Angiotensin II Type 1 Research Articles

Abstract P248: Estrogen Replacement Mitigated Blood Pressure Elevation Via Suppression Of Sodium Cotransporter In Angiotensin Ii-infused Ovariectomized Female Rats

Introduction: Female rats with lower proximal sodium transporters are known to excrete natriuresis faster than male rats. However, it is not sure whether the protective effect would be conserved in menopausal rats. Hypothesis: We assessed the hypothesis that ovariectomy would change renal sodium transporters in female rats and the estrogen supplementation could reverse angiotensin II (ANGII)-induced changes in renal sodium transporters and natriuresis. Methods: Six-week female Sprague Dawley rats (n=22) were ovariectomized, and half of them (n=11) were treated with estradiol 2 weeks later for 4 weeks, and then ANGII (n=14) or vehicle (n=8) was infused via osmotic minipumps for 2 weeks. Blood pressure (BP) was measured by the tail-cuff sphygmomanometer. Blood, urine, and kidney samples were collected. Results: The ANGII induced significant BP elevation in ovariectomized (OVX) and OVX with estradiol (OVX+E) rats. OVX affected elevating BP even in the sham rats. Albuminuria significantly increased in ANGII-infused OVX rats and did not change in ANGII-infused OVX+E rats. Urine sodium was significantly decreased in ANGII-infused OVX rats, while it increased in ANGII-infused OVX+E rats. Sodium transporters in the proximal tubule (sodium-hydrogen exchange 3, sodium phosphate cotransporter) were not different between OVX and OVX+E irrespective of ANGII infusion. Among the distal tubule transporters (α/β/γ-epithelial sodium channel (α/β/γENaC), sodium chloride cotransporter (NCC), phosphorylated NCC (pNCC)), pNCC were markedly augmented in ANGII-infused OVX rats, whereas not changed in ANGII-infused OVX+E rats. ANGII infusion affected increasing ANGII type 2 receptor (AT 2 R) in OVX+E rats but did not influence AT 2 R levels in OVX rats. Conclusions: Estradiol has the protective effect from elevating BP in ANGII-infused OVX rats. It was achieved via augmentation of natriuresis, which was connected to the suppression of NCC.

Angiotensin II enhances bacterial clearance via myeloid signaling in a murine sepsis model

Sepsis, defined as organ dysfunction caused by a dysregulated host-response to infection, is characterized by immunosuppression. The vasopressor norepinephrine is widely used to treat low blood pressure in sepsis but exacerbates immunosuppression. An alternative vasopressor is angiotensin-II, a peptide hormone of the renin-angiotensin system (RAS), which displays complex immunomodulatory properties that remain unexplored in severe infection. In a murine cecal ligation and puncture (CLP) model of sepsis, we found alterations in the surface levels of RAS proteins on innate leukocytes in peritoneum and spleen. Angiotensin-II treatment induced biphasic, angiotensin-II type 1 receptor (AT1R)-dependent modulation of the systemic inflammatory response and decreased bacterial counts in both the blood and peritoneal compartments, which did not occur with norepinephrine treatment. The effect of angiotensin-II was preserved when treatment was delivered remote from the primary site of infection. At an independent laboratory, angiotensin-II treatment was compared in LysM-Cre AT1aR-/- (Myeloid-AT1a-) mice, which selectively do not express AT1R on myeloid-derived leukocytes, and littermate controls (Myeloid-AT1a+). Angiotensin-II treatment significantly reduced post-CLP bacteremia in Myeloid-AT1a+ mice but not in Myeloid-AT1a- mice, indicating that the AT1R-dependent effect of angiotensin-II on bacterial clearance was mediated through myeloid-lineage cells. Ex vivo, angiotensin-II increased post-CLP monocyte phagocytosis and ROS production after lipopolysaccharide stimulation. These data identify a mechanism by which angiotensin-II enhances the myeloid innate immune response during severe systemic infection and highlight a potential role for angiotensin-II to augment immune responses in sepsis.

Nonopioid analgesics discovery and the Valley of Death: EMA401 from concept to clinical trial.

Translation of promising preclinical efficacy data for investigational analgesics to positive clinical trial outcomes is limited, despite the large collective effort to date. However, one target with positive proof-of-concept clinical trial data is the angiotensin II type 2 (AT2) receptor. This review addresses the obstacles impeding successful preclinical to clinical research translation in the novel analgesics field, and it also provides an overview of the discovery and development of EMA401, a peripherally restricted, highly selective, orally active, small-molecule AT2 receptor antagonist for relief of neuropathic pain. Multiple AT2 receptor antagonists evoked dose-dependent antiallodynia in the chronic constriction injury of the sciatic nerve rat model of neuropathic pain. In AT2 receptor knockout chronic constriction injury mice, antiallodynia was abolished, affirming the AT2 receptor as the target. Subsequently, AT2 receptor antagonists were shown to evoke pain relief in multiple rodent chronic pain models. EMA401 (sodium salt) was selected as the drug candidate based on its >10,000-fold binding selectivity c.f. the angiotensin II type 1 receptor, good potency, and favourable pharmacokinetics. Animal toxicology and safety testing along with phase 1 clinical trials in healthy volunteers showed that oral EMA401 was safe and well-tolerated. Based on these data, a proof-of-concept clinical trial of oral EMA401 was undertaken in patients with postherpetic neuralgia. This 4-week trial showed that EMA401 evoked superior relief of postherpetic neuralgia relative to placebo and there were no serious adverse events in the EMA401 group.

A REVIEW ON COMPARISON OF DIFFERENT TECHNIQUES USED TO ENHANCE DISSOLUTION OF VALSARTAN AND TELMISARTAN ORAL SOLID DOSAGE FORM

Telmisartan and Valsartan are strong angiotensin-II type 1 receptor inhibitor, applied in the care of elevated blood pressure. Telmisartan and also Valsartan comes under Class II category of BCS classification. Valsartan and Telmisartan both are highly pH dependent and poor soluble drug which result in improper absorption and low bioavailability (43% and 23% respectively). In order to control the poor solubility as well as bioavailability of both Telmisartan and Valsartan, different formulation techniques are compared on the basis of dissolution. In this review article, solid dispersion by kneading method, pelletization by pan coating, modified microcrystalline cellulose (MCC) pellets and solid self-micro-emulsifying drug delivery system (SMEDDS) formulation techniques are discussed for Telmisartan. Whereas, in case of Valsartan, liquisolid compact technique, fast disintegrating tablets (FDT), and formulation optimized by 23 factorial designs are evaluated. To sum up, the analogy of Telmisartan formulations demonstrates that solid dispersion (TS5) and fast dissolving pellet formulation (TP3), both the techniques showed better drug release profile than MCC pellet and SMEDDS techniques. However, when it comes to dissolution rate, fast dissolving pellet formulation reflects notably best results among all. Furthermore, Valsartan formulation techniques evaluation leads us to conclude that liquisolid method showed good release profile as compare to conventional products but the method incorporates some complex requirements of load factor calculation and saturation solubility studies. In addition to that, Valsartan formulation optimized by factorial design as well as fast dissolving tablet (FDT) formulation signifies more conventional approach as well as good drug release profile.

Activation of TRPC6 by AngⅡ Induces Podocyte Injury and Participates in Proteinuria of Nephrotic Syndrome.

Background: Nephrotic syndrome (NS) is a common glomerular disease, and podocyte injury is the character of primary NS, usually caused by minimal change disease and membranous nephropathy. Podocytopathy is primarily associated with glomerular proteinuria. Losartan, an angiotensin receptor blocker (ARB), is commonly used in the treatment of NS, and the AngiotensinⅡ (AngⅡ)–transient receptor potential ion channel 6 (TRPC6) axis has been reported to act on podocytes to regulate proteinuria in NS. Therefore, the purpose of this study was to explore the relationship in between AngⅡ–TRPC6, podocyte injury, and proteinuria based on the adriamycin (ADR) NS rat model. Method: All male rats were divided into three groups: control group, model group, and ARB group. The rats in the model group were induced by ADR, and the rats in the ARB group received losartan after induction of renal injury for 4 weeks. The changes in parameters related to renal dysfunction, and glomerular and podocyte structural damage, such as AngⅡ, AngⅡ type I receptor (AT1R), TRPC6, CaN, Caspase-3, Nephrin, and Podocin, were analyzed. Furthermore, the kidneys were isolated for study via transmission electron microscopy (TEM), immunohistochemistry, and western blot (WB) after the rats were sacrificed. In vitro, immortalized mouse MPC5 podocytes were used to investigate the regulatory effect of flufenamic acid (Flu) and SAR7334 (SAR) on the AngⅡ-TRPC6 signaling axis. Flow cytometry and WB were conducted to determine the relationship between podocyte injury and AngⅡ-TRPC6. Results: In vivo results showed that NS rats developed massive albuminuria and abnormal renal function, accompanied by abnormally increased levels of AngⅡ, TRPC6, AT1R, and CaN and a decreased expression of actin molecules in podocytes, extensive fusion of foot processes (FP), loss of glomerular structural integrity, collapse of podocyte structure, and skeletal reorganization. In vitro experiments indicated that both AngⅡ and Flu (the specific agonist of TRPC6) stimulated the expressions of TRPC6, AT1R, and Caspase-3 in podocytes. The AngⅡ receptor–blocker losartan and TRPC6-specific inhibitor SAR blocked the overexpression of the aforementioned proteins. In addition, SAR also attenuated the degradation of podocyte structural proteins and inhibited the fluorescence intensity of intracellular calcium (Ca2+) and cell apoptosis. Conclusion: The involvement of AngⅡ in the occurrence of NS proteinuria may be related to podocyte injury induced by activated TRPC6.

Olmesartan ameliorates cyclophosphamide-induced hemorrhagic cystitis in rats via Nrf2/HO-1 signaling pathway

Hemorrhagic cystitis (HC) is considered a fatal complication of cyclophosphamide (CP). Down-regulation of Nrf2 and induction of pro-inflammatory mediators are the main pathological factors. Recently, ameliorative potential of the angiotensin II (AII) type-1 (AT1) receptor blocker olmesartan (OLM) on oxidative stress and inflammatory cytokines was reported. The current study aims to investigate the possible protective effect of OLM on CP-induced HC in Wistar rats. The animals were divided into the control group (0.5% W/V carboxymethylcellulose, p.o.); OLM group (20 mg/kg, p.o., for 21 days); CP group (a single dose of 100 mg/kg, i.p.); and the remaining groups that received CP i.p. with oral OLM 5, 10 and 20 mg/kg for 21 days, respectively. The bladder tissue was collected for histopathology, immunohistochemistry, ELISA, Western blot, and oxidative stress assay. The OLM at doses of 10 and 20 mg/kg attenuated increase in TNF-α, IL-6, NF-kB, iNOS, and COX-2 induced by CP. Additionally, it up-regulated the Nrf2/HO-1 pathway, bladder GSH content, and CAT and SOD activities. The data indicated that OLM inhibited ROS-induced NF-kB, which caused inhibition of pro-inflammatory cytokines and activation of the Nrf2/HO-1 pathway. Hence, OLM holds great promise for preventing CP-induced HC.

The protective effects of Azilsartan against hypoxia in endometrial stromal cells: an implication in endometriosis

IntroductionEndometriosis is a reproductive disorder closely associated with hypoxia stress. Increasing evidences have implied the important roles of angiotensin II (ANG II) receptors in the pathophysiology of endometriosis. Thus, we speculated that Azilsartan (AZL), an ANG II receptor blocker, might have an effective function in controlling endometriosis.Material and methodsThe endometriotic animal model was established in female SD rats (6-8 weeks old, 200-220 g). Rats were divided into sham group and endometriosis (EMS) group. Rats in EMS group were anaesthetized by halothane and a mid-ventral incision was performed to expose the bowels. Human endometrial stromal cell line T-HESC was used for the in vitro assays. The T-HESC cells were cultured in DMEM-F12 mediumwith 10% fetal bovine serum (FBS, Hyclone), and 4 mM L-glutamine, 0.25% HEPES plus necessary antibiotics (Sigma-Aldrich, USA), at 37°C in a humidified atmosphere of 5% CO2.ResultsThe results show that upregulation of ANG II type 1 (AT1) receptor was observed in the endometriotic rat models. Treatment with AZL prevented the development of endometriotic lesions and suppressed the expressions of HIF-1α and cyclooxygenase 2 (COX-2) in endometriotic rats. In vitro assays proved that hypoxia-induced proliferation, migration, and invasion of T-HESC cells were attenuated by AZL. AZL inhibited the expression levels of hypoxia-inducible factor-1α (HIF-1α), COX-2, and prostaglandin E2 (PGE2) production in hypoxia-induced T-HESC cells. Overexpression of HIF-1α blocked the effects of AZL on T-HESC cells in response to hypoxia.ConclusionsAZL showed therapeutic function on endometriosis through inhibiting hypoxia-induced cell proliferation, migration, and invasion of T-HESC cells via HIF-1α/COX-2/PGE2 signaling.

G Protein-Coupled Receptors-Receptors With New Tricks Up Their Sleeves.

G Protein-Coupled Receptors-Receptors With New Tricks Up Their Sleeves.

Modulation of Vasomotor Function by Perivascular Adipose Tissue of Renal Artery Depends on Severity of Arterial Dysfunction to Nitric Oxide and Severity of Metabolic Parameters.

Perivascular adipose tissue (PVAT) enhances vascular relaxation of mesenteric arteries in SHRSP.Z-Leprfa/IzmDmcr rats (SPZF), a metabolic syndrome model. We investigated and compared the effects of PVAT on the renal artery in SPZF with those on SHR/NDmcr-cp rats (CP). Renal arteries with and without PVAT were isolated from 23-week-old SPZF and CP. The effects of PVAT on acetylcholine- and nitroprusside-induced relaxation were examined using bioassays with phenylephrine-contracted arterial rings. Acetylcholine-induced relaxations without PVAT in SPZF and CP were 0.7- and 0.5-times lower in females than in males, respectively. In the presence of PVAT, acetylcholine-induced relaxations increased 1.4- and 2-times in male and female CP, respectively, but did not differ in SPZF. Nitroprusside-induced relaxation with and without PVAT was 0.7-times lower in female than in male SPZF but did not differ in CP. Angiotensin-II type-1 receptor (AT1R)/AT1R-associated protein mRNA ratios were lower in CP than in the SPZF and negatively correlated with the difference in arterial relaxation with and without PVAT. The effects of renal artery PVAT differed between the SPZF and CP groups. Higher levels of enhanced AT1R activity in SPZF PVAT may drive these differences by impairing the vascular smooth muscle responses to nitric oxide.

Gentiopicroside Ameliorates Diabetic Renal Tubulointerstitial Fibrosis via Inhibiting the AT1R/CK2/NF-κB Pathway.

Renal tubulointerstitial fibrosis (TIF), characterized by epithelial-to-mesenchymal transition (EMT) of renal tubular epithelial cells, is the typical pathological alteration in diabetic nephropathy. Gentiopicroside (GPS), a natural compound with anti-inflammatory activity, has been demonstrated to alleviate glomerulosclerosis, whereas whether GPS inhibits TIF via regulating inflammation remains unclear. In this study, diabetic db/db mice and high glucose (HG)-stimulated renal tubular epithelial cells (NRK-52E) were applied to explore the effects and mechanisms of GPS on TIF. The results in vivo showed that GPS effectively improves glycolipid metabolism disorder, renal dysfunction, and TIF. In particular, GPS treatment reversed the abnormal expressions of EMT marker proteins including elevated α-smooth muscle actin and vimentin and decreased E-cadherin in the kidney of db/db mice. Moreover, GPS treatment also inhibited protein expressions of angiotensinⅡ type 1 receptor (AT1R) and CK2α and the activation of the NF-κB pathway. Importantly, the aforementioned effects of GPS acted in vivo were further observed in vitro in HG-stimulated NRK-52E cells, which were independent of its effects on glucose and lipid-lowering activity but were reversed by AT1R over-expression. Together, our results indicate that GPS that directly inhibits the CK2/NF-κB inflammatory signaling pathway via AT1R may also contribute to the amelioration of TIF in diabetes.

Angiotensin II type 1 receptor blockade attenuates gefitinib-induced cardiac hypertrophy via adjusting angiotensin II-mediated oxidative stress and JNK/P38 MAPK pathway in a rat model

Gefitinib is a tyrosine kinase inhibitor (TKI) of the epidermal growth factor receptor (EGFR), used for the treatment of advanced or metastatic non-small cell lung cancer. Recently, studies proved that Gefitinib-induced cardiotoxicity through induction of oxidative stress leads to cardiac hypertrophy. The current study was conducted to understand the mechanisms underlying gefitinib-induced cardiac hypertrophy through studying the roles of angiotensin II (AngII), oxidative stress, and mitogen-activated protein kinase (MAPK) pathway. Male Wistar albino rats were treated with valsartan, gefitinib, or both for four weeks. Blood samples were collected for AngII and cardiac markers measurement, and hearts were harvested for histological study and biochemical analysis. Gefitinib caused histological changes in the cardiac tissues and increased levels of cardiac hypertrophy markers, AngII and its receptors. Blocking of AngII type 1 receptor (AT1R) via valsartan protected hearts and normalized cardiac markers, AngII levels, and the expression of its receptors during gefitinib treatment. valsartan attenuated gefitinib-induced NADPH oxidase and oxidative stress leading to down-regulation of JNK/p38-MAPK pathway. Collectively, AT1R blockade adjusted AngII-induced NADPH oxidase and JNK/p38-MAPK leading to attenuation of gefitinib-induced cardiac hypertrophy. This study found a pivotal role of AngII/AT1R signaling in gefitinib-induced cardiac hypertrophy, which may provide novel approaches in the management of EGFRIs-induced cardiotoxicity.

Kidney Angiotensin in Cardiovascular Disease: Formation and Drug Targeting.

The concept of local formation of angiotensin II in the kidney has changed over the last 10–15 years. Local synthesis of angiotensinogen in the proximal tubule has been proposed, combined with prorenin synthesis in the collecting duct. Binding of prorenin via the so-called (pro)renin receptor has been introduced, as well as megalin-mediated uptake of filtered plasma-derived renin-angiotensin system (RAS) components. Moreover, angiotensin metabolites other than angiotensin II [notably angiotensin-(1-7)] exist, and angiotensins exert their effects via three different receptors, of which angiotensin II type 2 and Mas receptors are considered renoprotective, possibly in a sex-specific manner, whereas angiotensin II type 1 (AT1) receptors are believed to be deleterious. Additionally, internalized angiotensin II may stimulate intracellular receptors. Angiotensin-converting enzyme 2 (ACE2) not only generates angiotensin-(1-7) but also acts as coronavirus receptor. Multiple, if not all, cardiovascular diseases involve the kidney RAS, with renal AT1 receptors often being claimed to exert a crucial role. Urinary RAS component levels, depending on filtration, reabsorption, and local release, are believed to reflect renal RAS activity. Finally, both existing drugs (RAS inhibitors, cyclooxygenase inhibitors) and novel drugs (angiotensin receptor/neprilysin inhibitors, sodium-glucose cotransporter-2 inhibitors, soluble ACE2) affect renal angiotensin formation, thereby displaying cardiovascular efficacy. Particular in the case of the latter three, an important question is to what degree they induce renoprotection (e.g., in a renal RAS-dependent manner). This review provides a unifying view, explaining not only how kidney angiotensin formation occurs and how it is affected by drugs but also why drugs are renoprotective when altering the renal RAS.Significance StatementAngiotensin formation in the kidney is widely accepted but little understood, and multiple, often contrasting concepts have been put forward over the last two decades. This paper offers a unifying view, simultaneously explaining how existing and novel drugs exert renoprotection by interfering with kidney angiotensin formation.

Candesartan Effectively Preserves Cognition in Senescence Accelerated Mouse Prone 8 (SAMP8) mice.

Background:Alzheimer’s disease (AD) has become a worldwide crisis with no effective therapeutic options. The medications currently available for AD are only palliative; their effect is temporary, and they are associated with unfavorable side effects. Even the newest medication aducanumab, granted accelerated FDA approval in 2021, failed to show cognitive benefits in clinical trials and continued approval requires verification in subsequent clinical trials. There is an urgent need for safe and effective therapies to preserve cognition and effectively manage AD. Generally, a new drug product takes several years for FDA approval and exceeds 2.5 billion dollars in research and development, with most new drug products never even reaching the market. This has led to a recent shift for repurposing/repositioning existing FDA-approved medications, to new therapeutic indications.Objective:To investigate the effects of long-term treatment with candesartan, an FDA-approved angiotensin-II type-1 receptor blocker (ARB), on the development of cognitive impairment associated with premature aging.Methods:Candesartan was given at a dose of 1 mg/kg/d in an AD model of senescence-accelerated mouse prone-8 (SAMP8) and senescence-accelerated mouse resistant (SAMR1) mice. Oral treatment with candesartan or vehicle was started, in 2-month-old mice and administered continuously for 4-months.Results:Low-dose candesartan prevented the development of cognitive impairment, otherwise associated with accelerated aging, in SAMP8 mice, by reducing inflammation and nitro-oxidative stress. Candesartan did not affect the cognitive function of control SAMR1 mice.Conclusion:Early ARB treatment might be beneficial in preventing age-related cognitive deficits in AD-prone individuals.

Vasoconstrictor and Pressor Effects of Des-Aspartate-Angiotensin I in Rat.

This study investigated the vasoactive effects of des-aspartate-angiotensin-I (DAA-I) in male Wistar rats on whole body vascular bed, isolated perfused kidneys, and aortic rings. Dose–response curves to DAA-I were compared with those to angiotensin II (Ang II). The Ang II-type-1 (AT1) receptor blocker, losartan, was used to evaluate the role of AT1 receptors in the responses to DAA-I. Studies were also conducted of the responsiveness in aortic rings after endothelium removal, nitric oxide synthase inhibition, or AT2 receptor blockade. DAA-I induced a dose-related systemic pressor response that was shifted to the right compared with Ang II. Losartan markedly attenuated the responsiveness to DAA-I. DAA-I showed a similar pattern in renal vasculature and aortic rings. In aortic rings, removal of endothelium and nitric oxide inhibition increased the sensitivity and maximal response to DAA-I and Ang II. AT2 receptor blockade did not significantly affect the responsiveness to DAA-I. According to these findings, DAA-I increases the systemic blood pressure and vascular tone in conductance and resistance vessels via AT1 receptor activation. This vasoconstrictor effect of DAA-I participates in the homeostatic control of arterial pressure, which can also contribute to the pathogenesis of hypertension. DAA-I may therefore be a potential therapeutic target in cardiovascular disease.

Divergent roles of angiotensin II upon the immediate and sustained increases of renal blood flow following unilateral nephrectomy.

Although the molecular and functional responses related to renal compensatory hypertrophy after unilateral nephrectomy (UNX) has been well described, many aspects of these events remain unclear. One question is how the remaining kidney senses the absence of the contralateral organ, and another is what the role of the renin-angiotensin system is in these responses. Both acute anesthetized and chronic unanesthetized experiments were performed using the angiotensin II type 1 receptor blocker losartan and the renin inhibitor aliskiren to determine the contribution of the renin-angiotensin system to immediate changes and losartan for chronic changes of renal blood flow (RBF) and the associated hypertrophic events in male Sprague-Dawley rats. Chronic experiments used implanted RBF probes and arterial catheters for continuous data collection, and the glomerular filtration rate was determined by noninvasive transcutaneous FITC-sinistrin measurements. The results of the acute experiments found that RBF increased nearly 25% (4.6 ± 0.5 to 5.6 ± 0.6 mL/min/g kidney wt) during the first 15 min following UNX and that this response was abolished by losartan (6.7 ± 0.7 to 7.0 ± 0.7 mL/min/g kidney wt) or aliskiren (5.8 ± 0.4 to 6.0 ± 0.4 mL/min/g kidney wt) treatment. Thereafter, RBF increased progressively over 7 days, and kidney weight increased by 19% of pre-UNX values. When normalized to kidney weight determined at day 7 after UNX, RBF was not significantly different from pre-UNX levels. Semiquantification of CD31-positive capillaries revealed increases of the glomeruli and peritubular capillaries that paralleled the kidney hypertrophy. None of these chronic changes was inhibited by losartan treatment, indicating that neither the compensatory structural nor the RBF changes were angiotensin II type 1 receptor dependent.NEW & NOTEWORTHY This study found that the immediate increases of renal blood flow (RBF) following unilateral nephrectomy (UNX) are a consequence of reduced angiotensin II type 1 (AT1) receptor stimulation. The continuous monitoring of RBF and intermittent measurement of glomerular filtration rate (GFR) in conscious rats during the 1-wk period of rapid hypertrophy following UNX provided unique insights into the regulation of RBF and GFR when faced with increased metabolic loads. It was found that neither kidney hypertrophy nor the associated increase of capillaries was an AT1-dependent phenomenon.

Protective Role of Angiotensin II type 2 receptor (AT2R) in High Salt Diet‐Induced Low Molecular Weight Proteinuria and Loss of Megalin in the Kidney

Proteinuria is a cause and a risk factor for tubulointerstitial injury with the progression of end‐stage kidney disease. Proteinuria is a function of the glomerular filtration of protein and the reabsorption of protein from the post‐glomerular filtrate by the endocytic receptors, megalin and cubilin, localized in the renal proximal tubules. We have shown that treatment with the angiotensin‐II type 2 receptor (AT2R) agonist compound 21 (C21) for 2 weeks reduces proteinuria in obese Zucker rats (OZR) fed with high salt diet (HSD). OZR is a salt‐sensitive model but has no effect on blood pressure in the first 3 days of HSD treatment. However, the early cellular and molecular mechanism of proteinuria in response to HSD and the protective effect of AT2R activation is unknown. Therefore, the present study is designed to determine the molecular/cellular mechanism of AT2R‐mediated protection against HSD‐induced proteinuria, independent of glomerular injury in obesity. We hypothesize that AT2R activation prevents the loss of megalin in proximal tubule epithelial cells and thereby decreases the urinary excretion of low molecular weight (LMW) proteins in HSD fed obese rats. Male OZR (11–14 weeks of age) were fed on normal salt diet (NSD) (0.4%) or HSD (4%) for 2 days with and without treatment with C21. The animals were placed in metabolic cages for collecting urine at various time intervals namely 6, 12, 24 and 48 hours. We observed that HSD caused proteinuria at 24 hrs. and was prevented by C21 treatment. Further analysis by gel electrophoresis revealed that proteinuria was based on LMW protein (<60 kDa) excretion in the urine. This observation was confirmed by no change in albuminuria by HSD and C21. Dot blot analysis and confocal immunofluorescence microscopy revealed that megalin and not cubilin, was significantly decreased in HSD treatment group and the remaining megalin was mostly present in the cytosolic compartment with negligible expression on plasma membrane, suggesting megalin recycling impairment. The C21 treatment restored megalin back to the plasma membrane. FcRn is an exclusive receptor for albumin transport, which remained unaltered by HSD and C21. Western blot of nephrin and podocin, indices of glomerular filtration apparatus, remained unchanged suggesting structural integrity of the glomerular filtration assembly. Consistent to this notion, GFR measured by creatinine clearance method remained same in all the three groups. HSD caused a significant increase in the urinary sodium excretion, which was not affected by C21 treatment and the plasma sodium concentration in all the groups remained the same. Overall, the data suggest that acute feeding of HSD causes LMW proteinuria due to reduction as well as cytosolic expression of megalin in proximal tubule and not due to the change in the glomerular filtration. AT2R activation restores megalin expression and prevents proteinuria with a potential of long‐term protection against tubule‐interstitial injury and kidney disease.

Angiotensin II As A Natural Suppressor On Cardiac Natriuretic Peptide System: Molecular Insights And Novel Therapeutic Design

<h3>Introduction</h3> Therapeutic strategies harnessing both renin-angiotensin system (RAS) and natriuretic peptide system (NPS) mediated effects, such as Sacubitril/Valsartan, has been proven to be promising in treating human heart failure (HF). However, molecular understanding of the interaction between RAS and NPS remains to be fully elucidated. While angiotensin II (ANGII), the central RAS hormone, is thought to interact with NPS at multiple levels, whether and how it may influence the actions of particulate guanylyl cyclase A (pGC-A), the only functional receptor for both atrial and b-type natriuretic peptide (ANP and BNP), has not been investigated. <h3>Hypothesis</h3> We hypothesize that ANGII naturally suppresses pGC-A and the inhibition of this crosstalk would be a novel therapeutic strategy to combat cardiovascular disease (CVD) of which RAS hyperactivation is a hallmark feature. <h3>Methods</h3> Plasma ANP, BNP, cGMP, and ANGII were measured in 128 healthy humans to define the balance between ANGII and NPS. cGMP responses to acute infusion of ANP alone and in the presence of ANGII was characterized in normal rats. The molecular mechanisms including involvement of ANGII type I receptor (AT1R) and its downstream target protein kinase C (PKC) were investigated in HEK293 cell overexpressing pGC-A and together with AT1R. CRRL-58, an innovative dual-functional peptide was designed to activate pGC-A and inhibit PKC, and tested for cGMP generation in HEK293 cells. <h3>Results</h3> In healthy human, plasma cGMP was positively associated with ANP or BNP only in low (≤ 4.5 pg/mL) but not those with high (> 4.5 pg/mL) ANGII levels (see Figure). Infusion of ANP (300 pmol/kg/min) in normal rats increased plasma and urinary cGMP, however ANP mediated cGMP generation was reduced in the presence of ANGII (50 pmol/kg/min). Notably, the suppressive effect of ANGII on pGC-A was recapitulated in HEK293 cell overexpressing both pGC-A and AT1R, but not in HEK293 cell overexpressing pGC-A alone. Meanwhile, we found PKC, a well-established downstream target of AT1R, was a key mediator for this observed crosstalk, as the suppression effect of ANGII was largely ablated by Go6983, a pan PKC inhibitor. Notably, CRRL-58 had superior potency in cGMP generation compared to the currently best-in-class ANP-analog, MANP, in vitro. <h3>Conclusions</h3> Our human and experimental data demonstrate that ANGII is a natural suppressor of pGC-A activation via AT1R and PKC signaling, but not via pGC-A per se. Moreover, we report for the first time that CRRL-58, an innovative bioengineered peptide that activates pGC-A receptor while inhibiting PKC signaling, potently generates cGMP. Together, our study provides new insights into the interaction between RAS and NPS, and highlights a novel and mechanism-based therapeutic avenue for treating HF and other CVDs.

Efficacy of Losartan in Hospitalized Patients With COVID-19–Induced Lung Injury

SARS-CoV-2 viral entry may disrupt angiotensin II (AII) homeostasis, contributing to COVID-19 induced lung injury. AII type 1 receptor blockade mitigates lung injury in preclinical models, although data in humans with COVID-19 remain mixed. To test the efficacy of losartan to reduce lung injury in hospitalized patients with COVID-19. This blinded, placebo-controlled randomized clinical trial was conducted in 13 hospitals in the United States from April 2020 to February 2021. Hospitalized patients with COVID-19 and a respiratory sequential organ failure assessment score of at least 1 and not already using a renin-angiotensin-aldosterone system (RAAS) inhibitor were eligible for participation. Data were analyzed from April 19 to August 24, 2021. Losartan 50 mg orally twice daily vs equivalent placebo for 10 days or until hospital discharge. The primary outcome was the imputed arterial partial pressure of oxygen to fraction of inspired oxygen (Pao2:Fio2) ratio at 7 days. Secondary outcomes included ordinal COVID-19 severity; days without supplemental o2, ventilation, or vasopressors; and mortality. Losartan pharmacokinetics and RAAS components (AII, angiotensin-[1-7] and angiotensin-converting enzymes 1 and 2)] were measured in a subgroup of participants. A total of 205 participants (mean [SD] age, 55.2 [15.7] years; 123 [60.0%] men) were randomized, with 101 participants assigned to losartan and 104 participants assigned to placebo. Compared with placebo, losartan did not significantly affect Pao2:Fio2 ratio at 7 days (difference, -24.8 [95%, -55.6 to 6.1]; P = .12). Compared with placebo, losartan did not improve any secondary clinical outcomes and led to fewer vasopressor-free days than placebo (median [IQR], 9.4 [9.1-9.8] vasopressor-free days vs 8.7 [8.2-9.3] vasopressor-free days). This randomized clinical trial found that initiation of orally administered losartan to hospitalized patients with COVID-19 and acute lung injury did not improve Pao2:Fio2 ratio at 7 days. These data may have implications for ongoing clinical trials. ClinicalTrials.gov Identifier: NCT04312009.

AT1 Receptors: Their Actions from Hypertension to Cognitive Impairment.

Hypertension is one of the most prevalent cardiovascular disorders worldwide, affecting 1.13 billion people, or 14% of the global population. Hypertension is the single biggest risk factor for cerebrovascular dysfunction. According to the American Heart Association, high blood pressure (BP), especially in middle-aged individuals (~ 40 to 60 years old), is associated with an increased risk of dementia, later in life. Alzheimer’s disease and cerebrovascular disease are the two leading causes of dementia, accounting for around 80% of the total cases and usually combining mixed pathologies from both. Little is known regarding how hypertension affects cognitive function, so the impact of its treatment on cognitive impairment has been difficult to assess. The brain renin-angiotensin system (RAS) is essential for BP regulation and overactivity of this system has been established to precede the development and maintenance of hypertension. Angiotensin II (Ang-II), the main peptide within this system, induces vasoconstriction and impairs neuro-vascular coupling by acting on brain Ang-II type 1 receptors (AT1R). In this review, we systemically analyzed the association between RAS and biological mechanisms of cognitive impairment, from the perspective of AT1R located in the central nervous system. Additionally, the possible contribution of brain AT1R to global cognition decline in COVID-19 cases will be discussed as well.

Angiotensin Type-1 Receptor Inhibition Reduces NLRP3 Inflammasome Upregulation Induced by Aging and Neurodegeneration in the Substantia Nigra of Male Rodents and Primary Mesencephalic Cultures.

The tissue renin–angiotensin system (RAS) has been shown to be involved in prooxidative and proinflammatory changes observed in aging and aging-related diseases such as dopaminergic degeneration in Parkinson’s disease (PD). We studied the activation of the NLRP3 inflammasome in the substantia nigra with aging and early stages of dopaminergic degeneration in PD models and, particularly, if the brain RAS, via its prooxidative proinflammatory angiotensin II (AngII) type 1 (AT1) receptors, mediates the inflammasome activation. Nigras from aged rats and mice and 6-hydroxydopamine PD models showed upregulation in transcription of inflammasome-related components (NLRP3, pro-IL1β and pro-IL18) and IL1β and IL18 protein levels, which was inhibited by the AT1 receptor antagonist candesartan. The role of the AngII/AT1 axis in inflammasome activation was further confirmed in rats intraventricularly injected with AngII, and in primary mesencephalic cultures treated with 6-hydroxydopamine, which showed inflammasome activation that was blocked by candesartan. Observations in the nigra of young and aged AT1 and AT2 knockout mice confirmed the major role of AT1 receptors in nigral inflammasome activation. In conclusion, the inflammasome is upregulated by aging and dopaminergic degeneration in the substantia nigra, possibly related with a decrease in dopamine levels, and it is mediated by the AngII/AT1 axis.