[Antipsychotic Treatment of Alcohol Withdrawal Syndrome with Focus on Delirium Tremens: a Systematic Review]. / Systematische Übersichtsarbeit Antipsychotische Behandlung des Alkoholentzugssyndroms: Fokus Delirium Tremens.

BACKGROUND: Delirium tremens (DT) is a common complication of alcohol withdrawal. Pharmacological treatment of hospitalized patients with DT is important in addiction medicine but also in other medical disciplines where DT can occur as a complication of hospitalization. Patients suffering from DT require treatment with benzodiazepines (short-acting benzodiazepines for elderly patients to reduce accumulation), and in cases of psychotic symptoms, treatment with antipsychotics. Benzodiazepines are a first-line treatment for DT. A specific guideline for the use of antipsychotics has yet to be developed. This review discusses the current guidelines and literature on the antipsychotic treatment options in DT. AIM: Systematic presentation of relevant antipsychotics for the treatment of DT. METHODS: A systematic literature search was conducted using Scopus and PubMed. The last search was conducted on May 22nd 2022. Original articles and reviews on antipsychotic treatment in alcohol withdrawal and DT were included in this review. Further, international guidelines were also considered. The review was registered using the PROSPERO database (https://www.crd.york.ac.uk/prospero/); CRD42021264611. RESULTS: Haloperidol is mainly recommended for use in the intensive care unit. There is little literature on the use of atypical antipsychotics to treat DT. Treatment with antipsychotics always should be combined with benzodiazepines, and physicians should watch out for complications like neuroleptic malignant syndrome, QTc interval prolongation, extrapyramidal symptoms and withdrawal seizures resulting from lowering the threshold for seizures. CONCLUSION: Antipsychotic treatment should depend on the experience of the physician. Beside haloperidol, no other clear recommendations are available.

Efficacy of human C1 esterase inhibitor concentrate for treatment of ACE-inhibitor induced angioedema.

BACKGROUND: ACE inhibitor (ACEi) induced angioedema predominantly affects the upper aerodigestive tract. As ACEi induced angioedema is mediated by bradykinin, therapeutic response to antihistamines and glucocorticoids remains unsatisfactory. In bradykinin mediated hereditary angioedema, C1-esterase inhibitor (C1INH) is an effective and approved treatment since many years. Our aim was to evaluate the therapeutic effect of C1INH in ACEi induced angioedema. METHODS: We performed a double-blind, parallel-group, multicentre randomised placebo-controlled trial between December 2013 and September 2018. Eligible were adults with ACEi induced angioedema with airway obstruction. Participants were randomised 1:1 to single doses of either C1INH (20 IU/kg) or placebo (0.9% NaCl) i.v in addition to standard care (i.v. 500 mg prednisolone and 2.68 mg clemastine) i.v. Composite symptom scores were assessed at baseline and up to 48 h, at discharge and 1 week after discharge. Physician assessed time to complete oedema resolution (TCER) and time to onset of relief (TOR). RESULTS: 30 patients (16 C1INH, 14 placebo) were randomised and dosed. 25 (9 C1INH, 12 placebo) completed the study. TCER was 29.63 h ± 15.56 h in the C1INH and 17.29 h ± 10.40 h in the placebo arm (p = 0.0457). TORs were 4.13 h ± 3.38 h and 2.86 h ± 1.29 h for C1INH and placebo, respectively (p = 0.4443). There were no adverse events related to study medication. CONCLUSIONS: In the context of baseline application of steroids and antihistamines C1INH was inferior in the treatment of ACEi induced angioedema when compared to placebo with respect to time to complete resolution of symptoms. Eudra-CT Number: 2012-001670-28.

Alterations in endothelial nitric oxide synthase activity and their relevance to blood pressure.

Among all physiologic functions of nitric oxide (NO) known so far, NO-dependent regulation of vascular tone is one of the most important. Under physiological conditions vascular NO is mainly generated by endothelial NO-synthase (eNOS), the major isoform of NOS in the cardiovascular system. NO produced in vascular endothelial cells displays complex physiologic activities considered to be vasoprotective. Of those, the initially detected vasodilation was most rigorously investigated. Increasing the activity of eNOS by genetic approaches in mouse models, non-pharmacologic interventions such as exercise training and treatment with a variety of drugs, for example ACE-inhibitors, reduces blood pressure. Conversely, several experimental and clinical conditions reducing the activity of eNOS and/or initiating the development of endothelial dysfunction show the opposite effect. While robust evidence suggest that endothelial dysfunction occurs in overt hypertension, it is still a matter of debate whether endothelial dysfunction might be an underlying cause of essential hypertension. Therefore, investigations using transgenic mice expressing mutant eNOS enzymes as well as clinical studies demonstrating an association of hypertension with some loss-of-function alleles in the promoter and in exon 7 of the eNOS gene were highlighted in this review. It is concluded that present experimental and clinical data strongly support the view that endothelial dysfunction contributes to the well-known genetic causes of hypertension and should be considered as a pre-hypertensive treatment option.

Contribution of cyclooxygenase-1-dependent prostacyclin synthesis to bradykinin-induced dermal extravasation.

BACKGROUND: Non-allergic angioedema is a potentially life-threatening condition caused by accumulation of bradykinin and subsequent activation of bradykinin type 2 receptors (B2). Since COX activity plays a pivotal role in B2 signaling, the aim of this study was to determine which prostaglandins are the key mediators and which COX, COX-1 or COX-2, is predominantly involved. METHODS: We used Miles assays to assess the effects of inhibitors of COX, 5-lipoxygenase, epoxyeicosatrienoic acid generation, cytosolic phospholipase A2α and a variety of prostaglandin receptor antagonists on bradykinin-induced dermal extravasation in C57BL/6 and COX-1-deficient mice (COX-1-/-). In addition, the prostacyclin metabolite 6-keto-PGF1α was quantified by ELISA in subcutaneous tissue from C57BL/6 and human dermal microvascular endothelial cells. In the latter, 6-keto-PGF1α was also quantified and identified by LC-MS/MS. RESULTS: Unspecific COX inhibition by ibuprofen and diclofenac significantly reduced B2-mediated dermal extravasation in C57BL/6 but not COX-1-/-. Likewise, inhibition of cytosolic phospholipase A2α showed similar effects. Furthermore, extravasation in COX-1-/- was generally lower than in C57BL/6. Of the prostaglandin antagonists used, only the prostacyclin receptor antagonist RO1138452 showed a significant reduction of dermal extravasation. Moreover, 6-keto-PGF1α concentrations were increased after bradykinin treatment in subcutaneous tissue from C57BL/6 as well as in human dermal microvascular endothelial cells and this increase was abolished by diclofenac. CONCLUSION: Our findings suggest that COX-1-dependent prostacyclin production is critically involved in dermal extravasation after activation of B2 in small dermal blood vessels. Targeting prostacyclin production and/or signaling appears to be a suitable option for acute treatment of non-allergic angioedema.

Characteristics of antipsychotic drug-induced hypothermia in psychogeriatric inpatients.

OBJECTIVE: Hypothermia is a potentially lethal adverse reaction to typical and atypical antipsychotic drugs (APD). Among predisposing factors are advanced age and comorbid somatic diseases. The aim of this study was to assess the incidence of hypothermia and quantify risk factors. METHOD: Charts of N = 3002 psychogeriatric inpatients were screened for incidence of hypothermia (body core temperature <35.0°C). The frequency of hypothermia was compared between patients treated with versus without APD and, within the sample of APD-treated patients, for (1) specific APD, (2) sex, (3) main diagnosis, and (4) age. RESULTS: N = 54 cases (2.6%) of hypothermia occurred in APD-treated patients and 12 cases (1.3%) in non-APD-treated patients (p = 0.024). In APD-treated patients, only male sex (p = 0.038) and pipamperone were associated with a higher incidence of hypothermia (p = 0.0017). Whereas the main diagnosis delirium showed a trend to significance, age did not correlate with hypothermia. CONCLUSION: Medication with pipamperone was associated with an increased risk of hypothermia. The advanced age of our sample might as well explain the high incidence of hypothermia within our sample and the failure to detect high age as a risk factor due to a ceiling effect.

Cyclooxygenase activity in bradykinin-induced dermal extravasation. A study in mice and humans.

BACKGROUND: Non-allergic angioedema is largely driven by increased plasma levels of bradykinin and over-activation of bradykinin receptor type II (B2), but the specific downstream signalling pathways remain unclear. The aim of this study was to identify signal transduction events involved in bradykinin-induced dermal extravasation. METHODS: Quantification of dermal extravasation was accomplished following intradermal (i.d.) injection of bradykinin or the B2 agonist labradimil in mice with endothelial NO-synthase (eNOS) deficiency and in C57BL/6J mice pre-treated with vehicle, NO-synthase or cyclooxygenase (COX) inhibitors. In the multicentre clinical study ABRASE, 38 healthy volunteers received i.d. bradykinin injections into the ventral forearm before and after oral treatment with the COX inhibitor ibuprofen (600 mg). The primary endpoint of ABRASE was the mean time to complete resolution of wheals (TTCR) and the secondary endpoint was the change of maximal wheal size. RESULTS: Neither NOS inhibitors nor eNOS deficiency altered bradykinin-induced extravasation. In striking contrast, the COX inhibitors ibuprofen, diclofenac, SC560 and celecoxib significantly diminished this extravasation when given before injection. As for diclofenac, a similar but significantly lower effect was observed when given after i.d. injection of bradykinin. Similar results were obtained when bradykinin was replaced by labradimil. In volunteers, ibuprofen significantly reduced TTCR (P < 0.001) and maximal wheal size (P = 0.0044). CONCLUSION: These data suggest that COX activity contributes to bradykinin-induced dermal extravasation in mice and humans. In addition, our findings may open new treatment options and point to a potential activity of drugs interfering with the release of the COX substrate arachidonic acid, e.g. glucocorticoids.

The Influence of ACE Inhibition on C1-Inhibitor: A Biomarker for ACE Inhibitor-Induced Angioedema?

AIMS: Angioedema is a rare side effect of angiotensin-converting enzyme (ACE) inhibitors. It remains unclear why it is only induced in a few patients taking ACE inhibitors, often after a long period of uneventful treatment. The aim of this study was to analyze the influence of ACE inhibitor treatment on C1-inhibitor (C1-INH) levels. METHODS: Captopril (5 mg/25 mg) was added to blood samples of 5 healthy subjects. C1-INH levels were measured before and after incubation for 180 min. The second section of the study was done with 17 patients who received therapy with an ACE inhibitor for the first time. C1-INH levels were measured before ACE inhibitor treatment, 24 h after first drug administration, and 4 weeks later. RESULTS: After incubation of blood samples with 5 mg captopril, there was no detectable change in C1-INH levels. After incubation with 25 mg, C1-INH activity was decreased by an average of 29% and the C1-INH concentration was decreased by an average of 0.06 g/L. In the second study section, inconsistent effects on C1-INH levels were detected. In the majority of patients, 24 h after the first ACE inhibitor administration C1-INH activity was tending to be increased. CONCLUSIONS: A dose-dependent effect on C1-INH levels in captopril-incubated blood samples of healthy test persons was shown. In patients with new ACE inhibitor treatment, heterogeneous reactions of C1-INH values were detected. Larger studies are needed over a longer period of time to find correlations between the effect of ACE inhibitor therapy on C1-INH levels and the clinical course/development of side effects.

Mechanisms of N-oleoyldopamine activation of central histaminergic neurons.

Histaminergic (HA) neurons located in the tuberomamillary nucleus (TMN) of the posterior hypothalamus fire exclusively during waking and support many physiological functions. We investigated the role of the endovanilloid N-oleoyldopamine (OLDA) in TMN, where dopamine synthesis and its conjugation with oleic acid likely occur. We show that several known targets of OLDA including TRPV1 and cannabinoid receptors are expressed in HA neurons. In contrast to capsaicin, which failed to increase firing of HA neurons in TRPV1 knockout mice (TRPVI KO), OLDA was still able to induce excitation. This excitation was not sensitive to the blockade of cannabinoid receptors 1 and 2 and could result from OLDA interaction with GPR119, as the ligand of GPR119, oleoylethanolamide (OEA), also increased the firing of HA neurons. However, we ruled out this possibility as OEA- (but not OLDA-) excitation was abolished by the PPAR (peroxisome proliferator activated receptor) alpha antagonist MK886. The dopamine uptake blocker nomifensine blanked OLDA-excitation and dopamine receptor antagonists abolished the OLDA action in TRPV1 KO mice. Therefore OLDA excites HA neurons through multiple targets suggesting a central role of the histaminergic system in the behavioral stimulation seen after systemic OLDA application.

The role of bradykinin receptor type 2 in spontaneous extravasation in mice skin: implications for non-allergic angio-oedema.

BACKGROUND AND PURPOSE: Non-allergic angio-oedema is a life-threatening disease mediated by activation of bradykinin type 2 receptors (B2 receptors). The aim of this study was to investigate whether activation of B2 receptors by endogenous bradykinin contributes to physiological extravasation. This may shed new light on the assumption that treatment with an angiotensin converting enzyme inhibitor (ACEi) results in an alteration in the vascular barrier function predisposing to non-allergic angio-oedema. EXPERIMENTAL APPROACH: We generated a new transgenic mouse model characterized by endothelium-specific overexpression of the B2 receptor (B2tg ) and established a non-invasive two-photon laser microscopy approach to measure the kinetics of spontaneous extravasation in vivo. The B2tg mice showed normal morphology and litter size as compared with their transgene-negative littermates (B2n ). KEY RESULTS: Overexpression of B2 receptors was functional in conductance vessels and resistance vessels as evidenced by B2 receptor-mediated aortic dilation to bradykinin in presence of non-specific COX inhibitor diclofenac and by significant hypotension in B2tg respectively. Measurement of dermal extravasation by Miles assay showed that bradykinin induced extravasation was significantly increased in B2tg as compared with B2n . However, neither endothelial overexpression of B2 receptors nor treatment with the ACEi moexipril or B2 antagonist icatibant had any effect on spontaneous extravasation measured by two-photon laser microscopy. CONCLUSIONS AND IMPLICATIONS: Activation of B2 receptors does not appear to be involved in spontaneous extravasation. Therefore, the assumption that treatment with an ACEi results in an alteration in the physiological vascular barrier function predisposing to non-allergic angio-oedema is not supported by our findings.

Selective impairment of blood pressure reduction by endothelial nitric oxide synthase dimer destabilization in mice.

OBJECTIVES: Endothelial dysfunction and oxidative stress are associated with hypertension but whether endothelial superoxide may play a role in the early development of essential hypertension remains uncertain. We investigated whether endothelial nitric oxide synthase (eNOS)-derived endothelial oxidative stress is involved in the regulation of SBP. METHODS: Wild-type eNOS [mice with endothelium-specific overexpression of bovine endothelial NO-synthase (eNOS-Tg)] or a novel dimer-destabilized eNOS-mutant harboring a partially disrupted zinc-finger [mice with endothelium-specific overexpression of destabilized bovine eNOS destabilized by replacement of Cys 101 to Ala (C101A-eNOS-Tg)] was introduced in C57BL/6 in an endothelial-specific manner. Mice were monitored for aortic endothelium-dependent relaxation, SBP, levels of superoxide and several posttranslational modifications indicating activity and/or increased vascular oxidative stress. Some groups of mice underwent voluntary exercise training for 4 weeks or treatment with the superoxide dismutase mimetic Tempol. RESULTS: C101A-eNOS-Tg showed significantly increased superoxide generation, protein-tyrosine-nitration and eNOS-tyrosine-nitration, eNOS-S-glutathionylation, eNOS phosphorylation and AMP kinase-α phosphorylation at Thr172 in aorta, skeletal muscle, left ventricular myocardium and lung as compared with eNOS-Tg and wild-type controls. Exercise training increased phosphorylation of eNOS at Ser and AMP kinase-α in wild-type. These physiologic adaptations were absent in C101A-eNOS-Tg. Maximal aortic endothelium-dependent relaxation was similar in all strains. C101A-eNOS-Tg displayed normal SBP despite higher levels of eNOS, whereas eNOS-Tg showed significant hypotension. Tempol completely reversed the occurring protein modifications and significantly reduced SBP in C101A-eNOS-Tg but not in wild-type. CONCLUSION: Oxidative stress generated by endothelial-specific expression of genetically destabilized C101A-eNOS selectively prevents SBP-reducing activity of vascular eNOS, while having no effect on aortic endothelium-dependent relaxation. These data suggest that oxidative stress in microvascular endothelium may play a role for the development of essential hypertension.

Nitric oxide up-regulates endothelial expression of angiotensin II type 2 receptors.

Increasing vascular NO levels following up-regulation of endothelial nitric oxide synthase (eNOS) is considered beneficial in cardiovascular disease. Whether such beneficial effects exerted by increased NO-levels include the vascular renin-angiotensin system remains elucidated. Exposure of endothelial cells originated from porcine aorta, mouse brain and human umbilical veins to different NO-donors showed that expression of the angiotensin-II-type-2-receptor (AT2) mRNA and protein is up-regulated by activation of soluble guanylyl cyclase, protein kinase G and p38 mitogen-activated protein kinase without changing AT2 mRNA stability. In mice, endothelial-specific overexpression of eNOS stimulated, while chronic treatment with the NOS-blocker l-nitroarginine inhibited AT2 expression. The NO-induced AT2 up-regulation was associated with a profound inhibition of angiotensin-converting enzyme (ACE)-activity. In endothelial cells this reduction of ACE-activity was reversed by either the AT2 antagonist PD 123119 or by inhibition of transcription with actinomycin D. Furthermore, in C57Bl/6 mice an acute i.v. bolus of l-nitroarginine did not change AT2-expression and ACE-activity suggesting that inhibition of ACE-activity by endogenous NO is crucially dependent on AT2 protein level. Likewise, three weeks of either voluntary or forced exercise training increased AT2 expression and reduced ACE-activity in C57Bl/6 but not in mice lacking eNOS suggesting significance of this signaling interaction for vascular physiology. Finally, aortic AT2 expression is about 5 times greater in female as compared to male C57Bl/6 and at the same time aortic ACE activity is reduced in females by more than 50%. Together these findings imply that endothelial NO regulates AT2 expression and that AT2 may regulate ACE-activity.

Effects of varenicline on alpha4-containing nicotinic acetylcholine receptor expression and cognitive performance in mice.

Nicotinic acetylcholine receptor (nAChR) subtypes containing the α4 subunit, particularly α4ß2 nAChRs, play an important role in cognitive functioning. The impact of the smoking cessation aid varenicline, a selective partial α4ß2 nAChR agonist, on (1) changes of central protein and mRNA expression of this receptor and (2) on memory deficits in a mouse model of cognitive impairment was investigated. Protein and mRNA expression of both the α4 and ß2 receptor subunits in mouse brain endothelial and hippocampal cells as well as hippocampus and neocortex tissues were determined by western blot and realtime PCR, respectively. The ß2 antibody showed low specificity, though. Tissues were examined following a 2-week oral treatment with various doses of varenicline (0.01, 0.1, 1, 3 mg/kg/day) or vehicle. In addition, episodic memory of mice was assessed following this treatment with an object recognition task using (1) normal mice and (2) animals with anticholinergic-induced memory impairment (i.p. injection of 0.5 mg/kg scopolamine). Varenicline dose-dependently increased protein expression of both the α4 and ß2 subunit in cell cultures and brain tissues, respectively, but had no effect on mRNA expression of both subunits. Scopolamine injection induced a significant reduction of object memory in vehicle-treated mice. By contrast, cognitive performance was not altered by scopolamine in varenicline-treated mice. In conclusion, a 2-week oral treatment with varenicline prevented memory impairment in the scopolamine mouse model. In parallel, protein, but not mRNA expression was upregulated, suggesting a posttranscriptional mechanism. Our findings suggest a beneficial effect of varenicline on cognitive dysfunction.

Preservation of Endothelial and Smooth Muscle Function of Human Saphenous Vein Transplants.

OBJECTIVES: Methods for conservation and preservation of vascular grafts are often controversially discussed. Furthermore, immunologic monitoring or immunotherapy for allogeneic graft is not considered necessary in many cases. The present study was initiated to examine the cellular vitality and functional efficiency of vein transplant during preservation. MATERIALS AND METHODS: Twenty-seven human vein segments (vena saphena magna) were stored after explant in University of Wisconsin solution or histidine-tryptophan-ketoglutarate solution at 4 °C. After 3, 24, 48, 72, and 96 hours, vein functionality was tested. Ring segments were fixed by triangles in Krebs-Henseleit buffer. Contractile function was measured after addition of potassium chloride solution (80 mM) and phenylephrine (0.2, 2, or 20 µM). To investigate endothelium-dependent vasorelaxation, 1 µM acetylcholine was added. RESULTS: Of 27 segments, 5 showed endothelium-dependent relaxation. Vasorelaxation continued for up to 48 hours after administration of acetylcholine in University of Wisconsin solution and for up to 24 hours in histidine-tryptophane-ketoglutarate solution. At 48 hours, potassium chloride solution-induced vasocontraction was 17% more effective than phenylephrine in University of Wisconsin solution. University of Wisconsin solution was significantly more effective than histidine-tryptophane-ketoglutarate solution in terms of preservation of phenylephrine (0.2, 2 µM)-induced vasocontraction. Phenylephrine (2 µM)-induced contraction was retained in University of Wisconsin solution after 24 hours by 81% and after 48 hours by 55%, with comparable results in histidine-tryptophane-ketoglutarate solution of only 62% and 34% after 24 and 48 hours. CONCLUSIONS: At 48 hours, human saphenous vein transplants had better endothelium and smooth muscle function when preserved in University of Wisconsin solution versus histidine-tryptophane-ketoglutarate solution.

Deletion of Hyaluronan Synthase 3 Inhibits Neointimal Hyperplasia in Mice.

OBJECTIVE: Hyaluronan (HA) is a polymeric glucosaminoglycan that forms a provisional extracellular matrix in diseased vessels. HA is synthesized by 3 different HA synthases (HAS1, HAS2, and HAS3). Aim of this study was to unravel the role of the HAS3 isoenzyme during experimental neointimal hyperplasia. APPROACH AND RESULTS: Neointimal hyperplasia was induced in Has3-deficient mice by ligation of the carotid artery. HA in the media of Has3-deficient mice was decreased 28 days after ligation, and neointimal hyperplasia was strongly inhibited. However, medial and luminal areas were unaffected. Cell density, proliferation, and apoptosis were not altered, suggesting a proportional decrease of both, the number of cells and extracellular matrix. In addition, endothelial function as determined by acetylcholine-induced relaxation of aortic rings, immunoblotting of endothelial nitric oxide synthase, and arterial blood pressure were not affected. Furthermore, the oxidative stress response was not affected as determined in total protein extracts from aortae. Transcriptome analysis comparing control versus ligated carotid arteries hinted toward a mitigated differential regulation of various signaling pathways in Has3-deficient mice in response to ligation that were related to vascular smooth muscle cell (VSMC) migration, including focal adhesions, integrins, mitogen-activated protein kinase, and phosphatidylinositol signaling system. Lentiviral overexpression of HAS3 in VSMC supported the migratory phenotype of VSMC in response to platelet-derived growth factor BB in vitro. Accordingly, knockdown of HAS3 reduced the migratory response to platelet-derived growth factor BB and in addition decreased the expression of PDGF-B mRNA. CONCLUSIONS: HAS3-mediated HA synthesis after vessel injury supports seminal signaling pathways in activation of VSMC, increases platelet-derived growth factor BB-mediated migration, and in turn enhances neointimal hyperplasia in vivo.

Identification of histaminergic neurons through histamine 3 receptor-mediated autoinhibition.

Using a reporter mouse model with expression of the tomato fluorescent protein under the dopamine transporter promoter (Tmt-DAT) we discovered a new group of neurons in the histaminergic tuberomamillary nucleus (TMN), which, in contrast to tuberoinfundibular dopaminergic neurons of the dorsomedial arcuate nucleus, do not express tyrosine hydroxylase but can synthesize and store dopamine. Tmt-DAT neurons located within TMN share electrophysiological properties with histaminergic neurons: spontaneous firing at a membrane potential around -50 mV and presence of hyperpolarization-activated cyclic nucleotide-gated ion channels. Histamine (30 µM) depolarizes and excites Tmt-DAT neurons through H1R activation but inhibits histaminergic neurons through H3R activation thus allowing a pharmacological identification of the different neurons. Single-cell RT-PCR revealed that all histaminergic neurons expressing histidine decarboxylase (HDC) also express H3R. This includes neurons retrogradely traced from the striatum whose inhibition by a selective H3R agonist was indistinguishable from the whole population. Prolonged depolarization reduces the autoinhibition. The potency of histamine at H3R depends on membrane potential and on extracellular and intracellular calcium. Autoinhibition can be impaired by preincubation with capsaicin, a ligand of the calcium-permeable TRPV1 channel or by blockade of Ca(2+)-ATPase with thapsigargin. The pharmacology of autoinhibition is revisited and physiological conditions for its functionality are determined. Usage of reporter mouse models for the safe identification of aminergic neurons under pathophysiological conditions is recommended. This article is part of the Special Issue entitled 'Histamine Receptors'.

Impact of eNOS-Dependent Oxidative Stress on Endothelial Function and Neointima Formation.

AIMS: Vascular oxidative stress generated by endothelial NO synthase (eNOS) was observed in experimental and clinical cardiovascular disease, but its relative importance for vascular pathologies is unclear. We investigated the impact of eNOS-dependent vascular oxidative stress on endothelial function and on neointimal hyperplasia. RESULTS: A dimer-destabilized mutant of bovine eNOS where cysteine 101 was replaced by alanine was cloned and introduced into an eNOS-deficient mouse strain (eNOS-KO) in an endothelial-specific manner. Destabilization of mutant eNOS in cells and eNOS-KO was confirmed by the reduced dimer/monomer ratio. Purified mutant eNOS and transfected cells generated less citrulline and NO, respectively, while superoxide generation was enhanced. In eNOS-KO, introduction of mutant eNOS caused a 2.3-3.7-fold increase in superoxide and peroxynitrite formation in the aorta and myocardium. This was completely blunted by an NOS inhibitor. Nevertheless, expression of mutant eNOS in eNOS-KO completely restored maximal aortic endothelium-dependent relaxation to acetylcholine. Neointimal hyperplasia induced by carotid binding was much larger in eNOS-KO than in mutant eNOS-KO and C57BL/6, while the latter strains showed comparable hyperplasia. Likewise, vascular remodeling was blunted in eNOS-KO only. INNOVATION: Our results provide the first in vivo evidence that eNOS-dependent oxidative stress is unlikely to be an initial cause of impaired endothelium-dependent vasodilation and/or a pathologic factor promoting intimal hyperplasia. These findings highlight the importance of other sources of vascular oxidative stress in cardiovascular disease. CONCLUSION: eNOS-dependent oxidative stress is unlikely to induce functional vascular damage as long as concomitant generation of NO is preserved. This underlines the importance of current and new therapeutic strategies in improving endothelial NO generation.

Sustained hypertension despite endothelial-specific eNOS rescue in eNOS-deficient mice.

The aim of the study was to evaluate the possible contribution of non-endothelial eNOS to the regulation of blood pressure (BP). To accomplish this, a double transgenic strain expressing eNOS exclusively in the vascular endothelium (eNOS-Tg/KO) has been generated by endothelial-specific targeting of bovine eNOS in eNOS-deficient mice (eNOS-KO). Expression of eNOS was evaluated in aorta, myocardium, kidney, brain stem and skeletal muscle. Organ bath studies revealed a complete normalization of aortic reactivity to acetylcholine, phenylephrine and the NO-donors in eNOS-Tg/KO. Function of eNOS in resistance arteries was demonstrated by acute i.v. infusion of acetylcholine and the NOS-inhibitor L-NAME. Acetylcholine decreased mean arterial pressure in all strains but eNOS-KO responded significantly less sensitive as compared eNOS-Tg/KO and C57BL/6. Likewise, acute i.v. L-NAME application elevated mean arterial pressure in C57BL/6 and eNOS-Tg/KO, but not in eNOS-KO. In striking contrast to these findings, mean, systolic and diastolic BP in eNOS-Tg/KO remained significantly elevated and was similar to values of eNOS-KO. Chronic oral treatment with L-NAME increased BP to the level of eNOS-KO only in C57BL/6, but had no effect on hypertension in eNOS-KO and eNOS-Tg/KO. Taken together, functional reconstitution of eNOS in the vasculature of eNOS-KO not even partially lowered BP. These data suggest that the activity of eNOS expressed in non-vascular tissue might play a role in physiologic BP regulation.

Effect of C1-Esterase-inhibitor in angiotensin-converting enzyme inhibitor-induced angioedema.

OBJECTIVES/HYPOTHESIS: The study objective was to generate pilot data to evaluate the effectiveness and safety of C1-esterase-inhibitor concentrate (C1-INH) compared to standard treatment in patients with angiotensin-converting enzyme inhibitor (ACEi)-induced angioedema affecting the upper aerodigestive tract. STUDY DESIGN: Proof-of-concept case series with historical control. METHODS: Adult patients with angioedema in the upper aerodigestive tract presenting to the emergency department were included. After establishing the diagnosis of ACEi-induced angioedema based on patient history and thorough clinical examination, all patients were administered 1,000 international units (IU) of C1-INH intravenously. A historical control group consisting of adult patients with ACEi-induced angioedema who had been treated with intravenous corticosteroids and antihistamines at the same institution over the past 8 years was used for comparison. The most important parameters assessed were the time to complete resolution of symptoms and the need for intubation or tracheotomy. RESULTS: Ten patients were included in the C1-INH group and 47 in the corticosteroid/antihistamine group. The time to complete resolution of symptoms was considerably longer in the historical control group (33.1 ± 19.4 hours) than in the C1-INH group (10.1 ± 3.0 hours). No intubation or tracheotomy was needed in the C1-INH group (0/10 patients), whereas three out of the 47 historical controls required tracheotomy and two were intubated (5/47). CONCLUSION: The results suggest a role for C1-INH as an effective and safe therapeutic option in patients with ACEi-induced angioedema, which needs to be confirmed by further larger and double-blinded studies. LEVEL OF EVIDENCE: 4.

A randomized trial of icatibant in ACE-inhibitor-induced angioedema.

BACKGROUND: Angioedema induced by treatment with angiotensin-converting-enzyme (ACE) inhibitors accounts for one third of angioedema cases in the emergency room; it is usually manifested in the upper airway and the head and neck region. There is no approved treatment for this potentially life-threatening condition. METHODS: In this multicenter, double-blind, double-dummy, randomized phase 2 study, we assigned patients who had ACE-inhibitor-induced angioedema of the upper aerodigestive tract to treatment with 30 mg of subcutaneous icatibant, a selective bradykinin B2 receptor antagonist, or to the current off-label standard therapy consisting of intravenous prednisolone (500 mg) plus clemastine (2 mg). The primary efficacy end point was the median time to complete resolution of edema. RESULTS: All 27 patients in the per-protocol population had complete resolution of edema. The median time to complete resolution was 8.0 hours (interquartile range, 3.0 to 16.0) with icatibant as compared with 27.1 hours (interquartile range, 20.3 to 48.0) with standard therapy (P=0.002). Three patients receiving standard therapy required rescue intervention with icatibant and prednisolone; 1 patient required tracheotomy. Significantly more patients in the icatibant group than in the standard-therapy group had complete resolution of edema within 4 hours after treatment (5 of 13 vs. 0 of 14, P=0.02). The median time to the onset of symptom relief (according to a composite investigator-assessed symptom score) was significantly shorter with icatibant than with standard therapy (2.0 hours vs. 11.7 hours, P=0.03). The results were similar when patient-assessed symptom scores were used. CONCLUSIONS: Among patients with ACE-inhibitor-induced angioedema, the time to complete resolution of edema was significantly shorter with icatibant than with combination therapy with a glucocorticoid and an antihistamine. (Funded by Shire and the Federal Ministry of Education and Research of Germany; ClinicalTrials.gov number, NCT01154361.).