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

The Application of PiCCO-guided Fluid Resuscitation in Patients With Traumatic Shock

BACKGROUND

The aim of this study was to evaluate the application of pulse contour cardiac output (PiCCO) in patients with traumatic shock.

METHODS

Seventy-eight patients with traumatic shock were included and grouped. The control group (CG, n = 39) underwent fluid resuscitation through transthoracic echocardiography (TTE) monitoring, and the research group (RG, n = 39) received PiCCO-guided fluid resuscitation.

RESULTS

The mechanical ventilation time, duration of vasoactive drug use, and duration of stay in the intensive care unit were lower in the RG compared to the CG (P < .05). At 72 h after fluid resuscitation, the mean arterial pressure and central venous pressure in the RG were higher than those in the CG (P < .05). The stroke volume variation and distensibility index of the inferior vena cava were lower at 72 h after fluid resuscitation, but the levels of extravascular lung water, global end-diastolic volume index, and intrathoracic blood volume index were higher in the RG (P < .05). The levels of endothelial 1, nitrogen monoxide, tumor necrosis factor-α, procalcitonin, C-reactive protein, and partial pressure of carbon dioxide at 72 h after fluid resuscitation in the RG were lower than those in the CG (P < .05).

CONCLUSION

PiCCO-guided liquid resuscitation may help to accurately evaluate the volumetric parameters, alleviate symptoms of ischemia and hypoxia, regulate hemodynamics and blood gas analysis, reduce inflammatory reactions, improve endothelial functions, and effectively guide the usage of vascular active drugs.

Optimisation of mitochondrial function as a novel target for resuscitation in haemorrhagic shock: a systematic review

INTRODUCTION

Traumatic injury is one of the leading causes of death worldwide, and despite significant improvements in patient care, survival in the most severely injured patients remains unchanged. There is a crucial need for innovative approaches to improve trauma patient outcomes; this is particularly pertinent in remote or austere environments with prolonged evacuation times to definitive care. Studies suggest that maintenance of cellular homeostasis is a critical component of optimal trauma patient management, and as the cell powerhouse, it is likely that mitochondria play a pivotal role. As a result, therapies that optimise mitochondrial function could be an important future target for the treatment of critically ill trauma patients.

METHODS

A systematic review of the literature was undertaken in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses protocol to determine the potential role of mitochondria in traumatic injury and haemorrhagic shock (HS) and to identify current evidence for mitochondrial optimisation therapies in trauma. Articles were included if they assessed a mitochondrial targeted therapy in comparison to a control group, used a model of traumatic injury and HS and reported a method to assess mitochondrial function.

RESULTS

The search returned 918 articles with 37 relevant studies relating to mitochondrial optimisation identified. Included studies exploring a range of therapies with potential utility in traumatic injury and HS. Therapies were categorised into the key mitochondrial pathways impacted following traumatic injury and HS: ATP levels, cell death, oxidative stress and reactive oxygen species.

CONCLUSION

This systematic review provides an overview of the key cellular functions of the mitochondria following traumatic injury and HS and identifies why mitochondrial optimisation could be a viable and valuable target in optimising outcome in severely injured patients in the future.

Cigarette smoke exposure reduces hemorrhagic shock induced circulatory dysfunction in mice with attenuated glucocorticoid receptor function

Introduction

We previously showed that attenuated glucocorticoid receptor (GR) function in mice (GRdim/dim) aggravates systemic hypotension and impairs organ function during endotoxic shock. Hemorrhagic shock (HS) causes impaired organ perfusion, which leads to tissue hypoxia and inflammation with risk of organ failure. Lung co-morbidities like chronic obstructive pulmonary disease (COPD) can aggravate tissue hypoxia via alveolar hypoxia. The most common cause for COPD is cigarette smoke (CS) exposure. Therefore, we hypothesized that affecting GR function in mice (GRdim/dim) and pre-traumatic CS exposure would further impair hemodynamic stability and organ function after HS.

Methods

After 3 weeks of CS exposure, anesthetized and mechanically ventilated GRdim/dim and GR+/+ mice underwent pressure-controlled HS for 1h via blood withdrawal (mean arterial pressure (MAP) 35mmHg), followed by 4h of resuscitation with re-transfusion of shed blood, colloid fluid infusion and, if necessary, continuous intravenous norepinephrine. Acid–base status and organ function were assessed together with metabolic pathways. Blood and organs were collected at the end of the experiment for analysis of cytokines, corticosterone level, and mitochondrial respiratory capacity. Data is presented as median and interquartile range.

Results

Nor CS exposure neither attenuated GR function affected survival. Non-CS GRdim/dim mice had a higher need of norepinephrine to keep target hemodynamics compared to GR+/+ mice. In contrast, after CS exposure norepinephrine need did not differ significantly between GRdim/dim and GR+/+ mice. Non-CS GRdim/dim mice presented with a lower pH and increased blood lactate levels compared to GR+/+ mice, but not CS exposed mice. Also, higher plasma concentrations of some pro-inflammatory cytokines were observed in non-CS GRdim/dim compared to GR+/+ mice, but not in the CS group. With regards to metabolic measurements, CS exposure led to an increased lipolysis in GRdim/dim compared to GR+/+ mice, but not in non-CS exposed animals.

Conclusion

Whether less metabolic acidosis or increased lipolysis is the reason or the consequence for the trend towards lower catecholamine need in CS exposed GRdim/dim mice warrants further investigation.

Physiological roles of hydrogen sulfide in mammalian cells, tissues and organs

H2S belongs to the class of molecules known as gasotransmitters, which also includes nitric oxide (NO) and carbon monoxide (CO). Three enzymes are recognized as endogenous sources of H2S in various cells and tissues: cystathionine g-lyase (CSE), cystathionine β-synthase (CBS) and 3-mercaptopyruvate sulfurtransferase (3-MST). The current article reviews the regulation of these enzymes as well as the pathways of their enzymatic and non-enzymatic degradation and elimination. The multiple interactions of H2S with other labile endogenous molecules (e.g. NO) and reactive oxygen species are also outlined. The various biological targets and signaling pathways are discussed, with special reference to H2S and oxidative posttranscriptional modification of proteins, the effect of H2S on channels and intracellular second messenger pathways, the regulation of gene transcription and translation and the regulation of cellular bioenergetics and metabolism. The pharmacological and molecular tools currently available to study H2S physiology are also reviewed, including their utility and limitations. In subsequent sections, the role of H2S in the regulation of various physiological and cellular functions is reviewed. The physiological role of H2S in various cell types and organ systems are overviewed. Finally, the role of H2S in the regulation of various organ functions is discussed as well as the characteristic bell-shaped biphasic effects of H2S. In addition, key pathophysiological aspects, debated areas, and future research and translational areas are identified A wide array of significant roles of H2S in the physiological regulation of all organ functions emerges from this review.

Effects of Sodium Thiosulfate During Resuscitation From Trauma-and-Hemorrhage in Cystathionine Gamma Lyase (CSE) Knockout Mice

BACKGROUND

Sodium thiosulfate (Na2S2O3) is a clinically established drug with antioxidant and sulphide-releasing properties. Na2S2O3 mediated neuro- and cardioprotective effects in ischemia/reperfusion models and anti-inflammatory effects in LPS-induced acute lung injury. Moreover, Na2S2O3 improved lung function during resuscitation from hemorrhagic shock in swine with pre-existing atherosclerosis, characterized by decreased expression of cystathionine γ-lyase (CSE), a major source of hydrogen sulfide (H2S) synthesis in the vasculature. Based on these findings, we investigated the effects of Na2S2O3 administration during resuscitation from trauma-and-hemorrhage in mice under conditions of whole body CSE deficit.

METHODS

After blast wave-induced blunt chest trauma and surgical instrumentation, CSE knockout (CSE-/-) mice underwent 1 h of hemorrhagic shock (MAP 35 ± 5 mm Hg). At the beginning of resuscitation comprising retransfusion, norepinephrine support and lung-protective mechanical ventilation, animals received either i.v. Na2S2O3 (0.45 mg g-1, n = 12) or vehicle (saline, n = 13). Hemodynamics, acid-base status, metabolism using stable isotopes, and visceral organ function were assessed. Blood and organs were collected for analysis of cytokines, mitochondrial respiratory capacity, and immunoblotting.

RESULTS

Na2S2O3 treatment improved arterial paO2 (P = 0.03) coinciding with higher lung tissue glucocorticoid receptor expression. Norepinephrine requirements were lower in the Na2S2O3 group (P < 0.05), which was associated with lower endogenous glucose production and higher urine output. Na2S2O3 significantly increased renal tissue IκBα and heme oxygenase-1 expression, whereas it lowered kidney IL-6 and MCP-1 levels.

CONCLUSION

Na2S2O3 exerted beneficial effects during resuscitation of murine trauma-and-hemorrhage in CSE-/- mice, confirming and extending the previously described organ-protective and anti-inflammatory properties of Na2S2O3. The findings make Na2S2O3 a potentially promising therapeutic option in the context of impaired CSE activity and/or reduced endogenous H2S availability.

ΔMST and the Regulation of Cardiac CSE and OTR Expression in Trauma and Hemorrhage

Genetic deletion of 3-mercaptopyruvate sulfurtransferase (MST) is known to result in hypertension and cardiac hypertrophy in older mice, and is associated with increased anxiety-like behaviors. Endogenous hydrogen sulfide (H2S) produced by MST in the mitochondria is also known to be involved in physiological and cellular bioenergetics, and its dysfunction associated with depressive behavior and increased cardiovascular morbidity. Interestingly, early life stress has been shown to lead to a significant loss of cystathionine-γ-lyase (CSE) and oxytocin receptor (OTR) expression in the heart. Thus, we were interested in testing the hypothesis of whether genetic MST mutation (ΔMST) would affect cardiac CSE and OTR expression and affect the mitochondrial respiration in a clinically relevant, resuscitated, mouse model of trauma and hemorrhagic shock. In ΔMST mice, we found a reduction of CSE and OTR in both the naive as well as injured state, in contrast to the wild type (wt) controls. Interestingly, the ΔMST showed a different complex IV response to injury than the wt controls, although our claims are based on the non-demonstrated assumption that naive wt and naive ΔMST mice have comparable complex IV activity. Finally, hemorrhagic shock led to a reduction of CSE and OTR, confirming previous results in the injured mouse heart. To date, the exact mechanisms of the cardiac interaction between H2S and OT are not clear, but they point the way to potential cardioprotective therapies.

Mouse Intensive Care Unit (MICU)

The translation of preclinical results into successful clinical therapies remains a challenge in sepsis research. One reason for this lack of translation might be the discrepancy between preclinical models and the clinical reality: nonresuscitated young healthy rodents in contrast to elderly comorbid patients in an intensive care unit. We introduce the mouse intensive care unit (MICU) as a concept to address the lack of resuscitation in preclinical studies as one of the limiting issues in translational research. The MICU reflects standard procedures of the clinical intensive care unit: fluid resuscitation, lung-protective mechanical ventilation, and hemodynamic monitoring and management, all tailored to organ- and function-specific targets. Thus, the MICU gives an experimental animal the intermediate possibility of recovery and survival due to "patient" management, which is not reflected in less complex experimental scenarios, which either result in acute survival or death.

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.

Hydrogen sulfide: An endogenous regulator of the immune system

Hydrogen sulfide (H₂S) is now recognized as an endogenous signaling gasotransmitter in mammals. It is produced by mammalian cells and tissues by various enzymes - predominantly cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE) and 3-mercaptopyruvate sulfurtransferase (3-MST) - but part of the H₂S is produced by the intestinal microbiota (colonic H₂S-producing bacteria). Here we summarize the available information on the production and functional role of H₂S in the various cell types typically associated with innate immunity (neutrophils, macrophages, dendritic cells, natural killer cells, mast cells, basophils, eosinophils) and adaptive immunity (T and B lymphocytes) under normal conditions and as it relates to the development of various inflammatory and immune diseases. Special attention is paid to the physiological and the pathophysiological aspects of the oral cavity and the colon, where the immune cells and the parenchymal cells are exposed to a special "H₂S environment" due to bacterial H₂S production. H₂S has many cellular and molecular targets. Immune cells are "surrounded" by a "cloud" of H₂S, as a result of endogenous H₂S production and exogenous production from the surrounding parenchymal cells, which, in turn, importantly regulates their viability and function. Downregulation of endogenous H₂S producing enzymes in various diseases, or genetic defects in H₂S biosynthetic enzyme systems either lead to the development of spontaneous autoimmune disease or accelerate the onset and worsen the severity of various immune-mediated diseases (e.g. autoimmune rheumatoid arthritis or asthma). Low, regulated amounts of H₂S, when therapeutically delivered by small molecule donors, improve the function of various immune cells, and protect them against dysfunction induced by various noxious stimuli (e.g. reactive oxygen species or oxidized LDL). These effects of H₂S contribute to the maintenance of immune functions, can stimulate antimicrobial defenses and can exert anti-inflammatory therapeutic effects in various diseases.

Effect of 3-mercaptopyruvate Sulfurtransferase Deficiency on the Development of Multiorgan Failure, Inflammation, and Wound Healing in Mice Subjected to Burn Injury

The gaseous transmitter hydrogen sulfide (H2S) has been implicated in various forms of critical illness. Here, we have compared the outcome of scald burn injury in wild-type mice and in mice deficient in 3-mercaptopyruvate sulfurtransferase (3-MST), a mammalian H2S-generating enzyme. Outcome variables included indices of organ injury, clinical chemistry parameters, and plasma levels of inflammatory mediators. Plasma levels of H2S significantly increased in response to burn in wild-type mice, but remained unchanged in 3-MST-/- mice. The capacity of tissue homogenates to produce H2S from 3-mercaptopyruvate was unaffected by burn injury. In 3-MST-/- mice, compared to wild-type controls, there was a significant enhancement in the accumulation of polymorphonuclear cells (as assessed by the quantification of myeloperoxidase) in the liver (but not heart, lung, or skin) at 7 days postburn. Oxidative tissue damage (as assessed by malon dialdehyde content) was comparable between wild-type and 3-MST-deficient mice in all tissues studied. 3-MST-/- and wild-type mice exhibited comparable burn-induced elevations in circulating plasma levels of hepatic injury; however, 3-MST-/- mice exhibited a higher degree of renal injury (as reflected by elevated blood urea nitrogen levels) at 7 days postburn. Inflammatory mediators (eg, TNF-α, IL-1β, IL-2, IL-6, IL-10, and IL-12) increased in burn injury, but without significant differences between the 3-MST-/- and wild-type groups. The healing of the burn wound was also unaffected by 3-MST deficiency. In conclusion, the absence of the H2S-producing enzyme 3-MST slightly exacerbates the development of multiorgan dysfunction but does not affect inflammatory mediator production or wound healing in a murine model of burn injury.

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 (GR^dim/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 (GR^dim/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 GR^dim/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, GR^dim/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, GR^dim/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.