Molecular biology of multiple organ dysfunction syndrome: injury, adaptation, and apoptosis

Microcirculatory Function during Endotoxemia-A Functional Citrulline-Arginine-NO Pathway and NOS3 Complex Is Essential to Maintain the Microcirculation

Competition for the amino acid arginine by endothelial nitric-oxide synthase (NOS3) and (pro-)inflammatory NO-synthase (NOS2) during endotoxemia appears essential in the derangement of the microcirculatory flow. This study investigated the role of NOS2 and NOS3 combined with/without citrulline supplementation on the NO-production and microcirculation during endotoxemia. Wildtype (C57BL6/N background; control; n = 36), Nos2-deficient, (n = 40), Nos3-deficient (n = 39) and Nos2/Nos3-deficient mice (n = 42) received a continuous intravenous LPS infusion alone (200 μg total, 18 h) or combined with L-citrulline (37.5 mg, last 6 h). The intestinal microcirculatory flow was measured by side-stream dark field (SDF)-imaging. The jejunal intracellular NO production was quantified by in vivo NO-spin trapping combined with electron spin-resonance (ESR) spectrometry. Amino-acid concentrations were measured by high-performance liquid chromatography (HPLC). LPS infusion decreased plasma arginine concentration in control and Nos3^−/− compared to Nos2^−/− mice. Jejunal NO production and the microcirculation were significantly decreased in control and Nos2^−/− mice after LPS infusion. No beneficial effects of L-citrulline supplementation on microcirculatory flow were found in Nos3^−/− or Nos2^−/−/Nos3^−/− mice. This study confirms that L-citrulline supplementation enhances de novo arginine synthesis and NO production in mice during endotoxemia with a functional NOS3-enzyme (control and Nos2^−/− mice), as this beneficial effect was absent in Nos3^−/− or Nos2^−/−/Nos3^−/− mice.

Scald Injury-Induced T Cell Dysfunction Can Be Mitigated by Gr1+ Cell Depletion and Blockage of CD47/CD172a Signaling

Infection is a common and severe complication of burn injury: Sepsis accounts for 47% of postburn mortality. Burn-induced T cell suppression likely contributes to the increased infection susceptibility in burn patients. However, little is known about the kinetics of T cell dysfunction after burn and its underlying mechanisms. In this study, we show in a murine scald injury model that T cell activation of both CD4⁺ and CD8⁺ T cells as well as T cell cytokine production is suppressed acutely and persistently for at least 11 days after burn injury. Purified T cells from scald-injured mice exhibit normal T cell functions, indicating an extrinsically mediated defect. We further show that T cell dysfunction after burn appears to be cell-to-cell contact dependent and can be ameliorated by depletion of myeloid-derived suppressor cells. These cells expand after burn injury, particularly a subset expressing the checkpoint inhibitor CD172a, and infiltrate germinal centers. Expression of CD172a appears to be driven by ingestion of immature reticulocytes. Immature reticulocytes are drastically increased in the spleen of scald mice and may contribute to immunosuppression through more direct mechanisms as well. Overall, our study newly identifies two cell populations, myeloid-derived suppressor cells and immature reticulocytes, as well as the CD47/CD172a-signaling pathways as mediators of T cell suppressors after burn and thus opens up new research opportunities in the search for new therapies to combat increased infection susceptibility and the associated morbidity and mortality in burn victims.

Danger Signals in the ICU

OBJECTIVES

Sterile and infectious critical illnesses often result in vasoplegic shock and a robust systemic inflammatory response that are similar in presentation. The innate immune system is at the center of the response to both infectious and traumatic insults. Damage-associated molecular patterns are small molecules that are released from stressed or dying cells. Damage-associated molecular patterns activate pattern recognition receptors and coordinate the leading edge of the innate immune response. This review introduces the concept of damage-associated molecular patterns and how they activate a systemic inflammatory response, specifically in trauma, neurologic injury, and infection. It also explores how, when carried to extremes, damage-associated molecular patterns may even perpetuate multisystem organ failure.

DATA SOURCES

Basic and clinical studies were obtained from a PubMed search through August 2017.

STUDY SELECTION

Articles considered include original articles, review articles, and conference proceedings.

DATA EXTRACTION

An analysis of scientific, peer-reviewed data was performed. High quality preclinical and clinical studies adjudicated by the authors were included and summarized.

DATA SYNTHESIS

Pattern recognition receptors respond to damage-associated molecular patterns and then activate inflammatory pathways. Damage-associated molecular patterns have been linked to the recruitment of sentinel leukocytes and the initiation of the inflammatory cascade. Damage-associated molecular patterns have been linked to many conditions in critical care illnesses. Preclinical models have added insight into how they may mediate distant organ dysfunction.

CONCLUSIONS

Damage-associated molecular pattern activation and release is an important research for intensive care practitioners. It will add to our understanding of the phase and state of the innate immune response to an insult. Early work is encouraging. However, only with improved understanding of damage-associated molecular pattern activation and function, we can perhaps hope to target damage-associated molecular patterns as diagnostic and/or therapeutic modalities in the future.

Innate and adaptive immune dysregulation in critically ill ICU patients

This study aimed to evaluate whether ICU patients who developed persistent critical illness displayed an immune profile similar to an aged immune phenotype and any associations with patient outcomes. Twenty two critically ill ICU patients (27–76 years, 15 males), at day 5 of mechanical ventilation, and 22 healthy age-matched controls (27–77 years, 13 males) were recruited. Frequency and phenotype of innate and adaptive immune cells and telomere length in peripheral blood mononuclear cells (PBMCs) were measured. An elevated granulocyte count (p < 0.0001), increased numbers of immature granulocytes (p < 0.0001), increased CD16^++ve monocytes (p = 0.003) and CD14^+ve HLADR^dim/low monocytes (p = 0.004) and lower NK cell numbers (p = 0.007) were observed in ICU patients compared to controls. Critically ill patients also had lower numbers of total T lymphocytes (p = 0.03), naïve CD4 T cells (p = 0.003) and PTK7^+ve recent thymic emigrants (p = 0.002), and increased senescent CD28^−ve CD57^+ve CD4 T cells (p = 0.02), but there was no difference in PBMC telomere length. Regulatory immune cell frequency was affected with reduced circulating CD19^+veCD24^hiCD38^hi regulatory B cells (p = 0.02). However, only a raised neutrophil:lymphocyte ratio and reduced frequency of CD14^+ve HLADR^dim/low monocytes were associated with poor outcomes. We conclude that persistent critical illness results in changes to immune cell phenotype only some of which are similar to that seen in physiological ageing of the immune system.

Mitochondria-meditated pathways of organ failure upon inflammation

Liver failure induced by systemic inflammatory response (SIRS) is often associated with mitochondrial dysfunction but the mechanism linking SIRS and mitochondria-mediated liver failure is still a matter of discussion. Current hypotheses suggest that causative events could be a drop in ATP synthesis, opening of mitochondrial permeability transition pore, specific changes in mitochondrial morphology, impaired Ca²⁺ uptake, generation of mitochondrial reactive oxygen species (mtROS), turnover of mitochondria and imbalance in electron supply to the respiratory chain. The aim of this review is to critically analyze existing hypotheses, in order to highlight the most promising research lines helping to prevent liver failure induced by SIRS. Evaluation of the literature shows that there is no consistent support that impaired Ca⁺⁺ metabolism, electron transport chain function and ultrastructure of mitochondria substantially contribute to liver failure. Moreover, our analysis suggests that the drop in ATP levels has protective rather than a deleterious character. Recent data suggest that the most critical mitochondrial event occurring upon SIRS is the release of mtROS in cytoplasm, which can activate two specific intracellular signaling cascades. The first is the mtROS-mediated activation of NADPH-oxidase in liver macrophages and endothelial cells; the second is the acceleration of the expression of inflammatory genes in hepatocytes. The signaling action of mtROS is strictly controlled in mitochondria at three points, (i) at the site of ROS generation at complex I, (ii) the site of mtROS release in cytoplasm via permeability transition pore, and (iii) interaction with specific kinases in cytoplasm. The systems controlling mtROS-signaling include pro- and anti-inflammatory mediators, nitric oxide, Ca²⁺ and NADPH-oxidase. Analysis of the literature suggests that further research should be focused on the impact of mtROS on organ failure induced by inflammation and simultaneously providing a new theoretical basis for a targeted therapy of overwhelmed inflammatory response.

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Relationship between mitochondrial dysfunction and high lethality upon sepsis.

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Criteria to define critical for lethality mitochondrial dysfunction.

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ATP, calcium, mitochondrial ultrastructure and apoptosis, upon inflammation.

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Regulation of inflammatory processes by mitochondrial ROS.

Local and distant trauma after hypervelocity ballistic impact to the pig hind limb

The development of high-energy weapons could increase the velocity of projectiles to well over 1000 m/s. The nature of the injuries caused by the ballistic impact of projectiles at velocities much faster than 1000 m/s is unclear. This study characterizes the mechanical and biochemical alterations caused by high-speed ballistic impact generated by spherical steel ball to the hind limbs of the pig. That the local and distal injuries caused by hypervelocity ballistic impact to the living body are also identified. It is showed that the severity of the injury was positively correlated with the velocity of the projectile. And 4000 m/s seems to be the critical velocity for the 5.6 mm spherical steel ball, which would cause severe damage to either local or distal organs, as below that speed the projectile penetrated the body while above that speed it caused severe damage to the body. In addition, vaporization prevented the projectile from penetrating the body and the consequent pressure wave seems to be the causal factor for the distant damage.

The role of neutrophils in immune dysfunction during severe inflammation

Critically ill post-surgical, post-trauma and/or septic patients are characterised by severe inflammation. This immune response consists of both a pro- and an anti-inflammatory component. The pro-inflammatory component contributes to (multiple) organ failure whereas occurrence of immune paralysis predisposes to infections. Strikingly, infectious complications arise in these patients despite the presence of a clear neutrophilia. We propose that dysfunction of neutrophils potentially increases the susceptibility to infections or can result in the inability to clear existing infections. Under homeostatic conditions these effector cells of the innate immune system circulate in a quiescent state and serve as the first line of defence against invading pathogens. In severe inflammation, however, neutrophils are rapidly activated, which affects their functional capacities, such as chemotaxis, phagocytosis, intra-cellular killing, NETosis, and their capacity to modulate adaptive immunity. This review provides an overview of the current understanding of neutrophil dysfunction in severe inflammation. We will discuss the possible mechanisms of downregulation of anti-microbial function, suppression of adaptive immunity by neutrophils and the contribution of neutrophil subsets to immune paralysis.

Increased apoptosis of peripheral blood neutrophils is associated with reduced incidence of infection in trauma patients with hemorrhagic shock

OBJECTIVE

We aimed to describe the relationship between early peripheral leukocyte apoptosis and incidence of subsequent infection in trauma patients with hemorrhagic shock (T/HS).

METHODS

T/HS patients requiring emergency surgery were prospectively enrolled. Nucleosome ELISA and TUNEL staining were performed on peripheral blood drawn pre-operatively, post-operatively and at 24 h. Subjects were followed for 30 days or until death or hospital discharge to record all episodes of infection.

RESULTS

Forty-one subjects were enrolled. Six died within 24 h of surgery and were not included in the analysis. Nucleosome levels peaked post-operatively and dropped to baseline levels at 24 h (p = 0.03). TUNEL analysis revealed that polymorphonuclear neutrophils (PMNs) accounted for 72% of apoptotic leukocytes; the remaining apoptotic cells were mainly lymphocytes. Increased post-operative leukocyte apoptosis was associated with decreased systemic inflammatory response syndrome (SIRS) severity. Seventeen of the 35 survivors (48.6%) developed infections, while 18 (51.4%) did not. Pre-operative and post-operative nucleosome levels were 2.5 and 3 times higher, respectively, in T/HS patients who did not develop infection compared to those who did. Increased nucleosome levels were associated in particular with protection against sepsis (p=0.03) and multiple infections (p = 0.01).

CONCLUSION

Peripheral blood PMN apoptosis in the early resuscitative period is associated with decreased incidence of subsequent infection in T/HS patients.

Toward computational identification of multiscale "tipping points" in acute inflammation and multiple organ failure

Sepsis accounts annually for nearly 10% of total U.S. deaths, costing nearly $17 billion/year. Sepsis is a manifestation of disordered systemic inflammation. Properly regulated inflammation allows for timely recognition and effective reaction to injury or infection, but inadequate or overly robust inflammation can lead to Multiple Organ Dysfunction Syndrome (MODS). There is an incongruity between the systemic nature of disordered inflammation (as the target of inflammation-modulating therapies), and the regional manifestation of organ-specific failure (as the subject of organ support), that presents a therapeutic dilemma: systemic interventions can interfere with an individual organ system's appropriate response, yet organ-specific interventions may not help the overall system reorient itself. Based on a decade of systems and computational approaches to deciphering acute inflammation, along with translationally-motivated experimental studies in both small and large animals, we propose that MODS evolves due to the feed-forward cycle of inflammation → damage → inflammation. We hypothesize that inflammation proceeds at a given, "nested" level or scale until positive feedback exceeds a "tipping point." Below this tipping point, inflammation is contained and manageable; when this threshold is crossed, inflammation becomes disordered, and dysfunction propagates to a higher biological scale (e.g., progressing from cellular, to tissue/organ, to multiple organs, to the organism). Finally, we suggest that a combination of computational biology approaches involving data-driven and mechanistic mathematical modeling, in close association with studies in clinically relevant paradigms of sepsis/MODS, are necessary in order to define scale-specific "tipping points" and to suggest novel therapies for sepsis.

Data driven linear algebraic methods for analysis of molecular pathways: application to disease progression in shock/trauma

MOTIVATION

Although trauma is the leading cause of death for those below 45years of age, there is a dearth of information about the temporal behavior of the underlying biological mechanisms in those who survive the initial trauma only to later suffer from syndromes such as multiple organ failure. Levels of serum cytokines potentially affect the clinical outcomes of trauma; understanding how cytokine levels modulate intra-cellular signaling pathways can yield insights into molecular mechanisms of disease progression and help to identify targeted therapies. However, developing such analyses is challenging since it necessitates the integration and interpretation of large amounts of heterogeneous, quantitative and qualitative data. Here we present the Pathway Semantics Algorithm (PSA), an algebraic process of node and edge analyses of evoked biological pathways over time for in silico discovery of biomedical hypotheses, using data from a prospective controlled clinical study of the role of cytokines in multiple organ failure (MOF) at a major US trauma center. A matrix algebra approach was used in both the PSA node and PSA edge analyses with different matrix configurations and computations based on the biomedical questions to be examined. In the edge analysis, a percentage measure of crosstalk called XTALK was also developed to assess cross-pathway interference.

RESULTS

In the node/molecular analysis of the first 24h from trauma, PSA uncovered seven molecules evoked computationally that differentiated outcomes of MOF or non-MOF (NMOF), of which three molecules had not been previously associated with any shock/trauma syndrome. In the edge/molecular interaction analysis, PSA examined four categories of functional molecular interaction relationships--activation, expression, inhibition, and transcription--and found that the interaction patterns and crosstalk changed over time and outcome. The PSA edge analysis suggests that a diagnosis, prognosis or therapy based on molecular interaction mechanisms may be most effective within a certain time period and for a specific functional relationship.

Translational systems approaches to the biology of inflammation and healing

Inflammation is a complex, non-linear process central to many of the diseases that affect both developed and emerging nations. A systems-based understanding of inflammation, coupled to translational applications, is therefore necessary for efficient development of drugs and devices, for streamlining analyses at the level of populations, and for the implementation of personalized medicine. We have carried out an iterative and ongoing program of literature analysis, generation of prospective data, data analysis, and computational modeling in various experimental and clinical inflammatory disease settings. These simulations have been used to gain basic insights into the inflammatory response under baseline, gene-knockout, and drug-treated experimental animals for in silico studies associated with the clinical settings of sepsis, trauma, acute liver failure, and wound healing to create patient-specific simulations in polytrauma, traumatic brain injury, and vocal fold inflammation; and to gain insight into host-pathogen interactions in malaria, necrotizing enterocolitis, and sepsis. These simulations have converged with other systems biology approaches (e.g., functional genomics) to aid in the design of new drugs or devices geared towards modulating inflammation. Since they include both circulating and tissue-level inflammatory mediators, these simulations transcend typical cytokine networks by associating inflammatory processes with tissue/organ impacts via tissue damage/dysfunction. This framework has now allowed us to suggest how to modulate acute inflammation in a rational, individually optimized fashion. This plethora of computational and intertwined experimental/engineering approaches is the cornerstone of Translational Systems Biology approaches for inflammatory diseases.

Early release of high mobility group box nuclear protein 1 after severe trauma in humans: role of injury severity and tissue hypoperfusion

Introduction

High mobility group box nuclear protein 1 (HMGB1) is a DNA nuclear binding protein that has recently been shown to be an early trigger of sterile inflammation in animal models of trauma-hemorrhage via the activation of the Toll-like-receptor 4 (TLR4) and the receptor for the advanced glycation endproducts (RAGE). However, whether HMGB1 is released early after trauma hemorrhage in humans and is associated with the development of an inflammatory response and coagulopathy is not known and therefore constitutes the aim of the present study.

Methods

One hundred sixty eight patients were studied as part of a prospective cohort study of severe trauma patients admitted to a single Level 1 Trauma center. Blood was drawn within 10 minutes of arrival to the emergency room before the administration of any fluid resuscitation. HMGB1, tumor necrosis factor (TNF)-α, interleukin (IL)-6, von Willebrand Factor (vWF), angiopoietin-2 (Ang-2), Prothrombin time (PT), prothrombin fragments 1+2 (PF1+2), soluble thrombomodulin (sTM), protein C (PC), plasminogen activator inhibitor-1 (PAI-1), tissue plasminogen activator (tPA) and D-Dimers were measured using standard techniques. Base deficit was used as a measure of tissue hypoperfusion. Measurements were compared to outcome measures obtained from the electronic medical record and trauma registry.

Results

Plasma levels of HMGB1 were increased within 30 minutes after severe trauma in humans and correlated with the severity of injury, tissue hypoperfusion, early posttraumatic coagulopathy and hyperfibrinolysis as well with a systemic inflammatory response and activation of complement. Non-survivors had significantly higher plasma levels of HMGB1 than survivors. Finally, patients who later developed organ injury, (acute lung injury and acute renal failure) had also significantly higher plasma levels of HMGB1 early after trauma.

Conclusions

The results of this study demonstrate for the first time that HMGB1 is released into the bloodstream early after severe trauma in humans. The release of HMGB1 requires severe injury and tissue hypoperfusion, and is associated with posttraumatic coagulation abnormalities, activation of complement and severe systemic inflammatory response.

The acute inflammatory response in trauma / hemorrhage and traumatic brain injury: current state and emerging prospects

Traumatic injury/hemorrhagic shock (T/HS) elicits an acute inflammatory response that may result in death. Inflammation describes a coordinated series of molecular, cellular, tissue, organ, and systemic responses that drive the pathology of various diseases including T/HS and traumatic brain injury (TBI). Inflammation is a finely tuned, dynamic, highly-regulated process that is not inherently detrimental, but rather required for immune surveillance, optimal post-injury tissue repair, and regeneration. The inflammatory response is driven by cytokines and chemokines and is partially propagated by damaged tissue-derived products (Damage-associated Molecular Patterns; DAMP's). DAMPs perpetuate inflammation through the release of pro-inflammatory cytokines, but may also inhibit anti-inflammatory cytokines. Various animal models of T/HS in mice, rats, pigs, dogs, and non-human primates have been utilized in an attempt to move from bench to bedside. Novel approaches, including those from the field of systems biology, may yield therapeutic breakthroughs in T/HS and TBI in the near future.

The NF-kappaB factor RelB and histone H3 lysine methyltransferase G9a directly interact to generate epigenetic silencing in endotoxin tolerance

The interplay of transcription factors, histone modifiers, and DNA modification can alter chromatin structure that epigenetically controls gene transcription. During severe systemic inflammatory (SSI), the generation of facultative heterochromatin from euchromatin reversibly silences transcription of a set of acute proinflammatory genes. This gene-specific silencing is a salient feature of the endotoxin tolerant phenotype that is found in blood leukocytes of SSI patients and in a human THP-1 cell model of SSI. We previously reported that de novo induction of the NF-kappaB transcription factor RelB by endotoxin activation is necessary and sufficient for silencing transcription of acute proinflammatory genes in the endotoxin tolerant SSI phenotype. Here, we examined how RelB silences gene expression and found that RelB induces facultative heterochromatin formation by directly interacting with the histone H3 lysine 9 methyltransferase G9a. We found that heterochromatin protein 1 (HP1) and G9a formed a complex at the interleukin-1beta promoter that is dependent on the Rel homology domain (RHD) of RelB. RelB knockdown disassociated the complex and reversed transcription silencing. We also observed that whereas RelB chromatin binding was independent of G9a, RelB transcriptional silencing required G9a accumulation at the silenced promoter. Binding between RelB and G9a was confirmed by glutathione S-transferase pulldown in vitro and coimmunoprecipitation in vivo. These data provide novel insight into how RelB is required to initiate silencing in the phenotype associated with severe systemic inflammation in humans, a disease with major morbidity and mortality.

Non-pathogenic Sindbis virus causes hemorrhagic fever in the absence of alpha/beta and gamma interferons

The role of interferon-gamma (IFNgamma) in antiviral innate immune responses during acute alphavirus infection is not well defined. We examined the contribution of IFNgamma to the protection of adult mice from Sindbis virus (SB)-induced disease by comparing subcutaneous infection of mice lacking receptors for either IFNalpha/beta (A129), IFNgamma (G129) or both (AG129) to normal mice (WT129). While neither G129 nor WT129 mice exhibited clinical signs of disease, infection of A129 or AG129 mice was fatal with AG129 mice succumbing more rapidly. Furthermore, AG129 mice developed signs of viral hemorrhagic fever (VHF), including extensive hepatocellular damage, inflammatory infiltrates in multiple organs and vascular leakage, which were significantly delayed and/or partially ameliorated during fatal A129 infections. We conclude that: (i) IFNalpha/beta is the primary mediator of innate immunity to SB infection, however; (ii) IFNgamma is directly antiviral in vivo, acting before the adaptive immune response appears and; (iii) development of VHF may involve viral suppression of both IFNalpha/beta and IFNgamma responses.

Acupuncture stimulation of ST36 (Zusanli) attenuates acute renal but not hepatic injury in lipopolysaccharide-stimulated rats

BACKGROUND

We sought to determine the effects of ST36 acupuncture on sepsis-induced kidney and liver injuries.

METHODS

A total of 120 rats were randomized into 10 groups: 1) lipopolysaccharide (LPS), 2) normal saline (N/S), 3) LPS + ST36, 4) ST36, 5) LPS + P-ST36, 6) P-ST36, 7) LPS + Sham, 8) Sham, 9) LPS + P-Sham, and 10) P-Sham groups. Rats in the LPS + ST36, ST36, LPS +Sham, and Sham groups received ST36 (designated as "ST36") or a nonacupoint (designated as "Sham") acupuncture for 30 min followed by LPS or N/S injection. Rats in the LPS + P-ST36, P-ST36, LPS + P-Sham, and P-Sham groups received LPS or N/S injection for 3 h followed by a 30 min of ST36 or a "nonacupoint" acupuncture. Rats were killed at 6 h after LPS injection.

RESULTS

LPS caused prominent kidney and liver injuries. The renal and hepatic nitric oxide (NO) concentrations and inducible NO synthase (iNOS) expression were also increased by LPS. ST36 acupuncture pretreatment significantly attenuated the LPS-induced kidney injury and the increases in renal NO concentration and iNOS expression. However, ST36 acupuncture pretreatment did not affect the LPS-induced liver injury and increases in hepatic NO concentration or iNOS expression. Furthermore, ST36 acupuncture performed after LPS did not affect the LPS-induced organ injuries or increases in NO concentration and iNOS expression.

CONCLUSIONS

ST36 acupuncture pretreatment significantly attenuated sepsis-induced kidney, but not liver, injury in rats, whereas ST36 acupuncture performed after sepsis induction had no protective effects against sepsis-induced organ injuries.

Evidence-based modeling of critical illness: an initial consensus from the Society for Complexity in Acute Illness

INTRODUCTION

Given the complexity of biological systems, understanding their dynamic behaviors, such as the Acute Inflammatory Response (AIR), requires a formal synthetic process. Dynamic Mathematical Modeling (DMM) represents a suite of methods intended for inclusion within the required synthetic framework. The DMM, however, is a relatively novel approach in the practice of biomedical research. The Society for Complexity in Acute Illness (SCAI) was formed in 2004 from the leading research groups using DMM in the study of acute inflammation. This society believes that it is important to offer guidelines for the design, development, and use of DMM in the setting of AIR research to avoid the "garbage in, garbage out" problem. Accordingly, SCAI identified a need for and carried out a critical appraisal of DMM as currently used in the setting of acute illness.

METHODS

The SCAI annual meeting in 2005, the Fourth International Conference on Complexity in Acute Illness (Cologne, Germany), was structured with the intent of developing a consensus statement on the methods and execution of DMM in AIR research. The conference was organized to include a series of interactive breakout sessions that included thought leaders from both the DMM and acute illness fields, the results of which were then presented in summary form to the entire group for discussion and consensus. The information in this article represents the concatenation of those presentations.

RESULTS

The output from the Fourth International Conference on Complexity in Acute Illness involved consensus statements for the following topics: (1) the need for DMM; (2) a suggested approach for the process of establishing a modeling project; (3) the type of "wet" laboratory experiments and data needed to establish a modeling project; (4) general quality measures for data to be input to a modeling project; and (5) a descriptive list of several types of DMM to provide guidance in selection of a method for a project.

CONCLUSION

We believe that the complexity of biological systems requires that DMM needs to be among the methods used to improve understanding and make progress with attempts to characterize and manipulate the AIR. We believe that this consensus statement will help guide the integration, rational implementation, and standardization of DMM into general biomedical research.

Endotoxin tolerance attenuates LPS-induced TLR4 mobilization to lipid rafts: a condition reversed by PKC activation

Endotoxin tolerance is characterized by attenuated macrophage activation to subsequent LPS challenge and can be reversed through nonspecific protein kinase C (PKC) activation, and activation by LPS within naïve cells requires the activation of the cell surface receptors CD14 and TLR4 on lipid rafts. The effect of PKC activation and endotoxin tolerance on lipid raft receptor complex assembly is unknown and the focus of this study. Tolerance was induced in THP-1 cells through LPS pre-exposure. Naïve and tolerant cells were stimulated with LPS, with or without PMA pretreatment to activate PKC. TLR4 surface expression and LPS binding were determined by flow cytometry and immunohistochemistry. Cellular and lipid raft protein was analyzed for the presence and activation of the TLR4 complex components. Harvested supernatants were examined for TNF-alpha production. Total TLR4 surface expression and LPS binding were not affected by tolerance induction. LPS stimulation of naïve cells resulted in TLR4 and heat shock protein (HSP)70 lipid raft mobilization, MAPK activation, and TNF-alpha production. LPS stimulation of tolerant cells was associated with attenuation of all of these cellular events. Although PKC activation by PMA had no effect on naïve cells, it did result in reversal in tolerance-induced suppression of TLR4 and HSP70 lipid raft mobilization, MAPK activation, and TNF-alpha production. In addition, the effects associated with PMA were reversed with exposure to a myristoylated PKC-zeta pseudosubstrate. Thus, endotoxin tolerance appears to be induced through attenuated TLR4 formation following LPS stimulation. This complex formation appears to be PKC-dependent, and restoration of PKC activity reverses tolerance.

The pathogenesis of pulmonary contusion: an open chest model in the rat

BACKGROUND

Chemokines direct leukocytes to areas of inflammation or injury. In general, CC chemokines (MCP-1, MIP-1alpha, RANTES) are chemoattractants for mononuclear cells and CXC (CINC-1, MIP-2alpha) for polymorphonuclear cells (PMNs). Herein we describe an open chest model of pulmonary contusion (PC) in a rodent (rat) and have identified a possible role for CC and CXC chemokines in the pathogenesis of PC.

METHODS

Sprague-Dawley rats (350 g) underwent thoracotomy. The exposed lung was struck with a piston at 5.2 m/s (150 J/M2). Blood, bronchoalveolar lavage (BAL), and lung tissue were collected at 3 hours and 24 hours after injury. PaO2/FiO2 (P/F) ratio was calculated at 15-minute intervals for 3 hours after contusion. Serum was evaluated for cytokine and chemokine expression using ELISA. Cell count/differential was performed on BAL, and lung tissue was obtained for histologic analysis, protein expression and wet to dry weights. Data are reported as pg/mL +/- SE. Data were analyzed using Student's t test to identify significant differences (p < or = 0.05 significant) between sham and injured animals.

RESULTS

Piston impact caused PC based upon morphologic and histologic criteria. BAL cell count and lung wet to dry weights were increased and P/F ratio was decreased after PC. Systemic levels of IL-ra, MCP-1, and the CXC chemokines MIP-2alpha and CINC-1 were significantly elevated at 3 hours when sham and injured animals were compared. All chemokines were found to be significantly elevated at 24 hours, consistent with the early PMN and subsequent mononuclear infiltration observed in the contused lung. Pulmonary expression of TNF-alpha, IL-1beta, CINC-1, MIP-2alpha, ICAM-1, and elastase were increased and activated systemic neutrophils showed increased CD-11b.

CONCLUSION

A model of PC is described in which innate inflammation is activated locally and systemically. Systemic levels of CC and CXC chemokines are increased after PC. This correlates with elevated PMN CD-11b expression, enhanced pulmonary ICAM-1 expression, and mononuclear and PMN infiltration into the lung and alveolar space. Elevated levels of CC and CXC chemokines are seen after PC and may be involved in the lung's inflammatory response to injury.

Sepsis

Sepsis results from the host response to infection. While a localized and controlled inflammatory reaction helps to control infection, a dysregulated response may lead to multiple organ failure and determines the course and prognosis of the septic patient. Despite intensive care, mortality remains as high as 54% for severe sepsis and septic shock. As the mechanisms are becoming better defined, interventions aiming to interfere with the host response have been undertaken, largely with disappointing results. Thus, many evidence-based recommendations suggest waiving of resource-consuming interventions. Nevertheless, several seminal studies have indicated that early and systematic supportive therapy according to pathophysiological principles, most notably early goal-directed therapy, low-dose hydrocortisone and activated protein C, can disrupt dysfunctional cascades and can favourably influence the course of the disease. In parallel, efforts to better define nationwide epidemiology and treatment habits for severe sepsis by the German competence network "SepNet" indicate that therapy of severe sepsis is generally in poor compliance with guidelines, while the personal perception of physicians in charge would suggest high rates of adherence. Thus, strategies of change management, such as implementation of sepsis bundles are warranted to achieve a better standard of care toward the aim of the "surviving sepsis campaign", i.e. a reduction of mortality by 25% within the next 5 years.

Regional microvascular function and vascular reactivity in patients with different degrees of multiple organ dysfunction syndrome

The pathophysiology of multiple organ dysfunction syndrome (MODS) is believed to be related to that of microcirculatory dysfunction. We hypothesized that the severity of MODS is determined by measuring regional variables of microvascular function and vascular reactivity in critically ill patients. Therefore, we compared (a) reactive hyperemia response in the forearm using transcutaneous Po2/Pco2 electrodes and laser Doppler velocimetry, (b) microvascular permeability assessed by strain-gauge plethysmography in legs, and (c) variables derived from gastric tonometry in hemodynamically stable patients with moderate (n = 15) and severe (n = 15) MODS. There were no differences in systemic oxygen delivery, consumption, and oxygen extraction ratio between the groups. Mortality was 20% in patients with moderate MODS and 60% in patients with severe MODS (P = 0.025). Patients with a high MODS score had significantly larger arterial lactate concentrations (3.81 +/- 2.7 mmol/L) than patients with moderate MODS (1.66 +/- 0.82 mmol/L; P = 0.006). No significant differences in gastric pHi, gastric regional-to-arterial Pco2 difference, capillary filtration coefficient, isovolumetric venous pressure, and skin reactive hyperemia response were observed between patients with moderate and severe MODS. Once MODS is established, regional variables of microvascular function and vascular reactivity measured in this study do not reflect severity of organ dysfunction.

Intestinal anastomosis surgery with no septic shock primes for a dysregulatory response to a second stimulus

BACKGROUND

Major surgery is believed to contribute to immune dysregulation and high susceptibility to microbes. Recently, the inflammatory "two-hit" model has been accepted to elucidate development of multiple organ failure in surgical patients. Our purpose was to examine whether intestinal surgery, which causes a minor insult with no septic shock, may modify the immune response to exogenous LPS as a second stimulus.

MATERIALS AND METHODS

Using a rat intestinal transection and anastomosis surgery model, we sequentially examined blood cell counts, body temperatures, and plasma cytokines. Rats were administered with LPS intravenously or intratracheally various days after surgery. Phagocytic activity and TNFalpha production in bronchoalveolar lavage (BAL) cells, plasma cytokines, and survival rates were evaluated.

RESULTS

The surgery itself caused no severe shock or circulating cytokine elevation, whereas the number of granulocytes in the blood was significantly elevated after surgery. LPS-induced elevation of circulating IFNgamma attenuated 3 days after surgery. In contrast, IL-10 was enhanced 3-10 days after surgery. Hyporesponsiveness of BAL cells to LPS was observed 3 days after surgery but not the next day after surgery. However, rats intratracheally exposed to LPS 10-13 days after surgery exhibited higher mortality.

CONCLUSIONS

Although our surgical procedure was not supposed to be a severe insult, it sufficiently primed rats for an altered response to a second stimulus (endotoxin), which included enhanced mortality. This study provided an improved understanding of pathophysiological changes following surgery and described a useful model for developing preventive and therapeutic strategies for complications after surgery.

Male gender is associated with increased risk for postinjury pneumonia

Nosocomial pneumonia in trauma patients is a significant source of resource utilization and mortality. We have previously described increased rates of pneumonia in male trauma patients in a single institution study. In that study, female trauma patients had a lower incidence of postinjury pneumonia but a higher relative risk for mortality when they did develop pneumonia. We sought to investigate the hypothesis that male trauma patients have an increased incidence of postinjury pneumonia in a separate population-based dataset. Prospective data were collected on 30,288 trauma patients (26,231 blunt injuries, 4057 penetrating injuries) admitted to all trauma centers (n = 26) in Pennsylvania over 24 months (January 1996 to December 1997). Gender differences in pneumonia were determined for the entire dataset. A second analysis examined all blunt injury patients and excluded all patients with a hospital length of stay less than 24 h, eliminating patients who expired early after admission. In trauma patients with minor injury (ISS < 15), there was no significant difference between male and female patients in the rate of postinjury pneumonia (male 1.37%, female 1.11%). In the moderate-injury group (ISS > 15), male trauma patients had a significantly increased incidence of postinjury pneumonia (ISS 15-30, male 8.85%, female 6.45%; ISS > 30, male 24.35%, female 17.30%). Logistic regression analysis of blunt trauma patients revealed that gender, ISS, injury type, admission Revised Trauma Score (RTS), admission respiratory rate, history of cardiac disease, and history of cancer were all independent predictors of pneumonia. Trauma patients with nosocomial pneumonia had a significantly higher mortality rate (P < 0.001) than patients without pneumonia. There was no gender-specific difference in mortality among pneumonia patients. Male gender is significantly associated with an increased incidence of postinjury pneumonia. In contrast to our initial study, there was no gender difference in postinjury pneumonia mortality rates identified in this population-based study.

Injury research in the genomic era

With the development of trauma systems, improved resuscitation, and organ system support, survival after severe injury is common, but is often complicated by nosocomial infection and organ failure. These complications are costly, and can lead to death or disability. Although much is known about the pathophysiology of post-traumatic nosocomial infection and organ failure, findings have been limited by our ability to generate and analyse large amounts of experimental and observational data. However, technological advances in nucleic acid and protein analysis, coupled with increased computational capacity, provide an opportunity to characterise the determinants of and the responses to injury and sepsis on a genome-wide scale. New large-scale collaborative efforts aim to investigate the genome for variation (gene polymorphisms), characterise multiple levels of the biological response to injury (transcriptome and proteome), and relate these to clinical phenotypes. In this article, we summarise recent findings and explore where promising new technologies might have the greatest potential for increasing our knowledge. It will now be important to determine how these recent technological advances can be used and integrated with our existing approaches, to reduce death, disability, and the economic consequences of trauma.

Multiorgan dysfunction in the perinatal patient

MODS is a rare but potentially lethal complication of pregnancy. Pregnancy induces physiologic changes in all major maternal organ systems that mimic early changes seen in SIRS and MODS. When a potentially life-threatening event occurs, such as hemorrhage,sepsis, or severe preeclampsia, the perinatal nurse must monitor subtle changes in maternal and fetal status and intervene to optimize maternal status.

Association of proinflammatory molecules with apoptotic markers and survival in critically ill multiple organ dysfunction patients

Recent evidence supports the involvement of apoptosis in multiple organ dysfunction (MODS). The authors examined the hypothesis that nitric oxide (NO), interleukin (IL)-6, tumor necrosis factor (TNF)-alpha, and cortisol correlate with Fas and Fas ligand (FasL) expression on peripheral blood mononuclear cells and that Fas and FasL, therefore, mediate their association with MODS severity. Thirty-five critically ill adult MODS patients were followed for up to 14 days and were compared to non-MODS matched controls. Fas, FasL, nitrate, cortisol, and IL-6 were elevated in MODS patients (P < 0.05). Nitrate and cortisol correlated with Fas expression (P < 0.05). All factors studied, except for TNF-alpha, correlated with MODS severity (P < 0.05); however, by multivariate analyses, Fas and FasL were independently associated with severity and survival (P < 0.05). The inflammatory molecules studied may mediate the association of apoptotic constituents with MODS severity and survival only in part.

Molecular diagnostics of injury and repair responses in critical illness: what is the future of "monitoring" in the intensive care unit?

OBJECTIVE

To identify potential future means of monitoring injury and repair in critical illness.

DESIGN

Review of the literature.

RESULTS

Critically ill patients are monitored extensively and intensively by such means as hemodynamics, laboratory values, and radiologic studies. In general, however, the goal of monitoring has been to measure the degree of injury and to prevent further injury, rather than to measure repair. Measures of repair have been limited to phenotypic end points such as return of organ function, as measured by blood chemistry. In this article, I examine how it may be possible in the future to monitor the progress of repair using genomic and proteomic biomarkers. These types of monitors would enable clinicians to control the healing environment using real time, rapid biomarkers, and sophisticated techniques to target therapy to the patient's current inflammatory state, taking into account the genetic makeup of the patient and his or her likely response to a given drug.

CONCLUSIONS

The rapidly evolving sciences of genomics, proteomics, computational biology, and complex system theory can be used a) to model critical illness; b) to model adaptive and maladaptive responses to critical illness; c) to tailor treatments to create an ideal inflammatory environment for repair and regeneration, taking into account the individual genetic contribution; and d) to monitor the progress of repair. The major obstacles to reaching these goals are technological, and experience suggests that they will be overcome.

Nitric oxide synthase inhibition as therapy for sepsis: a decade of promise

BACKGROUND

Inhibition of nitric oxide synthase (NOS) has held promise as a novel and important therapeutic target for sepsis for over a decade. However, the question as to whether an inhibitor of NOS will prove to be efficacious in human septic shock remains unanswered.

METHODS

Review of the pertinent English-language medical literature.

RESULTS

Observations of the induction of NOS (iNOS, NOS2) by proinflammatory cytokines led to the hypothesis that nitric oxide (NO) relaxes vascular smooth muscle, thereby producing vasodilation and hypotension in sepsis. Other effects of NO in vascular tone may be manifested by refractoriness to vasopressors or myocardial dysfunction. However, such negative effects of NO are balanced by the role of NO in maintaining microvascular perfusion and host defenses against invading pathogens. Initial animal studies of septic shock modulated by the administration of competitive inhibitors of NOS demonstrated that NOS inhibition might be beneficial therapy for clinical septic shock. However, subsequent animal studies have produced variable results, and a phase III clinical trial of a nonselective NOS inhibitor has failed to show benefit for therapy of septic shock.

CONCLUSION

A better understanding of the effects of NOS and its inhibitors is needed as is an understanding of the underlying pathophysiology of sepsis. Moreover, a nontoxic, short-acting, titratable, specific inhibitor of NOS2 has yet to be identified and tested. Until then, efforts should be designed to describe more completely the role of NO in the pathophysiology of sepsis.