Elif Gelmez-Bitterlich

PhD Student

Dunja Bruder

Project Leader

To regain the homeostatic balance in chronically inflamed conditions the organism relies on regulatory mechanisms not observable under acute inflammatory conditions. On the molecular level these mechanisms are in part related to epigenetic gene regulation. Specific patterns of posttranslational histone modifications correlate with different gene activity states. The impact of posttranslational histone modification on maladaptive processes during chronic inflammatory conditions at the intestinal barrier remains unknown. To access inflammation induced histone modification in the intestinal epithelium at different disease states we will use the DSS colitis model to induce acute intestinal inflammation (group I) followed by convalescence (reestablishment of tissue homeostasis; group II), chronic intestinal inflammation (group III) as well as colorectal cancer (group IV, DSS treatment in combination with the carcinogen azoxymethane). Ex vivo isolated IEC will be subjected to histone acetylation and methylation analyses. Matching conventional transcription microarray analysis allows linking identified histone modifications to transcriptional alterations and cellular phenotypes (e.g. senescence, malignant transformation, cooperation with Project 1). Molecular signatures identified in the murine model will be validated in tissue biopsies obtained from human IBD and colorectal cancer patients (collaboration with Dr. Schulz, Clinic for Gastroenterology). To elucidate if inflammation-related molecular imprinting of IEC alters the micromilieu and immune cell composition in the gut emphasis will be put on the stage-specific characterization of secreted mediators (chemokines, cytokines, immunosuppressive mediators) as well as surface molecules involved in the direct interaction with intestinal immune cells (cooperation with Project 6 and Project 8). To evaluate the impact of IEC maladaptation on capillary function we will ascertain the endothelial phenotype (cellular senescence, expression of adhesion molecules, glycocalyx, cooperation with Project 1, Project 4, and Project 5). The mechanistic relevance of newly identified targets will be determined using genetic or pharmacological inhibitory approaches (cooperation with Project 8). These studies will uncover molecular and cellular maladaptive processes promoting the transition from acute to chronic intestinal inflammation and predisposing to tumor development.

Epigenetic modification in iEpiC in the perturbation of intestinal inflammation and the development of colitis-associated cancer (CAC). A: Environmental triggers induce acute damage in iEpiC (1), resulting in transient immune activation and immune cell recruitment. In general, intestinal inflammation is self-limiting. B: In case of sustained epithelial damage (B), recruited inflammatory immune cells and their mediators result in exaggerated oxidative stress response (2) which can induce DNA damage and epigenetic alterations in iEpiC (3), resulting in perpetuation of inflammation, further epithelial barrier dysfunction (4) and eventually progression of chronic intestinal inflammation to colitis-associated cancer (CAC, 5). C: Schematic representation of the proposed disease mechanisms.

Wiebke Seidler

PhD Student

Dunja Bruder

Project Leader

Coming soon!

Mahyar Aghapour

PhD Student

Dunja Bruder

Project Leader

Chronic obstructive pulmonary diseases (COPD) is a heterogeneous respiratory disorder with huge economic and health burdens. Cigarette smoking is considered as the major risk factor for development of COPD, inducing sustained inflammatory response as well as decline in lung function. Acute worsening of COPD symptoms or COPD exacerbation is thought to be caused by bacterial and viral infections. Streptococcus pneumoniae (S. pneumoniae) is a third frequent bacteria isolated during COPD exacerbation that escalates condition by eliciting further oxidative stress and inflammation. Mitochondria are not only responsible for cellular bioenergetics but also recently found to be involved in innate immune responses to pathogens. Mitochondrial function is impaired in lung epithelial cells of COPD patients as well as smokers. However, the mechanistic pathway linking mitochondrial dysfunction to airway epithelial innate immune responses in COPD exacerbation is still lacking. In particular, host defense peptides/proteins (HDPs) constitute a robust innate immune defense restricting pathogens in epithelial luminal surface. Decreased production or activity of HDPs in airway epithelial cells may contribute to pathogenesis of COPD exacerbation. We hypothesize that mitochondrial dysfunction as a result of cigarette smoke exposure dampens innate immune response to S. pneumoniae in airway epithelium, which leads to decrease in HDPs, epithelial barrier disruption and as such further susceptibility to other pathogens. For this objective, we will be exploited state-of-the-art in vitro models of COPD exacerbation. First, mitochondrial dysfunction will be induced by submerging immortalized airway epithelial cells in cigarette smoke extract (CSE) followed by infecting with S. pneumoniae. To confirm induction of mitochondrial dysfunction, the protein levels of mitochondrial damage-sensitive proteins will be quantified. Furthermore, mitochondrial-specific reactive oxygen species (mtROS) and intracellular ROS levels, which are representative of oxidative stress status in the cells, will be measured. In order to characterize the role of mitochondrial dysfunction in airway epithelial innate immune responses, restoration of mitochondrial antioxidant activity by mitochondrial-targeted antioxidant MitoTEMPO will be tested. The impact of mitochondrial dysfunction on airway epithelial innate immune responses will be examined by quantifying the expression of neutrophil chemoattractant genes, the levels of cytokines and proteins involved in inflammatory pathways and host defense, as well as antibacterial activity of the epithelial cells. Changes in mitochondrial oxidative respiration activity will be determined by using Seahorse test (cooperation with Project 5). Furthermore, COPD exacerbation model will be induced by directly exposing well-differentiated primary airway epithelial cells from healthy and COPD subjects to CS and S. pneumoniae to fully recapitulate the condition (in collaboration with Prof. Pieter Hiemstra, LUMC, The Netherlands).

Schematic representation of proposed model of airway epithelial barrier disruption in COPD exacerbation. Cigarette smoke exposure induces mitochondrial dysfunction in airway epithelial cells that may in turn disrupt innate immune responses to pneumococci and increase the permeability of airway epithelial cells.

Ilka Jorde

PhD Student

Dunja  Bruder

Project Leader

Over the last decades the incidence of allergic diseases such as allergic asthma was on the rise in western industrial countries. By now there are over 300 million asthmatics worldwide. Asthma is a heterogeneous chronic respiratory disease and about 60 % of adult asthmatics suffer from allergic asthma, which is mainly Th2‑driven. Patients suffer from airway hyperreactivity, variable bronchial obstruction, increased mucus production and structural changes of the airways. It has been proposed that allergic sensitization and inflammation in asthma can be affected by Staphylococcus aureus (S. aureus). S. aureus is a gram-positive bacterium and facultative pathogen which colonizes up to 30 % of the adult population. In newborns the colonization rate is even higher as in 70 % of all newborns S. aureus could be detected. The anterior nares of the nose are the most frequent carriage site of S. aureus. Beside the upper airways S. aureus colonizes the skin, the pharynx as well as the gastrointestinal tract. The described associations with allergic asthma are of high medical relevance but are not well understood to date. The project aims at elucidating the immunological mechanisms underlying the association between S. aureus and allergic asthma in relevant mouse models. One major focus is the immune regulatory potential of Staphylococcal enterotoxin B (SEB) in allergic asthma. SEB is a small protein with a molecular weight of 28.4 kDa, one of the major superantigens produced by S. aureus and a potent activator of the immune system. The effects of an intranasal treatment with SEB alone or additional SEB-treatment during different phases of allergic asthma in a mouse model will be analyzed regarding histological changes, respiratory and systemic inflammation as well as IgE responses. The local inflammation, assessing immune cell populations and their activation status will be characterized. Furthermore concentrations of different cytokines and chemokines will be analyzed, as well as OVA‑specific and SEB‑specific IgE-levels. Additionally, detailed histological examinations will be performed and airway hyperreactivity will be assessed in order to address SEB-mediated effects on airway hyperreactivity in the asthma mouse-model. Taken together, these detailed analyses of the immunological mediators, recruited immune cells, IgE levels and lung function parameters in SEB‑treated, asthmatic, SEB-treated asthmatic and control mice will yield a comprehensive insight into SEB-mediated immune modulation as well as into its effects on allergic asthma. Importantly, these analyses will build a solid basis for future projects such as pre-clinical interventional studies. Here, the contribution of key mediators could be analyzed e.g. through neutralization via specific antibodies or using knock-out mouse models.