Expression of the cathelicidin LL-37 is modulated by short chain fatty acids in colonocytes: relevance of signalling pathways
- J Schauber1,
- C Svanholm2,*,
- S Termén3,*,
- K Iffland1,
- T Menzel1,
- W Scheppach1,
- R Melcher1,
- B Agerberth3,
- H Lührs1,
- G H Gudmundsson4
- 1Department of Medicine, Division of Gastroenterology, University of Würzburg, Germany
- 2Microbiology and Tumour Biology Centre, Karolinska Institute, Stockholm, Sweden
- 3Department of Medical Biochemistry and Biophysics, Karolinska Institute, Stockholm, Sweden
- 4Microbiology and Tumour Biology Centre, Karolinska Institute, Stockholm, Sweden, and Institute of Biology, University of Iceland, Reykjavik, Iceland
- Correspondence to:
Dr J Schauber, Medizinische Klinik, Schwerpunkt Gastroenterologie, Josef-Schneider-Str 2, 97080 Würzburg, Germany;
- Accepted 12 November 2002
Background and aims: Short chain fatty acids (SCFA) exert profound effects on the colonic mucosa. In particular, SCFA modulate mucosal immune functions. The antimicrobial cathelicidin LL-37 is expressed by colon epithelial cells. In the present study the effect of SCFA on LL-37 expression was investigated.
Methods: LL-37 expression in vivo was assessed by immunohistochemistry. Real time quantitative reverse transcription-polymerase chain reaction was employed to determine LL-37 expression in colonocytes in vitro after treatment with various cytokines, SCFA, or flavone. LL-37 levels were correlated to cell differentiation which was determined by alkaline phosphatase (AP) activity. In addition, intracellular signalling pathways such as MEK-ERK (mitogen/extracellular signal protein kinase (MEK)/extracellular signal regulated protein kinase (ERK)) and p38/mitogen activated protein (MAP) kinase were explored.
Results: In vivo, LL-37 expression in healthy mucosa was restricted to differentiated epithelial cells in human colon and ileum. In colonocytes, increased LL-37 expression associated with cell differentiation was detected in vitro following treatment with butyrate, isobutyrate, propionate, and trichostatin A. Flavone induced LL-37 transcription but did not affect AP activity while cytokines had no effect. To dissect pathways mediating differentiation and LL-37 expression, specific inhibitors were applied. Inhibition of the protein kinase MEK enhanced butyrate induced AP activity while LL-37 expression in colon epithelial cells was blocked. In contrast, inhibition of p38/MAP kinase blocked cell differentiation without inhibiting LL-37 expression.
Conclusions: Expression of the cathelicidin LL-37 in colonocytes and cellular differentiation are separately modulated by SCFA via distinct signalling pathways. These data may provide a rationale for dietary modulation of mucosal defence mechanisms.
- MEK, mitogen/extracellular signal protein kinase
- ERK, extracellular signal regulated protein kinase
- MAP, mitogen activated protein
- SCFA, short chain fatty acids
- AP, alkaline phosphatase
- RT-PCR, reverse transcription-polymerase chain reaction
- FCS, fetal calf serum
- GAPDH, glyceraldehyde-3-phosphate dehydrogenase
- CBB, cold binding buffer
↵* C Svanholm and S Termén contributed equally to this work.