TLR Cross-Talk Mechanism of Hemorrhagic Shock-Primed Pulmonary Neutrophil Infiltration

Discovering myeloid cell heterogeneity in the lung by means of next generation sequencing

The lung plays a vital role in maintaining homeostasis, as it is responsible for the exchange of oxygen and carbon dioxide. Pulmonary homeostasis is maintained by a network of tissue-resident cells, including epithelial cells, endothelial cells and leukocytes. Myeloid cells of the innate immune system and epithelial cells form a critical barrier in the lung. Recently developed unbiased next generation sequencing (NGS) has revealed cell heterogeneity in the lung with respect to physiology and pathology and has reshaped our knowledge. New phenotypes and distinct gene signatures have been identified, and these new findings enhance the diagnosis and treatment of lung diseases. Here, we present a review of the new NGS findings on myeloid cells in lung development, homeostasis, and lung diseases, including acute lung injury (ALI), lung fibrosis, chronic obstructive pulmonary disease (COPD), and lung cancer.

TLRs in pulmonary diseases

Toll-like receptors (TLRs) comprise a clan of proteins involved in identification and triggering a suitable response against pathogenic attacks. As lung is steadily exposed to multiple infectious agents, antigens and host-derived danger signals, the inhabiting stromal and myeloid cells of the lung express an aggregate of TLRs which perceive the endogenously derived damage-associated molecular patterns (DAMPs) along with pathogen associated molecular patterns (PAMPs) and trigger the TLR-associated signalling events involved in host defence. Thus, they form an imperative component of host defence activation in case of microbial infections as well as non-infectious pulmonary disorders such as interstitial lung disease, acute lung injury and airways disease, such as COPD and asthma. They also play an equally important role in lung cancer. Targeting the TLR signalling network would pave ways to the design of more reliable and effective vaccines against infectious agents and control deadly infections, desensitize allergens and reduce inflammation. Moreover, TLR agonists may act as adjuvants by increasing the efficiency of cancer vaccines, thereby contributing their role in treatment of lung cancer too. Overall, TLRs present a compelling and expeditiously bolstered area of research and addressing their signalling events would be of significant use in pulmonary diseases.

Toll-like receptor 2 and Toll-like receptor 4 exhibit distinct regulation of cancer cell stemness mediated by cell death-induced high-mobility group box 1

BACKGROUND

High-mobility group box 1 (HMGB1), a common extracellular damage associated molecular pattern molecule, is overexpressed in several solid tumors including pancreatic carcinoma. We previously observed that radiotherapy induced dying cells secrete HMGB1 and accelerate pancreatic carcinoma progression through an unclear mechanism.

METHODS

Using the Millicell system as an in vitro co-culture model, we performed quantitative reverse transcriptase-polymerase chain reaction, western blot and sphere forming ability analyses to access the effect of dying-cell-derived HMGB1 on CD133+ cancer cell stemness in vitro and in vivo. Interactions between HMGB1 and Toll-like receptor 2(TLR2)/TLR4 were studied by co- immunoprecipitation. Western blot and short-hairpin RNA-based knockdown assays were conducted to detect HMGB1 and TLR2/TLR4 signaling activity.

FINDINGS

Radiation-associated, dying-cell-derived HMGB1 maintained stemness and contributed to CD133+ cancer stem cell self-renewal in vitro and in vivo. In overexpressing and silencing experiments, we demonstrated that the process was activated by TLR2 receptor, whereas TLR4 antagonized HMGB1-TLR2 signaling. Wnt/β-catenin signaling supported the HMGB1-TLR2 mediated stemness of CD133+ cancer cells.

INTERPRETATION

Our results show how irradiation-induced cell death might enhance the stemness of resident cancer cells, and indicate HMGB1-TLR2 signaling as a potential therapeutic target for preventing pancreatic cancer recurrence.

HIV-1-neutrophil interactions trigger neutrophil activation and Toll-like receptor expression

Although neutrophils are the first-line of host defense against infection and express a wide number of pattern recognition receptors (PRRs), the function of these PRRs, including Toll-like receptors (TLRs), in HIV-1 infection remains unclear. TLRs play an important role in innate immunity, and while their involvement in viral immune pathogenesis was recently proposed, little is known about their expression and function during the neutrophil response to HIV-1 exposure. Here, we have shown that freshly isolated human neutrophils from healthy donors exhibited altered TLR expression, which may affect their function, after being challenged with HIV-1, alone or in the presence of TLR agonists. TLRs may promote neutrophil activation, pro-inflammatory cytokine secretion, and the production of reactive oxygen species. To our knowledge, this study is the first demonstration of functional TLR expression on neutrophils in response to HIV-1 treatment, suggesting a possible neutrophil/HIV-1 interaction through TLRs. Although additional studies are required to confirm the function of TLRs in neutrophils, our data clearly suggest that they play a role in the regulation of innate immunity by neutrophils, which could be engaged in HIV-1 pathogenesis or host defense.

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.

Downregulation of Lung Toll-Like Receptor 4 Could Effectively Attenuate Liver Transplantation-Induced Pulmonary Damage at the Early Stage of Reperfusion

Acute lung injury (ALI) is a severe complication of orthotopic liver transplantation (OLT) with unclear underline mechanism. Toll-like receptor 4 (TLR4) has been identified as a key receptor mediating inflammation. We hypothesized that TLR4-mediated pulmonary inflammation may contribute to development of ALI during OLT. Patients with or without ALI were observed for serum cytokines and expression of TLR4 on peripheral blood polymorphonuclear leukocytes (PMNs). Next, rats which underwent orthotopic autologous liver transplantation (OALT) were divided into sham and model groups. Pulmonary function and the level of TLR4 expression and cytokines were analyzed. Furthermore, the role of TLR4 in OALT-mediated ALI was assessed in rats treated with TLR4-siRNA before OALT. The PMNs TLR4 expression and the serum TNF-α and IL-β level were higher in patients with ALI than those with non-ALI. Interestingly, lung TLR4 expression was significantly increased after 8 hours of OALT with increased levels of TNF-α and IL-β, which lead to lung pathological damage and an increase of lung myeloperoxidase content. Moreover, knockdown of TLR4 reduced lung cytokines release and reversed the above pathologic changes after OALT and finally improved rats' survival rate. In conclusion, TLR4 overexpression, potentially by stimulating proinflammatory cytokine overproduction, contributes to the development of ALI after OLT.

DUOX-Mediated Signaling Is Not Required for LPS-Induced Neutrophilic Response in the Airways

Oxidant production from DUOX1 has been proposed to lead to neutrophil recruitment into the airways when lung homeostasis is compromised. The objective of this study was to determine whether DUOX-derived hydrogen peroxide is required for LPS-induced neutrophil recruitment, using a functional DUOX knock out mouse model. We found that LPS induced profound neutrophilic lung inflammation in both Duoxa+/+ and Duoxa-/- mice between 3h and 24h. Duoxa-/- mice had significantly higher neutrophil influx 24h after LPS instillation despite similar cytokine levels (KC, MIP-2, or TGF-α) between the two groups. These findings suggest that LPS-TLR-4-induced KC or MIP-2 cytokine induction and subsequent neutrophil recruitment in the airway does not require DUOX-derived hydrogen peroxide from airway epithelium.

PECAM-1 and caveolae form the mechanosensing complex necessary for NOX2 activation and angiogenic signaling with stopped flow in pulmonary endothelium

We showed that stop of flow triggers a mechanosignaling cascade that leads to the generation of reactive oxygen species (ROS); however, a mechanosensor coupled to the cytoskeleton that could potentially transduce flow stimulus has not been identified. We showed a role for KATP channel, caveolae (caveolin-1), and NADPH oxidase 2 (NOX2) in ROS production with stop of flow. Based on reports of a mechanosensory complex that includes platelet endothelial cell adhesion molecule-1 (PECAM-1) and initiates signaling with mechanical force, we hypothesized that PECAM-1 could serve as a mechanosensor in sensing disruption of flow. Using lungs in situ, we observed that ROS production with stop of flow was significantly reduced in PECAM-1(-/-) lungs compared with lungs from wild-type (WT) mice. Lack of PECAM-1 did not affect NOX2 activation machinery or the caveolin-1 expression or caveolae number in the pulmonary endothelium. Stop of flow in vitro triggered an increase in angiogenic potential of WT pulmonary microvascular endothelial cells (PMVEC) but not of PECAM-1(-/-) PMVEC. Obstruction of flow in lungs in vivo showed that the neutrophil infiltration as observed in WT mice was significantly lowered in PECAM-1(-/-) mice. With stop of flow, WT lungs showed higher expression of the angiogenic marker VEGF compared with untreated (sham) and PECAM-1(-/-) lungs. Thus PECAM-1 (and caveolae) are parts of the mechanosensing machinery that generates superoxide with loss of shear; the resultant ROS potentially drives neutrophil influx and acts as an angiogenic signal.

Recombinant human lactoferrin induces human and mouse dendritic cell maturation via Toll-like receptors 2 and 4

Lactoferrin, a key component of innate immunity, is a cationic monomeric 80-kDa glycoprotein of the transferrin superfamily. Recombinant human lactoferrin, known as talactoferrin (TLF), induces a distinct functional maturation program in human dendritic cells (DCs) derived from peripheral blood monocytes. However, the receptors and molecular mechanisms involved in this induction have not been fully determined. By exploiting genome-wide transcription profiling of immature DCs, TNF-α- and IL-1β-matured DCs (m-DCs), and TLF-matured DCs (TLF-DCs), we have detected a set of transcripts specific for m-DCs and one specific for TLF-DCs. Functional network reconstruction highlighted, as expected, the association of m-DC maturation with IL-1β, TNF-α, and NF-κB, whereas TLF-DC maturation was associated with ERK and NF-κB. This involvement of ERK and NF-κB transduction factors suggests direct involvement of Toll-like receptors (TLRs) in TLF-induced maturation. We have used MyD88 inhibition and siRNA silencing TLRs on human DCs and mouse TLR-2-knockout cells, to show that TLF triggers the maturation of both human and mouse DCs through TLR-2 and TLR-4.

Eritoran attenuates tissue damage and inflammation in hemorrhagic shock/trauma

BACKGROUND

Severe injury and associated hemorrhagic shock lead to an inflammatory response and subsequent increased tissue damage. Numerous reports have shown that injury-induced inflammation and the associated end-organ damage is driven by Toll-like receptor 4 (TLR4) activation via damage-associated molecular patterns. We examined the effectiveness of Eritoran tetrasodium (E5564), an inhibitor of TLR4 function, in reducing inflammation induced during hemorrhagic shock with resuscitation (HS/R) or after peripheral tissue injury (bilateral femur fracture, BFF).

MATERIAL AND METHODS

Mice underwent HS/R or BFF with or without injection of Eritoran (5 mg/kg body weight) or vehicle control given before, both before and after, or only after HS/R or BFF. Mice were sacrificed after 6 h and plasma and tissue cytokines, liver damage (histology; aspartate aminotransferase/alanine aminotransferase), and inflammation (NF-κB) and gut permeability were assessed.

RESULTS

In HS/R Eritoran significantly reduced liver damage (values ± SEM: alanine aminotransferase 9910 ± 3680 U/L versus 1239 ± 327 U/L and aspartate aminotransferase 5863 ± 2000 U/L versus 1246 ± 243 U/L, P < 0.01) at 6 h compared with control when given just before HS and again just prior to resuscitation. Eritoran administration also led to lower IL-6 levels in plasma and liver and less NF-κB activation in liver. Increases in gut barrier permeability induced by HS/R were also prevented with Eritoran. Eritoran similarly diminished BFF-mediated systemic inflammatory responses.

CONCLUSION

These data suggest Eritoran can inhibit tissue damage and inflammation induced via TLR4/myeloid differentiation factor 2 signaling from damage-associated molecular patterns released during HS/R or BFF. Eritoran may represent a promising therapeutic for trauma patients to prevent multiple organ failure.

Abnormal expression of Toll-like receptor 4 is associated with susceptibility to ethanol-induced gastric mucosal injury in mice

BACKGROUND AND AIMS

Toll-like receptor 4 (TLR4) contributes to ethanol-induced gastric mucosal injury. This study aimed to determine its precise role in this pathogenic state and the related signaling pathway.

METHODS

Ethanol-induced gastric mucosal injury models were generated in TLR4(-/-) mice (C3H/HeJ: point mutation; C57BL/10ScNJ: gene deletion), their respective TLR4(+/+) wild-type counterparts, and heterozygous TLR4(+/-) mice. Lipopolysaccharide (LPS) or pyrrolidine dithiocarbamate (PDTC) was injected intraperitoneally 1 h or 30 min before ethanol administration. At 1 h post-ethanol treatment, gastric or serum specimens were evaluated.

RESULTS

Ethanol intra-gastric administration induced significant gastric mucosal injury in all mice, but the damaged area was larger in TLR4(-/-) mice. LPS preconditioning and up-regulated TLR4 expression led to significantly larger areas of gastric mucosal damage. Upon ethanol administration, TLR4(+/+), and not TLR4(-/-), mice showed significant increases in TLR4, myeloid differentiation factor 88 (MyD88), cytoplasmic high mobility group box 1 (HMGB1), and nuclear factor-kappa B p65 (NF-κB p65). PDTC pretreatment significantly attenuated the ethanol-induced gastric mucosal damaged areas, inhibited nuclear NF-κB p65 expression, and suppressed HMGB1 translocation out of the nucleus. In addition, PDTC pretreatment reduced ethanol-stimulated expression of the inflammatory modulators, interleukin-1β (IL-1β) and tumor necrosis factor-alpha (TNF-α), in serum.

CONCLUSIONS

Both deficient and excessive expression of TLR4 promotes ethanol-induced gastric mucosal injury. The underlying mechanism involves the MyD88/NF-κB signaling pathway and the HMGB1, TLR4 activator ligand. The increased expression of HMGB1 may lead to increased secretion and binding to TLR4, further stimulating the TLR4/MyD88/NF-κB signaling pathway and aggravating the ethanol-induced gastric mucosal injury.

Time dependency and topography of hepatic nuclear factor κB activation after hemorrhagic shock and resuscitation in mice

The leading causes of death in people aged 1 to 44 years are unintentional injuries with associated hemorrhagic shock. Hemorrhagic shock followed by resuscitation (H/R) activates the nuclear factor κB (NF-κB) pathway. To further address the association between liver damage and NF-κB activation, we analyzed the H/R-induced activation of NF-κB using cis-NF-κB reporter gene mice. In these mice, the expression of green fluorescent protein (GFP) is linked to the activation of NF-κB, and therefore tracing of GFP colocalizes NF-κB activation. Mice were hemorrhaged to a mean arterial blood pressure of 30mmHg for 90 min, followed by resuscitation. Six, 14, or 24 h after resuscitation, mice were killed. Compared with sham-operated mice, H/R led to a profound hepatic and cellular damage as measured by aspartate aminotransferase, creatine kinase, and lactate dehydrogenase levels, which was accompanied by an elevation in interleukin 6 levels and hepatic leukocyte infiltration. Interleukin 10 levels in plasma were elevated 6 h after H/R. Using serial liver sections, we found an association between necrotic areas, oxidative stress, and enhanced GFP-positive cells. Furthermore, enhanced GFP-positive cells surrounded areas of necrotic liver tissue, predominantly in a penumbra-like-shape pericentrally. These results elucidate spatial relationship between oxidative stress, liver necrosis, and NF-κB activation, using an in vivo approach and therefore might help to further analyze mechanisms of NF-κB activation after resuscitated blood loss.

TLR2 in pleural fluid is modulated by talc particles during pleurodesis

The aim of this study was to examine the role of TLR2 molecule in pleural space during thoracoscopic talc pleurodesis period in patients with malignant pleural effusion. We analyzed TLR2 molecule in soluble form as well as on membrane of granulocytes in pleural fluid. Pleural fluid examination was done at three intervals during pleurodesis procedure: 1st—before the thoracoscopic procedure, 2nd—2 hours after the terminating thoracoscopic procedure with talc insufflation, 3rd—24 hours after the thoracoscopic procedure. We reported significant increase of soluble TLR2 molecule in pleural fluid effusion during talc pleurodesis from preoperative value. This increase was approximately 8-fold in the interval of 24 hours. The changes on granulocyte population were quite different. The mean fluorescent intensity of membrane TLR2 molecule examined by flow cytometry on granulocyte population significantly decreased after talc exposure with comparison to prethoracoscopic density. To estimate the prognostic value of TLR2 expression in pleural fluid patients were retrospectively classified into either prognostically favourable or unfavourable groups. Our results proved that patients with favourable prognosis had more than 3-fold higher soluble TLR2 level in pleural fluid early, 2 hours after talc pleurodesis intervention.

Activation of toll-like receptor 4 is necessary for trauma hemorrhagic shock-induced gut injury and polymorphonuclear neutrophil priming

Interactions of toll-like receptors (TLRs) with nonmicrobial factors play a major role in the pathogenesis of early trauma-hemorrhagic shock (T/HS)-induced organ injury and inflammation. Thus, we tested the hypothesis that TLR4 mutant (TLR4 mut) mice would be more resistant to T/HS-induced gut injury and polymorphonuclear neutrophil (PMN) priming than their wild-type littermates and found that both were significantly reduced in the TLR4 mut mice. In addition, the in vivo and ex vivo PMN priming effect of T/HS intestinal lymph observed in the wild-type mice was abrogated in TLR4 mut mice as well the TRIF mut-deficient mice and partially attenuated in Myd88 mice, suggesting that TRIF activation played a more predominant role than MyD88 in T/HS lymph-induced PMN priming. Polymorphonuclear neutrophil depletion studies showed that T/HS lymph-induced acute lung injury was PMN dependent, because lung injury was totally abrogated in PMN-depleted animals. Because the lymph samples were sterile and devoid of endotoxin or bacterial DNA, we investigated whether the effects of T/HS lymph was related to endogenous nonmicrobial TLR4 ligands. High-mobility group box 1 protein 1, heat shock protein 70, heat shock protein 27, and hyaluronic acid all have been implicated in ischemia-reperfusion-induced tissue injury. None of these "danger" proteins appeared to be involved, because their levels were similar between the sham and shock lymph samples. In conclusion, TLR4 activation is important in T/HS-induced gut injury and in T/HS lymph-induced PMN priming and lung injury. However, the T/HS-associated effects of TLR4 on gut barrier dysfunction can be uncoupled from the T/HS lymph-associated effects of TLR4 on PMN priming.

Functional properties of granulocytes after thermal injury

Thermal injury, as well as other forms of severe trauma, induces simultaneous hyper- and anti-inflammatory response. While data about decreased number and responsiveness of T lymphocytes are largely consistent, reports concerning granulocytes following trauma are contradictory. Contrary to the evidence on the increased accumulation of granulocytes in the lungs or liver, the results from our laboratory demonstrated reduced granulocyte influx in the wound that heals in conditions of thermal injury. We also demonstrated evidence that indicates impaired signal transduction in granulocytes following thermal injury, as well as their divergent response regarding the adhesiveness, oxidative burst and nitric oxide production at the wound site.

Creating a pro-survival and anti-inflammatory phenotype by modulation of acetylation in models of hemorrhagic and septic shock

Shock, regardless of etiology, is characterized by decreased tissue perfusion resulting in cell death, organ dysfunction, and poor survival. Current therapies largely focus on restoring tissue perfusion through resuscitation but have failed to address the specific cellular dysfunction caused by shock. Acetylation is rapidly emerging as a key mechanism that regulates the expression of numerous genes (epigenetic modulation through activation of nuclear histone proteins), as well as functions of multiple cytoplasmic proteins involved in key cellular functions such as cell survival, repair/healing, signaling, and proliferation. Cellular acetylation can be increased immediately through the administration of histone deacetylase inhibitors (HDACI). A series of studies have been performed using: (1) cultured cells; (2) single-organ ischemia-reperfusion injury models; (3) rodent models of lethal septic and hemorrhagic shock; (4) swine models of lethal hemorrhagic shock and multi-organ trauma; and (5) tissues from severely injured trauma patients, to fully characterize the changes in acetylation that occur following lethal insults and in response to treatment with HDACI. These data demonstrate that: (1) shock causes a decrease in acetylation of nuclear and cytoplasmic proteins; (2) hypoacetylation can be rapidly reversed through the administration of HDACI; (3) normalization of acetylation prevents cell death, decreases inflammation, attenuates activation of pro-apoptotic pathways, and augments pro-survival pathways; (4) the effect of HDACI significantly improves survival in lethal models of septic shock, hemorrhagic shock, and complex poly-trauma without need for conventional fluid resuscitation or blood transfusion; and (5) improvement in survival is not due to better resuscitation but due to an enhanced ability of cells to tolerate lethal insults.As different models of hemorrhagic or septic shock have specific strengths and limitations, this chapter will summarize our attempts to create "pro-survival and anti-inflammatory phenotype" in various models of hemorrhagic shock and septic shock.

Burn-induced acute lung injury requires a functional Toll-like receptor 4

The role of the Toll-like receptor 4 (TLR4), a component of the innate immune system, in the development of burn-induced acute lung injury (ALI) has not been completely defined. Recent data suggested that an intact TLR4 plays a major role in the development of organ injury in sterile inflammation. We hypothesized that burn-induced ALI is a TLR4-dependent process. Male C57BL/6J (TLR4 wild-type [WT]) and C57BL/10ScN (TLR4 knockout [KO]) mice were subjected to a 30% total body surface area steam burn. Animals were killed at 6 and 24 h after the insult. Lung specimens were harvested for histological examination after hematoxylin-eosin staining. In addition, lung myeloperoxidase (MPO) and intercellular adhesion molecule 1 immunostaining was performed. Lung MPO was measured by an enzymatic assay. Total lung keratinocyte-derived chemoattractant (IL-8) content was measured by enzyme-linked immunosorbent assay. Western blot was performed to quantify phosphorylated IκBα, phosphorylated nuclear factor κB p65 (NF-κBp65), and high mobility group box 1 expression. Acute lung injury, characterized by thickening of the alveolar-capillary membrane, hyaline membrane formation, intraalveolar hemorrhage, and neutrophil infiltration, was seen in WT but not KO animals at 24 h. Myeloperoxidase and intercellular adhesion molecule 1 immunostaining of KO animals was also similar to sham but elevated in WT animals. In addition, a reduction in MPO enzymatic activity was observed in KO mice as well as a reduction in IL-8 levels compared with their WT counterparts. Burn-induced ALI develops within 24 h after the initial thermal insult in our model. Toll-like receptor 4 KO animals were clearly protected and had a much less severe lung injury. Our data suggest that burn-induced ALI is a TLR4-dependent process.

A new model of severe hemorrhagic shock in rats

We here introduce a fixed-pressure model of hemorrhagic shock in rats that maximizes effects on mean arterial blood pressure (MAP) during shock and yet maintains high reproducibility and controllability. The MAP of rats was adjusted to 25 to 30 mm Hg by blood withdrawals during 30 min. After a shock period of 60 min, rats were resuscitated either with lactated Ringer solution (LR) only or with the collected blood 3-fold diluted with LR (LR + blood) and monitored for further 150 min. Throughout the experiment, vital parameters and plasma marker enzyme activities and creatinine concentration were assessed. Thereafter, liver, kidneys, small intestine, heart, and lung were harvested and evaluated histopathologically. Vital parameters, plasma marker enzyme activities, creatinine concentration, and histopathology indicated pronounced but reliable and reproducible systemic effects and marked organ damage due to hemorrhagic shock and resuscitation. In contrast to rats that received LR + blood, which survived the postresuscitation period, rats receiving LR only invariably died shortly after resuscitation. The hemorrhagic shock model we present here maximally affects MAP and yet is highly reproducible in rats, allowing the study of various aspects of hemorrhagic shock and resuscitation under clinically relevant conditions.

Life or death? A physiogenomic approach to understand individual variation in responses to hemorrhagic shock

Severe hemorrhage due to trauma is a major cause of death throughout the world. It has often been observed that some victims are able to withstand hemorrhage better than others. For decades investigators have attempted to identify physiological mechanisms that distinguish survivors from nonsurvivors for the purpose of providing more informed therapies. As an alternative approach to address this issue, we have initiated a research program to identify genes and genetic mechanisms that contribute to this phenotype of survival time after controlled hemorrhage. From physiogenomic studies using inbred rat strains, we have demonstrated that this phenotype is a heritable quantitative trait, and is therefore a complex trait regulated by multiple genes. Our work continues to identify quantitative trait loci as well as potential epigenetic mechanisms that might influence survival time after severe hemorrhage. Our ultimate goal is to improve survival to traumatic hemorrhage and attendant shock via regulation of genetic mechanisms and to provide knowledge that will lead to genetically-informed personalized treatments.

A dynamic view of trauma/hemorrhage-induced inflammation in mice: principal drivers and networks

BACKGROUND

Complex biological processes such as acute inflammation induced by trauma/hemorrhagic shock/ (T/HS) are dynamic and multi-dimensional. We utilized multiplexing cytokine analysis coupled with data-driven modeling to gain a systems perspective into T/HS.

METHODOLOGY/PRINCIPAL FINDINGS

Mice were subjected to surgical cannulation trauma (ST) ± hemorrhagic shock (HS; 25 mmHg), and followed for 1, 2, 3, or 4 h in each case. Serum was assayed for 20 cytokines and NO(2) (-)/NO(3) (-). These data were analyzed using four data-driven methods (Hierarchical Clustering Analysis [HCA], multivariate analysis [MA], Principal Component Analysis [PCA], and Dynamic Network Analysis [DyNA]). Using HCA, animals subjected to ST vs. ST + HS could be partially segregated based on inflammatory mediator profiles, despite a large overlap. Based on MA, interleukin [IL]-12p40/p70 (IL-12.total), monokine induced by interferon-γ (CXCL-9) [MIG], and IP-10 were the best discriminators between ST and ST/HS. PCA suggested that the inflammatory mediators found in the three main principal components in animals subjected to ST were IL-6, IL-10, and IL-13, while the three principal components in ST + HS included a large number of cytokines including IL-6, IL-10, keratinocyte-derived cytokine (CXCL-1) [KC], and tumor necrosis factor-α [TNF-α]. DyNA suggested that the circulating mediators produced in response to ST were characterized by a high degree of interconnection/complexity at all time points; the response to ST + HS consisted of different central nodes, and exhibited zero network density over the first 2 h with lesser connectivity vs. ST at all time points. DyNA also helped link the conclusions from MA and PCA, in that central nodes consisting of IP-10 and IL-12 were seen in ST, while MIG and IL-6 were central nodes in ST + HS.

CONCLUSIONS/SIGNIFICANCE

These studies help elucidate the dynamics of T/HS-induced inflammation, complementing other forms of dynamic mechanistic modeling. These methods should be applicable to the analysis of other complex biological processes.

The role of toll-like receptors in acute and chronic lung inflammation

By virtue of its direct contact with the environment, the lung is constantly challenged by infectious and non-infectious stimuli that necessitate a robust yet highly controlled host response coordinated by the innate and adaptive arms of the immune system. Mammalian Toll-like receptors (TLRs) function as crucial sentinels of microbial and non-infectious antigens throughout the respiratory tract and mediate host innate immunity. Selective induction of inflammatory responses to harmful environmental exposures and tolerance to innocuous antigens are required to maintain tissue homeostasis and integrity. Conversely, dysregulated innate immune responses manifest as sustained and self-perpetuating tissue damage rather than controlled tissue repair. In this article we review aspects of Toll-like receptor function that are relevant to the development of acute lung injury and chronic obstructive lung diseases as well as resistance to frequently associated microbial infections.

Association of Toll-like receptor signaling and reactive oxygen species: a potential therapeutic target for posttrauma acute lung injury

Acute lung injury (ALI) frequently occurs in traumatic patients and serves as an important component of systemic inflammatory response syndrome (SIRS). Hemorrhagic shock (HS) that results from major trauma promotes the development of SIRS and ALI by priming the innate immune system for an exaggerated inflammatory response. Recent studies have reported that the mechanism underlying the priming of pulmonary inflammation involves the complicated cross-talk between Toll-like receptors (TLRs) and interactions between neutrophils (PMNs) and alveolar macrophages (AMvarphi) as well as endothelial cells (ECs), in which reactive oxygen species (ROS) are the key mediator. This paper summarizes some novel mechanisms underlying HS-primed lung inflammation focusing on the role of TLRs and ROS, and therefore suggests a new therapeutic target for posttrauma ALI.