RESUMEN
Butyrate, a short-chain fatty acid released by colonic bacteria and administered therapeutically in inflammatory bowel diseases, exerts immunomodulatory properties. The aim of the study was to determine the functional consequences of butyrate exposure on the proinflammatory responsiveness of human intestinal epithelial cells (IEC). IL-8 promoter activity in IEC pretreated with butyrate then exposed to proinflammatory stimuli was assayed by transfection of luciferase constructs. IL-8 secretion was determined by ELISA and neutrophil migration by flow cytometry. Receptor mRNA was assessed by reverse transcriptase-polymerase chain reaction (RT-PCR). Butyrate modulated proinflammatory IL-8 secretion differentially in Caco-2 and HT-29 cells on the transcriptional level. Pointing to the potentially underlying mechanism of increased IL-1 beta-stimulated IL-8 secretion in HT-29 cells, butyrate up-regulated IL-1RI mRNA but not IL-1RII. Butyrate pretreatment of IEC lines stimulated by IL-1 beta modulated neutrophil migration significantly: reduction towards Caco-2 and enhancement towards HT-29/p cells. Pharmacological inhibition of protein tyrosine phosphatases or treatment with mesalamine or sulphasalazine diminished IL-1 beta-stimulated IL-8 secretion by butyrate-exposed HT-29 cells substantially. Immunomodulatory effects of butyrate on IEC are functionally relevant for neutrophil migration. Pharmacological inhibition of enhanced IL-1 beta-mediated IL-8 secretion in a subpopulation of IEC may improve the clinical efficacy of butyrate.