The ACE2/Ang-(1-7)/Mas Axis Regulates the Development of Pancreatic Endocrine Cells in Mouse Embryos

COVID-19 and Preexisting Comorbidities: Risks, Synergies, and Clinical Outcomes

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its associated symptoms, named coronavirus disease 2019 (COVID-19), have rapidly spread worldwide, resulting in the declaration of a pandemic. When several countries began enacting quarantine and lockdown policies, the pandemic as it is now known truly began. While most patients have minimal symptoms, approximately 20% of verified subjects are suffering from serious medical consequences. Co-existing diseases, such as cardiovascular disease, cancer, diabetes, and others, have been shown to make patients more vulnerable to severe outcomes from COVID-19 by modulating host-viral interactions and immune responses, causing severe infection and mortality. In this review, we outline the putative signaling pathways at the interface of COVID-19 and several diseases, emphasizing the clinical and molecular implications of concurring diseases in COVID-19 clinical outcomes. As evidence is limited on co-existing diseases and COVID-19, most findings are preliminary, and further research is required for optimal management of patients with comorbidities.

Use of Novel Antidiabetic Agents in Patients with Type 2 Diabetes and COVID-19: A Critical Review

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes coronavirus disease 2019 (COVID-19). The latter is a pandemic that has the potential of developing into a severe illness manifesting as systemic inflammatory response syndrome, acute respiratory distress syndrome, multi-organ involvement and shock. In addition, advanced age and male sex and certain underlying health conditions, like type 2 diabetes mellitus (T2DM), predispose to a higher risk of greater COVID-19 severity and mortality. This calls for an urgent identification of antidiabetic agents associated with more favourable COVID-19 outcomes among patients with T2DM, as well as recognition of their potential underlying mechanisms. It is crucial that individuals with T2DM be kept under very stringent glycaemic control in order to avoid developing various cardiovascular, renal and metabolic complications associated with more severe forms of COVID-19 that lead to increased mortality. The use of novel antidiabetic agents dipeptidyl peptidase 4 inhibitors (DPP4i), sodium-glucose co-transporter 2 inhibitors (SGLT2i) and glucagon-like peptide 1 receptor agonists (GLP-1RAs) in subjects with T2DM may have beneficial effects on COVID-19 outcomes. However, relevant studies either show inconsistent results (DPP4i) or are still too few (SGLT2i and GLP-1RAs). Further research is therefore needed to assess the impact of these agents on COVID-19 outcomes.

ACE2 function in the pancreatic islet: Implications for relationship between SARS-CoV-2 and diabetes

The molecular link between SARS-CoV-2 infection and susceptibility is not well understood. Nonetheless, a bi-directional relationship between SARS-CoV-2 and diabetes has been proposed. The angiotensin-converting enzyme 2 (ACE2) is considered as the primary protein facilitating SARS-CoV and SARS-CoV-2 attachment and entry into the host cells. Studies suggested that ACE2 is expressed in the endocrine cells of the pancreas including beta cells, in addition to the lungs and other organs; however, its expression in the islets, particularly beta cells, has been met with some contradiction. Importantly, ACE2 plays a crucial role in glucose homoeostasis and insulin secretion by regulating beta cell physiology. Given the ability of SARS-CoV-2 to infect human pluripotent stem cell-derived pancreatic cells in vitro and the presence of SARS-CoV-2 in pancreatic samples from COVID-19 patients strongly hints that SARS-CoV-2 can invade the pancreas and directly cause pancreatic injury and diabetes. However, more studies are required to dissect the underpinning molecular mechanisms triggered in SARS-CoV-2-infected islets that lead to aggravation of diabetes. Regardless, it is important to understand the function of ACE2 in the pancreatic islets to design relevant therapeutic interventions in combatting the effects of SARS-CoV-2 on diabetes pathophysiology. Herein, we detail the function of ACE2 in pancreatic beta cells crucial for regulating insulin sensitivity, secretion, and glucose metabolism. Also, we discuss the potential role played by ACE2 in aiding SARS-COV-2 entry into the pancreas and the possibility of ACE2 cooperation with alternative entry factors as well as how that may be linked to diabetes pathogenesis.

Therapy of Type 2 Diabetes in Patients with SARS-CoV-2 Infection

COVID-19 infection poses an important clinical therapeutic problem, especially in patients with coexistent diseases such as type 2 diabetes. Potential pathogenetic links between COVID-19 and diabetes include inflammation, effects on glucose homeostasis, haemoglobin deoxygenation, altered immune status and activation of the renin-angiotensin-aldosterone system (RAAS). Moreover, drugs often used in the clinical care of diabetes (dipeptidyl peptidase 4 inhibitors, glucagon-like peptide 1 receptor agonists, sodium-glucose cotransporter 2 inhibitors, metformin and insulin) may influence the course of SARS-CoV-2 infection, so it is very important to verify their effectiveness and safety. This review summarises the new advances in diabetes therapy and COVID-19 and provides clinical recommendations that are essential for medical doctors and for patients suffering from type 2 diabetes.

Effect of plasma glucose at admission on COVID-19 mortality: experience from a tertiary hospital

OBJECTIVE

Plasma glucose has been correlated with in-hospital mortality among many diseases including infections. We aimed to study the plasma glucose at the admission of hospitalized patients with COVID-19 at a tertiary care referral hospital at Jodhpur, India and its relation with mortality.

DESIGN

A hospital-based clinical study of plasma glucose of COVID-19 patients conducted from May 15 to June 30, 2020 after ethical approval.

MEASUREMENTS

Random blood samples at admission were collected for plasma glucose, interleukin-6 (IL6) and high sensitivity C-reactive protein (hsCRP) after written informed consent was obtained. Plasma glucose was analyzed by the automated analyzer, IL6 by chemiluminescent immunoassay and hsCRP by immune-turbidimetric assay.

RESULTS

A total of 386 patients were studied (female 39.6%); 11.1% had severe disease and 4.1% expired. There were 67 (17.4%) patients with known diabetes mellitus (DM). Patients with a history of DM had three times higher mortality (6/67, 9%) than those without DM (10/309, 3.1%). Patients with moderate and severe disease according to ICMR and WHO grading had higher plasma glucose than those with asymptomatic or mild disease (P < 0.0001). Plasma glucose levels at admission were significantly higher in non-survivors when compared to those who survived (297 ± 117 vs 131 ± 73; P < 0.0001). COVID-19 patients showed increased mortality with incremental plasma glucose levels. The hazard ratio for mortality was 1.128 (95% CI 0.86-14.860), 1.883 (95% CI 0.209-16.970), and 4.005 (95% CI 0.503-32.677) in random plasma glucose group of >100-200, >200-300 and >300 mg/dL, respectively, compared to those with random plasma glucose of <100 mg/dL at admission. Plasma glucose was strongly correlated with hsCRP (P < 0.001) and IL6 (P < 0.0001).

CONCLUSIONS

Plasma glucose at admission in hospitalized COVID-19 patients is a strong predictor of mortality.

Coronavirus Receptors as Immune Modulators

The Coronaviridae family includes the seven known human coronaviruses (CoV) that cause mild to moderate respiratory infections (HCoV-229E, HCoV-NL63, HCoV-OC43, HCoV-HKU1) as well as severe illness and death (MERS-CoV, SARS-CoV, SARS-CoV-2). Severe infections induce hyperinflammatory responses that are often intensified by host adaptive immune pathways to profoundly advance disease severity. Proinflammatory responses are triggered by CoV entry mediated by host cell surface receptors. Interestingly, five of the seven strains use three cell surface metallopeptidases (CD13, CD26, and ACE2) as receptors, whereas the others employ O-acetylated-sialic acid (a key feature of metallopeptidases) for entry. Why CoV evolved to use peptidases as their receptors is unknown, but the peptidase activities of the receptors are dispensable, suggesting the virus uses/benefits from other functions of these molecules. Indeed, these receptors participate in the immune modulatory pathways that contribute to the pathological hyperinflammatory response. This review will focus on the role of CoV receptors in modulating immune responses.

ACE2 and energy metabolism: the connection between COVID-19 and chronic metabolic disorders

The renin-angiotensin system (RAS) has currently attracted increasing attention due to its potential function in regulating energy homeostasis, other than the actions on cellular growth, blood pressure, fluid, and electrolyte balance. The existence of RAS is well established in metabolic organs, including pancreas, liver, skeletal muscle, and adipose tissue, where activation of angiotensin-converting enzyme (ACE) - angiotensin II pathway contributes to the impairment of insulin secretion, glucose transport, fat distribution, and adipokines production. However, the activation of angiotensin-converting enzyme 2 (ACE2) - angiotensin (1-7) pathway, a novel branch of the RAS, plays an opposite role in the ACE pathway, which could reverse these consequences by improving local microcirculation, inflammation, stress state, structure remolding, and insulin signaling pathway. In addition, new studies indicate the protective RAS arm possesses extraordinary ability to enhance brown adipose tissue (BAT) activity and induces browning of white adipose tissue, and consequently, it leads to increased energy expenditure in the form of heat instead of ATP synthesis. Interestingly, ACE2 is the receptor of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is threating public health worldwide. The main complications of SARS-CoV-2 infected death patients include many energy metabolism-related chronic diseases, such as diabetes. The specific mechanism leading to this phenomenon is largely unknown. Here, we summarize the latest pharmacological and genetic tools on regulating ACE/ACE2 balance and highlight the beneficial effects of the ACE2 pathway axis hyperactivity on glycolipid metabolism, as well as the thermogenic modulation.

COVID-19 and diabetes mellitus: from pathophysiology to clinical management

Initial studies found increased severity of coronavirus disease 2019 (COVID-19), caused by infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), in patients with diabetes mellitus. Furthermore, COVID-19 might also predispose infected individuals to hyperglycaemia. Interacting with other risk factors, hyperglycaemia might modulate immune and inflammatory responses, thus predisposing patients to severe COVID-19 and possible lethal outcomes. Angiotensin-converting enzyme 2 (ACE2), which is part of the renin-angiotensin-aldosterone system (RAAS), is the main entry receptor for SARS-CoV-2; although dipeptidyl peptidase 4 (DPP4) might also act as a binding target. Preliminary data, however, do not suggest a notable effect of glucose-lowering DPP4 inhibitors on SARS-CoV-2 susceptibility. Owing to their pharmacological characteristics, sodium-glucose cotransporter 2 (SGLT2) inhibitors might cause adverse effects in patients with COVID-19 and so cannot be recommended. Currently, insulin should be the main approach to the control of acute glycaemia. Most available evidence does not distinguish between the major types of diabetes mellitus and is related to type 2 diabetes mellitus owing to its high prevalence. However, some limited evidence is now available on type 1 diabetes mellitus and COVID-19. Most of these conclusions are preliminary, and further investigation of the optimal management in patients with diabetes mellitus is warranted.

SARS-CoV-2 Receptor Angiotensin I-Converting Enzyme Type 2 (ACE2) Is Expressed in Human Pancreatic β-Cells and in the Human Pancreas Microvasculature

Increasing evidence demonstrated that the expression of Angiotensin I-Converting Enzyme type 2 (ACE2) is a necessary step for SARS-CoV-2 infection permissiveness. In light of the recent data highlighting an association between COVID-19 and diabetes, a detailed analysis aimed at evaluating ACE2 expression pattern distribution in human pancreas is still lacking. Here, we took advantage of INNODIA network EUnPOD biobank collection to thoroughly analyze ACE2, both at mRNA and protein level, in multiple human pancreatic tissues and using several methodologies. Using multiple reagents and antibodies, we showed that ACE2 is expressed in human pancreatic islets, where it is preferentially expressed in subsets of insulin producing β-cells. ACE2 is also highly expressed in pancreas microvasculature pericytes and moderately expressed in rare scattered ductal cells. By using different ACE2 antibodies we showed that a recently described short-ACE2 isoform is also prevalently expressed in human β-cells. Finally, using RT-qPCR, RNA-seq and High-Content imaging screening analysis, we demonstrated that pro-inflammatory cytokines, but not palmitate, increase ACE2 expression in the β-cell line EndoC-βH1 and in primary human pancreatic islets. Taken together, our data indicate a potential link between SARS-CoV-2 and diabetes through putative infection of pancreatic microvasculature and/or ductal cells and/or through direct β-cell virus tropism.

The AI-discovered aetiology of COVID-19 and rationale of the irinotecan+ etoposide combination therapy for critically ill COVID-19 patients

We present the AI-discovered aetiology of COVID-19, based on a precise disease model of COVID-19 built under five weeks that best matches the epidemiological characteristics, transmission dynamics, clinical features, and biological properties of COVID-19 and consistently explains the rapidly expanding COVID-19 literature. We present that SARS-CoV-2 implements a unique unbiased survival strategy of balancing viral replication with viral spread by increasing its dependence on (i) ACE2-expressing cells for viral entry and spread, (ii) PI3K signaling in ACE2-expressing cells for viral replication and egress, and (iii) viral- non-structural-and-accessory-protein-dependent immunomodulation to balance viral spread and viral replication. We further propose the combination of irinotecan (an in-market topoisomerase I inhibitor) and etoposide (an in-market topoisomerase II inhibitor) could potentially be an exceptionally effective treatment to protect critically ill patients from death caused by COVID-19-specific cytokine storms triggered by sepsis, ARDS, and other fatal comorbidities.

SARS-CoV-2 Receptor ACE2 Is Enriched in a Subpopulation of Mouse Tongue Epithelial Cells in Nongustatory Papillae but Not in Taste Buds or Embryonic Oral Epithelium

As a result of the COVID-19 pandemic, evidence revealed that SARS-CoV-2 infection caused taste loss at a rate higher than that of influenza. ACE2, the entry receptor of SARS-CoV-2, has been identified in the oral epithelium; however, it is unclear at what developmental stage ACE2 expression emerges and whether ACE2 is expressed in taste buds. To identify the specific developmental stage, we analyzed RNA-Seq data from embryonic and newborn mouse oral tissue. We found that robust ACE2 expression was observed in the newborn oral epithelium. In contrast, only extremely low levels, if any, of ACE2 transcripts in the embryonic stage oral tissue were found (E12.5 and E14.5). Analyses of three public scRNA-seq data sets of adult mouse tongue epithelial cells showed that receptors for various viruses were enriched in distinct clusters of tongue epithelial cells. ACE2 was enriched in a subpopulation of epithelial cells in the basal region of nongustatory filiform papillae but not in the taste papillae or taste buds. Expression of ACE2 was detected in a small proportion of type III taste cells. Our results indicate that when applied across species, nongustatory papilla epithelial cells are the prime targets for SARS-CoV-2 infection in the tongue; thus, taste loss in COVID-19 patients is likely not caused by a direct infection of SARS-CoV-2 to taste bud cells. Additionally, fetuses at different stages of development may have distinct susceptibility to SARS-CoV-2 infection.

Angiotensin-(1-7) Improves Islet Function in a Rat Model of Streptozotocin- Induced Diabetes Mellitus by Up-Regulating the Expression of Pdx1/Glut2

OBJECTIVE

To observe the effects of angiotensin-(1-7) (Ang-(1-7)) on glucose metabolism, islet function and insulin resistance in a rat model of streptozotocin-induced diabetes mellitus (DM) and investigate its mechanism.

METHODS

Thirty-four male Wistar rats were randomly divided into 3 groups: control group, which was fed a standard diet, DM group, high-fat diet and injected with streptozotocin, and Ang-(1-7) group receiving an injection of streptozotocin followed by Ang-(1-7) treatment. Blood glucose level, fasting serum Ang II and insulin levels, and homeostasis model assessment of insulin resistance (HOMA-IR) were measured. The pancreases were collected for histological examination, protein and gene expression analysis.

RESULTS

Compared with the control group, fasting blood glucose, serum angiotensin II level, and HOMA-IR value increased, while serum insulin level decreased in the DM group. Moreover, islet structure was damaged, β cells were irregularly arranged, the cytoplasm was loose in the DM group. Expressions of Pancreatic duodenal homeobox-1 (Pdx1), glucose transporter-2 (Glut2) and glucokinase (Gk) were significantly decreased in the DM group compared with the control group. However, the DM-associated changes were dramatically reversed following Ang-(1-7) treatment.

CONCLUSION

Ang-(1-7) protects against streptozotocin-induced DM through the improvement of insulin secretion, insulin resistance and islet fibrosis, which is associated with the upregulation of Pdx1, Glut2 and Gk expressions.

COVID-19 infection presenting as pancreatitis in a pregnant woman: A case report

Background

The coronavirus 2019 (COVID-19) pandemic has posed unique challenges in healthcare. In obstetrics, there is little information available to guide practice. As new data emerge, the spectrum of initial presenting symptoms has expanded from fever, cough, and dyspnea to gastrointestinal and other symptoms in both pregnant and non-pregnant patients.

Case

A 36-year-old woman, G4P2, at 33 weeks of gestation presented very early in the COVID-19 course with four days of cough and fever, without recent travel or known exposure. She appeared well, with stable vital signs, and was sent home to self-quarantine after a specimen for COVID-19 testing was collected. Two days later, she presented with nausea, vomiting, and abdominal pain, and was diagnosed with acute pancreatitis.

Conclusion

To date, no cases of human pancreatitis have been identified as related to a COVID-19 infection, although multiple other gastrointestinal symptoms have been described. Given the lack of other etiology, we consider the possibility that patient's acute pancreatitis could be secondary to COVID-19 infection.

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COVID-19 has a variety of different presentations, including gastrointestinal symptoms.

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Nausea, vomiting, and epigastric pain in pregnancy can have many different etiologies and should be thoroughly evaluated.

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Pancreatitis can have a viral etiology, including COVID-19.

The ACE2/Angiotensin-(1-7)/MAS Axis of the Renin-Angiotensin System: Focus on Angiotensin-(1-7)

The renin-angiotensin system (RAS) is a key player in the control of the cardiovascular system and hydroelectrolyte balance, with an influence on organs and functions throughout the body. The classical view of this system saw it as a sequence of many enzymatic steps that culminate in the production of a single biologically active metabolite, the octapeptide angiotensin (ANG) II, by the angiotensin converting enzyme (ACE). The past two decades have revealed new functions for some of the intermediate products, beyond their roles as substrates along the classical route. They may be processed in alternative ways by enzymes such as the ACE homolog ACE2. One effect is to establish a second axis through ACE2/ANG-(1-7)/MAS, whose end point is the metabolite ANG-(1-7). ACE2 and other enzymes can form ANG-(1-7) directly or indirectly from either the decapeptide ANG I or from ANG II. In many cases, this second axis appears to counteract or modulate the effects of the classical axis. ANG-(1-7) itself acts on the receptor MAS to influence a range of mechanisms in the heart, kidney, brain, and other tissues. This review highlights the current knowledge about the roles of ANG-(1-7) in physiology and disease, with particular emphasis on the brain.

The novel NADPH oxidase 4 selective inhibitor GLX7013114 counteracts human islet cell death in vitro

It has been proposed that pancreatic beta-cell dysfunction in type 2 diabetes is promoted by oxidative stress caused by NADPH oxidase (Nox) over-activity. The aim of the present study was to evaluate the efficacy of novel Nox inhibitors as protective agents against cytokine- or high glucose + palmitate-induced human beta-cell death. The Nox2 protein was present mainly in the cytoplasm and was induced by cytokines. Nox4 protein immunoreactivity, with some nuclear accumulation, was observed in human islet cells, and was not affected by islet culture in the presence of cytokines or high glucose + palmitate. Nox inhibitors with partial or no isoform selectivity (DPI, dapsone, GLX351322, and GLX481372) all reduced ROS production of human islet cells exposed to high glucose + palmitate. This was paralleled by improved viability and reduced caspase 3 activation. The Nox1 selective inhibitor ML171 failed to reduce human islet cell death in response to both cytokines and high glucose + palmitate. The selective Nox2 inhibitor Phox-I2 also failed to protect against cytokines, but protected partially against high glucose + palmitate-induced cellular death. The highly selective Nox4 inhibitor GLX7013114 protected islet cells against both cytokines and high glucose + palmitate. However, as no osmotic control for high glucose was used, we cannot exclude the possibility that the high glucose effect was due to osmosis. It is concluded that Nox4 may participate in stress-induced islet cell death in human islets in vitro. We propose that Nox4 mediates pro-apoptotic effects in intact islets under stressful conditions and that selective Nox4-inhibition may be a therapeutic strategy in type 2 diabetes.

Oxidative Stress in Pancreatic Beta Cell Regeneration

Pancreatic β cell neogenesis and proliferation during the neonatal period are critical for the generation of sufficient pancreatic β cell mass/reserve and have a profound impact on long-term protection against type 2 diabetes (T2D). Oxidative stress plays an important role in β cell neogenesis, proliferation, and survival under both physiological and pathophysiological conditions. Pancreatic β cells are extremely susceptible to oxidative stress due to a high endogenous production of reactive oxygen species (ROS) and a low expression of antioxidative enzymes. In this review, we summarize studies describing the critical roles and the mechanisms of how oxidative stress impacts β cell neogenesis and proliferation. In addition, the effects of antioxidant supplements on reduction of oxidative stress and increase of β cell proliferation are discussed. Exploring the roles and the potential therapeutic effects of antioxidants in the process of β cell regeneration would provide novel perspectives to preserve and/or expand pancreatic β cell mass for the treatment of T2D.

Angiotensin II Type 2 Receptor Activation With Compound 21 Augments Islet Function and Regeneration in Streptozotocin-Induced Neonatal Rats and Human Pancreatic Progenitor Cells

OBJECTIVES

We investigated the effects of compound 21 (C21), a nonpeptide angiotensin II type 2 receptor agonist, on islet cell function and survival in streptozotocin (STZ)-treated neonatal rats and human pancreatic progenitor cells.

METHODS

Neonatal rats were randomized into 5 groups, including a control, an STZ (100 mg/kg, intraperitoneally), and 3 STZ + C21 (0.25, 0.5, and 1 mg/kg per day for 7 days, intraperitoneally) groups. Body weight and blood glucose were monitored daily. On the last experimental day, serum insulin levels and glucose tolerance were assessed, and the rat pups' pancreata were extracted for examination of islet cell function/mass and involvement of signaling pathways.

RESULTS

The C21-treated STZ rats, particularly in the 0.5- and 1 mg/kg-dosage groups, had significantly decreased blood glucose, increased serum insulin concentrations, higher glucose-stimulated insulin secretion activity, and greater islet-cell mass and up-regulated expression of insulin and Ngn3 in the pancreas than did the control groups; these rats also demonstrated increased β-cell proliferation, lower superoxide levels and enhanced SOD1 expression, and up-regulated phospho-AKT expression; consistently, similar results were also observed in human pancreatic progenitor cells.

CONCLUSIONS

These data suggest that C21 has a beneficial effect on islet cell function and regeneration, probably via proliferative and antioxidative pathways.

Glucagon-producing cells are increased in Mas-deficient mice

It has been shown that angiotensin(1-7) (Ang(1-7)) produces several effects related to glucose homeostasis. In this study, we aimed to investigate the effects of genetic deletion of Ang(1-7), the GPCR Mas, on the glucagon-producing cells. C57BL6/N Mas^-/- mice presented a significant and marked increase in pancreatic α-cells (number of cells: 146 ± 21 vs 67 ± 8 in WT; P < 0.001) and the percentage per islet (17.9 ± 0.91 vs 12.3 ± 0.9% in WT; P < 0.0001) with subsequent reduction of β-cells percentage (82.1 ± 0.91 vs 87.7 ± 0.9% in WT; P < 0.0001). Accordingly, glucagon plasma levels were increased (516.7 ± 36.35 vs 390.8 ± 56.45 pg/mL in WT; P < 0.05) and insulin plasma levels were decreased in C57BL6/N Mas^-/- mice (0.25 ± 0.01 vs 0.31 ± 56.45 pg/mL in WT; P = 0.02). In order to eliminate the possibility of a background-related phenotype, we determined the number of glucagon-producing cells in FVB/N Mas^-/- mice. In keeping with the observations in C57BL6/N Mas^-/- mice, the number and percentage of pancreatic α-cells were also significantly increased in these mice (number of α-cells: 260 ± 22 vs 156 ± 12 in WT, P < 0.001; percentage per islet: 16 ± 0.8 vs 10 ± 0.5% in WT, P < 0.0001). These results suggest that Mas has a previously unexpected role on the pancreatic glucagon production.

The Angiotensin-(1-7)/Mas Axis Counteracts Angiotensin II-Dependent and -Independent Pro-inflammatory Signaling in Human Vascular Smooth Muscle Cells

Background and Aims: Targeting inflammation is nowadays considered as a challenging pharmacological strategy to prevent or delay the development of vascular diseases. Angiotensin-(1-7) is a member of the renin-angiotensin system (RAS) that binds Mas receptors and has gained growing attention in the last years as a regulator of vascular homeostasis. Here, we explored the capacity of Ang-(1-7) to counteract human aortic smooth muscle cell (HASMC) inflammation triggered by RAS-dependent and -independent stimuli, such as Ang II or interleukin (IL)-1β.

Methods and Results: In cultured HASMC, the expression of inducible nitric oxide synthase (iNOS) and the release of nitric oxide were stimulated by both Ang II and IL-1β, as determined by Western blot and indirect immunofluorescence or the Griess method, respectively. iNOS induction was inhibited by Ang-(1-7) in a concentration-dependent manner. This effect was equally blocked by two different Mas receptor antagonists, A779 and D-Pro⁷-Ang-(1-7), suggesting the participation of a unique Mas receptor subtype. Using pharmacological inhibitors, the induction of iNOS was proven to rely on the consecutive upstream activation of NADPH oxidase and nuclear factor (NF)-κB. Indeed, Ang-(1-7) markedly inhibited the activation of the NADPH oxidase and subsequently of NF-κB, as determined by lucigenin-derived chemiluminescence and electromobility shift assay, respectively.

Conclusion: Ang-(1-7) can act as a counter-regulator of the inflammation of vascular smooth muscle cells triggered by Ang II, but also by other stimuli beyond the RAS. Activating or mimicking the Ang-(1-7)/Mas axis may represent a pharmacological opportunity to attenuate the pro-inflammatory environment that promotes and sustains the development of vascular diseases.