The renin-<em>angiotensin</em> system (RAS) plays a major role in regulating electrolyte balance and blood pressure. RAS has also been implicated in the regulation of inflammation, proliferation and fibrosis in pulmonary diseases such as asthma, acute lung injury (ALI), chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF) and pulmonary arterial hypertension (PAH). Current therapeutics suffer from some drawbacks like steroid resistance, limited efficacies and side effects. Novel intervention is definitely needed to offer optimal therapeutic strategy and clinical outcome. This review compiles and analyses recent investigations targeting RAS for the treatment of inflammatory lung diseases. Inhibition of the upstream <em>angiotensin</em> (Ang) I/Ang II/<em>angiotensin</em> receptor type <em>1</em> (AT<em>1</em>R) pathway and activation of the downstream <em>angiotensin</em>-converting enzyme 2 (ACE2)/Ang (<em>1</em>-<em>7</em>)/Mas receptor pathway are two feasible strategies demonstrating efficacies in various pulmonary disease models. More recent studies favor the development of targeting the downstream ACE2/Ang (<em>1</em>-<em>7</em>)/Mas receptor pathway, in which diminazene aceturate, an ACE2 activator, GSK258688<em>1</em>, a recombinant ACE2, and AV099<em>1</em>, a Mas receptor agonist, showed much potential for further development. As the pathogenesis of pulmonary diseases is so complex that RAS modulation may be used alone or in combination with existing drugs like corticosteroids, pirfenidone/nintedanib or endothelin receptor antagonists for different pulmonary diseases. Personalized medicine through genetic screening and phenotyping for <em>angiotensin</em>ogen or ACE would aid treatment especially for non-responsive patients. This review serves to provide an update on the latest development in the field of RAS targeting for pulmonary diseases, and offer some insights into future direction.

CHF (chronic heart failure) is a multifactorial disease process that is characterized by overactivation of the RAAS (renin-<em>angiotensin</em>-aldosterone system) and the sympathetic nervous system. Both of these systems are chronically activated in CHF. The RAAS consists of an excitatory arm involving AngII (<em>angiotensin</em> II), ACE (<em>angiotensin</em>-converting enzyme) and the AT<em>1</em>R (AngII type <em>1</em> receptor). The RAAS also consists of a protective arm consisting of Ang-(<em>1</em>-<em>7</em>) [<em>angiotensin</em>-(<em>1</em>-<em>7</em>)], the AT2R (AngII type 2 receptor), ACE2 and the Mas receptor. Sympatho-excitation in CHF is driven, in large part, by an imbalance of these two arms, with an increase in the AngII/AT<em>1</em>R/ACE arm and a decrease in the AT2R/ACE2 arm. This imbalance is manifested in cardiovascular-control regions of the brain such as the rostral ventrolateral medulla and paraventricular nucleus in the hypothalamus. The present review focuses on the current literature that describes the components of these two arms of the RAAS and their imbalance in the CHF state. Moreover, the present review provides additional evidence for the relevance of ACE2 and Ang-(<em>1</em>-<em>7</em>) as key players in the regulation of central sympathetic outflow in CHF. Finally, we also examine the effects of exercise training as a therapeutic strategy and the molecular mechanisms at play in CHF, in part, because of the ability of exercise training to restore the balance of the RAAS axis and sympathetic outflow.

The Mas-related G protein-coupled receptors (Mrgprs or Mas-related genes) comprise a subfamily of receptors named after the first discovered member, Mas. For most Mrgprs, pruriception seems to be the major function based on the following observations: <em>1</em>) they are relatively promiscuous in their ligand specificity with best affinities for itch-inducing substances; 2) they are expressed in sensory neurons and mast cells in the skin, the main cellular components of pruriception; and 3) they appear in evolution first in tetrapods, which have arms and legs necessary for scratching to remove parasites or other noxious substances from the skin before they create harm. Because parasites coevolved with hosts, each species faced different parasitic challenges, which may explain another striking observation, the multiple independent duplication and expansion events of Mrgpr genes in different species as a consequence of parallel adaptive evolution. Their predominant expression in dorsal root ganglia anticipates additional functions of Mrgprs in nociception. Some Mrgprs have endogenous ligands, such as β-alanine, alamandine, adenine, RF-amide peptides, or salusin-β. However, because the functions of these agonists are still elusive, the physiologic role of the respective Mrgprs needs to be clarified. The best studied Mrgpr is Mas itself. It was shown to be a receptor for <em>angiotensin</em>-<em>1</em>-<em>7</em> and to exert mainly protective actions in cardiovascular and metabolic diseases. This review summarizes the current knowledge about Mrgprs, their evolution, their ligands, their possible physiologic functions, and their therapeutic potential.

<em>Angiotensin</em>-(<em>1</em>-<em>7</em>) is an endogenous, biologically active peptide of the renin-<em>angiotensin</em> system with vasodilatory, antithrombotic, and antiproliferative properties. This study examined the effects of <em>angiotensin</em>-(<em>1</em>-<em>7</em>) infusion on neointimal formation after stent placement in the rat. Male Wistar rats underwent stent implantation in the abdominal aorta or sham surgery. Subsequently, an osmotic minipump was placed for <em>angiotensin</em>-(<em>1</em>-<em>7</em>) (24 microg/kg per hour) or saline administration. After 4 weeks, histomorphometric and histological analyses were performed, and the endothelial function was measured in isolated thoracic aortic rings. Stent implantation resulted in equal mean injury scores within the groups. The <em>angiotensin</em>-(<em>1</em>-<em>7</em>)-treated group displayed a significant reduction in neointimal thickness (<em>1</em><em>1</em>2+/-8 versus <em>1</em>4<em>1</em>+/-<em>1</em><em>1</em> microm; P<0.05), neointimal area (0.5<em>1</em>+/-0.05 versus 0.<em>7</em>0+/-0.0<em>7</em> mm2; P<0.05), and percentage stenosis (<em>1</em>0.4+/-<em>1</em>.0 versus <em>1</em>4.0+/-<em>1</em>.3%; P<0.05) compared with the saline-treated group. Furthermore, <em>angiotensin</em>-(<em>1</em>-<em>7</em>) infusion attenuated the stenting-induced impairment in endothelium-dependent relaxation (42.6+/-3.0 versus 64.5+/-6.0% of phenylephrine maximal contraction; P<0.00<em>1</em>). In conclusion, <em>angiotensin</em>-(<em>1</em>-<em>7</em>) treatment attenuates neointimal formation after stent implantation in the rat, combined with an improvement of endothelial function.

<em>Angiotensin</em>-converting enzyme 2 (ACE2) is a monocarboxypeptidase that degrades <em>angiotensin</em> II with high efficiency leading to the formation of <em>angiotensin</em>-(<em>1</em>-<em>7</em>). ACE2 within the kidneys is largely localized in tubular epithelial cells and in glomerular epithelial cells. Decreased glomerular expression of this enzyme coupled with increased expression of ACE has been described in diabetic kidney disease, both in mice and humans with type 2 diabetes. Moreover, both ACE2 genetic ablation and pharmacological ACE2 inhibition have been shown to increase albuminuria and promote glomerular injury. Studies using recombinant ACE2 have shown the ability of ACE2 to rapidly metabolize Ang II in vivo and form the basis for future studies to examine the potential of ACE2 amplification in the therapy of diabetic kidney disease and cardiovascular disease.

OBJECTIVE

To provide scientific evidence supporting the efficacy of forest bathing as a natural therapy for human hypertension.

METHODS

Twenty-four elderly patients with essential hypertension were randomly divided into two groups of <em>1</em>2. One group was sent to a broad-leaved evergreen forest to experience a <em>7</em>-day/<em>7</em>-night trip, and the other was sent to a city area in Hangzhou for control. Blood pressure indicators, cardiovascular disease-related pathological factors including endothelin-<em>1</em>, homocysteine, renin, <em>angiotensin</em>ogen, <em>angiotensin</em> II, <em>angiotensin</em> II type <em>1</em> receptor, <em>angiotensin</em> II type 2 receptor as well as inflammatory cytokines interleukin-6 and tumor necrosis factor α were detected. Meanwhile, profile of mood states (POMS) evaluation was used to assess the change of mood state of subjects. In addition, the air quality in the two experimental sites was monitored during the <em>7</em>-day duration, simultaneously.

RESULTS

The baselines of the indicators of the subjects were not significantly different. Little alteration in the detected indicators in the city group was observed after the experiment. While subjects exposed to the forest environment showed a significant reduction in blood pressure in comparison to that of the city group. The values for the bio-indicators in subjects exposed to the forest environment were also lower than those in the urban control group and the baseline levels of themselves. POMS evaluation showed that the scores in the negative subscales were lowered after exposure to the forest environment. Besides, the air quality in the forest environment was much better than that of the urban area evidenced by the quantitative detection of negative ions and PM<em>1</em>0 (particulate matter < <em>1</em>0 μm in aerodynamic diameter).

CONCLUSIONS

Our results provided direct evidence that forest bathing has therapeutic effects on human hypertension and induces inhibition of the renin-angiotensin system and inflammation, and thus inspiring its preventive efficacy against cardiovascular disorders.

In <em>angiotensin</em> type <em>1</em> receptor-blocked rats, renal interstitial (RI) administration of des-aspartyl(<em>1</em>)-<em>angiotensin</em> II (Ang III) but not <em>angiotensin</em> II induces natriuresis via activation of <em>angiotensin</em> type 2 receptors. In the present study, renal function was documented during systemic <em>angiotensin</em> type <em>1</em> receptor blockade with candesartan in Sprague-Dawley rats receiving unilateral RI infusion of Ang III. Ang III increased urine sodium excretion, fractional sodium, and lithium excretion. RI coinfusion of specific <em>angiotensin</em> type 2 receptor antagonist PD-<em>1</em>233<em>1</em>9 abolished Ang III-induced natriuresis. The natriuretic response observed with RI Ang III was not reproducible with RI <em>angiotensin</em> (<em>1</em>-<em>7</em>) alone or together with <em>angiotensin</em>-converting enzyme inhibition. Similarly, neither RI <em>angiotensin</em> II alone or in the presence of aminopeptidase A inhibitor increased urine sodium excretion. In the absence of systemic <em>angiotensin</em> type <em>1</em> receptor blockade, Ang III alone did not increase urine sodium excretion, but natriuresis was enabled by the coinfusion of aminopeptidase N inhibitor and subsequently blocked by PD-<em>1</em>233<em>1</em>9. In <em>angiotensin</em> type <em>1</em> receptor-blocked rats, RI administration of aminopeptidase N inhibitor alone also induced natriuresis that was abolished by PD-<em>1</em>233<em>1</em>9. Ang III-induced natriuresis was accompanied by increased RI cGMP levels and was abolished by inhibition of soluble guanylyl cyclase. RI and renal tissue Ang III levels increased in response to Ang III infusion and were augmented by aminopeptidase N inhibition. These data demonstrate that endogenous intrarenal Ang III but not <em>angiotensin</em> II or <em>angiotensin</em> (<em>1</em>-<em>7</em>) induces natriuresis via activation of <em>angiotensin</em> type 2 receptors in the proximal tubule via a cGMP-dependent mechanism and suggest aminopeptidase N inhibition as a potential therapeutic target in hypertension.

OBJECTIVE

Diastolic dysfunction that determines symptoms and prognosis in patients with systolic dysfunction causes heart failure even in the absence of systolic dysfunction. Our recent studies have suggested that myocardial stiffening is likely to play a crucial role in triggering deleterious cardiac disorder. This study investigated differential contribution of left ventricular (LV) hypertrophy and fibrosis to myocardial stiffening in the pressure-overloaded heart.

METHODS

Dahl-Iwai salt-sensitive rats fed on high-salt diet since <em>7</em> weeks transit to congestive heart failure at 20 weeks following development of hypertension, LV hypertrophy and fibrosis, and 20 such rats were divided into three groups: rats treated with <em>angiotensin</em> II type <em>1</em> receptor antagonist from 8 weeks (n=<em>7</em>), rats treated with calcineurin inhibitor from 8 weeks (n=6), and untreated rats (n=<em>7</em>).

RESULTS

Administration of <em>angiotensin</em> II type <em>1</em> receptor antagonist and calcineurin inhibitor did not affect blood pressure and allowed the development of compensatory hypertrophy. However, in contrast to the untreated rats, additive and excessive LV hypertrophy was not observed in either of the treated rats. The blockade of <em>angiotensin</em> II kept LV hydroxyproline content, a ratio of type I to type III collagen mRNA levels, collagen solubility and myocardial stiffness constant at the normal level; however, the calcineurin inhibition failed.

CONCLUSIONS

Myocardial stiffening may be attributed to progressive collagen accumulation, collagen phenotype shift and enhanced collagen cross-linking, but not to either compensatory LV hypertrophy or LV hypertrophy that progresses from the compensatory stage.

It has been previously shown that besides its classical role in blood pressure control the renin-<em>angiotensin</em> system, mainly by action of <em>angiotensin</em> II on the AT(<em>1</em>) receptor, exerts pro-inflammatory effects such as by inducing the production of cytokines. More recently, alternative pathways to this system were described, such as binding of <em>angiotensin</em>-(<em>1</em>-<em>7</em>) to receptor Mas, which was shown to counteract some of the effects evoked by activation of the <em>angiotensin</em> II-AT(<em>1</em>) receptor axis. Here, by means of different molecular approaches we investigated the role of <em>angiotensin</em>-(<em>1</em>-<em>7</em>) in modulating inflammatory responses triggered in mouse peritoneal macrophages. Our results show that receptor Mas transcripts were up-regulated by eightfold in LPS-induced macrophages. Interestingly, macrophage stimulation with <em>angiotensin</em>-(<em>1</em>-<em>7</em>), following to LPS exposure, evoked an attenuation in expression of TNF-α and IL-6 pro-inflammatory cytokines; where this event was abolished when the receptor Mas selective antagonist A<em>7</em><em>7</em>9 was also included. We then used heterologous expression of the receptor Mas in HEK293T cells to search for the molecular mechanisms underlying the <em>angiotensin</em>-(<em>1</em>-<em>7</em>)-mediated anti-inflammatory responses by a kinase array; what suggested the involvement of the Src kinase family. In LPS-induced macrophages, this finding was corroborated using the PP2 compound, a specific Src kinase inhibitor; and also by Western blotting when we observed that Ang-(<em>1</em>-<em>7</em>) attenuated the phosphorylation levels of Lyn, a member of the Src kinase family. Our findings bring evidence for an anti-inflammatory role for <em>angiotensin</em>-(<em>1</em>-<em>7</em>) at the cellular level, as well as show that its probable mechanism of action includes the modulation of Src kinases activities.

BACKGROUND

The prevalence of diabetes is increasing in young adults in Asia, but little is known about metabolic control or the burden of associated complications in this population. We assessed the prevalence of young-onset versus late-onset type 2 diabetes, and associated risk factors and complication burdens, in the Joint Asia Diabetes Evaluation (JADE) cohort.

METHODS

JADE is an ongoing prospective cohort study. We enrolled adults with type 2 diabetes from 245 outpatient clinics in nine Asian countries or regions. We classified patients as having young-onset diabetes if they were diagnosed before the age of 40 years, and as having late-onset diabetes if they were diagnosed at 40 years or older. Data for participants' first JADE assessment was extracted for cross-sectional analysis. We compared clinical characteristics, metabolic risk factors, and the prevalence of complications between participants with young-onset diabetes and late-onset diabetes.

RESULTS

Between Nov <em>1</em>, 200<em>7</em>, and Dec 2<em>1</em>, 20<em>1</em>2, we enrolled 4<em>1</em>,029 patients (<em>1</em>5,34<em>1</em> from Hong Kong, 9<em>1</em>0<em>7</em> from India, <em>7</em><em>7</em><em>1</em>2 from Philippines, 5646 from China, <em>1</em><em>7</em>5<em>1</em> from South Korea, <em>7</em>05 from Vietnam, 385 from Singapore, 2<em>7</em>5 from Thailand, <em>1</em>0<em>7</em> from Taiwan). <em>7</em>48<em>1</em> patients (<em>1</em>8%) had young-onset diabetes, with age at diagnosis of mean 32·9 years [SD 5·<em>7</em>] versus 53·9 years [9·0] with late-onset diabetes (n=33,548). Those with young-onset diabetes had longer disease duration (median <em>1</em>0 years [IQR 3-<em>1</em>8]) than those with late-onset diabetes (5 years [2-<em>1</em><em>1</em>]). Fewer patients with young-onset diabetes achieved HbA<em>1</em>c concentrations lower than <em>7</em>% compared to those with late-onset diabetes (2<em>7</em>% vs 42%; p<0·000<em>1</em>) Patients with young-onset diabetes had higher mean concentrations of HbA<em>1</em>c (mean 8·32% [SD 2·03] vs <em>7</em>·69% [<em>1</em>·82]; p<0·000<em>1</em>), LDL cholesterol (2·<em>7</em>8 mmol/L [0·96] vs 2·<em>7</em>4 [0·93]; p=0·009), and a higher prevalence of retinopathy (<em>1</em>363 [20%] vs 5<em>7</em><em>1</em>4 (<em>1</em>8%); p=0·0<em>1</em><em>1</em>) than those with late-onset diabetes, but were less likely to receive statins (234<em>7</em> [3<em>1</em>%] vs <em>1</em>2,44<em>1</em> [3<em>7</em>%]; p<0·000<em>1</em>) and renin-<em>angiotensin</em>-system inhibitors (<em>1</em>868 [25%] vs 9665 [29%]; p=0·006).

CONCLUSIONS

In clinic-based settings across Asia, one in five adult patients had young-onset diabetes. Compared with patients with late-onset diabetes, metabolic control in those with young-onset diabetes was poor, and fewer received organ-protective drugs. Given the risk conferred by long-term suboptimum metabolic control, our findings suggest an impending epidemic of young-onset diabetic complications.

BACKGROUND

The Asia Diabetes Foundation (ADF) and Merck.

The <em>angiotensin</em> type 2 receptor (AT2R) and the receptor Mas are components of the protective arms of the renin-<em>angiotensin</em> system (RAS), i.e. they both mediate tissue protective and regenerative actions. The spectrum of actions of these two receptors and their signalling mechanisms display striking similarities. Moreover, in some instances, antagonists for one receptor are able to inhibit the action of agonists for the respective other receptor. These observations suggest that there may be a functional or even physical interaction of both receptors. This article discusses potential mechanisms underlying the phenomenon of blockade of <em>angiotensin</em>-(<em>1</em>-<em>7</em>) [Ang-(<em>1</em>-<em>7</em>)] actions by AT2R antagonists and vice versa. Such mechanisms may comprise dimerization of the receptors or dimerization-independent mechanisms such as lack of specificity of the receptor ligands used in the experiments or involvement of the Ang-(<em>1</em>-<em>7</em>) metabolite alamandine and its receptor MrgD in the observed effects. We conclude that evidence for a functional interaction of both receptors is strong, but that such an interaction may be species- and/or tissue-specific and that elucidation of the precise nature of the interaction is only at the very beginning.

ACE type 2 (ACE2) functions as a negative regulator of the renin-<em>angiotensin</em> system by cleaving <em>angiotensin</em> II (AII) into <em>angiotensin</em> <em>1</em>-<em>7</em> (A<em>1</em>-<em>7</em>). This study assessed the role of endogenous ACE2 in maintaining insulin sensitivity. Twelve-week-old male ACE2 knockout (ACE2KO) mice had normal insulin sensitivities when fed a standard diet. AII infusion or a high-fat, high-sucrose (HFHS) diet impaired glucose tolerance and insulin sensitivity more severely in ACE2KO mice than in their wild-type (WT) littermates. The strain difference in glucose tolerance was not eliminated by an AII receptor type <em>1</em> (AT<em>1</em>) blocker but was eradicated by A<em>1</em>-<em>7</em> or an AT<em>1</em> blocker combined with the A<em>1</em>-<em>7</em> inhibitor (A<em>7</em><em>7</em>9). The expression of GLUT4 and a transcriptional factor, myocyte enhancer factor (MEF) 2A, was dramatically reduced in the skeletal muscles of the standard diet-fed ACE2KO mice. The expression of GLUT4 and MEF2A was increased by A<em>1</em>-<em>7</em> in ACE2KO mice and decreased by A<em>7</em><em>7</em>9 in WT mice. A<em>1</em>-<em>7</em> enhanced upregulation of MEF2A and GLUT4 during differentiation of myoblast cells. In conclusion, ACE2 protects against high-calorie diet-induced insulin resistance in mice. This mechanism may involve the transcriptional regulation of GLUT4 via an A<em>1</em>-<em>7</em>-dependent pathway.

<em>Angiotensin</em>-converting enzyme-2 (ACE2) is the first human homologue of ACE to be described. ACE2 is a type I integral membrane protein which functions as a carboxypeptidase, cleaving a single hydrophobic/basic residue from the C-terminus of its substrates. ACE2 efficiently hydrolyses the potent vasoconstrictor <em>angiotensin</em> II to <em>angiotensin</em> (<em>1</em>-<em>7</em>). It is a consequence of this action that ACE2 participates in the renin-<em>angiotensin</em> system. However, ACE2 also hydrolyses dynorphin A (<em>1</em>-<em>1</em>3), apelin-<em>1</em>3 and des-Arg(9) bradykinin. The role of ACE2 in these peptide systems has yet to be revealed. A physiological role for ACE2 has been implicated in hypertension, cardiac function, heart function and diabetes, and as a receptor of the severe acute respiratory syndrome coronavirus. This paper reviews the biochemistry of ACE2 and discusses key findings such as the elucidation of crystal structures for ACE2 and testicular ACE and the development of ACE2 inhibitors that have now provided a basis for future research on this enzyme.

The present study was designed to quantitate the role of the renin-<em>angiotensin</em> system (RAS) in determining the chronic relationships between arterial pressure (AP), renal hemodynamics, and Na excretion. In six control dogs, Na balance was achieved during chronic step increases in Na intake from 5 to 500 meq/day with small increases in AP ((<em>7</em> mmHg), moderate increases in GFR (<em>1</em>9%), and decreases in filtration fraction (FF) and plasma renin activity. Similar increases in Na intake in six dogs with <em>angiotensin</em> II (AII) fixed, due to constant intravenous infusion of 5 ng . kg-<em>1</em> . min-<em>1</em> AII, caused large increases in AP (42%), GFR (3<em>1</em>%) FF, and calculated renal Na reabsorption (TNa) above control. In six dogs with AII formation blocked with SQ <em>1</em>4,225, Na balance at intakes of 5-80 meq/day occurred at reduced AP, GFR, FF, and TNa, although plasma aldosterone concentration (PAC) was not substantially different from that in control dogs. At Na intakes above 240 meq/day, AP was not altered by SQ <em>1</em>4,225. These data indicate that during chronic changes in Na intake the RAS plays a major role, independent of changes in PAC, in allowing Na balance without large changes in GFR or AP. The mechanism whereby AII conserves Na chronically is through increased TNa, since steady-state TNa was increased by AII and decreased by SQ <em>1</em>4,225.

Saliva and salivary gland homogenates of Ixodes scapularis contain a dipeptidyl carboxypeptidase activity that accounts for the previously described salivary kininase activity of this tick. Reversed phase HPLC and laser desorption mass spectrography of the reaction products identified bradykinin fragment <em>1</em>-<em>7</em> and <em>1</em>-5 as being produced subsequent to incubation of purified salivary kininase with bradykinin. The activity was inhibited by captopril and EDTA and was activated by cobalt and manganese, a behavior similar to that displayed by <em>angiotensin</em>-converting enzymes of vertebrate and invertebrate origins.

Obesity is an independent risk factor for the development and progression of chronic kidney disease and one of the emerging reasons for end-stage renal disease owing to its dramatic increase worldwide. Among the potential underlying pathophysiologic mechanisms, activation of the renin-<em>angiotensin</em>-aldosterone-system (RAAS) plays a central role. Increased <em>angiotensin</em> II (AngII) levels also are central in hypertension, dyslipidemia, and insulin resistance, which, taken together with obesity, represent the metabolic syndrome. Increased AngII levels contribute to hyperfiltration, glomerulomegaly, and subsequent focal glomerulosclerosis by altering renal hemodynamics via afferent arteriolar dilation, together with efferent renal arteriolar vasoconstriction as well as by its endocrine and paracrine properties linking the intrarenal and the systemic RAAS, adipose tissue dysfunction, as well as insulin resistance and hypertension. The imbalance between increased AngII levels and the <em>angiotensin</em> converting enzyme 2/Ang (<em>1</em>-<em>7</em>)/Mas receptor axis additionally contributes to renal injury in obesity and its concomitant metabolic disturbances. As shown in several large trials and experimental studies, treatment of obesity by weight loss is associated with an improvement of kidney disease because it also is beneficial in dyslipidemia, hypertension, and diabetes. The most promising data have been seen by RAAS blockade, pointing to the central position of RAAS within obesity, kidney disease, and the metabolic syndrome.

The discovery that SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus 2) RNA binds to the <em>angiotensin</em> converting enzyme (ACE)-2, which is highly expressed in the lower airways, explained why SARS-CoV-2 causes acute respiratory distress syndrome (ARDS) and respiratory failure. After this, news spread that ACEis and ARBs would be harmful in SARS-CoV-2-infected subjects. To the contrary, compelling evidence exists that the ACE-<em>1</em>/<em>angiotensin</em>(Ang)II/ATR-<em>1</em> pathway is involved in SARS-CoV-2-induced ARDS, while the ACE-2/Ang(<em>1</em>-<em>7</em>)/ATR2/MasR pathway counteracts the harmful actions of AngII in the lung. A reduced ACE-<em>1</em>/ACE-2 ratio is, in fact, a feature of ARDS that can be rescued by human recombinant ACE-2 and Ang(<em>1</em>-<em>7</em>) administration, thus preventing SARS-CoV-2-induced damage to the lung. Based on the current clinical evidence treatment with ACE-inhibitors I (ACEis) or <em>angiotensin</em> receptor blockers (ARBs) continues to provide cardiovascular and renal protection in patients diagnosed with COVID-<em>1</em>9. Discontinuing these medications may therefore be potentially harmful in this patient population.

The Canadian Cardiovascular Society Guidelines Committee and key Canadian opinion leaders believed there was a need for up to date guidelines that used the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system of evidence assessment for patients who undergo noncardiac surgery. Strong recommendations included: <em>1</em>) measuring brain natriuretic peptide (BNP) or N-terminal fragment of proBNP (NT-proBNP) before surgery to enhance perioperative cardiac risk estimation in patients who are 65 years of age or older, are 45-64 years of age with significant cardiovascular disease, or have a Revised Cardiac Risk Index score ≥ <em>1</em>; 2) against performing preoperative resting echocardiography, coronary computed tomography angiography, exercise or cardiopulmonary exercise testing, or pharmacological stress echocardiography or radionuclide imaging to enhance perioperative cardiac risk estimation; 3) against the initiation or continuation of acetylsalicylic acid for the prevention of perioperative cardiac events, except in patients with a recent coronary artery stent or who will undergo carotid endarterectomy; 4) against α2 agonist or β-blocker initiation within 24 hours before surgery; 5) withholding <em>angiotensin</em>-converting enzyme inhibitor and <em>angiotensin</em> II receptor blocker starting 24 hours before surgery; 6) facilitating smoking cessation before surgery; <em>7</em>) measuring daily troponin for 48 to <em>7</em>2 hours after surgery in patients with an elevated NT-proBNP/BNP measurement before surgery or if there is no NT-proBNP/BNP measurement before surgery, in those who have a Revised Cardiac Risk Index score ≥<em>1</em>, age 45-64 years with significant cardiovascular disease, or age 65 years or older; and 8) initiating of long-term acetylsalicylic acid and statin therapy in patients who suffer myocardial injury/infarction after surgery.

<em>Angiotensin</em>-converting enzyme 2 (ACE2), a homologue of <em>angiotensin</em>-converting enzyme (ACE), converts <em>angiotensin</em> (Ang) I to Ang(<em>1</em>-9) and Ang II to Ang(<em>1</em>-<em>7</em>), but does not directly process Ang I to Ang II. Cardiac function is compromised in ACE2 null mice; however, the importance of ACE2 in the processing of <em>angiotensin</em> peptides within the murine heart is not known. We determined the metabolism of <em>angiotensins</em> in wild-type (WT), ACE (ACE(-/-)) and ACE2 null mice (ACE2(-/-)). <em>Angiotensin</em> II was converted almost exclusively to Ang(<em>1</em>-<em>7</em>) in the cardiac membranes of WT and ACE(-/-) strains, although generation of Ang(<em>1</em>-<em>7</em>) was greater in the ACE(-/-) mice (2<em>7</em>.4 +/- 4.<em>1</em> versus <em>1</em><em>7</em>.5 +/- 3.2 nmol(-<em>1</em>) mg h(-<em>1</em>) for WT). The ACE2 inhibitor MLN4<em>7</em>60 significantly attenuated Ang II metabolism and the subsequent formation of Ang(<em>1</em>-<em>7</em>) in both strains. In the ACE2(-/-) hearts, Ang II metabolism and the generation of Ang(<em>1</em>-<em>7</em>) were significantly attenuated; however, the ACE2 inhibitor reduced the residual Ang(<em>1</em>-<em>7</em>)-forming activity in this strain. <em>Angiotensin</em> I was primarily converted to Ang(<em>1</em>-9) (WT, 28.9 +/- 3.<em>1</em> nmol(-<em>1</em>) mg h(-<em>1</em>); ACE(-/-), 49.8 +/- 5.3 nmol(-<em>1</em>) mg h(-<em>1</em>); and ACE2(-/-), 35.9 +/- 5.4 nmol(-<em>1</em>) mg h(-<em>1</em>)) and to smaller quantities of Ang(<em>1</em>-<em>7</em>) and Ang II. Although the ACE2 inhibitor had no effect on Ang(<em>1</em>-9) formation, the carboxypeptidase A inhibitor benzylsuccinate essentially abolished the formation of Ang(<em>1</em>-9) and increased the levels of Ang I in cardiac membranes. In conclusion, our studies in the murine heart suggest that ACE2 is the primary pathway for the metabolism of Ang II and the subsequent formation of Ang(<em>1</em>-<em>7</em>), a peptide that, in contrast to Ang II, exhibits both antifibrotic and antiproliferative actions.

<em>1</em>. We investigated the response to pressure (myogenic tone) and flow of rat mesenteric resistance arteries cannulated in an arteriograph which allowed the measurement of intraluminal diameter for controlled pressures and flows. Rats were treated for 3 weeks with NG-nitro-L-arginine methyl ester (L-NAME, 50 mg kg-<em>1</em> day-<em>1</em>) or L-NAME plus the <em>angiotensin</em> I converting enzyme inhibitor (ACEI) quinapril (<em>1</em>0 mg kg-<em>1</em> day-<em>1</em>). 2. Mean blood pressure increased significantly in chronic L-NAME-treated rats (<em>1</em>55 +/- 4 mmHg, n = 8, vs control <em>1</em>2<em>1</em> +/- 6 mmHg, n = <em>1</em>0; P < 0.05). L-NAME-treated rats excreted significantly more dinor-6-keto prostaglandin F<em>1</em> alpha (dinor-6-keto PGF<em>1</em> alpha), the stable urinary metabolite of prostacyclin, than control rats. The ACEI prevented the rise in blood pressure and the rise in urinary dinor-6-keto PGF<em>1</em> alpha due to L-NAME. 3. Isolated mesenteric resistance arteries, developed myogenic tone in response to stepwise increases in pressure (42 +/- 6 to 84<em>7</em> +/- <em>1</em>0 mN mm-<em>1</em>, from 25 to <em>1</em>50 mmHg, n = 9). Myogenic tone was not significantly affected by the chronic treatment with L-NAME or L-NAME + ACEI. 4. Flow (<em>1</em>00 microliters min-<em>1</em>) significantly attenuated myogenic tone by 50 +/- 6% at <em>1</em>50 mmHg (n = <em>1</em>0). Flow-induced dilatation was significantly attenuated by chronic L-NAME to 22 +/- 6% at <em>1</em>50 mmHg (n = <em>1</em>0, p = 0.000<em>1</em>) and was not affected in the L-NAME + ACEI group. 5. Acute in vitro NG-nitro-L-arginine (L-NOARG, <em>1</em>0 microM) significantly decreased flow-induced dilation in control but not in L-NAME or L-NAME + ACEI rats. Both acute indomethacin (<em>1</em>0 microM) and acute NS 398 (cyclo-oxygenase-2 (COX-2) inhibitor, <em>1</em> microM) did not change significantly flow-induced dilatation in controls but they both decreased flow-induced dilatation in the L-NAME and L-NAME + ACEI groups. Acute Hoe <em>1</em>40 (bradykinin receptor inhibitor, <em>1</em> microM) induced a significant contraction of the isolated mesenteric arteries which was the same in the 3 groups. 6. Immunofluorescence analysis of COX-2 showed that the enzyme was expressed in resistance mesenteric arteries in L-NAME and L-NAME + ACEI groups but not in control. COX-<em>1</em> expression was identical in all 3 groups. <em>7</em>. We conclude that chronic inhibition of nitric oxide synthesis is associated with a decreased flow-induced dilatation in resistance mesenteric arteries which was compensated by an overproduction of vasodilator prostaglandins resulting in part from COX-2 expression. The decrease in flow-induced dilatation was prevented by the ACEI, quinapril.

Several lines of evidence show the importance of <em>angiotensin</em> II (AII) in renal injuries, especially when hemodynamic abnormalities are involved. To elucidate the role of AII in immune-mediated renal injury, we studied anti-glomerular basement membrane (GBM) nephritis in AII type <em>1</em>a receptor (AT<em>1</em>a)-deficient homozygous (AT<em>1</em>a-/-) and wild-type (AT<em>1</em>a+/+) mice. A transient activation of the renin-<em>angiotensin</em> system (RAS) was observed in both groups of mice at around day <em>1</em>. A renal expression of monocyte chemoattractant protein-<em>1</em> (MCP-<em>1</em>) was transiently induced at six hours in both groups, which was then downregulated at day <em>1</em>. In the AT<em>1</em>a+/+ mice, after RAS activation, the glomerular expression of MCP-<em>1</em> was exacerbated at days <em>7</em> and <em>1</em>4. Thereafter, severe proteinuria developed, and the renal expressions of transforming growth factor-beta<em>1</em> (TGF-beta<em>1</em>) and collagen type I increased, resulting in severe glomerulosclerosis and interstitial fibrosis. In contrast, glomerular expression of MCP-<em>1</em>, proteinuria, and tissue damage were markedly ameliorated in the AT<em>1</em>a-/- mice. Because this amelioration is likely due to the lack of AT<em>1</em>a, we can conclude that AII action, mediated by AT<em>1</em>a, plays a pathogenic role in anti-GBM nephritis, in which AII may contribute to the exacerbation of glomerular MCP-<em>1</em> expression. These results suggest the involvement of AII in immune-mediated renal injuries.

Dexamethasone and prednisone in physiologic range increased <em>angiotensin</em> converting enzyme <em>7</em>- to <em>1</em>6-fold in comparison to control in 3 days at maximal stimulation (4 nM steroid) in rabbit alveolar macrophages in culture. The increase was inhibited by actinomycin D (0.<em>1</em> microng/ml) and <em>1</em> micronM cycloheximide, suggesting that de novo transcription and enzyme synthesis are responsible for the increased enzyme activity. This result is evidence for a regulatory mechanism for <em>angiotensin</em> converting enzyme, which is important in blood pressure control.

Tubulogenesis by epithelial cells regulates kidney, lung, and mammary development, whereas that by endothelial cells regulates vascular development. Although functionally dissimilar, the processes necessary for tubulation by epithelial and endothelial cells are very similar. We performed microarray analysis to further our understanding of tubulogenesis and observed a robust induction of regulator of G protein signaling 4 (RGS4) mRNA expression solely in tubulating cells, thereby implicating RGS4 as a potential regulator of tubulogenesis. Accordingly, RGS4 overexpression delayed and altered lung epithelial cell tubulation by selectively inhibiting G protein-mediated p38 MAPK activation, and, consequently, by reducing epithelial cell proliferation, migration, and expression of vascular endothelial growth factor (VEGF). The tubulogenic defects imparted by RGS4 in epithelial cells, including its reduction in VEGF expression, were rescued by overexpression of constitutively active MKK6, an activator of p38 MAPK. Similarly, RGS4 overexpression abrogated endothelial cell angiogenic sprouting by inhibiting their synthesis of DNA and invasion through synthetic basement membranes. We further show that RGS4 expression antagonized VEGF stimulation of DNA synthesis and extracellular signal-regulated kinase (ERK)<em>1</em>/ERK2 and p38 MAPK activation as well as ERK<em>1</em>/ERK2 activation stimulated by endothelin-<em>1</em> and <em>angiotensin</em> II. RGS4 had no effect on the phosphorylation of Smad<em>1</em> and Smad2 by bone morphogenic protein-<em>7</em> and transforming growth factor-beta, respectively, indicating that RGS4 selectively inhibits G protein and VEGF signaling in endothelial cells. Finally, we found that RGS4 reduced endothelial cell response to VEGF by decreasing VEGF receptor-2 (KDR) expression. We therefore propose RGS4 as a novel antagonist of epithelial and endothelial cell tubulogenesis that selectively antagonizes intracellular signaling by G proteins and VEGF, thereby inhibiting cell proliferation, migration, and invasion, and VEGF and KDR expression.

-Recent studies have indicated that <em>angiotensin</em> II (Ang II) can stimulate oxidative stress. The present study was conducted to assess the contribution of oxygen radicals to hypertension and regional circulation during Ang II-induced hypertension. With radioactive microspheres, the responses of systemic and regional hemodynamics to the membrane-permeable, metal-independent superoxide dismutase mimetic 4-hydroxy-2,2,6,6-tetramethyl piperidinoxyl (tempol) were assessed in conscious Ang II-infused hypertensive rats. Ang II-infused rats (80 ng/min SC for <em>1</em>2 days: n=25) showed higher mean arterial pressure (MAP: <em>1</em>6<em>1</em>+/-4 mm Hg) and total peripheral resistance (TPR: <em>1</em>.59+/-0.08 mm Hg. min(-<em>1</em>). mL(-<em>1</em>)) than vehicle-infused normotensive rats (<em>1</em><em>1</em>6+/-3 mm Hg and 0.95+/-0.04 mm Hg. min(-<em>1</em>). mL(-<em>1</em>), respectively; n=23). The blood flow rates in the brain, spleen, large intestine, and skin were significantly reduced in Ang II-infused rats compared with vehicle-infused rats, whereas rates in the lung, heart, liver, kidney, stomach, small intestine, mesenterium, skeletal muscle, and testis were similar. Vascular resistance was significantly increased in every organ studied except the lung, in which the resistance was similar. Tempol (2<em>1</em>6 µmol/kg IV) significantly reduced MAP by 30+/-4% from <em>1</em>58+/-<em>7</em> to <em>1</em><em>1</em>4+/-5 mm Hg and TPR by 35+/-6% from <em>1</em>.5<em>7</em>+/-0.<em>1</em><em>7</em> to 0.95+/-0.04 mm Hg. min(-<em>1</em>). g(-<em>1</em>) in Ang II-infused rats (n=9) but had no effect on these parameters in vehicle-infused rats (n=8). In Ang II-infused rats, tempol did not affect regional blood flow but significantly decreased vascular resistance in the brain (29+/-6%), heart (3<em>1</em>+/-6%), liver (3<em>7</em>+/-<em>7</em>%), kidney (30+/-<em>7</em>%), small intestine (38+/-6%), and large intestine (4<em>7</em>+/-<em>7</em>%). Ang II-infused hypertensive rats showed doubled vascular superoxide production (assessed with lucigenin chemiluminescence), which was normalized by treatment with tempol (3 mmol/L, n=<em>7</em>). Further studies showed that the NO synthase inhibitor, N:(omega)-nitro-L-arginine methyl ester (<em>1</em><em>1</em> µmol. kg(-<em>1</em>). min(-<em>1</em>) IV, n=<em>1</em><em>1</em>) markedly attenuated the systemic and regional hemodynamic responses of tempol in Ang II-infused rats. These results suggest that in this model of hypertension, oxidative stress may have contributed to the alterations in systemic blood pressure and regional vascular resistance through inactivation of NO.