Morphologic and ultrastructural evidence for interleukin‐6 induced platelet activation

Abstract

The in vitro effect of IL-6 on platelet activation was investigated. When human platelets were incubated with high (1,000 ng/ml) or low (1 ng/ml) dose IL-6, expression of GMP-140 was enhanced by 42% (N = 6; P < 0.009) and 46% (N = 6; P < 0.061) in 1 hr low and high dose IL-6-platelet incubations, respectively, as assessed by flow cytometry. In platelet specimens incubated with high dose IL-6 for 3 hr, a 70% (N = 6; P < 0.009) increase in GMP-140 expression over control was observed. Parallel high dose IL-6 incubations subjected to scanning electron microscopic studies revealed a 3.4-fold increase (N = 6; P < 0.001) in spheroid morphologic platelet forms in 1 hr incubations in comparison to control platelet preparations, whereas in 3 hr IL-6-platelet incubations, a 96% increase in dendritic platelet forms was observed (N = 6; P < 0.001). Significant increases in platelet ATP levels were observed in both 1 min and 1 hr high dose and low dose IL-6 platelet incubations. In 3 hr high dose-IL-6 platelet incubations, a significant 18% (N = 8; P < 0.001) decrease in platelet ATP was parallelled by a significant 40% increase (N = 8; P < 0.014) in plasma ATP in the same specimens. This increased plasma ATP was highly correlated with a reduction in platelet ATP when analyzed by bivariate regression analysis. Lastly, transmission electron microscopic analysis demonstrated a significant reduction in dense granule number and ratio of dense granule surface area/cell surface area in 3 hr high dose IL-6 incubations. These findings suggests that IL-6 activates platelets in vitro.

Cytokine Induction of Platelet Activation

“…Addition of ng/mL concentrations of IL-6 (approximately X1000 the concentration used here) resulted in increased expression of p-Selectin and significant alternations in platelet morphology and intracellular ATP levels. 8 . Although no activational effects from IL-8 have been reported, previous data have shown that platelets express functional IL-8 receptors on their membranes that are upregulated in inflammatory disease states, and that potentially could respond to levels of the exogenous ligand.…”

“…Fresh platelets were incubated with exogenous cytokines at levels that routinely accumulate in platelet products, and activation was assayed by measuring the expression ofp-Selectin (CD 62) on the surface of the platelets. [4][5][6][7][8] Our studies provide evidence that platelets are directly activated by IL-6 and IL-8 at concentrations that accumulate during routine storage of platelet products, thus potentially contributing to the platelet storage lesion.…”

Cytometric analysis of high shear-induced platelet microparticles and effect of cytokines on microparticle generation

“…It was recently shown that some cytokines, such as granulocyte-colony stimulating factor (G-CSF; 11), stem cell factor (SCF; 12), IL-6 (13), and thrombopoietin (TPO; 14 -17), modulate platelet activation. In particlular, Oda et al (15) reported that TPO dose dependently increased initial velocity as well as the maximum extent of SIPA.…”

Morphological Differences between GPIb Antibody-Induced and Shear Stress-Induced Platelet Aggregates

“…Cytokines also affect platelet activation or aggregation. For example, granulocyte-colony stimulating factor (G-CSF) [21], stem cell factor (SCF) [22], IL-6 [23] and thrombopoietin (TPO) [24][25][26][27] modulate platelet activation. In particular, Oda et al [25] reported that TPO dose-dependently increased the initial velocity as well as the maximum extent of SIPA.…”

“…In addition, there are many reports that some cytokines modulate platelet function. For example, in vitro studies by Oleksowicz et al [23,42] utilizing human platelets have shown that IL-6 enhances agonist-induced platelet aggregation, enhances granules and thromboxane B 2 secretion, and stimulates platelet cytoskeletal assembly, and have also indicated based on electron-microscopic findings that IL-6 has a platelet-activating effect as well as enhanced P-selectin expression. In addition, G-CSF is reported to enhance ADP-induced platelet aggregation [21], and SCF enhances secondary aggregation by ADP or epinephrine [22].…”