Semaphorin 7A coordinates Neutrophil response during pulmonary inflammation and sepsis

RATIONALE

Pulmonary defense mechanisms are critical for host integrity during pneumonia and sepsis. This defense is fundamentally dependent on the activation of neutrophils during the innate immune response. Recent work has shown that Semaphorin 7A (Sema7A) holds significant impact on platelet function, yet its role on neutrophil function within the lung is not well understood.

OBJECTIVE

To identify the role of Sema7A during pulmonary inflammation and sepsis.

MEASUREMENTS AND MAIN RESULTS

In ARDS patients we were able to show a correlation between Sema7A and oxygenation levels. During subsequent workup we found that Sema7A binds to the neutrophil PlexinC1 receptor, increasing integrins and L-selectin on neutrophils. Sema7A prompted neutrophil chemotaxis in-vitro and the formation of platelet-neutrophil complexes in-vivo. We also observed altered adhesion and transmigration of neutrophils in Sema7A-/- animals in the lung during pulmonary inflammation. This effect resulted in increased number of neutrophils in the interstitial space of Sema7A-/- animals but reduced numbers of neutrophils in the alveolar space during pulmonary sepsis. This finding was associated with significantly worse outcome of Sema7A-/- animals in a model of pulmonary sepsis.

CONCLUSIONS

Sema7A has an immunomodulatory effect in the lung affecting pulmonary sepsis and ARDS. This effect influences the response of neutrophils to external aggression and might influence patient outcome.

Semaphorin 7A is protective during inflammatory peritonitis through integrin receptor signaling

Introduction

The study explores the role of endothelial Semaphorin 7A (SEMA7A) in inflammatory processes. SEMA7A is known for enhancing inflammation during tissue hypoxia and exhibiting anti-inflammatory properties in the intestinal system during colitis. This research extends the understanding of SEMA7A's function by examining its role in inflammatory peritonitis and intestinal inflammation.

Methods

The research involved inducing peritonitis in SEMA7A knockout (SEMA7A-/-) and wild-type (WT) animals through Zymosan A (ZyA) injection. The inflammatory response was assessed by measuring cell count and cytokine release. In parallel, the study investigated the expression of SEMA7A in intestinal epithelial cells under inflammatory stimuli and its impact on interleukin 10 (IL-10) production using an in vitro co-culture model of monocytes and epithelial cells. Additionally, the distribution of SEMA7A target receptors, particularly ITGAV/ITGB1 (CD51/CD29), was analyzed in WT animals.

Results

The results revealed that SEMA7A-/- animals exhibited increased inflammatory peritonitis compared to the WT animals. Inflammatory conditions in intestinal epithelial cells led to the induction of SEMA7A. The co-culture experiments demonstrated that SEMA7A induced IL-10 production, which depended on integrin receptors and was independent of PLXNC1 expression. Furthermore, ITGAV/ITGB1 emerged as the predominant SEMA7A receptor in the intestinal area of WT animals.

Discussion

These findings underscore the multifaceted role of SEMA7A in inflammatory processes. The differential responses in peritonitis and intestinal inflammation suggest that SEMA7A's function is significantly influenced by the expression and distribution of its target receptors within different organ systems. The study highlights the complex and context-dependent nature of SEMA7A in mediating inflammatory responses.

A key role for platelet GPVI in neutrophil recruitment, migration, and NETosis in the early stages of acute lung injury

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are associated with high morbidity and mortality. Excessive neutrophil infiltration into the pulmonary airspace is the main cause for the acute inflammation and lung injury. Platelets have been implicated in the pathogenesis of ALI/ARDS, but the underlying mechanisms are not fully understood. Here, we show that the immunoreceptor tyrosine-based activation motif-coupled immunoglobulin-like platelet receptor, glycoprotein VI (GPVI), plays a key role in the early phase of pulmonary thrombo-inflammation in a model of lipopolysaccharide (LPS)-induced ALI in mice. In wild-type (WT) control mice, intranasal LPS application triggered severe pulmonary and blood neutrophilia, hypothermia, and increased blood lactate levels. In contrast, GPVI-deficient mice as well as anti-GPVI-treated WT mice were markedly protected from pulmonary and systemic compromises and showed no increased pulmonary bleeding. High-resolution multicolor microscopy of lung sections and intravital confocal microcopy of the ventilated lung revealed that anti-GPVI treatment resulted in less stable platelet interactions with neutrophils and overall reduced platelet-neutrophil complex (PNC) formation. Anti-GPVI treatment also reduced neutrophil crawling and adhesion on endothelial cells, resulting in reduced neutrophil transmigration and alveolar infiltrates. Remarkably, neutrophil activation was also diminished in anti-GPVI-treated animals, associated with strongly reduced formation of PNC clusters and neutrophil extracellular traps (NETs) compared with that in control mice. These results establish GPVI as a key mediator of neutrophil recruitment, PNC formation, and NET formation (ie, NETosis) in experimental ALI. Thus, GPVI inhibition might be a promising strategy to reduce the acute pulmonary inflammation that causes ALI/ARDS.

Platelets and the Cybernetic Regulation of Ischemic Inflammatory Responses through PNC Formation Regulated by Extracellular Nucleotide Metabolism and Signaling

Ischemic events are associated with severe inflammation and are here referred to as ischemic inflammatory response (IIR). Recent studies identified the formation of platelet–neutrophil complexes (PNC) as key players in IIR. We investigated the role of extracellular platelet nucleotide signaling in the context of IIR and defined a cybernetic circle, including description of feedback loops. Cybernetic circles seek to integrate different levels of information to understand how biological systems function. Our study specifies the components of the cybernetic system of platelets in IIR and describes the theoretical progression of IIR passing the cybernetic cycle with positive and negative feedback loops based on nucleotide-dependent signaling and functional regulation. The cybernetic components and feedback loops were explored by cytometry, immunohistological staining, functional blocking antibodies, and ADP/ATP measurements. Using several ex vivo and in vivo approaches we confirmed cybernetic parameters, such as controller, sensor, and effector (VASP phosphorylation, P2Y₁₂, ADORAs and GPIIb/IIIa activity), as well as set points (ADP, adenosine) and interfering control and disturbance variables (ischemia). We demonstrate the impact of the regulated platelet–neutrophil complex (PNC) formation in blood and the resulting damage to the affected inflamed tissue. Taken together, extracellular nucleotide signaling, PNC formation, and tissue damage in IIR can be integrated in a controlled cybernetic circle of platelet function, as introduced through this study.

[Early Pulmonary Rehabilitation after Long Term Mechanical Ventilation]

Einleitung  Unter Frührehabilitation versteht man eine frühzeitig bei- oder nach akuter Erkrankung einsetzende, rehabilitationsmedizinische Behandlung die im § 39SGB V verankert ist. Ziel dieser Untersuchung ist es, die Ergebnisqualität der pneumologischen Frührehabilitation zu untersuchen und darzustellen.

Methoden  Prospektive Erhebung von funktionellen Parametern, Beatmungsstatus und Entlass-Disposition in einer spezialisierten Abteilung für pneumologische Frührehabilitation über den Zeitraum von einem Jahr.

Ergebnisse  Von den 190 Patienten waren 179 (94,2 %) zuvor invasiv beatmet. Während einer Behandlungsdauer von 39 ± 17 Tagen stieg der FAM-Index von 84,4 ± 19,8 auf 118,5 ± 23,3 (Ci 30,9 – 37,3, Cohen’s d 1,58; p < 0,001), der Barthel-Index von 30,5 ± 13,8 auf 58,3 ± 16,2 (Ci 25,4 – 33,8, Cohen’s d 1,4; p < 0,001) und die Wegstrecke von 12,9 ± 40,1 m auf 131,4 ± 85,2 m (Ci 105,6 – 131,4 m, Cohen’s d 1,78; p < 0,001). Die Patienten wurden weniger häufig in eine weitere Anschlussheilbehandlung verlegt, wenn sie beatmet waren.

Diskussion  Patienten in der pneumologischen Frührehabilitation sind bei Aufnahme schwer kompromittiert, es lässt sich aber eine sehr gute Ergebnisqualität erzielen, die unabhängig davon zu sein scheint, ob der Patient eigenständig atmet oder mittels nicht-invasiver oder invasiver Beatmung versorgt wird. Die weitere Disposition dieser Patienten ist vor allem dann schwierig, wenn eine Beatmung vorliegt.

Red blood cell-derived semaphorin 7A promotes thrombo-inflammation in myocardial ischemia-reperfusion injury through platelet GPIb

Myocardial ischemia is one of the leading health problems worldwide. Therapy consists of the restitution of coronary perfusion which is followed by myocardial inflammation. Platelet–neutrophil interaction is a crucial process during inflammation, yet its consequences are not fully understood. Here, we show that platelet–neutrophil complexes (PNCs) are increased in patients with acute myocardial infarction and that this is associated with increased levels of neuronal guidance protein semaphorin 7A (SEMA7A). To investigate this further, we injected WT animals with Sema7a and found increased infarct size with increased numbers of PNCs. Experiments in genetically modified animals identify Sema7a on red blood cells to be crucial for this condition. Further studies revealed that Sema7a interacts with the platelet receptor glycoprotein Ib (GPIb). Treatment with anti-Sema7a antibody protected from myocardial tissue injury. In summary, we show that Sema7a binds to platelet GPIb and enhances platelet thrombo-inflammatory activity, aggravating post-ischemic myocardial tissue injury.

Reperfusion injury following myocardial ischemia is aggravated by inflammation and platelet–neutrophil complex formation. Here the authors show that semaphorin 7A binds to platelet GPIb, enhancing platelet–neutrophil interaction and increasing post-ischemic myocardial tissue injury, and that blockage of semaphorin 7A is protective.

Inhibition of CXCR4 and CXCR7 Is Protective in Acute Peritoneal Inflammation

Our previous studies revealed a pivotal role of the chemokine stromal cell-derived factor (SDF)-1 and its receptors CXCR4 and CXCR7 on migratory behavior of polymorphonuclear granulocytes (PMNs) in pulmonary inflammation. Thereby, the SDF-1-CXCR4/CXCR7-axis was linked with adenosine signaling. However, the role of the SDF-1 receptors CXCR4 and CXCR7 in acute inflammatory peritonitis and peritonitis-related sepsis still remained unknown. The presented study provides new insight on the mechanism of a selective inhibition of CXCR4 (AMD3100) and CXCR7 (CCX771) in two models of peritonitis and peritonitis-related sepsis by injection of zymosan and fecal solution. We observed an increased expression of SDF-1, CXCR4, and CXCR7 in peritoneal tissue and various organs during acute inflammatory peritonitis. Selective inhibition of CXCR4 and CXCR7 reduced PMN accumulation in the peritoneal fluid and infiltration of neutrophils in lung and liver tissue in both models. Both inhibitors had no anti-inflammatory effects in A_2B knockout animals (A_2B–/–). AMD3100 and CCX771 treatment reduced capillary leakage and increased formation of tight junctions as a marker for microvascular permeability in wild type animals. In contrast, both inhibitors failed to improve capillary leakage in A_2B–/– animals, highlighting the impact of the A_2B-receptor in SDF-1 mediated signaling. After inflammation, the CXCR4 and CXCR7 antagonist induced an enhanced expression of the protective A_2B adenosine receptor and an increased activation of cAMP (cyclic adenosine mono phosphate) response element-binding protein (CREB), as downstream signaling pathway of A_2B. The CXCR4- and CXCR7-inhibitor reduced the release of cytokines in wild type animals via decreased intracellular phosphorylation of ERK and NFκB p65. In vitro, CXCR4 and CXCR7 antagonism diminished the chemokine release of human cells and increased cellular integrity by enhancing the expression of tight junctions. These protective effects were linked with functional A_2B-receptor signaling, confirming our in vivo data. In conclusion, our study revealed new protective aspects of the pharmacological modulation of the SDF-1-CXCR4/CXCR7-axis during acute peritoneal inflammation in terms of the two hallmarks PMN migration and barrier integrity. Both anti-inflammatory effects were linked with functional adenosine A_2B-receptor signaling.

Expression patterns and functional evaluation of RGMa during the early phase of peripheral nerve regeneration using the mouse median nerve model

BACKGROUND

In this study, we evaluate the role of RGMa (Repulsive Guidance Molecule a) during peripheral nerve regeneration using the mouse median nerve model.

METHODS

By real-time PCR and Western Blot analysis, we examined expression changes of RGMa mRNA and RGMa protein in neural tissue after transection and microsurgical repair of the mouse median nerve distal to the transection site. We evaluated histomorphometrical changes in neural tissue distal to the injury site and functional recovery of the grasping force after median nerve transection and repair in wild-type mice and RGMa+/- heterozygous mice.

RESULTS

RT-PCR revealed a 1,8 fold increase of RGMa mRNA two weeks and a 4,4 fold increase of RGMa mRNA 3 weeks after nerve transection and repair in the nerve segment distal to the injury site. In Western blot analysis, we could show a high increase of RGMa in the nerve segment distal to the injury site at day 14. Histomorphometrical analysis showed significant differences between wild-type animals and heterozygous animals. The absolute number of myelinated fibres was significantly higher in operated heterozygous RGMa+/- animals compared to operated wildtye animals. Using the functional grasping test, we could demonstrate that peripheral nerve regeneration is significantly diminished in heterozygous RGMa+/- mice.

CONCLUSIONS

Employing the mouse median nerve model in transgenic animals, we demonstrate that RGMa plays an important role during peripheral nerve regeneration.

[The Role of Air Pollutants for Health - A Reply to the Expert Opinion of the International Society for Environmental Epidemiology (ISEE) and the European Respiratory Society (ERS)]

In Deutschland gibt es regionale Fahrverbote für ältere Dieselfahrzeuge ohne SCR-Katalysator bei Überschreitung der Grenzwerte für NO2. Dies hat zu einer intensiven Diskussion über die Rolle der Luftschadstoffe für die Gesundheit geführt. In der Replik wird dargestellt, dass die Daten zur Wirkung von Stickstoffdioxid (NO2) und Feinstaub (PM10 und PM2,5) nicht ausreichen, um die Fahrverbote zu begründen.

Für NO2 gibt es passagere Reaktionen bei unbehandelten Asthmatikern ab 500 µg/m3. Die deutschen Grenzwerte (Jahresmittelwert 40 µg/m3) fußen im Wesentlichen auf einer Metaanalyse von 9 Studien aus Innenraumbelastungen wobei nur in 4 Studien NO2 gemessen wurde. In der großen europäischen Escape-Studie von 2014 wurde kein Einfluss von NO2 auf die Mortalität gefunden.

Als Surrogatparameter für andere Schadstoffe ist NO2 ebenfalls nicht mehr geeignet, da seit Einführung der Partikelfilter bei Dieselautos (etwa ab 2000) der KFZ-Anteil am Feinstaub an der Straße unter 10 % liegt. Der Feinstaub besteht im Wesentlichen aus Aufwirbelung von mineralischen, organischen Bodensubstanzen sowie Reifenabrieb und wird am stärksten durch Wetterphänomene, vor allen Dingen durch Sonneneinstrahlung beeinflusst.

Die Grenzwerte für NO2 und Feinstaub werden errechnet aus epidemiologischen Beobachtungsstudien. Es findet sich zumeist eine schwache Assoziation zwischen der Konzentra-tion und zahlreichen Erkrankung sowie der Mortalität. Epidemiologische Beobachtungsstudien erlauben nur die Bildung einer Hypothese. Permanente Wiederholungen der Beobachtungsstudien betätigen nur, dass manche gefundenen Phänomene nicht zufällig sind. Eine Kausalität kann daraus nicht abgeleitet werden, da es zahlreiche Erklärungsmodelle neben dem NO2 und Feinstaub gibt. Dazu wären Interventionsstudien im Niedrigdosisbereich sowie Tierexperimente erforderlich. Diese Daten fehlen nahezu komplett bzw. sind, soweit vorhanden, allesamt negativ.

Nie diskutiert wird eine starke Widerlegung der Hypothese der Gefährdung von NO2 und Feinstaub im Grenzwertbereich durch das Inhalationsrauchen. Die Raucher stellen quasi einen inhalationstoxikologischen Großversuch dar. Der Zigarettenrauch enthält sehr hohe Feinstaub-, Stickstoffmonoxid- (NO) und NO2-Konzentrationen, die vom Organismus erstaunlich gut toleriert werden. Das hängt damit zusammen, dass NO ein Naturstoff ist, der in den Zellen oder auch in den Nasennebenhöhlen in z. T. sehr hohen Konzentrationen (über 30 000 µg/m3) vorkommt. Eines der Abbauprodukte von NO ist NO2, was im Wasser zu Nitrat und Nitrit disproportioniert wird. Ein Teil von NO2 wird zur Synthese von Fettsäuren verwendet.

Zigaretten haben ein Kondensat von ca. 7 – 10 mg. Nimmt man als Vergleich eine lebenslange Dauerbelastung durch Feinstaub und NO2 in den Grenzwertkonzentrationen an, müssten alle Raucher nach wenigen Tagen bis Monaten zahlreiche Erkrankungen entwickeln, die dem Feinstaub und NOx angelastet werden. Auch die Mortalität müsste drastisch erhöht sein; nahezu alle Raucher müssten bereits nach 1 packyear verstorben sein. Der Unterschied wird noch größer, wenn man die nachgewiesene Toxizität und Kanzerogenität des Zigarettenrauchs im Vergleich zu dem i. d. R. deutlich weniger gefährlichen Feinstaub an der Straße ins Verhältnis setzt.

Die überschätzte Beeinflussung der Exazerbationsrate bei COPD durch Inhalativa (LABA, LAMA, ICS)

Durch zahlreiche Studien ist belegt, dass inhalative, langwirksame Beta-2-Mimetika (LABA) und Anticholinergika (LAMA) sowie Steroide (ICS) die Exazerbationsrate bei COPD signifikant reduzieren. Allerdings konnte auch in aufwendigen und länger dauernden Studien nicht gezeigt werden, dass diese Reduktion der Exazerbation auch die Lebenserwartung reduziert. Im Gegensatz dazu zeigen zahlreiche Studien, dass die Lebenserwartung mit zunehmender Schwere und Häufigkeit der Exazerbation vermindert wird.

In dieser Übersicht werden diese Studien gegenübergestellt und die Relevanz der Reduktion der Exazerbationsraten durch LABA, LAMA und ICS durch Bewertung ihrer Effektstärke mittels Cohen’s d bewertet. Dabei zeigt sich in den Studien ein gleiches Muster. Die Reduktion der Exazerbationsrate zeigt nur bei den geringen Schweregraden einen kleinen Effekt (Cohen’s d max. 0,21). Bei Exazerbation mit höherem Schweregrad und bei Vergleich der Substanzen untereinander fällt Cohen’s d unter 0,1, was zeigt, dass die Wirkung der Medikamente klinisch praktisch bedeutungslos ist. Die Wirkung von LABA, LAMA und ICS auf die Exazerbationsrate bei COPD ist deutlich überschätzt.

The neuroimmune guidance cue netrin-1 controls resolution programs and promotes liver regeneration

Hepatic ischemia/reperfusion (I/R) is a major adverse reaction to liver transplantation, hemorrhagic shock, or resection. Recently, the anti-inflammatory properties of the axonal guidance cue netrin-1 were reported. Here, we demonstrate that netrin-1 also impacts the resolution of inflammation and promotes hepatic repair and regeneration during liver I/R injury. In initial studies, we investigated the induction of netrin-1 and its receptors in murine liver tissues after I/R injury. Hepatic I/R injury was performed in mice with a partial genetic netrin-1 deficiency (Ntn1(+/-) ) or wild-type C57BL/6 treated with exogenous netrin-1 to examine the endogenous and therapeutically administered impact of netrin-1. These investigations were corroborated by studies determining the characteristics of intravascular leukocyte flow, clearance of apoptotic neutrophils (polymorphonuclear cells [PMNs]), production of specialized proresolving lipid mediators (SPMs), generation of specific growth factors contributing to the resolution of inflammation, and liver repair. Hepatic I/R was associated with a significant reduction of netrin-1 transcript and protein in murine liver tissue. Subsequent studies in netrin-1-deficient mice revealed lower efficacies in reducing PMN infiltration, proinflammatory cytokine levels, and hepatic-specific injury enzymes. Conversely, mice treated with exogenous netrin-1 exhibited increased liver protection and repair, reducing neutrophil influx into the injury site, decreasing proinflammatory mediators, increasing efferocytosis of apoptotic PMNs, and stimulating local endogenous biosynthesis of SPMs and the generation of specific growth factors. Finally, genetic studies implicated the A2B adenosine receptor in netrin-1-mediated protection during hepatic I/R injury.

CONCLUSION

The present study indicates a previously unrecognized role for netrin-1 in liver protection and its contribution to tissue homeostasis and regeneration.

Semaphorin 7A Aggravates Pulmonary Inflammation during Lung Injury

The extent of pulmonary inflammation during lung injury ultimately determines patient outcome. Pulmonary inflammation is initiated by the migration of neutrophils into the alveolar space. Recent work has demonstrated that the guidance protein semaphorin 7A (SEMA7A) influences the migration of neutrophils into hypoxic tissue sites, yet, its role during lung injury is not well understood. Here, we report that the expression of SEMA7A is induced in vitro through pro-inflammatory cytokines. SEMA7A itself induces the production of pro-inflammatory cytokines in endothelial and epithelial cells, enhancing pulmonary inflammation. The induction of SEMA7A facilitates the transendothelial migration of neutrophils. In vivo, animals with deletion of SEMA7A expression showed reduced signs of pulmonary inflammatory changes following lipopolysaccharide challenge. We define here the role of SEMA7A in the development of lung injury and identify a potential pathway to interfere with these detrimental changes. Future anti-inflammatory strategies for the treatment of lung injury might be based on this finding.

[Standardization of spirometry: 2015 update. Published by German Atemwegsliga, German Respiratory Society and German Society of Occupational and Environmental Medicine]

Spirometry is a simple test and considered the gold standard in lung function. An obstructive ventilatory defect is a disproportionate reduction of maximal airflow from the lung in relation to the maximal volume that can be displaced from the lung. It implies airway narrowing and is defined by a reduced FEV1/FVC ratio below the 5th percentile of the predicted value (lower limit of normal, LLN). A restrictive disorder may be suspected when vital capacity (FVC) is reduced and FEV1/FVC is normal. It is definitely proven, however, only by a decrease in TLC below the 5th percentile of predicted value (LLN). The measurement of TLC by body plethysmography is necessary to confirm or exclude a restrictive defect or hyperinflation of the lung when FVC is below the LLN. 2012 a task force of the ERS published new reference values based on 74,187 records from healthy non-smoking males and females from 26 countries. The new reference equations for the 3-95 age range are now available that include appropriate age-dependent mean values and lower limits of normal (LLN). This presentation aims at providing the reader with recommendations dealing with standardization and interpretation of spirometry.

Crucial role of Plexin C1 for pulmonary inflammation and survival during lung injury

Acute pulmonary inflammation during lung injury is initiated by the migration of neutrophils into the alveolar space. The severity of these inflammatory changes within the pulmonary tissue determines the severity of lung injury and ultimately patient outcome. Recent work has demonstrated that the guidance protein Semaphorin 7A propagates the infiltration of neutrophils into an hypoxic tissue site, yet the role of its target receptor Plexin C1 (PLXNC1) during lung injury is to date unknown. We demonstrate here that PLXNC1(+) neutrophils are present within the alveolar space and that PLXNC1 is induced in vitro and in vivo during lung injury. In a model of high-pressure ventilation PLXNC1(-/-) animals show decreased signs of alveolar inflammation and improved survival compared with wild-type controls. Studies employing chimeric animals identified the hematopoietic expression of PLXNC1 to be of crucial importance for the observed results. Functional inhibition of PLXNC1 resulted in improved survival and ameliorated the signs of inflammation within the lung. Furthermore, the injection of a peptide binding to PLXNC1 resulted in improved survival and attenuated pulmonary inflammation. As such we demonstrate here, that previously unknown PLXNC1 holds significant importance for degree of pulmonary inflammation and determines outcome during experimental lung injury.

Gαi2- and Gαi3-deficient mice display opposite severity of myocardial ischemia reperfusion injury

G-protein-coupled receptors (GPCRs) are the most abundant receptors in the heart and therefore are common targets for cardiovascular therapeutics. The activated GPCRs transduce their signals via heterotrimeric G-proteins. The four major families of G-proteins identified so far are specified through their α-subunit: Gα_i, Gα_s, Gα_q and G_12/13. Gα_i-proteins have been reported to protect hearts from ischemia reperfusion injury. However, determining the individual impact of Gα_i2 or Gα_i3 on myocardial ischemia injury has not been clarified yet. Here, we first investigated expression of Gα_i2 and Gα_i3 on transcriptional level by quantitative PCR and on protein level by immunoblot analysis as well as by immunofluorescence in cardiac tissues of wild-type, Gα_i2-, and Gα_i3-deficient mice. Gα_i2 was expressed at higher levels than Gα_i3 in murine hearts, and irrespective of the isoform being knocked out we observed an up regulation of the remaining Gα_i-protein. Myocardial ischemia promptly regulated cardiac mRNA and with a slight delay protein levels of both Gα_i2 and Gα_i3, indicating important roles for both Gα_i isoforms. Furthermore, ischemia reperfusion injury in Gα_i2- and Gα_i3-deficient mice exhibited opposite outcomes. Whereas the absence of Gα_i2 significantly increased the infarct size in the heart, the absence of Gα_i3 or the concomitant upregulation of Gα_i2 dramatically reduced cardiac infarction. In conclusion, we demonstrate for the first time that the genetic ablation of Gα_i proteins has protective or deleterious effects on cardiac ischemia reperfusion injury depending on the isoform being absent.

Evaluating the role of Netrin-1 during the early phase of peripheral nerve regeneration using the mouse median nerve model

BACKGROUND

Less is known about the role of Netrin-1 in the peripheral nervous system. In this study, we evaluated the role of Netrin-1 using the mouse median nerve model for assessment of peripheral nerve regeneration.

METHODS

Using real-time PCR and western blot analysis, we examined expression changes of netrin-1 mRNA and Netrin-1 protein after transection and repair of the mouse median nerve in Wild-type animals. We further evaluated histomorphometrical changes as well as the functional recovery of the grasping force after median nerve transection and repair in WT mice and Netrin-1(+/-) heterozygous mice.

RESULTS

RT-PCR revealed a 1, 9 fold increase of Netrin-1 mRNA two weeks after nerve transection and repair in the nerve segment distal to the injury site. In Western blot analysis, we could show a high increase of Netrin-1 in the nerve segment distal to the injury site at day 14. Histomorphometrical analysis showed significantly higher cross sectional area and a lower fibre density in heterozygous Netrin-1(+/-) mice. Using the functional grasping test, we could show that peripheral nerve regeneration is significantly diminished in heterozygous Netrin-1(+/-) mice.

CONCLUSIONS

Employing the mouse median nerve model in transgenic animals, we demonstrate that Netrin-1 plays an important role during peripheral nerve regeneration.

[Weaning from long-term mechanical ventilation: data of a single weaning center from 2007 to 2011]

INTRODUCTION

Regional weaning centers play a more and more important role in the weaning process of long-term ventilated patients. The medical center Kloster Grafschaft is one of the oldest and largest centers in Germany. There is very little published data from larger weaning centers in Europe.

METHODS

From 2007 to 2011 all weaning patients were registered in a database. Additional information of the transferring hospitals was inquired. Prolonged weaning was defined by a period of at least 7 days of mechanical ventilation as well as three unsuccessful weaning trials.

RESULTS

Data from 867 of 916 registered patients could be analyzed. 71.1% could be successfully weaned from mechanical ventilation. All patients were suffering from a hypercapnic insufficiency as well as a variety of secondary diagnoses, on average 15.1 per patient. The median of age was 70 years, 62 % were male. Prior to hospital transfer patients had been ventilated for a median of 41 days. Time to successful removal of the artificial airway was 8 days according to the DRG code directive and 13.4 days when non-invasive ventilation (NIV) time was included. Of the 616 patients who could be successfully weaned, 42 % were discharged on NIV. Out of the 251 patients who could not be weaned, 107 were discharged. The remaining 144 (16.7 %) patients died, 33 % due to the primary underlying disease or a complication. 66 % of the deceased patients received palliative care. Patients with successful and unsuccessful weaning did not differ by age, by duration of mechanical ventilation or time until tracheostomy. Postoperative patients could be weaned more often than medical patients (p < 0.05). Discrimination between patients with successful and unsuccessful weaning was not possible by the point in time of the first spontaneous breathing trial in regard to the duration of ventilation but only by the duration of this trial after transfer to our unit (150 vs. 60 min; p < 10-6). The TISS-28 and the SAPS-II-Score did not differ between the two groups. Patients with successful weaning had less agitation according to the RASS-Score (0.47 vs. 0.15; p < 0.005).

CONCLUSION

It becomes apparent that in a specialized weaning center the majority of difficult to wean patients can be liberated in short time from mechanical ventilation.

Repression of the equilibrative nucleoside transporters dampens inflammatory lung injury

Acute lung injury (ALI) is a devastating disorder of the lung that is characterized by hypoxemia, overwhelming pulmonary inflammation, and a high mortality in the critically ill. Adenosine has been implicated as an anti-inflammatory signaling molecule, and previous studies showed that extracellular adenosine concentrations are increased in inflamed tissues. Adenosine signaling is terminated by the uptake of adenosine from the extracellular into the intracellular compartment via equilibrative nucleoside transporters (ENTs). However, their role in controlling adenosine signaling during pulmonary inflammation remains unknown. After inflammatory in vitro experiments, we observed a repression of ENT1 and ENT2 that was associated with an attenuation of extracellular adenosine uptake. Experiments using short, interfering RNA silencing confirmed a significant contribution of ENT repression in elevating extracellular adenosine concentrations during inflammation. Furthermore, an examination of the ENT2 promoter implicated NF-κB as a key regulator for the observed ENT repression. Additional in vivo experiments using a murine model of inflammatory lung injury showed that the pharmacological inhibition of ENT1 and ENT2 resulted in improved pulmonary barrier function and reduced signs of acute inflammation of the lung. Whereas experiments on Ent1(-/-) or Ent2(-/-) mice revealed lung protection in LPS-induced lung injury, an examination of bone marrow chimeras for ENTs pointed to the nonhematopoetic expression of ENTs as the underlying cause of dampened pulmonary inflammation during ALI. Taken together, these findings reveal the transcriptional repression of ENTs as an innate protective response during acute pulmonary inflammation. The inhibition of ENTs could be pursued as a therapeutic option to ameliorate inflammatory lung injury.

Expression patterns and functional evaluation of the UNC5b receptor during the early phase of peripheral nerve regeneration using the mouse median nerve model

INTRODUCTION

In this study, we evaluated the role of the Netrin-1 receptor UNC5b (Uncoordinated), a neuronal guidance molecule, during peripheral nerve regeneration using the mouse median nerve model.

MATERIALS AND METHODS

Using Western blot analysis, we examined the expression changes of UNC5b after transection and microsurgical repair of the mouse median nerve distal to the transection site. We evaluated the histomorphometrical changes and functional recovery of the grasping force after median nerve transection and repair in wild-type (WT) mice and UNC5b(+/-) heterozygous mice.

RESULTS

In Western blot analysis, we could show a high increase of UNC5b in the nerve segment distal to the injury site at day 14. Histomorphometrical analysis did not show any significant differences between WT animals and heterozygous animals. Using the functional grasping test, we could demonstrate that peripheral nerve regeneration is significantly diminished in heterozygous UNC5b(+/-) mice.

CONCLUSION

By using the mouse median nerve model in transgenic animals, we demonstrate that the Netrin-1 receptor UNC5b plays an important role during peripheral nerve regeneration.

Vasodilator phosphostimulated protein (VASP) protects endothelial barrier function during hypoxia

The endothelial barrier controls the passage of solutes from the vascular space. This is achieved through active reorganization of the actin cytoskeleton. A central cytoskeletal protein involved into this is vasodilator-stimulated phosphoprotein (VASP). However, the functional role of endothelial VASP during hypoxia has not been thoroughly elucidated. We determined endothelial VASP expression through real-time PCR (Rt-PCR), immunhistochemistry, and Western blot analysis during hypoxia. VASP promoter studies were performed using a PGL3 firefly luciferase containing plasmid. Following approval by the local authorities, VASP ( -/- ) mice and littermate controls were subjected to normobaric hypoxia (8% O(2), 92% N(2)) after intravenous injection of Evans blue dye. In in vitro studies, we found significant VASP repression in human microvascular and human umbilical vein endothelial cells through Rt-PCR, immunhistochemistry, and Western blot analysis. The VASP promoter construct demonstrated significant repression in response to hypoxia, which was abolished when the binding of hypoxia-inducible factor 1 alpha was excluded. Exposure of wild-type (WT) and VASP ( -/- ) animals to normobaric hypoxia for 4 h resulted in an increase in Evans blue tissue extravasation that was significantly increased in VASP ( -/- ) animals compared to WT controls. In summary, we demonstrate here that endothelial VASP holds significant importance for endothelial barrier properties during hypoxia.

[Scope and limitations of the median nerve mouse model in research on peripheral nerve regeneration]

INTRODUCTION

Peripheral nerve regeneration is usually studied in rat animal models (N. medianus or N. ischiadicus). In this article, we further evaluate the mouse median nerve model with its advantages and possible pitfalls.

MATERIALS AND METHODS

24 mice (C57BL/6) were operated. The median nerve was exposed in the left axilla. After transection, immediate microsurgical repair followed using 11/0 sutures. In the contralateral axilla, 1 cm of median nerve was resected. After the operation, functional regeneration of the median nerve was assessed using the grasping test. Histological analysis was performed after staining with toluidine blue.

RESULTS

All animals survived the procedure. Grip strength increased starting at day 10 and reached its maximum at day 35. Myelinated fibres in the regenerated nerves showed a smaller diameter and a thinner myelin sheath and the typical microfasciculation of regenerated nerve fibres in comparison to the uninjured nerve.

CONCLUSION

The mouse median nerve model is technically demanding but opens a wide field of possible research options using genetically modified mice.

The uncoordinated-5 homolog B receptor affects hepatic ischemia reperfusion injury

Recent evidence has demonstrated additional roles for the neuronal guidance protein receptor UNC5B outside the nervous system. Given the fact that ischemia reperfusion injury (IRI) of the liver is a common source of liver dysfunction and the role of UNC5B during an acute inflammatory response we investigated the role of UNC5B on acute hepatic IRI. We report here that UNC5B(+/-) mice display reduced hepatic IRI and neutrophil (PMN) infiltration compared to WT controls. This correlated with serum levels of lactate dehydrogenase (LDH), aspartate- (AST) and alanine- (ALT) aminotransferase, the presence of PMN within ischemic hepatic tissue, and serum levels of inflammatory cytokines. Moreover, injection of an anti-UNC5B antibody resulted in a significant reduction of hepatic IR injury. This was associated with reduced parameters of liver injury (LDH, ALT, AST) and accumulation of PMN within the injured hepatic tissue. In conclusion our studies demonstrate a significant role for UNC5B in the development of hepatic IRI and identified UNC5B as a potential drug target to prevent liver dysfunction in the future.

Bone marrow-derived human mesenchymal stem cells express cardiomyogenic proteins but do not exhibit functional cardiomyogenic differentiation potential

Despite their paracrine activites, cardiomyogenic differentiation of bone marrow (BM)-derived mesenchymal stem cells (MSCs) is thought to contribute to cardiac regeneration. To systematically evaluate the role of differentiation in MSC-mediated cardiac regeneration, the cardiomyogenic differentiation potential of human MSCs (hMSCs) and murine MSCs (mMSCs) was investigated in vitro and in vivo by inducing cardiomyogenic and noncardiomyogenic differentiation. Untreated hMSCs showed upregulation of cardiac tropopin I, cardiac actin, and myosin light chain mRNA and protein, and treatment of hMSCs with various cardiomyogenic differentiation media led to an enhanced expression of cardiomyogenic genes and proteins; however, no functional cardiomyogenic differentiation of hMSCs was observed. Moreover, co-culturing of hMSCs with cardiomyocytes derived from murine pluripotent cells (mcP19) or with murine fetal cardiomyocytes (mfCMCs) did not result in functional cardiomyogenic differentiation of hMSCs. Despite direct contact to beating mfCMCs, hMSCs could be effectively differentiated into cells of only the adipogenic and osteogenic lineage. After intramyocardial transplantation into a mouse model of myocardial infarction, Sca-1(+) mMSCs migrated to the infarcted area and survived at least 14 days but showed inconsistent evidence of functional cardiomyogenic differentiation. Neither in vitro treatment nor intramyocardial transplantation of MSCs reliably generated MSC-derived cardiomyocytes, indicating that functional cardiomyogenic differentiation of BM-derived MSCs is a rare event and, therefore, may not be the main contributor to cardiac regeneration.

Phosphorylation of vasodilator-stimulated phosphoprotein (VASP) dampens hepatic ischemia-reperfusion injury

Recent work has demonstrated that the formation of platelet neutrophil complexes (PNCs) affects inflammatory tissue injury. Vasodilator-stimulated phosphoprotein (VASP) is crucially involved into the control of PNC formation and myocardial reperfusion injury. Given the clinical importance of hepatic IR injury we pursued the role of VASP during hepatic ischemia followed by reperfusion. We report here that VASP^−/− animals demonstrate reduced hepatic IR injury compared to wildtype (WT) controls. This correlated with serum levels of lactate dehydrogenase (LDH), aspartate (AST) and alanine (ALT) aminotransferase and the presence of PNCs within ischemic hepatic tissue and could be confirmed using repression of VASP through siRNA. In studies employing bone marrow chimeric mice we identified hematopoietic VASP to be of crucial importance for the extent of hepatic injury. Phosphorylation of VASP on Ser¹⁵³ through Prostaglandin E1 or on Ser²³⁵ through atrial natriuretic peptide resulted in a significant reduction of hepatic IR injury. This was associated with a reduced presence of PNCs in ischemic hepatic tissue. Taken together, these studies identified VASP and VASP phosphorylation as crucial target for future hepatoprotective strategies.

Phosphorylation of vasodilator-stimulated phosphoprotein prevents platelet-neutrophil complex formation and dampens myocardial ischemia-reperfusion injury

BACKGROUND

Recent work has suggested that the formation of platelet-neutrophil complexes (PNCs) aggravates the severity of inflammatory tissue injury. Given the importance of vasodilator-stimulated phosphoprotein (VASP) for platelet function, we pursued the role of VASP on the formation of PNCs and its impact on the extent of myocardial ischemia-reperfusion (IR) injury.

METHODS AND RESULTS

In initial in vitro studies we found that neutrophils facilitated the movement of platelets across endothelial monolayers. Phosphorylation of VASP reduced the formation of PNCs and transendothelial movement of PNCs. During myocardial IR injury, VASP(-/-) animals demonstrated reduced intravascular formation of PNCs and reduced presence of PNCs within the ischemic myocardial tissue. This was associated with reduced IR injury. Studies using platelet transfer and bone marrow chimeric animals showed that hematopoietic VASP expression was crucial for the intravascular formation of PNCs the presence of PNCs within ischemic myocardial tissue and the extent of myocardial IR injury. Furthermore, phosphorylation of VASP on Ser153 or Ser235 reduced intravascular PNC formation and presence of PNCs within ischemic myocardial tissue. This finding was associated with reduced myocardial IR injury.

CONCLUSION

Previously unappreciated, the phosphorylation of VASP performs a key function for the formation of PNCs that is crucially important for the extent of myocardial IR injury.