The release of phosphorylated-HSP27 from activated platelets of obstructive sleep apnea syndrome (OSAS) patients

Obstructive sleep apnea syndrome (OSAS) is a well known risk of arterial thrombosis that results in cardiovascular morbidity. It has been reported that platelet aggregability is enhanced in patients with OSAS. In the present study, we investigated whether phosphorylated-HSP27 is released from the activated platelets of OSAS patients. Patients diagnosed with OSAS (n = 21) were recruited, and platelet-rich plasma (PRP) was stimulated by ADP, ristosetin, collagen, and thrombin receptor-activating peptide. Platelet aggregation was measured using an aggregometer with a laser-scattering system. The levels of protein phosphorylation and the released levels of phosphorylated-HSP27 were determined by Western blot analysis and an ELISA, respectively. The phosphorylation of HSP27 in the platelets was induced by the stimulators. The released levels of phosphorylated-HSP27 was correlated with the levels of phosphorylated-HSP27 stimulated by ADP or collagen. The levels of ADP-induced phosphorylated-HSP27 were correlated with those of both phosphorylated-protein kinase B (Akt) and phosphorylatd-p38 mitogen-activated protein kinase; however, the levels of phosphorylated-HSP27 stimulated by collagen were correlated with phosphorylated-Akt levels only. The ED50 value of ADP on the platelet aggregation in OSAS (1.067 ± 0.128 μM) was lower than that in healthy subjects (1.778 ± 0.122 μM) and was inversely correlated with both the value of minimum SpO2 and the released level of phosphorylated-HSP27 stimulated by ADP. The results strongly suggest that phosphorylated-HSP27 is released from the activated platelets of OSAS patients.