Leukotoxin from Aggregatibacter actinomycetemcomitans causes shrinkage and P2X receptor-dependent lysis of human erythrocytes.
Leukotoxin (LtxA) is a virulence factor secreted by the bacterium Aggregatibacter actinomycetemcomitans, which can cause localized aggressive periodontitis and endocarditis. LtxA belongs to the repeat-in-toxin (RTX) family of exotoxins of which other members inflict lysis by formation of membrane pores. Recently, we documented that the haemolytic process induced by another RTX toxin [α-haemolysin (HlyA) from Escherichia coli] requires P2X receptor activation and consists of sequential cell shrinkage and swelling. In contrast, the cellular and molecular mechanisms of LtxA-mediated haemolysis are not fully understood. Here, we investigate the effect of LtxA on erythrocyte volume and whether P2 receptors also play a part in LtxA-mediated haemolysis. We observed that LtxA initially decreases the cell size, followed by a gradual rise in volume until the cell finally lyses. Moreover, LtxA triggers phosphatidylserine (PS) exposure in the erythrocyte membrane and both the shrinkage and the PS-exposure is preceded by increments in the intracellular Ca(2+) concentration ([Ca(2+)](i)). Interestingly, LtxA-mediated haemolysis is significantly potentiated by ATP release and P2X receptor activation in human erythrocytes. Furthermore, the LtxA-induced [Ca(2+)](i) increase and following volume changes partially depend on P2 receptor activation. Theseobservations imply that intervention against local P2-mediated auto- and paracrine signalling may prevent LtxA-mediated cell damage.
Department of Biomedicine, Health, Aarhus University, Denmark.
Peter Svenssen
PS
Munksgaard
Thomas
T
Vorup-Jensen
Jesper
J
Reinholdt
Carl Martin
CM
Söderström
Knud
K
Poulsen
Jens
J
Leipziger
Helle A
HA
Praetorius
Marianne
M
Skals
D002118:Calcium / Q000032:analysis; D048429:Cell Size; D003593:Cytoplasm / Q000737:chemistry; D004912:Erythrocytes / Q000166:cytology / Q000187:drug effects*; D004926:Escherichia coli; D005098:Exotoxins / Q000633:toxicity*; D006461:Hemolysis; D006801:Humans; D008954:Models, Biological; D015661:Pasteurellaceae / Q000472:pathogenicity*; D058469:Receptors, Purinergic P2X / Q000378:metabolism*
D005098:Exotoxins; D058469:Receptors, Purinergic P2X; C018579:leukotoxin; D002118:Calcium