Acute ACE inhibition causes plasma extravasation in mice that is mediated by bradykinin and substance P

Angioedema After Use of Recombinant Tissue-Type Plasminogen Activators in Stroke

Angioedema without concomitant urticaria is a well-known complication of treatment with the recombinant tissue-type plasminogen activator (r-tPA) alteplase and its genetically modified variant tenecteplase. It is potentially lethal when causing airway obstruction and can require intubation. The latest guideline for the early management of patients with acute ischemic stroke from the American Heart Association/American Stroke Association advises to treat this complication initially by interfering with the histamine pathway. This article aims to clarify the pathophysiological mechanism of r-tPA-induced angioedema and provides several arguments that this condition is primarily bradykinin-mediated and hence should be treated initially by intervening with the bradykinin pathway. Second, other-less frequently reported-adverse symptoms after r-tPA therapy and their proposed pathophysiological mechanisms leading to specific treatment are described. This manuscript describes the need for an update of the section "3.5 IV alteplase" from the American Heart Association/American Stroke Association guideline to treat this r-tPA-induced angioedema adequately and prevent potentially fatal outcomes.

The Role of Substance P Within Traumatic Brain Injury and Implications for Therapy

This review examines the role of the neuropeptide substance P within the neuroinflammation that follows traumatic brain injury. It examines it in reference to its preferential receptor, the neurokinin-1 receptor, and explores the evidence for antagonism of this receptor in traumatic brain injury with therapeutic intent. Expression of substance P increases following traumatic brain injury. Subsequent binding to the neurokinin-1 receptor results in neurogenic inflammation, a cause of deleterious secondary effects that include an increased intracranial pressure and poor clinical outcome. In several animal models of TBI, neurokinin-1 receptor antagonism has been shown to reduce brain edema and the resultant rise in intracranial pressure. A brief overview of the history of substance P is presented, alongside an exploration into the chemistry of the neuropeptide with a relevance to its functions within the central nervous system. This review summarizes the scientific and clinical rationale for substance P antagonism as a promising therapy for human TBI.

Angiotensin-Related Peptides and Their Role in Pain Regulation

Angiotensin (Ang)-generating system has been confirmed to play an important role in the regulation of fluid balance and blood pressure and is essential for the maintenance of biological functions. Ang-related peptides and their receptors are found throughout the body and exhibit diverse physiological effects. Accordingly, elucidating novel physiological roles of Ang-generating system has attracted considerable research attention worldwide. Ang-generating system consists of the classical Ang-converting enzyme (ACE)/Ang II/AT1 or AT2 receptor axis and the ACE2/Ang (1-7)/MAS1 receptor axis, which negatively regulates AT1 receptor-mediated responses. These Ang system components are expressed in various tissues and organs, forming a local Ang-generating system. Recent findings indicate that changes in the expression of Ang system components under pathological conditions are involved in the development of neuropathy, inflammation, and their associated pain. Here, we summarized the effects of changes in the Ang system on pain transmission in various organs and tissues involved in pain development process.

Alloferon-1 ameliorates acute inflammatory responses in λ-carrageenan-induced paw edema in mice

Alloferon-1 have been proposed as an effective peptide to enhance antitumoral immunity, antiviral defense and anti-inflammatory activity. This work aimed to assess anti-inflammatory effects of alloferon-1 against acute inflammation and histopathological deformations in λ-carrageenan-induced paw edema in mice. Systemic pretreatment with alloferon-1 (22.0 mg/kg) intraperitoneally injected mice showed a significant reduction in paw thickness and vascular permeability. Alloferon-1 prevented λ-carrageenan-evoked exudation and the neutrophil influx to the mouse pleura and the neutrophil migration into carrageenan-stimulated mouse air pouches based on the histopathological changes in the paw tissues. Administration of alloferon-1 also suppressed the expression of the inflammatory cytokines in the inflamed paw tissues such as tumor necrosis factor-α (TNF-α), monocyte chemoattractant protein 1 (MCP1), interleukin-5 (IL-5), etc. detected by Luminex liquid chip. Collectively, the present study provides evidences for the marked anti-inflammatory effects of alloferon-1 which might represent new therapeutic options for the treatment of acute inflammatory diseases.

Isolated Angioedema: A Review of Classification and Update on Management

OBJECTIVE

The purpose of this article is to review the various types of angioedema including diagnosis and treatment.

DATA SOURCES

PubMed search of articles in the English language various types of angioedema STUDY SELECTION: Articles on the subject matter were selected and reviewed.

RESULTS

Herein, a case based approach is presented for discussing the major types of angioedema including: hereditary angioedema (HAE) TypesI/II and normal complement, acquired angioedema, Angiotensin converting enzyme (ACE) induced angioedema, as well as histaminergic and non-histaminergic angioedema. Emerging treatments of HAE including targets of pre-kalikrein, DNA vector technology replacing C1INH protein, and CRIPSR technology targeting PKK among many others are explored. In addition, other causes as well as mimickers of angioedema are briefly reviewed. Finally, a novel algorithm is proposed to help guide the treating physician through the work up and management of patients with suspected idiopathic angioedema unresponsive to conventional therapy with antihistamines.

CONCLUSION

Over the years, many strides have been made in both understanding the pathophysiology of various types of angioedema as well as expansion of treatment options. It is important for clinicians to be aware of current and emerging treatment options. We provide a novel practical algorithm to guide clinicians in challenging cases of idiopathic angioedema refractory to antihistamines.

Targeting vascular inflammation through emerging methods and drug carriers

Acute inflammation is a common dangerous component of pathogenesis of many prevalent conditions with high morbidity and mortality including sepsis, thrombosis, acute respiratory distress syndrome (ARDS), COVID-19, myocardial and cerebral ischemia-reperfusion, infection, and trauma. Inflammatory changes of the vasculature and blood mediate the course and outcome of the pathology in the tissue site of insult, remote organs and systemically. Endothelial cells lining the luminal surface of the vasculature play the key regulatory functions in the body, distinct under normal vs. pathological conditions. In theory, pharmacological interventions in the endothelial cells might enable therapeutic correction of the overzealous damaging pro-inflammatory and pro-thrombotic changes in the vasculature. However, current agents and drug delivery systems (DDS) have inadequate pharmacokinetics and lack the spatiotemporal precision of vascular delivery in the context of acute inflammation. To attain this level of precision, many groups design DDS targeted to specific endothelial surface determinants. These DDS are able to provide specificity for desired tissues, organs, cells, and sub-cellular compartments needed for a particular intervention. We provide a brief overview of endothelial determinants, design of DDS targeted to these molecules, their performance in experimental models with focus on animal studies and appraisal of emerging new approaches. Particular attention is paid to challenges and perspectives of targeted therapeutics and nanomedicine for advanced management of acute inflammation.

Chronic Intestinal Inflammation Suppresses Brain Activity by Inducing Neuroinflammation in Mice

Chronic gut inflammation such as inflammatory bowel disease is believed to be associated with neurodegenerative diseases in humans. However, the direct evidence for and the underlying mechanism of this brain-gut interaction remain elusive. In this study, manganese-enhanced magnetic resonance imaging was used to assess functional brain activity from awake and freely moving mice with chronic colitis. Manganese ion uptake (indicative of Ca2+ influx into neuronal cells) and accumulation were reduced in the hippocampus of chronic colitis mice compared with control mice. Long-term memory declined and neuroinflammatory signals, including IL-1β production and activation of caspase-1, caspase-11, and gasdermin, were induced. High-mobility group box 1 (HMGB1) levels were elevated both in the serum and in the hippocampus; however, lipopolysaccharide (LPS) levels remained at low levels without significant changes in these samples. The blood-brain barrier permeability was increased in chronic colitis mice. In the presence of LPS, HMGB1 treatment induced the activation of caspase-11 and gasdermin in the mouse microglial cell line SIM-A9. These findings suggest that HMGB1 released from the inflamed intestine may move to the brain through the blood circulatory system; in conjunction with a low level of endogenous LPS, elevated HMGB1 can subsequently activate caspase-mediated inflammatory responses in the brain.

Role of nitric oxide, bradykinin B2 receptor, and TRPV1 in the airway alterations caused by simvastatin in rats

Dry cough has been reported in patients receiving statin therapy. However, the underlying mechanism or other possible alterations in the airways induced by statins remain unknown. Thus, the aim of this study was to evaluate whether simvastatin promotes alterations in airways, such as bronchoconstriction and plasma extravasation, as well as the mechanism involved in these events. Using methods to detect alterations in airway resistance and plasma extravasation, we demonstrated that simvastatin [20 mg/kg, intravenous (i.v.)] caused plasma extravasation in the trachea (79.8 + 14.8 μg/g/tissue) and bronchi (73.3 + 8.8 μg/g/tissue) of rats, compared to the vehicle (34.2 + 3.6 μg/g/tissue and 29.3 + 5.3 μg/g/tissue, respectively). NG-nitro-L-arginine methyl ester (L-NAME, 30 mg/kg, intraperitoneal), a nitric oxide (NO) synthase inhibitor, Icatibant [HOE 140, 10 nmol/50 μl, intratracheal (i.t.)], a bradykinin B2 antagonist, and capsazepine (100 nmol/50 μl, i.t.), a TRPV1 antagonist, attenuated simvastatin-induced plasma extravasation. Simvastatin (5, 10 and 20 mg/kg) did not cause bronchoconstriction per se, but exacerbated the bronchoconstrictive response to bradykinin (30 nmol/kg, i.v.), a B2 agonist (0.7 + 0.1 ml/H2O), or capsaicin (30 nmol/kg, i.v.), a TRPV1 agonist (0.8 + 0.1 ml/H2O), compared to the vehicle (0.1 + 0.04 ml/H2O and 0.04 + 0.01 ml/H2O, respectively). The bronchoconstriction elicited by bradykinin (100 nmol/kg, i.v.) in simvastatin non-treated rats was inhibited by L-NAME. The exacerbation of bronchoconstriction induced by bradykinin or capsaicin in simvastatin-treated rats was inhibited by L-NAME, HOE 140 or capsazepine. These results suggest that treatment with simvastatin promotes the release of bradykinin, which, via B2 receptors, releases NO that can then activate the TRPV1 to promote plasma extravasation and bronchoconstriction.

Case Report: Compromised Airway Following Anesthesia and Its Correlation With the Use of ACE Inhibitors-An Unexpected Clinical Event and Review of Literature

Angiotensin-converting enzyme inhibitors associated angioedema involving the upper aerodigestive tract is indisputably a hazardous airway condition which is clinically poorly recognized and frequently underestimated. We describe and present case of a 70-year old man on ramipril who developed massive tongue swelling post-operatively after unremarkable laryngeal mask anaesthesia which was fortuitously managed conservatively. High index of suspicion, timely recognition and knowledge of pathophysiology and the clinical course should guide airway and further supportive management in these patients.

ACE inhibitor induced visceral angioedema: an elusive diagnosis

ACE inhibitors are widely used and well-tolerated drugs. Angioedema is a well-known adverse effect, which involves the viscera rarely. This is a case of a 44-year-old African-American man with newly diagnosed hypertension, who presented with lower abdominal pain and diarrhoea. Based on the clinical picture and radiographic findings, lisinopril-induced intestinal angioedema was diagnosed. He recovered with supportive treatment, and the lisinopril was permanently discontinued. The mechanism of angioedema is thought to be the inhibition of ACE-mediated degradation of bradykinin, which is a peptide responsible for vasodilation and increased vascular permeability. While the external angioedema is unmistakable, intestinal angioedema has a relatively non-specific presentation and chronology, often leading to missed diagnosis and unnecessary interventions. Most common symptoms are abdominal pain and diarrhoea. Characteristic radiographic findings include ‘doughnut sign’ and ‘stacked coin’ appearance. Treatment is supportive. ACE inhibitors should be discontinued to prevent a recurrence.

The effects of functionalization of carbon nanotubes on toxicological parameters in mice

Carbon nanotubes (CNTs) have emerged as a new class of multifunctional nanoparticles in biomedicine, but their multiple in vivo effects remain unclear. Also, the impact of various functionalization types and duration of exposures are still unidentified. Herein, we report a complete toxicological study to evaluate the effects of single- and multiwalled carbon nanotubes (SWCNTs and MWCNTs) with either amine or carboxylic acid (COOH) surface functional groups. The results showed that significant oxidative stress and the subsequent cell apoptosis could be resulted in both acute and, mainly, in chronic intravenous administrations. Also, male reproductive parameters were altered during these exposures. The amino-functionalized CNTs had more toxic properties compared with the COOH functionalized group, and also, in some groups, the multiwalled nanotubes were more active in eliciting cytotoxicity than the single-walled nanotubes. Interestingly, the SWCNTs-COOH had the least alterations in most of the parameters. Evidently, it is concluded that the toxicity of CNTs in specific organs can be minimized through particular surface functionalizations.

Genetic susceptibility to angiotensin-converting enzyme-inhibitor induced angioedema: A systematic review and evaluation of methodological approaches

Angiotensin-converting enzyme (ACE) converts angiotensin I to angiotensin II which causes vasoconstriction. ACE inhibitors reduce blood pressure by inhibiting ACE. A well-known adverse drug reaction to ACE inhibitors is ACE inhibitor-induced angioedema (ACEi-AE). Angioedema is a swelling of skin and mucosa, which can be fatal if the airway is compromised. We have performed a systematic review of the evidence suggesting that genetic polymorphisms are associated with ACEi-AE and evaluated the methodological approaches of the included studies. The Cochrane Database of Systematic Reviews, Google Scholar, and PubMed were searched. Studies investigating the association between genetic markers and ACEi-AE were included. The Q-genie tool was used to evaluate the quality of the study methodologies. Seven studies were included. With the exception of one whole genome study, all of the included studies were candidate gene association studies. Study quality assessment scores ranged from 36 to 55. One study was found to be of good quality, suggesting that the detected associations may be unreliable. The inferior quality of some studies was due to poor organization, lack of analyses and missing information. Polymorphisms within XPEPNP2, BDKRB2–9/+ 9 and neprilysin genes, were reported to be associated with increased risk of ACEi-AE. However, due to low quality, these associations need to be confirmed in larger studies.

Changes in blood-brain barrier permeability and ultrastructure, and protein expression in a rat model of cerebral hypoperfusion

Cerebral hypoperfusion involved a reduction in cerebral blood flow, leading to neuronal dysfunction, microglial activation and white matter degeneration. The effects on the blood-brain barrier (BBB) however, have not been well-documented. Here, two-vessel occlusion model was adopted to mimic the condition of cerebral hypoperfusion in Sprague-Dawley rats. The BBB permeability to high and low molecular weight exogenous tracers i.e. Evans blue dye and sodium fluorescein respectively, showed marked extravasation of the Evans blue dye in the frontal cortex, posterior cortex and thalamus-midbrain at day 1 following induction of cerebral hypoperfusion. Transmission electron microscopy revealed brain endothelial cell and astrocyte damages including increased pinocytotic vesicles and formation of membrane invaginations in the endothelial cells, and swelling of the astrocytes' end-feet. Investigation on brain microvessel protein expressions using two-dimensional (2D) gel electrophoresis coupled with LC-MS/MS showed that proteins involved in mitochondrial energy metabolism, transcription regulation, cytoskeleton maintenance and signaling pathways were differently expressed. The expression of aconitate hydratase, heterogeneous nuclear ribonucleoprotein, enoyl Co-A hydratase and beta-synuclein were downregulated, while the opposite observed for calreticulin and enhancer of rudimentary homolog. These findings provide insights into the BBB molecular responses to cerebral hypoperfusion, which may assist development of future therapeutic strategies.

Di-(2-ethylhexyl) phthalate induced an increase in blood pressure via activation of ACE and inhibition of the bradykinin-NO pathway

Epidemiological studies and animal experiments have suggested that exposure to Di-(2-ethylhexyl) phthalate (DEHP) is strongly associated with an increase in blood pressure. However, the mechanisms that result in the detrimental effects of DEHP exposure on blood pressure are unclear. In our study, mice were orally exposed to DEHP dosages of 0.1, 1, 10 mg/kg/day for 6 weeks. The results showed that DEHP could induce a significant increase in systolic blood pressure (SBP) and heart rate, and a significant thickening of the ventricular wall. To explore the underlying mechanism, we measured the level of: angiotensin converting enzyme (ACE); bradykinin B2 receptor (BK2R); endothelial nitric oxide synthase (eNOS); bradykinin and Ca²⁺ in cardiac cytoplasm as well as in serum nitric oxide (NO). The results suggested that DEHP could induce an increase in ACE levels, and a decrease in bradykinin levels. Moreover, BK2R, Ca²⁺, eNOS and NO decreased when mice were exposed to 10 mg/kg/day DEHP. Interestingly, 5 mg/kg/day angiotensin converting enzyme inhibitor (ACEI) treatment inhibited the increase in blood pressure, and inhibited the decrease in the levels of BK2R, Ca²⁺, eNOS, and NO, that were induced by DEHP exposure. Our results suggest that DEHP might increase blood pressure by activating ACE expression, and inhibiting the bradykinin-NO pathway.

Cutaneous Adverse Effects of Diabetes Mellitus Medications and Medical Devices: A Review

Diabetes mellitus is one of the most prevalent chronic diseases in the USA. If uncontrolled, diabetes can lead to devastating complications. Diabetes medications and medical devices largely contribute to the significant financial expense that the disease inflicts on affected individuals and society. Alongside significant economic burden, there are numerous cutaneous adverse effects associated with diabetes medications and medical devices. Despite the large and increasing number of individuals living with diabetes and the wide use of the related medications and medical devices, there is limited literature that comprehensively documents their cutaneous adverse effects. These cutaneous adverse effects are significant as they can worsen glycemic control, increase disease distress, and may increase risk of associated complications. Thus, it is important that providers can recognize these cutaneous adverse effects, identify the culprit agents, and can properly manage them. In this article, we provide a critical review of the cutaneous adverse effects of medications and devices used in the management of diabetes and provide insight into risk factors and prevention and an overview of therapeutic management. An emphasis is placed on clinical recognition and treatment for use of the medical providers who, regardless of practice setting, will treat patients with diabetes.

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 (B2^tg ) and established a non-invasive two-photon laser microscopy approach to measure the kinetics of spontaneous extravasation in vivo. The B2^tg 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 B2^tg respectively. Measurement of dermal extravasation by Miles assay showed that bradykinin induced extravasation was significantly increased in B2^tg 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.

Angiotensin-converting Enzyme Inhibitor and Other Drug-associated Angioedema

Nonsteroidal antiinflammatory agents, β-lactam antibiotics, non-β lactam antibiotics, and angiotensin-converting enzyme inhibitors are the most common classes of drugs that cause angioedema. Drug-induced angioedema is known to occur via mechanisms mediated by histamine, bradykinin, or leukotriene, and an understanding of these mechanisms is crucial in guiding therapeutic decisions. Nonallergic angioedema occurs in patients with genetic variants that affect metabolism or synthesis of bradykinin, substance P, prostaglandins, or leukotrienes, or when patients are taking drugs that have synergistic mechanisms. The mainstay in treatment of nonallergic drug-induced angioedema is cessation of the offending agents.

Thioredoxin-1 attenuates sepsis-induced cardiomyopathy after cecal ligation and puncture in mice

BACKGROUND

Sepsis is a leading cause of mortality among patients in intensive care units across the USA. Thioredoxin-1 (Trx-1) is an essential 12 kDa cytosolic protein that, apart from maintaining the cellular redox state, possesses multifunctional properties. In this study, we explored the possibility of controlling adverse myocardial depression by overexpression of Trx-1 in a mouse model of severe sepsis.

METHODS

Adult C57BL/6J and Trx-1Tg/+ mice were divided into wild-type sham (WTS), wild-type cecal ligation and puncture (WTCLP), Trx-1Tg/+sham (Trx-1Tg/+S), and Trx-1Tg/+CLP groups. Cardiac function was evaluated before surgery, 6 and 24 hours after CLP surgery. Immunohistochemical and Western blot analysis were performed after 24 hours in heart tissue sections.

RESULTS

Echocardiography analysis showed preserved cardiac function in the Trx-1Tg/+ CLP group compared with the WTCLP group. Similarly, Western blot analysis revealed increased expression of Trx-1, heme oxygenase-1 (HO-1), survivin (an inhibitor of apoptosis [IAP] protein family), and decreased expression of thioredoxin-interacting protein (TXNIP), caspase-3, and 3- nitrotyrosine in the Trx-1Tg/+CLP group compared with the WTCLP group. Immunohistochemical analysis showed reduced 4-hydroxynonenal, apoptosis, and vascular leakage in the cardiac tissue of Trx-1Tg/+CLP mice compared with mice in the WTCLP group.

CONCLUSIONS

Our results indicate that overexpression of Trx-1 attenuates cardiac dysfunction during CLP. The mechanism of action may involve reduction of oxidative stress, apoptosis, and vascular permeability through activation of Trx-1/HO-1 and anti-apoptotic protein survivin.

Recurrent angioedema associated with pharmacological inhibition of dipeptidyl peptidase IV

Angioedema (AE) of the upper airways is a severe and potentially life-threatening condition. The incidence has been increasing in the past two decades, primarily due to increased use of medications inhibiting the degradation of vasoactive peptides. Acquired angioedema related to angiotensin-converting enzyme inhibitors (ACEI-AAE) is well known, but other pharmaceutical agents also affect the degradation of bradykinin and substance P. We present a middle-aged man with recurrent episodes of severe AE of the oral cavity, hypopharynx and larynx due to pharmacological inhibition of dipeptidyl peptidase IV.

Etiology and treatment of cough in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive disease of dysregulated wound healing leading to unremitting scarring and loss of lung function. The predominant symptoms are dyspnea on exertion and a persistent dry cough. For patients with IPF, cough is more than just bothersome; it has a significant negative impact on quality of life and is a marker of disease severity and progression. The etiology of cough in IPF is unclear but may be due to architectural distortion of the lungs, increased sensitivity of the cough reflex, airway inflammation, or changes in mucus production and clearance. There also may be an overlap between IPF cough and cough due to other common etiologies such as asthma, gastroesophageal reflux disease, upper airway cough syndrome, and medications. There are no approved therapies to specifically treat IPF cough, and recently approved medications for IPF have not been evaluated in cough. Few clinical trials have focused on treatments for IPF cough. To date, there is only one randomized, placebo control therapeutic study for IPF cough with thalidomide, which significantly reduced IPF cough and improved quality of life. Two additional cohort studies report that interferon-α and prednisolone also decrease IPF cough. However, no medication is approved to treat IPF cough. Currently, the mainstay of therapy for IPF cough is standard cough suppressants, which have limited efficacy and often intolerable side effects. Future studies are needed to determine an effective therapy to alleviate this particularly debilitating symptom and improve overall quality of life for patients suffering with IPF.

Effect of bradykinin receptor antagonism on ACE inhibitor-associated angioedema

BACKGROUND

The B₂ receptor antagonist icatibant is approved for treatment of attacks of hereditary angioedema. Icatibant has been reported to decrease time-to-resolution of angiotensin-converting enzyme (ACE) inhibitor-associated angioedema in 1 study of European patients.

OBJECTIVE

We sought to test the hypothesis that a bradykinin B₂ receptor antagonist would shorten time-to-resolution from ACE inhibitor-associated angioedema.

METHODS

Patients with ACE inhibitor-associated angioedema (defined as swelling of lips, tongue, pharynx, or face during ACE inhibitor use and no swelling in the absence of ACE inhibitor use) were enrolled at Vanderbilt University Medical Center from October 2007 through September 2015 and at Massachusetts General Hospital in 2012. C1 inhibitor deficiency and patients with bowel edema only were excluded. Patients were randomized within 6 hours of presentation to subcutaneous icatibant 30 mg or placebo at 0 and 6 hours later. Patients assessed severity of swelling using a visual analog scale serially following study drug administration or until discharge.

RESULTS

Thirty-three patients were randomized and 31 received treatment, with 13 receiving icatibant and 18 receiving placebo. One patient randomized to icatibant did not complete the visual analog scale and was excluded from analyses. Two-thirds of patients were black and two-thirds were women. Time-to-resolution of symptoms was similar in placebo and icatibant treatment groups (P = .19 for the primary symptom and P > .16 for individual symptoms of face, lip, tongue, or eyelid swelling). Frequency of administration of H1 and H2 blockers, corticosteroids, and epinephrine was similar in the 2 treatment groups. Time-to-resolution of symptoms was similar in black and white patients.

CONCLUSIONS

This study does not support clinical efficacy of a bradykinin B₂ receptor antagonist in ACE inhibitor-associated angioedema.

Analgesic and Anti-Inflammatory Properties of Gelsolin in Acetic Acid Induced Writhing, Tail Immersion and Carrageenan Induced Paw Edema in Mice

Plasma gelsolin levels significantly decline in several disease conditions, since gelsolin gets scavenged when it depolymerizes and caps filamentous actin released in the circulation following tissue injury. It is well established that our body require/implement inflammatory and analgesic responses to protect against cell damage and injury to the tissue. This study was envisaged to examine analgesic and anti-inflammatory activity of exogenous gelsolin (8 mg/mouse) in mice models of pain and acute inflammation. Administration of gelsolin in acetic acid-induced writhing and tail immersion tests not only demonstrated a significant reduction in the number of acetic acid-induced writhing effects, but also exhibited an analgesic activity in tail immersion test in mice as compared to placebo treated mice. Additionally, anti-inflammatory function of gelsolin (8 mg/mouse) compared with anti-inflammatory drug diclofenac sodium (10 mg/kg)] was confirmed in the carrageenan injection induced paw edema where latter was measured by vernier caliper and fluorescent tomography imaging. Interestingly, results showed that plasma gelsolin was capable of reducing severity of inflammation in mice comparable to diclofenac sodium. Analysis of cytokines and histo-pathological examinations of tissue revealed administration of gelsolin and diclofenac sodium significantly reduced production of pro-inflammatory cytokines, TNF-α and IL-6. Additionally, carrageenan groups pretreated with diclofenac sodium or gelsolin showed a marked decrease in edema and infiltration of inflammatory cells in paw tissue. Our study provides evidence that administration of gelsolin can effectively reduce the pain and inflammation in mice model.

Pharmacodynamic effects of C-domain-specific ACE inhibitors on the renin-angiotensin system in myocardial infarcted rats

INTRODUCTION

The renin-angiotensin system (RAS) is a dynamic network that plays a critical role in blood pressure regulation and fluid and electrolyte homeostasis. Modulators of the RAS, such as angiotensin-converting enzyme (ACE) inhibitors, are widely used to treat hypertension, heart failure and myocardial infarction.

METHODS

The effect of ACE inhibitors (lisinopril and C-domain-selective LisW-S) on the constituent peptides of the RAS following myocardial infarction was examined in rats. Ten angiotensin peptides were analysed using a sensitive LC-MS/MS-based assay to examine both the circulating and equilibrium levels of these peptides.

RESULTS

Administration of lisinopril or LisW-S caused a significant decrease in Ang 1-8/Ang 1-10 ratios as determined by circulating and equilibrium peptide level analysis. Furthermore, Ang 1-7 levels were elevated by both ACE inhibitors, but only lisinopril decreased the Ang 1-5/Ang 1-7 ratio. This indicates LisW-S C-domain specificity as Ang 1-5 is generated by hydrolysis of Ang 1-7 by the N-domain. Further corroboration of LisW-S C-domain specificity is that only lisinopril increased the circulating levels of the N-domain ACE substrate Ac-SDKP.

CONCLUSION

LisW-S is able to effectively block ACE in vivo by C-domain-selective inhibition. The LC-MS/MS-based assay allows the evaluation of the pharmacologic impact of RAS inhibitors in different pathophysiological conditions.

Safety of dipeptidyl peptidase 4 inhibitors: a perspective review

Dipeptidyl peptidase 4 (DPP-4) inhibitors are a relatively new class of oral antihyperglycemic agent that enhance insulin secretion by reducing degradation of endogenous glucagon-like peptide 1. Currently, sitagliptin, vildagliptin, saxagliptin, linagliptin and alogliptin have been approved by the US Food and Drug Administration or the European Medicines Agency for use in patients with type 2 diabetes. Their glycemic efficacy has been well documented; however, data regarding their long-term safety are as yet inconclusive. While preclinical studies have indicated a potential cardioprotective effect of DPP-4 inhibitors, current clinical data from cardiovascular safety trials suggest a neutral effect on cardiovascular outcomes. Moreover, postmarketing experience has given rise to concerns about specific adverse events, including pancreatitis and hypersensitivity reactions. This review summarizes available evidence regarding safety of DPP-4 inhibitors. Overall, DPP-4 inhibitors appear to be a safe option for patients with type 2 diabetes. However, close pharmacovigilance is necessary to address the uncertainty regarding pancreas-related adverse events, while their potential impact on cardiovascular outcomes will be further elucidated after completion of more long-term studies.

Interkingdom pharmacology of Angiotensin-I converting enzyme inhibitor phosphonates produced by actinomycetes

The K-26 family of bacterial secondary metabolites are N-modified tripeptides terminated by an unusual phosphonate analog of tyrosine. These natural products, produced via three different actinomycetales, are potent inhibitors of human angiotensin-I converting enzyme (ACE). Herein we investigate the interkingdom pharmacology of the K-26 family by synthesizing these metabolites and assessing their potency as inhibitors of both the N-terminal and C-terminal domains of human ACE. In most cases, selectivity for the C-terminal domain of ACE is displayed. Co-crystallization of K-26 in both domains of human ACE reveals the structural basis of the potent inhibition and has shown an unusual binding motif that may guide future design of domain-selective inhibitors. Finally, the activity of K-26 is assayed against a cohort of microbially produced ACE relatives. In contrast to the synthetic ACE inhibitor captopril, which demonstrates broad interkingdom inhibition of ACE-like enzymes, K-26 selectively targets the eukaryotic family.

Fragment-based design for the development of N-domain-selective angiotensin-1-converting enzyme inhibitors

ACE (angiotensin-1-converting enzyme) is a zinc metallopeptidase that plays a prominent role in blood pressure regulation and electrolyte homeostasis. ACE consists of two homologous domains that despite similarities of sequence and topology display differences in substrate processing and inhibitor binding. The design of inhibitors that selectively inhibit the N-domain (N-selective) could be useful in treating conditions of tissue injury and fibrosis due to build-up of N-domain-specific substrate Ac-SDKP (N-acetyl-Ser-Asp-Lys-Pro). Using a receptor-based SHOP (scaffold hopping) approach with N-selective inhibitor RXP407, a shortlist of scaffolds that consisted of modified RXP407 backbones with novel chemotypes was generated. These scaffolds were selected on the basis of enhanced predicted interaction energies with N-domain residues that differed from their C-domain counterparts. One scaffold was synthesized and inhibitory binding tested using a fluorogenic ACE assay. A molecule incorporating a tetrazole moiety in the P2 position (compound 33RE) displayed potent inhibition (K(i)=11.21±0.74 nM) and was 927-fold more selective for the N-domain than the C-domain. A crystal structure of compound 33RE in complex with the N-domain revealed its mode of binding through aromatic stacking with His388 and a direct hydrogen bond with the hydroxy group of the N-domain specific Tyr369. This work further elucidates the molecular basis for N-domain-selective inhibition and assists in the design of novel N-selective ACE inhibitors that could be employed in treatment of fibrosis disorders.

Pro-inflammatory Effect of Quercetin by Dual Blockade of Angiotensin Converting-enzyme and Neutral EndopeptidaseIn Vivo

The effect of the flavonoid quercetin on substance P- and bradykinin-induced plasma extravasation in rat tissues (duodenum, heart, pancreas, trachea and urinary bladder) was studied, and its modulation by endogenous peptidases. Plasma protein extravasation was assayed by extravasated Evans blue dye. Intravenous injection of substance P (1, 3 and 10 nmol/kg) increased the plasma extravasation in a dose-dependent manner in heart, pancreas, trachea and urinary bladder. Bradykinin (3 and 10 nmol/kg, i.v.) increased plasma extravasation in a dose-dependent manner in duodenum, pancreas, trachea and urinary bladder. Pre-treatment with a selected dose of quercetin potentiated the substance P-induced plasma extravasation in heart, pancreas and urinary bladder, and also the bradykinin-induced plasma extravasation in duodenum, heart, trachea and urinary bladder. The selective pharmacological inhibition of neutral endopeptidase and angiotensin-converting enzyme potentiated the substance P- and bradykinin-induced plasma extravasation, respectively; furthermore, treatment with receptor antagonists showed that the mediators involved in the potentiation of plasma extravasation by quercetin are substance P and bradykinin. Analysis of plasma angiotensin-converting enzyme activity demonstrated that quercetin inhibited this enzyme. These results suggest that quercetin potentiates plasma extravasation induced by substance P and bradykinin, and that this may result from inhibition of the degradative enzymes of these peptides.

Genetic variants associated with angiotensin-converting enzyme inhibitor-associated angioedema

OBJECTIVE

The objective of this study was to identify genetic variants associated with angiotensin-converting enzyme (ACE) inhibitor-associated angioedema.

PARTICIPANTS AND METHODS

We carried out a genome-wide association study in 175 individuals with ACE inhibitor-associated angioedema and 489 ACE inhibitor-exposed controls from Nashville (Tennessee) and Marshfield (Wisconsin). We tested for replication in 19 cases and 57 controls who participated in Ongoing Telmisartan Alone and in Combination with Ramipril Global Endpoint Trial (ONTARGET).

RESULTS

There were no genome-wide significant associations of any single-nucleotide polymorphism (SNP) with angioedema. Sixteen SNPs in African Americans and 41 SNPs in European Americans were associated moderately with angioedema (P<10) and evaluated for association in ONTARGET. The T allele of rs500766 in PRKCQ was associated with a reduced risk, whereas the G allele of rs2724635 in ETV6 was associated with an increased risk of ACE inhibitor-associated angioedema in the Nashville/Marshfield sample and ONTARGET. In a candidate gene analysis, rs989692 in the gene encoding neprilysin (MME), an enzyme that degrades bradykinin and substance P, was significantly associated with angioedema in ONTARGET and Nashville/Marshfield African Americans.

CONCLUSION

Unlike other serious adverse drug effects, ACE inhibitor-associated angioedema is not associated with a variant with a large effect size. Variants in MME and genes involved in immune regulation may be associated with ACE inhibitor-associated angioedema.

Pharmacogenetics of ACE inhibitor-induced angioedema and cough: a systematic review and meta-analysis

AIM

Angioedema and cough are the two most important adverse effects of ACE inhibitors (ACEIs). Evidence exists that ACEI-related angioedema/cough is partly genetically determined and several genes have been identified to play a role in the development of ACEI-related adverse effects.

MATERIALS & METHODS

This study was performed in order to evaluate the evidence of these genetic associations and ACEIs' adverse effects. After removing duplicates and critical appraisal, 19 studies were considered to be eligible to review; 14 articles about cough and five articles about angioedema. A separate meta-analysis was performed for the most studied ACE insertion/deletion polymorphism (rs4646994) and its association with cough.

RESULTS & CONCLUSION

One gene region (XPNPEP2) was associated with ACEI-induced angioedema in three studies. In our meta-analysis we did not find a significant association between the ACE insertion/deletion polymorphism and ACEI cough.

Sequential, timely and controlled expression of hVEGF165 and Ang-1 effectively improves functional angiogenesis and cardiac function in vivo

We aimed to control the gene expression of vascular endothelial growth factor (VEGF) and angiopoietin-1 (Ang-1) in the ischemic heart to explore the feasibility of sequential, timely and controlled multigene expression as a means of improving therapeutic angiogenesis in vivo. Adult rabbit myocardial infarction models were surgically established (n=120). Hypoxia-inducible factor-1α-hypoxic response element (HIF1α-HRE) and Tet (tetracycline)-On advanced gene control systems were reconstructed for controlled expression of the human VEGF165 (hVEGF165) and Ang-1 genes, respectively. Recombinant adeno-associated viruses (rAAV)-9HRE-hVEGF165 and rAAV-TRE-Tight-Ang-1 were delivered into the ischemic myocardium for 12 weeks. Reverse transcription-polymerase chain reaction, western blotting and immunofluorescence staining were used to detect gene and protein expression. Vessel functionality, vascular permeability and animal cardiac function were also evaluated. Under the control of the HIF1α-HRE and Tet-On gene control systems, the expression of the exogenous hVEGF165 and Ang-1 genes was consistent in the ischemia control. In the sequential group, we found that the number of functional vessels with a larger diameter and more vascular branches was increased, and vascular permeability was significantly reduced. In addition, animal heart function was significantly improved compared with the non-sequential and hVEGF165- or Ang-1-only groups (P<0.05, P<0.05, respectively). Sequential, timely and controlled expression of the hVEGF165 and Ang-1 genes in vivo is a new therapeutic angiogenesis strategy that can effectively promote functional vessel regeneration and can improve cardiac function in ischemic heart disease.

Life-Threatening ACE Inhibitor-Induced Angioedema After Eleven Years on Lisinopril

Angiotensin-converting enzyme inhibitors (ACE-Is) are the primary medication class implicated in drug-associated angioedema. Angioedema is most common early in ACE-I therapy, yet episodes can occur late in therapy and have been reported even as late as 10 years after single treatment initiation. We present a case of a 65-year-old African American woman who experienced 2 episodes of angioedema, with the second being life threatening after receiving several concomitant agents known to cause angioedema, most notably lisinopril for 11 years.

Sex-dependent and race-dependent association of XPNPEP2 C-2399A polymorphism with angiotensin-converting enzyme inhibitor-associated angioedema

BACKGROUND

Angioedema is a rare adverse effect of angiotensin-converting enzyme (ACE) inhibitors, which occurs more commonly in women and black Americans. Angioedema is thought to result from decreased degradation of vasoactive peptides. During ACE inhibition, bradykinin is primarily inactivated by aminopeptidase P (APP). Earlier studies have provided conflicting data with regard to serum APP activity in patients with a history of ACE inhibitor-associated angioedema. A single nucleotide polymorphism, -2399C>A (rs3788853, C-2399A), in XPNPEP2, the X-linked gene that encodes membranous APP, has been reported to associate with APP activity.

OBJECTIVE

To test the hypothesis that the relationship between XPNPEP2 C-2399A genotype and APP activity or ACE inhibitor-associated angioedema is sex-dependent and race-dependent.

METHODS

We compared C-2399A genotype frequencies in 169 cases with a history of ACE inhibitor-associated angioedema and 397 ACE inhibitor-exposed controls. Controls were prespecified to be 50% white, 50% black, and 50% women. Cases and controls were group matched for age and smoking.

RESULTS

XPNPEP2 C-2399A genotype associated with serum APP activity in both men and women. Serum APP activity was lower in men than in women, independent of genotype. XPNPEP2 -2399 A/ genotype was associated with an increased risk of angioedema in men [odds ratio 2.17 (1.09-4.32), P=0.03] in multivariate analysis. The A/ genotype was associated with angioedema in black men (P=0.03) but not in white men.

CONCLUSION

APP activity is lower in men and the XPNPEP2 C-2399A polymorphism associates with ACE inhibitor-associated angioedema in men but not women.

Antinociceptive and anti-exudative synergism between dexketoprofen and tramadol in a model of inflammatory pain in mice

Preclinical studies have demonstrated antinociceptive synergism between dexketoprofen (DEX) and tramadol (TRM) in acute animal models of nociception. The aim of the present study was to investigate the type of interaction between DEX and TRM in a chronic musculoskeletal pain model in mice, which fairly replicates the characteristics of chronic osteoarticular pain in humans. Inflammation was induced by a subplantar injection of complete Freund's adjuvant (CFA) in male CF1 mice. Nociceptive thresholds were evaluated using the hot plate, the nocifensive spontaneous behavior and the acetone tests, while plasma extravasation (PE) was assessed with Evan's blue. We used the following experimental groups: control (no inflammation), acute (1 day after CFA injection), and chronic inflammation (7 days after CFA). Dose-response curves for DEX and TRM, individually and combined in a 1 : 1 proportion based on their potency were obtained, and the doses that produced a 50% inhibition calculated. The isobolographic analysis revealed that in all groups of study (no inflammation, acute, and chronic inflammation), the combination of DEX : TRM was synergistic, for both the inhibition of nociception and the PE. The results suggest that the DEX : TRM (1 : 1) combination could be useful in the management of acute and chronic inflammatory musculoskeletal pains in humans; in addition, the synergistic interaction between the drugs observed both during acute and chronic inflammation suggests that less doses would be required of each drug to obtain effective analgesia.

Association of angiotensin-converting enzyme inhibitor-associated angioedema with transplant and immunosuppressant use

BACKGROUND

Immunosuppressants decrease circulating dipeptidyl peptidase IV (DPPIV) activity in transplant patients, and decreased DPPIV activity has been associated with angiotensin-converting enzyme (ACE) inhibitor-associated angioedema. One study has reported an increased incidence of ACE inhibitor-associated angioedema among transplant patients compared to published rates, while several case series report angioedema in patients taking specific immunosuppressant agents.

OBJECTIVE

To test the hypothesis that transplant patients are at increased risk of ACE inhibitor-associated angioedema.

METHODS

We assessed the proportion of transplant patients in 145 cases with ACE inhibitor-associated angioedema and 280 ACE inhibitor-exposed controls. We measured the relationship between case-control status, transplant status, and immunosuppressant use and circulating DPPIV activity. We also assessed the incidence of angioedema among consecutive patients who underwent renal or cardiac transplant and were treated with an ACE inhibitor.

RESULTS

Transplant patients were significantly overrepresented among ACE inhibitor-associated angioedema cases compared to controls (odds ratio 18.5, 95% CI 2.3-147.2, P = 0.0004). Immunosuppressant use, chronic renal failure, seasonal allergies and smoking were also associated with ACE inhibitor-associated angioedema in univariate analysis. The association of transplant status with ACE inhibitor-associated angioedema was no longer significant after inclusion of immunosuppressant therapy in a multivariate analysis. Dipeptidyl peptidase IV activity was significantly decreased in sera from cases compared to ACE inhibitor-exposed controls, as well as in individuals taking immunosuppressants. Two of 47 ACE inhibitor-treated renal transplant patients and one of 36 ACE inhibitor-treated cardiac transplant patients developed angioedema.

CONCLUSION

Transplant patients are at increased risk of ACE inhibitor-associated angioedema possibly because of the effects of immunosuppressants on the activity of DPPIV.

Angiotensin converting enzyme inhibitor induced angio-oedema: a review of the pathophysiology and risk factors

Angio-oedema (AE) is a known adverse effect of angiotensin converting enzyme inhibitor (ACE-I) therapy. Over the past several decades, evidence of failure to diagnose this important and potentially fatal reaction is commonly found in the literature. Because this reaction is often seen first in the primary care setting, a review was undertaken to analyse and document the keys to both diagnostic criteria as well as to investigate potential risk factors for ACE-I AE occurrence. A general review of published literature was conducted through Medline, EMBASE, and the Cochrane Database, targeting ACE-I-related AE pathomechanism, diagnosis, epidemiology, risk factors, and clinical decision making and treatment. The incidence and severity of AE appears to be on the rise and there is evidence of considerable delay in diagnosis contributing to significant morbidity and mortality for patients. The mechanism of AE due to ACE-I drugs is not fully understood, but some genomic and metabolomic information has been correlated. Additional epidemiologic data and clinical treatment outcome predictors have been evaluated, creating a basis for future work on the development of clinical prediction tools to aid in risk identification and diagnostic differentiation. Accurate recognition of AE by the primary care provider is essential to limit the rising morbidity associated with ACE-I treatment-related AE. Research findings on the phenotypic indicators relevant to this group of patients as well as basic research into the pathomechanism of AE are available, and should be used in the construction of better risk analysis and clinical diagnostic tools for ACE-I AE.

Dipeptidyl peptidase-IV inhibitor use associated with increased risk of ACE inhibitor-associated angioedema

Dipeptidyl peptidase-IV (DPP-IV) inhibitors decrease degradation of the incretins. DPP-IV inhibitors also decrease degradation of peptides, such as substance P, that may be involved in the pathogenesis of angiotensin-converting enzyme (ACE) inhibitor-associated angioedema. This study tested the hypothesis that DPP-IV inhibition affects risk of clinical angioedema, by comparing the incidence of angioedema in patients treated with the DPP-IV inhibitor vildagliptin versus those treated with comparator in Phase III randomized clinical trials. Prospectively defined angioedema-related events were adjudicated in a blinded fashion by an internal medicine adjudication committee and expert reviewer. Concurrent ACE inhibitor or angiotensin receptor blocker exposure was ascertained from case report forms. Study drug exposure was ascertained from unblinded data from phase III studies. Odds ratios and 95% confidence intervals comparing angioedema risk in vildagliptin-treated and comparator-treated patients were calculated for the overall population and for patients taking ACE inhibitors or angiotensin receptor blockers, using both an analysis of pooled data and a meta-analysis (Peto method). Overall, there was no association between vildagliptin use and angioedema. Among individuals taking an ACE inhibitor, however, vildagliptin use was associated with an increased risk of angioedema (14 confirmed cases among 2754 vildagliptin users versus 1 case among 1819 comparator users: odds ratio 4.57 [95% confidence interval 1.57 to 13.28]) in the meta-analysis. Vildagliptin use may be associated with increased risk of angioedema among patients taking ACE inhibitors, although absolute risk is small. Physicians confronted with angioedema in a patient taking an ACE inhibitor and DPP-IV inhibitor should consider this possible drug-drug interaction.

Effects of angiotensin II and angiotensin II type 1 receptor blockade on neointimal formation after stent implantation

BACKGROUND

To evaluate the effect of supraphysiological levels of angiotensin II and selective angiotensin II type 1 receptor (AT1-receptor) blockade on neointimal formation and systemic endothelial function after stent implantation in the rat abdominal aorta.

METHODS

Male Wistar rats were randomized to one of three groups; control (n=8), angiotensin II infusion (n=9, 200 ng/kg/min), or candesartan cilexetil (n=8,AT1-receptor blocker; rats received 14.4 mg kg(-1) day(-1)). Stents were implanted in the abdominal aorta. Histological analyses were performed at 4 weeks. Endothelial function was determined in isolated thoracic aortic rings.

RESULTS

Neointimal area was increased in the angiotensin II treated group versus the control group, 0.88 mm(2)+/-0.21 versus 0.66 mm(2)+/-0.16 (P<0.05). Neointimal thickness was 171 microm+/-44 in angiotensin II treated animals and 120 microm+/-25 in the control group (P<0.05). In addition, endothelial function was attenuated in angiotensin II treated animals (P=0.01). Candesartan cilexetil treatment did not result in reduction of neointimal area and did not reduce neointimal thickness compared to the control group. Candesartan had no effect on endothelial function.

CONCLUSIONS

Supraphysiological levels of angiotensin II aggravates neointimal formation in the stented rat abdominal aorta, and in parallel decreases endothelial function. AT1-receptor blockade does not reduce neointimal formation in rats without supraphysiological angiotensin II levels.

Retinal plasma extravasation in streptozotocin-diabetic rats mediated by kinin B(1) and B(2) receptors

BACKGROUND AND PURPOSE

We investigated whether or not kinin receptors play a role in diabetic blood-retinal barrier breakdown, which is a leading cause of vision loss.

EXPERIMENTAL APPROACH

Blood-retinal barrier breakdown was quantified using Evans blue, and expression of kinin B(1) receptor mRNA was measured using quantitative reverse transcrition-PCR. Diabetic rats (streptozotocin (STZ), 65 mg kg(-1)) received a single intraocular injection of bradykinin (BK) or des-Arg(9)-BK, alone, or in combination with antagonists for B(1) (des-Arg(10)-Hoe140, R-715) and/or B(2) (Hoe140) receptors, given intraocularly or intravenously (i.v.).

KEY RESULTS

In control rats, BK (0.1-10 nmol) dose-dependently increased plasma extravasation, which was inhibited by Hoe140 (0.2 nmol), whereas des-Arg(9)-BK (0.1 and 1 nmol) was without effect. B(1) receptor mRNA was markedly increased in retinas of diabetic rats, and this was prevented by N-acetyl-L-cysteine (1 g kg(-1) day(-1) for 7 days). Plasma extravasation in retinas of STZ-diabetic rats was higher than in controls and enhanced by des-Arg(9)-BK. Response to des-Arg(9)-BK was inhibited by intraocular or i.v. injection of B(1) receptor antagonists. Diabetes-induced plasma extravasation was inhibited only by a combination of des-Arg(10)-Hoe140 and Hoe 140 (100 nmol kg(-1), i.v. 15 min earlier) or by R-715 (1 micromol kg(-1), i.v.) injected daily for 7 days.

CONCLUSIONS AND IMPLICATIONS

Kinin B(1) receptors are upregulated in retinas of STZ-diabetic rats through a mechanism involving oxidative stress. Both kinin B(1) and B(2) receptors contribute to increased plasma extravasation in diabetic retinopathy. Chronic inhibition of both kinin receptors, possibly with antioxidant adjuvants, may be a novel therapeutic strategy for diabetic retinopathy.

Dipeptidyl peptidase IV in angiotensin-converting enzyme inhibitor associated angioedema

Angioedema is a potentially life-threatening adverse effect of angiotensin-converting enzyme inhibitors. Bradykinin and substance P, substrates of angiotensin-converting enzyme, increase vascular permeability and cause tissue edema in animals. Studies indicate that amino-terminal degradation of these peptides, by aminopeptidase P and dipeptidyl peptidase IV, may be impaired in individuals with angiotensin-converting enzyme inhibitor-associated angioedema. This case-control study tested the hypothesis that dipeptidyl peptidase IV activity and antigen are decreased in sera of patients with a history of angiotensin-converting enzyme inhibitor-associated angioedema. Fifty subjects with a history of angiotensin-converting enzyme inhibitor-associated angioedema and 176 angiotensin-converting enzyme inhibitor-exposed control subjects were ascertained. Sera were assayed for angiotensin-converting enzyme activity, aminopeptidase P activity, aminopeptidase N activity, dipeptidyl peptidase IV activity, and antigen and the ex vivo degradation half-lives of bradykinin, des-Arg(9)-bradykinin, and substance P in a subset. The prevalence of smoking was increased and of diabetes decreased in case versus control subjects. Overall, dipeptidyl peptidase IV activity (26.6+/-7.8 versus 29.6+/-7.3 nmol/mL per minute; P=0.026) and antigen (465.8+/-260.8 versus 563.1+/-208.6 ng/mL; P=0.017) were decreased in sera from individuals with angiotensin-converting enzyme inhibitor-associated angioedema compared with angiotensin-converting enzyme inhibitor-exposed control subjects without angioedema. Dipeptidyl peptidase IV activity (21.5+/-4.9 versus 29.8+/-6.7 nmol/mL per minute; P=0.001) and antigen (354.4+/-124.7 versus 559.8+/-163.2 ng/mL; P=0.003) were decreased in sera from cases collected during angiotensin-converting enzyme inhibition but not in the absence of angiotensin-converting enzyme inhibition. The degradation half-life of substance P correlated inversely with dipeptidyl peptidase IV antigen during angiotensin-converting enzyme inhibition. Environmental or genetic factors that reduce dipeptidyl peptidase IV activity may predispose individuals to angioedema.

Dipeptidyl peptidase IV deficiency increases susceptibility to angiotensin-converting enzyme inhibitor-induced peritracheal edema

BACKGROUND

Serum dipeptidyl peptidase IV (DPPIV) activity is decreased in some individuals with ACE inhibitor-associated angioedema. ACE and DPPIV degrade substance P, an edema-forming peptide. The contribution of impaired degradation of substance P by DPPIV to the pathogenesis of ACE inhibitor-associated angioedema is unknown.

OBJECTIVES

We sought to determine whether DPPIV deficiency results in increased edema formation during ACE inhibition. We also sought to develop an animal model using magnetic resonance imaging to quantify ACE inhibitor-induced edema.

METHODS

The effect of genetic DPPIV deficiency on peritracheal edema was assessed in F344 rats after treatment with saline, captopril (2.5 mg/kg), or captopril plus the neurokinin receptor antagonist spantide (100 mug/kg) by using serial T2-weighted magnetic resonance imaging.

RESULTS

Serum dipeptidyl peptidase activity was dramatically decreased in DPPIV-deficient rats (P < .001). The volume of peritracheal edema was significantly greater in captopril-treated DPPIV-deficient rats than in saline-treated DPPIV-deficient rats (P = .001), saline-treated rats of the normal substrain (P < .001), or captopril-treated rats of the normal substrain (P = .001). Cotreatment with spantide attenuated peritracheal edema in captopril-treated DPPIV-deficient rats (P = .005 vs captopril-treated DPPIV-deficient rats and P = .57 vs saline-treated DPPIV-deficient rats).

CONCLUSIONS

DPPIV deficiency predisposes to peritracheal edema formation when ACE is inhibited through a neurokinin receptor-dependent mechanism. Magnetic resonance imaging is useful for modeling ACE inhibitor-associated angioedema in rats.

CLINICAL IMPLICATIONS

Genetic or environmental factors that decrease DPPIV activity might increase the risk of ACE inhibitor-associated angioedema.

Mechanisms of Disease: the tissue kallikrein–kinin system in hypertension and vascular remodeling

The pathogenesis of arterial hypertension often involves a rise in systemic vascular resistance (vasoconstriction and vascular remodeling) and impairment of salt excretion in the kidney (inappropriate salt retention despite elevated blood pressure). Experimental and clinical evidence implicate an imbalance between endogenous vasoconstrictor and vasodilator systems in the development and maintenance of hypertension. Kinins (bradykinin and lys-bradykinin) are endogenous vasodilators and natriuretic peptides known best for their ability to antagonize angiotensin-induced vasoconstriction and sodium retention. In humans, angiotensin-converting enzyme inhibitors, a potent class of antihypertensive agents, lower blood pressure at least partially by favoring enhanced kinin accumulation in plasma and target tissues. The beneficial actions of kinins in renal and cardiovascular disease are largely mediated by nitric oxide and prostaglandins, and extend beyond their recognized role in lowering blood pressure to include cardioprotection and nephroprotection. This article is a review of exciting, recently generated genetic, biochemical and clinical data from studies that have examined the importance of the tissue kallikrein-kinin system in protection from hypertension, vascular remodeling and renal fibrosis. Development of novel therapeutic approaches to bolster kinin activity in the vascular wall and in specific compartments in the kidney might be a highly effective strategy for the treatment of hypertension and its complications, including cardiac hypertrophy and renal failure.