Angiotensin II Receptor Subtypes Research Articles

Impact of interferon-γ on the target cell tropism of nanoparticles

Interferon-γ (IFN-γ) is well known to reduce the infectivity of viral pathogens by altering their tissue tropism. This effect is induced by upregulation of cholesterol 25-hydroxylase (CH25H). Given the similarity of viral pathogens and ligand-functionalized nanoparticles in the underlying strategy of receptor-mediated cell recognition, it appears conceivable that IFN-γ exceeds similar effects on nanoparticles. Concretely, IFN-γ-induced activation of CH25H could decrease nanoparticle avidity for target cells via depletion of clathrin-coated pits. We hypothesized that this effect would cause deterioration of target-cell specific accumulation of nanoparticles. To prove our hypothesis, we investigated the cell tropism of angiotensin II functionalized nanoparticles (NPLys-Ang II) in a co-culture system of angiotensin II subtype 1 receptor (AT1R) positive rat mesangial target cells (rMCs) and AT1R-negative HeLa off-target cells. In the presence of IFN-γ we observed an up to 5-fold loss of target cell preference for NPLys-Ang II. Thus, our in vitro results suggest a strong influence of IFN-γ on nanoparticle distribution, which is relevant in the context of nanotherapeutic approaches to cancer treatment, as IFN-γ is strongly expressed in tumors. For the target cell tropism of viruses, our results provide a conclusive hypothesis for the underlying mechanism behind non-directed viral distribution in the presence of IFN-γ.

Higher Angiotensin II Type 1 Receptor Levels and Activity in the Postmortem Brains of Older Persons with Alzheimer's Dementia.

Aging is a key risk factor in Alzheimer's dementia (AD) development and progression. The primary dementia-protective benefits of angiotensin II subtype 1 receptor (AT1R) blockers are believed to arise from systemic effects on blood pressure. However, a brain-specific renin-angiotensin system (b-RAS) exists, which can be altered by AT1R blockers. Brain RAS acts mainly through 3 angiotensin receptors: AT1R, AT2R, and AT4R. Changes in these brain angiotensin receptors may accelerate the progression of AD. Using postmortem frontal cortex brain samples of age- and sex-matched cognitively normal individuals (n = 30) and AD patients (n = 30), we sought to dissect the b-RAS changes associated with AD and assess how these changes correlate with brain markers of oxidative stress, inflammation, and mitochondrial dysfunction as well as amyloid-β and paired helical filament tau pathologies. Our results show higher protein levels of the pro-inflammatory AT1R and phospho-ERK (pERK) in the brains of AD participants. Brain AT1R levels and pERK correlated with higher oxidative stress, lower cognitive performance, and higher tangle and amyloid-β scores. This study identifies molecular changes in b-RAS and offers insight into the role of b-RAS in AD-related brain pathology.

High-dose nitrate therapy recovers the expression of subtypes \u03b11 and \u03b2-adrenoceptors and Ang II receptors of the renal cortex in rats with myocardial infarction-induced heart failures

BackgroundFew studies examined the effect of long-acting nitrates on renal function in chronic heart failure (CHF). Thus, we aimed to investigate the effect of long-acting nitrate on the expression of adrenoceptors (AR) and angiotensin II receptor (ATR) subtypes of the renal cortex, in rats with myocardial infarction-induced CHF.MethodsRats were randomly divided into the following groups: control, sham-operated, CHF, low- and high-dose nitrate, positive drug control (olmesartan), and high-dose of long-acting nitrate + olmesartan. Ultrasound echocardiography markers were compared, and the levels of AR subtypes, AT1R, and AT2R were measured using reverse transcription-polymerase chain reaction and western blot analysis. Histopathology of the kidney was determined on hematoxylin and eosin-stained sections.ResultsCHF significantly increased plasma renin activity (PRA) and angiotensin II levels, upregulated AT1R expression and downregulated α1A-, β1-, β2-AR, and AT2R expression compared to the sham control. High-dose nitrate or olmesartan alone, and especially in combination, decreased the levels of PRA and angiotensin II and downregulated the CHF-induced expression of AT1R, α1A-, β1-, and β2-AR, and AT2R. CHF resulted in significant impairment of the renal tissue, including inflammatory cells infiltration to the tubular interstitium and surrounding the renal glomerulus, and tubular necrosis, which was alleviated in all treatment groups to different degrees.ConclusionsLong-acting nitrates could reverse CHF-induced changes in AR and ATR subtypes in the kidney, and improve cardiac function to protect renal function. Compared with monotherapy, the combination of nitrates and olmesartan shows more significant benefits in regulating AR and ATR subtypes.

Analysis of angiotensin II-Induced rat urinary bladder contractions in the presence of angiotensin II receptors blockers

Objective An application of a specific analysis on recordings obtained from urinary bladder (UB) preparations influenced with Angiotensin II (AngII) and AngII receptor (ATR) blockers was performed. Methods UB preparations were divided as follows: group 1 stimulated with AngII only; group 2:PD123319 (ATR type-2 blocker)+AngII; group 3:Losartan (ATR type-1 blocker)+AngII. The averaged time and force parameters of the contractions were processed by a spline interpolation and graphic images of the different patterns of the contractile activity were obtained. Results The speed of AngII-induced UB contraction, when PD123319 was administered, was significantly higher than those, registered by the application of AngII alone and Losartan + AngII. The presence of Losartan markedly delayed the speed of the overall AngII-induced contraction. Conclusion The study indicates the contribution of both ATR subtypes for the development of AngII-induced UB contraction. Our results showed that probably ATR mediate a reciprocal dynamic response to AngII in the bladder.

10. Angiotensin II modulates the pathogenesis of preeclampsia through sflt-1 production from extravillous cytotrophoblast

Introduction Preeclampsia (PE) is characterized by disturbed extravillous trophoblast migration toward uterine spiral arteries leading to increased uteroplacental vascular resistance and by vascular dysfunction resulting in reduced systemic vasodilatory property. It is known that such pathogenesis is mediated by soluble fms related tyrosine kinase 1 (sFlt-1) and Endoglin (sEng). Our objective was to evaluate the effect of angiotensin II (AngII) on the production of sFlt-1 and sEng from cytotrophoblast. Methods Plasma concentration of sFlt-1 and sEng in our PE model mouse was calculated with AngII receptor subtype 2 (AT2) stimulator (C21). Jar cell and HTR-8 cell was cultured and stimulated by AngII with or without AngII receptor subtype 1 (AT1) inhibitor and AT2 inhibitor. The concentration of sFlt-1 and sEng was calculated in culture medium of the cells using ELISA. Results C21 reduced plasma concentration of sFlt-1 resulted in improved hypertension and proteinuria but did not affect that of sEng. sFlt-1 concentration in the medium of HTR-8 was reduced by AT1 inhibitor and stimulated by AT2 inhibitor. sFlt-1 production of Jar cell could not be responded by AngII. Conclusions This study demonstrated that extravillous trophoblast (HTR-8) could produce sFlt-1 in response to AT1 and AT2; however, cytotrophoblast (Jar) could not be responded by AngII. It is suggested that extravillous trophoblast could be involved in the pathogenesis of PE through the effect of AngII and C21 could be a candidate of new therapy pf PE.

P90. Effect of angiotensin II receptor subtype2 stimulant on the pathogenesis of preeclampsia

Objective Early in pregnancy is a critical period for preeclampsia pathogenesis. We already succeeded in developing a new breed of preeclampsia model mouse using CD40L gene-transfection at implantation. Renin–angiotensin system is reportedly activated in preeclampsia. Angiotensin II (AII) receptor subtype 1 antagonist is a major antihypertensive agent; however, the drug cannot be used during pregnancy because of the fetal nephrotoxic action. Then, we evaluated the effect of AII receptor subtype 2 agonist (C21) on preeclampsia-phenotype expressed mice. Methods Blastocysts were collected from pregnant ICR mice and incubated with adenovirus including CD40L gene and transferred into the uterine horns of pseudopregnant ICR mice. An osmotic pump was placed subcutaneously on the dorsal side with C21 or saline. Blood pressure was measured using the tail cuff method and urine samples were collected using metabolism cage for measuring albumin concentration. On e17.5, uterus and placenta was retrieved from the mice and investigated the structure. Results In CD40L mice, blood pressure was significantly increased from the mid pregnancy and was decreased by C21 during mid pregnancy; however, blood pressure was increased on e17.5 again. The concentration of albuminuria was also significantly increased from the mid pregnancy and slightly decreased by C21 during mid pregnancy; however, the concentration was increased on e17.5 again. The weight of neonates and placentas was also increased by C21. Conclusion C21 influenced renal function, blood pressure only in mid pregnancy. Placental and neonatal weight was improved by C21. It is thought that C21 exerts a favorable influence on preeclampsia. However, the effects do not last for a long time. We should further examine to decide the detail of the amount of C21 for longer and stronger effects.

AT2 receptor activities and pathophysiological implications.

Although angiotensin II subtype-2 receptor (AT2R) was discovered over 2 decades ago, its contribution to physiology and pathophysiology is not fully elucidated. Current knowledge suggests that under normal physiologic conditions, AT2R counterbalances the effects of angiotensin II subtype-1 receptor (AT1R). A major obstacle for AT2R investigations was the lack of specific agonists. Most of the earlier AT2R studies were performed using the peptidic agonist, CG42112A, or the nonpeptidic antagonist PD123319. CGP42112A is nonspecific for AT2R and in higher concentrations can bind to AT1R. Recently, the development of specific nonpeptidic AT2R agonists boosted the efforts in identifying the therapeutic potentials for AT2R stimulation. Unlike AT1R, AT2R is involved in vasodilation by the release of bradykinin and nitric oxide, anti-inflammation, and healing from injury. Interestingly, the vasodilatory effects of AT2R stimulation were not associated with significant reduction in blood pressure. In the kidney, AT2R stimulation produced natriuresis, increased renal blood flow, and reduced tissue inflammation. In animal studies, enhanced AT2R function led to reduction of cardiac inflammation and fibrosis, and reduced the size of the infarcted area. Similarly, AT2R stimulation demonstrated protective effects in vasculature and brain.

Modeling of the Renal Kinetics of the AT1 Receptor Specific PET Radioligand [11C]KR31173

Purpose. The radioligand [11C]KR31173 has been introduced for PET imaging of the angiotensin II subtype 1 receptor (AT1R). The purpose of the present project was to employ and validate a compartmental model for quantification of the kinetics of this radioligand in a porcine model of renal ischemia followed by reperfusion (IR). Procedures. Ten domestic pigs were included in the study: five controls and five experimental animals with IR of the left kidney. To achieve IR, acute ischemia was created with a balloon inserted into the left renal artery and inflated for 60 minutes. Reperfusion was achieved by deflation and removal of the balloon. Blood chemistries, urine specific gravity and PH values, and circulating hormones of the renin angiotensin system were measured and PET imaging was performed one week after IR. Cortical time-activity curves obtained from a 90 min [11C]KR31173 dynamic PET study were processed with a compartmental model that included two tissue compartments connected in parallel. Radioligand binding quantified by radioligand retention (80 min value to maximum value ratio) was compared to the binding parameters derived from the compartmental model. A binding ratio was calculated as DVR = DVS/DVNS, where DVS and DVNS represented the distribution volumes of specific binding and nonspecific binding. Receptor binding was also determined by autoradiography in vitro. Results. Correlations between rate constants and binding parameters derived by the convolution and deconvolution curve fittings were significant (r > 0.9). Also significant was the correlation between the retention parameter derived from the tissue activity curve (Y ret) and the retention parameter derived from the impulse response function (f ret). Furthermore, significant correlations were found between these two retention parameters and DVR. Measurements with PET showed no significant changes in the radioligand binding parameters caused by IR, and these in vivo findings were confirmed by autoradiography performed in vitro. Conclusions. Correlations between various binding parameters support the concept of the parallel connectivity compartmental model. If an arterial input function cannot be obtained, simple radioligand retention may be adequate for estimation of in vivo radioligand binding.

Regulation of angiotensin II receptors beyond the classical pathway

The RAS (renin-angiotensin system) plays a role not only in the cardiovascular system, including blood pressure regulation, but also in the central nervous system. AngII (angiotensin II) binds two major receptors: the AT(1) receptor (AngII type 1 receptor) and AT(2) receptor (AngII type 2 receptor). It has been recognized that AT(2) receptor activation not only opposes AT(1) receptor actions, but also has unique effects beyond inhibitory cross-talk with AT(1) receptor signalling. Novel pathways beyond the classical actions of RAS, the ACE (angiotensin-converting enzyme)/AngII/AT(1) receptor axis, have been highlighted: the ACE2/Ang-(1-7) [angiotensin-(1-7)]/Mas receptor axis as a new opposing axis against the ACE/AngII/AT(1) receptor axis, novel AngII-receptor-interacting proteins and various AngII-receptor-activation mechanisms including dimer formation. ATRAP (AT(1)-receptor-associated protein) and ATIP (AT(2)-receptor-interacting protein) are well-characterized AngII-receptor-associated proteins. These proteins could regulate the functions of AngII receptors and thereby influence various pathophysiological states. Moreover, the possible cross-talk between PPAR (peroxisome-proliferator-activated receptor)-γ and AngII receptor subtypes is an intriguing issue to be addressed in order to understand the roles of RAS in the metabolic syndrome, and interestingly some ARBs (AT(1)-receptor blockers) have been reported to have an AT(1)-receptor-blocking action with a partial PPAR-γ agonistic effect. These emerging concepts concerning the regulation of AngII receptors are discussed in the present review.

Spinophilin regulates central angiotensin II-mediated effect on blood pressure

Central angiotensin II (AngII) plays an important role in the regulation of the sympathetic nervous system. The underlining molecular mechanisms are largely unknown. Spinophilin (SPL) is a regulator of G protein-coupled receptor signaling. Deletion of SPL induces sympathetically mediated arterial hypertension in mice. We tested the hypothesis that SPL restrains blood pressure (BP) by regulating AngII activity. We equipped SPL(-/-) and SPL(+/+) mice with telemetric devices and applied AngII (1.0mgkg(-1)day(-1), minipumps) or the AngII subtype 1 receptor (AT1-R) blocker valsartan (50mgkg(-1)day(-1), gavage). We assessed autonomic nervous system activity through intraperitoneal application of trimethaphan, metoprolol, and atropine. We also tested the effect of intracerebroventricular (icv) AngII on blood pressure in SPL(-/-) and in SPL(+/+) mice. Chronic infusion of AngII upregulates SPL expression in the hypothalamus of SPL(+/+) mice. Compared with SPL(+/+) mice, SPL(-/-) mice showed a greater increase in daytime BP with AngII (19.2 ± 0.8 vs. 13.5 ± 1.6mmHg, p < 0.05). SPL(-/-) showed a greater depressor response to valsartan. BP and heart rate decreased more with trimethaphan and metoprolol in AngII-treated SPL(-/-) than in AngII-treated SPL(+/+) mice. SPL(-/-) mice responded more to icv AngII. Furthermore, brainstem AT1-R and AngII type 2 receptor (AT2-R) expression was reduced in SPL(-/-) mice. AngII treatment normalized AT1-R and AT2-R expression levels. In summary, our findings suggest that SPL restrains AngII-mediated sympathetic nervous system activation. SPL is a hitherto unrecognized molecule with regard to central blood pressure control and may pave the way to novel strategies for the treatment of hypertension.

Similar renoprotection after renin-angiotensin-dependent and -independent antihypertensive therapy in 5/6-nephrectomized Ren-2 transgenic rats: are there blood pressure-independent effects?

1. Hypertension plays a critical role in the progression of chronic kidney disease (CKD) to end-stage renal disease (ESRD), but it has also been postulated that antihypertensive drugs that block the renin-angiotensin system (RAS) show class-specific renoprotective actions beyond their blood pressure (BP)-lowering effects. 2. Because this notion has recently been questioned, in the present study we compared the effects of a RAS-dependent antihypertensive therapy (a combination of trandolapril, an angiotensin-converting enzyme inhibitor (ACEI) and losartan, an angiotensin-II (AngII) receptor subtype 1A receptor antagonist) with a 'RAS-independent' antihypertensive therapy (a combination of labetalol, an alfa- and beta-adrenoreceptor antagonist with the diuretics, hydrochlorothiazide and furosemide) on the progression of CKD after 5/6 renal ablation (5/6 NX) in Ren-2 renin transgenic rats (TGR), a model of AngII-dependent hypertension. Normotensive transgene-negative Hannover Sprague-Dawley (HanSD) rats after 5/6 NX served as controls. 3. RAS-dependent and -independent antihypertensive therapies normalized BP and survival rate, and prevented the development of cardiac hypertrophy and glomerulosclerosis to the same degree in 5/6 NX HanSD rats and in 5/6 NX TGR. The present findings show that renoprotection, at least in rats after 5/6 NX, is predominantly BP-dependent. When equal lowering of BP was achieved, leading to normotension, cardio- and renoprotective effects were equivalent irrespective of the type of antihypertensive therapy. 4. These findings should be taken into consideration in attempts to develop new therapeutic approaches and strategies aimed to prevent the progression of CKD and to lower the incidence of ESRD.

Radioligands for the Angiotensin II Subtype 1 (AT1) Receptor

Over the last years, ligands for angiotensin II subtype 1 receptor (AT1R) have been developed as an alternative to the use of angiotensin-converting enzyme (ACE) inhibitors for controlling high blood pressure. Radiolabeled versions of these ligands have proven vital to the development of more potent and specific drugs for the treatment of hypertension. Imaging studies using radiolabeled AT1R ligands have also elucidated the role these receptors play in angiogenesis as well as in various disease states beyond hypertension.

E0148 Changes in expression of ERK1/2, Angiotensin II receptors in hibernating myocardium

ObjectiveTo investigate the variation and significance of ERK1/2, Angiotensin II subtype 1 receptor (AT1R) and Angiotensin II subtype 2 receptor (AT2R) in hibernating myocardium.Methods6 little domestic Chinese pigs were implanted...

Change of expression of renal α1-adrenergic receptor and angiotensin II receptor subtypes with aging in rats

It has been considered that the functional decline of renal vasoconstriction during senescence is associated with an alteration in renal alpha1-adrenergic receptor (alpha1-AR) expression. While alterations in renal angiotensin II receptor (ATR) expression was considered to have an effect on renal structure and function, until now little information has been available concerning alpha1-AR and ATR expression variations over the entire aging continuum. The present study was undertaken to examine the expression levels of alpha1-AR and ATR subtypes in renal tissue during the spectrum running from young adulthood, to middle age, to the presenium, and to the senium. Semiquantitative Reverse Transcription Polymerase Chain Reaction (RT-PCR) and Western Blot were used to quantify the messenger RNA (mRNA) and protein levels of alpha1-AR and ATR subtypes in renal tissue in 3-month-old (young adult), 12-month-old (middle age), 18-month-old (presenium) and 24-month-old (senium) Wistar rats. alpha1A-AR expression decreased gradually with aging: it was decreased during middle age, the presenium and the senium, compared, respectively, with young adult values (p<0.01), and there was a significant decline both in the presenium with respect to middle age and in the senium with respect to the presenium. alpha1B-AR and alpha1D-AR expression were unmodified during senescence. AT1R expression was unaffected by aging during young adulthood and middle age, but exhibited a remarkable downregulation in the presenium and senium periods (p<0.01). AT2R expression was markedly increased in the senium (p<0.01). These results suggest that there are considerable variations in the expression levels of renal alpha1-AR and ATR subtypes during aging. alpha1A-AR expression downregulation may account for the reduced reactivity of renal alpha1-AR to vasoconstrictors and to renal function decline in the senium. Both the downregulation of AT1R and the upregulation of AT2R may be influential in maintaining normal physiological renal function during aging.

Alteration of messenger RNA and protein levels of cardiac alpha(1)-adrenergic receptor and angiotensin II receptor subtypes during aging in rats

Structural and functional alterations in the senescent heart have been associated with an activated sympathetic nervous system and a regional cardiac renin-angiotensin system. To date, however, limited information related to their expression alteration during the whole procress of growth and development has been reported. To examine the expression of alpha(1)-adrenergic receptor (alpha(1)-AR) and angiotensin II receptor (ATR) subtypes in the left ventricle of hearts from young adult, middle-aged, presenescent and senescent rats. Semiquantitative reverse transcriptase polymerase chain reaction and Western blot were used to quantitate the messenger RNA and protein of alpha(1)-AR and ATR subtypes, respectively, in the left ventricles of three- (young adult), 12- (middle age), 18- (presenescent) and 24-month-old (senescent) Wistar rats. alpha(1A)-AR expression decreased gradually with age, and alpha(1D)-AR expression was repressed in middle age and presenescence, while the expression of alpha(1B)-AR remained unchanged during senescence. AT(1)R expression was unaffected by aging from young adulthood to presenescence, but exhibited a remarkable upregulation in senescence. There were no significant discrepancies of cardiac AT(2)R expression among the four age groups, but both messenger RNA and protein had a tendency to upregulate during aging. The results suggest that there are considerable changes of expression of cardiac alpha(1)-AR and ATR subtypes during growth and development. The change of cardiac alpha(1)-AR and ATR expression during aging is a protective response to senescence by keeping normal myocardial contractility, while the upregulation of AT(1)R and AT(2)R promotes age-related myocardium hypertrophy and cardiac remodelling.

Positron-Emission Tomography Imaging of the Angiotensin II Subtype 1 Receptor in Swine Renal Artery Stenosis

The angiotensin II subtype 1 receptor (AT(1)R) has been linked to the development and progression of renovascular hypertension. In this study we applied a pig model of renovascular hypertension to investigate the AT(1)R in vivo with positron-emission tomography (PET) and in vitro with quantitative autoradiography. AT(1)R PET measurements were performed with the radioligand [(11)C]KR31173 in 11 control pigs and in 13 pigs with hemodynamically significant renal artery stenosis; 4 were treated with lisinopril for 2 weeks before PET imaging. The radioligand impulse response function was calculated by deconvolution analysis of the renal time-activity curves. Radioligand binding was quantified by the 80-minute retention of the impulse response function. Median values and interquartile ranges were used to illustrate group statistics. Radioligand retention was significantly increased (P=0.044) in hypoperfused kidneys of untreated (0.225; range: 0.150 to 0.373) and lisinopril-treated (0.237; range:0.224 to 0.272) animals compared with controls (0.142; range:0.096 to 0.156). Increased binding of [(11)C]KR31173 documented by PET in vivo was confirmed by in vitro autoradiography. Both in vivo and in vitro binding measurements showed that the effect of renal artery stenosis on the AT(1)R was not abolished by lisinopril treatment. These studies provide insight into kidney biology as the first in vivo/in vitro experimental evidence about AT(1)R regulation in response to reduced perfusion of the kidney. The findings support the concept of introducing AT(1)R PET as a diagnostic biomarker of renovascular disease.

Effects of irbesartan and perindopril on forearm reactive hyperemia and inflammatory process, in normotensive patientswith coronary artery disease

The suppression of angiotensin II production by angiotensin converting enzyme inhibitors (ACEi), reduces the stimulation of both angiotensin-II receptor subtypes (AT1 and AT2), whereas angiotensin receptors antagonists preferentially block AT1 and leave AT2 unopposed [ [1] Levy B.I. Can angiotensin II type 2 receptors have deleterious effects in cardiovascular disease? Implications for therapeutic blockade of the renin–angiotensin system. Circulation. 2004; 109: 8-13 Crossref PubMed Scopus (149) Google Scholar ]. Long-term administration of AT1 antagonists increases plasma angiotensin-II and thereby over-stimulates AT2. However, it is unclear whether the beneficial effects observed with AT1 arise from the fall in blood pressure or to activation of AT2[ [1] Levy B.I. Can angiotensin II type 2 receptors have deleterious effects in cardiovascular disease? Implications for therapeutic blockade of the renin–angiotensin system. Circulation. 2004; 109: 8-13 Crossref PubMed Scopus (149) Google Scholar ]. Both ACEi and AT1 antagonists have anti-inflammatory properties [ [2] Schieffer B. Bunte C. Witte J. et al. Comparative effects of AT1-antagonism and angiotensin-converting enzyme inhibition on markers of inflammation and platelet aggregation in patients with coronary artery disease. J Am Coll Cardiol. 2004; 44: 362 Abstract Full Text Full Text PDF PubMed Scopus (217) Google Scholar ], although data comparing their effects are still limited.

Role of Renin-Angiotensin System in Vascular Endothelial Dysfunction of Pregnancy-Induced Hypertension

During pregnancy, the renin-angiotensin system (RAS) plays an important role in regulating the markedly expanded circulating blood volume in the uteroplacental circulation. RAS is activated during normal pregnancy; however, blood pressure decreases from the 1st trimester to the 2nd trimester. Vascular responsiveness to angiotensin II (AngII) decreases early in pregnancy; on the other hand, pregnant women who subsequently develop PIH are exquisitely sensitive to the pressor effect of AngII. Interestingly. the maternal circulating RAS and the placental concentration of AngII receptor (ATR) are stable or reduced in PIH. The balance of expression between ATR subtype 1 (AT1) and 2 (AT2) is potentially important in the regulation of vascular tone during pregnancy. Increased AT1/AT2 may explain the loss of vascular refractoriness to AngII in the pathogenesis of PIH. Recently, endothelial progenitor cell (EPC) has been found in the peripheral blood of pregnant women. Although AngII stimulates EPC proliferation, the mobilization is inhibited in PIH. Impairment of EPC mobilization may contribute to insufficient regeneration of endothelium in the impaired utero-placental circulation of PIH. This review focuses on vascular endothelial dysfunction and the effect of RAS in the pathophysiology of PIH.

Altered expression of angiotensin II receptor subtypes and transforming growth factor-? in the heart of nitrofen-induced diaphragmatic hernia in rats

The renin-angitensin system (RAS) plays an important role as a growth factor in cardiac development. Angiotensin converting enzyme is involved in converting angiotensin I to angiotensin II (Ag-II). The effects of Ag-II are mediated by two primary receptors, type 1 (AT1) and type 2 (AT2). Ag-II stimulates transforming growth factor-beta1(TGF-beta1) and acts as a potent stimulant of myocyte growth and fetal contractile protein gene transcription. The aim of this study was to determine the expression of Ag-II receptor subtypes and TGF-beta1 in the hypoplastic heart of nitrofen-induced congenital diaphragmatic hernia (CDH). CDH was induced in pregnant rats following administration of 100 mg nitrofen on day 9.5. The fetuses were divided into three groups: normal controls (n=16), nitrofen-treated without CDH (n=16), and nitrofen-induced CDH (n=16). Reverse transcriptase-polymerase chain reaction was performed to evaluate mRNA expression of AT1, AT2, and TGF-beta1. Levels of mRNA were expressed as a ratio of the band density divided by that of beta-actin. AT1 and AT2 mRNA expressions were significantly decreased in CDH heart compared with controls (0.43+/-0.33 vs. 1.0+/-0.48 and 0.62+/-0.23 vs. 1.4+/-0.43, respectively). TGF-beta1 mRNA expressions were also significantly decreased in CDH heart compared with controls (0.38+/-0.17 vs. 0.72+/-0.26). No significant difference was found between the hearts of controls and nitrofen-treated rats without CDH. The decreased expression of AT1, AT2, and TGF-beta1 mRNA in the hypoplastic heart suggests that the downregulation of RAS may be involved in the pathogenesis of cardiac hypoplasia in nitrofen-induced CDH.

Vessel-Specific Regulation of Angiotensin II Receptor Subtypes During Ovine Development

Umbilical and systemic responses to angiotensin II differ in term fetal sheep, and peripheral vascular responses are attenuated or absent before and after birth. These observations may reflect developmental differences in angiotensin II receptor (AT) subtypes in vascular smooth muscle (VSM). Studies of AT subtype ontogeny and regulation are generally limited to the aorta, which may not be extrapolated to other arteries, and neither is completely described during ovine development. We therefore characterized VSM AT subtype expression and regulation throughout an extended period of development in umbilical and carotid artery and aorta from fetal (85-146 d gestation), postnatal (5-23 d), and adult sheep, measuring AT(1) and AT(2) mRNA and protein and performing immunohistochemistry. Parallel increases in umbilical AT(1) mRNA and protein began early in gestation and continued to term, and although AT(2) mRNA was unchanged, protein levels decreased >90% at term. Fetal carotid AT(1) mRNA was <40% of adult values and unchanged before birth; however, AT(1) protein rose >2-fold at term. After birth, AT(1) mRNA increased to 85% of adult values and was associated with another 2-fold rise in protein. In contrast, carotid AT(2) mRNA and protein fell in parallel throughout development and were barely detectable in the newborn and the adult. Immunostaining was consistent with observations in both arteries. A third pattern occurred in aortic VSM. The ontogeny of AT subtype expression and regulation is vessel specific, with changes in umbilical VSM beginning very early in development. Although the mechanisms that regulate mRNA and protein expression are unclear, these changes parallel differences in VSM maturation and function and local blood flow.