Triagem neonatal para imunodeficiência combinada grave / Newborn screening for severe combined immunodeficiency

As imunodeficiências primárias (IDP) são uma área recente e aindapouco conhecida da medicina. Pacientes com IDP apresentam, na maior parte dos casos, infecções graves e recorrentes de início precoce, elevada morbidade e mortalidade, resultando frequentemente em sequelas,elevado custo social e sofrimento dos familiares. Embora na Américado Norte e Europa se estime que sua incidência seja semelhante à dafenilcetonúria e do hipotireoidismo congênito (afecções congênitas quecontam com triagem neonatal), ainda faltam dados quanto à sua real incidência na população brasileira.O projeto em desenvolvimento no Instituto de Ciências Biomédicasda USP e Escola Paulista de Medicina da UNIFESP, visa contribuir para o avanço na implementação de testes de triagem neonatal para asimunodeficiências primárias, mais especificamente, ImunodeficiênciasCombinadas Graves, que constituem um grupo de doenças com diferentesdefeitos genéticos, que evoluem para o óbito precoce se não foremdiagnosticadas e tratadas a tempo e a Síndrome de DiGeorge, que seestima ser a síndrome genética de deleção mais prevalente (1:3.000nascidos vivos).Seguindo esta linha de pensamento, nossa hipótese é que no Brasilexiste um número desconhecido de pacientes com IDP não diagnosticadosou subdiagnosticados que após a implementação de técnicas de detecção molecular por triagem neonatal para a SCID e síndrome de DiGeorge, passarão a ser contabilizados e tratados corretamente, diminuindo portanto,a morbidade e mortalidade.

Primary immunodeficiency disorders (PIDD) are a recently-recognizedand relatively unstudied area of medicine. Patients with PIDD frequentlypresent with the early onset of severe recurrent infections, high morbidityand mortality, frequently resulting in sequelae, high social cost, andfamily burden. While in North America and Europe it is estimated thatits incidence is similar to phenylketonuria and congenital hypothyroidism(congenital disorders that rely on neonatal screening), there is a lack ofdata on its actual incidence in Brazil.The project being developed at Institute of Biomedical Sciences,University of São Paulo and Federal University of São Paulo MedicalSchool, aims to contribute to the implementation of neonatal screeningtests for primary immunodeficiencies. More specifically, severe combinedimmunodeficiencies, a group of diseases with several genetic defects,may progress to early death if not diagnosed and treated early in life;and DiGeorge Syndrome, which is estimated to be the most prevalentgenetic deletion syndrome (1:3,000).Our hypothesis is that, in Brazil there is an unknown number ofpatients with undiagnosed or underdiagnosed disease, which, after theimplementation of detection techniques through newborn screening forSCID and DiGeorge Syndrome, will be accounted for and treated properly,reducing therefore, the morbidity and mortality.

Diapocynin versus apocynin as pretranscriptional inhibitors of NADPH oxidase and cytokine production by peripheral blood mononuclear cells.

Apocynin has been extensively used as an inhibitor of NADPH oxidase (NOX) in many experimental models using phagocytic and non-phagocytic cells. Currently, there is some controversy about the efficacy of apocynin in non-phagocytic cells, but in phagocytes the reported results are consistent, which could be due to the presence of myeloperoxidase in these cells. This enzyme has been proposed as responsible for activating apocynin by generating its dimer, diapocynin, which is supposed to be the active compound that prevents NADPH oxidase complex assembly and activation. Here, we synthesized diapocynin and studied its effect on inhibition of gp91(phox) RNA expression. We found that diapocynin strongly inhibited the expression of gp91(phox)mRNA in peripheral blood mononuclear cells (PBMC). Only at a higher concentration, apocynin was able to exert the same effect. We also compared the apocynin and diapocynin efficacy as inhibitors of tumor necrosis factor-alpha (TNF-alpha) and interleukin-10 (IL-10) production in response to lipopolysaccharide (LPS)-activated PBMC. Although apocynin did inhibit TNF-alpha production, diapocynin had a much more pronounced effect, on both TNF-alpha and IL-10 production. In conclusion, these findings suggest that the bioconversion of apocynin to diapocynin is an important issue not limited to enzymatic activity inhibition, but also for other biological effects as gp91(phox) mRNA expression and cytokine production. Hence, as diapocynin can be easily prepared from apocynin, a one-step synthesis, we recommend its use in studies where the biological effects of apocynin are searched.

The reactivity of ortho-methoxy-substituted catechol radicals with sulfhydryl groups: contribution for the comprehension of the mechanism of inhibition of NADPH oxidase by apocynin.

Redox processes are involved in the mechanism of action of NADPH oxidase inhibitors such as diphenyleneiodonium and apocynin. Here, we studied the structure-activity relationship for apocynin and analogous ortho-methoxy-substituted catechols as inhibitors of the NADPH oxidase in neutrophils and their reactivity with peroxidase. Aiming to alter the reduction potential, the ortho-methoxy-catechol moiety was kept constant and the substituents at para position related to the hydroxyl group were varied. Two series of compounds were employed: methoxy-catechols bearing electron-withdrawing groups (MC-W) such as apocynin, vanillin, 4-nitroguaiacol, 4-cyanoguaiacol, and methoxy-catechol bearing electron-donating groups (MC-D) such as 4-methylguaiacol and 4-ethylguaiacol. We found that MC-D were weaker inhibitors compared to MD-W. Furthermore, the radicals generated by oxidation of MC-W via MPO/H(2)O(2), but not for MC-D, were able to oxidize glutathione (GSH) as verified by the formation of thiyl radicals, depletion of GSH, and recycling of the ortho-methoxy-catechols during their oxidations. The capacity of oxidizing sulfhydryl (SH) groups was also verified when ovalbumin was incubated with MC-W, but not for MC-D. Since the effect of apocynin has been correlated with inactivation of the cytosolic fractions of the NADPH oxidase complex and its oxidation during the inhibitory process develops a special role in this process, we suggest that the close relationship between the reactivity of the radicals of MC-W compounds with thiol groups and their efficacy as NADPH oxidase inhibitor could be the chemical pathway behind the mechanism of action of apocynin and should be taken into account in the design of new and specific NADPH oxidase inhibitors.

Chemiluminescent determination of leukocyte alkaline phosphatase: an advantageous alternative to the cytochemical assay.

The determination of leukocyte alkaline phosphatase (LAP) is used as an aid to diagnose many diseases in the laboratory. For example, it can be used to distinguish chronic myeloid leukemia (CML) from other myeloproliferative disorders (particularly myelofibrosis and polycythemia) and leukemoid reactions (LR). Traditionally, this test is performed with the use of subjective cytochemical assays that assign a score to the level of LAP. Here we present a nonsubjective, quantitative, sensitive, and inexpensive chemiluminescent technique that determines LAP based on the commercial reagent Immulite (AMPPD). To validate this methodology, intact leukocytes obtained from 32 healthy subjects, nine CML patients, and nine LR patients were submitted to the optimized protocol. By measuring the light emission elicited by four concentrations of neutrophils, we were able to estimate the activity of LAP per cell (the slope of the curve obtained by linear regression). A high linear correlation was found between the chemiluminescent result (slope) and the cytochemical score. The slope for healthy individuals ranged between 0.61 and 8.49 (10(-5) mV.s/cell), with a median of 2.04 (10(-5) mV.s/cell). These results were statistically different from those of CML patients (range=0.07-1.75, median=0.79) and LR patients (range= 3.84-47.24, median=9.58; P<0.05).

The oxidation of apocynin catalyzed by myeloperoxidase: proposal for NADPH oxidase inhibition.

Apocynin has been used as an efficient inhibitor of the NADPH oxidase complex and its mechanism of inhibition is linked to prior activation through the action of peroxidases. Here we studied the oxidation of apocynin catalyzed by myeloperoxidase (MPO) and activated neutrophils. We found that apocynin is easily oxidized by MPO/H2O2 or activated neutrophils and has as products dimer and trimer derivatives. Since apocynin impedes the migration of the cytosolic component p47phox to the membrane and this effect could be related to its conjugation with essential thiol groups, we studied the reactivity of apocynin and its MPO-catalyzed oxidation products with glutathione (GSH). We found that apocynin and its oxidation products do not react with GSH. However, this thiol compound was efficiently oxidized by the apocynin radical during the MPO-catalyzed oxidation. We suggest that the reactivity of apocynin radical with thiol compounds could be involved in the inhibitory effect of this methoxy-catechol on NADPH oxidase complex.