Desensitization of erythrocyte P2 receptors reduces lysis induced by α‐hemolysin

α‐hemolysin (HlyA) from E. coli requires ATP release and purinergic signaling to produce hemolysis.(1) Both the P2X 1 and the P2X 7 receptor are involved in this process. Here we expand the investigation of the role of purinergic signaling in HlyA‐induced hemolysis in human erythrocytes. By [Ca 2+ ] I imaging we show that ATP (1 mM) induced a biphasic [Ca 2+ ] I response with an initial transient followed by a sustained increase in fluo 4 fluorescence. This is consistent with P2X‐receptor‐mediated Ca 2+ influx. Desensitization of P2 receptors with ATP reduced the HlyA‐dependent hemolysis, which was totally abolished at 1 mM of ATP. Ecto‐ATPase‐inhibition (ARL 67156 ) is known to enhance the amount of extracellular ATP, which likely results in P2‐receptor desensitization. ARL 67156 concentration‐dependently reduces HlyA‐induced hemolysis. The opposite was observed by scavenging extracellular ATP by low concentrations of apyrase and hexokinase/glucose. This resulted in small augmentation of HlyA‐induced hemolysis. Taken together, these data underscore that erythrocytes have P2 receptors. These receptors are functionally necessary for pore‐forming toxins such as HlyA to produce hemolysis. Funded by The Danish Council for Independent Research, Medical Sciences.