Abstract
Cajaninstilbene acid (CSA) is a major active component present in the leaves of Cajanus cajan (L.) Millsp. The present study explores the underlying cellular mechanisms for CSA-induced relaxation in rat renal arteries. Vascular reactivity was examined in arterial rings that were suspended in a Multi Myograph System and the expression of signaling proteins was assessed by Western blotting method. CSA (0.1–10 µM) produced relaxations in rings pre-contracted by phenylephrine, serotonin, 9, 11-dideoxy-9α, 11α-epoxymethanoprostaglandin F2α (U46619), and 60 mM KCl. CSA-induced relaxations did not show difference between genders and were unaffected by endothelium denudation, nor by treatment with NG-nitro-L-arginine methyl ester, indomethacin, ICI-182780, tetraethylammonium ion, BaCl2, glibenclamide, 4-aminopyridine or propranolol. CSA reduced contraction induced by CaCl2 (0.01–5 mM) in Ca2+-free 60 mM KCl solution and by 30 nM (−)-Bay K8644 in 15 mM KCl solution. CSA inhibited 60 mM KCl-induced Ca2+ influx in smooth muscle of renal arteries. In addition, CSA inhibited contraction evoked by phorbol 12-myristate 13-acetate (PMA, protein kinase C agonist) in Ca2+-free Krebs solution. Moreover, CSA reduced the U46619- and PMA-induced phosphorylation of myosin light chain (MLC) at Ser19 and myosin phosphatase target subunit 1 (MYPT1) at Thr853 which was associated with vasoconstriction. CSA also lowered the phosphorylation of protein kinase C (PKCδ) at Thr505. In summary, the present results suggest that CSA relaxes renal arteries in vitro via multiple cellular mechanisms involving partial inhibition of calcium entry via nifedipine-sensitive calcium channels, protein kinase C and Rho kinase.
Highlights
Cajaninstilbene acid (CSA, Figure 1), one of the main effective ingredients, is present in the leaves of Cajanus cajan (L.) Millsp [1] which is commonly used to treat ischemic necrosis of femoral head in traditional Chinese medicine
The present study examined the vascular reactivity of cajaninstilbene acid in rat renal arteries and provided novel findings regarding its pharmacological properties
The endothelium regulates vascular tone, while hypertension and atherosclerosis are associated with the impaired endothelial function; the latter is usually caused by disturbed balance in endothelium-derived relaxing and contracting factors [15]
Summary
Cajaninstilbene acid (CSA, Figure 1), one of the main effective ingredients, is present in the leaves of Cajanus cajan (L.) Millsp (pigeon pea) [1] which is commonly used to treat ischemic necrosis of femoral head in traditional Chinese medicine. CSA-containing extracts protect against amyloidb 25–35-induced cognitive deficits in mice through increasing the activity of choline acetyl transferase and anti-oxidation [8]. The stilbene extracts containing CSA reverse the elevation of the concentration of follicle stimulating hormone and luteinizing hormone and improve femoral morphological structure similar to the effect produced by 17b-estradiol supplementation without affecting the serum 17b-estradiol level and uterine weight in ovariectomized rats, suggesting that CSA may exert a phytoestrogenic activity [11]. The extract containing 76% CSA markedly lowers levels of serum and hepatic total cholesterol, triglyceride and LDL cholesterol in diet-induced hypercholesterolemic mice, indicating that CSA could be potentially useful for the attenuation of atherosclerosis [12,13]
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