Differential activation of cytokine secretion in primary human colonic fibroblast/myofibroblast cultures

Background: Fibroblasts and myofibroblasts are known to secrete a wide spec trum of cytokines, but the individual spectrum is tissue-specific. We inves tigated the effect of cell activation on cytokine secretion of isolated hum an colonic fibroblasts/myofibroblasts from control patients and patients wi th mucosal inflammation. Methods: Primary cultures of human colonic submuco sal fibroblasts/myofibroblasts were incubated with IL-1 alpha (100 U/ml), I L-1 beta (10 ng/ml), IL-10 (10 ng/ml), TNF (10 ng/ml), PMA (10 ng/ml), LPS (50 ng/ml), IL-4 (10 ng/ml), or a combination of EL-I and TNF. Secreted cyt okines were determined by ELISA. NF-kappaB activation was demonstrated by e lectrophoretic mobility-shift assays (EMSA). Results: Incubation of colonic fibroblasts/myofibroblasts with IL-1, LPS, TNF and PMA induced secretion o f IL-6, IL-8, M-CSF and GM-CSF. IL-8 and IL-6 secretion could be stimulated by IL-1 alpha, IL-1 beta, TNF, PMA and LPS within 6 h of incubation. IL-6 secretion was stimulated from 0.5 +/- 0.01 pg/h x mug fibroblast protein to 18.5 +/- 2.6 pg/h x mug fibroblast protein with IL-1 beta (P < 0.01). IL-8 secretion was stimulated from 1.0 <plus/minus> 0.1 pg/h x mug fibroblast p rotein to 41.1 +/- 3.6 pg/h x pg (P < 0.005). IL-4 and IL-10 did not change cytokine secretion significantly. No significant differences between cultu res from normal and inflamed mucosa were observed. TNF and IL-1 induced NF- <kappa>B activation. ALLN, a proteasome and NF-kappaB activation inhibitor, reduced TNF-mediated IL-8, GM-CSF and M-CSF induction significantly, where as induction of IL-6 secretion remained unchanged. Conclusion: Human coloni c myofibroblasts can secrete large amounts of IL-6, IL-8, M-CSF and GM-CSF upon stimulation. The induction of IL-8, M-CSF and GM-CSF, but not of IL-6 secretion, is mediated mainly by NF-kappaB activation. The cytokine profile and the total amounts of cytokines released suggest that colonic myofibrob lasts can play a role in leukocyte recruitment and during mucosal inflammat ion. They therefore have to be regarded as an important part of the mucosal immune system.