Identifying pathways involved in leptin-dependent aggregation of human platelets.
OBJECTIVE
To investigate the role of phospholipase C (PLC), phospholipase A(2) (PLA(2)), calcium, and protein kinase C (PKC) in mediating leptin-enhanced aggregation of human platelets.


METHODS
In vitro, ex vivo study.


METHODS
Outpatient's Service for Prevention and Treatment of Obesity at the University Hospital of Messina, Italy.


METHODS
In total, 14 healthy normal-weight male (age 31.4+/-1.9 y; body mass index 22.7+/-0.6 kg/m2) subjects.


METHODS
Adenosine diphosphate-(ADP-) induced platelet aggregation and platelet free calcium were measured after incubation of platelets with leptin alone (5-500 ng/ml), or leptin (50 and 100 ng/ml) in combination with anti-human leptin receptor long form antibody (anti-ObRb-Ab, 1:800-1:100 dilutions), PLC inhibitor U73122 (3.125-25 microM), PLA(2) inhibitor AACOCF3 (1.25-10 microM), or PKC inhibitor Ro31-8220 (1.25-10 microM).


RESULTS
Platelet stimulation with leptin leads to a significant and dose-dependent increase in ADP-induced platelet aggregation and platelet free calcium concentrations. Leptin effects on both platelet aggregation and calcium mobilization were completely abated by the co-incubation with leptin and anti-ObRb-Ab. Leptin-induced platelet aggregation was dose-dependently inhibited by U73122, AACOCF3, or Ro31-8220. The effect of leptin on intracellular calcium was inhibited in a dose-dependent manner by incubation with U73122 and AACOCF3, but not with Ro31-8220.


CONCLUSIONS
Our study confirms that leptin is able to enhance ADP-induced aggregation of human platelets, and raise the possibility that PLC, PKC, PLA(2), and calcium could play a relevant role in mediating the proaggregating action of leptin.
Corsonello
A
A
Italian National Research Centres on Aging (INRCA), I-87100 Cosenza, Italy. andrea_corsonello@tin.it
Malara
A
A
De Domenico
D
D
Perticone
F
F
Valenti
A
A
Buemi
M
M
Ientile
R
R
Corica
F
F
D000244:Adenosine Diphosphate / Q000378:metabolism; D000328:Adult; D000704:Analysis of Variance; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D001095:Arachidonic Acids / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D004963:Estrenes / Q000494:pharmacology; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D020738:Leptin / Q000276:immunology / Q000378:metabolism / Q000494:pharmacology*; D008297:Male; D010741:Phospholipases A / Q000037:antagonists & inhibitors / Q000378:metabolism; D010974:Platelet Aggregation / Q000187:drug effects* / Q000502:physiology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D011760:Pyrrolidinones / Q000494:pharmacology; D015398:Signal Transduction; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism
D000911:Antibodies, Monoclonal; D001095:Arachidonic Acids; D004963:Estrenes; D007211:Indoles; D020738:Leptin; D011760:Pyrrolidinones; C081565:arachidonyltrifluoromethane; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D000244:Adenosine Diphosphate; D011493:Protein Kinase C; D010741:Phospholipases A; D010738:Type C Phospholipases; D002118:Calcium; C064758:Ro 31-8220