Abstract 13622: Coupling Factor 6 Enhances Spontaneous Microaggregation of Platelets through Decrease in Cytosolic cAMP Irrespectively of Antithrombotic Therapy
Backgrounds: Spontaneous microaggregation of platelets (SMAP) is a marker for the prognosis of patients with cardiovascular diseases. Coupling factor 6 (CF6) binds to the plasma membrane ATP synthase and functions as a pro-atherogenic molecule in the cardiovascular system. However, the role of CF6 in SMAP remains unknown.
Methods: We investigated the effect of CF6 on SMAP in the platelet-rich plasma obtained from 424 patients with a recent onset of stroke (atherothrombotic stroke, 173; lacunar, 71; cardioembolic, 95; hemorrhagic, 85), and 36 healthy adult volunteers. SMAP was measured by the laser light scattering aggregometer.
Results: The area under curve (AUC) of small-sized aggregates in spontaneous platelet aggregation (mV x count x min) was greater in patients with stroke than in healthy subjects (1.34±0.08×107 vs 0.65±0.16×107, p<0.01). AUC did not differ among the patient groups with the 4 types of stroke. CF6 at 10-7M increased SMAP in patients with stroke and healthy subjects to a similar degree (43.8±7.5 and 78.3±22.5%, respectively) after binding to α- and β-subunits of ATP synthase, which was detected as the decreased immunoreactivity for the α- and β-subunits antibodies at the surface of platelets, and inducing intracellular acidosis, which was measured by BCECF. The increase in SMAP was abolished by pretreatment with antibodies against α- or β-subunit of ATP synthase, and its inhibitor efrapeptin. CF6 at 10-7M increased SMAP in the groups with and without antithrombotic agents. There were no difference among the subgroups of the patients taking aspirin, P2Y12 blocker thienopyridine, and cAMP phosphodiesterase 3 inhibitor cilostazol (71.2±32.6%, 45.7±13.2% and 65.0±36.4%, respectively). The cytosolic cAMP in platelets was decreased by 17.4±5.1% by CF6. Pretreatment with Gs activator cholera toxin blocked it, whereas neither Gi inactivator pertussis toxin nor cilostazol influenced it. CF6-induced acceleration of SMAP was suppressed by cholera toxin, but not by cilostazol and pertussis toxin.
Conclusions: CF6 enhanced SMAP in patients with stroke and healthy subject by decreasing cytosolic cAMP through Gs signaling irrespectively of antithrombotic therapy. CF6 seems to be a novel target for antithrombotic therapy.
- © 2012 by American Heart Association, Inc.