Histone deacetylase-mediated regulation of the antimicrobial peptide hBD2 differs in intestinal cell lines and cultured tissue

Abstract Histone deacetylase inhibition (HDACi) has been suggested as a promising approach to bolster TLR-mediated induction of antimicrobial peptides such as human β-defensin 2 (hBD2). In inflammatory bowel disease (IBD), Crohn’s disease (CD) patients display an attenuated expression of hBD2 as compared to ulcerative colitis (UC). Here, we aimed to study if combining HDACi with the therapeutic E. coli Nissle 1917 (EcN), a strong hBD2 inducer, might be a feasible strategy to further modify protective immune responses. Monolayer epithelial cell lines versus cultured human biopsies from healthy controls and CD and UC patients showed diverse effects. In mono-cell systems, we observed a strong NF-kB-dependent enhancement of TLR- but also IL1β-mediated hBD2 induction after HDACi. In contrast, multicellular colonic biopsy culture showed the opposite result and HDACi was associated with an abolished TLR-mediated hBD2 induction in all tested patient groups. Of note, CD patients showed an attenuated induction of hBD2 by E. coli Nissle as compared to UC. We conclude that the role of HDACs in hBD2 regulation is context-dependent and likely modified by different cell types. Differential induction in different IBD entities suggests different clinical response patterns based on still unknown hBD2-associated mechanisms

Gastric Antimicrobial Peptides Fail to Eradicate Helicobacter pylori Infection Due to Selective Induction and Resistance

Background: Although antimicrobial peptides protect mucus and mucosa from bacteria, Helicobacter pylori is able to colonize the gastric mucus. To clarify in which extend Helicobacter escapes the antimicrobial defense, we systematically assessed susceptibility and expression levels of different antimicrobial host factors in gastric mucosa with and without H. pylori infection. Materials and Methods: We investigated the expression levels of HBD1 (gene name DEFB1), HBD2 (DEFB4A), HBD3 (DEFB103A), HBD4 (DEFB104A), LL37 (CAMP) and elafin (PI3) by real time PCR in gastric biopsy samples in a total of 20 controls versus 12 patients colonized with H. pylori. Immunostaining was performed for HBD2 and HBD3. We assessed antimicrobial susceptibility by flow cytometry, growth on blood agar, radial diffusion assay and electron microscopy. Results: H. pylori infection was associated with increased gastric levels of the inducible defensin HBD2 and of the antiprotease elafin, whereas the expression levels of the constitutive defensin HBD1, inducible HBD3 and LL37 remained unchanged. HBD4 was not expressed in significant levels in gastric mucosa. H. pylori strains were resistant to the defensins HBD1 as well as to elafin, and strain specific minimally susceptible to HBD2, whereas HBD3 and LL37 killed all H. pylori strains effectively. We demonstrated the binding of HBD2 and LL37 on the surface of H. pylori cells. Comparing the antibacterial activity of extracts from H. pylori negative and positive biopsies, we found only a minimal killing against H. pylori that was not increased by the induction of HBD2 in H. pylori positive samples. Conclusion: These data support the hypothesis that gastric H. pylori evades the host defense shield to allow colonization

Antimicrobial activity of biopsy extracts.

<p>In <i>H. pylori</i> positive biopsy extracts antimicrobial activity towards <i>H. pylori</i> remained consistent compared with Helicobacter negative extracts. Thus Helicobacter did not induce helicobactericidal factors, whereas in Helicobacter positive extracts the antimicrobial effect towards <i>E. coli</i> was increased.</p