Prevalence of AT1R antibody (AT1R-Ab) among Malaysian multi-ethnic population

BackgroundAngiotensin II type 1 receptor antibody (AT1R-Ab) is a non-HLA antibody that has been reported to cause antibody-mediated rejection and graft loss in kidney transplantation. The prevalence of positive AT1R-Ab varies between 8% and 18% in different regions. Thus, this study aims to determine the prevalence of AT1R-Ab among the Malaysian population.MethodologyAll sera for AT1R-Ab were collected at the University Malaya Medical Centre (UMMC), Kuala Lumpur, Malaysia. The sera were centrifuged and kept refrigerated at −80 °C before being transported to the South Australian Transplantation and Immunogenetics Laboratory (SATIS). Enzyme-linked immunosorbent assay kit (One Lambda) was used for the detection of AT1R-Ab, and it was performed according to the manufacturer's instructions. The level of >17.1 U/mL was considered to be AT1R-Ab positive; 10.0–17.1 U/mL at risk, and <10.0 U/mL negative.ResultsA total of 115 samples were collected from 99 patients pre and post-kidney transplant recipients. From the pre-transplant sera (n = 68) 17.7% were positive, 35.3% were at risk and 47.0% were negative. The positive AT1R-Ab cohort were relatively younger, with a mean age of 34.7 ± 8.3 years old and statistically significant, with a p-value of 0.028. Among the sera that were tested positive, 19.0% were from the Chinese ethnicity, 6.7% from Malay and 16.7% from Indian. There was no difference in the rejection episodes, persistent or de novo HLA-DSA, and graft function between the group (AT1R-Ab negative vs AT1R-Ab at risk and positive) and the results were consistent in a model adjusted for all potential confounders.ConclusionThe prevalence of positive (>17.1 U/mL) pre-transplant AT1R-Ab was 17.7% and 35.3% were at risk (10.0–17.1 U/mL) in our pre-transplant cohort.     

MAS受体与AT1受体的相互作用

RAS的2个重要成员Ang-(1-7)和血管紧张素II（Ang II）主要作用于MAS受体和AT1受体发挥作用。Ang-(1-7)和Ang II之间存在着复杂的相互作用，两者的受体在细胞和组织中相互作用，其可能的机制之一是受体的寡聚化     

Enhanced osmotic responsiveness in angiotensin AT1a receptor deficient mice: evidence for a role for AT1b receptors

Experiments were performed to study the role of angiotensin (Ang) AT1a and AT1b receptor subtypes in osmotic regulation of blood pressure using gene deletion and pharmacological methods. The cardiovascular effects of hypertonic saline (HS) or vasopressin (VP) delivered via vascular catheters were measured in Ang AT1a gene deletion (AT1a−/−) and control (AT1a+/+) mice. Blood pressure (BP) and heart rate (HR) were recorded in conscious mice using direct carotid catheters. Plasma osmolality and VP concentration were also measured. The major finding was that deletion of AT1a receptors resulted in enhanced BP response to osmotic stimulation. This was seen after acute HS injection (20 μl, 20% NaCl). The peak percentage change in mean arterial pressure (MAP) was 15.4 ± 1.9% versus 28.1 ± 2.4% (AT1a+/+ versus AT1a −/−, respectively). Losartan (AT1 antagonist), but not PD123319 (AT2 antagonist), inhibited the HS-induced MAP response, specifically in AT1a−/− mice. Plasma osmolality and VP concentration were elevated after HS injection with no differences noted between groups. Vascular injection of VP (5 ng g⁻¹) increased BP and HR, with similar MAP response between groups. Evidence shows that removal of Ang AT1a receptors results in a significant enhancement in the pressor response to acute osmotic stimulation. Studies of AT1 receptor blockade indicate that complementary Ang AT1b receptors, but not AT2 receptors, may be involved in the osmotic response.     

A DNA polymorphism at the angiotensin II type 1 receptor (AT1R) locus and myocardial infarction

Two hundred and thirty-five survivors of myocardial infarction (MI) were compared to 384 controls with respect to distribution of genotypes and gene frequencies in the A1166C polymorphism at the angiotensin II type 1 receptor (AT1R) locus. No differences in allele frequencies or genotype distribution were observed when all patients were compared with all controls. When comparing CC homozygotes with the combined group of CA heterozygotes and AA homozygotes (CA/AA), a difference in borderline significance between the MI group and controls was observed (p = 0.05). In males alone, this difference was much more pronounced because of the larger proportion of males with the CC genotype in MI cases than in male controls (p = 0.01). No significant differences were observed between female cases and controls. No interaction between the insertion/deletion (I/D) polymorphism at the angiotensin I-converting enzyme (ACE) locus and the polymorphism at the AT1R locus was detected. When subdividing the subjects into a "low-risk" and a "high-risk" group, based on levels of apolipoprotein B (apoB) and body mass index (BMI), and whether or not the person used lipid-lowering drugs, the frequency of CC homozygotes in male cases of the "low-risk" group differed significantly compared to the frequency in male controls of the "low-risk" group (p < 0.001). No differences were observed in females, but the number of "low-risk" group female cases was low (n = 3). Thus, CC homozygosity appears to be associated with MI in Norwegian males, especially among those with a "low-risk" phenotype.     

Activating auto-antibodies against the AT1 receptor in preeclampsia

Immune mechanisms have been shown to be important in the pathogenesis of preeclampsia. Here, we review our studies of agonistic antibodies against the AT1 receptor in the pathogenesis as well as a pathologic phenotype of this disorder, focusing on observations in our laboratory. We have demonstrated their specificity of the binding by Western blotting, co-localization, and co-immunoprecipitation experiments. AT1-AA induce signaling in vascular cells and trophoblasts including AP-1 and nuclear factor-kappaB (NF-kappaB) activation. The signaling results in tissue factor production and reactive oxygen species (ROS) generation, both of which have been implicated in preeclampsia. The role of AT1-AA in preeclampsia and other severe hypertensive conditions has not yet been proven with certainty. However, we believe the findings are compelling and warrant further study.     

THE BODY SPEAKS: BION'S PROTOMENTAL SYSTEM AT WORK1

Psychoanalysis has primarily explored somatic experience in relation to love and intimacy. This paper focuses on the body in relation to work. It explores the experience that what patients increasingly present for analysis are the traumas and pleasures of being caught up with and belonging to a body larger than their own, whether in a couple, a group, a work organization or the body politic. It begins with an exploration of Bion's idea of a relationship between protomentality and group disease. It goes on to consider what can be conceived of as his ecological methodology, which enables movement between different ‘fields of study’ ( Bion 1962 ). These are applied to the health risks encountered by psychotherapists and the profession as a whole. Finally, there is a proposal for mentoring to address professional health, as an under‐developed element in the profession.     

Angiotensin II subtype 1A (AT1A) receptors in the rat sensory vagal complex: subcellular localization and association with endogenous angiotensin

Angiotensin II (Ang II) type 1 (AT1) receptors are prevalent in the sensory vagal complex including the nucleus tractus solitarii (NTS) and area postrema, each of which has been implicated in the central cardiovascular effects produced by Ang II. In rodents, these actions prominently involve the AT1A receptor. Thus, we examined the electron microscopic dual immunolabeling of antisera recognizing the AT1A receptor and Ang II to determine interactive sites in the sensory vagal complex of rat brain. In both the area postrema and adjacent dorsomedial NTS, many somatodendritic profiles were dually labeled for the AT1A receptor and Ang II. In these profiles, AT1A receptor-immunoreactivity was often seen in the cytoplasm beneath labeled portions of the plasma membrane and in endosome-like granules as well as Golgi lamellae and outer nuclear membranes. In addition, AT1A receptor labeling was detected on the plasma membrane and in association with cytoplasmic membranes in many small axons and axon terminals. These terminals were morphologically heterogeneous containing multiple types of vesicles and forming either inhibitory- or excitatory-type synapses. In the area postrema, AT1A receptor labeling also was detected in many non-neuronal cells including glia, capillary endothelial cells and perivascular fibroblasts that were less prevalent in the NTS.We conclude that in the rat sensory vagal complex, AT1A receptors are strategically positioned for involvement in modulation of the postsynaptic excitability and intracrine hormone-like effects of Ang II. In addition, these receptors have distributions consistent with diverse roles in regulation of transmitter release, regional blood flow and/or vascular permeability.     

AT1 receptor antagonism improves endothelial dysfunction in postmenopausal women

The menopause is associated with an increased incidence of atherosclerotic disease. Estrogen deficiency causes AT1 receptor overexpression which is involved in the development of vascular dysfunction. The effect of a 6 week-treatment with the AT1 receptor antagonist candesartan (16 mg/d) on endothelium-dependent vasorelaxation was compared to the treatment with placebo or the calcium channel antagonist felodipine (5 mg/d) in 29 postmenopausal women in the absence or presence of hormone replacement therapy (HRT) in a prospective, double-blind, randomized cross-over study. Endothelial function was assessed by measurement of forearm blood flow (FBF) by venous occlusion plethysmography. FBF during reactive hyperemia was significantly improved by candesartan in patients without HRT (hyperemic peak flow and area under the FBF curve), whereas felodipine and placebo exerted no effect. In patients with HRT, no treatment regimen showed a significant effect on endothelial function. Nitroglycerin-induced vasorelaxation and basal FBF were not significantly altered in all groups. AT1 receptor antagonism improves vascular function in postmenopausal women without HRT. Thus, AT1 receptor blockade may resemble an efficient approach for the prevention of vascular dysfunction in estrogen-deficient women.     

AT1R Activating Autoantibodies in Hematopoietic Stem Cell Transplantation

Angiotensin II type 1 receptor activating autoantibodies (AT1R-AAs) have gained attention in solid organ transplant as non-HLA antibodies associated with rejection, vasculopathy, and graft dysfunction. These antibodies have also been reported in the context of pre-eclampsia, scleroderma, and isolated hypertension. Here, we present 3 post-hematopoietic stem cell transplant (HSCT) cases with patients demonstrating elevated levels of AT1R-AAs detected within the first year post-HSCT. All patients had hypertension, and 2 patients exhibited profound diarrhea and hypokalemia. The hypertension, in all cases, was refractory to multiple classes of antihypertensives. Upon autoantibody identification, an angiotensin receptor blocker, losartan, was promptly initiated, and all patients showed blood pressure improvement. The 2 patients with electrolyte disturbances had rapid normalization of these levels and resolution of the diarrhea. These cases demonstrate a previously unreported association of elevated AT1R-AA levels in post-HSCT patients with a rapid response to angiotensin receptor blockade initiation.     

AT1 receptor-mediated angiotensin II activation and chemotaxis of T lymphocytes

Angiotensin II (Ang II), a central renin–angiotensin system (RAS) effector molecule, and its receptors, AT₁ and AT₂, have been shown to be involved in the inflammatory aspects of different diseases, however the cellular mechanisms underlying the regulation of immunity are not fully understood. In this work, using spleen-derived CD4⁺ and CD8⁺ T lymphocytes activated in vitro, we tested the influence of Ang II on different aspects of the T cell function, such as activation and adhesion/transmigration through endothelial basal membrane proteins. The addition of 10⁻⁸ M Ang II did not change any of the parameters evaluated. However, 10⁻⁶ M losartan, an AT₁ receptor antagonist: (i) reduced the percentage of CD25⁺ and CD69⁺ cells of both subsets; (ii) inhibited adhesion of these cells to fibronectin or laminin by 53% or 76%, respectively and (iii) significantly reduced transmigration through fibronectin or laminin by 57% or 43%, respectively. In addition, 10⁻⁶ M captopril, an angiotensin-converting enzyme inhibitor had similar effects to Ang II, however its effects were reverted by exogenous Ang II (10⁻⁸ M). None of these responses was modified by 10⁻⁷ M PD123319, an AT₂ antagonist. These data reinforce the notion of endogenous production of Ang II by T cells, which is important for T cell activation, and adhesion/transmigration induced on interaction with basal membrane proteins, possibly involving AT₁ receptor activation. Moreover, AT₁ receptor expression is 10-fold higher in activated T lymphocytes compared with naive cells, but AT₂ receptor expression did not change after T cell receptor triggering.     

Effect of AT1 receptor blockade on intermittent hypoxia-induced endothelial dysfunction

Chronic intermittent hypoxia (CIH) raises arterial pressure, impairs vasodilator responsiveness, and increases circulating angiotensin II (Ang II); however, the role of Ang II in CIH-induced vascular dysfunction is unknown. Rats were exposed to CIH or room air (NORM), and a subset of these animals was treated with losartan (Los) during the exposure period. After 28 days, vasodilatory responses to acetylcholine or nitroprusside were measured in isolated gracilis arteries. Superoxide levels and Ang II receptor protein expression were measured in saphenous arteries. After 28 days, arterial pressure was increased and acetylcholine-induced vasodilation was blunted in CIH vs. NORM, and this was prevented by Los. Responses to nitroprusside and superoxide levels did not differ between CIH and NORM. Expression of AT(2)R was decreased and the AT(1)R:AT(2)R ratio was increased in CIH vs. NORM, but this was unaffected by Los. These results indicate that the blood pressure elevation and endothelial dysfunction associated with CIH is dependent, at least in part, on RAS signaling.     

AT1-receptor autoantibodies and uteroplacental RAS in pregnancy and pre-eclampsia

Pre-eclampsia is a common, pregnancy-induced disorder, consisting of hypertension and proteinuria. The condition is one of the leading causes for maternal and perinatal morbidity and mortality. Nonetheless, the underlying molecular mechanisms remain unclear. Immunological mechanisms and the renin–angiotensin system have been implicated in the development of pre-eclampsia. Agonistic autoantibodies to the angiotensin II type I receptor (AT1-AA) have been identified in pre-eclamptic patients, unifying the two hypothesis. Evidence has also accumulated for the existence and importance of a local, utroplacental renin–angiotensin system. We summarize recent data emphasizing the pathophysiological role for the autoantibodies and the uteroplacental renin–angiotensin system.     

On the different roles of AT1 and AT2 receptors in stretch-induced changes of connexin43 expression and localisation

Cyclic mechanical stretch (CMS) and angiotensin II (ATII) play an important role in cardiac remodelling. Thus, we aimed to examine how ATII affects CMS-induced changes in localisation and expression of the gap junction protein connexin43 (Cx43). Neonatal rat cardiomyocytes cultured on gelatin-coated Flexcell cell culture plates were kept static or were exposed to CMS (110?% of resting length, 1?Hz) for 24?h with or without additional ATII (0.1?μmol/L). Moreover, inhibitors of ATII receptors (AT-R) were used (for AT₁-R: losartan 0.1?μmol/L, for AT₂-R: PD123177 0.1?μmol/L). Thereafter, the cardiomyocytes were investigated by immunohistology, PCR and Western blot. After 24?h of CMS, cardiomyocytes were significantly elongated and orientated 75?±?1.6° nearly perpendicular to the stretch axis. Furthermore, CMS significantly accentuated Cx43 at the cell poles (ratio Cx43 polar/lateral static: 2.32?±?0.17; CMS: 10.08?±?3.2). Additional ATII application significantly reduced Cx43 polarisation (ratio Cx43 polar/lateral ATII: 4.61?±?0.42). The combined administration of ATII and losartan to CMS further reduced Cx43 polarisation to control levels, whilst the AT₂-R blocker PD123177 restored polarisation. Moreover, CMS and ATII application resulted in a significant Cx43 protein and Cx43 mRNA up-regulation which could be blocked by losartan but not by PD123177. Thus, CMS results in a self-organisation of the cardiomyocytes leading to elongated cells orientated transversely towards the stretch axis with enhanced Cx43 expression and Cx43 accentuation at the cell poles. ATII enhances total Cx43 mRNA and protein expression probably via AT₁-R (=inhibitory effect of losartan) and reduces Cx43 polarisation presumably via AT₂-R, since PD123177 (but not losartan) inhibited the negative effects of ATII on polarisation.     

AT1 receptor-mediated angiotensin II activation and chemotaxis of T lymphocytes

Angiotensin II (Ang II), a central renin-angiotensin system (RAS) effector molecule, and its receptors, AT(1) and AT(2), have been shown to be involved in the inflammatory aspects of different diseases, however the cellular mechanisms underlying the regulation of immunity are not fully understood. In this work, using spleen-derived CD4(+) and CD8(+) T lymphocytes activated in vitro, we tested the influence of Ang II on different aspects of the T cell function, such as activation and adhesion/transmigration through endothelial basal membrane proteins. The addition of 10(-8)M Ang II did not change any of the parameters evaluated. However, 10(-6)M losartan, an AT(1) receptor antagonist: (i) reduced the percentage of CD25(+) and CD69(+) cells of both subsets; (ii) inhibited adhesion of these cells to fibronectin or laminin by 53% or 76%, respectively and (iii) significantly reduced transmigration through fibronectin or laminin by 57% or 43%, respectively. In addition, 10(-6)M captopril, an angiotensin-converting enzyme inhibitor had similar effects to Ang II, however its effects were reverted by exogenous Ang II (10(-8)M). None of these responses was modified by 10(-7)M PD123319, an AT(2) antagonist. These data reinforce the notion of endogenous production of Ang II by T cells, which is important for T cell activation, and adhesion/transmigration induced on interaction with basal membrane proteins, possibly involving AT(1) receptor activation. Moreover, AT(1) receptor expression is 10-fold higher in activated T lymphocytes compared with naive cells, but AT(2) receptor expression did not change after T cell receptor triggering.     

Novel role of mechanosensitive AT1B receptors in myogenic vasoconstriction

Myogenic vasoconstriction is an inherent property of vascular smooth muscle cells (VSMCs) of resistance arteries harboring ill-defined mechanosensing and mechanotransducing elements. G protein-coupled receptors (GPCRs) are discussed as mechanosensors in VSMCs. In this study, we sought to identify and characterize the role and impact of GPCRs on myogenic vasoconstriction. Thus, we analyzed mRNA expression levels of GPCRs in resistance versus preceding conduit arteries revealing a significant enrichment of several GPCRs in resistance vessels. Selective pharmacological blockade of the highly expressed GPCRs in isolated murine mesenteric arteries ex vivo decreased myogenic vasoconstriction. In particular, candesartan and losartan most prominently suppressed myogenic tone, suggesting that AT₁ receptors play a central role in myogenic vasoconstriction. Analyzing angiotensinogen^?/? mice, a relevant contribution of locally produced angiotensin II to myogenic tone could be excluded. Investigation of AT_1A ^?/? and AT_1B ^?/? murine mesenteric arteries revealed that AT_1B, but not AT_1A, receptors are key components of myogenic regulation. This notion was supported by examining fura-2-loaded isolated AT_1A ^?/? and AT_1B ^?/? VSMCs. Our results indicate that in VSMCs, AT_1B receptors are more mechanosensitive than AT_1A receptors even at comparable receptor expression levels. Furthermore, we demonstrate that the mechanosensitivity of GPCRs is agonist-independent and positively correlates with receptor expression levels.     

AT1-AA通过上调细胞自噬诱导大鼠心功能不全

目的:建立血管紧张素Ⅱ1型受体自身抗体(AT1-AA)主动免疫大鼠模型,观察AT1-AA对心肌细胞自噬和凋亡的影响,并探究其引起心功能不全的作用机制.方法:以人工合成的血管紧张素Ⅱ1型受体细胞外第二环肽段主动免疫建立大鼠模型;小动物超声仪检测心脏功能和结构变化;HE染色观察心脏结构变化;TUNEL染色检测心肌细胞凋亡情...