1-Nitropyrene (1-NP) induces apoptosis and apparently a non-apoptotic programmed cell death (paraptosis) in Hepa1c1c7 cells.
Mechanistic studies of nitro-PAHs (polycyclic aromatic hydrocarbons) of interest might help elucidate which chemical characteristics are most important in eliciting toxic effects. 1-Nitropyrene (1-NP) is the predominant nitrated PAH emitted in diesel exhaust. 1-NP-exposed Hepa1c1c7 cells exhibited marked changes in cellular morphology, decreased proliferation and different forms of cell death. A dramatic increase in cytoplasmic vacuolization was observed already after 6 h of exposure and the cells started to round up at 12 h. The rate of cell proliferation was markedly reduced at 24 h and apoptotic as well as propidium iodide (PI)-positive cells appeared. Electron microscopic examination revealed that the vacuolization was partly due to mitochondria swelling. The caspase inhibitor Z-VAD-FMK inhibited only the apoptotic cell death and Nec-1 (an inhibitor of necroptosis) exhibited no inhibitory effects on either cell death or vacuolization. In contrast, cycloheximide markedly reduced both the number of apoptotic and PI-positive cells as well as the cytoplasmic vacuolization, suggesting that 1-NP induced paraptotic cell death. All the MAPKs; ERK1/2, p38 and JNK, appear to be involved in the death process since marked activation was observed upon 1-NP exposure, and their inhibitors partly reduced the induced cell death. The ERK1/2 inhibitor PD 98057 completely blocked the induced vacuolization, whereas the other MAPKs inhibitors only had minor effects on this process. These findings suggest that 1-NP may cause apoptosis and paraptosis. In contrast, the corresponding amine (1-aminopyrene) elicited only minor apoptotic and necrotic cell death, and cells with characteristics typical of paraptosis were absent.
Asare
Nana
N
Division of Environmental Medicine, Norwegian Institute of Public Health, P.O. Box 4404 Nydalen, N-0403 Oslo, Norway.
Landvik
Nina E
NE
Lagadic-Gossmann
Dominique
D
Rissel
Mary
M
Tekpli
Xavier
X
Ask
Kjetil
K
Låg
Marit
M
Holme
Jørn A
JA
D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D020169:Caspases / Q000502:physiology; D016923:Cell Death / Q000187:drug effects*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004396:Coloring Agents; D003470:Culture Media; D003513:Cycloheximide / Q000494:pharmacology; D003593:Cytoplasm / Q000187:drug effects / Q000648:ultrastructure; D005434:Flow Cytometry; D006801:Humans; D007150:Immunohistochemistry; D008854:Microscopy, Electron; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology; D010588:Phagosomes / Q000187:drug effects; D011419:Propidium; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D011721:Pyrenes / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects; D014617:Vacuoles / Q000187:drug effects / Q000648:ultrastructure
D000590:Amino Acid Chloromethyl Ketones; D004396:Coloring Agents; D003470:Culture Media; D011500:Protein Synthesis Inhibitors; D011721:Pyrenes; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D011419:Propidium; D003513:Cycloheximide; D020928:Mitogen-Activated Protein Kinases; D020169:Caspases; C032668:1-nitropyrene