Este trabalho apresenta dados relativos a oxidação de melatonina catalisada por peroxidase de rábano (HRP, horseradish peroxidase) e mieloperoxidase (MPO). Em presença de peróxido de hidrogênio (H2O2), HRP catalisa a oxidação de melatonina com formação de um produto de clivagem do anel indólico, a N1-acetil-N2-formil-5-metoxiquinuramina. Esta reação consome oxigênio e apresenta quimiluminescência na região de 440-540 nm. Quimiluminescência e a formação da quinuramina também foram observados quando HRP/H2O2 foram substituídos por neutrófilos ativados por acetato de forbol miristato ou zimosan opsonizado. Em neutrófilos, tanto a emissão de luz quanto a formação do produto foram inibidos pela adição de azida, um inibidor de MPO. Superóxido dismutase tem um forte efeito inibidor sobre a emissão de luz enquanto que catalase e ácido úrico não apresentam qualquer efeito. A oxidação de melatonina por neutrófilos ativados pode ser relevante in vivo e estar associada com algumas das funções descritas para mieloperoxidase e melatonina. A possível implicação biológica da oxidação de melatonina por neutrófilos, especialmente em condições inflamatórias, é discutida. / In the presence of hydrogen peroxide, horseradish peroxidase (HRP) catalyzes the production of N1-acetyl-N2-formyl-5-methoxykynuramine from melatonin. This reaction consumes oxygen and exhibits chemiluminescence in the 440-540 nm region. The excited cleavage product derived from the thermolysis of an intermediate dioxetane is suggested to be the emitting species. Chemiluminescence and the indole ring cleavage product were also observed when HRP/H2O2 was replaced by phorbol myristate acetate or opsonized zymosan-activated neutrophils. Azide, a myeloperoxidase inhibitor, strongly suppressed melatonin oxidation. Superoxide dismutase has a strong inhibitory effect on light emission but catalase and uric acid are without effect on the emission. The oxidation of melatonin by activated neutrophils may be relevant to the in vivo functions of myeloperoxidase and melatonin. The possible biological implication of melatonin oxidation by neutrophils, especially in inflammatory conditions, is discussed.

No presente trabalho, estudaram-se os efeitos da l-alanil glutamina (Ala-Gln), do precondicionamento isquÃmico (PCI) e das duas tÃcnicas concomitantemente sobre a lesÃo pulmonar provocada por isquemia e reperfusÃo (I/R) causada por pinÃamento da aorta infra-renal em ratos. Foram utilizados 60 ratos machos Wistar, randomizados em cinco grupos (n = 12) divididos em dois tempos (n = 6): Grupo Simulado, Grupo I/R, Grupo PCI + I/R, Grupo Ala-Gln + I/R, Grupo Ala-Gln + PCI + I/R. Tempos: T1 (4h de isquemia) e T2 (4 horas de isquemia e 1h de reperfusÃo). Todos os grupos receberam soluÃÃo salina previamente, menos os grupos prÃ-tratados com Ala-Gln que receberam o dipeptÃdeo e soluÃÃo salina em igual volume. Foi utilizado o modelo de pinÃamento da aorta infra-renal com 4 horas de isquemia e 1 hora de reperfusÃo. Determinaram-se as concentraÃÃes de mieloperoxidase (MPO) pulmonar, substÃncias reativas ao Ãcido tiobarbitÃrico (TBARS) e glutationa reduzida (GSH) no sangue e pulmÃo para avaliar os grupos em estudo. O teste de Kolmogorov-Smirnoff mostrou distribuiÃÃo normal dos dados. Dados expressos como mÃdia acompanhada pelo seu desvio padrÃo (MÃdia  DPM) sendo realizado teste t de Student. Para anÃlise comparativa simultÃnea de trÃs grupos utilizou-se o teste Anova com pÃs-teste de Tukey. Em todos os casos foi adotado o nÃvel de significÃncia de p<0,05. Houve elevaÃÃo das concentraÃÃes de MPO pulmonar tanto no grupo submetido à isquemia quanto no grupo que realizou a I/R. Ocorreu reduÃÃo significante das concentraÃÃes de MPO pulmonar nos grupos submetidos à isquemia prÃ-tratados com Ala-Gln e com PCI. Na avaliaÃÃo dos grupos que sofreram I/R nÃo foi observada alteraÃÃo nas concentraÃÃes de MPO nos grupos prÃ-tratados Ala-Gln ou PCI. O grupo prÃ-tratado com as duas tÃcnicas apresentou aumento significante da MPO nos tempos estudados. A Ala-Gln como prÃ-tratamento isolado reduziu TBARS plasmÃtico na isquemia e o aumentou no pulmÃo na I/R. Jà no pulmÃo durante isquemia e no plasma na I/R houve reduÃÃo da GSH. O PCI como prÃ-tratamento isolado elevou o TBARS pulmonar na I/R e reduziu a GSH pulmonar na I/R. A associaÃÃo da Ala-Gln e PCI acresceu o TBARS plasmÃtico na isquemia, tambÃm o elevando no pulmÃo e mÃsculo na I/R. Jà a GSH, com os dois prÃ-tratamentos, sofre reduÃÃo plasmÃtica na isquemia e pulmonar na I/R, com elevaÃÃo plasmÃtica na I/R. O presente estudo demonstra que tanto o prÃ-tratamento com Ala-Gln como o PCI protegem contra a lesÃo isquÃmica à distÃncia, em modelo murino de pinÃamento da aorta infra-renal quando avaliado MPO pulmonar. O mesmo nÃo ocorre na lesÃo por I/R. NÃo hà benefÃcio, e sim agravamento de lesÃo à distÃncia pulmonar, na associaÃÃo dos dois prÃ-tratamentos ao mensurar a MPO pulmonar. / The present work determined the effects of pre-treatment with L-alanyl glutamine (Ala-Gln) and ischemic preconditioning (IPC), alone and in combination, against lesions caused by I/R by clamping the infrarenal aorta in rats. Sixty Wistar rats were distributed into five groups (n = 12) divided into two times (n = 6): Control, Group I/R, Group IPC + I/R, Group Ala-Gln + I/R, Group Ala-Gln + IPC + I/R. Times: T1 (infrarenal-aorta clamping ischemia-4h); T2 (ischemia-4h plus reperfusion-1h). Pulmonary myeloperoxidase (MPO) and plasma TBARS concentrations were measured. Data expressed as mean  standard-deviation, analyzed by Studentâs t-test and ANOVA/Tukeyâs post-test. P-values < 0,05 were considered significant. Increased MPO concentrations in ischemic group and in I/R group occurred as compared to control. Reduction in MPO concentrations happened in ischemic groups pre-treated with either Ala-Gln or IPC. I/R induced no change in MPO concentrations in groups pre-treated with either Ala-Gln or IPC. Pre-treating with the two procedures showed increased MPO at both times studied. Reduction in TBARS concentrations occurred in Ala-Gln pre-treated group, whereas significant elevation was observed when Ala-Gln and IPC were associated in ischemic animals. Ischemia/reperfusion induced elevation of plasma TBARS. Pre-treatment with either Ala-Gln or IPC protects against distant pulmonary lesion due to ischemia. The same did not occur in I/R lesion. Combining the two procedures aggravated inflammation indicated by increased MPO concentrations. Elevated TBARS concentrations in ischemic animals pre-treated with the two procedures indicate increased lipid peroxidation, whereas pre-treatment with Ala-Gln induced decreased TBARS concentrations.

Os neutrófilos representam a primeira linha de defesa do hospedeiro, atuando na contenção e eliminação de patógenos. Contudo, alterações na vida média, no excessivo recrutamento e ativação dos neutrófilos estão associados a danos teciduais e a doenças inflamatórias e autoimunes. A modulação das funções efetoras dos neutrófilos pode auxiliar no tratamento de tais patologias. Neste sentido, os produtos naturais constituem uma importante fonte de novas substâncias imunomoduladoras. Um estudo recente demonstrou que, a inibição do metabolismo oxidativo de neutrófilos pelo extrato etanólico bruto das folhas de Baccharis dracunculifolia (EEBBd) correlaciona-se com a proporção entre ácido cafeico (CaA) e outros compostos fenólicos contidos nesta amostra. Para dar prosseguimento à investigação do potencial imunomodulador do EEBBd e do CaA, os objetivos do presente estudo foram avaliar o efeito modulador desses produtos naturais: (i) em três funções efetoras de neutrófilos humanos - fagocitose, atividade microbicida e metabolismo oxidativo estimulado por agentes independentes de receptores (forbol-12-miristato-13-acetato; PMA) e dependentes apenas de receptores Fcgama (imunocomplexos não-opsonizados; IC) ou de receptores Fcgama associados a receptores do complemento (imunocomplexos opsonizados com complemento; IC-SHN); (ii) na atividade da mieloperoxidase (MPO); (iii) na expressão de receptores de membrana; (iv) e na captura (scavenger) de H2O2 e HOCl. O CaA foi mais efetivo do que o EEBBd em inibir a atividade da MPO e em capturar H2O2 e HOCl. A análise in silico revelou que o CaA bloqueia a entrada do sítio ativo da MPO através da interação com os resíduos Gln-91, His-95 e Arg-239; os dois últimos resíduos são essenciais para clivar o H2O2 e para estabilizar o sítio ativo, respectivamente. A eficiência dos agentes utilizados para estimular o metabolismo oxidativo, medido por quimioluminescência dependente de lucigenina e de luminol, ocorreu na seguinte ordem: PMA > IC-SHN > IC. Embora o PMA tenha sido o agente mais efetivo em estimular o metabolismo oxidativo, ambas as amostras (EEBBd e CaA) inibiram com maior intensidade esta função celular estimulada por PMA do que a mesma função estimulada por IC-SHN e IC. Além disso, ambas, EEBBd e CaA, não alteraram os níveis de expressão dos receptores TLR2, TLR4, CD16, CD32, e CD11b/CD18. Nas maiores concentrações avaliadas, EEBBd (50 ug/mL) e CaA (90 ug/mL) não foram citotóxicos para os neutrófilos. O EEBBd inibiu intensamente a capacidade fagocítica e reduziu discretamente a capacidade microbicida dos neutrófilos frente à Candida albicans. Portanto, o CaA contribui para ação inibitória do EEBBd no metabolismo oxidativo e na atividade da MPO, mas não na capacidade fagocítica e microbicida de neutrófilos. Por fim, o efeito imunomodulador do CaA e do EEBBd não é mediado por alterações na viabilidade celular ou na expressão de receptores de membrana em neutrófilos. O conjunto de resultados obtidos pode auxiliar na elucidação do mecanismo de ação destes produtos naturais sobre as funções efetoras de neutrófilos, bem como no desenvolvimento de novos fármacos para o tratamento de doenças inflamatórias mediadas pela ativação exacerbada de neutrófilos. / Neutrophils represent the first line of host defense that acts in the containment and clearance of pathogens. However, changes in life span and excessive recruitment and activation of neutrophils are associated with tissue damage and inflammatory and autoimmune diseases. Modulation of the effector functions of neutrophils can help to treat these pathologies. In this sense, natural products constitute an important source of novel immunomodulating compounds. A recent study has demonstrated that the neutrophil oxidative metabolism inhibition by the crude ethanol extract of Baccharis dracunculifolia (EEBBd) leaves correlates with the ratio of caffeic acid (CaA) to other phenolic compounds that exist in it. To continue investigating the immunomodulating potential of EEBBd and CaA, the present study aimed to examine whether these natural products modulate: (i) three effector functions of human neutrophils phagocytosis, microbial killing, and oxidative metabolism elicited by a receptor-independent stimulus (phorbol-12-myristate-13-acetate; PMA) and by receptor-dependent stimuli that bind Fcgama receptors alone (non-opsonized immune complexes; IC) or in combination with complement receptors (complement-opsonized immune complexes; IC-SHN); (ii) myeloperoxidase (MPO) activity; (iii) expression of membrane receptors; (iv) H2O2 e HOCl scavenging. CaA was more effective than EEBBd in inhibiting MPO activity and scavenging H2O2 and HOCl. The in silico analysis revealed that CaA blocks the entrance of the active site of MPO through the interaction with Gln-91, His-95, and Arg-239; the two last residues are essential to cleave H2O2 and stabilize the active site, respectively. The agents used to stimulate the oxidative metabolism, as measured by the lucigenin- and luminol-dependent chemiluminescence assays, acted in the following ranking order of efficiency: PMA > IC-SHN > IC. Although PMA was the most efficient agent at stimulating the neutrophil oxidative metabolism, both samples (EEBBd and CaA) suppressed the PMA-induced oxidative metabolism more effectively than they suppressed the same cell function elicited by IC-SHN and IC. Both EEBBd and CaA did not alter the levels of TLR2, TLR4, CD16, CD32, and CD11b/CD18 receptors expression. At the highest concentrations tested, EEBBd (50 ug/mL) and CaA (90 ug/mL) were not toxic towards neutrophils. EEBBd strongly diminished the phagocytic capacity and slightly reduced the Candida albicans killing ability of neutrophils. In conclusion, CaA contributes to the EEBBd inhibitory action on the oxidative metabolism and MPO activity but not on the phagocytic capacity and microbial killing ability of neutrophils. Furthermore, the immunomodulating effect of CaA and EEBBd is not mediated by alterations in either cell viability or expression of membrane receptors in neutrophils. Together, the results can help to unravel the mechanism of action of these natural products on the effector functions of neutrophils, and to develop new drugs to treat inflammatory diseases mediated by neutrophil overactivation.

O Ácido Indol Acético (AIA) é um hormônio, denominado auxina e há uma correlação direta entre o efeito citotóxico do AIA e da atividade da peroxidase nas células animais. Os Neutrófilos apresentam uma alta atividade de peroxidase e o AIA gera uma mudança ultra-estrutural e morte destas células em cultura. Entretanto, estudos in vivo mostram que a administração de AIA em baixas doses não promove um efeito prooxidante em neutrófilos e esta suplementação aumenta o englobamento de partículas de Zymosan por estas células. No presente estudo foram avaliados os efeitos da administração do AIA na capacidade fagocitária e na integridade celular de neutrófilos de ratos, observando os seguintes parâmetros: i) capacidade fagocitária – englobamento e morte de Staphylococcus aureus; ii) integridade celular – integridade da membrana plasmática, fragmentação de DNA e potencial transmembrana mitocondrial e iii) atividade de mieloperoxidase. O tratamento aplicado com AIA não apresentou alteração significante na capacidade de englobamento e morte de S. aureus pelos neutrófilos quando aos controles. A integridade celular e atividade de mieloperoxidase nos neutrófilos não foram alteradas pela suplementação com AIA comparadas aos controles. A administração de AIA em baixas doses não mostrou efeito na morte de S. aureus pelos neutrófilos o mesmo também não alterou a integridade celular e a atividade da mieloperoxidase destas células. / Indole acetic acid is (IAA) a hormone termed auxins and there is a direct correlation between the cytotoxic effect of IAA and the peroxidase activity of the animal cells. Neutrophils present a higher peroxidase activity and the IAA leads to marked ultra structural changes and death on these cells in culture. However studies in vivo show that IAA administration at low doses does not promoting a prooxidant effect on neutrophil and this supplementation to increase of the engulfment of Zymosan particles by these cells. In present study were evaluated the effect of IAA administration in the phagocytic capacity and cellular integrity on rat’s neutrophils from the following parameters: i) phagocytic capacity – engulfment and killing of the Staphylococcus aureus; ii) cellular integrity – plasma membrane integrity, DNA fragmentation and mitochondrial transmembrane potential and iii) myeloperoxidase activity. The IAA treatment imposed did not show another significant alteration in the S. aureus engulfment and killing capacity by neutrophils to compare with controls. The cellular integrity and myeloperoxidase activity in the neutrophils did not have alteration by IAA supplementation to compare with the controls. In conclusion the IAA administration at low doses did not show effective action in S. aureus killing by neutrophils and the same time as did not alter the cellular integrity and myeloperoxidase activity by this cell.

1. SUMMARYMyeloperoxidase (MPO) which belongs to the peroxidase family, is found in mammalian neutrophils. This heme enzyme contributes to the production of (pseudo)halogenous acid such as HOCl which oxidizes proteins, cell membrane, DNA and RNA causing death for the pathogens. It has an antimicrobial effect due to HOCl secreting inside the phagosomes of the neutrophils, whereas it will be released outside neutrophils causing oxidative damages for the host tissues. Proteins, lipids, lipoproteins, DNA and RNA are potential targets of the MPO resulting in several chronic syndromes. Many researchers have discovered the harmful effects of MPO and its products demonstrating its role in many inflammatory chronic diseases such as: Cardiovascular diseases as in atherosclerosis. MPO contribution in atherosclerosis development has been demonstrated. Neurodegenerative diseases also was related to MPO: such as Alzheimer’s disease (AD), multiple sclerosis (MSc) and Parkinson’s disease The enzyme has been also pointed out in other diseases such as renal disease and cancer.For these reasons, MPO as a target of drug discovery has attracted the attention of many researchers. X-ray 3D structures were resolved for this enzyme, biological activity and mechanism of action were investigated in depth, and many medicinal chemists have investigated and screened for new MPO inhibitors. Indeed, this cumulative work including X-ray data, the role of MPO in different pathologies, MPO inhibitory mechanism of action, screening and various chemical entities that inhibit MPO, provided sufficient elements to start a new drug design and drug discovery process on MPO.The aim of the present study was to apply a rational drug design approach to the myeloperoxidase inhibition: from in silico to pharmacological activity. This includes:─ Conducting high throughput virtual screening in order to find new potential hits to inhibit MPO followed by mechanism of inhibition determination. ─ Selecting one hit and then implementing a whole pharmacomodulation process in order to increase the potency of the inhibition greater than the starting hit and to improve the selectivity.Firstly, a rational drug design process was launched to find new hits using high throughput virtual screening. The chosen database for the screening was ASINEX database published in ZINC.X-ray structure of human peroxidase complexed to cyanide and thiocyanate (PDB 1DNW) was selected to conduct High-Throughput Virtual Screening (HTVS). Three successive protocols with different levels of accuracy in the docking and scoring processes were used starting with HTVS, followed by Standard Precision (SP) and finally with Xtra Precision (XP). The quality of the docking process performed was validated by docking a set of 60 chosen molecules of varying chemical structure and known as MPO inhibitors. From the result of the HTVS conducted on 1,350,000 compounds, the 100 best compounds were selected. Among them, 81 molecules were available for purchase from ASINEX, those compounds were tested with a MPO inhibition assay. Thirty-two compounds (39 %) were active, but only 8 compounds were selected, featuring different chemical structures with IC50 values ranging between 0.46 ± 0.07 and 12 ± 3 μM. Among these molecules, two compounds were the best and considered as hits. One has purinedione structure which is similar with the structure of thioxanthine derivatives (F9, IC50=0.46±0.07μM). The second compound has a hexahydropyrimidine structure (A1, IC50 = 0.5 ± 0.1 μM) The most common interactions found among all 8 docked ligands are the ionic bond with Glu102 and a stacking (shifted or not) with pyrrole ring D of the prosthetic group. Hydrogen bonds with Glu102, Thr100, Gln91, Arg239, or the propionate groups of the heme are also found in several docked geometries of the complexes. Interestingly, interactions with Glu102 and pyrrole ring D of the heme were also seen with fluorotryptamine derivatives and also salicylhydroxamic acid (SHA).For measuring MPO-dependent LDL oxidation, the two best compounds were tested. Compounds A1 and F9 showed good inhibition on MPO-dependent LDL oxidation (62 ± 6, 4.5 ± 0.9, 11 ± 2% and 11 ± 2, 2.6 ± 0.8, 6 ± 4%, respectively).Consequently, in order to determine the mechanism of inhibition transient-state kinetics were further investigated of all the 8 selected compounds.Both new lead compounds (A1 and F9) act as electron donors of both Compound I and Compound II of MPO. The reaction with Compound I was significantly faster (k2 ≫ k3). As a consequence, the enzyme is trapped in the Compound II state. They reversibly inactivated the enzyme blocking the harmful halogenation activity of MPO by transferring it to the MPO peroxidase cycle. In the present study, 8 active and reversible MPO inhibitors were selected. They act as electron donors of the oxidoreductase and efficiently block the halogenation activity with reversible inactivation. Two of the selected compounds have a submicromolar activity and inhibit MPO-dependent LDL oxidation. The high-throughput virtual screening was proved to be a successful tool to find new leads of MPO inhibitors. Conducting HTVS on a large-scale database enabled selection of novel scaffolds of MPO inhibitors never explored before in less time and at less expenses.Finding 8 new different chemical scaffolds through the first step of this drug discovery process led us to choose a new hit, compound A1, which has a hexahydropyrimidine structure, compound F9 was not chosen despite being more active due to its similarity to compounds discovered by AstraZeneca. To conduct pharmacomodulation, a validation of the docking procedure was conducted by comparing the X-ray structures of MPO with 2-(3,5-bistrifluoromethylbenzylamino)-6-oxo-1H-pyrimidine-5- carbohydroxamic acid, HX1, and SHA in the X-ray structures of human MPO in complex with cyanide and thiocyanate (PDB code 1DNW) as well as in complex with HX1 (PDB code 4C1M). Compound A1 was docked into both target structures 1DNW and 4C1M. In both cases, A1 showed almost the same poses.Based on the binding modes of A1, different strategies were developed for the design of derivatives which were mainly focused on the substitution of the aromatic rings A and B, the 2 amino groups and the side chain bridges.Pharmacomodulation was carried out on the hit A1 with different strategies:─ Investigating the role of hydroxyl groups on both aromatic rings─ Shifting the position of the amino groups in the hexahydropyrimidine ring to obtain piperazine derivatives and introduction of fluorine ─ Eliminating of one ring and of an amino group in the hexahydropyrimidine ring leading to piperidine derivatives ─ Opening the hexahydropyrimidine ring while keeping amine function and changing the length of the bridge between this amino group and aromatic ring as well as the impact of substitutions on aromatic rings.─ Hybridization of fluorotryptamine derivatives (effective MPO inhibitors) with hit A1.Based on of the docking experiments, 37 designed compounds were synthesized. The assessment of inhibition of the chlorination activity of MPO was undertaken over the 37 compounds. The hit A1 IC50 = 500 nM. The best compounds inhibiting MPO exhibited the following characteristics:─ One amino group on the bridge between aromatic rings was sufficient for the establishment of binding to Glu102 ─ The presence of three methylene groups between the secondary amine and an aromatic ring improved the inhibition of chlorination and thus decreased the IC50 values. These results showed that the position of the hydroxyl group is important. The distance between the hydrogen bond acceptor (HBA) group of one aromatic ring and the amino group is very important. The docking experiments of bisarylpropylamine derivatives showed ionic and hydrogen bonding interactions between Glu102 and hydroxyl group on aromatic ring linked to the longer side chain.─ Hybridized compounds which carry a fluorotryptamine instead of the phenol ring obtained by hybridization of hit A1 and the potent MPO inhibitors fluorotryptamine derivatives. Actually, compound 38 (which had one aromatic ring and a propyl bridge attached to indole ring) had an IC50 = 54 nM which was 10 times more powerful than the starting hit.The 3 best compounds were tested to examine the transient kinetics. They act as electron donors of the oxidoreductase and efficiently shift MPO from the chlorination cycle to the peroxidase cycle. Due to the similarity of the best compound 38 to serotonin it was tested with the two other best compounds on serotonin transporter (SERT) to examine the selectivity between MPO and SERT.Compound 38 had higher selectivity over MPO but the best selective compound was 28 that contains two aromatic rings carrying one hydroxyl and one fluorine.Electron density maps were conducted to predict the site of oxidation. Results suggested it occurs preferentially at the benzene ring or the indole ring in the best compounds.Determination of redox potentials for the synthesized compounds were tested. Best compounds act as electron donors allowing a one-electron reduction of Compound I.In conclusion, the present study succeeded through rational drug design including structure-based drug design and HTVS to identify new chemical entities for MPO inhibition. Eight compounds were more active than the starting hit A1 with submicromolar inhibition potency. Hybridization and structure based design also gave improvement of selectivity of inhibitors against MPO such as compound 38. Bis-arylalkylamine derivatives are a new group of MPO inhibitors with higher selectivity which could be a new hit for future development. / Doctorat en Sciences biomédicales et pharmaceutiques (Pharmacie) / info:eu-repo/semantics/nonPublished

No description available.

In our organism, mucous surfaces are important boundaries against the environmental milieu with defined fluxes of metabolites through these surfaces and specific rules for defense reactions. Major mucous surfaces are formed by epithelia of the respiratory system and the digestive tract. The heme peroxidases lactoperoxidase (LPO), myeloperoxidase (MPO), and eosinophil peroxidase (EPO) contribute to immune protection at epithelial surfaces and in secretions. Whereas LPO is secreted from epithelial cells and maintains microbes in surface linings on low level, MPO and EPO are released from recruited neutrophils and eosinophils, respectively, at inflamed mucous surfaces. Activated heme peroxidases are able to oxidize (pseudo)halides to hypohalous acids and hypothiocyanite. These products are involved in the defense against pathogens, but can also contribute to cell and tissue damage under pathological conditions. This review highlights the beneficial and harmful functions of LPO, MPO, and EPO at unperturbed and inflamed mucous surfaces. Among the disorders, special attention is directed to cystic fibrosis and allergic reactions.

The heme protein myeloperoxidase (MPO) is a major constituent of neutrophils. As a key mediator of the innate immune system, neutrophils are rapidly recruited to inflammatory sites, where they recognize, phagocytose, and inactivate foreign microorganisms. In the newly formed phagosomes, MPO is involved in the creation and maintenance of an alkaline milieu, which is optimal in combatting microbes. Myeloperoxidase is also a key component in neutrophil extracellular traps. These helpful properties are contrasted by the release of MPO and other neutrophil constituents from necrotic cells or as a result of frustrated phagocytosis. Although MPO is inactivated by the plasma protein ceruloplasmin, it can interact with negatively charged components of serum and the extracellular matrix. In cardiovascular diseases and many other disease scenarios, active MPO and MPO-modified targets are present in atherosclerotic lesions and other disease-specific locations. This implies an involvement of neutrophils, MPO, and other neutrophil products in pathogenesis mechanisms. This review critically reflects on the beneficial and harmful functions of MPO against the background of immune response.

No description available.

Dois importantes fatores inter-relacionados estão envolvidos na patogênese da doença periodontal: ativação do sistema imune e produção de peroxidases. Os objetivos deste estudo foram comparar os níveis da atividade do sistema peroxidase presentes no fluido gengival (MPO/FG) e saliva da parótida (POS) em pacientes portadores de periodontite crônica em relação a pacientes periodontalmente saudáveis e avaliar o efeito do tratamento periodontal não cirúrgico nestes indivíduos nestes parâmetros enzimáticos. MATERIAL E MÉTODO: Foram coletados dados dos parâmetros clínicos periodontais e amostras de FG e saliva da glândula parótida de 17 pacientes clinicamente saudáveis (GC) e de 17 pacientes portadores de periodontite crônica generalizada (GP) antes e depois do tratamento periodontal pareados em idade e sexo. As atividades de MPO/FG e POS Parótida foram avaliadas por espectofotometria. RESULTADOS: O GP apresentou valores maiores nos parâmetros clínicos periodontais em relação ao GC, sendo que os mesmos foram reduzidos após tratamento periodontal. Além disso, o GP apresentou valores mais elevados de atividade de MPO no FG (p=0,04) do que o GC. Após tratamento periodontal os níveis de MPO/FG (p<0,001) e POS parótida (p=0,013) foram reduzidos significativamente. No GP houve correlação negativa e significativa entre POS da parótida e MPO no FG (r=-0,59, p=0,02). CONCLUSÕES: Na doença periodontal, as atividades de MPO no FG são maiores quando comparados ao grupo controle, e tanto de MPO/FG e POS parótida são reduzidas após tratamento periodontal. / Two important and interrelated factors are involved in the pathophysiology of periodontal diseases: the activation of immune system and the production of peroxidases. The objectives of this study were to examine the peroxidase activities present in Gingival Crevicular Fluid (MPO/GCF) and in Parotid Saliva (POS) in patients with generalized chronic periodontitis with healthy controls and to compare the effects of periodontal therapy on enzyme activities. MATERIAL AND METHOD: Periodontal clinical measurements, parotid saliva and GCF samples were obtained of 17 age-matched healthy controls (PC) and 17 patients with chronic periodontal disease (PD) before treatment and after periodontal treatment. The MPO/GCF and POS parotid activities were determined spectrophotometrically. RESULTS: In PD group, clinical parameters, MPO/GCF (p=0,04) activities presented higher values than controls. After periodontal treatment levels of MPO/GCF (p<0.001) and POS parotid (p=0,013) were significantly reduced. In PD there was significant negative correlation between POS and MPO in the parotid FG (r =-0,59, p=0,02). CONCLUSIONS: In periodontal disease MPO/GCF presented higher levels than controls and MPO/GCF and POS parotid are reduced after treatment.