Modulating Role of Ang1-7 in Control of Blood Pressure and Renal Function in AngII-infused Hypertensive Rats

Activation of Mas and pGCA receptor pathways protects renal epithelial cell damage against oxidative-stress-induced injury

Over-activation of the renin-angiotensin-aldosterone system (RAAS) is a leading cause of cardio-renal complications. Oxidative stress is one of the major contributing factors in the over-activation of RAAS. Angiotensin-converting enzyme2/Angiotensin1-7/MasR and natriuretic peptide/particulate guanylyl cyclase receptor-A pathways play a key role in cardiorenal disease protection. Even though individual activation of these pathways possesses cardiorenal protective effects. However, the dual activation of these pathways under stress conditions and the underlying mechanism has not been explored. The study aimed to investigate whether activation of these pathways by dual-acting peptide (DAP) shows a protective effect in-vitro in oxidative stress-induced renal epithelial cells. Oxidative stress was induced in renal epithelial NRK-52E cells with H₂O₂. Co-treatment with Ang 1-7, BNP, and DAP was given for 30 min. AT1, MasR, and pGCA expression were measured by RT-PCR. The markers of oxidative stress and apoptosis were measured by confocal microscopy and FACS analysis. A significant increase in AT1, renin, α-SMA, and NFk-β expression and a significant decrease in MasR and pGCA expression was observed in H₂O₂-induced cells. DAP improved H₂O₂-induced pathological changes in NRK-52E cells. The effect of DAP was superior to that of Ang1-7 and BNP alone. Interestingly, MasR and pGCA inhibitors could block the effect of DAP in H₂O₂-induced cells. DAP shows superior anti-RAAS activity, and it is effective against H₂O₂-induced oxidative stress, apoptosis, fibrosis, and inflammation compared to Ang1-7 and BNP alone. The protective effect is mediated by the dual activation of MasR and pGCA.

The mechanism of low-level arsenic exposure-induced hypertension: Inhibition of the activity of the angiotensin-converting enzyme 2

It is now well-established that arsenic exposure induces hypertension in humans. Although arsenic-induced hypertension is reported in many epidemiological studies, the underlying molecular mechanism of arsenic-induced hypertension is not fully characterized. In the human body, blood pressure is primarily regulated by a well-known physiological system known as the renin-angiotensin system (RAS). Hence, we explored the potential molecular mechanisms of arsenic-induced hypertension by investigating the regulatory roles of the RAS. Adult C57BL/6JJcl male mice were divided into four groups according to the concentration of arsenic in drinking water (0, 8, 80, and 800 ppb) provided for 8 weeks. Arsenic significantly raised blood pressure in arsenic-exposed mice compared to the control group, and significantly raised plasma MDA and Ang II and reduced Ang (1-7) levels. RT-PCR results showed that arsenic significantly downregulated ACE2 and MasR in mice aortas. In vitro studies of endothelial HUVEC cells treated with arsenic showed increased level of MDA and Ang II and lower levels of Ang (1-7), compared with the control. Arsenic significantly downregulated ACE2 and MasR expression, as well as those of Sp1 and SIRT1; transcriptional activators of ACE2, in HUVECs. Arsenic also upregulated markers of endothelial dysfunction (MCP-1, ICAM-1) and inflammatory cytokines (IL-6, TNF-α) in HUVECs. Our findings suggest that arsenic-induced hypertension is mediated, at least in part, by oxidative stress-mediated inhibition of ACE2 as well as by suppressing the vasoprotective axes of RAS, in addition to the activation of the classical axis.

Maladaptation of Renal Hemodynamics Contributes to Kidney Dysfunction Resulting from Thoracic Spinal Cord Injury in Mice

Renal dysfunction is a hallmark of spinal cord injury (SCI). Several SCI sequalae are implicated, however, the exact pathogenic mechanism of renal dysfunction is unclear. Herein, we found that T3 (T3Tx) or T10 (T10Tx) complete thoracic spinal cord transection induced hypotension, bradycardia, and hypothermia immediately after injury. T3Tx-induced hypotension but not bradycardia or hypothermia slowly recovered to levels in T10Tx SCI and uninjured mice ~16 h after injury as determined by continuous radiotelemetry monitoring. Both types of thoracic SCI led to a marked decrease in albuminuria and proteinuria in all phases of SCI, while the kidney injury marker, NGAL, rapidly increased in the acute phase, remaining elevated in the chronic phase of T3Tx SCI. Renal interstitial and vascular elastin fragmentation after SCI were worsened during chronic T3Tx SCI. In the chronic phase, renal vascular resistance response to a step increase in renal perfusion pressure or a bolus injection of Ang II or NE was almost completely abolished after T3Tx SCI. Bulk RNAseq analysis showed enrichment of genes involved in extracellular matrix (ECM) remodeling and chemokine signaling in the kidney from T3Tx SCI mice. Serum levels of interleukin 6 was elevated in the acute but not chronic phase of T3Tx and T10Tx SCI, while serum amyloid A1 level was elevated in both acute and chronic phases. We conclude that tissue fibrosis and hemodynamic impairment are involved in renal dysfunction resulting from thoracic SCI; these pathological alterations, exacerbated by high thoracic-level injury, is mediated at least partly by renal microvascular ECM remodeling.

Carvacrol reduces blood pressure, arterial responsiveness and increases expression of MAS receptors in spontaneously hypertensive rats

AIM

To analyze the effect of the use of carvacrol in the cardiovascular system of spontaneously hypertensive rats (SHR).

METHODS

Methods: Twenty animals were allocated in four groups, one group control Wistar receiving only sorbitol, used as vehicle of administration of the carvacrol (Wistar-Vehicle), one control group SHR, also receive only sorbitol (SHR-Vehicle), a third, treated with losartan (SHR-Losartan/50 mg/kg), and the fourth, treated with carvacrol (SHR - Carvacrol/20 mg/kg). Sorbitol, losartan and carvacrol were administered by oral gavage daily for 30-day. Hemodynamic variables, vascular reactivity, biochemical parameters, and expression of Mas and AT1 receptors in kidney tissues were analyzed.

RESULTS

SHR- Carvacrol group showed a maximal effect of inhibition of 56% in the curve of norepinephrine. The Emax of the curves with Ca²⁺ were smaller in the groups SHR-losartan (40.17%) and SHR-carvacrol (35.71%) when compared to the SHR-Vehicle. The carvacrol increased the expression of the MAS receptors in kidney tissue.

CONCLUSION

Thirty days of treatment with carvacrol showed an antihypertensive effect associated with less peripheral vascular resistance. Also, treatment with carvacrol increased the expression of MAS receptors in kidney tissue.

Role of Ang1-7 in renal haemodynamics and excretion in streptozotocin diabetic rats

The contribution of angiotensin (1-7) (Ang1-7) to control of extrarenal and renal function may be modified in diabetes. We investigated the effects of Ang1-7 supplementation on blood pressure, renal circulation and intrarenal reactivity (IVR) to vasoactive agents in normoglycaemic (NG) and streptozotocin diabetic rats (DM). In Sprague Dawley DM and NG rats, 3 weeks after streptozotocin (60 mg/kg i.p.) or solvent injection, Ang1-7 was administered (400 ng/min) over the next 2 weeks using subcutaneously implanted osmotic minipumps. For a period of 5 weeks, blood pressure (BP), 24 h water intake and diuresis were determined weekly. In anaesthetised rats, BP, renal total and cortical (CBF), outer (OMBF) and inner medullary (IMBF) perfusion and urine excretion were determined. To check IVR, a short-time infusion of acetylcholine or norepinephrine was randomly given to the renal artery. Unexpectedly, BP did not differ between NG and DM, and this was not modified by Ang-1-7 supplementation. Baseline IMBF was higher in NG vs. DM, and Ang1-7 treatment did not change it in NG but decreased it in DM. In the latter, Ang1-7 increased cortical IVR to vasoconstrictor and vasodilator stimuli. IMBF decrease after high acetylcholine dose seen in untreated NG was reverted to an increase in Ang1-7 treated rats. Irrespective of the glycaemia level, Ang1-7 did not modify BP. However, it impaired medullary circulation in DM, whereas in NG it rendered the medullary vasculature more sensitive to vasodilators. Possibly, the medullary hypoperfusion in DM was mediated by Ang1-7 activation of angiotensin AT-1 receptors which are upregulated by hyperglycaemia.

Downregulation of ACE2 is associated with advanced pathological features and poor prognosis in clear cell renal cell carcinoma

Aims: The aim of this study was to explore the alteration in ACE2 expression and correlation between ACE2 expression and immune infiltration in clear cell renal cell carcinoma (ccRCC). Methods: The authors first analyzed the expression profiles and prognostic value of ACE2 in ccRCC patients using The Cancer Genome Atlas public database. The authors used ESTIMATE and CIBERSORT algorithms to analyze the correlation between ACE2 expression and tumor microenvironment in ccRCC samples. Results: ACE2 was correlated with sex, distant metastasis, clinical stage, tumor T stage and histological grade. Moreover, downregulation of ACE2 was correlated with unfavorable prognosis. In addition, ACE2 expression was associated with different immune cell subtypes. Conclusion: The authors' analyses suggest that ACE2 plays an important role in the development and progression of ccRCC and may serve as a potential prognostic biomarker in ccRCC patients.

Protective effect of alamandine on doxorubicin‑induced nephrotoxicity in rats

BACKGROUND

This study aimed to evaluate the protective effects of alamandine, a new member of the angiotensin family, against doxorubicin (DOX)-induced nephrotoxicity in rats.

METHODS

Rats were intraperitoneally injected with DOX (3.750 mg/kg/week) to reach a total cumulative dose of 15 mg/kg by day 35. Alamandine (50 µg/kg/day) was administered to the rats via mini-osmotic pumps for 42 days. At the end of the experiment, rats were placed in the metabolic cages for 24 h so that their water intake and urine output could be measured. After scarification, the rats' serum and kidney tissues were collected, and biochemical, histopathological, and immunohistochemical studies were carried out.

RESULTS

DOX administration yielded increases in pro-inflammatory cytokines, including interleukin (IL)-1β and IL-6, pro-fibrotic proteins transforming growth factor-β (TGF-β), pro-inflammatory transcription factor nuclear kappa B (NF-κB), kidney malondialdehyde (MDA), creatinine clearance, blood urea nitrogen (BUN), and water intake. On the other hand, the DOX-treated group exhibited decreased renal superoxide dismutase (SOD), renal glutathione peroxidase (GPx) activity, and urinary output. Alamandine co-therapy decreased these effects, as confirmed by histopathology and immunohistochemical analysis.

CONCLUSIONS

The results suggest that alamandine can prevent nephrotoxicity induced by DOX‎ in rats.

Targeting Neprilysin (NEP) pathways: A potential new hope to defeat COVID-19 ghost

COVID-19 is an ongoing viral pandemic disease that is caused by SARS-CoV2, inducing severe pneumonia in humans. However, several classes of repurposed drugs have been recommended, no specific vaccines or effective therapeutic interventions for COVID-19 are developed till now. Viral dependence on ACE-2, as entry receptors, drove the researchers into RAS impact on COVID-19 pathogenesis. Several evidences have pointed at Neprilysin (NEP) as one of pulmonary RAS components. Considering the protective effect of NEP against pulmonary inflammatory reactions and fibrosis, it is suggested to direct the future efforts towards its potential role in COVID-19 pathophysiology. Thus, the review aimed to shed light on the potential beneficial effects of NEP pathways as a novel target for COVID-19 therapy by summarizing its possible molecular mechanisms. Additional experimental and clinical studies explaining more the relationships between NEP and COVID-19 will greatly benefit in designing the future treatment approaches.

Kidney dopamine D1-like receptors and angiotensin 1-7 interaction inhibits renal Na+ transporters

The role of dopamine D₁-like receptors (DR) in the regulation of renal Na⁺ transporters, natriuresis, and blood pressure is well established. However, the involvement of the angiotensin 1-7 (ANG 1-7)-Mas receptor in the regulation of Na⁺ balance and blood pressure is not clear. The present study aimed to investigate the hypothesis that ANG 1-7 can regulate Na⁺ homeostasis by modulating the renal dopamine system. Sprague-Dawley rats were infused with saline alone (vehicle) or saline with ANG 1-7, ANG 1-7 antagonist A-779, DR agonist SKF38393, and antagonist SCH23390. Infusion of ANG 1-7 caused significant natriuresis and diuresis compared with saline alone. Both natriuresis and diuresis were blocked by A-779 and SCH23390. SKF38393 caused a significant, SCH23390-sensitive natriuresis and diuresis, and A-779 had no effect on the SKF38393 response. Concomitant infusion of ANG 1-7 and SKF38393 did not show a cumulative effect compared with either agonist alone. Treatment of renal proximal tubules with ANG 1-7 or SKF38393 caused a significant decrease in Na⁺-K⁺-ATPase and Na⁺/H⁺ exchanger isoform 3 activity. While SCH23390 blocked both ANG 1-7- and SKF38393-induced inhibition, the DR response was not sensitive to A-779. Additionally, ANG 1-7 activated PKG, enhanced tyrosine hydroxylase activity via Ser⁴⁰ phosphorylation, and increased renal dopamine production. These data suggest that ANG 1-7, via PKG, enhances tyrosine hydroxylase activity, which increases renal dopamine production and activation of DR and subsequent natriuresis. This study provides evidence for a unidirectional functional interaction between two G protein-coupled receptors to regulate renal Na⁺ transporters and induce natriuresis.

Naringenin Ameliorates Renovascular Hypertensive Renal Damage by Normalizing the Balance of Renin-Angiotensin System Components in Rats

Background: Naringenin, a member of the dihydroflavone family, has been shown to have a protective function in multiple diseases. We previously demonstrated that naringenin played a protective role in hypertensive myocardial hypertrophy by decreasing angiotensin-converting enzyme (ACE) expression. The kidney is a primary target organ of hypertension. The present study tested the effect of naringenin on renovascular hypertensive kidney damage and explored the underlying mechanism. Methods and Results: An animal model of renovascular hypertension was established by performing 2-kidney, 1-clip (2K1C) surgery in Sprague Dawley rats. Naringenin (200 mg/kg/day) or vehicle was administered for 10 weeks. Blood pressure and urinary protein were continuously monitored. Plasma parameters, renal pathology and gene expression of nonclipped kidneys were evaluated by enzyme-linked immunosorbent assay, histology, immunohistochemistry, real-time polymerase chain reaction, and Western blot at the end of the study. Rats that underwent 2K1C surgery exhibited marked elevations of blood pressure and plasma Ang II levels and renal damage, including mesangial expansion, interstitial fibrosis, and arteriolar thickening in the nonclipped kidneys. Naringenin significantly ameliorated hypertensive nephropathy and retarded the rise of Ang II levels in peripheral blood but had no effect on blood pressure. 2K1C rats exhibited increases in the ACE/ACE2 protein ratio and AT1R/AT2R protein ratio in the nonclipped kidney compared with sham rats, and these increases were significantly suppressed by naringenin treatment. Conclusions: Naringenin attenuated renal damage in a rat model of renovascular hypertension by normalizing the imbalance of renin-angiotensin system activation. Our results suggest a potential treatment strategy for hypertensive nephropathy.

Effect of novel GPCR ligands on blood pressure and vascular homeostasis

Maintenance of normal blood pressure under conditions of drug treatment is a measure of system-wide neuro-hormonal controls and electrolyte/fluid volume homeostasis in the body. With increased interest in designing and evaluating novel drugs that may functionally select or allosterically modulate specific GPCR signaling pathways, techniques that allow us to measure acute and long-term effects on blood pressure are very important. Therefore, this chapter describes techniques to measure acute and long-term impact of novel GPCR ligands on blood pressure regulation. We will use the angiotensin type 1 receptor, a powerful blood pressure regulating GPCR, in detailing the methodology. Normal blood pressure maintenance depends upon dynamic modulation of angiotensin type 1 receptor activity by the hormone peptide angiotensin II. Chronic activation of angiotensin type 1 receptor creates hypertension and related cardiovascular disease states which are treated with angiotensin type 1 receptor blockers (ARBs). Thus, a prototype for evaluation of blood pressure control under experimental evaluation of novel drugs.

Dimerization of AT2 and Mas Receptors in Control of Blood Pressure

PURPOSE OF REVIEW

Angiotensin type 2 receptor (AT₂R) and receptor Mas (MasR) are part of the "protective arm" of the renin angiotensin system. Gene and pharmacological manipulation studies reveal that AT₂R and MasR are involved in natriuretic, vasodilatory, and anti-inflammatory responses and in lowering blood pressure in various animal models under normal and pathological conditions such as salt-sensitive hypertension, obesity, and diabetes. The scope of this review is to discuss co-localization and heterodimerization as potential molecular mechanisms of AT₂R- and MasR-mediated functions including antihypertensive activities.

RECENT FINDINGS

Accumulating evidences show that AT₂R and MasR are co-localized, make a heterodimer, and are functionally interdependent in producing their physiological responses. Moreover, ang-(1-7) preferably may be an AT₁R-biased agonist while acting as a MasR agonist. The physical interactions of AT₂R and MasR appear to be an important mechanism by which these receptors are involved in blood pressure regulation and antihypertensive activity. Whether heteromers of these receptors influence affinity or efficacy of endogenous or synthetic agonists remains a question to be considered.