Novel role of macrophage migration inhibitory factor in angiotensin II regulation of neuromodulation in rat brain.

Previously we determined that angiotensin II (Ang II) activates neuronal AT(1) receptors, located in the hypothalamus and the brainstem, to stimulate noradrenergic pathways. To link Ang II to the regulation of norepinephrine metabolism in neurons cultured from newborn rat hypothalamus and brainstem we have used cDNA arrays for high throughput gene expression profiling. Of several genes that were regulated, we focused on macrophage migration inhibitory factor (MIF), which has been associated with the modulation of norepinephrine metabolism. In the presence of the selective AT(2) receptor antagonist PD123,319 (10 microM), incubation of cultures with Ang II (100 nM; 1-24 h) elicited an increase in MIF gene expression. Western immunoblots further revealed that Ang II (100 nM; 1-24 h) increased neuronal MIF protein expression. This effect was inhibited by the AT(1) receptor antagonist losartan (10 microM), the PLC inhibitor U-73122 (10 or 25 microM), the PKC inhibitor chelerythrine (10 microM), and the Ca(2+) chelator 1,2-bis-[2-aminophenoxy]-ethane-N,N,N',N'-tetraacetic acid tetrakis acetoxymethyl ester (10 microM). Taken together with our observation that MIF is expressed in the terminal fields of noradrenergic neurons (hypothalamus) and that Ang II increases the expression of MIF in this region in vivo, our data may suggest a novel role of Ang II in norepinephrine metabolism.

Gene expression profiling of rat brain neurons reveals angiotensin II-induced regulation of calmodulin and synapsin I: possible role in neuromodulation.

Angiotensin (Ang II) activates neuronal AT(1) receptors located in the hypothalamus and the brainstem and stimulates noradrenergic neurons that are involved in the control of blood pressure and fluid intake. In this study we used complementary DNA microarrays for high throughput gene expression profiling to reveal unique genes that are linked to the neuromodulatory actions of Ang II in neuronal cultures from newborn rat hypothalamus and brainstem. Of several genes that were regulated, we focused on calmodulin and synapsin I. Ang II (100 nM; 1-24 h) elicited respective increases and decreases in the levels of calmodulin and synapsin I messenger RNAs, effects mediated by AT(1) receptors. This was associated with similar changes in calmodulin and synapsin protein expression. The actions of Ang II on calmodulin expression involve an intracellular pathway that includes activation of phospholipase C, increased intracellular calcium, and stimulation of protein kinase C. Taken together with studies that link calmodulin and synapsin I to axonal transport and exocytotic processes, the data suggest that Ang II regulates these two proteins via a Ca(2+)-dependent pathway, and that this may contribute to longer term or slower neuromodulatory actions of this peptide.

Expression of angiotensin AT(1) and AT(2) receptors in adult rat cardiomyocytes after myocardial infarction. A single-cell reverse transcriptase-polymerase chain reaction study.

The effector hormone of the renin-angiotensin system, angiotensin II, plays a major role in cardiovascular regulation. In rats, both angiotensin receptor subtypes, AT(1) and AT(2), are up-regulated after myocardial infarction but previous studies failed to identify the cell types which express the AT(2) receptor in the heart. To address this question we established a single-cell reverse transcriptase-polymerase chain reaction for AT(1) and AT(2) receptors to determine whether these receptor subtypes are expressed in adult rat cardiomyocytes before and 1 day after myocardial infarction. By laser-assisted cell picking, section profiles of single cells without genomic DNA contamination were isolated. After dividing samples into two identical aliquots, polymerase chain reaction amplification for AT(1) and AT(2) receptors was carried out and polymerase chain reaction products were subjected to gel electrophoresis. Compared to control (n = 4) and sham-operated animals (n = 4), the number of cardiomyocytes expressing the AT(1) receptor mRNA 1 day after myocardial infarction (n = 4) was not changed (42% and 33% versus 45%, respectively). On the other hand, AT(2) receptor mRNA was expressed in 8% and 13%, respectively, of cardiomyocytes gained from control (n = 4) and sham-operated animals (n = 4) and in 14% isolated after myocardial infarction (n = 4). These results demonstrate for the first time that the AT(2) receptor is expressed in adult cardiomyocytes in vivo. They further suggest that the previously observed up-regulation of cardiac AT(1) and AT(2) receptors after myocardial infarction involves cell types other than cardiomyocytes.

The angiotensin II type 2 receptor: an enigma with multiple variations.

Since it was discovered ten years ago, the angiotensin II (ANG II) type 2 (AT(2)) receptor has been an enigma. This receptor binds ANG II with a high affinity but is not responsible for mediating any of the classical physiological actions of this peptide, all of which involve the ANG II type 1 (AT(1)) receptor. Furthermore, the AT(2) receptor exhibits dramatic differences in biochemical and functional properties and in patterns of expression compared with the AT(1) receptor. During the past decade, much information has been gathered about the AT(2) receptor, and the steadily increasing number of publications indicates a growing interest in this new and independent area of research. A number of studies suggest a role of AT(2) receptors in brain, renal, and cardiovascular functions and in the processes of apoptosis and tissue regeneration. Despite these advances, nothing stands out as the major singular function of these receptors. The study of AT(2) receptors has reached a crossroads, and innovative approaches must be considered so that unifying mechanisms as to the function of these unique receptors can be put forward. In this review we will discuss the advances that have been made in understanding the biology of the AT(2) receptor. Furthermore, we will consider how these discoveries, along with newer experimental approaches, may eventually lead to the elusive physiological and pathophysiological functions of these receptors.

AT2 receptor stimulation induces generation of ceramides in PC12W cells.

The angiotensin AT2 receptor has been implicated in both regeneration and apoptosis. To further investigate the molecular mechanisms leading to AT2 receptor-induced programmed cell death in PC12W cells we studied the effects of angiotensin II (ANG II) on ceramide levels by HPTLC analysis. We could demonstrate that ANG II time- (1-10 h) and dose-dependently (10(-8)-5 X 10(-6) M) increased ceramide levels by maximally 175% but did not affect sphingomyelin degradation. The ANG 11 effects were mediated by AT2 receptors since they were completely abolished by co-incubation with the AT2 receptor antagonist, PD123177 (10(-5) M), but not by the AT1 receptor antagonist, losartan (10(-5) M). These data suggest a novel signal transduction pathway to the AT2 receptor leading to apoptosis in neuronal cells.

Beyond blood pressure: new roles for angiotensin II.

Since the discovery 100 years ago by Tigerstedt and Bergman of renin, an acid protease generating angiotensin peptide, numerous discoveries have advanced our understanding of the renin-angiotensin system (RAS). The recent cloning of angiotensin receptors and the availability of specific receptor ligands have allowed characterization of angiotensin-receptor-mediated actions, and an increasing number of studies using biochemical, pharmacological and molecular biological methods has focused on the many different physiological actions of the RAS in various tissues. Angiotensin II, the main effector peptide of the RAS, exerts most of its known actions in blood pressure control and body fluid homeostasis via the AT, receptor. AT, receptors not only play a role in growth control and cell differentiation but have been implicated in apoptosis and tissue regeneration. This review focuses on the extrarenal functions of angiotensin, especially in neuronal cells and the nervous system, and on recent advances in angiotensin receptor research.

[Improved eyedrop administration and compliance in glaucoma patients. A clinical study]. / Verbesserung der Augentropfenapplikation und Compliance bei Glaukompatienten. Eine klinische Studie.

BACKGROUND: Poor compliance can be dangerous to successful medical treatment of glaucoma. Among other things one reason for non-compliance represents the inability of the patients to place drops in the eye appropriately. Therefore information regarding the patients ability to administer an eyedrop safely are a prerequisite to determining a therapy scheme which ensures the compliance of glaucoma patients. PATIENTS AND METHODS: 100 glaucoma patients on medical therapy who first presented in the outpatient glaucoma clinic of the University Eye Hospital of Würzburg were examined by standardised questionnaire and ability tests. We evaluated: 1. Can the eyedrop administration of glaucoma patients be improved by a standardised instruction? 2. Can the eyedrop administration be improved by the use of a drop aid (Autodrop)? 3. Can the accuracy of aiming and the manual ability be evaluated with a target-test on a sheet of paper with a series of concentric circles? 4. How do patients on combined therapy distinguish between their different bottles and where is the dosage regimen noted? 5. What kind of distinguishing marks of eyedrop-bottles do the patients prefer? RESULTS: 1. Before verbal instruction 76% of the patients applied the eyedrops appropriately, after instruction 94% (p < 0.001) were capable. Touching the eye with the tip of the dropper was reduced significantly. Touching the eye before instruction was found in 63% of the patients, after instruction it was found in 41% (p < 0.001). 2. When patients used the drop aid 81% were able to place a drop in the eye appropriately. Only by 46% of the patients the Autodrop was welcomed. 3. 16% of the patients were not able to place a drop within 1.5 cm of the center of the target (according to the size of an eye). 4. 47% of the patients who use more than one eyedrop bottle admitted problems in distinguishing the bottles, only 38% of the patients read the labels. 5. 76% of the patients would prefer markable stickers of different colours for the bottom of the bottles to improve distinguishing the bottles in combined therapy. CONCLUSION: Instruction improves eyedrop administration in 18% of our patients. In combined therapy with several drugs new distinguishing marks are requested by the patients. To improve compliance combination preparations should be administered if available.

Efficacy of apraclonidine ophthalmic solution (Iopidine) in presumed silicon oil-induced glaucoma and primary open-angle glaucoma.

BACKGROUND: This pilot study evaluated the acute effects of topical ocular apraclonidine 1% (Iopidine) in 10 patients with presumed silicone oil-induced secondary glaucoma (SOIG) and in 10 patients with high-pressure primary open-angle glaucoma (POAG) despite maximum tolerated medical therapy. METHODS: Intraocular pressure (IOP) measurements were carried out before and 1, 2 and 3 h after a single drop of apraclonidine. RESULTS: Patients with SIOG presented with a mean IOP of 30.0 +/- 2.8 mmHg, which was reduced to 21.7 +/- 2.9 mmHg (P < 0.001) after 1 h, to 20.4 +/- 2.3 mmHg (P < 0.001) after 2 h and to 20.0 +/- 2.5 mmHg (P < 0.001) after 3 h. In the POAG group, IOP was reduced from 25.9 +/- 1.9 mmHg before treatment to 18.9 +/- 1.4 mmHg after 1 h (P < 0.001), 17.7 +/- 1.2 mmHg after 2 h (P < 0.001) and 16.9 +/- 0.9 mmHg after 3 h (P < 0.001). There were no significant changes in blood pressure or pulse rate. CONCLUSION: This study confirmed the activity of apraclonidine as an IOP suppressant.