Angiotensinogen is secreted by pure rat neuronal cell cultures

Previous studies are divided between those which support a neuroglial (astrocyte) source for brain angiotensinogen and those which indicate that both astrocytes and neurones synthesize the precursor of angiotensin II. In this study, separate cultures of astrocytes and neuronal cells were prepared and established as being essentially pure by appropriate immunocytochemical cell markers. Angiotensinogen production by these cultures, as measured by a direct radioimmunoassay, was 20.74 +/- 3.62 ng angiotensinogen/10(6) cells/24 h (mean +/- S.D., n = 8) for astrocytes and 4.39 +/- 0.94 ng/10(6) cells/24 h (mean +/- S.D., n = 29) for neurones. Angiotensinogen secretion from both cell types was unaffected by treatments which stimulate the regulatory secretory pathway by modulating intracellular cAMP levels. In contrast, it was reduced from 23.20 +/- 2.14 to 8.14 +/- 1.31 ng/10(6) cells/24 h (S.E.M., n = 7) in astrocyte cultures by the constitutive pathway inhibitor, monensin. Angiotensinogen secreted by astrocytes and neurones was compared to pure angiotensinogen and that in plasma and cerebrospinal fluid (CSF) by cation-exchange mono S column chromatography. Pure angiotensinogen eluted as two separate peaks corresponding to the major forms of plasma angiotensinogen, whereas angiotensinogen in CSF and culture media coeluted with a third minor form of plasma angiotensinogen. It was concluded that neuronal cells as well as astrocytes secrete angiotensinogen which is distinctly different from plasma angiotensinogen.     

The Profile of the Cytokines Secreted During the Generation of T-Helper Cells from Atopic Asthmatic Subjects

This study investigated cytokine release by T-cell lines from atopic and nonatopic individuals in the presence of specific aeroallergen. Cell lines from atopic and nonatopic individuals secreted IL-2 for less than 14 and more than 21 days, respectively. All of the atopic, but not the nonatopic, cell lines exhibited a biphasic peak in IL-4 and IL-5 secretion. Flow cytometry revealed that, after 35 days, 89.3% of the atopic cells were T helpers and 73.2% were activated. Only 7.4% of the nonatopic cells displayed activation markers. In conclusion, T-cell differentiation may be controlled by other factors in addition to stimulation by aeroallergens.     

Induction of Angiotensinogen Synthesis and Secretion by Angiotensin II

ABSTRACT

The effect of angiotensin II (ANG II) on the secretion of angiotensinogen was studied in isolated rat hepatocytes, obtained by the collagenase perfusion technique and Percoll-density gradient centrifugation, and in the isolated perfused rat liver. In isolated hepatocytes, steady state concentrations of about 1, 10 or 100 nM of ANG II during 90 min of preincubation resulted in a 5, 27 and 33% increase of angiotensinogen secreted during a subsequent 3 hour incubation period. Secretion rates during the last hour of incubation were increased by about 70% by the two higher ANG II concentrations, as compared to controls. Hydrocortisone also induced an increased secretion of angiotensinogen in hepatocytes. The effect of ANG II was prevented by saralasin, a competitive ANG II antagonist and by actinomycin D. ANG II had no effect of the rate of albumin secretion and of total protein secretion. In the isolated perfused liver, ANG II induced a similar increase of angiotensinogen secretion, without affecting albumin and total protein secretion rates. These observations are consistent with the view that ANG II is participating in a feed back stimulation system of angiotensinogen synthesis and secretion in vivo.     

Inhibitors of Renin: Present and Future

Four classes of compounds have been demonstrated to be renin inhibitors of high potency: specific antibody, general peptide inhibitors of acid proteases, analogs of angiotensinogen and peptides that are related to the amino-terminal sequence of renin's precursor (Prorenin). With the purification of renin, specific polyclonal or monoclonal antibodies have become available. The former have already been used extensively in physiologic studies in intact animals. Pepstatin is an inhibitor of many acid proteases. Its in vivo application has been retarded by its relative insolubility, but recent chemical modifications, particularly the addition of charged amino acids at the carboxy-terminus have rendered it more useful. The minimal substrate for renin is an octapeptide segment of the protein substrate: His-Pro-Phe-His-Leu-Leu-Val-Tyr. Variants of this sequence have resulted in competitive inhibitors that are useful in vivo. Recently, remarkably active inhibitors have been synthesized by reducing the peptide bond that is cleaved by renin, producing what may be a transition state inhibitor. Several of these peptides have been shown to be effective as in vivo inhibitors of the hypertensive effect of the enzyme. The development of inhibitors based on Pro-renin sequences are awaited with interest.     

Advanced Glycation End Products Stimulate Angiotensinogen Production in Renal Proximal Tubular Cells

Background

Elevated advanced glycation end products (AGE) in diabetes mellitus (DM) are implicated in the progression of DM-associated tissue injury, including diabetic nephropathy. The intrarenal renin-angiotensin system, in particular augmentation of angiotensinogen (AGT) in proximal tubular cells (PTC), plays a crucial role in the development of diabetic nephropathy. This study investigated hypothesis that AGE stimulates AGT production in PTC.

口服避孕药暴露及血管紧张素基因多态与女性脑卒中发病风险的关联研究

目的 <\b>探讨口服避孕药(OC)暴露和血管紧张素原(AGT)基因多态及其联合作用与中国女性脑卒中发病风险的关联.方法 <\b>在“女性避孕药和宫内节育器使用队列”随访的基础上前瞻性收集确诊的脑卒中新发病例,采用病例对照研究方法(按年龄和地区匹配健康对照和医院对照),应用实时荧光定量PCR(Taqman)检测其基因型.结果 <\b>(1)OC轻度升高出血型脑卒中发病风险(OR=1.83,95％CI:1.25～ 2.66).(2)A-6G的AG/GG基因型降低脑卒中发病风险(OR=0.78,95％CI:0.61 ～ 0.99)；Cl1535A的CA/AA基因型使梗塞型脑卒中风险略有降低(OR=0.62,95％CI:0.45 ～ 0.85),AA基因型则使出血型脑卒中的发病风险升高(OR=2.57,95％CI:1.03～6.42).(3)OC和AGT基因的联合作用使得出血型脑卒中的发病风险略有升高.结论 <\b>AGT基因多态性与中国女性脑卒中的发病有关,OC与AGT基因多态性之间的联合作用可能升高出血型脑卒中的发病风险.     

The renin-angiotensin system in transgenic rats

Transgenic animals are used to study the function, regulation and in vivo expression of genes. The effects of the genes of the renin-angiotension system on blood pressure regulation and hypertension were investigated in transgenic rats. The role of the renin-angiotensin system in the development of cardiovascular hypertrophy of hypertensive renal damage was analysed, as well as its interaction with other hormonal systems, i.e. adrenal steroids. The development of a transgenic rat strain carrying the mouse REN-2 gene has provided a new model of hypertension with systolic blood pressure values of 200 mmHg. This model is characterised by low active plasma renin, hyperproreninaemia and high expression of renin in the adrenal gland and other extrarenal tissues. Transgenic rats with thehuman components of the renin-angiotensin system expressed the human renin and angiotensinogen proteins which interacted species-specifically in transgenic rats. These transgenic models demonstrate the feasibility of studying the function of candidate hypertension genes in transgenic animals. In the future, further refinements in transgene construction, mutation, and modification can be tested in such transgenic animal models.     

Genetic variants of the renin-angiotensin system, diabetic nephropathy and hypertension

Summary Recent studies have suggested an association between a deletion (D) variant of the angiotensin-converting-enzyme (ACE) gene and diabetic nephropathy. However, this finding has not been confirmed by all investigators. Furthermore, an M235T variant of the angiotensinogen (AGT) gene has been associated with hypertension, an important risk factor for the development and progression of diabetic nephropathy. The objective of our study was therefore to examine the relationship between these genetic variants of the renin-angiotensin system and diabetic nephropathy and hypertension, respectively, in a large (n = 661) group of Caucasian patients with insulin-dependent (n = 360) or non-insulin-dependent (n = 301) diabetes mellitus. The study had a power of 0.8 to detect a doubling of risk of nephropathy or hypertension in patients with the ACE-DD or AGT-235TT genotype, respectively. Allelic frequencies of the ACE-D and AGT-235T alleles were similar between patients with and without nephropathy in either type of diabetes, and accordingly, there was no significant association between diabetic nephropathy and the ACE or AGT genotype. Likewise, there was no significant association between the ACE or AGT genotype and hypertension. Thus, our data, in this large and ethnically homogeneous group of patients, do not support the hypothesis that these genetic variants of the renin-angiotensin system are strongly associated with either nephropathy or hypertension in patients with insulin-dependent or non-insulin-dependent diabetes mellitus. These genetic markers are therefore unlikely to serve as clinically useful predictors of either nephropathy or hypertension in Caucasian patients with diabetes. [Diabetologia (1997) 40: 193–199] Received: 16 July 1996 and in revised form: 17 October 1996     

Renin-angiotensin system polymorphisms in Taiwanese primary vesicoureteral reflux

We studied the angiotensin-converting enzyme (ACE), angiotensinogen (AGT), and angiotensin II type 1 receptor (AT1R) gene polymorphisms for association with susceptibility to primary vesicoureteral reflux (VUR) and disease progression in 74 Taiwanese children, including 16 with end-stage renal disease (ESRD), and 117 normal controls. Polymerase chain reaction-amplified products containing the ACE gene T-5491C, A-5466C, T-3892C, A-3692C, A-240T, Alu I/D, the AGT gene C-532T, G-217A, G-152A, A-20C, A-6G, T174M, T235M, and the AT1R gene A-1138T, T-810A, T-713G, C-521T, AG-214CC, A-153G, A1166C polymorphisms were analyzed by restriction enzyme digestion, gel electrophoresis, or single-strand conformation polymorphism analysis. All the polymorphisms examined were in Hardy-Weinberg equilibrium. The strong non-random association within the ACE, AGT, and AT1R genes suggests low levels of intragenic recombination. None of these polymorphisms showed association with VUR susceptibility. However, the allele frequency distribution of the six ACE polymorphisms among primary VUR patients with or without ESRD was statistically different. The linked ACE T-A-T-A-A-I allele was observed significantly more frequently in VUR children with ESRD (P<0.001). A significant increase of left ventricular mass index was also found in the linked ACE T-A-T-A-A-I allele group compared with the non-ACE T-A-T-A-A-I allele group of patients aged 18 years with renal progression. The AGT A-6G genotype frequencies were significantly different when the analysis was stratified by genotype of the ACE polymorphisms. The data showed that ACE gene polymorphisms were associated with progressive renal deterioration in Taiwanese children with VUR and might act synergistically with the –6 G allele of the AGT gene.Kuo-Pao Liu and Ching-Yuang Lin contributed equally to this work