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The role of serum amyloid A and sphingosine-1-phosphate on high-density lipoprotein functionality
(2017)
The high-density lipoprotein (HDL) is one of the most important endogenous cardiovascular protective markers. HDL is an attractive target in the search for new pharmaceutical therapies and in the prevention of cardiovascular events. Some of HDL’s anti-atherogenic properties are related to the signaling molecule sphingosine-1-phosphate (S1P), which plays an important role in vascular homeostasis. However, for different patient populations it seems more complicated. Significant changes in HDL’s protective potency are reduced under pathologic conditions and HDL might even serve as a proatherogenic particle. Under uremic conditions especially there is a change in the compounds associated with HDL. S1P is reduced and acute phase proteins such as serum amyloid A (SAA) are found to be elevated in HDL. The conversion of HDL in inflammation changes the functional properties of HDL. High amounts of SAA are associated with the occurrence of cardiovascular diseases such as atherosclerosis. SAA has potent pro-atherogenic properties, which may have impact on HDL’s biological functions, including cholesterol efflux capacity, antioxidative and anti-inflammatory activities. This review focuses on two molecules that affect the functionality of HDL. The balance between functional and dysfunctional HDL is disturbed after the loss of the protective sphingolipid molecule S1P and the accumulation of the acute-phase protein SAA. This review also summarizes the biological activities of lipid-free and lipid-bound SAA and its impact on HDL function.
Serious knee pain and related disability have an annual prevalence of approximately 25% on those over the age of 55 years. As curative treatments for the common knee problems are not available to date, knee pathologies typically progress and often lead to osteoarthritis (OA). While the roles that the meniscus plays in knee biomechanics are well characterized, biological mechanisms underlying meniscus pathophysiology and roles in knee pain and OA progression are not fully clear. Experimental treatments for knee disorders that are successful in animal models often produce unsatisfactory results in humans due to species differences or the inability to fully replicate disease progression in experimental animals. The use of animals with spontaneous knee pathologies, such as dogs, can significantly help addressing this issue. As microscopic and macroscopic anatomy of the canine and human menisci are similar, spontaneous meniscal pathologies in canine patients are thought to be highly relevant for translational medicine. However, it is not clear whether the biomolecular mechanisms of pain, degradation of extracellular matrix, and inflammatory responses are species dependent. The aims of this review are (1) to provide an overview of the anatomy, physiology, and pathology of the human and canine meniscus, (2) to compare the known signaling pathways involved in spontaneous meniscus pathology between both species, and (3) to assess the relevance of dogs with spontaneous meniscal pathology as a translational model. Understanding these mechanisms in human and canine meniscus can help to advance diagnostic and therapeutic strategies for painful knee disorders and improve clinical decision making.
While the impact of dietary cholesterol on the progression of atherosclerosis has probably been overestimated, increasing evidence suggests that dietary cholesterol might favor the transition from blunt steatosis to non-alcoholic steatohepatitis (NASH), especially in combination with high fat diets. It is poorly understood how cholesterol alone or in combination with other dietary lipid components contributes to the development of lipotoxicity. The current study demonstrated that liver damage caused by dietary cholesterol in mice was strongly enhanced by a high fat diet containing soybean oil-derived ω6-poly-unsaturated fatty acids (ω6-PUFA), but not by a lard-based high fat diet containing mainly saturated fatty acids. In contrast to the lard-based diet the soybean oil-based diet augmented cholesterol accumulation in hepatocytes, presumably by impairing cholesterol-eliminating pathways. The soybean oil-based diet enhanced cholesterol-induced mitochondrial damage and amplified the ensuing oxidative stress, probably by peroxidation of poly-unsaturated fatty acids. This resulted in hepatocyte death, recruitment of inflammatory cells, and fibrosis, and caused a transition from steatosis to NASH, doubling the NASH activity score. Thus, the recommendation to reduce cholesterol intake, in particular in diets rich in ω6-PUFA, although not necessary to reduce the risk of atherosclerosis, might be sensible for patients suffering from non-alcoholic fatty liver disease.
Experimental studies have reported on the anti-inflammatory properties of polyphenols. However, results from epidemiological investigations have been inconsistent and especially studies using biomarkers for assessment of polyphenol intake have been scant. We aimed to characterise the association between plasma concentrations of thirty-five polyphenol compounds and low-grade systemic inflammation state as measured by high-sensitivity C-reactive protein (hsCRP). A cross-sectional data analysis was performed based on 315 participants in the European Prospective Investigation into Cancer and Nutrition cohort with available measurements of plasma polyphenols and hsCRP. In logistic regression analysis, the OR and 95 % CI of elevated serum hsCRP (>3 mg/l) were calculated within quartiles and per standard deviation higher level of plasma polyphenol concentrations. In a multivariable-adjusted model, the sum of plasma concentrations of all polyphenols measured (per standard deviation) was associated with 29 (95 % CI 50, 1) % lower odds of elevated hsCRP. In the class of flavonoids, daidzein was inversely associated with elevated hsCRP (OR 0 center dot 66, 95 % CI 0 center dot 46, 0 center dot 96). Among phenolic acids, statistically significant associations were observed for 3,5-dihydroxyphenylpropionic acid (OR 0 center dot 58, 95 % CI 0 center dot 39, 0 center dot 86), 3,4-dihydroxyphenylpropionic acid (OR 0 center dot 63, 95 % CI 0 center dot 46, 0 center dot 87), ferulic acid (OR 0 center dot 65, 95 % CI 0 center dot 44, 0 center dot 96) and caffeic acid (OR 0 center dot 69, 95 % CI 0 center dot 51, 0 center dot 93). The odds of elevated hsCRP were significantly reduced for hydroxytyrosol (OR 0 center dot 67, 95 % CI 0 center dot 48, 0 center dot 93). The present study showed that polyphenol biomarkers are associated with lower odds of elevated hsCRP. Whether diet rich in bioactive polyphenol compounds could be an effective strategy to prevent or modulate deleterious health effects of inflammation should be addressed by further well-powered longitudinal studies.
Degenerative disc disease is associated with increased expression of pro-inflammatory cytokines in the intervertebral disc (IVD). However, it is not completely clear how inflammation arises in the IVD and which cellular compartments are involved in this process. Recently, the endoplasmic reticulum (ER) has emerged as a possible modulator of inflammation in age-related disorders. In addition, ER stress has been associated with the microenvironment of degenerated IVDs. Therefore, the aim of this study was to analyze the effects of ER stress on inflammatory responses in degenerated human IVDs and associated molecular mechanisms. Gene expression of ER stress marker GRP78 and pro-inflammatory cytokines IL-6, IL-8, IL-1 beta, and TNF-alpha was analyzed in human surgical IVD samples (n = 51, Pfirrmann grade 2-5). The expression of GRP78 positively correlated with the degeneration grade in lumbar IVDs and IL-6, but not with IL-1 beta and TNF-alpha. Another set of human surgical IVD samples (n = 25) was used to prepare primary cell cultures. ER stress inducer thapsigargin (Tg, 100 and 500 nM) activated gene and protein expression of IL-6 and induced phosphorylation of p38 MAPK. Both inhibition of p38 MAPK by SB203580 (10 mu M) and knockdown of ER stress effector CCAAT-enhancer-binding protein homologous protein (CHOP) reduced gene and protein expression of IL-6 in Tg-treated cells. Furthermore, the effects of an inflammatory microenvironment on ER stress were tested. TNF-alpha (5 and 10 ng/mL) did not activate ER stress, while IL-1 beta (5 and 10 ng/mL) activated gene and protein expression of GRP78, but did not influence [Ca2+](i) flux and expression of CHOP, indicating that pro-inflammatory cytokines alone may not induce ER stress in vivo. This study showed that IL-6 release in the IVD can be initiated following ER stress and that ER stress mediates IL-6 release through p38 MAPK and CHOP. Therapeutic targeting of ER stress response may reduce the consequences of the harsh microenvironment in degenerated IVD.
Cancer cachexia, of which the most notable symptom is severe and rapid weight loss, is present in the majority of patients with advanced cancer. Inflammatory mediators play an important role in the development of cachexia, envisaged as a chronic inflammatory syndrome. The white adipose tissue (WAT) is one of the first compartments affected in cancer cachexia and suffers a high rate of lipolysis. It secretes several cytokines capable of directly regulating intermediate metabolism. A common pathway in the regulation of the expression of pro-inflammatory cytokines in WAT is the activation of the nuclear transcription factor kappa-B (NF-κB). We have examined the gene expression of the subunits NF-κBp65 and NF-κBp50, as well as NF-κBp65 and NF-κBp50 binding, the gene expression of pro-inflammatory mediators under NF-κB control (IL-1β, IL-6, INF-γ, TNF-α, MCP-1), and its inhibitory protein, nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor, alpha (IκB-α). The observational study involved 35 patients (control group, n = 12 and cancer group, n = 23, further divided into cachectic and non-cachectic). NF-κBp65 and its target genes expression (TNF-α, IL-1β, MCP-1 and IκB-α) were significantly higher in cachectic cancer patients. Moreover, NF-κBp65 gene expression correlated positively with the expression of its target genes. The results strongly suggest that the NF-κB pathway plays a role in the promotion of WAT inflammation during cachexia.
Insulinresistenz ist ein zentraler Bestandteil des metabolischen Syndroms und trägt maßgeblich zur Ausbildung eines Typ-2-Diabetes bei. Eine mögliche Ursache für die Entstehung von Insulinresistenz ist eine chronische unterschwellige Entzündung, welche ihren Ursprung im Fettgewebe übergewichtiger Personen hat. Eingewanderte Makrophagen produzieren vermehrt pro-inflammatorische Mediatoren, wie Zytokine und Prostaglandine, wodurch die Konzentrationen dieser Substanzen sowohl lokal als auch systemisch erhöht sind. Darüber hinaus weisen übergewichtige Personen einen gestörten Fettsäuremetabolismus und eine erhöhte Darmpermeabilität auf. Ein gesteigerter Flux an freien Fettsäuren vom Fettgewebe in andere Organe führt zu einer lokalen Konzentrationssteigerung in diesen Organen. Eine erhöhte Darmpermeabilität erleichtert das Eindringen von Pathogenen und anderer körperfremder Substanzen in den Körper.
Ziel dieser Arbeit war es, zu untersuchen, ob hohe Konzentrationen von Insulin, des bakteriellen Bestandteils Lipopolysaccharid (LPS) oder der freien Fettsäure Palmitat eine Entzündungsreaktion in Makrophagen auslösen oder verstärken können und ob diese Entzündungsantwort zur Ausbildung einer Insulinresistenz beitragen kann. Weiterhin sollte untersucht werden, ob Metabolite und Signalsubstanzen, deren Konzentrationen beim metabolischen Syndrom erhöht sind, die Produktion des Prostaglandins (PG) E2 begünstigen können und ob dieses wiederum die Entzündungsreaktion und seine eigene Produktion in Makrophagen regulieren kann. Um den Einfluss dieser Faktoren auf die Produktion pro-inflammatorischer Mediatoren in Makrophagen zu untersuchen, wurden Monozyten-artigen Zelllinien und primäre humane Monozyten, welche aus dem Blut gesunder Probanden isoliert wurden, in Makrophagen differenziert und mit Insulin, LPS, Palmitat und/ oder PGE2 inkubiert. Überdies wurden primäre Hepatozyten der Ratte isoliert und mit Überständen Insulin-stimulierter Makrophagen inkubiert, um zu untersuchen, ob die Entzündungsanwort in Makrophagen an der Ausbildung einer Insulinresistenz in Hepatozyten beteiligt ist.
Insulin induzierte die Expression pro-inflammatorischer Zytokine in Makrophagen-artigen Zelllinien wahrscheinlich vorrangig über den Phosphoinositid-3-Kinase (PI3K)-Akt-Signalweg mit anschließender Aktiverung des Transkriptionsfaktors NF-κB (nuclear factor 'kappa-light-chain-enhancer' of activated B-cells). Die dabei ausgeschütteten Zytokine hemmten in primären Hepatozyten der Ratte die Insulin-induzierte Expression der Glukokinase durch Überstände Insulin-stimulierter Makrophagen.
Auch LPS oder Palmitat, deren lokale Konzentrationen im Zuge des metabolischen Syndroms erhöht sind, waren in der Lage, die Expression pro-inflammatorischer Zytokine in Makrophagen-artigen Zelllinien zu stimulieren. Während LPS seine Wirkung, laut Literatur, unbestritten über eine Aktivierung des Toll-ähnlichen Rezeptors (toll-like receptor; TLR) 4 vermittelt, scheint Palmitat jedoch weitestgehend TLR4-unabhängig wirken zu können. Vielmehr schien die de novo-Ceramidsynthese eine entscheidene Rolle zu spielen. Darüber hinaus verstärkte Insulin sowohl die LPS- als auch die Palmitat-induzierte Ent-zündungsantwort in beiden Zelllinien. Die in Zelllinien gewonnenen Ergebnisse wurden größtenteils in primären humanen Makrophagen bestätigt.
Desweiteren induzierten sowohl Insulin als auch LPS oder Palmitat die Produktion von PGE2 in den untersuchten Makrophagen. Die Daten legen nahe, dass dies auf eine gesteigerte Expression PGE2-synthetisierender Enzyme zurückzuführen ist.
PGE2 wiederum hemmte auf der einen Seite die Stimulus-abhängige Expression des pro-inflammatorischen Zytokins Tumornekrosefaktor (TNF) α in U937-Makrophagen. Auf der anderen Seite verstärkte es jedoch die Expression der pro-inflammatorischen Zytokine Interleukin- (IL-) 1β und IL-8. Darüber hinaus verstärkte es die Expression von IL-6-Typ-Zytokinen, welche sowohl pro- als auch anti-inflammatorisch wirken können. Außerdem vestärkte PGE2 die Expression PGE2-synthetisierender Enzyme. Es scheint daher in der Lage zu sein, seine eigene Synthese zu verstärken.
Zusammenfassend kann die Freisetzung pro-inflammatorischer Mediatoren aus Makro-phagen im Zuge einer Hyperinsulinämie die Entstehung einer Insulinresistenz begünstigen. Insulin ist daher in der Lage, einen Teufelskreis der immer stärker werdenden Insulin-resistenz in Gang zu setzen.
Auch Metabolite und Signalsubstanzen, deren Konzentrationen beim metabolischen Syndrom erhöht sind (zum Beispiel LPS, freie Fettsäuren und PGE2), lösten Entzündungsantworten in Makrophagen aus. Das wechselseitige Zusammenspiel von Insulin und diesen Metaboliten und Signalsubstanzen löste eine stärkere Entzündungsantwort in Makrophagen aus als jeder der Einzelkomponenten. Die dadurch freigesetzten Zytokine könnten zur Manifestation einer Insulinresistenz und des metabolischen Syndroms beitragen.
We recently demonstrated that the sympathetic nervous system can be voluntarily activated following a training program consisting of cold exposure, breathing exercises, and meditation. This resulted in profound attenuation of the systemic inflammatory response elicited by lipopolysaccharide (LPS) administration. Herein, we assessed whether this training program affects the plasma metabolome and if these changes are linked to the immunomodulatory effects observed. A total of 224 metabolites were identified in plasma obtained from 24 healthy male volunteers at six timepoints, of which 98 were significantly altered following LPS administration. Effects of the training program were most prominent shortly after initiation of the acquired breathing exercises but prior to LPS administration, and point towards increased activation of the Cori cycle. Elevated concentrations of lactate and pyruvate in trained individuals correlated with enhanced levels of anti-inflammatory interleukin (IL)-10. In vitro validation experiments revealed that co-incubation with lactate and pyruvate enhances IL-10 production and attenuates the release of pro-inflammatory IL-1 beta and IL-6 by LPS-stimulated leukocytes. Our results demonstrate that practicing the breathing exercises acquired during the training program results in increased activity of the Cori cycle. Furthermore, this work uncovers an important role of lactate and pyruvate in the anti-inflammatory phenotype observed in trained subjects.
Interplay of Dietary Fatty Acids and Cholesterol Impacts Brain Mitochondria and Insulin Action
(2020)
Overconsumption of high-fat and cholesterol-containing diets is detrimental for metabolism and mitochondrial function, causes inflammatory responses and impairs insulin action in peripheral tissues. Dietary fatty acids can enter the brain to mediate the nutritional status, but also to influence neuronal homeostasis. Yet, it is unclear whether cholesterol-containing high-fat diets (HFDs) with different combinations of fatty acids exert metabolic stress and impact mitochondrial function in the brain. To investigate whether cholesterol in combination with different fatty acids impacts neuronal metabolism and mitochondrial function, C57BL/6J mice received different cholesterol-containing diets with either high concentrations of long-chain saturated fatty acids or soybean oil-derived poly-unsaturated fatty acids. In addition, CLU183 neurons were stimulated with combinations of palmitate, linoleic acid and cholesterol to assess their effects on metabolic stress, mitochondrial function and insulin action. The dietary interventions resulted in a molecular signature of metabolic stress in the hypothalamus with decreased expression of occludin and subunits of mitochondrial electron chain complexes, elevated protein carbonylation, as well as c-Jun N-terminal kinase (JNK) activation. Palmitate caused mitochondrial dysfunction, oxidative stress, insulin and insulin-like growth factor-1 (IGF-1) resistance, while cholesterol and linoleic acid did not cause functional alterations. Finally, we defined insulin receptor as a novel negative regulator of metabolically stress-induced JNK activation.
The ever-increasing fat content in Western diet, combined with decreased levels of physical activity, greatly enhance the incidence of metabolic-related diseases. Cancer cachexia (CC) and Metabolic syndrome (MetS) are both multifactorial highly complex metabolism related syndromes, whose etiology is not fully understood, as the mechanisms underlying their development are not completely unveiled. Nevertheless, despite being considered “opposite sides”, MetS and CC share several common issues such as insulin resistance and low-grade inflammation. In these scenarios, tissue macrophages act as key players, due to their capacity to produce and release inflammatory mediators. One of the main features of MetS is hyperinsulinemia, which is generally associated with an attempt of the β-cell to compensate for diminished insulin sensitivity (insulin resistance). There is growing evidence that hyperinsulinemia per se may contribute to the development of insulin resistance, through the establishment of low grade inflammation in insulin responsive tissues, especially in the liver (as insulin is secreted by the pancreas into the portal circulation). The hypothesis of the present study was that insulin may itself provoke an inflammatory response culminating in diminished hepatic insulin sensitivity. To address this premise, firstly, human cell line U937 differentiated macrophages were exposed to insulin, LPS and PGE2. In these cells, insulin significantly augmented the gene expression of the pro-inflammatory mediators IL-1β, IL-8, CCL2, Oncostatin M (OSM) and microsomal prostaglandin E2 synthase (mPGES1), and of the anti-inflammatory mediator IL-10. Moreover, the synergism between insulin and LPS enhanced the induction provoked by LPS in IL-1β, IL-8, IL-6, CCL2 and TNF-α gene. When combined with PGE2, insulin enhanced the induction provoked by PGE2 in IL-1β, mPGES1 and COX2, and attenuated the inhibition induced by PGE2 in CCL2 and TNF-α gene expression contributing to an enhanced inflammatory response by both mechanisms. Supernatants of insulin-treated U937 macrophages reduced the insulin-dependent induction of glucokinase in hepatocytes by 50%. Cytokines contained in the supernatant of insulin-treated U937 macrophages also activated hepatocytes ERK1/2, resulting in inhibitory serine phosphorylation of the insulin receptor substrate. Additionally, the transcription factor STAT3 was activated by phosphorylation resulting in the induction of SOCS3, which is capable of interrupting the insulin receptor signal chain. MicroRNAs, non-coding RNAs linked to protein expression regulation, nowadays recognized as active players in the generation of several inflammatory disorders such as cancer and type II diabetes are also of interest. Considering that in cancer cachexia, patients are highly affected by insulin resistance and inflammation, control, non-cachectic and cachectic cancer patients were selected and the respective circulating levels of pro-inflammatory mediators and microRNA-21-5p, a posttranscriptional regulator of STAT3 expression, assessed and correlated. Cachectic patients circulating cytokines IL-6 and IL-8 levels were significantly higher than those of non-cachectic and controls, and the expression of microRNA-21-5p was significantly lower. Additionally, microRNA-21-5p reduced expression correlated negatively with IL-6 plasma levels. These results indicate that hyperinsulinemia per se might contribute to the low grade inflammation prevailing in MetS patients and thereby promote the development
of insulin resistance particularly in the liver. Diminished MicroRNA-21-5p expression may enhance inflammation and STAT3 expression in cachectic patients, contributing to the development of insulin resistance.
Eccentric exercise is discussed as a treatment option for clinical populations, but specific responses in terms of muscle damage and systemic inflammation after repeated loading of large muscle groups have not been conclusively characterized. Therefore, this study tested the feasibility of an isokinetic protocol for repeated maximum eccentric loading of the trunk muscles. Nine asymptomatic participants (5 f/4 m; 34±6 yrs; 175±13 cm; 76±17 kg) performed three isokinetic 2-minute all-out trunk strength tests (1x concentric (CON), 2x eccentric (ECC1, ECC2), 2 weeks apart; flexion/extension, 60°/s, ROM 55°). Outcomes were peak torque, torque decline, total work, and indicators of muscle damage and inflammation (over 168 h). Statistics were done using the Friedman test (Dunn’s post-test). For ECC1 and ECC2, peak torque and total work were increased and torque decline reduced compared to CON. Repeated ECC bouts yielded unaltered torque and work outcomes. Muscle damage markers were highest after ECC1 (soreness 48 h, creatine kinase 72 h; p<0.05). Their overall responses (area under the curve) were abolished post-ECC2 compared to post-ECC1 (p<0.05). Interleukin-6 was higher post-ECC1 than CON, and attenuated post-ECC2 (p>0.05). Interleukin-10 and tumor necrosis factor-α were not detectable. All markers showed high inter-individual variability. The protocol was feasible to induce muscle damage indicators after exercising a large muscle group, but the pilot results indicated only weak systemic inflammatory responses in asymptomatic adults.
Macrophages in pathologically expanded dysfunctional white adipose tissue are exposed to a mix of potential modulators of inflammatory response, including fatty acids released from insulin-resistant adipocytes, increased levels of insulin produced to compensate insulin resistance, and prostaglandin E₂ (PGE₂) released from activated macrophages. The current study addressed the question of how palmitate might interact with insulin or PGE₂ to induce the formation of the chemotactic pro-inflammatory cytokine interleukin-8 (IL-8). Human THP-1 cells were differentiated into macrophages. In these macrophages, palmitate induced IL-8 formation. Insulin enhanced the induction of IL-8 formation by palmitate as well as the palmitate-dependent stimulation of PGE₂ synthesis. PGE₂ in turn elicited IL-8 formation on its own and enhanced the induction of IL-8 release by palmitate, most likely by activating the EP4 receptor. Since IL-8 causes insulin resistance and fosters inflammation, the increase in palmitate-induced IL-8 formation that is caused by hyperinsulinemia and locally produced PGE₂ in chronically inflamed adipose tissue might favor disease progression in a vicious feed-forward cycle.
Das Selenoprotein Glutathionperoxidase 2 (GPx2) ist ein epithelzellspezifisches, Hydroperoxide-reduzierendes Enzym, welches im Darmepithel, vor allem in den proliferierenden Zellen des Kryptengrundes, exprimiert wird. Die Aufrechterhaltung der GPx2-Expression im Kryptengrund auch bei subadäquatem Selenstatus könnte darauf hinweisen, dass sie hier besonders wichtige Funktionen wahrnimmt. Tatsächlich weisen GPx2 knockout (KO)-Mäuse eine erhöhte Apoptoserate im Kryptengrund auf. Ein Ziel dieser Arbeit war es deshalb, die physiologische Funktion der GPx2 näher zu untersuchen. In Kryptengrundepithelzellen aus dem Colon selenarmer GPx2 KO-Mäuse wurde eine erhöhte Caspase 3/7-Aktivität im Vergleich zum Wildtyp (WT) festgestellt. Zudem wiesen diese Zellen eine erhöhte Suszeptibilität für oxidativen Stress auf. Die GPx2 gewährleistet also den Schutz der proliferierenden Zellen des Kryptengrundes auch bei subadäquater Selenversorgung. Des Weiteren wurde im Colon selenarmer (-Se) und -adäquater (+Se) GPx2 KO-Mäuse im Vergleich zum WT eine erhöhte Tumornekrosefaktor α-Expression und eine erhöhte Infiltration von Makrophagen festgestellt. Durch Fütterung einer selensupplementierten Diät (++Se) konnte dies verhindert werden. In GPx2 KO-Mäusen liegt demnach bereits basal eine niedriggradige Entzündung vor. Dies unterstreicht, dass GPx2 vor allem eine wichtige antiinflammatorische Funktion im Darmepithel besitzt. Dem Mikronährstoff Selen werden protektive Funktionen in der Colonkanzerogenese zugeschrieben. In einem Mausmodell der Colitis-assoziierten Colonkanzerogenese wirkte GPx2 antiinflammatorisch und hemmte so die Tumorentstehung. Auf der anderen Seite wurden jedoch auch prokanzerogene Eigenschaften der GPx2 aufgedeckt. Deshalb sollte in dieser Arbeit untersucht werden, welchen Effekt ein GPx2 knockout in einem Modell der sporadischen, durch Azoxymethan (AOM) induzierten, Colonkanzerogenese hat. Im WT kam es in präneoplastischen Läsionen häufig zu einer erhöhten GPx2-Expression im Vergleich zur normalen Darmmucosa. Eine derartige Steigerung der GPx2-Expression wurde auch in der humanen Colonkanzerogenese beschrieben. Das Fehlen der GPx2 resultierte in einer verminderten Entstehung von Tumoren (-Se und ++Se) und präneoplastischen Läsionen (-Se und +Se). Somit förderte GPx2 die Tumorentstehung im AOM-Modell. Acht Stunden nach AOM-Gabe war im GPx2 KO-Colon im Vergleich zum WT eine erhöhte Apoptoserate in der Kryptenmitte (-Se, +Se), nicht jedoch im Kryptengrund oder in der ++Se-Gruppe zu beobachten. Möglicherweise wirkte GPx2 prokanzerogen, indem sie die effiziente Elimination geschädigter Zellen in der Tumorinitiationsphase verhinderte. Eine ähnliche Wirkung wäre auch durch die erhöhte GPx2-Expression in der Promotionsphase denkbar. So könnte GPx2 proliferierende präneoplastische Zellen vor oxidativem Stress, Apoptosen, oder auch der Antitumorimmunität schützen. Dies könnte durch ein Zusammenwirken mit anderen Selenoproteinen wie GPx1 und Thioredoxinreduktasen, für die ebenfalls auch prokanzerogene Funktionen beschrieben wurden, verstärkt werden. Eine wichtige Rolle könnte hier die Modulation des Redoxstatus in Tumorzellen spielen. Die Variation des Selengehalts der Diät hatte im WT einen eher U-förmigen Effekt. So traten in der –Se und ++Se-Gruppe tendenziell mehr und größere Tumore auf, als in der +Se Gruppe. Zusammenfassend schützt GPx2 also die proliferierenden Zellen des Kryptengrundes. Sie könnte jedoch auch proliferierende transformierte Zellen schützen und so die sporadische, AOM-induzierte Colonkanzerogenese fördern. In einem Modell der Colitis-assoziierten Colonkanzerogenese hatte GPx2 auf Grund ihrer antiinflammatorischen Wirkung einen gegenteiligen Effekt und hemmte die Tumorentstehung. Die Rolle der GPx2 in der Colonkanzerogenese ist also abhängig vom zugrunde liegenden Mechanismus und wird maßgeblich von der Beteiligung einer Entzündung bestimmt.
Bei der Entdeckung der Glutathionperoxidase-2 (GPx2) wurde zunächst davon ausgegangen, dass die Funktion dieses Enzyms im Kryptengrund des Colons einzig in der Reduktion von H2O2 besteht. Im Laufe der weiteren Erforschung zeigte sich, dass GPx2 auch in verschiedenen Tumorgeweben vermehrt exprimiert wird. Dabei wird diskutiert, ob die Wirkung von GPx2 im Tumor eher als pro- oder als antikarzinogen einzustufen ist. Mehrere Experimente in vitro und in vivo zeigten antiinflammatorische Eigenschaften der GPx2. Aufgrund dieser Befunde wird derzeit über weitere Funktionen der GPx2 spekuliert. In dieser Arbeit wurde die physiologische Funktion von GPx2 näher erforscht, dazu wurden Wildtyp- und GPx2-Knockout-Mäuse in Hinblick auf Veränderungen der Enzymexpression und der Colonmorphologie untersucht. Es wurden drei verschiedene Selendiäten verfüttert: selenarmes, selenadäquates und selensupplementiertes Futter. Unter physiologischen Bedingungen ist am Kryptengrund des Colons, innerhalb der proliferierenden Zone, die Mitoserate am höchsten. Der Großteil der apoptotischen Zellen ist hingegen an der Kryptenspitze vorzufinden. Durch den Knockout von GPx2 kam es zu einer signifikanten Erhöhung der Apoptoserate am Kryptengrund. Dabei war der größte Effekt auf selenarmem Futter zu verzeichnen. Hierbei wurde sogar eine Veränderung der Colonmorphologie dokumentiert, da die Verschiebung der Proliferationszone in Richtung Kryptenspitze eine Verlängerung der Krypten nach sich zog. Im Wildtyp wurden keine Apoptosen im Kryptengrund detektiert. GPx1 wird unter physiologischen Bedingungen im Gegensatz zur GPx2 in der Kryptenspitze exprimiert und ist im Selenmangel nicht mehr detektierbar. Der Knockout von GPx2 erhöhte die GPx1-Expression im Kryptengrund auf allen drei Selendiäten. Diese Überexpression von GPx1 am Kryptengrund soll vermutlich den Verlust von GPx2 an dieser Stelle kompensieren. Da jedoch dort die massive Apoptoserate detektiert wurde, kann die GPx1 nicht die komplette Funktion von GPx2 kompensieren. Diese Ergebnisse deuten darauf hin, dass die Funktion von GPx2 nicht nur in der Reduktion von H2O2 liegt. Vielmehr kann eine Rolle bei der Aufrechterhaltung der Homöostase von Zellen postuliert werden. Ein weiterer Bestandteil dieser Arbeit war die Klärung der Frage, welchen Einfluss GPx2 auf die entzündungsassoziierte Colonkarzinogenese ausübt. In dem hierfür verwendeten AOM/DSS-Model wird der karzinogene Prozess durch Entzündung vorangetrieben. Es erfolgte sowohl im Wildtyp als auch im GPx2-Knockout zum einen die Bewertung des Entzündungsstatus des Colons und zum anderen wurde die Anzahl von ACF und Tumoren verglichen. Das Colon im GPx2-Knockout war wesentlich stärker entzündet als im Wildtyp. Diese Ergebnisse bestätigen die für die GPx2 postulierte antiinflammatorische Funktion. Normalerweise führt eine Erhöhung der Mitoseanzahl zur Regeneration des entzündeten Gewebes. Jedoch beeinflusst der Verlust von GPx2 vermutlich den Ablauf der Entzündung, indem beispielsweise die Regeneration des Gewebes durch die enorm hohe Apoptoserate am Kryptengrund verlangsamt wird. Des Weiteren hatten sich im GPx2-Knockout tendenziell mehr Tumore entwickelt. Somit korrelierte die Entzündung des Colons mit der Entwicklung von Tumoren. Der Verlust von GPx2 begünstigte vermutlich sowohl die Tumorinitiation als auch die Tumorprogression. Allerdings stimulierte die Expression von GPx2 ebenfalls das Tumorwachstum. Es kann geschlussfolgert werden, dass eine adäquate GPx2-Expression vor Entzündung schützt und somit das Risiko für Colonkrebs senkt. Ob GPx2 aber insgesamt pro- oder antikarzinogen wirkt, hängt vermutlich vom Stadium des Colonkarzinogenese ab.
PURPOSE. Graves' orbitopathy (GO) is an autoimmune orbital disorder associated with Graves' disease caused by thyrotropin receptor autoantibodies. Orbital fibroblasts (OFs) and CD40 play a key role in disease pathogenesis. The bioactive lipid sphingosine-1-phosphate (S1P) has been implicated in promoting adipogenesis, fibrosis, and inflammation in OFs. We investigated the role of CD40 signaling in inducing S1P activity in orbital inflammation.
METHODS. OFs and T cells were derived from GO patients and healthy control (Ctl) persons. S1P abundance in orbital tissues was evaluated by immunofluorescence. OFs were stimulated with CD40 ligand and S1P levels were determined by ELISA. Further, activities of acid sphingomyelinase (ASM), acid ceramidase, and sphingosine kinase were measured by ultraperformance liquid chromatography. Sphingosine and ceramide contents were analyzed by mass spectrometry. Finally, the role for S1P in T-cell attraction was investigated by T-cell migration assays.
RESULTS. GO orbital tissue showed elevated amounts of S1P as compared to control samples. Stimulation of CD40 induced S1P expression in GO-derived OFs, while Ctl-OFs remained unaffected. A significant increase of ASM and sphingosine kinase activities, as well as lipid formation, was observed in GO-derived OFs. Migration assay of T cells in the presence of SphK inhibitor revealed that S1P released by GO-OFs attracted T cells for migration.
CONCLUSIONS. The results demonstrated that CD40 ligand stimulates GO fibroblast to produce S1P, which is a driving force for T-cell migration. The results support the use of S1P receptor signaling modulators in GO management.
Accumulating data indicates a link between a pro-inflammatory status and occurrence of chronic disease-related fatigue. The questions are whether the observed inflammatory profile can be (a) improved by anti-inflammatory diets, and (b) if this improvement can in turn be translated into a significant fatigue reduction. The aim of this narrative review was to investigate the effect of anti-inflammatory nutrients, foods, and diets on inflammatory markers and fatigue in various patient populations. Next to observational and epidemiological studies, a total of 21 human trials have been evaluated in this work. Current available research is indicative, rather than evident, regarding the effectiveness of individuals’ use of single nutrients with anti-inflammatory and fatigue-reducing effects. In contrast, clinical studies demonstrate that a balanced diet with whole grains high in fibers, polyphenol-rich vegetables, and omega-3 fatty acid-rich foods might be able to improve disease-related fatigue symptoms. Nonetheless, further research is needed to clarify conflicting results in the literature and substantiate the promising results from human trials on fatigue.