[Show abstract][Hide abstract] ABSTRACT: To determine the effects and underlying mechanisms of treatment with the beta-receptor blockers nebivolol and metoprolol on penile endothelial function in apolipoprotein E (ApoE)-/- mice, wild-type (WT) and ApoE-/- mice were fed with a cholesterol-rich diet for 7 weeks. ApoE-/- mice were treated with nebivolol (10 mg/kg/day) or metoprolol (90 mg/kg/day). Endothelial function of aortic and corpora cavernosal tissue was assessed by pharmacological stimulation with carbachol (endothelium dependent) or glycerol trinitrate (endothelium independent) in organ bath experiments. Atherosclerotic lesion formation was evaluated with oil-red staining, and modulation of reactive oxygen species (ROS) production was determined with lipid peroxidation. Heart rate, but not blood pressure, was decreased in nebivolol- and metoprolol-treated ApoE-/- mice (p < 0.01) compared with controls and WT mice without significant intergroup differences. Atherosclerotic lesion formation in the aortic root was increased in ApoE-/- mice (p < 0.01) with a more significant improvement in nebivolol- (p < 0.01) compared with metoprolol-treated mice (p < 0.05). Endothelium-dependent relaxation of the corpora cavernosa was significantly impaired in ApoE-/- mice (p < 0.05), which improved in nebivolol- versus metoprolol-treated mice. Efficacy of endothelium-dependent relaxation was comparable in aortic and penile tissue. Quantification of ROS production via lipid peroxidation revealed a significant reduction of superoxide anion production in nebivolol-treated (p < 0.05) but not metoprolol-treated mice compared with ApoE-/- controls. Nebivolol improves penile endothelial function as a surrogate of erectile function in ApoE-/- mice. These effects may be related to a reduction of ROS production, which is independent of heart rate reduction, because metoprolol did not increase endothelial function.
Preview · Article · Jun 2008 · Journal of Pharmacology and Experimental Therapeutics
[Show abstract][Hide abstract] ABSTRACT: Effects of bacterial lipopolysaccharide (Escherichia coli serotype, 055:B5, 20 mg kg(-1), i.p., for 6 h) and a Rho-kinase inhibitor, (+)-(R)-trans-4-(1-aminoethyl)-N-(4-pyridyl) cyclohexanecarboxamide dihydrochloride monohydrate, Y-27632 (10(-9)-10(-5) M) were investigated on the contractile responses of the rat mesenteric artery to phenylephrine (10(-9)-3 x 10(-5) M), angiotensin-2 (10(-10)-10(-6) M) and endothelin-1 (10(-10)-10(-7) M). Moreover, alteration in the level of Rho-kinase (ROCK-2) expression was examined in the superior mesenteric artery obtained from saline- and lipopolysaccharide-treated rats by Western blotting. Endotoxemic rat mesenteric rings exhibited no different contractions to phenylephrine and angiotensin-2 but augmented contractile activity to endothelin-1. In the mesenteric artery obtained from the endotoxemic rats, acetylcholine-induced vasorelaxation did not differ; pD2 value for acetylcholine was 7.85+/-0.12 in the endotoxemic rings; however, it was 7.81+/-0.15 in the control rings (P>0.05). Y-27632 induced relaxation, which was the same in the control arteries as in endotoxemic ones when contracting agent was phenylephrine. However, when endothelin-1 was used to precontract the rings, Y-27632 produced enhanced relaxation in endotoxemic vessels. pD2 values for Y-27632 were, respectively, 7.69+/-0.12 and 8.20+/-0.10 in control and endotoxemic rings precontracted by endothelin-1 (10(-8) M) (P<0.01). Moreover, Y-27632 (10(-5) M) suppressed the contraction induced by angiotensin-2 (10(-10)-10(-6) M). Western blot analysis revealed that Rho-kinase was upregulated significantly in the mesenteric artery obtained from the rats treated with LPS for 6 h. In addition, serum NO2-/NO3- level, which was detected by Griess method, was 10.0+/-1.4 microM in endotoxemic rats; however, it was 6.6+/-0.5 microM in control (P<0.05). Taken together, these results show that the expression of the contractile protein Rho-kinase could be upregulated in endotoxemic mesenteric artery and this upregulation may be coincided with an enhanced contraction to endothelin-1 but not phenylephrine and angiotensin-2.
Full-text · Article · Sep 2004 · European Journal of Pharmacology
[Show abstract][Hide abstract] ABSTRACT: A role for the small G protein rho and rho-kinase has been shown in smooth muscle contraction regarding Ca++ sensitivity. However, there are no data in the literature assessing how this system operates in human umbilical arteries (HUA). Therefore, we evaluated the effects of HA-1077 and Y-27632, two rho-kinase inhibitors, on agonist-(5-hydroxytryptamine [5-HT]) and depolarization-induced (KCl) contractions of HUA. HA-1077 and Y-27632 inhibited 5-HT-induced contractile responses at 10-4M concentration but not at 10(-5) M. HA-1077 at 10(-4) M also significantly attenuated contractions induced by 20 mM KCl. In addition, HUA precontracted with 5-HT relaxed concentration dependently in response to HA-1077 and Y-27632. When precontracted with KCl, HUA also relaxed dose-dependently in response to HA-1077, but the maximal relaxation was significantly smaller than the response obtained when precontracted with 5-HT. To determine possible involvement of rho-kinase on agonist-induced intracellular calcium-mediated contractions, tissues were precontracted with 5-HT in Ca++-free Krebs solution before cumulative addition of HA-1077 or Y-27632 (10(-7) to 10(-4) M). Both rho-kinase inhibitors relaxed HUA completely. Maximum relaxations of HUA to HA-1077 and Y-27632 were significantly larger than the responses seen in normal Krebs solution and were obtained with lower concentrations of the drugs considered to be more specific for rho-kinase inhibition. However, preincubation of HUA with HA-1077 or Y-27632 (10(-5) M for both) did not affect the 5-HT-induced contractions in this medium. Finally, immunoblot experiments revealed the expression of rho-kinase isoform rockII protein in HUA. These results indicate that rhoA/rho-kinase pathway can contribute to agonist-induced contractions of HUA. However, this effect appears to be limited to intracellular calcium-induced contractions and may be more important in sustaining contractions rather than the initial phase of force development.
No preview · Article · Feb 2004 · Cell biochemistry and biophysics
[Show abstract][Hide abstract] ABSTRACT: Rho-kinase expression was investigated in the rat mesenteric artery and the effects of its inhibitors, (+)-(R)-trans-4-(1-aminoethyl)-N-(4-pyridyl) cyclohexanecarboxamide dihydrochloride monohydrate (Y-27632) and fasudil (HA-1077), were examined on the increase in perfusion pressure induced by two different receptor agonists, namely the alpha-adrenoceptor agonist, phenylephrine and, the endothelin ET(A) and ET(B) receptor agonist, endothelin-1. Y-27632 and fasudil produced a concentration-dependent decrease in perfusion pressure. There was no difference between the concentration-response lines of these two inhibitors. The maximum decrease in the perfusion pressure induced by 10(-5) M Y-27632 was 85.8+/-3.7% when the tone was increased by phenylephrine. However, it was 48.1+/-5.4% (P<0.001) when the perfusion pressure was elevated by endothelin-1. Saponin perfusion (100 mg l(-1), for 10 min), which abolished acetylcholine-induced relaxation, did not significantly modify the Y-27632-elicited relaxation. Western blot analysis revealed that rat mesenteric artery expresses Rho-kinase protein with a molecular weight of approximately 160 kDa. These results show that Rho-kinase enzyme is expressed in rat mesenteric artery and that it contributes to the control of vascular resistance. Moreover, endothelium removal had no marked effect on the vasodilatation induced by Y-27632. In addition, the endothelin-1-induced vasoconstriction was more resistant to the Rho-kinase inhibitors than was that induced by phenylephrine, probably because excitatory endothelin receptors are associated with this signal transduction pathway at a different level from that of alpha-adrenoceptors.
Full-text · Article · Feb 2004 · European Journal of Pharmacology
[Show abstract][Hide abstract] ABSTRACT: Isolated rabbit corpus cavernosum relaxed in response to ultraviolet (UV) light (365 nm). The UV light-induced relaxation (photorelaxation) was diminished on repeated UV irradiation from 30.5+/-4.0% (the first photorelaxation) to 15.5+/-2.7% (the last photorelaxation). Hydroxocobolamine of 100 microM and hemoglobin (Hb) of 10 microM, which are nitric oxide (NO) scavengers, and 10 microM 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), a soluble guanylyl cyclase inhibitor, markedly reduced photorelaxation. However, 300 microM 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (carboxy-PTIO) failed to inhibit photorelaxation. NaNO(2) and N(G)-nitro-L-arginine (L-NA) but not 3-nitro-L-tyrosine (3-NT) were found to be photosensitive in that these compounds are photolysed to release NO, as demonstrated by use of an amperometric NO probe; NO signals produced by 500 microM NaNO(2), and 500 microM L-NA were 133.3+/-28.9 and 54.4+/-10.4 pA, respectively. Not 3-NT but the other compounds (all 200 microM) also enhanced photorelaxation of the cavernosal tissue. Based on these findings, the substance, which mediates photorelaxation, could be NO released from putative stores in the rabbit corpus cavernosum, and L-NA as well as NaNO(2) but not 3-NT produce NO under the influence of UV light.
Full-text · Article · Feb 2003 · European Journal of Pharmacology