Human neutrophil peptide defensins induce single strand DNA breaks in target cells.
To investigate whether target cell DNA injury participates in cytolysis by human neutrophil defensins (HNP), we analyzed HNP-treated cells for single strand breaks by the alkaline unwinding assay and the activation of ADPribose polymerase, a DNA repair enzyme. Strand breaks and ADP-ribosylation were first detected in K562 and Raji targets 6-8 hr after incubation with HNP and increased to maximal levels by 18 hr. DNA was not degraded into nucleosome-sized fragments. To assess the impact of DNA injury on cytolysis, we increased strand breakage by coincubating targets with HNP and two inhibitors of ADPribose polymerase, 3-aminobenzamide, or nicotinamide. Concurrently with inhibiting polymerase activity and increasing DNA injury, these agents significantly enhanced HNP-mediated cytolysis. Enhancement occurred only at time points (over 6 hr) and in targets (only nucleated targets) where HNP-induced DNA injury could be occurring. These data indicate that neutrophil defensins can induce DNA injury in targets and suggest such injury may be involved in target cell death.
Gera
J F
JF
Department of Medicine, V.A. Wadsworth-UCLA Medical Center 90073.
Lichtenstein
A
A
D001549:Benzamides / Q000494:pharmacology; D001798:Blood Proteins / Q000494:pharmacology*; D016923:Cell Death / Q000187:drug effects; D002857:Chromium / Q000378:metabolism; D004249:DNA Damage; D004277:DNA, Single-Stranded / Q000187:drug effects*; D023082:Defensins; D004790:Enzyme Induction / Q000187:drug effects; D006461:Hemolysis / Q000187:drug effects; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D009504:Neutrophils / Q000378:metabolism*; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D011065:Poly(ADP-ribose) Polymerases / Q000096:biosynthesis
D001549:Benzamides; D001798:Blood Proteins; D004277:DNA, Single-Stranded; D023082:Defensins; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D002857:Chromium; C025160:3-aminobenzamide; D006861:Hydrogen Peroxide; D011065:Poly(ADP-ribose) Polymerases