Reduced Monocyte and Neutrophil Infiltration and Activation by P-Selectin/CD62P Inhibition Enhances Thrombus Resolution in Mice

BACKGROUND

Venous thromboembolism is a major health problem. After thrombus formation, its resolution is essential to re-establish blood flow, which is crucially mediated by infiltrating neutrophils and monocytes in concert with activated platelets and endothelial cells. Thus, we aimed to modulate leukocyte function during thrombus resolution post-thrombus formation by blocking P-selectin/CD62P-mediated cell interactions.

METHODS

Thrombosis was induced by inferior vena cava stenosis through ligation in mice. After 1 day, a P-selectin-blocking antibody or isotype control was administered and thrombus composition and resolution were analyzed.

RESULTS

Localizing neutrophils and macrophages in thrombotic lesions of wild-type mice revealed that these cells enter the thrombus and vessel wall from the caudal end. Neutrophils were predominantly present 1 day and monocytes/macrophages 3 days after vessel ligation. Blocking P-selectin reduced circulating platelet-neutrophil and platelet-Ly6Chigh monocyte aggregates near the thrombus, and diminished neutrophils and Ly6Chigh macrophages in the cranial thrombus part compared with isotype-treated controls. Depletion of neutrophils 1 day after thrombus initiation did not phenocopy P-selectin inhibition but led to larger thrombi compared with untreated controls. In vitro, P-selectin enhanced human leukocyte function as P-selectin-coated beads increased reactive oxygen species production by neutrophils and tissue factor expression of classical monocytes. Accordingly, P-selectin inhibition reduced oxidative burst in the thrombus and tissue factor expression in the adjacent vessel wall. Moreover, blocking P-selectin reduced thrombus density determined by scanning electron microscopy and increased urokinase-type plasminogen activator levels in the thrombus, which accelerated caudal fibrin degradation from day 3 to day 14. This accelerated thrombus resolution as thrombus volume declined more rapidly after blocking P-selectin.

CONCLUSIONS

Inhibition of P-selectin-dependent activation of monocytes and neutrophils accelerates venous thrombosis resolution due to reduced infiltration and activation of innate immune cells at the site of thrombus formation, which prevents early thrombus stabilization and facilitates fibrinolysis.

Intrahepatic neutrophil accumulation and extracellular trap formation are associated with posthepatectomy liver failure

BACKGROUND

Posthepatectomy liver failure (PHLF) represents a life-threatening complication with limited therapeutic options. Neutrophils play a critical and dynamic role during regeneratory processes, but their role in human liver regeneration is incompletely understood, especially as underlying liver disease, detectable in the majority of patients, critically affects hepatic regeneration. Here we explored intrahepatic neutrophil accumulation and neutrophil extracellular traps (NETs) in patients with PHLF and validated the functional relevance of NETs in a murine partial hepatectomy (PHx) model.

METHODS

We investigated the influx of neutrophils, macrophages, eosinophils, and mast cells and the presence of their respective extracellular traps in liver biopsies of 35 patients undergoing hepatectomy (10 patients with PHLF) before and after the initiation of liver regeneration by fluorescence microscopy. In addition, NET formation and neutrophil activation were confirmed by plasma analysis of 99 patients (24 patients with PHLF) before and up to 5 days after surgery. Furthermore, we inhibited NETs via DNase I in a murine PHx model of mice with metabolically induced liver disease.

RESULTS

We detected rapid intrahepatic neutrophil accumulation, elevated levels of myeloperoxidase release, and NET formation in regenerating human livers, with a significantly higher increase of infiltrating neutrophils and NETs in patients with PHLF. Circulating markers of neutrophil activation, including elastase, myeloperoxidase, and citrullinated histone H3, correlated with markers of liver injury. In a murine PHx model, we showed that the inhibition of NET accelerated hepatocyte proliferation and liver regeneration.

CONCLUSIONS

Patients with PHLF showed accelerated intrahepatic neutrophil infiltration and NET formation, which were associated with liver damage. Further, we identified postsurgical myeloperoxidase levels as predictive markers for adverse outcomes and observed that blocking NETs in a murine PHx model accelerated tissue regeneration.

Neutrophil extracellular traps induce persistent lung tissue damage via thromboinflammation without altering virus resolution in a mouse coronavirus model

BACKGROUND

During infection, neutrophil extracellular traps (NETs) are associated with severity of pulmonary diseases such as acute respiratory disease syndrome. NETs induce subsequent immune responses, are directly cytotoxic to pulmonary cells, and are highly procoagulant. Anticoagulation treatment was shown to reduce in-hospital mortality, indicating thromboinflammatory complications. However, data are sparsely available on the involvement of NETs in secondary events after virus clearance, which can lead to persistent lung damage and postacute sequelae with chronic fatigue and dyspnea.

OBJECTIVES

This study focuses on late-phase events using a murine model of viral lung infection with postacute sequelae after virus resolution.

METHODS

C57BL/6JRj mice were infected intranasally with the betacoronavirus murine coronavirus (MCoV, strain MHV-A95), and tissue samples were collected after 2, 4, and 10 days. For NET modulation, mice were pretreated with OM-85 or GSK484 and DNase I were administered intraperitoneally between days 2 to 5 and days 4 to 7, respectively.

RESULTS

Rapid, platelet-attributed thrombus formation was followed by a second, late phase of thromboinflammation. This phase was characterized by negligible virus titers but pronounced tissue damage, apoptosis, oxidative DNA damage, and presence of NETs. Inhibition of NETs during the acute phase did not impact virus burden but decreased lung cell apoptosis by 67% and oxidative stress by 94%. Prevention of neutrophil activation by immune training before virus infection reduced damage by 75%, NETs by 31%, and pulmonary thrombi by 93%.

CONCLUSION

NETs are detrimental inducers of tissue damage during respiratory virus infection but do not contribute to virus clearance.

Short-term toll-like receptor 9 inhibition leads to left ventricular wall thinning after myocardial infarction

AIMS

Ischaemia-reperfusion injury (IRI) following myocardial infarction remains a challenging topic in acute cardiac care and consecutively arising heart failure represents a severe long-term consequence. The extent of neutrophil infiltration and neutrophil-mediated cellular damage are thought to be aggravating factors enhancing primary tissue injury. Toll-like receptor 9 was found to be involved in neutrophil activation as well as chemotaxis and may represent a target in modulating IRI, aspects we aimed to illuminate by pharmacological inhibition of the receptor.

METHODS AND RESULTS

Forty-nine male adult Sprague-Dawley rats were used. IRI was induced by occlusion of the left coronary artery and subsequent snare removal after 30 min. Oligonucleotide (ODN) 2088, a toll-like receptor 9 (TLR9) antagonist, control-ODN, or DNase, were administered at the time of reperfusion and over 24 h via a mini-osmotic pump. The hearts were harvested 24 h or 4 weeks after left coronary artery occlusion and immunohistochemical staining was performed. Echocardiography was done after 1 and 4 weeks to determine ventricular function. Inhibition of TLR9 by ODN 2088 led to left ventricular wall thinning (P = 0.003) in association with drastically enhanced neutrophil infiltration (P = 0.005) and increased markers of tissue damage. Additionally, an up-regulation of the chemotactic receptor CXCR2 (P = 0.046) was found after TLR9 inhibition. No such effects were observed in control-ODN or DNase-treated animals. We did not observe changes in monocyte content or subset distribution, hinting towards neutrophils as the primary mediators of the exerted tissue injury.

CONCLUSIONS

Our data indicate a TLR9-dependent, negative regulation of neutrophil infiltration. Blockage of TLR9 appears to prevent the down-regulation of CXCR2, followed by an uncontrolled migration of neutrophils towards the area of infarction and the exertion of disproportional tissue injury resulting in potential aneurysm formation. In comparison with previous studies conducted in TLR^-/- mice, we deliberately chose a transient pharmacological inhibition of TLR9 to highlight effects occurring in the first 24 h following IRI.

Staphylococcus aureus extracellular adherence protein (Eap) reduces immune cell phenotype in developing but not in established atherosclerotic lesions

Atherosclerosis is a chronic, inflammatory disease of the vessel wall where triggered immune cells bind to inflamed endothelium, extravasate and sustain local inflammation. Leukocyte adhesion and extravasation are mediated by adhesion molecules expressed by activated endothelial cells, like intercellular adhesion molecule 1 (ICAM-1). Extracellular adherence protein (Eap) from Staphylococcus aureus binds to a plethora of extracellular matrix proteins, including ICAM-1 and its ligands macrophage-1 antigen (Mac-1, αMβ2) and lymphocyte function-associated antigen 1 (LFA-1, αLβ2), thereby disrupting the interaction between leukocytes and endothelial cells. We aimed to use Eap to inhibit the interaction of leukocytes with activated endothelial cells in settings of developing and established atherosclerosis in apolipoprotein E (ApoE) deficient mice on high-fat diet. In developing atherosclerosis, Eap treatment reduced circulating platelet-neutrophil aggregates as well as infiltration of T cells and neutrophils into the growing plaque, accompanied by reduced formation of neutrophil extracellular traps (NETs). However, plaque size did not change. Intervention treatment with Eap of already established plaques did not result in cellular or morphological plaque changes, whereas T cell infiltration was increased and thereby again modulated by Eap. We conclude that although Eap leads to cellular changes in developing plaques, clinical implications might be limited as patients are usually treated at a more advanced stage of disease progression. Hence, usage of Eap might be an interesting mechanistic tool for cellular infiltration during plaque development in basic research but not a clinical target.

Platelet p110β mediates platelet-leukocyte interaction and curtails bacterial dissemination in pneumococcal pneumonia

Phosphatidylinositol 3-kinase catalytic subunit p110β is involved in tumorigenesis and hemostasis. However, it remains unclear if p110β also regulates platelet-mediated immune responses, which could have important consequences for immune modulation during anti-cancer treatment with p110β inhibitors. Thus, we investigate how platelet p110β affects inflammation and infection. Using a mouse model of Streptococcus pneumoniae-induced pneumonia, we find that both platelet-specific p110β deficiency and pharmacologic inhibition of p110β with TGX-221 exacerbate disease pathogenesis by preventing platelet-monocyte and neutrophil interactions, diminishing their infiltration and enhancing bacterial dissemination. Platelet p110β mediates neutrophil phagocytosis of S. pneumoniae in vitro and curtails bacteremia in vivo. Genetic deficiency or inhibition of platelet p110β also impairs macrophage recruitment in an independent model of sterile peritonitis. Our results demonstrate that platelet p110β dysfunction exacerbates pulmonary infection by impeding leukocyte functions. Thereby, our findings provide important insights into the immunomodulatory potential of PI3K inhibitors in bacterial infection.

Interleukin-4 receptor alpha signaling regulates monocyte homeostasis

Interleukin‐4 (IL‐4) and its receptors (IL‐4R) promote the proliferation and polarization of macrophages. However, it is unknown if IL‐4R also influences monocyte homeostasis and if steady state IL‐4 levels are sufficient to affect monocytes. Employing full IL‐4 receptor alpha knockout mice (IL‐4Rα^−/−) and mice with a myeloid‐specific deletion of IL‐4Rα (IL‐4Rα^f/f LysM^cre), we show that IL‐4 acts as a homeostatic factor regulating circulating monocyte numbers. In the absence of IL‐4Rα, murine monocytes in blood were reduced by 50% without altering monocytopoiesis in the bone marrow. This reduction was accompanied by a decrease in monocyte‐derived inflammatory cytokines in the plasma. RNA sequencing analysis and immunohistochemical staining of splenic monocytes revealed changes in mRNA and protein levels of anti‐apoptotic factors including BIRC6 in IL‐4Rα^−/− knockout animals. Furthermore, assessment of monocyte lifespan in vivo measuring BrdU⁺ cells revealed that the lifespan of circulating monocytes was reduced by 55% in IL‐4Rα^−/− mice, whereas subcutaneously applied IL‐4 prolonged it by 75%. Treatment of human monocytes with IL‐4 reduced the amount of dying monocytes in vitro. Furthermore, IL‐4 stimulation reduced the phosphorylation of proteins involved in the apoptosis pathway, including the phosphorylation of the NFκBp65 protein. In a cohort of human patients, serum IL‐4 levels were significantly associated with monocyte counts. In a sterile peritonitis model, reduced monocyte counts resulted in an attenuated recruitment of monocytes upon inflammatory stimulation in IL‐4Rα^f/f LysM^cre mice without changes in overall migratory function. Thus, we identified a homeostatic role of IL‐4Rα in regulating the lifespan of monocytes in vivo.

PI3K Signaling in Dendritic Cells Aggravates DSS-Induced Colitis

Aberrant innate immune responses to the gut microbiota are causally involved in the pathogenesis of inflammatory bowel diseases (IBD). The exact triggers and main signaling pathways activating innate immune cells and how they modulate adaptive immunity in IBD is still not completely understood. Here, we report that the PI3K/PTEN signaling pathway in dendritic cells enhances IL-6 production in a model of DSS-induced colitis. This results in exacerbated Th1 cell responses and increased mortality in DC-specific PTEN knockout (PTENΔDC) animals. Depletion of the gut microbiota using antibiotics as well as blocking IL-6R signaling rescued mortality in PTENΔDC mice, whereas adoptive transfer of Flt3L-derived PTEN-/- DCs into WT recipients exacerbated DSS-induced colitis and increased mortality. Taken together, we show that the PI3K signaling pathway in dendritic cells contributes to disease pathology by promoting IL-6 mediated Th1 responses.

More than Just a Monolayer: the Multifaceted Role of Endothelial Cells in the Pathophysiology of Atherosclerosis

Purpose of the Review

In this review, we summarize current insights into the versatile roles of endothelial cells in atherogenesis.

Recent Findings

The vascular endothelium represents the first barrier that prevents the entry of lipoproteins and leukocytes into the vessel wall, thereby controlling two key events in the pathogenesis of atherosclerosis. Disturbance of endothelial homeostasis increases vascular permeability, inflammation, and cellular trans-differentiation, which not only promotes the build-up of atherosclerotic plaques but is also involved in life-threatening thromboembolic complications such as plaque rupture and erosion. In this review, we focus on recent findings on endothelial lipoprotein transport, inflammation, cellular transitions, and barrier function.

Summary

By using cutting-edge technologies such as single-cell sequencing, epigenetics, and cell fate mapping, novel regulatory mechanisms and endothelial cell phenotypes have been discovered, which have not only challenged established concepts of endothelial activation, but have also led to a different view of the disease.

The Global Atmosphere-aerosol Model ICON-A-HAM2.3-Initial Model Evaluation and Effects of Radiation Balance Tuning on Aerosol Optical Thickness

The Hamburg Aerosol Module version 2.3 (HAM2.3) from the ECHAM6.3-HAM2.3 global atmosphere-aerosol model is coupled to the recently developed icosahedral nonhydrostatic ICON-A (icon-aes-1.3.00) global atmosphere model to yield the new ICON-A-HAM2.3 atmosphere-aerosol model. The ICON-A and ECHAM6.3 host models use different dynamical cores, parameterizations of vertical mixing due to sub-grid scale turbulence, and parameter settings for radiation balance tuning. Here, we study the role of the different host models for simulated aerosol optical thickness (AOT) and evaluate impacts of using HAM2.3 and the ECHAM6-HAM2.3 two-moment cloud microphysics scheme on several meteorological variables. Sensitivity runs show that a positive AOT bias over the subtropical oceans is remedied in ICON-A-HAM2.3 because of a different default setting of a parameter in the moist convection parameterization of the host models. The global mean AOT is biased low compared to MODIS satellite instrument retrievals in ICON-A-HAM2.3 and ECHAM6.3-HAM2.3, but the bias is larger in ICON-A-HAM2.3 because negative AOT biases over the Amazon, the African rain forest, and the northern Indian Ocean are no longer compensated by high biases over the sub-tropical oceans. ICON-A-HAM2.3 shows a moderate improvement with respect to AOT observations at AERONET sites. A multivariable bias score combining biases of several meteorological variables into a single number is larger in ICON-A-HAM2.3 compared to standard ICON-A and standard ECHAM6.3. In the tropics, this multivariable bias is of similar magnitude in ICON-A-HAM2.3 and in ECHAM6.3-HAM2.3. In the extra-tropics, a smaller multivariable bias is found for ICON-A-HAM2.3 than for ECHAM6.3-HAM2.3.

Adipose Triglyceride Lipase Deficiency Attenuates In Vitro Thrombus Formation without Affecting Platelet Activation and Bleeding In Vivo

According to genome-wide RNA sequencing data from human and mouse platelets, adipose triglyceride lipase (ATGL), the main lipase catalyzing triglyceride (TG) hydrolysis in cytosolic lipid droplets (LD) at neutral pH, is expressed in platelets. Currently, it is elusive to whether common lipolytic enzymes are involved in the degradation of TG in platelets. Since the consequences of ATGL deficiency in platelets are unknown, we used whole-body and platelet-specific (plat)Atgl-deficient (-/-) mice to investigate the loss of ATGL on platelet function. Our results showed that platelets accumulate only a few LD due to lack of ATGL. Stimulation with platelet-activating agonists resulted in comparable platelet activation in Atgl-/-, platAtgl-/-, and wild-type mice. Measurement of mitochondrial respiration revealed a decreased oxygen consumption rate in platelets from Atgl-/- but not from platAtgl-/- mice. Of note, global loss of ATGL was associated with an anti-thrombogenic phenotype, which was evident by reduced thrombus formation in collagen-coated channels in vitro despite unchanged bleeding and occlusion times in vivo. We conclude that genetic deletion of ATGL affects collagen-induced thrombosis without pathological bleeding and platelet activation.

Quantitative and Functional Assessment of the Influence of Routinely Used Cryopreservation Media on Mononuclear Leukocytes for Medical Research

Quantitative and functional analysis of mononuclear leukocyte populations is an invaluable tool to understand the role of the immune system in the pathogenesis of a disease. Cryopreservation of mononuclear cells (MNCs) is routinely used to guarantee similar experimental conditions. Immune cells react differently to cryopreservation, and populations and functions of immune cells change during the process of freeze–thawing. To allow for a setup that preserves cell number and function optimally, we tested four different cryopreservation media. MNCs from 15 human individuals were analyzed. Before freezing and after thawing, the distribution of leukocytes was quantified by flow cytometry. Cultured cells were stimulated using lipopolysaccharide, and their immune response was quantified by flow cytometry, quantitative polymerase chain reaction (qPCR), and enzyme-linked immunosorbent assay (ELISA). Ultimately, the performance of the cryopreservation media was ranked. Cell recovery and viability were different between the media. Cryopreservation led to changes in the relative number of monocytes, T cells, B cells, and their subsets. The inflammatory response of MNCs was altered by cryopreservation, enhancing the basal production of inflammatory cytokines. Different cryopreservation media induce biases, which needs to be considered when designing a study relying on cryopreservation. Here, we provide an overview of four different cryopreservation media for choosing the optimal medium for a specific task.

PI3K Isoform Signalling in Platelets

Platelets are unique anucleated blood cells that constantly patrol the vasculature to seal and prevent injuries in a process termed haemostasis. Thereby they rapidly adhere to the subendothelial matrix and recruit further platelets, resulting in platelet aggregates. Apart from their central role in haemostasis, they also kept some of their features inherited by their evolutionary ancestor-the haemocyte, which was also involved in immune defences. Together with leukocytes, platelets fight pathogenic invaders and guide many immune processes. In addition, they rely on several signalling pathways which are also relevant to immune cells. Among these, one of the central signalling hubs is the PI3K pathway. Signalling processes in platelets are unique as they lack a nucleus and therefore transcriptional regulation is absent. As a result, PI3K subclasses fulfil distinct roles in platelets compared to other cells. In contrast to leukocytes, the central PI3K subclass in platelet signalling is PI3K class Iβ, which underlines the uniqueness of this cell type and opens new ways for potential platelet-specific pharmacologic inhibition. An overview of platelet function and signalling with emphasis on PI3K subclasses and their respective inhibitors is given in this chapter.

Innate Immune Training with Bacterial Extracts Enhances Lung Macrophage Recruitment to Protect from Betacoronavirus Infection

Training of the innate immune system with orally ingested bacterial extracts was demonstrated to have beneficial effects on infection clearance and disease outcome. The aim of our study was to identify cellular and molecular processes responsible for these immunological benefits. We used a murine coronavirus (MCoV) A59 mouse model treated with the immune activating bacterial extract Broncho-Vaxom (BV) OM-85. Tissue samples were analysed with qPCR, RNA sequencing, histology, and flow cytometry. After BV OM-85 treatment, interstitial macrophages accumulated in lung tissue leading to a faster response of type I interferon (IFN) signalling after MCoV infection resulting in overall lung tissue protection. Moreover, RNA sequencing showed that lung tissue from mice receiving BV OM-85 resembled an intermediate stage between healthy and viral infected lung tissue at day 4, indicating a faster return to normal tissue homoeostasis. The pharmacologic effect was mimicked by adoptively transferring naive lung macrophages into lungs from recipient mice before virus infection. The beneficial effect of BV OM-85 was abolished when inhibiting initial type I IFN signalling. Overall, our data suggest that BV OM-85 enhances lung macrophages allowing for a faster IFN response towards a viral challenge as part of the oral-induced innate immune system training.

Orthotic treatment of idiopathic toe walking with a lower leg orthosis with circular subtalar blocking

BACKGROUND

There is no universally accepted treatment standard for idiopathic toe walking patients (ITW) in the current literature. None of the established methods provide homogenous satisfying results. In our department we treat ITW patients with lower leg orthoses with a circular foot unit for a total of 16 weeks. In this study we reviewed our database to evaluate the success of our treatment protocol for a 24 months follow up period.

RESULTS

Twenty-two patients were included in this study. Age at the beginning of treatment was 7.0 years +/- 2.9 (range 2.5-13.1). Percentage of ITW at the beginning of treatment according to the perception of the parents was 89% +/- 22.2 (range 50-100). Immediately after the treatment with our device, percentage of ITW dropped to 11% +/- 13.2 (range 0-50). After 12 months, 73% of the patients (16/22) walked completely normal or showed ITW less than 10% of the day. After 24 months, 64% of the patients kept a normal gait (14/22).

CONCLUSION

This study provides evidence that the treatment of idiopathic toe walking with lower leg orthoses with a circular foot unit results in satisfying long-term results in two thirds of the patients.

Pharmacological inhibition of fatty acid oxidation reduces atherosclerosis progression by suppression of macrophage NLRP3 inflammasome activation

BACKGROUND

Inflammation is a key process during atherosclerotic lesion development and propagation. Recent evidence showed clearly that especially the inhibition of interleukin (IL)-1β reduced atherosclerotic adverse events in human patients. Fatty acid oxidation (FAO) was previously demonstrated to interact with the NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) pathway which is required for mature IL-1β secretion. To understand possible anti-inflammatory properties of FAO inhibition, we tested the effect of pharmacological FAO inhibition using the inhibitor for long-chain 3-ketoacyl coenzyme A thiolase trimetazidine on atherosclerotic plaque development and inflammation.

EXPERIMENTAL APPROACH

The effect of FAO inhibition was determined in LDL-R^-/- male mice on a C57/BL6 background. In vitro effects of trimetazidine treatment were analyzed in human umbilical vein endothelial cells and human monocyte derived macrophages.

KEY RESULTS

We were able to demonstrate that inhibition of FAO reduced atherosclerotic plaque growth. We did not find direct anti-inflammatory properties of trimetazidine in endothelial cells or macrophages in vitro. However, we found that the activation of the NLRP3 system and the secretion of IL-1β were significantly reduced in macrophages after FAO inhibition. These results were confirmed in atherosclerotic lesions of mice treated with trimetazidine as they showed a significant reduction of IL-1β and cleaved caspase-1 in the atherosclerotic lesion as well as of IL-1β and IL-18 in the circulation.

CONCLUSION

Overall, we therefore suggest that the main mechanism of reducing inflammation of trimetazidine and FAO inhibition is the reduction of the NLRP-3 activation leading to reduced levels of the proinflammatory cytokine IL-1β.

The inflammatory kinase IKKα phosphorylates and stabilizes c-Myc and enhances its activity

Background

The IκB kinase (IKK) complex, comprising the two enzymes IKKα and IKKβ, is the main activator of the inflammatory transcription factor NF-κB, which is constitutively active in many cancers. While several connections between NF-κB signaling and the oncogene c-Myc have been shown, functional links between the signaling molecules are still poorly studied.

Methods

Molecular interactions were shown by co-immunoprecipitation and FRET microscopy. Phosphorylation of c-Myc was shown by kinases assays and its activity by improved reporter gene systems. CRISPR/Cas9-mediated gene knockout and chemical inhibition were used to block IKK activity. The turnover of c-Myc variants was determined by degradation in presence of cycloheximide and by optical pulse-chase experiments.. Immunofluorescence of mouse prostate tissue and bioinformatics of human datasets were applied to correlate IKKα- and c-Myc levels. Cell proliferation was assessed by EdU incorporation and apoptosis by flow cytometry.

Results

We show that IKKα and IKKβ bind to c-Myc and phosphorylate it at serines 67/71 within a sequence that is highly conserved. Knockout of IKKα decreased c-Myc-activity and increased its T58-phosphorylation, the target site for GSK3β, triggering polyubiquitination and degradation. c-Myc-mutants mimicking IKK-mediated S67/S71-phosphorylation exhibited slower turnover, higher cell proliferation and lower apoptosis, while the opposite was observed for non-phosphorylatable A67/A71-mutants. A significant positive correlation of c-Myc and IKKα levels was noticed in the prostate epithelium of mice and in a variety of human cancers.

Conclusions

Our data imply that IKKα phosphorylates c-Myc on serines-67/71, thereby stabilizing it, leading to increased transcriptional activity, higher proliferation and decreased apoptosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12943-021-01308-8.

Automated image analysis of stained cytospins to quantify Schwann cell purity and proliferation

In response to injury, adult Schwann cells (SCs) re-enter the cell cycle, change their expression profile, and exert repair functions important for wound healing and the re-growth of axons. While this phenotypical instability of SCs is essential for nerve regeneration, it has also been implicated in cancer progression and de-myelinating neuropathies. Thus, SCs became an important research tool to study the molecular mechanisms involved in repair and disease and to identify targets for therapeutic intervention. A high purity of isolated SC cultures used for experimentation must be demonstrated to exclude that novel findings are derived from a contaminating fibroblasts population. In addition, information about the SC proliferation status is an important parameter to be determined in response to different treatments. The evaluation of SC purity and proliferation, however, usually depends on the time consuming, manual assessment of immunofluorescence stainings or comes with the sacrifice of a large amount of SCs for flow cytometry analysis. We here show that rat SC culture derived cytospins stained for SC marker SOX10, proliferation marker EdU, intermediate filament vimentin and DAPI allowed the determination of SC identity and proliferation by requiring only a small number of cells. Furthermore, the CellProfiler software was used to develop an automated image analysis pipeline that quantified SCs and proliferating SCs from the obtained immunofluorescence images. By comparing the results of total cell count, SC purity and SC proliferation rate between manual counting and the CellProfiler output, we demonstrated applicability and reliability of the established pipeline. In conclusion, we here combined the cytospin technique, a multi-colour immunofluorescence staining panel, and an automated image analysis pipeline to enable the quantification of SC purity and SC proliferation from small cell aliquots. This procedure represents a solid read-out to simplify and standardize the quantification of primary SC culture purity and proliferation.

Genetic platelet depletion is superior in platelet transfusion compared to current models

Genetically modified mice have advanced our knowledge on platelets in hemostasis and beyond tremendously. However, mouse models harbor certain limitations, including availability of platelet specific transgenic strains, and off-target effects on other cell types. Transfusion of genetically modified platelets into thrombocytopenic mice circumvents these problems. Additionally, ex vivo treatment of platelets prior to transfusion eliminates putative side effects on other cell types. Thrombocytopenia is commonly induced by administration of anti-platelet antibodies, which opsonize platelets to cause rapid clearance. However, antibodies do not differentiate between endogenous or exogenous platelets, impeding transfusion efficacy. In contrast, genetic depletion with the inducible diphtheria toxin receptor (iDTR) system induces thrombocytopenia via megakaryocyte ablation without direct effects on circulating platelets. We compared the iDTR system with antibody-based depletion methods regarding their utility in platelet transfusion experiments, outlining advantages and disadvantages of both approaches. Antibodies led to thrombocytopenia within two hours and allowed the dose-dependent adjustment of the platelet count. The iDTR model caused complete thrombocytopenia within four days, which could be sustained for up to 11 days. Neither platelet depletion approach caused platelet activation. Only the iDTR model allowed efficient platelet transfusion by keeping endogenous platelet levels low and maintaining exogenous platelet levels over longer time periods, thus providing clear advantages over antibody-based methods. Transfused platelets were fully functional in vivo, and our model allowed examination of transgenic platelets. Using donor platelets from already available genetically modified mice or ex vivo treated platelets, may decrease the necessity of platelet-specific mouse strains, diminishing off-target effects and thereby reducing animal numbers.

Platelet PI3K Modulates Innate Leukocyte Extravasation during Acid-Induced Acute Lung Inflammation

Introduction Blood platelets are increasingly recognized as modulators of leukocyte effector functions in various pathologies including acute lung injury (ALI). ALI is a life-threatening disease, caused by damage to the alveolar epi- and endothelium. Excessive accumulation of leukocytes leads to severe lung inflammation, resulting in impaired lung function and hypoxemia.

Objective Since leukocyte migration is modulated by activated platelets and phosphatidylinositol 3-kinase (PI3K) signaling is involved in platelet function, we aimed to elucidate the effect of PI3K on platelet-mediated immune responses.

Materials and Methods We generated a mouse model with a platelet-specific deletion of p85α, the most important regulatory subunit of the class IA PI3K, and evaluated platelet function and platelet–leukocyte interactions. Moreover, we analyzed the impact of platelet-specific p85α gene deficiency during sterile peritonitis and acid-induced ALI.

Results In vitro analyses of platelets revealed that lack of p85α led to decreased downstream signaling and diminished expression of surface activation markers, for example, CD62P and CD63, as well as reduced platelet aggregation. Moreover, platelet PI3K essentially mediated direct interactions of platelets with monocytes and neutrophils. In mice, platelet-specific p85α deficiency prevented leukocyte infiltration into the peritoneum and the bronchoalveolar compartment during sterile peritonitis and ALI, respectively. Additionally, the release of the inflammatory cytokine interleukin-12/23 was diminished in platelet p85α-deficient mice during ALI. In contrast to PI3K, neither overexpression nor depletion of platelet phosphatase and tensin homolog, the endogenous antagonist of PI3K, significantly modulated platelet function.

Conclusion Our data indicate a crucial role of platelet PI3K signaling for leukocyte extravasation upon inflammatory stimuli in various diseases models.

Platelets in Sepsis: An Update on Experimental Models and Clinical Data

Beyond their important role in hemostasis, platelets play a crucial role in inflammatory diseases. This becomes apparent during sepsis, where platelet count and activation correlate with disease outcome and survival. Sepsis is caused by a dysregulated host response to infection, leading to organ dysfunction, permanent disabilities, or death. During sepsis, tissue injury results from the concomitant uncontrolled activation of the complement, coagulation, and inflammatory systems as well as platelet dysfunction. The balance between the systemic inflammatory response syndrome (SIRS) and the compensatory anti-inflammatory response (CARS) regulates sepsis outcome. Persistent thrombocytopenia is considered as an independent risk factor of mortality in sepsis, although it is still unclear whether the drop in platelet count is the cause or the consequence of sepsis severity. The role of platelets in sepsis development and progression was addressed in different experimental in vivo models, particularly in mice, that represent various aspects of human sepsis. The immunomodulatory function of platelets depends on the experimental model, time, and type of infection. Understanding the molecular mechanism of platelet regulation in inflammation could bring us one step closer to understand this important aspect of primary hemostasis which drives thrombotic as well as bleeding complications in patients with sterile and infectious inflammation. In this review, we summarize the current understanding of the contribution of platelets to sepsis severity and outcome. We highlight the differences between platelet receptors in mice and humans and discuss the potential and limitations of animal models to study platelet-related functions in sepsis.

Cell Type-Specific Roles of NF-κB Linking Inflammation and Thrombosis

The transcription factor NF-κB is a central mediator of inflammation with multiple links to thrombotic processes. In this review, we focus on the role of NF-κB signaling in cell types within the vasculature and the circulation that are involved in thrombo-inflammatory processes. All these cells express NF-κB, which mediates important functions in cellular interactions, cell survival and differentiation, as well as expression of cytokines, chemokines, and coagulation factors. Even platelets, as anucleated cells, contain NF-κB family members and their corresponding signaling molecules, which are involved in platelet activation, as well as secondary feedback circuits. The response of endothelial cells to inflammation and NF-κB activation is characterized by the induction of adhesion molecules promoting binding and transmigration of leukocytes, while simultaneously increasing their thrombogenic potential. Paracrine signaling from endothelial cells activates NF-κB in vascular smooth muscle cells and causes a phenotypic switch to a “synthetic” state associated with a decrease in contractile proteins. Monocytes react to inflammatory situations with enforced expression of tissue factor and after differentiation to macrophages with altered polarization. Neutrophils respond with an extension of their life span—and upon full activation they can expel their DNA thereby forming so-called neutrophil extracellular traps (NETs), which exert antibacterial functions, but also induce a strong coagulatory response. This may cause formation of microthrombi that are important for the immobilization of pathogens, a process designated as immunothrombosis. However, deregulation of the complex cellular links between inflammation and thrombosis by unrestrained NET formation or the loss of the endothelial layer due to mechanical rupture or erosion can result in rapid activation and aggregation of platelets and the manifestation of thrombo-inflammatory diseases. Sepsis is an important example of such a disorder caused by a dysregulated host response to infection finally leading to severe coagulopathies. NF-κB is critically involved in these pathophysiological processes as it induces both inflammatory and thrombotic responses.

Neutrophil-Mediated Proteolysis of Thrombospondin-1 Promotes Platelet Adhesion and String Formation

Thrombospondin-1 (TSP-1) is primarily expressed by platelets and endothelial cells (ECs) and rapidly released upon their activation. It functions in haemostasis as a bridging molecule in platelet aggregation, by promoting platelet adhesion to collagen and by protecting von Willebrand factor strings from degradation. In blood of patients undergoing surgery and in co-cultures of neutrophils with platelets or ECs, we observed proteolysis of the 185 kDa full-length TSP-1 to a 160-kDa isoform. We hypothesized that TSP-1 processing may alter its haemostatic properties. Selective enzyme inhibitors in co-cultures revealed that neutrophil proteases elastase and cathepsin G mediate TSP-1 processing. The cut site of cathepsin G was mapped to TSP-1 amino acids R237/T238 by Edman sequencing. Formation of neutrophil extracellular traps protected TSP-1 from complete degradation and promoted controlled processing to the 160-kDa isoform. Haemostatic properties were tested by platelet aggregation, adhesion, coagulation and string formation under flow. Platelets from TSP-1 deficient mice did not differ from wild-type in platelet aggregation but showed severe impairment of platelet adhesion to collagen and string formation under flow. Reconstitution experiments revealed that the 160-kDa TSP-1 isoform was markedly more potent than the 185-kDa full-length molecule in restoring function. Thus, TSP-1 processing by neutrophil proteases yields a 160-kDa isoform which shows enhanced potency to promote platelet adhesion and string formation. This finding reveals a novel mechanism of neutrophil-mediated thrombus formation and provides first evidence for the impact of TSP-1 proteolysis on its haemostatic properties.

Periodontal treatment limits platelet activation in patients with periodontitis-a controlled-randomized intervention trial

AIM

Periodontitis results in platelet activation and enhanced risk for cardiovascular disease. As it is currently unknown whether periodontal treatment reverses platelet hyper-reactivity, we aimed to investigate the role of periodontal treatment on platelet activation.

MATERIALS AND METHODS

In a prospective controlled therapeutic trial, 52 patients were enrolled and randomly selected for periodontal treatment or monitored without treatment for 3 months. Patient blood was analysed by flow cytometry for platelet activation markers and by light transmission aggregometry for platelet aggregation in response to pro-thrombotic stimuli.

RESULTS

In this study, platelet activation in the control group aggravated over the observation period of 3 months, whereas patients that underwent periodontal treatment showed unchanged levels of platelet activation, measured by surface expression of CD62P, CD40L, generation of reactive oxygen production, activation of GPIIb/IIIa and fibrinogen binding. Moreover, platelet turnover, measured by platelet RNA content and platelet aggregation in response to collagen, differed significantly between patients that were treated and those who were untreated.

CONCLUSIONS

Subgingival debridement reduces the risk of aggravated platelet activation and therefore might potentially diminish subsequent diseases such as cardiovascular disease in periodontal patients.

Is unilateral lower leg orthosis with a circular foot unit in the treatment of idiopathic clubfeet a reasonable bracing alternative in the Ponseti method? Five-year results of a supraregional paediatric-orthopaedic centre

Background

In the Ponseti treatment of idiopathic clubfoot, children are generally provided with a standard foot abduction orthosis (FAO). A significant proportion of these patients experience irresolvable problems with the FAO leading to therapeutic non-compliance and eventual relapse. Accordingly, these patients were equipped with a unilateral lower leg orthosis (LLO) developed in our institution. The goal of this retrospective study was to determine compliance with and the efficacy of the LLO as an alternative treatment measure. The minimum follow-up was 5 years.

Results

A total of 45 patients (75 ft) were retrospectively registered and included in the study. Compliance with the bracing protocol was 91% with the LLO and 46% with the FAO. The most common problems with the FAO were sleep disturbance (50%) and cutaneous problems (45%). Nine percent of patients experienced sleep disturbance, and no cutaneous problems occurred with the LLO. Thirteen percent of patients being treated with an FAO until the age of four (23 patients; 40 ft) underwent surgery because of relapse, defined by rigid recurrence of any of the components of a clubfoot. Fourteen percent of patients being treated with an LLO (22 patients; 35 ft), mostly following initial treatment with an FAO, experienced recurrence.

Conclusion

Changing from FAO to LLO at any point during treatment did not result in an increased rate of surgery and caused few problems.

Electronic supplementary material

The online version of this article (10.1186/s12891-018-2160-1) contains supplementary material, which is available to authorized users.

Androgen receptor dampens tissue factor expression via nuclear factor-κB and early growth response protein 1

Essentials Androgen deprivation increases the rate of venous thromboembolism in prostate cancer patients. We characterized androgen receptor-mediated tissue factor regulation in prostate epithelial cells. Androgen receptor is dampening tissue factor expression in prostate epithelial cells. Androgen deprivation could enhance tissue factor expression and raise venous thromboembolism rates.

SUMMARY

Background Prostate cancer is one of the leading causes of cancer death in men. Advanced prostate cancer is usually treated by androgen deprivation therapy (ADT), which is aimed at reducing circulating testosterone levels to reduce cancer growth. There is growing evidence that ADT can increase the rate of venous thromboembolism (VTE) in prostate cancer patients. The tissue factor (TF) gene is one of the most important mediators of coagulation and VTE, but, so far, there are limited data on androgen receptor (AR)-mediated TF gene expression. Objectives To characterize AR-mediated TF regulation in vitro and in vivo. Methods We used the androgen-dependent prostate cancer cell lines LNCaP and MyC-CaP to test whether TF expression is regulated by AR. Furthermore, we cloned the TF gene promoter into a luciferase reporter vector to identify the transcription factor-binding sites that mediate TF regulation downstream of AR. Finally, we used castration experiments in mice to characterize AR-mediated TF regulation in vivo. Results TF is directly regulated by AR. In LNCaP cells, nuclear factor-κB signaling and EGR1 mediate TF expression. By using castration experiments in mice, we could detect upregulation of TF and early growth response protein 1 mRNA and protein expression in prostate epithelial cells. Conclusion AR is crucial for dampening TF expression, which could be important for increased TF expression and TF-positive microvesicle release in androgen-deprived prostate cancer patients.

A novel method for automated assessment of megakaryocyte differentiation and proplatelet formation

Transfusion of platelet concentrates represents an important treatment for various bleeding complications. However, the short half-life and frequent contaminations with bacteria restrict the availability of platelet concentrates and raise a clear demand for platelets generated ex vivo. Therefore, in vitro platelet generation from megakaryocytes represents an important research topic. A vital step for this process represents accurate analysis of thrombopoiesis and proplatelet formation, which is usually conducted manually. We aimed to develop a novel method for automated classification and analysis of proplatelet-forming megakaryocytes in vitro. After fluorescent labelling of surface and nucleus, MKs were automatically categorized and analysed with a novel pipeline of the open source software CellProfiler. Our new workflow is able to detect and quantify four subtypes of megakaryocytes undergoing thrombopoiesis: proplatelet-forming, spreading, pseudopodia-forming and terminally differentiated, anucleated megakaryocytes. Furthermore, we were able to characterize the inhibitory effect of dasatinib on thrombopoiesis in more detail. Our new workflow enabled rapid, unbiased, quantitative and qualitative in-depth analysis of proplatelet formation based on morphological characteristics. Clinicians and basic researchers alike will benefit from this novel technique that allows reliable and unbiased quantification of proplatelet formation. It thereby provides a valuable tool for the development of methods to generate platelets ex vivo and to detect effects of drugs on megakaryocyte differentiation.

Measuring and interpreting platelet-leukocyte aggregates

Platelets, besides their specialised role in haemostasis and atherothrombosis, actively modulate innate and adaptive immune responses with crucial roles in immune surveillance, inflammation and host defence during infection. An important prerequisite for platelet-mediated changes of immune functions involves direct engagement with different types of leukocytes. Indeed, increased platelet-leukocyte aggregates (PLAs) within the circulation and/or locally at the site of inflammation represent markers of many thrombo-inflammatory diseases, such as cardiovascular diseases, acute lung injury, renal and cerebral inflammation. Therefore, measurement of PLAs could provide an attractive and easily accessible prognostic and/or diagnostic tool for many diseases. To measure PLAs in different (patho-)physiological settings in human and animal models flow cytometric and microscopic approaches have been applied. These techniques represent complementary tools to study different aspects relating to the involvement of leukocyte subtypes and molecules, as well as location of PLAs within tissues, dynamics of their interactions and/or dynamic changes in leukocyte and platelet behaviour. This review summarises various approaches to measure and interpret PLAs and discusses potential experimental factors influencing platelet binding to leukocytes. Furthermore, we summarise insights gained from studies regarding the underlying mechanism of platelet-leukocyte interactions and discuss implications of these interactions in health and disease.

Optimized plasma preparation is essential to monitor platelet-stored molecules in humans

Platelets store a plethora of different molecules within their granules, modulating numerous pathways, not only in coagulation, but also in angiogenesis, wound healing, and inflammatory diseases. These molecules get rapidly released upon activation and therefore represent an easily accessible indirect marker for platelet activation. Accurate analysis of platelet-derived molecules in the plasma requires appropriate anticoagulation to avoid in vitro activation and subsequent degranulation of platelets, potentially causing artificially high levels and masking biologically relevant differences within translational research studies. However, there is still enormous heterogeneity among anticoagulants used to prevent unwanted platelet activation, so that plasma levels reported for platelet granule contents range over several orders of magnitude. To address this problem and to define the most robust method of plasma preparation to avoid in vitro platelet activation during processing, we compared plasma concentrations of the three platelet-stored factors thrombospondin (TSP-1), platelet factor 4 (PF4), and soluble P-selectin (sCD62P) between human blood samples anticoagulated with either citrate-theophylline-adenosine-dipyridamole (CTAD), acid-citrate-dextrose (ACD), citrate, ethylenediaminetetraacetic acid (EDTA) or heparin. Additionally, we assessed the effect of storage temperature and time between blood drawing and sample processing within the differentially anticoagulated samples. Our data strongly support the use of CTAD as anticoagulant for determining plasma concentrations of platelet-stored molecules, as anticoagulation with heparin or EDTA led to a 12.4- or 8.3-fold increase in plasma levels of PF4, respectively. Whereas ACD was similar effective as CTAD, citrate only showed comparable PF4 plasma levels when plasma was kept at 4°C. Moreover, blood sampling with CTAD as anticoagulant resulted in the most reproducible values, even when samples were processed at ambient temperature or after storage over 6 hours. In the latter case, anticoagulation with heparin or EDTA led to artificially high plasma levels indicative of in vitro platelet activation. Therefore, we want to raise scientific awareness for choosing CTAD as optimal anticoagulant for the detection of platelet-stored molecules in plasma.

Abstract 527: Myeloid PTEN deficiency impairs tumor immune surveillance via immune checkpoint inhibition

In the current study we are investigating the effects of PTEN-deficient myeloid cells on tumor immune surveillance. We could previously show that hyper-activation of the PI3K signaling cascade by genetic knock-out of the counteracting phosphatase PTEN induced an anti-inflammatory phenotype in myeloid cells. This resulted in protection of conditional knock-out mice in models of acute infection and inflammation.

A reduction in pro-inflammatory responses could however increase tumor burden. To address this question we induced colitis associated colon cancer in conditional PTEN-KO mice and found an increase in tumor burden and a reduction in survival in male KO mice. This was accompanied by increased numbers of splenic antigen-presenting cells (APC) expressing the immune checkpoint regulators PD-L1 and PD-L2. Furthermore, transcriptome analysis in these cells revealed a shift towards gene expression profiles found in professional APCs capable of cross-presentation. As expected, ex-vivo stimulated T-cells from KO-mice showed a reduction in proliferative capacity. These findings were further substantiated by findings in a second tumor model using implanted B16 melanoma cells. In this model myeloid PTEN-deficient mice showed a decrease in T-cell activation and a reduction in melanoma cell killing capacity.

Taken together, our findings show that genetic deletion of PTEN in cells of myeloid origin increases splenic APCs expressing immune checkpoint regulators resulting in a decrease in tumor immune surveillance. Our study shows that PI3K-inhibitors which are currently tested as anti-cancer drugs might have additional beneficial effects on immune cells by shifting their inflammatory phenotype.

Citation Format: Mario Kuttke, Emine Sahin, Julia Pisoni, Sophie Percig, Andrea Vogel, Daniel Kraemmer, Leslie Hanzl, Julia Stefanie Brunner, Hannah Paar, Klara Soukup, Angela Halfmann, Alexander Dohnal, Carl-Walter Steiner, Stephan Blüml, Jose Basilio, Bernhard Hochreiter, Manuel Salzmann, Bastian Hoesel, Günther Lametschwandtner, Robert Eferl, Johannes Schmid, Gernot Schabbauer. Myeloid PTEN deficiency impairs tumor immune surveillance via immune checkpoint inhibition. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 527.

Myeloid PTEN deficiency impairs tumor-immune surveillance via immune-checkpoint inhibition

Tumor-host interaction is determined by constant immune surveillance, characterized by tumor infiltration of myeloid and lymphoid cells. A malfunctioning or diverted immune response promotes tumor growth and metastasis. Recent advances had been made, by treating of certain tumor types, such as melanoma, with T-cell checkpoint inhibitors. This highlights the importance of understanding the molecular mechanisms underlying the crosstalk between tumors and their environment, in particular myeloid and lymphoid cells. Our aim was to study the contribution of the myeloid PI3K/PTEN-signaling pathway in the regulation of tumor-immune surveillance in murine models of cancer. We made use of conditional PTEN-deficient mice, which exhibit sustained activation of the PI3K-signaling axis in a variety of myeloid cell subsets such as macrophages and dendritic cells (DCs). In colitis-associated colon cancer (CAC), mice deficient in myeloid PTEN showed a markedly higher tumor burden and decreased survival. We attributed this observation to the increased presence of immune-modulatory conventional CD8α(+) DCs in the spleen, whereas other relevant myeloid cell subsets were largely unaffected. Notably, we detected enhanced surface expression of PD-L1 and PD-L2 on these DCs. As a consequence, tumoricidal T-cell responses were hampered or redirected. Taken together, our findings indicated an unanticipated role for the PI3K/PTEN-signaling axis in the functional regulation of splenic antigen-presenting cells (APCs). Our data pointed at potential, indirect, tumoricidal effects of subclass-specific PI3K inhibitors, which are currently under clinical investigation for treatment of tumors, via myeloid cell activation.

Platelet Interaction with Innate Immune Cells

Beyond their traditional role in haemostasis and thrombosis, platelets are increasingly recognised as immune modulatory cells. Activated platelets and platelet-derived microparticles can bind to leukocytes, which stimulates mutual activation and results in rapid, local release of platelet-derived cytokines. Thereby platelets modulate leukocyte effector functions and contribute to inflammatory and immune responses to injury or infection. Platelets enhance leukocyte extravasation, differentiation and cytokine release. Platelet-neutrophil interactions boost oxidative burst, neutrophil extracellular trap formation and phagocytosis and play an important role in host defence. Platelet interactions with monocytes propagate their differentiation into macrophages, modulate cytokine release and attenuate macrophage functions. Depending on the underlying pathology, platelets can enhance or diminish leukocyte cytokine production, indicating that platelet-leukocyte interactions represent a fine balanced system to restrict excessive inflammation during infection. In atherosclerosis, platelet interaction with neutrophils, monocytes and dendritic cells accelerates key steps of atherogenesis by promoting leukocyte extravasation and foam cell formation. Platelet-leukocyte interactions at sites of atherosclerotic lesions destabilise atherosclerotic plaques and promote plaque rupture. Leukocytes in turn also modulate platelet function and production, which either results in enhanced platelet destruction or increased platelet production. This review aims to summarise the key effects of platelet-leukocyte interactions in inflammation, infection and atherosclerosis.

Platelet activation at the onset of human endotoxemia is undetectable in vivo

Infection induces platelet activation and consumption, which leads to thrombocytopenia, enhances microvascular thrombosis, impairs microcirculation and eventually triggers disseminated intravascular coagulation (DIC). It is well characterized that endotoxemia results in a pro-inflammatory and pro-coagulatory state, which favors platelet activation. However the early, direct effects of endotoxemia on platelets have not been investigated so far. Therefore we aimed to determine the early effects of the endotoxin lipopolysaccharide (LPS) on platelet function in vivo. In a human endotoxemia model, 15 healthy volunteers were stimulated with LPS (2 ng/kg). Blood was drawn before, 10, 30 and 60 min after LPS challenge and platelet activation analyzed by flow cytometry (GPIIb/IIIa activation, surface CD62P and CD40L, intraplatelet reactive oxygen formation and platelet-leukocyte aggregates) and ELISA (sCD40L, sCD62P and CXCL4). In parallel, blood samples and platelets were spiked with LPS (50 pg/ml) in vitro and monitored over 60 min for the same platelet activation markers. In vitro platelet stimulation with LPS activated platelets independent of the presence of leukocytes and enhanced their adhesion to endothelial cells. In contrast, in vivo no increase in GPIIb/IIIa activation or surface expression of CD62P was observed. However, endotoxemia resulted in a significant drop in platelet count and elevated the plasma CXCL4 levels already 10 min after the LPS challenge. These data indicate that LPS rapidly activates platelets, leading to α-granule release and endothelial adhesion. This might explain the drop in platelet count observed at the onset of endotoxemia.

[Spastic foot deformities in children: surgical management]

Although the neurological defects associated with cerebral palsy are not progressive, secondary musculoskeletal disorders due to growth and gravity are variable. In the clinical analysis of spastic foot deformities different mechanisms that produce a variety of deformities have to be analyzed. The goals of surgical treatment are correction of the deformity, reestablishment of stability of the foot and preservation of functionally important ranges of motion and muscle strength. The most common spastic foot deformities are equinus, planovalgus, equinovarus and calcaneus. For treatment soft tissue surgery, such as muscle lengthening and transfer together with bone surgery, such as osteotomy or arthrodesis are used and combinations of these methods are often required. Subsequently postoperative plasters are necessary followed by dynamic orthotic management.

[Determination of activity levels in patients with cerebral palsy]

AIM

The aim of this study is the determination of physical activity in everyday life of handicapped persons due to cerebral palsy using standardised testing procedures.

METHOD

The subjects were examined according to the Conconi test on a treadmill at increasing speeds for their fitness. We used a continuous heart rate monitoring, 3-axis acceleration sensors, lactate measurements and pedography.

RESULTS

Three groups of subjects could be differentiated. In one group, a rapid rise in heart rate even at lower walking speed was observed. In a second group of persons with poor motor coordination, the maximum walking speed was limited. Single subjects were not limited neither in their physical performance nor in their condition.

CONCLUSION

In the physical therapy for patients with cerebral palsy one should not lose sight of possible cardiovascular limitations additional to the physical disabilities.

[Primary malignant bone tumors]

Among human neoplasms, primary malignant bone tumors are fairly rare. They present an incidence rate of roughly 10 cases per 1 million inhabitants per year. During childhood (<15 years), the percentage of malignant bone tumors amounts to 6% of all infantile malignancies. Only leukemia and lymphoma show a higher incidence in adolescence. Of all primary malignant bone tumors, 60% affect patients younger than 45 years and the peak incidence of all bone tumors occurs between 15 and 19 years. The most common primary malignant bone tumors are osteosarcoma (35%), chondrosarcoma (25%), and Ewing's sarcoma (16%). Less frequently (≤ 5%) occurring tumors are chordoma, malignant fibrous histiocytoma of bone, and fibrosarcoma of bone. Vascular primary malignant tumors of bone and adamantinoma are very rare. Staging of the lesion is essential for systemic therapeutic decision-making and includes complete imaging and histo-pathological confirmation of the suspected entity. In most cases, this is established by open- or image-guided biopsy. Based on this information, an interdisciplinary tumor board will determine the individual therapeutic approach. Endoprosthetic or biological reconstruction following wide tumor resection is the most common surgical therapy for primary malignant bone tumors. There is vital importance in a thorough postoperative follow-up and continous after-care by a competent tumor center which is permanentely in charge of therapy.

CSF biomarkers in posterior cortical atrophy

OBJECTIVE

To describe CSF biomarker profiles in posterior cortical atrophy (PCA), which induces high-order visual deficits often associated with Alzheimer disease (AD) pathology, and relate these findings to clinical and neuropsychological assessment.

METHODS

This prospective observational study included 22 patients with PCA who underwent CSF biomarker analysis of total tau (t-tau), phosphorylated tau on amino acid 181 (p-tau181), and amyloid β (Aβ(42)). At group level, the CSF profiles of patients with PCA were compared to those of patients with typical AD and patients with other dementia (OD). Individually, the clinical presentation of patients with PCA was correlated to their CSF profile to assess the predictability of clinical features for diagnosis of underlying AD pathology.

RESULTS

At group level, the PCA biomarker profile was not different from that of the AD group, but very different from that of the OD group (p < 0.001). More than 90% of patients with PCA had CSF profiles consistent with AD. All patients with PCA with either isolated higher-order visual deficit (n = 8) or visual deficit associated with memory impairment (n = 11) had CSF profiles consistent with AD. Only one of the 3 patients with PCA with asymmetric motor signs fulfilled biological CSF criteria for AD.

CONCLUSIONS

PCA syndrome is usually associated with CSF biomarkers suggestive of AD, as shown by previous neuropathologic studies. This does not apply in case of motor signs suggesting associated corticobasal syndrome. CSF biomarkers help to discriminate AD from non-AD processes associated with this condition.