Zugl.: Giessen, Univ., Diss., 2005

Universiẗat, Diss., 2005--Giessen.

Zugl.: Giessen, Universiẗat, Diss., 2008.

Zugl.: Giessen, Universiẗat, Diss., 2008.

Marburg, Univ., Diss., 2009

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.

Background: With the COVID-19 pandemic, there has been an influx of patients with acute respiratory distress syndrome (ARDS), an inflammatory lung condition. ARDS survivors are at high risk for developing post-traumatic stress disorder (PTSD) due to intensive care unit (ICU) medical treatments/procedures. They are known to have traumatic memories triggered by their sensorium months to years after being discharged from the ICU. One study found that 23% of ARDS survivors experienced long-term PTSD symptoms 2-3 years after hospital discharge (Bienvenu et al., 2018). Unknown is whether there are similarities in the memories and sensory triggers of PTSD amongst ARDS and COVID ARDS survivors. Purpose: The purpose of this study was to 1) identify the most common vivid ICU memories and sensory triggers for PTSD symptoms in survivors of ARDS and COVID positive ARDS; 2) to analyze the frequency of sensory triggers and determine whether differences exist between ARDS and COVID ARDS survivors. Method: A multi-step, thematic analysis of qualitative data from 27 patients was completed (20 COVID ARDS patients and 7 ARDS patients) by a team of 7 researchers. Patients were asked a series of open-ended questions regarding vivid memories and sensory triggers for them. Major themes were generated from their responses. Results: Major themes identified were prevalent in both COVID ARDS and ARDS groups. Prominent vivid memories included medical treatment/procedures, emergence delirium, illusions/hallucinations, vivid nonsense dreams and sensory to dream conversion. Common sensory triggers included seeing medical equipment, hearing beeping/alarms, seeing media depictions of the hospital setting, hospital smells and seeing doctors, nurses, hospitals. Differences between COVID-ARDS and ARDS groups were not notable. Conclusion: The data collected in this study revealed ARDS and COVID ARDS patients experience sensory inputs during their ICU stay that contribute to the development of vivid, long-lasting memories and subsequent PTSD symptoms. Survivors' everyday lives are altered by these symptoms, impacting their ability to work, familial relationships, and likelihood to seek out healthcare. Data from this study is being used in a compressed exposure therapy trial and should be incorporated into future PTSD preventative and treatment interventions.

No description available.

The cardiopulmonary effects of endotoxin administration (1 microgram/kg) were evaluated in 8-10 week old SPF-derived Yorkshire pigs, both because endotoxemia is a common and important swine problem, and because the pig is a good model for human adult respiratory distress syndrome. Physiological changes included sustained increases in mean pulmonary artery pressure, pulmonary vascular resistance, pulmonary arterial wedge pressure, heart rate, hematocrit, and the arterial partial pressure of carbon dioxide. Transient increases were also observed in central venous pressure and airway pressure. Transient increases, followed by decreases, were observed in mean systemic arterial pressures and systemic vascular resistance. Decreases were seen in cardiac output, cardiac index, arterial partial pressure of oxygen and oxygen saturation. The number of circulating leukocytes, lymphocytes and segmented neutrophils decreased with endotoxin infusion. To investigate the role of airway smooth muscle, bronchial rings were isolated and exposed to contractile agents in tissue baths. A hyperresponsiveness of the third generation bronchi to substance P, carbachol, bradykinin and electric field stimulation was observed. However the increase in response to bradykinin and electric field stimulation were not statistically significant. Histopathology of the lungs demonstrated congestion, hemorrhage and neutrophilic infiltration. / Master of Science

Die Bauchlagerung von intubierten ARDS-Patient/innen mit einer schlechten Oxygenierung wird laut Leitlinie seit mehreren Jahren als supportive Therapiemaßnahme empfohlen. Im Rahmen der COVID-19 Pandemie wurde nun erstmalig die Bauchlagerung auch bei hypoxämischen, nicht-intubierten Patient/innen untersucht. Diese Fragestellung wurde in der vorliegenden Arbeit mittels einer systematischen Übersichtsarbeit betrachtet. Aufgrund der aktuellen Pandemiesituation wurden neben ARDS-Patient/innen im Allgemeinen insbesondere COVID-19 Patient/innen mit einem akuten Lungenversagen als Subgruppe untersucht. Am 21.11.2020 wurde eine systematische Suche nach Studien in den Datenbanken MEDLINE, Cochrane COVID-19 Study Register und Living Overview of the Evidence platform durchgeführt. Die Ergebnisse wurden, wo möglich, in Form einer Meta-Analyse zusammengefasst, in Tabellen darstellt oder deskriptiv beschrieben. Das Risiko für Bias wurde jeweils für die eingeschlossenen kontrollierten Studien mittels ROBINS-I beurteilt. Die Vertrauenswürdigkeit der Evidenz der gesamten Arbeit wurde mit Hilfe des GRADE-Ansatzes untersucht. Insgesamt wurden 30 Studien eingeschlossen, davon 4 kontrollierte Studien, keine RCTs. In 3 der kontrollierten Studien wurde die Bauchlagerung bei COVID-19 Patient/innen untersucht, in einer bei Patient/innen mit einem anderweitig verursachten ARDS. Es ist unklar, ob die Bauchlagerung die Intubationsrate (RR = 0,92; 95% KI: 0,59 - 1,44; I² = 65%; sehr niedrige Vertrauenswürdigkeit der Evidenz), die Mortalität (RR = 0,55; 95% KI: 0,23 - 1,30; I² = 60%; sehr niedrige Vertrauenswürdigkeit der Evidenz) und die Wahrscheinlichkeit für eine Aufnahme auf die Intensivstation (RR = 0,94; 95% KI: 0,54 - 1,63; I2 = 71%; sehr niedrige Vertrauenswürdigkeit der Evidenz) verringern kann. Auch für die anderen betrachteten Endpunkte konnte kein signifikanter Effekt der Bauchlagerung nachgewiesen werden Im Vergleich der Subgruppen „Nicht-COVID-19“ (8 Studien) und „COVID-19“ (22 Studien) konnten in Bezug auf alle betrachteten Endpunkte keine relevanten Unterschiede festgestellt werden. Insgesamt ist die Evidenz nicht ausreichend, um Vor- und Nachteile der Bauchlagerung für nicht-intubierte ARDS Patient/innen gegenüber der üblichen Rückenlagerung aufzuzeigen und diese für die Praxis zu empfehlen. / Prone positioning of intubated ARDS patients with poor oxygenation has been recommended as a supportive therapy for several years. In the context of the COVID-19 pandemic, prone positioning has now been investigated for the first time in hypoxemic, non-intubated patients. This issue was examined by our systematic review. Because of the current pandemic situation, we assessed the effects of prone positioning in COVID-19 patients with acute respiratory failure in particular as a subgroup in addition to ARDS patients in general. A systematic search for studies was performed in MEDLINE, Cochrane COVID-19 Study Register, and Living Overview of the Evidence platform databases on 21 November 2020. Where possible, results were analyzed in the form of meta-analysis, presented in tables, or described descriptively. Risk of bias was assessed for each of the included controlled studies using ROBINS-I. The quality of evidence for the entire systematic review was assessed using the GRADE approach. A total of 30 studies were included, 4 of which were controlled trials, but no RCTs. 3 of the controlled trials investigated prone positioning in COVID-19 patients, one trial in patients with ARDS caused by other means. It is unclear whether prone positioning can reduce intubation rate (RR =0.92; 95% CI: 0.59-1.44; I²=65%; very low quality evidence), mortality (RR =0.55; 95% CI: 0.23-1.30; I²=60%; very low quality evidence), and the likelihood of ICU admission (RR =0.94; 95% CI: 0.54-1.63; I2 =71%; very low quality evidence). No significant effect of prone positioning was demonstrated for the other outcomes considered either. When comparing the "non-COVID-19" (8 studies) and "COVID-19" (22 studies) subgroups, no relevant differences were found for all outcomes assessed. Overall, the evidence is insufficient to demonstrate benefits and harms of prone positioning for non-intubated ARDS patients compared with usual care and to translate the results into practice.