Hyperosmotic stress stimulates tissue plasminogen activator expression by a PKC-independent pathway.
Shear, stretch, and the generation of oxygen radicals stimulate increases in tissue plasminogen activator (t-PA) mRNA levels and antigen production, suggesting that environmental stress may regulate t-PA gene expression. We have examined whether t-PA production is also responsive to a hyperosmotic environment. Endothelial and HeLa cells were treated with hyperosmotic medium, and t-PA mRNA and antigen secretion were measured. Endothelial cells incubated in hyperosmotic medium showed a dose-dependent decrease in cell volume and a 1.9 +/- 0.3- and 3.7 +/- 0.9-fold increase in t-PA secretion at 425 and 485 mosmol/kgH2O, respectively. HeLa cells showed a 3.3 +/- 0.6- and 5.1 +/- 1.2-fold increase at the same osmolalities. Increased secretion began between 8 and 16 h and continued through 24 h. Cultures returned to isosmotic medium after 8 h of treatment continued to release 98.1 +/- 7% of the maximum levels of t-PA for the next 16 h, despite the reversal of other responses to hyperosmotic environment. t-PA mRNA levels also increased between 8 and 16 h to five times control levels but returned to baseline by 24 h. No change in intracellular Ca2+ concentration, inositol 1,4,5-trisphosphate, or diacylglycerol content was detected, suggesting that a different intracellular signal pathway may be involved in the response to hyperosmolar stimulus. Thus environmental stress may be a general stimulatory signal through which t-PA production can be induced.
Levin
E G
EG
Department of Molecular and Experimental Medicine, Scripps Research Institute, La Jolla, California 92037.
Santell
L
L
Saljooque
F
F
D001483:Base Sequence; D002118:Calcium / Q000378:metabolism; D003470:Culture Media; D004075:Diglycerides / Q000378:metabolism; D011464:Epoprostenol / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D007295:Inositol Phosphates / Q000378:metabolism; D007552:Isotonic Solutions; D008353:Mannitol / Q000494:pharmacology; D008969:Molecular Sequence Data; D009994:Osmolar Concentration; D009995:Osmosis; D011493:Protein Kinase C / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D013312:Stress, Physiological / Q000378:metabolism*; D010959:Tissue Plasminogen Activator / Q000235:genetics / Q000378:metabolism*
D003470:Culture Media; D004075:Diglycerides; D007295:Inositol Phosphates; D007552:Isotonic Solutions; D012333:RNA, Messenger; D008353:Mannitol; D011464:Epoprostenol; D011493:Protein Kinase C; D010959:Tissue Plasminogen Activator; D002118:Calcium