Inhibitory Effect Of The Methanolic Extract Of Verbascum Latisepalum Hub.-Mor. On Endothelium-Dependent Relaxation In Rat Thoracic Aorta

The leaves and flowers of Verbascum species are used to treat respiratory disorders, haemorrhoids, rheumatic pain, and wounds as well as for the treatment of eczema and other types of inflammatory skin conditions in traditional Turkish medicine. We examined the effect of the methanolic extract of the aerial parts of Verbascum latisepalum Hub.-Mor. on the endothelium-dependent relaxation response in rat aortic rings which is mediated by nitric oxide (NO). Six fractions, A F, were obtained from the methanolic extract through bioassay-guided fractionation procedures. The phenylethanoid glycoside verbascoside was isolated from fraction D and its structure elucidated by spectral techniques. The inhibitory effects of the extract, its fractions, and verbascoside on the acetylcholine-induced relaxation response in phenylephrine-precontracted aorta was examined in the absence and presence of L-arginine, a precursor in the synthesis of NO. The observation that the effects of the methanolic extract, of fraction D, and of verbascoside were reversed by L-arginine, indicates that verbascoside has an inhibitory effect on the synthesis of NO. This effect should be taken into consideration in view of the wide range of uses of Verbascum species in Turkish folk medicine.WoSScopu

c-Fos expression in ouabain-treated vascular smooth muscle cells from rat aorta: evidence for an intracellular-sodium-mediated, calcium-independent mechanism

In this study, we examined the effect of Na+–K+ pump inhibition on the expression of early response genes in vascular smooth muscle cells (VSMC) as possible intermediates of the massive RNA synthesis and protection against apoptosis seen in ouabain-treated VSMC in our previous experiments. Incubation of VSMC with ouabain resulted in rapid induction of c-Fos protein expression with an approximately sixfold elevation after 2 h of incubation. c-Jun expression was increased by approximately fourfold after 12 h, whereas expression of activating transcription factor 2, cAMP/Ca2+ response element binding protein (CREB)-1 and c-Myc was not altered. Markedly augmented c-Fos expression was also observed under Na+–K+ pump inhibition in potassium-depleted medium. Na+–K+ pump inhibition triggered c-Fos expression via elevation of the [Na+]i/[K+]i ratio. This conclusion follows from experiments showing the lack of effect of ouabain on c-Fos expression in high-potassium-low-sodium medium and from the comparison of dose responses of Na+–K+ pump activity, [Na+]i and [K+]i content and c-Fos expression to ouabain. A fourfold increment of c-Fos mRNA was revealed 30 min following addition of ouabain to the incubation medium. At this time point, treatment with ouabain resulted in an approximately fourfold elevation of [Na+]i but did not affect [K+]i. Augmented c-Fos expression was also observed under VSMC depolarization in high-potassium medium. Increments in both c-Fos expression and 45Ca uptake in depolarized VSMC were abolished under inhibition of L-type Ca2+ channels with 0.1 μM nicardipine. Ouabain did not affect the free [Ca2+]i or the content of exchangeable [Ca2+]i. Ouabain-induced c-Fos expression was also insensitive to the presence of nicardipine and [Ca2+]o, as well as chelators of [Ca2+]o (EGTA) and [Ca2+]i (BAPTA). The effect of ouabain and serum on c-Fos expression was additive. In contrast to serum, however, ouabain failed to activate the Elk-1, serum response factor, CREB and activator protein-1 transcription factors identified within the c-Fos promoter. These results suggest that Na+–K+ pump inhibition triggers c-Fos expression via [Na+]i-sensitive [Ca2+]i-independent transcription factor(s) distinct from factors interacting with known response elements of this gene promoter