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Dirk Haller

Publications and source records attributed to Dirk Haller.

12 recordsLinked to original sources
PubMed2024

Exclusive enteral nutrition initiates individual protective microbiome changes to induce remission in pediatric Crohn's disease.

Exclusive enteral nutrition (EEN) is a first-line therapy for pediatric Crohn's disease (CD), but protective mechanisms remain unknown. We established a prospective pediatric cohort to characterize the function of fecal microbiota and metabolite changes of treatment-naive CD patients in response to EEN (German Clinical Trials DRKS00013306). Integrated multi-omics analysis identified network clusters from individually variable microbiome profiles, with Lachnospiraceae and medium-chain fatty acids as protective features. Bioorthogonal non-canonical amino acid tagging selectively identified bacterial species in response to medium-chain fatty acids. Metagenomic analysis identified high strain-level dynamics in response to EEN. Functional changes in diet-exposed fecal microbiota were further validated using gut chemostat cultures and microbiota transfer into germ-free Il10-deficient mice. Dietary model conditions induced individual patient-specific strain signatures to prevent or cause inflammatory bowel disease (IBD)-like inflammation in gnotobiotic mice. Hence, we provide evidence that EEN therapy operates through explicit functional changes of temporally and individually variable microbiome profiles.

Crohn Disease↗
PubMed2006

Functional diversity of flavonoids in the inhibition of the proinflammatory NF-kappaB, IRF, and Akt signaling pathways in murine intestinal epithelial cells.

The molecular understanding of nutritional factors in the process of host factor-mediated activation of the intestinal epithelium may play an important role in the assessment of adjunct nutritional therapy for chronic intestinal inflammation. We characterized the molecular mechanisms of flavonoids including apigenin, luteolin, genistein, 3'-hydroxy-flavone, and flavone in inhibiting tumor necrosis factor-alpha (TNF)-induced interferon-induced protein (IP)-10 gene expression in the murine intestinal epithelial cell (IEC) line Mode-K. We demonstrated that 3'-hydroxy-flavone but not the chemical core structure flavone blocked TNF-alpha-induced nuclear factor (NF)-kappaB transcriptional activity and IP-10 expression at the level of NF-kappaB/IkappaBalpha phosphorylation/degradation by inhibiting IkappaB kinase activity. Although 3'-hydroxy-flavone effectively triggered p38 mitogen-activated protein kinase signaling and late caspase-3 cleavage, the induction of apoptotic cell death in TNF-activated IEC was not the primary mechanism inhibiting NF-kappaB transcriptional activity and IP-10 expression. In addition to the compound-specific inhibition of TNF-induced NF-kappaB DNA binding and NF-kappaB transcriptional activity, apigenin and luteolin selectively blocked Akt phosphorylation/activity. The ability of these polyphenolic compounds to target various signal transduction pathways was further supported by the observation that luteolin and 3'-hydroxy-flavone selectively induced interferon regulatory factor (IRF)-1 degradation. Finally, we showed that genistein blocked IP-10 but not IL-6 expression through NF-kappaB, IRF, and Akt independent mechanisms, demonstrating the functional diversity of flavonoids in inhibiting proinflammatory processes in IEC. In conclusion, we provide molecular evidence for the presence of characteristic inhibition patterns of these polyphenolic compounds to inhibit proinflammatory gene expression in IEC through the specific modulation of the NF-kappaB, IRF and Akt signaling pathways.

Animals↗
PubMed2006

IL-10 gene-deficient mice lack TGF-beta/Smad-mediated TLR2 degradation and fail to inhibit proinflammatory gene expression in intestinal epithelial cells under conditions of chronic inflammation.

Nonpathogenic enteric bacterial species initiate and perpetuate experimental colitis in interleukin-10 geneeficient mice (IL-10(-/-)). Bacteria-specific effects on the epithelium are difficult to distinguish because of the complex nature of the gut microflora. We showed that IL-10(-/-) mice compared to wild-type mice fail to inhibit pro-inflammatory gene expression in native intestinal epithelial cells after the colonization with colitogenic Gram-positive Enterococcus faecalis. Of interest, pro-inflammatory gene expression was transient after 1 week of E. faecalis monoassociation in IECs from wild-type mice but persisted after 14 weeks of bacterial colonization in IL-10(-/-) mice. Accordingly, wild-type IECs expressed phosphorylated NF-kappaB subunit RelA (p65) and phosphorylated Smad2 only at day 7 after bacterial colonization, whereas E. faecalis-monoassociated IL-10(-/-) mice triggered persistent RelA but no Smad2 phosphorylation in IECs at days 3, 7, 14, and 28. Consistent with the induction of TLR2-mediated RelA phosphorylation and pro-inflammatory gene expression in E. faecalis-stimulated cell lines, TLR2 protein expression was absent after day 7 from E. faecalis-monoassociated wild-type mice but persisted in IL-10(-/-) IECs. Of note, TGF-beta-activated Smad signaling was associated with the loss of TLR2 protein expression and the inhibition of NF-kappa Bependent gene expression in E. faecalis-stimulated IEC lines. In conclusion, E. faecalis-monoassociated IL-10(-/-) but not wild-type mice lack protective TGF-beta/Smad signaling and fail to inhibit TLR2-mediated pro-inflammatory gene expression in the intestinal epithelium, suggesting a critical role for IL-10 and TGF-beta in maintaining normal epithelial cell homeostasis in the interplay with commensal enteric bacteria.

Animals↗
PubMed2005

IL-10 gene-deficient mice lack TGF-beta/Smad signaling and fail to inhibit proinflammatory gene expression in intestinal epithelial cells after the colonization with colitogenic Enterococcus faecalis.

Nonpathogenic enteric bacterial species initiate and perpetuate experimental colitis in IL-10 gene-deficient mice (IL-10(-/-)). Bacteria-specific effects on the epithelium are difficult to dissect due to the complex nature of the gut microflora. We showed that IL-10(-/-) mice compared with wild-type mice fail to inhibit proinflammatory gene expression in native intestinal epithelial cells (IEC) after the colonization with colitogenic Gram-positive Enterococcus faecalis. Interestingly, proinflammatory gene expression was transient after 1 wk of E. faecalis monoassociation in IEC from wild-type mice, but persisted after 14 wk of bacterial colonization in IL-10(-/-) mice. Accordingly, wild-type IEC expressed phosphorylated NF-kappaB subunit RelA (p65) and phosphorylated Smad2 only at day 7 after bacterial colonization, whereas E. faecalis-monoassociated IL-10(-/-) mice triggered persistent RelA, but no Smad2 phosphorylation in IEC at days 3, 7, 14, and 28. Consistent with the induction of TLR2-mediated RelA phosphorylation and proinflammatory gene expression in E. faecalis-stimulated cell lines, TLR2 protein expression was absent after day 7 from E. faecalis-monoassociated wild-type mice, but persisted in IL-10(-/-) IEC. Of note, TGF-beta1-activated Smad signaling was associated with the loss of TLR2 protein expression and the inhibition of NF-kappaB-dependent gene expression in IEC lines. In conclusion, E. faecalis-monoassociated IL-10(-/-), but not wild-type mice lack protective TGF-beta/Smad signaling and fail to inhibit TLR2-mediated proinflammatory gene expression in the intestinal epithelium, suggesting a critical role for IL-10 and TGF-beta in maintaining normal epithelial cell homeostasis in the interplay with commensal enteric bacteria.

Animals↗
PubMed2005

Innate mechanisms for Bifidobacterium lactis to activate transient pro-inflammatory host responses in intestinal epithelial cells after the colonization of germ-free rats.

Bifidobacteria comprise a dominant microbial population group in the human intestinal tract with purported beneficial health effects on the host. In this study, we characterized the molecular mechanisms for the initial interaction of probiotic Bifidobacterium lactis strain BB12 with native and intestinal epithelial cell (IEC) lines. We showed that B. lactis-monoassociated Fisher F344 rats transiently induce phosphorylation/activation of the NF-kappaB transcriptionally active subunit RelA and the mitogen-activated protein kinase (MAPK) p38 in native IEC at day 5 after initial bacterial colonization. In addition, Interleukin 6 (IL-6) gene expression was significantly increased at day 5, demonstrating the physiological relevance of transient transcription factor activation in IEC. In contrast, Bacteroides vulgatus-monoassociated Fisher rats revealed RelA but not p38 MAPK phosphorylation and failed to trigger significant IL-6 gene expression in native IEC. Moreover, we demonstrated that B. lactis triggers NF-kappaB RelA and p38 MAPK phosphorylation in IEC lines. Adenoviral delivery of mutant IKK-beta (Ad5dnIKKbeta) and inhibition of the p38 MAPK pathway through the pharmacological inhibitor SB203580 significantly blocked B. lactis-induced IL-6 gene expression in IEC, suggesting that B. lactis triggers NF-kappaB and MAPK signaling to induce gene expression in the intestinal epithelium. Regarding the mechanisms of bacteria epithelial cell cross-talk, B. lactis-induced IL-6 gene expression was completely inhibited in TLR2 deficient mouse embryogenic fibroblasts (MEF TLR2-/-) as well as TLR2DeltaTIR transfected Mode-K cells. In conclusion, we demonstrated that probiotic bacteria transiently trigger innate signal transduction and pro-inflammatory gene expression in the intestinal epithelium at early stages of bacterial colonization.

Animals↗
PubMed2004

15-deoxy-delta12,14-prostaglandin J2-mediated ERK signaling inhibits gram-negative bacteria-induced RelA phosphorylation and interleukin-6 gene expression in intestinal epithelial cells through modulation of protein phosphatase 2A activity.

We have previously shown that non-pathogenic Gram-negative Bacteroides vulgatus induces transient RelA phosphorylation (Ser-536), NF-kappaB activity, and pro-inflammatory gene expression in native and intestinal epithelial cell (IEC) lines. We now demonstrate that 15-deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)) but not prostaglandin E(2) inhibits lipopolysaccharide (LPS) (B. vulgatus)/LPS (Escherichia coli)-induced RelA phosphorylation and interleukin-6 gene expression in the colonic epithelial cell line CMT-93. This inhibitory effect of 15d-PGJ(2) was mediated independently of LPS-induced IkappaBalpha phosphorylation/degradation and RelA nuclear translocation as well as RelA DNA binding activity. Interestingly, although B. vulgatus induced nuclear expression of peroxisome proliferator-activated receptor gamma (PPARgamma) in native epithelium of monoassociated Fisher rats, PPARgamma-specific knock-down in CMT-93 cells using small interference RNA failed to reverse the inhibitory effects of PPARgamma agonist 15d-PGJ(2), suggesting PPARgamma-independent mechanisms. In addition, 15d-PGJ(2) but not the synthetic high affinity PPARgamma ligand rosiglitazone triggered ERK1/2 phosphorylation in IEC, and most importantly, MEK1 inhibitor PD98059 reversed the inhibitory effect of 15dPGJ(2) on LPS-induced RelA phosphorylation and interleukin-6 gene expression. Calyculin A, a specific phosphoserine/phospho-threonine phosphatase inhibitor increased the basal phosphorylation of RelA and reversed the inhibitory effect of 15d-PGJ(2) on LPS-induced RelA phosphorylation. We further demonstrated in co-immunoprecipitation experiments that 15d-PGJ(2) triggered protein phosphatase 2A activity, which directly dephosphorylated RelA in LPS-stimulated CMT-93 cells. We concluded that 15d-PGJ(2) may help to control NF-kappaB signaling and normal intestinal homeostasis to the enteric microflora by modulating RelA phosphorylation in IEC through altered protein phosphatase 2A activity.

Animals↗
PubMed2003

Transforming growth factor-beta 1 inhibits non-pathogenic Gram negative bacteria-induced NF-kappa B recruitment to the interleukin-6 gene promoter in intestinal epithelial cells through modulation of histone acetylation.

We have shown that non-pathogenic enteric Gram-negative Bacteroides vulgatus induces RelA phosphorylation, NF-kappaB activation, and proinflammatory gene expression in primary and intestinal epithelial cell (IEC) lines. We now demonstrate the transient induction of nuclear phospho-RelA (day 3) followed by persistent activation of phospho-Smad2 (days 3 and 7) in IEC from mucosal tissue sections of B. vulgatus-monoassociated rats, indicating that both NF-kappaB and transforming growth factor-beta1 (TGF-beta1) signaling are induced in vivo following bacterial colonization. Interestingly, TGF-beta1 inhibited B. vulgatus- and lipopolysaccharide (LPS)-induced NF-kappaB transcriptional activity as well as interleukin-6 (IL-6) mRNA accumulation and protein secretion in IEC. The inhibitory effect of TGF-beta1 is mediated independently of B. vulgatus/LPS-induced IkappaBalpha, Akt, and RelA phosphorylation as well as NF-kappaB DNA binding activity. Moreover, the specific histone deacetylase inhibitor trichostatin A blocked B. vulgatus/LPS-induced histone acetylation/phosphorylation (Lys-9/Ser-10) and reversed TGF-beta1-mediated inhibition of IL-6 gene expression. Chromatin immunoprecipitation analysis revealed that B. vulgatus/LPS-induced RelA recruitment to the IL-6 promoter is inhibited by TGF-beta1 treatment. Adenoviral delivery of Smad7 and dominant negative Smad3 (SmadDelta3) reversed the TGF-beta1-mediated inhibition of NF-kappaB transcriptional activity and NF-kappaB recruitment to the IL-6 promoter. In addition, TGF-beta1 and Ad5Smad3/4 prevent B. vulgatus/LPS-induced CBP/p300 and p65 nuclear co-association. We concluded that the TGF-beta1/Smad signaling pathway helps maintain normal intestinal homeostasis to commensal luminal enteric bacteria by regulating NF-kappaB signaling in IEC through altered histone acetylation.

Acetylation↗
PubMed2002

IKK beta and phosphatidylinositol 3-kinase/Akt participate in non-pathogenic Gram-negative enteric bacteria-induced RelA phosphorylation and NF-kappa B activation in both primary and intestinal epithelial cell lines.

Pathogenic and enteroinvasive bacteria have been shown to trigger the I kappa B/NF-kappa B transcriptional system and proinflammatory gene expression in epithelial cells. In this study, we investigated the molecular mechanism of the commensal Gram-negative Bacteroides vulgatus-induced NF-kappa B signal transduction in intestinal epithelial cells (IEC). We report that B. vulgatus induced interleukin-1 receptor-associated kinase-1 degradation, I kappa B alpha phosphorylation/degradation, RelA and Akt phosphorylation, as well as NF-kappa B DNA binding and NF-kappa B transcriptional activity in rat non-transformed IEC-6 cells. B. vulgatus- but not interleukin-1 beta-mediated NF-kappa B transcriptional activity was inhibited by dominant negative (dn) toll-like receptor 4. Of importance, B. vulgatus induced I kappa B alpha phosphorylation/degradation and IKK alpha/beta and RelA phosphorylation in primary IEC derived from germ-free or mono-associated HLA-B27 transgenic and wild type rats, demonstrating the physiological relevance of non-pathogenic bacterial signaling in IEC. Adenoviral delivery of dn IKK beta or treatment with wortmannin inhibited B. vulgatus-induced endogenous RelA Ser-536 and GST-p65TAD (Ser-529/Ser-536) phosphorylation as well as NF-kappa B transcriptional activity in IEC-6 cells, suggesting a critical role of IKK beta and phosphatidylinositol 3-kinase/Akt in bacteria-induced RelA phosphorylation and NF-kappa B activation. Interestingly, B. vulgatus-induced I kappa B alpha degradation and NF-kappa B transcriptional activity in IEC transwell cultures were inhibited in the presence of lymphocytes. We propose that non-pathogenic B. vulgatus activates the NF-kappa B signaling pathway through both I kappa B degradation and RelA phosphorylation but that immune cells mediate tolerance of IEC to this commensal bacteria.

Animals↗
PubMed2002

IL-10 producing CD14low monocytes inhibit lymphocyte-dependent activation of intestinal epithelial cells by commensal bacteria.

Intestinal epithelial cell (IEC) activation by non-pathogenic, commensal bacteria was demonstrated to require the presence of immunocompetent cells. In this study, HT-29 and CaCO-2 transwell cultures, reconstituted with CD4+ and CD8+ T cells, CD19+ B cells and CD14high monocytes, were challenged with non-pathogenic Gram negative Escherichia coli and Gram positive lactobacilli. Cytokine expression was analysed by reverse transcription-polymerase chain reaction (RT-PCR) and enzyme linked immunosorbent assays (ELISA). Expression of tumour necrosis factor alpha (TNF-alpha) and interleukin (IL)-8 mRNA in E. coli or L. sakei challenged IEC was promoted by lymphocyte populations predominantly CD4+ T cells, while monocytes failed to mediate an inflammatory cytokine response. The monocyte phenotype and function were further characterised by flow cytometry and mixed lymphocyte reaction (MLR). During the co-culture with IEC and bacterial stimulated IEC, CD14high peripheral blood monocytes acquired a CD14low CD16low phenotype with reduced expression co-stimulatory (CD80, CD86, CD58) cell surface molecules. Immunosuppressive functions of IEC conditioned CD14low monocytes were demonstrated by the predominant secretion of IL-10 and IL-IRa and their reduced potential to trigger an allogeneic lymphocyte response. In conclusion, IEC contribute to the development of CD14low CD16low monocytes with immunosuppressive function and antagonised a lymphocyte-mediated activation of the intestinal epithelium in response to intestinal and food derived bacteria. These results strengthen the hypothesis that the gut epithelium constitutes an important functional element in the regulation of mucosal immune homeostasis towards commensal bacteria.

Biomarkers↗
PubMedDate not supplied

[Detection of drug transport using X-ray techniques].

The purpose of the paper was to show X-ray techniques used to discover drugs transported inside the body (body packers), on the body surface, in the garments or luggage, in goods and vehicles. The analysis was based on the X-ray findings of 141 body packers caught in Hamburg between 1989 and 2004 as well as individual cases from personal collections. The use of X-rays for border and security checks is described, different technical concepts are demonstrated and examples are given, e. g. transmission (fluoroscopic) and backscatter imaging of humans, luggage, goods, and vehicles as well as X-ray spectroscopy. The results showed that body packers produce characteristic findings in native X-ray photographs, which are even more pronounced in CT scans and after application of contrast media. Backscatter imaging allows the investigation of the body surface and the clothing. Transmission and backscatter imaging is suitable for checking humans, goods, passenger cars, trucks and containers. With the help of X-ray spectroscopy suspicious substances can be identified without opening the packaging material. According to present findings, the radiation dose applied seems low compared with exposure to environmental radiation and cosmic radiation during flights. The pictures obtained with the backscatter technique show the person checked in the nude, which raises the question of privacy versus the right of the state to carry out inspections and controls.

Aircraft↗