Bronchiolitis obliterans syndrome (BOS) is the leading cause of death after lung transplantation. Treatment is challenging, as the precise pathophysiology remains unclear.We hypothesize that T H 17 lineage plays a key role in the pathophysiology of BOS by linking T-cell activation to neutrophil influx and chronic inflammation.

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Summary Antimicrobial peptides like human β‐defensin‐2 (HBD‐2) play an important role in the innate immune system protecting the intestinal mucosa against bacterial invasion. The dietary histone deacetylase (HDAC) inhibitors sulforaphane (SFN) and butyrate have received a great deal of attention because of their ability to simultaneously modulate multiple cellular targets involved in cellular protection. In this study the influence of SFN and butyrate on HBD‐2 expression as well as the molecular pathways involved in SFN‐mediated induction of HBD‐2 were scrutinized. Treatment of Caco‐2, HT‐29 and SW480 cells with SFN led to a time‐ and dose‐dependent upregulation of HBD‐2 mRNA expression as determined by semi‐quantitative reverse transcription–polymerase chain reaction. Moreover, HBD‐2 protein production increased in response to SFN, measured by enzyme‐linked immunosorbent assay. Induction of HBD‐2 was also observed in response to butyrate. Immunofluorescence analysis revealed that the protein was localized in the cytosol. Coincubation of SFN with a vitamin D receptor (VDR), or an extracellular‐regulated kinase 1/2 or a nuclear factor‐κB inhibitor all reduced HBD‐2 mRNA upregulation. In contrast, transfection of cells with a dominant‐negative peroxisome proliferator‐activated receptor γ (PPARγ) mutant vector to inhibit PPARγ wild‐type action and inhibition of p38 mitogen‐activated protein kinase (MAPK) signalling did not affect SFN‐mediated upregulation of HBD‐2 mRNA. Moreover, SFN induced the expression of VDR, PPARγ and phosphorylated ERK1/2 but did not affect p38 MAPK activation. The data clearly demonstrate for the first time that the dietary HDAC inhibitor SFN is able to induce antimicrobial peptides in colonocytes. In this process HBD‐2 expression is regulated via VDR, mitogen‐activated protein kinase kinase/extracellular‐regulated kinase and nuclear factor‐κB signalling.

This study clearly demonstrates that mesalazine-mediated pro-apoptotic and anti-proliferative actions are regulated via PPARgamma-dependent and -independent pathways in colonocytes.

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