Aspirin-Induced Microscopic Surface Changes Stimulate Thrombopoiesis in Rat Megakaryocytes

Abstract

During the process of thrombopoiesis, invaginations of the plasma membrane occur in megakaryocytes. Since acetylsalicylic acid (aspirin), the most commonly used anti-inflammatory and antiplatelet drug, interacts with the lipid bilayers of the plasma membranes, this drug would affect the process of thrombopoiesis. In the present study, employing a standard patch-clamp whole-cell recording technique, we examined the effects of aspirin on delayed rectifier K(+)-channel (Kv1.3) currents and the membrane capacitance in megakaryocytes. Using confocal imaging of di-8-butyl-amino-naphthyl-ethylene-pyridinium-propyl-sulfonate (di-8-ANEPPS) staining, we also monitored the membrane invaginations in megakaryocytes. Aspirin suppressed both the peak and the pulse-end currents with a significant increase in the membrane capacitance. Massive di-8-ANEPPS staining after treatment with aspirin demonstrated the impaired membrane micro-architecture of megakaryocytes. This study demonstrated for the first time that aspirin induces microscopic surface changes in megakaryocytes. Such surface changes were thought to stimulate thrombopoiesis in megakaryocytes as detected by the increase in the membrane invaginations.

Amphipaths Differentially Modulate Membrane Surface Deformation in Rat Peritoneal Mast Cells During Exocytosis

“…At higher concentrations than 3 mM, salicylate is known to cause necrosis or apoptosis of the cells [31]. In the present study, however, since we delivered the drugs to single, isolated mast cells by a puff application method, there was the possibility of partial and insufficient exposure of the drugs to the cells [17,26,27]. Therefore, in addition to 0.3 mM, we also tried a significantly higher concentration at 3 mM.…”

“…In our recent study, aspirin, a synthetic derivative of salicylate, changed the plasma membrane curvature in rat megakaryocytes [17], which affected the process of thrombopoiesis. In the present study, since salicylate and chlorpromazine were thought to modulate the exocytotic process in mast cells (Fig.…”

“…We conducted standard whole-cell patch-clamp recordings using an EPC-9 patch-clamp amplifier system (HEKA Electronics, Lambrecht, Germany) as described previously [17,23]. The patch pipette resistance was 4-6 MΩ when filled with internal (patch pipette) solution containing (in mM): K-glutamate, 145; MgCl 2 , 2.0; Hepes, 5.0 (pH 7.2 adjusted with KOH).…”

“…Therefore, as a control, we applied the external solution alone to the cells, and compared with those containing either drug. We delivered the solutions by the standing hydrostatic pressure of 3 cm H 2 O from a nearby pipette as described previously [17,26,27]. The mast cells were exposed to the drugs for 20 s in the middle of exocytosis induced by GTP-γ-S.…”

“…Since both salicylate and chlorpromazine are amphiphilic [16], they are preferentially partitioned into the lipid bilayers of the plasma membranes. In our recent study, aspirin, a synthetic derivative of salicylate, changed the plasma membrane curvature in rat megakaryocytes [17], which affected the process of thrombopoiesis. Because megakaryocytes share common membranous features with degranulating mast cells in that they have many blebs on their cell surface [18], salicylate and chlorpromazine would also induce some morphological changes in mast cells and thus may affect their exocytotic process.…”