Hemorrhagic shock augments lung endothelial cell activation: role of temporal alterations of TLR4 and TLR2

Imaging Reactive Oxygen Radicals in Excised Mouse Lung Trapped by Reaction with Hydroxylamine Probes Using 1 GHz Rapid Scan Electron Paramagnetic Resonance

PURPOSE

Oxidative stress is proposed to be critical in acute lung disease, but methods to monitor radicals in lungs are lacking. Our goal is to develop low-frequency electron paramagnetic resonance (EPR) methods to monitor radicals that contribute to the disease.

PROCEDURES

Free radicals generated in a lipopolysaccharide-induced mouse model of acute respiratory distress syndrome reacted with cyclic hydroxylamines CPH (1-hydroxy-3-carboxy-2,2,5,5-tetramethylpyrrolidine hydrochloride) and DCP-AM-H (4-acetoxymethoxycarbonyl-1-hydroxy-2,2,5,5-tetramethylpyrrolidine-3-carboxylic acid), which were converted into the corresponding nitroxide radicals, CP• and DCP•. The EPR signals of the nitroxide radicals in excised lungs were imaged with a 1 GHz EPR spectrometer/imager that employs rapid scan technology.

RESULTS

The small numbers of nitroxides formed by reaction of the hydroxylamine with superoxide result in low signal-to-noise in the spectra and images. However, since the spectral properties of the nitroxides are known, we can use prior knowledge of the line shape and hyperfine splitting to fit the noisy data, yielding well-defined spectra and images. Two-dimensional spectral-spatial images are shown for lung samples containing (4.5 ± 0.5) ×1014 CP• and (9.9 ± 1.0) ×1014 DCP• nitroxide spins. These results suggest that a probe that accumulates in cells gives a stronger nitroxide signal than a probe that is more easily washed out of cells.

CONCLUSION

The nitroxide radicals in excised mouse lungs formed by reaction with hydroxylamine probes CPH and DCP-AM-H can be imaged at 1 GHz.

Anti-high mobility group box 1 monoclonal antibody suppressed hyper-permeability and cytokine production in human pulmonary endothelial cells infected with influenza A virus

Objective

High mobility group box-1 (HMGB1) has been reported to be involved in influenza A virus-induced acute respiratory distress syndrome (ARDS). We studied the efficacy of an anti-HMGB1 mAb using an in vitro model of TNF-α stimulation or influenza A virus infection in human pulmonary microvascular endothelial cells (HMVECs).

Methods

Vascular permeability of HMVECs was quantified using the Boyden chamber assay under tumor necrosis factor-α (TNF-α) stimulation or influenza A virus infection in the presence of anti-HMGB1 mAb or control mAb. The intracellular localization of HMGB1 was assessed by immunostaining. Extracellular cytokine concentrations and intracellular viral mRNA expression were quantified by the enzyme-linked immunosorbent assay and quantitative reverse transcription PCR, respectively.

Results

Vascular permeability was increased by TNF-α stimulation or influenza A infection; HMVECs became elongated and the intercellular gaps were extended. Anti-HMGB1 mAb suppressed both the increase in permeability and the cell morphology changes. Translocation of HMGB1 to the cytoplasm was observed in the non-infected cells. Although anti-HMGB1 mAb did not suppress viral replication, it did suppress cytokine production in HMVECs.

Conclusion

Anti-HMGB1 mAb might be an effective therapy for severe influenza ARDS.

Cardiopulmonary Bypass Induces Acute Lung Injury via the High-Mobility Group Box 1/Toll-Like Receptor 4 Pathway

During cardiopulmonary bypass (CPB), pulmonary ischemia/reperfusion (I/R) injury can cause acute lung injury (ALI). Our previous research confirmed that abnormal high-mobility group box 1 (HMGB1) release after CPB was closely related to ALI. However, the mechanism underlying the HMGB1-mediated induction of ALI after CPB is unclear. Our previous study found that HMGB1 binds Toll-like receptor 4 (TLR4), leading to lung injury, but direct evidence of a role for these proteins in the mechanism of CPB-induced lung injury has not been shown. We examined the effects of inhibiting HMGB1 or reducing TLR4 expression on CPB-induced lung injury in rats administered anti-HMBG1 antibody or TLR4 short-hairpin RNA (shTLR4), respectively. In these rat lungs, we studied the histologic changes and levels of interleukin- (IL-) 1β, tumour necrosis factor- (TNF-) α, HMGB1, and TLR4 after CPB. After CPB, the lung tissues from untreated rats showed histologic features of injury and significantly elevated levels of IL-1β, TNF-α, HMGB1, and TLR4. Treatment with anti-HMGB1 attenuated the CPB-induced morphological inflammatory response and protein levels of IL-1β, TNF-α, HMGB1, and TLR4 in the lung tissues and eventually alleviated the ALI after CPB. Treatment with shTLR4 attenuated the CPB-induced morphological inflammatory response and protein levels of IL-1β, TNF-α, and TLR4 in the lung tissues and eventually alleviated the ALI after CPB, but could not alleviate the HMGB1 protein levels induced by CPB. In summary, the present study demonstrated that the HMGB1/TLR4 pathway mediated the development of ALI induced by CPB.

Temporal Dysregulation of the Angiopoietin-2/-1 Ratio After Trauma and Associations With Injury Characteristics and Outcomes

Traumatic injury and hemorrhagic shock result in endothelial cell activation and vascular dysfunction that, if not corrected, can propagate multiorgan failure. Angiopoietin-1 and angiopoietin-2 are important regulators of endothelial cell function, and the ratio of plasma angiopoietin-2-to-1 is a useful indicator of overall vascular health. We therefore characterized plasma angiopoietin-2/-1 ratios over time after trauma in adults in an effort to gain insight into the pathophysiology that may drive post-traumatic vasculopathy and organ injury. We performed a single-center prospective observational study to measure plasma angiopoietin-1 and -2 levels and determine angiopoietin-2/-1 ratios in adult trauma patients upon hospital arrival and after 12, 24, and 48 h. Compared with levels in healthy adults, angiopoietin-1 levels were significantly elevated at hospital arrival, and angiopoietin-2 levels were significantly elevated at 12, 24, and 48 h. These kinetics translated in angiopoietin-2/-1 ratios that were significantly greater than controls at 24 and 48 h. After regression analysis, elevated angiopoietin-2 levels were independently associated with blunt injuries at admission, with coagulopathy at admission and 12 h, and with hemorrhagic shock at 24 and 48 h. Significant correlations were observed between both angiopoietins and 24-h transfusion requirements. Angiopoietin-2/-1 ratios correlated with mechanical ventilation duration and intensive care unit and hospital lengths of stay. In this study, we demonstrate novel temporal associations between angiopoietin dysregulation and blunt injuries, acute coagulopathy, and hemorrhagic shock. Moreover, our findings highlight the presence of endothelial activation following traumatic insults in adults that may contribute to worse clinical outcomes.

Function and mechanism of pyrin and IL-10 in the regulation of the inflammasome in pulmonary vascular endothelial cells following hemorrhagic shock

The present study aimed to evaluate the function of pyrin and interleukin-10 (IL-10) and the potential mechanisms underlying the regulation of inflammation in pulmonary vascular endothelial cells (ECs) following hemorrhagic shock (HS). Adult female Sprague-Dawley rats were divided into 4 groups (n=6 in each group) to examine the changes in pyrin expression following HS-lipopolysaccharide (LPS) administration, including the following groups: A sham operation (SM) + tracheal injection of saline (SAL) group; a HS + SAL group; a SM + LPS group (with a tracheal injection of endotoxin); and a HS + LPS group. An additional 4 groups were used to evaluate the function of IL-10, by the additional intratracheal injection of recombinant IL-10. Western blot analysis and immunofluorescence were performed in order to investigate the changes to pyrin and IL-10 expression in pulmonary vascular ECs. The expression levels of pyrin in the SM + LPS group were significantly increased in comparison with the SM + SAL group (P<0.01). Additionally, the expression levels of pyrin were significantly increased in the HS + LPS group compared with the HS + SAL group (P<0.01). The expression levels of caspase-1 were significantly increased in the HS + LPS group compared with those in the other three groups (P<0.01). The expression levels of pyrin in the HS + LPS + IL-10 group were significantly increased compared with the HS + LPS group (P<0.01). The expression levels of caspase-1 were significantly decreased following IL-10 treatment compared with those in the HS + LPS group (P<0.01). Therefore, HS attenuated LPS-induced pyrin expression in pulmonary vascular ECs and may also inhibit the expression of IL-10, resulting in the activation of caspase-1 subsequent to a second LPS insult.

Use of a high platelet-to-RBC ratio of 2:1 is more effective in correcting trauma-induced coagulopathy than a ratio of 1:1 in a rat multiple trauma transfusion model

BACKGROUND

Platelet dysfunction importantly contributes to trauma-induced coagulopathy (TIC). Our aim was to examine the impact of transfusing platelets (PLTs) in a 2:1 PLT-to-red blood cell (RBC) ratio versus the standard 1:1 ratio on transfusion requirements, correction of TIC, and organ damage in a rat multiple trauma transfusion model.

METHODS

Mechanically ventilated male Sprague Dawley rats were traumatized by crush injury to the small intestine and liver and a fracture of the femur, followed by exsanguination until a mean arterial pressure (MAP) of 40 mmHg. Animals were randomly assigned to receive resuscitation in a high PLT dose (PLT to plasma to RBC in a ratio of 2:1:1) or a standard PLT dose (ratio of 1:1:1) until a MAP of 60 mmHg was reached (n = 8 per group). Blood samples were taken for biochemical and thromboelastometry (ROTEM) assessment. Organs were harvested for histopathology.Outcome measures were transfusion requirements needed to reach a pretargeted MAP, as well as ROTEM correction and organ failure.

RESULTS

Trauma resulted in coagulopathy as assessed by deranged ROTEM results. Mortality rate was 19%, with all deaths occurring in the standard dose group. The severity of hypovolemic shock as assessed by lactate and base excess was not different in both groups. The volume of transfusion needed to reach the MAP target was lower in the high PLT dose group compared to the standard dose, albeit not statistically significant (p = 0.054). Transfusion with a high PLT dose resulted in significant stronger clot firmness compared to the standard dose at all time points following trauma, while platelet counts were similar. Organ failure as assessed by biochemical analysis and histopathology was not different between groups, nor were there any thromboembolic events recorded.

CONCLUSIONS

Resuscitation with a high (2:1) PLT-to-RBC ratio was more effective compared to standard (1:1) PLT-to-RBC ratio in treating TIC, with a trend towards reduced transfusion volumes. Also, high PLT dose did not aggravate organ damage. Transfusion strategies using higher PLT dose regiments might be a feasible treatment option in hemorrhaging trauma patients for the correction of TIC.

Tlr2 on Bone Marrow and Non-Bone Marrow Derived Cells Regulates Inflammation and Organ Injury in Cooperation with Tlr4 During Resuscitated Hemorrhagic Shock

BACKGROUND

Although the role of TLR4 in driving inflammation and organ injury after hemorrhagic shock and resuscitation (H/R) is well established, the role of TLR2-another receptor for damage-associated molecular pattern (DAMP) molecules-is not. In this study, we used a combination of TLR2 and wild type (WT) mice treated with anti-TLR2 and anti-TLR4 neutralizing monoclonal antibodies (mAb) to discern the contribution of TLR2 relative to TLR4 to the systemic inflammatory response in murine H/R.

MATERIAL AND METHODS

WT mice, TLR2, and WT mice receiving an anti-TLR2 or an anti-TLR4 mAB (given as a pretreatment) were sacrificed at 6 or 20 h post-H/R. Bone marrow TLR2/WT chimeric mice were created to assess the importance of immune and nonimmune cell-associated TLR2.

RESULTS

TLR2 mice subjected to H/R exhibited significantly less liver damage and lower markers of systemic inflammation only at 20 h. Bone marrow chimeric mice using combinations of TLR2 mice and WT mice demonstrated that TLR2 on non-bone marrow derived cells played a dominant role in the differences at 20 h. Interestingly, WT mice treated with anti-TLR2 mAB demonstrated a reduction in organ damage and systemic inflammation at both 6 and 20 h following H/R. A combination of anti-TLR2 mAB and anti-TLR4 mAB showed that both receptors drive IP-10 and KC levels and that there is cooperation for increases in IL-6, MIG, and MCP-1 levels between TLR2 and TLR4.

CONCLUSION

These data also support the conclusion that TLR2 and TLR4 act in concert as important receptors in the host immune response to H/R.

Hemorrhagic Shock and the Microvasculature

The microvasculature plays a central role in the pathophysiology of hemorrhagic shock and is also involved in arguably all therapeutic attempts to reverse or minimize the adverse consequences of shock. Microvascular studies specific to hemorrhagic shock were reviewed and broadly grouped depending on whether data were obtained on animal or human subjects. Dedicated sections were assigned to microcirculatory changes in specific organs, and major categories of pathophysiological alterations and mechanisms such as oxygen distribution, ischemia, inflammation, glycocalyx changes, vasomotion, endothelial dysfunction, and coagulopathy as well as biomarkers and some therapeutic strategies. Innovative experimental methods were also reviewed for quantitative microcirculatory assessment as it pertains to changes during hemorrhagic shock. The text and figures include representative quantitative microvascular data obtained in various organs and tissues such as skin, muscle, lung, liver, brain, heart, kidney, pancreas, intestines, and mesentery from various species including mice, rats, hamsters, sheep, swine, bats, and humans. Based on reviewed findings, a new integrative conceptual model is presented that includes about 100 systemic and local factors linked to microvessels in hemorrhagic shock. The combination of systemic measures with the understanding of these processes at the microvascular level is fundamental to further develop targeted and personalized interventions that will reduce tissue injury, organ dysfunction, and ultimately mortality due to hemorrhagic shock. Published 2018. Compr Physiol 8:61-101, 2018.

Early resuscitation with exendin-4 alleviates acute lung injury after hemorrhagic shock in rats

BACKGROUND

Oxidative stress induced by hemorrhagic shock (HS) is known to initiate a systemic inflammatory response, which leads to subsequent acute lung injury. This study is aimed to assess the efficacy of exendin-4 (Ex-4) in attenuating lung injury in a rat model of HS and resuscitation (HS/R).

METHODS

HS was induced in sodium pentobarbital-anesthetized adult male Wistar rats by withdrawing blood to maintain a mean arterial pressure of 30-35 mm Hg for 50 min. Then, the animals received Ex-4 (5 μg/kg) or vehicle (saline) intravenously and were resuscitated with a volume of normal saline 1.5 times that of the shed blood volume. Mean arterial pressure was measured throughout the experiment, and acid-base status, oxidative stress, inflammation, and lung injury were evaluated at 2 h after resuscitation.

RESULTS

Ex-4 infusion reduced the methemoglobin content, the malondialdehyde content, the myeloperoxidase activity, and the expression of tumor necrosis factor-α and interleukin-6 in the lungs. The histologic injury was also markedly decreased in the Ex-4 group compared with the vehicle group.

CONCLUSIONS

Ex-4 ameliorates the oxidative stress, inflammatory response, and subsequent acute lung injury occurring after HS/R. Although future studies are required to elucidate the underlying mechanism, our results indicate that Ex-4 infusion may be a promising strategy for improving lung injury in the treatment of HS.

Perpetual change: autophagy, the endothelium, and response to vascular injury

Current studies of vascular health, aging, and autophagy emphasize how the endothelium adapts to stress and contributes to disease. The endothelium is far from an inert barrier to blood-borne cells, pathogens, and chemical signals; rather, it actively translates circulating mediators into tissue responses, changing rapidly in response to physiologic stressors. Macroautophagy-the cellular ingestion of effete organelles and protein aggregates to provide anabolic substrates to fuel bioenergetics in times of stress-plays an important role in endothelial cell homeostasis, vascular remodeling, and disease. These roles include regulating vascular tone, sustaining or limiting cell survival, and contributing to the development of atherosclerosis secondary to infection, inflammation, and angiogenesis. Autophagy modulates these critical functions of the endothelium in a dynamic and perpetual response to tissue and intravascular cues.

[Association between high-mobility group box 1 and neonatal respiratory distress syndrome]

OBJECTIVE

To study the association between serum level of high-mobility group box 1(HMGB1) and neonatal respiratory distress syndrome (NRDS).

METHODS

A total of 35 infants with NRDS and 35 normal neonates (control group) were enrolled. Peripheral venous blood samples were collected with 12-24 hours after birth. ELISA was used to measure the serum level of HMGB1.

RESULTS

The infants with mild and severe NRDS had a significantly higher serum level of HMGB1 than the control group (P<0.05). The infants with severe NRDS had a significantly higher serum level of HMGB1 than those with mild NRDS (P<0.05). The infants with NRDS who died had a significantly higher serum level of HMGB1 than those who survived (P<0.05). The receiver operating characteristic (ROC) curve showed that the optimal cut-off value for serum level of HMGB1 to predict NRDS was 625.3 pg/mL with an area under the ROC curve (AUC) of 0.846 (95%CI: 0.755-0.936), and the optimal cut-off value for serum level of HMGB1 to predict the death of infants with NRDS was 772.2 pg/mL with an AUC of 0.916 (95%CI: 0.813-1.000).

CONCLUSIONS

Infants with NRDS have a significant increase in the serum level of HMGB1, and the serum level of HMGB1 can well predict the development and prognosis of NRDS.

ROS Signaling in the Pathogenesis of Acute Lung Injury (ALI) and Acute Respiratory Distress Syndrome (ARDS)

The generation of reactive oxygen species (ROS) plays an important role for the maintenance of cellular processes and functions in the body. However, the excessive generation of oxygen radicals under pathological conditions such as acute lung injury (ALI) and its most severe form acute respiratory distress syndrome (ARDS) leads to increased endothelial permeability. Within this hallmark of ALI and ARDS, vascular microvessels lose their junctional integrity and show increased myosin contractions that promote the migration of polymorphonuclear leukocytes (PMNs) and the transition of solutes and fluids in the alveolar lumen. These processes all have a redox component, and this chapter focuses on the role played by ROS during the development of ALI/ARDS. We discuss the origins of ROS within the cell, cellular defense mechanisms against oxidative damage, the role of ROS in the development of endothelial permeability, and potential therapies targeted at oxidative stress.

TLR2 Regulates Complement-Mediated Inflammation Induced by Blood Loss During Hemorrhage

Hemorrhagic shock resulting from blood loss directs the majority of the blood to the vital organs, dramatically reducing blood flow to the intestines and resulting in damage and inflammation. The excessive intestinal inflammatory response includes pro-inflammatory cytokines and complement activation, although the mechanism is not clear. Toll-like receptors play a vital role in the innate immune response and toll-like receptor 2 (TLR2) is required for intestinal ischemia/reperfusion-induced injury. We hypothesized that TLR2 plays an integral role in the intestinal inflammatory response after hemorrhage and subjected C57Bl/6 wild-type and Tlr2(-/-) mice to atraumatic loss of ∼30% total blood volume. Two hours after blood removal, the intestinal injury and inflammation were assessed. We demonstrate that compared with wild-type control mice, Tlr2(-/-) mice sustain less intestinal damage and inflammation. Importantly, TLR2 regulated eicosanoid and complement activation and IL-12 and TNFα secretions, indicating interactions between TLR2 and complement in response to significant blood loss.

Resolvin D2 decreases TLR4 expression to mediate resolution in human monocytes

TLRs are critical for innate immunity, but excessive activation can lead to tissue damage and disease. Specialized proresolving mediators (SPMs), including resolvin D2 (RvD2), promote the active resolution of inflammation. How SPMs regulate early LPS signaling, including activation of TLR4, is unknown. We treated human THP-1 monocytic cells and primary human blood monocytes with RvD2 and LPS to evaluate modulation of TLRs. miRNA-146a overexpression and inhibition were used to dissect the mechanism of RvD2-mediated actions. We validated our studies using ELISAs for cytokines, PCR, Western blot analysis, and flow cytometry. Cells treated with 0.1% ethanol (control for RvD2) and/or PBS (control for LPS), and control microRNA mimics and inhibitors were used as controls. RvD2 reduced LPS-induced cytokines and TLR4 expression in human monocytes by up to 75%. In THP-1 cells, RvD2 reduced expression of TLR4, lymphocyte antigen 96 (MD-2), and downstream signals (MyD88, TRIF, and TAK1). These effects were partially mediated through RvD2 induction of microRNA-146a, and RvD2's actions were blocked by microRNA-146a inhibition. These new findings reveal the ability of RvD2 to reduce TLR4 expression and attenuate LPS-induced inflammation, providing a new area of SPM activity to investigate in this major area of therapeutic research.-Croasdell, A., Sime, P. J., Phipps, R. P. Resolvin D2 decreases TLR4 expression to mediate resolution in human monocytes.

Pathogenesis of infection in surgical patients

Purpose of review

Despite the application of prophylactic antimicrobial therapy and advanced technologies, infection remains one of the most common causes of morbidity and mortality in surgical patients. Understanding the pathogenesis of surgical infection would offer new insights into the development of biomarkers to predict and stratify infection in patients, and to explore specific strategies to minimize this serious postoperative complication.

Recent findings

The acute nonspecific inflammatory response triggered by endogenous danger signals evoked by surgical insult is beneficial, while paradoxically associated with reduced resistance to infection. There is growing evidence indicating that primed inflammation by surgical insult exaggerates the dysregulation of the immune-inflammatory response to the invasion of pathogens postoperatively. Innate immune receptors, such as Toll-like receptors (TLRs), contribute to detecting both pathogen-associated molecular patterns and endogenous damage-associated molecular patterns, and to further amplifying inflammatory responses to infection. Current evidence shows the fascinating role of non-TLRs in the process of infection. Non-TLRs, such as membrane-associated triggering receptor expressed on myeloid cells family, cytosolic nucleotide-binding oligomerization domain-like receptors and nuclear receptor nuclear family 4 subgroup A receptors, are also crucial in triggering the immune responses and mounting an effective defense against surgical insults and the second hit of infection.

Summary

Understanding the pivotal role of non-TLRs in sensing exogenous and endogenous molecules, and the influence of primed systemic inflammation and depressed immune status on the defense against pathogen after surgical insult, would be helpful to fully explore the relevant sophisticated phenomena of surgical infection, and to elucidate the occurrence of heterogeneous constellations of clinical signs and symptoms among this special population.

The Role of HMGB1 in Cardiovascular Biology: Danger Signals

SIGNIFICANCE

Cardiovascular disease (CVD) is the leading cause of mortality worldwide. Accumulating evidence shows that dysregulated immune response contributes to several types of CVDs such as atherosclerosis and pulmonary hypertension (PH). Vascular intimal impairment and low-density lipoprotein oxidation trigger a complex network of innate immune responses and sterile inflammation.

RECENT ADVANCES

High-mobility group box 1 (HMGB1), a nuclear DNA-binding protein, was recently discovered to function as a damage-associated molecular pattern molecule (DAMP) that initiates the innate immune responses. These findings lead to the understanding that HMGB1 plays a critical role in the inflammatory response in the pathogenesis of CVD.

CRITICAL ISSUES

In this review, we highlight the role of extracellular HMGB1 as a proinflammatory mediator as well as a DAMP in coronary artery disease, cerebral artery disease, peripheral artery disease, and PH.

FUTURE DIRECTIONS

A key focus for future researches on HMGB1 location, structure, modification, and signaling will reveal HMGB1's multiple functions and discover a targeted therapy that can eliminate HMGB1-mediated inflammation without interfering with adaptive immune responses.

Inhibitory effect of post-hemorrhagic shock mesenteric lymph drainage on the HMGB1 and RAGE in mouse kidney

BACKGROUND

Excessively inflammatory response is one of mechanisms that underlie the acute kidney injury (AKI) induced by severe hemorrhagic shock, which could be ameliorated by post-hemorrhagic shock mesenteric lymph (PHSML) blockage. Recent studies demonstrate that high mobility group box 1 (HMGB1) and the receptor for advanced glycation end products (RAGE) are critical mediators of local inflammations. The present study was sought to investigate whether the PHSML drainage inhibits the HMGB1 and RAGE in mouse kidney to ameliorate the renal inflammatory responses.

METHODS

A mouse hemorrhagic shock model (40 ± 2 mmHg for 90 min, fluid resuscitation for 30 min) was employed, and the PHMSL drainage was performed at the end of the resuscitation. After 3 h of resuscitation, the expressions of mRNA and protein for the renal HMGB1 and RAGE and the levels of interleukin (IL)-1β and IL-18 were assessed by the real-time reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay, respectively.

RESULTS

Hemorrhagic shock elicited significant increases in the mRNA expressions of HMGB1 and RAGE and in the protein expressions of HMGB1, RAGE, IL-1β and IL-18 in kidney. The PHSML drainage abolished these potentiating effects.

CONCLUSION

The present study demonstrates that PHSML blockade reduces the increased HMGB1 and RAGE and pro-inflammatory factors following hemorrhagic shock, suggesting that the PHSML elicits the inflammatory responses via enhancing the HMGB1 and RAGE production in the kidney.

Vascular endothelial cell Toll-like receptor pathways in sepsis

The endothelium forms a vast network that dynamically regulates vascular barrier function, coagulation pathways and vasomotor tone. Microvascular endothelial cells are uniquely situated to play key roles during infection and injury, owing to their widespread distribution throughout the body and their constant interaction with circulating blood. While not viewed as classical immune cells, endothelial cells express innate immune receptors, including the Toll-like receptors (TLRs), which activate intracellular inflammatory pathways mediated through NF-κB and the MAP kinases. TLR agonists, including LPS and bacterial lipopeptides, directly upregulate microvascular endothelial cell expression of inflammatory mediators. Intriguingly, TLR activation also modulates microvascular endothelial cell permeability and the expression of coagulation pathway intermediaries. Microvascular thrombi have been hypothesized to trap microorganisms thereby limiting the spread of infection. However, dysregulated activation of endothelial inflammatory pathways is also believed to lead to coagulopathy and increased vascular permeability, which together promote sepsis-induced organ failure. This article reviews vascular endothelial cell innate immune pathways mediated through the TLRs as they pertain to sepsis, highlighting links between TLRs and coagulation and permeability pathways, and their role in healthy and pathologic responses to infection and sepsis.

Inhibition of peptidylarginine deiminase attenuates inflammation and improves survival in a rat model of hemorrhagic shock

BACKGROUND

We have recently shown that inhibition of peptidylarginine deiminase (PAD) improves survival in a rodent model of lethal cecal ligation and puncture. The roles of PAD inhibitors in hemorrhagic shock (HS), however, are largely unknown. The goal of this study was to investigate the effects of YW3-56, a novel PAD inhibitor, on survival after severe HS.

METHODS

Mouse macrophages were exposed to hypoxic conditions followed by reoxygenation in the presence or absence of YW3-56. Enzyme-linked immunosorbent assay (ELISA) was performed to measure levels of secreted tumor necrosis factor α and interleukin-6 in the culture medium. Cell viability was determined by methyl thiazolyl tetrazolium assay. In the survival experiment, anesthetized male Wistar-Kyoto rats (n = 10/group) were subjected to 55% blood loss, and treated with or without YW3-56 (10 mg/kg, intraperitoneally). Survival was monitored for 12 h. In the nonsurvival experiment, morphologic changes of the lungs were examined. Levels of circulating cytokine-induced neutrophil chemoattractant 1 (CINC-1) and myeloperoxidase (MPO) in the lungs were measured by ELISA. Expression of lung intercellular adhesion molecules-1 (ICAM-1) was also determined by Western blotting.

RESULTS

Hypoxia/reoxygenation (H/R) insult induced tumor necrosis factor α and interleukin-6 secretion from macrophages, which was significantly attenuated by YW3-56 treatment. YW3-56 treatment also increased cell viability when macrophages were exposed to H/R up to 6/15 h and improved survival rate from 20% to 60% in lethal HS rat model. Compared to the sham groups, pulmonary MPO activity and ICAM-1 expression in the HS group were significantly increased, and acute lung injury was associated with a higher degree of CINC-1 levels in serum. Intraperitoneal delivery of YW3-56 significantly reduced pulmonary MPO and ICAM-1 expression and attenuated acute lung injury.

CONCLUSIONS

Our results demonstrate for the first time that administration of YW3-56, a novel PAD inhibitor, can improve survival in a rat model of HS and in a cell culture model of H/R. The survival advantage is associated with an attenuation of local and systemic pro-inflammatory cytokines and the protection against acute lung injury after hemorrhage. Thus, PAD inhibition may represent a novel and promising therapeutic strategy for severe HS.

TLR4 Deters Perfusion Recovery and Upregulates Toll-like Receptor 2 (TLR2) in Ischemic Skeletal Muscle and Endothelial Cells

Toll-like receptors (TLRs) play an important role in regulating muscle regeneration and angiogenesis in response to ischemia. TLR2 knockout mice exhibit pronounced skeletal muscle necrosis and abnormal vessel architecture after femoral artery ligation, suggesting that TLR2 signaling is protective during ischemia. TLR4, an important receptor in inflammatory signaling, has been shown to regulate TLR2 expression in other systems. We hypothesize that a similar relationship between TLR4 and TLR2 may exist in hindlimb ischemia in which TLR4 upregulates TLR2, a mediator of angiogenesis and perfusion recovery. We examined the expression of TLR2 in unstimulated and in TLR-agonist treated endothelial cells (ECs). TLR2 expression (low in control ECs) was upregulated by lipopolysaccharide, the danger signal high mobility group box-1, and hypoxia in a TLR4-dependent manner. Endothelial tube formation on Matrigel as well as EC permeability was assessed as in vitro measures of angiogenesis. Time-lapse imaging demonstrated that ECs lacking TLR4 formed more tubes, whereas TLR2 knockdown ECs exhibited attenuated tube formation. TLR2 also mediated EC permeability, an initial step during angiogenesis, in response to high-mobility group box-1 (HMGB1) that is released by cells during hypoxic injury. In vivo, ischemia-induced upregulation of TLR2 required intact TLR4 signaling that mediated systemic inflammation, as measured by local and systemic IL-6 levels. Similar to our in vitro findings, vascular density and limb perfusion were both enhanced in the absence of TLR4 signaling, but not if TLR2 was deleted. These findings indicate that TLR2, in the absence of TLR4, improves angiogenesis and perfusion recovery in response to ischemia.

Attenuation of hyperoxia-induced lung injury in neonatal rats by 1α,25-Dihydroxyvitamin D3

BACKGROUND

Mounting evidence suggests that Toll-like receptor (TLRs) plays an important role in oxidative stress and is implicated in the pathogenesis of hyperoxic lung injury. 1α,25-Dihydroxyvitamin D3 (1,25(OH)2D3), the hormonally active form of vitamin D, not only plays an essential role in mineral balance, but also possesses immunomodulatory and antioxidant properties. Besides, Vitamin D3 is involved in the regulation of TLRs signaling. The present study was designed to investigate whether 1,25(OH)2D3 attenuates hyperoxia-induced lung injury by regulating TLRs signaling in neonatal rats.

METHODS

Pups were divided into four groups: normoxia control group (NC), normoxia plus 1,25(OH)2D3 treatment group (ND), hyperoxia control group (HC), and hyperoxia plus 1,25(OH)2D3 treatment group (HD). Lung tissues were collected for histological examination and detection of mRNA and protein expressions.

RESULTS

Treatment of hyperoxia-exposed animals with 1,25(OH)2D3 resulted in significantly increased body weight and reduced hyperoxia-induced lung injury. Moreover, 1,25(OH)2D3 significantly downregulated the expression of TLR4, NF-κB, and the inflammatory cytokines TNF-α, IL-1β, and IL-6.

CONCLUSIONS

1,25(OH)2D3 could attenuate hyperoxia-induced lung injury in neonatal rats, possibly by regulating TLR4/NF-κB signaling.

TACTIC: Trans-Agency Consortium for Trauma-Induced Coagulopathy

Trauma-induced coagulopathy (TIC) includes heterogeneous coagulopathic syndromes with different underlying causes, and treatment is challenged by limited diagnostic tests to discriminate between these entities in the acute setting. We provide an overview of progress in understanding the mechanisms of TIC and the context for several of the hypotheses that will be tested in 'TACTIC'. Although connected to ongoing clinical trials in trauma, TACTIC itself has no intent to conduct clinical trials. We do anticipate that 'early translation' of promising results will occur. Functions anticipated at this early translational level include: (i) basic science groundwork for future therapeutic candidates; (ii) development of acute coagulopathy scoring systems; (iii) coagulation factor composition-based computational analysis; (iv) characterization of novel analytes including tissue factor, polyphosphates, histones, meizothrombin and α-thrombin-antithrombin complexes, factor XIa, platelet and endothelial markers of activation, signatures of protein C activation and fibrinolysis markers; and (v) assessment of viscoelastic tests and new point-of-care methods.

Hydrogen sulfide in posthemorrhagic shock mesenteric lymph drainage alleviates kidney injury in rats

Posthemorrhagic shock mesenteric lymph (PHSML) is a key factor in multiple organ injury following hemorrhagic shock. We investigated the role of hydrogen sulfide (H₂S) in PHSML drainage in alleviating acute kidney injury (AKI) by administering D,L-propargylglycine (PPG) and sodium hydrosulfide hydrate (NaHS) to 12 specific pathogen-free male Wistar rats with PHSML drainage. A hemorrhagic shock model was established in 4 experimental groups: shock, shock+drainage, shock+drainage+PPG (45 mg/kg, 0.5 h prehemorrhage), and shock+drainage+NaHS (28 µmol/kg, 0.5 h prehemorrhage). Fluid resuscitation was performed after 1 h of hypotension, and PHMSL was drained in the last three groups for 3 h after resuscitation. Renal function and histomorphology were assessed along with levels of H₂S, cystathionine-γ-lyase (CSE), Toll-like receptor 4 (TLR4), interleukin (IL)-10, IL-12, and tumor necrosis factor (TNF)-α in renal tissue. Hemorrhagic shock induced AKI with increased urea and creatinine levels in plasma and higher H₂S, CSE, TLR4, IL-10, IL-12, and TNF-α levels in renal tissue. PHSML drainage significantly reduced urea, creatinine, H₂S, CSE, and TNF-α but not TLR4, IL-10, or IL-12. PPG decreased creatinine, H₂S, IL-10, and TNF-α levels, but this effect was reversed by NaHS administration. In conclusion, PHSML drainage alleviated AKI following hemorrhagic shock by preventing increases in H₂S and H₂S-mediated inflammation.

Increased serum HMGB1 levels in patients with Henoch-Schönlein purpura

High-mobility group box-1 (HMGB1) has been implicated as a pro-inflammatory cytokine in the pathogenesis of various inflammatory and autoimmune diseases. However, information about HMGB1 in Henoch-Schönlein purpura (HSP) is still unclear. Herein, we investigated the role of HMGB1 in patients with HSP and the pro-inflammatory effects of HMGB1 on human dermal microvascular endothelial cell line (HMEC-1). Serum HMGB1 levels in patients with HSP together with patients with allergic vasculitis (AV) and urticarial vasculitis (UV) were detected by enzyme-linked immunosorbent assay (ELISA). HMEC-1 cells were treated with HMGB1 at concentrations ranging from 4 ng/ml to 100 ng/ml. Serum HMGB1 levels were significantly increased in patients with HSP, AV and UV, when compared with those in control group. Moreover, abundant cytoplasmic expression of HMGB1 was observed in endothelial cells in lesional skin of HSP patients. Using membrane cytokine antibody array, we indicate that HMGB1 markedly induced TNF-α and IL-6 release in cultured supernatant. Furthermore, by real-time quantitative PCR and ELISA, the effects of HMGB1 on these cytokines production in HMEC-1 cells were established. Finally, Western blot data revealed that HMGB1 can induce phosphorylation of inhibitor of κB-α (IκBα) and the nuclear translocation of nuclear factor-κB (NF-κB) p65 in HMEC-1 cells. In conclusion, this study provides first observations on the association of HMGB1 with HSP. We suggest that HMGB1 may be an important mediator of endothelial inflammation through the induction of TNF-α and IL-6 production and may play a crucial role in the pathogenesis of HSP.

Impact of haemorrhagic shock intensity on the dynamic of alarmins release in porcine poly-trauma animal model

PURPOSE

Traumatic insults result in an altered inflammatory response, in which alarmins release has a central role. The impact of haemorrhagic shock intensity on the long-term kinetics of alarmins is not yet fully elucidated. We investigated these aspects in a combined trauma (chest, abdominal, and extremities injury) porcine model with different severities and durations of haemorrhagic shock.

METHODS

After induction of combined trauma (tibia fracture, lung contusion, and liver laceration), haemorrhagic shock was induced at different intensities: moderate haemorrhage (MH; n = 15): mean arterial pressure (MAP) <30 ± 5 mmHg [maximum loss of total blood volume (TBVmax): 45 %] for 90 min, and severe haemorrhage (SH; n = 10): MAP <25 ± 5 mmHg (TBVmax 50 %) for 120 min. Resuscitation was performed using a standardized crystalloid infusion protocol. Animals were mechanically ventilated and underwent ICU-monitoring for 48 h (MH) and 48.5 h (SH). Blood samples were collected over the clinical time course, and systemic levels of serum alarmins [High-Mobility Group Protein B-1 (HMGB-1) and Heat Shock Protein 70 (HSP70)] were measured using an ELISA kit.

RESULTS

Heart rate, systemic blood pressure, lactate, and base excess were significantly altered as a function of haemorrhagic shock in both trauma groups (MH and SH). Systemic HMGB-1 levels were significantly elevated in both trauma groups when compared to the sham group. Haemorrhagic shock severity and duration were positively correlated with HMGB-1 levels and compared to baseline values, concentrations remained significantly increased in SH when compared to MH. On the other hand, we observed a significant decrease in the systemic HSP70 levels of trauma groups (MH, and SH) when compared to the sham group, which was significantly decreased compared to baseline values in SH over the entire time course.

CONCLUSION

Our data show that haemorrhagic shock duration and severity affect the systemic levels of HMGB-1 and HSP70. This early alarmins release after trauma can be used to guide the treatment strategies (e.g. surgical procedures) of polytrauma patients.

Host response to leptospira infection

Pathogenic Leptospira has the capacity to infect a broad range of mammalian hosts. Leptospirosis may appear as an acute, potentially fatal infection in accidental hosts, or progress into a chronic, largely asymptomatic infection in natural maintenance hosts. The course that Leptospira infection follows is dependent upon poorly understood factors, but is heavily influenced by both the host species and bacterial serovar involved in infection. Recognition of pathogen-associated molecular patterns (PAMPs) by a variety of host pattern recognition receptors (PRRs) activates the host immune system. The outcome of this response may result in bacterial clearance, limited bacterial colonization of a few target organs, principally the kidney, or induction of sepsis as the host succumbs to infection and dies. This chapter describes current knowledge of how the host recognizes Leptospira and responds to infection using innate and acquired immune responses. Aspects of immune-mediated pathology and pathogen strategies to evade the host immune response are also addressed.

HMGB1 in health and disease

Complex genetic and physiological variations as well as environmental factors that drive emergence of chromosomal instability, development of unscheduled cell death, skewed differentiation, and altered metabolism are central to the pathogenesis of human diseases and disorders. Understanding the molecular bases for these processes is important for the development of new diagnostic biomarkers, and for identifying new therapeutic targets. In 1973, a group of non-histone nuclear proteins with high electrophoretic mobility was discovered and termed high-mobility group (HMG) proteins. The HMG proteins include three superfamilies termed HMGB, HMGN, and HMGA. High-mobility group box 1 (HMGB1), the most abundant and well-studied HMG protein, senses and coordinates the cellular stress response and plays a critical role not only inside of the cell as a DNA chaperone, chromosome guardian, autophagy sustainer, and protector from apoptotic cell death, but also outside the cell as the prototypic damage associated molecular pattern molecule (DAMP). This DAMP, in conjunction with other factors, thus has cytokine, chemokine, and growth factor activity, orchestrating the inflammatory and immune response. All of these characteristics make HMGB1 a critical molecular target in multiple human diseases including infectious diseases, ischemia, immune disorders, neurodegenerative diseases, metabolic disorders, and cancer. Indeed, a number of emergent strategies have been used to inhibit HMGB1 expression, release, and activity in vitro and in vivo. These include antibodies, peptide inhibitors, RNAi, anti-coagulants, endogenous hormones, various chemical compounds, HMGB1-receptor and signaling pathway inhibition, artificial DNAs, physical strategies including vagus nerve stimulation and other surgical approaches. Future work further investigating the details of HMGB1 localization, structure, post-translational modification, and identification of additional partners will undoubtedly uncover additional secrets regarding HMGB1's multiple functions.

Induction of acute lung inflammation in mice with hemorrhagic shock and resuscitation: role of HMGB1

Background

Hemorrhagic shock and resuscitation (HS/R) can induce multiple organ failure which is associated with high mortality. The lung is an organ commonly affected by the HS/R. Acute lung injury is a major cause of dysfunction in other organ systems. The objective of this study is to test the hypothesis that HS/R causes increased gut permeability which results in induction of high mobility group box1 protein (HMGB1) and further leads to the development of acute lung inflammation.

Materials and methods

A mouse model of HS/R was employed in this study. Gut permeability and bacterial translocation were assessed with circulating FD4 and lipopolysaccharide (LPS). Circulating HMGB1 was determined with ELISA. Acute lung inflammation (ALI) was determined with lung myeloperoxidase (MPO) activity and pulmonary protein leakage.

Results

HS/R induced intestinal barrier dysfunction as evidenced by increased circulating FD4 and LPS at 30 min and 2 hrs after resuscitation, respectively. In addition, circulating HMGB1 levels were increased in mice with HS/R as compared with sham animals (p < 0.05). HS/R resulted in ALI (increased lung MPO activity and pulmonary protein leakage in mice with HS/R compared with sham mice, p < 0.05). Inhibition of HMGB1 (A-box and TLR4^−/−) attenuated the ALI in mice with HS/R. However, inhibition of HMGB1 did not show protective effect on gut injury in early phase of HS/R in mice.

Conclusions

Our results suggest that induction of HMGB1 is important in hemorrhagic shock and resuscitation-induced acute lung inflammation.

Neutrophils counteract autophagy-mediated anti-inflammatory mechanisms in alveolar macrophage: role in posthemorrhagic shock acute lung inflammation

Acute lung injury (ALI) is a major component of multiple organ dysfunction syndrome after hemorrhagic shock (HS) resulting from major surgery and trauma. The increased susceptibility in HS patients to the development of ALI suggests not yet fully elucidated mechanisms that enhance proinflammatory responses and/or suppress anti-inflammatory responses in the lung. Alveolar macrophages (AMϕ) are at the center of the pathogenesis of ALI after HS. We have previously reported that HS-activated polymorphonuclear neutrophils (PMNs) interact with macrophages to influence inflammation progress. In this study, we explore a novel function of PMNs regulating AMϕ anti-inflammatory mechanisms involving autophagy. Using a mouse "two-hit" model of HS/resuscitation followed by intratracheal injection of muramyl dipeptide, we demonstrate that HS initiates high mobility group box 1/TLR4 signaling, which upregulates NOD2 expression in AMϕ and sensitizes them to subsequent NOD2 ligand muramyl dipeptide to augment lung inflammation. In addition, upregulated NOD2 signaling induces autophagy in AMϕ, which negatively regulates lung inflammation through feedback suppression of NOD2-RIP2 signaling and inflammasome activation. Importantly, we further demonstrate that HS-activated PMNs that migrate in alveoli counteract the anti-inflammatory effect of autophagy in AMϕ, possibly through NAD(P)H oxidase-mediated signaling to enhance I-κB kinase γ phosphorylation, NF-κB activation, and nucleotide-binding oligomerization domain protein 3 inflammasome activation, and therefore augment post-HS lung inflammation. These findings explore a previously unidentified complexity in the mechanisms of ALI, which involves cell-cell interaction and receptor cross talk.

Penehyclidine hydrochloride decreases pulmonary microvascular permeability by upregulating beta arrestins in a murine cecal ligation and puncture model

BACKGROUND

Penehyclidine hydrochloride (PHC) is a new anticholinergic drug, which has been shown to have a good curative effect for sepsis. Beta arrestins have been demonstrated to play important roles in sepsis. This study is to investigate the effects of PHC on pulmonary microvascular permeability and on expressions of beta arrestins in lung injury induced by the cecal ligation and puncture (CLP) procedure.

MATERIALS AND METHODS

Thirty healthy female mice were randomly divided into three groups (n = 10 each): sham operation group (control group), CLP group (CLP group), and PHC 0.45 mg/kg group (PHC group). In the PHC group, mice were given an intraperitoneal injection of PHC 0.45 mg/kg 1 h before surgery. Mice in the other two groups received an intraperitoneal injection of the same volume of normal saline. At 12 h after surgery, serum and bronchoalveolar lavage fluid were collected to examine lung permeability index. The lung tissue samples were collected to examine expressions of myosin light chain kinase (MLCK), vascular endothelial-cadherin (VE-cadherin), vascular cell adhesion molecule 1 (VCAM-1), myeloperoxidase (MPO), NF-κB, and beta arrestins.

RESULTS

Compared with the control group, pulmonary microvascular permeability, MPO activity, NF-κB, VCAM-1, and MLCK expressions were significantly increased, whereas VE-cadherin and beta-arrestin protein expressions were obviously decreased in CLP group. Furthermore, compared with the CLP group, PHC group markedly decreased pulmonary microvascular permeability, MPO activity, NF-κB, VCAM-1, and MLCK expressions, and increased expressions of VE-cadherin and beta arrestins.

CONCLUSIONS

This study suggests that in the CLP-induced lung injury model, PHC could reduce pulmonary microvascular permeability by upregulating expressions of beta arrestins.

MyD88 and TRIF mediate divergent inflammatory and regenerative responses to skeletal muscle ischemia

We have previously shown that MyD88 KO mice appear protected from ischemic muscle injury while TRIF KO mice exhibit sustained necrosis after femoral artery ligation (FAL). However, our previous data did not differentiate whether the protective effect of absent MyD88 signaling was secondary to attenuated injury after FAL or quicker recovery from the insult. The purpose of this study was to delineate these different possibilities. On the basis of previous findings, we hypothesized that MyD88 signaling promotes enhanced inflammation while TRIF mediates regeneration after skeletal muscle ischemia. Our results show that after FAL, both MyD88 KO mice and TRIF KO mice have evidence of ischemia, as do their control counterparts. However, MyD88 KO mice had lower levels of serum IL‐6 24 h after FAL, while TRIF KO mice demonstrated sustained serum IL‐6 up to 1 week after injury. Additionally, MyD88 KO mice had higher nuclear content and larger myofibers than control animals 1 week after injury. IL‐6 is known to have differential effects in myoblast function, and can inhibit proliferation and differentiation. In tibialis anterior muscle harvested from injured animals, IL‐6 levels were higher and the proliferative marker MyoD was lower in TRIF KO mice by PCR. Furthermore, expression of MyD88 appeared to be higher in skeletal muscle of TRIF KO mice. In vitro, we showed that myoblast differentiation and proliferation were attenuated in response to IL‐6 treatment giving credence to the finding that low IL‐6 in MyD88 KO mice may be responsible for larger myocyte sizes 1 week after FAL. We conclude that MyD88 and TRIF work in concert to mediate a balanced response to ischemic injury.

We describe opposing roles of MyD88 and TRIF, both downstream signaling molecules of TLR4, in the inflammatory and regenerative processes that follow limb ischemia. MyD88 appears to mediate inflammation, while TRIF appears to be required for modulation of MyD88 activity and promoting regeneration. Absence of MyD88 may ultimately have a protective effect in muscle recovery after ischemic injury.

Effect of dexmedetomidine on lung ischemia‑reperfusion injury

Dexmedetomidine, a specific selective α₂-adrenergic agonist, does not only have the characteristics of being a sedative and analgesic, but also exhibits a protective role in brain ischemia-reperfusion injury and inhibits the inflammation in animals with sepsis. The objective of the present study was to investigate whether dexmedetomidine is capable of attenuating rat pulmonary damage induced by ischemia-reperfusion injury, which is a type of acute sterile lung injury. Sprague-Dawley rats were randomly assigned into six groups: The sham-operated (sham) group, the lung ischemia-reperfusion (I/R) group, intravenous injection of dexmedetomidine 2.5 μg/kg/h (Dex2.5) or 5 μg/kg/h (Dex5) for 1 h prior to ischemia, combination of α₂-adrenergic antagonist yohimbine prior to dexmedetomidine pre-treatment (Dex+Yoh) and pre-administration of yohimbine alone (Yoh) prior to ischemia. Lung injury was assessed by the histopathological changes, arterial blood gas, wet/dry (w/d) weight ratio and myeloperoxidase (MPO) activity of the lung. The concentration of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and monocyte chemoattractant protein-1 (MCP-1) in bronchoalveolar lavage fluid (BALF) was measured by an enzyme-linked immunosorbent assay. The expression of toll-like receptor-4 (TLR4) and myeloid differentiation factor 88 (MyD88) mRNA in the lung were determined by quantitative PCR, and phosphorylated levels of c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK)1/2 were determined by western blotting. Pre-treatment with dexmedetomidine significantly reduced the lung injury, w/d weight ratio and MPO activity, and decreased the concentration of TNF-α, IL-6 and MCP-1 in BALF compared with the I/R group. The expression of TLR4 and MyD88 mRNA and the levels of phosphorylated JNK and ERK1/2 in the lung tissue were markedly downregulated by intravenous injection of dexmedetomidne for 1 h prior to lung I/R. The protective effects of dexmedetomidine on the lung were not completely reversed by the α₂-adrenergic antagonist, yohimbine. Pre-treatment with dexmedetomidine is capable of reducing pulmonary damage and inhibiting sterile inflammation induced by lung I/R injury. TLR4/MyD88/mitogen-activated protein kinase (MAPK) signaling is involved in the protective mechanism of dexmedetomidine through α₂-adrenoceptor independence.

Extracellular histone release in response to traumatic injury: implications for a compensatory role of activated protein C

BACKGROUND

Tissue injury leads to the release of DAMPs (damage-associated molecular patterns) that may drive a sterile inflammatory response; however, the role of extracellular histone levels after traumatic injury remains unexplored. We hypothesized that extracellular histone levels would be increased and associated with poor outcomes after traumatic injury.

METHODS

In this prognostic study, plasma was prospectively collected from 132 critically injured trauma patients on arrival and 6 hours after admission to an urban Level I trauma intensive care unit. Circulating extracellular histone levels and plasma clotting factors were assayed and linked to resuscitation and outcome data.

RESULTS

Of 132 patients, histone levels were elevated to a median of 14.0 absorbance units (AU) on arrival, declining to 6.4 AU by 6 hours. Patients with elevated admission histone levels had higher ISS (Injury Severity Score), lower admission GCS (Glasgow Coma Scale) score, more days of mechanical ventilation, and higher incidences of multiorgan failure, acute lung injury, and mortality (all p ≤ 0.05). Histone levels correlated with prolonged international normalized ratio and partial thromboplastin time, fibrinolytic markers D-dimer and tissue-type plasminogen activator, and anticoagulants tissue factor pathway inhibitor and activated protein C (aPC; all p < 0.03). Increasing histone level from admission to 6 hours was a multivariate predictor of mortality (hazard ratio, 1.005; p = 0.013). When aPC level trends were included, the impact of histone level increase on mortality was abrogated (p = 0.206) by a protective effect of increasing aPC levels (hazard ratio, 0.900; p = 0.020).

CONCLUSION

Extracellular histone levels are elevated in response to traumatic injury and correlate with fibrinolysis and activation of anticoagulants. An increase in histone levels from admission to 6 hours is predictive of mortality, representing evidence of ongoing release of intracellular antigens similar to that seen in sepsis. Concomitant elevation of aPC abrogates this effect, suggesting a possible role for aPC in mitigating the sterile inflammatory response after trauma through the proteolysis of circulating histones.

LEVEL OF EVIDENCE

Prognostic study, level III.

Serum amyloid A activation of human coronary artery endothelial cells exhibits a neutrophil promoting molecular profile

BACKGROUND

Serum amyloid A (SAA) has been shown to be an active participant in atherosclerosis and cardiovascular diseases. SAA-stimulated human coronary artery endothelial cells (HCAEC) were reported to release pro-inflammatory cytokines, chemokines and adhesion molecules; however it remains unclear which putative SAA receptors are present in these cells and how they act. We investigated the effects of inflammatory stimuli on the expression of SAA receptors, signaling pathways and molecular profiles in HCAEC.

METHODOLOGY/PRINCIPLE FINDINGS

HCAEC were cultured in vitro and stimulated with SAA (1000nM) or IL-1β (1000pg/ml). Expression of mRNA was determined by qPCR, and expression and quantification of proteins were assessed by dot array blots and ELISA, respectively. Protein phosphorylation was determined by dot blot arrays and Western blots. We report that all potential SAA receptors tested (FPR2/ALX, RAGE, TANIS, TLR2, TLR4 and CLA-1/hSR-B1) are expressed in HCAEC. Importantly, IL-1β or SAA significantly increased solely the expression of the innate immune receptor TLR2. SAA upregulated the phosphorylation of ERK1/2, NF-κB (p65, p105) and JNK, as well as expression/release of IL-6, IL-8, G-CSF, GM-CSF, ICAM-1 and VCAM-1, all potent molecules involved in neutrophil-related activities. A TLR2-dependent positive feedback mechanism of SAA expression was found.

CONCLUSION/SIGNIFICANCE

SAA stimulated responses in HCAEC target neutrophil rather than monocyte/macrophage activation.

Uncovering the neuroenteric-pulmonary axis: vagal nerve stimulation prevents acute lung injury following hemorrhagic shock

AIMS

Trauma/hemorrhagic shock (T/HS) induced gut injury is known to initiate a systemic inflammatory response which can lead to secondary lung injury. We have shown that vagal nerve stimulation (VNS) protects intestinal epithelial integrity after a severe burn insult. We hypothesize that VNS will protect the lung from injury following T/HS by preventing intestinal barrier failure.

MAIN METHODS

Male Balb/c mice were subjected to a T/HS model with and without cervical VNS. Intestinal injury was evaluated by measuring changes in gut barrier function and tight junction protein localization. Lung injury was evaluated using histology and markers of lung inflammation. Using NF-kB-luciferase (NF-kB-luc) transgenic mice, NF-kb-DNA binding was measured by photon emission analysis at 4 after injury.

KEY FINDINGS

T/HS is associated gut injury characterized by histologic injury, increased epithelial permeability, and altered localization of gut tight junction proteins. Cervical VNS prevented the T/HS-induced changes in gut barrier integrity. Gut injury after T/HS was associated with acute lung injury at 24 h characterized by histologic injury, increased number of MPO positive stained cells and MPO enzymatic activity, and increased ICAM-1 expression in lung endothelium. VNS decreased T/HS-induced lung injury with a marked decrease in lung inflammation compared to T/HS alone. Lungs harvested from NF-kB-luc mice at 4h post VNS+T/HS demonstrated decreased DNA binding of NF-kB compared to T/HS alone as measured by changes in bioluminescence.

SIGNIFICANCE

VNS is effective in protecting against acute lung injury caused by hemorrhagic shock through its ability to prevent gut barrier dysfunction.

Knockdown of myeloid differentiation protein-2 reduces acute lung injury following orthotopic autologous liver transplantation in a rat model

BACKGROUND

Acute lung injury (ALI) is a serious complication that commonly occurs during orthotopic liver transplantation (OLT). Toll-like receptor 2/4 (TLR2/4) are the main membrane receptors that respond to inflammatory stimuli and mediate NF-kappa B (NF-κB) signal pathway. We previously showed that TLR2/4 expression on monocytes and serum cytokine levels were increased in patients with ALI induced by OLT. Myeloid differentiation protein-2 (MD-2) expresses the functional domains that combines TLRs and play a key regulatory role in TLRs activation. Therefore, we hypothesized that blocking MD-2 would inhibit the TLR2/4-mediated inflammatory response and lessen ALI induced by liver transplantation.

METHOD

Thirty-two Sprague Dawley (SD) rats were randomly divided into four groups. One group received a sham operation (Group S), and the other three groups underwent orthotopic autologous liver transplantation (OALT) 48 h after intratracheal administration of saline (Model group; Group M), non-targeting siRNA (negative siRNA control group; Group NC) or siRNA against MD-2 (intervention group; Group RNAi). Lung pathology, lung water content, PaO2, and expression levels of MD-2, TLR2/4, NF-κB, TNF-α, IL-1β and IL-6 were assessed 8 h after OALT.

RESULTS

In Groups M and NC, OALT produced marked lung pathology with decreased PaO2 levels and increased MD-2, TLR2/4 gene and protein expression levels. Furthermore, the nuclear translocation of the NF-κB P65 subunit, was increased, as were lung concentrations of TNF-α, IL-1β and IL-6. The pathology of ALI and the severity of the above biochemical changes induced by OALT were significantly reduced in the group treated with MD-2 siRNA.

CONCLUSION

MD-2 gene knock-down attenuated the increase in TLR2/4 activation and reduced ALI after OALT.

Danger-associated molecular patterns (DAMPs) in acute lung injury

Danger-associated molecular patterns (DAMPs) are host-derived molecules that can function to regulate the activation of pathogen recognition receptors (PRRs). These molecules play a critical role in modulating the lung injury response. DAMPs originate from multiple sources, including injured and dying cells, the extracellular matrix, or exist as immunomodulatory proteins within the airspace and interstitium. DAMPs can function as either toll-like receptor (TLR) agonists or antagonists, and can modulate both TLR and nod-like receptor (NLR) signalling cascades. Collectively, this diverse group of molecules may represent important therapeutic targets in the prevention and/or treatment of acute lung injury (ALI) and its more severe form, acute respiratory distress syndrome (ARDS).

TLR2 and TLR4 mediate differential responses to limb ischemia through MyD88-dependent and independent pathways

Introduction

The danger signal HMGB1 is released from ischemic myocytes, and mediates angiogenesis in the setting of hindlimb ischemia. HMGB1 is a ligand for innate immune receptors TLR2 and TLR4. While both TLR2 and TLR4 signal through myeloid differentiation factor 88 (MyD88), TLR4 also uniquely signals through TIR-domain-containing adapter-inducing interferon-β (TRIF). We hypothesize that TLR2 and TLR4 mediate ischemic myocyte regeneration and angiogenesis in a manner that is dependent on MyD88 signaling.

Methods

Mice deficient in TLR2, TLR4, MyD88 and TRIF underwent femoral artery ligation in the right hindlimb. Laser Doppler perfusion imaging was used to assess the initial degree of ischemia and the extent of perfusion recovery. Muscle regeneration, necrosis and fat replacement at 2 weeks post-ligation were assessed histologically and vascular density was quantified by immunostaining. In vitro, endothelial tube formation was evaluated in matrigel in the setting of TLR2 and TLR4 antagonism.

Results

While control and TLR4 KO mice demonstrated prominent muscle regeneration, both TLR2 KO and TRIF KO mice exhibited marked necrosis with significant inflammatory cell infiltrate. However, MyD88 KO mice had a minimal response to the ischemic insult with little evidence of injury. This observation could not be explained by differences in perfusion recovery which was similar at two weeks in all the strains of mice. TLR2 KO mice demonstrated abnormal vessel morphology compared to other strains and impaired tube formation in vitro.

Discussion

TLR2 and TRIF signaling are necessary for muscle regeneration after ischemia while MyD88 may instead mediate muscle injury. The absence of TLR4 did not affect muscle responses to ischemia. TLR4 may mediate inflammatory responses through MyD88 that are exaggerated in the absence of TLR2. Additionally, the actions of TLR4 through TRIF may promote regenerative responses that are required for recovery from muscle ischemia.

Alveolar macrophages and Toll-like receptor 4 mediate ventilated lung ischemia reperfusion injury in mice

BACKGROUND

Ischemia-reperfusion (I-R) injury is a sterile inflammatory process that is commonly associated with diverse clinical situations such as hemorrhage followed by resuscitation, transient embolic events, and organ transplantation. I-R injury can induce lung dysfunction whether the I-R occurs in the lung or in a remote organ. Recently, evidence has emerged that receptors and pathways of the innate immune system are involved in recognizing sterile inflammation and overlap considerably with those involved in the recognition of and response to pathogens.

METHODS

The authors used a mouse surgical model of transient unilateral left pulmonary artery occlusion without bronchial involvement to create ventilated lung I-R injury. In addition, they mimicked nutritional I-R injury in vitro by transiently depriving cells of all nutrients.

RESULTS

Compared with sham-operated mice, mice subjected to ventilated lung I-R injury had up-regulated lung expression of inflammatory mediator messenger RNA for interleukin-1β, interleukin-6, and chemokine (C-X-C motif) ligand-1 and -2, paralleled by histologic evidence of lung neutrophil recruitment and increased plasma concentrations of interleukin-1β, interleukin-6, and high-mobility group protein B1 proteins. This inflammatory response to I-R required toll-like receptor-4 (TLR4). In addition, the authors demonstrated in vitro cooperativity and cross-talk between human macrophages and endothelial cells, resulting in augmented inflammatory responses to I-R. Remarkably, the authors found that selective depletion of alveolar macrophages rendered mice resistant to ventilated lung I-R injury.

CONCLUSIONS

The data reveal that alveolar macrophages and the pattern recognition receptor toll-like receptor-4 are involved in the generation of the early inflammatory response to lung I-R injury.

Toll-like receptor 2 deficiency increases resistance to Pseudomonas aeruginosa pneumonia in the setting of sepsis-induced immune dysfunction

BACKGROUND

Sepsis is characterized by a dysregulated inflammatory response followed by immunosuppression that favors the development of secondary infections. Toll-like receptors (TLRs) are major regulators of the host's response to infections. How variability in TLR signaling may impact the development of sepsis-induced immune dysfunction has not been established. We sought to establish the role of TLR2, TLR4, and TLR5 in postseptic mice with Pseudomonas aeruginosa pneumonia.

METHODS

We used an experimental model of sublethal polymicrobial sepsis induced by cecal ligation and puncture (CLP). Wild-type, tlr2(-/-), tlr4(-/-), tlr5(-/-), tlr2 4(-/-) mice that underwent CLP were secondarily subjected to P. aeruginosa pulmonary infection.

RESULTS

Postseptic wild-type and tlr4(-/-) and tlr5(-/-) mice displayed high susceptibility to P. aeruginosa pneumonia. In contrast, TLR2-deficient mice, either tlr2(-/-)or tlr2 4(-/-), that underwent CLP were resistant to the secondary pulmonary infection. As compared to wild-type mice, tlr2(-/-) mice displayed improvement in bacterial clearance, decreased bacteremic dissemination, and attenuated lung damage. Furthermore, tlr2(-/-) mice exhibited a pulmonary proinflammatory cytokine balance, with increased production of tumor necrosis factor α and decreased release of interleukin 10.

CONCLUSIONS

In a model of secondary P. aeruginosa pneumonia in postseptic mice, TLR2 deficiency improves survival by promoting efficient bacterial clearance and restoring a proinflammatory cytokine balance in the lung.

ERK5 protein promotes, whereas MEK1 protein differentially regulates, the Toll-like receptor 2 protein-dependent activation of human endothelial cells and monocytes

Endothelial cell (EC) Toll-like receptor 2 (TLR2) activation up-regulates the expression of inflammatory mediators and of TLR2 itself and modulates important endothelial functions, including coagulation and permeability. We defined TLR2 signaling pathways in EC and tested the hypothesis that TLR2 signaling differs in EC and monocytes. We found that ERK5, heretofore unrecognized as mediating TLR2 activation in any cell type, is a central mediator of TLR2-dependent inflammatory signaling in human umbilical vein endothelial cells, primary human lung microvascular EC, and human monocytes. Additionally, we observed that, although MEK1 negatively regulates TLR2 signaling in EC, MEK1 promotes TLR2 signaling in monocytes. We also noted that activation of TLR2 led to the up-regulation of intracellularly expressed TLR2 and inflammatory mediators via NF-κB, JNK, and p38-MAPK. Finally, we found that p38-MAPK, JNK, ERK5, and NF-κB promote the attachment of human neutrophils to lung microvascular EC that were pretreated with TLR2 agonists. This study newly identifies ERK5 as a key regulator of TLR2 signaling in EC and monocytes and indicates that there are fundamental differences in TLR signaling pathways between EC and monocytes.

The role of toll-like receptor-4 in the development of multi-organ failure following traumatic haemorrhagic shock and resuscitation

Haemorrhagic shock and resuscitation (HS/R) following major trauma results in a global ischaemia and reperfusion injury that may lead to multiple organ dysfunction syndrome (MODS). Systemic activation of the immune system is fundamental to the development of MODS in this context, and shares many features in common with the systemic inflammatory response syndrome (SIRS) that complicates sepsis. An important advancement in the understanding of the innate response to infection involved the identification of mammalian toll-like receptors (TLRs) expressed on cells of the immune system. Ten TLR homologues have been identified in humans and toll-like receptor-4 (TLR4) has been studied most intensively. Initially found to recognise bacterial lipopolysaccharide (LPS), it has also recently been discovered that TLR4 is capable of activation by endogenous 'danger signal' molecules released following cellular injury; this has since implicated TLR4 in several non-infectious pathophysiologic processes, including HS/R. The exact events leading to multi-organ dysfunction following HS/R have not yet been clearly defined, although TLR4 is believed to play a central role as has been shown to be expressed at sites including the liver, lungs and myocardium following HS/R. Multi-organ dysfunction syndrome remains an important cause of morbidity and mortality in trauma patients, and current therapy is based on supportive care. Understanding the pathophysiology of HS/R will allow for the development of targeted therapeutic strategies aimed at minimising organ dysfunction and improving patient outcomes following traumatic haemorrhage. A review of the pathogenesis of haemorrhagic shock is presented, and the complex, yet critical role of TLR4 as both a key mediator and therapeutic target is discussed.

Endothelial cell activation in emergency department patients with sepsis-related and non-sepsis-related hypotension

Previous studies found increased circulating levels of biomarkers related to endothelial cell activation in patients with sepsis, particularly in the most severe sepsis stages of sepsis shock. It remains unclear, however, whether this activation is mainly driven by sepsis-specific mechanisms or occurs as a generalized inflammatory response. The objective of this analysis was to compare patterns of biomarkers of endothelial cell activation in patients with hypotension due to sepsis and nonsepsis etiologies. This is a secondary analysis of a prospective, observational cohort study including emergency department patients older than17 years with an episode of hypotension defined as any systolic blood pressure measurement less than 100 mmHg. Etiology of hypotension episodes was classified as sepsis or nonsepsis (eg, cardiac or hemorrhagic). Endothelial activation biomarkers of cell adhesion (E-selectin, vascular cell adhesion molecule 1 [VCAM-1], and intercellular adhesion molecule 1 [ICAM-1]), coagulation (plasminogen activator inhibitor 1 [PAI-1]), and vascular endothelial growth factor (VEGF) signaling (VEGF, soluble fms-like tyrosine kinase 1 [sFLT-1]) were assayed. A total of 161 patients were analyzed. Hypotension was classified as sepsis (n = 69), nonsepsis (cardiac [n = 35], hemorrhagic [n = 12]), or indeterminate (n = 45). With the exception of PAI-1, median plasma levels of all endothelial markers were significantly higher in patients with sepsis compared with nonsepsis etiology (P < 0.05 for all comparisons). Logistic regression analysis, adjusted for age, sex, mean blood pressure level, and mortality, confirmed a significant association of E-selectin (odds ratio [OR], 3.7; 95% confidence interval [CI], 1.7-7.8, P < 0.001) and sFLT-1 (OR, 2.0; CI, 1.1-3.8; P < 0.03) with sepsis etiology. Biomarkers VCAM-1 (OR, 2.0; CI, 0.88-4.4; P = 0.1), VEGF (OR, 1.5; CI, 0.98-2.2; P = 0.06), ICAM-1 (OR, 1.5; CI, 0.9-2.6; P = 0.2), and PAI-1 (OR, 1.4; CI, 0.8-2.3; P = 0.2) did not reach statistical significance. This study found a sepsis-specific activation of endothelium activation markers, particularly E-selectin and sFLT-1, in emergency department patients with hypotension.

Activation of endothelial TLR2 by bacterial lipoprotein upregulates proteins specific for the neutrophil response

The vascular endothelium is integrally involved in the host response to infection and in organ failure during acute inflammatory disorders such as sepsis. Gram-negative and Gram-positive bacterial lipoproteins circulate in sepsis and can directly activate the endothelium by binding to endothelial cell (EC) TLR2. In this report, we perform the most comprehensive analysis to date of the immune-related genes regulated after activation of endothelial TLR2 by bacterial di- and triacylated lipopeptides. We found that TLR2 activation specifically induces the expression of the genes IL-6, IL-8, CSF2, CSF3, ICAM1 and SELE by human umbilical vein ECs and human lung microvascular ECs. These proteins participate in neutrophil recruitment, adherence and activation at sites of inflammation. Significantly, our studies demonstrate that TLR2-mediated EC responses are specifically geared towards recruitment, activation, and survival of neutrophils and not mononuclear leukocytes, that ECs do not require priming by other inflammatory stimuli to respond to bacterial lipopeptides and, unlike mononuclear leukocytes, TLR2 agonists do not induce ECs to secrete TNF-α. This study suggests that endothelial TLR2 may be an important regulator of neutrophil trafficking to sites of infection in general, and that direct activation of lung endothelial TLR2 may contribute to acute lung injury during sepsis.

Protection by 20-5,14-HEDGE against surgically induced ischemia reperfusion lung injury in rats

BACKGROUND

We previously reported that the cytochrome P450 product 20-hydroxyeicosatetraenoic acid has prosurvival effects in pulmonary artery endothelial cells and ex vivo pulmonary arteries. We tested the potential of a 20-hydroxyeicosatetraenoic acid analog N-[20-hydroxyeicosa-5(Z),14(Z)-dienoyl]glycine (20-5,14-HEDGE) to protect against lung ischemic reperfusion injury in rats. Furthermore, we examined activation of innate immune system components, high mobility group box 1 (HMGB1) and toll-like receptor 4 (TLR4), in this model as well as the effect of 20-5,14-HEDGE on this signaling pathway.

METHODS

Sprague-Dawley rats treated with 20-5,14-HEDGE or vehicle were subjected to surgically induced, unilateral lung ischemia for 60 minutes followed by reperfusion for 2 hours in vivo. Injury was assessed histologically by hematoxylin and eosin, and with identification of myeloperoxidase immunohistochemically. The HMGB1 and TLR4 proteins were identified by Western blot. Caspase 3 activity or 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, a yellow tetrazole, incorporation were used to measure apoptosis and cell survival.

RESULTS

The ischemia reperfusion injury evoked atelectasis and hemorrhage, an influx of polymorphonuclear cells, and increased TLR4 and HMGB1 expression. Caspase 3 activity was increased, and 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide incorporation was decreased. The 20-5,14-HEDGE protected against each of these endpoints, including infiltration of polymorphonuclear cells, with no changes in caspase 3 activity in other organs.

CONCLUSIONS

Lung ischemia reperfusion produces apoptosis and activation of the innate immune system including HMGB1 and TLR4 within 2 hours of reperfusion. Treatment with 20-5,14-HEDGE decreases activation of this response system, and salvages lung tissue.

Hemorrhagic shock activation of NLRP3 inflammasome in lung endothelial cells

Hemorrhagic shock (HS) due to major trauma and surgery predisposes the host to the development of systemic inflammatory response syndrome (SIRS), including acute lung injury (ALI), through activating and exaggerating the innate immune response. IL-1β is a crucial proinflammatory cytokine that contributes to the development of SIRS and ALI. Lung endothelial cells (EC) are one important source of IL-1β, and the production of active IL-1β is controlled by the inflammasome. In this study, we addressed the mechanism underlying HS activation of the inflammasome in lung EC. We show that high mobility group box 1 acting through TLR4, and a synergistic collaboration with TLR2 and receptor for advanced glycation end products signaling, mediates HS-induced activation of EC NAD(P)H oxidase. In turn, reactive oxygen species derived from NAD(P)H oxidase promote the association of thioredoxin-interacting protein with the nucleotide-binding oligomerization domain-like receptor protein NLRP3 and subsequently induce inflammasome activation and IL-1β secretion from the EC. We also show that neutrophil-derived reactive oxygen species play a role in enhancing EC NAD(P)H oxidase activation and therefore an amplified inflammasome activation in response to HS. The present study explores a novel mechanism underlying HS activation of EC inflammasome and thus presents a potential therapeutic target for SIRS and ALI induced after HS.

Toll-like receptor 2 induced angiogenesis and invasion is mediated through the Tie2 signalling pathway in rheumatoid arthritis

Background

Angiogenesis is a critical early event in inflammatory arthritis, facilitating leukocyte migration into the synovium resulting in invasion and destruction of articular cartilage and bone. This study investigates the effect of TLR2 on angiogenesis, EC adhesion and invasion using microvascular endothelial cells and RA whole tissue synovial explants ex-vivo.

Methods

Microvascular endothelial cells (HMVEC) and RA synovial explants ex vivo were cultured with the TLR2 ligand, Pam3CSK4 (1 µg/ml). Angiopoietin 2 (Ang2), Tie2 and TLR2 expression in RA synovial tissue was assessed by immunohistology. HMVEC tube formation was assessed using Matrigel matrix assays. Ang2 was measured by ELISA. ICAM-1 cell surface expression was assessed by flow cytometry. Cell migration was assessed by wound repair scratch assays. ECM invasion, MMP-2 and -9 expression were assessed using transwell invasion chambers and zymography. To examine if the angiopoietin/Tie2 signalling pathway mediates TLR2 induced EC tube formation, invasion and migration assays were performed in the presence of a specific neutralising anti-Tie2mAb (10 ug/ml) and matched IgG isotype control Ab (10 ug/ml).

Results

Ang2 and Tie2 were localised to RA synovial blood vessels, and TLR2 was localised to RA synovial blood vessels, sub-lining infiltrates and the lining layer. Pam3CSK4 significantly increased angiogenenic tube formation (p<0.05), and upregulated Ang2 production in HMVEC (p<0.05) and RA synovial explants (p<0.05). Pam3CSK4 induced cell surface expression of ICAM-1, from basal level of 149±54 (MFI) to 617±103 (p<0.01). TLR-2 activation induced an 8.8±2.8 fold increase in cell invasion compared to control (p<0.05). Pam3CSK4 also induced HMVEC cell migration and induced MMP-2 and -9 from RA synovial explants. Neutralisation of the Ang2 receptor, Tie2 significantly inhibited Pam3CSK4-induced EC tube formation and invasion (p<0.05).

Conclusion

TLR2 activation promotes angiogenesis, cell adhesion and invasion, effects that are in part mediated through the Tie2 signalling pathway, key mechanisms involved in the pathogenesis of RA.

Fixed volume or fixed pressure: a murine model of hemorrhagic shock

It is common knowledge that severe blood loss and traumatic injury can lead to a cascade of detrimental signaling events often resulting in mortality. ^{1, 2, 3, 4, 5} These signaling events can also lead to sepsis and/or multiple organ dysfunction (MOD). ^{6, 7, 8, 9} It is critical then to investigate the causes of suppressed immune function and detrimental signaling cascades in order to develop more effective ways to help patients who suffer from traumatic injuries. ¹⁰ This fixed pressure Hemorrhagic Shock (HS) procedure, although technically challenging, is an excellent resource for investigation of these pathophysiologic conditions. ^{11, 12, 13} Advances in the assessment of biological systems, i.e. Systems Biology have enabled the scientific community to further understand complex physiologic networks and cellular communication patterns. ¹⁴ Hemorrhagic Shock has proven to be a vital tool for unveiling these cellular communication patterns as they relate to immune function. ^{15, 16, 17, 18} This procedure can be mastered! This procedure can also be used as either a fixed volume or fixed pressure approach. We adapted this technique in the murine model to enhance research in innate and adaptive immune function. ^{19, 20, 21} Due to their small size HS in mice presents unique challenges. However due to the many available mouse strains, this species represents an unparalleled resource for the study of the biologic responses. The HS model is an important model for studying cellular communication patterns and the responses of systems such as hormonal and inflammatory mediator systems, and danger signals, i.e. DAMP and PAMP upregulation as it elicits distinct responses that differ from other forms of shock. ^{22, 23, 24, 25} The development of transgenic murine strains and the induction of biologic agents to inhibit specific signaling have presented valuable opportunities to further elucidate our understanding of the up and down regulation of signal transduction after severe blood loss, i.e. HS and trauma ^{26, 27, 28, 29, 30}.

There are numerous resuscitation methods (R) in association with HS and trauma. ^{31, 32, 33, 34} A fixed volume resuscitation method of solely lactated ringer solution (LR), equal to three times the shed blood volume, is used in this model to study endogenous mechanisms such as remote organ injury and systemic inflammation. ^{35, 36, 38} This method of resuscitation is proven to be effective in evaluating the effects of HS and trauma ^{38, 39}.

The essential roles of Toll-like receptor signaling pathways in sterile inflammatory diseases

Toll-like receptors (TLRs) form a family of pattern recognition receptors with at least 11 members in human and 13 in mouse. TLRs recognize a wide variety of putative host-derived agonists that have emerged as key mediators of innate immunity. TLR signaling also plays an important role in the activation of the adaptive immune system by inducing pro-inflammatory cytokines and upregulating costimulatory molecules of antigen presenting cells. Inappropriate activation of TLRs by self-components generated by damaged tissues may result in sterile inflammation. This review discusses the contribution of TLR signaling to the initiation and progression of non-infectious inflammatory processes, such as ischemia and reperfusion (I/R) injury, tissue repair and regeneration and autoimmune diseases. The involvement of TLR signaling in the pathogenesis of sterile inflammation-related diseases may provide novel targets for the development of therapeutics.

Systemic inflammation and liver injury following hemorrhagic shock and peripheral tissue trauma involve functional TLR9 signaling on bone marrow-derived cells and parenchymal cells

Hemorrhagic shock due to trauma (HS/T) induces an inflammatory response that can contribute to end-organ injury. The pathways involved in the initiation and propagation of HS/T-induced inflammation are incompletely understood. Here, we hypothesized that the DNA sensor TLR9 would have a role in inflammatory signaling after HS/T. Using mice expressing a nonfunctional, mutant form of TLR9, we identified a role of TLR9 in driving the initial cytokine response and liver damage in a model of hemorrhagic shock and bilateral femur fracture. Circulating DNA levels were found to correlate with the degree of tissue damage. Experiments using chimeric mice show that TLR9 on both bone marrow-derived cells and parenchymal cells are important for the TLR9-mediated liver and tissue damage, as well as systemic inflammation after HS/T. These data suggest that release of DNA may be a driver of the inflammatory response to severe injury as well as a marker of the extent of tissue damage. One of the sensors of DNA in the setting of HS/T seems to be TLR9.