Transforming growth factor-β1 inhibits L-arginine-derived relaxing factor(s) from smooth muscle cells

Abstract

The effects of human recombinant interleukin-1β were investigated on the release of nonprostanoid relaxing substances from cultured aortic smooth muscle cells from Wistar rats. Cells cultured on microcarrier beads were packed in columns. The perfusate over these beads was bioassayed by measuring changes in isometric tension of contracted arteries without endothelium. The perfusates from interleukin-1β-treated smooth muscle cells, but not from control cells, evoked relaxations. The relaxations persisted when the transit time between the cultured smooth muscle cells and the detector was increased to 5 min. The effect of relaxing substance(s) was inhibited by cycloheximide, nitro-L-arginine, methylene blue, and transforming growth factor-β1. L- Arginine but not D-arginine overcame the blockade by nitro-L-arginine. Superoxide dismutase potentiated the relaxations. In cells cultured in multiwell plates, interleukin-1β evoked a time- and concentration-dependent accumulation of nitrite in the extracellular medium that was inhibited dose dependently by transforming growth factor-β1. These studies demonstrate that cultured smooth muscle cells can be stimulated to produce nitric oxide- related substances and that the inducible pathway is modulated by transforming growth factor-β1.