Abstract
Transforming growth factor-β 1 released from platelet α-granules may preserve endothelial functions in injured vessels. However, direct evidence is lacking regarding how this cytokine modifies the antithrombotic function of injured endothelial cells. We performed an in vitro study to investigate the effects of transforming growth factor-β 1 on platelet functions in the presence of cultured endothelial cells exposed to anoxia-reoxygenation injury. Cultured bovine aorta endothelial cells were placed in an anoxic chamber (0.5% O 2, 5% CO 2) for 60 minutes followed by a 90-minute reoxygenation. Collagen (2 μg/mL)-induced platelet aggregation (10 8 platelets/mL), as determined by impedance aggregometry, was potently inhibited in the presence of control endothelial cells (17.4±3.3 Ω) at a concentration of 5×10 4 cells/mL, as compared to their absence (68.2±2.2 Ω). Inhibition of platelet aggregation was attenuated in endothelial cells exposed to anoxia-reoxygenation (54.6±2.5 Ω). However, preincubation of endothelial cells with transforming growth factor-β 1 (1.0 ng/mL) for 16 hours partially recovered the inhibitory capability of platelet aggregation by injured endothelial cells (40.6±3.8 Ω). Cell viability, confirmed by a trypan blue dye exclusion test, was similar (93–96%), including control, 1.0 ng/mL transforming growth factor-β 1- and/or anoxia-reoxygenation-pretreated cells. The capability of platelet inhibition was restored when the endothelial cells were preincubated for 4 hours or more. Restoration of antiplatelet capacity in endothelial cells by transforming growth factor-β 1 was suggested to be due to several mechanisms, including an increase in nitric oxide synthase activity, up-regulation of prostacyclin release, and restoration of adenosine triphosphate diphosphohydrolase activity, which was attenuated by anoxia-reoxygenation pretreatment. In summary, transforming growth factor-β 1 released from activated platelets may play a compensatory role in the preservation of endothelial functions to inhibit platelet activation.
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