Knock-on effect of anthrax lethal toxin on macrophages potentiates cytotoxicity to endothelial cells.
Herein we report the knock-on cytotoxic effect of lethal toxin (LeTx) on human umbilical vascular endothelial cells (HUVECs). HUVECs were treated either directly with LeTx or indirectly with LeTx conditioned medium (LeTxCM) prepared from RAW264.7 macrophage cells. Cytotoxicity assays were done on HUVECs and A549 cells using LeTx. HUVECs were more susceptible to LeTx (61-74% survivals) as compared to A549 cells (83-94% survivals, P < 0.005). However, LeTxCM from RAW264.7 further potentiated killing of HUVECs (37% survival) compared to the LeTxCM from A549 cells (up to 70-100% survivals). LeTxCM challenge induced an apoptotic cell death in HUVECs, and this was confirmed by reduction of BCL-2 levels to 54%. Protective antigen (PA) binding to macrophage cell line RAW264.7 > HUVECs >> A549 cells. Thus, we postulate that after the initial prodormal phase of pulmonary entry, LeTx causes not only significant direct damage to macrophages and endothelial cells, but also mediates additional indirect damage to endothelial cells mediated by a knock-on effect of LeTx on macrophages that causes apoptotic cell death in endothelial cells.
Pandey
Jaya
J
Developmental Biology Program, Saban Research Institute, Childrens Hospital of Los Angeles, 4650, Sunset Blvd., Los Angeles, CA 90027, USA.
Warburton
David
D
D000818:Animals; D000942:Antigens, Bacterial / Q000494:pharmacology / Q000633:toxicity*; D017209:Apoptosis; D001408:Bacillus anthracis / Q000378:metabolism / Q000472:pathogenicity*; D001427:Bacterial Toxins / Q000494:pharmacology / Q000633:toxicity*; D002460:Cell Line; D002478:Cells, Cultured; D017077:Culture Media, Conditioned / Q000494:pharmacology; D042783:Endothelial Cells / Q000187:drug effects*; D004730:Endothelium, Vascular; D006801:Humans; D008264:Macrophages / Q000187:drug effects*; D051379:Mice; D014471:Umbilical Veins
D000942:Antigens, Bacterial; D001427:Bacterial Toxins; D017077:Culture Media, Conditioned; C030325:anthrax toxin