Pathogenic Gram-negative Yersinia species preferentially target and inactivate phagocytic cells of the innate immune defense by translocation of effector Yersinia outer proteins (Yops) into the cells via a type III secretion system. This indicates that inactivation and avoidance of the early innate immune response is an efficient way for Yersinia species to avoid elimination and to cause diseases ranging from mild gastroenteritis (Y. pseudotuberculosis and Y. enterocolitica) to plague (Y. pestis). In this project, we aimed to study the interaction between enteropathogenic Y. pseudotuberculosis and phagocytic cells during early infection. In situ interaction studies on infected intestinal tissues showed that Y. pseudotuberculosis mainly interacts with dendritic cells (DCs) in lymphoid tissues of the intestine during initial infection. After massive recruitment of polymorphonuclear neutrophils (PMNs) to the infected tissues, wild-type (wt) bacteria also interacted with this phagocyte. In contrast to the wt, mutants lacking the anti-phagocytic effectors YopH and YopE are avirulent in mice and unable to spread systemically. Interestingly, our interaction assay showed that these mutants not only interacted with DCs, but also with PMNs during the initial stage of infection. Thus, indicating that Y. pseudotuberculosis can avoid interaction with PMNs during early infection and that this is Yop-dependent. In a phagocytosis assay Y. pseudotuberculosis was demonstrated to inhibit internalization by DCs in a YopE-dependent manner, while both YopH and YopE were shown to be involved in the blocking of phagocytosis by macrophages and PMNs. Thus, indicating that YopH has cell type-specific effects. To further investigate the role of DCs during initial stages of infection, a mouse DC depletion model (CD11c-DTRtg) was applied. However, the DTx-mediated depletion of DCs in CD11c-DTRtg mice induced neutrophilia and the model could not give a definite answer to whether DCs play an important role in either restricting or stimulating progression of Y. pseudotuberculosis infection. To investigate involvement of PMNs during early infection mice were injected with the depleting antibody α-Ly6G. In absence of PMNs wt, as well as yopH and yopE mutants became more virulent, which further supports the importance of these Yops for the ability of Y. pseudotuberculosis to disseminate from the initial infection sites in the intestine to cause systemic disease. In summary, our studies show that inhibiting internalization and maturation of DCs and avoiding phagocytosis by and interaction with macrophages and PMNs during the early stages of infection are important virulence strategies for Y. pseudotuberculosis to be able to colonize tissues, proliferate and disseminate systemically.

Neutrophil (PMN) inflammatory functions, including cell adhesion, diapedesis, and phagocyto-sis, are dependent on the mobilization and release of various intracellular granules/vesicles. In this study, I found that treating PMN with damnacanthal, a Ras family GTPase inhibitor, resulted in a specific release of secondary granules, but not primary or tertiary granules, and caused dy-sregulation of PMN chemotactic transmigration and cell surface protein interactions. Analysis of the activities of Ras members identified Ral GTPase as a key regulator during PMN activation and degranulation. In particular, Ral was active in freshly isolated PMN, while chemoattractant stimulation induced a quick deactivation of Ral that correlated with PMN degranulation. Over-expression of a constitutively active Ral (Ral23V) in PMN inhibited chemoattractant-induced secondary granule release. By subcellular fractionation, I found that Ral, which was associatedwith the plasma membrane under the resting condition, was redistributed to secondary granules after chemoattractant stimulation. Blockage of cell endocytosis appeared to inhibit Ral transloca-tion intracellularly. In conclusion, these results demonstrate that Ral is a critical regulator in PMN that specifically controls secondary granule release during PMN response to chemoattrac-tant stimulation.

Neutrophil extravasation into tissues is an essential process required for the inflammatory response. Upon receiving an inflammatory cue, neutrophils begin accumulating on the luminal surface of the endothelium. Neutrophil recruitment is initiated by selectin-mediated tethering and rolling of neutrophils along the endothelial monolayer, followed by integrin-mediated firm adhesion. Adherent neutrophils then traverse the endothelium in a process known as transendothelial migration. The events mediating the rolling and adhesion steps are well characterised, but research into the molecular mechanisms regulating transendothelial migration is an area of intense focus. A previous study conducted in our laboratory found that the activation of endothelial extracellular signal-regulated kinase (ERK) 1/2 was required for neutrophil transmigration. Furthermore, it was found that endothelial ERK was activated in response to a soluble protein produced by fMLP- or IL-8-stimulated neutrophils. In the present study, the soluble ERK-activating neutrophil protein was identified as annexin A1, which was selected as a possible candidate following mass spectrometry analysis of proteins secreted from activated neutrophils. Annexin A1 antibodies (Abs) were found to block endothelial ERK activation induced by conditioned medium harvested from stimulated neutrophils. Annexin A1 Abs were additionally able to inhibit neutrophil transmigration across human umbilical vein endothelial cell (HUVEC) monolayers in an in vitro transmigration assay. Following the purification of recombinant annexin A1, it was demonstrated that it could activate endothelial ERK in a similar manner to neutrophil conditioned medium. Upon further investigation, ERK activation was found to be induced by a truncated form of annexin A1 present in the protein preparation rather than the full length protein. Calpain I, a calcium dependent protease that is activated upon neutrophil stimulation and is known to cleave annexin A1 within the N-terminal domain, was shown to process full length inactive recombinant annexin A1 into an unidentified product that could activate endothelial ERK. A calpain I inhibitor was also found to prevent stimulated neutrophils from secreting an ERK-activating protein, thus further suggesting a role for calpain I in this process. As full length annexin A1 has been reported to signal through the formyl peptide receptor (FPR) family, a pan-FPR antagonist was incubated with endothelial cells and was found to inhibit ERK activation induced by neutrophil conditioned medium, indicating that pro-inflammatory annexin A1 is also a FPR ligand. Endothelial projections termed “transmigratory cups” form around neutrophils during extravasation, of which ICAM-1 is a major component. Using an assay that examined transmigratory cups during neutrophil transmigration, it was found that annexin A1 Abs could inhibit neutrophil adhesion and transmigration through HUVEC monolayers by interfering with transmigratory cup formation around neutrophils, as shown by monitoring ICAM-1 during the process. Quantification of transmigrating neutrophils highlighted that the majority of neutrophils were emigrating via a transcellular pathway, which is in opposition to many in vitro studies where paracellular transmigration predominates. The results generated from this study identified a novel pro-inflammatory role for annexin A1 in neutrophil transendothelial migration. Preliminary experiments suggested that the pro-inflammatory annexin A1 responsible for endothelial ERK activation was a truncated form. Calpain I appears to be a likely candidate responsible for the generation of this uncharacterised, truncated annexin A1 product, however further experiments are required to confirm this hypothesis. Pro-inflammatory annexin A1 represents a new target for the treatment of inflammatory disorders. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1374554 / Thesis (Ph.D.) -- University of Adelaide, School of Molecular and Biomedical Science, 2009

Thesis (Ph. D.)--University of Missouri--Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaves : 118-129). Also available on the Internet.

Thesis (Ph. D.)--University of Virginia, 2006. / Includes bibliographical references (leaves 109-130). Also available online through Digital Dissertations.

Horses are at high risk to develop systemic inflammation due to the release of bacterial endotoxin from an inflamed gastrointestinal tract. Neutrophils are critical for mounting an immune response to bacterial endotoxins. Neutrophil activation following engagement of bacterial endotoxin expands their lifespan through suppression of their constitutive apoptosis. The prolonged lifespan of neutrophils propagates acute inflammation and delays the resolution of inflammation. Since equine neutrophil lifespan has not been well-studied, I investigated the occurrence of equine neutrophil apoptosis in vitro and in vivo. First, I investigated the effect of Escherichia coli lipopolysaccharide (LPS) treatment on the occurrence of equine neutrophil apoptosis in vitro. LPS treatment delayed in vitro equine neutrophil apoptosis in a dose-dependent manner at concentrations of 0.1-10 μg/ml through toll-like receptor (TLR)-4 signaling and down-regulation of the intrinsic pathway of apoptosis, specifically through reduced caspase-9 activity. Next, I found that ex vivo neutrophil apoptosis was delayed in two models of intestinal inflammation, jejunal ischemia and reperfusion (IR) and oligofructose-induced colitis, through down-regulation of both the intrinsic and extrinsic apoptosis pathways via reduced caspase-3, -8, and -9 activities. Pulmonary intravascular macrophages (PIMs) depletion with systemic gadolinium chloride (GC) prevented the prolongation of ex vivo neutrophil lifespan in horses undergoing jejunal IR through modulation of caspase-3, -8 and -9 activities. PIM depletion in IR horses resulted in an earlier and greater increase in tumor necrosis factor-alpha and a concomitant decrease in interleukin-10 to suggest an enhanced systemic pro-inflammatory response. I examined the effect of neutrophil concentration and co-incubation with aged, apoptotic neutrophils on the occurrence of neutrophil apoptosis in vitro. Neutrophil apoptosis was delayed with increasing concentrations of neutrophils in vitro, which may contribute to delayed neutrophil apoptosis in systemic inflammation. However, co-incubation with aged, apoptotic neutrophils did not alter in vitro neutrophil lifespan. Taken together, the data show that LPS delays equine neutrophils apoptosis in vitro in a TLR4-dependent manner through inhibition of caspase-9. Ex vivo neutrophil apoptosis was also delayed with systemic inflammation via down-regulation of caspase activity. A novel finding of this work was the reversal of delayed neutrophil apoptosis by depletion of PIMs in horses experiencing intestinal IR.

Neutrophils as key effector cells of the innate immune system migrate from the circulation into sites of inflammation and are essential for the containment, killing and clearance of invading pathogens through a variety of highly regulated cell functions. Despite this beneficial role their involvement can also be detrimental. In a number of diseases dysregulated neutrophil influx and activation results in significant tissue damage and worsening of the acute inflammatory event as well as long term tissue injury, scarring and fibrosis. One such pulmonary condition is acute respiratory distress syndrome (ARDS) which, despite decades of intensive research and multiple clinical trials, remains without a cure and has an associated mortality rate of approximately 40%. Delineating and understanding the key pathogenic mediators that drive neutrophil recruitment into the lung in the context of both bacterial and sterile injury is therefore vital in the development of novel therapies. Neutrophils migrate towards a variety of agents but amongst such factors a hierarchy exists with bacterial-derived products, including formylated peptides, dominant in this process. In sterile tissue injury where no bacterial factors are present the mediators involved change but a hierarchy still exists. Mitochondrial formylated peptides are released following necrotic cell death and bind to formyl peptide receptor 1 (FPR1) on the neutrophil surface inducing migration and activation. Like bacterial formylated peptides they are powerful chemoattractants and are therefore likely to be important in recruiting neutrophils to sites of injury and inflammation. Hypothesis: The central hypothesis of this thesis is that mitochondrial formylated peptides, as end-target chemoattractants, are elevated in patients with ARDS and drive neutrophil recruitment through binding to FPR1. Inhibition of FPR1 in models of acute lung injury will therefore result in attenuation of this inflammatory response through multiple FPR1-mediated effects implicating both formylated peptides and their cognate receptor in the pathogenesis of sterile ARDS. Results: Free mitochondrial DNA and formylated peptides were elevated in the circulation of patients with ARDS or severe paracetamol-induced hepatic failure relative to healthy controls. In addition, FPR1 receptor number was increased on the surface of neutrophils isolated from critically ill septic patients. Isolated mitochondrial formylated peptides induced FPR1- dependent chemotaxis in primary human neutrophils in vitro. Alongside this, FPR1 ligand binding resulted in increased cell surface β2-integrin expression [integrin alpha M beta 2 (ITGB2); also called CD11b/CD18, Mac-1 or CR3] through intracellular activation of PI-3Kand MAPK-dependent signalling pathways. Indeed, blockade of neutrophil cell-surface integrin alpha M (ITGAM; also known as CD11b)) resulted in a reduction in mitochondrial formylated peptide-induced chemotaxis. To determine the production of human neutrophil IL-1β, a pivotal chemokine within a sterile inflammatory environment, a novel method for the in vitro isolation of ultrapure neutrophils was developed. Neutrophils were isolated by autofluorescence-based flow sorting as determined by intrinsic differences in neutrophil and eosinophil autofluorescence and their size and granularity relative to circulating mononuclear cells. Analysis of this approach demonstrated the ability to rapidly collect a highly pure neutrophil population (99.95 ± 0.03%). Flow sorting did not alter the activation state or functional capacity of these cells relative to unsorted neutrophils with regards to several measures of neutrophil behaviour/function. Cells also remained fully responsive to a variety of neutrophil agonists with no evidence of neutrophil priming. The capacity of highly pure neutrophils to secrete IL-1β was determined to be approximately 160-fold lower than equivalent numbers of circulating peripheral blood mononuclear cells. In the context of an inflammatory environment however this is likely to be of biological significance given the large number of infiltrating neutrophils. In sterile hydrochloric acid-induced acute lung injury pharmacological inhibition of FPR1 with cyclosporin H (CsH), or use of transgenic FPR1-/- mice, resulted in inhibition of neutrophil migration into the alveolar space 24 hours after injury. This was associated with a reduction in pulmonary haemorrhage, extravascular protein leak and pro-inflammatory cytokine expression with improved histological appearances. Furthermore, the HCl acid-induced reduction in alveolar macrophage numbers was inhibited by CsH with interstitial macrophages displaying an alternatively activated phenotype. Importantly, delivery of CsH 12 hours after the onset of injury also reduced acute lung inflammation demonstrating its potential therapeutic relevance in the treatment of human disease. In non-sterile E. coli-mediated acute lung injury partial antagonism of FPR1 with CsH resulted in a reduction in neutrophil migration and vascular leak with no effect on pulmonary bacterial load. A narrow therapeutic window existed however as increased concentrations of CsH, or infection in FPR1-/- mice, resulted in a reduction in alveolar neutrophil number and increase in E. coli at 24 hours. Alongside effects on myeloid cells within the lung FPR1 was found to be expressed on mouse lung epithelial cells. A technique to isolate and culture mouse type 1 alveolar epithelial (AT1) cells was therefore developed. Flow sorting of anti-type 1 alpha (anti-T1α) stained single cell lung homogenates with subsequent culture on transwell membranes resulted in the development of confluent AT1 cell monolayers after 10 days. Formylated peptides appear to induce a reduction in transepithelial resistance and increase in permeability across a monolayer in vitro alongside an increase in release of the neutrophil chemo-attractant mouse CXCL8 (KC). Conclusions: Taken together, mitochondrial formylated peptides released following cell necrosis and FPR1 play a significant role in the pathogenesis of sterile acute lung injury. This is likely to be predominantly through neutrophil-dependent means but data presented here also suggests that their role in macrophage function and alveolar epithelial cell permeability may be important. Inhibition of FPR1 may therefore represent a novel and multi-cellular therapeutic target in the treatment of ARDS.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / Os efeitos locais provocados por venenos botrÃpicos sÃo caracterizados por edema, hemorragia e dor local. No entanto, os mecanismos fisiopatolÃgicos relacionados a esses venenos podem variar de acordo com a espÃcie. Esta caracterÃstica espÃcie-especÃfica pode prejudicar a eficÃcia da soroterapia. Desta forma, considerando a diversidade da resposta fisiopatolÃgica dos venenos, investigamos os mecanismos e mediadores envolvidos na resposta inflamatÃria local induzida pelo veneno da Bothrops jararacussu (VBjsu). Camundongos Swiss fÃmeas foram submetidos à injeÃÃo intraplantar de soluÃÃo salina ou VBjsu (0,125-8 Âg/pata). Para o estudo dos mecanismos e mediadores envolvidos, diferentes sub-grupos de animais foram submetidas ao prÃ-tratamento com loratadina (um antagonista do receptor H1), composto 48/80 (para induzir a depleÃÃo dos mastÃcitos), capsaicina (para promover a dessensibilizaÃÃo das fibras C), infliximabe (um anticorpo anti-TNF-&#945;), indometacina (um inibidor nÃo-especÃfico da COX), celecoxibe (um inibidor seletivo da COX-2) ou fucoidina (um modulador de P- e L-selectinas) administrados antes do VBjsu. O edema da pata foi medido por pletismografia. AlÃm disso, os tecidos da pata foram recolhidos para determinaÃÃo da atividade da mieloperoxidase (MPO), dosagem dos nÃveis de TNF-&#945;, IL-1 e da imunoexpressÃo da COX-2. O efeito quimiotÃtico direto do VBjsu tambÃm foi estudado por meio do ensaio da cÃmara de Boyden, e o estado de ativaÃÃo dos neutrÃfilos humanos foi avaliado atravÃs da dinÃmica intracelular de cÃlcio em neutrÃfilos realizado in vitro com auxilio da microscopia confocal. O VBjsu causou uma resposta edematogÃnica concentraÃÃo e tempo dependentes com aumento da produÃÃo local de TNF-&#945;, IL-1&#946; e da imunoexpressÃo da COX-2 nos tecidos quando comparado ao grupo salina (P<0,05). Ambos, edema e migraÃÃo de neutrÃfilos foram impedidos pelos inibidores da COX (indometacina ou celecoxibe), ou pelo modulador de P - e L-selectinas (fucoidina) vs. VBjsu (P<0,05). O exame histopatolÃgico revelou que o VBjsu induz uma precoce migraÃÃo de neutrÃfilos para o local da lesÃo vs. o grupo salina (P<0,05). AlÃm disso, o VBjsu induz a quimiotaxia e ativa neutrÃfilos in vitro aumentando diretamente a dinÃmica de cÃlcio intracelular quando comparado ao RPMI (P<0,05). Portanto, o VBjsu induz uma resposta edematogÃnica precoce dependente da produÃÃo de prostanoides e da migraÃÃo de neutrÃfilos. / Local tissue reactions provoked by Bothrops venoms are characterized by edema, hemorrhage, pain, and inflammation; however, the mechanisms of tissue damage vary depending upon the species of snake. This mechanistic variability reduces the efficacy of antivenom treatment. Considering the diversity of intraspecific pathophysiological responses, we investigated the mechanisms and mediators involved in the local inflammatory response induced by the Bothrops jararacussu venom (VBjsu). Female Swiss mice were injected with either saline or VBjsu (0.125-8 Âg/paw). In a subset of VBjsu-treated mice, loratadine (an H1 receptor antagonist), compound 48/80 (for mast cell depletion), capsaicin (for C-fiber desensitization), infliximab (an anti-TNF-&#945; antibody), indomethacin (a non-specific COX inhibitor), celecoxib (a selective COX-2 inhibitor) or fucoidan (a P- and L-selectins modulator) were administered before VBjsu treatment. Paw edema was measured by plethysmography. In addition, paw tissues were collected for the measurement of myeloperoxidase (MPO) activity, TNF-&#945; and IL-1 levels, and COX-2 immunoexpression. The direct chemotactic effect of VBjsu was also studied using a Boyden chamber assay, and the in vitro calcium dynamic in neutrophils was investigated using confocal microscopy. VBjsu caused concentration- and time-dependent edematogenic responses and increased the local production of TNF-&#945; and IL-1&#946; as well as COX-2 expression vs. saline group (P<0.05). Both edema and neutrophil migration were prevented by pretreatment with cyclooxygenase inhibitors (indomethacin or celecoxib) or by the P- and L-selectins modulator, fucoidan vs. VBjsu (P<0.05). Furthermore, VBjsu induced a direct in vitro neutrophil chemotaxis by increasing intracellular calcium vs. RPMI (P<0.05). Therefore, VBjsu induces an early onset edema dependent upon prostanoid production and neutrophil migration.

Neutrophils are key effector cells of the innate immune system. They employ a number of powerful ‘weapons’ to eliminate pathogens, including an array of destructive proteins packaged into distinctive granule subsets. In addition to their microbicidal activity, these granule proteins are capable of causing substantial tissue damage if inappropriately deployed. To mitigate against this possibility, most physiological stimuli induce minimal extracellular degranulation. Sites of inflammation and infection are usually hypoxic, and it has been shown that oxygen depletion compromises neutrophil function by impairing the generation of reactive oxygen species and hence bacterial killing. The key finding reported in this thesis is that hypoxia substantially increases the release of all neutrophil granule subsets, as measured by the release of (active) hallmark proteins (elastase, myeloperoxidase, lactoferrin and matrix metalloproteinase-9). In consequence, supernatants from hypoxic neutrophils induced substantially more damage to lung epithelial cell layers than supernatants from neutrophils cultured under normoxic conditions; this damage was protein- and protease-dependent. This pattern of damage was seen consistently across lung adenocarcinoma-derived epithelial cells, primary immortalised lung epithelial cells, and primary human bronchial epithelial cells grown in physiological air-liquid interface culture. Surprisingly, the mechanism of hypoxia-augmented degranulation was found to be independent of protein synthesis and specifically, of the transcription factor HIF-1α (the ‘master-regulator’ of hypoxic responses); thus, hypoxia did not affect mRNA transcript or protein abundance of the major granule components, and hypoxia mimetics failed to recapitulate the phenotype. Inhibition of the key pathways known to be involved in neutrophil degranulation, including, phosphatidylinositol 3-kinase and phospholipase C, but not calcium flux prevented augmented granule release under hypoxia In conclusion, hypoxia induces a destructive neutrophil phenotype, with increased release of multiple histotoxic proteases. This may contribute to tissue injury and disease pathogenesis in a range of clinically important conditions.

京都大学 / 0048 / 新制・課程博士 / 博士(医科学) / 甲第18903号 / 医科博第59号 / 新制||医科||4(附属図書館) / 31854 / 京都大学大学院医学研究科医科学専攻 / (主査)教授 妻木 範行, 教授 山下 潤, 教授 斎藤 通紀 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM