G Proteins and Phospholipase C Mediate Thrombin-lnduced Generation of Plasminogen Activator Inhibitor-1 from Vascular Smooth Muscle Cells

Abstract

The present study investigated transcellular signalling mechanism involved in thrombin-induced production of plasminogen activator inhibitor-1 (PAI-1) in cultured vascular baboon aortic smooth muscle cells (BASMC). Treatments with thrombin dose-dependently increased the steady state levels of PAI-1 mRNA and the generation of PAI-1 antigen from BASMC. Thrombin receptor-activating peptide mimicked the effect of thrombin on the generation of PAI-1. Sodium fluoride (1 mM) stimulated PAI-1 generation from BASMC. Pertussis toxin dose-dependently suppressed thrombin-induced increase of PAI-1 generation. Treatment with 5 mM neomycin, 10 µM U73122 or 1 µM calphostin C blocked thrombin-induced PAI-1 generation. Phorbol myristate acetate at 10 nM for 3 h strongly stimulated the generation of PAI-1 from BASMC. Forskolin (100 µM)or 8-bromo-cAMP (100 µM)suppressed thrombin-induced PAI-1 generation. The responses of quiescent BASMC to thrombin or the inhibitors on PAI-1 generation were comparable to that of growing cells. The results of the present study suggest that pertussis toxin-sensitive G proteins and a phospholipase C are involved in thrombin-induced generation of PAI-1 in BASMC, which may transmit signals from occupied thrombin receptor to protein kinase C and thereby increase the generation of PAI-1. Elevated levels of intracellular cAMP may negatively regulate the generation of PAI-1 from vascular SMC.

Regulation of plasminogen activator inhibitor‐1 secretion by urokinase and tissue plasminogen activator in rat epithelioid‐type smooth muscle cells

“…However, inhibition of PKA itself had no effect on PAI‐1 level. These effects of PKA and PKC activation on PAI‐1 generation induced by uPA and tPA appeared to be similar to that reported for PAI‐1 upregulation by thrombin (Ren et al , 1997).…”

“…VSMCs secrete PAI‐1 constitutively and various stimuli have been found to stimulate PAI‐1 in these cells (Wojta et al , 1993; Cockell et al , 1995; Bochaton‐Piallat et al , 1998). A signal transduction mechanism has been reported to date using thrombin as the stimulus (Ren et al , 1997). We have shown here that uPA and tPA utilized multiple and similar pathways to modulate PAI‐1 secretion.…”

“…Certain growth factors, hormones and cytokines could stimulate PAI‐1 production in VSMCs (Wojta et al , 1993; Cockell et al , 1995; Bochaton‐Piallat et al , 1998). Investigation into the intracellular signalling pathways leading to PAI‐1 secretion in VSMCs have so far been conducted with thrombin as the stimulating agent (Ren et al , 1997).…”

Transcellular Signaling and Pharmacological Modulation of Thrombin-Induced Production of Plasminogen Activator Inhibitor-1 in Vascular Smooth Muscle Cells

“…Sodium fluoride stimulated the release of PAI-1 antigen from BASMC, and PTX inhibited thrombin-induced PAI-1 re lease from those cells. 22 The results of the present study further demonstrate that PTX inhibited thrombininduced PAI-1 mRNA in BASMC (Fig. 3).…”

Posttranscriptional regulation of PAI-1 gene expression

“…In human, rat, and bovine vascular endothelial cells, incubation with forskolin, cAMP analogues or IBMX results in decreased PAI-1 secreted into the media (33,34), decreased PAI-1 synthesis (35,36) or decreased PAI-1 mRNA levels (37,38). Similar observations have been made in studies with human fibroblasts (39)(40)(41), mink lung epithelial cells (42) rat and baboon smooth muscle cells (43,44), rat and monkey sertoli cells (45,46) rat osteoblasts and osteogenic sarcoma cells (47), astrocytes (48) and peritubular cells (49).…”