Aspirin acetylates nitric oxide synthase type 3 in platelets thereby increasing its activity.

Aims: Acute administration of aspirin increases nitric oxide (NO) synthesis by platelets, an effect not shared by other non-steroidal anti-inflammatory drugs. The aim of the present study was to determine the mechanism by which aspirin acutely increases the activity of NO synthase type 3 (NOS-3), the predominant NOS isoform expressed by platelets, and specifically whether this occurs through an increase in its acetylation.

Methods And Results: Platelets isolated from the blood of healthy human subjects were exposed in vitro to vehicle or aspirin at different concentrations (5 micromol/L-4 mmol/L).

Age decreases nitric oxide synthesis and responsiveness in human platelets and increases formation of monocyte-platelet aggregates.

Objective: Ageing is associated with an increase in atherothrombotic disease. Platelet-derived nitric oxide (NO) inhibits platelet activation, but the effect of age on platelet NO signaling is unknown. We investigated platelet NO biosynthesis and responsiveness in older (> 45 years old) as compared with younger (< 30 years old) healthy human subjects.

beta-Actin regulates platelet nitric oxide synthase 3 activity through interaction with heat shock protein 90.

Cytoskeletal proteins are crucial in maintaining cellular structure and, in certain cell types, also play an essential role in motility and shape change. Nitric oxide (NO) is an important paracrine mediator of vascular and platelet function and is produced in the vasculature by the enzyme NO synthase type 3 (NOS-3). Here, we demonstrate in human platelets that the polymerization state of beta-actin crucially regulates the activation state of NOS-3, and hence NO formation, through altering its binding of heat shock protein 90 (Hsp90).

Mechanisms underlying beta2-adrenoceptor-mediated nitric oxide generation by human umbilical vein endothelial cells.

Endothelial beta(2)-adrenoceptor (beta(2)AR) stimulation increases nitric oxide (NO) generation, but the underlying cellular mechanisms are unclear. We examined the role of l-arginine transport and of phosphorylation of NO synthase 3 (NOS-3) in beta(2)AR-mediated NO biosynthesis by human umbilical vein endothelial cells (HUVEC). To this end, we assessed l-arginine uptake, NOS activity (from l-arginine to l-citrulline conversion), membrane potential (using [(3)H]tetraphenylphosphonium), as well as serine phosphorylation of NOS-3 (by Western blotting and mass spectrometry), in HUVEC treated with betaAR agonists or cyclic AMP-elevating agents.

Nitric oxide-dependent beta2-adrenergic dilatation of rat aorta is mediated through activation of both protein kinase A and Akt.

Vasorelaxation to beta(2)-adrenoceptor stimulation occurs through both endothelium-dependent and endothelium-independent mechanisms, and the former is mediated through Ca(2+)-independent activation of endothelial-type nitric oxide synthase (NOS-3). Since Ca(2+)-independent NOS-3 activation may occur through its serine phosphorylation via protein kinase A (PKA) or Akt, we determined the PKA and Akt dependency of beta(2)-adrenergic relaxation of rat aorta. Rat aortic rings were pre-incubated with the PKA inhibitor H-89 (10(-7) m), the phosphatidylinositol 3-kinase (PI3K) inhibitor wortmannin (5 x 10(-7) m), Akt inhibitor (10(-5) m), or vehicle, in the absence or presence of the NOS inhibitor N(G)-nitro-l-arginine methyl ester (l-NAME, 10(-4) m).

Aspirin modifies nitric oxide synthase activity in platelets: effects of acute versus chronic aspirin treatment.

Objective: We examined the effects of aspirin on basal and beta-adrenoceptor (beta-AR)-mediated nitric oxide synthase (NOS) activity in normal platelets.

Methods: NOS activity was determined from the conversion of L-[3H]arginine to L-[3H]citrulline, both basally and following beta-AR stimulation, in platelets from healthy human subjects following both short- and long-term aspirin administration.

Results: Basal L-[3H]citrulline increased following aspirin 800 mg administered intravenously in vivo, from 0.

Amlodipine, but not verapamil or nifedipine, dilates rabbit femoral artery largely through a nitric oxide- and kinin-dependent mechanism.

1. We investigated the nitric oxide (NO) dependence of vasorelaxation in response to different calcium channel blockers (CCB), in rabbit femoral artery in vivo. 2.