The response of the host microcirculation to bacterial sepsis: does the pathogen matter?

Investigation of the effects of urotensin II receptors in LPS-induced inflammatory response in HUVEC cell line through calcineurin/NFATc/IL-2 pathway

PURPOSE

The effect of urotensin II (U-II), a powerful endogenous vasoconstrictor substance, on the immune system and its mediators is very important. It was herein aimed to demonstrate the possible relationship between the calcineurin/nuclear factor of activated T-cells cytoplasmic 1/interleukin-2 (CaN/NFATc/IL-2) pathway and urotensin receptors (UTRs) in inflammatory response due to lipopolysaccharide (LPS).

METHODS

An LPS-induced inflammation model was used on the human umbilical vein endothelial cells (HUVEC) cell line and drugs were applied accordingly, forming the following groups: Control Group, LPS Group, Agonist Group (10-8 ​M U-II), Antagonist Group (10-6 ​M palosuran), Tacrolimus (TAC) Group (10 ​ng/mL FK-506), Agonist ​+ ​TAC Group, and Antagonist ​+ ​TAC Group. Gene expression analyses were performed using real-time polymerase chain reaction (RT-PCR).

RESULTS

In the analysis of the cell viability at 48 and 72 ​h, there was a decrease in the Agonist Group, while in the Agonist ​+ ​TAC Group, the cell viability increased. In the Antagonist Group, cell viability was maintained when compared to the LPS Group, while in the TAC Group, this effect was reduced. The mRNA expression levels of UTR, CaN, NFATc, IL-2 receptor (IL-2R), IL-6 and nuclear factor kappa B (NF-κB) were higher in the LPS Group than in the Control Group, and even the UTR, CaN, NFATc, IL-2R were higher with agonist administration. This effect of the agonist was shown to be completely mitigated in the presence of the CaN inhibitor.

CONCLUSION

U-II and its receptors can perform key functions regarding the endothelial cell damage via the CaN/NFATc/IL-2 pathway.

Differentiating infection, colonisation, and sterile inflammation in critical illness: the emerging role of host-response profiling

Infection results when a pathogen produces host tissue damage and elicits an immune response. Critically ill patients experience immune activation secondary to both sterile and infectious insults, with overlapping clinical phenotypes and underlying immunological mechanisms. Patients also undergo a shift in microbiota with the emergence of pathogen-dominant microbiomes. Whilst the combination of inflammation and microbial shift has long challenged intensivists in the identification of true infection, the advent of highly sensitive molecular diagnostics has further confounded the diagnostic dilemma as the number of microbial detections increases. Given the key role of the host immune response in the development and definition of infection, profiling the host response offers the potential to help unravel the conundrum of distinguishing colonisation and sterile inflammation from true infection. This narrative review provides an overview of current approaches to distinguishing colonisation from infection using routinely available techniques and proposes matrices to support decision-making in this setting. In searching for new tools to better discriminate these states, the review turns to the understanding of the underlying pathobiology of the host response to infection. It then reviews the techniques available to assess this response in a clinically applicable context. It will cover techniques including profiling of transcriptome, protein expression, and immune functional assays, detailing the current state of knowledge in diagnostics along with the challenges and opportunities. The ultimate infection diagnostic tool will likely combine an assessment of both host immune response and sensitive pathogen detection to improve patient management and facilitate antimicrobial stewardship.

Posterior Reversible Encephalopathy in Sepsis-Associated Encephalopathy: Experience from a Single Center

BACKGROUND

Sepsis-associated encephalopathy (SAE) is frequently encountered in sepsis and is often accompanied by neuroimaging findings indicating ischemia, hemorrhage, and edema. Posterior reversible encephalopathy syndrome (PRES) has been vastly underrecognized in previously reported cohorts of patients with sepsis and SAE. Our aim was to determine the prevalence and distinguishing clinical, neuroimaging, and electroencephalography features of PRES in SAE.

METHODS

In this prospective observational study, patients with radiologically identified PRES were selected from a consecutively enrolled cohort of 156 patients with SAE and assessed for neurological outcome using the extended Glasgow Outcome Scale for 12 months. Patients with SAE and PRES and other types of brain lesions were compared in terms of clinical and diagnostic workup features.

RESULTS

Fourteen of 156 patients (8.9%) were determined to be radiologically compatible with PRES, whereas 48 patients displayed other types of acute brain lesions. Patients with PRES often showed lesions in atypical regions, including frontal lobes, the corpus callosum, and the basal ganglia. Source of infection was mostly gram-negative bacteria originating from pneumonia or intraabdominal infections. Patients with PRES were not different from other patients with SAE with brain lesions in terms of features of sepsis and neurological outcome. However, patients with PRES showed increased prevalence of seizures and intraabdominal source of infection.

CONCLUSIONS

PRES is highly prevalent in SAE, often encompasses unusual brain regions, and usually presents with generalized seizures. Patients with SAE and PRES do not appear to have distinguishing clinical and diagnostic workup features. However, generalized seizures may serve as warning signs for presence of PRES in patients with SAE.

Selenocompounds and Sepsis: Redox Bypass Hypothesis for Early Diagnosis and Treatment: Part A-Early Acute Phase of Sepsis: An Extraordinary Redox Situation (Leukocyte/Endothelium Interaction Leading to Endothelial Damage)

Significance: Sepsis is a health disaster. In sepsis, an initial, beneficial local immune response against infection evolves rapidly into a generalized, dysregulated response or a state of chaos, leading to multiple organ failure. Use of life-sustaining supportive therapies creates an unnatural condition, enabling the complex cascades of the sepsis response to develop in patients who would otherwise die. Multiple attempts to control sepsis at an early stage have been unsuccessful. Recent Advances: Major events in early sepsis include activation and binding of leukocytes and endothelial cells in the microcirculation, damage of the endothelial surface layer (ESL), and a decrease in the plasma concentration of the antioxidant enzyme, selenoprotein-P. These events induce an increase in intracellular redox potential and lymphocyte apoptosis, whereas apoptosis is delayed in monocytes and neutrophils. They also induce endothelial mitochondrial and cell damage. Critical Issues: Neutrophil production increases dramatically, and aggressive immature forms are released. Leukocyte cross talk with other leukocytes and with damaged endothelial cells amplifies the inflammatory response. The release of large quantities of reactive oxygen, halogen, and nitrogen species as a result of the leukocyte respiratory burst, endothelial mitochondrial damage, and ischemia/reperfusion processes, along with the marked decrease in selenoprotein-P concentrations, leads to peroxynitrite damage of the ESL, reducing flow and damaging the endothelial barrier. Future Directions: Endothelial barrier damage by activated leukocytes is a time-sensitive event in sepsis, occurring within hours and representing the first step toward organ failure and death. Reducing or stopping this event is necessary before irreversible damage occurs.

Targeting Endothelial Barrier Dysfunction Caused by Circulating Bacterial and Mitochondrial N-Formyl Peptides With Deformylase

Despite recent advances in our understanding of the mechanisms underlying systemic inflammatory response syndrome (SIRS) and sepsis, the current therapeutic approach to these critically ill patients is centered around supportive care including fluid resuscitation, vasopressors and source control. The incidence of SIRS and sepsis continues to increase in the United States and patients die due to failure to respond to the traditional therapies of nitric oxide blockade, adrenergic agonists, etc. Bacterial and mitochondrial N-formyl peptides (NFPs) act as damage-associated molecular patterns and activate the innate immune system through formyl peptide receptors (FPR) located in immune and non-immune cells, including the vascular endothelium. The resulting inflammatory response manifests as capillary leak, tissue hypoperfusion and vasoplegia, partially due to endothelium barrier breakdown. Potential strategies to prevent this response include decreasing NFP release, breakdown of NFPs, and blocking NFPs from binding FPR. We propose the use of deformylase, the degrading enzyme for NFPs, as potential therapeutic approach to prevent the deleterious effects of NFPs in SIRS and sepsis.

Companion and Point-of-Care Sensor System for Rapid Multiplexed Detection of a Panel of Infectious Disease Markers

A nanochannel-based electrochemical biosensor has been demonstrated for rapid and multiplexed detection of a panel of three biomarkers associated with rapid detection of sepsis. The label-free biosensor detected procalcitonin (PCT), lipoteichoic acid (LTA), and lipopolysaccharide (LPS) from human whole blood. The biosensor comprises a nanoporous nylon membrane integrated onto a microelectrode sensor platform for nanoconfinement effects. Charge perturbations due to biomarker binding are recorded as impedance changes using electrochemical impedance spectroscopy. The measured impedance change is used to quantitatively determine the concentration of the three biomarkers using antibody receptors from the tested sample. We were successful in detecting and quantifying the three biomarkers from whole blood. The limit of detection was 0.1 ng/mL for PCT and 1 µg/mL for LPS and LTA. The sensor was able to demonstrate a dynamic range of detection from 01.1 ng/mL to 10 µg/mL for PCT and from 1 µg/mL to 1000 µg/mL for LPS and LTA biomarkers. This novel technology has promising preliminary results toward the design of sensors for rapid and sensitive detection of the three panel biomarkers in whole blood toward diagnosis and classification of sepsis.

Neutrophil-to-Lymphocyte Ratio, Monocyte-to-Lymphocyte Ratio, Platelet-to-Lymphocyte Ratio, and Mean Platelet Volume-to-Platelet Count Ratio as Biomarkers in Critically Ill and Injured Patients: Which Ratio to Choose to Predict Outcome and Nature of Bacteremia?

Background

Neutrophil-to-lymphocyte ratio (NLR), monocyte-to-lymphocyte ratio (MLR), platelet-to-lymphocyte ratio (PLR), and mean platelet volume-to-platelet count (MPV/PC) ratio are readily available parameters that might have discriminative power regarding outcome. The aim of our study was to assess prognostic value of these biomarkers regarding outcome in critically ill patients with secondary sepsis and/or trauma.

Methods

A total of 392 critically ill and injured patients, admitted to surgical ICU, were enrolled in a prospective observational study. Leukocyte and platelet counts were recorded upon fulfilling Sepsis-3 criteria and for traumatized Injury Severity Score > 25 points. Patients were divided into four subgroups: peritonitis, pancreatitis, trauma with sepsis, and trauma without sepsis.

Results

NLR and MPV/PC levels were significantly higher in nonsurvivors (AUC/ROC of 0.681 and 0.592, resp., in the peritonitis subgroup; 0.717 and 0.753, resp., in the pancreatitis subgroup); MLR and PLR did not differ significantly. There was no significant difference of investigated biomarkers between survivors and nonsurvivors in trauma patients with and without sepsis except for PLR in the trauma without sepsis subgroup (significantly higher in nonsurvivors, AUC/ROC of 0.719). Independent predictor of lethal outcome was NLR in the whole cohort and in the peritonitis subgroup as well as MPV in the pancreatitis subgroup. Also, there were statistically significant differences in MPV/PC, MLR, and PLR values regarding nature of bacteremia. In general, the lowest levels had been found in patients with Gram-positive blood cultures.

Conclusions

NLR and MPV were very good independent predictors of lethal outcome. For the first time, we demonstrate that nature of bacteremia influences MPV/PC, MLR, and PLR. In heterogeneous cohort subgroup, analysis is essential.

Impact of Unsaturated Fatty Acids on Cytokine-Driven Endothelial Cell Dysfunction

Polyunsaturated fatty acids (PUFA) are reported to exert prophylactic and acute therapeutic effects in diseases linked to endothelial dysfunction. In the present study, the consequences of a PUFA enrichment of endothelial cells (cell line TIME) on cell viability, expression of the cytokines interleukin-6 (IL-6), interleukin-8 (IL-8), granulocyte-macrophage colony-stimulating factor (GM-CSF), and monocyte chemoattractant protein 1 (MCP-1), synthesis of the adhesion molecules intercellular adhesion molecule 1 (ICAM-1) and vascular adhesion molecule 1 (VCAM-1), and production of the coagulation factors plasminogen activator inhibitor-1 (PAI-1), von Willebrand factor (vWF), and tissue factor (TF) was analyzed in parallel. PUFA of both the n3 and the n6 family were investigated in a physiologically relevant concentration of 15 µM, and experiments were performed in both the presence and the absence of the pro-inflammatory cytokines interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and interferon-γ (IFN-γ). Supplementation of the culture medium with particular fatty acids was found to have a promoting effect on cellular production of the cytokines IL-6, IL-8, GM-CSF, and MCP-1. Further on, PUFA treatment in the absence of a stimulant diminished the percentage of endothelial cells positive for ICAM-1, and adversely affected the stimulation-induced upregulation of VCAM-1. Cell viability and production of coagulation factors were not or only marginally affected by supplemented fatty acids. Altogether, the data indicate that PUFA of either family are only partially able to counterbalance the destructive consequences of an endothelial dysfunction.

Review article: the role of the microcirculation in liver cirrhosis

BACKGROUND

Intrahepatic microvascular derangements and microcirculatory dysfunction are key in the development of liver cirrhosis and its associated complications. While much has been documented relating to cirrhosis and the dysfunction of the microcirculation in the liver parenchyma, far less is known about the state of the extrahepatic microcirculation and the role this may have in the pathogenesis of multiple organ failure in end stage liver cirrhosis.

AIM

To provide an update on the role of the microcirculation in the pathophysiology of cirrhosis and its associated complications and briefly discuss some of the imaging techniques which may be used to directly investigate the microcirculation.

METHODS

A Medline literature search was conducted using the following search terms: 'cirrhosis', 'microcirculation', 'circulation', 'systemic', 'inflammation', 'peripheral', 'hepatorenal' and 'hepatopulmonary'.

RESULTS

Significant heterogeneous microvascular alterations exist in patients with cirrhosis. Data suggest that the systemic inflammation, associated with advanced cirrhosis, induces microcirculatory dysregulation and contributes to haemodynamic derangement. The resultant vasoconstriction and hypoperfusion in the systemic extrahepatic microvasculature, is likely to be instrumental in the pathophysiology of organ failure in decompensated cirrhosis, however the mechanistic action of vasoactive agents used to correct the circulatory disturbance of advanced cirrhosis is poorly understood.

CONCLUSIONS

Further research into the role of the microcirculation in patients with liver cirrhosis, will improve physicians understanding of the pathophysiology of cirrhosis, and may provide a platform for real time evaluation of an individual's microcirculatory response to vasoactive mediators, thus guiding their therapy.

Companion and Point-of-Care Sensor System for Rapid Multiplexed Detection of a Panel of Infectious Disease Markers

A nanochannel-based electrochemical biosensor has been demonstrated for rapid and multiplexed detection of a panel of three biomarkers associated with rapid detection of sepsis. The label-free biosensor detected procalcitonin (PCT), lipoteichoic acid (LTA), and lipopolysaccharide (LPS) from human whole blood. The biosensor comprises a nanoporous nylon membrane integrated onto a microelectrode sensor platform for nanoconfinement effects. Charge perturbations due to biomarker binding are recorded as impedance changes using electrochemical impedance spectroscopy. The measured impedance change is used to quantitatively determine the concentration of the three biomarkers using antibody receptors from the tested sample. We were successful in detecting and quantifying the three biomarkers from whole blood. The limit of detection was 0.1 ng/mL for PCT and 1 µg/mL for LPS and LTA. The sensor was able to demonstrate a dynamic range of detection from 01.1 ng/mL to 10 µg/mL for PCT and from 1 µg/mL to 1000 µg/mL for LPS and LTA biomarkers. This novel technology has promising preliminary results toward the design of sensors for rapid and sensitive detection of the three panel biomarkers in whole blood toward diagnosis and classification of sepsis.

Microcirculatory dysfunction in sepsis: pathophysiology, clinical monitoring, and potential therapies

Abnormal microvascular perfusion, including decreased functional capillary density and increased blood flow heterogeneity, is observed in early stages of the systemic inflammatory response to infection and appears to have prognostic significance in human sepsis. It is known that improvements in systemic hemodynamics are weakly correlated with the correction of microcirculatory parameters, despite an appropriate treatment of macrohemodynamic abnormalities. Furthermore, conventional hemodynamic monitoring systems available in clinical practice fail to detect microcirculatory parameter changes and responses to treatments, as they do not evaluate intrinsic events that occur in the microcirculation. Fortunately, some bedside diagnostic methods and therapeutic options are specifically directed to the assessment and treatment of microcirculatory changes. In the present review we discuss fundamental aspects of septic microcirculatory abnormalities, including pathophysiology, clinical monitoring, and potential therapies.

Broad spectrum immunomodulation using biomimetic blood cell margination for sepsis therapy

Sepsis represents a systemic inflammatory response caused by microbial infection in blood. Herein, we present a novel comprehensive approach to mitigate inflammatory responses through broad spectrum removal of pathogens, leukocytes and cytokines based on biomimetic cell margination. Using a murine model of polymicrobial sepsis induced by cecal ligation and puncture (CLP), we performed extracorporeal blood filtration with the developed microfluidic blood margination (μBM) device. Circulating bacteremia, leukocytes and cytokines in blood decreased post-filtration and significant attenuation of immune cell and cytokine responses were observed 3-5 days after intervention, indicating successful long-term immunomodulation. A dose-dependent effect on long-term immune cell count was also achieved by varying filtration time. As proof of concept for human therapy, the μBM device was scaled up to achieve ∼100-fold higher throughput (∼150 mL h(-1)). With further multiplexing, the μBM technique could be applied in clinical settings as an adjunctive treatment for sepsis and other inflammatory diseases.

Does plasma membrane lipid composition impact the miRNA-mediated regulation of vascular inflammation?

BACKGROUND

Both PUFA and miRNAs are believed to be of importance in vascular diseases. On the one hand diverse nutrition societies recommend PUFA consumption to dampen inflammatory processes. On the other hand scientists intensify efforts to use miRNAs for diagnostics or therapy in context of vascular disorders.

PRESENTATION OF THE HYPOTHESIS

There might be is a causal link between the plasma membrane lipid composition and the miRNA expression of monocytes and endothelial cells. PUFA enrichment of cells may affect the type and the amount of particular miRNAs produced. In this way dietary fatty acids are supposed to impact the miRNA-mediated regulation of vascular inflammatory processes.

PROPOSED EXPERIMENTAL SETTING TO TEST THE HYPOTHESIS

PUFA-supplemented monocytes and endothelial cells are analyzed with respect to membrane fatty acid patterns, typical markers of vascular inflammation and miRNA expression. Experiments are performed both for undifferentiated/unstimulated as well as for differentiated/stimulated cells. Verification of identified miRNA targets is performed by means of mimics/antagomirs.

IMPLICATIONS OF THE HYPOTHESIS

Innovative mechanism of action, which could point the way to a new understanding of the PUFA-mediated modulation of cellular signal transduction. If confirmed experimentally, it might stimulate vascular inflammation research and immunologic lipid science, hence, acting as source of inspiration for future therapeutic interventions in vascular diseases.

Cytokine profile in severe Gram-positive and Gram-negative abdominal sepsis

Sepsis is a principal cause of death in critical care units worldwide and consumes considerable healthcare resources. The aim of our study was to determine whether the early cytokine profile can discriminate between Gram-positive and Gram-negative bacteraemia (GPB and GNB, respectively) and to assess the prognostic value regarding outcome in critically ill patients with severe abdominal sepsis. The outcome measure was hospital mortality. Blood samples were obtained from 165 adult patients with confirmed severe abdominal sepsis. Levels of the proinflammatory mediators TNF-α, IL-8, IL-12 and IFN-γ and the anti-inflammatory mediators IL-1ra, IL-4, IL-10 and TGF-β1 were determined and correlated with the nature of the bacteria isolated from the blood culture and outcome. The cytokine profile in our study indicated that the TNF-α levels were 2-fold, IL-8 were 3.3-fold, IFN-γ were 13-fold, IL-1ra were 1.05-fold, IL-4 were 1.4-fold and IL-10 were 1.83-fold higher in the GNB group compared with the GPB group. The TNF-α levels were 4.7-fold, IL-8 were 4.6-fold, IL-1ra were 1.5-fold and IL-10 were 3.3-fold higher in the non-survivors compared with the survivors.

Acute inflammatory response in the subcutaneous versus periprosthethic space after incisional hernia repair: an original article

BACKGROUND

The acute inflammatory response following mesh implantation has been often evaluated in vitro and in animal models. The aim of this study was to evaluate the acute inflammatory response near the prosthesis in human by analysing some inflammatory indicators.

METHODS

We used a cohort of twelve male patients affected by midline incisional hernia, who were admitted for surgical mesh repair. A suction drain was placed between the mesh and rectal muscles whereas, the other one was placed between the subcutaneous tissue and the oblique external sheath. The acute inflammatory response was analyzed by measuring the production of interleukin [IL]-1, IL-10, IL-1ra, C-Reactive Protein (CRP), total proteins, albumin and pH in the drain fluids.

RESULTS

The dynamics of CRP and ILs production resulted similar in both drainages. Comparing drain over mesh and subcutaneous drain at all times, IL-1 and CRP values always resulted significantly higher in the first one, whereas IL-1ra and IL-10 values were significantly higher in the last one. Total protein and albumin were similar in both drains at all time; only in the drain over mesh fluid, pH values resulted significantly reduced in the fourth post-operative day.

CONCLUSIONS

Our data showed that an acute inflammatory reaction is present in both sites examined. However, it was significantly higher in the space after mesh implantation.

The renal microcirculation in sepsis

Despite identification of several cellular mechanisms being thought to underlie the development of septic acute kidney injury (AKI), the pathophysiology of the occurrence of AKI is still poorly understood. It is clear, however, that instead of a single mechanism being responsible for its aetiology, an orchestra of cellular mechanisms failing is associated with AKI. The integrative physiological compartment where these mechanisms come together and exert their integrative deleterious action is the renal microcirculation (MC). This is why it is opportune to review the response of the renal MC to sepsis and discuss the determinants of its (dys)function and how it contributes to the pathogenesis of renal failure. A main determinant of adequate organ function is the adequate supply and utilization of oxygen at the microcirculatory and cellular level to perform organ function. The highly complex architecture of the renal microvasculature, the need to meet a high energy demand and the fact that the kidney is borderline ischaemic makes the kidney a highly vulnerable organ to hypoxaemic injury. Under normal, steady-state conditions, oxygen (O2) supply to the renal tissues is well regulated; however, under septic conditions the delicate balance of oxygen supply versus demand is disturbed due to renal microvasculature dysfunction. This dysfunction is largely due to the interaction of renal oxygen handling, nitric oxide metabolism and radical formation. Renal tissue oxygenation is highly heterogeneous not only between the cortex and medulla but also within these renal compartments. Integrative evaluation of the different determinants of tissue oxygen in sepsis models has identified the deterioration of microcirculatory oxygenation as a key component in the development AKI. It is becoming clear that resuscitation of the failing kidney needs to integratively correct the homeostasis between oxygen, and reactive oxygen and nitrogen species. Several experimental therapeutic modalities have been found to be effective in restoring microcirculatory oxygenation in parallel to improving renal function following septic AKI. However, these have to be verified in clinical studies. The development of clinical physiological biomarkers of AKI specifically aimed at the MC should form a valuable contribution to monitoring such new therapeutic modalities.

Barriers to the effective treatment of sepsis: antimicrobial agents, sepsis definitions, and host-directed therapies

Sepsis is a complex clinical syndrome involving both infection and a deleterious host immune response. Antimicrobial agents are key elements of sepsis treatment, yet despite great strides in antimicrobial development in the last decades, sepsis continues to be associated with unacceptably high mortality (~30%). This is the result, on one hand, of the rise of antimicrobial resistant organisms and, on the other hand, of the dearth of effective host-directed immune therapies. A major obstacle to the development of good host-directed therapies is the lack of understanding of the host immune response. The problem is exacerbated by poor nonspecific clinical definitions of disease. Poor definitions have had a profound impact on sepsis research, from epidemiologic studies to the failed clinical trials of host-directed therapies. Therefore, better definitions must be developed to enable advancement in the field.

Thermo-nanoimprinted biomimetic probe for LPS and LTA immunosensing

A complex prepolymerized film comprising monomers, cross-linkers, and initiator is usually used to create molecularly imprinted polymers. We herein exploit ready-to-use resist materials and link molecular surface imprinting with UV- and thermo-nanoimprinting techniques to create a sensor layer for the specific recognition of the bacterial surface markers lipopolysaccharide (LPS) and lipoteichoic acid (LTA). To account for the highly polar moieties of LPS and LTA, we evaluate different resist and stamp materials of distinct surface properties by AFM and molecularly imprinted sorbent assays. Thermo nanoimprinting of LPS and LTA micelles to Epon 1002F films exhibits excellent sensitivity of up to 13 times increased signals compared to those of the nonimprinted films and negligible cross-reaction with the tested nonspecific analyte. Additionally, the sensitivity and selectivity of the thermo nanoimprints is compared to conventional molecular surface imprints using a cocktail of acrylic monomers in QCM measurements.

Cardiovascular Disease and High-Mobility Group Box 1—Is a New Inflammatory Killer in Town?

High-mobility group box 1 (HMGB-1) is a nuclear protein physiologically involved in the maintaining of DNA structure in the nucleus. When tissue damage occurs, necrotic cells as well as inflammatory cells, once activated, release this protein in circulating blood, where it seems to exert a direct proinflammatory action. Thus, HMGB-1 might be involved in the pathophysiology of several diseases, including cardiovascular disease. However, the experimental evidence has not yet clarified its cardiovascular role which is still debated. Specifically, it is still not completely resolved whether HMGB-1 plays a protective or detrimental role on cardiovascular function. In this review, we consider the role of HMGB-1 in pathological conditions and comment on the role of this protein in the cardiovascular disease.

Experimental data suggesting that inflammation mediated rat liver mitochondrial dysfunction results from secondary hypoxia rather than from direct effects of inflammatory mediators

Systemic inflammatory response (SIR) comprises both direct effects of inflammatory mediators (IM) and indirect effects, such as secondary circulatory failure which results in tissue hypoxia (HOX). These two key components, SIR and HOX, cause multiple organ failure (MOF). Since HOX and IM occur and interact simultaneously in vivo, it is difficult to clarify their individual pathological impact. To eliminate this interaction, precision cut liver slices (PCLS) were used in this study aiming to dissect the effects of HOX and IM on mitochondrial function, integrity of cellular membrane, and the expression of genes associated with inflammation. HOX was induced by incubating PCLS or rat liver mitochondria at pO2 < 1% followed by reoxygenation (HOX/ROX model). Inflammatory injury was stimulated by incubating PCLS with IM (IM model). We found upregulation of inducible nitric oxide synthase (iNOS) expression only in the IM model, while heme oxygenase 1 (HO-1) expression was upregulated only in the HOX/ROX model. Elevated expression of interleukin 6 (IL-6) was found in both models reflecting converging pathways regulating the expression of this gene. Both models caused damage to hepatocytes resulting in the release of alanine aminotransferase (ALT). The leakage of aspartate aminotransferase (AST) was observed only during the hypoxic phase in the HOX/ROX model. The ROX phase of HOX, but not IM, drastically impaired mitochondrial electron supply via complex I and II. Additional experiments performed with isolated mitochondria showed that free iron, released during HOX, is likely a key prerequisite of mitochondrial dysfunction induced during the ROX phase. Our data suggests that mitochondrial dysfunction, previously observed in in vivo SIR-models, is the result of secondary circulatory failure inducing HOX rather than the result of a direct interaction of IM with liver cells.

CD137 expressed on neutrophils plays dual roles in antibacterial responses against Gram-positive and Gram-negative bacterial infections

Severe sepsis and septic shock caused mainly by bacterial infections are life-threatening conditions that urge the development of novel therapies. However, host responses to and pathophysiology of sepsis have not been clearly understood, which remains a major obstacle for the development of effective therapeutics. Recently, we have shown that stimulation of a costimulatory molecule, CD137, enhanced survival of mice infected with the Gram-positive (G(+)) intracellular bacterium Listeria monocytogenes but decreased survival in a polymicrobial sepsis model. Herein, we report that CD137 deficiency or blocking of CD137 signaling decreased antibacterial responses of mice infected with G(+) bacteria (Staphylococcus aureus, Streptococcus pneumoniae, and Enterococcus faecalis) but increased these responses in mice infected with Gram-negative (G(-)) bacteria (Escherichia coli, Pseudomonas aeruginosa, and Salmonella enterica serovar Typhimurium). Consistent with these findings, stimulation of CD137 by administration of agonistic antibody enhanced responses against G(+) bacteria, whereas it decreased these responses against G(-) bacteria. Neutrophils were responsible for CD137-mediated opposite roles in control of G(+) and G(-) bacterial infections. Stimulation of CD137 enhanced activities of neutrophils against S. aureus but decreased these activities against E. coli, while CD137 blocking produced opposite results with the stimulation of CD137 in vivo and in vitro. Furthermore, we found that combined signaling of CD137 and Toll-like receptor 2 (TLR2) induced synergistic production of tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6) by neutrophils, but combined signaling of CD137 and TLR4 did not. Our data strongly suggest that CD137 may play a dual role in sepsis in association with TLRs.

Lipoteichoic acid induces surfactant protein-A biosynthesis in human alveolar type II epithelial cells through activating the MEK1/2-ERK1/2-NF-κB pathway

BACKGROUND

Lipoteichoic acid (LTA), a gram-positive bacterial outer membrane component, can cause septic shock. Our previous studies showed that the gram-negative endotoxin, lipopolysaccharide (LPS), could induce surfactant protein-A (SP-A) production in human alveolar epithelial (A549) cells.

OBJECTIVES

In this study, we further evaluated the effect of LTA on SP-A biosynthesis and its possible signal-transducing mechanisms.

METHODS

A549 cells were exposed to LTA. Levels of SP-A, nuclear factor (NF)-κB, extracellular signal-regulated kinase 1/2 (ERK1/2), and mitogen-activated/extracellular signal-regulated kinase kinase (MEK)1 were determined.

RESULTS

Exposure of A549 cells to 10, 30, and 50 μg/ml LTA for 24 h did not affect cell viability. Meanwhile, when exposed to 30 μg/ml LTA for 1, 6, and 24 h, the biosynthesis of SP-A mRNA and protein in A549 cells significantly increased. As to the mechanism, LTA enhanced cytosolic and nuclear NF-κB levels in time-dependent manners. Pretreatment with BAY 11-7082, an inhibitor of NF-κB activation, significantly inhibited LTA-induced SP-A mRNA expression. Sequentially, LTA time-dependently augmented phosphorylation of ERK1/2. In addition, levels of phosphorylated MEK1 were augmented following treatment with LTA.

CONCLUSIONS

Therefore, this study showed that LTA can increase SP-A synthesis in human alveolar type II epithelial cells through sequentially activating the MEK1-ERK1/2-NF-κB-dependent pathway.

Beneficial effect of garlic on D-galactosamine and lipopolysaccharide-induced acute hepatic failure in male albino rats

BACKGROUND AND AIMS

Activation of the pro-inflammatory and anti-inflammatory cytokine cascade, including tumour necrosis factor (TNF)-alpha and interleukin (IL)-4, is considered to play an important role in severe liver injury. Kupffer cells, resident macrophages of the liver, activated with lipopolysaccharide (LPS) release pro-inflammatory cytokine. D-Galactosamine (D-GalN), a hepatocyte-specific inhibitor of RNA synthesis, is known to sensitise animals to the lethal effects of LPS. In the present study we seek to reverse some altered parameters, immunological and histopathological, to normal values of rats pre-treated with garlic.

METHODS

Acute hepatic failure was induced in male albino rats by the intraperitoneal injection of 500 mg D-GalN and 50 μg LPS/kg body weight. Expression levels of TNF-α and IL-4 were detected by ELISA. Leukocytes proliferation was carried out by differential count. For histopathology, liver sections were stained with haematoxylin and eosin. Data were analysed by SPSS program version 13.0.

RESULTS

The data showed significant increase in the numbers of granulocytes, but with significant decreases in lymphocyte and monocytes proliferation and the TNF-alpha and IL-4 levels in D-GalN/LPS-induced group. Garlic pre-treatment of liver-injured rats induced significant amelioration in the numbers of monocytes and lymphocytes, with significant increase in granulocytes numbers, TNF-α level and IL-4 level.

CONCLUSIONS

Results of this study revealed that garlic could afford a significant protection in the alleviation of D-GalN/LPS-induced hepatocellular injury.

A microfluidics approach towards high-throughput pathogen removal from blood using margination

Sepsis is an adverse systemic inflammatory response caused by microbial infection in blood. This paper reports a simple microfluidic approach for intrinsic, non-specific removal of both microbes and inflammatory cellular components (platelets and leukocytes) from whole blood, inspired by the invivo phenomenon of leukocyte margination. As blood flows through a narrow microchannel (20 × 20 µm), deformable red blood cells (RBCs) migrate axially to the channel centre, resulting in margination of other cell types (bacteria, platelets, and leukocytes) towards the channel sides. By using a simple cascaded channel design, the blood samples undergo a 2-stage bacteria removal in a single pass through the device, thereby allowing higher bacterial removal efficiency. As an application for sepsis treatment, we demonstrated separation of Escherichia coli and Saccharomyces cerevisiae spiked into whole blood, achieving high removal efficiencies of ∼80% and ∼90%, respectively. Inflammatory cellular components were also depleted by >80% in the filtered blood samples which could help to modulate the host inflammatory response and potentially serve as a blood cleansing method for sepsis treatment. The developed technique offers significant advantages including high throughput (∼1 ml/h per channel) and label-free separation which allows non-specific removal of any blood-borne pathogens (bacteria and fungi). The continuous processing and collection mode could potentially enable the return of filtered blood back to the patient directly, similar to a simple and complete dialysis circuit setup. Lastly, we designed and tested a larger filtration device consisting of 6 channels in parallel (∼6 ml/h) and obtained similar filtration performances. Further multiplexing is possible by increasing channel parallelization or device stacking to achieve higher throughput comparable to convectional blood dialysis systems used in clinical settings.

Stimulatory type A CpG-DNA induces a Th2-like response in human endothelial cells

Unmethylated CpG-DNA motifs from pathogens are detected by the pattern recognition receptor toll-like receptor 9 (TLR9), eliciting an inflammatory immune response. These DNA sequences have been identified as potent immune modifiers and are used as adjuvants in vaccine research. Since we previously found TLR9 expression and function in human endothelial cells, we have here investigated whether endothelial cells play a role in the recognition of respective ligands and whether their response might contribute to vaccination success. We determined the effect of CpG-DNA on the inflammatory response of human endothelial cells of aortic or skin microvascular origin (HAoEC, HDMEC and HMEC-1) and compared the effects to those of two identically treated human macrophage cell lines. Using the same CpG-DNA D19(chimera) sequence in both cell types, we find the known up-regulation of pro-inflammatory cytokines in macrophages but consistent and significant inhibition of the pro-inflammatory response (IL-6, IL-8, and IFN-beta1) in endothelial cells. This inhibition is accompanied by enhanced proliferation and an increase in IL-10 gene expression. This anti-inflammatory response persists even in the presence of pro-inflammatory cytokines and low LPS concentrations, and is overruled only in the presence of relatively high concentrations of LPS. By testing different sequences, we find the strongest response with phosphorothioate bonds. Our results demonstrate an important regulatory function of endothelial cells in inflammatory responses, and the apparent Th2-like endothelial response in the human system may contribute significantly to the adjuvant activity of CpG-DNA.

Fatal outcome in bacteremia is characterized by high plasma cell free DNA concentration and apoptotic DNA fragmentation: a prospective cohort study

INTRODUCTION

Recent studies have shown that apoptosis plays a critical role in the pathogenesis of sepsis. High plasma cell free DNA (cf-DNA) concentrations have been shown to be associated with sepsis outcome. The origin of cf-DNA is unclear.

METHODS

Total plasma cf-DNA was quantified directly in plasma and the amplifiable cf-DNA assessed using quantitative PCR in 132 patients with bacteremia caused by Staphylococcus aureus, Streptococcus pneumoniae, ß-hemolytic streptococcae or Escherichia coli. The quality of cf-DNA was analyzed with a DNA Chip assay performed on 8 survivors and 8 nonsurvivors. Values were measured on days 1-4 after positive blood culture, on day 5-17 and on recovery.

RESULTS

The maximum cf-DNA values on days 1-4 (n = 132) were markedly higher in nonsurvivors compared to survivors (2.03 vs 1.26 ug/ml, p<0.001) and the AUCROC in the prediction of case fatality was 0.81 (95% CI 0.69-0.94). cf-DNA at a cut-off level of 1.52 ug/ml showed 83% sensitivity and 79% specificity for fatal disease. High cf-DNA (>1.52 ug/ml) remained an independent risk factor for case fatality in a logistic regression model. Qualitative analysis of cf-DNA showed that cf-DNA displayed a predominating low-molecular-weight cf-DNA band (150-200 bp) in nonsurvivors, corresponding to the size of the apoptotic nucleosomal DNA. cf-DNA concentration showed a significant positive correlation with visually graded apoptotic band intensity (R = 0.822, p<0.001).

CONCLUSIONS

Plasma cf-DNA concentration proved to be a specific independent prognostic biomarker in bacteremia. cf-DNA displayed a predominating low-molecular-weight cf-DNA band in nonsurvivors corresponding to the size of apoptotic nucleosomal DNA.