AT1 Receptor mRNA Research Articles

Association of Perinatal Cardiovascular Features with Angiotensin System Expressions in Maternal Preeclampsia.

We hypothesized and investigated whether prenatal exposure to preeclampsia (PE) would simultaneously affect perinatal cardiovascular features and angiotensin system expressions. This prospective study was composed of mother-neonate dyads with (n = 49) and without maternal preeclampsia (n = 48) in a single tertiary medical center. The neonates exposed to PE had significantly larger relative sizes for the left and right coronary arteries and a higher cord plasma level of aminopeptidase-N, which positively correlated with the maternal diastolic blood pressures and determined the relative sizes of the left and right coronary arteries, whereas the encoding aminopeptidase-N (ANPEP) mRNA level in the PE cord blood leukocytes was significantly decreased, positively correlated with the neonatal systolic blood pressures (SBPs), and negatively correlated with the cord plasma-induced endothelial vascular cell adhesion molecule-1 mRNA levels. The PE cord plasma significantly induced higher endothelial mRNA levels of angiotensin II type 1 receptor (AT1R) and AT4R, whereas in the umbilical arteries, the protein expressions of AT2R and AT4R were significantly decreased in the PE group. The endothelial AT1R mRNA level positively determined the maternal SBPs, and the AT4R mRNA level positively determined the neonatal chamber size and cardiac output. In conclusion, PE may influence perinatal angiotensin system and cardiovascular manifestations of neonates across placentae. Intriguing correlations between these two warrant further mechanistic investigation.

Angiotensinergic and GABAergic transmission in the medial preoptic area: role in urinary bladder and cardiovascular control in female rats.

Introduction: The medial preoptic area (mPOA) participates in thermoregulatory control and blood pressure modulation as shown by studies with electrical stimulation of this area or cobalt chloride injection, a non-selective synapse inhibitor. This study aimed to investigate whether angiotensin II (Ang II) and GABA could act or not in the mPOA to mediate the cardiovascular and micturition control pathways. Methods: Female Wistar rats were submitted to stereotaxic surgery for implantation of a guide cannula into the mPOA 7days prior to the experiments. Afterwards, the animals were isoflurane- anesthetized and submitted to the catheterization of the femoral artery and vein and urinary bladder cannulation for mean arterial pressure (MAP), heart rate (HR), and intravesical pressure (IP) recordings, respectively. After the baseline MAP, HR, and IP recordings for 15min, Ang II (0.1nM, 1μL), losartan (AT-1 receptor antagonist, 100nM, 1μL), GABA (50mM, 1μL) or saline (1μL) were injected into the mPOA, and the variables were measured for additional 30min. In a different group of rats, the AT-1 receptor, angiotensin II converting enzyme (ACE), and GABAa receptor gene expression was evaluated in mPOA samples by qPCR. The data are as mean ± SEM and submitted to One-way ANOVA (Tukey posttest) or paired Student t-test (P <0.05). Results: The injection of Ang II into the mPOA evoked a significant hypotension (-37±10mmHg, n = 6, p = 0.024) and bradycardia (-47 ± 20bpm, p = 0.030) compared to saline (+1 ± 1mmHg and +6 ± 2bpm, n = 6). A significant increase in IP was observed after Ang II injection into the mPOA (+72.25 ± 17.91%, p = 0.015 vs. -1.80 ± 2.98%, n = 6, saline). No significant changes were observed in MAP, HR and IP after the losartan injection in the mPOA compared to saline injection. Injection of GABA into the mPOA evoked a significant fall in MAP and HR (-68 ± 2mmHg, n = 6, p < 0.0001 and -115 ± 14bpm, n = 6, p = 0.0002 vs. -1 ± 1mmHg and +4 ± 2bpm, n = 6, saline), but no significant changes were observed in IP. The AT-1 receptor, ACE and GABAa receptor mRNA expression was observed in all mPOA samples. Discussion: Therefore, in female rats, Ang II mediated transmission in the mPOA is involved in the cardiovascular regulation and in the control of central micturition pathways. A phasic control dependent on AT-1 receptors in the mPOA seems to be involved in the regulation of those cardiovascular and intravesical 3 parameters. In contrast, GABAergic transmission in the mPOA participates in the pathways of cardiovascular control in anesthetized female rats, nevertheless, this neurotransmission is not involved in the micturition control.

PS-B12-10: CLASSIC CARDIOVASCULAR PROTECTIVE SIGNALING IN ANGIOTENSIN II-INDUCED NOVEL PREECLAMPSIA RAT MODEL

Angiotensin II (Ang II)-induces vasoconstriction, in vivo perfusion has been shown to induce preeclampsia (PE) in pregnant rats. In this study, we aimed to examine the protein and mRNA expressions of endothelial and neuronal NOS (eNOS, nNOS) as well as angiotensin II type 2 receptor (AT2R) in normal pregnant and Ang II-induced PE rats. Pregnant (8 weeks) and non-pregnant SD rats (8 weeks, GD-8) were infused with Ang II via an osmotic minipump (1 ug/kg/min), and the rats (GD-21) were sacrificed 13 days later. Pregnant and non-pregnant rats without Ang II were taken as sham controls. The fetal weight, crown-rump length and placental weight of PE rats were significantly lower compared to those without Ang II infusion. Immunohistochemistry results showed an approximately 30% increase in glomerular volume, suggesting morphological changes in the kidney and Ang II infusion exhibits a PE phenotype. Ang II infusion did not affect AT2R, AT1R and nNOS protein or mRNA expression in the uterus of non-pregnant or pregnant rats. However, eNOS mRNA expression was reduced in PE rats (p &lt; 0.0001) although protein expression was not affected by Ang II infusion. However, in the placenta, AT1R and AT2R protein expression were not different in PE, but AT2R mRNA was decreased (p &lt; 0.0001). eNOS protein was only expressed in fetal vascular endothelial cells, and eNOS protein expression was higher in PE rats (P = 0.001) but eNOS mRNA was decreased (p = 0.0096). Notably, strong nNOS expression was observed in placental trophoblast cell groups of sham and PE rats, and both mRNA and protein expression of nNOS was decreased in placental lysates of Ang II rats (respectively p = 0.0287 and p &lt; 0.0001). These results demonstrate that we have recapitulated the PE model of Ang II infusion in rats. The expression of nNOS was reduced, and the localization of nNOS in the trophoblast suggested a new functional remodeling in the fetal vasculature. In the placenta, decreased expression of AT2R and nNOS may be a novel mechanism of impaired fetal development.

Functional Characterization of Human Induced Pluripotent Stem Cell-Derived Endothelial Cells.

Endothelial cells derived from human induced pluripotent stem cells (hiPSC-ECs) provide a new opportunity for mechanistic research on vascular regeneration and drug screening. However, functions of hiPSC-ECs still need to be characterized. The objective of this study was to investigate electrophysiological and functional properties of hiPSC-ECs compared with primary human cardiac microvascular endothelial cells (HCMECs), mainly focusing on ion channels and membrane receptor signaling, as well as specific cell functions. HiPSC-ECs were derived from hiPS cells that were generated from human skin fibroblasts of three independent healthy donors. Phenotypic and functional comparison to HCMECs was performed by flow cytometry, immunofluorescence staining, quantitative reverse-transcription polymerase chain reaction (qPCR), enzyme-linked immunosorbent assay (ELISA), tube formation, LDL uptake, exosome release assays and, importantly, patch clamp techniques. HiPSC-ECs were successfully generated from hiPS cells and were identified by endothelial markers. The mRNA levels of KCNN2, KCNN4, KCNMA1, TRPV2, and SLC8A1 in hiPSC-ECs were significantly higher than HCMECs. AT1 receptor mRNA level in hiPSC-ECs was higher than in HCMECs. AT2 receptor mRNA level was the highest among all receptors. Adrenoceptor ADRA2 expression in hiPSC-ECs was lower than in HCMECs, while ADRA1, ADRB1, ADRB2, and G-protein GNA11 and Gai expression were similar in both cell types. The expression level of muscarinic and dopamine receptors CHRM3, DRD2, DRD3, and DRD4 in hiPSC-ECs were significantly lower than in HCMECs. The functional characteristics of endothelial cells, such as tube formation and LDL uptake assay, were not statistically different between hiPSC-ECs and HCMECs. Phenylephrine similarly increased the release of the vasoconstrictor endothelin-1 (ET-1) in hiPSC-ECs and HCMECs. Acetylcholine also similarly increased nitric oxide generation in hiPSC-ECs and HCMECs. The resting potentials (RPs), ISK1–3, ISK4 and IK1 were similar in hiPSC-ECs and HCMECs. IBK was larger and IKATP was smaller in hiPSC-ECs. In addition, we also noted a higher expression level of exosomes marker CD81 in hiPSC-ECs and a higher expression of CD9 and CD63 in HCMECs. However, the numbers of exosomes extracted from both types of cells did not differ significantly. The study demonstrates that hiPSC-ECs are similar to native endothelial cells in ion channel function and membrane receptor-coupled signaling and physiological cell functions, although some differences exist. This information may be helpful for research using hiPSC-ECs.

CLASSIC CARDIOVASCULAR PROTECTIVE SIGNALING IN ANGIOTENSIN II-INDUCED NOVEL PREECLAMPSIA RAT MODEL

Objective: Angiotensin II (Ang II)-induces vasoconstriction, in vivo perfusion has been shown to induce preeclampsia (PE) in pregnant rats. In this study, we aimed to examine the protein and mRNA expressions of endothelial and neuronal NOS (eNOS, nNOS) as well as angiotensin II type 2 receptor (AT2R) in normal pregnant and Ang II-induced PE rats. Design and method: Pregnant (8 weeks) and non-pregnant SD rats (8 weeks, GD-8) were infused with Ang II via an osmotic minipump (1 ug/kg/min), and the rats (GD-21) were sacrificed 13 days later. Pregnant and non-pregnant rats without Ang II were taken as sham controls. The fetal weight, crown-rump length and placental weight of PE rats were significantly lower compared to those without Ang II infusion. Immunohistochemistry results showed an approximately 30% increase in glomerular volume, suggesting morphological changes in the kidney and Ang II infusion exhibits a PE phenotype. Results: Ang II infusion did not affect AT2R, AT1R and nNOS protein or mRNA expression in the uterus of non-pregnant or pregnant rats. However, eNOS mRNA expression was reduced in PE rats (p &lt; 0.0001) although protein expression was not affected by Ang II infusion. However, in the placenta, AT1R and AT2R protein expression were not different in PE, but AT2R mRNA was decreased (p &lt; 0.0001). eNOS protein was only expressed in fetal vascular endothelial cells, and eNOS protein expression was higher in PE rats (P = 0.001) but eNOS mRNA was decreased (p = 0.0096). Notably, strong nNOS expression was observed in placental trophoblast cell groups of sham and PE rats, and both mRNA and protein expression of nNOS was decreased in placental lysates of Ang II rats (respectively p = 0.0287 and p &lt; 0.0001). Conclusions: These results demonstrate that we have recapitulated the PE model of Ang II infusion in rats. The expression of nNOS was reduced, and the localization of nNOS in the trophoblast suggested a new functional remodeling in the fetal vasculature. In the placenta, decreased expression of AT2R and nNOS may be a novel mechanism of impaired fetal development.

Sexually dimorphic role of smooth muscle cell estrogen receptor alpha in aging‐associated arterial stiffness

BackgroundAging is associated with rising arterial stiffness (AS), an independent risk factor for cardiovascular disease. The development of aging‐associated AS follows a sexually dimorphic pattern with women developing AS later in life. Estrogen and estrogen receptor alpha (ERα) are protective in the premenopausal state, potentially due to the regulation of the vasoprotective angiotensin II type 2 receptor (AT2R), however, the role of estrogen/ERα in aging‐associated AS has not been defined and the mechanisms of the sexually‐dimorphic development of aging‐associated AS are unknown.Methods/ResultsAll studies were conducted in accordance with the FASEB Statement of Principles for the use of Animals in Research and Education. We generated novel smooth muscle cell‐specific ERα‐KO mice and measured aortic pulse wave velocity (PWV), an index of AS, in 3, 12, and 18 month old male and female intact and KO mice. Male mice develop increases in AS from 3 to 12 months compared to 3 to 18 months in females (p&lt;0.05). SMC‐ERα‐KO protected females from the aging‐associated increase in AS (p&lt;0.05). Circulating estrogens also declined in 18 month old females vs. 3 mo. (p&lt;0.05), suggesting a role for unliganded SMC‐ERα in aging‐associated AS. SMC‐ERα‐KO females were also protected from the aging‐associated decline in aortic AT2R expression observed in intact females (p&lt;0.05). To further investigate the potential role of unliganded SMC‐ERα in AS, we performed ovariectomy (OVX) or sham surgeries in young female SMC‐ERα‐Intact and KO mice and measured PWV. Results demonstrated an OVX‐driven increase in AS that was prevented by SMC‐ERα‐KO (p&lt;0.05). This was also associated with an OVX‐mediated decrease in aortic expression of the AT2R, which was prevented by SMC‐ERα‐KO. To determine the in vivo role of AT2R in the vascular protection observed in 12 month old female mice, we treated 12 month old male and female mice with AT2R antagonist PD‐123319 (3mg/kg/day) or vehicle via osmotic minipumps for 4 weeks. Chronic inhibition of the AT2R increased AS in 12 month old females (p&lt;0.05), but not males, suggesting that AT2R‐mediated protection contributes to the delay in aging‐associated AS in female mice. In vitro studies also demonstrated that estrogen upregulates AT2R mRNA and protein in female mouse aortic SMC, supporting an estrogen‐mediated mechanism of AT2R driven vascular protection in females.ConclusionThese data indicate sex differences in the time course of the development of aging‐associated arterial stiffness and suggest the presence of unliganded SMC‐ERα contributes specifically to aging‐associated arterial stiffness in females via reductions in vascular AT2R. Further, these results implicate that AT2R agonist therapy may improve cardiovascular outcomes in aging women to retain the beneficial downstream effects of estrogen signaling, without the potential detrimental effects of hormone replacement therapy.

Exploring AT2R and its Polymorphism in Different Diseases: An Approach to Develop AT2R as a Drug Target beyond Hypertension.

The Angiotensin II type 2 Receptor (AT2R) is one of the critical components of the renin- angiotensin system (RAS), which performs diverse functions like inhibiting cell differentiation, cell proliferation, vasodilatation, reduces oxidative stress and inflammation. AT2R is relatively less studied in comparison to other components of RAS despite its uniqueness (sex-linked) and diverse functions. The AT2R is differentially expressed in different tissues, and its gene polymorphisms are associated with several diseases. The molecular mechanism behind the association of AT2R and its gene polymorphisms with the diseases remains to be fully understood, which hinders the development of AT2R as a drug target. Single nucleotide polymorphisms (SNPs) in AT2R are found at different locations (exons, introns, promoter, and UTR regions) and were studied for association with different diseases. There may be different mechanisms behind these associations as some AT2R SNP variants were associated with differential expression, the SNPs (A1675G/ A1332G) affect the alternate splicing of AT2R mRNA, A1332G genotype results in shortening of the AT2R mRNA and subsequently defective protein. Few SNPs were found to be associated with the diseases in either females (C4599A) or males (T1334C). Several other SNPs were expected to be associated with other similar/related diseases, but studies have not been done yet. The present review emphasizes on the significance of AT2R and its polymorphisms associated with the diseases to explore the precise role of AT2R in different diseases and the possibility to develop AT2R as a potential drug target.

Valsartan Prevented Neointimal Hyperplasia and Inhibited SRSF1 Expression and the TLR4-iNOS-ERK-AT1 Receptor Pathway in the Balloon-injured Rat Aorta.

Valsartan has the potential to attenuate neointimal hyperplasia and to suppress the inflammatory response. This study aimed to evaluate the role of valsartan in neointimal hyperplasia and the toll-like receptor 4 (TLR4)-nitric oxide synthase (NOS) pathway in the balloon-injured rat aorta.Forty-eight Wistar rats were randomly allocated to three groups: sham control (control), balloon-injured group (surgery), and balloon-injured+valsartan-treated group (valsartan). Rats were killed at 14 and 28 days after balloon-injury, and then the aortic tissues were collected for morphometric analysis as well as for measurements of the mRNA or protein expression of angiotensin II, angiotensin II type 1 (AT1) receptor, angiotensin II type 2 (AT2) receptor, TLR4, endothelial nitric oxide synthase (eNOS), inducible NOS (iNOS), serine/arginine-rich splicing factor 1(SRSF1) and extracellular signal regulated kinase (ERK). Valsartan at a dose of 20 mg/kg/day markedly decreased neointimal hyperplasia in the aorta of balloon-injured rats, and significantly reduced the mRNA or protein expression of TLR4, AT1 receptor, SRSF1 and phosphorylated-ERK (p-ERK) as well as the aortic levels of iNOS (all p < 0.05). Moreover, valsartan increased the eNOS level and AT2 receptor mRNA and protein expression levels (all p < 0.05). Valsartan prevented neointimal hyperplasia and inhibited SRSF1 expression and the TLR4-iNOS-ERK-AT1 receptor pathway in the balloon-injured rat aorta.

Increased AT1 receptor expression mediates vasoconstriction leading to hypertension in Snx1-/- mice.

Angiotensin II type 1 receptor (AT1R) is a vital therapeutic target for hypertension. Sorting nexin 1 (SNX1) participates in the sorting and trafficking of the renal dopamine D5 receptor, while angiotensin and dopamine are counterregulatory factors in the regulation of blood pressure. The effect of SNX1 on AT1R is not known. We hypothesized that SNX1, through arterial AT1R sorting and trafficking, is involved in blood pressure regulation. CRISPR/Cas9 system-generated SNX1-/- mice showed dramatic elevations in blood pressure compared to their wild-type littermates. The angiotensin II-mediated contractile reactivity of the mesenteric arteries and AT1R expression in the aortas were also increased. Moreover, immunofluorescence and immunoprecipitation analyses revealed that SNX1 and AT1R were colocalized and interacted in the aortas of wild-type mice. In vitro studies revealed that AT1R protein levels and downstream calcium signaling were upregulated in A10 cells treated with SNX1 siRNA. This may have resulted from decreased AT1R protein degradation since the AT1R mRNA levels showed no changes. AT1R protein was less degraded when SNX1 was downregulated, as reflected by a cycloheximide chase assay. Furthermore, proteasomal rather than lysosomal inhibition increased AT1R protein content, and this effect was accompanied by decayed binding of ubiquitin and AT1R after SNX1 knockdown. Confocal microscopy revealed that AT1R colocalized with PSMD6, a proteasomal marker, and the colocalization was reduced after SNX1 knockdown. These findings suggest that SNX1 sorts AT1R for proteasomal degradation and that SNX1 impairment increases arterial AT1R expression, leading to increased vasoconstriction and blood pressure.

Localization of angiotensin II type 1 receptor gene expression in rodent and human kidneys.

The kidneys are an important target for angiotensin II (ANG II). In adult kidneys, the effects of ANG II are mediated mainly by ANG II type 1 (AT1) receptors. AT1 receptor expression has been reported for a variety of different cell types within the kidneys, suggesting a broad spectrum of actions for ANG II. Since there have been heterogeneous results in the literature regarding the intrarenal distribution of AT1 receptors, this study aimed to obtain a comprehensive overview about the localization of AT1 receptor expression in mouse, rat, and human kidneys. Using the cell-specific and high-resolution RNAscope technique, we performed colocalization experiments with various cell markers to specifically discriminate between different segments of the tubular and vascular system. Overall, we found a similar pattern of AT1 mRNA expression in mouse, rat, and human kidneys. AT1 receptors were detected in mesangial cells and renin-producing cells. In addition, AT1 mRNA was found in interstitial cells of the cortex and outer medulla. In rodents, late afferent and early efferent arterioles expressed AT1 receptor mRNA, but larger vessels of the investigated species showed no AT1 expression. Tubular expression of AT1 mRNA was species dependent with a strong expression in proximal tubules of mice, whereas expression was undetectable in human tubular cells. These findings suggest that the (juxta)glomerular area and tubulointerstitium are conserved expression sites for AT1 receptors across species and might present the main target sites for ANG II in adult human and rodent kidneys.NEW & NOTEWORTHY Angiotensin II (ANG II) type 1 (AT1) receptors are essential for mediating the effects of ANG II in the kidneys. This study aimed to obtain a comprehensive overview about the cell-specific localization of AT1 receptor expression in rodent and human kidneys using the novel RNAscope technique. We found that the conserved AT1 receptor mRNA expression sites across species are the (juxta)glomerular areas and tubulointerstitium, which might present main target sites for ANG II in adult human and rodent kidneys.

Kinin B1 Receptor Blockade Attenuates Hypertension via Angiotensin II Mediated Signaling in Neurons

Interaction between renin‐angiotensin system (RAS) and kallikrein‐kinin system (KKS) has been shown to play an important role in the regulation of blood pressure. We previously reported that kinin B1 receptor (B1R) expression is increased in the neurons of hypertensive mice with elevated angiotensin II (Ang II) levels in the brain. However, the role of B1R in neurogenic hypertension and its interaction with Ang II type 1 receptor (AT1R), the major receptor of Ang II, have not been studied. Ang II treatment (1 μg/kg/min, SC, 2 weeks) significantly increased blood pressure (radiotelemetry) in male wild‐type (WT) mice (145 ±13 mmHg, n=6, p&lt;0.01) compared to control mice (103 ±6 mmHg, n=6). This increase in blood pressure was attenuated in B1R knockout (B1RKO) mice with Ang II infusion (118 ±12 mmHg, n=6, p&lt;0.01). In addition, B1R knockdown significantly reduced Ang II‐induced AT1R expression and vasopressin levels. In order to further confirm the causative role of B1R on inducing hypertension, we used a specific B1R agonist Lys‐des‐Arg9‐BK (LDABK) to activate central B1R and measured blood pressure response using telemetry transmitters. A single bolus intracerebroventricular injection of 50 ng of LDABK, significantly increased blood pressure compared to artificial cerebrospinal fluid (18 ±5 mmHg vs. 4 ±2 mmHg, n=6, p&lt;0.01), supporting the hypothesis that B1R activation can induce hypertensive response. To further understand the neuron specific B1R mediated signaling, we isolated mouse neonatal primary hypothalamic neuronal cultures from WT and B1RKO mice and investigated the interaction between Ang II and B1R activation. Stimulation of primary neurons with LDABK (300 nM, 24 h), significantly increased the expression of AT1R mRNA (3‐fold vs. vehicle; n=6; p&lt;0.05) and resulted in neuroinflammation as indicated by upregulated expression of inflammatory markers interleukin (IL)‐1β, IL‐6, tumor necrosis factor, and monocyte chemoattractant protein 1. These changes were attenuated in B1RKO neurons or pretreatment of WT neurons with R715 (a B1R specific peptide antagonist). Together, these data provide novel evidence that kinin B1R plays an important role in mediating hypertension possibly via modulating angiotensin signaling in the brain.

Endogenous AT1 receptor-protein kinase C activity in the hypothalamus augments glutamatergic input and sympathetic outflow in hypertension.

The angiotensin AT1 receptor expression and protein kinase C (PKC)-mediated NMDA receptor phosphorylation levels in the hypothalamus are increased in a rat genetic model of hypertension. Blocking AT1 receptors or PKC activity normalizes the increased pre- and postsynaptic NMDA receptor activity of hypothalamic presympathetic neurons in hypertensive animals. Inhibition of AT1 receptor-PKC activity in the hypothalamus reduces arterial blood pressure and sympathetic nerve discharges in hypertensive animals. AT1 receptors in the hypothalamus are endogenously activated to sustain NMDA receptor hyperactivity and elevated sympathetic outflow via PKC in hypertension. Increased synaptic N-methyl-d-aspartate receptor (NMDAR) activity in the hypothalamic paraventricular nucleus (PVN) plays a major role in elevated sympathetic output in hypertension. Although exogenous angiotensin II (AngII) can increase NMDAR activity in the PVN, whether endogenous AT1 receptor-protein kinase C (PKC) activity mediates the augmented NMDAR activity of PVN presympathetic neurons in hypertension is unclear. Here we show that blocking AT1 receptors with losartan or inhibiting PKC with chelerythrine significantly decreased the frequency of NMDAR-mediated miniature excitatory postsynaptic currents (mEPSCs) and the amplitude of puff NMDA currents of retrogradely labelled spinally projecting PVN neurons in spontaneously hypertensive rats (SHRs). Also, treatment with chelerythrine abrogated the potentiating effect of AngII on mEPSCs and puff NMDA currents of labelled PVN neurons in SHRs. In contrast, neither losartan nor chelerythrine had any effect on mEPSCs or puff NMDA currents in labelled PVN neurons in Wistar-Kyoto (WKY) rats. Furthermore, levels of AT1 receptor mRNA and PKC-mediated NMDAR phosphorylation in the PVN were significantly higher in SHRs than in WKY rats. In addition, microinjection of losartan or chelerythrine into the PVN substantially reduced blood pressure and renal sympathetic nerve discharges in SHRs but not in WKY rats. Chelerythrine blocked sympathoexcitatory responses to AngII microinjected into the PVN. Our findings suggest that endogenous AT1 receptor-PKC activity is essential for presynaptic and postsynaptic NMDAR hyperactivity of PVN presympathetic neurons and for the augmented sympathetic outflow in hypertension. This information advances our mechanistic understanding of the interplay between angiotensinergic and glutamatergic excitatory inputs in hypertension.

Hypogonadal Hypertension in Male Sprague‐Dawley Rats Is Reversed by Testosterone Replacement Therapy, which Suppresses Renin‐Angiotensin System Expression

Testosterone (TES) and other androgens are efficacious vasodilators acutely, both in vitro and in vivo; however, their long‐term effects on arterial blood pressure (BP) are unclear. We previously reported that castration (CsX) produced hypertension in normal male rats, and that TES replacement therapy (TRT) was antihypertensive and normalized BP. Thus, long‐term effects of endogenous TES and exogenous TRT on BP and renin‐angiotensin system (RAS) function were studied in intact (InT) and castrated (CsX) male Sprague‐Dawley (SD) and Testicular‐feminized male (Tfm, androgen receptor defective) rats (12–13 wk old). Weekly measurements of systolic BP (tail cuff plethysmography) revealed a progressive rise in BP over 10 wks in CsX (108 ± 0.9 vs. 139 ± 1.2 mmHg), while BP remained stable in InT (109 ± 3.1 vs. 115 ± 0.5). During the next 5 weeks, half of CsX received TRT (CsX+TES‐enanthate‐replaced; 1.75 mg/kg, 2X/wk). BP gradually declined to normal in CsX+TES replaced rats (115 ± 1.2), while BP remained elevated in CsX (141 ± 1.2) and normal in InT (113 ± 0.3). In separate CsX‐SD rats, treatment with Losartan (LST; 250 mg/L drinking water) prevented development of hypertension at 10 wks (95 ± 0.8 CsX+LST vs. 139 ± 1.2 in CsX). During the next 5 weeks with TRT, BP declined in CsX+TES (113 ± 1.3) and remained lower in CsX+LST (99 ± 0.4). In Tfm, CsX resulted in a similar rise in BP (108 ± 0.6 vs. 139 ± 0.4 mmHg), and TRT reduced BP to a similar extent (106 ± 1.5). Real‐time PCR (rt‐PCR) of kidney from InT, CsX, and CsX+TES rats revealed that CsX increased expression of renin (45.5%), AT1 receptor (AT1R; 38%), and angiotensin converting enzyme (ACE; 239%) mRNA, while TRT normalized expression of renin, AT1R, and ACE mRNA to levels of InT rats. In contrast, CsX reduced expression of angiotensinogen (Angt) mRNA (59%) while TRT restored Angt mRNA to 78% of InT rats. 24 hr urine output (UO) in InT‐SD was 48.3 ml/kg at baseline, 34.3 at 10 wks, 38.4 at 12 wks, and 34.8 at 15 wks. UO in CsX‐SD was 47.6, 30.3, 25.2, and 27.7; UO in CsX+TRT was 46.1, 29.2 36.2, and 29.5. These data suggest that: 1) endogenous androgens (TES) exert antihypertensive effects in male SD and Tfm rats; 2) the antihypertensive effect of TES appear to involve a diuretic effect on the kidney, which is non‐genomically mediated; and 3) these antihypertensive effects may involve TES‐induced reductions in RAS expression in the kidney.Support or Funding InformationState of TexasThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Upregulation of AT1 Receptor Mediates a Pressor Effect Through ROS-SAPK/JNK Signaling in Glutamatergic Neurons of Rostral Ventrolateral Medulla in Rats With Stress-Induced Hypertension.

The present study examined whether angiotensin II (Ang II) mediates the pressor effect through nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-derived reactive oxygen species (ROS)-mitogen-activated protein kinase (MAPK) signaling in the glutamatergic neurons of the rostral ventrolateral medulla (RVLM) in stress-induced hypertensive rats (SIHR). The SIHR model was established using electric foot-shocks combined with noises for 15 days. We observed that Ang II type 1 receptor (AT1R) and the glutamatergic neurons co-localized in the RVLM of SIHR. Furthermore, glutamate levels in the intermediolateral column of the spinal cord were higher in SIHR than in controls. Microinjection of Ang II into the RVLM of SIHR activated stress-activated protein kinase/Jun N-terminal kinase (SAPK/JNK), extracellular signal-regulated protein kinase (ERK) 1/2, and p38MAPK. Compared with controls, the activation of SAPK/JNK, ERK1/2, p38MAPK, and ROS in the RVLM were higher in SIHR, an effect that was blocked by an NADPH oxidase inhibitor (apocynin) and an AT1R antagonist (candesartan). RVLM microinjection of apocynin or a SAPK/JNK inhibitor (SP600125), but not an ERK1/2 inhibitor (U0126) or a p38MAPK inhibitor (SB203580), decreased AT1R mRNA and mean arterial blood pressure (MABP) in SIHR. The increase of AT1R protein expression and MABP was inhibited by intracerebroventricular infusion (ICV), for 14 days, of SP600125, but not U0126 or SB203580 in SIHR. We conclude that Ang II modulates the pressor effect through AT1R-dependent ROS-SAPK/JNK signaling in glutamatergic neurons in the RVLM of SIHR.

Age-Related Changes in Ang II Receptor Localization and Expression in the Developing Auditory Pathway.

We studied Ang II receptor localization in different nuclei of the auditory system, by means of binding autoradiography, during brain development. The inferior colliculus (IC), a large midbrain structure which serves as an obligatory synaptic station in both the ascending and descending auditory pathways, exhibited high Ang II AT2 binding at all ages (P0, P8, P15, P30), being maximal at P15. These observations were confirmed by in situ hybridization and immunofluorescence at P15, demonstrating that AT2 receptor mRNA localized at the same area recognized by AT2 antibodies and anti β III-tubulin suggesting the neuronal nature of the reactive cells. Ang II AT1 receptors were absent at early developmental ages (P0) in all nuclei of the auditory system and a low level was observed in the IC at the age P8. AT2 receptors were present at ventral cochlear nucleus and superior olivary complex, being higher at P15 and P8, respectively. We also explored the effect of prenatal administration of Ang II or PD123319 (AT2 antagonist) on binding of Ang II receptors at P0, P8, P15. Both treatments increased significantly the level of AT2 receptors at P0 and P8 in the IC. Although total binding in the whole IC from P15 animals showed no difference between treatments, the central nucleus of the IC exhibited higher binding. Our results supports a correlation between the timing of the higher expression of Ang II AT2 receptors in different nuclei, the onset of audition and the establishment of neuronal circuits of the auditory pathway.

Abstract TP423: Hesperidin in Citrus Fruits Juice Improves Brain Ischemia-Induced Cognitive Impairment

Introduction: We recently reported that drinking Citrus iyo juice (CI) inhibited more effectively vascular remodeling in inflammation-induced vascular injury mouse model than Citrus unshiu juice (CU) (PLoS One. 2015). These results led us to explore the possibility that citrus fruits juice drinking could attenuate cognitive decline in transient cerebral ischemia model, focusing on the effects of flavanone, hesperidin, which is more abundantly contained in CI compared with CU and has antioxidant activity. Methods: Eight-week-old male C57BL/6 mice were administrated 10 % CI or CU in drinking water or 100 mg/kg/day hesperidin orally by gavage. Two weeks after administration, brain ischemia was induced by bilateral common carotid artery occlusion (BCCAO) for 18 minutes. The Y maze task was performed 2 weeks after BCCAO operation. After cognitive task, cerebral blood flow (CBF) was measured by a laser speckle flowmetry. Cerebral superoxide anion production 24 hours after BCCAO was measured by dihydroethidium (DHE) staining. mRNA levels were measured by quantitative real-time RT-PCR. Results: Administration of CI, CU or hesperidin did not influence systolic blood pressure, bodyweight and brain weight. Cognitive function was impaired with the increase in superoxide anion production after BCCAO. The cognitive impairment was more effectively attenuated by the administration of CI with the significant increase in CBF than sham group. Interestingly, we also observed that the treatment with hesperidin significantly prevented cognitive decline after BCCAO. Superoxide anion production determined by DHE was attenuated by CI or hesperidin, not by CU. The increases in mRNA levels of tumor necrosis factor (TNF)-α in the brain of the brain 24 hours after BCCAO was prevented by hesperidin. Two weeks after BCCAO, expression of mRNA of NADPH oxidase subunits in the brain tended to decrease in treatment with hesperidin. AT1, AT2 and Mas receptor mRNA expression in the brain did not differ among three groups. Conclusion: These results suggest that the intake of hesperidin in citrus fruits juice should prevent cognitive decline after brain ischemia at least in part due to reduction of oxidative stress, inflammatory cytokine and an increase in CBF.

Renal sympathetic denervation lowers arterial pressure in canines with obesity-induced hypertension by regulating GAD65 and AT1R expression in rostral ventrolateral medulla

ABSTRACTTo explore the roles of glutamate acid decarboxylase 65 (GAD65) and angiotensin II type 1 receptor (AT1R) in the action of renal sympathetic denervation (RSD) on obesity-induced hypertension in canines. Thirty-two beagles were randomly divided into a hypertensive model (n = 22) and control (n = 10) groups. A hypertensive canine model was established by feeding a high-fat diet. Twenty hypertensive beagles were randomized equally to a sham-surgery and RSD-treated group receiving catheter-based radiofrequency RSD. Compared with the control group, the sham-surgery group exhibited significant increases in blood pressure, serum angiotensin II level, rostral ventrolateral medulla (RVLM) glutamate level, and AT1R mRNA and protein expression and decreases in γ-amino acid butyric acid (γ-GABA) level and GAD65 mRNA and protein expression in the RVLM (all P < 0.05). Treatment with RSD significantly attenuated the above abnormal alterations (all P < 0.05). Linear correlation analysis revealed that angiotensin II level was positively correlated with glutamate level (r = 0.804) and inversely correlated with γ-GABA level (r = −0.765). GAD65 protein expression was positively correlated with γ-GABA level (r = 0.782). Catheter-based radiofrequency RSD can decrease blood pressure in obesity-induced hypertensive canines. The antihypertensive mechanism might be linked to upregulation of GAD65 and downregulation of AT1R in the RVLM.

Esculetin ameliorates vascular perturbation by intervening in the occupancy of H2BK120Ub at At1, At2, Tgfβ1 and Mcp1 promoter gene in thoracic aorta of IR and T2D rats

Micro and macro vascular complications under diabetic condition are the responses to pathological stimuli exerted by up regulated renin angiotensin system (RAS) via deteriorating vascular physiology. Up-regulated RAS could influence in the adaptive mechanisms of target tissues to alter the abundance of angiotensin II type 1 receptor (AT1) and angiotensin II type 2 receptor (AT2). Such differential regulation of AT1 and AT2 have been reported to be associated with post-translational histone modifications (PTHMs). Additionally, recent evidences provide, esculetin (6,7-dihydroxycoumarin) reverses post-translational histone modifications (PTHMs) in diabetic cardiomyopathy and nephropathy. On account of these evidences, we further pursued this study to investigate the effects of esculetin on PTHMs in progressive vascular complications under insulin resistance (IR) and type 2 diabetic (T2D) conditions. Esculetin treatment in both IR and T2D conditions substantially improved vascular reactivity, increased eNos and decreased Vcam1 mRNA levels, and reduced collagen deposition in rat thoracic aorta. Further, the fold changes in At1 and At2 receptor mRNA in IR and T2D were reversed by esculetin treatment. Modifications in histone H2B lysine 120 monoubiquitination (H2BK120Ub) were also reversed in esculetin treatment group. Further, modification in the occupancy of H2BK120Ub at At1a, At2, Tgfβ and Mcp1 promoter genes was evidenced by treatment with esculetin. Taken together, our investigation concluded with the involvement of esculetin in the amelioration of vascular perturbation by modifying H2BK120Ub along with occupancy at At1, At2, Tgfβ1 and Mcp1 promoter gene.

Abstract P198: Combination of Undaria Pinnatifida Sporophyll and Vinegar Remarkably Decreases Blood Pressure in 2-kidney, 1-clip Renovascular Hypertensive Rats

Objective: One of foods necessary to Japanese cuisine “Washoku” is algae, including Saccharina japonica (SJ) and Undaria pinnatifida (UP). The intake of SJ was observed to decrease blood pressure (BP) in spontaneously hypertensive rats in some studies, and in 2-kidney, 1-clip hypertensive (2K1C) rats in our studies. Furthermore, we observed the interactive effects of SJ and vinegar on BP in 2K1C rats (Kitamura S et al; Hypertension 2013, Maruyama S et al; Hypertension 2016). In the present study, we investigated the interactive effects of UP sporophyll (UPS) and vinegar, as well as the effect of UPS, on BP in 2K1C rats. We also evaluated angiotensin II type 1 receptor (AT1R) mRNA expression, in the mechanism. Methods: Male Sprague-Dawley rats (6 wks) were treated with sham operation (SHAM) or clipping the left renal artery (2K1C). After surgery, the rats started receiving a control diet (C) or a diet with 5.0% (w/w) UPS, and a tap water or a water containing 5.0% (v/v) rice vinegar (V) for 6 weeks. Systolic BP (SBP) was measured by a tail-cuff method every week. At the end of the protocol, mean arterial pressure (MAP) was measured in each rat under anesthesia. Then, the aortas were removed for extracting mRNA. AT1R mRNA expression was evaluated using real-time RT-PCR. Results: Through the experiment period, SBP was significantly higher in 2K1C-C than in SHAM-C ( P &lt; 0.001). Neither 2K1C-V nor -UPS showed significant differences in SBP from 2K1C-C. However, 2K1C-UPS+V provided a significant reduction in SBP compared with 2K1C-C, -V, and -UPS ( P &lt; 0.01). At the end of the protocol, 2K1C-C was higher in SBP than SHAM-C (166 ± 3 vs 137 ± 3 mmHg, P &lt; 0.001). 2K1C-UPS+V (155 ± 4 mmHg) was tended to be lower than 2K1C-C, -V (162 ± 8 mmHg), and -UPS (164 ± 3 mmHg). Thus, BP was reduced only in 2K1C-UPS+V in 2K1C animals. The observations in MAP were similar to in the SBP. No significant differences in AT1R mRNA expression were observed among SHAM-C (1.3 ± 0.2), 2K1C-C (1.2 ± 0.3), -V (1.0 ± 0.2), -UPS (1.3 ± 0.2) and -UPS+V (1.0 ± 0.2). Conclusion: UPS and vinegar may decrease BP collaboratively in 2K1C rats. AT1R mRNA may not play an important role in the mechanism.

Abstract P353: Attenuation of Cardiac Fibrosis, Hypertrophy and Myopathy by AT2R Agonist NP-6A4

Adverse cardiac remodeling (hypertrophy, fibrosis and myopathy) underlies cardiac dysfunction and heart failure. Male Zucker obese (ZO:fa/fa) rat that suffers from cardiac dysfunction, adverse remodeling, and heart failure with preserved ejection fraction is a useful model to study the effects of cardioprotective drugs. We reported that NP-6A4 (Novopyxis Inc. Cambridge, MA), a peptide agonist of the Angiotensin II Type 2 Receptor (AT2R), protected mouse cardiomyoblast HL-1 cells and human coronary artery vascular smooth muscle cells (hCAVSMCs) from acute nutrient serum deficiency stress better than β-AR-Blockers, ARBs, and AT2R agonist CGP42112A. This effect was inhibited by AT2R-specific antagonist PD123319, confirming that NP-6A4 acts through AT2R. AT2R is a cardiac and vascular reparative molecule that protects the heart and vasculature from structural damage and fibrosis. No current drugs increase AT2R expression. We report that NP-6A4 treatment (1μM) increased AT2R mRNA (up to 4 fold; p≤0.05) in hCAVSMCs and human coronary artery endothelial cells (up to 8 fold; p≤0.05). This effect was inhibited by PD123319 (10 μM). Treatment of 11-week old male ZO rats with heart disease with NP-6A4 (1.8mg/kg/day in saline, delivered once daily subcutaneously; N=7) increased cardiac AT2R expression and mitigated cardiac dysfunction and adverse remodeling. Quantitative RT-PCR and immunohistochemistry analysis showed that 2 weeks of NP-6A4 treatment increased cardiac AT2R mRNA (up to 9 fold) and protein (1.5-3 fold) compared to controls (N=6) receiving saline (p&lt;0.01). NP-6A4 treatment improved cardiac parameters; endocardial circumferential strain (p≤0.05), myocardial performance index (MPI) (p≤0.005), and E/E’ ratio (p≤0.002). NP-6A4 treatment also increased cardiac capillary density (118% compared to saline treatedl; p≤0.002), and reduced interstitial fibrosis (77% compared to saline treated; p≤0.039.) At 19-weeks (after 8 weeks of treatment), cardiac tissues from 5 out of 6 control rats exhibited regions of myopathy. Only 2 out 7 NP-6A4 treated rats exhibited similar levels of myopathy in the heart. We propose that NP-6A4 attenuates adverse remodeling and improves cardiac function by increasing AT2R expression in cardiac cells.