Specific processing of poly(ADP-ribose) polymerase, accompanied by activation of caspase-3 and elevation/reduction of ceramide/hydrogen peroxide levels, during induction of apoptosis in host HL-60 cells infected by the human granulocytic ehrlichiosis (HGE) agent.
We studied the mechanism by which the human granulocytic ehrlichiosis (HGE) agent induces programmed cell death (apoptosis) in human promyelocytic HL-60 leukemia cells. Using several New York HGE isolates, we show that the HGE agent-elicited apoptosis is accompanied by increased processing of nuclear enzyme poly(ADP-ribose) polymerase (PARP), concurrent with a noticeable increase in caspase 3 activities. A marked increase in the amounts of the signaling molecule ceramide but not of diacylglycerol was also observed in HGE agent-infected HL-60 cells, compared with the amounts in uninfected controls. Simultaneous or prior treatment of infected HL-60 cells with the ceramide synthase inhibitor fumonisin B1 did not affect the magnitude of infection by the intracellular pathogen, as determined by both the presence of morulae and the expression of its outer surface membrane protein, p44. These results suggest that the observed changes in ceramide are generated through the sphingomyelinase pathway and not by way of de novo synthesis of ceramide. We also assayed for changes in intracellular hydrogen peroxide and show that the HGE agent causes a decrease in its concentrations in infected cells.
DiPietrantonio
A M
AM
Department of Biochemistry and Molecular Biology, New York Medical College, Valhalla 10595, USA.
Hsieh
T C
TC
Wu
J M
JM
D017209:Apoptosis; D015153:Blotting, Western; D002264:Carboxylic Acids / Q000494:pharmacology; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism*; D002518:Ceramides / Q000378:metabolism*; D004075:Diglycerides / Q000378:metabolism; D016873:Ehrlichiosis / Q000378:metabolism* / Q000382:microbiology*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D037341:Fumonisins; D018922:HL-60 Cells; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism*; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism; D017382:Reactive Oxygen Species; D015398:Signal Transduction; D013997:Time Factors
D002264:Carboxylic Acids; D002518:Ceramides; D004075:Diglycerides; D004791:Enzyme Inhibitors; D037341:Fumonisins; D011506:Proteins; D017382:Reactive Oxygen Species; C056933:fumonisin B1; D006861:Hydrogen Peroxide; C499320:PARP1 protein, human; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases