Lipopolysaccharide (LPS) induced pulmonary neutrophil recruitment and platelet activation is mediated via the P2Y and P2Y receptors in mice.

Platelet activation occurs during host defence and in various inflammatory disorders. In animal models of infection and inflammation, experimental depletion of platelets leads to significantly reduced leukocyte recruitment and impaired clearance of pathogens from the lung. It is now appreciated that purinergic receptor activation is required for leukocyte activation, motility and adhesion, and platelet interactions with leukocytes can be modulated by purinergic stimulation of platelets. Here, we have investigated the role of platelet P2Y P2Y, P2Y, and P2X receptors on leukocyte recruitment and chemotaxis. Mice were administered either vehicle controls or selective P2Y P2Y, P2Y, or P2X antagonists intravenously before intranasal administration of lipopolysaccharide (LPS) to investigate the effect of these drugs on pulmonary leukocyte recruitment, peripheral platelet counts, bleeding times, and ex vivo platelet aggregation. Separately, platelets were incubated with P2Y P2Y, P2X antagonists, or P2Y agonists to assess effects on platelet-induced neutrophil chemotaxis in vitro. Pulmonary neutrophil recruitment induced by intranasal LPS administration was inhibited in mice administered either with P2Y or P2Y antagonists, but not with P2Y or P2X antagonists. Furthermore, the administration of either a P2Y or a P2Y antagonist reversed the incidence of peripheral thrombocytopaenia associated with LPS exposure. Bleeding times were significantly increased in mice administered P2Y P2Y, or P2X antagonists, whilst ex vivo platelet aggregation to ADP was significantly reduced. These haemostatic responses remained unaltered following antagonism of P2Y. In vitro chemotaxis assays revealed direct antagonism of platelet P2Y but not P2Y or P2X receptors suppressed platelet-dependent neutrophil motility towards Macrophage derived chemokine (MDC, CCL22). Furthermore, the stimulation of platelets with selective P2Y agonists (UDP-glucose, MRS2690) resulted in significant platelet-dependent neutrophil chemotaxis. These results reveal a role for P2Y and P2Y activation of platelets following exposure to LPS, whilst haemostatic indices were unaffected by inhibition of platelet function with the P2Y antagonist in response to LPS.