Piezo1 gain of function induces a platelet preactivation state.

BACKGROUND

Hereditary xerocytosis (HX) is a dominant red blood cell membrane disorder characterized by dehydration and hemolysis. Most HX cases result from gain-of-function (GOF) mutations in the PIEZO1 gene, which encodes a mechanosensitive ion channel permeable to calcium when activated. Evolution of HX is characterized by frequent thromboembolic events after splenectomy.

OBJECTIVES

Given the major role of calcium during platelet activation, we hypothesized that Piezo1 GOF may increase platelet activation and contribute to thrombosis.

METHODS

Human washed platelets were activated by various agonists in the presence of Yoda1 (a chemical Piezo1 activator). Aggregation was monitored in an aggregometer, secretion by flow cytometry and calpain activation by western blot. Mouse models were the R2482H knock-in, mimicking the human recurrent R2456H GOF mutation of PIEZO1, and the megakaryocyte lineage-specific Piezo1/2 knockout (KO). Ex vivo thrombus formation was performed under flow on a collagen surface. In vivo, tail bleeding time was measured.

RESULTS

Yoda1 alone had no effect on human platelets but potentiated agonist-induced platelet aggregation, secretion, and procoagulant activity, involving calpain activation. In ex vivo, GOF mouse platelets aggregated more than wild type, especially in flow conditions. Conversely, blood from KO mice formed smaller thrombi. In vivo, a shorter total tail bleeding time was found in Piezo1 GOF mice, while KO mice had a longer first bleeding time.

CONCLUSION

These results therefore support a correlation between Piezo1 activated status and platelet activation and are consistent with the involvement of platelet Piezo1 GOF in thrombotic events reported in patients with HX.