COVID-19 in the heart and the lungs: could we "Notch" the inflammatory storm?

From January 2020, coronavirus disease (COVID-19) originated in China has spread around the world. The disease is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The presence of myocarditis, cardiac arrest, and acute heart failure in COVID-19 patients suggests the existence of a relationship between SARS-CoV-2 infection and cardiac disease. The Notch signalling is a major regulator of cardiovascular function and it is also implicated in several biological processes mediating viral infections. In this report we discuss the possibility to target Notch signalling to prevent SARS-CoV-2 infection and interfere with the progression of COVID-19- associated heart and lungs disease.

Angiotensin-converting enzyme 2 regulates endoplasmic reticulum stress and mitochondrial function to preserve skeletal muscle lipid metabolism.

OBJECTIVE: Endoplasmic reticulum (ER) stress and mitochondrial function affected intramuscular fat accumulation. However, there is no clear evident on the effect of the regulation of ER stress and mitochondrial function by Angiotensin-converting enzyme 2 (ACE2) on the prevention of intramuscular fat metabolism. We investigated the effects of ACE2 on ER stress and mitochondrial function in skeletal muscle lipid metabolism. METHODS: The triglyceride (TG) content in skeletal muscle of ACE2 knockout mice and Ad-ACE2-treated db/db mice were detected by assay kits. Meanwhile, the expression of lipogenic genes (ACCα, SREBP-1c, LXRα, CPT-1α, PGC-1α and PPARα), ER stress and mitochondrial function related genes (GRP78, eIF2α, ATF4, BCL-2, and SDH6) were analyzed by RT-PCR. Lipid metabolism, ER stress and mitochondrial function related genes were analyzed by RT-PCR in ACE2-overexpression C2C12 cell. Moreover, the IKKß/NFκB/IRS-1 pathway was determined using lysate sample from skeletal muscle of ACE2 knockout mice. RESULTS: ACE2 deficiency in vivo is associated with increased lipid accumulation in skeletal muscle. The ACE2 knockout mice displayed an elevated level of ER stress and mitochondrial dysfunctions in skeletal muscle. In contrast, activation of ACE2 can ameliorate ER stress and mitochondrial function, which slightly accompanied by reduced TG content and down-regulated the expression of skeletal muscle lipogenic proteins in the db/db mice. Additionally, ACE2 improved skeletal muscle lipid metabolism and ER stress genes in the C2C12 cells. Mechanistically, endogenous ACE2 improved lipid metabolism through the IKKß/NFκB/IRS-1 pathway in skeletal muscle. CONCLUSIONS: ACE2 was first reported to play a notable role on intramuscular fat regulation by improving endoplasmic reticulum and mitochondrial function. This study may provide a strategy for treating insulin resistance in skeletal muscle.

Bone Marrow-Derived Cells Restore Functional Integrity of the Gut Epithelial and Vascular Barriers in a Model of Diabetes and ACE2 Deficiency.

RATIONALE: There is incomplete knowledge of the impact of bone marrow cells on the gut microbiome and gut barrier function. OBJECTIVE: We postulated that diabetes mellitus and systemic ACE2 (angiotensin-converting enzyme 2) deficiency would synergize to adversely impact both the microbiome and gut barrier function. METHODS AND RESULTS: Bacterial 16S rRNA sequencing and metatranscriptomic analysis were performed on fecal samples from wild-type, ACE2-/y, Akita (type 1 diabetes mellitus), and ACE2-/y-Akita mice. Gut barrier integrity was assessed by immunofluorescence, and bone marrow cell extravasation into the small intestine was evaluated by flow cytometry. In the ACE2-/y-Akita or Akita mice, the disrupted barrier was associated with reduced levels of myeloid angiogenic cells, but no increase in inflammatory monocytes was observed within the gut parenchyma. Genomic and metatranscriptomic analysis of the microbiome of ACE2-/y-Akita mice demonstrated a marked increase in peptidoglycan-producing bacteria. When compared with control cohorts treated with saline, intraperitoneal administration of myeloid angiogenic cells significantly decreased the microbiome gene expression associated with peptidoglycan biosynthesis and restored epithelial and endothelial gut barrier integrity. Also indicative of diabetic gut barrier dysfunction, increased levels of peptidoglycan and FABP-2 (intestinal fatty acid-binding protein 2) were observed in plasma of human subjects with type 1 diabetes mellitus (n=21) and type 2 diabetes mellitus (n=23) compared with nondiabetic controls (n=23). Using human retinal endothelial cells, we determined that peptidoglycan activates a noncanonical TLR-2 (Toll-like receptor 2) associated MyD88 (myeloid differentiation primary response protein 88)-ARNO (ADP-ribosylation factor nucleotide-binding site opener)-ARF6 (ADP-ribosylation factor 6) signaling cascade, resulting in destabilization of p120-catenin and internalization of VE-cadherin as a mechanism of deleterious impact of peptidoglycan on the endothelium. CONCLUSIONS: We demonstrate for the first time that the defect in gut barrier function and dysbiosis in ACE2-/y-Akita mice can be favorably impacted by exogenous administration of myeloid angiogenic cells.

Angiotensin 1-7 alleviates aging-associated muscle weakness and bone loss, but is not associated with accelerated aging in ACE2-knockout mice.

The angiotensin-converting enzyme 2 (ACE2)-angiotensin 1-7 (A1-7)-A1-7 receptor (Mas) axis plays a protective role in the renin-angiotensin system (RAS). We recently found that ACE2 knockout (ACE2KO) mice exhibit earlier aging-associated muscle weakness, and that A1-7 alleviates muscle weakness in aging mice. In the present study, we investigated the role of the A1-7-Mas pathway in the effect of ACE2 on physiological aging. Male wild-type, ACE2KO, and Mas knockout (MasKO) mice were subjected to periodical grip strength measurement, followed by administration of A1-7 or vehicle for 4 weeks at 24 months of age. ACE2KO mice exhibited decreased grip strength after 6 months of age, while grip strength of MasKO mice was similar to that of wild-type mice. A1-7 improved grip strength in ACE2KO and wild-type mice, but not in MasKO mice. Muscle fibre size was smaller in ACE2KO mice than that in wild-type and MasKO mice, and increased with A1-7 in ACE2KO and WT mice, but not in MasKO mice. Centrally nucleated fibres (CNFs) and expression of the senescence-associated gene p16INK4a in skeletal muscles were enhanced only in ACE2KO mice and were not altered by A1-7. ACE2KO mice, but not MasKO mice, exhibited thinning of peripheral fat along with increased adipose expression of p16INK4a A1-7 significantly increased bone volume in wild-type and ACE2KO mice, but not in MasKO mice. Our findings suggest that the impact of ACE2 on physiological aging does not depend on the endogenous production of A1-7 by ACE2, while overactivation of the A1-7-Mas pathway could alleviate sarcopenia and osteoporosis in aged mice.

Angiotensin-converting enzyme 2 deficiency accelerates and angiotensin 1-7 restores age-related muscle weakness in mice.

BACKGROUND: A pharmacologic strategy for age-related muscle weakness is desired to improve mortality and disability in the elderly. Angiotensin-converting enzyme 2 (ACE2) cleaves angiotensin II into angiotensin 1-7, a peptide known to protect against acute and chronic skeletal muscle injury in rodents. Since physiological aging induces muscle weakness via mechanisms distinct from other muscle disorders, the role of ACE2-angiotensin 1-7 in age-related muscle weakness remains undetermined. Here, we investigated whether deletion of ACE2 alters the development of muscle weakness by aging and whether angiotensin 1-7 reverses muscle weakness in older mice. METHODS: After periodic measurement of grip strength and running distance in male ACE2KO and wild-type mice until 24 months of age, we infused angiotensin 1-7 or vehicle for 4 weeks, and measured grip strength, and excised tissues. Tissues were also excised from younger (3-month-old) and middle-aged (15-month-old) mice. Microarray analysis of RNA was performed using tibialis anterior (TA) muscles from middle-aged mice, and some genes were further tested using RT-PCR. RESULTS: Grip strength of ACE2KO mice was reduced at 6 months and was persistently lower than that of wild-type mice (p < 0.01 at 6, 12, 18, and 24-month-old). Running distance of ACE2KO mice was shorter than that of wild-type mice only at 24 months of age [371 ± 26 vs. 479 ± 24 (m), p < 0.01]. Angiotensin 1-7 improved grip strength in both types of older mice, with larger effects observed in ACE2KO mice (% increase, 3.8 ± 1.5 and 13.3 ± 3.1 in wild type and ACE2KO mice, respectively). Older, but not middle-aged ACE2KO mice had higher oxygen consumption assessed by a metabolic cage than age-matched wild-type mice. Angiotensin 1-7 infusion modestly increased oxygen consumption in older mice. There was no difference in a wheel-running activity or glucose tolerance between ACE2KO and wild-type mice and between mice with vehicle and angiotensin 1-7 infusion. Analysis of TA muscles revealed that p16INK4a, a senescence-associated gene, and central nuclei of myofibers increased in middle-aged, but not younger ACE2KO mice. p16INK4a and central nuclei increased in TA muscles of older wild-type mice, but the differences between ACE2KO and wild-type mice remained significant (p < 0.01). Angiotensin 1-7 did not alter the expression of p16INK4a or central nuclei in TA muscles of both types of mice. Muscle ACE2 expression of wild-type mice was the lowest at middle age (2.6 times lower than younger age, p < 0.05). CONCLUSIONS: Deletion of ACE2 induced the early manifestation of muscle weakness with signatures of muscle senescence. Angiotensin 1-7 improved muscle function in older mice, supporting future application of the peptide or its analogues in the treatment of muscle weakness in the elderly population.

Loss of Angiotensin-Converting Enzyme 2 Exacerbates Diabetic Retinopathy by Promoting Bone Marrow Dysfunction.

Angiotensin-converting enzyme 2 (ACE2) is the primary enzyme of the vasoprotective axis of the renin angiotensin system (RAS). We tested the hypothesis that loss of ACE2 would exacerbate diabetic retinopathy by promoting bone marrow dysfunction. ACE2-/y were crossed with Akita mice, a model of type 1 diabetes. When comparing the bone marrow of the ACE2-/y -Akita mice to that of Akita mice, we observed a reduction of both short-term and long-term repopulating hematopoietic stem cells, a shift of hematopoiesis toward myelopoiesis, and an impairment of lineage- c-kit+ hematopoietic stem/progenitor cell (HS/PC) migration and proliferation. Migratory and proliferative dysfunction of these cells was corrected by exposure to angiotensin-1-7 (Ang-1-7), the protective peptide generated by ACE2. Over the duration of diabetes examined, ACE2 deficiency led to progressive reduction in electrical responses assessed by electroretinography and to increases in neural infarcts observed by fundus photography. Compared with Akita mice, ACE2-/y -Akita at 9-months of diabetes showed an increased number of acellular capillaries indicative of more severe diabetic retinopathy. In diabetic and control human subjects, CD34+ cells, a key bone marrow HS/PC population, were assessed for changes in mRNA levels for MAS, the receptor for Ang-1-7. Levels were highest in CD34+ cells from diabetics without retinopathy. Higher serum Ang-1-7 levels predicted protection from development of retinopathy in diabetics. Treatment with Ang-1-7 or alamandine restored the impaired migration function of CD34+ cells from subjects with retinopathy. These data support that activation of the protective RAS within HS/PCs may represents a therapeutic strategy for prevention of diabetic retinopathy. Stem Cells 2018;36:1430-1440.

Role of the angiotensin-converting enzyme in the G-CSF-induced mobilization of progenitor cells.

In addition to being a peptidase, the angiotensin-converting enzyme (ACE) can be phosphorylated and involved in signal transduction. We evaluated the role of ACE in granulocyte-colony-stimulating factor (G-CSF)-induced hematopoietic progenitor cell (HPC) mobilization and detected a significant increase in mice-lacking ACE. Transplantation experiments revealed that the loss of ACE in the HPC microenvironment rather than in the HPCs increased mobilization. Indeed, although ACE was expressed by a small population of bone-marrow cells, it was more strongly expressed by endosteal bone. Interestingly, there was a physical association of ACE with the G-CSF receptor (CD114), and G-CSF elicited ACE phosphorylation on Ser1270 in vivo and in vitro. A transgenic mouse expressing a non-phosphorylatable ACE (ACES/A) mutant demonstrated increased G-CSF-induced HPC mobilization and decreased G-CSF-induced phosphorylation of STAT3 and STAT5. These results indicate that ACE expression/phosphorylation in the bone-marrow niche interface negatively regulates G-CSF-induced signaling and HPC mobilization.

Resveratrol Inhibits Growth of Experimental Abdominal Aortic Aneurysm Associated With Upregulation of Angiotensin-Converting Enzyme 2.

OBJECTIVE: Recent evidence suggests an important role for angiotensin-converting enzyme 2 (ACE2) in limiting abdominal aortic aneurysm (AAA). This study examined the effect of ACE2 deficiency on AAA development and the efficacy of resveratrol to upregulate ACE2 in experimental AAA. APPROACH AND RESULTS: Ace2 deletion in apolipoprotein-deficient mice (ApoE-/-Ace2-/y ) resulted in increased aortic diameter and spontaneous aneurysm of the suprarenal aorta associated with increased expression of inflammation and proteolytic enzyme markers. In humans, serum ACE2 activity was negatively associated with AAA diagnosis. ACE2 expression was lower in infrarenal biopsies of patients with AAA than organ donors. AAA was more severe in ApoE-/-Ace2-/y mice compared with controls in 2 experimental models. Resveratrol (0.05/100-g chow) inhibited growth of pre-established AAAs in ApoE-/- mice fed high-fat chow and infused with angiotensin II continuously for 56 days. Reduced suprarenal aorta dilatation in mice receiving resveratrol was associated with elevated serum ACE2 and increased suprarenal aorta tissue levels of ACE2 and sirtuin 1 activity. In addition, the relative phosphorylation of Akt and ERK (extracellular signal-regulated kinase) 1/2 within suprarenal aorta tissue and gene expression for nuclear factor of kappa light polypeptide gene enhancer in B cells 1, angiotensin type-1 receptor, and metallopeptidase 2 and 9 were significantly reduced. Upregulation of ACE2 in human aortic smooth muscle cells by resveratrol in vitro was sirtuin 1-dependent. CONCLUSIONS: This study provides experimental evidence of an important role for ACE2 in limiting AAA development and growth. Resveratrol upregulated ACE2 and inhibited AAA growth in a mouse model.

Alternative Roles of STAT3 and MAPK Signaling Pathways in the MMPs Activation and Progression of Lung Injury Induced by Cigarette Smoke Exposure in ACE2 Knockout Mice.

Inflammation-mediated abnormalities in the renin-angiotensin system (RAS) and expression of matrix metalloproteinases (MMPs) are implicated in the pathogenesis of lung injury. Angiotensin converting enzyme II (ACE2), an angiotensin converting enzyme (ACE) homologue that displays antagonist effects on ACE/angiotensin II (Ang II) axis, could also play a protective role against lung diseases. However, the relationship between ACE2 and MMPs activation in lung injury is still largely unclear. The purpose of this study is to investigate whether MMPs activity could be affected by ACE2 and which ACE2 derived signaling pathways could be also involved via using a mouse model with lung injury induced by cigarette smoke (CS) exposure for 1 to 3 weeks. Wild-type (WT; C57BL/6) and ACE2 KO mice (ACE2(-/-)) were utilized to study CS-induced lung injury. Increases in the resting respiratory rate (RRR), pulmonary immunokines, leukocyte infiltration and bronchial hyperplasia were observed in the CS-exposed mice. Compared to WT mice, more serious physiopathological changes were found in ACE2(-/-) mice in the first week of CS exposure. CS exposure increased pulmonary ACE and ACE2 activities in WT mice, and significantly increased ACE in ACE2(-/-) mice. Furthermore, the activity of pulmonary MMPs was decreased in CS-exposed WT mice, whereas this activity was increased in ACE2(-/-) mice. CS exposure increased the pulmonary p-p38, p-JNK and p-ERK1/2 level in all mice. In ACE2(-/-) mice, a significant increase p-STAT3 signaling was detected; however, no effect was observed on the p-STAT3 level in WT mice. Our results support the hypothesis that ACE2 deficiency influences MMPs activation and STAT3 phosphorylation signaling to promote more pulmonary inflammation in the development of lung injury.

Angiotensin converting enzyme 2 and the kidney.

PURPOSE OF REVIEW: Angiotensin-converting enzyme 2 (ACE2) is a monocarboxypeptidase that metabolizes angiotensin II (AngII). AngII levels can be modulated by ACE2 in tissues where the enzyme is highly expressed, such as the kidney. In the kidney, ACE2 has the potential to regulate the intrarenal renin-angiotensin system (RAS), which can impact blood pressure and renal injury. Thus, in disease states where the RAS is often upregulated, the function of ACE2 plays a particularly important role. This review highlights the results of recent studies that demonstrate the interplay between ACE2 and the kidney under normal and pathological conditions. RECENT FINDINGS: ACE2 has been reported to play a key role in renal and cardiovascular function. Recent studies have implicated shedding of the membrane-bound ectodomain of ACE2 as one way in which the enzyme can be regulated and enzymatic activity altered. This posttranslational modification releases a fragment which retains enzymatic activity, and thus provides a novel mechanism by which the RAS can be altered in response to physiological stimuli. Decreased ACE2 activity is associated with increased blood pressure, diabetes, and oxidative stress, whereas, increased levels of ACE2 appear to be renoprotective. SUMMARY: A growing body of evidence, involving both experimental and human studies, points out the crucial role that ACE2 plays on the modulation of renal injury. Thus, therapeutic targets aiming to increase ACE2 activity and the ACE2-Ang(1-7)-MasR axis could potentially become clinically relevant, especially in disease states where the renal RAS is upregulated.

ACE2 Deficiency Worsens Epicardial Adipose Tissue Inflammation and Cardiac Dysfunction in Response to Diet-Induced Obesity.

Obesity is increasing in prevalence and is strongly associated with metabolic and cardiovascular disorders. The renin-angiotensin system (RAS) has emerged as a key pathogenic mechanism for these disorders; angiotensin (Ang)-converting enzyme 2 (ACE2) negatively regulates RAS by metabolizing Ang II into Ang 1-7. We studied the role of ACE2 in obesity-mediated cardiac dysfunction. ACE2 null (ACE2KO) and wild-type (WT) mice were fed a high-fat diet (HFD) or a control diet and studied at 6 months of age. Loss of ACE2 resulted in decreased weight gain but increased glucose intolerance, epicardial adipose tissue (EAT) inflammation, and polarization of macrophages into a proinflammatory phenotype in response to HFD. Similarly, human EAT in patients with obesity and heart failure displayed a proinflammatory macrophage phenotype. Exacerbated EAT inflammation in ACE2KO-HFD mice was associated with decreased myocardial adiponectin, decreased phosphorylation of AMPK, increased cardiac steatosis and lipotoxicity, and myocardial insulin resistance, which worsened heart function. Ang 1-7 (24 µg/kg/h) administered to ACE2KO-HFD mice resulted in ameliorated EAT inflammation and reduced cardiac steatosis and lipotoxicity, resulting in normalization of heart failure. In conclusion, ACE2 plays a novel role in heart disease associated with obesity wherein ACE2 negatively regulates obesity-induced EAT inflammation and cardiac insulin resistance.

Deletion of angiotensin-converting enzyme 2 exacerbates renal inflammation and injury in apolipoprotein E-deficient mice through modulation of the nephrin and TNF-alpha-TNFRSF1A signaling.

BACKGROUND: The renin-angiotensin system (RAS) has been implicated in atherosclerotic lesions and progression to chronic kidney diseases. We examined regulatory roles of angiotensin-converting enzyme 2 (ACE2) in the apolipoprotein E (ApoE) knockout (KO) kidneys. METHODS: The 3-month-old wild-type, ApoEKO, ACE2KO and ApoE/ACE2 double-KO (DKO) mice in a C57BL/6 background were used. The ApoEKO mice were randomized to daily deliver either Ang II (1.5 mg/kg) and/or human recombinant ACE2 (rhACE2; 2 mg/kg) for 2 weeks. We examined changes in pro-inflammatory cytokines, renal ultrastructure, and pathological signaling in mouse kidneys. RESULTS: Downregulation of ACE2 and nephrin levels was observed in ApoEKO kidneys. Genetic ACE2 deletion resulted in modest elevations in systolic blood pressure levels and Ang II type 1 receptor expression and reduced nephrin expression in kidneys of the ApoE/ACE2 DKO mice with a decrease in renal Ang-(1-7) levels. These changes were linked with marked increases in renal superoxide generation, NADPH oxidase (NOX) 4 and proinflammatory factors levels, including interleukin (IL)-1beta, IL-6, IL-17A, RANTES, ICAM-1, Tumor necrosis factor-alpha (TNF-alpha) and TNFRSF1A. Renal dysfunction and ultrastructure injury were aggravated in the ApoE/ACE2 DKO mice and Ang II-infused ApoEKO mice with increased plasma levels of creatinine, blood urea nitrogen and enhanced levels of Ang II in plasma and kidneys. The Ang II-mediated reductions of renal ACE2 and nephrin levels in ApoEKO mice were remarkably rescued by rhACE2 supplementation, along with augmentation of renal Ang-(1-7) levels. More importantly, rhACE2 treatment significantly reversed Ang II-induced renal inflammation, superoxide generation, kidney dysfunction and adverse renal injury in ApoEKO mice with suppression of the NOX4 and TNF-alpha-TNFRSF1A signaling. However, rhACE2 had no effect on renal NOX2 and TNFRSF1B expression and circulating lipid levels. CONCLUSIONS: ACE2 deficiency exacerbates kidney inflammation, oxidative stress and adverse renal injury in the ApoE-mutant mice through modulation of the nephrin, NOX4 and TNF-alpha-TNFRSF1A signaling. While rhACE2 supplementation alleviates inflammation, renal dysfunction and glomerulus injury in the ApoE-mutant mice associated with upregulations of Ang-(1-7) levels and nephrin expression and suppression of the TNF-alpha-TNFRSF1A signaling. Strategies aimed at enhancing the ACE2/Ang-(1-7) actions may have important therapeutic potential for atherosclerotic renal injury and kidney diseases.

Iatrogenic angioedema associated with ACEi, sitagliptin, and deficiency of 3 enzymes catabolizing bradykinin.

New concepts of idiopathic and iatrogenic angioedema underline the role of bradykinin, and the importance of catabolizing enzymes. A case is described of Angiotensin converting enzyme inhibitor (ACEi) and sitagliptin induced angioedema, where AO attacks decreased after the withdrawal of lisinopril but resolved only after the withdrawal of sitagliptin, an inhibitor of dipeptylpeptidase IV. ACE, aminopeptidase P and carboxypeptidase N were decreased down to 17%, 42%, 64% of median references values, and remained low one year after the interruption of these drugs: 56%, 28% and 50%, respectively. The combined deficiency of APP and CPN might enhance the inhibiting effect of the DPP IV inhibitor. The fact that this triple deficiency remained latent before and after the treatment indicates that searching for latent enzyme deficiencies should be carried out when there is intention to treat with a combination of drugs interfering with the bradykinin metabolism.

Angiotensin-converting enzyme (ACE and ACE2) imbalance correlates with the severity of cerulein-induced acute pancreatitis in mice.

Angiotensin-converting enzyme (ACE) and its effector peptide angiotensin II (Ang II) have been implicated in the pathogenesis of pancreatitis. Angiotensin-converting enzyme 2 (ACE2) degrades Ang II to angiotensin-(1-7) [Ang-(1-7)] and has recently been described to have an antagonistic effect on ACE signalling. However, the specific underlying role of ACE2 in the pathogenesis of severe acute pancreatitis (SAP) is unclear. In the present study, the local imbalance of ACE and ACE2, as well as Ang II and Ang-(1-7) expression, was compared in wild-type (WT) and ACE2 knock-out (KO) or ACE2 transgenic (TG) mice subjected to cerulein-induced SAP. Serum amylase, tumour necrosis factor-α, interleukin (IL)-1ß, IL-6 and IL-10 levels and histological morphometry were used to determine the severity of pancreatitis. In WT mice, pancreatic ACE and Ang II and serum Ang II expression increased (P < 0.05), while pancreatic ACE2 and Ang-(1-7) and serum Ang-(1-7) levels were also significantly elevated (P < 0.05) from 2 to 72 h after the onset of SAP. However, the ratio of pancreatic ACE2 to ACE expression was significantly reduced (from 1.46 ± 0.09 to 0.27 ± 0.05, P < 0.001) and paralleled the severity of pancreatitis. The Ace2 KO mice exhibited increased levels of tumour necrosis factor-α, IL-1ß, IL-6, multifocal coagulative necrosis and inflammatory infiltrate, and lower levels of serum IL-10 and pancreatic Ang-(1-7) (4.70 ± 2.13 versus 10.87 ± 2.51, P < 0.001) compared with cerulein-treated WT mice at the same time point. Conversely, Ace2 TG mice with normal ACE expression were more resistant to SAP challenge as evidenced by a decreased inflammatory response, attenuated pathological changes and increased survival rates. These data suggest that the ACE2-ACE imbalance plays an important role in the pathogenesis of SAP and that pancreatic ACE2 is an important factor in determining the severity of SAP.

Deletion of angiotensin-converting enzyme 2 promotes the development of atherosclerosis and arterial neointima formation.

AIMS: Angiotensin-converting enzyme 2 (ACE2) is known as a negative regulator of the renin-angiotensin system. We aimed to determine the roles of ACE2 on the development of vascular diseases. METHODS AND RESULTS: Using two diversely different models of vascular diseases, hyperlipidaemia-induced atherosclerosis in apolipoprotein E knockout (KO) mice and mechanical injury-induced arterial neointimal hyperplasia in C57Bl6 mice, we examined whether ACE2 deficiency could affect formation of the vascular lesions. ACE2 deficiency resulted in significantly larger vascular lesions in both aortic atherosclerotic plaques and arterial neointima formation, compared with ACE2(+) control. These ACE2-deficient vascular lesions exhibited enhanced accumulation of macrophages into the lesions and proliferation of vascular smooth muscle cells (VSMCs), accompanied with increased angiotensin-II (Ang-II) levels and enhanced expression of vascular inflammation-related genes, including vascular cell adhesion molecule (VCAM)-1, monocyte chemoattractant protein (MCP)-1, and matrix metalloproteinase (MMP)9 in aorta/artery tissues. Primary bone marrow macrophages and aortic VSMCs isolated from ACE2 KO mice also displayed enhanced pro-inflammatory responsiveness such as up-regulated gene/protein expression of VCAM-1, MCP-1, and MMP9 to stimulation with tumour necrosis factor-α and Ang-II. The similar phenotype was shown in human macrophages and aortic VSMCs that were transfected with ACE2-specific siRNA. In ACE2-deficient VSMCs, inhibition of c-Jun N-terminal kinase (JNK) by pharmacological blockade with SP600125 or genetic knockdown with JNK-specific siRNA significantly attenuated their pro-inflammatory phenotype. CONCLUSION: ACE2 deficiency promotes the development of vascular diseases associated with Ang-II-mediated vascular inflammation and activation of the JNK signalling, leading to the notion that ACE2 potentially confers protection against vascular diseases.

Contributions of leukocyte angiotensin-converting enzyme to development of atherosclerosis.

OBJECTIVE: This study determined the role of angiotensin-converting enzyme (ACE) on the development of angiotensin I-induced atherosclerosis and the contribution of leukocyte-specific expression of this enzyme. APPROACH AND RESULTS: To define the contribution of ACE-dependent activity to angiotensin II synthesis in atherosclerotic development, male low-density lipoprotein receptor(-/-) mice were fed a fat-enriched diet and infused with either angiotensin I or angiotensin II. The same infusion rate of these peptides had equivalent effects on atherosclerotic development. Coinfusion of an ACE inhibitor, enalapril, ablated angiotensin I-augmented atherosclerosis but had no effect on angiotensin II-induced lesion development. ACE protein was detected in several cell types in atherosclerotic lesions, with a predominance in macrophages. This cell type secreted angiotensin II, which was ablated by ACE inhibition. To study whether leukocyte ACE contributed to atherosclerosis, irradiated male low-density lipoprotein receptor(-/-) mice were repopulated with bone marrow-derived cells from either ACE(+/+) or ACE(-/-) mice and fed the fat-enriched diet for 12 weeks. Chimeric mice with ACE deficiency in bone marrow-derived cells had modestly reduced atherosclerotic lesions in aortic arches but had no effects in aortic roots. CONCLUSIONS: ACE mediates angiotensin I-induced atherosclerosis, and ACE expression in leukocytes modestly contributes to atherosclerotic development in hypercholesterolemic mice.