Vascular adhesion protein-1 (VAP-1) in vascular inflammatory diseases.

Vascular adhesion protein-1 (VAP-1) also known as amino oxidase copper containing 3 (AOC3) is a pro-inflammatory and versatile molecule with adhesive and enzymatic properties. VAP-1 is a primary amine oxidase belonging to the semicarbazide-sensitive amine oxidase (SSAO) family, which catalyzes the oxidation of primary amines leading to the production of ammonium, formaldehyde, methylglyoxal, and hydrogen peroxide. VAP-1 is mainly expressed by endothelial cells, smooth muscle cells, adipocytes and pericytes. It is involved in a repertoire of biological functions, e.g., immune cell extravasation, angiogenesis, and vascularization. Research into VAP-1 has intensified within the last decade on its role as a novel clinical biomarker and as a potential therapeutic target of vascular inflammatory disorders such as atherosclerosis, stroke, diabetes, neurovascular disorders (e.g., Alzheimer's Disease), hepatic disease (e.g., non-alcoholic steatohepatitis), and skin conditions (e.g., psoriasis). This is the most up-to-date and comprehensive review on VAP-1 focusing on the translational aspects of VAP-1. Compared to recent reviews, our review provides novel insights on VAP-1 and heart failure, stroke and frailty, diabetes, endometriosis, osteoarthritis, COVID-19, conjunctivitis associated systemic lupus erythematosus, hematopoietic stem cells, gliomas, treatment of colorectal cancer with a novel VAP-1 inhibitor (U-V269), promoting recovery of motor functions and habit learning with a novel VAP-1 inhibitor (PXS-4681A), and 68Ga-DOTA-Siglec-9, a labelled peptide of Siglec-9 (a VAP-1 ligand), which appears to be a safe PET tracer for inflammation in rheumatoid arthritis. Finally, we present the emerging role of VAP-1 in pregnancy as a gatekeeper of immune cells, which are critical for spiral arterial remodeling, the deficiency of which could lead to vascular disorders of pregnancy such as preeclampsia. Future research should prioritize clinical trials on VAP-1 small-molecule inhibitors and monoclonal antibodies, thus, maximizing the potential of VAP-1 targeted therapy as well as research into sVAP-1 as a clinical biomarker of diseases and its prognosis.

Human Copper-Containing Amine Oxidases in Drug Design and Development.

Two members of the copper-containing amine oxidase family are physiologically important proteins: (1) Diamine oxidase (hDAO; AOC1) with a preference for diamines is involved in degradation of histamine and (2) Vascular adhesion protein-1 (hVAP-1; AOC3) with a preference for monoamines is a multifunctional cell-surface receptor and an enzyme. hVAP-1-targeted inhibitors are designed to treat inflammatory diseases and cancer, whereas the off-target binding of the designed inhibitors to hDAO might result in adverse drug reactions. The X-ray structures for both human enzymes are solved and provide the basis for computer-aided inhibitor design, which has been reported by several research groups. Although the putative off-target effect of hDAO is less studied, computational methods could be easily utilized to avoid the binding of VAP-1-targeted inhibitors to hDAO. The choice of the model organism for preclinical testing of hVAP-1 inhibitors is not either trivial due to species-specific binding properties of designed inhibitors and different repertoire of copper-containing amine oxidase family members in mammalian species. Thus, the facts that should be considered in hVAP-1-targeted inhibitor design are discussed in light of the applied structural bioinformatics and structural biology approaches.

Molecular cloning, expression, and functional analysis of the copper amine oxidase gene in the endophytic fungus Shiraia sp. Slf14 from Huperzia serrata.

Huperzine A (HupA) is a drug used for the treatment of Alzheimer's disease. However, the biosynthesis of this medicinally important compound is not well understood. The HupA biosynthetic pathway is thought to be initiated by the decarboxylation of lysine to form cadaverine, which is then converted to 5-aminopentanal by copper amine oxidase (CAO). In this study, we cloned and expressed an SsCAO gene from a HupA-producing endophytic fungus, Shiraia sp. Slf14. Analysis of the deduced protein amino acid sequence showed that it contained the Asp catalytic base, conserved motif Asn-Tyr-Asp/Glu, and three copper-binding histidines. The cDNA of SsCAO was amplified and expressed in Escherichia coli BL21(DE3), from which a 76 kDa protein was obtained. The activity of this enzyme was tested, which provided more information about the SsCAO gene in the endophytic fungus. Gas Chromatograph-Mass Spectrometry (GC-MS) revealed that this SsCAO could accept cadaverine as a substrate to produce 5-aminopentanal, the precursor of HupA. Phylogenetic tree analysis indicated that the SsCAO from Shiraia sp. Slf14 was closely related to Stemphylium lycopersici CAO. This is the first report on the cloning and expression of a CAO gene from HupA-producing endophytic fungi. Functional characterization of this enzyme provides new insights into the biosynthesis of the HupA an anti-Alzheimer's drug.

Histamine, histamine intoxication and intolerance.

Excessive accumulation of histamine in the body leads to miscellaneous symptoms mediated by its bond to corresponding receptors (H1-H4). Increased concentration of histamine in blood can occur in healthy individuals after ingestion of foods with high contents of histamine, leading to histamine intoxication. In individuals with histamine intolerance (HIT) ingestion of food with normal contents of histamine causes histamine-mediated symptoms. HIT is a pathological process, in which the enzymatic activity of histamine-degrading enzymes is decreased or inhibited and they are insufficient to inactivate histamine from food and to prevent its passage to blood-stream. Diagnosis of HIT is difficult. Multi-faced, non-specific clinical symptoms provoked by certain kinds of foods, beverages and drugs are often attributed to different diseases, such as allergy and food intolerance, mastocytosis, psychosomatic diseases, anorexia nervosa or adverse drug reactions. Correct diagnosis of HIT followed by therapy based on histamine-free diet and supplementation of diamine oxidase can improve patient's quality of life.

Effects of amine oxidases in allergic and histamine-mediated conditions.

This review provides an update on histamine, on diamine oxidase (DAO) and on their implications in allergy and various conditions or affections, such as food histaminosis, ischemia and inflammatory bowel diseases (IBD). The review also presents, in brief, patent coverage on therapies for allergy and IBD with the focus on histamine-related treatments.

Plant histaminase as an investigational drug in splanchnic artery occlusion and reperfusion.

BACKGROUND: Amine oxidases are ubiquitous enzymes involved in the metabolism of biogenic amines. Copper amine oxidases catalyze the oxidative deamination of primary amine groups of several biogenic amines, such as putrescine, cadaverine and histamine. OBJECTIVE: In the present review the effects of a plant amine oxidase (histaminase, EC1.4.3.6), purified from pea seedlings, in the prevention of splanchnic postischemic reperfusion damage are reported. CONCLUSION: Various studies have clearly indicated that the use of histaminase will offer a good perspective for a novel therapeutic approach in the medical treatment of intestinal ischemia.

Pea seedling histaminase as a novel therapeutic approach to anaphylactic and inflammatory disorders. A plant histaminase in allergic asthma and ischemic shock.

Amine oxidases (AOs) are ubiquitous enzymes involved in the metabolism of biogenic amines. Copper AOs (Cu-AOs) catalyze the oxidative deamination of primary amine groups of several biogenic amines, such as putrescine, cadaverine, and histamine. In the present review, the effects of a plant amine oxidase (Cu-AO, histaminase, EC1.4.3.6) purified from pea seedlings in the modulation of IgE-mediated allergic reactions, and in the prevention of cardiac and splachnic postischemic reperfusion damage are reported.

Beneficial effects of a plant histaminase in a rat model of splanchnic artery occlusion and reperfusion.

Splanchnic artery occlusion (SAO) followed by reperfusion causes endothelial injury and inflammation which contribute to the pathophysiology of shock. We investigated the effects of pea seedling (Latyrus cicera) histaminase, known to afford protection against the deleterious effects of cardiac ischemia/reperfusion, given to rats subjected to SAO/reperfusion-induced splanchnic injury. Histaminase (80 IU kg, 15 min before reperfusion) significantly reduced the drop of blood pressure and high mortality rate caused by SAO/reperfusion. Histaminase also reduced histopathological changes, leukocyte infiltration (myeloperoxidase), and expression of endothelial cell adhesion molecules in the ileum. Histaminase counteracted free radical-mediated tissue injury, as judged by a significant decrease in the plasma and tissue levels of peroxidation and nitration products (oxidized rhodamine, malondialdehyde, nitrotyrosine), DNA damage markers (8-hydroxy-2'-deoxyguanosine, poly-adenosine diphosphate-ribosylated DNA) and consumption of tissue antioxidant enzymes (superoxide dismutase). As a result, histaminase led to a reduction of ileal cell apoptosis (caspase 3, terminal deoxynucleotidyltransferase-mediated UTP end labeling-positive cells). These results show that histaminase exerts a clear-cut protective effect in SAO/reperfusion-induced splanchnic injury, likely caused by oxidative catabolism of proinflammatory histamine and antioxidant effects resulting in hindrance of free radical-mediated tissue injury, endothelial dysfunction, and leukocyte recruitment. Thus, histaminase could be used therapeutically in intestinal ischemia.

Sensitization of human colon adenocarcinoma cells (LoVo) to reactive oxygen species by a lysosomotropic compound.

The in situ formation of cytotoxic metabolites by an enzyme-catalyzed reaction is a recent approach in cancer therapy. The present results show that multidrug-resistant human colon adenocarcinoma cells (LoVo) are significantly more sensitive than corresponding wild-type cells to hydrogen peroxide and aldehydes, the products of bovine serum amine oxidase (BSAO)-catalyzed oxidation of spermine. Pre-treatment of the cells with N1,N4-bis(2,3-butadienyl)-1,4-butanediamine (MDL 72527), a lysosomotropic compound, sensitized both cell lines to the subsequent exposure to spermine metabolites, as was evident from the decrease of cell survival by a log unit. The sensitizing effect was greater in the case of the multidrug-resistant cell line, an aspect of particular importance with respect to potential therapeutic applications of the method, since conventional cancer therapy suffers from the development of drug resistance. Cell viability was determined using a clonogenic assay. MDL 72527 (at 300 microM) produced numerous cytoplasmic vacuoles, presumably of lysosomal origin, after 6-h exposure, which decreased in size and number (in the presence of the drug) by 24 h and had almost disappeared completely at 48 h. Mitochondrial damage, as observed by transmission electron microscopy, seemed to correlate better with the cytotoxic effects of the treatment than the formation of vacuoles. We suggest that the release of lysosomal enzymes into the cytosol by MDL 72527 is the main reason for its sensitizing effect. It is known that lysosomotropic compounds, which release lysosomal enzymes, produce oxidative stress and apoptosis.

Cardiac anaphylaxis: pathophysiology and therapeutic perspectives.

Cardiac anaphylaxis refers to the functional and metabolic changes in the heart caused by the anaphylactic release of histamine and vasoactive products of arachidonic acid cascade by mast cells and basophils. As in most type I hypersensitivity-based diseases, histamine plays a key role in the pathophysiology of cardiac anaphylaxis. In the heart, mast cell activation and histamine release are controlled by multiple endogenous mechanisms, including adrenergic neural control, histamine-dependent negative feedback operated through H2 receptors, and the endogenous generation of nitric oxide (NO) and carbon monoxide (CO). All these mechanisms can be targeted by substances that have revealed a clear-cut effect in blunting cardiac anaphylaxis in experimental animal models, and could be developed as potential, novel anti-anaphylactic drugs. In this article, we discuss new findings and significant trends related to this topic.

Anti-tumoral effect of native and immobilized bovine serum amine oxidase in a mouse melanoma model.

Bovine serum amine oxidase (BSAO) oxidatively deaminates polyamines containing primary amine groups, spermidine and spermine, to form the cytotoxic products hydrogen peroxide and aldehyde(s). Polyamines are present at elevated levels in many tumor tissues. The aims of the study were to evaluate the anti-tumoral activities of native and immobilized BSAO in mouse melanoma and also to determine the mechanism of tumor cell death. C57BL mice received a subcutaneous injection of B16 melanoma cells to induce formation of tumors, prior to antitumor treatments with native and immobilized BSAO. The enzyme was immobilized in a poly(ethylene glycol) (PEG) biocompatible matrix. Antitumor treatments consisted of a single injection of enzyme into the tumor. When immobilized BSAO (2.5mU) was injected into the tumor, there was a marked decrease of 70% of the tumor growth. This was compared with a decrease of only 32% of tumor size when the same amount of native BSAO was administered. The type of cell death was analysed in tumors that were treated with native or immobilized BSAO. When tumors were treated with immobilized BSAO, there was induction of a high level of apoptosis (around 70%), compared to less than 10% with the native enzyme. Apoptotic cell death was assessed by nuclear chromatin condensation using Hoechst staining and labelling of externalized phosphatidylserine using Annexin V. However, native BSAO, probably due to a burst of cytotoxic products, induced a high level of necrosis of about 40%, compared to less than 10% with immobilized BSAO. In conclusion, the advantage is that immobilized BSAO can act by allowing the slow release of cytotoxic products, which induces tumor cell death by apoptosis rather than necrosis.

Effect of a plant histaminase on asthmalike reaction induced by inhaled antigen in sensitized guinea pig.

This study evaluates the effects of a copper amine oxidase (histaminase) purified from the pea seedling as a free or immobilized enzyme on asthmalike reactions to inhaled antigen in actively sensitized guinea pig in vivo. Male albino guinea pigs, sensitized with ovalbumin, were challenged with the antigen given by aerosol; free histaminase or CNBr-Sepharose immobilized histaminase was given intraperitoneally (20 microg, 3 or 24 h before antigen challenge) or by aerosol (4 microg, 30 min before or during ovalbumin aerosol). The following parameters were examined: latency time for the onset of respiratory abnormalities, cough severity score, and occurrence and duration of dyspnea. We also evaluated lung histopathology, mast cell degranulation, and lung myeloperoxidase and malonydialdehyde levels. Histaminase significantly reduced the severity of cough and the occurrence of dyspnea and delayed the onset of respiratory abnormalities. Both enzymes prevented bronchial constriction, pulmonary air space inflation, leukocyte infiltration (evaluated as myeloperoxidase activity), and lipoperoxidation of cell membranes (evaluated as malonyldialdehyde production). No relevant differences in pharmacological potency were noted between free or immobilized enzyme. This study provides evidence that histaminase counteracts acute allergic asthmalike reaction in actively sensitized guinea pigs, raising the possibility of new therapeutic strategies for allergic asthma in humans.

Protective effects of a plant histaminase in myocardial ischaemia and reperfusion injury in vivo.

Grass pea seedling histaminase (a copper-diamine oxidase) was found to exert a significant cardioprotection against post-ischaemic reperfusion damage. Electrocardiogram (ECG) recordings from the rats subjected in vivo to ischaemia and reperfusion showed ventricular tachycardia (VT) and ventricular fibrillations (VF) occurring in 9 out of 12 untreated rats whereas no ventricular arrhythmias were found under histaminase (80U/kg body weight) treatment (n=16 rats). Computer-assisted morphometry of the ischaemic reperfused hearts stained with nitroblue tetrazolium showed the extension of damaged myocardium (area at risk and infarct size) significantly reduced in rats treated with histaminase, in comparison with the non-treated rats, whereas no protection was found with the semicarbazide inactivated histaminase. Biochemical markers of ischaemia-reperfusion myocardial tissue damage: malonyldialdehyde (MDA), tissue calcium concentration, myeloperoxidase (MPO), and apoptosis indicator caspase-3 were significantly elevated in untreated post-ischaemic reperfused rats, but significantly reduced under histaminase protection. In conclusion, plant histaminase appears to protect hearts from ischaemia-reperfusion injury by more than one mechanism, essentially involving histamine oxidation, and possibly as reactive oxygen species scavenger, presenting good perspectives for a novel therapeutic approach in treatment of ischaemic heart pathology.

Inhibition of post-ischemic reperfusion injury of the kidney by diamine oxidase.

To elucidate the role of histamine in the pathogenesis of post-ischemic reperfusion injury of tissues, the effect of diamine oxidase (DAO) was studied on the changes in renal functions induced by 30 min occlusion followed by reperfusion of the renal vessels of unilaterally nephrectomized rats. Kinetic analysis using radiolabeled albumin revealed that vascular permeability of the kidney increased markedly after reperfusion. Although the intensity of neutrophil-dependent chemiluminescence of the blood remained unchanged during the occlusion, it increased significantly after reperfusion. Histological examination revealed a marked degeneration of glomeruli and proximal tubules in the reperfused kidney. Transtubular transport of phenolsulfophthalein (PSP) decreased markedly after reperfusion with concomitant increase in plasma levels of creatinine. Intravenously administered DAO markedly inhibited the reperfusion-induced increase in vascular permeability, preserved the structure of the kidney and normalized the rate of clearance of PSP and creatinine. Combined use of diphenylhydramine and ranitidine also inhibited the reperfusion injury of the kidney. These results suggested that histamine and its receptors might play critical roles in post-ischemic reperfusion injury of the kidney.