Platelet activation results in changes in a number of cell surface molecules including an increase in P-Selectin (CD62P) that may be rapidly and conveniently measured by immunofluorescent flow cytometry. The ADVIA 120 (Bayer) is a new system that facilitates more accurate measurement of platelet volume and in addition provides an approximate measure of the mean refractive index (RI) of the platelets reported as mean platelet component (MPC) concentration. We were interested to determine whether changes in MPC might reflect changes in platelet activation status. To investigate this, the platelet CD62P expression, determined by flow cytometry, and change in MPC, measured on the ADVIA 120 system, was first examined in vitro after stimulation of EDTA anticoagulated whole blood with submaximal concentrations of bovine thrombin in the presence or absence of the thromboxane synthase inhibitor, Ridogrel. Thrombin produced a dose-dependent increase in platelet CD62P expression and a decrease in MPC that could be inhibited by Ridogrel at physiological concentrations. In the second set of experiments, blood from 20 normal controls was collected into both EDTA and sodium citrate (SC) anticoagulants. Within 30 min of venesection and again at 3 h post-venesection after storage at room temperature, the platelet MPC and CD62P expression were determined. Platelets in all samples with both anticoagulants showed very low levels of CD62P expression when first analysed. At 3 h there was a small increase in CD62P expression on platelets in whole blood anticoagulated with SC, but a significant (P F 0.001) increase was observed on platelets anti-coagulated with EDTA. A negative correlation was found between the change in MPC of the platelets and the increase in the mean fluorescence intensity (MFI) (r 0.69, P F 0.001, n 20) and the percentage (r 0.72, P F 0.001, n 20) of CD62P positive platelets at 3 h in blood anticoagulated with EDTA. We conclude that a reduction in MPC as measured by the ADVIA 120 may be used to detect anticoagulant induced, as well as thrombin stimulated, in vitro platelet activation in blood anticoagulated with EDTA. Further, we conclude that platelet activation is negligible for up to 3 h in sodium citrate anticoagulated whole blood. Cytometry (Comm.

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 buVer. 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-1 (IL-1 ), tumour necrosis factor (TNF-), thromboxane B 2 (TXB 2 ), and prostaglandin E 2 (PGE 2 ), but not interferon (IFN-). Mucosal release of IL-1 , TNF-, TXB 2 and PGE 2 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. (Gut 2000;46:487-492)

Platelet activation results in changes in a number of cell surface molecules including an increase in P‐Selectin (CD62P) that may be rapidly and conveniently measured by immunofluorescent flow cytometry. The ADVIA 120 (Bayer) is a new system that facilitates more accurate measurement of platelet volume and in addition provides an approximate measure of the mean refractive index (RI) of the platelets reported as mean platelet component (MPC) concentration. We were interested to determine whether changes in MPC might reflect changes in platelet activation status. To investigate this, the platelet CD62P expression, determined by flow cytometry, and change in MPC, measured on the ADVIA 120 system, was first examined in vitro after stimulation of EDTA anticoagulated whole blood with submaximal concentrations of bovine thrombin in the presence or absence of the thromboxane synthase inhibitor, Ridogrel. Thrombin produced a dose‐dependent increase in platelet CD62P expression and a decrease in MPC that could be inhibited by Ridogrel at physiological concentrations. In the second set of experiments, blood from 20 normal controls was collected into both EDTA and sodium citrate (SC) anticoagulants. Within 30 min of venesection and again at 3 h post‐venesection after storage at room temperature, the platelet MPC and CD62P expression were determined. Platelets in all samples with both anticoagulants showed very low levels of CD62P expression when first analysed. At 3 h there was a small increase in CD62P expression on platelets in whole blood anticoagulated with SC, but a significant (P < 0.001) increase was observed on platelets anti‐coagulated with EDTA. A negative correlation was found between the change in MPC of the platelets and the increase in the mean fluorescence intensity (MFI) (r = −0.69, P < 0.001, n = 20) and the percentage (r = −0.72, P < 0.001, n = 20) of CD62P positive platelets at 3 h in blood anticoagulated with EDTA. We conclude that a reduction in MPC as measured by the ADVIA 120 may be used to detect anticoagulant induced, as well as thrombin stimulated, in vitro platelet activation in blood anticoagulated with EDTA. Further, we conclude that platelet activation is negligible for up to 3 h in sodium citrate anticoagulated whole blood. Cytometry (Comm. Clin. Cytometry) 38:250–255, 1999.  © 1999 Wiley‐Liss, Inc.

Background: Platelets play an important role in inflammation and are activated in inflammatory bowel disease. Micro‐vascular thrombosis in the gut wall leading to intestinal micro‐infarction may be a pathogenic feature of Crohn’s disease. 5‐Aminosalicylic acid is an effective treatment for patients with inflammatory bowel disease. Aims: To assess the effects of 5‐aminosalicylic acid on platelet activation, when taken orally and in vitro by patients with inflammatory bowel disease. Methods: Spontaneous and thrombin‐induced platelet activation were studied using fluorescent antibodies to the activated platelet surface glycoprotein P‐selectin and flow cytometry. Results: Baseline platelet activation in inflammatory bowel disease was significantly greater than that in controls (P=0.0003). Independent of diagnosis or disease activity, spontaneous ex‐vivo platelet activation was 50% lower in patients with inflammatory bowel disease taking 5‐aminosalicylic acid orally than in those not on such treatment (P < 0.05). In vitro, 5‐aminosalicylic acid significantly reduced both spontaneous (P < 0.03 for ≥1 μM 5‐aminosalicylic acid) and thrombin‐induced platelet activation (P < 0.02 for ≥ 1 μM 5‐aminosalicylic acid). Conclusions: 5‐Aminosalicylic acid given either orally or in vitro inhibits platelet activation. If this effect reflects an in vivo action in the gut, it could contribute to the beneficial actions of 5‐aminosalicylic acid in inflammatory bowel disease.

The pathophysiology of inflammatory bowel disease (IBD) is gradually being unravelled and new therapies are being developed to target the disturbed biological processes. This article outlines the clinical features of IBD, its current therapy and pathogenesis. The difficulties for clinical pharmacologists and gastroenterologists associated with designing, executing and interpreting clinical trials in IBD are then discussed. The final section reviews methods that can used to demonstrate the pharmacological actions of new treatments in patients with IBD. It is emphasized that proof of the therapeutic efficacy of a novel agent with a specific mechanism of action yields not only clinical benefit to patients with IBD, but also indicates the importance of the targeted biochemical pathway in the pathogenesis of the disease.