 concentration and activity may help us to improve the risk prediction of cardiometabolic disease, guide early diagnosis and feasible therapies, and develop and test new therapeutic targets.

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.

Hypothesis: Efficacy of early treatments with some NSAIDs in COVID-19: Might it also depend on their direct and/or indirect zinc chelating ability?

The present work argues for the involvement of the zinc chelating ability of some non-steroidal anti-inflammatory drugs as an additive mechanism able to increase their efficacy against COVID-19.

Renal angiotensin I-converting enzyme-deficient mice are protected against aristolochic acid nephropathy

The renal renin-angiotensin system (RAS) is involved in the development of chronic kidney disease. Here, we investigated whether mice with reduced renal angiotensin I-converting enzyme (ACE^-/-) are protected against aristolochic acid nephropathy (AAN). To further elucidate potential molecular mechanisms, we assessed the renal abundances of several major RAS components. AAN was induced using aristolochic acid I (AAI). Glomerular filtration rate (GFR) was determined using inulin clearance and renal protein abundances of renin, angiotensinogen, angiotensin I-converting enzyme (ACE) 2, and Mas receptor (Mas) were determined in ACE^-/- and C57BL/6J control mice by Western blot analyses. Renal ACE activity was determined using a colorimetric assay and renal angiotensin (Ang) (1-7) concentration was determined by ELISA. GFR was similar in vehicle-treated mice of both strains. AAI decreased GFR in controls but not in ACE^-/- mice. Furthermore, AAI decreased renal ACE activity in controls but not in ACE^-/- mice. Vehicle-treated ACE^-/- mice had significantly higher renal ACE2 and Mas protein abundances than controls. AAI decreased renal ACE2 protein abundance in both strains. Furthermore, AAI increased renal Mas protein abundance, although the latter effect did not reach statistical significance in the ACE^-/- mice. Renal Ang(1-7) concentration was similar in vehicle-treated mice of both strains. AAI increased renal Ang(1-7) concentration in the ACE^-/- mice but not in the controls. Mice with reduced renal ACE are protected against AAN. Our data suggest that in the face of renal ACE deficiency, AAI may activate the ACE2/Ang(1-7)/Mas axis, which in turn may deploy its reno-protective effects.

Angiotensin converting enzyme 2 level and its significance in COVID-19 and other diseases patients

BACKGROUND

Angiotensin-converting enzyme 2 (ACE2) expressions and its modulation are of great interest as being a key receptor for severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) and the protective arm of the rennin-angiotensin axis, maintaining cardiovascular homeostasis. However, ACE2 expressions and their modulation in the healthy and disease background are yet to be explored.

METHOD

We performed a meta-analysis, extracting the data for ACE2 expression in human subjects with various diseases, including SARS-CoV2 infection without or with co-morbidity. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed. Out of 203 studies, 39 met the inclusion criteria with SARS-CoV2 patients without co-morbidity, SARS-CoV2 patients with co-morbidity, cardiovascular (CVD) patients, diabetes patients, kidney disorders patients, pulmonary disease patients, and other viral infections patients.

RESULTS

Angiotensin-converting enzyme 2 expression was significantly increased in all diseases. There was an elevated level of ACE2, especially membrane-bound ACE2, in COVID-19 patients compared to healthy controls. A statistically significant increase in ACE2 expression was observed in CVD patients and patients with other viral diseases compared to healthy subjects. Moreover, subgroup analysis of ACE2 expression as soluble and membrane-bound ACE2 revealed a remarkable increase in membrane-bound ACE2 in CVD patients, patients with viral infection compared to soluble ACE2 and pooled standard mean difference (SMD) with the random-effects model was 0.37 and 2.23 respectively.

CONCLUSION

It was observed that utilizing the ACE2 by SARS-CoV2 for its entry and its consequence leads to several complications. So there is a need to investigate the underlying mechanism along with novel therapeutic strategies.

Circulating Plasma Concentrations of ACE2 in Primary Aldosteronism and Cardiovascular Outcomes

CONTEXT

The plasma concentrations of angiotensin-converting enzyme 2 (pACE2) has been independently associated with cardiovascular diseases.

OBJECTIVE

Higher pACE2 concentrations may be found in patients with primary aldosteronism (PA) and might lead to increased cardiovascular events.

METHODS

Using an inception observational cohort, we examined pACE2 among 168 incident patients with PA. The expression of ACE2, serine protease 2 (TMPRSS2), and metalloprotease 17 (ADAM17) were assessed in peripheral blood mononuclear cells.

RESULTS

Incident PA and essential hypertension (EH) patients had similarly elevated pACE2 (47.04 ± 22.06 vs 46.73 ± 21.06 ng/mL; P = .937). Age was negatively (β = -2.15; P = .033) and higher serum potassium level (β = 2.29; P = .024) was positively correlated with higher pACE2 in PA patients. Clinical complete hypertension remission after adrenalectomy (Primary Aldosteronism Surgery Outcome criteria) was achieved in 36 (50%) of 72 surgically treated unilateral PA (uPA) patients. At follow-up, pACE2 decreased in surgically treated patients who had (P < .001) or had no (P = .006) hypertension remission, but the pACE2 attenuation was not statistically significant in uPA (P = .085) and bilateral PA (P = .409) administered with mineralocorticoid receptor antagonist (MRA). Persistently elevated pACE2 (> 23 ng/mL) after targeted treatments was related to all-cause mortality and cardiovascular events among PA patients (hazard ratio = 8.8; P = .04); with a mean follow-up of 3.29 years. TMPRSS2 messenger RNA (mRNA) expression was higher in uPA (P = .018) and EH (P = .038) patients than in normotensive controls; it was also decreased after adrenalectomy (P < .001).

CONCLUSION

PA and EH patients had elevated pACE2 and higher expression of TMPRSS2 mRNA compared to those of normotensive population. Persistently elevated pACE2 (> 23 ng/mL) after targeted treatments was associated risk of mortality and incident cardiovascular events.

Plasma Angiotensin Converting Enzyme 2 (ACE2) Activity in Healthy Controls and Patients with Cardiovascular Risk Factors and/or Disease

Angiotensin converting enzyme 2 (ACE2) is an endogenous negative regulator of the renin-angiotensin system, a key factor in the development of cardiovascular disease (CVD). ACE2 is also used by SARS-CoV-2 for host cell entry. Given that COVID-19 is associated with hypercoagulability, it is timely to explore the potential relationship between plasma ACE2 activity and the coagulation profile. In this cross-sectional study, ACE2 activity and global coagulation assays (GCA) including thromboelastography, thrombin, and fibrin generation were measured in adult healthy controls (n = 123; mean age 41 ± 17 years; 35% male) and in patients with cardiovascular risk factors and/or disease (n = 258; mean age 65 ± 14 years; 55% male). ACE2 activity was significantly lower in controls compared to patients with cardiovascular risk factors and/or disease (median 0.10 (0.02, 3.33) vs. 5.99 (1.95, 10.37) pmol/mL/min, p < 0.001). Of the healthy controls, 48% had undetectable ACE2 activity. Controls with detectable ACE2 had lower maximum amplitude (p < 0.001). In patients with cardiovascular risk factors and/or disease, those in the 3rd tertile were older and male (p = 0.002), with a higher Framingham grade and increased number of cardiovascular risk factors (p < 0.001). In conclusion, plasma ACE2 activity is undetectable to very low in young healthy controls with minimal clinically relevant associations to GCA. Patients with cardiovascular risk factors and/or disease have increased plasma ACE2 activity, suggesting that it may be an important biomarker of endothelial dysfunction and atherosclerosis.

The Need for Individualized Risk Assessment in Cardiovascular Disease

Cardiovascular disease remains the leading cause of death in the era of modern medicine despite major advancements in this field. Current available clinical surrogate markers and blood tests do not adequately predict individual risk of cardiovascular disease. A more precise and sophisticated tool that can reliably predict the thrombosis and bleeding risks at an individual level is required in order for clinicians to confidently recommend early interventions with a favorable risk–benefit profile. Critical to the development of this tool is the assessment and understanding of Virchow’s triad and its complex interactions between hypercoagulability, endothelial dysfunction and vessel flow, a fundamental concept to the development of thrombosis. This review explores the pathophysiology of cardiovascular disease stemming from the triad of factors and how individualized risk assessment can be improved through the multimodal use of tools such as global coagulation assays, endothelial biomarkers and vessel flow assessment.

Combined sodium glucose co-transporter-2 inhibitor and angiotensin-converting enzyme inhibition upregulates the renin-angiotensin system in chronic kidney disease with type 2 diabetes: Results of a randomized, double-blind, placebo-controlled exploratory trial

AIM

Sodium glucose co-transporter-2 inhibitors (SGLT-2i) improve cardiorenal outcomes in patients with chronic kidney disease (CKD), with and without type 2 diabetes. The molecular mechanisms underlying these pleiotropic effects remain unclear, yet it is speculated that SGLT-2i elicit a neurohormonal modulation resulting in renin-angiotensin system (RAS) activation. We hypothesized that combined SGLT-2 and angiotensin-converting enzyme inhibition (ACEi) favours RAS regulation towards the beneficial angiotensin-(1-7)-driven axis.

MATERIALS AND METHODS

This randomized controlled prospective study investigated the effect of 12 weeks treatment with the SGLT-2i empagliflozin on top of ACEi on the molecular RAS dynamics in 24 diabetic and 24 non-diabetic patients with CKD. Systemic RAS peptides were quantified by mass spectrometry.

RESULTS

In patients with type 2 diabetes, combined SGLT-2i and ACEi significantly upregulated plasma renin activity [pre-treatment median and interquartile range 298.0 (43.0-672.0) pmol/L versus post-treatment 577.0 (95.0-1543.0) pmol/L; p = .037] and angiotensin I levels [pre-treatment 289.0 (42.0-668.0) pmol/L versus post-treatment 573.0 (93.0-1522.0) pmol/L; p = .037], together with a significant increase of angiotensin-(1-7) levels [pre-treatment 14.0 (2.1-19.0) pmol/L versus post-treatment 32.0 (5.7-99.0) pmol/L; p = .012]. Empagliflozin treatment resulted in a 1.5 to 2-fold increase in main RAS peptides in patients with diabetes compared with placebo. No significant effect of empagliflozin on top of ACEi on RAS peptides was found in patients with CKD without diabetes.

CONCLUSION

A distinct RAS modulation by SGLT-2i occurs in diabetic kidney disease reflected by enhancement of the beneficial angiotensin-(1-7) providing a molecular background for this renoprotective therapeutic approach.

Higher Soluble ACE2 Levels and Increased Risk of Infection-Related Hospitalization in Patients on Maintenance Hemodialysis

Background

Angiotensin-converting enzyme 2 (ACE2) works as an endogenous counter-regulator of the renin-angiotensin system, which has pivotal roles in preventing both cardiovascular disease (CVD) and inflammation. In general populations, higher plasma soluble ACE2 levels were reported to be associated with increased risks of all-cause death and major CVD. Because infections are fatal in patients on maintenance hemodialysis, we aimed to explore whether soluble ACE2 levels are associated with an increased risk of infection-related hospitalization in these patients.

Methods

Using data from a prospective, multicenter, cohort study conducted in Tokyo, Japan, we performed a post-hoc analyses of 724 clinically stable patients on maintenance hemodialysis. We measured baseline serum soluble ACE2 levels and assessed potential determinants of its with infection-related hospitalization as a primary outcome as well as all-cause death and CVD as secondary outcomes using a Cox proportional hazards model.

Results

The soluble ACE2 level (median, 0.16 ng/ml; interquartile range, 0.07–0.57 ng/ml) showed a weak negative association with age. During a median follow-up of 39 months, 106 patients (14.6%) were hospitalized with infectious diseases. Compared with the lower half of soluble ACE2 levels, the higher half was associated with an increased risk of infection-related hospitalization (hazard ratio, 1.57; 95% confidence interval, 1.02–2.41) with adjustment by other risk factors. On the other hand, there were no significant associations between soluble ACE2 and risks of all-cause death and CVD.

Conclusion

Higher soluble ACE2 levels may associate with an increased risk of infection-related hospitalization in patients on maintenance hemodialysis.

Changes of FGF23 and the Renin-Angiotensin-System in Male Mouse Models of Chronic Kidney Disease and Cardiac Hypertrophy

Serum fibroblast growth factor 23 (FGF23) levels and the renin-angiotensin-aldosterone system (RAAS) are elevated in chronic kidney disease (CKD) patients, and their association with left ventricular hypertrophy (LVH) has been reported. However, whether the FGF23 elevation is the cause or result of LVH remains unclear. At 10 weeks, male C57BL/6J mice were divided into 4 groups: sham, CKD (5/6 nephrectomy), LVH (transaortic constriction), and CKD/LVH group. At 16 weeks, the mice were euthanized, and blood and urine, cardiac expressions of FGF23 and RAAS-related factors, and cardiac histological analyses were performed. Heart weight, serum FGF23 levels, and cardiac expression of FGF23 and RAAS-related factors, except for angiotensin-converting enzyme 2, were more increased in the CKD/LVH group compared to the other groups. A significant correlation between LVH and cardiac expressions of FGF23 and RAAS-related factors was observed. Furthermore, there was a significantly close correlation of the cardiac expression of FGF23 with LVH and RAAS-related factors. The coexisting CKD and LVH increased serum and cardiac FGF23 and RAAS-related factors, and there was a significant correlation between them. A close correlation of cardiac, but not serum FGF23, with LVH and RAAS suggests that local FGF23 levels may be associated with LVH and RAAS activation.

Exploring Renal Changes after Bariatric Surgery in Patients with Severe Obesity

Obesity-related hyperfiltration leads to an increased glomerular filtration rate (GFR) and hyperalbuminuria. These changes are reversible after bariatric surgery (BS). We aimed to explore obesity-related renal changes post-BS and to seek potential mechanisms. Sixty-two individuals with severe obesity were prospectively examined before and 3, 6 and 12 months post-BS. Anthropometric and laboratory data, 24 h-blood pressure, renin-angiotensin-aldosterone system (RAS) components, adipokines and inflammatory markers were determined. Both estimated GFR (eGFR) and albuminuria decreased from the baseline at all follow-up times (p-for-trend <0.001 for both). There was a median (IQR) of 30.5% (26.2–34.4) reduction in body weight. Plasma glucose, glycosylated hemoglobin, fasting insulin and HOMA-index decreased at 3, 6 and 12 months of follow-up (p-for-trend <0.001 for all). The plasma aldosterone concentration (median (IQR)) also decreased at 12 months (from 87.8 ng/dL (56.8; 154) to 65.4 (56.8; 84.6), p = 0.003). Both leptin and hs-CRP decreased (p < 0.001) and adiponectine levels increased at 12 months post-BS (p = 0.017). Linear mixed-models showed that body weight (coef. 0.62, 95% CI: 0.32 to 0.93, p < 0.001) and plasma aldosterone (coef. −0.07, 95% CI: −0.13 to −0.02, p = 0.005) were the independent variables for changes in eGFR. Conversely, glycosylated hemoglobin was the only independent variable for changes in albuminuria (coef. 0.24, 95% CI: 0.06 to 0.42, p = 0.009). In conclusion, body weight and aldosterone are the main factors that mediate eGFR changes in obesity and BS, while albuminuria is associated with glucose homeostasis.

Angiotensin-converting enzyme 2: a key enzyme in key organs

2020 marked the 20th anniversary of the discovery of the angiotensin-converting enzyme 2 (ACE2). This major event that changed the way we see the renin-angiotensin system today could have passed quietly. Instead, the discovery that ACE2 is a major player in the severe acute respiratory syndrome coronavirus 2 pandemic has blown up the literature regarding this enzyme. ACE2 connects the classical arm renin-angiotensin system, consisting mainly of angiotensin II peptide and its AT1 receptor, with a protective arm, consisting mainly of the angiotensin 1-7 peptide and its Mas receptor. In this brief article, we have reviewed the literature to describe how ACE2 is a key protective arm enzyme in the function of many organs, particularly in the context of brain and cardiovascular function, as well as in renal, pulmonary and digestive homeostasis. We also very briefly review and refer to recent literature to present an insight into the role of ACE2 in determining the course of coronavirus diseases 2019.

Non-classical Vitamin D Actions for Renal Protection

Chronic Kidney Disease (CKD), a disorder that affects 11% of the world's population, is characterized by an acceleration in skeletal, immune, renal, and cardiovascular aging that increases the risk of cardiovascular mortality by 10- to 20-fold, compared to that in individuals with normal renal function. For more than two decades, the progressive impairment in renal capacity to maintain normal circulating levels of the hormonal form of vitamin D (1,25-dihydroxyvitamin D or calcitriol) was considered the main contributor to the reduced survival of CKD patients. Accordingly, calcitriol administration was the treatment of choice to attenuate the progression of secondary hyperparathyroidism (SHPT) and its adverse impact on bone health and vascular calcification. The development of calcitriol analogs, designed to mitigate the resistance to calcitriol suppression of PTH associated with CKD progression, demonstrated survival benefits unrelated to the control of SHPT or skeletal health. The exhaustive search for the pathophysiology behind survival benefits associated with active vitamin D analogs has identified novel anti-inflammatory, anti-hypertensive, anti-aging actions of the vitamin D endocrine system. A major paradigm shift regarding the use of calcitriol or active vitamin D analogs to improve survival in CKD patients emerged upon demonstration of a high prevalence of vitamin D (not calcitriol) deficiency at all stages of CKD and, more significantly, that maintaining serum levels of the calcitriol precursor, 25(OH)vitamin D, above 23 ng/ml delayed CKD progression. The cause of vitamin D deficiency in CKD, however, is unclear since vitamin D bioactivation to 25(OH)D occurs mostly at the liver. Importantly, neither calcitriol nor its analogs can correct vitamin D deficiency. The goals of this chapter are to present our current understanding of the pathogenesis of vitamin D deficiency in CKD and of the causal link between defective vitamin D bioactivation to calcitriol and the onset of molecular pathways that promote CKD progression independently of the degree of SHPT. An understanding of these mechanisms will highlight the need for identification of novel sensitive biomarkers to assess the efficacy of interventions with vitamin D and/or calcitriol(analogs) to ameliorate CKD progression in a PTH-independent manner.

COVID-19 and RAAS inhibitors: is there a final conclusion?

Coronavirus disease 2019 (COVID-19), the first pandemic caused by a human infecting coronavirus, has drawn global attention from the first time it appeared in Wuhan city of China in late December 2019. Detection of the responsible viral pathogen, named as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by WHO, and its possible pathogenesis lead to the forming of many hypotheses about the factors that may affect the patients' outcome. One of the SARS-CoV-2 infection concerns was the potential role of angiotensin-converting enzyme (ACE) inhibitors and angiotensin-receptor blockers (ARBs) in COVID-19 patients' morbidity and mortality. Studies demonstrated that because SARS-CoV-2 uses human ACE2 cell receptors as an entry receptor to invade the cells, there might be an association between antihypertensive drugs such as RAAS inhibitors (specifically ACEIs and ARBs) and the COVID-19 disease. Data are scarce and conflicting regarding ACEI or ARB consumption and how it influences disease outcomes, and a single conclusion has not been reached yet. According to the literature review in our article, the most evidentially supported theory about the use of RAAS inhibitors in COVID-19 is that these medications, including ACEI/ARB, are not associated with the increased risk of infection, disease severity, and patient prognosis. However, further studies are needed to support the hypothesis.

Apelin-13 in septic shock: effective in supporting hemodynamics in sheep but compromised by enzymatic breakdown in patients

Sepsis is a prevalent life-threatening condition related to a systemic infection, and with unresolved issues including refractory septic shock and organ failures. Endogenously released catecholamines are often inefficient to maintain blood pressure, and low reactivity to exogenous catecholamines with risk of sympathetic overstimulation is well documented in septic shock. In this context, apelinergics are efficient and safe inotrope and vasoregulator in rodents. However, their utility in a larger animal model as well as the limitations with regards to the enzymatic breakdown during sepsis, need to be investigated. The therapeutic potential and degradation of apelinergics in sepsis were tested experimentally and in a cohort of patients. (1) 36 sheep with or without fecal peritonitis-induced septic shock (a large animal experimental design aimed to mimic the human septic shock paradigm) were evaluated for hemodynamic and renal responsiveness to incremental doses of two dominant apelinergics: apelin-13 (APLN-13) or Elabela (ELA), and (2) 52 subjects (33 patients with sepsis/septic shock and 19 healthy volunteers) were investigated for early levels of endogenous apelinergics in the blood, the related enzymatic degradation profile, and data regarding sepsis outcome. APLN-13 was the only one apelinergic which efficiently improved hemodynamics in both healthy and septic sheep. Endogenous apelinergic levels early rose, and specific enzymatic breakdown activities potentially threatened endogenous apelin system reactivity and negatively impacted the outcome in human sepsis. Short-term exogenous APLN-13 infusion is helpful in stabilizing cardiorenal functions in ovine septic shock; however, this ability might be impaired by specific enzymatic systems triggered during the early time course of human sepsis. Strategies to improve resistance of APLN-13 to degradation and/or to overcome sepsis-induced enzymatic breakdown environment should guide future works.

Association of renin–angiotensin system blockers with COVID-19 diagnosis and prognosis in patients with hypertension: a population-based study

Background

The effect of renin–angiotensin system (RAS) blockade either by angiotensin-converting enzyme inhibitors (ACEis) or angiotensin-receptor blockers (ARBs) on coronavirus disease 2019 (COVID-19) susceptibility, mortality and severity is inadequately described. We examined the association between RAS blockade and COVID-19 diagnosis and prognosis in a large population-based cohort of patients with hypertension (HTN).

Methods

This is a cohort study using regional health records. We identified all individuals aged 18–95 years from 87 healthcare reference areas of the main health provider in Catalonia (Spain), with a history of HTN from primary care records. Data were linked to COVID-19 test results, hospital, pharmacy and mortality records from 1 March 2020 to 14 August 2020. We defined exposure to RAS blockers as the dispensation of ACEi/ARBs during the 3 months before COVID-19 diagnosis or 1 March 2020. Primary outcomes were: COVID-19 infection and severe progression in hospitalized patients with COVID-19 (the composite of need for invasive respiratory support or death). For both outcomes and for each exposure of interest (RAS blockade, ACEi or ARB) we estimated associations in age-, sex-, healthcare area- and propensity score-matched samples.

Results

From a cohort of 1 365 215 inhabitants we identified 305 972 patients with HTN history. Recent use of ACEi/ARBs in patients with HTN was associated with a lower 6-month cumulative incidence of COVID-19 diagnosis {3.78% [95% confidence interval (CI) 3.69–3.86%] versus 4.53% (95% CI 4.40–4.65%); P &lt; 0.001}. In the 12 344 patients with COVID-19 infection, the use of ACEi/ARBs was not associated with a higher risk of hospitalization with need for invasive respiratory support or death [OR = 0.91 (0.71–1.15); P = 0.426].

Conclusions

RAS blockade in patients with HTN is not associated with higher risk of COVID-19 infection or with a worse progression of the disease.

SARS-CoV-2 Infection Modulates ACE2 Function and Subsequent Inflammatory Responses in Swabs and Plasma of COVID-19 Patients

Angiotensin converting enzyme 2 (ACE2) is a host ectopeptidase and the receptor for the SARS-CoV-2 virus, albeit virus-ACE2 interaction goes far beyond viral entry into target cells. Controversial data exists linking viral infection to changes in ACE2 expression and function, which might influence the subsequent induction of an inflammatory response. Here, we tested the significance of soluble ACE2 enzymatic activity longitudinally in nasopharyngeal swabs and plasma samples of SARS-CoV-2 infected patients, along with the induction of inflammatory cytokines. Release of soluble functional ACE2 increases upon SARS-CoV-2 infection in swabs and plasma of infected patients, albeit rapidly decreasing during infection course in parallel with ACE2 gene expression. Similarly, SARS-CoV-2 infection also induced the expression of inflammatory cytokines. These changes positively correlated with the viral load. Overall, our results demonstrate the existence of mechanisms by which SARS-CoV-2 modulates ACE2 expression and function, intracellular viral sensing and subsequent inflammatory response, offering new insights into ACE2 dynamics in the human upper respiratory tract and pointing towards soluble ACE2 levels as a putative early biomarker of infection severity.

Which ones, when and why should renin-angiotensin system inhibitors work against COVID-19?

The article describes the possible pathophysiological origin of COVID-19 and the crucial role of renin-angiotensin system (RAS), providing several “converging” evidence in support of this hypothesis. SARS-CoV-2 has been shown to initially upregulate ACE2 systemic activity (early phase), which can subsequently induce compensatory responses leading to upregulation of both arms of the RAS (late phase) and consequently to critical, advanced and untreatable stages of COVID-19 disease. The main and initial actors of the process are ACE2 and ADAM17 zinc-metalloproteases, which, initially triggered by SARS-CoV-2 spike proteins, work together in increasing circulating Ang 1–7 and Ang 1–9 peptides and downstream (Mas and Angiotensin type 2 receptors) pathways with anti-inflammatory, hypotensive and antithrombotic activities. During the late phase of severe COVID-19, compensatory secretion of renin and ACE enzymes are subsequently upregulated, leading to inflammation, hypertension and thrombosis, which further sustain ACE2 and ADAM17 upregulation. Based on this hypothesis, COVID-19-phase-specific inhibition of different RAS enzymes is proposed as a pharmacological strategy against COVID-19 and vaccine-induced adverse effects. The aim is to prevent the establishment of positive feedback-loops, which can sustain hyperactivity of both arms of the RAS independently of viral trigger and, in some cases, may lead to Long-COVID syndrome.

The Impact of Age on Mortality in Chronic Haemodialysis Popu-Lation with COVID-19

Age and chronic kidney disease have been described as mortality risk factors for coronavirus disease 2019 (COVID-19). Currently, an important percentage of patients in haemodialysis are elderly. Herein, we investigated the impact of age on mortality among haemodialysis patients with COVID-19. Data was obtained from the Spanish COVID-19 chronic kidney disease (CKD) Working Group Registry. From 18 March 2020 to 27 August 2020, 930 patients on haemodialysis affected by COVID-19 were included in the Registry. A total of 254 patients were under 65 years old and 676 were 65 years or older (elderly group). Mortality was 25.1% higher (95% CI: 22.2-28.0%) in the elderly as compared to the non-elderly group. Death from COVID-19 was increased 6.2-fold in haemodialysis patients as compared to the mortality in the general population in a similar time frame. In the multivariate Cox regression analysis, age (hazard ratio (HR) 1.59, 95% CI: 1.31-1.93), dyspnea at presentation (HR 1.51, 95% CI: 1.11-2.04), pneumonia (HR 1.74, 95% CI: 1.10-2.73) and admission to hospital (HR 4.00, 95% CI: 1.83-8.70) were identified as independent mortality risk factors in the elderly haemodialysis population. Treatment with glucocorticoids reduced the risk of death (HR 0.68, 95% CI: 0.48-0.96). In conclusion, mortality is dramatically increased in elderly haemodialysis patients with COVID-19. Our results suggest that this high risk population should be prioritized in terms of protection and vaccination.

Renin-Angiotensin System Blockers and the Risk of COVID-19-Related Mortality in Patients with Kidney Failure

BACKGROUND AND OBJECTIVES

There is concern about potential deleterious effects of angiotensin-converting enzyme inhibitors (ACEis) and angiotensin II receptor blockers (ARBs) in patients with coronavirus disease 2019 (COVID-19). Patients with kidney failure, who often use ACEis/ARBs, are at higher risk of more severe COVID-19. However, there are no data available on the association of ACEi/ARB use with COVID-19 severity in this population.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

From the European Renal Association COVID-19 database (ERACODA), we retrieved data on kidney transplant recipients and patients on dialysis who were affected by COVID-19, between February 1 and October 1, 2020, and had information on 28-day mortality. We used Cox proportional-hazards regression to calculate hazard ratios for the association between ACEi/ARB use and 28-day mortality risk. Additionally, we studied the association of discontinuation of these agents with 28-day mortality.

RESULTS

We evaluated 1511 patients: 459 kidney transplant recipients and 1052 patients on dialysis. At diagnosis of COVID-19, 189 (41%) of the transplant recipients and 288 (27%) of the patients on dialysis were on ACEis/ARBs. A total of 88 (19%) transplant recipients and 244 (23%) patients on dialysis died within 28 days of initial presentation. In both groups of patients, there was no association between ACEi/ARB use and 28-day mortality in both crude and adjusted models (in transplant recipients, adjusted hazard ratio, 1.12; 95% confidence interval [95% CI], 0.69 to 1.83; in patients on dialysis, adjusted hazard ratio, 1.04; 95% CI, 0.73 to 1.47). Among transplant recipients, ACEi/ARB discontinuation was associated with a higher mortality risk after adjustment for demographics and comorbidities, but the association was no longer statistically significant after adjustment for severity of COVID-19 (adjusted hazard ratio, 1.36; 95% CI, 0.40 to 4.58). Among patients on dialysis, ACEi/ARB discontinuation was not associated with mortality in any model. We obtained similar results across subgroups when ACEis and ARBs were studied separately, and when other outcomes for severity of COVID-19 were studied, e.g., hospital admission, admission to the intensive care unit, or need for ventilator support.

CONCLUSIONS

Among kidney transplant recipients and patients on dialysis with COVID-19, there was no significant association of ACEi/ARB use or discontinuation with mortality.

Variants in ACE2; potential influences on virus infection and COVID-19 severity

The third pandemic of coronavirus infection, called COVID-19 disease, was first detected in November 2019th. Various determinants of disease progression such as age, sex, virus mutations, comorbidity, lifestyle, host immune response, and genetic background variation have caused clinical variability of COVID-19. The causative agent of COVID-19 is an enveloped coronavirus named severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) that invades host cells using an endocytic pathway. The SARS-CoV-2 spike protein is the main viral protein that contributes to the fusion of the virus particle to the host cell through angiotensin-converting enzyme 2 (ACE2). The highly conserved expression of ACE2 is found in various animals, which indicates its pivotal physiological function. The ACE2 has a crucial role in vascular, renal, and myocardial physiology. Genetic factors contributing to the outcome of SARS-CoV-2 infection are unknown; however, variants in the specific sites of ACE2 gene could be regarded as a main genetic risk factor for COVID-19. Given that ACE2 is the main site for virus landing on host cells, the effect of amino acid sequences of ACE2 on host susceptibility to COVID-19 seems reasonable. It would likely have a substantial role in the occurrence of a wide range of clinical symptoms. Several ACE2 variants can affect the protein stability, influencing the interaction between spike protein and ACE2 through imposing conformational changes while some other variants are known to cause a decrease or an increase in the ligand-receptor affinity. The other variations are located at the proteolytic cleavage site, which can influence virus infection; because soluble ACE2 can act as a decoy receptor for virus and decrease virus intake by cell surface ACE2. Notably, polymorphisms of regulatory and non-coding regions such as promoter in ACE2, can play crucial role in different expression levels of ACE2 among different individuals. Many studies should be performed to investigate the involvement of ACE2 polymorphism with susceptibility to COVID-19. Herein, we discuss some reported associations between variants of ACE2 and COVID-19 in details. In addition, the mode of action of ACE2 and its role in SARS-CoV-2 infection are highlighted which is followed by addressing the effects of several ACE2 variants on its protein stability, viral tropism or ligand-receptor affinity, secondary and tertiary structure or protein conformation, proteolytic cleavage site, and finally inter-individual clinical variability in COVID-19. The polymorphisms of regulatory regions of ACE2 and their effect on expression levels of ACE2 are also provided in this review. Such studies can improve the prediction of the affinity of mutant ACE2 variations with spike protein, and help the biopharmaceutical industry to design effective approaches for recombinant hACE2 therapy and vaccination of COVID-19 disease.

Should We Be Concerned about the Association of Diabetes Mellitus and Periodontal Disease in the Risk of Infection by SARS-CoV-2? A Systematic Review and Hypothesis

The objective of this article was to conduct a systematic review of the literature to contrast the existing evidence regarding the relationship between periodontal disease (PD) and diabetes mellitus (DM) with the possibly increased risk of SARS-CoV-2 infection, as well as to establish a hypothesis that explains the ways in which this interaction could take place. A literature search up from 1 January 2020 to 21 March 2021 was conducted in three electronic databases, namely, PubMed, Web of Science, and Scopus, in order to identify studies on periodontal disease alone or in conjunction with diabetes mellitus, reporting any relation with SARS-CoV-2 infection as a primary outcome. Only articles published in the English language were included. Due to the lack of studies, we decided to collect all the theoretical and clinical evidence suggesting a possible biological pathway evidencing the relationship among PD, DM, and SARS-CoV-2 infection. From a total of 29 articles, 12 were included for final review studies (five reviews, two hypotheses, one Special Issue, one perspective, one commentary, one case–control study, and one case report). In addition, this systematic review article hypothesizes the correlation between PD and type 2 diabetes mellitus (T2DM) by expression of angiotensin-converting enzyme 2 (ACE2) in periodontal tissue and the risk of SARS-CoV-2 infection. T2DM is a metabolic disorder characterized by high blood glucose levels resulting from altered insulin secretion or action. Likewise, periodontitis and T2DM are inflammatory disorders with a bidirectional association, and both diseases have a similar immunomodulatory cascade and cytokine profile. ACE2 is a crucial component of the renin–angiotensin system (RAS) and the key factor of entry in the cells by the new SARS-CoV-2. ACE2 is widely distributed in the lung and kidneys, and interestingly has a great distribution in the oral cavity, principally in the tongue and periodontal tissue. ACE2 in periodontal tissue plays a crucial role between health and disease. Moreover, the ACE2/Ang-(1-7)/MasR axis is downregulated in the dysbiotic and inflammatory periodontal environment. Nevertheless, the balance of ACE2 activity is modified in the context of concurrent diabetes, increasing the expression of ACE2 by the uncontrolled glycemia chronic in T2DM. Therefore, the uncontrolled hyperglycemia possibly increases the risk of developing periodontitis and triggering overexpression of ACE2 in periodontal tissue of T2DM patients, with these events potentially being essential to SARS-CoV-2 infection and the development of mild-to-severe form of COVID-19. In this sense, we would like to point out that the need for randomized controlled trials is imperative to support this association.

Levels of angiotensin-converting enzyme 1 and 2 in serum and urine of children with Sickle Cell Disease

Introduction:

Sickle cell nephropathy begins in childhood and presents early increases in glomerular filtration, which, over the long term, can lead to chronic renal failure. Several diseases have increased circulating and urinary angiotensin-converting enzyme (ACE) activity, but there is little information about changes in ACEs activity in children with sickle cell disease (SCD).

Objective:

We examined circulating and urinary ACE 1 activity in children with SCD.

Methods:

This cross-sectional study compared children who were carriers of SCD with children who comprised a control group (CG). Serum and urinary activities of ACE were evaluated, as were biochemical factors, urinary album/creatinine rates, and estimated glomerular filtration rate.

Results:

Urinary ACE activity was significantly higher in patients with SCD than in healthy children (median 0.01; range 0.00-0.07 vs median 0.00; range 0.00-0.01 mU/mL·creatinine, p < 0.001. No significant difference in serum ACE activities between the SCD and CG groups was observed (median 32.25; range 16.2-59.3 vs median 40.9; range 18.0-53.4) mU/m`L·creatinine, p < 0.05.

Conclusion:

Our data revealed a high urinary ACE 1 activity, different than plasmatic level, in SCD patients suggesting a dissociation between the intrarenal and systemic RAAS. The increase of urinary ACE 1 activity in SCD patients suggests higher levels of Ang II with a predominance of classical RAAS axis, that can induce kidney damage.

A comprehensive guide to the pharmacologic regulation of angiotensin converting enzyme 2 (ACE2), the SARS-CoV-2 entry receptor

The recent emergence of coronavirus disease-2019 (COVID-19) as a global pandemic has prompted scientists to address an urgent need for defining mechanisms of disease pathology and treatment. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent for COVID-19, employs angiotensin converting enzyme 2 (ACE2) as its primary target for cell surface attachment and likely entry into the host cell. Thus, understanding factors that may regulate the expression and function of ACE2 in the healthy and diseased body is critical for clinical intervention. Over 66% of all adults in the United States are currently using a prescription drug and while earlier findings have focused on possible upregulation of ACE2 expression through the use of renin angiotensin system (RAS) inhibitors, mounting evidence suggests that various other widely administered drugs used in the treatment of hypertension, heart failure, diabetes mellitus, hyperlipidemias, coagulation disorders, and pulmonary disease may also present a varied risk for COVID-19. Specifically, we summarize mechanisms on how heparin, statins, steroids and phytochemicals, besides their established therapeutic effects, may also interfere with SARS-CoV-2 viral entry into cells. We also describe evidence on the effect of several vitamins, phytochemicals, and naturally occurring compounds on ACE2 expression and activity in various tissues and disease models. This comprehensive review aims to provide a timely compendium on the potential impact of commonly prescribed drugs and pharmacologically active compounds on COVID-19 pathology and risk through regulation of ACE2 and RAS signaling.

Age-associated difference in circulating ACE2, the gateway for SARS-COV-2, in humans: results from the InCHIANTI study

Levels of angiotensin-converting enzyme 2 (ACE2), the gateway for COVID-19 virus into the cells, have been implicated in worse COVID-19 outcomes associated with aging and cardiovascular disease (CVD). Data on age-associated differences in circulating ACE2 levels in humans and the role of CVD and medications is limited. We analyzed data from 967 participants of the InCHIANTI study, a community-dwelling cohort in the Chianti region, Italy. Relative abundance of ACE2 in plasma was assessed using a proteomics platform. CVD diagnoses, use of renin-angiotensin-aldosterone system (RAAS) antagonists: ACEi, ARBs, and aldosterone antagonists, were ascertained. Multiple linear analyses were performed to examine the independent association of ACE2 with age, CVD, and RAAS antagonist use. Age was independently associated with lower log (ACE2) in persons aged ≥ 55 years (STD β = - 0.12, p = 0.0002). ACEi treatment was also independently associated with significantly lower ACE2 levels, and ACE2 was inversely associated with weight, and positively associated with peripheral artery disease (PAD) status. There was a trend toward higher circulating ACE2 levels in hypertensive individuals, but it did not reach statistical significance. In a stratified analysis, the association between log (ACE2) and log (IL-6) was more evidenced in participants with PAD. Circulating ACE2 levels demonstrate curvilinear association with age, with older individuals beyond the sixth decade age having lower levels. ACEi was associated with greater circulating ACE2 levels. Interestingly, ACE2 was elevated in PAD and positively associated with inflammatory markers, suggesting compensatory upregulation in the setting of chronic inflammation. Further studies are needed to comprehensively characterize RAAS components with aging and disease, and assess its prognostic role in predicting COVID-19 outcomes.

RAAS Blockade and COVID-19: Mechanistic Modeling of Mas and AT1 Receptor Occupancy as Indicators of Pro-Inflammatory and Anti-Inflammatory Balance

ACE inhibitors (ACEis) and angiotensin receptor blockers (ARBs) are standard-of-care treatments for hypertension and diabetes, common comorbidities among hospitalized patients with coronavirus disease 2019 (COVID-19). Their use in the setting of COVID-19 has been heavily debated due to potential interactions with ACE2, an enzyme that links the pro-inflammatory and anti-inflammatory arms of the renin angiotensin system, but also the entryway by which severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) invades cells. ACE2 expression is altered by age, hypertension, diabetes, and the virus itself. This study integrated available information about the renin angiotensin aldosterone system (RAAS) and effects of SARS-CoV-2 and its comorbidities on ACE2 into a mechanistic mathematical model and aimed to quantitatively predict effects of ACEi/ARBs on the RAAS pro-inflammatory/anti-inflammatory balance. RAAS blockade prior to SARS-CoV-2 infection is predicted to increase the mas-AT1 receptor occupancy ratio up to 20-fold, indicating that in patients already taking an ACEi/ARB before infection, the anti-inflammatory arm is already elevated while the pro-inflammatory arm is suppressed. Predicted pro-inflammatory shifts in the mas-AT1 ratio due to ACE2 downregulation by SARS-CoV-2 were small relative to anti-inflammatory shifts induced by ACEi/ARB. Predicted effects of changes in ACE2 expression with comorbidities of diabetes, hypertension, or aging on mas-AT1 occupancy ratio were also relatively small. Last, predicted changes in the angiotensin (Ang(1-7)) production rate with ACEi/ARB therapy, comorbidities, or infection were all small relative to exogenous Ang(1-7) infusion rates shown experimentally to protect against acute lung injury, suggesting that any changes in the ACE2-Ang(1-7)-mas arm may not be large enough to play a major role in COVID-19 pathophysiology.

Angiotensin-converting enzyme 2 and COVID-19: patients, comorbidities, and therapies

On March 11, 2020, the World Health Organization declared coronavirus disease 2019 (COVID-19) a pandemic, and the reality of the situation has finally caught up to the widespread reach of the disease. The presentation of the disease is highly variable, ranging from asymptomatic carriers to critical COVID-19. The availability of angiotensin-converting enzyme 2 (ACE2) receptors may reportedly increase the susceptibility and/or disease progression of COVID-19. Comorbidities and risk factors have also been noted to increase COVID-19 susceptibility. In this paper, we hereby review the evidence pertaining to ACE2's relationship to common comorbidities, risk factors, and therapies associated with the susceptibility and severity of COVID-19. We also highlight gaps of knowledge that require further investigation. The primary comorbidities of respiratory disease, cardiovascular disease, renal disease, diabetes, obesity, and hypertension had strong evidence. The secondary risk factors of age, sex, and race/genetics had limited-to-moderate evidence. The tertiary factors of ACE inhibitors and angiotensin II receptor blockers had limited-to-moderate evidence. Ibuprofen and thiazolidinediones had limited evidence.

Upregulation of the Renin-Angiotensin System Pathways and SARS-CoV-2 Infection: The Rationale for the Administration of Zinc-Chelating Agents in COVID-19 Patients

The article describes the rationale for the administration of zinc-chelating agents in COVID-19 patients. In a previous work I have highlighted that the binding of the SARS-CoV spike proteins to the zinc-metalloprotease ACE2 has been shown to induce ACE2 shedding by activating the zinc-metalloprotease ADAM17, which ultimately leads to systemic upregulation of ACE2 activity. Moreover, based on experimental models, it was also shown the detrimental effect of the excessive systemic activity of ACE2 through its downstream pathways, which leads to "clinical" manifestations resembling COVID-19. In this regard, strong upregulation of circulating ACE2 activity was recently reported in COVID-19 patients, thus supporting the previous hypothesis that COVID-19 may derive from upregulation of ACE2 activity. Based on this, a reasonable hypothesis of using inhibitors that curb the upregulation of both ACE2 and ADAM17 zinc-metalloprotease activities and consequent positive feedback-loops (initially triggered by SARS-CoV-2 and subsequently sustained independently on viral trigger) is proposed as therapy for COVID-19. In particular, zinc-chelating agents such as citrate and ethylenediaminetetraacetic acid (EDTA) alone or in combination are expected to act in protecting from COVID-19 at different levels thanks to their both anticoagulant properties and inhibitory activity on zinc-metalloproteases. Several arguments are presented in support of this hypothesis and based on the current knowledge of both beneficial/harmful effects and cost/effectiveness, the use of chelating agents in the prevention and therapy of COVID-19 is proposed. In this regard, clinical trials (currently absent) employing citrate/EDTA in COVID-19 are urgently needed in order to shed more light on the efficacy of zinc chelators against SARS-CoV-2 infection in vivo.

Controversial Roles of the Renin Angiotensin System and Its Modulators During the COVID-19 Pandemic

Since December 2019, the coronavirus 2019 (COVID-19) pandemic has rapidly spread and overwhelmed healthcare systems worldwide, urging physicians to understand how to manage this novel infection. Early in the pandemic, more severe forms of COVID-19 have been observed in patients with cardiovascular comorbidities, who are often treated with renin-angiotensin aldosterone system (RAAS)-blockers, such as angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin receptor blockers (ARBs), but whether these are indeed independent risk factors is unknown. The cellular receptor for the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the membrane-bound angiotensin converting enzyme 2 (ACE2), as for SARS-CoV(-1). Experimental data suggest that expression of ACE2 may be increased by RAAS-blockers, raising concerns that these drugs may facilitate viral cell entry. On the other hand, ACE2 is a key counter-regulator of the RAAS, by degrading angiotensin II into angiotensin (1-7), and may thereby mediate beneficial effects in COVID-19. These considerations have raised concerns about the management of these drugs, and early comments shed vivid controversy among physicians. This review will describe the homeostatic balance between ACE-angiotensin II and ACE2-angiotensin (1-7) and summarize the pathophysiological rationale underlying the debated role of the RAAS and its modulators in the context of the pandemic. In addition, we will review available evidence investigating the impact of RAAS blockers on the course and prognosis of COVID-19 and discuss why retrospective observational studies should be interpreted with caution. These considerations highlight the importance of solid evidence-based data in order to guide physicians in the management of RAAS-interfering drugs in the general population as well as in patients with more or less severe forms of SARS-CoV-2 infection.

Ex uno, plures-From One Tissue to Many Cells: A Review of Single-Cell Transcriptomics in Cardiovascular Biology

Recent technological advances have revolutionized the study of tissue biology and garnered a greater appreciation for tissue complexity. In order to understand cardiac development, heart tissue homeostasis, and the effects of stress and injury on the cardiovascular system, it is essential to characterize the heart at high cellular resolution. Single-cell profiling provides a more precise definition of tissue composition, cell differentiation trajectories, and intercellular communication, compared to classical bulk approaches. Here, we aim to review how recent single-cell multi-omic studies have changed our understanding of cell dynamics during cardiac development, and in the healthy and diseased adult myocardium.

Inflammation Triggered by SARS-CoV-2 and ACE2 Augment Drives Multiple Organ Failure of Severe COVID-19: Molecular Mechanisms and Implications

The widespread occurrence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has led to a pandemic of coronavirus disease 2019 (COVID-19). The S spike protein of SARS-CoV-2 binds with angiotensin-converting enzyme 2 (ACE2) as a functional "receptor" and then enters into host cells to replicate and damage host cells and organs. ACE2 plays a pivotal role in the inflammation, and its downregulation may aggravate COVID-19 via the renin-angiotensin system, including by promoting pathological changes in lung injury and involving inflammatory responses. Severe patients of COVID-19 often develop acute respiratory distress syndrome and multiple organ dysfunction/failure with high mortality that may be closely related to the hyper-proinflammatory status called the "cytokine storm." Massive cytokines including interleukin-6, nuclear factor kappa B (NFκB), and tumor necrosis factor alpha (TNFα) released from SARS-CoV-2-infected macrophages and monocytes lead inflammation-derived injurious cascades causing multi-organ injury/failure. This review summarizes the current evidence and understanding of the underlying mechanisms of SARS-CoV-2, ACE2 and inflammation co-mediated multi-organ injury or failure in COVID-19 patients.

COVID-19, Angiotensin-Converting Enzyme 2 and Renin-Angiotensin System Inhibition: Implications for Practice

BACKGROUND

Recent studies suggested that patients with coronavirus disease 2019 (COVID-19) who use renin-angiotensin system (RAS) inhibitors have an increased risk of respiratory failure and death. The hypothesis was that angiotensin-converting enzyme inhibitor (ACEIs) or angiotensin receptor blocker (ARBs) may up-regulate ACE2 expression that is used as receptor for viral entry into cells.

OBJECTIVE

The purpose of this review is to discuss the existing evidence on the interaction between COVID-19 infection, ACE2 and ACEIs or ARBs and to examine the main implications for clinical practice. In addition, novel therapeutic strategies for blocking ACE2-mediated COVID-19 infection will be displayed.

METHODS

We performed a comprehensive review of the literature to identify data from clinical and experimental studies for the association between COVID-19 infection, ACE2 and RAS inhibition.

RESULTS

The current clinical and experimental evidence for ACEIs or ARBs to facilitate severe acute respiratory distress syndrome-coronavirus-2 (SARS-CoV-2) is insufficient to suggest discontinuing these drugs. Several observational studies arrive at the conclusion that the continued use of RAS inhibitors is unlike to be harmful in COVID-19-positive patients.

CONCLUSIONS

Further randomized trials are needed to answer definitely the question of whether RAS inhibitors are harmful or beneficial to patients with COVID-19.

Outbreak of SARS-CoV2: Pathogenesis of infection and cardiovascular involvement

Since the new severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) has emerged from China, the infection (novel corona virus disease-2019, COVID-19) has affected many countries and led to many deaths worldwide. Like SARS-CoV, angiotencin converting enzyme (ACE)2 as a functional receptor for SARS-CoV2 is essential for the virus to make an entry into the cell. ACE2 is a part of Renin-Angiotensin-Aldosterone System, which is expressed in several organs that opposes the angiotensin (Ang) II functions by converting Ang II to Ang (1-7), the one with vasodilation effects. The death rate of COVID-19 is estimated to be approximately 3.4%; however, some comorbid conditions like underlying cardiovascular disease, hypertension, and diabetes increase the risk of mortality. In addition, cardiovascular involvement as a complication of SARS-CoV2 could be direct through either ACE2 receptors that are expressed tremendously in the heart, or by the surge of different cytokines or by acute respiratory distress syndrome-induced hypoxia. Traditional risk factors could aggravate the process of COVID-19 infection that urges the triage of these high-risk patients for SARS-CoV2. Currently, there is no effective, proven treatment or vaccination for COVID-19, but many investigators are struggling to find a treatment strategy as soon as possible. Some potential medications like chloroquine by itself or in combination with azithromycin and some protease inhibitors used for the treatment of COVID-19 have cardiovascular adverse effects, which should be kept in mind while the patients taking these medications are being closely monitored.

Pandemic Perspective: Commonalities Between COVID-19 and Cardio-Oncology

Overlapping commonalities between coronavirus disease of 2019 (COVID-19) and cardio-oncology regarding cardiovascular toxicities (CVT), pathophysiology, and pharmacology are special topics emerging during the pandemic. In this perspective, we consider an array of CVT common to both COVID-19 and cardio-oncology, including cardiomyopathy, ischemia, conduction abnormalities, myopericarditis, and right ventricular (RV) failure. We also emphasize the higher risk of severe COVID-19 illness in patients with cardiovascular disease (CVD) or its risk factors or cancer. We explore commonalities in the underlying pathophysiology observed in COVID-19 and cardio-oncology, including inflammation, cytokine release, the renin-angiotensin-aldosterone-system, coagulopathy, microthrombosis, and endothelial dysfunction. In addition, we examine common pharmacologic management strategies that have been elucidated for CVT from COVID-19 and various cancer therapies. The use of corticosteroids, as well as antibodies and inhibitors of various molecules mediating inflammation and cytokine release syndrome, are discussed. The impact of angiotensin converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) is also addressed, since these drugs are used in cardio-oncology and have received considerable attention during the COVID-19 pandemic, since the culprit virus enters human cells via the angiotensin converting enzyme 2 (ACE2) receptor. There are therefore several areas of overlap, similarity, and interaction in the toxicity, pathophysiology, and pharmacology profiles in COVID-19 and cardio-oncology syndromes. Learning more about either will likely provide some level of insight into both. We discuss each of these topics in this viewpoint, as well as what we foresee as evolving future directions to consider in cardio-oncology during the pandemic and beyond. Finally, we highlight commonalities in health disparities in COVID-19 and cardio-oncology and encourage continued development and implementation of innovative solutions to improve equity in health and healing.

Viral replication of SARS-CoV-2 could be self-limitative - The role of the renin-angiotensin system on COVID-19 pathophysiology

Currently, the world is suffering with one of the biggest pandemics of recent history. Caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the coronavirus disease 2019 (COVID-19) is provoking devastating consequences on economic and social fields throughout all continents. Therefore, pathophysiological knowledge about COVID-19 is imperative for better planning of preventive measures, diagnosis, and therapeutics of the disease. Based on previous studies, this work proposes new hypothesis related to the role of the renin-angiotensin system on the pathophysiology of COVID-19, and its purpose is to enrich the discussion and to offer alternative ways for experimental and clinical studies aiming at the formulation of new diagnosis and/or treatment methods.

Angiotensin Converting Enzyme Inhibitor and Angiotensin II Receptor Blocker Use Among Outpatients Diagnosed With COVID-19

Coronavirus disease 2019 (COVID-19) is a viral pandemic precipitated by the severe acute respiratory syndrome coronavirus 2. Since previous reports suggested that viral entry into cells may involve angiotensin converting enzyme 2, there has been growing concern that angiotensin converting enzyme inhibitor (ACEI) and angiotensin II receptor blocker (ARB) use may exacerbate the disease severity. In this retrospective, single-center US study of adult patients diagnosed with COVID-19, we evaluated the association of ACEI/ARB use with hospital admission. Secondary outcomes included: ICU admission, mechanical ventilation, length of hospital stay, use of inotropes, and all-cause mortality. Propensity score matching was performed to account for potential confounders. Among 590 unmatched patients diagnosed with COVID-19, 78 patients were receiving ACEI/ARB (median age 63 years and 59.7% male) and 512 patients were non-users (median age 42 years and 47.1% male). In the propensity matched population, multivariate logistic regression analysis adjusting for age, gender and comorbidities demonstrated that ACEI/ARB use was not associated with hospital admission (OR 1.2, 95%CI 0.5 to 2.7, p = 0.652). CAD and CKD/end stage renal disease [ESRD] remained independently associated with admission to hospital. All-cause mortality, ICU stay, need for ventilation, and inotrope use was not significantly different between the 2 study groups. In conclusion, among patients who were diagnosed with COVID-19, ACEI/ARB use was not associated with increased risk of hospital admission.

Potential therapeutic targets for combating SARS-CoV-2: Drug repurposing, clinical trials and recent advancements

The present pandemic of SARS-CoV-2 has been a tough task for the whole world to deal with. With the absence of specific drugs or vaccines against SARS-CoV-2, the situation is very difficult to control. Apart from the absence of specific therapies, the lack of knowledge about potential therapeutic targets and individual perception is adding to the complications. The present review describes the novel SARS-CoV-2 structure, surface proteins, asymptomatic and symptomatic transmission in addition to the genotype and phenotype of SARS-CoV-2 along with genetic strains and similarity between SARS, MERS and SARS-CoV-2. Therapeutic strategies such as inhibition of the endocytic pathway and suppressing RNA polymerase activity by metal ions, which could be quite beneficial for controlling COVID-19, are outlined. The drug repurposing for SARS-CoV-2 is discussed in detail along with therapeutic classes such as antivirals, antibiotics, and amino quinolones and their probable role in suppressing SARS-CoV-2 with reference to case studies. The ongoing clinical trials both with respect to drug repurposing and vaccines are summarized along with a brief description. The recent advancements and future perspective of ongoing research for therapy and detection of SARS-CoV-2 are provided. The review, in brief, summarizes epidemiology, therapy and the current scenario for combating SARS-CoV-2.

Angiotensin-converting enzyme 2 influences pancreatic and renal function in diabetic mice

Type 1 diabetes is a T-cell mediated autoimmune disease characterized by pancreatic beta cells destruction. Angiotensin-converting enzyme 2 (ACE2), a component of renin-angiotensin system (RAS) has been identified in pancreas from type 2 diabetic mice and its overexpression prevents beta cell dysfunction. We studied the effect of ACE2 deletion on pancreatic and renal function in the nonobese diabetic mice, a model that mimics type 1 diabetes. ACE2-deficient NOD mice and the respective controls were generated. Pancreas function and immunohistochemistry studies were performed. Renal function and RAS gene expression were also analyzed. Renal proximal tubular cells were obtained from these animals to dissect the effect of ACE2 deficiency in these cells. In NOD mice, ACE2 deletion significantly worsened glucose homeostasis, decreased islet insulin content, increased beta cell oxidative stress, and RIPK1-positive islets as compared with control mice. Angiotensin-converting enzyme and angiotensin II type 1 receptor (AT1R) were also increased in ACE2-deficient mice. In kidneys of 30-day diabetic mice, ACE2 deletion decreased podocyte number within the glomeruli, and altered renal RAS gene expression in tubules. ACE2 deletion influenced the expression of fibrosis-related genes in isolated primary renal proximal tubular cells before diabetes onset in NOD mice. Our findings suggest that ACE2 deletion may have a deleterious impact on beta cell and renal function, by promoting oxidative stress and increasing necroptosis mediators. In addition, this effect is accompanied by RAS alterations in both pancreas and renal proximal tubular cells, indicating that ACE2 may exert a renopancreatic protective effect on type 1 diabetes, which is activated before diabetes starts.

Circulating ADAMs are associated with renal and cardiovascular outcomes in chronic kidney disease patients

BACKGROUND

A disintegrin and metalloproteinase (ADAM) 17, also known as tumour necrosis factor α-converting enzyme (TACE), is a metalloproteinase that releases the ectodomains of most growth factors, cytokines, receptors and enzymes and has been associated with the presence of chronic kidney disease (CKD) and cardiovascular (CV) disease. The role of circulating ADAMs in the progression of renal function and CV events in CKD patients is unknown.

METHODS

A total of 2570 subjects from an observational and multicentre study with CKD Stages 3-5, CKD Stage 5D and controls without any history of CV disease were studied. Circulating ADAM activity was assessed using a fluorometric technique. Progression of renal disease was defined as a 30% increase in serum creatinine or dialysis requirement after 24 months of follow-up. CV outcomes were assessed after 48 months of follow-up.

RESULTS

Patients with advanced CKD had higher ADAM activity as compared with patients with moderate CKD or controls. Male patients with progression of CKD had higher ADAM levels at baseline compared with patients with stable renal function {22.19 relative fluorescence units/μL/h [95% confidence interval (CI) 11.22-37.32] versus 12.15 (7.02-21.50)}. After multivariate adjustment, higher ADAM activity was identified as a risk factor for progression of CKD in male patients [30% increase in the creatinine odds ratio (OR) 2.72 (95% CI 1.58-4.68), P < 0.001; dialysis requirement OR 3.00 (95% CI 1.65-5.46), P < 0.001; dialysis requirement or 30% increase in the creatinine OR 3.15 (95% CI 2.06-4.81), P < 0.001]. ADAM activity was also identified as an independent risk factor for CV events [hazard ratio (HR) 1.68 (95% CI 1.20-2.36), P = 0.003].

CONCLUSIONS

High ADAMs activity levels are independently associated with CKD progression in males and with CV events in CKD patients.

The current understanding and potential therapeutic options to combat COVID-19

The ongoing wreaking global outbreak of the novel human beta coronavirus (CoV) pathogen was presumed to be from a seafood wholesale market in Wuhan, China, belongs to the Coronaviridae family in the Nidovirales order. The virus is highly contagious with potential human-human transmission which was named as the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), has spread across six continents and emerged as a global pandemic in short span with alarming levels of spread and severity. This virus associated symptoms and infectious respiratory illness is designated as coronavirus disease 19 (COVID-19). The SARS-CoV-2 possesses enveloped club-like spike protein projections with positive-sense large RNA genome and has a unique replication strategy. This virus was believed to have zoonotic origin with genetical identity to bat and pangolin CoV. In the current review, we introduce a general overview about the human CoVs and the associated diseases, the origin, structure, replication and key clinical events that occur in the COVID-19 pathogenicity. Furthermore, we focused on possible therapeutic options such as repurposing drugs including antimalarials, antivirals, antiparasitic drugs, and anti-HIV drugs, as well as monoclonal antibodies, vaccines as potential treatment options. Also we have summarized the latest research progress on the usage of stem cell therapy, human convalescent serum, interferon's, in the treatment of COVID-19.

Association between COVID-19 and cardiovascular disease

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes coronavirus disease 2019 (COVID-19) has reached a pandemic level. SARS-CoV-2 infects host cells through ACE2 receptors, leading to COVID-19-related pneumonia. The rapid increase in confirmed cases makes the prevention and control of COVID-19 extremely serious. Real-time reverse transcription-PCR (RT-PCR) assays remain the molecular test of choice for the etiologic diagnosis of SARS-CoV-2 infection while radiographic findings (chest computed tomography [CT]) and antibody-based techniques are being introduced as supplemental tools. Novel virus also cause chronic damage to the cardiovascular system, and attention should be given to cardiovascular protection during treatment for COVID-19. Acute cardiac injury determined by elevated high-sensitivity troponin levels is commonly observed in severe cases and is strongly associated with mortality. This review suggests that cardiovascular comorbidities are common in patients with COVID-19 and such patients are at higher risk of morbidity and mortality. The continuation of clinically indicated ACE inhibitor and ARB medications is recommended in COVID-19. We review the basics of coronaviruses, novel molecular targets for the coronaviruses with a focus on COVID-19, along with their effects on the cardiovascular system.

Risks of ACE Inhibitor and ARB Usage in COVID-19: Evaluating the Evidence

Concerns have been raised regarding the safety of angiotensin converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) in patients with coronavirus disease of 2019 (COVID-19), based on the hypothesis that such medications may raise expression of ACE2, the receptor for severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2). We conducted a literature review of studies (n = 12) in experimental animals and human subjects (n = 12) and evaluated the evidence regarding the impact of administration of ACEIs and ARBs on ACE2 expression. We prioritized studies that assessed ACE2 protein expression data, measured directly or inferred from ACE2 activity assays. The findings in animals are inconsistent with respect to an increase in ACE2 expression in response to treatment with ACEIs or ARBs. Control/sham animals show little to no effect in the plurality of studies. Those studies that report increases in ACE2 expression tend to involve acute injury models and/or higher doses of ACEIs or ARBs than are typically administered to patients. Data from human studies overwhelmingly imply that administration of ACEIs/ARBs does not increase ACE2 expression. Available evidence, in particular, data from human studies, does not support the hypothesis that ACEI/ARB use increases ACE2 expression and the risk of complications from COVID-19. We conclude that patients being treated with ACEIs and ARBs should continue their use for approved indications.

Alteration and association between serum ACE2/ angiotensin(1-7)/Mas axis and oxidative stress in chronic kidney disease: A pilot study

Activation of the renin angiotensin system and renal oxidative stress (OS) are critical contributors in the progression of chronic kidney disease(CKD). Recent studies have confirmed that the angiotensin-converting enzyme 2-angiotensin (1-7)-Mas(ACE2/Ang(1-7)/Mas) axis, the important components of renin angiotensin system, protected kidneys against damage by antagonizing angiotensin II and attenuating OS in rats with several nephropathy models, but its effect needs to be further evaluated in clinic. In this study, we aimed to detected serum ACE2/Ang (1-7)/Mas axis, OS conditions and described its clinical associations in patients with CKD at different stages.A total of 48 patients with CKD and 6 healthy controls (CT) were enrolled, and serum angiotensin converting enzyme (ACE), ACE2, Ang (1-7), 8-hydroxy-2'-deoxyguanosine (8-OHdG) were determined by ELISA. Serum extracellular glutathione peroxidase(eGSH-Px) activity and renal functions were determined by the biochemical method.Serum ACE and ACE2 levels in CKD stages 3 to 5 and serum Ang(1-7) levels in CKD stages 4 to 5 without Ang II receptor blockers treatment significantly increased compared to those in the CT group. However, ACE2 was decreased and Ang(1-7) level increased in early CKD stage with Ang II receptor blockers treatment. Higher serum 8-OHdG levels and lower eGSH-Px activity were noted in CKD stages 4 to 5. Serum 8-OHdG level was correlated with serum ACE2, Ang(1-7) expression. Estimated glomerular filtration rate (eGFR) was correlated with serum ACE, ACE2, Ang(1-7), 8-OHdG, Hcy levels and serum eGSH-Px activity. Multiple-regression analysis eGFR was predicted by ACE, Hcy, eGSH-Px, and also can be predicted by ACE2, Ang(1-7), Hcy in CT subgroup.The ACE2/Ang(1-7)/Mas axis is associated with OS, and both them were associated with eGFR in the progression of CKD. Activation of ACE2/Ang(1-7)/Mas axis may have renoprotective effect and can be a potential therapeutic target in patients with early CKD stages.

The Yin and Yang of ACE/ACE2 Pathways: The Rationale for the Use of Renin-Angiotensin System Inhibitors in COVID-19 Patients

The article describes the rationale for inhibition of the renin-angiotensin system (RAS) pathways as specific targets in patients infected by SARS-CoV-2 in order to prevent positive feedback-loop mechanisms. Based purely on experimental studies in which RAS pathway inhibitors were administered in vivo to humans/rodents, a reasonable hypothesis of using inhibitors that block both ACE and ACE2 zinc metalloproteases and their downstream pathways in COVID-19 patients will be proposed. In particular, metal (zinc) chelators and renin inhibitors may work alone or in combination to inhibit the positive feedback loops (initially triggered by SARS-CoV-2 and subsequently sustained by hypoxia independently on viral trigger) as both arms of renin-angiotensin system are upregulated, leading to critical, advanced and untreatable stages of the disease.