Short Communication: A Circadian Rhythm may Exist in Healthy Controls for Soluble P-Selectin and Platelet Count

A reliable plasma marker of platelet activation: does it exist?

Despite the clear importance of the platelet in various conditions and diseases, there are few opportunities to assess the physiological and pathological functions of this cell. Those without access to a flow cytometer or platelet aggregometer rely on secreted or release products of the platelet. Principle among these molecules are alpha granule components beta thromboglobulin and platelet factor four, and membrane constituents such as P selectin, gpV and glycocalicin. However, notwithstanding the ease of measurement of these markers (i.e., by ELISA) each one has its own particular disadvantage, mostly of methodology and specificity. Nevertheless, if our goal is to improve our ability to recognize and treat subjects with thrombotic disorders, then additional studies on these molecules may prove to be a sound investment.

Interleukin-8 (IL-8) may contribute to the activation of neutrophils in patients with peripheral arterial occlusive disease (PAOD)

OBJECTIVES

to investigate the levels of interleukin-8 (IL-8) in patients with peripheral arterial occlusive disease (PAOD) and healthy control subjects both before and after an acute exercise test.

MATERIALS AND METHODS

twenty-six patients with intermittent claudication and 22 matched healthy control subjects each had IL-8 levels measured before and after a standard acute treadmill-exercise test. Subjects walked for 10 min or until stopped by claudication pain. Serum IL-8 levels were measured before exercise was commenced and 1, 5 and 10 min after exercise was stopped.

RESULTS

patients with PAOD had statistically significantly higher levels of IL-8 than healthy control subjects, before and after an acute exercise test (p <0.00001, Mann-Whitney). Ratios of the change of IL-8 levels post-exercise showed a statistically significant difference at the post-5-min time point (p =0.005), showing a difference in the change of IL-8 levels at this time point between the patient group and control group.

CONCLUSIONS

The increased levels and the failure of the cytokine levels to fall by the same extent after exercise in the patient group may be due to a combination of increased neutrophil activation, reduced blood flow and increased cytokine production during ischaemia-reperfusion, which is not observed in the healthy controls.

Decrease in P-selectin levels in patients with hypercholesterolaemia and peripheral arterial occlusive disease after lipid-lowering treatment

At sites of thrombosis and vascular injury, interactions occur among platelets, leucocytes and endothelial cells. Patients with peripheral arterial occlusive disease (PAOD) have been shown to have raised total serum cholesterol and serum triglycerides and increased sP-selectin levels when compared with controls. A total of 31 patients with PAOD and hypercholesterolaemia took part in this three-staged study. Soluble P-selectin (sP-selectin) levels were significantly lowered after 12 weeks of fluvastatin treatment (157.0 ng/ml versus 113.77 ng/ml, p = 0.01), whereas 12 weeks of placebo treatment had no statistically significant effect on sP-selectin levels (150.0 ng/ml versus 139.4 ng/ml). An unpaired t-test almost reached statistical significance (p = 0.051) when the levels by which sP-selectin fell after 12 weeks of active or placebo treatment were compared. The placebo group was then put onto long-term, active treatment and sP-selectin levels were significantly lowered by fluvastatin when compared to pre-treatment levels (150.0 ng/ml versus 110.0 ng/ml, p = 0.03). By lowering the levels of P-selectin, fluvastatin may not only attenuate atherosclerotic progression but may also decrease the platelet activation associated with PAOD.

Soluble cell adhesion molecules--P-selectin and ICAM-1, and disease activity in patients receiving sulphasalazine for active rheumatoid arthritis

The aim of this pilot study was to examine soluble cell adhesion molecules before and after sulphasalazine (SSZ) therapy in active RA. Assessment of RA patients (n = 13) was undertaken before and after 3 months of SSZ. sICAM-1, sVCAM-1, sP- and sE-selectin were measured using an ELISA. The mean (+/-SEM) C-reactive protein (CRP) and sP-selectin levels were significantly reduced from 3.9(0.89) to 2.01(0.53) mg/dl and from 332.8 (48.2) to 116.2 (11.1) respectively, after 3 months of SSZ. The sICAM-1 and sP-selectin levels were significantly higher in RA patients at baseline and a reduction occurred of sICAM-1, sVCAM-1 and sE-selectin levels, however this was not significant. The fall in mean (SEM) sICAM-1, from 345.0 (29.8) to 333.5 (30.2), correlated with the change in CRP (r=0.66; p = 0.018), but the fall in sP-selectin did not. SSZ therapy reduced sP-selectin and sICAM-1 levels in active RA, sICAM-1 correlates with disease activity. SSZ may reduce platelet and/or endothelial activity in RA which may be a useful marker of response, however studies of longer duration and more patients are required.