Flow cytometric analysis of platelet activation throughout normal gestation

Platelet Adhesion and Thrombus Formation in Whole Blood at Arterial Shear Rate at the End of Pregnancy

PROBLEM

Platelet reactivity has not been evaluated in integrated functional testing during normal pregnancy. Here, we analysed platelet functions under arterial shear rate in comparison with static conditions.

METHOD OF STUDY

Thirty pregnant women with uncomplicated pregnancies and 30 healthy non-pregnant women were enrolled in this study. Platelet adhesion to collagen and fibrinogen and subsequent thrombus formation were measured at arterial shear rate in whole blood using a microfluidic and imaging system. Standard light transmission aggregometry, flow cytometry of activation markers in washed platelets and impedance aggregometry in whole blood were also used to assess platelet responsiveness in static conditions.

RESULTS

Compared to non-pregnant controls, thrombus formation on collagen fibres and firm platelet adhesion on fibrinogen under arterial shear rate were significantly reduced in pregnant women. Platelet aggregometry assays in suspension showed a slight increase in platelet reactivity in pregnant women.

CONCLUSION

While platelet aggregometry and platelet activation markers in static conditions show little changes in platelet reactivity, monitoring of platelet adhesion and thrombus growth on collagen or fibrinogen under flow condition in whole blood indicates a significant decrease in pregnant women compared to controls. This decrease might contribute to counteract a hypercoagulable state and to reduce the risk of arterial thrombosis.

Physiologic and pathologic changes of platelets in pregnancy

Platelets are key players in haemostasis and thrombus formation. Defects affecting platelets during pregnancy can lead to heterogeneous complications, such as thrombosis, first trimester miscarriage and postpartum haemorrhage. The incidence of complications is increased in women who have heritable platelet function disorders. Modifications of platelet count or platelet functions during normal pregnancy and preeclampsia will be summarized and the management of pregnant women with heritable platelet function disorders will be discussed.

Flow Cytometric Investigation of CD40-CD40 Ligand System in Preeclampsia and Normal Pregnancy

Our aim was to investigate the CD40-CD40 ligand system in preeclamptic women. We also studied CD62P and platelet—monocyte aggregates, which have been closely linked to the CD40—CD40L system. Platelet expression of CD40L and CD62P and expression of CD40 on monocytes and platelet—monocyte aggregates were determined by flow cytometry in whole blood from 23 preeclamptic women, 23 normotensive pregnant women, and 23 nonpregnant women. The preeclamptic women showed a significant increase in CD40L and CD62P on platelets and in CD40 on monocytes when compared with normotensive pregnant women and nonpregnant women (all P < .001). There was a significant increase in platelet—monocyte aggregates in preeclamptic women (P < .001) and normotensive pregnant women (P = .003) compared with nonpregnant women. Preeclampsia is associated with activation of the CD40—CD40L system. The activation of this system may contribute to the development or maintenance of the proinflammatory and prothrombotic milieu found in preeclampsia.

Caffedymine from cocoa has COX inhibitory activity suppressing the expression of a platelet activation marker, P-selectin

Caffedymine (N-caffeoyldopamine) is a clovamide-type phenylpropenoic acid amide found in plants. Previous studies indicate that caffedymine inhibits P-selectin expression via increasing cAMP through beta-2 adrenoceptors, but the inhibition was only partially repressed by beta-2 adrenoceptor antagonists, suggesting additional mechanisms underlying the inhibitory effect. Therefore, in this study, the effect of caffedymine and its analogues (N-caffeoyltyramine, N-feruloyltyramine, N-coumaroyltyramine, N-cinnamoyltyramine) on COX enzymes (I and II) was investigated, because COX enzymes are deeply involved in regulating P-selectin expression on human platelets. The decreasing order of COX-I inhibitory activity was caffedymine>N-caffeoyltyramine>N-feruloyltyramine>N-coumaroyltyramine>N-cinnamoyltyramine. Caffedymine was the most potent compound tested, able to inhibit COX-I enzyme activity by 43% (P<0.013) at the concentration of 0.01 microM. At the same concentration, caffedymine was also able to inhibit COX-II enzyme activity by 36% (P<0.015), and the decreasing order of COX-II inhibitory activity was similar as that of COX-I. As a result of the COX inhibition, the production of thromboxane B2 (thromboxane A2 derivative) also decreased significantly in mouse blood treated with caffedymine and its analogues (0.05 microM). Caffedymine and N-caffeoyltyramine, both with potent COX inhibitory activity, were also able to inhibit P-selectin expression and platelet-leukocyte interactions. These data indicate that COX inhibition is likely to be another mechanism for caffedymine to inhibit P-selectin expression on platelets.

Helicobacter pylori infection and platelet counts during pregnancy

OBJECTIVE

To investigate whether there is any correlation between Helicobacter pylori infection and platelet counts during pregnancy.

METHODS

One hundred and twenty pregnant women without any complications were evaluated. Platelet counts were determined during pregnancy and postpartum. H. pylori infection was assessed by the detection of serum antibodies at the 3rd day postpartum. Statistically significant differences of platelet count between H. pylori-positive and -negative patients were determined.

RESULTS

H. pylori infection was found in 29 of 120 (24.2%). Platelet counts in the 3rd trimester were 22.7+/-4.7 x 10(3)/microl in H. pylori-positive group and 22.8+/-5.6 x 10(3)/microl in negative group (p=0.98). Platelet count in the 3rd trimester in positive and negative patients were 93+/-17% and 94+/-20%, respectively, of that of the 1st trimester (p=0.92). The incidence of hyperemesis gravidarum in both groups was not significant (p=0.28).

CONCLUSION

A correlation between H. pylori infection and thrombocytopenia during pregnancy was not found in this study.

Different levels of platelet activation in preeclamptic, normotensive pregnant, and nonpregnant women

OBJECTIVE

The aims of our study were to determine the basal platelet activation state in women with preeclampsia compared with normotensive pregnant women and nonpregnant women and to investigate the platelet reactivity on in vitro stimulation with adenosine diphosphate or thrombin receptor activation peptide.

STUDY DESIGN

Platelet expression of CD61 (fibrinogen receptor), CD42a (von Willebrand factor receptor), CD62P (P-selectin), CD63 (Glycoprotein 53), and PAC-1 binding (activated fibrinogen receptor) were determined in 20 pairs of women with preeclampsia/normotensive pregnant women and in 12 nonpregnant women, with the use of flow cytometry.

RESULTS

Basal platelet expression of CD61, CD42a and CD62P, and adenosine diphosphate-stimulated CD62P expression were increased in women with preeclampsia compared with normotensive pregnant women. Platelets from women with preeclampsia and normotensive pregnant women differed from platelets from nonpregnant women by expressing higher basal CD63 levels and being more responsive to in vitro agonist stimulation, which was demonstrated by increased expression of CD61, CD62P, and CD63.

CONCLUSION

This study supports the notion that platelets are important in the pathophysiologic condition of preeclampsia.

Soluble P-selectin levels during normal pregnancy: a longitudinal study

OBJECTIVE

To investigate soluble P-selectin (sP-selectin) levels and platelet parameters in normal pregnant women compared with non-pregnant control subjects.

DESIGN

A longitudinal case-control study.

SETTING

Obstetric outpatient clinic in the Jubilee Maternity Hospital, Belfast.

POPULATION

One hundred and twenty normal pregnant women and 41 non-pregnant age-matched control subjects.

METHODS

The plasma concentration of sP-selectin in pregnant women sampled at 12, 20 and 35 weeks of gestation, and, in a subgroup at three days postpartum, and non-pregnant controls sampled in parallel, was determined using a commercial quantitative sandwich immunoassay kit. Platelet parameters on each blood sample were also recorded using a SYSMEX SE 9500 analyser.

MAIN OUTCOME MEASURES

Plasma sP-selectin as a measure of platelet activation in normal pregnancy.

RESULTS

Soluble P-selectin was significantly higher in pregnant women than in non-pregnant control subjects at 20 and 35 weeks of gestation, (P < 0.01, and P < 0.001, respectively). Correlation analyses showed positive correlation between sP-selectin and platelet count in pregnant women at 20 and 35 weeks of gestation (r = 0.247, P < 0.05 and r = 0.360, P < 0.001, respectively). Soluble P-selectin concentration per platelet was also significantly higher in pregnant women than in non-pregnant control subjects at 20 and 35 weeks of gestation (P < 0.001).

CONCLUSIONS

Our results show that sP-selectin concentration is significantly higher in the second and third trimester of pregnancy when compared with non-pregnant control subjects sampled in parallel. This finding clarifies previous conflicting results on platelet activation in normal pregnancy, and is in agreement with those earlier studies which reported, using other methods, increased platelet activation in normal pregnancy.

Platelet activation in the hypertensive disorders of pregnancy

OBJECTIVE

The purpose of this study was to determine whether platelet activation occurs only in preeclampsia or also in normal pregnancy.

STUDY DESIGN

Thirty women with preeclampsia, 30 women with gestational hypertension, 20 women with essential hypertension, 30 pregnant women with normotension, and 30 nonpregnant women were recruited at St George Hospital, Sydney, Australia. Platelet activation was determined by flow cytometry on whole blood samples.

RESULTS

Platelet activation was similar in all groups, except the group with preeclampsia. Compared with normal pregnant women, women with preeclampsia had significantly greater CD62 expression (1.35% vs 0.61%; P =.002), CD63 expression (1.73% vs 0.95%; P <.0001) and annexin V binding (1.03% vs 0.66%;P =.03) and significantly fewer circulating platelet microparticles (33 vs 49 x10(9)/L; P =.001). This was unrelated to other parameters that included platelet counts. Women with gestational hypertension in whom preeclampsia developed did not have enhanced platelet activation profiles.

CONCLUSION

Platelet activation is increased in preeclampsia but not in other hypertensive disorders or in normal pregnancy. This may be part of the pathophysiologic factors of preeclampsia complications but is not predictable by the platelet count and is not apparent in all women with preeclampsia.

Soluble adhesion molecule profile in normal pregnancy and pre-eclampsia

OBJECTIVE

An exaggerated inflammatory response has been implicated as the cause of endothelial cell dysfunction and the maternal syndrome of pre-eclampsia. Adhesion molecules play a central role in the adherence of leukocytes to endothelial cells and the subsequent migration of white blood cells into perivascular tissue. Cellular forms of adhesion molecules mediate specific steps of leukocyte-endothelial cell interaction, and have been implicated in the pathophysiology of preeclampsia. Soluble forms of these molecules can be detected in plasma, and their concentrations are thought to reflect the degree of activation of a particular cell type. Elevations in soluble P-selectin (sP-selectin) reflect platelet activation; changes in soluble L-selectin (sL-selectin) suggest leukocyte activation; and an increase in soluble forms of E-selectin (sE-selectin), vascular cell adhesion molecule 1 (sVCAM-1), intercellular adhesion molecule 1 (sICAM-1) and platelet endothelial cell adhesion molecule (sPECAM-1) indicate endothelial cell activation/dysfunction. The objective of this study was to determine whether normal pregnancy and pre-eclampsia were associated with changes in the concentrations of soluble selectins and members of the immunoglobulin superfamily of adhesion molecules.

STUDY DESIGN

A cross-sectional study was conducted to determine the plasma concentrations of sL-selectin, sE-selectin, sP-selectin, sVCAM-1, sICAM-1 and sPECAM-1 in peripheral blood obtained from non-pregnant women (n = 20), normal pregnant women (n = 100) and patients with pre-eclampsia (n = 55). Concentrations of soluble adhesion molecules were determined with enzyme-linked immunoassays. Parametric statistics were used for data analysis.

RESULTS

Normal pregnancy was associated with a significant increase in the maternal plasma concentration of sP-selectin, a decrease in sL-selectin, and no change in sE-selectin, sVCAM-1, sICAM-1 and sPECAM-1. In contrast, pre-eclampsia was associated with a significant increase in sP-selectin, sE-selectin and sVCAM-1, a decrease in sL-selectin, but no change in sICAM-1 and sPECAM-1 concentrations.

CONCLUSIONS

The increased concentration of sP-selectin and decreased sL-selectin, as well as the lack of change in endothelial cell-associated soluble adhesion molecules suggest that pregnancy is associated with platelet and leukocyte activation, but not endothelial cell activation. In contrast, pre-eclampsia appears to be characterized by activation of platelets, leukocytes and endothelial cells.