Platelet-specific P2Y1receptor deficient mice have suppressed leukocyte recruitment in response to lipopolysaccharide

A role for the P2Y 1 receptor in inflammation has been established using a pharmacological approach over an acute 4 hour time span. However, nucleotide-structure P2Y 1 receptor antagonists have limited experimental use due to inadequate pharmacokinetics, and inability to decipher global versus cell specific effects in vivo . The creation of a conditional knock out (platelet) P2Y 1 transgenic mouse model was designed to overcome these restrictions. A homozygous P2Y 1 LoxP mouse colony was created using CRISPR/Cas9 technology, and crossed with a hemizygous P2Y 1 LoxP with PF4-cre to provide offspring that are homozygous for P2Y 1 LoxP flanked allele, and hemizygous for the PF4cre (platelet P2Y 1 -/- ) and offspring homozygous for P2Y 1 LoxP flanked allele, but non-carriers for PF4cre (control mice). Animals were intranasally administered LPS to induce pulmonary inflammation to assess the influence of phenotype on leukocyte recruitment. 24 hours post intranasal LPS administration; pulmonary neutrophil and platelet recruitment were significantly suppressed, despite the fact that neutrophils retained the ability to migrate to fMLP ex vivo . Circulating platelet and leukocyte numbers were not different between control and platelet P2Y 1 -/- animals. Tail bleeding times revealed the platelet P2Y 1 -/- mice had a severe bleeding phenotype. This is the first demonstration of a platelet specific P2Y 1 -/- mouse model to confirm the importance of platelet P2Y 1 receptors in the regulation of inflammatory responses with a 60-70% inhibition of leukocyte recruitment over an extended time period compared to previous pharmacological studies. platelet P2Y 1 -/- mice will help further elucidate the mechanisms by which P2Y 1 receptors regulate platelet activation during inflammation. Key Points Mice selectively deficient in the platelet P2Y 1 have suppressed leukocyte and platelet recruitment during inflammation. We provide a methodology to determine mechanistic relevance that is otherwise limited by pharmacological approaches.