Interacting neuroendocrine and innate and acquired immune pathways regulate neutrophil mobilization from bone marrow following hemorrhagic shock

Adrenergic orchestration of immune cell dynamics in response to cardiac stress

Immune cells contribute approximately 5-10 % of the heart's total cell population, including several myeloid cell and lymphocyte cell subsets, which, despite their relatively small percentages, play important roles in cardiac homeostasis and remodeling responses to various forms of injury and long-term stress. Pathological cardiac stress activates the sympathetic nervous system (SNS), resulting in the release of the catecholamines epinephrine and norepinephrine either systemically or from sympathetic nerve terminals within various lymphoid organs. Acting at α- or β-adrenergic receptors (αAR, βAR), catecholamines regulate immune cell hematopoiesis, egress and migration in response to stress. Classically, αAR stimulation tends to promote inflammatory responses while βAR stimulation has typically been shown to be immunosuppressive, though the effects can be nuanced depending on the immune cells subtype, the site of regulation and pathophysiological context. Herein, we will discuss several facets of SNS-mediated regulation of immune cells and their response to cardiac stress, including: catecholamine response to cardiovascular stress and action at their receptors, adrenergic regulation of hematopoiesis, immune cell retention and release from the bone marrow, adrenergic regulation of splenic immune cells and their retention, as well as adrenergic regulation of immune cell recruitment to the injured heart, including neutrophils, monocytes and macrophages. A particular focus will be given to βAR-mediated effects on myeloid cells in response to acute or chronic cardiac stress.

Defining spatiotemporal gene modules in liver regeneration using Analytical Dynamic Visual Spatial Omics Representation (ADViSOR)

BACKGROUND

The liver is the only organ with the ability to regenerate following surgical or toxicant insults, and partial hepatectomy serves as an experimental model of liver regeneration (LR). Dynamic changes in gene expression occur from the periportal to pericentral regions of the liver following partial hepatectomy; thus, spatial transcriptomics, combined with a novel computational pipeline (ADViSOR [Analytic Dynamic Visual Spatial Omics Representation]), was employed to gain insights into the spatiotemporal molecular underpinnings of LR.

METHODS

ADViSOR, comprising Time-Interval Principal Component Analysis and sliding dynamic hypergraphs, was applied to spatial transcriptomics data on 100 genes assayed serially through LR, including key components of the Wnt/β-catenin pathway at critical timepoints after partial hepatectomy.

RESULTS

This computational pipeline identified key functional modules demonstrating cell signaling and cell-cell interactions, inferring shared regulatory mechanisms. Specifically, ADViSOR analysis suggested that macrophage-mediated inflammation is a critical component of early LR and confirmed prior studies showing that Ccnd1, a hepatocyte proliferative gene, is regulated by the Wnt/β-catenin pathway. These findings were subsequently validated through protein localization, which provided further confirmation and novel insights into the spatiotemporal changes in the Wnt/β-catenin pathway during LR.

CONCLUSIONS

Thus, ADViSOR may yield novel insights in other complex, spatiotemporal contexts.

Sustained induction of IP-10 by MRP8/14 via the IFNβ-IRF7 axis in macrophages exaggerates lung injury in endotoxemic mice

Background

As a damage-associated molecular pattern, the myeloid-related protein 8/14 (MRP8/14) heterodimer mediates various inflammatory diseases, such as sepsis. However, how MRP8/14 promotes lung injury by regulating the inflammatory response during endotoxemia remains largely unknown. This study aims at illuminating the pathological functions of MRP8/14 in endotoxemia.

Methods

An endotoxemic model was prepared with wild-type and myeloid cell-specific Mrp8 deletion (Mrp8ΔMC) mice for evaluating plasma cytokine levels. Lung injury was evaluated by hematoxylin and eosin (H&E) staining, injury scoring and wet-to-dry weight (W/D) ratio. The dynamic profile of interferon γ (IFNγ)-inducible protein 10 (IP-10) mRNA expression induced by macrophage MRP8/14 was determined by quantitative real-time polymerase chain reaction (qPCR). Immunoblotting was used to evaluate the increase in IP-10 level induced by activation of the JAK-STAT signaling pathway. Luciferase reporter assay was performed to detect the involvement of IRF7 in Ip-10 gene transcription. In vivo air pouch experiments were performed to determine the biological function of IP-10 induced by MRP8/14.

Results

Experiments with Mrp8ΔMC mice showed that MRP8/14 promoted the production of cytokines, including IP-10, in the bronchoalveolar lavage fluid (BALF) and lung injury in endotoxic mice. The result of qPCR showed sustained expression of Ip-10 mRNA in macrophages after treatment with MRP8/14 for 12 h. Neutralization experiments showed that the MRP8/14-induced Ip-10 expression in RAW264.7 cells was mediated by extracellular IFNβ. Western blotting with phosphorylation-specific antibodies showed that the JAK1/TYK2-STAT1 signaling pathway was activated in MRP8/14-treated RAW264.7 cells, leading to the upregulation of Ip-10 gene expression. IRF7 was further identified as a downstream regulator of the JAK-STAT pathway that mediated Ip-10 gene expression in macrophages treated with MRP8/14. In vivo air pouch experiments confirmed that the IFNβ-JAK1/TYK2-STAT1-IRF7 pathway was required for chemokine (C-X-C motif) receptor 3 (CXCR3)+ T lymphocyte migration, which promoted lung injury in the context of endotoxemia.

Conclusions

In summary, our study demonstrates that MRP8/14 induces sustained production of IP-10 via the IFNβ-JAK1/TYK2-STAT1-IRF7 pathway to attract CXCR3+ T lymphocytes into lung tissues and ultimately results in lung injury by an excessive inflammatory response in the context of endotoxemia.

Inferring Tissue-Specific, TLR4-Dependent Type 17 Immune Interactions in Experimental Trauma/Hemorrhagic Shock and Resuscitation Using Computational Modeling

Trauma/hemorrhagic shock followed by resuscitation (T/HS-R) results in multi-system inflammation and organ dysfunction, in part driven by binding of damage-associated molecular pattern molecules to Toll-like Receptor 4 (TLR4). We carried out experimental T/HS-R (pseudo-fracture plus 2 h of shock followed by 0-22 h of resuscitation) in C57BL/6 (wild type [WT]) and TLR4-null (TLR4^-/-) mice, and then defined the dynamics of 20 protein-level inflammatory mediators in the heart, gut, lung, liver, spleen, kidney, and systemic circulation. Cross-correlation and Principal Component Analysis (PCA) on data from the 7 tissues sampled suggested that TLR4^-/- samples express multiple inflammatory mediators in a small subset of tissue compartments as compared to the WT samples, in which many inflammatory mediators were localized non-specifically to nearly all compartments. We and others have previously defined a central role for type 17 immune cells in human trauma. Accordingly, correlations between IL-17A and GM-CSF (indicative of pathogenic Th17 cells); between IL-17A and IL-10 (indicative of non-pathogenic Th17 cells); and IL-17A and TNF (indicative of memory/effector T cells) were assessed across all tissues studied. In both WT and TLR4^-/- mice, positive correlations were observed between IL-17A and GM-CSF, IL-10, and TNF in the kidney and gut. In contrast, the variable and dynamic presence of both pathogenic and non-pathogenic Th17 cells was inferred in the systemic circulation of TLR4^-/- mice over time, suggesting a role for TLR4 in efflux of these cells into peripheral tissues. Hypergraph analysis - used to define dynamic, cross compartment networks - in concert with PCA-suggested that IL-17A was present persistently in all tissues at all sampled time points except for its absence in the plasma at 0.5h in the WT group, supporting the hypothesis that T/HS-R induces efflux of Th17 cells from the circulation and into specific tissues. These analyses suggest a complex, context-specific role for TLR4 and type 17 immunity following T/HS-R.

Protective/reparative cytokines are suppressed at high injury severity in human trauma

Background

Trauma elicits a complex inflammatory response that, among multiple presenting factors, is greatly impacted by the magnitude of injury severity. Herein, we compared the changes in circulating levels of mediators with known proinflammatory roles to those with known protective/reparative actions as a function of injury severity in injured humans.

Methods

Clinical and biobank data were obtained from 472 (trauma database-1 (TD-1), University of Pittsburgh) and 89 (trauma database-2 (TD-2), Indiana University) trauma patients admitted to the intensive care unit (ICU) and who survived to discharge. Injury severity was estimated based on the Injury Severity Score (ISS), and this was used as both a continuous variable and for the purpose of grouping patients into severity-based cohorts. Samples within the first 24 hours were obtained from all patients and then daily up to day 7 postinjury in TD-1. Sixteen cytokines were assayed using Luminex and were analyzed using two-way analysis of variance (p<0.05).

Results

Patients with higher ISSs had longer ICU and hospital stays, days on mechanical ventilation and higher rates of nosocomial infection when compared with the mild and moderate groups. Time course analysis and correlations with ISS showed that 11 inflammatory mediators correlated positively with injury severity, consistent with previous reports. However, five mediators (interleukin (IL)-9, IL-21, IL-22, IL-23 and IL-17E/25) were suppressed in patients with high ISS and inversely correlated with ISS.

Discussion

These findings suggest that severe injury is associated with a suppression of a subset of cytokines known to be involved in tissue protection and regeneration (IL-9, IL-22 and IL-17E/25) and lymphocyte differentiation (IL-21 and IL-23), which in turn correlates with adverse clinical outcomes. Thus, patterns of proinflammatory versus protective/reparative mediators diverge with increasing ISS.

Are Markers of Systemic Inflammatory Response Useful in the Management of Patients With Neuroendocrine Neoplasms?

Given the increasing incidence of neuroendocrine neoplasms (NENs) over the past few decades, a more comprehensive knowledge of their pathophysiological bases and the identification of innovative NEN biomarkers represents an urgent unmet need. There is still little advance in the early diagnosis and management of these tumors, due to the lack of sensible and specific markers with prognostic value and ability to early detect the response to treatment. Chronic systemic inflammation is a predisposing factor for multiple cancer hallmarks, as cancer proliferation, progression and immune-evading. Therefore, the relevance of inflammatory biomarkers has been identified as critical in several types of tumours, including NENs. A bidirectional relationship between chronic inflammation and development of NENs has been reported. Neuroendocrine cells can be over-stimulated by chronic inflammation, leading to hyperplasia and neoplastic transformation. As the modulation of inflammatory response represents a therapeutic target, inflammatory markers could represent a promising new key tool to be applied in the diagnosis, the prediction of response to treatment and also as prognostic biomarkers in NENs field. The present review provides an overview of the pre-clinical and clinical data relating the potentially usefulness of circulating inflammatory markers: neutrophil-lymphocyte ratio (NLR), platelet-lymphocyte ratio (PLR), cytokines and tissue inflammatory markers (PD-1/PD-L1), in the management of NENs. (1) NLR and PLR have both demonstrated to be promising and simple to acquire biomarkers in patients with advanced cancer, including NEN. To date, in the context of NENs, the prognostic role of NLR and PLR has been confirmed in 15 and 4 studies, respectively. However, the threshold value, both for NLR and PLR, still remains not defined. (2) Cytokines seem to play a central role in NENs tumorigenesis. In particular, IL-8 levels seems to be a good predictive marker of response to anti-angiogenic treatments. (3) PD-1 and PD-L1 expression on tumour cells and on TILs, have demonstrated to be promising predictive and prognostic biomarkers in NENs. Unfortunately, these two markers have not been validated so far and further studies are needed to establish their indications and utility.

Periodontal Inflammation Primes the Systemic Innate Immune Response

The presence of periodontal diseases (PDs) often strongly correlates with other severe chronic inflammatory conditions, including cardiovascular disease, diabetes, and arthritis. However, the mechanisms through which these diseases interact are unclear. In PD, tissue and bone destruction in the mouth is driven by elevated recruitment of polymorphonuclear neutrophils (PMNs), which are primed and recruited from the circulation to sites of inflammation. We predicted that systemic effects on PMN mobilization or priming could account for the interaction between PD and other inflammatory conditions. We tested this using a mouse model of ligature-induced PD and found elevated PMN counts specifically in bone marrow, supporting a systemic effect of periodontal tissue inflammation on PMN production. In contrast, mice with induced peritonitis had elevated PMN counts in the blood, peritoneum, and colon. These elevated counts were further significantly increased when acute peritonitis was induced after ligature-induced PD in mice, revealing a synergistic effect of multiple inflammatory events on PMN levels. Flow cytometric analysis of CD marker expression revealed enhanced priming of PMNs from mice with both PD and peritonitis compared to mice with peritonitis alone. Thus, systemic factors associated with PD produce hyperinflammatory PMN responses during a secondary infection. To analyze this systemic effect in humans, we induced gingival inflammation in volunteers and also found significantly increased activation of blood PMNs in response to ex vivo stimulation, which reverted to normal following resolution of gingivitis. Together, these results demonstrate that periodontal tissue inflammation has systemic effects that predispose toward an exacerbated innate immune response. This indicates that peripheral PMNs can respond synergistically to simultaneous and remote inflammatory triggers and therefore contribute to the interaction between PD and other inflammatory conditions. This suggests larger implications of PD beyond oral health and reveals potential new approaches for treating systemic inflammatory diseases that interact with PD.

Hepatic Estrogen Sulfotransferase Distantly Sensitizes Mice to Hemorrhagic Shock-Induced Acute Lung Injury

Hemorrhagic shock (HS) is a potential life-threatening condition that may lead to injury to multiple organs, including the lung. The estrogen sulfotransferase (EST, or SULT1E1) is a conjugating enzyme that sulfonates and deactivates estrogens. In this report, we showed that the expression of Est was markedly induced in the liver but not in the lung of female mice subject to HS and resuscitation. Genetic ablation or pharmacological inhibition of Est effectively protected female mice from HS-induced acute lung injury (ALI), including interstitial edema, neutrophil mobilization and infiltration, and inflammation. The pulmonoprotective effect of Est ablation or inhibition was sex-specific, because the HS-induced ALI was not affected in male Est-/- mice. Mechanistically, the pulmonoprotective phenotype in female Est-/- mice was accompanied by increased lung and circulating levels of estrogens, attenuated pulmonary inflammation, and inhibition of neutrophil mobilization from the bone marrow and neutrophil infiltration to the lung, whereas the pulmonoprotective effect was abolished upon ovariectomy, suggesting that the protection was estrogen dependent. The pulmonoprotective effect of Est ablation was also tissue specific, as loss of Est had little effect on HS-induced liver injury. Moreover, transgenic reconstitution of human EST in the liver of global Est-/- mice abolished the pulmonoprotective effect, suggesting that it is the EST in the liver that sensitizes mice to HS-induced ALI. Taken together, our results revealed a sex- and tissue-specific role of EST in HS-induced ALI. Pharmacological inhibition of EST may represent an effective approach to manage HS-induced ALI.

Defining Early Life Stress as a Precursor for Autoimmune Disease

Childhood exposure to traumatic events, termed early life stress (ELS), is now widely recognized for causing long-term negative health effects that may not manifest until adulthood. Allostatic load (AL) describes the cumulative "wear-and-tear" effects of chronic stress on the body that may adversely affect human health by accelerating other disease processes. Recent epidemiological studies have reported higher stress levels in industrialized countries and trends of increasing prevalence in autoimmune diseases during recent decades. To elucidate mechanisms of stress-related immune dysregulation, most animal studies up to now have focused on AL and stress-triggered events occurring in adults but have not explored ELS in the context of autoimmune disorders. We have identified a current gap in understanding the impact of ELS on immune system ontogeny and its potential for priming genetically susceptible individuals who are at increased risk for autoimmune diseases later in life, through mechanisms involving neuroendocrine-immune cross talk. In this review, we highlight the intersection between stress and immune function, with a focus on ELS as consequential for increased autoimmune disorder risks later in life.

Young and Aged Blunt Trauma Patients Display Major Differences in Circulating Inflammatory Mediator Profiles after Severe Injury

BACKGROUND

Aging is accompanied by alterations in immune functions. How these changes translate into levels of circulating inflammatory mediators and network expression after severe trauma is not well characterized. To address this, we compared time-dependent changes in the levels of an extensive biomarker panel in cohorts of severely injured young and aged adults.

STUDY DESIGN

Cohorts of young (18 to 30 years old, n = 115) and aged (65 to 90 years old, n = 101) blunt trauma patients admitted to the ICU with plasma sampled 3 times within the first 24 hours and daily from day 1 to day 7 were assayed for 30 inflammatory biomarkers using Luminex analyzer. Stringently matched groups controlling for sex ratio and Injury Severity Score (n = 56 young vs n = 56 aged) were generated. Data were analyzed using 2-way ANOVA, area under the curve analysis, Dynamic Bayesian Network inference, and Dynamic Network Analysis.

RESULTS

In the overall cohorts, the young group had a significantly higher Injury Severity Score, which was associated with higher circulating levels of 18 inflammatory mediators from admission to day 7. The aged group had higher levels of C-X-C motif chemokine ligand 10/interferon gamma-induced protein 10 and C-X-C motif chemokine ligand 9/monokine induced by gamma interferon. In groups that were matched for Injury Severity Score, the significantly higher levels of interferon gamma-induced protein 10 and monokine induced by gamma interferon persisted in the aged. Dynamic Bayesian Network revealed interferon gamma-induced protein 10 and monokine induced by gamma interferon as key mediators in the aged, and Dynamic Network Analysis revealed higher network complexity in the aged.

CONCLUSIONS

These findings indicate that differences in the early inflammatory networks between young and aged trauma patients are not simply a suppression of pro-inflammatory responses in the aged, but are characterized by a major shift in the mediator profile patterns with high levels of CXC chemokines in the aged.

IL-17A - A regulator in acute inflammation: Insights from in vitro, in vivo and in silico studies

Acute inflammation following sterile injury is both inevitable and necessary to restore homeostasis and promote tissue repair. However, when excessive, inflammation can jeopardize the viability of organs and cause detrimental systemic effects. Identifying key-regulators of the immune cascade induced by surgery is vital to attenuating excessive inflammation and its subsequent effects. In this review, we describe the emerging role of IL-17A as a key-regulator in acute inflammation. The role of IL-17A in chronic disease states, such as rheumatoid arthritis, psoriasis and cancer has been well documented, but its significance in acute inflammation following surgery, sepsis, or traumatic injury has not been well studied. We aim to highlight the role of IL-17A in acute inflammation caused by trauma, liver ischemia, and organ transplantation, as well as in post-operative surgical infections. Further investigation of the roles of this cytokine in acute inflammation may stimulate novel therapies or diagnostic modalities.

Development of a Novel Backbone Cyclic Peptide Inhibitor of the Innate Immune TLR/IL1R Signaling Protein MyD88

MyD88 is a cytoplasmic adaptor protein that plays a central role in signaling downstream of the TLRs and the IL1R superfamily. We previously demonstrated that MyD88 plays a critical role in EAE, the murine model of multiple sclerosis, and showed that the MyD88 BB-loop decoy peptide RDVLPGT ameliorates EAE. We now designed and screened a library of backbone cyclized peptides based on the linear BB loop peptide, to identify a metabolically stable inhibitor of MyD88 that retains the binding properties of the linear peptide. We identified a novel cyclic peptide protein mimetic that inhibits inflammatory responses to TLR ligands, and NFκB activation in response to IL-1 activation. The inhibitor, c(MyD 4-4), is metabolically stable in comparison to the linear peptide, blocks MyD88 in a specific manner, and inhibits MyD88 function by preventing MyD88 dimerization. Finally, treatment of mice with c(MyD 4-4) reduced the severity of clinical disease in the murine EAE model of multiple sclerosis. Thus, modulation of MyD88-dependent signaling using c(MyD 4-4) is a potential therapeutic strategy to lower innate immune inflammation in autoimmune CNS disease.

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.

Altered Neuroendocrine Immune Responses, a Two-Sword Weapon against Traumatic Inflammation

During the occurrence and development of injury (trauma, hemorrhagic shock, ischemia and hypoxia), the neuroendocrine and immune system act as a prominent navigation leader and possess an inter-system crosstalk between the reciprocal information dissemination. The fundamental reason that neuroendocrinology and immunology could mix each other and permeate toward the field of traumatology is owing to their same biological languages or chemical information molecules (hormones, neurotransmitters, neuropeptides, cytokines and their corresponding receptors) shared by the neuroendocrine and immune systems. The immune system is not only modulated by the neuroendocrine system, but also can modulate the biological functions of the neuroendocrine system. The interactive linkage of these three systems precipitates the complicated space-time patterns for the courses of traumatic inflammation. Recently, compelling evidence indicates that the network linkage pattern that initiating agents of neuroendocrine responses, regulatory elements of immune cells and effecter targets for immune regulatory molecules arouse the resistance mechanism disorders, which supplies the beneficial enlightenment for the diagnosis and therapy of traumatic complications from the view of translational medicine. Here we review the alternative protective and detrimental roles as well as possible mechanisms of the neuroendocrine immune responses in traumatic inflammation.

Computational Analysis Supports an Early, Type 17 Cell-Associated Divergence of Blunt Trauma Survival and Mortality

OBJECTIVE

Blunt trauma patients may present with similar demographics and injury severity yet differ with regard to survival. We hypothesized that this divergence was due to different trajectories of systemic inflammation and utilized computational analyses to define these differences.

DESIGN

Retrospective clinical study and experimental study in mice.

SETTING

Level 1 trauma center and experimental laboratory.

PATIENTS

From a cohort of 493 victims of blunt trauma, we conducted a pairwise, retrospective, case-control study of patients who survived over 24 hours but ultimately died (nonsurvivors; n = 19) and patients who, after ICU admission, went on to be discharged(survivors; n = 19).

INTERVENTIONS

None in patients. Neutralizing anti-interleukin-17A antibody in mice.

MEASUREMENTS AND MAIN RESULTS

Data on systemic inflammatory mediators assessed within the first 24 hours and over 7 days were analyzed with computational modeling to infer dynamic networks of inflammation. Network density among inflammatory mediators in nonsurvivors increased in parallel with organ dysfunction scores over 7 days, suggesting the presence of early, self-sustaining, pathologic inflammation involving high-mobility group protein B1, interleukin-23, and the Th17 pathway. Survivors demonstrated a pattern commensurate with a self-resolving, predominantly lymphoid response, including higher levels of the reparative cytokine interleukin-22. Mice subjected to trauma/hemorrhage exhibited reduced organ damage when treated with anti-interleukin-17A.

CONCLUSIONS

Variable type 17 immune responses are hallmarks of organ damage, survival, and mortality after blunt trauma and suggest a lymphoid cell-based switch from self-resolving to self-sustaining inflammation.

Hemorrhagic shock primes for lung vascular endothelial cell pyroptosis: role in pulmonary inflammation following LPS

Hemorrhagic shock (HS) often renders patients more susceptible to lung injury by priming for an exaggerated response to a second infectious stimulus. Acute lung injury (ALI) is a major component of multiple organ dysfunction syndrome following HS and regularly serves as a major cause of patient mortality. The lung vascular endothelium is an active organ that has a central role in the development of ALI through synthesizing and releasing of a number of inflammatory mediators. Cell pyroptosis is a caspase-1-dependent regulated cell death, which features rapid plasma membrane rupture and release of proinflammatory intracellular contents. In this study, we demonstrated an important role of HS in priming for LPS-induced lung endothelial cell (EC) pyroptosis. We showed that LPS through TLR4 activates Nlrp3 (NACHT, LRR, and PYD domains containing protein 3) inflammasome in mouse lung vascular EC, and subsequently induces caspase-1 activation. However, HS induced release of high-mobility group box 1 (HMGB1), which acting through the receptor for advanced glycation end products initiates EC endocytosis of HMGB1, and subsequently triggers a cascade of molecular events, including cathepsin B release from ruptured lysosomes followed by pyroptosome formation and caspase-1 activation. These HS-induced events enhance LPS-induced EC pyroptosis. We further showed that lung vascular EC pyroptosis significantly exaggerates lung inflammation and injury. The present study explores a novel mechanism underlying HS-primed ALI and thus presents a potential therapeutic target for post-HS ALI.

Injury-induced MRP8/MRP14 stimulates IP-10/CXCL10 in monocytes/macrophages

Trauma/hemorrhagic shock is associated with morbidity and mortality due to dysregulated inflammation, which is driven in part by monocytes/macrophages stimulated by injury-induced release of damage-associated molecular pattern (DAMP) molecules. MRP8/MRP14 is an endogenous DAMP involved in various inflammatory diseases, though its mechanism of action is unclear. Circulating MRP8/MRP14 levels in human blunt trauma nonsurvivors were significantly lower than those of survivors (P < 0.001). Human monocytic THP-1 cells stimulated with MRP8/MRP14 expressed the chemokine IFN-γ inducible protein 10 (IP-10)/CXCL10. Circulating IP-10 levels in human blunt trauma patients were correlated positively with MRP8/MRP14 levels (r = 0.396, P < 0.001), and were significantly lower in trauma nonsurvivors than in survivors (P < 0.001). We therefore sought to determine the mechanisms by which MRP8/MRP14 stimulates IP-10 in monocytes/macrophages, and found that induction of IP-10 by MRP8/MRP14 required Toll-like receptor 4 and TRIF but not MyD88. Full induction of IP-10 by MRP8/MRP14 required synergy between the transcription factors NF-κB and IFN regulatory factor 3 (IRF3). The receptor for IP-10 is CXCR3, and MRP8/MRP14-induced chemotaxis of CXCR3(+) cells was dependent on the production of IP-10 in monocytes/macrophages. Furthermore, in vivo study with a mouse trauma/hemorrhagic shock model showed that administration of neutralizing antibody against MRP8 prevented activation of NF-κB and IRF3 as well as IP-10 production. Thus, the current study identified a novel signaling mechanism that controls IP-10 expression in monocytes/macrophages by MRP8/MRP14, which may play an important role in injury-induced 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.

HMGB1 in hormone-related cancer: a potential therapeutic target

High-mobility group box 1 (HMGB1) is a dynamic nuclear protein participating in transcription, chromatin remodelling, and DNA recombination and repair processes. Accumulating evidence indicates that its function now extends beyond the nucleus, notably its extracellular role in inflammation. HMGB1 is implicated as a late mediator of sepsis and is also believed to promote atherosclerosis and other inflammatory diseases such as rheumatoid arthritis and systemic lupus erythematosus. Interestingly, deregulation of HMGB1 is shown to be associated with the hallmarks of cancer development. Moreover, several clinical studies have shown that HMGB1 is a promising biomarker for a variety of cancer types. In this review, we provide novel insights into the role and mechanisms of HMGB1, in particular, to hormone-related cancers and its potential to serve as a therapeutic target.

Molecular characterization and expression analysis of Toll-like receptor 21 cDNA from Paralichthys olivaceus

Toll-like receptor (TLR) is believed to play crucial role in host defense of pathogenic microbes in innate immune system. In the present study, the full-length cDNA of Paralichthys olivaceus Toll-like receptor 21 (Po-TLR21) was cloned by homology cloning and rapid amplification of cDNA ends (RACE) technique. The Po-TLR21 cDNA sequence was 3687 bp, containing an open reading frame of 2922 bp encoding 973 amino acids. TMHMM and SMART program analysis indicated that protein contained one transmembrane domain, eighteen leucine-rich repeats (LRRs), and one Toll/IL-1 receptor homology domain (TIR). Multiple alignment analysis of the Po-TLR21 protein-coding sequence with other known TLR21 from grouper, pufferfish, zebrafish, cod, catfish, carp and chicken showed the homology of 67%, 63%, 54%, 52%, 51%, 49%, and 39%, respectively. The Po-TLR21 mRNA expression patterns were measured by real-time PCR. The results revealed that TLR21 is widely expressed in various tested healthy tissues, and highly expressed in spleen and gill. In vivo immunostimulation experiments revealed that expression of TLR21 is modulated by Vibrio anguillarum (V. anguillarum), CpG oligodeoxynucleotides (CpG ODN) and poly I:C. Moreover, the inhibitor of homodimerization of myeloid differentiation factor 88 (MyD88) could significantly reduce the up-regulation of TLR21, MyD88, and tumor necrosis factor (TNF) expression in CpG ODN or poly I:C-treated head kidney cells in vitro. These results indicate that TLR21 may be involved in the pathogen recognition in the early innate immune.

High-mobility group protein B1: a new biomarker of metabolic syndrome in obese children

INTRODUCTION

Obesity is associated with a chronic low-grade inflammation. High-mobility group box 1 protein (HMGB1) plays a key role in inflammation and immunostimulatory and chemotactic processes. The aim of the study was to assess the role of HMGB1 in obese children and to evaluate its diagnostic profile in identifying childhood obesity-related complications, such as the metabolic syndrome (MS).

PATIENTS AND METHODS

Sixty obese children were enrolled and compared with 40 healthy children (control). Homeostasis model assessment of insulin resistance (HOMA-IR), lipid profile, thyroid hormones, and pro- and anti-inflammatory peptides such as C-reactive protein (CRP), adiponectin, interleukin 6 (IL6), IL18, IL23, TNFα, resistin, and HMGB1 were evaluated. Receiver operating characteristics (ROC) analysis was employed to calculate the area under the curve (AUC) for HMGB1, IL6, and adiponectin to find the best cutoff values capable of identifying MS in obese children.

RESULTS

HMGB1 levels were statistically higher in obese patients than in the control group (19.4±6.8 vs 3.7±1.2 ng/ml; P<0.0001). In obese patients, IL18, IL6, and resistin levels were significantly high, while adiponectin levels were low. At multivariate analysis, HMGB1 was found to be independently correlated with BMI, IL23, IL6, free triiodothyronine, HDL, and HOMA-IR. At ROC analysis, HMGB1 showed higher sensitivity and specificity (AUC, 0. 992; sensitivity, 94.7%; specificity, 97.5%) than IL6 and adiponectin in identifying MS in obese children.

CONCLUSION

HMGB1 plays an important role in the inflammatory process associated with childhood obesity. This peptide may be an important diagnostic marker for obesity-related complications, such as MS.

Altered leucocyte progenitor profile in human bone marrow from patients with major trauma during the recovery phase

Background

Changes in human bone marrow associated with the systemic inflammatory response to injury are little understood. It was hypothesized that major trauma results in an altered bone marrow leucocyte progenitor profile, with either uniform depletion or the balance between multipotent and committed progenitors varying, depending on whether self-renewal is favoured over differentiation.

Methods

Bone marrow aspirate and peripheral blood samples were obtained at definitive surgery in adults with pelvic fractures from blunt trauma (major trauma with Injury Severity Score (ISS) at least 18, or isolated fractures) and control patients undergoing iliac crest bone grafting. ISS, interval to surgery and transfusion in the first 24 h were recorded. Bone marrow aspirate flow cytometry was used to identify haemopoietic progenitor cells (CD34+), multipotent cells (CD34+ CD45+ CD38−) and oligopotent cells (CD34+ CD45+ CD38lo/+ and CD34+ CD45+ CD38BRIGHT(++ +) subsets). Peripheral blood levels of inflammatory markers were measured, and the ratio of immature to mature (CD35−/CD35+) granulocytes was determined.

Results

The median (range) interval between injury and sampling was 7 (1–21) and 5 (1–21) days in the major trauma and isolated fracture groups respectively. The CD34+ pool was significantly depleted in the major trauma group (P = 0·017), particularly the CD34+ CD45+ CD38BRIGHT(++ +) oligopotent pool (P = 0·003). Immature CD35− granulocytes increased in bone marrow with increasing injury severity (P = 0·024) and massive transfusion (P = 0·019), and in peripheral blood with increasing interval to surgery (P = 0·005).

Conclusion

Major blunt trauma resulted in changes in the bone marrow CD34+ progenitor pool. At the point in recovery when these samples were obtained, oligopotent progenitors were lost from the bone marrow, with continued release of immature cells.

Role of macrophages in mobilization of hematopoietic progenitor cells from bone marrow after hemorrhagic shock

The release of hematopoietic progenitor cells (HPCs) from bone marrow (BM) is under tight homeostatic control. Under stress conditions, HPCs migrate from BM and egress into circulation to participate in immune response, wound repair, or tissue regeneration. Hemorrhagic shock with resuscitation (HS/R), resulting from severe trauma and major surgery, promotes HPC mobilization from BM, which, in turn, affects post-HS immune responses. In this study, we investigated the mechanism of HS/R regulation of HPC mobilization from BM. Using a mouse HS/R model, we demonstrate that the endogenous alarmin molecule high-mobility group box 1 mediates HS/R-induced granulocyte colony-stimulating factor secretion from macrophages (Mϕ in a RAGE [receptor for advanced glycation end products] signaling-dependent manner. Secreted granulocyte colony-stimulating factor, in turn, induces HPC egress from BM. We also show that activation of β-adrenergic receptors on Mϕ by catecholamine mediates the HS/R-induced release of high-mobility group box 1. These data indicate that HS/R, a global ischemia-reperfusion stimulus, regulates HPC mobilization through a series of interacting pathways that include neuroendocrine and innate immune systems, in which Mϕ play a central role.

The Effects of Isoproterenol and Propranolol on Cytokine Profile Secretion by Cultured Tumor-infiltrating Lymphocytes Derived from Colorectal Cancer Patients

OBJECTIVE

Anti-tumor immunity and cytokine profiles have important roles in the development of cancer. Norepinephrine (NE) release due to sympathetic activation leads to a Th2 deviation via the beta-2 adrenergic receptor Beta-2 adrenergic receptor (β-2AR) and could increase cancer progression. This study intends to determine the effects of isoproterenol (ISO; beta-agonist) and propranolol (PRO; beta-antagonist) on the production of IFN-γ, IL-4, and IL-17. Cytokine levels have been examined in tumor-infiltrating lymphocytes (TILs) and peripheral blood mononuclear cells (PBMCs) of patients with colorectal cancer (CRC). The β-2AR expression on lymphocyte subsets was also assessed.

MATERIALS AND METHODS

In this experimental study, TILs were isolated from fresh CRC tissue and patient PBMCs were obtained just prior to surgery. The cells were cultured in medium for 72 hours. Concomitantly, cells were stimulated with 10 µg/ml phytohemagglutinin (PHA) alone or in the presence of either 1 µmol/L of PRO or 1 µmol/L ISO. The concentration of cytokines in the supernatants was measured by ELISA. Three-color flow cytometry was used to determine the expression of β-2AR on the lymphocyte subsets. Statistical analyses were performed via paired or independent t-test.

RESULTS

Levels of IFN-γ, IL-4 and IL-17 were elevated after PHA-stimulation of PBMCs and TILs. However, the elevation of IFN-γ and IL-17 production by TILs in response to PHA was significantly lower than PBMCs. In the presence of ISO, the IFN-γ/IL-4 ratio reduced in all groups, but this reduction was very low in TILs. Interestingly, the effects of PRO on cytokine production were, at least partially, comparable to those of ISO. Depressed levels of β-2AR expression were demonstrated on CD4+IFN-γ+ and CD4+IL-17+ lymphocytes in patients' PBMCs and TILs.

CONCLUSION

This study has demonstrated the effects of ISO and PRO on cytokine production by TILs and determined β-2AR expression on these cells. ISO failed to induce a shift toward the expected Th2 cytokine profile in CRC patients' TILs, which might be due to the downregulation of β-2AR expression on TILs. Additionally, in this study, PRO induced a shift to a Th2 profile in PBMCs.

Early activation of the inflammatory response in the liver of brain-dead non-human primates

BACKGROUND

Donor brain death (BD) triggers a systemic inflammatory response that reduces organ quality and increases immunogenicity of the graft. We characterized the early innate immune response induced by BD in the liver and peripheral blood of hemodinamically stable non-human primates (NHP).

METHODS

Rhesus macaques were assigned to either brain death or control group. BD was induced by inflation of a subdurally placed catheter and confirmed clinically and by cerebral angiography. Animals were monitored for 6 h after BD and managed to maintain hemodynamic stability.

RESULTS

Cortisol, epinephrine, nor-epinephrine, and IL-6 levels were elevated immediately after BD induction. Neutrophils and monocytes significantly increased in circulation following BD induction, while dendritic cells were decreased at 6 h post-induction. Flow cytometry revealed increased expression of chemokine receptors CxCR1, CxCR2, CCR2, and CCR5 in peripheral blood leukocytes from NHP subjected to BD. Microarray analysis demonstrated a significant up-regulation of genes related to innate inflammatory responses, toll-like receptor signaling, stress pathways, and apoptosis/cell death in BD subjects. Conversely, pathways related to glucose, lipid, and protein metabolism were down-regulated. In addition, increased expression of SOCS3, S100A8/A9, ICAM-1, MHC class II, neutrophil accumulation, and oxidative stress markers (carboxy-methyl-lysine and hydroxynonenal) were detected by immunoblot and immunohistochemistry.

CONCLUSIONS

Activation of the innate immune response after BD in association with a down-regulation of genes associated with cell metabolism pathways in the liver. These findings may provide a potential explanation for the reduced post-transplant function of organs from brain dead donors. In addition, this work suggests potential novel targets to improve donor management strategies.

Enhanced HMGB1 expression may contribute to Th17 cells activation in rheumatoid arthritis

Rheumatoid arthritis(RA) is a common autoimmune disease associated with Th17 cells, but what about the effect of high-mobility group box chromosomal protein 1 (HMGB1) and the relationship between Th17-associated factors and HMGB1 in RA remains unknown. In the present study, we investigated the mRNA levels of HMGB1, RORγt, and IL-17 in peripheral blood mononuclear cells (PBMCs) from patients with rheumatoid arthritis by quantitative real-time PCR (RT-qPCR), and the concentrations of HMGB1, IL-17, and IL-23 in plasma were detected by ELISA. And then, the effect of HMGB1 on Th17 cells differentiation was analyzed in vitro. Our clinical studies showed that the mRNAs of HMGB1, RORγt, and IL-17 in patients were higher than that in health control (P < 0.05), especially in active RA patients (P < 0.05). The plasma HMGB1, IL-17, and IL-23 in RA patients were also higher than that in health control (P < 0.05); there was a positive correlation between the expression levels of HMGB1 and the amount of CRP, ERS, and RF in plasma. In vitro, the IL-17-produced CD4(+)T cells were increased with 100 ng/mL rHMGB1 for 12h, which indicated that the increased HMGB1 might contribute to Th17 cells activation in RA patients.

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.

Beta-blockade prevents hematopoietic progenitor cell suppression after hemorrhagic shock

BACKGROUND

Severe injury is accompanied by sympathetic stimulation that induces bone marrow (BM) dysfunction by both suppression of hematopoietic progenitor cell (HPC) growth and loss of cells via HPC mobilization to the peripheral circulation and sites of injury. Previous work demonstrated that beta-blockade (BB) given prior to tissue injury both reduces HPC mobilization and restores HPC colony growth within the BM. This study examined the effect and timing of BB on BM function in a hemorrhagic shock (HS) model.

METHODS

Male Sprague-Dawley rats underwent HS via blood withdrawal, maintaining the mean arterial blood pressure at 30-40 mm Hg for 45 min, after which the extracted blood was reinfused. Propranolol (10 mg/kg) was given either prior to or immediately after HS. Blood pressure, heart rate, BM cellularity, and death were recorded. Bone marrow HPC growth was assessed by counting colony-forming unit-granulocyte-, erythrocyte-, monocyte-, megakaryocyte (CFU-GEMM), burst-forming unit-erythroid (BFU-E), and colony-forming unit-erythroid (CFU-E) cells.

RESULTS

Administration of BB prior to injury restored HPC growth to that of naïve animals (CFU-GEMM 59 ± 11 vs. 61 ± 4, BFU-E 68 ± 9 vs. 73 ± 3, and CFU-E 81 ± 35 vs. 78 ± 14 colonies/plate). Beta-blockade given after HS increased the growth of CFU-GEMM, BFU-E, and CFU-E significantly and improved BM cellularity compared with HS alone. The mortality rate was not increased in the groups receiving BB.

CONCLUSION

Administration of propranolol either prior to injury or immediately after resuscitation significantly reduced post-shock BM suppression. After HS, BB may improve BM cellularity by decreasing HPC mobilization. Therefore, the early use of BB post-injury may play an important role in attenuating the BM dysfunction accompanying HS.

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.

Epinephrine-primed murine bone marrow-derived dendritic cells facilitate production of IL-17A and IL-4 but not IFN-γ by CD4+ T cells

Sympathetic activation leading to the release of epinephrine and norepinephrine, is known as an important regulatory circuit related to immune-mediated diseases. However, questions still remain on the behavior of antigen presenting cells (APC) dictated by stress-induced sympathetic neurotransmitters. The purpose of this study was to examine the fate of bone marrow-derived dendritic cell (BMDC)-associated influences on resting CD4(+) T cell activation. We hypothesize that pre-exposure of dendritic cells (DCs) can modify the intensity of cytokine production, leading to preference in resting CD4(+) T cell activation. BMDCs were pre-treated with epinephrine for 2h followed by subsequent treatment of lipopolysaccharide (LPS). Subsequently, BMDCs were cocultured with purified CD4(+) T cells from mouse spleen in the absence or presence of anti-CD3 stimulation in epinephrine-free media. Epinephrine pre-treatment enhanced surface expression of MHCII, CD80 and CD86. Quantitative RT-PCR showed that epinephrine pre-treatment induced a significant transcriptional decrease of IL-12p40 and a significant increase of IL-12p35 and IL-23p19. In addition, β2-adrenergic-blockade was shown to reverse these effects. Epinephrine pre-treatment also induced a significant decrease of IL-12p70 and a significant increase of IL-23 and IL-10 cytokine production. Importantly, these changes corresponded with increased IL-4 and IL-17A, but not IFN-g cytokine production by CD4(+) T cells in a b2-adrenergic receptor-dependent manner. These results suggest that exposure to stress-derived epinephrine dictates dendritic cells to generate a dominant Th2/Th17 phenotype in the context of subsequent exposure to a pathogenic stimulus.

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.

Linking oxidative stress to inflammation: Toll-like receptors

Injury caused by oxidative stress occurs in many clinical scenarios involving ischemia and reperfusion such as organ transplantation, hemorrhagic shock (HS), myocardial infarction, and cerebral vascular accidents. Activation of the immune system as a result of disturbances in the redox state of cells seems to contribute to tissue and organ damage in these conditions. The link between oxidative stress and inflammatory pathways is poorly understood. Recently, Toll-like receptors (TLRs) have been shown to mediate the inflammatory response seen in experimental ischemia and reperfusion (I/R). The TLR family of receptors involved in alerting the innate immune system of danger seems to be activated by damage-associated molecular pattern molecules (DAMPs) that are released during conditions of oxidative stress. In this review, we examine the role of TLRs in various experimental models of oxidative stress such as HS and I/R. We also report on potential DAMPs that may interact with TLRs in mediating injury. Finally, potential mechanisms by which reactive oxygen species from NADPH oxidase can signal the commencement of inflammatory pathways through TLRs are explored.

Hemorrhagic shock activates lung endothelial reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase via neutrophil NADPH oxidase

The vascular endothelium plays an important role in the regulation of inflammatory responses after trauma and hemorrhage. Interactions of neutrophils with endothelial cells (ECs) contribute to the activation of specific EC responses involved in innate immunity. We have previously reported that oxidants derived from the neutrophil reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase is a critical regulator to EC activation. Our objective was to test the role of neutrophil NADPH oxidase-derived oxidants in mediating and enhancing hemorrhagic shock (HS)-induced activation of lung endothelial NADPH oxidase. Mice were subjected to HS and neutrophil depletion. The mice were also replenished with the neutrophil from NADPH oxidase-deficient mice. The resultant activation of lung NADPH oxidase was analyzed. The in vivo studies were also recapitulated with in vitro neutrophil-EC coculture system. HS induces NADPH oxidase activation in neutrophils and lung through high-mobility group box 1/Toll-like receptor 4-dependent signaling. In neutropenic mice, shock-induced NADPH oxidase activation in the lung was reduced significantly, but was restored upon repletion with neutrophils obtained from wild-type mice subjected to shock, but not with neutrophils from shock mice lacking the gp91(phox) subunit of NADPH oxidase. The findings were recapitulated in mouse lung vascular ECs cocultured with neutrophils. The data further demonstrate that neutrophil-derived oxidants are key factors mediating augmented High mobility group box 1 (HMGB1)-induced endothelial NADPH oxidase activation through a Rac1-dependent, but p38 mitogen-activated protein kinase-independent, pathway. Oxidant signaling by neutrophil NADPH oxidase is an important determinant of activation of endothelial NADPH oxidase after HS.

Targeting TLR/IL-1R signalling in human diseases

The members of Toll-like receptor/Interleukin (IL)-1 receptor (TLR/IL-1R) superfamily play a fundamental role in the immune response. These receptors detect microbial components and trigger complex signalling pathways that result in increased expression of multiple inflammatory genes. On the other hand, an aberrant activation of TLR/IL-1R signalling can promote the onset of inflammatory and autoimmune diseases, raising the interest in the development of therapeutic strategies for the control of their function. In this review, we illustrate the structural and functional features of TLR/IL-1R proteins and discuss some recent advances in the approaches undertaken to develop anti-inflammatory therapeutic drugs. In particular, we will focus on inhibitors, such as decoy peptides and synthetic mimetics, that interfere with protein-protein interactions between signalling molecules of the TLR/IL-1R superfamily. Given their central role in innate and adaptive immune responses, it is foreseen that pharmaceutical modulation of TLR/IL-1R signalling pathways by these drugs might yield clinical benefits in the treatment of inflammatory and autoimmune diseases.

Pattern recognition receptor-dependent mechanisms of acute lung injury

Acute lung injury (ALI) that clinically manifests as acute respiratory distress syndrome is caused by an uncontrolled systemic inflammatory response resulting from clinical events including sepsis, major surgery and trauma. Innate immunity activation plays a central role in the development of ALI. Innate immunity is activated through families of related pattern recognition receptors (PRRs), which recognize conserved microbial motifs or pathogen-associated molecular patterns (PAMPs). Toll-like receptors were the first major family of PRRs discovered in mammals. Recently, NACHT-leucine-rich repeat (LRR) receptors and retinoic acid-inducible gene-like receptors have been added to the list. It is now understood that in addition to recognizing infectious stimuli, both Toll-like receptors and NACHT-LRR receptors can also respond to endogenous molecules released in response to stress, trauma and cell damage. These molecules have been termed damage-associated molecular patterns (DAMPs). It has been clinically observed for a long time that infectious and noninfectious insults initiate inflammation, so confirmation of overlapping receptor-signal pathways of activation between PAMPs and DAMPs is no surprise. This review provides an overview of the PRR-dependent mechanisms of ALI and clinical implication. Modification of PRR pathways is likely to be a logical therapeutic target for ALI/acute respiratory distress syndrome.

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

Hemorrhagic shock (HS) due to major trauma predisposes the host to the development of acute lung inflammation and injury. The lung vascular endothelium is an active organ that plays a central role in the development of acute lung injury through generating reactive oxygen species and synthesizing and releasing of a number of inflammatory mediators, including leukocyte adhesion molecules that regulate neutrophils emigration. Previous study from our laboratory has demonstrated that in a setting of sepsis, toll-like receptor-4 (TLR4) signaling can induce TLR2 expression in endothelial cells (ECs), thereby increasing the cells' response to TLR2 ligands. The present study tested the hypothesis that TLR4 activation by HS and the resultant increased TLR2 surface expression in ECs might contribute to the mechanism underlying HS-augmented activation of lung ECs. The results show that high-mobility group box 1 (HMGB1) through TLR4 signaling mediates HS-induced surface expression of TLR2 in the lung and mouse lung vascular endothelial cells (MLVECs). Furthermore, the results demonstrate that HMGB1 induces activation of NAD(P)H oxidase and expression of ICAM-1 in the lung, and MLVECs sequentially depend on TLR4 in the early phase and on TLR2 in the late phase following HS. Finally, the data indicate an important role of the increased TLR2 surface expression in enhancing the activation of MLVECs and augmenting pulmonary neutrophil infiltration in response to TLR2 agonist peptidoglycan. Thus, induction of TLR2 surface expression in lung ECs, induced by HS and mediated by HMGB1/TLR4 signaling, is an important mechanism responsible for endothelial cell-mediated inflammation and organ injury following trauma and hemorrhage.