Background and aims: Neutrophil granulocytes infiltrate the intestinal mucosa in active ulcerative colitis (UC), and may contribute to tissue damage and inflammation. The aim of this investigation was to study the importance of locally produced factors and the impact of steroid treatment on neutrophil functions in UC.
Patients and methods: Intestinal perfusion fluids from 11 patients with active distal UC before and after seven and 28 days of treatment with prednisolone and from seven control patients were used in the study. Neutrophil migration towards perfusion fluid was measured in a microchemotaxis chamber. The effect of perfusion fluids on neutrophil activation was assessed as the surface expression of CD66b by flow cytometry. Neutrophil survival was evaluated by staining with propidium iodide, annexin V, and fluorescein di-acetate. We also assessed the viability of freshly isolated tissue neutrophils from rectal biopsy samples.
Results: Perfusion fluids from untreated patients caused increased migration, activation, and survival of neutrophils. Perfusion fluids collected after treatment had no effect on neutrophil migration, but some of the activation and anti-apoptotic effects remained after 7 days. Anti-granulocyte-macrophage colony-stimulating factor (GM-CSF) inhibited the anti-apoptotic effect of perfusion fluids. Rectal tissue neutrophils from patients with active proctitis had increased viability compared to patients with inactive proctitis and control subjects.
Conclusions: These data show that mediators in the colon of patients with active UC stimulate the migration, activation, and survival of neutrophils. The activities were partly neutralized by topical steroid treatment. We also identified GM-CSF as an anti-apoptotic factor for neutrophils in inflamed colon.