The effect of sodium thiosulfate on immune cell metabolism during porcine hemorrhage and resuscitation.

Introduction: Sodium thiosulfate (Na2S2O3), an H2S releasing agent, was shown to be organ-protective in experimental hemorrhage. Systemic inflammation activates immune cells, which in turn show cell type-specific metabolic plasticity with modifications of mitochondrial respiratory activity. Since H2S can dose-dependently stimulate or inhibit mitochondrial respiration, we investigated the effect of Na2S2O3 on immune cell metabolism in a blinded, randomized, controlled, long-term, porcine model of hemorrhage and resuscitation. For this purpose, we developed a Bayesian sampling-based model for 13C isotope metabolic flux analysis (MFA) utilizing 1,2-13C2-labeled glucose, 13C6-labeled glucose, and 13C5-labeled glutamine tracers. Methods: After 3 h of hemorrhage, anesthetized and surgically instrumented swine underwent resuscitation up to a maximum of 68 h. At 2 h of shock, animals randomly received vehicle or Na2S2O3 (25 mg/kg/h for 2 h, thereafter 100 mg/kg/h until 24 h after shock). At three time points (prior to shock, 24 h post shock and 64 h post shock) peripheral blood mononuclear cells (PBMCs) and granulocytes were isolated from whole blood, and cells were investigated regarding mitochondrial oxygen consumption (high resolution respirometry), reactive oxygen species production (electron spin resonance) and fluxes within the metabolic network (stable isotope-based MFA). Results: PBMCs showed significantly higher mitochondrial O2 uptake and lower O 2 • - production in comparison to granulocytes. We found that in response to Na2S2O3 administration, PBMCs but not granulocytes had an increased mitochondrial oxygen consumption combined with a transient reduction of the citrate synthase flux and an increase of acetyl-CoA channeled into other compartments, e.g., for lipid biogenesis. Conclusion: In a porcine model of hemorrhage and resuscitation, Na2S2O3 administration led to increased mitochondrial oxygen consumption combined with stimulation of lipid biogenesis in PBMCs. In contrast, granulocytes remained unaffected. Granulocytes, on the other hand, remained unaffected. O 2 • - concentration in whole blood remained constant during shock and resuscitation, indicating a sufficient anti-oxidative capacity. Overall, our MFA model seems to be is a promising approach for investigating immunometabolism; especially when combined with complementary methods.

Target arterial PO2 according to the underlying pathology: a mini-review of the available data in mechanically ventilated patients.

There is an ongoing discussion whether hyperoxia, i.e. ventilation with high inspiratory O2 concentrations (FIO2), and the consecutive hyperoxaemia, i.e. supraphysiological arterial O2 tensions (PaO2), have a place during the acute management of circulatory shock. This concept is based on experimental evidence that hyperoxaemia may contribute to the compensation of the imbalance between O2 supply and requirements. However, despite still being common practice, its use is limited due to possible oxygen toxicity resulting from the increased formation of reactive oxygen species (ROS) limits, especially under conditions of ischaemia/reperfusion. Several studies have reported that there is a U-shaped relation between PaO2 and mortality/morbidity in ICU patients. Interestingly, these mostly retrospective studies found that the lowest mortality coincided with PaO2 ~ 150 mmHg during the first 24 h of ICU stay, i.e. supraphysiological PaO2 levels. Most of the recent large-scale retrospective analyses studied general ICU populations, but there are major differences according to the underlying pathology studied as well as whether medical or surgical patients are concerned. Therefore, as far as possible from the data reported, we focus on the need of mechanical ventilation as well as the distinction between the absence or presence of circulatory shock. There seems to be no ideal target PaO2 except for avoiding prolonged exposure (> 24 h) to either hypoxaemia (PaO2 < 55-60 mmHg) or supraphysiological (PaO2 > 100 mmHg). Moreover, the need for mechanical ventilation, absence or presence of circulatory shock and/or the aetiology of tissue dysoxia, i.e. whether it is mainly due to impaired macro- and/or microcirculatory O2 transport and/or disturbed cellular O2 utilization, may determine whether any degree of hyperoxaemia causes deleterious side effects.

Effects of Acute Subdural Hematoma-Induced Brain Injury On Energy Metabolism in Peripheral Blood Mononuclear Cells.

ABSTRACT: In activated immune cells, differentiation and function are determined by cell type-specific modifications of metabolic patterns. After traumatic brain injury both immune cell activation and suppression were reported. Therefore, we sought to explore immune cell energy metabolism in a long-term, resuscitated porcine model of acute subdural hematoma (ASDH)-induced acute brain injury devoid of impaired systemic hemodynamics and oxygen transport.Before and up to 50 h after induction of ASDH, peripheral blood mononuclear cells (PBMCs) were separated by density gradient centrifugation, and cell metabolism was analyzed using high-resolution respirometry for mitochondrial respiration and electron spin resonance for reactive oxygen species production. After incubation with stable isotope-labeled 1,2-13C2-glucose or 13C5-glutamine, distinct labeling patterns of intermediates of glycolysis or tricarboxylic acid (TCA) cycle and 13CO2 production were measured by gas chromatography-mass spectroscopy. Principal component analysis was followed by a varimax rotation on the covariance across all measured variables and all measured time points.After ASDH induction, average PBMC metabolic activity remained unaffected, possibly because strict adherence to intensive care unit guidelines limited trauma to ASDH induction without any change in parameters of systemic hemodynamics, oxygen transport, and whole-body metabolism. Despite decreased glycolytic activity fueling the TCA cycle, the principal component analysis indicated a cell type-specific activation pattern with biosynthetic and proliferative characteristics.

Metabolic substrate utilization in stress-induced immune cells.

Immune cell activation leads to the acquisition of new functions, such as proliferation, chemotaxis, and cytokine production. These functional changes require continuous metabolic adaption in order to sustain ATP homeostasis for sufficient host defense. The bioenergetic demands are usually met by the interconnected metabolic pathways glycolysis, TCA cycle, and oxidative phosphorylation. Apart from glucose, other sources, such as fatty acids and glutamine, are able to fuel the TCA cycle.Rising evidence has shown that cellular metabolism has a direct effect on the regulation of immune cell functions. Thus, quiescent immune cells maintain a basal metabolic state, which shifts to an accelerated metabolic level upon immune cell activation in order to promote key effector functions.This review article summarizes distinct metabolic signatures of key immune cell subsets from quiescence to activation and demonstrates a methodical concept of how to assess cellular metabolic pathways. It further discusses why metabolic functions are of rising interest for translational research and how they can be affected by the underlying pathophysiological condition and/or therapeutic interventions.

H2S in acute lung injury: a therapeutic dead end(?).

This review addresses the plausibility of hydrogen sulfide (H2S) therapy for acute lung injury (ALI) and circulatory shock, by contrasting the promising preclinical results to the present clinical reality. The review discusses how the narrow therapeutic window and width, and potentially toxic effects, the route, dosing, and timing of administration all have to be balanced out very carefully. The development of standardized methods to determine in vitro and in vivo H2S concentrations, and the pharmacokinetics and pharmacodynamics of H2S-releasing compounds is a necessity to facilitate the safety of H2S-based therapies. We suggest the potential of exploiting already clinically approved compounds, which are known or unknown H2S donors, as a surrogate strategy.

In-depth characterization of a long-term, resuscitated model of acute subdural hematoma-induced brain injury.

OBJECTIVE: Acute subdural hematoma (ASDH) is a leading entity in brain injury. Rodent models mostly lack standard intensive care, while large animal models frequently are only short term. Therefore, the authors developed a long-term, resuscitated porcine model of ASDH-induced brain injury and report their findings. METHODS: Anesthetized, mechanically ventilated, and instrumented pigs with human-like coagulation underwent subdural injection of 20 mL of autologous blood and subsequent observation for 54 hours. Continuous bilateral multimodal brain monitoring (intracranial pressure [ICP], cerebral perfusion pressure [CPP], partial pressure of oxygen in brain tissue [PbtO2], and brain temperature) was combined with intermittent neurological assessment (veterinary modified Glasgow Coma Scale [MGCS]), microdialysis, and measurement of plasma protein S100ß, GFAP, neuron-specific enolase [NSE], nitrite+nitrate, and isoprostanes. Fluid resuscitation and continuous intravenous norepinephrine were targeted to maintain CPP at pre-ASDH levels. Immediately postmortem, the brains were taken for macroscopic and histological evaluation, immunohistochemical analysis for nitrotyrosine formation, albumin extravasation, NADPH oxidase 2 (NOX2) and GFAP expression, and quantification of tissue mitochondrial respiration. RESULTS: Nine of 11 pigs survived the complete observation period. While ICP significantly increased after ASDH induction, CPP, PbtO2, and the MGCS score remained unaffected. Blood S100ß levels significantly fell over time, whereas GFAP, NSE, nitrite+nitrate, and isoprostane concentrations were unaltered. Immunohistochemistry showed nitrotyrosine formation, albumin extravasation, NOX2 expression, fibrillary astrogliosis, and microglial activation. CONCLUSIONS: The authors describe a clinically relevant, long-term, resuscitated porcine model of ASDH-induced brain injury. Despite the morphological injury, maintaining CPP and PbtO2 prevented serious neurological dysfunction. This model is suitable for studying therapeutic interventions during hemorrhage-induced acute brain injury with standard brain-targeted intensive care.

In-Depth Characterization of the Effects of Cigarette Smoke Exposure on the Acute Trauma Response and Hemorrhage in Mice.

INTRODUCTION: Hemorrhagic shock accounts for a large amount of trauma-related mortality. The severity of trauma can be further aggravated by an additional blunt chest trauma (TxT), which independently contributes to mortality upon the development of an acute lung injury (ALI). Besides, cigarette smoke (CS) exposure before TxT enhanced posttraumatic inflammation, thereby aggravating ALI. We therefore aimed to characterize the impact of an acute and/or chronic lung injury on organ dysfunction in a murine model of traumatic hemorrhagic shock (HS). METHODS: After 3 weeks of CS exposure, anesthetized mice underwent HS with/without TxT. Hemorrhagic shock was implemented for 1 h followed by retransfusion of shed blood and intensive care therapy for 4 h including lung-protective mechanical ventilation, fluid resuscitation, and noradrenaline titrated to maintain mean arterial pressure ≥50 mmHg. Lung mechanics and gas exchange were assessed together with systemic hemodynamics, metabolism, and acid-base status. Postmortem blood and tissue samples were analyzed for cytokine and chemokine levels, protein expression, mitochondrial respiration, and histological changes. RESULTS: CS exposure and HS alone coincided with increased inflammation, decreased whole blood sulfide concentrations, and decreased diaphragmatic mitochondrial respiration. CS-exposed mice, which were subjected to TxT and subsequent HS, showed hemodynamic instability, acute kidney injury, and high mortality. CONCLUSIONS: Chronic CS exposure per se had the strongest impact on inflammatory responses. The degree of inflammation was similar upon an additional TxT, however, mice presented with organ dysfunction and increased mortality rates. Hence, in mice the degree of inflammation may be dissociated from the severity of organ dysfunction or injury.

Effects of Psychosocial Stress on Subsequent Hemorrhagic Shock and Resuscitation in Male Mice.

BACKGROUND: Hypoxemia and tissue ischemia during hemorrhage as well as formation of oxygen and nitrogen radicals during resuscitation promote hyperinflammation and, consequently, trigger severe multi-organ failure (MOF). Individuals diagnosed with stress-related disorders or reporting a life history of psychosocial stress are characterized by chronic low-grade inflammation and a reduced glucocorticoid (GC) signaling. We hypothesized that exposure to chronic psychosocial stress during adulthood prior to hemorrhagic shock increases oxidative/nitrosative stress and therefore the risk of developing MOF in mice. METHODS AND FINDINGS: To induce chronic psychosocial stress linked to mild immune activation and reduced GC signaling in male mice, the chronic subordinate colony housing (CSC) paradigm was employed. Single-housed (SHC) mice were used as controls. Subsequently, CSC and SHC mice were exposed to hemorrhagic shock following resuscitation to investigate the effects of prior psychosocial stress load on survival, organ function, metabolism, oxidative/nitrosative stress, and inflammatory readouts. An increased adrenal weight in CSC mice indicates that the stress paradigm reliably worked. However, no effect of prior psychosocial stress on outcome after subsequent hemorrhage and resuscitation could be detected. CONCLUSIONS: Chronic psychosocial stress during adulthood is not sufficient to promote hemodynamic complications, organ dysfunction, metabolic disturbances and did not increase the risk of MOF after subsequent hemorrhage and resuscitation. Intravenous norepinephrine to keep target hemodynamics might have led to a certain level of oxidative stress in both groups and, therefore, disguised potential effects of chronic psychosocial stress on organ function after hemorrhagic shock in the present murine trauma model.

The Effects of Genetic 3-Mercaptopyruvate Sulfurtransferase Deficiency in Murine Traumatic-Hemorrhagic Shock.

INTRODUCTION: Hemorrhagic shock is a major cause of death after trauma. An additional blunt chest trauma independently contributes to mortality upon the development of an acute lung injury (ALI) by aggravating pathophysiological consequences of hemorrhagic shock. The maintenance of hydrogen sulfide availability is known to play an important role during hemorrhage and ALI. We therefore tested the impact of a genetic 3-mercaptopyruvate sulfurtransferase mutation (Δ3-MST) in a resuscitated murine model of traumatic-hemorrhagic shock. METHODS: Anesthetized wild-type (WT) and Δ3-MST mice underwent hemorrhagic shock with/without blunt chest trauma. Hemorrhagic shock was implemented for 1 h followed by retransfusion of shed blood and intensive care therapy for 4 h, including lung-protective mechanical ventilation, fluid resuscitation, and noradrenaline titrated to maintain a mean arterial pressure at least 50 mmHg. Systemic hemodynamics, metabolism, and acid-base status were assessed together with lung mechanics and gas exchange. Postmortem tissue samples were analyzed for immunohistological protein expression and mitochondrial oxygen consumption. RESULTS: 3-MST-deficient mice showed similar results in parameters of hemodynamics, gas exchange, metabolism, acid base status, and survival compared with the respective WT controls. Renal albumin extravasation was increased in Δ3-MST mice during hemorrhagic shock, together with a decrease of LEAK respiration in heart tissue. In contrast, mitochondrial oxygen consumption in the uncoupled state was increased in kidney and liver tissue of Δ3-MST mice subjected to the combined trauma. CONCLUSIONS: In summary, in a resuscitated murine model of traumatic-hemorrhagic shock, 3-MST deficiency had no physiologically relevant impact on hemodynamics and metabolism, which ultimately lead to unchanged mortality regardless of an additional blunt chest trauma.

The Mitochondria-Targeted H2S-Donor AP39 in a Murine Model of Combined Hemorrhagic Shock and Blunt Chest Trauma.

Hemorrhagic shock (HS) accounts for 30% to 40% of trauma-induced mortality, which is due to multi-organ-failure subsequent to systemic hyper-inflammation, triggered by hypoxemia and tissue ischemia. The slow-releasing, mitochondria-targeted H2S donor AP39 exerted beneficial effects in several models of ischemia-reperfusion injury and acute inflammation. Therefore, we tested the effects of AP39-treatment in a murine model of combined blunt chest trauma (TxT) and HS with subsequent resuscitation. METHODS: After blast wave-induced TxT or sham procedure, anesthetized and instrumented mice underwent 1 h of hemorrhage followed by 4 h of resuscitation comprising an i.v. bolus injection of 100 or 10 nmol kg AP39 or vehicle, retransfusion of shed blood, fluid resuscitation, and norepinephrine. Lung mechanics and gas exchange were assessed together with hemodynamics, metabolism, and acid-base status. Blood and tissue samples were analyzed for cytokine and chemokine levels, western blot, immunohistochemistry, mitochondrial oxygen consumption (JO2), and histological changes. RESULTS: High dose AP39 attenuated systemic inflammation and reduced the expression of inducible nitric oxide synthase (iNOS) and IκBα expression in lung tissue. In the combined trauma group (TxT + HS), animals treated with high dose AP39 presented with the lowest mean arterial pressure and thus highest norepinephrine requirements and higher mortality. Low dose AP39 had no effects on hemodynamics, leading to unchanged norepinephrine requirements and mortality rates. CONCLUSION: AP39 is a systemic anti-inflammatory agent. In our model of trauma with HS, there may be a narrow dosing and timing window due to its potent vasodilatory properties, which might result in or contribute to aggravation of circulatory shock-related hypotension.

Impaired Glucocorticoid Receptor Dimerization Aggravates LPS-Induced Circulatory and Pulmonary Dysfunction.

Background: Sepsis, that can be modeled by LPS injections, as an acute systemic inflammation syndrome is the most common cause for acute lung injury (ALI). ALI induces acute respiratory failure leading to hypoxemia, which is often associated with multiple organ failure (MOF). During systemic inflammation, the hypothalamus-pituitary-adrenal axis (HPA) is activated and anti-inflammatory acting glucocorticoids (GCs) are released to overcome the inflammation. GCs activate the GC receptor (GR), which mediates its effects via a GR monomer or GR dimer. The detailed molecular mechanism of the GR in different inflammatory models and target genes that might be crucial for resolving inflammation is not completely identified. We previously observed that mice with attenuated GR dimerization (GRdim/dim) had a higher mortality in a non-resuscitated lipopolysaccharide (LPS)- and cecal ligation and puncture (CLP)-induced inflammation model and are refractory to exogenous GCs to ameliorate ALI during inflammation. Therefore, we hypothesized that impaired murine GR dimerization (GRdim/dim) would further impair organ function in LPS-induced systemic inflammation under human like intensive care management and investigated genes that are crucial for lung function in this setup. Methods: Anesthetized GRdim/dim and wildtype (GR+/+) mice were challenged with LPS (10 mg·kg-1, intraperitoneal) and underwent intensive care management ("lung-protective" mechanical ventilation, crystalloids, and norepinephrine) for 6 h. Lung mechanics and gas exchange were assessed together with systemic hemodynamics, acid-base status, and mitochondrial oxygen consumption (JO2). Western blots, immunohistochemistry, and real time quantitative polymerase chain reaction were performed to analyze lung tissue and inflammatory mediators were analyzed in plasma and lung tissue. Results: When animals were challenged with LPS and subsequently resuscitated under intensive care treatment, GRdim/dim mice had a higher mortality compared to GR+/+ mice, induced by an increased need of norepinephrine to achieve hemodynamic targets. After challenge with LPS, GRdim/dim mice also displayed an aggravated ALI shown by a more pronounced impairment of gas exchange, lung mechanics and increased osteopontin (Opn) expression in lung tissue. Conclusion: Impairment of GR dimerization aggravates systemic hypotension and impairs lung function during LPS-induced endotoxic shock in mice. We demonstrate that the GR dimer is an important mediator of hemodynamic stability and lung function, possibly through regulation of Opn, during LPS-induced systemic inflammation.

Cardiac Effects of Hyperoxia During Resuscitation From Hemorrhagic Shock in Swine.

Hyperoxia (ventilation with FIO2 = 1.0) has vasoconstrictor properties, in particular in the coronary vascular bed, and, hence, may promote cardiac dysfunction. However, we previously showed that hyperoxia attenuated myocardial injury during resuscitation from hemorrhage in swine with coronary artery disease. Therefore, we tested the hypothesis whether hyperoxia would also mitigate myocardial injury and improve heart function in the absence of chronic cardiovascular comorbidity.After 3 h of hemorrhage (removal of 30% of the calculated blood volume and subsequent titration of mean arterial pressure to 40 mm Hg) 19 anesthetized, mechanically ventilated, and instrumented pigs received FIO2 = 0.3(control) or hyperoxia(FIO2 = 1.0) during the first 24 h. Before, at the end of and every 12 h after shock, hemodynamics, blood gases, metabolism, cytokines, and cardiac function (pulmonary artery thermodilution, left ventricular pressure-conductance catheterization) were recorded. At 48 h, cardiac tissue was harvested for western blotting, immunohistochemistry, and mitochondrial respiration.Except for higher left ventricular end-diastolic pressures at 24 h (hyperoxia 21 (17;24), control 17 (15;18) mm Hg; P = 0.046), hyperoxia affected neither left ventricular function cardiac injury (max. Troponin I at 12 h: hyperoxia:9 (6;23), control:17 (11;24) ng mL; P = 0.395), nor plasma cytokines (except for interleukin-1ß: hyperoxia 10 (10;10) and 10 (10;10)/control 14 (10;22), 12 (10;15) pg mL, P = 0.023 and 0.021 at 12 and 24 h, respectively), oxidation and nitrosative stress, and mitochondrial respiration. However, hyperoxia decreased cardiac tissue three-nitrotyrosine formation (P < 0.001) and inducible nitric oxide synthase expression (P = 0.016). Ultimately, survival did not differ significantly either.In conclusion, in contrast to our previous study in swine with coronary artery disease, hyperoxia did not beneficially affect cardiac function or tissue injury in healthy swine, but was devoid of deleterious side effects.

Interaction of the hydrogen sulfide system with the oxytocin system in the injured mouse heart.

BACKGROUND: Both the hydrogen sulfide/cystathionine-γ-lyase (H2S/CSE) and oxytocin/oxytocin receptor (OT/OTR) systems have been reported to be cardioprotective. H2S can stimulate OT release, thereby affecting blood volume and pressure regulation. Systemic hyper-inflammation after blunt chest trauma is enhanced in cigarette smoke (CS)-exposed CSE-/- mice compared to wildtype (WT). CS increases myometrial OTR expression, but to this point, no data are available on the effects CS exposure on the cardiac OT/OTR system. Since a contusion of the thorax (Txt) can cause myocardial injury, the aim of this post hoc study was to investigate the effects of CSE-/- and exogenous administration of GYY4137 (a slow release H2S releasing compound) on OTR expression in the heart, after acute on chronic disease, of CS exposed mice undergoing Txt. METHODS: This study is a post hoc analysis of material obtained in wild type (WT) homozygous CSE-/- mice after 2-3 weeks of CS exposure and subsequent anesthesia, blast wave-induced TxT, and surgical instrumentation for mechanical ventilation (MV) and hemodynamic monitoring. CSE-/- animals received a 50 µg/g GYY4137-bolus after TxT. After 4h of MV, animals were exsanguinated and organs were harvested. The heart was cut transversally, formalin-fixed, and paraffin-embedded. Immunohistochemistry for OTR, arginine-vasopressin-receptor (AVPR), and vascular endothelial growth factor (VEGF) was performed with naïve animals as native controls. RESULTS: CSE-/- was associated with hypertension and lower blood glucose levels, partially and significantly restored by GYY4137 treatment, respectively. Myocardial OTR expression was reduced upon injury, and this was aggravated in CSE-/-. Exogenous H2S administration restored myocardial protein expression to WT levels. CONCLUSIONS: This study suggests that cardiac CSE regulates cardiac OTR expression, and this effect might play a role in the regulation of cardiovascular function.

Hyperoxia toxicity in septic shock patients according to the Sepsis-3 criteria: a post hoc analysis of the HYPER2S trial.

BACKGROUND: Criteria for the Sepsis-3 definition of septic shock include vasopressor treatment to maintain a mean arterial pressure > 65 mmHg and a lactate concentration > 2 mmol/L. The impact of hyperoxia in patients with septic shock using these criteria is unknown. METHODS: A post hoc analysis was performed of the HYPER2S trial assessing hyperoxia versus normoxia in septic patients requiring vasopressor therapy, in whom a plasma lactate value was available at study inclusion. Mortality was compared between patients fulfilling the Sepsis-3 septic shock criteria and patients requiring vasopressors for hypotension only (i.e., with lactate ≤ 2 mmol/L). RESULTS: Of the 434 patients enrolled, 397 had available data for lactate at inclusion. 230 had lactate > 2 mmol/L and 167 ≤ 2 mmol/L. Among patients with lactate > 2 mmol/L, 108 and 122 were "hyperoxia"- and "normoxia"-treated, respectively. Patients with lactate > 2 mmol/L had significantly less COPD more cirrhosis and required surgery more frequently. They also had higher illness severity (SOFA 10.6 ± 2.8 vs. 9.5 ± 2.5, p = 0.0001), required more renal replacement therapy (RRT), and received vasopressor and mechanical ventilation for longer time. Mortality rate at day 28 was higher in the "hyperoxia"-treated patients with lactate > 2 mmol/L as compared to "normoxia"-treated patients (57.4% vs. 44.3%, p = 0.054), despite similar RRT requirements as well as vasopressor and mechanical ventilation-free days. A multivariate analysis showed an independent association between hyperoxia and mortality at day 28 and 90. In patients with lactate ≤ 2 mmol/L, hyperoxia had no effect on mortality nor on other outcomes. CONCLUSIONS: Our results suggest that hyperoxia may be associated with a higher mortality rate in patients with septic shock using the Sepsis-3 criteria, but not in patients with hypotension alone.

Effects of Hyperoxia During Resuscitation From Hemorrhagic Shock in Swine With Preexisting Coronary Artery Disease.

OBJECTIVES: Investigation of the effects of hyperoxia during resuscitation from hemorrhagic shock in swine with preexisting coronary artery disease. DESIGN: Prospective, controlled, randomized trial. SETTING: University animal research laboratory. SUBJECTS: Nineteen hypercholesterolemic pigs with preexisting coronary artery disease. INTERVENTIONS: Anesthetized, mechanically ventilated, and surgically instrumented pigs underwent 3 hours of hemorrhagic shock (removal of 30% of the calculated blood volume and subsequent titration of mean arterial blood pressure ≈40 mm Hg). Postshock resuscitation (48 hr) comprised retransfusion of shed blood, crystalloids (balanced electrolyte solution), and norepinephrine support. Pigs were randomly assigned to "control" (FIO2 0.3, adjusted for arterial oxygen saturation ≥ 90%) and "hyperoxia" (FIO2 1.0 for 24 hr) groups. MEASUREMENTS AND MAIN RESULTS: Before, at the end of shock and every 12 hours of resuscitation, datasets comprising hemodynamics, calorimetry, blood gases, cytokines, and cardiac and renal function were recorded. Postmortem, organs were sampled for immunohistochemistry, western blotting, and mitochondrial high-resolution respirometry. Survival rates were 50% and 89% in the control and hyperoxia groups, respectively (p = 0.077). Apart from higher relaxation constant τ at 24 hours, hyperoxia did not affect cardiac function. However, troponin values were lower (2.2 [0.9-6.2] vs 6.9 [4.8-9.8] ng/mL; p < 0.05) at the end of the experiment. Furthermore, hyperoxia decreased cardiac 3-nitrotyrosine formation and increased inducible nitric oxide synthase expression. Plasma creatinine values were lower in the hyperoxia group during resuscitation coinciding with significantly improved renal mitochondrial respiratory capacity and lower 3-nitrotyrosine formation. CONCLUSIONS: Hyperoxia during resuscitation from hemorrhagic shock in swine with preexisting coronary artery disease reduced renal dysfunction and cardiac injury, potentially resulting in improved survival, most likely due to increased mitochondrial respiratory capacity and decreased oxidative and nitrosative stress. Compared with our previous study, the present results suggest a higher benefit of hyperoxia in comorbid swine due to an increased susceptibility to hemorrhagic shock.

Gaseous Mediators and Mitochondrial Function: The Future of Pharmacologically Induced Suspended Animation?

The role of nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S) as poisonous gases is well-established. However, they are not only endogenously produced but also, at low concentrations, exert beneficial effects, such as anti-inflammation, and cytoprotection. This knowledge initiated the ongoing debate, as to whether these molecules, also referred to as "gaseous mediators" or "gasotransmitters," could serve as novel therapeutic agents. In this context, it is noteworthy, that all gasotransmitters specifically target the mitochondria, and that this interaction may modulate mitochondrial bioenergetics, thereby subsequently affecting metabolic function. This feature is of crucial interest for the possible induction of "suspended animation." Suspended animation, similar to mammalian hibernation (and/or estivation), refers to an externally induced hypometabolic state, with the intention to preserve organ function in order to survive otherwise life-threatening conditions. This hypometabolic state is usually linked to therapeutic hypothermia, which, however, comes along with adverse effects (e.g., coagulopathy, impaired host defense). Therefore, inducing an on-demand hypometabolic state by directly lowering the energy metabolism would be an attractive alternative. Theoretically, gasotransmitters should reversibly interact and inhibit the mitochondrial respiratory chain during pharmacologically induced suspended animation. However, it has to be kept in mind that this effect also bears the risk of cytotoxicity resulting from the blockade of the mitochondrial respiratory chain. Therefore, this review summarizes the current knowledge of the impact of gasotransmitters on modulating mitochondrial function. Further, we will discuss their role as potential candidates in inducing a suspended animation.

Non-Hemodynamic Effects of Catecholamines.

Circulatory shock is defined as an imbalance between tissue oxygen supply and demand, and mostly results from a loss of blood volume, cardiac pump failure, and/or reduction of vasomotor tone. The clinical hallmarks of circulatory shock are arterial hypotension and lactate acidosis. Since the degree and duration of hypotension are major determinants of outcome, vasopressor administration represents a cornerstone therapy to treat these patients. Current guidelines recommend the use of catecholamines as the drug of first choice. However, apart from their hemodynamic effects, which depend on the different receptor profile, receptor affinity, receptor density, and the relative potency of the individual molecule, catecholamines have numerous other biological effects as a result of the ubiquitous presence of their receptors. In shock states, catecholamines aggravate hypermetabolism by promoting hyperglycemia and hyperlactatemia, and further increase oxygen demands, which can contribute to further organ damage. In the mitochondria, catecholamines may promote mitochondrial uncoupling, and aggravate oxidative stress, thereby contributing to the progression of mitochondrial dysfunction. Immunological side effects have also gained specific attention. Although both pro- and anti-inflammatory effects have been described, current evidence strongly indicates an immunosuppressive effect, thereby making patients potentially vulnerable to secondary infections. Catecholamines may not only decrease splanchnic perfusion due to their vasoconstrictor properties, but can also directly impair gastrointestinal motility. This article reviews the non-hemodynamic effects of different catecholamines, both under physiologic and pathophysiologic conditions, with a special focus on energy metabolism, mitochondrial function, immune response, and the gastrointestinal system.

The Role of Cystathionine-γ-Lyase In Blunt Chest Trauma in Cigarette Smoke Exposed Mice.

Pretraumatic cigarette smoke (CS) exposure aggravates posttraumatic acute lung injury (ALI). Cystathionine-γ-lyase (CSE) protects against ALI and CS exposure-induced chronic obstructive lung disease (COPD). Therefore, we tested the hypothesis whether genetic CSE knockout (CSE) would aggravate posttraumatic ALI after CS exposure. After 3 to 4 weeks of CS exposure, anesthetized wild-type (WT) and CSE mice underwent blunt chest trauma, surgical instrumentation and 4 h of lung-protective mechanical ventilation. We measured hemodynamics, lung mechanics, gas exchange, metabolism, and acid-base status together with blood and tissue cytokine and chemokine levels, tissue expression of mediator proteins, parameters of oxidative and nitrosative stress, and histology. CSE mice without CS exposure showed higher cytokine and chemokine levels, and this was further enhanced by CS exposure, particularly in males. CS exposure in WT mice aggravated posttraumatic alveolar membrane thickening, dystelectasis, and inflammatory cell accumulation, which was associated with higher thoracopulmonary compliance. Pretraumatic CS exposure in CSE mice produced a similar response, except for less alveolar membrane thickening, most likely due to lung hyperinflation. CS-exposed WT mice showed the most pronounced metabolic acidosis, while CS exposure in CSE mice resulted in the lowest blood glucose levels. Urinary output and anesthesia rate were highest in male CS-exposed CSE animals. In conclusion, in murine acute-on-chronic pulmonary disease, CSE knockout aggravated posttraumatic inflammation, which was further worsened upon pretraumatic CS exposure, and this effect was particularly pronounced in males. Hence, maintaining CSE expression is critically important for stress adaptation during ALI and CS-induced COPD, most likely in a gender-dependent manner.

Does hyperoxia enhance susceptibility to secondary pulmonary infection in the ICU?

Hyperoxia is common practice in the acute management of circulatory shock, and observational studies report that it is present in more than 50 % of mechanically ventilated patients during the first 24 h after intensive care unit (ICU) admission. On the other hand, "oxygen toxicity" due to the increased formation of reactive oxygen species limits its use due to serious deleterious side effects. However, formation of reactive oxygen species to boost bacterial killing is one of the body's anti-microbial auto-defense mechanisms and, hence, O2 has been referred to as an antibiotic. Consequently, hyperoxia during the peri-operative period has been advocated for surgical patients in order to reduce surgical site infection. However, there is ample evidence that long-term exposure to hyperoxia impaired bacterial phagocytosis and thereby aggravated both bacterial burden and dissemination. Moreover, a recent retrospective study identified the number of days with hyperoxia, defined as a PaO2 > 120 mmHg only, as an independent risk factor of ventilator-associated pneumonia in patients needing mechanical ventilation for more than 48 h. Since so far the optimal oxygenation target is unknown for ICU patients, "conservative" O2 therapy represents the treatment of choice to avoid exposure to both hypoxemia and excess hyperoxemia.