Biomedical subjects

Michael Bader

Publications and source records attributed to Michael Bader.

At least 73 records · Page 4Linked to original sources

PubMed2005

Mouse knockout models of hypertension.

Gene-targeting technology allows the planned alteration of any gene in the mouse genome and has been very successfully employed to study the function of numerous gene products in a complete animal. The method includes the design of a suitable targeting construct, its transfection into pluripotential embryonic stem cells, selection for cells in which one allele of the endogenous gene has been exchanged for the construct by homologous recombination, and the transfer of these cells into host blastocysts. The blastocysts are then transferred into the uterus of a pseudopregnant foster mother giving birth to chimeras, which are bred to yield heterozygous and finally homozygous mutant mice for the targeted gene.

Animals↗

PubMed2005

Production of transgenic models in hypertension.

This chapter describes the generation of transgenic mice and rats by microinjection of DNA constructs into the pronucleus of a zygote. The transgene DNA is randomly integrated as several tandem copies at one site into the genome and is transmitted to the offspring of the founder animal derived from the injected embryo, thereby creating a stable transgenic line. The technology includes the following steps: design and generation of the transgene construct, superovulation of donor animals, isolation of fertilized oocytes, microinjection of the transgene construct into one pronucleus of the zygotes, transfer of injected embryos into the oviduct of a foster mother, and identification of transgenic animals in the offspring.

Animals↗

PubMed2005

Induction and analysis of cardiac hypertrophy in transgenic animal models.

Myocardial hypertrophy is an adaptational process of the heart to increased workload caused by mechanical stress, growth factors, cytokines, catecholamines, or primary genetic abnormalities. Chronic induction of hypertrophy leads to the gradual deterioration of ventricular function and is an independent risk factor for cardiac-related morbidity and mortality in patients with hypertension and ventricular arrythmias. Transgenic animals are very useful models to study the factors involved in the pathogenesis of cardiac hypertrophy. To achieve this goal, rodents lacking or overexpressing a specific gene are subjected to banding of the abdominal aorta, an experimental model of cardiac hypertrophy that leads to pressure overload on the heart. After periods between 3 and 21 d, parameters such as cardiac hemodynamics, morphologic alterations, and expression of marker genes (e.g., the gene for atrial natriuretic peptide) are analyzed in genetically modified animals and compared with controls elucidating a possible implication of the modified gene in the pathogenic process leading to myocardial hypertrophy. This article summarizes the techniques necessary to induce left ventricular hypertrophy by aortic banding and to analyze the effects of this experimental model on hemodynamics, cardiac morphology, and gene expression of transgenic and control animals.

Animals↗

PubMed2005

Molecular structure and transcriptional regulation by nuclear factor-kappaB of the mouse kinin B1 receptor gene.

Kinins are important mediators in cardiovascular homeostasis, inflammation, and nociception. Two kinin receptors have been described, B 1 and B 2 . The B 1 receptor is normally absent in healthy tissues, but is highly induced under pathological conditions. To understand the molecular mechanism of B 1 receptor up-regulation, we determined the mouse B 1 receptor gene structure, isolated and characterized the promoter region and studied its transcriptional regulation. The mouse B 1 receptor gene contains two exons (with the entire coding region located in the second exon) and a TATA-less promoter with multiple transcription start sites. A 7.7-kbp portion of the 5'-flanking region was examined for promoter activity in vascular smooth muscle cells (VSMCs). A minimal 92-bp fragment, located immediately upstream of the transcription start region, exerted basal and lipopolysaccharide (LPS)-inducible transcription activity in the sense and antisense orientation, and was thereby identified as an enhancer element. Nuclear extracts from VSMCs showed basal and LPS-inducible binding activity of nuclear factor (NF)-kappaB at this sequence. B 1 receptor transcription activation in response to LPS was abolished by cotransfection with IkappaBalphaDeltaN, an NF-kappaB repressor. In summary, our results reveal the structure of the mouse B 1 receptor gene and the involvement of NF-kappaB in the inducible mouse kinin B 1 receptor expression under pathological conditions.

Animals↗

PubMed2005

Longitudinal study to explore chronic neuropsychologic effects on solvent exposed workers.

AIM: The aim of the study was to examine possible neurotoxic effects on the central nervous system (CNS) in relation to a chronic solvent exposure at the workplace. METHOD: The collective included 127 workers exposed to solvent mixtures, such as spray painters and printers. They were examined twice by means of a physical examination, neuropsychological testbattery, biological and air monitoring. RESULTS: Major component of the solvents were white spirits in concentrations up to 127 ppm in air and 2,666 microg/l in blood. Single substances were mainly toluene and xylenes in concentrations below current threshold values at the workplace. During the 2 yr interval, the concentrations of solvents decreased, and no significant associations between the neuropsychological tests and the solvent exposure were found. Regarding the whole working history of each participant, we found a significant reduction on information processing velocity and performance in the trailmaking test, as well as more complaints of workers with higher solvent exposure in the past. CONCLUSIONS: A slight increase of subjective complaints and a deteriorated power of concentration seems to be associated with chronic solvent exposure.

Adult↗

PubMed2005

Early prediction of response to chemotherapy in metastatic breast cancer using sequential 18F-FDG PET.

UNLABELLED: Chemotherapy is currently the treatment of choice for patients with high-risk metastatic breast cancer. Clinical response is determined after several cycles of chemotherapy by changes in tumor size as assessed by conventional imaging procedures including CT, MRI, plain film radiography, or ultrasound. The aim of this study was to evaluate the use of sequential 18F-FDG PET to predict response after the first and second cycles of standardized chemotherapy for metastatic breast cancer. METHODS: Eleven patients with 26 metastatic lesions underwent 31 (18)F-FDG PET examinations (240-400 MBq of 18F-FDG; 10-min 2-dimensional emission and transmission scans). Clinical response, as assessed by conventional imaging after completion of chemotherapy, served as the reference. 18F-FDG PET images after the first and second cycles of chemotherapy were analyzed semiquantitatively for each metastatic lesion using standardized uptake values (SUVs) normalized to patients' blood glucose levels. In addition, whole-body 18F-FDG PET images were viewed for overall changes in the 18F-FDG uptake pattern of metastatic lesions within individual patients and compared with conventional imaging results after the third and sixth cycles of chemotherapy. RESULTS: After completion of chemotherapy, 17 metastatic lesions responded, as assessed by conventional imaging procedures. In those lesions, SUV decreased to 72% +/- 21% after the first cycle and 54% +/- 16% after the second cycle, when compared with the baseline PET scan. In contrast, 18F-FDG uptake in lesions not responding to chemotherapy (n = 9) declined only to 94% +/- 19% after the first cycle and 79% +/- 9% after the second cycle. The differences between responding and nonresponding lesions were statistically significant after the first (P = 0.02) and second (P = 0.003) cycles. Visual analysis of 18F-FDG PET images correctly predicted the response in all patients as early as after the first cycle of chemotherapy. As assessed by 18F-FDG PET, the overall survival in nonresponders (n = 5) was 8.8 mo, compared with 19.2 mo in responders (n = 6). CONCLUSION: In patients with metastatic breast cancer, sequential 18F-FDG PET allowed prediction of response to treatment after the first cycle of chemotherapy. The use of 18F-FDG PET as a surrogate endpoint for monitoring therapy response offers improved patient care by individualizing treatment and avoiding ineffective chemotherapy.

Adult↗

PubMed2004

Renal effects of Tamm-Horsfall protein (uromodulin) deficiency in mice.

The Tamm-Horsfall protein (THP; uromodulin), the dominant protein in normal urine, is produced exclusively in the thick ascending limb of Henle's loop. THP mutations are associated with disease; however, the physiological role of THP remains obscure. We generated THP gene-deficient mice (THP -/-) and compared them with wild-type (WT) mice. THP -/- mice displayed anatomically normal kidneys. Steady-state electrolyte handling was not different between strains. Creatinine clearance was 63% lower in THP -/- than in WT mice (P < 0.05). Sucrose loading induced no changes between strains. However, water deprivation for 24 h decreased urine volume from 58 +/- 9 to 28 +/- 4 microl x g body wt(-1) x 24 h(-1) in WT mice (P < 0.05), whereas in THP -/- mice this decrease was less pronounced (57 +/- 4 to 41 +/- 5 microl x g body wt(-1) x 24 h(-1); P < 0.05), revealing significant interstrain difference (P < 0.05). We further used RT-PCR, Northern and Western blotting, and histochemistry to study renal transporters, channels, and regulatory systems under steady-state conditions. We found that major distal transporters were upregulated in THP -/- mice, whereas juxtaglomerular immunoreactive cyclooxygenase-2 (COX-2) and renin mRNA expression were both decreased in THP -/- compared with WT mice. These observations suggest that THP influences transporters in Henle's loop. The decreased COX-2 and renin levels may be related to an altered tubular salt load at the macula densa, whereas the increased expression of distal transporters may reflect compensatory mechanisms. Our data raise the hypothesis that THP plays an important regulatory role in the kidney.

Animals↗

PubMed2004

Improvement of defective sarcoplasmic reticulum Ca2+ transport in diabetic heart of transgenic rats expressing the human kallikrein-1 gene.

The bradykinin-forming enzyme kallikrein-1 is expressed in the heart. To examine whether contractile performance and sarcoplasmic reticulum Ca2+ transport of the diabetic heart can be rescued by targeting the kallikrein-kinin system, we studied left ventricular function and sarcoplasmic reticular Ca2+ uptake after induction of streptozotocin-induced diabetes mellitus in transgenic rats expressing the human tissue kallikrein-1 gene. Six weeks after a single injection of either streptozotocin (70 mg/kg ip) or vehicle, left ventricular performance was determined using a Millar-Tip catheter system. The Ca2+-transporting activity of reticulum-derived membrane vesicles was determined in left ventricular homogenates as oxalate-supported 45Ca2+ uptake. Western blot analysis was used to quantify the reticular Ca2+-ATPase SERCA2a, phospholamban, and the phosphorylation status of the latter. Contractile performance and Ca2+ uptake activity were similar in nondiabetic wild-type and transgenic rats. Severely diabetic wild-type animals exhibited impaired left ventricular performance and decreased reticular Ca2+ uptake (-39% vs. wild-type rats, P<0.05, respectively). These changes were attenuated in diabetic transgenic rats that, in addition, exhibited a markedly increased phospholamban phosphorylation at the Ca2+/calmodulin kinase-specific site threonine17 (2.2-fold vs. diabetic wild-type rats, P<0.05). These transgene-related effects were abolished after treatment with the bradykinin B2 receptor antagonist icatibant (Hoe 140). The SERCA2-to-phospholamban ratio, phosphoserine16-phospholamban levels, and the apparent affinity for Ca2+ of the uptake reaction did not differ between the groups. Increasing the activity of the kallikrein-kinin system by expressing a human kallikrein-1 transgene protects rat heart against diabetes-induced contractile and reticular Ca2+ transport dysfunctions. An increased phosphorylation of the SERCA2 regulatory protein phospholamban at threonine17 via a B2 receptor-mediated mechanism is thereby involved.

Animals↗

PubMed2004

Combining mass spectrometry and pull-down techniques for the study of receptor heteromerization. Direct epitope-epitope electrostatic interactions between adenosine A2A and dopamine D2 receptors.

Previous results from FRET and BRET experiments and computational analysis (docking simulations) have suggested that a portion of the third intracellular loop (I3) of the human dopamine D2 receptor (D2R) and the C-tail from the human adenosine A2A receptor (A2AR) are involved in A2AR-D2R heteromerization. The results of the present studies, using pull-down and mass spectrometry experiments, suggest that A2AR-D2R heteromerization depends on an electrostatic interaction between an Arg-rich epitope from the I3 of the D2R (217RRRRKR222) and two adjacent Asp residues (DD401-402) or a phosphorylated Ser (S374) residue in the C-tail of the A2AR. A GST-fusion protein containing the C-terminal domain of the A2AR (GST-A2ACT) was able to pull down the whole D2R solubilized from D2R-tranfected HEK-293 cells. Second, a peptide corresponding to the Arg-rich I3 region of the D2R (215VLRRRRKRVN224) and bound to Sepharose was able to pull down both GST-A2ACT and the whole A2AR solubilized from A2AR-tranfected HEK-293 cells. Finally, mass spectometry and pull-down data showed that the Arg-rich D2R epitope binds to two different epitopes from the C-terminal part of the A2AR, containing the two adjacent Asp residues or the phosphorylated Ser residue (388HELKGVCPEPPGLDDPLAQDGAVGS412 and 370SAQEpSQGNT378). The present results are the first example of epitope-epitope electrostatic interaction underlying receptor heteromerization, a new, expanding area of protein-protein interactions.

Amino Acid Sequence↗

PubMed2004

Nonpeptide AVE 0991 is an angiotensin-(1-7) receptor Mas agonist in the mouse kidney.

It has been described recently that the nonpeptide AVE 0991 (AVE) mimics the effects of angiotensin-(1-7) [Ang-(1-7)] in bovine endothelial cells. In this study, we tested the possibility that AVE is an agonist of the Ang-(1-7) receptor Mas, in vitro and in vivo. In water-loaded C57BL/6 mice, AVE (0.58 nmol/g body weight) produced a significant reduction in urinary volume (0.06+/-0.03 mL/60 min [n=9] versus 0.27+/-0.05 [n=9]; P<0.01), associated with an increase in urinary osmolality. The Ang-(1-7) antagonist A-779 completely blocked the antidiuretic effect of AVE. As observed previously for Ang-(1-7), the antidiuretic effect of AVE after water load was blunted in Mas-knockout mice (0.37+/-0.10 mL/60 min [n=9] versus 0.27+/-0.03 mL/60 min [n=11] AVE-treated mice). In vitro receptor autoradiography in C57BL/6 mice showed that the specific binding of 125I-Ang-(1-7) to mouse kidney slices was displaced by AVE, whereas no effects were observed in the binding of 125I-angiotensin II or 125I-angiotensin IV. Furthermore, AVE displaced the binding of 125I-Ang-(1-7) in Mas-transfected monkey kidney cells (COS) cells (IC50=4.75x10(-8) mol/L) and of rhodamine-Ang-(1-7) in Mas-transfected Chinese hamster ovary (CHO) cells. It also produced NO release in Mas-transfected CHO cells blocked by A-779 but not by angiotensin II type-1 (AT1) and AT2 antagonists. Contrasting with these data, the antidiuretic effect of AVE was totally blocked by AT2 antagonists and partially blocked (approximately 60%) by AT1 antagonists. The binding data, the results obtained in Mas-knockout mice and in Mas-transfected cells, show that AVE is a Mas receptor agonist. Our data also suggest the involvement of AT2/AT1-related mechanisms, including functional antagonism, oligomerization or cross-talk, in the renal responses to AVE.

Angiotensin I↗

PubMed2004

Blockade of endothelin receptors attenuates end-organ damage in homozygous hypertensive ren-2 transgenic rats.

BACKGROUND/AIMS: A growing body of evidence suggests that the interplay between the endothelin (ET) and the renin-angiotensin systems (RAS) plays an important role in the development of the malignant phase of hypertension. The present study was performed to evaluate the role of an interaction between ET and RAS in the development of hypertension and hypertension-associated end-organ damage in homozygous male transgenic rats harboring the mouse Ren-2 renin gene (TGRs) under conditions of normal-salt (NS, 0.45% NaCl) and high-salt (HS, 2% NaCl) intake. METHODS: Twenty-eight-day-old homozygous male TGRs and age-matched transgene-negative male normotensive Hannover Sprague-Dawley (HanSD) rats were randomly assigned to groups with NS or HS intake. Nonselective ET(A/B) receptor blockade was achieved with bosentan (100 mg/kg/day). Systolic blood pressure (BP) was measured in conscious animals by tail plethysmography. Rats were placed into metabolic cages to determine proteinuria and clearance of endogenous creatinine. At the end of the experiment the final arterial BP was measured directly in anesthetized rats. Kidneys were taken for morphological examination. RESULTS: All male HanSD fed either the NS or HS diet exhibited a 100% survival rate until 180 days of age (end of experiment). The survival rate in untreated homozygous male TGRs fed the NS diet was 41%, which was markedly improved by treatment with bosentan to 88%. The HS diet reduced the survival rate in homozygous male TGRs to 10%. The survival rate in homozygous male TGRs on the HS diet was significantly improved by bosentan to 69%. Treatment with bosentan did not influence either the course of hypertension or the final levels of BP in any of the experimental groups of HanSD rats or TGRs. Although the ET-1 content in the renal cortex did not differ between HanSD rats and TGRs, ET-1 in the left heart ventricle of TGRs fed the HS diet was significantly higher compared with all other groups. Administration of bosentan to homozygous male TGRs fed either the NS or HS diet markedly reduced proteinuria, glomerulosclerosis and attenuated the development of cardiac hypertrophy compared with untreated TGR. CONCLUSIONS: Our data show that nonselective ET(A/B) receptor blockade markedly improves the survival rate and ameliorates end-organ damage in homozygous male TGRs without significantly lowering BP.

Animals↗

PubMed2004

Acute effects of cyclooxygenase-2 inhibition on renal function in heterozygous ren-2-transgenic rats on normal or low sodium intake.

BACKGROUND/AIMS: Since there are no data available so far on the role of renal cyclooxygenase-2 (COX-2) in hypertensive Ren-2-transgenic rats (TGR), in the present study we evaluated renal cortical COX-2 protein expression and prostaglandin E2 (PGE2) concentrations as well as renal functional responses to acute COX-2 inhibition in male heterozygous TGR and in normotensive Hannover Sprague-Dawley (HanSD) rats fed either a normal-sodium (NS) or a low-sodium (LS) diet. METHODS: In rats fed either the NS or the LS diet for 12 days and prepared for clearance experiments with left ureteral catheterization, the renal functional responses of the left kidney were evaluated after intrarenal COX-2 inhibition with DuP-697 or NS-398. In renal cortical tissue, COX-2 protein expression was assessed by immunoblotting, and the concentration of PGE2 as a marker of COX-2 activity was determined by enzyme immunoassay. Mean arterial pressure in the right femoral artery was monitored by means of a pressure transducer. RESULTS: In heterozygous TGR, to our surprise, the LS diet normalized the mean arterial pressure. Despite significantly higher renocortical expression of COX-2 and PGE2 concentrations as well as urinary PGE2 excretion in TGR as compared with HanSD rats kept on the NS diet, selective intrarenal COX-2 inhibition did not influence renal function either in TGR or in HanSD rats. The LS diet increased renocortical COX-2 expression and PGE2 concentrations as well as urinary PGE2 excretion significantly stronger in TGR than in HanSD rats. Regardless of these increases, the intrarenal COX-2 inhibition caused comparable decreases in glomerular filtration rate, in absolute and fractional sodium excretion, as well as in urinary PGE2 excretion in TGR and HanSD rats kept on the LS diet. CONCLUSIONS: The present data show that a LS diet normalizes the mean arterial pressure in heterozygous male TGR. This first study on the role of renal COX-2 in TGR also demonstrates that COX-2-derived vasodilatory prostanoids do not act as renal compensatory vasodilator and natriuretic substances in this model of hypertension.

Animals↗

PubMed2004

Differential regulation of central vasopressin receptors in transgenic rats with low brain angiotensinogen.

The consequences of permanent alteration to the brain renin-angiotensin system (RAS) on central vasopressinergic system was studied in transgenic rats with low brain angiotensinogen [TGR(ASrAOGEN)]. Levels of vasopressin (AVP) and V1a receptor mRNAs were measured by ribonuclease protection assay (RPA) and AVP by radioimmunoassay (RIA). AVP (100 pmol/50 nl) was microinjected into the nucleus tractus solitarii (NTS) of urethane-anesthetized TGR(ASrAOGEN) and Sprague-Dawley (SD) rats and the mean arterial pressure (MAP) and heart rate (HR) baroreflex induced by phenylephrine were evaluated. AVP but not its mRNA levels were significantly lower in the hypothalamus and hypophysis of TGR(ASrAOGEN) rats. Brainstem V1a mRNA levels were significantly higher in TGR(ASrAOGEN) in comparison to SD rats (5.2+/-0.4% vs. 3.3+/-0.2% of beta-actin mRNA, P<0.05). In contrast, the hypothalamic V1a mRNA levels in TGR(ASrAOGEN) were not different from those found in SD rats. AVP microinjections induced a greater decrease in MAP in TGR(ASrAOGEN) in comparison with SD rats (-19.9+/-5.2 vs. -7.5+/-0.7 mm Hg, P<0.01). The significantly higher baroreflex sensitivity observed in TGR compared to that of SD rats was normalized after AVP microinjection. The increased brainstem V1a mRNA levels and sensitivity to AVP in TGR(ASrAOGEN) rats indicates a functional upregulation of AVP receptors in the NTS. The fact that the hypothalamic V1a mRNA levels are not altered indicates that these receptors are differentially regulated in different brain regions. This study demonstrates that a permanent deficit in brain angiotensinogen synthesis can alter the functionality of central vasopressinergic system.

Angiotensinogen↗

PubMed2004

Role of kinin B1 and B2 receptors in the development of pilocarpine model of epilepsy.

The tissue sclerosis found in epilepsy of limbic origin is characterized by shrunken gliotic hippocampus, granule cell loss in the dentate gyrus and extensive pyramidal cell loss in Ammon's horn. Evidence has indicated that sprouting of dentate granule cell axons into the inner molecular layer of the dentate gyrus is related to hyperexcitability. Trying to understand the role of kinin B1 and B2 receptors in the physiopathology of temporal lobe epilepsy (TLE), the present work was delineated to study the development of the epilepsy model induced by pilocarpine in B1 and B2 knockout mice (B1KO and B2KO, respectively). Behavior parameters, cell death and mossy fiber sprouting were analyzed. B1KO mice showed increased latency for the first seizure, associated to a decreased frequency of spontaneous seizures, when compared with wild-type mice. In addition, B1KO mice showed less cell death in all hippocampal formation associated to a reduced grade of mossy fiber sprouting. Furthermore, B2KO mice presented minor duration of the silent period and an increased frequency of spontaneous seizures, when compared with wild-type mice. B2KO and their control lineage showed similar pattern of cell death in the hippocampus, which was very intense when compared with saline-treated animals. The mossy fiber sprouting was also increased in B2KO mice, when compared to wild-type mice and saline-treated animals. Taken together, these data suggest a deleterious effect for kinin B1 receptor and a protective effect for kinin B2 receptor during the development of the temporal lobe epilepsy.

Animals↗

PubMed2004

Rat corin gene: molecular cloning and reduced expression in experimental heart failure.

Stored cardiac pro-atrial natriuretic peptide (pro-ANP) is converted to ANP and released upon stretch from the atria into the circulation. Corin is a serin protease with pro-ANP-converting properties and may be the rate-limiting enzyme in ANP release. This study was aimed to clone and sequence corin in the rat and to analyze corin mRNA expression in heart failure when ANP release upon stretch is blunted. Full-length cDNA of rat corin was obtained from atrial RNA by RT-PCR and sequenced. Tissue distribution as well as regulation of corin mRNA expression in the atria were determined by RT-PCR and RNase protection assay. Heart failure was induced by an infrarenal aortocaval shunt. Stretch was applied to the left atrium in a working heart modus, and ANP was measured in the perfusates. The sequence of rat corin cDNA was found to be 93.6% homologous to mouse corin cDNA. Corin mRNA was expressed almost exclusively in the heart with highest concentrations in both atria. The aortocaval shunt led to cardiac hypertrophy and heart failure. Stretch-induced ANP release was blunted in shunt animals (control 1,195 +/- 197 fmol.min(-1).g(-1); shunt: 639 +/- 99 fmol.min(-1).g(-1), P < 0.05). Corin mRNA expression was decreased in both atria in shunt animals [right atrium: control 0.638 +/- 0.004 arbitrary units (AU), shunt 0.566 +/- 0.014 AU, P < 0.001; left atrium: control 0.564 +/- 0.009 AU, shunt 0.464 +/- 0.009 AU, P < 0.001]. Downregulation of atrial corin mRNA expression may be a novel mechanism for the blunted ANP release in heart failure.

Amino Acid Sequence↗

PubMed2004

Expression of an angiotensin-(1-7)-producing fusion protein produces cardioprotective effects in rats.

Angiotensin-(1-7) [ANG-(1-7)] is a recently described heptapeptide product of the renin-angiotensin system. Because biosynthesis of ANG-(1-7) increases in animals treated with cardioprotective drugs and inactivation of the gene for angiotensin converting enzyme 2 [an enzyme involved in the biosynthesis of ANG-(1-7)] leads to the development of cardiac dysfunction, it has been suggested that ANG-(1-7) has cardioprotective properties. To directly test this possibility, we have generated transgenic rats that chronically overproduce ANG-(1-7) by using a novel fusion protein methodology. TGR(A1-7)3292 rats show testicular-specific expression of a cytomegalovirus promoter-driven transgene, resulting in a doubling of circulating ANG-(1-7) compared with nontransgenic control rats. Radiotelemetry hemodynamic measurements showed that transgenic rats presented a small but significant increase in daily and nocturnal heart rate and a slight but significant increase in daily and nocturnal cardiac contractility estimated by dP/d t measurements. Strikingly, TGR(A1-7)3292 rats were significantly more resistant than control animals to induction of cardiac hypertrophy by isoproterenol. In addition, transgenic rats showed a reduced duration of reperfusion arrhythmias and an improved postischemic function in isolated Langendorff heart preparations. These results support a cardioprotective role for circulating ANG-(1-7) and provide a novel tool for evaluating the functional role of ANG-(1-7).

Angiotensin I↗

PubMed2004

The synthesis and distribution of the kinin B1 and B2 receptors are modified in the hippocampus of rats submitted to pilocarpine model of epilepsy.

Kinins, a special class of polypeptides, are represented by bradykinin (BK), kallidin (Lys-BK), as well as their metabolites. The biological actions of these polypeptides binding on their receptors (B1 and B2) have been related to inflammation process, cytokines action, glutamate release and prostaglandins production. Usually, kinin B1 receptor is not expressed at a significant level under physiologic conditions in most tissues, but its expression is induced by injury, or upon exposure in vivo or in vitro to pro-inflammatory mediators. The kinin B2 receptor subtype is constitutively and widely expressed throughout the central and peripheral nervous system. These data raise the possibility for de novo expression of those receptors during the temporal lobe epilepsy (TLE), which has been related to cell death, gliosis and hippocampal reorganization. To correlate kinin system and TLE, adult male Wistar rats were submitted to pilocarpine model of epilepsy. The hippocampi were removed 6 h, 5 and 60 days after status epilepticus (SE) onset. The collected tissues were used to study the expression of kinin B1 and B2 mRNA receptors, using Real-Time PCR. Immunohistochemistry assay was also employed to visualize kinin B1 and B2 distribution in the hippocampus. The results show increased kinin B1 and B2 mRNA levels during acute, silent and chronic periods and changes in the kinin B1 and B2 receptors distribution. In addition, the immunoreactivity against kinin B1 receptor was increased mainly during the silent period, where neuron clusters of could be visualized. The kinin B2 receptor immunoreactivity also showed augmentation but mainly during the acute and silent periods. Our results suggest that kinin B1 and B2 receptors play an important role in the epileptic phenomena.

Animals↗

PubMed2004

Bradykinin B1 receptor expression induced by tissue damage in the rat portal vein: a critical role for mitogen-activated protein kinase and nuclear factor-kappaB signaling pathways.

The bradykinin B1 receptor (B1R) is normally absent under physiological conditions, but is highly inducible during inflammatory conditions or following tissue damage. The present study attempted to determine some of the mechanisms underlying B1R upregulation following tissue injury in rat portal vein. Damage induced by tissue isolation and in vitro incubation caused a significant and time-dependent increase in des-Arg9-bradykinin (des-Arg9-BK) responsiveness that paralleled the B1R mRNA expression, as confirmed by real-time quantitative PCR. In vitro incubation of rat portal vein also induced the activation of some members of the mitogen activated protein kinase (MAPK) family, namely, extracellular signal-regulated kinase (ERK), c-Jun NH2-terminal kinase (JNK), and p38 MAPK, an effect accompanied by degradation of the inhibitory protein IkappaBalpha and translocation of nuclear transcription factor-kappaB (NF-kappaB) to the nucleus. The blockade of p38 MAPK, JNK or NF-kappaB, but not ERK pathways with selective inhibitors, resulted in a significant reduction of the upregulated contractile response caused by the selective B1R agonist des-Arg9-BK, and largely prevented the induction of B1R mRNA expression in the rat portal vein. Together, these results demonstrate that in vitro tissue damage induces activation of several intracellular signaling pathways that have a key role in the control of B1R expression. B1R could exert a pivotal role in the development of the cardiovascular response associated with vascular damage.

Animals↗