Angiotensin AT1 Receptor Antagonist Research Articles

Effect of Combined Treatment with AT1 Receptor Antagonists and Tiagabine on Seizures, Memory and Motor Coordination in Mice.

Losartan and telmisartan, angiotensin AT1 receptor antagonists, are widely used antihypertensive drugs in patients. It is also known that arterial hypertension is often present in people with epilepsy, therefore, drug interactions between AT1 receptor antagonists and antiepileptic drugs can occur in clinical practice. The aim of the current study was to assess the effect of losartan and telmisartan on the anticonvulsant activity of tiagabine, asecond-generation antiepileptic drug, in mice. Additionally, the effect of the combined treatment with AT1 receptor antagonists and TGB on long-term memory and motor coordination has been assessed in animals. The study was performed on male Swiss mice. Convulsions were examined in the maximal electroshock seizure threshold test. Long-term memory was measured in the passive-avoidance task and motor coordination was evaluated in the chimney test. AT1 receptor antagonists and TGB were administered intraperitoneally. Losartan (50 mg/kg) or telmisartan (30 mg/kg) did not influence the anticonvulsant activity of TGB applied at doses of 2, 4and 6mg/kg. However, both AT1 receptor antagonists in combinations with TGB (6mg/kg) impaired motor coordination in the chimney test. The concomitant treatment of the drugs did not decrease retention in the passive avoidance task. It is suggested that losartan and telmisartan should not affect the anticonvulsant action of TGB in people with epilepsy. Because the combined treatment with AT1 receptor antagonists and TGB led to neurotoxic effects in animals, caution is advised during concomitant use of these drugs in patients.

Effect of Combined Treatment with AT1 Receptor Antagonists and Tiagabine on Seizures, Memory and Motor Coordination in Mice*

Background. Losartan and telmisartan, angiotensin AT1 receptor antagonists, are widely used antihypertensive drugs in patients. It is also known that arterial hypertension is often present in people with epilepsy, therefore, drug interactions between AT1 receptor antagonists and antiepileptic drugs can occur in clinical practice.Objectives. The aim of the current study was to assess the effect of losartan and telmisartan on the anticonvulsant activity of tiagabine, a second-generation antiepileptic drug, in mice. Additionally, the effect of the combined treatment with AT1 receptor antagonists and TGB on long-term memory and motor coordination has been assessed in animals.Material and Methods. The study was performed on male Swiss mice. Convulsions were examined in the maximal electroshock seizure threshold test. Long-term memory was measured in the passive-avoidance task and motor coordination was evaluated in the chimney test. AT1 receptor antagonists and TGB were administered intraperitoneally.Results. Losartan (50 mg/kg) or telmisartan (30 mg/kg) did not influence the anticonvulsant activity of TGB applied at doses of 2, 4 and 6 mg/kg. However, both AT1 receptor antagonists in combinations with TGB (6 mg/kg) impaired motor coordination in the chimney test. The concomitant treatment of the drugs did not decrease retention in the passive avoidance task.Conclusion. It is suggested that losartan and telmisartan should not affect the anticonvulsant action of TGB in people with epilepsy. Because the combined treatment with AT1 receptor antagonists and TGB led to neurotoxic effects in animals, caution is advised during concomitant use of these drugs in patients.

Interactions between levetiracetam and cardiovascular drugs against electroconvulsions in mice

BackgroundHypertension and heart failure belong to common comorbid conditions with epilepsy so drug interactions between antiepileptics and cardiovascular drugs are possible in clinical practice. The aim of this study was to evaluate the effects of angiotensin AT1 receptor antagonists (losartan potassium and candesartan cilexetil), angiotensin-converting enzyme (ACE) inhibitors (captopril and perindopril arginine) and diuretics (hydrochlorothiazide and ethacrynic acid) on the anticonvulsant activity of levetiracetam (LEV) in mice. MethodsThe protective action of LEV was examined in the maximal electroshock seizure threshold test. Drugs were administered intraperitoneally (ip). Additionally, combinations of cardiovascular drugs with LEV were tested for adverse effects in the passive avoidance task and the chimney test. ResultsLosartan potassium (50mg/kg), candesartan cilexetil (8mg/kg), captopril (50mg/kg), hydrochlorothiazide (100mg/kg) and ethacrynic acid (100mg/kg) did not affect the anticonvulsant activity of LEV. Perindopril arginine (10mg/kg) raised the convulsive threshold for LEV administered at doses of 100, 300 and 500mg/kg. This interaction could be pharmacodynamic in nature because the brain concentration of LEV remained unchanged by perindopril. The adverse effects of the combined treatment with LEV and cardiovascular drugs were not observed in the passive avoidance task or the chimney test. ConclusionsAlthough experimental data can be hardly extrapolated to clinical practice, it is suggested that perindopril arginine may positively influence the anticonvulsant action of LEV in epileptic patients. The use of losartan potassium, candesartan cilexetil, captopril, hydrochlorothiazide or ethacrynic acid in patients treated with LEV seems neutral regarding its anticonvulsant activity.

Angiotensinergic neurotransmission in the paraventricular nucleus of the hypothalamus modulates the pressor response to acute restraint stress in rats

We tested the hypothesis that the angiotensinergic neurotransmission, specifically in the paraventricular nucleus of the hypothalamus (PVN), is involved in the cardiovascular modulation during acute restraint stress (RS) in rats. The intravenous pretreatment with the angiotensin AT1 receptor antagonist losartan (5mg/kg) inhibited the pressor response to RS, but did not affect the concomitant RS-evoked tachycardiac response. Because similar effects were observed after the PVN pretreatment with CoCl2, and considering the high density of angiotensin receptors reported in the PVN, we studied the effect of the pretreatment of the PVN with either losartan or the angiotensin-converting enzyme (ACE) inhibitor lisinopril on the RS-evoked cardiovascular response. The bilateral microinjection of losartan (0.5nmol/100nL) or lisinopril (0.5nmol/100nL) into the PVN inhibited the RS-related pressor response without affecting the tachycardiac response, suggesting that the PVN angiotensinergic neurotransmission modulates the vascular component of the stress response. Finally, to exclude the possibility that centrally injected drugs could be leaking to the circulation and acting on peripheral vascular receptors, we tested the effect of the intravenous pretreatment with either losartan (0.5nmol/animal) or lisinopril (0.5nmol/animal), assuming the hypothesis of a total spread of drugs from the CNS to the peripheral circulation. When animals were pretreated with such doses of either losartan or lisinopril, the cardiovascular RS-evoked response was not affected, thus indicating that even if there were a complete leakage of the drug to the periphery, it would not affect the cardiovascular response to RS. This observation favors the idea that the effect of the intravenous injection of 5mg/kg of losartan on the RS-related cardiovascular response would be explained by an action across the blood–brain barrier, possibly in the PVN. In conclusion, the results suggest that an angiotensinergic neurotransmission in the PVN acting on AT1-receptors modulates the vascular component of the RS-evoked cardiovascular response.

Participation of 5-HT and AT1Receptors within the Rostral Ventrolateral Medulla in the Maintenance of Hypertension in the Goldblatt 1 Kidney-1 Clip Model

The hypothesis that changes in neurotransmission within the rostral ventrolateral medulla (RVLM) are important to maintain the high blood pressure (BP) was tested in Goldblatt one kidney-one clip hypertension model (1K-1C). Male Wistar rats were anesthetized (urethane 1.2 g/kg, i.v.), and the effects of bilateral microinjections into the RVLM of the following drugs were measured in 1K-1C or control groups: glutamate (0.1 mol/L, 100 nL) and its antagonist kynurenic acid (0.02 mol/L, 100 nL), the angiotensin AT1 receptor antagonist candesartan (0.01 mol/L, 100 nL), and the nonselective 5-HT receptor antagonist methiothepin (0.06 mol/L, 100 nL). Experiments in 1K-1C rats were performed 6 weeks after surgery. In anesthetized rats glutamate response was larger in hypertensive than in normotensive rats (H: Δ67 ± 6.5; N: Δ43 ± 3.54 mmHg). In contrast, kynurenic acid microinjection into the RVLM did not cause any change in BP in either group. The blockade of either AT1 or 5-HT receptors within the RVLM decreased BP only in 1K-1C rats. A largest depressor response was caused by 5-HT receptor blockade. The data suggest that 5-HT and AT1 receptors act tonically to drive RVLM in 1K-1C rats, and these actions within RVLM contribute to the pathogenesis of this model of hypertension.

Natriorexigenic effect of DAMGO is decreased by blocking AT1 receptors in the central nucleus of the amygdala

μ-Opioid receptor (μ-OR) activation with agonist [D-Ala2, N-Me-Phe4, Gly5-ol]-enkephalin (DAMGO) in the central nucleus of the amygdala (CeA) induces sodium (0.3M NaCl) intake in rats. The purpose of this study was to examine the effects of pre-injections of losartan (AT1 angiotensin receptor antagonist) into the CeA on 0.3M NaCl and water intake induced by DAMGO injected bilaterally in the same area in rats submitted to water deprivation–partial rehydration (WD–PR) and in rats treated with the diuretic furosemide (FURO) combined with a low dose of the angiotensin-converting enzyme inhibitor captopril (CAP) injected subcutaneously (FURO/CAP). Male Sprague–Dawley rats with stainless steel cannulas implanted bilaterally into the CeA were used. In WD–PR rats, bilateral injections of DAMGO (2nmol in 0.5μL) into the CeA induced 0.3M NaCl and water intake, and pre-treatment with losartan (108nmol in 0.5μL) injected into the CeA reduced 0.3M NaCl and water intake induced by DAMGO. In FURO/CAP rats, pre-treatment with losartan (108nmol in 0.5μL) injected into the CeA attenuated the increase in 0.3M NaCl and water intake induced by DAMGO (2nmol in 0.5μL) injected into the same site. The results suggest that the natriorexigenic effect of DAMGO injected into the CeA is facilitated by endogenous angiotensin II acting on AT1 receptors in the CeA, which drives rats to ingest large amounts of hypertonic NaCl.

Avosentan is protective in hypertensive nephropathy at doses not causing fluid retention

Multiple studies indicate that endothelin antagonism may have a protective effect for chronic kidney disease. Despite that, clinical studies using avosentan have been halted due to adverse effects including fluid overload. Therefore, we aimed at investigating whether avosentan may have protective effects against hypertensive nephropathy at doses below those inducing fluid-retention. We used double transgenic rats (dTGR), overexpressing both the human renin and angiotensinogen gene, which develop malignant hypertension. Effects of avosentan alone or in combination with low-dose of valsartan (angiotensin AT1 receptor antagonist) on end-organ damage were studied. Avosentan induced a decrease of diuresis (18.3%) with a consequent decrease in hematocrit (8.3%) only at the highest dose investigated (100mg/kg). Treatment with the combination of avosentan and valsartan (10 and 0.1mg/kg, once daily by gavage, respectively) decreased albuminuria to a greater extent than each compound given alone (avosentan: 19.6mg/24h; valsartan: 12.9mg/24h; avosentan+valsartan: 1.7mg/24h, data are median values). Histological severity score also showed a drastic reduction of kidney damage. Furthermore, avosentan alone or in combination therapy dramatically decreased mortality compared to the 100% in untreated animals. These data support a therapeutic effect of avosentan at doses below those inducing fluid overload.

Good and bad news about single and dual biphenyl endothelin ETA and angiotensin AT1 receptor antagonists

Good and bad news about single and dual biphenyl endothelin ETA and angiotensin AT1 receptor antagonists

Molecular modeling, quantum polarized ligand docking and structure-based 3D-QSAR analysis of the imidazole series as dual AT(1) and ET(A) receptor antagonists.

Both endothelin ETA receptor antagonists and angiotensin AT1 receptor antagonists lower blood pressure in hypertensive patients. A dual AT1 and ETA receptor antagonist may be more efficacious antihypertensive drug. In this study we identified the mode and mechanism of binding of imidazole series of compounds as dual AT1 and ETA receptor antagonists. Molecular modeling approach combining quantum-polarized ligand docking (QPLD), MM/GBSA free-energy calculation and 3D-QSAR analysis was used to evaluate 24 compounds as dual AT1 and ETA receptor antagonists and to reveal their binding modes and structural basis of the inhibitory activity. Pharmacophore-based virtual screening and docking studies were performed to identify more potent dual antagonists. 3D-QSAR models of the imidazole compounds were developed from the conformer generated by QPLD, and the resulting models showed a good correlation between the predicted and experimental activity. The visualization of the 3D-QSAR model in the context of the compounds under study revealed the details of the structure-activity relationship: substitution of methoxymethyl and cyclooctanone might increase the activity against AT1 receptor, while substitution of cyclohexone and trimethylpyrrolidinone was important for the activity against ETA receptor; addition of a trimethylpyrrolidinone to compound 9 significantly reduced its activity against AT1 receptor but significantly increased its activity against ETA receptor, which was likely due to the larger size and higher intensities of the H-bond donor and acceptor regions in the active site of ETA receptor. Pharmacophore-based virtual screening followed by subsequent Glide SP, XP, QPLD and MM/GBSA calculation identified 5 potential lead compounds that might act as dual AT1 and ETA receptor antagonists. This study may provide some insights into the development of novel potent dual ETA and AT1 receptor antagonists. As a result, five compounds are found to be the best dual antagonists against AT1R and ETA receptors.

Anti-hypertensive treatment preserves appetite suppression while preventing cardiovascular adverse effects of tesofensine in rats

Tesofensine is a novel triple monoamine reuptake inhibitor which is in development for the treatment of obesity. Preclinical and clinical data suggest that appetite suppression is an important mechanism by which tesofensine exerts its robust weight reducing effect. Notably, the strong hypophagic response to tesofensine treatment is demonstrated to be linked to central stimulation of noradrenergic and dopaminergic neurotransmission. The sympathomimetic mode of action of tesofensine may also associate with the elevated heart rate and blood pressure observed in clinical settings, and we therefore sought experimentally to address this issue. The anorexigenic and cardiovascular effects of tesofensine were studied simultaneously in telemetrized conscious rats in a combined real-time food intake and cardiovascular telemetry monitoring system. Acute administration of tesofensine caused a dose-dependent hypophagic effect as well as increased heart rate and blood pressure. Interestingly, combined treatment with metoprolol (b1 adrenoceptor blocker, 10-20 mg/kg, p.o.) fully prevented the cardiovascular sympathetic effects of tesofensine while leaving the robust inhibitory efficacy on food intake unaffected. Similarly, the angiotensin AT1 receptor antagonist telmisartan (1.0-3.0 mg/kg, p.o.) did not interfere with the anti-obesity effects of tesofensine, however, telmisartan only partially reversed the increase in systolic blood pressure and had no effect on the elevated heart rate induced by tesofensine. These data suggests that tesofensine causes elevations in heart rate and blood pressure by increasing sympathetic activity, and that different adrenoceptor subtypes may be responsible for the anti-obesity and cardiovascular effects of tesofensine.

Interactions between angiotensin AT1 receptor antagonists and second‐generation antiepileptic drugs in the test of maximal electroshock

The anticonvulsant activity of angiotensin AT1 receptor antagonists, losartan (2-n-butyl-4-chloro-5-hydroxymethyl-1-[(2'(1H-tetrazol-5-yl)-biphenil-4-yl)methyl]imidazole) and telmisartan (49-[(1,49-dimethyl-29-propyl[2,69-bi-1H-benzimidazo]-19-yl)methyl]-[1,19-biphenyl]-2-carboxylic acid), has been reported recently. It is suggested that AT1 receptor antagonists may affect the protective action of antiepileptic drugs. The aim of this study was to determine the influence of losartan and telmisartan on the anticonvulsant activity of some second-generation antiepileptics (lamotrigine - LTG, oxcarbazepine - OXC, and topiramate - TPM). For this purpose, the maximal electroshock seizure (MES) test in mice was used. Additionally, the drug combinations were checked for adverse effects in the passive avoidance and chimney tests. In the MES test, losartan at the doses of 30 and 50 mg/kg, administered intraperitoneally (i.p.), potentiated the protective action of LTG (P < 0.01). This interaction was not accompanied by a significant change of LTG level either in plasma or in the brain. Telmisartan at the dose of 30 mg/kg i.p. enhanced the anticonvulsant action of TPM (P < 0.01). However, this interaction was pharmacokinetic in nature, as telmisartan significantly increased plasma and total brain concentrations of TPM (P < 0.001). The combinations of AT1 receptor antagonists with antiepileptic drugs did not affect retention in the passive avoidance test or motor coordination in the chimney test. The potentiation of the anticonvulsant action of LTG by losartan probably on account of pharmacodynamic interactions, make this combination important for further experimental and clinical studies. The combination of telmisartan and TPM is less beneficial due to pharmacokinetic interactions.

Combined treatment with gabapentin and drugs affecting the renin–angiotensin system against electroconvulsions in mice

Recent experimental data suggest that certain angiotensin-converting enzyme (ACE) inhibitors and angiotensin AT1 receptor antagonists may possess anticonvulsant activity. The purpose of this study was to examine the effects of two ACE inhibitors, captopril and enalapril, and two AT1 receptor antagonists, losartan and telmisartan, on the protective action of gabapentin in the maximal electroshock seizure threshold test in mice. Additionally, the effects of the combined treatment with gabapentin and antihypertensive drugs on memory retention in the passive avoidance task and motor coordination in the chimney test were assessed. All drugs were injected intraperitoneally. Losartan (50mg/kg) significantly increased the convulsive threshold for gabapentin. The other antihypertensive drugs, captopril (50mg/kg), enalapril (30mg/kg) and telmisartan (30mg/kg), did not affect the anticonvulsant activity of gabapentin. The observed interaction between gabapentin and losartan could be pharmacokinetic in nature. Losartan increased plasma and total brain concentrations of gabapentin. In the chimney test, losartan (50mg/kg) administered with gabapentin (50mg/kg) caused motor impairment. In the passive avoidance test, memory retention was not affected by the combined treatment with gabapentin and antihypertensive drugs. It is suggested that the use of captopril, enalapril and telmisartan in epileptic patients receiving gabapentin is presumed neutral upon its anticonvulsant action. The utmost caution is advised when combining losartan and gabapentin in clinical practice due to the appearance of pharmacokinetic interactions between losartan and gabapentin as well as motor impairment evoked by these drugs in mice.

Blockade of the renin–angiotensin system improves cerebral microcirculatory perfusion in diabetic hypertensive rats

We examined the functional and structural microcirculatory alterations in the brain, skeletal muscle and myocardium of non-diabetic spontaneously hypertensive rats (SHR) and diabetic SHR (D-SHR), as well as the effects of long-term treatment with the angiotensin AT1-receptor antagonist olmesartan and the angiotensin-converting enzyme inhibitor enalapril. Diabetes was experimentally induced by a combination of a high-fat diet with a single low dose of streptozotocin (35mg/kg, intraperitoneal injection). D-SHR were orally administered with olmesartan (5mg/kg/day), enalapril (10mg/kg/day) or vehicle for 28days, and compared with vehicle-treated non-diabetic SHR or normotensive non-diabetic Wistar–Kyoto rats. The cerebral and skeletal muscle functional capillary density of pentobarbital-anesthetized rats was assessed using intravital fluorescence videomicroscopy. Chronic treatment with olmesartan or enalapril significantly lowered blood pressure and reversed brain functional capillary rarefaction. Brain oxidative stress was reduced to non-diabetic control levels in animals treated with olmesartan or enalapril. Histochemical analysis of the structural capillary density showed that both olmesartan and enalapril increased the capillary-to-fiber ratio in skeletal muscle and the capillary-to-fiber volume density in the left ventricle. Olmesartan and enalapril also prevented collagen deposition and the increase in cardiomyocyte diameter in the left ventricle. Our results suggest that the association between hypertension and diabetes results in microvascular alterations in the brain, skeletal muscle and myocardium that can be prevented by chronic blockade of the renin–angiotensin system.

Fluorescent Angiotensin AT1 Receptor Antagonists

AbstractFluorescent selective angiotensin AT1 receptor antagonists (sartans) that contain naphthalene (6, 7, 10, and 11), anthracene (12 and 14), acenaphthene (13 and 15), and coumarin (8 and 9) substituents have been prepared and their preliminary pharmacology evaluated in Chinese hamster ovary (CHO) cell based assays. Compounds 6–15 proved to be effective sartans with pKB estimates in the range of 6.7–10.5; their potential as cellular imaging agents is also discussed.

Abstract 444: Proximal Tubule Angiotensin AT2 Receptors Mediate Anti-inflammatory Response via Interleukin-10: Role in Renoprotection in Obese Rats.

The angiotensin AT2 receptor (AT2R) has been shown to lower inflammation in the kidney. However the role of the anti-inflammatory cytokine IL-10 in AT2R mediated attenuation of inflammation has not been elucidated. We hypothesized that AT2R activation is renoprotective by directly increasing the levels of anti-inflammatory cytokine IL-10 in the kidney via nitric oxide (NO) signaling. For in vitro studies, the human proximal tubule epithelial cell-line (HK-2) was treated with lipopolysaccharide (LPS, 1 μg/ml) and/or AT2R agonist C21 (1μM) for 24 hrs and media cytokine levels were assessed. Compared to control, LPS treatment significantly increased TNF-α (1.25 ± 0.22 vs 46.27 ± 3.22 pg/ml), IL-6 (1.43 ± 0.06 vs 5.204 ± 0.41 ng/ml) and IL-10 (5.11 ± 0.46 vs 13.35 ± 0.74 pg/ml) levels. C21 treatment with LPS lowered the levels of both, TNF-α and IL-6 by 65% but caused 55% increase in IL-10 levels. C21 treatment alone significantly increased IL-10 levels (5.11 ± 0.46 vs 18.37 ± 0.87 pg/ml) while there was no effect on TNF-α or IL-6 levels. The anti-inflammatory effect of C21 was abolished in the presence of neutralizing IL-10 antibody (1 μg/ml). Also, pre-incubation with NO synthase inhibitor L-NAME (1 mM) prevented the C21-mediated decrease in IL-6 levels and increase in IL-10 levels in activated cells. For in vivo studies, 5 wk old lean and obese Zucker rats (OZR) were treated for 2 wks with C21 (300 μg/kg/day, i.p) and/or AT2R antagonist (PD123319, 50 μg/kg/min, s.c. infusion). Compared to LZR, OZR had higher levels (pg/mg protein) of renal TNF-α (1.42 ± 0.14 vs 2.78 ± 0.42) and IL-6 (6.59 ± 0.77 vs 11.71 ± 0.42). C21 treatment decreased levels of TNF-α by 75% and IL-6 by 60% while PD had no effect. Conversely, PD treatment lowered the renal IL-10 levels in OZR (8.5 ± 0.49 vs 3.69 ± 0.65 pg/mg protein) while C21 had no effect. Renal morphometry revealed increased mesangial matrix expansion score in OZR (0.27 ± 0.08 vs 1.3 ± 0.12) which was worsened by PD (1.97 ± 0.16) and improved by C21 treatment (0.8 ± 0.13). Our findings suggest that proximal tubule AT2R activation is anti-inflammatory by increasing IL-10 production which is largely NO-dependent and thus offers renoprotection by preventing early inflammation-induced renal injury in obesity.

1033 DIRECT AT2-RECEPTOR STIMULATION IMPROVES NEUROLOGICAL OUTCOME IN A MOUSE MODEL OF MULTIPLE SCLEROSIS

Objectives: The angiotensin AT2-receptor (AT2R) acts neuroprotective in models of neuronal injury. Here we identify the impact of direct AT2R stimulation by the selective non-peptide agonist C21 in myelin oligodendrocyte glycoprotein (MOG) induced experimental autoimmune encephalomyelitis (MOG-EAE), a mouse model mimicking many aspects of multiple sclerosis. Furthermore, we examined the effects of C21 on remyelination using an in vitro model of neuroinflammation. Design and methods: C57BL/6 mice were immunized with the MOG35–55 fragment and treated from day 3 before immunization until day 28 after immunization with C21 (0.3 mg/kg bw i.p.) or vehicle. Neurological deficits were evaluated daily. Spinal cord tissue was extracted on day 28 post-immunization and stained by fluoromyelin for myelin quantification. Furthermore, to test whether AT2R-stimulation can promote remyelination, aggregating brain cell cultures consisting of neurons, astrocytes, oligodendrocytes and microglia were prepared from whole embryonic rat brain and treated for 7 days with C21 (1 μM) or vehicle after IFN-γ/LPS-induced demyelination. The degree of myelination was determined by immunofluorescence for MOG. Staining was quantified by ImageJ. <SY>Results:</SY> Preventive application of AT2R agonist C21 resulted in a significantly ameliorated course of MOG-EAE and prevented demyelination in spinal cord tissue. Additionally, AT2R stimulation led to a significant increase in MOG-positive area after IFN-γ/LPS-induced demyelination in vitro (93.02% vs 78.13%, p < 0.01) when compared to vehicle treated aggregates. In vitro effects of C21 were inhibited by the specific AT2R antagonist PD 123319. Conclusions: Direct AT2R stimulation improves neurological outcome, protects against demyelination and promotes remyelination. Our findings identify AT2R stimulation as a potential new therapeutic target for demyelinating diseases.

Protective role of the Angiotensin AT2 Receptor in obesity‐induced renal inflammation

The Angiotensin AT2 receptor (AT2R) is up‐regulated in response to tissue injury and is implicated in tissue protection and repair. Recent studies have also suggested an anti‐inflammatory role for the AT2R. The present study was designed to investigate whether chronic activation of the AT2R offers renoprotection by attenuating early stage obesity‐induced inflammation in the kidney. For this purpose, 5 weeks old lean and pre‐hypertensive obese Zucker rats (OZR) were treated for 2 weeks with either vehicle, AT2R agonist C21 (1 μg/kg/day, i.p.), AT2R antagonist PD123319 (50 μg/kg/min, osmotic pump) or both PD and C21. OZR had higher plasma and renal cortical levels of cytokines (TNF‐α, IL‐6 and MCP‐1) which were lowered by C21 treatment. Interestingly, C21 treatment raised the levels of the anti‐inflammatory cytokine IL‐10 in the plasma and renal cortices of OZR, while there was a marked reduction in IL‐10 levels in the OZR PD group. Renal histology revealed mesangial matrix expansion and mild mesangial hypercellularity in the OZR vehicle and PD treated rats, while the glomeruli of the OZR C21 group were normal. Our results suggest an anti‐inflammatory role for the AT2R in obesity‐linked renal inflammation. Pharmacological activation of AT2R in the early stages of obesity‐induced renal injury may serve as a potential therapy to prevent progression of the disease. Supported by NIH R01 DK‐61578.

Structural elucidation of impurities in 5-n-butyl-4-{4-[2-(1H-tetrazole-5-yl)-1H-pyrrol-1-yl]phenylmethyl}-2,4-dihydro-2-(2,6-dichlorophenyl)-3H-1,2,4-triazol-3-one (Ib), a novel nonpeptide angiotensin AT1 receptor antagonist

5-n-butyl-4-{4-[2-(1H-tetrazole-5-yl)-1H-pyrrol-1-yl]phenylmethyl}-2,4-dihydro-2-(2,6-dichlorophenyl)-3H-1,2,4-triazol-3-one (Ib), a new nonpeptide angiotensin AT1-receptor antagonist, has been observed to play a positive role in the treatment of hypertension in preclinical tests. Four process impurities of Ib were detected by LC-UV and LC/ESI-MS, and the impurities isolated by preparative HPLC chromatography were characterized by LC-MS/MS, high resolution MS (HRMS), NMR and IR analyses. The structures of impurities were confirmed as 5-n-butyl-4-{4-[2-chloro-5-(1H-tetrazole-5-yl)-1H-pyrrol-1-yl]phenylmethyl}-2,4-dihydro-2-(2,6-dichlorophenyl)-3H-1,2,4-triazol-3-one (I), 5-n-butyl-4-{4-[2-bromo-5-(1H-tetrazole-5-yl)-1H-pyrrol-1-yl]phenylmethyl}-2,4-dihydro-2-(2,6-dichlorophenyl)-3H-1,2,4-triazol-3-one (II), 5-n-butyl-4-{4-[4-chloro-2-(1H-tetrazole-5-yl)-1H-pyrrol-1-yl]phenylmethyl}-2,4-dihydro-2-(2,6-dichlorophenyl)-3H-1,2,4-triazol-3-one (III) and 5-n-butyl-4-{4-[4-bromo-2-(1H-tetrazole-5-yl)-1H-pyrrol-1-yl]phenylmethyl}-2,4-dihydro-2-(2,6-dichlorophenyl)-3H-1,2,4-triazol-3-one (IV), respectively. All of the four impurities were produced as the by-products of the bromination reaction by NBS (N-bromosuccinimide) in the synthesis of Ib.

Des-aspartate-angiotensin I exerts antiviral effects and attenuates ICAM-1 formation in rhinovirus-infected epithelial cells

The high frequency of rhinovirus (RV) infection and the lack of an effective treatment, underline the importance of research on novel anti-rhinoviral agents. The present study investigated the effects of des-aspartate-angiotensin I (DAA-I) on the survival of RV14-infected H1HeLa cells; and the early inflammatory processes in RV14-infected A549 lung epithelial cells. The study rationale was based on earlier findings showing that DAA-I is an effective anti-inflammatory agent, and that symptoms and severity of rhinoviral infection are related to the underling inflammation. RV14 concentration dependently caused the death of H1HeLa cells and DAA-I, at concentrations of 10−10 to 10−12M, attenuated the lethal action of RV14 indicating that that DAA-I exerts antiviral action. Unlike its action on H1HeLa cells, RV14 did not cause apparent cytopathic effect on A549 cells, and these cells were used to study the antiviral action of DAA-I. RV14 induced overexpression of ICAM-1, E-selectin and overproduction of superoxide in A549 cells, and DAA-I attenuated the three increases to basal level at concentrations of 10−10 to 10−12M. Losartan, an angiotensin AT1 receptor antagonist, blocked the inhibitory action of DAA-I on superoxide overproduction indicating that the AT1 receptor mediates the action of DAA-I. The present data represent a novel demonstration of the antiviral action of an angiotensin peptide, and a possible involvement of the renin angiotensin system in viral infection. Indeed the angiotensin AT1 receptor has been reported to be obligatory for the development of virus-induced myocardial injury through the proinflammatory action of angiotensin II via the NF-κB/cytokine pathway.

Kinins as Therapeutic Agents in Cardiovascular and Renal Diseases

A fair amount of data indicates that bradykinin and lysyl-bradykinin exert arterial, cardiac and renal effects which afford protection against organ damage in diseases, especially in the settings of ischemia or diabetes. The concept of kinins acting as therapeutic agents is supported by the wide use of angiotensin I-converting enzyme (ACE) inhibitors. These inhibitors indeed potentiate kinin action by inhibiting kinin degradation. Experimental evidence strongly suggests that the cardiac and renal effects of ACE inhibitors are due, at least in part, to kinins. Angiotensin AT1 receptor antagonists act also partly through kinins. This paper reviews available evidence supporting a role for kinins in the therapeutic effect of current drugs. It then discusses the opportunity to develop new drugs based on kinin action. Direct activation of the kinin B2 receptor by pharmacological agonists might provide higher therapeutic benefit than existing kinin- potentiating drugs. Possible occurrence of side effects is however a concern.