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Leptin induces the generation of procoagulant, tissue factor bearing microparticles by human peripheral blood
Silvia Petrini1, Tommaso Neri1, Stefania Lombardi2
1Laboratorio di Biologia Cellulare Respiratoria, Dipartimento di Patologia Chirurgica, Medica, Molecolare e dell'Area Critica, Università di Pisa and Azienda Ospedaliero-Universitaria Pisana, Pisa, Italy.
Background:
Obesity is linked to increased thrombotic risk. Circulating leptin concentration correlates with body mass index. Microparticles are small (.05-1 μm) vesicles shed by activated and apoptotic cells, involved in numerous pathophysiologically relevant phenomena including blood coagulation and thrombosis. We tested the hypothesis that leptin induces the shedding of procoagulant, tissue factor bearing microparticles by human peripheral blood mononuclear cells, and investigated the intracellular mechanisms leading to microparticle release upon incubation with leptin.
Methods:
Peripheral blood mononuclear cells were isolated from healthy donors. Cells were incubated with leptin in the presence or in the absence of a phospholipase C inhibitor, U73122, a calmodulin inhibitor, W-7, and three inhibitors of mitogen activated protein kinases. Microparticle generation was assessed as phosphatidylserine concentration with a prothrombinase assay and by cytofluorimetric analysis. Tissue factor expression on microparticles was measured with a one-stage clotting assay. Intracellular calcium concentration was assessed by a fluorescent probe.
Results:
Leptin increased intracellular calcium mobilization and stimulated the generation of tissue factor-bearing MP by peripheral blood mononuclear cells, as assessed by phosphatidylserine quantification, clotting tests and flow-cytometry. U73122, PD98059 (an extracellular signal-regulated kinase1/2 inhibitor), and W-7, significantly inhibited leptin-induced MP release. SB203580 (a p38 inhibitor), and SP600125 (a c-Jun N-terminal kinase inhibitor) had no effect.
Conclusion:
Leptin-induced generation of procoagulant microparticles might represent a link between obesity and atherothrombotic risk. Inhibition of leptin-induced microparticle generation might prove a viable strategy for the reduction of such risk in obese individuals.
Insights
Leptin, a hormone linked to obesity, triggers the release of procoagulant microparticles from immune cells. Inhibiting this process may reduce obesity-related thrombotic risk.
Area of Science:
- Biochemistry
- Hematology
- Cell Biology
Background:
- Obesity is associated with increased thrombotic risk.
- Leptin, a hormone correlated with BMI, plays a role in this risk.
- Microparticles (MPs) are vesicles involved in blood coagulation and thrombosis.
Purpose of the Study:
- To investigate if leptin induces the release of procoagulant, tissue factor-bearing MPs from human peripheral blood mononuclear cells (PBMCs).
- To explore the intracellular mechanisms involved in leptin-induced MP release.
Main Methods:
- PBMCs from healthy donors were incubated with leptin.
- Inhibitors of phospholipase C (U73122), calmodulin (W-7), and mitogen-activated protein kinases were used.
- MP generation and tissue factor expression were quantified using assays and flow cytometry.
Main Results:
- Leptin increased intracellular calcium and stimulated the generation of tissue factor-bearing MPs from PBMCs.
- U73122, PD98059 (ERK1/2 inhibitor), and W-7 significantly inhibited leptin-induced MP release.
- p38 and JNK inhibitors did not affect leptin-induced MP release.
Conclusions:
- Leptin-induced generation of procoagulant MPs may link obesity to atherothrombotic risk.
- Inhibiting this MP generation could be a therapeutic strategy for obese individuals.
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