[Electroacupuncture preconditioning improves pulmonary function via inhibiting inflammatory response and up-regulating expression of ACE2 and Ang (1-7) in lipopolysaccharide-induced acute lung injury rats]

OBJECTIVE

To observe the effect of electroacupuncture (EA) at "Zusanli"(ST36) pretreatment on lung functions, inflammatory response, and levels of angiotensin-converting enzyme 2 (ACE2) and angiotensin (1-7) ［Ang (1-7)］ in rats with sepsis-induced acute lung injury (ALI), so as to explore its mechanisms underlying improvement of ALI.

METHODS

Thirty male SD rats were randomly divided into normal, model and EA groups (n=10 in each group). The sepsis-related ALI model was established by intraperitoneal injection of lipopolysaccharide (LPS, 5 mg/kg). Rats of the EA group received EA (4 Hz/20 Hz, 1-3 mA) stimulation at bilateral ST36 for 30 min, once each day, for 7 days before modeling. The lung functions including forced vital capacity (FVC), forced expiratory volume at 0.1 second (FEV0.1) and FEV0.3 were detected using a respiratory function detector for small animals at 3 h after modeling. The bronchoalveolar lavage fluid (BALF) was collected for assaying the contents of Ang (1-7), tumor necrosis factor-α (TNF-α) and interleukin-1 β (IL-1β) using ELISA. The lung wet/dry weight (W/D) ratio, FEV0.1/FVC, and FEV0.3/FVC were calculated. The histopathological changes of lung tissues were displayed by hematoxylin-eosin (H.E.) staining. The expression of ACE2 and mitochondrial assembly receptor (MasR) mRNAs and proteins in the lung tissue was detected by fluorescence quantitative real-time PCR and Western blot, separately.

RESULTS

Following modeling, the levels of FVC, FEV0.1, FEV0.3, ratio of FEV0.1/FVC and FEV0.3/FVC, content of Ang (1-7) in the BALF, and the expression levels of ACE2 and MasR mRNAs and proteins in the lung tissue were significantly decreased (P<0.01), while the level of W/D ratio and TNF-α and IL-1β contents in the BALF significantly increased (P<0.01) in the model group relevant to the normal group. In comparison with the model group, the levels of FVC, FEV0.1, FEV0.3, ratio of FEV0.1/FVC and FEV0.3/FVC, content of Ang (1-7) in the BALF, and expression levels of ACE2 and MasR mRNAs and proteins in the lung tissue were significantly increased (P<0.05, P<0.01), whereas the level of W/D ratio, and TNF-α and IL-1β contents in the BALF were significantly decreased (P<0.05, P<0.01) in the EA group. H.E. staining showed pulmonary interstitial edema and alveolar septum thickening with severe inflammatory cell infiltration in the model group, which was relatively milder in the EA group.

CONCLUSION

EA preconditioning at ST36 can improve pulmonary function in sepsis-related ALI rats, which may be related to its effects in inhibiting inflammatory response and up-regulating ACE2 and MasR expression and Ang (1-7) content in the lung tissue.

The physiologic and physiopathologic roles of perivascular adipose tissue and its interactions with blood vessels and the renin-angiotensin system

The perivascular adipose tissue (PVAT) refers to an ectopic local deposit of connective tissue that anatomically surrounds most of the blood vessels. While it was initially known only as a structural support for vasculature, the landmark findings of Soltis and Cassis (1991), first demonstrating that PVAT reduces the contractions of norepinephrine in the isolated rat aorta, brought the potential vascular role of PVAT into the limelight. This seminal work implied the potential ability of PVAT to influence vascular responsiveness. Several vasoactive/vasocrine substances influencing vascular homeostasis were successively shown to be released from PVAT that include both adipocyte-derived relaxing and contracting factors. The PVAT is currently recognized as a metabolically active endocrine organ and is eventually considered as the 'protagonist' in vascular homeostasis. It plays prominent defending and opposing roles in vascular function, while the actual vascular influences of PVAT vary with an increase in adiposity. Recent studies have presented compelling evidence implicating the pivotal role of PVAT in the local activation of the renin-angiotensin system (RAS), which substantially impacts vascular physiology and physiopathology. Current findings have advanced our understanding of the role of PVAT in favorably or adversely modulating the vascular function through differential RAS activation. Given that adipocytes also produce major RAS components locally to influence vascular function, this review provides a scientific basis to distinctly understand the key role of PVAT in regulating the autocrine and paracrine functions of vascular RAS components and its potential as an emerging therapeutic target for mitigating cardiovascular complications.

Angiotensin (1-7) Inhibits Ang II-mediated ERK1/2 Activation by Stimulating MKP-1 Activation in Vascular Smooth Muscle Cells

The renin–angiotensin system (RAS) exerts profound physiological effects on blood pressure regulation and fluid homeostasis, mainly by modulating renal, cardiovascular, and central nervous systems. Angiotensin (Ang)-(1-7), an end-product of RAS, is recognized by its cardiovascular protective properties through stimulation of the Mas receptor, including vasodilation, anti-inflammatory, and antihypertensive actions, and consequently, counter-regulating the well-known Ang II-elicited actions. The overall hypothesis of this study is that Ang-(1-7) inhibits Ang II-induced ERK1/2 activation in vascular smooth muscle cells (VSMCs), via regulation of mitogen-activated protein phosphatase-1 (MKP-1) activity. Aortas from male Wistar rats were incubated with Ang-(1-7) or vehicle. Concentration-response curves to Ang II were performed in endothelium-denuded aortas, in the presence or absence of ERK1/2 (PD98059) inhibitor or Mas receptor (A-779) antagonist. Expression of proteins was assessed by western blot, and immunohistochemistry was conducted in VSMCs. Ang-(1-7) incubation decreased Ang II-induced contractile response in aortas, and this effect was not observed in the presence of PD98059 or A-779. Stimulation of VSMCs with Ang-(1-7) prevented Ang II-induced ERK1/2 phosphorylation, but not C-Raf-activation. Furthermore, Ang II decreased MKP-1 phosphorylation in VSMCs. Interestingly, simultaneous incubation of Ang-(1-7) with Ang II favored MKP-1 phosphorylation, negatively modulating ERK1/2 activation in VSMCs. The results suggest that Ang-(1-7) counter-regulates actions evoked by Ang II overproduction, as observed in cardiovascular diseases, mainly by modulating MKP-1 activity. This evidence suggests that the role of Ang-(1-7) in MKP-1-regulation represents a target for new therapeutic development.

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.

Angiotensin-(1-7) receptor Mas antagonist (A779) influenced gliosis and reduced synaptic density in the spinal cord after peripheral axotomy

The peptide angiotensin-(1-7) [Ang (1-7)] and its receptor Mas are involved in controlling arterial pressure and display actions on the nervous system. In a previous study, our laboratory showed that A779 [(peptidyl antagonist of the Ang-(1-7)] treatment had a negative effect following a lesion of the sciatic nerve, possibly by delaying the responses of Schwann cells, resulting in a decreased axonal organization along with a slowed functional return. In the present work, we investigated the central cellular changes after sciatic nerve injury in rodents treated with A779 after two weeks. In the lumbar spinal cords, where the neuronal bodies that make up the sciatic are, the treatment with A779 showed reduced reactivity of astrocytes (p = 0.004, Mann-Whitney U test) and less synaptic density (p = 0.004, Mann-Whitney U test) after injury. Also, the treatment upregulated microglia activity in both sides (p = 0.004, Mann-Whitney U test), ipsilateral and contralateral to the lesion, of the spinal cord. In addition, the Mas expression in spine neurons was increased in response to axotomy especially after two weeks (p = 0.03, Mann-Whitney U test) following the nerve lesion in comparison to earlier stages after injury. Therefore, we can conclude that Ang-(1-7)/Mas axis plays a role during spinal cord recovery after peripheral nerve injury.

Downregulation of spinal angiotensin converting enzyme 2 is involved in neuropathic pain associated with type 2 diabetes mellitus in mice

We have previously reported that the spinal angiotensin (Ang) system is involved in the modulation of streptozotocin (STZ)-induced diabetic neuropathic pain in mice. An important drawback of this model however is the fact that the neuropathic pain is independent of hyperglycemia and produced by the direct stimulation of peripheral nerves. Here, using the leptin deficient ob/ob mouse as a type 2 diabetic model, we examined whether the spinal Ang system was involved in naturally occuring diabetic neuropathic pain. Blood glucose levels were increased in ob/ob mice at 5-15 weeks of age. Following the hyperglycemia, persistent tactile and thermal hyperalgesia were observed at 11-14 and 9-15 weeks of age, respectively, which was ameliorated by insulin treatment. At 12 weeks of age, the expression of Ang-converting enzyme (ACE) 2 in the spinal plasma membrane fraction was decreased in ob/ob mice. Spinal ACE2 was expressed in neurons and microglia but the number of NeuN-positive neurons was decreased in ob/ob mice. In addition, the intrathecal administration of Ang (1-7) and SB203580, a p38 MAPK inhibitor, attenuated hyperalgesia in ob/ob mice. The phosphorylation of spinal p38 MAPK was also attenuated by Ang (1-7) in ob/ob mice. These inhibitory effects of Ang (1-7) were prevented by A779, a Mas receptor antagonist. In conclusion, we revealed that the Ang (1-7)-generating system is downregulated in ob/ob mice and is accompanied by a loss of ACE2-positive neurons. Furthermore, Ang (1-7) decreased the diabetic neuropathic pain through inhibition of p38 MAPK phosphorylation via spinal Mas receptors.

Novel Variants of Angiotensin Converting Enzyme-2 of Shorter Molecular Size to Target the Kidney Renin Angiotensin System

ACE2 is a monocarboxypeptidase which generates Angiotensin (1-7) from Angiotensin II (1-8). Attempts to target the kidney Renin Angiotensin System using native ACE2 to treat kidney disease are hampered by its large molecular size, 100 kDa, which precludes its glomerular filtration and subsequent tubular uptake. Here, we show that both urine and kidney lysates are capable of digesting native ACE2 into shorter proteins of ~60-75 kDa and then demonstrate that they are enzymatically very active. We then truncated the native ACE2 by design from the C-terminus to generate two short recombinant (r)ACE2 variants (1-605 and 1-619AA). These two truncates have a molecular size of ~70 kDa, as expected from the amino acid sequence and as shown by Western blot. ACE2 enzyme activity, measured using a specific substrate, was higher than that of the native rACE2 (1-740 AA). When infused to mice with genetic ACE2 deficiency, a single i.v. injection of 1-619 resulted in detectable ACE2 activity in urine, whereas infusion of the native ACE2 did not. Moreover, ACE2 activity was recovered in harvested kidneys from ACE2-deficient mice infused with 1-619, but not in controls (23.1 ± 4.3 RFU/µg creatinine/h and 1.96 ± 0.73 RFU/µg protein/hr, respectively). In addition, the kidneys of ACE2-null mice infused with 1-619 studied ex vivo formed more Ang (1-7) from exogenous Ang II than those infused with vehicle (AUC 8555 ± 1933 vs. 3439 ± 753 ng/mL, respectively, p < 0.05) further demonstrating the functional effect of increasing kidney ACE2 activity after the infusion of our short ACE2 1-619 variant. We conclude that our novel short recombinant ACE2 variants undergo glomerular filtration, which is associated with kidney uptake of enzymatically active proteins that can enhance the formation of Ang (1-7) from Ang II. These small ACE2 variants may offer a potentially useful approach to target kidney RAS overactivity to combat kidney injury.

A potential role of the renin-angiotensin-aldosterone system in epithelial-to-mesenchymal transition-induced renal abnormalities: Mechanisms and therapeutic implications

Epithelial-to-mesenchymal transition (EMT) is an orchestrated event where epithelial cells progressively undergo biochemical changes and transition into mesenchymal-like cells by gradually losing their epithelial characteristics. EMT plays a crucial pathologic role in renal abnormalities, especially renal fibrosis. A number of bench studies suggest the potential involvement of renin-angiotensin-aldosterone system (RAAS) in renal EMT process and associated renal abnormalities. EMT appears to be an important pathologic mechanism for the deleterious renal effects of angiotensin II and aldosterone, the two major RAAS components. Mechanistically, the renal RAAS-TGF-β-Smad3 signalling pathway plays an important pathologic role in EMT-associated renal abnormalities. Intriguingly, the RAAS antagonists such as losartan, telmisartan, eplerenone, and spironolactone have the potential to prevent renal EMT in bench studies. This review describes the key mechanistic role of RAAS overactivation in EMT-induced renal abnormalities. Moreover, drugs interrupting the RAAS at different levels in the cascade ameliorating the EMT-associated renal abnormalities are described.

Angiotensin (1-7) does not interact directly with MAS1, but can potently antagonize signaling from the AT1 receptor

Angiotensin (1-7) has been reported to be a ligand for the GPCR MAS1. Small molecule MAS1 modulators have also been recently characterized. Aside from convincing evidence for MAS1 activation of Gq signaling, little is known about MAS1 mediated signaling pathways initiated by these ligands, especially Ang (1-7). We performed a comprehensive characterization of recombinant MAS1 signaling induced by Ang (1-7) and small molecule ligands through numerous G protein-dependent and independent pathways, and in a signaling pathway agnostic approach. We find that small molecule ligands modulate numerous G protein-dependent and independent pathways through MAS1, including Gq and Gi pathways, GTPγS binding, β-arrestin recruitment, Erk1/2 and Akt phosphorylation, arachidonic acid release, and receptor internalization. Moreover, in dynamic mass redistribution (DMR) assays that provide a pathway-agnostic readout of cellular responses, small molecule agonists produced robust responses. In contrast, Ang (1-7) failed to induce or block signaling in any of these assay platforms. We detected specific binding of radiolabeled Ang (1-7) to rat aortic endothelial cell (RAEC) membranes, but not to recombinant MAS1. Biphasic, concentration-dependent biased signaling responses to Ang II were detected in RAEC. These phases were associated with vastly different DMR characteristics and this likely provides a molecular basis for previously observed concentration-dependent divergent physiological actions of Ang II. Both phases of Ang II signaling in RAECs were potently inhibited by Ang (1-7), providing a plausible molecular mechanism for Ang (1-7) as counter regulator of the Ang II- AT1 axis, responsible at least in part for Ang (1-7) physiological activities.

Inhibitory effect of angiotensin (1-7) on angiotensin III-induced nociceptive behaviour in mice

We have previously demonstrated that the intrathecal (i.t.) administration of angiotensin (Ang) II into mice produces a nociceptive behaviour consisting of scratching, biting and licking accompanied by the phosphorylation of p38 MAPK in the spinal cord, which was mediated through AT1 receptors. Both the p38 MAPK phosphorylation and subsequent nociceptive behaviour were attenuated by the i.t. co-administration of Ang (1-7), an N-terminal fragment of Ang II, that acted via Mas receptors. On the other hand, a C-terminal fragment of Ang II, namely Ang III, was also shown to induce a nociceptive behaviour by acting upon AT1 receptors on spinal astrocytes and neurons, and was found to be more potent than Ang II. However, the inhibitory effect of Ang (1-7) on the Ang III-induced nociceptive behaviour remains unclear. Thus, here we examined whether Ang (1-7) can attenuate the Ang III-induced nociceptive behaviour and activation of spinal p38 MAPK. The i.t. administration of Ang (1-7) (1-100fmol) dose-dependently attenuated the Ang III (1pmol)-induced nociceptive behaviour in mice. Moreover, the inhibitory effect of Ang (1-7) at a dose of 100fmol was prevented by A779 (30fmol), a Mas receptor antagonist. Western blot analysis showed that the phosphorylation of p38 MAPK induced by the i.t. administration of Ang III (1pmol) was also attenuated by Ang (1-7) (100fmol), and this inhibition was prevented by A779 (30fmol). Furthermore, we showed that in the lumbar superficial dorsal horn, Mas receptors are expressed in neurons and microglia but absent from astrocytes. Together, these results suggest that the i.t. administration of Ang (1-7) attenuates the nociceptive behaviour and accompanying p38 MAPK phosphorylation induced by Ang III, and that this effect is likely mediated through Mas receptors on spinal neurons.

Many Faces of Renin-angiotensin System - Focus on Eye

The renin-angiotensin system (RAS), that is known for its role in the regulation of blood pressure as well as in fluid and electrolyte homeostasis, comprises dozens of angiotensin peptides and peptidases and at least six receptors. Six central components constitute the two main axes of the RAS cascade. Angiotensin (1-7), an angiotensin converting enzyme 2 and Mas receptor axis (ACE2-Ang(1-7)-MasR) counterbalances the harmful effects of the angiotensin II, angiotensin converting enzyme 1 and angiotensin II type 1 receptor axis (ACE1-AngII-AT1R) Whereas systemic RAS is an important factor in blood pressure regulation, tissue-specific regulatory system, responsible for long term regional changes, that has been found in various organs. In other words, RAS is not only endocrine but also complicated autocrine system. The human eye has its own intraocular RAS that is present e.g. in the structures involved in aqueous humor dynamics. Local RAS may thus be a target in the development of new anti-glaucomatous drugs. In this review, we first describe the systemic RAS cascade and then the local ocular RAS especially in the anterior part of the eye.

Angiotensin (1-7) and Alamandine: Similarities and differences

A primary peptide of the renin angiotensin system (RAS), Angiotensin (Ang) II, is a vasoconstrictor and promotor of atherosclerosis. To counter this, the RAS also consists of peptides and receptors which increase nitric oxide release from the endothelium and decrease nicotinamide adenine dinucleotide phosphate oxidase-related superoxide production. Two peptides, Ang (1-7) and alamandine are vasodilators, by activating the nitric oxide pathway via different receptors in the endothelium. Thus, herein we focus on the similarities and differences between alamandine and Ang (1-7) and the counterbalancing hypothesis on Ang II during endothelial dysfunction and atherosclerosis.

Therapeutic uses for Angiotensin-(1-7)

INTRODUCTION

Angiotensin-(1-7) is a key component of the Renin-Angiotensin System, which can counter-regulate several deleterious effects caused by angiotensin II. Due to the potential for therapeutic use, several of its actions are specifically described in patents.

AREAS COVERED

In this review, the authors describe a plethora of therapeutic uses for Angiotensin-(1-7), claimed and supported by experimental evidence in patent documents and applications.

EXPERT OPINION

The clinical potential of Angiotensin-(1-7) as a therapeutic agent to treat several pathologies is evidenced by the variety of patents and clinical trials involving this peptide. Cancer treatment is one of the most advanced therapeutic areas, but clinical studies are also available in several other areas, such as cardiovascular, hematological, transplantation, surgical and medical procedures.

Long-term administration of angiotensin (1-7) prevents heart and lung dysfunction in a mouse model of type 2 diabetes (db/db) by reducing oxidative stress, inflammation and pathological remodeling

Congestive heart failure is one of the most prevalent and deadly complications of type 2 diabetes that is frequently associated with pulmonary dysfunction. Among many factors that contribute to development and progression of diabetic complications is angiotensin II (Ang2). Activation of pathological arm of renin-angiotensin system results in increased levels of Ang2 and signaling through angiotensin type 1 receptor. This pathway is well recognized for its role in induction of oxidative stress (OS), inflammation, hypertrophy and fibrosis. Angiotensin (1-7) [A(1-7)], through activation of Mas receptor, opposes the actions of Ang2 which can result in the amelioration of diabetic complications; enhancing the overall welfare of diabetic patients. In this study, 8 week-old db/db mice were administered A(1-7) daily via subcutaneous injections. After 16 weeks of treatment, echocardiographic assessment of heart function demonstrated significant improvement in cardiac output, stroke volume and shortening fraction in diabetic animals. A(1-7) also prevented cardiomyocyte hypertrophy, apoptosis, lipid accumulation, and decreased diabetes-induced fibrosis and OS in the heart tissue. Treatment with A(1-7) reduced levels of circulating proinflammatory cytokines that contribute to the low grade inflammation observed in diabetes. In addition, lung pathologies associated with type 2 diabetes, including fibrosis and congestion, were decreased with treatment. OS and macrophage infiltration were also reduced in the lungs after treatment with A(1-7). Long-term administration of A(1-7) to db/db mice is effective in improving heart and lung function in db/db mice. Treatment prevented pathological remodeling of the tissues and reduced OS, fibrosis and inflammation.

Ocular renin-angiotensin system with special reference in the anterior part of the eye

The renin-angiotensin system (RAS) regulates blood pressure (BP) homeostasis, systemic fluid volume and electrolyte balance. The RAS cascade includes over twenty peptidases, close to twenty angiotensin peptides and at least six receptors. Out of these, angiotensin II, angiotensin converting enzyme 1 and angiotensin II type 1 receptor (AngII-ACE1-AT1R) together with angiotensin (1-7), angiotensin converting enzyme 2 and Mas receptor (Ang(1-7)-ACE2-MasR) are regarded as the main components of RAS. In addition to circulating RAS, local RA-system exists in various organs. Local RA-systems are regarded as tissue-specific regulatory systems accounting for local effects and long term changes in different organs. Many of the central components such as the two main axes of RAS: AngII-ACE1-AT1R and Ang(1-7)-ACE2-MasR, have been identified in the human eye. Furthermore, it has been shown that systemic antihypertensive RAS- inhibiting medications lower intraocular pressure (IOP). These findings suggest the crucial role of RAS not only in the regulation of BP but also in the regulation of IOP, and RAS potentially plays a role in the development of glaucoma and antiglaucomatous drugs.

Angiotensin(1-7) and ACE2, "The Hot Spots" of Renin-Angiotensin System, Detected in the Human Aqueous Humor

Background:

The main purpose of the study was to establish whether essential components of the renin-angiotensin system (RAS) exist in the human aqueous humor.

Methods:

Forty-five patients ≥ 60 (74±7) years of age undergoing cataract surgery at Tampere University Hospital were randomly selected for the prospective study. The exclusion criterion was the use of oral antihypertensive medicine acting via renin-angiotensin system. Aqueous humor samples were taken at the beginning of normal cataract extraction. The samples were frozen and stored at -80 °C. The concentrations of intraocular endogenous RAS components Ang(1-7), ACE2, and ACE1 were measured using ELISA.

Results:

Concentration medians of Ang(1-7), ACE2, and ACE1 in the aqueous humor were: Ang(1-7) 4.08 ng/ml, ACE2 2.32 ng/ml and ACE1 0.35 ng/ml. The concentrations were significantly higher in glaucomatous than in non-glaucomatous eyes, ACE1 (p=0.014) and Ang(1-7) (p=0.026) vs non-glaucomatous eyes.

Conclusions:

Ang(1-7), ACE2 and ACE1 are found in the human aqueous humor. The observations are consistent with the conception that local tissue-RAS exists in the human eye and it might have a role in the control of intraocular pressure.

Regulation of insulin sensitivity, insulin production, and pancreatic β cell survival by angiotensin-(1-7) in a rat model of streptozotocin-induced diabetes mellitus

The aim of this study is to determine the antidiabetic activity of Ang-(1-7), an important component of the renin-angiotensin system, in a rat model of streptozotocin (STZ)-induced type 2 diabetes mellitus (DM). A total of 36 male Wistar rats were randomly divided into 3 groups: control group fed standard laboratory diet, DM group fed high-fat diet and injected with STZ, and Ang-(1-7) group receiving injection of STZ followed by Ang-(1-7) treatment. Body weight, blood glucose levels, fasting serum Ang II and insulin levels, and homeostasis model assessment of insulin resistance (HOMA-IR) were measured. The pancreas was collected for histological examination and gene expression analysis. Notably, the Ang-(1-7) group showed a significant decrease in fasting blood glucose and serum Ang II levels and HOMA-IR values and increase in fasting serum insulin levels. Pancreatic β cells in the control and Ang-(1-7) groups were normally distributed in the center of pancreatic islets with large clear nuclei. In contrast, pancreatic β cells in the DM group had a marked shrinkage of the cytoplasm and condensation of nuclear chromatin. Ang-(1-7) treatment significantly facilitated insulin production by β cells in diabetic rats. The DM-associated elevation of inducible nitric oxide synthase (iNOS), caspase-3, caspase-9, caspase-8, and Bax and reduction of Bcl-2 was significantly reversed by Ang-(1-7) treatment. Taken together, Ang-(1-7) protects against STZ-induced DM through improvement of insulin resistance, insulin secretion, and pancreatic β cell survival, which is associated with reduction of iNOS expression and alteration of the Bcl-2 family.

Angiotensin (1-7) increases the potassium current and the resting potential of arterial myocytes from vascular resistance vessels of normal adult rats: Pathophysiological implications

The influence of angiotensin (Ang) (1-7) on potassium current (Kv) and resting potential of smooth muscle cells isolated from mesenteric artery of Sprague Dawley rats was investigated. Measurements of potassium current were performed using the whole cell configuration of pCLAMP. The results indicated that Ang (1-7) (10(-9) M) increased the potassium current by 120% ± 2.6% (P < .05) and the resting potential of smooth muscle cells by 8 ± 2.8 mV (n = 23; P < .05). Ang II (10(-9) M) administered to the bath reduced the potassium current by 35% ± 3.6% (n = 23; P < .05) and depolarized the arterial myocytes by 7.8 ± 2.1 mV (n = 25; P < .05). The effect of the heptapeptide on potassium current was inhibited by a Mas receptor inhibitor (A779; 10(-8) M) as well as by a protein kinase A (PKA) inhibitor (10(-9) M) dialyzed into the cell. Intracellular dialysis of the catalytic subunit of PKA (5 × 10(-8) M) enhanced the potassium current by 38% ± 3.4% (n = 14; P < .05) but did not abolish the effect of Ang (1-7). On the other hand, Bis-1 (10(-9) M), which is a specific inhibitor of PKC, suppressed the effect of Ang (1-7) on potassium current. In conclusion, Ang (1-7) counteracts the effect of Ang II on potassium current and membrane potential of smooth muscle cells from mesenteric arteries, which are resistance vessels involved in the regulation of peripheral resistance and blood pressure. The activation of the cAMP/PKA cascade is essential for the effect of the heptapeptide. Pathophysiological implications are discussed.