Involvement of platelet-activating factor in cell death induced under ischemia/postischemia-like conditions in an immortalized hippocampal cell line.
The involvement of platelet-activating factor (PAF) in cell damage induced by ischemia/postischemia-like conditions was studied in a hippocampus-derived cell line, HN33.11. Cells exposed to N2-saturated glucose-free HEPES-buffered saline (ischemia) for 5 h followed by 18 h of incubation in serum-free control medium (postischemia reincubation) remained 67.4 +/- 2.4% viable in comparison with sham-treated cells. Analysis of DNA fragmentation in combination with Hoechst 33258 staining indicates that apoptosis is the dominant mode of cell death in the present model. PAF level during 10 h of ischemia was unchanged. However, an increase in PAF accumulation was found early during the reincubation period that followed 5 h of ischemia. Peak PAF concentrations were noted at 2 h after initiation of reincubation and rapidly declined to control level after 7 h of reincubation. Consistent with a role of PAF in mediating cell death under ischemia/postischemia reincubation in this model, the PAF antagonist BN 50739 exerted a dose-dependent protective effect. Maximal protection (85.7 +/- 5.4%) of the cells from ischemia/reincubation-induced cell damage was achieved at 0.1 microM BN 50739. The PAF antagonist lacked any protective effect against ischemia-induced cell death. On the other hand, the addition of the stable PAF analogue 1-O-hexadecyl-2-N-methylcarbamyl-sn-glycero-3-phosphocholine (MC-PAF) at the onset of ischemia potentiated ischemia/reincubation-induced apoptosis--an effect that was blocked by BN 50739. Pretreatment of HN33.11 cells with the Ca2+ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N,N-tetraacetic acid acetoxymethyl ester (BAPTA-AM) also provided a protective effect against ischemia/reincubation-induced cell damage. BAPTA-AM increased cell viability by 50%. Pretreatment with BAPTA-AM also decreased ischemia/reincubation-induced PAF accumulation in HN33.11 cells. The results suggest that PAF, acting via a PAF receptor, is at least in part mediating apoptosis under ischemia/postischemia-like conditions in HN33.11 cells.
Shi
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Department of Pharmacology, MCP-Hahnemann School of Medicine, Allegheny University of the Health Sciences, Philadelphia, Pennsylvania 19129, USA.
Wang
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Friedman
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D001381:Azepines / Q000494:pharmacology; D002118:Calcium / Q000502:physiology; D016923:Cell Death / Q000502:physiology; D002461:Cell Line, Transformed; D016291:Dizocilpine Maleate / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D006624:Hippocampus / Q000098:blood supply / Q000737:chemistry / Q000166:cytology*; D007511:Ischemia / Q000503:physiopathology*; D010972:Platelet Activating Factor / Q000032:analysis / Q000502:physiology*; D010980:Platelet Membrane Glycoproteins / Q000037:antagonists & inhibitors; D011726:Pyridinium Compounds / Q000494:pharmacology; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D015427:Reperfusion Injury / Q000503:physiopathology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D014230:Triazoles / Q000494:pharmacology
D001381:Azepines; D018691:Excitatory Amino Acid Antagonists; D010972:Platelet Activating Factor; D010980:Platelet Membrane Glycoproteins; D011726:Pyridinium Compounds; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D014230:Triazoles; C039351:platelet activating factor receptor; C053321:CV 6209; C064509:BN 50739; D016291:Dizocilpine Maleate; D002118:Calcium