Modifications of arterial phenotype in response to amine oxidase inhibition by semicarbazide

Increased atherosclerotic plaque in AOC3 knock-out in ApoE−/− mice and characterization of AOC3 in atherosclerotic human coronary arteries

Introduction

Amine oxidase copper containing 3 (AOC3) displays adhesion between leukocytes and endothelial cells and enzymatic functions. Given its controversial role in atherogenesis, we proposed to investigate the involvement of AOC3 in the formation of atherosclerotic plaques in ApoE^−/−AOC3^−/− mice and human coronary arteries.

Methods

Lesions, contractile markers, and AOC3 were studied in aortic tissues from 15- and 25-week-old mice and different stages of human coronary atherosclerotic arteries by immunohistochemistry (IHC) and/or western blot. Human VSMCs, treated or not with LJP1586, an AOC3 inhibitor, were used to measure differentiation markers by qPCR. AOC3 co-localization with specific cell markers was studied by using confocal microscopy in mice and human samples.

Results

At 15 weeks old, the absence of AOC3 was associated with increased lesion size, α-SMA, and CD3 staining in the plaque independently of a cholesterol modification. At 25 weeks old, advanced plaques were larger with equivalent staining for α-SMA while CD3 increased in the media from ApoE^−/−AOC3^−/− mice. At both ages, the macrophage content of the lesion was not modified. Contractile markers decreased whereas MCP-1 appeared augmented only in the 15-week-old ApoE^−/−AOC3. AOC3 is mainly expressed by mice and human VSMC is slightly expressed by endothelium but not by macrophages.

Conclusion

AOC3 knock-out increased atherosclerotic plaques at an early stage related to a VSMC dedifferentiation associated with a higher T cells recruitment in plaques explained by the MCP-1 augmentation. This suggests that AOC3 may have an important role in atherosclerosis independent of its canonical inflammatory effect. The dual role of AOC3 impacts therapeutic strategies using pharmacological regulators of SSAO activity.

Prognostic value of blood pressure in ambulatory heart failure: a meta-analysis and systematic review. Ambulatory blood pressure predicts heart failure prognosis

Previous primary studies have explored the association between blood pressure (BP) and mortality in ambulatory heart failure (HF) patients reporting varying and contrasting associations. The aim is to determine the pooled BP prognostic value and explore potential reasons for between-study inconsistency. We searched Medline, Cochrane, EMBASE and CINAHL from January 2005 to October 2018 for studies with ≥ 50 events (mortality and/or hospitalization) and included BP in a multivariable model in ambulatory HF patients. We pooled hazard ratios (random effects model) for systolic BP (SBP) or diastolic BP (DBP) effect on mortality and/or hospitalization risk. We used a priori defined sub-group analyses to explore heterogeneity and GRADE approach to assess the certainty of the evidence. Seventy-one eligible articles (239,467 screened) at low to moderate risk of bias included 235,752 participants. Higher SBP was associated with reduced all-cause mortality (HR 0.93, 95%CI 0.91-0.95, I2 = 87.13%, moderate certainty), all-cause hospitalization events (HR 0.91, 95%CI 0.88-0.93, I2 = 44.4%, high certainty) and their composite endpoint (HR 0.93 per 10 mmHg, 95%CI 0.91-0.94, I2 = 86.3%, high certainty). DBP did not demonstrate a statistically significant effect for all outcomes. The association strength was significantly weaker in studies following patients with either LVEF > 40%, higher average SBP (> 130 mmHg), increasing age and diabetes. All other a priori subgroup hypotheses did not explain between study differences. Higher ambulatory SBP is associated with reduced risk of all-cause mortality and hospitalization. Patients with lower BP and reduced LVEF are in a high-risk group of developing adverse events with moderate certainty of evidence.

Copper and lipid metabolism: A reciprocal relationship

BACKGROUND

Copper and lipid metabolism are intimately linked, sharing a complex, inverse relationship in the periphery (outside of the central nervous system), which remains to be fully elucidated.

SCOPE

Copper and lipids have independently been implicated in the pathogenesis of diseases involving dyslipidaemia, including obesity, cardiovascular disease and non-alcoholic fatty liver disease and also in Wilson disease, an inherited disorder of copper overload. Here we review the relationship between copper and lipid regulatory pathways, which are potential druggable targets for therapeutic intervention.

MAJOR CONCLUSIONS

While the inverse relationship between copper and lipids is apparent, tissue-specific roles for the copper regulatory protein, ATP7B provide further insight into the association between copper and lipid metabolism.

GENERAL SIGNIFICANCE

Understanding the relationship between copper and lipid metabolism is important for identifying druggable targets for diseases with disrupted copper and/or lipid metabolism; and may reveal similar connections within the brain and in neurological diseases with impaired copper and lipid transport.

Comparison of Inhibitor and Substrate Selectivity between Rodent and Human Vascular Adhesion Protein-1

Vascular adhesion protein-1 (VAP-1) is an ectoenzyme that functions as a copper-containing amine oxidase and is involved in leukocyte adhesion at sites of inflammation. Inhibition of VAP-1 oxidative deamination has become an attractive target for anti-inflammatory therapy with demonstrated efficacy in rodent models of inflammation. A previous comparison of purified recombinant VAP-1 from mouse, rat, monkey, and human gene sequences predicted that rodent VAP-1 would have higher affinity for smaller hydrophilic substrates/inhibitors because of its narrower and more hydrophilic active site channel. An optimized in vitro oxidative deamination fluorescence assay with benzylamine (BA) was used to compare inhibition of five known inhibitors in recombinant mouse, rat, and human VAP-1. Human VAP-1 was more sensitive compared to rat or mouse VAP-1 (lowest IC₅₀ concentration) to semicarbazide but was least sensitive to hydralazine and LJP-1207. Hydralazine had a lower IC₅₀ in rats compared to humans, although not significant. However, the IC₅₀ of hydralazine was significantly higher in the rat compared to mouse VAP-1. The larger hydrophobic compounds from Astellas (compound 35c) and Boehringer Ingelheim (PXS-4728A) were hypothesized to have higher binding affinity for human VAP-1 compared to rodent VAP-1 since the channel in human VAP-1 is larger and more hydrophobic than that in rodent VAP-1. Although the sensitivity of these two inhibitors was the lowest in the mouse enzyme, we found no significant differences between mouse, rat, and human VAP-1. Michaelis-Menten kinetics of the small primary amines phenylethylamine and tyramine were also compared to the common marker substrate BA demonstrating that BA had the highest affinity among the substrates. Rat VAP-1 had the highest affinity for all three substrates and mouse VAP-1 had intermediate affinity for BA and phenylethylamine, but tyramine was not a substrate for mouse VAP-1 under these assay conditions. These results suggest that comparing oxidative deamination in mouse and rat VAP-1 may be important if using these species for preclinical efficacy models.

Attenuation of Weight Gain and Prevention of Associated Pathologies by Inhibiting SSAO

Obesity is a worldwide prevalent metabolic disorder that is associated with diabetes, among many other diseases. Bearing this in mind, prevention and treatment ways need to be improved. Notably, activity of the enzyme semicarbazide-sensitive amine oxidase (SSAO) is found to be elevated in overweight subjects. Moreover, SSAO inhibition has resulted in an increase of histamine activity in adipose tissue and the limitation of body fat. The current review aims to overview the risks of obesity, rationalize the molecular ways of SSAO activity, and outline the strategies of inhibiting upregulated enzyme levels. It describes the differences between SSAO inhibitors and advances the prospective agents. Based on evidence, caffeine is proposed as an effective, safe, and reliable choice to inhibit SSAO activity. Furthermore, the histamine in adipocytes has been associated with SSAO activity. Therefore, it is suggested as one of the key compounds to be studied for obesity management. To conclude, inhibiting SSAO may attenuate weight gain and prevent related diseases.

Vascular Adhesion Protein-1: A Cell Surface Amine Oxidase in Translation

Significance: Vascular adhesion protein-1 (VAP-1) is an ectoenzyme that oxidates primary amines in a reaction producing also hydrogen peroxide. VAP-1 on the blood vessel endothelium regulates leukocyte extravasation from the blood into tissues under physiological and pathological conditions. Recent Advances: Inhibition of VAP-1 by neutralizing antibodies and by several novel small-molecule enzyme inhibitors interferes with leukocyte trafficking and alleviates inflammation in many experimental models. Targeting of VAP-1 also shows beneficial effects in several other diseases, such as ischemia/reperfusion, fibrosis, and cancer. Moreover, soluble VAP-1 levels may serve as a new prognostic biomarker in selected diseases. Critical Issues: Understanding the contribution of the enzyme activity-independent and enzyme activity-dependent functions, which often appear to be mediated by the hydrogen peroxide production, in the VAP-1 biology will be crucial. Similarly, there is a pressing need to understand which of the VAP-1 functions are regulated through the modulation of leukocyte trafficking, and what is the role of VAP-1 synthesized in adipose and smooth muscle cells. Future Directions: The specificity and selectivity of new VAP-1 inhibitors, and their value in animal models under therapeutic settings need to be addressed. Results from several programs studying the therapeutic potential of VAP-1 inhibition, which now are in clinical trials, will reveal the relevance of this amine oxidase in humans.

Past, Present and Future Anti-Obesity Effects of Flavin-Containing and/or Copper-Containing Amine Oxidase Inhibitors

Background: Two classes of amine oxidases are found in mammals: those with a flavin adenine dinucleotide as a cofactor, such as monoamine oxidases (MAO) and lysine-specific demethylases (LSD), and those with copper as a cofactor, including copper-containing amine oxidases (AOC) and lysyl oxidases (LOX). All are expressed in adipose tissue, including a semicarbazide-sensitive amine oxidase/vascular adhesion protein-1 (SSAO/VAP-1) strongly present on the adipocyte surface. Methods: Previously, irreversible MAO inhibitors have been reported to limit food intake and/or fat extension in rodents; however, their use for the treatment of depressed patients has not revealed a clear anti-obesity action. Semicarbazide and other molecules inhibiting SSAO/VAP-1 also reduce adiposity in obese rodents. Results: Recently, a LOX inhibitor and a subtype-selective MAO inhibitor have been shown to limit fattening in high-fat diet-fed rats. Phenelzine, which inhibits MAO and AOC, limits adipogenesis in cultured preadipocytes and impairs lipogenesis in mature adipocytes. When tested in rats or mice, phenelzine reduces food intake and/or fat accumulation without cardiac adverse effects. Novel amine oxidase inhibitors have been recently characterized in a quest for promising anti-inflammatory or anti-cancer approaches; however, their capacity to mitigate obesity has not been studied so far. Conclusions: The present review of the diverse effects of amine oxidase inhibitors impairing adipocyte differentiation or limiting excessive fat accumulation indicates that further studies are needed to reveal their potential anti-obesity properties.

Inhibition of semicarbazide-sensitive amine oxidase reduces atherosclerosis in apolipoprotein E-deficient mice

Inflammation, oxidative stress, and formation of advanced glycated end products (AGEs) and advanced lipoxidation end products (ALEs) are important for atherosclerosis. Vascular adhesion protein-1 (VAP-1) participates in inflammation and has semicarbazide-sensitive amine oxidase (SSAO) activity, which catalyzes oxidative deamination to produce hydrogen peroxide and aldehydes, leading to generation of AGEs and ALEs. However, the effect of VAP-1/SSAO inhibition on atherosclerosis remains controversial, and no studies used coronary angiography to evaluate if plasma VAP-1/SSAO is a biomarker for coronary artery disease (CAD). Here, we examined if plasma VAP-1/SSAO is a biomarker for CAD diagnosed by coronary angiography in humans and investigated the effect of VAP-1/SSAO inhibition by a specific inhibitor PXS-4728A on atherosclerosis in cell and animal models. In the study, VAP-1/SSAO expression was increased in plaques in humans and in apolipoprotein E (ApoE)-deficient mice, and colocalized with vascular endothelial cells and smooth muscle cells (SMCs). Patients with CAD had higher plasma VAP-1/SSAO than those without CAD. Plasma VAP-1/SSAO was positively associated with the extent of CAD. In ApoE-deficient mice, VAP-1/SSAO inhibition reduced atheroma and decreased oxidative stress. VAP-1/SSAO inhibition attenuated the expression of adhesion molecules, chemoattractant proteins, and proinflammatory cytokines in the aorta, and suppressed monocyte adhesion and transmigration across human umbilical vein endothelial cells. Consequently, the expression of markers for macrophage recruitment and activation in plaques was decreased by VAP-1/SSAO inhibition. Besides, VAP-1/SSAO inhibition suppressed proliferation and migration of A7r5 SMC. Our data suggest that plasma VAP-1/SSAO is a novel biomarker for the presence and the extent of CAD in humans. VAP-1/SSAO inhibition by PXS-4728A is a potential treatment for atherosclerosis.

Inhibition of Semicarbazide-sensitive Amine Oxidase Reduces Atherosclerosis in Cholesterol-fed New Zealand White Rabbits

Inflammation, oxidative stress, and the formation of advanced glycated end-products (AGEs) are important components of atherosclerosis. Vascular adhesion protein-1 (VAP-1) participates in inflammation. Its enzymatic activity, semicarbazide-sensitive amine oxidase (SSAO), can catalyze oxidative deamination reactions to produce hydrogen peroxide and aldehydes, leading to the subsequent generation of AGEs. This study aimed to investigate the effect of VAP-1/SSAO inhibition on atherosclerosis. In our study, immunohistochemical staining showed that atherosclerotic plaques displayed higher VAP-1 expression than normal arterial walls in apolipoprotein E-deficient mice, cholesterol-fed New Zealand White rabbits and humans. In cholesterol-fed rabbits, VAP-1 was expressed on endothelial cells and smooth muscle cells in the thickened intima of the aorta. Treatment with PXS-4728A, a selective VAP-1/SSAO inhibitor, in cholesterol-fed rabbits significantly decreased SSAO-specific hydrogen peroxide generation in the aorta and reduced atherosclerotic plaques. VAP-1/SSAO inhibition also lowered blood low-density lipoprotein cholesterol, reduced the expression of adhesion molecules and inflammatory cytokines, suppressed recruitment and activation of macrophages, and decreased migration and proliferation of SMC. In conclusion, VAP-1/SSAO inhibition reduces atherosclerosis and may act through suppression of several important mechanisms for atherosclerosis.

Semicarbazide disturbs the reproductive system of male zebrafish (Danio rerio) through the GABAergic system

Semicarbazide (SMC), an emerging water contaminant, exerts anti-estrogenic effects in female zebrafish. However, the exact influence of SMC on male reproduction remains unclear. In this study, adult male zebrafish were exposed to 1-1000μg/L SMC in a semi-static system for 28 d prior to examining the testicular somatic index (TSI), testis histology, plasma sex hormone levels, and the transcription of genes involved in reproduction. The results showed that testicular morphology was altered and TSI was down-regulated by high concentrations of SMC (≥100μg/L and 1000μg/L, respectively). Plasma testosterone and 17β-estradiol concentrations were significantly decreased by all of the SMC treatments, along with down-regulation of the corresponding steroidogenic gene transcripts. These changes were associated with the inhibition of gamma-aminobutyric acid synthesis and function, in addition to the decreased expression of reproductive regulators. Our results contribute to elucidating the mechanisms underlying the adverse reproductive effects of SMC in male zebrafish.

Anatomical distribution of primary amine oxidase activity in four adipose depots and plasma of severely obese women with or without a dysmetabolic profile

Semicarbazide-sensitive amine oxidase (SSAO), identical to primary amine oxidase or vascular adhesion protein-1, is a membrane enzyme that generates hydrogen peroxide. SSAO is highly expressed at the adipocyte surface, and its plasma levels increase with type 2 diabetes. Since visceral adipose tissue (AT) is more tightly associated with obesity complications than subcutaneous (SC) abdominal fat, we compared SSAO activity in plasma and 4 distinct AT locations in 48 severely obese women (body mass index (BMI), averaging 54 ± 11 kg/m²), with or without a dysmetabolic profile. Higher glucose and triacylglycerol levels vs lower high-density lipoprotein (HDL)-cholesterol characterized dysmetabolic women (DYS; n = 25) from non-dysmetabolic (NDYS; n = 23), age- and weight-matched subjects. SC, mesenteric (ME), omental (OM), and round ligament (RL) fat locations were collected during bariatric surgery. SSAO capacity to oxidize up to 1 mM benzylamine was determined in AT and plasma with radiometric and fluorimetric methods. Plasma SSAO was higher in the DYS group. SSAO activity was higher in fat than in plasma, when expressed as radiolabeled benzaldehyde per milligram of protein. In ATs from DYS women, protein content was 10 % higher, and basal hydrogen peroxide release lower than in NDYS subjects, except for RL location. The SSAO affinity towards benzylamine did not exhibit regional variation and was not altered by a dysmetabolic profile (K _m averaging 184 ± 7 μM; n = 183). Although radiometric and fluorimetric methods gave different estimates of oxidase activity, both indicated that AT SSAO activity did not vary according to anatomical location and/or metabolic status in severely obese women.

Inactivation of semicarbazide-sensitive amine oxidase induces the phenotypic switch of smooth muscle cells and aggravates the development of atherosclerotic lesions

BACKGROUND AND AIMS

Clinical studies have demonstrated that serum semicarbazide-sensitive amine oxidase (SSAO) activities positively correlate with the progression of atherosclerosis. The aim of the present study is to investigate the effect of SSAO inactivation on the development of atherosclerosis.

METHODS

Female LDLr knockout (KO) mice were given the Western-type diet for 6 and 9 weeks to induce the formation of early and advanced lesions, and semicarbazide (SCZ, 0.125%) was added into the drinking water to inactivate SSAO in vivo.

RESULTS

Despite no impact on plasma total cholesterol levels, abrogation of SSAO by SCZ not only resulted in the enlargement of both early (1.5-fold, p = 0.0043) and advanced (1.8-fold, p = 0.0013) atherosclerotic lesions, but also led to reduced/increased lesion contents of macrophages/smooth muscle cells (SMCs) (macrophage: ∼0.74-fold, p = 0.0002(early)/0.0016(advanced); SMC: ∼1.55-fold, p = 0.0003(early)/0.0001(advanced)), respectively. Moreover, SSAO inactivation inhibited the migration of circulating monocytes into peripheral tissues and reduced the amount of circulating Ly6C(high) monocytes (0.7-fold, p = 0.0001), which may account for the reduced macrophage content in lesions. In contrast, the increased number of SMCs in lesions of SCZ-treated mice is attributed to an augmented synthetic vascular SMC phenotype switch as evidenced by the increased proliferation of SMCs and accumulation of collagens in vivo.

CONCLUSION

SSAO inactivation by SCZ promotes the phenotypic switch of SMCs and the development of atherosclerosis. The enzymatic activity of SSAO may thus represent a potential target in the prevention and/or treatment of atherosclerosis.

Age-related formaldehyde interferes with DNA methyltransferase function, causing memory loss in Alzheimer's disease

Hippocampus-related topographic amnesia is the most common symptom of memory disorders in Alzheimer's disease (AD) patients. Recent studies have revealed that experience-mediated DNA methylation, which is regulated by enzymes with DNA methyltransferase (DNMT) activity, is required for the formation of recent memory as well as the maintenance of remote memory. Notably, overexpression of DNMT3a in the hippocampus can reverse spatial memory deficits in aged mice. However, a decline in global DNA methylation was found in the autopsied hippocampi of patients with AD. Exactly, what endogenous factors that affect DNA methylation still remain to be elucidated. Here, we report a marked increase in endogenous formaldehyde levels is associated with a decline in global DNA methylation in the autopsied hippocampus from AD patients. In vitro and in vivo results show that formaldehyde in excess of normal physiological levels reduced global DNA methylation by interfering DNMTs. Interestingly, intrahippocampal injection of excess formaldehyde before spatial learning in healthy adult rats can mimic the learning difficulty of early stage of AD. Moreover, injection of excess formaldehyde after spatial learning can mimic the loss of remote spatial memory observed in late stage of AD. These findings suggest that aging-associated formaldehyde contributes to topographic amnesia in AD patients.

Human copper-dependent amine oxidases

Copper amine oxidases (CAOs) are a class of enzymes that contain Cu(2+) and a tyrosine-derived quinone cofactor, catalyze the conversion of a primary amine functional group to an aldehyde, and generate hydrogen peroxide and ammonia as byproducts. These enzymes can be classified into two non-homologous families: 2,4,5-trihydroxyphenylalanine quinone (TPQ)-dependent CAOs and the lysine tyrosylquinone (LTQ)-dependent lysyl oxidase (LOX) family of proteins. In this review, we will focus on recent developments in the field of research concerning human CAOs and the LOX family of proteins. The aberrant expression of these enzymes is linked to inflammation, fibrosis, tumor metastasis/invasion and other diseases. Consequently, there is a critical need to understand the functions of these proteins at the molecular level, so that strategies targeting these enzymes can be developed to combat human diseases.

Malformations of the great vessels in the neonatal rat induced by N-(2-aminoethyl)ethanolamine

The reproductive and developmental toxicity of aminoethylethanolamine was evaluated in a standard screening study (OECD, 1995: Organisation for economic co-operation and development. Paris, France), in which groups of Wistar rats (10/sex/group) were administered the test substance by gavage at dosage levels of 50, 250, or 1000 mg/kg/day (groups 2-4, respectively). A control group received the vehicle, doubly distilled water. No live pups were delivered in group 4, and there was a higher incidence of stillborn offspring and reduced postnatal survival in group 3. Macroscopic changes in groups 2 and 3 were primarily related to the great vessels and characterized by dilations, aneurysms, and altered course of the aorta, pulmonary trunk, carotids, and the ductus arteriosus. A follow-up study was conducted to characterize the low dose-response, using dosage levels of 0, 0.2, 1, 5, or 50 mg/kg/day (groups 1-5, respectively). Given the expected scarcity of the lesions in control offspring, each group consisted of 25 animals of each sex. Macroscopic examination revealed a high incidence (18.5%) of aneurysm-bearing offspring in group 5 litters, and single offspring (0.3-0.4%) with aneurysms in groups 3 and 4. Microscopic examination revealed dissecting aneurysms in offspring from all aminoethylethanolamine treatment groups, without a clear dose-response between groups 2 and 4 (0.6%, 1.2%, and 0.3%, respectively), and focal hemorrhages in all groups including the control. In comparison, the background incidence of aneurysms in untreated 4-day old offspring was 0.2% (Treumann et al., 2011: Toxicol Pathol 39:969-974). Consequently, the findings in groups 2-4 cannot be conclusively attributed to treatment.

Developmental sensitivity to the induction of great vessel malformations by N-(2-aminoethyl)ethanolamine

N-(2-Aminoethyl)ethanolamine (AEEA) induced malformations of the great vessels in the offspring of rats treated during gestation and early lactation (Schneider et al., 2012. Birth Defects Res B Dev Reprod Toxicol [in press]). The aim of this study was to determine if in utero exposure alone was sufficient to induce these malformations or whether a peri-postnatal exposure or physiological component was required. Three groups of five time-mated female Wistar Han rats were administered AEEA (250 mg/kg/day) by gavage from gestation day (GD) 6 to GD 19 (groups 1 and 2) or from GD 6 to postnatal day 3 (group 3). Animals were euthanized on GD 21 (group 1) or postnatal day 4 (groups 2 and 3), and the hearts of the offspring were examined for changes to the great vessels. The incidence of malformations in group 1 was 91.1%, and primarily consisted of high aortic arch and abnormal carotid course. One fetus had an aortic aneurysm. All fetuses in groups 2 and 3 were malformed, primarily exhibiting abnormal carotid course and aneurysms, which mainly affected the aorta, ductus arteriosus, and pulmonary trunk. The incidence of high aortic arch was lower relative to group 1. Aneurysms were more prevalent in group 3 compared to group 2. These findings indicate that exposure to AEEA during gestation alone was sufficient to induce malformations of the great vessels and aneurysms, which may be triggered by physiological changes that occur during or after birth, but that the critical period of susceptibility to AEEA-induced aneurysms in the rat extends beyond gestation into the early postnatal period.

SSAO substrates exhibiting insulin-like effects in adipocytes as a promising treatment option for metabolic disorders

BACKGROUND

Benzylamine exerts insulin-like effects in adipocytes (e.g., glucose uptake and antilipolysis) and improves glucose handling in rodents.

RESULTS

In murine adipocytes, benzylamine mimics another insulin action: it enhances apelin expression in a manner that is blocked by the semicarbazide-sensitive amine oxidase/vascular adhesion protein-1 (SSAO/VAP-1) inhibitor semicarbazide. It is shown that in human adipocytes, benzylamine activates glucose transport, but its effects are not additive to maximal insulin stimulation. Benzylamine effects are hydrogen peroxide dependent. They can be reproduced by novel substrates, but not by benzaldehyde.

CONCLUSION

Owing to the parallelism between the in vitro insulin mimicry and the in vivo improvement of glucose handling elicited by benzylamine in rodents, the SSAO/VAP-1 substrates, with stronger effects on human adipocytes than benzylamine, show promising applications for the treatment of insulin resistance.

Vascular adhesion protein-1 inhibition provides antiinflammatory protection after an intracerebral hemorrhagic stroke in mice

The systemic immune response has a vital role in propagating the damage of an intracerebral hemorrhage (ICH). Vascular adhesion protein-1 (VAP-1), a semicarbazide (SCZ)-sensitive-amine-oxidase, was found in previous studies to have a role in migration of immune cells. In this study, we hypothesize that VAP-1 inhibition may decrease brain injury by attenuating the transmigration of immune cells to the injury site, and by doing so, reduce cerebral edema and improve neurobehavioral function in mice. Two VAP-1 inhibitors, LJP1586 and SCZ were given 1 hour after ICH induction by either collagenase or autologous blood injection. The VAP-1 siRNA, a VAP-1 gene silencer, and human recombinant AOC3 protein, a VAP-1 analogue, were delivered by intracerebroventricular injection. Postassessment included neurobehavioral testing, brain edema measurement, quantification of neutrophil infiltration and microglia/macrophage activation, and measurement of intercellular adhesion molecule-1 (ICAM-1), P-selectin, monocyte chemoattractant protein-1 (MCP-1), and tumor necrosis factor-α (TNF-α) expression 24 hours after ICH. We found that LJP1586 and SCZ reduced brain edema and neurobehavioral deficits 24 hours after ICH induction. These two drugs were also found to decrease levels of ICAM-1, MCP-1, TNF-α, and inhibit neutrophilic infiltration and microglia/macrophage activation. We conclude that VAP-1 inhibition provided antiinflammation effect by reducing adhesion molecule expression and immune cell infiltration after ICH.

Inhibition of semicarbazide-sensitive amine oxidase attenuates myocardial ischemia-reperfusion injury in an in vivo rat model

AIMS

This study tested the hypothesis that the inhibition of semicarbazide-sensitive amine oxidase (SSAO) after ischemia could attenuate myocardial ischemia-reperfusion (I/R) injury.

MAIN METHODS

Anesthetized male Sprague-Dawley rats underwent myocardial I/R injury. Saline, semicarbazide (SCZ, 30 mg/kg), hydralazine (HYD, 10mg/kg), or LJP 1207 (30 mg/kg) was administered intraperitoneally 3 min before reperfusion. After 30 min of ischemia and 180 min of reperfusion, the myocardial infarct size was determined using nitroblue tetrazolium staining. Myocardial myeloperoxidase activity was determined through biochemical assay. HE staining was used for histopathological evaluation. Myocardial SSAO activity was assayed with high performance liquid chromatography analysis. Additionally, the endothelial expression of P-selectin was evaluated using immunohistochemistry after 30 min of ischemia and 20 min of reperfusion.

KEY FINDINGS

Myocardial SSAO activity was increased in myocardial I/R injury. Administration of SCZ, HYD, or LJP 1207 reduced the myocardial infarct size and decreased leukocyte infiltration and endothelial P-selectin expression in myocardial I/R injury in vivo.

SIGNIFICANCE

These data suggest that myocardial I/R injury up-regulates myocardial SSAO activity, and the inhibition of SSAO prior to reperfusion is able to attenuate acute myocardial I/R injury.

Oral Administration of Semicarbazide Limits Weight Gain together with Inhibition of Fat Deposition and of Primary Amine Oxidase Activity in Adipose Tissue

An enzyme hitherto named semicarbazide-sensitive amine oxidase (SSAO), involved in the oxidation of primary amines, is abundantly expressed in adipocytes. Although SSAO physiological functions remain unclear, several molecules inhibiting its activity have been described to limit fat accumulation in preadipocyte cultures or to reduce body weight gain in obese rodents. Here, we studied whether oral administration of semicarbazide, a prototypical SSAO inhibitor, limits fat deposition in mice. Prolonged treatment with semicarbazide at 0.125% in drinking water limited food and water consumption, hampered weight gain, and deeply impaired fat deposition. The adiposomatic index was reduced by 31%, while body mass was reduced by 15%. Such treatment completely inhibited SSAO, but did not alter MAO activity in white adipose tissue. Consequently, the insulin-like action of the SSAO substrate benzylamine on glucose transport was abolished in adipocytes from semicarbazide-drinking mice, while their insulin sensitivity was not altered. Although semicarbazide is currently considered as a food contaminant with deleterious effects, the SSAO inhibition it induces appears as a novel concept to modulate adipose tissue development, which is promising for antiobesity drug discovery.

Age-related Susceptibility to Induction of Osteochondral and Vascular Lesions by Semicarbazide Hydrochloride in Rats

To compare the susceptibility to toxicity of semicarbazide hydrochloride (SEM-HCl) between young and adult rats, 3- and 20-week-old female SD rats were given a diet containing SEM-HCl at 0, 500, or 1,000 ppm and 0 or 1,000 ppm, respectively, for 4 weeks. Half of the animals were then maintained on basal diet for a further 2 weeks as recovery groups. Only in young rats was deformation of the knee joints as well as thorax and tail observed at 500 and 1,000 ppm. Histopathologically, severe osteochondral lesions, such as disarrangement and thickening of the epiphyseal cartilage and deformation of articular cartilage, were observed, but the severity of these lesions became reduced during the recovery period. In adult rats, osteochondral lesions were relatively mild. Fissures in the cartilage matrix of the tibia were characteristic of adult rats, and in these, reduction of severity was not obvious in the recovery group. In the thoracic aorta, the appearance of elastic laminae was altered only in young rats in both the 4-week treatment and recovery groups. These results suggest that growing animals are more susceptible to toxicity of SEM-HCl than adults are. Effects and the induced lesions link to the developing stage of the target organs.

A ninety-day toxicity study of semicarbazide hydrochloride in Wistar Hannover GALAS rats

A ninety-day toxicity study of semicarbazide hydrochloride (SEM-HCl) was conducted in male and female Wistar Hannover GALAS rats fed diet containing the compound at concentration of 0, 250, 500 and 1000 ppm. Suppression of body weight gain and food consumption was found in both sexes at 1000 ppm throughout the study. Enlargement and deformation of knee joints were obvious at 500 and 1000 ppm from week 3, together with deformation of the thorax and tail. Histopathologically, disarrangement of chondrocytes and fissures in the cartilage matrix were apparent at all doses tested in epiphyseal and articular cartilage. The severity of these lesions increased dose-dependently, accompanied by increased connective tissues and bone deformation at high doses. Additionally, compact bones at 1000 ppm became thin, suggesting loss of bone mass. In the thoracic aorta, the edges of elastic laminae became rough and the interlaminar spaces were altered from a fibrillar to a rod or globular appearance. No abnormalities were detected in any other organs. Taken together, toxicological effects of subchronic exposure to SEM-HCI were mainly observed in bone, cartilage and the aorta, with the no-observed-adverse-effect-level estimated from the present histopathological examination of less than 250 ppm in both sexes.