Activation of the aryl hydrocarbon receptor by clozapine induces preadipocyte differentiation and contributes to endothelial dysfunction.

BACKGROUND: The superior therapeutic benefit of clozapine is often associated with metabolic disruptions as obesity, insulin resistance, tachycardia, higher blood pressure, and even hypertension. AIMS: These adverse vascular/ metabolic events under clozapine are similar to those caused by polycyclic aromatic hydrocarbons (PAHs), and clozapine shows structural similarity to well-known ligands of the aryl hydrocarbon receptor (AhR). Therefore, we speculated that the side effects caused by clozapine might rely on AhR signaling. METHODS: We examined clozapine-induced AhR activation by luciferase reporter assays in hepatoma HepG2 cells and we proved upregulation of the prototypical AhR target gene Cyp1A1 by realtime-PCR (RT-PCR) analysis and enzyme activity. Next we studied the physiological role of AhR in clozapine's effects on human preadipocyte differentiation and on vasodilatation by myography in wild-type and AhR-/- mice. RESULTS: In contrast to other antipsychotic drugs (APDs), clozapine triggered AhR activation and Cyp1A1 expression in HepG2 cells and adipocytes. Clozapine induced adipogenesis via AhR signaling. After PGF2α-induced constriction of mouse aortic rings, clozapine strongly reduced the maximal vasorelaxation under acetylcholine in rings from wild-type mice, but only slightly in rings from AhR-/- mice. The reduction was also prevented by pretreatment with the AhR antagonist CH-223191. CONCLUSION: Identification of clozapine as a ligand for the AhR opens new perspectives to explain common clozapine therapy-associated adverse effects at the molecular level.

Angioedema induced by cardiovascular drugs: new players join old friends.

During the last years, two new cardiovascular drug classes, namely inhibitors of DPP IV or neprilysin, have been developed. In both cases, there is clinical evidence for their potential to induce angioedema as known already from blockers of the renin-angiotensin-aldosterone system (RAAS). The majority of angioedema induced by DPP IV inhibitors occurs during concomitant treatment with ACEi and is therefore likely mediated by overactivation of bradykinin type 2 receptors (B2). In striking contrast, the molecular pathways causing angioedema induced by neprilysin inhibitors, that is, sacubitril, are unclear, although a contribution of bradykinin appears likely. Nevertheless, there is no clinical evidence suggesting that inhibition of B2 might relieve the symptoms and/or prevent invasive treatment including coniotomy or tracheotomy in angioedema caused by these drugs. Therefore, the risk of angioedema should always be considered, especially in ambulatory care situations where patients have no rapid access to intensive care.

Stability of murine bradykinin type 2 receptor despite treatment with NO, bradykinin, icatibant, or C1-INH.

BACKGROUND: Little is known about factors which trigger and/or contribute to hereditary angioedema or ACE-inhibitor-mediated angioedema including variations in bradykinin type 2 receptor (B2R) expression and activity. METHODS: Protein and mRNA expression of B2R and the increase of intracellular calcium (iCa) in response to bradykinin were monitored in porcine and murine endothelial cells in response to NO donors or bradykinin. B2R protein expression was evaluated in skin, heart, and lung of (i) mice with endothelial-specific overexpression of eNOS (eNOS(tg) ), (ii) in eNOS(-/-) mice and (iii) in C57BL/6 mice treated with the NO donor pentaerythritol tetranitrate (PETN), the NOS inhibitor l-nitroarginine (L-NA), plasma pool C1-INH, and the B2R antagonist icatibant. Aortic reactivity to bradykinin was investigated including eNOS(-/-) mice. RESULTS: B2R protein and mRNA expression remained unchanged in cells subjected to L-NA, NO donors, and bradykinin in a time- and concentration-dependent manner. Likewise, increases of iCa in murine brain endothelial cells remained unchanged. B2R protein levels were similar in eNOS(tg) and eNOS(-/-) as compared to transgene-negative littermates. Likewise, treatment of C57BL/6 mice with PETN, L-NA, C1-INH or icatibant did not change B2R protein expression. In aortic rings of C57BL/6 mice, bradykinin induced B2R-dependent constrictions which were attenuated by endothelial NO and abolished by diclofenac indicating the functional importance of B2R-induced activation of endothelial NO synthase and cyclooxygenase. CONCLUSION: These data suggest that alterations of B2R protein expression induced by NO, bradykinin, C1-INH, or icatibant unlikely contribute to bradykinin-induced angioedema. This finding does not rule out a role for NO in bradykinin-induced extravasation and/or angioedema.

New topics in bradykinin research.

Bradykinin has been implicated to contribute to allergic inflammation and the pathogenesis of allergic conditions. It binds to endothelial B(1) and B(2) receptors and exerts potent pharmacological and physiological effects, notably, decreased blood pressure, increased vascular permeability and the promotion of classical symptoms of inflammation such as vasodilation, hyperthermia, oedema and pain. Towards potential clinical benefit, bradykinin has also been shown to exert potent antithrombogenic, antiproliferative and antifibrogenic effects. The development of pharmacologically active substances, such as bradykinin receptor blockers, opens up new therapeutic options that require further research into bradykinin. This review presents current understanding surrounding the role of bradykinin in nonallergic angioedema and other conditions seen by allergists and emergency physicians, and its potential role as a therapeutic target.

[Angiotensin-converting enzyme inhibitor induced angioedema : new therapy options]. / "Angiotensin-converting-enzyme"-Hemmer induziertes Angioödem : Neue Therapieoption.

Angiotensin-converting enzyme (ACE) inhibitors block the catalysis of angiotensin I to angiotensin II and also the breakdown of bradykinin. ACE inhibitor-induced angioedema is mediated by inhibited bradykinin degradation leading to enhanced bradykinin plasma levels. The efficacy of currently used standard treatments with antiallergic drugs is questionable. A patient with acute ACE inhibitor-induced angioedema was treated with icatibant, a specific bradykinin B2 receptor antagonist approved for the treatment of hereditary angioedema. A single subcutaneous injection of 30 mg icatibant resulted in a rapid onset of symptom relief and a remarkable shortening of duration of the attack.

[Emergency management of acute angioedema]. / Notfallsituation akutes Angioödem.

Angioedema is an oedematous swelling of the mucosa or submucosa of the skin. Acute angioedema represents a clinical emergency when the pharynx or larynx are involved and breathing of the patient is impaired. For rapid and effective treatment it is necessary to differentiate between allergic and non-allergic angioedema. Three of the five subforms of non-allergic angioedema are mediated by bradykinin: renin-angiotensin-aldosterone system (RAAS)-blocker-induced angioedema (RAE), hereditary angioedema (HAE) and acquired angioedema (AAE). Antihistamines, corticosteroids and adrenalin can be used to treat allergic angioedema but are ineffective in acute attacks of non-allergic angioedema. In these events the bradykinin-B2-receptor antagonist icatibant (in HAE, or RAE) or C1-INH concentrate (in HAE, or AAE) are therapeutic options for rapid alleviation of acute angioedema. The following article gives an overview of the diagnostics and treatment in the emergency situation of "acute angioedema", especially if swelling of the head-and-neck region is present.

Effect of oral organic nitrates on expression and activity of vascular soluble guanylyl cyclase.

BACKGROUND AND PURPOSE: The regulation of vascular soluble guanylyl cyclase (sGC) expression by nitric oxide (NO) is still under discussion. In vitro, NO has been shown to downregulate the expression of sGC but it is unclear if this mechanism is operative in vivo and occurs during nitrate treatment. EXPERIMENTAL APPROACH: We investigated whether high dose isosorbide mononitrate (ISMN) or pentaerythrityl tetranitrate (PETN) treatment changes vascular sGC expression and activity in vivo. New Zealand White rabbits received a standard diet, 2 or 200 mg ISMN kg(-1) d(-1) for 16 weeks, and C57BL/6 mice received a standard diet, 6, 60 or 300 mg PETN kg(-1) d(-1) for four weeks. Absorption was checked by measuring the plasma levels of the drug/metabolite. KEY RESULTS: Western blots of rabbit aortic rings showed similar protein levels of sGC alpha1- (P=0.2790) and beta1-subunits (P=0.6900) in all groups. Likewise, ANOVA showed that there was no difference in the expression of sGC in lungs of PETN-treated mice (P=0.0961 for alpha1 and P=0.3709 for beta1). The activities of isolated sGC in response to SNAP (1 microM-1 mM) were identical in aortae of ISMN-treated rabbits (P=0.0775) and lungs of PETN-treated mice (P=0.6348). The aortic relaxation response to SNAP slightly decreased at high ISMN but not at high PETN. CONCLUSIONS AND IMPLICATIONS: These data refute the hypothesis that therapeutic treatment with long acting NO donors has a significant impact on the regulation of vascular sGC expression and activity in vivo.

[ACE-inhibitor induced angioedema]. / Das ACE-Hemmer-induzierte Angioödem.

ACE-inhibitor induced angioedema is a non-allergic drug-related side effect. Inhibited bradykinin degradation leads to an unphysiological enhanced bradykinin plasma level with vascular leakage and, consequently, to angioedema. ACE-inhibitor induced angioedema develop rapidly in the head and neck region. Typical sites of manifestation are lips, tongue, and larynx. Novel pharmacotherapies may allow a causal treatment of the ACE-inhibitor induced angioedema in the future.

Nonallergic angioedema: role of bradykinin.

Angioedema is an underestimated clinical problem. Many cases are nonallergic reactions, e.g. bradykinin-induced angioedema caused by genetic defects and angiotensin-converting enzyme (ACE) inhibitors. This difference is crucial for successful therapy, in particular when complete emergency care is not available. Five important forms of nonallergic angioedema can be distinguished: hereditary (HAE), acquired (AAE), renin-angiotensin-aldosterone system (RAAS)-blocker-induced (RAE), pseudoallergic angioedema (PAE) and idiopathic angioedema (IAE). Some angioedema are present in the larynx and may cause death. A vast majority of nonallergic angioedema are RAE, particularly those caused by ACE inhibitors. It appears important to emphasize that in patients with complete intolerance to RAAS-blockers, cessation of RAAS-blockers is likely to be associated with increased cardiovascular risk. Currently, there is no published algorithm for diagnosis and treatment. Angioedema is usually treated by a conservative clinical approach using artificial ventilation, glucocorticoids and antihistamines. Today, a plasma pool C1-esterase inhibitor (C1-INH) concentrate is the therapy of choice in HAE. The current pharmacotherapy of nonallergic angioedema is not satisfactory, thus requiring the identification of effective agents in clinical trials. Recently, several new drugs were developed: a recombinant C1-INH, a kallikrein inhibitor (ecallantide) and a specific bradykinin-B2-receptor antagonist (icatibant). According to currently available reports, these drugs may improve the treatment of kinin-induced angioedema.

Increased cardiac endothelial nitric oxide synthase expression in patients taking angiotensin-converting enzyme inhibitor therapy.

BACKGROUND: The efficacy of angiotensin-converting enzyme (ACE) inhibitors has been demonstrated in large clinical trials, but knowledge of the underlying mechanisms remains incomplete. Therefore, this study investigated the impact of ACE inhibitor therapy on cardiac nitric oxide (NO) synthases in patients with coronary artery disease (CAD) or heart failure. PATIENTS AND METHODS: The mRNA expression was quantified by standard calibrated competitive RT-PCR, protein expression by Western blotting and NOS activity by monitoring the conversion of [3H]arginine to [3H]citrulline during enzymatic formation of NO in tissue homogenates of myocardium of patients with, or without, ACE inhibitor treatment before elective coronary artery bypass grafting or heart transplantation. RESULTS: The mRNA expression (amol microg(-1) RNA) of endothelial NO synthase (eNOS) was higher (22.5 +/- 4.8, n = 23) in the atrial myocardium of patients taking ACE inhibitor treatment, before elective coronary artery bypass grafting, compared with patients not taking this therapy (8.9 +/- 0.7, n = 33, P < 0.0001). The ACE inhibitor therapy increased eNOS protein expression from [(9 +/- 0.7) relative units (RUs) to (12 +/- 0.9) RUs, P < 0.05, respectively] and cardiac NOS activity from 17.6 +/- 1.3 to 23.7 +/- 1.1 pmol mg protein(-1) min(-1) (P < 0.001, respectively). Inducible and neuronal NO synthase expression was not changed by the ACE inhibition. A similar up-regulation of eNOS by ACE inhibition was found in the left ventricles of patients with heart failure. The augmented endothelial NOS expression and activity was not the result of differences in clinical characteristics and concomitant therapy between the patient groups. CONCLUSION: Increased eNOS expression and activity might contribute to the beneficial effects of ACE inhibitor therapy in the treatment of CAD and heart failure.

[Mona Lisa syndrome: idiopathic facial paralysis during pregnancy]. / Das Mona-Lisa-Syndrom--die periphere Fazialisparese in der Schwangerschaft.

Mona Lisa has been pregnant shortly before the famous painting of Leonardo da Vinci was created (1503-1506). Recently, it has been speculated that Mona Lisa's famous smile is caused by facial muscle contracture and/or synkinesis after Bell's palsy with incomplete nerval regeneration. During pregnancy the incidence of Bell's palsy is increased up to 3.3 times compared to nonpregnant women. The etiology, associated factors as well as various treatment options aiming at the prevention of associated complications and improving recovery of facial nerve function have intensively been evaluated over the past three decades. However, the preferred mode of therapy management, particularly in pregnant women, remains undecided. Corticosteroids may be beneficial if they are applied after the first trimester.

[Angioedema due to ACE inhibitors and AT(1) receptor antagonists]. / Angioödeme durch ACE-Hemmer und AT(1)-Rezeptorblocker.

Acute drug-induced angioedema is a non-pruritic swelling of subcutaneous and submucosal tissue. It most occur occurs the mouth and larynx as well as lips and eyelids; less often other skin regions or even the gut can be involved. ACE inhibitor (ACEi)- induced angioedema typical occurs after several years on medication. A 72-year-old woman developed recurrent ACEi-induced angioedema. The drug was stopped and she received an AT(1)-receptor antagonist as an alternative antihypertensive. This medication also led to angioedema, which was not immediately recognized as medication-associated. AT(1)-receptor antagonists are not suitable alternatives for ACEi because they also carry an increased risk for inducing angioedema.

Organic nitrates in cardiovascular disease.

Therapeutic activation of the vascular NO/cGMP pathway is induced by a variety of stimuli/mediators including physical activity, supplementation with the precursor L-arginine and organic nitrates which generate NO in the vasculature. The necessity of an enzymatic reduction for NO generation from these drugs as well as differences in the activity of the NO/cGMP pathway within the vascular tree determine the unique hemodynamic changes elicited by organic nitrates. These changes include preferential venodilation, vessel-size specific arterial dilation and improvement of the aortic distensibility and Windkessel-function. Some animal experiments and clinical investigations suggest that nitrates may also be endowed with cardioprotective and/or vasoprotective effects. "Early entry" therapy with nitrates do not significantly improve survival in myocardial infarction but increases the beneficial effects of the ACE-inhibitor enalapril by 50%. Furthermore, nitrates have been shown to improve survival in heart failure, but prognostic effects in stable angina pectoris are unknown. Short-term experimental and clinical investigations suggest that nitrate tolerance induced by nitroglycerin is associated with toxic effects in the vasculature, but this is not true for pentaerythrityl tetranitrate and isosorbide mononitrate. The observed endothelial dysfunction induced by a continuous treatment with nitroglycerin may be an additional risk for patients who receive continuous nitroglycerin to treat conditions such as unstable angina and acute heart failure. In general, nitrates are remarkably safe drugs and are well tolerated. Appropriate clinical trials are needed to answer the question whether nitrates can do more than symptomatic relief in cardiovascular disease.

Increased C-reactive protein in ACE-inhibitor-induced angioedema.

AIMS: This study was designed to identify new factors which may contribute to angiotensin-converting-enzyme-inhibitor (ACEI)-induced angioedema. METHODS: In a retrospective cohort study we examined 25 patients who used an ACEI and presented at our emergency room with acute angioedema as well as 18 patients with unknown cause of angioedema and a total of 21 patients on ACEI-therapy without previous angioedema. We measured markers of inflammation such as acute-phase proteins (C-reactive protein, fibrinogen), leukocyte count and body temperature. RESULTS: The mean interval between initiation of ACEI treatment and first manifestation of angioedema was 35.8 +/- 5.3 months. During symptomatic angioedema, mean plasma levels of C-reactive protein and fibrinogen were significantly increased by 7.3-fold and 1.5-fold, respectively, while leukocyte count and body temperature were normal. These changes disappeared after successful treatment of angioedema and were not found in patients with angioedema of unknown cause and those receiving ACEI without having experienced angioedema. CONCLUSION: Our findings demonstrate for the first time that ACEI-induced angioedema is associated with strongly increased plasma levels of CRP. We suggest that CRP is involved in the pathophysiology of ACEI-induced angioedema.

[ACE inhibitor-induced angioedema in the head and neck region. A matter of time?]. / Durch ACE-Hemmer induziertes Angioödem des Kopf-Hals-Bereichs. Eine Frage der Zeit?

BACKGROUND: Angioedema in the head and neck region is potentially life-threatening and may occur as a side effect of inhibitors of the angiotensin-converting-enzyme (ACEI). So far, little is known about the time between the first application of ACEI and the occurrence of angioedema, or of possible cofactors and laboratory changes. MATERIAL AND METHODS: A total of 21 patients with angioedema during the course of ACEI treatment were compared to 11 patients with angioedema of unknown cause. These were retrospectively analysed for the following criteria: (1) duration of ACEI medication, (2) leading and concomitant diseases, (3) history of allergies, (4) co-medication, (5) laboratory changes, (6) treatment success, and (7) manifestation of recurrent episodes. RESULTS: The mean interval between the initiation of ACEI therapy and the first occurrence of angioedema exceeded 2 years. Values for the acute phase proteins C-reactive protein (CRP) and fibrinogen were significantly increased in the ACEI group compared to the control group. CONCLUSIONS: In any case of angioedema in the head and neck region, a side effect of ACEI must be taken into consideration even if the medication has been taken for months or years.

[Symptoms and therapy for pregnancy rhinitis]. / Klinik und Therapie der Schwangerschafts-Rhinopathie.

Pregnancy rhinitis is a common condition with long-lasting nasal congestion without signs of infection, allergy or tumor, starting at any time during pregnancy and disappearing completely within 2 weeks of delivery. Risk factors are smoking, sensitisation to house dust mites and chronic sinusitis. Hormonal influences are most likely; however, a definitive pathophysiological concept does not exist. Various treatment options are presented and a stepwise therapeutic strategy for pregnancy rhinitis is developed.

The negative inotropic effect of sevoflurane is not mediated through nitric oxide synthase in rat papillary muscle.

Sevoflurane has dose-dependent negative inotropic effects on myocardial contractility. The current study investigated whether the nitric oxide pathway is involved in these effects. A laboratory, ex-vivo experiment was performed on 66 isolated papillary muscles. Effects of increasing concentrations of sevoflurane (1, 2 and 3 MAC) were assessed in control conditions, in the presence of Nw-nitro-L-arginine (L-NOARG) and in beta-adrenergic stimulated rat papillary muscles. Contractility was assessed by total developed tension. In baseline conditions, the administration of increasing concentrations of sevoflurane caused a dose-dependent reduction in contractility of respectively 8.6 +/- 1.7%, 14.4 +/- 4.8% and 23.6 +/- 3.9%. This negative inotropic effect was not significantly altered by the administration of the NO-synthase inhibitor L-NOARG (p = 0.09). Under continuous administration of 3 MAC sevoflurane, 4 consecutive concentrations of isoproterenol induced a mean increase of contractility of respectively 43.0 +/- 13.7%, 65.9 +/- 22.6%, 131.2 +/- 25.6% and 122.3 +/- 31.2%. After administration of L-NOARG, the 4 consecutive concentrations of isoproterenol induced a mean increase in contractility of respectively 36.0 +/- 8.5%, 75.0 +/- 17.8%, 143.0 +/- 42.8% and 120.0 +/- 51.4% (p = 0.85). These data indicated that the negative inotropic effects of sevoflurane in rat papillary muscles, both in basic as in beta-adrenergic stimulated conditions, were not altered by blocking the NO-cGMP-system.

The effect of peroxynitrite on the catalytic activity of soluble guanylyl cyclase.

Soluble guanylyl cyclase (sGC) is a key enzyme of the *NO/cGMP pathway. Many cardiovascular disorders are associated with reduced *NO-mediated effects, while vascular superoxide (O(2)*(-)) production is increased. Both radicals rapidly react to peroxynitrite. We investigated whether peroxynitrite affects the activity and protein expression of sGC in intact vascular preparations. Catalytic sGC activity and expression of the sGC-beta(1) subunit was measured by conversion of radiolabeled GTP and western blot, respectively, using cytosolic extracts from rat aorta that had been incubated for 4 h with *NO/O(2)*(-) systems (devoid of free *NO) generating either 0.13 microM or 7.5 microM peroxynitrite/min. Incubation of rat aorta with 0.13 microM peroxynitrite/min had no effect. In striking contrast, incubation with 7.5 microM peroxynitrite/min resulted in a shift of the concentration-response curve obtained with a *NO donor (p =.0004) and a reduction of maximal specific activity from 3579 +/- 495 to 2422 +/- 265 pmol cGMP/mg/min (p =.036). The expression of the sGC-beta(1) subunit was unchanged. Exposure of aorta to the O(2)*(-) component had no effect, while exposure to the *NO-component reduced sGC expression to 58.8 +/- 7% (p <.001) and maximal sGC activity from 4041 +/- 992 to 1429 +/- 491 pmol cGMP/mg/min (p =.031). These data suggest that continuous generation of extracellular peroxynitrite might interfere with the *NO/cGMP signaling in vascular cells.