A Barrier to Defend - Models of Pulmonary Barrier to Study Acute Inflammatory Diseases

Pulmonary diseases represent four out of ten most common causes for worldwide mortality. Thus, pulmonary infections with subsequent inflammatory responses represent a major public health concern. The pulmonary barrier is a vulnerable entry site for several stress factors, including pathogens such as viruses, and bacteria, but also environmental factors e.g. toxins, air pollutants, as well as allergens. These pathogens or pathogen-associated molecular pattern and inflammatory agents e.g. damage-associated molecular pattern cause significant disturbances in the pulmonary barrier. The physiological and biological functions, as well as the architecture and homeostatic maintenance of the pulmonary barrier are highly complex. The airway epithelium, denoting the first pulmonary barrier, encompasses cells releasing a plethora of chemokines and cytokines, and is further covered with a mucus layer containing antimicrobial peptides, which are responsible for the pathogen clearance. Submucosal antigen-presenting cells and neutrophilic granulocytes are also involved in the defense mechanisms and counterregulation of pulmonary infections, and thus may directly affect the pulmonary barrier function. The detailed understanding of the pulmonary barrier including its architecture and functions is crucial for the diagnosis, prognosis, and therapeutic treatment strategies of pulmonary diseases. Thus, considering multiple side effects and limited efficacy of current therapeutic treatment strategies in patients with inflammatory diseases make experimental in vitro and in vivo models necessary to improving clinical therapy options. This review describes existing models for studyying the pulmonary barrier function under acute inflammatory conditions, which are meant to improve the translational approaches for outcome predictions, patient monitoring, and treatment decision-making. Copyright © 2022 Herminghaus, Kozlov, Szabó, Hantos, Gylstorff, Kuebart, Aghapour, Wissuwa, Walles, Walles, Coldewey and Relja

A Barrier to Defend - Models of Pulmonary Barrier to Study Acute Inflammatory Diseases

Pulmonary diseases represent four out of ten most common causes for worldwide mortality. Thus, pulmonary infections with subsequent inflammatory responses represent a major public health concern. The pulmonary barrier is a vulnerable entry site for several stress factors, including pathogens such as viruses, and bacteria, but also environmental factors e.g. toxins, air pollutants, as well as allergens. These pathogens or pathogen-associated molecular pattern and inflammatory agents e.g. damage-associated molecular pattern cause significant disturbances in the pulmonary barrier. The physiological and biological functions, as well as the architecture and homeostatic maintenance of the pulmonary barrier are highly complex. The airway epithelium, denoting the first pulmonary barrier, encompasses cells releasing a plethora of chemokines and cytokines, and is further covered with a mucus layer containing antimicrobial peptides, which are responsible for the pathogen clearance. Submucosal antigen-presenting cells and neutrophilic granulocytes are also involved in the defense mechanisms and counterregulation of pulmonary infections, and thus may directly affect the pulmonary barrier function. The detailed understanding of the pulmonary barrier including its architecture and functions is crucial for the diagnosis, prognosis, and therapeutic treatment strategies of pulmonary diseases. Thus, considering multiple side effects and limited efficacy of current therapeutic treatment strategies in patients with inflammatory diseases make experimental in vitro and in vivo models necessary to improving clinical therapy options. This review describes existing models for studyying the pulmonary barrier function under acute inflammatory conditions, which are meant to improve the translational approaches for outcome predictions, patient monitoring, and treatment decision-making

Droplets Formation and Merging in Two-Phase Flow Microfluidics

Two-phase flow microfluidics is emerging as a popular technology for a wide range of applications involving high throughput such as encapsulation, chemical synthesis and biochemical assays. Within this platform, the formation and merging of droplets inside an immiscible carrier fluid are two key procedures: (i) the emulsification step should lead to a very well controlled drop size (distribution); and (ii) the use of droplet as micro-reactors requires a reliable merging. A novel trend within this field is the use of additional active means of control besides the commonly used hydrodynamic manipulation. Electric fields are especially suitable for this, due to quantitative control over the amplitude and time dependence of the signals, and the flexibility in designing micro-electrode geometries. With this, the formation and merging of droplets can be achieved on-demand and with high precision. In this review on two-phase flow microfluidics, particular emphasis is given on these aspects. Also recent innovations in microfabrication technologies used for this purpose will be discussed

Pravastatin and Gemfibrozil Modulate Differently Hepatic and Colonic Mitochondrial Respiration in Tissue Homogenates from Healthy Rats

Statins and fibrates are widely used for the management of hypertriglyceridemia but they also have limitations, mostly due to pharmacokinetic interactions or side effects. It is conceivable that some adverse events like liver dysfunction or gastrointestinal discomfort are caused by mitochondrial dysfunction. Data about the effects of statins and fibrates on mitochondrial function in different organs are inconsistent and partially contradictory. The aim of this study was to investigate the effect of pravastatin (statin) and gemfibrozil (fibrate) on hepatic and colonic mitochondrial respiration in tissue homogenates. Mitochondrial oxygen consumption was determined in colon and liver homogenates from 48 healthy rats after incubation with pravastatin or gemfibrozil (100, 300, 1000 μM). State 2 (substrate dependent respiration) and state 3 (adenosine diphosphate: ADP-dependent respiration) were assessed. RCI (respiratory control index)—an indicator for coupling between electron transport chain system (ETS) and oxidative phosphorylation (OXPHOS) and ADP/O ratio—a parameter for the efficacy of OXPHOS, was calculated. Data were presented as a percentage of control (Kruskal–Wallis + Dunn’s correction). In the liver both drugs reduced state 3 and RCI, gemfibrozil-reduced ADP/O (complex I). In the colon both drugs reduced state 3 but enhanced ADP/O. Pravastatin at high concentration (1000 µM) decreased RCI (complex II). Pravastatin and gemfibrozil decrease hepatic but increase colonic mitochondrial respiration in tissue homogenates from healthy rats

Post-traumatic sepsis is associated with increased C5a and decreased TAFI levels

Background: Sepsis frequently occurs after major trauma and is closely associated with dysregulations in the inflammatory/complement and coagulation system. Thrombin-activatable fibrinolysis inhibitor (TAFI) plays a dual role as an anti-fibrinolytic and anti-inflammatory factor by downregulating complement anaphylatoxin C5a. The purpose of this study was to investigate the association between TAFI and C5a levels and the development of post-traumatic sepsis. Furthermore, the predictive potential of both TAFI and C5a to indicate sepsis occurrence in polytraumatized patients was assessed. Methods: Upon admission to the emergency department (ED) and daily for the subsequent ten days, circulating levels of TAFI and C5a were determined in 48 severely injured trauma patients (injury severity score (ISS) ≥ 16). Frequency matching according to the ISS in septic vs. non-septic patients was performed. Trauma and physiologic characteristics, as well as outcomes, were assessed. Statistical correlation analyses and cut-off values for predicting sepsis were calculated. Results: Fourteen patients developed sepsis, while 34 patients did not show any signs of sepsis (no sepsis). Overall injury severity, as well as demographic parameters, were comparable between both groups (ISS: 25.78 ± 2.36 no sepsis vs. 23.46 ± 2.79 sepsis). Septic patients had significantly increased C5a levels (21.62 ± 3.14 vs. 13.40 ± 1.29 ng/mL; p < 0.05) and reduced TAFI levels upon admission to the ED (40,951 ± 5637 vs. 61,865 ± 4370 ng/mL; p < 0.05) compared to the no sepsis group. Negative correlations between TAFI and C5a (p = 0.0104) and TAFI and lactate (p = 0.0423) and positive correlations between C5a and lactate (p = 0.0173), as well as C5a and the respiratory rate (p = 0.0266), were found. In addition, correlation analyses of both TAFI and C5a with the sequential (sepsis-related) organ failure assessment (SOFA) score have confirmed their potential as early sepsis biomarkers. Cut-off values for predicting sepsis were 54,857 ng/mL for TAFI with an area under the curve (AUC) of 0.7550 (p = 0.032) and 17 ng/mL for C5a with an AUC of 0.7286 (p = 0.034). Conclusion: The development of sepsis is associated with early decreased TAFI and increased C5a levels after major trauma. Both elevated C5a and decreased TAFI may serve as promising predictive factors for the development of sepsis after polytrauma

Propofol improves colonic but impairs hepatic mitochondrial function in tissue homogenates from healthy rats

Evidence suggests that propofol infusion syndrome (PRIS) is caused by an altered mitochondrial function. The aim of this study was to examine the effects of propofol and the vehicle MCT on mitochondrial function in hepatic and colonic tissue. Mitochondrial oxygen consumption was determined in colon and liver homogenates after incubation with buffer (control), propofol (50, 75, 100, 500 mu M) or the carrier substances DMSO and MCT. State 2 (substrate-dependent) and state 3 (ADP-dependent respiration) were assessed. RCI (respiratory control index) - an indicator for coupling between electron transport chain system (ETS) and oxidative phosphorylation (OXPHOS) and ADP/O ratio - a parameter for efficacy of OXPHOS were calculated. Data were presented as % of control. In hepatic mitochondria, 500 mu M propofol reduced RCI formulation-independently (propofol/MCT 500 mu M: complex I: 66.3 +/- 8.7%*, complex II: 75.5 +/- 9.2%*; propofol/DMSO 500 mu M: complex I: 29.1 +/- 8.8%*, complex II: 49.3 +/- 15.5%*). 75 mu M Propofol/MCT reduced ADP/O for complex I (73.5 +/- 27.3%*). DMSO did not affect hepatic mitochondria whereas MCT reduced RCI for complex II (87.2 +/- 9.8%*) and ADP/0 for complex I (93.7 +/- 31.7%*). In colon 50 mu M Propofol/MCT increased RCI for complex I and II (complex I: 127.2 +/- 10.7%*, complex II: 136.8 +/- 33.9%") and 100 mu M Propofol/MCT for complex I (131.4 +/- 18.7%*). 500 mu M Propofol/DMSO increased ADP/O for complex I (139.4 +/- 41.4%*). DMSO did not affect RCI but increased ADP/O for both complexes (complex I: 119.9 +/- 25.8%*, complex II: 110.2 +/- 14.2%*). MCT increased RCI for complex I (123.0 +/- 31.6%*). In hepatic mitochondria propofol uncoupled ETS from OXPHOS formulation-independently and propofol/MCT reduced efficacy of OXPHOS. In colonic mitochondria, propofol/MCT strengthened the coupling and propofol/DMSO enhanced the efficacy of OXPHOS

Effect of Topical Iloprost and Nitroglycerin on Gastric Microcirculation and Barrier Function during Hemorrhagic Shock in Dogs

Background: Topical drug application is used to avoid systemic side effects. The aim of this study was to analyze whether locally applied iloprost or nitroglycerin influence gastric mucosal perfusion, oxygenation, and barrier function during physiological and hemorrhagic conditions. Methods: In repeated experiments, 5 anesthetized dogs received iloprost, nitroglycerin, or normal saline during physiological and hemorrhagic (-20% blood volume) conditions. Macro and microcirculatory variables were recorded continuously. Gastric barrier function was assessed via translocation of sucrose into the blood. Results: During hemorrhage, gastric mucosal oxygenation decreased from 77 +/- 4 to 37 +/- 7%. This effect was attenuated by nitroglycerin (78 +/- 6 to 47 +/- 13%) and iloprost (82 +/- 4 to 54 +/- 9%). Sucrose plasma levels increased during hemorrhage from 7 +/- 4 to 55 +/- 15 relative amounts. This was alleviated by nitroglycerin (5 8 to 29 +/- 38 relative amounts). These effects were independent of sys-temic hemodynamic variables. Conclusions: During hemorrhage, topical nitroglycerin and iloprost improve regional gastric oxygenation without affecting perfusion. Nitroglycerin attenuated the shock-induced impairment of the mucosal barrier integrity. Thus, local drug application improves gastric microcirculation without compromising systemic hemodynamic variables, and it may also protect mucosal barrier function. (C) 2017 S. Karger AG, Base

Exogenous vasopressin dose-dependently modulates gastric microcirculatory oxygenation in dogs via V1A receptor

Background Hypercapnia improves gastric microcirculatory oxygenation (mu HbO(2)) and increases vasopressin plasma levels, whereas V1A receptor blockade abolishes the increase of mu HbO(2). The aim of this study was to evaluate the effect of exogenous vasopressin (AVP) in increasing doses on microcirculatory perfusion and oxygenation and systemic hemodynamic variables. Furthermore, we evaluated the role of the vasopressin V1A receptor in mediating the effects. Methods In repetitive experiments, six anesthetized dogs received a selective vasopressin V1A receptor inhibitor ([Pmp(1), Tyr (Me)(2)]-Arg(8)-Vasopressin) or sodium chloride (control groups). Thereafter, a continuous infusion of AVP was started with dose escalation every 30 min (0.001 ng/kg/min-1 ng/kg/min). Microcirculatory variables of the oral and gastric mucosa were measured with reflectance spectrometry, laser Doppler flowmetry, and incident dark field imaging. Transpulmonary thermodilution was used to measure systemic hemodynamic variables. AVP plasma concentrations were measured during baseline conditions and 30 min after each dose escalation. Results During control conditions, gastric mu HbO(2) did not change during the course of experiments. Infusion of 0.001 ng/kg/min and 0.01 ng/kg/min AVP increased gastric mu HbO(2) to 87 +/- 4% and 87 +/- 6%, respectively, compared to baseline values (80 +/- 7%), whereas application of 1 ng/kg/min AVP strongly reduced gastric mu HbO(2) (59 +/- 16%). V1A receptor blockade prior to AVP treatment abolished these effects on mu HbO(2). AVP dose-dependently enhanced systemic vascular resistance (SVR) and decreased cardiac output (CO). After prior V1A receptor blockade, SVR was reduced and CO increased (0.1 ng/kg/min + 1 ng/kg/min AVP). Conclusions Exogenous AVP dose-dependently modulates gastric mu HbO(2), with an increased mu HbO(2) with ultra-low dose AVP. The effects of AVP on mu HbO(2) are abolished by V1A receptor inhibition. These effects are independent of a modulation of systemic hemodynamic variables

Local gastric RAAS inhibition improves gastric microvascular perfusion in dogs

During circulatory shock, gastrointestinal microcirculation is impaired, especially via activation of the renin-angiotensin-aldosterone system. Therefore, inhibition of the renin-angiotensin-aldosterone system might be beneficial in maintaining splanchnic microcirculation. The aim of this study was to analyze whether locally applied losartan influences gastric mucosal perfusion (mu flow, mu velo) and oxygenation (mu HbO(2)) without systemic hemodynamic changes. In repetitive experiments six anesthetized dogs received 30 mg losartan topically on the oral and gastric mucosa during normovolemia and hemorrhage (-20% blood volume). Microcirculatory variables were measured with reflectance spectrometry, laser Doppler flowmetry and incident dark field imaging. Transpulmonary thermodilution and pulse contour analysis were used to measure systemic hemodynamic variables. Gastric barrier function was assessed via differential absorption of inert sugars. During normovolemia, losartan increased gastric mu flow from 99 +/- 6 aU to 147 +/- 17 aU and mu velo from 17 +/- 1 aU to 19 +/- 1 all. During hemorrhage, losartan did not improve mu flow. mu velo decreased from 17 +/- 1 aU to 14 +/- 1 aU in the control group. Application of losartan did not significantly alter mu velo (16 +/- 1 aU) compared to the control group and to baseline levels (17 +/- 1 aU). No effects of topical losartan on macrohemodynamic variables or microcirculatory oxygenation were detected. Gastric microcirculatory perfusion is at least partly regulated by local angiotensin receptors. Topical application of losartan improves local perfusion via vasodilation without significant effects on systemic hemodynamics. During mild hemorrhage losartan had minor effects on regional perfusion, probably because of a pronounced upstream vasoconstriction