Measurement of in vivo rectal mucosal cytokine and eicosanoid production in ulcerative colitis using filter paper

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Abstract
BACKGROUND Excessive mucosal generation of cytokines and eicosanoids has been reported in vitro in ulcerative colitis (UC) using traumatising biopsy techniques, and in vivo using time consuming rectal dialysis. AIMS To validate a simple filter paper technique to profile rectal mucosal production of cytokines and eicosanoids in vivo in patients with UC compared with controls. PATIENTS Forty one patients with UC (21 with active disease) and 16 controls were studied. METHODS In vitro, recovery of known concentrations of cytokine or mediator applied to filter papers was measured by ELISA following incubation in buffer. In vivo, patients and controls had filter papers apposed to the rectal mucosa briefly through a rigid sigmoidoscope. Filter papers were then incubated prior to assay by ELISA. RESULTS In vitro validation studies showed that the filter paper technique could be used to measure mucosal release of interleukin-1β (IL-1β), tumour necrosis factor α (TNF-α), thromboxane B2(TXB2), and prostaglandin E2(PGE2), but not interferon γ (IFN-γ). Mucosal release of IL-1β, TNF-α, TXB2 and PGE2 were significantly increased in active UC (p=0.001) and correlated directly with disease activity (p=0.02). CONCLUSIONS The filter paper technique confirmed increased rectal mucosal release of cytokines and eicosanoids in UC, in proportion to disease activity. The simplicity, safety and speed of the technique make it a practicable option for use in the outpatient clinic to study the pathogenesis of inflammatory bowel disease, and potentially its response to treatment.