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.


METHODS
Platelet NO synthase (NOS) activity was evaluated by l-[3H]-arginine to l-[3H]-citrulline conversion, and cGMP was determined by radioimmunoassay. Platelet expression of NOS3, phosphoserine-1177-NOS3 and soluble guanylyl cyclase (sGC) were quantified by Western blotting. Circulating monocyte-platelet aggregates (MPA) were measured by flow cytometry.


RESULTS
Basal NOS activity was similar in both groups. By contrast, whereas both albuterol and collagen stimulated platelet NOS in younger subjects, stimulation was absent in older subjects. Platelet NOS3 expression was similar in both age groups, but NOS3 serine-1177 phosphorylation was greater in younger subjects. Basal, albuterol- and collagen-stimulated cGMP, as well as sGC expression, were all greater in younger than older subjects, and within the younger group both cGMP (basal and stimulated) and sGC expression were greater in women than in men. Circulating MPA were greater in older subjects and, whilst NOS inhibition increased MPA further in both groups, it did so to a lesser extent in the older age bracket.


CONCLUSIONS
These data suggest that platelet NO production and responsiveness decrease with age, and this is reflected in increased circulating MPA.
Goubareva
Iya
I
Department of Clinical Pharmacology, Cardiovascular Division, School of Medicine, King's College London, London, UK.
Gkaliagkousi
Eugenia
E
Shah
Ashish
A
Queen
Lindsay
L
Ritter
James
J
Ferro
Albert
A
D000328:Adult; D000367:Age Factors; D000375:Aging / Q000502:physiology*; D000420:Albuterol / Q000494:pharmacology; D050197:Atherosclerosis / Q000097:blood; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D015153:Blotting, Western; D002118:Calcium / Q000032:analysis; D002448:Cell Adhesion; D003094:Collagen / Q000494:pharmacology; D006152:Cyclic GMP / Q000032:analysis / Q000378:metabolism; D005260:Female; D006162:Guanylate Cyclase / Q000378:metabolism; D006801:Humans; D008297:Male; D008875:Middle Aged; D009000:Monocytes / Q000473:pathology*; D009569:Nitric Oxide / Q000378:metabolism*; D052250:Nitric Oxide Synthase Type III / Q000032:analysis / Q000378:metabolism; D010973:Platelet Adhesiveness; D012307:Risk Factors; D012737:Sex Factors; D015398:Signal Transduction / Q000502:physiology*; D013268:Stimulation, Chemical; D013481:Superoxides / Q000032:analysis / Q000378:metabolism; D013927:Thrombosis / Q000097:blood
D013481:Superoxides; D009569:Nitric Oxide; D003094:Collagen; C496314:NOS3 protein, human; D052250:Nitric Oxide Synthase Type III; D006162:Guanylate Cyclase; D006152:Cyclic GMP; D000420:Albuterol; D002118:Calcium