Differential regulation of tumor necrosis factor α and transforming growth factor β production by the plasminogen activator inhibitor 1 in endothelial and cancer cells

The plasminogen activator inhibitor (PAI-1) is the key component of fibrynolytic system, its synthesis is rapidly activated by cytokines and mediators driving inflammatory response, both acute and persistent low-grade. While tumor necrosis factor α (TNF-α) and transforming growth factor β (TGF-β) are established potent direct stimulators of PAI-1 production in numerous tissues, little is known of any feed- back regulation that might be accountable for effects of PAI-1 on their synthesis. Present study provides evidence for the existence of negative feed-back regulation between PAI-1 and its potent activator TGF-β in endothelial cells. Dose-dependent inhibition of TGF-β production was observed in HUVEC cultures with physiological (10 µg/ml) and supraphysiological (100 µg/ml) (p < 0.02) PAI-1 concentrations exerting significant suppressive effect in comparison to control (respectively p < 0.05; p < 0.02) as well as cultures spiked with subphysiological PAI-1 dose of 1 µg/ml (p < 0.0001; p < 0.02). No such regulation was demonstrated for cancer cells of lung and prostate origin which might implicate different regulatory mechanism in neoplastic cells. Similarly, no functional interplay between PAI-1 and TNF-α levels in 24 hrs cultures of any evaluated cell lines was observed.