title: P2X receptor-dependent erythrocyte damage by α-hemolysin from Escherichia coli triggers phagocytosis by THP-1 cells.
abstract: The pore-forming exotoxin α-hemolysin from E. coli causes a significant volume reduction of human erythrocytes that precedes the ultimate swelling and lysis. This shrinkage results from activation of Ca2+-sensitive K+ (KCa3.1) and Cl- channels (TMEM16A) and reduced functions of either of these channels potentiate the HlyA-induced hemolysis. This means that Ca2+-dependent activation of KCa3.1 and TMEM16A protects the cells against early hemolysis. Simultaneous to the HlyA-induced shrinkage, the erythrocytes show increased exposure of phosphatidylserine (PS) in the outer plasma membrane leaflet, which is known to be a keen trigger for phagocytosis. We hypothesize that exposure to HlyA elicits removal of the damaged erythrocytes by phagocytic cells. Cultured THP-1 cells as a model for erythrocytal phagocytosis was verified by a variety of methods, including live cell imaging. We consistently found the HlyA to very potently trigger phagocytosis of erythrocytes by THP-1 cells. The HlyA-induced phagocytosis was prevented by inhibition of KCa3.1, which is known to reduce PS-exposure in human erythrocytes subjected to both ionomycin and HlyA. Moreover, we show that P2X receptor inhibition, which prevents the cell damages caused by HlyA, also reduced that HlyA-induced PS-exposure and phagocytosis. Based on these results, we propose that erythrocytes, damaged by HlyA-insertion, are effectively cleared from the blood stream. This mechanism will potentially reduce the risk of intravascular hemolysis.
authors: Department of Biomedicine, Physiology, Aarhus University, Aarhus C, Denmark. steenfagerberg@gmail.com
authors: Steen K
authors: SK
authors: Fagerberg
authors: Marianne
authors: M
authors: Skals
authors: Jens
authors: J
authors: Leipziger
authors: Helle A
authors: HA
authors: Praetorius
mesh_terms: D001427:Bacterial Toxins / Q000633:toxicity*; D018929:Cell Culture Techniques; D002460:Cell Line; D048430:Cell Shape / Q000187:drug effects; D048429:Cell Size / Q000187:drug effects; D057899:Cytophagocytosis / Q000187:drug effects*; D004912:Erythrocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000633:toxicity*; D005434:Flow Cytometry; D005456:Fluorescent Dyes; D006460:Hemolysin Proteins / Q000633:toxicity*; D006461:Hemolysis / Q000187:drug effects*; D006801:Humans; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels / Q000037:antagonists & inhibitors / Q000378:metabolism; D008264:Macrophages / Q000166:cytology; D026902:Potassium Channel Blockers / Q000494:pharmacology; D058920:Purinergic P2X Receptor Antagonists / Q000494:pharmacology; D058469:Receptors, Purinergic P2X / Q000378:metabolism / Q000502:physiology*
chemical_list: D001427:Bacterial Toxins; D029968:Escherichia coli Proteins; D005456:Fluorescent Dyes; D006460:Hemolysin Proteins; C036507:Hlya protein, E coli; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels; C496923:KCNN4 protein, human; D026902:Potassium Channel Blockers; D058920:Purinergic P2X Receptor Antagonists; D058469:Receptors, Purinergic P2X