• Toxicological Research
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• v.22 no.4
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• pp.397-402
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• 2006

Lipid mediator such as lysophosphatidic acid (LPA) plays an important role in inflammation and wound heating, has been recently reported to induce influx of extracellular calcium into erythrocytes. This elevation in intracellular calcium level may cause destruction of membrane asymmetry and procoagulant microvesicle formation. Thus, we investigated if the lipid mediator could induce microvesicle formation as a result of extracellular calcium influx in human erythrocytes. Treatment with lipid mediator to erythrocytes resulted in microvesicle generation In a concentration-, time-dependent manner. Microvesicles formed expressed procoagulant phosphatidylserine (PS) on their surface membrane significantly as well. LPA did not affect the band 3 phosphorylation which is involved in morphological change in erythrocytes. Pretreatment with suramin did not inhibit LPA-induced microvesicle generation, suggesting microvesicle generation was not receptor-dependent pathway. Depletion of intracellular ATP levels in erythrocytes was suggested to be one of the mechanism for these events.

• Toxicological Research
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• v.25 no.4
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• pp.175-180
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• 2009

Lead (Pb) is a ubiquitously occurring environmental heavy metal which is widely used in industry and human life. Possibly due to a global industrial expansion, recent studies have revealed the prevalent human exposure to Pb and increased risk of Pb toxicity. Once ingested by human, 95% of absorbed Pb is accumulated into erythrocytes and erythrocytes are known to be a prime target for Pb toxicity. Most of the studies were however, focused on $Pb^{2+}$ whereas the effects of $Pb^{4+}$, another major form of Pb on erythrocytes are poorly understood yet. In this study, we investigated and compared the effects of $Pb^{4+}$, $Pb^{2+}$ and other heavy metals on procoagulant activation of erythrocytes, an important factor for the participation of erythrocytes in thrombotic events in an effort to address the cardiovascular toxicity of $Pb^{4+}$. Freshly isolated erythrocytes from human were incubated with $Pb^{4+}$, $Pb^{2+}$, $Cd^{2+}$ and $Ag^+$ and the exposure of phosphatidylserine (PS), key marker for procoagulant activation was measured using flow cytometry. As a result, while $Cd^{2+}$ and $Ag^+$ did not affect PS exposure, $Pb^{4+}$ and $Pb^{2+}$ induced significantly PS exposure in a dose-dependent manner. Of a particular note, $Pb^{4+}$ induced PS exposure with a similar potency with $Pb^{2+}$. PS bearing microvesicle (MV), another important contributor to procoagulant activation was also generated by $Pb^{4+}$. These PS exposure and MV generation by $Pb^{4+}$ were well in line with the shape change of erythrocyte from normal discocytes to MV shedding echinocytes following $Pb^{4+}$ treatment. Meanwhile, nonspecific hemolysis was not observed suggesting the specificity of $Pb^{4+}$-induced PS exposure and MV generation. These results indicated that $Pb^{4+}$ could induce procoagulant activation of erythrocytes through PS exposure and MV generation, suggesting that $Pb^{4+}$ exposure might ultimately lead to increased thrombotic events.