@phdthesis{Ganesh2013,
  author    = {Ganesh, Bhanu Priya},
  title     = {Host-microbe interactions in the inflamed gut},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-69558},
  school      = {Universit{\"a}t Potsdam},
  year      = {2013},
  abstract  = {Initiation and perpetuation of inflammatory bowel diseases (IBD) may result from an exaggerated mucosal immune response to the luminal microbiota in a susceptible host. We proposed that this may be caused either 1) by an abnormal microbial composition or 2) by weakening of the protective mucus layer due to excessive mucus degradation, which may lead to an easy access of luminal antigens to the host mucosa triggering inflammation. We tested whether the probiotic Enterococcus faecium NCIMB 10415 (NCIMB) is capable of reducing chronic gut inflammation by changing the existing gut microbiota composition and aimed to identify mechanisms that are involved in possible beneficial effects of the probiotic. To identify health-promoting mechanisms of the strain, we used interleukin (IL)-10 deficient mice that spontaneously develop gut inflammation and fed these mice a diet containing NCIMB (106 cells g-1) for 3, 8 and 24 weeks, respectively. Control mice were fed an identically composed diet but without the probiotic strain. No clear-cut differences between the animals were observed in pro-inflammatory cytokine gene expression and in intestinal microbiota composition after probiotic supplementation. However, we observed a low abundance of the mucin-degrading bacterium Akkermansia muciniphila in the mice that were fed NCIMB for 8 weeks. These low cell numbers were associated with significantly lower interferon gamma (IFN-γ) and IFN-γ-inducible protein (IP-10) mRNA levels as compared to the NCIMB-treated mice that were killed after 3 and 24 weeks of intervention. In conclusion, NCIMB was not capable of reducing gut inflammation in the IL-10-/- mouse model. To further identify the exact role of A. muciniphila and uncover a possible interaction between this bacterium, NCIMB and the host in relation to inflammation, we performed in vitro studies using HT-29 colon cancer cells. The HT-29 cells were treated with bacterial conditioned media obtained by growing either A. muciniphila (AM-CM) or NCIMB (NCIMB-CM) or both together (COMB-CM) in Dulbecco's Modified Eagle Medium (DMEM) for 2 h at 37 °C followed by bacterial cell removal. HT-29 cells treated with COMB-CM displayed reduced cell viability after 18 h (p<0.01) and no viable cells were detected after 24 h of treatment, in contrast to the other groups or heated COMB-CM. Detection of activated caspase-3 in COMB-CM treated groups indicated that death of the HT-29 cells was brought about by apoptosis. It was concluded that either NCIMB or A. muciniphila produce a soluble and heat-sensitive factor during their concomitant presence that influences cell viability in an in vitro system. We currently hypothesize that this factor is a protein, which has not yet been identified. Based on the potential effect of A. muciniphila on inflammation (in vivo) and cell-viability (in vitro) in the presence of NCIMB, we investigated how the presence of A. muciniphila affects the severity of an intestinal Salmonella enterica Typhimurium (STm)-induced gut inflammation using gnotobiotic C3H mice with a background microbiota of eight bacterial species (SIHUMI, referred to as simplified human intestinal microbiota). Presence of A. muciniphila in STm-infected SIHUMI (SIHUMI-AS) mice caused significantly increased histopathology scores and elevated mRNA levels of IFN-γ, IP-10, tumor necrosis factor alpha (TNF-α), IL-12, IL-17 and IL-6 in cecal and colonic tissue. The number of mucin filled goblet cells was 2- to 3- fold lower in cecal tissue of SIHUMI-AS mice compared to SIHUMI mice associated with STm (SIHUMI-S) or A. muciniphila (SIHUMI-A) or SIHUMI mice. Reduced goblet cell numbers significantly correlated with increased IFN-γ (r2 = -0.86, ***P<0.001) in all infected mice. In addition, loss of cecal mucin sulphation was observed in SIHUMI-AS mice. Concomitant presence of A. muciniphila and STm resulted in a drastic change in microbiota composition of the SIHUMI consortium. The proportion of Bacteroides thetaiotaomicron in SIHUMI, SIHUMI-A and SIHUMI-S mice made up to 80-90\% but was completely taken over by STm in SIHUMI-AS mice contributing 94\% to total bacteria. These results suggest that A. muciniphila exacerbates STm-induced intestinal inflammation by its ability to disturb host mucus homeostasis. In conclusion, abnormal microbiota composition together with excessive mucus degradation contributes to severe intestinal inflammation in a susceptible host.},
  language  = {en}
}
@phdthesis{Radloff2018,
  author    = {Radloff, Katrin},
  title     = {The role of the fatty acid profile and its modulation by cytokines in the systemic inflammation in cancer cachexia},
  school      = {Universit{\"a}t Potsdam},
  pages     = {156},
  year      = {2018},
  abstract  = {Systemic inflammation is a hallmark of cancer cachexia. Among tumor-host interactions, the white adipose tissue (WAT) is an important contributor to inflammation as it suffers morphological reorganization and lipolysis, releasing free fatty acids (FA), bioactive lipid mediators (LM) and pro-inflammatory cytokines, which accentuate the activation of pro-inflammatory signaling pathways and the recruitment of immune cells to the tissue. This project aimed to investigate which inflammatory factors are involved in the local adipose tissue inflammation and what is the influence of such factors upon enzymes involved in FA or LM metabolism in healthy individuals (Control), weight stable gastro-intestinal cancer patients (WSC) and cachectic cancer patients (CC). The results demonstrated that the inflammatory signature of systemic inflammation is different from local adipose tissue inflammation. The systemic inflammation of the cachectic cancer patients was characterized by higher levels of circulating saturated fatty acids (SFA), tumor-necrosis-factor-α (TNF-α), interleukins IL-6, IL-8 and CRP while levels of polyunsaturated fatty acids (PUFAs), especially n3-PUFAs, were lower in CC than in the other groups. In vitro and in adipose tissue explants, pro-inflammatory cytokines and SFAs were shown to increase the chemokines IL-8 and CXCL10 that were found to be augmented in adipose tissue inflammation in CC which was more profound in the visceral adipose tissue (VAT) than in subcutaneous adipose tissue (SAT). Systemic inflammation was negatively associated with the expression of PUFA synthesizing enzymes, though gene and protein expression did hardly differ between groups. The effects of inflammatory factors on enzymes in the whole tissue could have been masked by differentiated modulation of the diverse cell types in the same tissue. In vitro experiments showed that the expression of FA-modifying enzymes such as desaturases and elongases in adipocytes and macrophages was regulated into opposing directions by TNF-α, IL-6, LPS or palmitate. The higher plasma concentration of the pro-resolving LM resolvin D1 in CC cannot compensate the overall inflammatory status and the results indicate that inflammatory cytokines interfere with synthesis pathways of pro-resolving LM. In summary, the data revealed a complex inter-tissue and inter-cellular crosstalk mediated by pro-inflammatory cytokines and lipid compounds enhancing inflammation in cancer cachexia by feed-forward mechanisms.},
  language  = {en}
}
@phdthesis{Klauder2021,
  author    = {Klauder, Julia},
  title     = {Makrophagenaktivierung durch Hyperinsulin{\"a}mie als Ausl{\"o}ser eines Teufelkreises der Entz{\"u}ndung im Kontext des metabolischen Syndroms},
  doi       = {10.25932/publishup-52019},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-520199},
  school      = {Universit{\"a}t Potsdam},
  pages     = {IX, 227},
  year      = {2021},
  abstract  = {Insulinresistenz ist ein zentraler Bestandteil des metabolischen Syndroms und tr{\"a}gt maßgeblich zur Ausbildung eines Typ-2-Diabetes bei. Eine m{\"o}gliche Ursache f{\"u}r die Entstehung von Insulinresistenz ist eine chronische unterschwellige Entz{\"u}ndung, welche ihren Ursprung im Fettgewebe {\"u}bergewichtiger Personen hat. Eingewanderte Makrophagen produzieren vermehrt pro-inflammatorische Mediatoren, wie Zytokine und Prostaglandine, wodurch die Konzentrationen dieser Substanzen sowohl lokal als auch systemisch erh{\"o}ht sind. Dar{\"u}ber hinaus weisen {\"u}bergewichtige Personen einen gest{\"o}rten Fetts{\"a}uremetabolismus und eine erh{\"o}hte Darmpermeabilit{\"a}t auf. Ein gesteigerter Flux an freien Fetts{\"a}uren vom Fettgewebe in andere Organe f{\"u}hrt zu einer lokalen Konzentrationssteigerung in diesen Organen. Eine erh{\"o}hte Darmpermeabilit{\"a}t erleichtert das Eindringen von Pathogenen und anderer k{\"o}rperfremder Substanzen in den K{\"o}rper. Ziel dieser Arbeit war es, zu untersuchen, ob hohe Konzentrationen von Insulin, des bakteriellen Bestandteils Lipopolysaccharid (LPS) oder der freien Fetts{\"a}ure Palmitat eine Entz{\"u}ndungsreaktion in Makrophagen ausl{\"o}sen oder verst{\"a}rken k{\"o}nnen und ob diese Entz{\"u}ndungsantwort zur Ausbildung einer Insulinresistenz beitragen kann. Weiterhin sollte untersucht werden, ob Metabolite und Signalsubstanzen, deren Konzentrationen beim metabolischen Syndrom erh{\"o}ht sind, die Produktion des Prostaglandins (PG) E2 beg{\"u}nstigen k{\"o}nnen und ob dieses wiederum die Entz{\"u}ndungsreaktion 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 prim{\"a}re humane Monozyten, welche aus dem Blut gesunder Probanden isoliert wurden, in Makrophagen differenziert und mit Insulin, LPS, Palmitat und/ oder PGE2 inkubiert. {\"U}berdies wurden prim{\"a}re Hepatozyten der Ratte isoliert und mit {\"U}berst{\"a}nden Insulin-stimulierter Makrophagen inkubiert, um zu untersuchen, ob die Entz{\"u}ndungsanwort in Makrophagen an der Ausbildung einer Insulinresistenz in Hepatozyten beteiligt ist. Insulin induzierte die Expression pro-inflammatorischer Zytokine in Makrophagen-artigen Zelllinien wahrscheinlich vorrangig {\"u}ber 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 ausgesch{\"u}tteten Zytokine hemmten in prim{\"a}ren Hepatozyten der Ratte die Insulin-induzierte Expression der Glukokinase durch {\"U}berst{\"a}nde Insulin-stimulierter Makrophagen. Auch LPS oder Palmitat, deren lokale Konzentrationen im Zuge des metabolischen Syndroms erh{\"o}ht sind, waren in der Lage, die Expression pro-inflammatorischer Zytokine in Makrophagen-artigen Zelllinien zu stimulieren. W{\"a}hrend LPS seine Wirkung, laut Literatur, unbestritten {\"u}ber eine Aktivierung des Toll-{\"a}hnlichen Rezeptors (toll-like receptor; TLR) 4 vermittelt, scheint Palmitat jedoch weitestgehend TLR4-unabh{\"a}ngig wirken zu k{\"o}nnen. Vielmehr schien die de novo-Ceramidsynthese eine entscheidene Rolle zu spielen. Dar{\"u}ber hinaus verst{\"a}rkte Insulin sowohl die LPS- als auch die Palmitat-induzierte Ent-z{\"u}ndungsantwort in beiden Zelllinien. Die in Zelllinien gewonnenen Ergebnisse wurden gr{\"o}ßtenteils in prim{\"a}ren humanen Makrophagen best{\"a}tigt. 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 zur{\"u}ckzuf{\"u}hren ist. PGE2 wiederum hemmte auf der einen Seite die Stimulus-abh{\"a}ngige Expression des pro-inflammatorischen Zytokins Tumornekrosefaktor (TNF) α in U937-Makrophagen. Auf der anderen Seite verst{\"a}rkte es jedoch die Expression der pro-inflammatorischen Zytokine Interleukin- (IL-) 1β und IL-8. Dar{\"u}ber hinaus verst{\"a}rkte es die Expression von IL-6-Typ-Zytokinen, welche sowohl pro- als auch anti-inflammatorisch wirken k{\"o}nnen. Außerdem vest{\"a}rkte PGE2 die Expression PGE2-synthetisierender Enzyme. Es scheint daher in der Lage zu sein, seine eigene Synthese zu verst{\"a}rken. Zusammenfassend kann die Freisetzung pro-inflammatorischer Mediatoren aus Makro-phagen im Zuge einer Hyperinsulin{\"a}mie die Entstehung einer Insulinresistenz beg{\"u}nstigen. Insulin ist daher in der Lage, einen Teufelskreis der immer st{\"a}rker werdenden Insulin-resistenz in Gang zu setzen. Auch Metabolite und Signalsubstanzen, deren Konzentrationen beim metabolischen Syndrom erh{\"o}ht sind (zum Beispiel LPS, freie Fetts{\"a}uren und PGE2), l{\"o}sten Entz{\"u}ndungsantworten in Makrophagen aus. Das wechselseitige Zusammenspiel von Insulin und diesen Metaboliten und Signalsubstanzen l{\"o}ste eine st{\"a}rkere Entz{\"u}ndungsantwort in Makrophagen aus als jeder der Einzelkomponenten. Die dadurch freigesetzten Zytokine k{\"o}nnten zur Manifestation einer Insulinresistenz und des metabolischen Syndroms beitragen.},
  language  = {de}
}