Angiotensin 1-7 in an experimental septic shock model

BACKGROUND

Alterations in the renin-angiotensin system have been implicated in the pathophysiology of septic shock. In particular, angiotensin 1-7 (Ang-(1-7)), an anti-inflammatory heptapeptide, has been hypothesized to have beneficial effects. The aim of the present study was to test the effects of Ang-(1-7) infusion on the development and severity of septic shock.

METHODS

This randomized, open-label, controlled study was performed in 14 anesthetized and mechanically ventilated sheep. Immediately after sepsis induction by bacterial peritonitis, animals received either Ang-(1-7) (n = 7) or placebo (n = 7) intravenously. Fluid resuscitation, antimicrobial therapy, and peritoneal lavage were initiated 4 h after sepsis induction. Norepinephrine administration was titrated to maintain mean arterial pressure (MAP) between 65 and 75 mmHg.

RESULTS

There were no differences in baseline characteristics between groups. Septic shock was prevented in 6 of the 7 animals in the Ang-(1-7) group at the end of the 24-h period. Fluid balance and MAP were similar in the two groups; however, MAP was achieved with a mean norepinephrine dose of 0.4 μg/kg/min in the Ang-(1-7) group compared to 4.3 μg/kg/min in the control group. Heart rate and cardiac output index were lower in the Ang (1-7) than in the control group, as were plasma interleukin-6 levels, and creatinine levels. Platelet count and PaO₂/FiO₂ ratio were higher in the Ang-(1-7) group. Mean arterial lactate at the end of the experiment was 1.6 mmol/L in the Ang-(1-7) group compared to 7.4 mmol/L in the control group.

CONCLUSIONS

In this experimental septic shock model, early Ang-(1-7) infusion prevented the development of septic shock, reduced norepinephrine requirements, limited interleukine-6 increase and prevented renal dysfunction.

Angiotensin-(1-7) ameliorates sepsis-induced cardiomyopathy by alleviating inflammatory response and mitochondrial damage through the NF-κB and MAPK pathways

BACKGROUND

There is no available viable treatment for Sepsis-Induced Cardiomyopathy (SIC), a common sepsis complication with a higher fatality risk. The septic patients showed an abnormal activation of the renin angiotensin (Ang) aldosterone system (RAAS). However, it is not known how the Ang II and Ang-(1-7) affect SIC.

METHODS

Peripheral plasma was collected from the Healthy Control (HC) and septic patients and Ang II and Ang-(1-7) protein concentrations were measured. The in vitro and in vivo models of SIC were developed using Lipopolysaccharide (LPS) to preliminarily explore the relationship between the SIC state, Ang II, and Ang-(1-7) levels, along with the protective function of exogenous Ang-(1-7) on SIC.

RESULTS

Peripheral plasma Ang II and the Ang II/Ang-(1-7) levels in SIC-affected patients were elevated compared to the levels in HC and non-SIC patients, however, the HC showed higher Ang-(1-7) levels. Furthermore, peripheral plasma Ang II, Ang II/Ang-(1-7), and Ang-(1-7) levels in SIC patients were significantly correlated with the degree of myocardial injury. Additionally, exogenous Ang-(1-7) can attenuate inflammatory response, reduce oxidative stress, maintain mitochondrial dynamics homeostasis, and alleviate mitochondrial structural and functional damage by inhibiting nuclear factor-kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways, thus alleviating SIC.

CONCLUSIONS

Plasma Ang-(1-7), Ang II, and Ang II/Ang-(1-7) levels were regarded as significant SIC biomarkers. In SIC, therapeutic targeting of RAAS, for example with Ang-(1-7), may exert protective roles against myocardial damage.

Renal angiotensin I-converting enzyme-deficient mice are protected against aristolochic acid nephropathy

The renal renin-angiotensin system (RAS) is involved in the development of chronic kidney disease. Here, we investigated whether mice with reduced renal angiotensin I-converting enzyme (ACE^-/-) are protected against aristolochic acid nephropathy (AAN). To further elucidate potential molecular mechanisms, we assessed the renal abundances of several major RAS components. AAN was induced using aristolochic acid I (AAI). Glomerular filtration rate (GFR) was determined using inulin clearance and renal protein abundances of renin, angiotensinogen, angiotensin I-converting enzyme (ACE) 2, and Mas receptor (Mas) were determined in ACE^-/- and C57BL/6J control mice by Western blot analyses. Renal ACE activity was determined using a colorimetric assay and renal angiotensin (Ang) (1-7) concentration was determined by ELISA. GFR was similar in vehicle-treated mice of both strains. AAI decreased GFR in controls but not in ACE^-/- mice. Furthermore, AAI decreased renal ACE activity in controls but not in ACE^-/- mice. Vehicle-treated ACE^-/- mice had significantly higher renal ACE2 and Mas protein abundances than controls. AAI decreased renal ACE2 protein abundance in both strains. Furthermore, AAI increased renal Mas protein abundance, although the latter effect did not reach statistical significance in the ACE^-/- mice. Renal Ang(1-7) concentration was similar in vehicle-treated mice of both strains. AAI increased renal Ang(1-7) concentration in the ACE^-/- mice but not in the controls. Mice with reduced renal ACE are protected against AAN. Our data suggest that in the face of renal ACE deficiency, AAI may activate the ACE2/Ang(1-7)/Mas axis, which in turn may deploy its reno-protective effects.

Demystifying the dual role of the angiotensin system in neuropathic pain

Neuropathic Pain is caused by damage to a nerve or disease of the somatosensory nervous system. Apart from the blood pressure regulating actions of angiotensin ligands, studies have shown that it also modulates neuropathic pain. In the animal models including surgical, chemotherapeutic, and retroviral-induced neuropathic pain, an increase in the levels of angiotensin II has been identified and it has been proposed that an increase in angiotensin II may participate in the induction of neuropathic pain. The pain-inducing actions of the angiotensin system are primarily due to the activation of AT₁ and AT₂ receptors, which trigger the diverse molecular mechanisms including the induction of neuroinflammation to initiate and maintain the state of neuropathic pain. On the other hand, the pain attenuating action of the angiotensin system has been attributed to decreasing in the levels of Ang_(1-7), and Ang IV and an increase in the levels of bradykinin. Ang_(1-7) may attenuate neuropathic pain via activation of the spinal Mas receptor. However, the detailed molecular mechanism involved in Ang_(1-7) and Ang IV-mediated pain attenuating actions needs to be explored. The present review discusses the dual role of angiotensin ligands in neuropathic pain along with the possible mechanisms involved in inducing or attenuating the state of neuropathic pain.

Unraveling the Differentially Articulated Axes of the Century-Old Renin-Angiotensin-Aldosterone System: Potential Therapeutic Implications

Among numerous choices in cardiovascular therapies used for the management of hypertension and heart failure, drugs affecting the renin-angiotensin-aldosterone system (RAAS) hold substantial therapeutic roles. Therapies aimed at modifying the RAAS and its overactivation are employed for the management of various insidious disorders. In the pharmacologic perspective, RAAS is one of the frequently manipulated systems for the management of hypertension, heart failure, myocardial infarction, and renal disease. The RAAS pharmacologic interventions principally include the ACE inhibitors, the angiotensin II-AT1 receptor blockers, the mineralocorticoid receptor antagonists, and the direct renin inhibitors. In addition, therapeutic implication of ACE2/angiotensin (1-7)/Mas receptor activation using various ligands is being explored owing to their anti-inflammatory, anti-fibrotic, vasodilatory, and cardiovascular defensive roles. Moreover, being considered as the counter-regulatory arm of AT1 receptor, the potential role of AT2 receptor activation using selective AT2 receptor agonist is currently investigated for its efficacy in pulmonary complications. As an important regulator of fluid volume, blood pressure, and cardiovascular-renal function, the RAAS has been documented as a diversified intricate system with several therapeutic possibilities coupled with their fundamental structural and functional modulatory roles in cardiovascular, renal, and other systems. The RAAS possesses a number of regulatory, deregulatory, and counter-regulatory axes of physiopathologic importance in health and disease. The counter-regulatory arms of the RAAS might play an essential role in mitigating cardiovascular, renal, and pulmonary pathologies. In light of this background, we sought to explore the classical and counter-regulatory axes/arms of the RAAS and their imperative roles in physiologic functions and disease pathogenesis.

Scorpion bradykinin potentiating factor mitigates lung damage induced by γ-irradiation in rats: Insights on AngII/ACE/Ang(1-7) axis

The goal of this research is to study the mitigating impact of bradykinin potentiating factor (BPF) found in scorpion Androctonus bicolor venom on irradiation-induced lung damage as a new functional target for angiotensin-converting enzyme inhibitors (ACEIs). Male rats were exposed to 7 Gy of γ-radiation as a single dose, with a biweekly intraperitoneal injection of 1 μg/g BPF. Gamma irradiation not only boosted the ACE activity and angiotensin II (Ang II) level, in lung tissue but also significantly depressed the angiotensin (1-7) (Ang (1-7)) that, lead to lung toxicity through a significant elevation of pulmonary levels of CXC-chemokine receptor 4 (CXCR4), toll-like receptor 4 (TLR4), nitric oxide (NO) and lactate dehydrogenase (LDH) activity with a marked disruption in oxidative stress markers, via a reduction in the level of total thiol (tSH) and superoxide dismutase (SOD) activity associated with an elevation in protein carbonyl (PCO) contents. In addition, apoptotic consequences of gamma irradiation were evidenced by raising the levels of mitogen-activated protein kinase (MAPK), C-Jun N-Terminal Kinases (JNK), and cleaved caspase-3. BPF administration leads to ACE inhibition, consequently sustaining decreased Ang II alongside increased Ang (1-7) production. Those sensitive molecules reduce irradiated lung issues. In conclusion, BPF significantly diminished the biochemical and histopathological consequences of radiation through renin-angiotensin system (RAS) control and ACE suppression in the lung.

Diminazene aceturate extenuate the renal deleterious consequences of angiotensin-II induced by γ-irradiation through boosting ACE2 signaling cascade

AIM

This work aims to explore the role of diminazene aceturate (DIZE) in the enhancement of angiotensin-converting enzyme-2 (ACE2) to prevent the inflammatory and fibrotic response induced by γ-irradiation through activating the protective axis ACE2/angiotensin (1-7)/Mas receptor (ACE2/Ang(1-7)/Mas).

METHODS

Male rats were injected i.p. with 15 mg/kg DIZE daily for 7 days pre and post-irradiation, where 7.5 Gy of γ-radiation as a single dose was used.

KEY FINDINGS

Gamma radiation induced a significant elevation of renal biochemical parameters: urea, creatinine and blood urea nitrogen (BUN) in serum with a significant disturbance in oxidative stress markers: elevation in malondialdehyde (MDA) associated with a depletion of reduced glutathione (GSH) and superoxide dismutase (SOD). Beside elevation in the level of angiotensin II (AngII) that lead to remarkably increases in the levels of the renal inflammatory mediators: tumor necrosis factor-α (TNF-α), nuclear factor kappa B (NF-κB) and interleukin-1β (IL-1β) as well as renal fibrogenic markers: transforming growth factor-β1 (TGF-β1), connective tissue growth factor (CTGF), and hydroxyproline content in the renal tissues. DIZE caused marked expansion in the expression of ACE2 consequently decreased the expression of AngII and increased the expression of Ang(1-7) which through its Mas receptor ameliorates the biochemical and histopathological damage induced by radiation.

SIGNIFICANCE

DIZE-induced stimulation of ACE2 subdues the renal deleterious consequences induced by γ-radiation via activation of ACE2/Ang(1-7)/Mas axis in rats.

Angiotensin (1-7) through modulation of the NMDAR-nNOS-NO pathway and serotonergic metabolism exerts an anxiolytic-like effect in rats

Although recent studies have shown that angiotensin (1-7) (Ang [1-7]) exerts anti-stress and anxiolytic-like effects, the underlying mechanisms remain elusive. The ventral hippocampus (VH) is proposed to be a critical brain region for mood and stress management through the N-methyl-d-aspartate receptor (NMDAR) signaling pathway. However, the role of VH NMDAR signaling in the effects of Ang (1-7) remains unclear. In the present study, Ang (1-7) was injected into the bilateral VH of stressed rats, or in combination with a Fyn kinase inhibitor, NMDAR antagonist, neuronal nitric oxide synthase (nNOS) inhibitor, or nitric oxide (NO) scavenger. Anxiety-like behaviors were assessed using the open field test and elevated plus maze test, while alterations in NMDAR-nNOS-NO signaling and serotonergic metabolism were examined in the VH. After 21 days of chronic restraint stress, anxiety-like behaviors were evident. Levels of phosphorylated NR2B (a key NMDAR subunit), its upstream kinase Fyn, as well as activity of nNOS and monoamine oxidase (MAO) were markedly reduced. In contrast, levels of serotonin were increased. Bilateral VH infusion of Ang (1-7) recovered NMDAR-nNOS-NO signaling and MAO-mediated serotonin metabolism, as well as reducing anxiety-like behaviors in stressed rats. These effects were diminished by blockade of MasR (Ang [1-7]-specific receptor), Fyn kinase, NMDAR, nNOS, or NO production. Altogether, these findings indicate that Ang (1-7) exerts anxiolytic effects through modulation of the NMDAR-nNOS-NO pathway and serotonergic metabolism. Future translational research should focus on the relationship between Ang (1-7), glutamatergic neurotransmission, and serotonergic neurotransmission in the VH.

Activation of the Protective Arm of the Renin Angiotensin System in Demyelinating Disease

The renin angiotensin system (RAS), which is classically known for blood pressure regulation, has functions beyond this. There are two axes of RAS that work to counterbalance each other and are active throughout the body, including the CNS. The pathological axis, consisting of angiotensin II (A1-8), angiotensin converting enzyme (ACE) and the angiotensin II type 1 receptor (AT1R), is upregulated in many CNS diseases, including multiple sclerosis (MS). MS is an autoimmune and neurodegenerative disease of the CNS characterized by inflammation, demyelination and axonal degeneration. Published research has described increased expression of AT1R and ACE in tissues from MS patients and in animal models of MS such as experimental autoimmune encephalomyelitis (EAE). In contrast to the pathological axis, little is known about the protective axes of RAS in MS and EAE. In other neurological conditions the protective axis, which includes A1-7, ACE2, angiotensin II type 2 receptor and Mas receptor, has been shown to have anti-inflammatory, regenerative and neuroprotective effects. Here we show, for the first time, changes in the protective arm of RAS in both EAE and MS CNS tissue. We observed a significant increase in expression of the protective arm during stages of disease stabilization in EAE, and in MS tissue showing evidence of remyelination. These data provide evidence that the protective arm of RAS, through both ligand and receptor expression, is associated with reductions in the pathological processes that occur in the earlier stages of MS and EAE, possibly slowing the neurodegenerative process and enhancing neural repair. Graphical Abstract.

The Expression of MAS1, an Angiotensin (1-7) Receptor, in the Eutopic Proliferative Endometria of Endometriosis Patients

BACKGROUND/AIM

We demonstrated that AT1 and AT2 are expressed and both pathways balance the renin-angiotensin system in endometriosis. MAS1, a specific receptor of angiotensin (1-7), opposes AT1 pathway-associated tissue remodelling. It is not known whether MAS1 has an effect on the pathogenesis of endometriosis or not.

MATERIALS AND METHODS

Ovarian endometriotic tissues (endo-Ov) and eutopic endometrial tissues (endo-Em) were obtained from 29 patients with endometrial cysts. Normal endometrial tissues (cont-Em) were obtained from patients without endometriosis. Immunohistochemical staining was performed for MAS1, AT1 and AT2 in the endometriosis-associated tissues. The mRNA levels of these receptors were examined by quantitative reverse transcription PCR.

RESULTS

MAS1 was immune-positive at the apical side of the glandular epithelium in the endometriotic lesions. The MAS1 mRNA levels in endo-Ov were increased significantly, irrespective of the menstrual cycle phase. The MAS1 mRNA levels were significantly higher in the proliferative-tissues of the endometriosis patients than in those of the controls. The ratio of the MAS1 to the AT1 mRNA in the proliferative tissues was increased predominantly in the endometriosis patients compared with that in the controls.

CONCLUSION

High MAS1 expression in the endometrium might promote the initiation of endometriosis via migration of proliferative tissue.

SGLT-2 inhibitors: Their pleiotropic properties

Type 2 diabetes mellitus has become a global pandemic. Nowadays, it is estimated that approximately 415 million people all over the world have diabetes. The sodium glucose co-transporters 2 inhibitors are a new class of glucose-lowering agents, which act through a novel mechanism by producing a decline in glucose re-absorption in the kidney, thereby increasing glycosuria and decreasing serum glucose levels. Data suggest that apart from lowering HbA1c, they produce a small but significant weight loss and a small decrease in blood pressure. Also, they possess nephro-protective potential. These drugs are demonstrated to restore intra-glomerular pressure by increasing angiotensin (1-7), which exerts vasodilatory and anti-inflammatory effects. Their profile on cardiovascular events is still under investigation. In this review, the pleiotropic potential of this novel class of glucose-lowering levels will be discussed. Further research is warranted to determine their safety in the long term.

Brain renin-angiotensin system in the pathophysiology of cardiovascular diseases

Cardiovascular diseases (CVD) are among the main causes of death globally and in this context hypertension represents one of the key risk factors for developing a CVD. It is well established that the peripheral renin-angiotensin system (RAS) plays an important role in regulating blood pressure (BP). All components of the classic RAS can also be found in the brain but, in contrast to the peripheral RAS, how the endogenous RAS is involved in modulating cardiovascular effects in the brain is not fully understood yet. It is a complex system that may work differently in diverse areas of the brain and is linked to the peripheral system by the circumventricular organs (CVO), which do not have a blood brain barrier (BBB). In this review, we focus on the brain angiotensin peptides, their interactions with each other, and the consequences in the central nervous system (CNS) concerning cardiovascular control. Additionally, we present potential drug targets in the brain RAS for the treatment of hypertension.

The vasoprotective axes of the renin-angiotensin system: Physiological relevance and therapeutic implications in cardiovascular, hypertensive and kidney diseases

The renin-angiotensin system (RAS) is undisputedly one of the most prominent endocrine (tissue-to-tissue), paracrine (cell-to-cell) and intracrine (intracellular/nuclear) vasoactive systems in the physiological regulation of neural, cardiovascular, blood pressure, and kidney function. The importance of the RAS in the development and pathogenesis of cardiovascular, hypertensive and kidney diseases has now been firmly established in clinical trials and practice using renin inhibitors, angiotensin-converting enzyme (ACE) inhibitors, type 1 (AT₁) angiotensin II (ANG II) receptor blockers (ARBs), or aldosterone receptor antagonists as major therapeutic drugs. The major mechanisms of actions for these RAS inhibitors or receptor blockers are mediated primarily by blocking the detrimental effects of the classic angiotensinogen/renin/ACE/ANG II/AT₁/aldosterone axis. However, the RAS has expanded from this classic axis to include several other complex biochemical and physiological axes, which are derived from the metabolism of this classic axis. Currently, at least five axes of the RAS have been described, with each having its key substrate, enzyme, effector peptide, receptor, and/or downstream signaling pathways. These include the classic angiotensinogen/renin/ACE/ANG II/AT₁ receptor, the ANG II/APA/ANG III/AT₂/NO/cGMP, the ANG I/ANG II/ACE2/ANG (1-7)/Mas receptor, the prorenin/renin/prorenin receptor (PRR or Atp6ap2)/MAP kinases ERK1/2/V-ATPase, and the ANG III/APN/ANG IV/IRAP/AT₄ receptor axes. Since the roles and therapeutic implications of the classic angiotensinogen/renin/ACE/ANG II/AT₁ receptor axis have been extensively reviewed, this article will focus primarily on reviewing the roles and therapeutic implications of the vasoprotective axes of the RAS in cardiovascular, hypertensive and kidney diseases.

Ang (1-7) is a modulator of the vasoconstrictor actions of Ang I and Ang II

INTRODUCTION

The role of angiotensin (Ang) (1-7) on the vasoconstrictor effect induced by angiotensins could be different in the presence of an ACE inhibitor or an ARB because Ang II is formed through several pathways. Therefore, the role of Ang (1-7) in Ang I and Ang II contraction was evaluated in aortas from Wistar rats after 48-hour coronary occlusion treated with captopril or losartan.

METHODS

Concentration-response curves to Ang I or Ang II were conducted in the absence or presence of Ang (1-7) and A779: a) sham group; b) 48-hour coronary occlusion; c) treated with captopril or d) losartan (3.1 mg/kg, i.m.).

RESULTS

Captopril caused a significant increase in the contractile effect of Ang I and Ang II, while losartan reduced it. The presence of Ang (1-7) in the captopril group showed a reduction of the contraction compared to the sham group, while the treatment with losartan did not show a significant difference. Ang (1-7) presents effects different from Ang I or Ang II.

CONCLUSION

Ang (1-7) showed a modulatory role, suggesting Ang I did as well after treatment with an ACE inhibitor but not with an AT1 receptor antagonist.

Angiotensin (1-7) counteracts the negative effect of angiotensin II on insulin signalling in HUVECs

AIMS

Angiotensin II participates to the regulation of cardiovascular physiology and it is involved in molecular mechanisms of insulin resistance. Angiotensin (1-7), derived from angiotensin II metabolism, is able to counteract many of the haemodynamic and non-haemodynamic actions of angiotensin II. In this study, we investigated in human umbilical vein endothelial cells (HUVECs) the possible action of angiotensin (1-7) on the insulin signalling pathway.

METHODS AND RESULTS

We stimulated HUVECs with insulin, angiotensin II and angiotensin (1-7), testing the effects on endothelial nitric oxide synthase (eNOS) enzyme activation and on insulin receptor substrate-1 (IRS1) phosphorylation. Moreover, we analysed the involvement of angiotensin type1, type2, and Mas receptors in these actions. Finally, we measured the nitric oxide (NO) production, the intracellular cGMP and the PKG-related activity in HUVECs, and the subsequent functional vasoactive effect of angiotensin (1-7) in mesenteric arteries of mice. Angiotensin II inhibits the insulin-induced Akt and eNOS phosphorylation, reducing the NO production. On the other hand, angiotensin (1-7) counteracts the inhibitory effect of angiotensin II, being able to restore the insulin-induced Akt/eNOS activation and the NO production. This effect is mediated by the Mas receptor. The inhibitory effects of angiotensin II on insulin signalling are, at least in part, mediated by an increased serine phosphorylation of IRS₁. Angiotensin (1-7) inhibits the serine phosphorylation of IRS1 induced by angiotensin II.

CONCLUSION

In endothelial cells angiotensin (1-7) counteracts the negative effects of angiotensin II on insulin signalling and NO production. The balance between angiotensin II and angiotensin (1-7) could represent a key mechanism in the pathophysiological processes leading to endothelial dysfunction and insulin-resistance.

Interactions of neuropeptide y, catecholamines, and angiotensin at the vascular neuroeffector junction

Work from our laboratory has established that angiotensin II (Ang II) produces a greater enhancement of the nerve stimulation (NS)-induced release (overflow) of both norepinephrine (NE) and neuropeptide Y (NPY) and a greater increase in perfusion pressure of the mesenteric arterial bed obtained from the spontaneously hypertensive rat (SHR) compared to age-matched Wistar-Kyoto (WKY) or Sprague-Dawley rats. The enhancement of NS-induced NPY release was blocked by the AT1 receptor antagonist EMD 66684 and the AT2 receptor antagonist PD 123319. Both captopril and EMD 66684 decreased NPY and NE overflow from SHR mesenteric beds, suggesting an endogenous renin-angiotensin system (RAS) is active in the mesenteric artery. We also observed that the recently discovered new arm of the RAS, namely, angiotensin (1-7) (Ang-(1-7)), attenuated the NS-induced increase in NE and NPY release and the accompanied increased perfusion pressure. These inhibitory effects were greater in blood vessels obtained from SHR compared to WKY. We suggest that inhibition of sympathetic neurotransmission contributes to the mechanism(s) by which Ang-(1-7) acts to inhibit the vasoconstrictor effect of Ang II. Administration of the MAS receptor antagonist D-Ala(7)Ang-(1-7) attenuated the decrease in both NE and NPY release due to Ang-(1-7) administration. The AT2 receptor antagonist PD 123391 attenuated the effect of Ang-(1-7) on NE release without affecting the decrease in NPY release. We observed a shift in the balance between Ang II and Ang-(1-7) levels in the SHR with an increase in Ang II and a decrease in Ang-(1-7) in the blood and mesenteric artery. This appears to be due to an increase in angiotensin-converting enzyme (ACE) in the mesenteric artery of the SHR.