Suppression of interleukin-1β- and tumor necrosis factor-α-induced inflammatory responses by leukocytapheresis therapy in patients with ulcerative colitis

Background. To elucidate the molecular mechanisms involved in the therapeutic effects of leukocytapheresis (LCAP), we investigated the alterations in the cytokine responses of peripheral blood mononuclear cells (PBMCs) before and after LCAP therapy in ulcerative colitis (UC) patients. Methods. Twelve patients with UC who did not respond to steroid therapy were enrolled. Nine patients responded to LCAP therapy, but 3 patients did not show clinical improvement. PBMCs were isolated from peripheral venous blood obtained within 5 min before and after the first and second session of LCAP treatment. Cells were stimulated with interleukin (IL)-1beta and tumor necrosis factor (TNF)-alpha for 24 h, and the levels of secreted IL-8 and IL-6 were determined by enzyme-linked immunosorbent assay (ELISA). Results. LCAP induced a significant decrease in peripheral lymphocyte, monocyte, and platelet counts. IL-1beta- and TNF-alpha-induced IL-8 and IL-6 secretion was significantly decreased after the first and second LCAP treatments. These responses were associated with inhibitory effects on nuclear factor (NF)-kappaB DNA-binding activity. Conclusions. LCAP downregulates the IL-1beta- and TNF-alpha-induced inflammatory responses in PBMCs isolated from UC patients. The induction of hyporesponsiveness to proinflammatory cytokines may be an important factor mediating the clinical effects of LCAP in UC patients.