NAD depletion after in vitro exposure of murine lung slices to bleomycin.
Bleomycin (BLM), a DNA-cleaving, antitumor antibiotic, causes pulmonary fibrosis. It also causes cell injury and activates the nuclear enzyme poly(ADP-ribose) polymerase (PAP; EC 2.4.2.30) in lung slices exposed to the drug in vitro. 3-Aminobenzamide (3-AB), a PAP inhibitor, prevents enzyme activation and cell injury. We have examined the potential role of ATP and NAD depletion in injury of BLM-sensitive C57B1/6N and -resistant BALB/cN murine lung slices treated with BLM or deprived of glucose, the major metabolic substrate of lung. Lung slices either were treated for 45 min with injurious concentrations of BLM (10-500 micrograms/mL) or were incubated without glucose, in the presence or absence of 2.5 mM 3-AB. Only the highest concentration of BLM, 500 micrograms/mL, caused any ATP depletion, and this 35% decrease was transient, occurring at 220 min in C57B1/6N slices. In contrast, glucose deprivation caused 50-70% ATP depletion in slices from both strains. BLM alone at 100 and 500 micrograms/mL caused a sustained 30-70% NAD depletion from 75 min through 400 min in C57B1/6N mouse lung slices. In the resistant BALB/cN lung slices, NAD depletion by BLM was only seen at 400 min. 3-AB almost completely antagonized NAD depletion in slices from both strains. In contrast to BLM, glucose deprivation did not decrease NAD levels unless 3-AB was present in C57B1/6N slices. Thus, ATP depletion may play a role in the injurious effects of glucose deprivation, but does not appear to be a major factor in pneumocyte injury caused by BLM. NAD depletion or other effects of PAP activation appear to account for the strain-selective, injurious effect of BLM on lung tissue.
Hoyt
D G
DG
Department of Pharmacology, University of Pittsburgh, PA 15261.
Lazo
J S
JS
D000255:Adenosine Triphosphate / Q000032:analysis; D000818:Animals; D001549:Benzamides / Q000494:pharmacology; D001761:Bleomycin / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D005947:Glucose / Q000172:deficiency; D066298:In Vitro Techniques; D008168:Lung / Q000187:drug effects* / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D009243:NAD / Q000172:deficiency*; D011065:Poly(ADP-ribose) Polymerases; D013997:Time Factors
D001549:Benzamides; D009243:NAD; D001761:Bleomycin; C025160:3-aminobenzamide; D000255:Adenosine Triphosphate; D011065:Poly(ADP-ribose) Polymerases; D005947:Glucose