Neutrophils are a central component of the innate immune system, whose major role is to defend the host against invading microorganisms. As such they are integral players in the process of inflammation, the response of vascular tissues to injury. They are frequently the first immune cells recruited from the systemic circulation into a site of tissue injury or infection where they themselves play a key antimicrobial role. Direct killing of microbes can be accomplished by phagocytosis, degranulation, production of reactive oxygen species (ROS) or the release of DNA and antimicrobial peptides into the extracellular milieu (NETosis). In addition neutrophils orchestrate the recruitment and activation of other leucocytes, further contributing to host defence. The central importance of neutrophils in immunity is revealed by defects in either number or function leading to recurrent life threatening infection. However, as the toxic arsenal of neutrophil constituents lack specificity they can also be damaging to surrounding host tissues causing exacerbated inflammation. It is therefore essential that neutrophil function is tightly controlled to allow an appropriate response to be mounted against invading pathogens while simultaneously minimising host tissue injury. Therefore, once the inciting inflammatory insult has been successfully cleared or controlled it is imperative that these non-tissue resident specialised immune cells are rapidly ‘switched off’ or cleared to allow the return to homeostasis. This resolution phase of the inflammatory cascade is now recognised as an energy dependent, finely controlled endogenous process, the beginnings of which are activated at the onset of inflammation. One of the main aims of resolution is to ensure efficient clearance of leucocytes that are no longer necessary. It is likely that a major clearance route is by the highly regulated and energy dependent processes of neutrophil programmed cell death (apoptosis) with subsequent uptake and disposal of apoptotic neutrophils by tissue macrophages. This process of neutrophil apoptosis renders the neutrophils nonfunctional and preserves cell membrane integrity, thus preventing further release of histotoxic neutrophil-derived inflammatory mediators into the extracellular environment. Furthermore, the recognition, uptake and disposal of apoptotic neutrophils cause a dynamic change in the phagocytosing macrophage phenotype with alterations in inflammatory mediator production. The fundamental importance of neutrophil apoptosis and subsequent efferocytosis in inflammation resolution is highlighted by the pathological consequences of neutrophil necrosis or failed apoptotic cell clearance, which leads to enhanced tissue injury and autoimmunity. Acute lung infection (pneumonia) is a common and serious condition affecting both developed and developing countries; globally, childhood pneumonia is the leading cause of death in children aged less than 5 years and pneumonia is the most common fatal infection in the developed world. In over half of patients with community acquired pneumonia no causative organism is ever isolated suggesting that although the immune response has successfully controlled infection, continued uncontrolled neutrophilic inflammation in the lung continues to cause morbidity and mortality. Indeed, pneumonia frequently progresses to acute respiratory distress syndrome (ARDS), a devastating acute inflammatory condition of the lungs characterized by inflammatory cell recruitment and accumulation of protein rich oedema fluid leading to impaired lung function. ARDS affects 200,000 critically ill patients in the USA per year, and has a substantial mortality rate of up to 40%. Despite advances in intensive care treatment and antimicrobial therapy mortality from pneumonia has not fallen since the 1950s, and at present there are no specific therapies for infection-related lung inflammation or ARDS. Understanding the mechanism behind such uncontrolled, persisting inflammation, and the need for novel approaches to target infection related lung injury are therefore both urgent and essential. This thesis examines the potential of neutrophil apoptosis-inducing pharmacological agents as potential treatments for infection-associated lung inflammation. The primary agents used include a cyclin-dependent kinase inhibitor as well as plant-derived polyphenolic flavones. The ability of these compounds to induce human neutrophil apoptosis in vitro, the key importance of the intracellular neutrophil survival protein Mcl-1 in mediating this process, and the effect of targeting Mcl-1 in human macrophages is investigated. In addition, neutrophilic inflammation is modelled in zebrafish and mice with both sterile and bacterial-driven models of inflammation. A key role for Mcl-1 is delineated in vivo, with it acting as an endogenous controller of the innate immune response by influencing neutrophil apoptosis, but without effects on macrophage apoptosis or ability to phagocytose apoptotic cells. Driving neutrophil apoptosis by down-regulation of Mcl-1 accelerates resolution of inflammation in vivo. This therapeutic approach is also found to have indirect anti-bacterial effects in a model of E. Coli induced pneumonia, in stark contrast to established anti-inflammatory approaches which routinely cause immune paresis and life threatening infection. As such, targeting inflammatory cell apoptosis by changes in Mcl-1 offers a potential new therapeutic approach for the treatment of infection-associated inflammation.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / O presente teve por objetivo avaliar a diminuiÃÃo da resposta hipernociceptiva inflamatÃria no curso do desenvolvimento da colite experimental induzida pelo Ãcido TNBS em ratos, bem como avaliar o papel da via NO/GMPc/PKG/K+ATP e a participaÃÃo de opioides endÃgenos e endocanabinoides neste evento. Para tanto, as colites foram induzidas por TNBS (20mg) diluÃdo em etanol a 50% ou etanol a 50%. O grupo controle recebeu somente salina via transanal. TrÃs ou quatorze dias apÃs a induÃÃo das colites foram avaliados os seguintes parÃmetros: edema de pata por carragenina (Cg; 500μg/pata direita) ou dextrana (Dxt; 500μg/pata direita.) por pletismometria, atividade da enzima mieloperoxidase (MPO), migraÃÃo de neutrÃfilos para cavidade pleural induzidas por Cg (500μg/pata direita) e a hipernocicepÃÃo mecÃnica induzida por PGE2 (100ng/pata) ou Cg (500μg/pata) aferido por analgesÃmetro digital (InsightÂ). Para verificar a participaÃÃo da via NO/GMPc/PKG/K+ATP na diminuiÃÃo da resposta hipernocicetiva da colite induzida por TNBS foram usados o L-Noarg (antagonista da NOSi; 100ng/pata) , O ODQ (bloqueador da guanilato ciclase soluivel; 8μg/pata), o KT5823 (antagonista da PKG; 1,5 μg/pata) e a glibenclamida (bloqueadora dos canais de K+ATP; 160μg/pata). Depois, para avaliar a participaÃÃo opiÃide e canabinÃide nesse evento, naloxona (antagonista de receptor opioide, 1,0 μg/pata) ou AM251 (antagonista de receptor canabinoide ; 1, 80 μg/pata) ou AM630 (antagonista de receptor canabinoide tipo 2; 25 μg/pata) foram injetados respectivamente. Os animais com colite induzida por TNBS apresentaram uma inibiÃÃo significativa do edema de pata tanto com o Cg (TrÃs ou quatorze dias apÃs a induÃÃo) quanto com Dxt (TrÃs dias apÃs a induÃÃo), quando comparados com os outros grupos em estudo. Em nenhum dos dias estudados, foram observadas diferenÃas na atividade da MPO na pata e nem na avaliaÃÃo da migraÃÃo de neutrÃfilos para a cavidade pleural induzidas por Cg. Ratos com colite induzida por TNBS apresentavam diminuiÃÃo na resposta hipernociceptiva induzida por Cg e PGE2. O tratamento com o ODQ, KT5823 e glibenclamida, naloxona, AM251 e AM630 reverteram esse efeito. O L-Noarg tambÃm reverteu o efeito entinociceptivo da colite induzida por TNBS, mas com a administraÃÃo da L-Arginina esse efeito foi recuperado. Apartir dos nossos resultados podemos concluir que a colite induzida por TNBS diminuiu a hipernocicepÃÃo inflamatÃria induzida tanto por carragenina quanto por PGE2 por dimimuir parÃmetros inflamatÃrios agudos como a resposta edematogÃnica a estÃmulos inflamatÃrios. AlÃm disso, esse efeito antinociceptivo parece ser independente da infiltraÃÃo de neutrÃfilos, mas dependente da ativaÃÃo da via final NO/GMPc/PKG/K+ATP e estimulada pelas aÃÃes dos opiÃides e canabinÃides endÃgenos. / The aim of this study was to investigate a possible involvement of the opioids, endocannabinoids and NO/cGMP/PKG/K+ATP pathway in the antinociception of the CrohnÂs experimental model in hypernociception induced by carragenan ou PGE2. Colitis was induced in the male Wistar rats (200-250) by intracolonic administration of 20 mg of 2,4,6-trinitrobenzene sulfonic acid (TNBS) in 50% ethanol, ethanol 50% or an equivalent volume of saline. Three or fourteen days after the colitis induction several parameters were evaluated: paw edema induced by carrageenan (Cg; 500μg/hind paw) or dextran (Dxt, 500μg/hind paw), myeloperoxidase activity (MPO), neutrophil migration to pleural cavity. Paw edema was evaluated the right hind paw and measured by plethysmometry. Neutrophil migration was induced by Cg injection in the right hind paw or in the peritoneal cavity. After 4h, rats were sacrificed and the skin of the right hind paw was harvested to measure neutrophil infiltration by MPO assay. Neutrophil migration induced by Cg was also evaluated in the pleural cavity, with the total e differential leucocytes counted. The mechanical behavioral tests were performed by measuring the force in grams (g) applied through a digital analgesymeter (InsightÂ). In this test the rats received PGE2 (100ng/paw) or carrageenan (Cg; 500μg/paw) into the plantar surface. In order to investigate the involvement of the NO/cGMP/PKG/K+ATP pathway in this event there were used L-Noarg (antagonist of iNOS; 100ng/paw), ODQ ( guanilate ciclase blocker; 8μg/paw), L-Arg (200mg/kg), KT5823 ( PKG blocker; 1.5 μg/paw) and Glibenclamide ( K+ATP channels blocker; 160μg/paw). To evaluated the involvement of the opioids and cannabinoids in this event naloxone (opioids receptor blocker; 1 μg/paw) or AM251 ( cannabinoid receptor blocker type I; 80 μg/paw) or AM630 (cannabinoid receptor blocker type II; 25 μg/paw) were inject respectively. Our results shows that, in animals with TNBS-induced colitis, there was a significant inhibition in the Cg (3rd or 14th after colitis induction) and Dxt (3rd after colitis induction)-induced paw edema. There were no differences in MPO activity and neither in the pleural neutrophil infiltration induced by Cg in rats inoculated with TNBS -induced colitis (3rd after colitis induction) when compares to normal animals. Rats with colitis induced by TNBS showed an increased nociceptive threshold when induced by CG and PGE2. Treatment with ODQ, KT5823 and glibenclamide, naloxone, AM251 and AM630 decreased the nociceptive threshold when compared with TNBS colitis. L-NOARG decrease the nociceptive threshold in rats with colitis induced by TNBS and L-arginine reversed this effect. Our results suggest that the antinociceptive effect of the experimental model of CrohnÂs disease induced by TNBS seemed to be mediated a decrease of inflammatory response independent of neutrophil migration and activation of the NO⁄cGMP/PKG pathway followed by the opening of K+ ATP channels and activation of opioid and cannabinoid system.

The impact of microRNA (miRNA) as key players in the regulation of immune and neuronal gene expression and their role as master switches in the pathophysiology of neuropathic pain is increasingly recognized. miR-21 is a promising candidate that could be linked to the immune and the nociceptive system. To further investigate the pathophysiological role of miR-21 in neuropathic pain, we assesed mice deficient of B7 homolog 1 (B7-H1 ko), a protein with suppressive effect on inflammatory responses. B7-H1 ko mice and wildtype littermates (WT) of three different age-groups, young (8 weeks), middle-aged (6 months), and old (12 months) received a spared nerve injury (SNI). Thermal withdrawal latencies and mechanical withdrawal thresholds were determined. Further, we investigated anxiety-, depression-like and cognitive behavior. Quantitative real time PCR was used to determine miR-21 relative expression in peripheral nerves, dorsal root ganglia and white blood cells (WBC) at distinct time points after SNI. Naïve B7-H1 ko mice showed mechanical hyposensitivity with increasing age. Young and middle-aged B7-H1 ko mice displayed lower mechanical withdrawal thresholds compared to WT mice. From day three after SNI both genotypes developed mechanical and heat hypersensitivity, without intergroup differences. As supported by the results of three behavioral tests, no relevant differences were found for anxiety-like behavior after SNI in B7-H1 ko and WT mice. Also, there was no indication of depression-like behavior after SNI or any effect of SNI on cognition in both genotypes. The injured nerves of B7-H1 ko and WT mice showed higher miR-21 expression and invasion of macrophages and T cells 7 days after SNI without intergroup differences. Perineurial miR-21 inhibitor injection reversed SNI-induced mechanical and heat hypersensitivity in old B7-H1 ko and WT mice. This study reveals that reduced mechanical thresholds and heat withdrawal latencies are associated with miR-21 induction in the tibial and common peroneal nerve after SNI, which can be reversed by perineurial injection of a miR-21 inhibitor. Contrary to expectations, miR-21 expression levels were not higher in B7-H1 ko compared to WT mice. Thus, the B7-H1 ko mouse may be of minor importance for the study of miR-21 related pain. However, these results spot the contribution of miR-21 in the pathophysiology of neuropathic pain and emphasize the crucial role of miRNA in the regulation of neuronal and immune circuits that contribute to neuropathic pain. / Die Beteiligung von microRNA (miRNA) an der Genregulation immunologischer und neuronaler Prozesse und deren Rolle als Schlüsselelement in der Pathophysiologie von neuropathischem Schmerz gewinnt zunehmend an Bedeutung. miR-21 ist ein vielversprechender Kandidat, der sowohl das Immunsystem, als auch das nozizeptive System beeinflusst. Um die pathophysiologische Rolle von miR-21 bei neuropathischem Schmerz besser zu verstehen wurden Mäuse mit B7 homolog 1 Defizienz (B7-H1 ko), einem immunsupprimierendem Protein, untersucht. Eine frühere Studie zeigte eine Hochregulierung von miR-21 in murinen Lymphozyten. Junge (8 Wochen), mittelalte (6 Monate) und alte (12 Monate) B7-H1 ko Mäuse und Wildtypwurfgeschwister (WT) erhielten eine spared nerve injury (SNI) als neuropathischem Schmerzmodell. Es wurden thermische Rückzugslatenzen und mechanische Rückzugsschwellen bestimmt. Des weiteren wurde sowohl das Angstverhalten, das depressive Verhalten, als auch das kognitive Verhalten untersucht. Um die relative Expression von miR-21 in den peripheren Nerven, den Spinalganglien und in den weißen Blutzellen zu verschiedenen Zeitpunkten zu bestimmen, wurde die quantitative real time PCR angewandt. Naive B7-H1 ko Mäuse zeigten mit zunehmendem Alter eine mechanische Hyposensitivität. Bereits 3 Tage nach SNI entwickelten beide Genotypen eine Überempfindlichkeit gegenüber Hitze und mechanischer Stimulation. In drei durchgeführten Verhaltenstests konnten keine relevanten Unterschiede im Angstverhalten nach SNI von B7-H1 ko und WT Mäusen festgestellt werden. Bei beiden Genotypen gab es weder Hinweise auf depressives Verhalten nach SNI, noch wurde das kognitive Verhalten durch SNI beeinträchtigt. Die verletzen Nerven der B7-H1 ko und WT Mäuse zeigten 7 Tage nach SNI eine höhere miR-21 Expression und eine Invasion durch Makrophagen und T-Zellen ohne Gruppenunterschiede. Die perineurale Injektion eines miR-21 Inhibitors konnte die durch SNI induzierte mechanische und thermische Hypersensitivität lindern. Diese Studie zeigt, dass der Anstieg von miR-21 im N. tibialis und N. peroneus communis mit reduzierten Rückzugsschwellen gegen mechanische Reize und verkürzten Wegzugslatenzen bei Hitzestimulation einhergeht, welche durch perineurale Injektion eines miR-21 Inhibitors verringert werden können. Entgegen der Erwartungen zeigten B7-H1 ko Mäuse im Vergleich zu WT Mäusen keine erhöhte miR-21 Expression und sind daher möglicherweise von geringer Bedeutung für die Untersuchung von miR-21 assoziiertem Schmerz. Jedoch bekräftigen diese Ergebnisse eine Beteiligung von miR-21 an der Pathophysiologie von neuropathischem Schmerz und bestätigen die wichtige Rolle von miRNA bei der Regulation von neuronalen und immunologischen Prozessen, die zu neuropathischem Schmerz beitragen.

Purpose: The present study investigates the potential anti-inflammatory effects of in vivo oxytocin (OT) infusion on adipose tissue inflammation in the Watanabe Heritable Hyperlipidimic Rabbits (WHHL). Methods: Twenty-eight 3-month-old WHHL were surgically implanted with osmotic minipumps containing OT (n = 14, infusion rate 250 ng/kg/hr) or vehicle (n = 14). Blood samples were taken at baseline, midpoint, and endpoint for lipids and C-reactive protein (CRP). After 16 weeks, animals were sacrificed and samples of adipose tissue (epididiymal, retroperitoneal, mesenteric, pericardial, and subcutanous) were collected and analyzed for pro-inflammatory cytokine (IL-6, TNF-α, and MCP-1) and anti- inflammatory adipokine (adiponectin and IL-10) expression levels by Real Time- Polymerase Chain Reaction. Adipose tissue was also immunohistologically analyzed for macrophage infiltration. Aortas were dissected, formalin-fixed, and stained with oil-red O for en face quantification of lesion area. Student’s t-tests were used to compare group means for all measures. Results: Endpoint OT levels were significantly different (p < .05) between the control ( M = 11.28 pg/ml, SEM = 2.5) and treatment group (M = 132.35 pg/ml, SEM = 8.5). Plasma lipids were not altered by OT infusion. OT-treatment significantly decreased plasma CRP, a marker of systemic inflammation, at midpoint and endpoint compared to controls (p = 0.05). OT-treated animals displayed significantly less atherosclerosis in the thoracic aorta (p < 0.05); a finding similar to our previously published study in a mouse model of atherosclerosis. In some fat depots, there was a trend suggesting adiponectin gene expression increased in the OT-treatment group. There were no significant differences or trends regarding macrophage infiltration in adipose tissue. Conclusions: Oxytocin infusion attenuated thoracic aortic atherosclerosis, plasma CRP, and may affect inflammatory cytokine expression in adipose tissue in the WHHL model.

Drug induced idiosyncratic agranulocytosis has been attributed to oxidation by hypochlorite formed by bone marrow myeloperoxidase (MPO). Idiosyncratic liver toxicity could also involve drug oxidative activation by cytochrome P450 (in hepatocytes) or MPO (in Kupffer cells or infiltrating neutrophil/macrophages). Such drug reactive metabolites could cause cytotoxicity or release “danger signals” that attract immune cells which release H2O2 resulting from nicotinamide adenine dinucleotide phosphate oxidase (NADPH oxidase) activation. In vivo animal studies have shown that low level tissue inflammation markedly increased drug-induced tissue toxicity which was prevented by immune cell inhibitors and increased by cell activators. It is suggested that idiosyncratic drugs are much more toxic, taken during symptomless inflammation periods. Furthermore, it is hypothesized that hepatocytes are much more susceptible to some idiosyncratic drugs if they are exposed to hydrogen peroxide (H2O2)/myeloperoxidase or cytokines released by inflammatory cells. A hepatocyte inflammation model, in which hepatocytes were exposed to a non-toxic H2O2 generating system and peroxidase, was found to be much more vulnerable to four idiosyncratic drugs e.g., troglitazone, isoniazid, hydralazine and amodiaquine. The molecular cytotoxic mechanisms for this marked increase in cytotoxicity were investigated as follows: 1) A P450/H2O2-catalyzed pathway not involving oxidative stress e.g., hydralazine and isoniazid; 2) A P450/H2O2-catalyzed oxidative stress-mediated cytotoxic pathway e.g., hydrazine (an isoniazid metabolite) and hydralazine; and 3) A peroxidase/H2O2-catalyzed oxidative stress-mediated cytotoxic pathway e.g,, hydralazine, amodiaquine and troglitazone. Before cytotoxicity ensued, GSH oxidation, protein carbonyl formation and often lipid peroxidation occurred followed by a decrease in mitochondrial membrane potential indicating that oxidative stress was the molecular mechanism of cytotoxicity. In summary, a H2O2-enhanced hepatocyte system in the presence and absence of peroxidase may prove useful for a more robust screening of drugs for assessing the enhanced drug toxicity risk associated with taking drugs during periods of inflammation.

INTRODUCTION: Platelets are involved in the inflammatory and thrombotic complications associated with atherosclerosis. Human neutrophil peptides (HNP), released from activated neutrophils, demonstrate inflammatory effects related to lesion development. HNP bind the low-density lipoprotein receptor (LR) family member LRP1 and LRP8 is the only member on platelets. HYPOTHESIS: HNP enhance platelet activation and aggregation through interactions with LRP8. METHODS: Platelet activation and aggregation in response to HNP were determined using flow cytometry and aggregometry. Activation was also examined in the presence of recombinant LRP8 and in LRP8 knockout platelets. RESULTS: HNP activate platelets as determined by P-selectin expression and the formation of microparticles. HNP sensitize platelets enhancing their aggregatory response to ADP. Lastly, LRP8 plays a role in HNP-induced platelet activation. CONCLUSIONS: With an improved understanding of the mechanism by which HNP induce platelet activation, we may be able to devise therapeutic strategies to treat patients with cardiovascular diseases.

Short-chain fatty acids (SCFAs) are anaerobic bacterial metabolites. Cystic fibrosis (CF) lung disease is a condition caused by mutations in the cystic fibrosis transmembrane conductange regulator (CFTR) gene and is characterized by persistent lung inflammation and bacterial colonization. We measured the concentrations of SCFAs in sputum of patients with CF and tested the effect of these compounds on bacterial growth. Furthermore we found that SCFAs can influence the inflammatory protein expression and cytokine release in airway epithelial cells. SCFAs differentially alter cytokine release in CF bronchial epithelial cells (CFBE) compared to CFBE expressing wild-type CFTR. We also studied the effect of SCFAs in an acute lung injury model in BALB/cJ mice and found that intratracheally administered SCFAs can affect the inflammatory environment of the airways in vivo. We conclude that SCFAs may be important in the airways and that further investigation is warranted to understand their effects on inflammation and infection.

Short-chain fatty acids (SCFAs) are anaerobic bacterial metabolites. Cystic fibrosis (CF) lung disease is a condition caused by mutations in the cystic fibrosis transmembrane conductange regulator (CFTR) gene and is characterized by persistent lung inflammation and bacterial colonization. We measured the concentrations of SCFAs in sputum of patients with CF and tested the effect of these compounds on bacterial growth. Furthermore we found that SCFAs can influence the inflammatory protein expression and cytokine release in airway epithelial cells. SCFAs differentially alter cytokine release in CF bronchial epithelial cells (CFBE) compared to CFBE expressing wild-type CFTR. We also studied the effect of SCFAs in an acute lung injury model in BALB/cJ mice and found that intratracheally administered SCFAs can affect the inflammatory environment of the airways in vivo. We conclude that SCFAs may be important in the airways and that further investigation is warranted to understand their effects on inflammation and infection.

A growing demand for information on the human health and environmental effects of materials produced using nanotechnology has led to a new area of investigation known as nanotoxicology. Research in this field has widespread implications in facilitating the medical applications of nanomaterials but also in addressing occupational and environmental toxicity concerns. Improving our understanding of these issues also has broad appeal in the stewardship of nanotechnology and its acceptance by the public. This work represents some of the early research in burgeoning field of nanotoxicology. Using a variety of in vivo and in vitro models, as well as cellular and molecular techniques I first studied a possible role for the novel cytokine endothelial monocyte activating polypeptide-II (EMAP-II) in acute lung inflammation in rats (Chapter 2). This work demonstrated a significant increase in total EMAP-II concentration in lipopolysaccharide inflamed lungs as early as 1h post-treatment (P<0.05). Increased numbers of monocytes and granulocytes were also observed in lungs treated with mature EMAP-II relative to control rats (P<0.05), and the recruitment of cells did not occur via upregulation of either Interleukin-1β or Macrophage inflammatory protein-2. I further studied whether mature EMAP-II can be induced in pulmonary nanotoxicity studies by exposure to rosette nanotubes (RNT) (Chapters 3-5). In the first in vivo experiments in mice on the RNT(1)-G0 (Chapter 3) I showed an acute inflammatory response at the 50 µg dose by 24h, but this response was resolving by 7d post-exposure as evidenced by a decreased number of cells in the bronchoalveolar lavage fluid (P<0.05) and from histological examination. The results of this study indicated that water soluble and metal-free rosette nanotubes can demonstrate a favorable acute pulmonary toxicity profile in mice. Subsequently, I studied the responses of the pulmonary epithelium using the human Calu-3 cell line (Chapter 4). This experiment indicated that RNT(2)-K1 neither reduces cell viability at 1 or 5 µg/ml doses nor does it induce a dose-dependent inflammatory cytokine response in pulmonary epithelial cells in vitro. My final experiment (Chapter 5) studied the human U937 pulmonary macrophage cell line since the macrophage is one of the key defense mechanisms to encounter RNT in the lung environment. The data indicate that this cell line lacks a robust inflammatory response upon exposure to RNT and that when RNT length is changed by altering the conditions of nanotube self-assembly, cytokine release into the supernatant is not affected profoundly. Although, EMAP-II is upregulated in a lipopolysaccharide model of lung inflammation, it does not serve as a good marker of RNT exposure. The data indicate that RNT have a favourable toxicity profile and these experiments provide a framework upon which rosette nanotubes can be investigated for a range of biomedical applications. Furthermore, in light of media and scientific reports of nanomaterials showing signs of toxicity, this work demonstrates that a biologically inspired nanostructure such as the RNT can be introduced to physiological environments without acute toxicity.

INTRODUCTION: Platelets are involved in the inflammatory and thrombotic complications associated with atherosclerosis. Human neutrophil peptides (HNP), released from activated neutrophils, demonstrate inflammatory effects related to lesion development. HNP bind the low-density lipoprotein receptor (LR) family member LRP1 and LRP8 is the only member on platelets. HYPOTHESIS: HNP enhance platelet activation and aggregation through interactions with LRP8. METHODS: Platelet activation and aggregation in response to HNP were determined using flow cytometry and aggregometry. Activation was also examined in the presence of recombinant LRP8 and in LRP8 knockout platelets. RESULTS: HNP activate platelets as determined by P-selectin expression and the formation of microparticles. HNP sensitize platelets enhancing their aggregatory response to ADP. Lastly, LRP8 plays a role in HNP-induced platelet activation. CONCLUSIONS: With an improved understanding of the mechanism by which HNP induce platelet activation, we may be able to devise therapeutic strategies to treat patients with cardiovascular diseases.