P2Y receptor activation of platelets induces Ca mobilization and Rho-GTPase-dependent motility that requires an interaction with P2Y receptors.

BACKGROUND AND PURPOSE

Platelet function during inflammation is dependent on activation by endogenous nucleotides acting on purinergic receptors. The P2Y receptor has been reported to be expressed on platelets and is involved in leukocyte recruitment during inflammation. However, a role for P2Y receptors in platelet function has not yet been determined.

EXPERIMENTAL APPROACH

Platelets obtained from healthy human volunteers were incubated with the P2Y receptor agonist, UDP-Glucose (UDP-G), and PPTN, a selective P2Y receptor antagonist. Platelet activation was quantified using Ca mobilization, aggregation and chemotaxis assays. Cooperativity with P2Y receptor activation was also assessed after stimulation with UDP-G in the presence of MRS2500, a selective P2Y receptor antagonist.

KEY RESULTS

Ca mobilization occurred in platelets after incubation with UDP-G in a concentration-dependent manner, and this was suppressed in platelets treated with PPTN. Platelets did not aggregate, or bind to fibrinogen after incubation with UDP-G. However, platelet chemotaxis towards f-MLP was dependent on P2Y receptor stimulation with UDP-G and this was reduced by Rho-GTPase inhibitors. Furthermore, UDP-G-induced Ca mobilization and chemotaxis were also inhibited when platelets were pretreated with MRS2500. Conversely, ADP-induced Ca mobilization, chemotaxis and aggregation were not affected by the incubation with PPTN.

CONCLUSION AND IMPLICATIONS

Platelets can be activated via P2Y receptor stimulation to induce chemotaxis but not aggregation. Furthermore, this was dependent on concomitant activation of P2Y receptor. Activation of P2Y receptors on platelets may therefore be relevant during inflammation, but cooperation with P2Y receptor activation is required.