Acid Sphingomyelinase Regulates Platelet Cell Membrane Scrambling, Secretion, and Thrombus Formation

作者：Muenzer Patrick; Borst Oliver; Walker Britta; Schmid Evi; Feijge Marion A H; Cosemans Judith M E M; Chatterjee Madhumita; Schmidt Eva Maria; Schmidt Sebastian; Towhid Syeda T; Leibrock Christina; Elvers Margitta; Schaller Martin; Seizer Peter; Ferlinz Klaus; May Andreas E; Gulbins Erich; Heemskerk Johan W M; Gawaz Meinrad; Lang Florian^*

来源：Arteriosclerosis, Thrombosis, and Vascular Biology, 2014, 34(1): 61-+.

DOI：10.1161/ATVBAHA.112.300210

• acid sphingomyelinase
• amitriptyline
• granule secretion
• phosphatidylserine exposure
• platelets
• thrombus formation
• thrombin generation

Objective-Platelet activation is essential for primary hemostasis and acute thrombotic vascular occlusions. On activation, platelets release their prothrombotic granules and expose phosphatidylserine, thus fostering thrombin generation and thrombus formation. In other cell types, both degranulation and phosphatidylserine exposure are modified by sphingomyelinase-dependent formation of ceramide. The present study thus explored whether acid sphingomyelinase participates in the regulation of platelet secretion, phosphatidylserine exposure, and thrombus formation.
Approach and Results-Collagen-related peptide-induced or thrombin-induced ATP release and P-selectin exposure were significantly blunted in platelets from Asm-deficient mice (Smpd1(-/-)) when compared with platelets from wild-type mice (Smpd1(+/+)). Moreover, phosphatidylserine exposure and thrombin generation were significantly less pronounced in Smpd1(-/-) platelets than in Smpd1(+/+) platelets. In contrast, platelet integrin alpha(IIb)beta(3) activation and aggregation, as well as activation-dependent Ca2+ flux, were not significantly different between Smpd1(-/-) and Smpd1(+/+) platelets. In vitro thrombus formation at shear rates of 1700 s(-1) and in vivo thrombus formation after FeCl3 injury were significantly blunted in Smpd1(-/-) mice while bleeding time was unaffected. Asm-deficient platelets showed significantly reduced activation-dependent ceramide formation, whereas exogenous ceramide rescued diminished platelet secretion and thrombus formation caused by Asm deficiency. Treatment of Smpd1(+/+) platelets with bacterial sphingomyelinase (0.01 U/mL) increased, whereas treatment with functional acid sphingomyelinase-inhibitors, amitriptyline or fluoxetine (5 mu mol/L), blunted activation-dependent platelet degranulation, phosphatidylserine exposure, and thrombus formation. Impaired degranulation and thrombus formation of Smpd1(-/-) platelets were again overcome by exogenous bacterial sphingomyelinase.
Conclusions-Acid sphingomyelinase is a completely novel element in the regulation of platelet plasma membrane properties, secretion, and thrombus formation.

• 出版日期2014-1