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Biomedical subjects

Thomas Möller

Publications and source records attributed to Thomas Möller.

At least 19 recordsLinked to original sources
PubMed2006

Pulmonary arterial hypertension in adults born with a heart septal defect: the Euro Heart Survey on adult congenital heart disease.

AIM: To investigate the role of pulmonary arterial hypertension (PAH) in adult patients born with a cardiac septal defect, by assessing its prevalence and its relation with patient characteristics and outcome. METHODS AND RESULTS: From the database of the Euro Heart Survey on adult congenital heart disease (a retrospective cohort study with a 5-year follow-up), the relevant data on all 1877 patients with an atrial septal defect (ASD), a ventricular septal defect (VSD), or a cyanotic defect were analysed. Most patients (83%) attended a specialised centre. There were 896 patients with an ASD (377 closed, 504 open without and 15 with Eisenmenger's syndrome), 710 with a VSD (275, 352 and 83, respectively), 133 with Eisenmenger's syndrome owing to another defect and 138 remaining patients with cyanosis. PAH was present in 531 (28%) patients, or in 34% of patients with an open ASD and 28% of patients with an open VSD, and 12% and 13% of patients with a closed defect, respectively. Mortality was highest in patients with Eisenmenger's syndrome (20.6%). In case of an open defect, PAH entailed an eightfold increased probability of functional limitations (New York Heart Association class >1), with a further sixfold increase when Eisenmenger's syndrome was present. Also, in patients with persisting PAH despite defect closure, functional limitations were more common. In patients with ASD, the prevalence of right ventricular dysfunction increased with systolic pulmonary artery pressure (OR = 1.073 per mm Hg; p<0.001). Major bleeding events were more prevalent in patients with cyanosis with than without Eisenmenger's syndrome (17% vs 3%; p<0.001). CONCLUSION: In this selected population of adults with congenital heart disease, PAH was common and predisposed to more symptoms and further clinical deterioration, even among patients with previous defect closure and patients who had not developed Eisenmenger's physiology.

Adult↗
PubMed2006

Experimental autoimmune encephalomyelitis disrupts endocannabinoid-mediated neuroprotection.

Focal cerebral ischemia and traumatic brain injury induce an escalating amount of cell death because of harmful mediators diffusing from the original lesion site. Evidence suggests that healthy cells surrounding these lesions attempt to protect themselves by producing endocannabinoids (eCBs) and activating cannabinoid receptors, the molecular target for marijuana-derived compounds. Indeed, activation of cannabinoid receptors reduces the production and diffusion of harmful mediators. Here, we provide evidence that an exception to this pattern is found in experimental autoimmune encephalomyelitis (EAE), a mouse model of multiple sclerosis. We show that cell damage induced by EAE does not lead to increase in eCBs, even though cannabinoid receptors are functional because synthetic cannabinoid agonists are known to confine EAE-induced lesions. This lack of eCB increase is likely due to IFN-gamma, which is released by primed T cells invading the CNS. We show that IFN-gamma disrupts the functionality of purinergic P2X7 receptors, a key step controlling eCB production by microglia, the main source of eCBs in brain. Accordingly, induction of EAE in P2X7-/- mice results in even lower eCB levels and more pronounced cell damage than in wild-type mice. Our data suggest that the high level of CNS IFN-gamma associated with EAE disrupts eCB-mediated neuroprotection while maintaining functional cannabinoid receptors, thus providing additional support for the use of cannabinoid-based medicine to treat multiple sclerosis.

Animals↗
PubMed2006

Activation of microglial cells by thrombin: past, present, and future.

In addition to its role in the coagulation cascade, the serine proteinase thrombin (factor IIa) activates cell surface proteinase-activated receptors (PARs) both within and outside the vascular system. PARs are expressed in the central nervous system and mediate thrombin-induced cellular responses in a variety of neural cell types, including microglial cells. Microglial activation by thrombin was reported to induce proliferation, cytokine release, and intracellular calcium signaling. Recently, additional experiments questioned whether these effects are mediated either by thrombin's proteolytic activity or by thrombin itself. Analysis of commercially available plasma-derived thrombin frequently used in the earlier studies showed that cyto/chemokine release-activating properties were not residing with thrombin but were with high molecular weight contaminant(s). In the absence of such contamination, no microglial activation was seen. We compared commercial-grade plasma-derived thrombin to pharmaceutical-grade recombinant thrombin devoid of any measurable contamination. The pharmaceutical-grade thrombin displayed a much more limited profile of microglia-activating properties, triggering only intracellular calcium signals and small changes in surface antigen expression. The signals induced by the pharmaceutical-grade thrombin were completely abolished by proteolytic inhibition, indicating that they are proteolysis-dependent, are most likely PAR mediated, and reflect thrombin's true microglia-activating potential. Prior reports using nonpharmaceutical-grade thrombin need to be reinterpreted critically given these new findings.

Animals↗
PubMed2005

Comparison of pre-hospital combination-fibrinolysis plus conventional care with pre-hospital combination-fibrinolysis plus facilitated percutaneous coronary intervention in acute myocardial infarction.

AIMS: Early and complete reperfusion is the main treatment goal in ST-elevation myocardial infarction (STEMI). The timely optimal reperfusion strategy might be a pre-hospital initiated pharmacological reperfusion with subsequent facilitated percutaneous coronary intervention (PCI). This approach has been compared with pre-hospital combination-fibrinolysis only to determine whether either one of these methods offer advantages with respect to final infarct size. METHODS AND RESULTS: Patients with STEMI were randomized to either pre-hospital combination-fibrinolysis (half-dose reteplase+abciximab) with standard care (n=82) or pre-hospital combination-fibrinolysis with facilitated PCI (n=82). Primary endpoint was the infarct size assessed by delayed enhancement magnetic resonance. Secondary endpoints were ST-segment resolution at 90 min and a composite of death, re-myocardial infarction, major bleeding, and stroke at 6 months. The infarct size was lower after facilitated PCI with 5.2% [interquartile range (IQR) 1.3-11.2] as opposed to 10.4% (IQR 3.4-16.3) after pre-hospital combination-fibrinolysis (P=0.001). Complete ST-segment resolution was 80.0% after facilitated PCI vs. 51.9% after pre-hospital combination-fibrinolysis (P<0.001). After facilitated PCI, there was a trend towards a lower event rate in the combined clinical endpoint (15 vs. 25%, P=0.10, relative risk 0.57, 95% CI 0.28-1.13). CONCLUSION: In patients with STEMI, additional facilitated PCI after pre-hospital combination-fibrinolysis results in an improved tissue perfusion with subsequent smaller infarct size as opposed to pre-hospital combination-fibrinolysis alone. This translates into a trend towards a better clinical outcome.

Adult↗
PubMed2005

Astrocyte-derived ATP induces vesicle shedding and IL-1 beta release from microglia.

ATP has been indicated as a primary factor in microglial response to brain injury and inflammation. By acting on different purinergic receptors 2, ATP is known to induce chemotaxis and stimulate the release of several cytokines from these cells. The activation of purinergic receptors 2 in microglia can be triggered either by ATP deriving from dying cells, at sites of brain injury or by ATP released from astrocytes, in the absence of cell damage. By the use of a biochemical approach integrated with video microscopy experiments, we investigated the functional consequences triggered in microglia by ATP released from mechanically stimulated astrocytes, in mixed glial cocultures. Astrocyte-derived ATP induced in nearby microglia the formation and the shedding of membrane vesicles. Vesicle formation was inhibited by the ATP-degrading enzyme apyrase or by P2X(7)R antagonists. Isolation of shed vesicles, followed by IL-1beta evaluation by a specific ELISA revealed the presence of the cytokine inside the vesicular organelles and its subsequent efflux into the extracellular medium. IL-1beta efflux from shed vesicles was enhanced by ATP stimulation and inhibited by pretreatment with the P2X(7) antagonist oxidized ATP, thus indicating a crucial involvement of the pore-forming P2X(7)R in the release of the cytokine. Our data identify astrocyte-derived ATP as the endogenous factor responsible for microvesicle shedding in microglia and reveal the mechanisms by which astrocyte-derived ATP triggers IL-1beta release from these cells.

Adenosine Triphosphate↗
PubMed2005

Neuroinflammation in the pathogenesis of amyotrophic lateral sclerosis.

Amyotrophic lateral sclerosis is a devastating motor neuron disorder. Traditionally regarded as a 'neuron only' disease, recent evidence suggested that other cells contribute critically to the pathogenesis. This review provides a short synopsis of the role neuroinflammation and microglial cells play in the disease and its animal models. A better understanding of neuroinflammation in motor neuron degeneration and amyotrophic lateral sclerosis disease progression promises to improve the rational design of greatly needed therapies.

Amyotrophic Lateral Sclerosis↗
PubMed2005

Lentiviral transduction of microglial cells.

Microglial cells are the resident immune cells of the central nervous system. Their function resembles that of tissue macrophages and, as such, they share many properties with both peripheral macrophages and monocytes. One striking similarity is the difficulty with which these cells can be genetically manipulated via transfection or transduction. We have sought to overcome this challenge and generate stably transduced microglial cell lines. Based on encouraging results from macrophages, we hypothesized that lentiviral vectors might provide a valuable tool in the transduction of microglial cells. Using a lentiviral-based vector system expressing enhanced green fluorescent protein (eGFP) under the control of the murine stem cell virus promoter (MSCV), we found that multiplicities of infection (MOIs) of 1, 10, and 100 transduce >70%, >88%, and >95% of the cells, respectively. From the pool of transduced cells, we established lines of N9 and BV-2 microglial cells with distinct fluorescence intensities. Using real time-polymerase chain reaction (PCR), we correlated the integrated eGFP copy numbers to eGFP fluorescence measured by flow cytometry. When mixed, up to three lines with different eGFP intensities could be separated by flow cytometry and fluorescence microscopy. Neither infection nor transgene expression influenced microglial activation as assessed by nitric oxide (NO) production, cytokine release, and surface antigen expression. Our findings that microglial cells are easily transduced by lentiviral based vectors will facilitate research depending on genetic manipulation and help generate transgenic cell lines. In addition, the availability of microglial cell lines with defined fluorescence properties could replace elaborate staining procedures for microglial identification in co-culture experiments.

Animals↗
PubMed2005

Cannabinol delays symptom onset in SOD1 (G93A) transgenic mice without affecting survival.

Therapeutic options for amyotrophic lateral sclerosis (ALS), the most common adult-onset motor neuron disorder, remain limited. Emerging evidence from clinical studies and transgenic mouse models of ALS suggests that cannabinoids, the bioactive ingredients of marijuana (Cannabis sativa) might have some therapeutic benefit in this disease. However, Delta(9)-tetrahydrocannabinol (Delta(9)-THC), the predominant cannabinoid in marijuana, induces mind-altering effects and is partially addictive, compromising its clinical usefulness. We therefore tested whether cannabinol (CBN), a non-psychotropic cannabinoid, influences disease progression and survival in the SOD1 (G93A) mouse model of ALS. CBN was delivered via subcutaneously implanted osmotic mini-pumps (5 mg/kg/day) over a period of up to 12 weeks. We found that this treatment significantly delays disease onset by more than two weeks while survival was not affected. Further research is necessary to determine whether non-psychotropic cannabinoids might be useful in ameliorating symptoms in ALS.

Age Factors↗
PubMed2005

Unraveling thrombin's true microglia-activating potential: markedly disparate profiles of pharmaceutical-grade and commercial-grade thrombin preparations.

Microglia are the resident immune cells of the CNS. Brain injury triggers microglial activation, leading to proliferation, changes in antigenic profile, NO production and cytokine release. It is widely believed that serum factors inundating the injured tissue can prompt this activation, leading to long-term phenotypic changes. We and others have recently reported that commercial-grade preparations of thrombin, a serine protease known for its central function in blood coagulation, activate microglial cells. Recent findings, however, have called into question the involvement of thrombin itself in the induction of microglial cytokine release and led us to systematically re-investigate the ability of the protease to induce a broad spectrum of microglial activation parameters. We used a pharmaceutical-grade recombinant human thrombin (rh-thr) and compared it with a commercial-grade plasma-derived bovine thrombin (pb-thr) preparation that has been used extensively in the literature, including in our own earlier report. We investigated the effect of these two thrombin preparations on proliferation, NO production, interleukin-6 and tumour necrosis factor-alpha release, intracellular calcium signaling and cell surface expression of CD95 (Fas) and CD40. Pb-thr induced robust responses in all variables tested. In contrast, rh-thr triggered calcium signals and induced small but significant changes in the expression of cell surface antigens, but had no effect on proliferation, NO production or cytokine release. Control studies assured equivalent thrombin potencies and excluded both species-specific effects and endotoxin (lipopolysaccharide) contamination as possible causes of the disparity. Our results indicate a substantially more restricted role for thrombin itself in microglial activation than previously appreciated, but point to several potentially important co-stimulatory effects. In addition, these results suggest that previous studies examining thrombin's activation of microglia should be cautiously re-interpreted.

Amino Acid Chloromethyl Ketones↗
PubMed2004

Inflammatory mediators and growth factors in the spinal cord of G93A SOD1 rats.

Amyotrophic lateral sclerosis (ALS) is a devastating motor neuron disease. One mechanism involved in ALS pathology is neuroinflammation. Neuroinflammation is mediated by soluble pro-inflammatory molecules such as cytokines, prostaglandins and nitric oxide. Studies on transgenic mice demonstrated the expression of pro-inflammatory mediators in early stages of murine ALS. Recently a transgenic rat model became available. Since species differences in regard to cytokine expression have been reported in other disease models we set out to validate the neuroinflammatory hypothesis in the ALS-transgenic rat. We investigated the expression of inflammatory mediators and growth factors in the spinal cord by semi-quantitative RT-PCR. We found that several pro-inflammatory mediators are up-regulated at asymptomatic and end-stages, whereas VEGF, a neuroprotective factor was down-regulated.

Amyotrophic Lateral Sclerosis↗
PubMed2004

Increased cytotoxic potential of microglia from ALS-transgenic mice.

Amyotrophic lateral sclerosis is a fatal, adult-onset motor neuron disease. A subset of cases is caused by mutations of superoxide dismutase 1 (SOD1) gene. The mechanisms how the mutations in this ubiquitous enzyme mediate the highly selective motor neuron degeneration, however, remain poorly understood. Recent results from transgenic animal models suggest a "non-cell autonomous" mechanism; i.e., cells other than neurons play an active role in motor neuron death. To investigate a possible effect of mtSOD1 on microglial cells, we compared primary cultured microglia from mtSOD1-transgenic mice and nontransgenic litter controls at neonatal (3 days) and adult (60 days) age. We found that mtSOD1 expression increases the production of TNF-alpha and attenuates IL-6-release by LPS-activated adult microglia. Neonatal microglia, however, showed no differences. Our findings suggest an increased cytotoxic potential of adult mtSOD1 microglia, which only becomes apparent after microglial activation.

Age Factors↗
PubMed2004

The microglia-activating potential of thrombin: the protease is not involved in the induction of proinflammatory cytokines and chemokines.

The serine protease thrombin is known as a blood coagulation factor. Through limited cleavage of proteinase-activated receptors it can also control growth and functions in various cell types, including neurons, astrocytes, and microglia (brain macrophages). A number of previous studies indicated that thrombin induces the release of proinflammatory cytokines and chemokines from microglial cells, suggesting another important role for the protease beyond hemostasis. In the present report, we provide evidence that this effect is not mediated by any proteolytic or non-proteolytic mechanism involving thrombin proper. Inhibition of the enzymatic thrombin activity did not affect the microglial release response. Instead the cyto-/chemokine-inducing activity solely resided in a high molecular weight protein fraction that could be isolated in trace amounts even from apparently homogenous alpha- and gamma-thrombin preparations. High molecular weight material contained thrombin-derived peptides as revealed by mass spectrometry but was devoid of thrombin-like enzymatic activity. Separated from the high molecular weight fraction by fast protein liquid chromatography, enzymatically intact alpha- and gamma-thrombin failed to trigger any release. Our findings may force a revision of the notion that thrombin itself is a direct proinflammatory release signal for microglia. In addition, they could be relevant for the study of other cellular activities and their assignment to this protease.

Amino Acid Sequence↗
PubMed2004

HIV associated neurodegeneration requires p53 in neurons and microglia.

HIV infection of the central nervous system leads to HIV-associated dementia (HAD) in a substantial subset of infected individuals. The pathogenesis of neuronal dysfunction in HAD is not well understood, but previous studies have demonstrated evidence for activation of apoptotic pathways. The tumor suppressor transcription factor p53 is an apical mediator of neuronal apoptosis following a variety of injurious stimuli. To determine whether p53 participates in HAD, we exposed cerebrocortical cultures from wild-type and p53 deficient mice to the neurotoxic HIV envelope protein gp120. Using neuron/microglia co-culture of mixed p53 genotype, we observed that both neurons and microglia require p53 for gp120 induced neuronal apoptosis. Additionally, accumulation of p53 protein in neurons was recently reported in post-mortem cortical tissue from a small group of HAD patients. Using a much larger cohort of HAD cases, we extend this finding and report that p53 protein also increases in non-neuronal cells, including microglia. Taken together these findings demonstrate a novel role for p53 in the microglial response to gp120. Additionally, these findings, in conjunction with a recent report that monocytes expressing HIV-Tat also secrete neurotoxins that promote p53 activation, suggest that distinct HIV proteins may converge on the p53 pathway to promote neurotoxicity.

AIDS Dementia Complex↗
PubMed2004

P2X7 receptors control 2-arachidonoylglycerol production by microglial cells.

Endogenous cannabinoid ligands (endocannabinoids) produced by neurons, astrocytes, and microglial cells activate cannabinoid receptors, the molecular target for marijuana's bioactive ingredient Delta(9)-tetrahydrocannabinol. The molecular mechanism underlying the production of the most abundant endocannabinoid, 2-arachidonoylglycerol (2-AG), is unclear. A prevalent hypothesis proposes that activation of metabotropic receptors coupled to the phosphatidylinositol-specific phospholipase C and diacylglycerol (DG) lipase pathway will systematically lead to increases in 2-AG production. Here, we show that ATP increases 2-AG production by cultured microglial cells in a phosphatidylinositol-specific phospholipase C and DG lipase-dependent manner. However, efficacious activation of metabotropic P2Y purinergic receptors coupled to phosphatidylinositol-specific phospholipase C does not increase 2-AG production. This suggests that ionotropic, and not metabotropic, purinergic receptors control 2-AG production at an unexpected enzymatic step of its metabolic pathway. We show that activation of P2X(7) ionotropic receptors, which are highly permeable to calcium, is necessary and sufficient to increase 2-AG production in microglial cells. We also show that the sustained rise in intracellular calcium induced by activation of P2X(7) receptors directly increases DG lipase activity while inhibiting the activity of monoacylglycerol lipase, the enzyme that degrades 2-AG. This inverse sensitivity of DG lipase and monoacylglycerol lipase to calcium constitutes an original and efficient modality for sustained accumulation of 2-AG. Because prolonged increases in 2-AG amounts in brain parenchyma are thought to orchestrate neuroinflammation, the enzymatic steps involved in 2-AG synthesis and degradation by microglial cells constitute appealing targets for therapy aimed at controlling exacerbated neuroinflammation.

Adenosine Triphosphate↗
PubMed2003

Expression of proteinase-activated receptors in mouse microglial cells.

Microglia are the resident immune cells of the CNS: they are activated rapidly by CNS damage and perform the function of tissue macrophages. The first steps during microglial activation are currently under intense study, and it is widely believed that substances released from damaged brain tissue can trigger this process. We recently reported that the blood coagulation factor thrombin, which enters the CNS during breakdown of the blood-brain barrier, activates microglial cells. The cellular effects of thrombin and trypsin-like proteases are mediated by proteinase-activated receptors (PARs). Based on our prior data we hypothesized that microglial cells express these receptors. Using RT-PCR and flow cytometry, we report that primary mouse microglial cells, as well as the murine microglial cell lines BV-2 and N9, indeed express PARs, albeit at different levels. Demonstrating multiple PARs on microglia may enhance the attractiveness of PARs as therapeutic targets in neuroinflammatory disorders.

Animals↗
PubMed2003

Ethanol inhibits muscarinic receptor-mediated DNA synthesis and signal transduction in human fetal astrocytes.

We previously found that ethanol inhibits muscarinic receptor-induced proliferation of rat cortical astrocytes and human astrocytoma cells and suggested this as a possible mechanism involved in its developmental neurotoxicity. We also observed that, though several signal transduction pathways are relevant for carbachol-induced cell proliferation, activation of PKC zeta and p70S6 kinase is selectively inhibited by low concentrations of ethanol. In the present study we used fetal human astrocytes to expand these findings to a direct target of ethanol in humans. Astrocyte cultures, deriving from legally aborted fetuses, were stained for GFAP and shown to be 90-95% pure. Carbachol induced increases in [(3)H]thymidine and BrdU incorporation in synchronized cells. Carbachol-induced DNA synthesis was strongly inhibited by ethanol. Carbachol also induced phosphorylation of (Thr410)PKC zeta, (Ser473)Akt, and (Thr389)p70S6 kinase, and ethanol (50 mM) inhibited phosphorylation of PKC zeta and p70S6 kinase, but not of Akt. These results expand previous findings in rat astrocytes and human astrocytoma cells and suggest that intracellular signal transduction pathways activated by muscarinic receptors may represent a relevant target for the developmental neurotoxicity of ethanol in humans.

Astrocytes↗