Thrombin inhibits apoptosis of monocytes and plasminogen activator inhibitor 2 (PAI-2) is not responsible for this inhibition.
Plasminogen activator inhibitor 2 (PAI-2) has been shown to inhibit apoptosis in transfected cells. We have investigated this phenomenon in activated human monocytes, which are a physiological source of intracellular PAI-2. Apoptosis of monocytes was rapidly induced by removal of serum, addition of hydrogen peroxide, or binding of a monoclonal antibody to Fas. Treatment of monocytes with thrombin or lipopolysaccharide (LPS) inhibited apoptosis of monocytes and also up-regulated intracellular PAI-2. Increased apoptosis was accompanied with increased activity of caspases 3 and 8. Thrombin or LPS treatment of monocytes decreased the activity of both caspases, which correlated with protection from apoptosis. The role for PAI-2 in protection of monocytes from apoptosis was studied. Monocytes were transfected with antisense oligonucleotides that blocked PAI-2 antigen, and antisense for PAI-2 had no effect on apoptosis of monocytes. No interaction was evident between PAI-2 and recombinant caspases 3 and 8 in vitro. PAI-2 was not a substrate for caspases during apoptosis of monocytes, although some cleavage of recombinant PAI-2 by caspase 3 was evident in vitro. This study shows that thrombin or LPS protected monocytes from apoptosis and that PAI-2 did not mediate this inhibitory effect.
Ritchie
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Department of Molecular and Cell Biology, University of Aberdeen, Aberdeen, United Kingdom. Helen.Meldrum@unilver.com
Fragoyannis
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D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D001483:Base Sequence; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D008070:Lipopolysaccharides / Q000494:pharmacology; D009000:Monocytes / Q000166:cytology* / Q000187:drug effects / Q000502:physiology*; D020319:Oligodeoxyribonucleotides, Antisense / Q000235:genetics / Q000494:pharmacology; D017396:Plasminogen Activator Inhibitor 2 / Q000235:genetics / Q000502:physiology*; D011994:Recombinant Proteins / Q000378:metabolism; D013379:Substrate Specificity; D013917:Thrombin / Q000494:pharmacology*; D014162:Transfection
D008070:Lipopolysaccharides; D020319:Oligodeoxyribonucleotides, Antisense; D017396:Plasminogen Activator Inhibitor 2; D011994:Recombinant Proteins; D013917:Thrombin; C505407:CASP3 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases