Angiotensin-converting Enzyme Protein Expression Research Articles

Myocardial Angiotensin-Converting Enzyme 2 Protein Expression in Ischemic Heart Failure.

The angiotensin-converting enzyme 2 (ACE2)-angiotensin-(1-7)-Mas receptor axis plays a significant role in regulating myocardial remodeling and the development of heart failure (HF), with ACE2 being the primary focus. However, contemporary understanding of the membrane-bound form of the human ACE2 protein remains insufficient. The purpose of this study was to determine the expression of ACE2 protein in different cells of the left ventricular myocardium in non-diseased hearts and at various stages of ischemic HF. A total of 103 myocardial tissue samples from the left ventricle underwent quantitative and semi-quantitative immunohistochemical analysis. Upon assessing ACE2 immunostaining in all myocardial cells through unselective digital image analysis, there was no change in the stage A HF group. Nevertheless, the expression of ACE2 membrane protein in cardiomyocytes showed a tendency to increase, while non-cardiomyocyte ACE2 expression decreased significantly (p < 0.001). In the stage B HF group, the intensity of ACE2 immunostaining continued to increase with rising cardiomyocyte ACE2 expression (p < 0.001). Non-cardiomyocyte expression, in contrast, remained similar to that observed in the stage A HF group. In the stages C/D HF group, ACE2 expression reached its highest level in cardiomyocytes (p < 0.001), while ACE2 expression in non-cardiomyocytes was the lowest (p < 0.001). These changes in ACE2 protein levels are associated with left ventricular remodeling in ischemic HF.

SARS‐CoV‐2 virus associated angiotensin converting enzyme 2 expression modulation in colorectal cancer: Insights from mRNA and protein analysis COVID-19 associated (ACE2) expression in colorectal cancer

The SARS‐CoV‐2 virus gains entry into human cells by exploiting the angiotensin‐converting enzyme 2 (ACE2), a key component known as the spike protein (S), as a point of entry. Initially, SARS‐CoV‐2 suppresses the natural function of ACE2, leading to a gradual decline in cell health. Additionally, individuals with cancer are considered more susceptible to COVID-19. This study investigates the expression patterns of ACE2 in colorectal cancer (CRC) patients with and without a history of COVID-19 infection. RT-PCR was used to analyze samples from both cancerous and adjacent non-affected colorectal tissues of 47 CRC patients, comprising two groups: 24 CRC patients with no history of COVID-19 and 23 CRC patients with a recent history of COVID-19 infection. Epithelial CR cells were isolated from both types of tissues and cultured to evaluate cell adhesion. Immunohistochemistry analyses were conducted to examine ACE2 protein expression using various ACE2 antibodies for both cell types. The study revealed ACE2 mRNA expression in all CRC tissues of patients with and without a history of COVID-19. ACE2 expression was significantly higher in CRC patients without a history of COVID-19. Notably, the non-affected colorectal cancer (NACRC) tissues of patients without a history of COVID-19 also showed ACE2 expression, whereas no ACE2 expression was detected in the biopsies of CRC patients with a positive COVID-19 history. ACE2 antibodies were employed to validate ACE2 protein expression at the mRNA level. COVID-19 appears to downregulate ACE2 expression in both CRC and NACRC tissues of CRC patients with a positive history of COVID-19 infection.

Anisomeles indica Extracts and Their Constituents Suppress the Protein Expression of ACE2 and TMPRSS2 In Vivo and In Vitro.

Coronavirus disease 2019 (COVID-19), stemming from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has had a profound global impact. This highly contagious pneumonia remains a significant ongoing threat. Uncertainties persist about the virus's effects on human health, underscoring the need for treatments and prevention. Current research highlights angiotensin-converting enzyme 2 (ACE2) and transmembrane protease serine 2 (TMPRSS2) as key targets against SARS-CoV-2. The virus relies on ACE2 to enter cells and TMPRSS2 to activate its spike protein. Inhibiting ACE2 and TMPRSS2 expression can help prevent and treat SARS-CoV-2 infections. Anisomeles indica (L.) Kuntze, a medicinal plant in traditional Chinese medicine, shows various promising pharmacological properties. In this study, ethanolic extracts of A. indica were examined both in vivo (250 and 500 μM) and in vitro (500 μM). Through Western blotting analysis, a significant reduction in the expression levels of ACE2 and TMPRSS2 proteins was observed in HepG2 (human hepatocellular carcinoma) cells and HEK 293T (human embryonic kidney) cell lines without inducing cellular damage. The principal constituents of A. indica, namely, ovatodiolide (5 and 10 μM), anisomlic acid (5 and 10 μM), and apigenin (12.5 and 25 μM), were also found to produce the same effect. Furthermore, immunohistochemical analysis of mouse liver, kidney, and lung tissues demonstrated a decrease in ACE2 and TMPRSS2 protein expression levels. Consequently, this article suggests that A. indica and its constituents have the potential to reduce ACE2 and TMPRSS2 protein expression levels, thus aiding in the prevention of SARS-CoV-2 infections.

Pioglitazone Alters Ace/Ace 2 Balance to Favour Ace2 Independently Of Glycaemia Levels in Diabetic Rat Heart.

The activation of the renin-angiotensin system (RAS) contributes to the pathogenesis of cardiac damage during diabetes. In the present study, we investigated the role of pioglitazone, dapagliflozin and their combination on RAS components in streptozotocin-induced diabetic cardiomyopathy in Wistar rats. Blood glucose, serum lipids, and ACE (angiotensin-converting enzyme), ACE2 levels were determined. mRNA levels of Myh6 (myosins heavy chain), Myh7, Ace, Ace2, Nppa, Nppb (natriuretic peptide A, B) and Ppars (peroxisome proliferator activating receptors) genes in the heart were determined by real-time PCR (polymerase chain reaction). Protein expression of ACE and ACE2 was assessed by western blotting. After six weeks pioglitazone suppressed Ace mRNA and protein levels (p<0.05) and modified the Ace/Ace2 ratio (p<0.05) in the cardiac tissue of diabetic rats. Pioglitazone significantly decreased serum lipids (p<0.05) but did not significantly influence blood glucose and ACE serum levels of diabetic animals. Dapagliflozin had a significant glucose-lowering action (p<0.05) however, it had no impact on the Ace/Ace2 ratio. The combination of both compounds markedly improved blood glucose (p<0.05) as well as the Myh6/Myh7 ratio (p<0.05) but had no further impact on the Ace to Ace2 balance in cardiac tissue compared to pioglitazone monotherapy. We found that pioglitazone improves the cardiac Ace/ Ace2 ratio in diabetic rats suggesting a potential cardioprotective effect. This effect is independent of its antidiabetic and metabolic effects.

Identification and Screening of Potential ACE2 Activating Peptides from Soybean Protein Isolate Hydrolysate against Ang II-Induced Endothelial Dysfunction.

Angiotensin-converting enzyme 2 (ACE2) is a counterregulator against ACE by converting angiotensin II (Ang II) to Ang-(1-7), and its down-regulation leads to endothelial dysfunction in the vascular system. In the present study, we investigated the effects of soybean protein isolate hydrolysate (SPIH) on Ang II-induced endothelial dysfunction with its underlying mechanisms via ACE2 activation in human umbilical vein endothelial cells (HUVECs). We further screened potential ACE2 activating peptides by peptidomics analysis combined with bioinformatics tools. Results showed that SPIH remarkably attenuated Ang II-induced cell migration from 129 to 92%, decreased the ROS level from 2.22-fold to 1.45-fold, and increased NO concentration from 31.4 ± 0.7 to 43.7 ± 0.1 μM in HUVECs. However, these beneficial effects were reversed by ACE2 inhibitor MLN-4760 to a certain extent, indicating the modulation of ACE2. Further results revealed that SPIH (1 mg/mL) significantly increased the expression and activity of ACE2 and two novel ACE2 activating peptides with different mechanisms were explored from SPIH. IVPQ and IAVPT (50 μM) enhanced ACE2 activity, and only IVPQ (50 μM) increased ACE2 protein expression in HUVECs. These findings furthered our understanding of the antihypertensive mechanism of SPIH mediating the ACE2 activation on vascular endothelium.

ApoE4 associated with severe COVID-19 outcomes via downregulation of ACE2 and imbalanced RAS pathway

BackgroundRecent numerous epidemiology and clinical association studies reported that ApoE polymorphism might be associated with the risk and severity of coronavirus disease 2019 (COVID-19), and yielded inconsistent results. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection relies on its spike protein binding to angiotensin-converting enzyme 2 (ACE2) receptor expressed on host cell membranes.MethodsA meta-analysis was conducted to clarify the association between ApoE polymorphism and the risk and severity of COVID-19. Multiple protein interaction assays were utilized to investigate the potential molecular link between ApoE and the SARS-CoV-2 primary receptor ACE2, ApoE and spike protein. Immunoblotting and immunofluorescence staining methods were used to access the regulatory effect of different ApoE isoform on ACE2 protein expression.ResultsApoE gene polymorphism (ε4 carrier genotypes VS non-ε4 carrier genotypes) is associated with the increased risk (P = 0.0003, OR = 1.44, 95% CI 1.18–1.76) and progression (P < 0.00001, OR = 1.85, 95% CI 1.50–2.28) of COVID-19. ApoE interacts with both ACE2 and the spike protein but did not show isoform-dependent binding effects. ApoE4 significantly downregulates ACE2 protein expression in vitro and in vivo and subsequently decreases the conversion of Ang II to Ang 1–7.ConclusionsApoE4 increases SARS-CoV-2 infectivity in a manner that may not depend on differential interactions with the spike protein or ACE2. Instead, ApoE4 downregulates ACE2 protein expression and subsequently the dysregulation of renin–angiotensin system (RAS) may provide explanation by which ApoE4 exacerbates COVID-19 disease.

ACE2-Inhibitory Effects of Bromelain and Ficin in Colon Cancer Cells.

Background and Objectives: Bromelain and ficin are aqueous extracts from fruits of Ananas comosus and Ficus carcia plants, used widely for medical applications. Angiotensin-converting enzyme 2 (ACE2) is a homolog of ACE, degrading Ang II to angiotensin 1-7 and decreasing the cellular concentration of Ang II. Materials and Methods: In this study, we investigated the ACE2-inhibitory, antiproliferative, and apoptosis-inducing effects of ficin and bromelain on caco-2 cells. Results: We found that bromelain and ficin significantly reduced the viability of human colon cancer cells with IC50 value concentrations of 8.8 and 4.2 mg/mL for bromelain after 24 and 48 h treatments, and 8.8 and 4.2 mg/mL for ficin after 24 and 48 h treatments, respectively. The apoptosis of the caco-2 cell line treated with bromelain was 81.04% and 56.70%, observed after 24 and 48 h. Total apoptotic proportions in caco-2 cells treated with ficin after 24 and 48 h were 83.7% and 73.0%. An amount of 1.6 mg/mL of bromelain and ficin treatments on caco-2 cells after 24 h revealed a higher decrease than that of other concentrations in the expression of ACE2 protein. Conclusions: In conclusion, bromelain and ficin can dose-dependently decrease the expression of ACE2 protein in caco-2 cells.

State-of-the-art analytical methods of viral infections in human lung organoids.

Human-based organ models can provide strong predictive value to investigate the tropism, virulence, and replication kinetics of viral pathogens. Currently, such models have received widespread attention in the study of SARS-CoV-2 causing the COVID-19 pandemic. Applicable to a large set of organoid models and viruses, we provide a step-by-step work instruction for the infection of human alveolar-like organoids with SARS-CoV-2 in this protocol collection. We also prepared a detailed description on state-of-the-art methodologies to assess the infection impact and the analysis of relevant host factors in organoids. This protocol collection consists of five different sets of protocols. Set 1 describes the protein extraction from human alveolar-like organoids and the determination of protein expression of angiotensin-converting enzyme 2 (ACE2), transmembrane serine protease 2 (TMPRSS2) and FURIN as exemplary host factors of SARS-CoV-2. Set 2 provides detailed guidance on the extraction of RNA from human alveolar-like organoids and the subsequent qPCR to quantify the expression level of ACE2, TMPRSS2, and FURIN as host factors of SARS-CoV-2 on the mRNA level. Protocol set 3 contains an in-depth explanation on how to infect human alveolar-like organoids with SARS-CoV-2 and how to quantify the viral replication by plaque assay and viral E gene-based RT-qPCR. Set 4 provides a step-by-step protocol for the isolation of single cells from infected human alveolar-like organoids for further processing in single-cell RNA sequencing or flow cytometry. Set 5 presents a detailed protocol on how to perform the fixation of human alveolar-like organoids and guides through all steps of immunohistochemistry and in situ hybridization to visualize SARS-CoV-2 and its host factors. The infection and all subsequent analytical methods have been successfully validated by biological replications with human alveolar-like organoids based on material from different donors.

Thyroidal Angiotensin-Converting Enzyme 2 Protein Expression and Thyroid Function Tests in Patients with COVID-19: Results from a Retrospective Case Series and a Prospective Cohort Study.

Background: Infection with SARS-CoV-2 has initially been known as a respiratory disease but in the course of the pandemic the understanding has emerged that severity is owing to fatal inflammatory responses apart from lung injury. In this context, endocrine disorders such as thyroiditis as well as pituitary dysfunction in addition to nonthyroidal illness syndrome have been described. Furthermore, angiotensin-converting enzyme 2 (ACE2), the SARS-CoV-2 cell receptor, has been detected in most endocrine tissues, including the thyroid gland. Objective: To evaluate histopathologic changes and compare thyroidal ACE2 protein expression in thyroid tissue from patients who died from severe COVID-19 with thyroid tissue from patients without SARS-CoV-2 infection in a retrospective case series. Furthermore, to assess and compare alterations in thyroid function tests (TFTs) between patients with or without SARS-CoV-2 infection as well as association of TFTs with the severity of the disease in a prospective cohort study. Methods: Thyroid tissue of deceased COVID-19 patients (n = 23) was analyzed for histopathology and ACE2 expression by immunohistochemical staining. A total of 153 patients with confirmed SARS-CoV-2 were evaluated regarding TFTs and divided into a severe (intubation, intensive care treatment) and an intermediate group. Results: Thyroidal ACE2 expression was detected in 87% of the deceased COVID-19 patients. Normal thyroid tissue from patients without SARS-CoV-2 infection showed no ACE2 protein expression. Half of the severely ill COVID-19 patients had low free triiodothyronine (fT3) levels. Combination of low fT3 and thyrotropin (TSH) was associated significantly with deadly disease. Conclusion: The high percentage of positive ACE2 immunostaining in deceased patients compared with normal thyroid tissue of patients without SARS-CoV-2 infection suggests involvement of the thyroid in COVID-19, although further research will have to show the pathogenic role of thyroidal ACE2 in COVID-19. Abnormal fT3 and a TSH of ≤0.5 mU/L were associated with a fatal outcome in our severely ill SARS-CoV-2 patient cohort. Therefore, assessment of TFTs is crucial in the treatment of severely ill COVID-19 patients. Trial Registration: COVID-19 Registry of the LMU University Hospital Munich (CORKUM), WHO trial ID DRKS00021225.

Elevated angiotensin-converting enzyme 2 (ACE2) expression in cats with hypertrophic cardiomyopathy

Angiotensin-converting enzyme 2 (ACE2) is an enzyme within the renin-angiotensin-aldosterone system that plays a role in regulating blood pressure. However, it is also a cellular receptor for infection with SARS coronaviruses. Although most cats develop subclinical or mild disease following infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) acquired from human patients, a previous study has suggested hypertrophic cardiomyopathy (HCM) is a potential risk factor for the development of severe disease in the cat. Herein we investigate the ACE2 protein expression in the lung, heart, and kidney from a small subset of cats with (n = 10) and without HCM (n = 10) by immunohistochemistry. The abundance and intensity of ACE2 expression is slightly elevated in alveoli (p = 0.09; 0.07, respectively) and bronchioles (p = 0.095; 0.37, respectively). However, statistically elevated abundance and intensity of ACE-2 expression was only evident in the heart of cats with HCM (p = 0.032; p = 0.011, respectively). Further investigation did not demonstrate a statistical correlation between the ACE2 expression in the heart in relation to the heart weight to body weight ratio, and the ventricular wall ratio. Current findings suggest an overexpression of ACE2 in HCM cases but follow up study is warranted to understand the pathophysiological process.

Robust therapeutic effects on COVID-19 of novel small molecules: Alleviation of SARS-CoV-2 S protein induction of ACE2/TMPRSS2, NOX2/ROS, and MCP-1.

While new variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) constantly emerge to prolong the pandemic of COVID-19, robust and safe therapeutics are in urgent need. During the previous and ongoing fight against the pandemic in China, Traditional Chinese Medicine (TCM) has proven to be markedly effective in treating COVID-19. Among active ingredients of TCM recipes, small molecules such as quercetin, glabridin, gallic acid, and chrysoeriol have been predicted to target viral receptor angiotensin-converting enzyme 2 (ACE2) via system pharmacology/molecular docking/visualization analyses. Of note, endothelial dysfunction induced by oxidative stress and inflammation represents a critical mediator of acute respiratory distress syndrome (ARDS) and multi-organ injuries in patients with COVID-19. Hence, in the present study, we examined whether quercetin, glabridin, gallic acide and chrysoeriol regulate viral receptors of ACE2 and transmembrane serine protease 2 (TMPRSS2), redox modulator NADPH oxidase isoform 2 (NOX2), and inflammatory protein of monocyte chemoattractant protein-1 (MCP-1) in endothelial cells to mediate therapeutic protection against COVID-19. Indeed, quercetin, glabridin, gallic acide and chrysoeriol completely attenuated SARS-CoV-2 spike protein (S protein)-induced upregulation in ACE2 protein expression in endothelial cells. In addition, these small molecules abolished S protein upregulation of cleaved/active form of TMPRSS2, while native TMPRSS2 was not significantly regulated. Moreover, these small molecules completely abrogated S protein-induced upregulation in NOX2 protein expression, which resulted in alleviated superoxide production, confirming their preventive efficacies against S protein-induced oxidative stress in endothelial cells. In addition, treatment with these small molecules abolished S protein induction of MCP-1 expression. Collectively, our findings for the first time demonstrate that these novel small molecules may be used as novel and robust therapeutic options for the treatment of patients with COVID-19, via effective attenuation of S protein induction of endothelial oxidative stress and inflammation.

Association analysis and expression level of ACE polymorphisms with egg-laying trait in Taihang chicken

The number of egg-laying is an important indicator of reproduction performance in poultry breeding. To investigate the relationship between the function of Angiotensin-converting enzyme (ACE) and egg-laying performance of Taihang chicken, the mRNA and protein expression and single nucleotide polymorphism (SNP) of ACE were detected. Analysis of ACE bioinformatics and association analysis of polymorphisms were then performed. The polymorphisms analysis of ACE showed that three SNP loci (g.5066812A>C, g.5080076G>A, and g.5072728A>G) were detected in 800 Taihang chickens with egg-laying records. Association analysis of egg-laying found that ACE g.5066812A>C mutation was significantly associated with the egg-laying performance of Taihang chickens (P < 0.05), and the individuals with the g.5066812A>C mutation showed significantly increasing egg-laying. The mRNA expression was significantly higher in individuals with the AA genotype mutation than those with the AC and CC genotypes (P < 0.01), and the expression of ACE protein levels was consistent with the mRNA expression. Bioinformatics analysis indicated that these mutations affected the secondary and tertiary structure of ACE. This study provides new insights into ACE affecting chicken egg production and some basis for improving the egg production rate of Taihang chickens.

Soluble urinary somatic angiotensin converting enzyme is overexpressed in patients with preeclampsia: a potential new marker for the disease?

ABSTRACT Objective The aim of this study was to identify and quantify urinary Angiotensin-Converting-Enzyme (ACE) in hypertensive disorders of pregnancy. Methods Urine samples were analyzed by Western blot. Patients were classified into: normotensive pregnancy (N); preeclampsia and superimposed preeclampsia (PE+SPE); and gestational hypertension (GH). Results Somatic ACE protein expression was higher in PE+SPE compared to N and GH. There was a positive correlation between ACE and urinary protein to creatinine ratio, systolic and diastolic blood pressures. Conclusion These results indicate ACE overexpression in the urine of preeclamptic patients and suggest that it may be a new marker for the disease.

Cardiomyocyte-specific knockout of ADAM17 ameliorates left ventricular remodeling and function in diabetic cardiomyopathy of mice

Angiotensin-converting enzyme 2 (ACE2) has proven beneficial in attenuating diabetic cardiomyopathy (DCM) but has been found to be a substrate of a disintegrin and metalloprotease protein-17 (ADAM17). However, whether ADAM17 plays a role in the pathogenesis and intervention of DCM is obscure. In this study, we created cardiomyocyte-specific knockout of ADAM17 (A17α-MHCKO) mice, and left ventricular dimension, function, pathology and molecular biology were assessed in ADAM17fl/fl control, A17α-MHCKO control, ADAM17fl/fl diabetic and A17α-MHCKO diabetic mice. Both differentiated H9c2 cells and neonatal rat cardiomyocytes (NRCMs) were used to explore the molecular mechanisms underlying the effect of ADAM17 on DCM. The results showed that protein expression and activity of ADAM17 were upregulated whereas the protein expression of ACE2 was downregulated in the myocardium of diabetic mice. Cardiomyocyte-specific knockout of ADAM17 mitigated cardiac fibrosis and cardiomyocyte apoptosis and ameliorated cardiac dysfunction in mice with DCM. Bioinformatic analyses detected a number of genes enriched in metabolic pathways, in particular the AMPK signaling pathway, expressed differentially between the hearts of A17α-MHCKO and ADAM17fl/fl diabetic mice. The mechanism may involve activated AMPK pathway, increased autophagosome formation and improved autophagic flux, which reduced the apoptotic response in cardiomyocytes. In addition, hypoxia-inducible factor-1α (HIF-1α) might act as an upstream mediator of upregulated ADAM17 and ADAM17 might affect AMPK signaling via α1 A-adrenergic receptor (ADRA1A). These results indicated that ADAM17 activity and ACE2 shedding were enhanced in DCM, which was reversed by cardiomyocyte-specific ADAM17 knockout. Thus, inhibition of ADAM17 may provide a promising approach to the treatment of DCM.

Unveiling the Angiotensin-(1-7) Actions on the Urinary Bladder in Female Rats.

Angiotensin-(1–7) is a peptide produced by different pathways, and regardless of the route, the angiotensin-converting enzyme 2 (ACE-2) is involved in one of the steps of its synthesis. Angiotensin-(1–7) binds to Mas receptors localized in different cells throughout the body. Whether angiotensin-(1–7) exerts any action in the urinary bladder (UB) is still unknown. We investigated the effects of intravenous and topical (in situ) administration of angiotensin-(1–7) on intravesical pressure (IP) and cardiovascular variables. In addition, the Mas receptors and ACE-2 gene and protein expression were analyzed in the UB. Adult female Wistar rats were anesthetized with 2% isoflurane in 100% O2 and submitted to the catheterization of the femoral artery and vein for mean arterial pressure (MAP) and heart rate (HR) recordings, and infusion of drugs, respectively. The renal blood flow was acquired using a Doppler flow probe placed around the left renal artery and the renal conductance (RC) was calculated as a ratio of Doppler shift (kHz) and MAP. The cannulation of the UB was performed for IP recording. We observed that angiotensin-(1–7) either administered intravenously [115.8 ± 28.6% angiotensin-(1–7) vs. −2.9 ± 1.3% saline] or topically [147.4 ± 18.9% angiotensin-(1–7) vs. 3.2 ± 2.8% saline] onto the UB evoked a significant (p < 0.05) increase in IP compared to saline and yielded no changes in MAP, HR, and RC. The marked response of angiotensin-(1–7) on the UB was also investigated using quantitative real-time polymerase chain reaction and western blotting assay, which demonstrated the mRNA and protein expression of Mas receptors in the bladder, respectively. ACE-2 mRNA and protein expression was also observed in the bladder. Therefore, the findings demonstrate that angiotensin-(1–7) acts in the UB to increase the IP and suggest that this peptide can be also locally synthesized in the UB.

Amino acid sensor GCN2 promotes SARS-CoV-2 receptor ACE2 expression in response to amino acid deprivation

Angiotensin-converting enzyme 2 (ACE2) has been identified as a primary receptor for severe acute respiratory syndrome coronaviruses 2 (SARS-CoV-2). Here, we investigated the expression regulation of ACE2 in enterocytes under amino acid deprivation conditions. In this study, we found that ACE2 expression was upregulated upon all or single essential amino acid deprivation in human colonic epithelial CCD841 cells. Furthermore, we found that knockdown of general control nonderepressible 2 (GCN2) reduced intestinal ACE2 mRNA and protein levels in vitro and in vivo. Consistently, we revealed two GCN2 inhibitors, GCN2iB and GCN2-IN-1, downregulated ACE2 protein expression in CCD841 cells. Moreover, we found that increased ACE2 expression in response to leucine deprivation was GCN2 dependent. Through RNA-sequencing analysis, we identified two transcription factors, MAFB and MAFF, positively regulated ACE2 expression under leucine deprivation in CCD841 cells. These findings demonstrate that amino acid deficiency increases ACE2 expression and thereby likely aggravates intestinal SARS-CoV-2 infection.

Mitochondrial dysfunction is associated with lipid metabolism disorder and upregulation of angiotensin-converting enzyme 2.

Thymidine kinase 2 (TK2) deficiency in humans leads to a myopathic form of mitochondrial DNA (mtDNA) deficiency. Here we present a skeletal and cardiac muscle specific TK2 knockout mouse (mTk2 KO). The mice showed dilated hearts and markedly reduced adipose tissue during week 12 to 16. A severe decrease of mtDNA was found only in skeletal muscle and heart tissue in mTk2 KO mice. Expression analysis of key metabolic genes of 16 weeks knockout mice showed significant changes of genes involved in lipid metabolism, with different patterns in heart and skeletal muscle. Our study further suggests that lipoprotein lipase (LPL) from liver supports the metabolism when heart and skeletal muscle were impaired due to mitochondrial dysfunction. The angiotensin-converting enzyme 2 (ACE2), which is involved in glucose homeostasis, was also affected by mtDNA deficiency in our study. Interestingly, both the gene and protein expression of ACE2 were increased in cardiac tissue of mTk2 KO mice. Since ACE2 is a receptor for the SARS-CoV-2 virus, its regulation in relation to mitochondrial function may have important clinical implications.

Effect of age on human ACE2 and ACE2-expressing alveolar type II cells levels.

BackgroundAngiotensin-converting enzyme 2 (ACE2) is the receptor for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) which causes COVID-19. Viral entry requires ACE2 and transmembrane protease serine 2 (TMPRSS2). Transcriptomic studies showed that children display lower ACE2 than adults, though gene expression levels do not always correlate with protein levels. We investigated the effect of age on ACE2 and TMPRSS2 protein expression in alveolar type II (AT2) cells in the lungs of children compared to adults. We also analysed the ratio of Ang-(1–7) to Ang II as a surrogate marker of ACE2 activity in the subjects’ lung parenchyma.MethodsAng II and Ang-(1–7) levels and ACE2 and TMPRSS2 protein expression were measured by radioimmunoassay and immunohistochemistry, respectively.ResultsThe amount of ACE2-expressing AT2 cells and ACE2 protein content were lower in children than in adults. Ang II levels were higher in children compared to adults and inversely correlated with the amount of ACE2-expressing AT2 cells. Children presented lower Ang-(1–7)/Ang II ratio than adult suggesting lower ACE2 activity in children. TMPRSS2 protein expression was not influenced by age.ConclusionsThese results expand on previous transcriptomic studies and may partially explain the low susceptibility of children to SARS-CoV-2 infection.Category of studyClinical original researchImpact Children display lower ACE2 protein content and activity compared to adults.Ang II levels were higher in children compared to adults and inversely correlated with the amount of ACE2-expressing AT2 cellsTMPRSS2 protein expression was not influenced by age.These results expand on previous transcriptomic studies and may partially explain the low susceptibility of children to SARS-CoV-2 infection.

Angiotensin‐(1‐7) Restores Gut Barrier Integrity and Ameliorates Systemic Inflammation in Aging

BackgroundAdvancing of age decreases the barrier properties of intestinal epithelium which leads to sterile systemic inflammation. Chronic low‐grade chronic inflammation is an underlying cause for the age‐related comorbidities such as cardiovascular disorders. Renin Angiotensin System (RAS) plays an important role in the homeostasis of cardiovascular functions however, the role of RAS in the aging gut is poorly studied. The protective axis of RAS, which constitutes Angiotensin converting enzyme‐2 (ACE2)/ Angiotensin‐(1‐7) (Ang‐(1‐7))/Mas receptor (MasR) is known to be counter‐regulatory to the classical axis, ACE/Ang II/AT1 receptor (AT1R). This study tested the hypothesis that leaky gut with aging is associated with ACE2/ACE imbalance and that activation of MasR with Ang‐(1‐7) would restore gut barrier integrity and ameliorates systemic inflammation.MethodsStudy was carried out in Young (3‐4 months) and Old (20‐24 months) male mice. ACE and ACE2 enzyme activities were evaluated in the colon. Gene and protein expressions of RAS components were determined by western blotting. Ang‐(1‐7) was administered by subcutaneous osmotic pump (1 µg/Kg/min) for four weeks and the gut permeability was evaluated by using FITC‐dextran. Colon wall integrity was evaluated by immunohistochemistry of claudin 1 and occludin. Zonulin‐1, IL‐6, and TNFα were analyzed in the plasma. A779, MasR antagonist, was administered by an osmotic pump in selected experiments (1 µg/Kg/min, subcutaneous).ResultsACE2 protein and activity were decreased in Old group while that of ACE were increased (n=6) (n=8) in the colon of the Old mice compared to the Young. Protein expression of both AT1R and MasR was higher while that of AT2R was lower in the Old (P&lt;0.05, n=8). Protein expression of ACE2, ACE AT1R and MasR in the Old colons were restored to Young levels by treatment with Ang‐(1‐7). Gut permeability was higher in Old mice (P&lt;0.01 vs Young, n=6) that was reversed by Ang‐(1‐7). The beneficial effect of Ang‐(1‐7) was abolished by concurrent administration of A779. Hematoxylin &amp; Eosin staining revealed that aging was associated with atrophied villi in the gut wall that was normalized by Ang‐(1‐7). Gene expression of claudin 1 and occludin were lower in the Old colon wall that were restored by Ang‐(1‐7) and similar observations were made by immunohistochemistry. Importantly, plasma levels of Zonulin‐1, (P&lt;0.01) IL‐6 and TNFα (P&lt;0.05) (n=8) were higher in the Old group compared to the Young, which were lowered by Ang‐(1‐7) (n=5).ConclusionThese results suggest that activation of MasR ameliorates aging‐associated systemic inflammation by restoring gut barrier integrity, which at least in part contributes to the cardiovascular‐protective functions.

The activation status of integrin β1 determines the ACE‐2 expression and functions in renal epithelial and cancer cells

BackgroundIntegrins are heterodimeric cell surface receptors that participate in intracellular signaling and regulate multiple cellular functions. These membrane receptors are also crucial for the organ development, structural maintenance, and disease pathologies of the kidney. Integrin β1 is the major integrin subunit present in the kidney. Alteration of integrin β1 expression is a characteristic of many kidney diseases such as kidney cancer and chronic kidney disease. The purpose of this study is to find the importance of integrin β1 in the expression and function of angiotensin‐converting enzyme 2 (ACE‐2) in the kidney. We hypothesized that the expression and function of ACE‐2 depend on the activation status of integrin β1 in the renal epithelial and cancer cells.MethodKidney epithelial‐specific integrin β1 KO mice were generated by crossing between ITGBfl/fland γGT‐Cre mice. PCR‐based analysis of genomic DNA was used to confirm the gene deletion. Expression of integrin β1 in the kidney cortex was monitored by qRT‐PCR. Immunoblotting and qRT‐PCR were performed to observe protein expression and mRNA level of ACE‐2 in mouse kidneys. The pharmacological compound, BTT 3033, was used to inhibit integrin β1 in HK‐2 and Caki‐1 cells. Integrin β1 activation status was monitored by immunocytochemistry using a conformation‐specific antibody. SARS‐CoV‐2 spike protein was used to find out the functional importance of the integrin β1‐ACE‐2 complex. Statistical significance of the observed data was carried out using a two‐tail t‐test.ResultsDeletion of integrin β1 from the renal epithelial cells reduced expression of ACE‐2 in the mice kidneys (n=3; p<0.05). Immunoblotting and qRT‐PCR showed, expression of integrin β1 (n=3; p<0.05) and ACE‐2 (n=3; p<0.05) were higher in renal cancer cells than renal epithelial cells indicating a positive correlation in their expression patterns. With the treatment of BTT 3033, there was a significant decrease in the activation status of integrin β1 in kidney epithelial (HK‐) and cancer (Caki‐1) cells (n=30; p<0.05). ACE‐2 mRNA levels decreased in HK‐2 and Caki‐1 cells when treated with an integrin β1 antagonist, BTT 3033 (n=3; p<0.05). Treatment of HK‐2 and Caki‐1 with BTT 3033 also decreased the internalization of the SARS‐CoV‐2 spike protein.ConclusionResults from this study demonstrate the importance of matrix proteins receptor integrin β1 in maintaining the ACE‐2 expression and function in the kidney. This study will have implications in various chronic diseases where significant changes in the composition of matrix proteins and integrin expressions are observed. Further studies are needed to understand the role of altered matrix composition in ACE‐2 mediated physiological functions.