Inhibition of smoking-induced platelet aggregation by aspirin and pycnogenol.

The effects of a bioflavonoid mixture, Pycnogenol, were assessed on platelet function in humans. Cigarette smoking increased heart rate and blood pressure. These increases were not influenced by oral consumption of Pycnogenol or Aspirin just before smoking. However, increased platelet reactivity yielding aggregation 2 hours after smoking was prevented by 500 mg Aspirin or 100 mg Pycnogenol in 22 German heavy smokers. In a group of 16 American smokers, blood pressure increased after smoking. It was unchanged after intake of 500 mg Aspirin or 125 mg Pycnogenol. In another group of 19 American smokers, increased platelet aggregation was more significantly reduced by 200 than either 150 mg or 100 mg Pycnogenol supplementation. This study showed that a single, high dose, 200 mg Pycnogenol, remained effective for over 6 days against smoking-induced platelet aggregation. Smoking increased platelet aggregation that was prevented after administration of 500 mg Aspirin and 125 mg Pycnogenol. Thus, smoking-induced enhanced platelet aggregation was inhibited by 500 mg Aspirin as well as by a lower range of 100-125 mg Pycnogenol. Aspirin significantly (p<0.001) increased bleeding time from 167 to 236 seconds while Pycnogenol did not. These observations suggest an advantageous risk-benefit ratio for Pycnogenol.

GTP plus water mimic ATP in the active site of protein kinase CK2.

The structures of the catalytic subunit of protein kinase CK2 from Zea mays complexed with Mg2+ and with analogs of ATP or GTP were determined to 2.2 A resolution. Unlike most other protein kinases, CK2 from various sources shows 'dual-cosubstrate specificity', that is, the ability to efficiently use either ATP or GTP as a cosubstrate. The structures of these complexes demonstrate that water molecules are critical to switch the active site of CK2 from an ATP- to a GTP-compatible state. An understanding of the structural basis of dual-cosubstrate specificity may help in the design of drugs that target CK2 or other kinases with this property.