Selective roles for toll-like receptors 2, 4, and 9 in systemic inflammation and immune dysfunction following peripheral tissue injury

Resuscitative Strategies to Modulate the Endotheliopathy of Trauma: From Cell to Patient

Clinical data has supported the early use of plasma in high ratios of plasma to red cells to patients in hemorrhagic shock. The benefit from plasma seems to extend beyond its hemostatic effects to include protection to the post-shock dysfunctional endothelium. Resuscitation of the endothelium by plasma and one of its major constituents, fibrinogen, involves cell surface stabilization of syndecan-1, a transmembrane proteoglycan and the protein backbone of the endothelial glycocalyx. The pathogenic role of miRNA-19b to the endothelium is explored along with the PAK-1-mediated intracellular pathway that may link syndecan-1 to cytoskeletal protection. Additionally, clinical studies using fibrinogen and cyroprecipitate to aid in hemostasis of the bleeding patient are reviewed and new data to suggest a role for plasma and its byproducts to treat the dysfunctional endothelium associated with nonbleeding diseases is presented.

Endothelial glycocalyx in acute care surgery - what anaesthesiologists need to know for clinical practice

The endothelial glycocalyx (EG) is the thin sugar-based lining on the apical surface of endothelial cells. It has been linked to the physiological functioning of the microcirculation and has been found to be damaged in critical illness and after acute care surgery. This review aims to describe the role of EG in severely injured patients undergoing surgery, discuss specific situations (e.G. major trauma, hemorrhagic shock, trauma induced coagulopathy) as well as specific interventions commonly applied in these patients (e.g. fluid therapy, transfusion) and specific drugs related to perioperative medicine with regard to their impact on EG.EG in acute care surgery is exposed to damage due to tissue trauma, inflammation, oxidative stress and inadequate fluid therapy. Even though some interventions (transfusion of plasma, human serum albumin, hydrocortisone, sevoflurane) are described as potentially EG protective there is still no specific treatment for EG protection and recovery in clinical medicine.The most important principle to be adopted in routine clinical practice at present is to acknowledge the fragile structure of the EG and avoid further damage which is potentially related to worsened clinical outcome.

Syndecan-1 Predicts Outcome in Patients with ST-Segment Elevation Infarction Independent from Infarct-related Myocardial Injury

Syndecan-1 (sdc1) is a surface protein part of the endothelial glycocalyx (eGC). Soluble sdc1 is derived from shedding and indicates damaged eGC. We assessed the predictive value of plasma sdc1 concentrations for future cardiovascular events in acute reperfused ST-segment elevation myocardial infarction (STEMI) patients. A total of 206 patients admitted for STEMI were included in this study (29% female; age 65 ± 12 years) and followed-up for six months. Plasma samples were obtained post-intervention and analyzed for sdc1 by Enzyme-linked Immunosorbent Assay (ELISA). Primary outcome was six-month-mortality. Sdc1 did not correlate with biomarkers such as creatine kinase (CK) (r = 0.11; p = 0.01) or troponin (r = −0.12; p = 0.09), nor with infarct size (r = −0.04; p = 0.67) and myocardial salvage index (r = 0.11; p = 0.17). Sdc-1 was associated with mortality (changes per 100 ng/mL sdc-1 concentration; HR 1.08 95% 1.03–1.12; p = 0.001). An optimal cut-off was calculated at >120 ng/mL. After correction for known risk factors sdc1 >120 ng/mL was independently associated with mortality after 6 months. In our study, sdc1 is independently associated with six-month-mortality after STEMI. Combining clinical evaluation and different biomarkers assessing both infarct-related myocardial injury and systemic stress response might improve the accuracy of predicting clinical prognosis in STEMI patients.

New strategies for treatment of infectious sepsis

In this mini review, we describe the molecular mechanisms in polymicrobial sepsis that lead to a series of adverse events including activation of inflammatory and prothrombotic pathways, a faulty innate immune system, and multiorgan dysfunction. Complement activation is a well-established feature of sepsis, especially involving generation of C5a and C5b-9, along with engagement of relevant receptors for C5a. Activation of neutrophils by C5a leads to extrusion of DNA, forming neutrophil extracellular traps that contain myeloperoxidase and oxidases, along with extracellular histones. Generation of the distal complement activation product, C5b-9 (known as the membrane attack complex, MAC), also occurs in sepsis. C5b-9 activates the NLRP3 inflammasome, which damages mitochondria, together with appearance in plasma of IL-1β and IL-18. Histones are strongly proinflammatory as well as being prothrombotic, leading to activation of platelets and development of venous thrombosis. Multiorgan dysfunction is also a feature of sepsis. It is well known that septic cardiomyopathy, which if severe, can lead to death. This complication in sepsis is linked to reduced levels in cardiomyocytes of three critical proteins (SERCA2, NCX, Na⁺ /K⁺ -ATPase). The reductions in these three key proteins are complement- and histone-dependent. Dysfunction of these ATPases is linked to the cardiomyopathy of sepsis. These data suggest novel targets in the setting of sepsis in humans.

A Hypothesis for the Anti-Inflammatory and Mechanotransduction Molecular Mechanisms Underlying Acupuncture Tendon Healing

A previous study demonstrated that acupuncture increases the synthesis and reorganisation of collagen molecules in rat tendons after injury. Clinical studies have shown that acupuncture improves pain and functional activity in patients with tendinopathy. However, the molecular mechanisms underlying these effects are unknown. Recent studies have shown that acupuncture can modulate both anti-inflammatory (AI) and mechanotransduction (MT) molecular pathways. Moreover, the modulation of these pathways can increase type I collagen synthesis, which is the main factor that influences tendon biomechanical properties. Our hypothesis is that acupuncture increases synthesis and subsequent reorganisation of type I collagen during tendon healing by concomitant modulation of the Toll-like receptor-nuclear factor-κB AI pathway, the mitogen-activated protein kinases pathway and the Rho/Rac-F-actin MT pathway. Increased collagen synthesis and reorganisation requires that at least one acupoint is anatomically connected with the site of the injury because of the local tenoblast MT mechanism. Confirmation of this hypothesis will increase the knowledge of acupuncture modulation of the previously mentioned molecular pathways, and such confirmation may also help to establish the relationships between the different types of acupuncture needle stimulation and the influence of acupuncture stimuli on pathway activity levels. In addition, the downstream therapeutic effects of acupuncture therapy may be established. This hypothesis can be verified in a rat tendon healing model, and subsequent clinical protocols for tendon healing can be developed and evaluated as standalone therapies or as a component of a combination therapy.

Loss of Syndecan-1 Abrogates the Pulmonary Protective Phenotype Induced by Plasma After Hemorrhagic Shock

Syndecan-1 (Sdc1) is considered a biomarker of injury to the endothelial glycocalyx following hemorrhagic shock, with shedding of Sdc1 deleterious. Resuscitation with fresh frozen plasma (FFP) has been correlated with restitution of pulmonary Sdc1 and reduction of lung injury, but the precise contribution of Sdc1 to FFPs protection in the lung remains unclear. Human lung endothelial cells were used to assess the time and dose-dependent effect of FFP on Sdc1 expression and the effect of Sdc1 silencing on in vitro endothelial cell permeability and actin stress fiber formation. Wild-type and Sdc1 mice were subjected to hemorrhagic shock followed by resuscitation with lactated Ringers (LR) or FFP and compared with shock alone and shams. Lungs were harvested after 3 h for analysis of permeability, histology, and inflammation and for measurement of syndecan- 2 and 4 expression. In vitro, FFP enhanced pulmonary endothelial Sdc1 expression in time- and dose-dependent manners and loss of Sdc1 in pulmonary endothelial cells worsened permeability and stress fiber formation by FFP. Loss of Sdc1 in vivo led to equivalency between LR and FFP in restoring pulmonary injury, inflammation, and permeability after shock. Lastly, Sdc1 mice demonstrated a significant increase in pulmonary syndecan 4 expression after hemorrhagic shock and FFP-based resuscitation. Taken together, our findings support a key role for Sdc1 in modulating pulmonary protection by FFP after hemorrhagic shock. Our results also suggest that other members of the syndecan family may at least be contributing to FFP's effects on the endothelium, an area that warrants further investigation.

Persons with Chronic Spinal Cord Injury Have Decreased Natural Killer Cell and Increased Toll-Like Receptor/Inflammatory Gene Expression

Infections are the leading cause of death for individuals with traumatic spinal cord injury (SCI). Along with increased infection rates, inflammation is often also observed in persons with chronic SCI. Together, immunological changes post-SCI are also poised to impede neurological recovery and mediate common medical consequences of SCI, including atherogenesis and neuropathic pain. The molecular mechanisms contributing to increased infection susceptibility and inflammation in persons living with SCI are poorly understood. Here, we used tools of functional genomics to perform a pilot study to compare whole-blood gene expression in individuals with chronic SCI (≥1 year from initial injury; N = 31) and uninjured individuals (N = 26). We identified 1815 differentially expressed genes in all SCI participants and 2226 differentially expressed genes in persons with SCI rostral to thoracic level 5, compared to uninjured participants. This included marked downregulation of natural killer cell genes and upregulation of the proinflammatory Toll-like receptor signaling pathway. These data provide novel mechanistic insights into the causes underlying the symptoms of immune dysfunction in individuals living with SCI.

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.

Endothelial Glycocalyx as Biomarker for Cardiovascular Diseases: Mechanistic and Clinical Implications

INTRODUCTION

The endothelial surface layer is covered with abundant proteoglycans, of which syndecans and glycosaminoglycans are major constituents.

RECENT FINDINGS

Among the endothelial glycocalyx (eGC) constituents, syndecan-1 (sdc1) is a main component, and an elevated serum level of sdc1 may indicate the degradation of eGC. In patients with ischemic heart disease or heart failure, elevation of serum sdc1 has been associated with worsening cardiac and renal function; however, the causal relationship between degradation of eGC and clinical outcomes is unclear. Herein, we review the previous literature on eGC in cardiovascular and noncardiovascular diseases and their clinical implications.

Selective Biological Responses of Phagocytes and Lungs to Purified Histones

Histones invoke strong proinflammatory responses in many different organs and cells. We assessed biological responses to purified or recombinant histones, using human and murine phagocytes and mouse lungs. H1 had the strongest ability in vitro to induce cell swelling independent of requirements for toll-like receptors (TLRs) 2 or 4. These responses were also associated with lactate dehydrogenase release. H3 and H2B were the strongest inducers of [Ca2+]i elevations in phagocytes. Cytokine and chemokine release from mouse and human phagocytes was predominately a function of H2A and H2B. Double TLR2 and TLR4 knockout (KO) mice had dramatically reduced cytokine release induced in macrophages exposed to individual histones. In contrast, macrophages from single TLR-KO mice showed few inhibitory effects on cytokine production. Using the NLRP3 inflammasome protocol, release of mature IL-1β was predominantly a feature of H1. Acute lung injury following the airway delivery of histones suggested that H1, H2A, and H2B were linked to alveolar leak of albumin and the buildup of polymorphonuclear neutrophils as well as the release of chemokines and cytokines into bronchoalveolar fluids. These results demonstrate distinct biological roles for individual histones in the context of inflammation biology and the requirement of both TLR2 and TLR4.

THE GLYCOCALYX AND TRAUMA: A REVIEW

In the United States trauma is the leading cause of mortality among those under the age of 45, claiming approximately 192,000 lives each year. Significant personal disability, lost productivity, and long-term healthcare needs are common and contribute 580 billion dollars in economic impact each year. Improving resuscitation strategies and the early acute care of trauma patients has the potential to reduce the pathological sequelae of combined exuberant inflammation and immune suppression that can co-exist, or occur temporally, and adversely affect outcomes. The endothelial and epithelial glycocalyx has emerged as an important participant in both inflammation and immunomodulation. Constituents of the glycocalyx have been used as biomarkers of injury severity and have the potential to be target(s) for therapeutic interventions aimed at immune modulation. In this review, we provide a contemporary understanding of the physiologic structure and function of the glycocalyx and its role in traumatic injury with a particular emphasis on lung injury.

Toll-like receptor responses are suppressed in trauma ICU patients

BACKGROUND

Inflammation and activation of the innate immune system are often associated with traumatic injury and may involve alterations in toll-like receptor (TLR)-mediated responses.

METHODS

A prospective observational study was designed and conducted. Twenty-one severely injured (ISS = 16-41) trauma intensive care unit (ICU) patients and six healthy volunteers that served as controls were enrolled. Anticoagulated whole blood was collected at 2-12 d after ICU admission and incubated in the presence of media alone (baseline), zymosan (TLR2 agonist) or lipopolysaccharide (LPS; TLR4 agonist) for 3 h. Supernatant levels of inflammatory cytokines (IL-1β, IL-6, IL-10, and TNFα) were determined.

RESULTS

TLR2-mediated and TLR4-mediated activation of whole blood cell cultures from both healthy volunteers and subjects-induced elevated cytokine levels over that observed in unstimulated cultures. Baseline values of IL-6 were significantly elevated in subject cultures as compared to healthy volunteers. Healthy volunteer cultures had 2-3-fold greater levels of IL-6 and TNFα than subject cultures when stimulated with zymosan (TLR2 agonist) or LPS (TLR4 agonist). IL-1β and IL-10 levels did not differ significantly between healthy volunteers and subjects.

CONCLUSIONS

The ability of circulating leukocytes from trauma ICU patients to be activated by TLR agonists is markedly suppressed and may play a role in the development of subsequent infectious complications.

Proinflammatory Stimulation of Toll-Like Receptor 9 with High Dose CpG ODN 1826 Impairs Endothelial Regeneration and Promotes Atherosclerosis in Mice

Background

Toll-like receptors (TLR) of the innate immune system have been closely linked with the development of atherosclerotic lesions. TLR9 is activated by unmethylated CpG motifs within ssDNA, but also by CpG motifs in nucleic acids released during vascular apoptosis and necrosis. The role of TLR9 in vascular disease remains controversial and we sought to investigate the effects of a proinflammatory TLR9 stimulation in mice.

Methods and Findings

TLR9-stimulation with high dose CpG ODN at concentrations between 6.25nM to 30nM induced a significant proinflammatory cytokine response in mice. This was associated with impaired reendothelialization upon acute denudation of the carotid and increased numbers of circulating endothelial microparticles, as a marker for amplified endothelial damage. Chronic TLR9 agonism in apolipoprotein E-deficient (ApoE^-/-) mice fed a cholesterol-rich diet increased aortic production of reactive oxygen species, the number of circulating endothelial microparticles, circulating sca-1/flk-1 positive cells, and most importantly augmented atherosclerotic plaque formation when compared to vehicle treated animals. Importantly, high concentrations of CpG ODN are required for these proatherogenic effects.

Conclusions

Systemic stimulation of TLR9 with high dose CpG ODN impaired reendothelialization upon acute vascular injury and increased atherosclerotic plaque development in ApoE^-/- mice. Further studies are necessary to fully decipher the contradictory finding of TLR9 agonism in vascular biology.

Organ distribution of histones after intravenous infusion of FITC histones or after sepsis

Histones appear in plasma during infectious or non-infectious sepsis and are associated with multiorgan injury. In the current studies, intravenous infusion of histones resulted in their localization in major organs. In vitro exposure of mouse macrophages to histones caused a buildup of histones on cell membranes followed by localization into cytosol and into the nucleus. After polymicrobial sepsis (cecal ligation and puncture), histones appeared in plasma as well as in a multiorgan pattern, peaking at 8 h followed by decline. In lungs, histones and neutrophils appeared together, with evidence for formation of neutrophil extracellular traps (NETs), which represent an innate immune response to trap and kill bacteria and other infectious agents. In liver, there was intense NET formation, featuring linear patterns containing histones and strands of DNA. When neutrophils were activated in vitro with C5a or phorbol myristate acetate, NET formation ensued. While formation of NETs represents entrapment and killing of infectious agents, the simultaneous release from neutrophils of histones often results in tissue/organ damage.

Predisposition to Childhood Otitis Media and Genetic Polymorphisms within the Toll-Like Receptor 4 (TLR4) Locus

Background

Predisposition to childhood otitis media (OM) has a strong genetic component, with polymorphisms in innate immunity genes suspected to contribute to risk. Studies on several genes have been conducted, but most associations have failed to replicate in independent cohorts.

Methods

We investigated 53 gene polymorphisms in a Finnish cohort of 624 cases and 778 controls. A positive association signal was followed up in a tagging approach and tested in an independent Finnish cohort of 205 cases, in a British cohort of 1269 trios, as well as in two cohorts from the United States (US); one with 403 families and the other with 100 cases and 104 controls.

Results

In the initial Finnish cohort, the SNP rs5030717 in the TLR4 gene region showed significant association (OR 1.33, P = .003) to OM. Tagging SNP analysis of the gene found rs1329060 (OR 1.33, P = .002) and rs1329057 (OR 1.29, P = .003) also to be associated. In the more severe phenotype the association was stronger. This finding was supported by an independent Finnish case cohort, but the associations failed to replicate in the British and US cohorts. In studies on TLR4 signaling in 20 study subjects, the three-marker risk haplotype correlated with a decreased TNFα secretion in myeloid dendritic cells.

Conclusions

The TLR4 gene locus, regulating the innate immune response, influences the genetic predisposition to childhood OM in a subpopulation of patients. Environmental factors likely modulate the genetic components contributing to the risk of OM.

Circulating cell-free mitochondrial DNA as the probable inducer of early endothelial dysfunction in the prediabetic patient

Recent evidence has shown that 346million people in the world have diabetes mellitus (DM); this number will increase to 439million by 2030. In addition, current data indicate an increase in DM cases in the population between 40 and 59years of age. Diabetes is associated with the development of micro- and macro-vascular complications, derived from chronic hyperglycemia on the endothelium. Some reports demonstrate that people in a prediabetic state have a major risk of developing early endothelial dysfunction (ED). Today, it is accepted that individuals considered as prediabetic patients are in a pro-inflammatory state associated with endothelial and mitochondrial dysfunction. It is important to mention that impaired mitochondrial functionality has been linked to endothelial apoptosis and release of mitochondrial DNA (mtDNA) in patients with sepsis, cardiac disease, or atherosclerosis. This free mtDNA could promote ED, as well as other side effects on the vascular system through the activation of the toll-like receptor 9 (TLR9). TLR9 is expressed in different cell types (e.g., T or B lymphocytes, mastocytes, and epithelial and endothelial cells). It is localized intracellularly and recognizes non-methylated dinucleotides of viral, bacterial, and mitochondrial DNA. Recently, it has been reported that TLR9 is associated with the pathogenesis of lupus erythematosus, rheumatoid arthritis, and autoimmune diabetes. In this work, it is hypothesized that the increase in the levels of circulating mtDNA is the trigger of early ED in the prediabetic patient, and later on in the older patient with diabetes, through activation of the TLR9 present in the endothelium.

Anti-HMGB1 monoclonal antibody ameliorates immunosuppression after peripheral tissue trauma: attenuated T-lymphocyte response and increased splenic CD11b (+) Gr-1 (+) myeloid-derived suppressor cells require HMGB1

Although tissue-derived high mobility group box 1 (HMGB1) is involved in many aspects of inflammation and tissue injury after trauma, its role in trauma-induced immune suppression remains elusive. Using an established mouse model of peripheral tissue trauma, which includes soft tissue and fracture components, we report here that treatment with anti-HMGB1 monoclonal antibody ameliorated the trauma-induced attenuated T-cell responses and accumulation of CD11b⁺Gr-1⁺ myeloid-derived suppressor cells in the spleens seen two days after injury. Our data suggest that HMGB1 released after tissue trauma contributes to signaling pathways that lead to attenuation of T-lymphocyte responses and enhancement of myeloid-derived suppressor cell expansion.