Angiotensin II Type 1 Receptor Research Articles

The effect of dietary supplementation with blueberry, cyanidin-3-O-β-glucoside, yoghurt and its peptides on gene expression associated with glucose metabolism in skeletal muscle obtained from a high-fat-high-carbohydrate diet induced obesity model.

Obesity is a leading global health problem contributing to various chronic diseases, including type II diabetes mellitus (T2DM). The aim of this study was to investigate whether blueberries, yoghurt, and their respective bioactive components, Cyanidin-3-O-β-glucoside (C3G) and peptides alone or in combinations, alter the expression of genes related to glucose metabolism in skeletal muscles from diet-induced obese mice. In extensor digitorum longus (EDL), yoghurt up-regulated the expression of activation of 5’adenosine monophosphate-activated protein kinase (AMPK), insulin receptor substrate-1 (IRS-1), phosphatidylinositol-3 kinase (PI3K) and glucose transporter 4 (GLUT4), and down-regulated the expression of angiotensin II receptor type 1 (AGTR-1). The combination of blueberries and yoghurt down-regulated the mRNA expression of AGTR-1 and Forkhead box protein O1 (FoxO1) in the EDL. Whereas the combination of C3G and peptides down-regulated AGTR-1 and up-regulated GLUT4 mRNA expression in the EDL. In the soleus, blueberries and yoghurt alone, and their combination down-regulated AGTR-1 and up-regulated GLUT4 mRNA expression. In summary blueberries and yoghurt, regulated multiple genes associated with glucose metabolism in skeletal muscles, and therefore may play a role in the management and prevention of T2DM.

Abstract 073: Age-Dependent Hypertension-Related Cognitive Impairment And Neuroinflammation In Sprague Dawley Rats Can Be Reversed By An AT 1 R Antagonism

Aim: We hypothesize paraventricular nucleus (PVN)-specific blood brain barrier (BBB) disruption and neuroinflammation increase hypertension and sympathoexcitation with age, promoting cognitive impairment, that can be attenuated by an Angiotensin II Type 1 Receptor (AT 1 R)-dependent mechanism in the aging Sprague Dawley (SD) rat. Methods: In male and female SD rats aged 3, 8 and 16 months old (MO) (N=6/gp) and 16 MO male rats treated with losartan (21 days; sc 3 mg/kg/day), blood pressure (BP; femoral artery cannulation), sympathetic tone to the vasculature (iv hexamethonium) and plasma NE (ELISA) was measured. Memory function was assessed by the novel object recognition task. BBB disruption was assessed via FITC extravasation and IHC/IF was performed for microglia (CD11b/c), astrocytes (GFAP), IL-6 and TNF-α in the PVN. Results: Aged male, but not female, SD rats develop HTN, sympathoexcitation, and cognitive impairment. PVN neuroinflammation, proinflammatory cytokine production and BBB disruption increased in male, but not female, rats with age. Losartan significantly lowered BP, reduced sympathoexcitation, attenuated BBB disruption and neuroinflammation, and reversed cognitive impairment in aged male rats. Conclusions: Our data suggest there is a potential protective role of female sex steroids in preventing the development of age-dependent HTN which is associated with PVN neuroinflammation. Concurrent with recent clinical findings, we found lowering blood pressure improved cognitive function and, thus, an AT 1 R antagonism represents a new therapeutic modality to improve cognitive performance in hypertensive individuals.

Abstract P323: Direct Vascular Endothelial Actions Of Angiotensin II Via At 1 R And No Signaling Revealed By Intravital Multiphoton Microscopy.

The renin-angiotensin system (RAS) controls blood pressure and body fluid balance. The classic vasoactive effects of RAS are mediated by the binding of angiotensin II (ANGII) to ANGII type 1 receptors (AT 1 R) in vascular smooth muscle cells leading to vasoconstriction, or to opposing ANGII type 2 receptors (AT 2 R). However, only few studies investigated the direct effects of ANGII on vascular endothelial cells (VEC) in vivo and the mechanisms how VECs may mitigate ANGII-mediated vasoconstriction. The present study aimed to explore the molecular mechanisms and pathophysiological relevance of the direct actions of ANGII on VEC in the kidney. VEC calcium dynamics and NO synthesis were visualized by using intravital multiphoton microscopy (MPM) of Cdh5-G6 mice that selectively express the ratiometric Ca 2+ reporter GCaMP6f/tdTomato in VECs, or the endothelial uptake of iv injected nitric oxide (NO) sensitive dye DAF-FM, respectively. Bolus injection of ANGII (400 ng/kg, ia.) triggered a >4-fold increase in VEC calcium in afferent (AA) arterioles and glomerular capillaries, but not in peritubular capillaries. These responses were blocked by pretreatment with the AT 1 R inhibitor Losartan (60mg/kg ip.), but not by the AT 2 R inhibitor PD123319 (25mg/kg ip.)(1.2+/-0.4 p<0.001 and 5.6+/-0.9-fold, p=0.3, respectively). VEC responded to acute ANGII by increased NO synthesis as indicated by >1.5-fold increase in DAF-FM fluorescence intensity as compared to baseline (p<0.0001). In mice with unilateral ureteral obstruction (UUO), a well-known high ANGII and vasoconstrictor state associated with endothelial dysfunction, the ANGII induced calcium increase in VECs was significantly reduced (2.8+/-0.3-fold) as compared to control (4.6+/-0.4-fold, p<0.01). These results correlated with the significantly reduced AA diameter in UUO compared to control (8.2+/-0.4 and 10.43+/-0.3 μm, respectively, p<0.001). In summary, ANGII has major direct effects on VECs NO production that counterbalances agonist-induced vasoconstriction. These effects are diminished in conditions with endothelial dysfunction leading to increased vascular contractility. Cell-specific targeting of ANGII actions may represent exciting future therapeutic opportunities.

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.

Biometabolites of Tamarindus indica play a remarkable cardioprotective role as a functional food in doxorubicin-induced cardiotoxicity models

This research investigated the cardioprotective effects of Tamarindus indica extracts (TIEx) in doxorubicin (Dox)-induced cardiotoxicity model. TIEx was tested for phytochemical and antioxidative status followed by a randomized controlled intervention in Swiss albino models. The results were verified by in silico interactions of GC-MS characterized phytocompounds against AT1 (angiotensin II type 1) receptor antagonist complexed with PPARγ agonist. TIEx showed an excellent antioxidative effect and a significant (P < 0.05) decrease in C-reactive protein (CRP), Serum troponin I (STI), aspartate transaminase (AST), lactate dehydrogenase (LDH), and creatinine kinase-MB (CKMB), total cholesterol (TC), triglyceride (TG), low-density lipoprotein (LDL) and increase high-density lipoprotein (HDL) in treatment groups in comparison with standard drug valsartan. The selected bioactive compounds especially Thymine, 4H-Pyran-4-one, 2,3-dihydro-3,5-dihydroxy-6-methyl- showed the highest binding affinity with the human AT1 receptor antagonist complexed with PPARγ agonist. Results demonstrate that Tamarindus indica parts could be a food supplement for cardiac toxicity.

Olmesartan Improves Hepatic Sinusoidal Remodeling in Mice with Carbon Tetrachloride-Induced Liver Fibrosis.

Aim In mice with liver fibrosis produced by carbon tetrachloride (CCl4), the effects of olmesartan on intrahepatic angiogenesis and sinusoidal remodeling will be evaluated. Methods By injecting CCl4 into the peritoneal cavity, we established a mouse model of liver fibrosis. Using Sirius red and Masson trichrome staining, the extent of liver fibrosis in the animals was determined. Using immunohistochemical labeling and western blotting, the level of α-smooth muscle actin (α-SMA) expression, a characteristic of hepatic stellate cell activation, was assessed. Electron microscopy was used to determine the effect of olmesartan on hepatic sinusoidal capillarization, and immunohistochemical labeling was used to determine the expression levels of endothelial and basement membrane proteins in mouse liver tissues. Platelet-derived growth factor (PDGF), IL-10, vascular endothelial growth factor (VEGF), and angiotensin II levels in mouse serum were measured by Luminex multifactor analysis and ELISA. Olmesartan's effect on the angiotensin II type 1 receptor (AT1R) and the VEGF receptor (VEGFR) was evaluated using western blotting. Results Olmesartan reduced CCl4-induced inflammatory cell infiltration and collagen deposition to alleviate liver fibrosis. α-SMA expression was decreased, and HSC activation was inhibited in mouse liver tissues by olmesartan treatment. In addition, hepatic sinusoidal capillarization was improved under the action of olmesartan. The expression of collagen IV, fibronectin, CD31, and von Willebrand factor (VWF) in the olmesartan group was also markedly downregulated. In fibrotic mice, olmesartan medication decreased the levels of PDGF, VEGF, and angiotensin II, but it increased the level of IL-10. Moreover, olmesartan reduced the expression of VEGFR-1, VEGFR-2, and AT1R relative to CCl4-induced liver fibrosis. Conclusions In mice with CCl4-induced fibrosis, olmesartan lowers angiogenesis and improves hepatic sinusoidal remodeling, according to our findings. By acting on the angiotensin II-AT1R-VEGF axis, this is achieved.

The Remarkable Roles of the Receptor for Advanced Glycation End Products (RAGE) and Its Soluble Isoforms in COVID-19: The Importance of RAGE Pathway in the Lung Injuries.

The respiratory symptoms of acute respiratory distress syndrome (ARDS) in the coronavirus disease 2019 (COVID-19) patients is associated with accumulation of pre-inflammatory molecules such as advanced glycation end-products (AGES), calprotectin, high mobility group box family-1 (HMGB1), cytokines, angiotensin converting enzyme 2 (ACE2), and other molecules in the alveolar space of lungs and plasma. The receptor for advanced glycation end products (RAGEs), which is mediated by the mitogen-activated protein kinase (MAPK), plays a critical role in the severity of chronic inflammatory diseases such as diabetes mellitus (DM) and ARDS. The RAGE gene is most expressed in the alveolar epithelial cells (AECs) of the pulmonary system. Several clinical trials are now being conducted to determine the possible association between the levels of soluble isoforms of RAGE (sRAGE and esRAGE) and the severity of the disease in patients with ARDS and acute lung injury (ALI). In the current article, we reviewed the most recent studies on the RAGE/ligands axis and sRAGE/esRAGE levels in acute respiratory illness, with a focus on COVID-19–associated ARDS (CARDS) patients. According to the research conducted so far, sRAGE/esRAGE measurements in patients with CARDS can be used as a powerful chemical indicator among other biomarkers for assessment of early pulmonary involvement. Furthermore, inhibiting RAGE/MAPK and Angiotensin II receptor type 1 (ATR1) in CARDS patients can be a powerful strategy for diminishing cytokine storm and severe respiratory symptoms.

Angiotensin receptor blocker use is associated with upregulation of the memory-protective angiotensin type 4 receptor (AT4R) in the postmortem brains of individuals without cognitive impairment.

The reported primary dementia-protective benefits of angiotensin II type 1 receptor (AT1R) blockers (ARB) are believed, at least in part, to arise from systemic effects on blood pressure. However, there is a specific and independently regulated brain renin-angiotensin system (RAS). Brain RAS acts mainly through three receptor subtypes; AT1R, AT2R, and AT4R. The AT1R promotes inflammation and mitochondrial reactive oxygen species generation. AT2R increases nitric oxide. AT4R is essential for dopamine and acetylcholine release. It is unknown whether ARB use is associated with changes in the brain RAS. Here, we compared the impact of treatment with ARB on not cognitively impaired individuals and individuals with Alzheimer's dementia using postmortem frontal-cortex samples of age- and sex-matched participants (70-90years old, n = 30 in each group). We show that ARB use is associated with higher brain AT4R, lower oxidative stress, and amyloid-β burden in NCI participants. In AD, ARB use was associated with lower brain AT1R but had no impact on inflammation, oxidative stress, or amyloid-β burden. Our results may suggest a potential role for AT4R in the salutary effects for ARB on the brains of not cognitively impaired older adults.

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.

Inhibition of the angiotensin II type 2 receptor AT2R is a novel therapeutic strategy for glioblastoma

Glioblastoma (GBM) is an aggressive malignant primary brain tumor with limited therapeutic options. We show that the angiotensin II (AngII) type 2 receptor (AT2R) is a therapeutic target for GBM and that AngII, endogenously produced in GBM cells, promotes proliferation through AT2R. We repurposed EMA401, an AT2R antagonist originally developed as a peripherally restricted analgesic, for GBM and showed that it inhibits the proliferation of AT2R-expressing GBM spheroids and blocks their invasiveness and angiogenic capacity. The crystal structure of AT2R bound to EMA401 was determined and revealed the receptor to be in an active-like conformation with helix-VIII blocking G-protein or β-arrestin recruitment. The architecture and interactions of EMA401 in AT2R differ drastically from complexes of AT2R with other relevant compounds. To enhance central nervous system (CNS) penetration of EMA401, we exploited the crystal structure to design an angiopep-2-tethered EMA401 derivative, A3E. A3E exhibited enhanced CNS penetration, leading to reduced tumor volume, inhibition of proliferation, and increased levels of apoptosis in an orthotopic xenograft model of GBM.

Bovine Bone Gelatin-Derived Peptides: Food Processing Characteristics and Evaluation of Antihypertensive and Antihyperlipidemic Activities.

This study aimed to evaluate the food processing properties of bovine bone gelatin-derived peptides (BGPs) and their effects and mechanisms on hypertension and hypertension complications in spontaneously hypertensive rats (SHRs). BGPs had good acid, high temperature, and NaCl resistance abilities in vitro. Additionally, Maillard reaction of BGPs with low-dose reducing sugar (≤15%) exhibited a free radical scavenging effect. BGPs significantly reduced the blood pressure, triglyceride levels, and the low-density lipoprotein cholesterol/high-density lipoprotein cholesterol ratio in SHRs through downregulated angiotensin converting enzyme (ACE), angiotensin II (Ang II), and Ang II type 1 receptor (AT1R) levels and the upregulated Ang II type 2 receptor (AT2R) level. In brief, BGP could alleviate hypertension and dyslipidemia in SHRs by inhibiting ACE/Ang II/AT1R and activating the Ang II/AT2R signaling pathway. Our study suggests that BGP has good food processing properties and could be a potential nutraceutical for antihypertensive and antihyperlipidemic issues.

Hormone-Dependent Regulation of Renin and Effects on Prorenin Receptor Signaling in the Collecting Duct.

The production of renin by the principal cells of the collecting duct has widened our understanding of the regulation of intrarenal angiotensin II (Ang II) generation and blood pressure. In the collecting duct, Ang II increases the synthesis and secretion of renin by mechanisms involving the activation of Ang II type 1 receptor (AT1R) via stimulation of the PKCα, Ca2+, and cAMP/PKA/CREB pathways. Additionally, paracrine mediators, including vasopressin (AVP), prostaglandins, bradykinin (BK), and atrial natriuretic peptide (ANP), regulate renin in principal cells. During Ang II-dependent hypertension, despite plasma renin activity suppression, renin and prorenin receptor (RPR) are upregulated in the collecting duct and promote de novo formation of intratubular Ang II. Furthermore, activation of PRR by its natural agonists, prorenin and renin, may contribute to the stimulation of profibrotic factors independent of Ang II. Thus, the interactions of RAS components with paracrine hormones within the collecting duct enable tubular compartmentalization of the RAS to orchestrate complex mechanisms that increase intrarenal Ang II, Na+ reabsorption, and blood pressure.

(Pro)renin Receptor and Blood Pressure Regulation: A Focus on the Central Nervous System.

The renin-angiotensin system (RAS) is classically described as a hormonal system in which angiotensin II (Ang II) is one of the main active peptides. The action of circulating Ang II on its cognate Ang II type-1 receptor (AT1R) in circumventricular organs has important roles in regulating the autonomic nervous system, blood pressure (BP) and body fluid homeostasis, and has more recently been implicated in cardiovascular metabolism. The presence of a local or tissue RAS in various tissues, including the central nervous system (CNS), is well established. However, because the level of renin, the rate-limiting enzyme in the systemic RAS, is very low in the brain, how endogenous angiotensin peptides are generated in the CNS-the focus of this review-has been the subject of considerable debate. Notable in this context is the identification of the (pro)renin receptor (PRR) as a key component of the brain RAS in the production of Ang II in the CNS. In this review, we highlight cellular and anatomical locations of the PRR in the CNS. We also summarize studies using gain- and loss-of function approaches to elucidate the functional importance of brain PRR-mediated Ang II formation and brain RAS activation, as well as PRR-mediated Ang II-independent signaling pathways, in regulating BP. We further discuss recent developments in PRR involvement in cardiovascular and metabolic diseases and present perspectives for future directions.

Association of AGTR1 gene methylation and its genetic variant in Chinese farmer with hypertension: A case-control study.

The objective was to determine the potential associations of the angiotensin II receptor type 1 (AGTR1) gene polymorphism, methylation, and lipid metabolism in Chinese farmers with hypertension.A case-control study was conducted in Wuzhi county of Henan province in China in 2013 to 2014. A total of 1034 local residents (35–74 years, 386 hypertensive cases, and 648 normotensive subjects) were enrolled in this study. Triglyceride (TG), total cholesterol (TC), high-density lipoprotein, and low-density lipoprotein were measured using automatic chemistry analyzer. The AGTR1 gene promoter methylation level was measured using quantitative methylation-specific polymerase chain reaction method. The single nucleotide polymorphism rs275653 was genotyped with TaqMan probe assay at an applied biosystems platform.The gender, body mass index (BMI), TG, TC, and family history of hypertension in the hypertension group were significantly higher than those in control group (P < .05). No significant difference was observed in the distribution of AGTR1 rs275653 polymorphism in the hypertension and controls (P > .05). The AGTR1 gene methylation in subjects carrying different genotypes was not significantly observed (P > .05). The logistic regression analysis found the AGTR1 gene methylation level was negative correlation with hypertension in the present study (odds ratio, 0.946, 95% confidence interval, 0.896–0.999) through adjusting for age, gender, BMI, education, smoking, alcohol drinking, fruit and vegetable intake, pickles intake, and family history of hypertension.The association of AGTR1 gene hypomethylation and essential hypertension was observed in Chinese farmers; no significant difference was observed in the distribution of AGTR1 rs275653 polymorphism.

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

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

Hypertension in COVID-19, A Risk Factor for Infection or A Late Consequence?

There are a lot of data about the correlation of SARS-CoV-2 infection and hypertension (HTN), but most of them are in the increased risk of morbidity and mortality in patients with HTN. SARS-CoV-2 can interfere with host cells through the renin-angiotensin system (RAS) via the angiotensin-converting enzyme 2 (ACE2) receptor. RAS activation is associated with pro-inflammatory effects through the ACE/Ang II/ Angiotensin II type 1 receptor (AT1R) pathway or anti-inflammatory effects through ACE2/Ang1-7/Mas axis. In the current paper, we discuss the pathophysiology of newly diagnosed HTN and its effect on morbidity in patients with coronavirus disease 2019 (COVID-19).

G-protein-coupled receptor kinase 4 causes renal angiotensin II type 2 receptor dysfunction by increasing its phosphorylation.

Activation of the angiotensin II type 2 receptor (AT2R) induces diuresis and natriuresis. Increased expression or/and activity of G-protein-coupled receptor kinase 4 (GRK4) or genetic variants (e.g., GRK4γ142V) cause sodium retention and hypertension. Whether GRK4 plays a role in the regulation of AT2R in the kidney remains unknown. In the present study, we found that spontaneously hypertensive rats (SHRs) had increased AT2R phosphorylation and impaired AT2R-mediated diuretic and natriuretic effects, as compared with normotensive Wistar-Kyoto (WKY) rats. The regulation by GRK4 of renal AT2R phosphorylation and function was studied in human (h) GRK4γ transgenic mice. hGRK4γ142V transgenic mice had increased renal AT2R phosphorylation and impaired AT2R-mediated natriuresis, relative to hGRK4γ wild-type (WT) littermates. These were confirmed in vitro; AT2R phosphorylation was increased and AT2R-mediated inhibition of Na+-K+-ATPase activity was decreased in hGRK4γ142V, relative to hGRK4γ WT-transfected renal proximal tubule (RPT) cells. There was a direct physical interaction between renal GRK4 and AT2R that was increased in SHRs, relative to WKY rats. Ultrasound-targeted microbubble destruction of renal GRK4 decreased the renal AT2R phosphorylation and restored the impaired AT2R-mediated diuresis and natriuresis in SHRs. In vitro studies showed that GRK4 siRNA reduced AT2R phosphorylation and reversed the impaired AT2R-mediated inhibition of Na+-K+-ATPase activity in SHR RPT cells. Our present study shows that GRK4, at least in part, impairs renal AT2R-mediated diuresis and natriuresis by increasing its phosphorylation; inhibition of GRK4 expression and/or activity may be a potential strategy to improve the renal function of AT2R.

Relaxin Inhibits the Cardiac Myofibroblast NLRP3 Inflammasome as Part of Its Anti-Fibrotic Actions via the Angiotensin Type 2 and ATP (P2X7) Receptors.

Chronic NLRP3 inflammasome activation can promote fibrosis through its production of interleukin (IL)-1β and IL-18. Conversely, recombinant human relaxin (RLX) can inhibit the pro-fibrotic interactions between IL-1β, IL-18 and transforming growth factor (TGF)-β1. Here, the broader extent by which RLX targeted the myofibroblast NLRP3 inflammasome to mediate its anti-fibrotic effects was elucidated. Primary human cardiac fibroblasts (HCFs), stimulated with TGF-β1 (to promote myofibroblast (HCMF) differentiation), LPS (to prime the NLRP3 inflammasome) and ATP (to activate the NLRP3 inflammasome) (T+L+A) or benzoylbenzoyl-ATP (to activate the ATP receptor; P2X7R) (T+L+Bz), co-expressed relaxin family peptide receptor-1 (RXFP1), the angiotensin II type 2 receptor (AT2R) and P2X7R, and underwent increased protein expression of toll-like receptor (TLR)-4, NLRP3, caspase-1, IL-1β and IL-18. Whilst RLX co-administration to HCMFs significantly prevented the T+L+A- or T+L+Bz-stimulated increase in these end points, the inhibitory effects of RLX were annulled by the pharmacological antagonism of either RXFP1, AT2R, P2X7R, TLR-4, reactive oxygen species (ROS) or caspase-1. The RLX-induced amelioration of left ventricular inflammation, cardiomyocyte hypertrophy and fibrosis in isoproterenol (ISO)-injured mice, was also attenuated by P2X7R antagonism. Thus, the ability of RLX to ameliorate the myofibroblast NLRP3 inflammasome as part of its anti-fibrotic effects, appeared to involve RXFP1, AT2R, P2X7R and the inhibition of TLR-4, ROS and caspase-1.

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.