Neutrophils are important innate immune effector cells that primarily function during infection by engulfing and killing pathogens using a combination of toxic granule components and reactive oxygen species (ROS) generated by the NADPH oxidase. Francisella tularensis is a Gram-negative bacterium and the causative agent of tularemia, an infectious disease that, in the absence of treatment, results in 30-60% mortality. A closely related species, F. novicida, does not cause human disease but causes a tularemia-like illness in mice and productively infects human and murine cells in vitro; thus this organism is often employed as a model. In our previous work, we have shown that virulent and avirulent F. tularensis enters neutrophils without inducing a respiratory burst, as the NADPH oxidase fails to assemble on bacterial phagosomes. Further, this pathogen inhibits enzyme activity upon subsequent neutrophil stimulation despite successful oxidase assembly, indicating that F. tularensis employs multiple mechanisms to inhibit the NADPH oxidase. It remains unknown, however, whether F. novicida retains these mechanisms of oxidase inhibition, or whether its inability to modulate neutrophil function partially accounts for its avirulence in humans. Additional work has suggested a potential role for Francisella acid phosphatases and catalase genes in inhibited production and detoxification of neutrophil-derived ROS, respectively. In the current study, we employ subjective and objective techniques to evaluate the magnitude and location of ROS generation during infection with F. tularensis LVS, F. novicida, or F. novicida mutants acpA or katG. Our results demonstrate that serum-opsonized F. novicida, but not LVS, induced a prominent respiratory burst that coincided with oxidase assembly and intraphagosomal superoxide production in bacterial phagosomes. Furthermore, our data show for the first time that opsonized F. novicida, but not LVS, engaged Fc-gammaRIII (CD16) during phagocytosis by neutrophils suggesting that this receptor may play a role in signaling events that lead to respiratory burst induction. Despite its inability to evade burst induction, F. novicida inhibited post-assembly oxidase activity following sequential stimulation of neutrophils, similar to F. tularensis strains. Finally, we conclude that acpA and katG do not play a significant role in F. novicida-neutrophil interactions as these mutants did not induce a stronger respiratory burst during phagocytosis, and their ability to inhibit post-assembly NADPH oxidase activity and survive in neutrophils was indistinguishable from wild type organisms. Thus, these data strongly suggest that differential opsonization of F. novicida compared to F. tularensis results in engagement of specific receptors that function to activate these cells during infection. Further, the retained ability of F. novicida to inhibit post-assembly oxidase activity confirms that Francisella utilize two independent mechanisms by which they modulate NADPH oxidase function. Finally, our conclusions that acpA and katG are disposable for these interactions with neutrophils suggest that F. novicida encodes other important genes that enable them to productively infect these cells.

Diss. (sammanfattning) Umeå : Univ., 2003. / Härtill 4 uppsatser.

Diss. (sammanfattning) Umeå : Umeå universitet, 2006. / Härtill 4 uppsatser.

Resumo:Em humanos, a imunossupressão que ocorre em pacientes urêmicos está associada com a disfunção dos neutrófilos causada pelas toxinas urêmicas. O p-cresol se acumula no sangue de pacientes com insuficiência renal crônica (IRC) promovendo a inibição do metabolismo oxidativo dos neutrófilos. O presente trabalho teve como objetivo mensurar as concentrações plasmáticas de p-cresol em cães hígidos e com IRC e testar a hipótese de que o p-cresol livre causa disfunção neutrofílica. Para tal, foi quantificada a concentração plasmática de p-cresol por cromatografia de fase líquida (HPLC) em cães hígidos e com IRC no estágio IV. Também foi avaliado in vitro o efeito específico do p-cresol sobre o metabolismo oxidativo e a taxa de apoptose de neutrófilos de cães hígidos, considerando-se a maior concentração plasmática desta toxina observada in vivo em cães com IRC. Neutrófilos isolados de 20 cães saudáveis foram incubadas em meio de RPMI puro ou enriquecido com p-cresol e com plasma de cães com IRC. O metabolismo oxidativo dos neutrófilos foi avaliado por citometria de fluxo capilar utilizando as sondas hidroetidina e 2′,7′- diacetato de diclorofluoresceína com ou sem estímulos de acetato miristato de forbol e n-formil-metionil-leucilfenilalanina. A apoptose e a viabilidade dos neutrófilos foi quantificada em citômetro de fluxo capilar utilizando sistema Anexina V-PE, com ou sem estímulo de camptotecina. Cães com IRC apresentaram in vivo o quadro de estresse oxidativo e aumento do p-cresol plasmático. A maior concentração do p-cresol causou disfunção neutrofílica in vitro. Conclui-se que p-cresol pode estar envolvido com quadro de estresse oxidativo in vivo e que sua alta concentração diminua a viabilidade e leve a uma redução da produção de espécies reativas de oxigênio / Abstract:In humans, the immunosuppression observed in uremic patients is associated with the neutrophil dysfunction caused by uremic toxins. P-cresol accumulates in the blood of patients with chronic renal failure (CRF) promoting the inhibition of neutrophil oxidative metabolism. This study aimed to measure the plasma concentrations of p-cresol in dogs with CRF and test the hypothesis that free p-cresol causes neutrophil dysfunction. To this end, plasma concentration of p-cresol was determined using high pressure liquid chromatography (HPLC) in dogs presenting stage IV of CRF. The in vitro specific effect of p-cresol on the oxidative metabolism and apoptosis rate of neutrophils from healthy dogs was also evaluated, considering the highest plasma concentration of this toxin observed on the in vivo measurement of dogs with CRF. Isolated neutrophils from 20 healthy dogs were incubated in RPMI medium alone, supplemented with p-cresol or plasma from dogs with CRF. Neutrophil oxidative metabolism was assessed by capillary flow cytometry using the probes hydroethidine and 2',7'- dichlorofluorescein diacetate with or without stimulus with phorbol myristate acetate and N-formyl-methionyl-leucylphenylalanine. Apoptosis and viability of neutrophils were quantified also in capillary flow cytometry using Annexin V-PE system with or without stimulus with camptothecin. Dogs with CRF presented oxidative stress and increased plasma levels of p-cresol, the higher concentration of p-cresol caused in vitro neutrophil dysfunction. It can be concluded that p-cresol may be involved with in vivo oxidative stress that its higher concentration decreases the viability and lead to a reduced production of reactive oxygen species / Orientador:Paulo Cesar Ciarlini / Banca:Wagner Luis Ferreira / Banca:Alvaro José dos Santos Neto / Mestre

Resumo:Recentemente, foi relatado que na insuficiência renal crônica (IRC) canina ocorre estresse oxidativo e que a disfunção dos neutrófilos está associada ao aumento da apoptose. Dentre as muitas toxinas urêmicas que se concentram na IRC, há evidências em humanos de que as guanidinas inibem o metabolismo oxidativo dos neutrófilos, afetando a sua função bactericida. Uma revisão sistemática foi realizada sobre a relação entre os compostos guanidínicos e os neutrófilos em cães. Verificou-se que a literatura, sobre este tema, é escassa e contraditória, de modo que, foi investigado no presente estudo a relação entre a concentração de guanidina plasmática, a produção de superóxido e a apoptose de neutrófilos de cães com IRC. Aditivamente, foi investigado "in vitro" o efeito isolado do composto ácido guanidinoacético (AGA) sobre a produção de superóxido e a apoptose de neutrófilos de cães sadios. Foi possível comprovar que o grande aumento da guanidina plasmática observado em cães com IRC não está associado à alteração do metabolismo oxidativo e apoptose dos neutrófilos. O AGA inibiu o metabolismo oxidativo de neutrófilos de cães sadios sem afetar a viabilidade dessas células / Abstract:It has been recently reported that in canine chronic renal failure (CRF) there occurs oxidative stress, and that neutrophil dysfunction is associated with the increase of apoptosis. Among the many uremic toxins found in higher concentrations due to CRF, there is evidence - in humans - that guanidines inhibit the oxidative metabolism of neutrophils, affecting their bactericidal function. In this study, a systematic review of the relationship between guanidine compounds and neutrophils in dogs was undertaken. It was found that the literature on this subject is scarce and conflicting, which prompted this investigation of the relationship between the plasmatic concentration of guanidine, the production of superoxide, and the apoptosis of neutrophils in dogs with CRF. Morever, the effect of the isolated compound guanidine acetic acid (GAA) on the production of superoxide and on neutrophil apoptosis in healthy dogs was investigated in vitro. It was possible to verify that the large increase of plasmatic guanidine observed in dogs with CRF is not associated with the altered oxidative metabolism and the apoptosis of the neutrophils. The GAA inhibited the oxidative metabolism of the neutrophils in healthy dogs without affecting the viability of these cells / Orientador:Paulo Cesar Ciarlini / Banca:Fabiano Antonio Cadioli / Banca:Aureo Evangelista Santana / Mestre

Made available in DSpace on 2015-10-06T13:02:50Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-03-21. Added 1 bitstream(s) on 2015-10-06T13:19:28Z : No. of bitstreams: 1 000848868.pdf: 401988 bytes, checksum: 08ca73724d8938b9b116d34fb50815a0 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / In humans, the immunosuppression observed in uremic patients is associated with the neutrophil dysfunction caused by uremic toxins. P-cresol accumulates in the blood of patients with chronic renal failure (CRF) promoting the inhibition of neutrophil oxidative metabolism. This study aimed to measure the plasma concentrations of p-cresol in dogs with CRF and test the hypothesis that free p-cresol causes neutrophil dysfunction. To this end, plasma concentration of p-cresol was determined using high pressure liquid chromatography (HPLC) in dogs presenting stage IV of CRF. The in vitro specific effect of p-cresol on the oxidative metabolism and apoptosis rate of neutrophils from healthy dogs was also evaluated, considering the highest plasma concentration of this toxin observed on the in vivo measurement of dogs with CRF. Isolated neutrophils from 20 healthy dogs were incubated in RPMI medium alone, supplemented with p-cresol or plasma from dogs with CRF. Neutrophil oxidative metabolism was assessed by capillary flow cytometry using the probes hydroethidine and 2',7'- dichlorofluorescein diacetate with or without stimulus with phorbol myristate acetate and N-formyl-methionyl-leucylphenylalanine. Apoptosis and viability of neutrophils were quantified also in capillary flow cytometry using Annexin V-PE system with or without stimulus with camptothecin. Dogs with CRF presented oxidative stress and increased plasma levels of p-cresol, the higher concentration of p-cresol caused in vitro neutrophil dysfunction. It can be concluded that p-cresol may be involved with in vivo oxidative stress that its higher concentration decreases the viability and lead to a reduced production of reactive oxygen species

Made available in DSpace on 2015-10-06T13:03:21Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-01-17. Added 1 bitstream(s) on 2015-10-06T13:18:35Z : No. of bitstreams: 1 000848874.pdf: 475629 bytes, checksum: 8f3083521bd5dbb20833e54b2e295e0b (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / It has been recently reported that in canine chronic renal failure (CRF) there occurs oxidative stress, and that neutrophil dysfunction is associated with the increase of apoptosis. Among the many uremic toxins found in higher concentrations due to CRF, there is evidence - in humans - that guanidines inhibit the oxidative metabolism of neutrophils, affecting their bactericidal function. In this study, a systematic review of the relationship between guanidine compounds and neutrophils in dogs was undertaken. It was found that the literature on this subject is scarce and conflicting, which prompted this investigation of the relationship between the plasmatic concentration of guanidine, the production of superoxide, and the apoptosis of neutrophils in dogs with CRF. Morever, the effect of the isolated compound guanidine acetic acid (GAA) on the production of superoxide and on neutrophil apoptosis in healthy dogs was investigated in vitro. It was possible to verify that the large increase of plasmatic guanidine observed in dogs with CRF is not associated with the altered oxidative metabolism and the apoptosis of the neutrophils. The GAA inhibited the oxidative metabolism of the neutrophils in healthy dogs without affecting the viability of these cells

O objetivo foi avaliar a atividade funcional dos polimorfonucleares (PMN) do sangue de bezerros neonatos \"in vitro\" - metabolismo oxidativo induzida por: S. aureus, E. coli e PMA e fagocitose para S. aureus e E. coli, em citômetro de fluxo. Quinze animais avaliados nos tempos: t0 (antes da ingestão de colostro/leite); t1(até 48 hs. p.n); t2 (48 - 96 hs. p.n.); t3 (96 - 144 hs. p.n.); t4 (144-192 hs. p.n.); t5 (192-240 hs.p.n.) receberam quatro litros (grupo 1 - G1), dois litros de colostro ( grupo 2 - G2) e somente leite (grupo 3 - G3). O metabolismo oxidativo basal não diferiu em nenhum dos grupos e idades. Entre os grupos este foi menor em G1 do que em G3 (t3). Induzido pela S. aureus foi maior entre t1 e t3 (grupo 1), entre t2 e t3 (grupo 2) e sem diferenças (grupo 3). Entre os grupos G1 foi maior que G3 (t1). Induzido pela E.coli foi maior entre t1 e t3 (grupo 1), maior em t2 (grupo 2) e sem diferenças (grupo 3). Entre os grupos G1 foi maior que G2 e G3 (t1). O PMA estimulou a explosão respiratória em G1, G2 e G3 entre t0 e t5. Entre os grupos G1 foi menor para do que G2 e G3. A comparação entre metabolismo basal e induzido para G1 foi maior para PMA e S. aureus entre t0 e t5 e para E. coli entre t1 e t5; para G2 foi maior para o PMA entre t0 e t5, para S. aureus entre t0 e t3 e para a E. coli entre t2 e t4; para G3 foi maior para o PMA e S.aureus entre t0 e t5 e para a E. coli entre t3 e t5. A fagocitose induzida pela S. aureus foi maior nos tempos t1, t2 e t4 (grupo1) e o percentual de fagocitose foi maior após t0; para o grupo 2, foi maior em t2 e t3 e o percentual foi maior após t0; para o grupo 3, não diferiram entre os tempos. Entre os grupos G1 foi maior que G2 e G3 (t4) e o percentual foi maior para G1 e G2 (t3) do que G3 e maior para G1 do que G2 (t5). A fagocitose induzida pela E. coli e o percentual de fagocitose não diferiram em nenhum grupo. Entre os grupos G1 foi maior do que G3 (t0) e o percentual foi maior para G1 do que G2 (t2). Conclusão: o colostro não interferiu no metabolismo oxidativo basal e estimulado pelo PMA, a S. aureus estimulou o metabolismo oxidativo e a fagocitose antes e após a ingestão de colostro. A E. coli não induziu o metabolismo oxidativo (G3) e não foi eficiente para estimular a fagocitose. Não ficou esclarecida a influência da idade sobre a atividade dos PMNs. O fornecimento de quatro litros de colostro melhora resposta funcional dos PMNs para as bactérias. / The aim of this study was to evaluate \"in vitro\" functional activities of neonatal calves blood polymorphonuclear leukocytes (PMNs) - respiratory burst and phagocytosis induced by S.aureus, E.coli and PMA, measured by flow cytometry. Fifteen calves were tested at times: t0 (before milk/colostrum ingestion); t1 (until 48 hours post partum); t2 (48-96 hrs p.p.); t3 (96 - 144 hrs. p.p.); t4 (144-192 hrs. p.p.); t5 (192-240 hrs. p.p.) and the groups intakes were 4 liters of colostrum (group 1), 2 liters of colostrum (group 2) and only milk (group 3). The basal respiratory burst did not differ among groups but it was lower in G1 than G3 (t3). The burst induced by S.aureus was higher between t1 and t3 (G1) and t2 and t3 (G2) and showed no difference (G3). The G1 values were higher than G3 (t1). E.coli induced higher values between t1 and t3 (G1), higher on t2 (G2) and showed no difference (G3). Among groups G1 was higher than G2 and G3 (t1). The PMA induced the respiratory burst in G1, G2 and G3 between t0 and t5. Among groups G1 was lower in G2 than G3. The induced basal metabolism was compared and G1 was higher to PMA and S.aureus between t0 and t5 and to E.coli between t1 and t5. The G2 showed higher values to PMA between t0 and t5, to S.aureus between t0 and t3 and E.coli between t2 and t4. The G3 showed higher values in PMA and S.aureus between t0 and t5 and E.coli between t3 and t5. The S.aureus induced phagocytosis was higher on t1, t2 and t4 (G1) and the phagocystosis percentage was higher after t0. G2 groups showed higher values on t2 and t3 and higher percentage after t0. G3 had no difference on times. G1 showed higher values than G2 and G3 (t4) and G1 and G2 (t3) had higher percentage than G3 with G1 higher than G2 (t5). The E.coli induced phagocytosis and its percentage did not differ among groups. G1 was higher than G3 (t0) and G1 showed higher phagocytosis percentage than G2 (t2). Conclusion: the colostrum did not affect either, the basal respiratory burst and the one stimulated by PMA. S. aureus stimulated the respiratory burst and phagocytosis before and after the colostrum intake. E.coli did not induce the respiratory burst (G3) and did not stimulate the phagocytosis. The age influence in PMNs activity was not totally clarified. The intake of 4 litters of colostrum increases the PMNs activity against the species of bacteria studied.

Neutrophil granulocytes play an important role in the host defence against invading microorganisms and constitute the frontline of defence within the innate immune system and are among the first cells to arrive at the site of inflammation. Effective phagocytosis and killing of invading pathogens by neutrophils is of significant importance for successful resistance to infectious diseases. An important complication in diabetes mellitus is an increased sensitivity to infections and increased tissue damage, leading to many secondary diseases. This may in part be explained by an impaired function of neutrophil granulocytes. Since the exact mechanisms underlying defective neutrophil function in diabetes mellitus are not fully understood, the aim of the present study was to investigate the effects of elevated glucose and insulin concentrations on phagocytosis of opsonized yeast and on production of reactive oxygen metabolites (ROS) in normal human neutrophils. Elevated D-glucose concentrations (15-25 mM) inhibited the phagocytosis of C3bi- or IgG-opsonized yeast particles, which was neither an osmotic effect nor an effect due to reduced binding of opsonized yeast particles to the neutrophils. Inhibition of protein kinase C (PKC) by GF109203X or Go6976 could completely reverse the inhibitory effect of 25 mM D-glucose on phagocytosis. Diacylglycerol (DAG) dose-dependently inhibited phagocytosis and suboptimal inhibitory concentrations of DAG and glucose showed an additive inhibitory effect. Elevated concentrations of insulin (80-160 μU/ml) also inhibited neutrophil phagocytosis, an effect shown in part to be due to a delayed phagocytosis process. Insulin was found to increase the accumulation of cortical F-actin, without affecting the total cellular F-actin content. The PKCalpha/beta inhibitor, Go6976, abolished the insulin-mediated increase in cortical F-actin content and both Go6976 and the PKCalpha/beta/delta/epsilon-specific inhibitor GF109203X reversed the inhibitory effects of insulin on phagocytosis. The inhibition of phagocytosis by either glucose or insulin resulted in an expected reduction of intracellular respiratory burst. However, the extracellular release of ROS during phagocytosis was increased by insulin, but inhibited by glucose. The ability of insulin to enhance ROS production was found to be F-actin dependent. Data suggests that glucose inhibited intracellular respiratory burst activation by interfering with intracellular signaling downstream of PKC activation, whereas extracellular release of ROS was inhibited by glucose upstream of PKC signaling. Taken together these results suggest that both hyperglycemia and hyperinsulinemia inhibit complement receptor and Fc receptor-mediated phagocytosis in human neutrophils. Insulin, but not glucose, also induced an enhanced extracellular release of ROS during phagocytosis. The combination of reduced phagocytosis and alterations in ROS production may possibly explain both the increased sensitivity to infections and tissue damage seen in type 2 diabetes.

No description available.