Cell-specific regulation of plasminogen activator inhibitor 1 and tissue type plasminogen activator release by human kidney mesangial cells.
Human mesangial cells in culture synthesize and secrete plasminogen activator inhibitor 1 (PAI-1) and tissue-type plasminogen activator (t-PA). Phorbol myristate acetate (PMA), a known activator of protein kinase C, induces a three to four-fold increase in t-PA and PAI-1 release over a period of 24 h, whereas cell-associated t-PA and PAI-1 levels remain relatively stable. A similar effect is obtained with oleylacetyl glycerol, a more physiologic protein kinase C activator. The effect of PMA is suppressed in the presence of H7, an inhibitor of cellular protein kinases, and by cycloheximide and actinomycin D, indicating a requirement for de novo protein and RNA synthesis, respectively. Northern blot analysis of PMA-treated cells reveals a rapid and transient increase in PAI-1 mRNA reaching a maximum after 4-8 h, whereas increase in t-PA mRNA levels requires 24 h. Activation of protein kinase A by addition of 8-bromocyclic AMP (8-bromo cAMP) has no significant effect on PAI-1 release but inhibits the PMA-mediated increases in PAI-1 antigen and mRNA. Addition of 8-bromo cAMP alone does not affect t-PA release. When added to PMA-stimulated cells, 8-bromo cAMP inhibits t-PA release in a dose-dependent manner, but causes a superinduction of t-PA mRNA. 8-bromo cAMP also induces a decrease in PMA-stimulated intracellular t-PA release. Similar inhibition is observed after stimulation of endogenous adenylate cyclase with prostaglandin E1 or isoproterenol. This indicates that protein kinase A activation may inhibit PMA-stimulated t-PA release via a post-transcriptional effect, e.g. inhibition of protein synthesis or activation of protein degradation. In conclusion, hormones or mediators which activate protein kinase C can stimulate t-PA and PAI-1 synthesis in human mesangial cells. Protein kinase A activation has no effect on the basal release of PAI-1 and t-PA by human mesangial cells, and, in contrast to endothelial cells, it inhibits both PMA-stimulated PAI-1 and t-PA releases. This cell-specific regulation of t-PA and PAI-1 seems to be mediated by differential transcriptional and post transcriptional mechanisms.
Peraldi
M N
MN
INSERM U 64, Hôpital Tenon, Paris, France.
Rondeau
E
E
Medcalf
R L
RL
Hagège
J
J
Lacave
R
R
Delarue
F
F
Schleuning
W D
WD
Sraer
J D
JD
D015152:Blotting, Northern; D002478:Cells, Cultured; D004789:Enzyme Activation; D004797:Enzyme-Linked Immunosorbent Assay; D005786:Gene Expression Regulation / Q000502:physiology*; D005920:Glomerular Mesangium / Q000378:metabolism*; D006801:Humans; D015849:Plasminogen Inactivators / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D010959:Tissue Plasminogen Activator / Q000235:genetics / Q000378:metabolism*
D015849:Plasminogen Inactivators; D012333:RNA, Messenger; D011494:Protein Kinases; D011493:Protein Kinase C; D010959:Tissue Plasminogen Activator; D013755:Tetradecanoylphorbol Acetate