Immunology
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12503/30814
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Browsing Immunology by Author "Dick, Gregory"
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Item Cardiovascular Response to Endotoxin-Mediated Sepsis: A Dose-Response Study(2022) Aguirre, David Salinas; Martinez, Richard; Warne, Cooper; Mallet, Robert T.; Dick, Gregory; Tune, Johnathan; Hodge, LisaPurpose: Our long-term goal is to advance our understanding and treatment of sepsis, a potentially life-threatening condition that occurs when the response to infection causes tissue and organ damage. Sepsis can be caused by lipopolysaccharide (LPS), a major component of the outer membrane of Gram-negative bacteria. We used a swine model of LPS-induced sepsis to study the impact of the lymphatic and immune systems on the disease progression. Our first experiments were aimed at determining the optimal dose of Escherichia coli LPS in order to study the effect of sepsis on the cardiovascular system. We hypothesized that 2-hour intravenous infusions of 1- 50 µg/kg LPS would reveal dose- and time-dependent changes in hemodynamic parameters that are consistent with sepsis. Methods: Yorkshire pigs (61 ± 4 kg, n = 4, 2 male) were sedated, intubated, and ventilated. Femoral artery and venous lines were placed to allow measurement of blood pressure, infusion of LPS, and blood gas sampling. A thoracotomy was performed in order to secure a Transonic flow probe around the left anterior descending coronary artery and to insert a sampling catheter in the anterior cardiac vein. A dose of LPS (1, 5, 25, and 50 µg/kg) was given to each pig over 2 hours. Blood samples were collected immediately before LPS infusion and for every 30 minutes during and after LPS infusion for blood gas measurements. Vital signs were recorded as the animals developed sepsis. Results: Only the pig given the lowest dose of LPS (1 µg/kg) survived the full 6 hours (mean survival time in remaining 3 pigs was 180 ± 30 min). At 150 min, a ≈55% decrease in mean arterial pressure was observed (107 ± 4 to 48 ± 13 mmHg), resulting in a ≈60% increase in heart rate (91 ± 9 to 146 ± 14 beats/min). Coronary blood flow and myocardial oxygen consumption decreased ≈28% (0.53 ± 0.06 to 0.38 ± 0.02 ml/min/g) and ≈33% (60 ± 6 to 44 ± 2 µl/min/g), respectively. Ventricular fibrillation was the cause of death in the 3 non-surviving pigs. Conclusion: A dose of 1 µg/kg appears to be an optimal dose for future studies, as this dose was survivable in the desired time frame, while causing hypotension and tachycardia. In future studies, this model will allow us to study the effect of novel therapeutics during acute sepsis.Item Cytokine Response in an Endotoxin-Mediated Sepsis Model(2022) Martinez, Richard; Aguirre, David Salinas; Warne, Cooper; Dick, Gregory; Mallet, Robert T.; Tune, Johnathan; Hodge, LisaPurpose: Sepsis is a life-threatening condition that develops secondary to infection and can manifest acute organ dysfunction due to the body's overactive systemic response. Sepsis affects approximately 1.7 million US adults and claims 270,000 lives as a result. The long-term goal of our project is to gain a better understanding of the roles of the lymphatic and immune systems in the progression of sepsis. The purpose of this study is to collect pilot data using a translational swine model of endotoxin-mediated sepsis. We chose a swine model because it closely mimics how sepsis progresses in humans. Sepsis was induced by infusion of lipopolysaccharide (LPS) from Escherichia coli. LPS was chosen because it is a key mediator in the activation of the immune system and the development of sepsis. We hypothesized that the administration of LPS would increase the concertation of the proinflammatory cytokines interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-?) in a dose-dependent manner over time. Methods: Yorkshire pigs (61 � 4 kg, n = 4, 2 male) were sedated, intubated, and ventilated. Thoracotomy was performed under anesthesia to record flow data and sample cardiac blood for use in another study. Femoral artery and venous lines were placed to allow measurement of blood pressure and infusion of LPS. Specifically, LPS was prepared at 1, 5, 25, or 50 ?g/kg (pig body weight) in sterile saline. LPS was infused into anesthetized pigs over a 2-hour period. Blood samples were collected immediately prior to LPS administration and at 30 min intervals during 2 hours of LPS infusion up to 4 hours following LPS infusion. The plasma was analyzed via enzyme-linked immunosorbent immunoassay (ELISA) for the concentrations of IL-6 and TNF-? using commercially available kits. Results: As hypothesized, the infusion of LPS increased the concentration of the inflammatory mediators IL-6 and TNF-? over time compared to pre-LPS infusion. Specifically, the greatest increase in IL-6 was seen at 180 minutes in both the 50 and 25 ?g/kg LPS infused pigs. TNF-? concentration peaked between 30 to 90 minutes during LPS infusion in both the 50 and 25 ?g/kg LPS infused pigs. The lower doses of 1 and 5 ?g/kg LPS produced little to no IL-6 or TNF-?. Furthermore, we discovered that the pigs who received 50 or 25 ?g/kg of LPS died from septic shock within 180 minutes of LPS infusion, whereas the pigs that received 1or 5 ?g/kg of LPS survived longer. Conclusion: In this study, we identified the impact of increasing the doses of LPS on the production of IL-6 and TNF-? in swine. Our preliminary results suggest a dose range of 10-20 ?g/kg of LPS may be ideal to study the inflammatory response in this model. The acquisition of these data are essential to pursue our long-term research objective, which is to identify the role of the lymphatic and immune systems during sepsis.