ATP-dependent astrocyte-endothelial calcium signaling following mechanicaldamage to a single astrocyte in astrocyte-endothelial co-cultures

In the brain, endfeet of perivascular astrocytes make close contact with ca pillary endothelial cells that form the blood-brain barrier. The aim of the present work was to investigate whether and how calcium signals can be com municated from astrocytes to endothelial cells following acute mechanical c ell damage. The experiments were performed on astrocyte-endothelial co-cult ures prepared from primary rat brain astrocytes and an endothelial cell lin e (ECV304), A single astrocyte was acutely damaged by mechanical stimulatio n of sufficient strength with a micropipette, and the resulting cytoplasmic calcium changes were monitored using fura-2 and digital calcium imaging. M echanical damage to a single astrocyte triggered a large intercellular calc ium wave that propagated to surrounding astrocytes and also to even remotel y located (several hundred micrometers) endothelial cells. Astrocyte-endoth elial calcium waves induced by mechanical cell damage were largely deflecte d by fast superfusion, were able to cross a cell-free lane, were dose-depen dently inhibited by suramin, a P-2-purinoceptor blocker, and were largely r educed in size in the presence of the ATP-degrading enzyme apyrase, Our res ults indicate that mechanical damage to a single astrocyte can produce far reaching calcium signals that are propagated by the release of a calcium mo bilizing P-2-purinergic agonist and that can be communicated to endothelial cells. As endothelial cytoplasmic calcium is an important factor in the re gulation of blood-brain barrier permeability and transport, mechanical cell damage-induced astrocyte-endothelial calcium signals are hypothesized to p lay a role in the initiation of brain edema and the stimulation of brain gl ucose uptake.