RAGE controls activation and anti-inflammatory signalling of protein C

Advanced glycated end-products inhibit dilation through constitutive endothelial RAGE and Nox1/4 in rat isolated skeletal muscle arteries

OBJECTIVE

This study investigated the actions of advanced glycated end-products (AGE), their receptors (RAGE), and NAD(P)H oxidase (Nox) subtypes 1, 2, and 4 on mechanisms of endothelium-dependent dilation of the rat cremaster muscle artery (CMA).

METHODS

Immunofluorescence studies were used to examine expression of RAGE in rat arteries. ROS accumulation was measured using luminescence and fluorescence assays. Functional studies were performed using pressure myography.

RESULTS

High levels of RAGE expression were shown in the endothelial cells of the CMA, compared with low endothelial expression in middle cerebral and mesenteric arteries and the aorta. Exogenous AGE (in vitro glycated bovine serum albumin) stimulated H2O2 accumulation in CMA, which was prevented by the RAGE antagonist FPS-ZM1, the NAD(P)H oxidase (Nox) inhibitor apocynin and inhibited by the Nox1/4 inhibitor setanaxib, but not the Nox2 inhibitor GSK2795039. In functional studies, AGE inhibited vasodilation of CMA stimulated by acetylcholine, sodium nitroprusside, and the BKCa activator NS1619, but not adenosine-induced dilation. FPS-ZM1, apocynin, and setanaxib prevented the inhibitory effects of AGE on responses to acetylcholine and NS-1619.

CONCLUSION

These observations suggest RAGE are constitutively expressed in the endothelium of the rat CMA and may be activated by AGE to stimulate Nox1/4 and ROS formation with resulting inhibition of NO and BKCa-mediated endothelium-dependent dilation.

Dysregulated Hemostasis and Immunothrombosis in Cerebral Cavernous Malformations

Cerebral cavernous malformation (CCM) is a neurovascular disease that affects 0.5% of the general population. For a long time, CCM research focused on genetic mutations, endothelial junctions and proliferation, but recently, transcriptome and proteome studies have revealed that the hemostatic system and neuroinflammation play a crucial role in the development and severity of cavernomas, with some of these publications coming from our group. The aim of this review is to give an overview of the latest molecular insights into the interaction between CCM-deficient endothelial cells with blood components and the neurovascular unit. Specifically, we underscore how endothelial dysfunction can result in dysregulated hemostasis, bleeding, hypoxia and neurological symptoms. We conducted a thorough review of the literature and found a field that is increasingly poised to regard CCM as a hemostatic disease, which may have implications for therapy.

Relationships Among Circulating Levels of Hemostasis Inhibitors, Chemokines, Adhesion Molecules, and MRI Characteristics in Multiple Sclerosis

Background: Several studies suggested cross talk among components of hemostasis, inflammation, and immunity pathways in the pathogenesis, neurodegeneration, and occurrence of cerebral microbleeds (CMBs) in multiple sclerosis (MS).

Objectives: This study aimed to evaluate the combined contribution of the hemostasis inhibitor protein C (PC) and chemokine C-C motif ligand 18 (CCL18) levels to brain atrophy in MS and to identify disease-relevant correlations among circulating levels of hemostasis inhibitors, chemokines, and adhesion molecules, particularly in CMB occurrence in MS.

Methods: Plasma levels of hemostasis inhibitors (ADAMTS13, PC, and PAI1), CCL18, and soluble adhesion molecules (sNCAM, sICAM1, sVCAM1, and sVAP1) were evaluated by multiplex in 138 MS patients [85 relapsing-remitting (RR-MS) and 53 progressive (P-MS)] and 42 healthy individuals (HI) who underwent 3-T MRI exams. Association of protein levels with MRI outcomes was performed by regression analysis. Correlations among protein levels were assessed by partial correlation and Pearson's correlation.

Results: In all patients, regression analysis showed that higher PC levels were associated with lower brain volumes, including the brain parenchyma (p = 0.002), gray matter (p < 0.001), cortex (p = 0.001), deep gray matter (p = 0.001), and thalamus (p = 0.001). These associations were detectable in RR-MS but not in P-MS patients. Higher CCL18 levels were associated with higher T2-lesion volumes in all MS patients (p = 0.03) and in the P-MS (p = 0.003). In the P-MS, higher CCL18 levels were also associated with lower volumes of the gray matter (p = 0.024), cortex (p = 0.043), deep gray matter (p = 0.029), and thalamus (p = 0.022). PC-CCL18 and CCL18-PAI1 levels were positively correlated in both MS and HI, PC–sVAP1 and PAI1–sVCAM1 only in MS, and PC–sICAM1 and PC–sNCAM only in HI. In MS patients with CMBs (n = 12), CCL18–PAI1 and PAI1–sVCAM1 levels were better correlated than those in MS patients without CMBs, and a novel ADAMTS13–sVAP1 level correlation (r = 0.78, p = 0.003) was observed.

Conclusions: Differences between clinical phenotype groups in association of PC and CCL18 circulating levels with MRI outcomes might be related to different aspects of neurodegeneration. Disease-related pathway dysregulation is supported by several protein level correlation differences between MS patients and HI. The integrated analysis of plasma proteins and MRI measures provide evidence for new relationships among hemostasis, inflammation, and immunity pathways, relevant for MS and for the occurrence of CMBs.

Serum levels of advanced glycation end products and their receptors sRAGE and Galectin-3 in chronic pancreatitis

BACKGROUND

/Objectives: AGE and their receptors like RAGE and Galectin-3 can activate inflammatory pathways and have been associated with chronic inflammatory diseases. Several studies investigated the role of AGE, Galectin-3 and sRAGE in pancreatic diseases, whereas no comprehensive data for chronic pancreatitis (CP) are available.

METHODS

Serum samples from CP patients without an active inflammatory process (85 ACP; 26 NACP patients) and 40 healthy controls were collected. Levels of AGE, sRAGE and Galectin-3 were measured by ELISA. To exclude potential influences of previously described RAGE SNPs on detected serum levels, we analyzed variants rs207128, rs207060, rs1800625, and rs1800624 by melting curve technique in 378 CP patients and 338 controls.

RESULTS

AGE and Galectin-3 serum levels were significantly elevated in both ACP and NACP patients compared to controls (AGE: 56.61 ± 3.043 vs. 31.71 ± 2.308 ng/mL; p < 0.001; Galectin-3: 16.63 ± 0.6297 vs. 10.81 ± 0.4835 ng/mL; p < 0.001). In contrast, mean serum sRAGE levels were significantly reduced in CP patients compared to controls (sRAGE: 829.7 ± 37.10 vs. 1135 ± 55.74 ng/mL; p < 0.001). All results were consistent after correction for gender, age and diabetes mellitus. No genetic association with CP was found.

CONCLUSIONS

Our extensive analysis demonstrated the importance of aging related pathways in the pathogenesis of CP. As the results were consistent in ACP and NACP, both entities most likely share common pathomechanisms. Most probably the involved pathways are a general hallmark of an inflammatory state in CP that is even present in symptom-free intervals.

Thrombomodulin induces anti-inflammatory effects by inhibiting the rolling adhesion of leukocytes in vivo

Thrombomodulin (TM) is an integral membrane protein expressed on the surface of vascular endothelial cells that suppresses blood coagulation. Recent studies have shown that TM exhibits anti-inflammatory effects by inhibiting leukocyte recruitment. However, the actual modes of action of TM in vivo remain unclear. Here, we describe the pharmacological effects of recombinant human soluble TM (TM alfa) on leukocyte dynamics in living mice using intravital imaging techniques. Under control conditions, neutrophils exhibited three distinct types of adhesion behavior in vessels: 1) "non-adhesion", in which cells flowed without vessel adhesion; 2) "rolling adhesion", in which cells transiently interacted with the endothelium; and 3) "tight binding", in which cells bound strongly to the endothelial cells. Compared to control conditions, local lipopolysaccharide stimulation resulted in an increased frequency of rolling adhesion that was not homogeneously distributed on vessel walls but occurred at specific endothelial sites. Under inflammatory conditions, TM alfa, particularly the D1 domain which is a lectin-like region of TM, significantly decreased the frequency of rolling adhesion, but did not influence the number of tight bindings. This was the first study to demonstrate that TM alfa exerts anti-inflammatory effects by inhibiting rolling adhesion of neutrophils to vascular endothelial cells in living mice.

Dystrophin deficiency promotes leukocyte recruitment in mdx mice

BACKGROUND

A growing body of evidence defines inflammation as a hallmark feature of disease pathogenesis of Duchenne muscular dystrophy. To tailor potential immune modulatory interventions, a better understanding of immune dysregulation in Duchenne muscular dystrophy is needed. We now asked whether dystrophin deficiency affects the cascade of leukocyte recruitment.

METHODS

We performed intravital microscopy on the cremaster muscle of wild-type and dystrophin-deficient mdx mice. Recruitment was triggered by preparation alone (traumatic inflammation) or in combination with scrotal TNFα injections. Neutrophilic infiltration of the cremaster muscle was assessed on tissue sections. Integrin expression on circulating neutrophils and serum levels of pro-inflammatory cytokines were measured by flow cytometry.

RESULTS

Mdx mice show increased rolling and adhesion at baseline (traumatic inflammation) and a more profound response upon TNFα injection compared with wild-type animals. In both models, neutrophilic infiltration of the cremaster muscle is increased. Upregulation of the integrins LFA-1 and Mac-1 on circulating leukocytes and pro-inflammatory cytokines IL-6 and CCL2 in the serum points toward systemically altered immune regulation in mdx mice.

CONCLUSION

We are the first to show exaggerated activation of the leukocyte recruitment cascade in a dystrophin-deficient organism in vivo.

Thrombomodulin Regulation of Mitogen-Activated Protein Kinases

The multifaceted role of mitogen-activated protein kinases (MAPKs) in modulating signal transduction pathways in inflammatory conditions such as infection, cardiovascular disease, and cancer has been well established. Recently, coagulation factors have also emerged as key players in regulating intracellular signaling pathways during inflammation. Among coagulation factors, thrombomodulin, as a high affinity receptor for thrombin on vascular endothelial cells, has been discovered to be a potent anti-inflammatory and anti-tumorigenic signaling molecule. The protective signaling function of thrombomodulin is separate from its well-recognized role in the clotting cascade, which is to function as an anti-coagulant receptor in order to switch the specificity of thrombin from a procoagulant to an anti-coagulant protease. The underlying protective signaling mechanism of thrombomodulin remains largely unknown, though a few published reports link the receptor to the regulation of MAPKs under different (patho)physiological conditions. The goal of this review is to summarize what is known about the regulatory relationship between thrombomodulin and MAPKs.

LPS-induced maternal inflammation promotes fetal leukocyte recruitment and prenatal organ infiltration in mice

BACKGROUND

A pro-inflammatory intrauterine milieu accounts for increased perinatal morbidity and mortality. We asked how maternal inflammation as seen in endotoxemia affects fetal leukocyte recruitment in vivo during late gestation.

METHODS

Inflammation was induced in pregnant LysEGFP-mice by intraperitoneal LPS injection between gestational day 14 and 18 (E14-E18). After 20 h, intravital fluorescence microscopy was performed on fetal yolk sac venules to examine leukocyte rolling (number of rolling cells/min) and adhesion (>30 s). Infiltration of neutrophils into chorion/amnion, lung, and kidney were quantified by immunofluorescence microscopy.

RESULTS

At high doses (2 × 1 mg/kg), LPS triggered preterm birth (PTB) and intrauterine fetal death (IUFD), with early gestations at high risk of IUFD and late gestations prone to PTB. Lower LPS dosing (2 × 0.25 mg/kg) did not induce labor, but promoted maternal and fetal cytokine production, as well as neutrophilic infiltration of fetal membranes, as seen in chorioamnionitis (CAM). Baseline fetal leukocyte recruitment increased throughout gestation, and maternal inflammation further augmented adhesion at E16-E18. Enhanced leukocyte recruitment ultimately translated into prominent infiltration of fetal lung and kidney.

CONCLUSION

LPS-induced maternal endotoxemia promotes IUFD, PTB, and fetal leukocyte recruitment depending on gestational age. Our proposed model may serve as a platform to test novel perinatal immune modulators.

Effects of S100A12 reduction on H2O2-induced injury of human vascular smooth muscle cells (HVSMCs)

Thoracic aortic dissection is a catastrophic acute aortic disease with a high postoperative mortality. Although TAD results from various risk factors, the final common pathway for its development is tunica media dysfunction with vascular inflammation. The aim of the present study was to investigate the protective effects of S100A12 reduction on hydrogen peroxide (H2O2)-induced human vascular smooth muscle cells (HVSMCs) injury and evaluate the relevance of S100A12 and aortic disease. In this study, HVSMCs were exposed to the H2O2 in the presence or absence of S100A12, then cell viability was detected by MTT assay, cell apoptosis was performed with the flow cytometry kit, IL-6 and TNFα production evaluated by ELISA and apoptotic proteins were investigated by western blot. The results showed that H2O2 inhibited cell proliferation, induced cell apoptosis, IL-6 and TNFα release, the increase of caspase-3 protein and the decrease of Bcl-2, while transfection with S10012A shRNA significantly repaired the situation above. Our findings suggested that reduction of S100A12 protects HVSMCs against H2O2-induced injury, and may be useful as a treatment for aortic disease.

LXR agonist T0901317 upregulates thrombomodulin expression in glomerular endothelial cells by inhibition of nuclear factor‑κB

Dysfunction of glomerular endothelial cells (GECs) induces a variety of symptoms, including proteinuria, inflammation, vascular diseases, fibrosis and thrombosis. Thrombomodulin (TM) acts as a vasoprotective molecule on the surface of the vascular endothelial cells to maintain the homeostasis of the endothelial microenvironment by suppressing cellular proliferation, adhesion and inflammatory responses. Liver X receptor (LXR), a nuclear receptor (NR) and a bile acid‑activated transcription factor, regulates metabolism and cholesterol transport, vascular tension and inflammation. Previous studies indicated that TM expression is upregulated by various NRs; however, it is unclear whether pharmacological modulation of LXR may affect TM expression and GEC function. The current study revealed that LXR activation by its agonist, T0901317, upregulates the expression and activity of TM. This effect was mediated specifically through LXR‑α, and not through LXR‑β. Additionally, T0901317 treatment inhibited nuclear factor‑κB (NF‑κB) signaling and the secretion of high glucose‑induced proinflammatory mediators, including tumor necrosis factor‑α and interleukin‑1β in GECs. Co‑immunoprecipitation experiments determined that treatment with T0901317 enhances the interaction between LXR‑α and the transcriptional coactivator, p300, in GEC extracts. The present findings suggest that NF‑κB may be a negative regulator of TM expression, and its removal may contribute to TM gene expression, particularly when in competition with the T0901317‑enhanced formation of the LXR/p300 complex. Therefore, LXR may be a novel molecular target for manipulating TM in GECs, which may advance the treatment of endothelial cell‑associated diseases.

Pulmonary receptor for advanced glycation end-products promotes asthma pathogenesis through IL-33 and accumulation of group 2 innate lymphoid cells

BACKGROUND

Single nucleotide polymorphisms in the human gene for the receptor for advanced glycation end-products (RAGE) are associated with an increased incidence of asthma. RAGE is highly expressed in the lung and has been reported to play a vital role in the pathogenesis of murine models of asthma/allergic airway inflammation (AAI) by promoting expression of the type 2 cytokines IL-5 and IL-13. IL-5 and IL-13 are prominently secreted by group 2 innate lymphoid cells (ILC2s), which are stimulated by the proallergic cytokine IL-33.

OBJECTIVE

We sought to test the hypothesis that pulmonary RAGE is necessary for allergen-induced ILC2 accumulation in the lung.

METHODS

AAI was induced in wild-type and RAGE knockout mice by using IL-33, house dust mite extract, or Alternaria alternata extract. RAGE's lung-specific role in type 2 responses was explored with bone marrow chimeras and induction of gastrointestinal type 2 immune responses.

RESULTS

RAGE was found to drive AAI by promoting IL-33 expression in response to allergen and by coordinating the inflammatory response downstream of IL-33. Absence of RAGE impedes pulmonary accumulation of ILC2s in models of AAI. Bone marrow chimera studies suggest that pulmonary parenchymal, but not hematopoietic, RAGE has a central role in promoting AAI. In contrast to the lung, the absence of RAGE does not affect IL-33-induced ILC2 influx in the spleen, type 2 cytokine production in the peritoneum, or mucus hypersecretion in the gastrointestinal tract.

CONCLUSIONS

For the first time, this study demonstrates that a parenchymal factor, RAGE, mediates lung-specific accumulation of ILC2s.

The olive oil-based lipid clinoleic blocks leukocyte recruitment and improves survival during systemic inflammation: a comparative in vivo study of different parenteral lipid emulsions

Although fish oil-based and olive oil-based lipid emulsions have been shown to exert anti-inflammatory functions, the immunomodulating properties of lipids are still controversial. Therefore, we investigated the anti-inflammatory effect of three different parenterally administered lipid emulsions in vivo: olive oil-based Clinoleic, fish oil-based Smoflipid, and soybean oil-based Lipofundin. We observed leukocyte recruitment in inflamed murine cremaster muscle using intravital microscopy and survival in a murine model of LPS-induced systemic inflammation and analyzed expression of leukocyte and endothelial adhesion molecules. Olive oil-based Clinoleic and fish oil-based Smoflipid profoundly inhibited leukocyte adhesion compared to Lipofundin during LPS-induced inflammation of the murine cremaster muscle. In the trauma model of cremaster muscle inflammation, Lipofundin was the only lipid emulsion that even augmented leukocyte adhesion. In contrast to Smoflipid and Lipofundin, Clinoleic effectively blocked leukocyte recruitment and increased survival during lethal endotoxemia. Flow chamber experiments and analysis of adhesion molecule expression suggest that both endothelial and leukocyte driven mechanisms might contribute to anti-inflammatory effects of Clinoleic. We conclude that the anti-inflammatory properties of Clinoleic are superior to those of Smoflipid and Lipofundin even during systemic inflammation. Thus, these results should stimulate further studies investigating parenteral lipids as an anti-inflammatory strategy in critically ill patients.

Overexpression of activated protein C hampers bacterial dissemination during pneumococcal pneumonia

Background

During pneumonia, inflammation and coagulation are activated as part of anti-bacterial host defense. Activated protein C (APC) has anticoagulant and anti-inflammatory properties and until recently was a registered drug for the treatment of severe sepsis. Streptococcus (S.) pneumoniae is the most common causative pathogen in community-acquired pneumonia.

Methods

We aimed to investigate the effect of high APC levels during experimental pneumococcal pneumonia. Wild type (WT) and APC overexpressing (APC^high)-mice were intranasally infected with S. pneumoniae and sacrificed after 6, 24 or 48 hours, or followed in a survival study.

Results

In comparison to WT mice, APC^high-mice showed decreased bacterial dissemination to liver and spleen, while no differences in bacterial loads were detected at the primary site of infection. Although no differences in the extent of lung histopathology were seen, APC^high-mice showed a significantly decreased recruitment of neutrophils into lung tissue and bronchoalveolar lavage fluid. Activation of coagulation was not altered in APC^high-mice. No differences in survival were observed between WT and APC^high-mice (P =0.06).

Conclusion

APC overexpression improves host defense during experimental pneumococcal pneumonia. This knowledge may add to a better understanding of the regulation of the inflammatory and procoagulant responses during severe Gram-positive pneumonia.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-014-0559-3) contains supplementary material, which is available to authorized users.