Question: 

Lysophosphatidic acid (LPA) induces a significant increase in the intracellular calcium concentration in human erythrocytes. Previous experiments give evidence that it is mediated by calcium channels rather than by a nonspecific calcium leak. However, the molecular identity of the channel is still not resolved. The present study aimed to identify the LPA signal pathway in erythrocytes.

Methods: 

Blood samples were taken from healthy human donors, wild type and the transient receptor potential channel C6 (TRPC6) knock out mice. Calcium imaging was used to investigate the LPA induced calcium influx. Pharmacological experiments were performed to identify the related signal pathway. Single cell analysis was utilized to analyze data.

Results: 

We found calcium influx induced by LPA in erythrocytes is inhomogeneous amongst individual cells, which can not be extracted from traditional erythrocyte research methods, e.g. flux measurements. We determined the IC₅₀ of LPA for calcium increase to be approximately 5mM. Furthermore we probed the relation of LPA induced signaling to TRPC6, which has been shown to be present in human and mice erythrocytes. LPA induced calcium influx was not fully inhibited in knock out TRPC6 (TRPC6^(-/-)) mice, which suggests the coexistence of at least 2 signal pathways. We aimed to identify these signaling pathways by pharmacological means.

Conclusions: 

This study revealed novel insights into LPA induced calcium-signaling, which might be pharmacologically relevant for erythrocyte associated blood clotting.