Interleukin-4 Modulation of Platelet-Derived Growth Factor–Induced Smooth Muscle Cell Urokinase Plasminogen Activator

Platelet-derived growth factor (PDGF) stimulates smooth muscle cell (SMC) migration owing to stimulation of SMC tissue plasminogen activator (t-PA) production. In this study we examined the effects of the T-cell lymphokine interleukin-4 (IL-4) on PDGF induction of human aortic SMC antigen levels of urokinase-type plasminogen activator (u-PA) and those of plasminogen activator inhibitor-1 (PAI-1), the endogenous inhibitor of t-PA and u-PA, measured by enzyme-linked immunosorbent assays (ELISAs). u-PA antigen levels from human aortic SMC incubated with PDGF 100 ng/mL and IL-4 500 U/mL were significantly greater than those incubated with PDGF 100 ng/mL alone. Coincubation of PDGF with IL-4 did not significantly increase SMC u-PA antigen levels in cellular lysates. Coincubation with PDGF 100 ng/mL and IL-4 500 U/mL did not significantly affect SMC PAI-1 antigen levels in conditioned media or cellular lysates. Therefore, interleukin-4 modulates vascular SMC u-PA production induced by PDGF.