Glucocorticoid and cyclic nucleotide regulation of plasminogen activator and plasminogen activator-inhibitor gene expression in primary cultures of rat hepatocytes.
Primary cultures of rat hepatocytes produce tissue-type plasminogen activator (tPA) and plasminogen activator-inhibitor type 1 (PAI-1). Incubation of hepatocytes with 50 microM 8-(4-chlorophenylthio)cAMP (CPT-cAMP) results in a 4-fold increase in tPA activity, whereas the synthetic glucocorticoid dexamethasone (1 microM) causes a more than 90% decrease. In combination, dexamethasone completely overcomes the CPT-cAMP effect and markedly decreases PA activity. PAI-1 is induced by both CPT-cAMP and dexamethasone, and the effects of these agents are additive. Accumulation of tPA mRNA is increased more than 4-fold by CPT-cAMP and is greatly decreased by incubation with dexamethasone. Dexamethasone in combination with CPT-cAMP totally blocks this cAMP effect. The protein synthesis inhibitor cycloheximide does not prevent either the dexamethasone-induced decrease or the CPT-cAMP-induced increase in tPA message and, in fact, augments the cAMP-induced increase in tPA mRNA. Hepatocyte PAI-1 mRNA levels are increased 2-fold by incubation with either CPT-cAMP or dexamethasone; in combination, these effectors cause a 4-fold increase in PAI-1 mRNA. Cycloheximide alone causes a marked increase in PAI-1 mRNA, but does not block the induction by either CPT-cAMP or dexamethasone. We conclude that incubation of hepatocytes with CPT-cAMP induces tPA activity by increasing tPA mRNA accumulation and that dexamethasone causes a decrease in tPA activity by both decreasing tPA mRNA and increasing PAI-1 mRNA and activity. Concomitant protein synthesis is not required for the regulation of tPA or PAI-1 mRNA by either CPT-cAMP or dexamethasone, indicating a primary effect of these agents on gene transcription or mRNA stability.
Heaton
J H
JH
Department of Human Genetics, University of Michigan Medical School, Ann Arbor 48109-0618.
Nebes
V L
VL
O'Dell
L G
LG
Morris
S M
SM
Gelehrter
T D
TD
D000818:Animals; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000031:analogs & derivatives* / Q000494:pharmacology; D003513:Cycloheximide / Q000494:pharmacology; D003907:Dexamethasone / Q000494:pharmacology*; D004347:Drug Interactions; D005786:Gene Expression Regulation / Q000187:drug effects*; D006023:Glycoproteins / Q000235:genetics*; D006801:Humans; D008099:Liver / Q000378:metabolism*; D008297:Male; D015849:Plasminogen Inactivators; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D011919:Rats, Inbred Strains; D013873:Thionucleotides / Q000494:pharmacology*; D010959:Tissue Plasminogen Activator / Q000235:genetics*
D006023:Glycoproteins; D015849:Plasminogen Inactivators; D012333:RNA, Messenger; D013873:Thionucleotides; C015929:8-((4-chlorophenyl)thio)cyclic-3',5'-AMP; D003907:Dexamethasone; D003513:Cycloheximide; D000242:Cyclic AMP; D010959:Tissue Plasminogen Activator