Inhibition by triptoquinone-A of LPS- and IL-1 beta-primed induction of NO synthase in rat thoracic aorta

We investigated the effect of triptoquinone-A (TQA), an active principal of Triptergium wilfordii, on the induction of nitric oxide synthase (NOS) promoted by endotoxin (LPS) and interleukin-1 beta (IL-1 beta). Prophylactic application of TQA selectively prevented LPS-primed initiation of L-arginine (Arg)-induced relaxation, and cGMP formation of rat thoracic aorta, and LPS-stimulated nitrite production by cultured aortic smooth muscle cells, which appear to be mediated by NOS expressed by LPS in vascular smooth muscle. TQA also prevented IL-1 beta-triggered initiation of Arg-induced relaxation and nitrite accumulation. These results suggest that TQA prevents LPS- or IL-1 beta-promoted induction of NOS in vascular smooth muscle, thus inhibiting development of Arg-induced vasorelaxation.