Young-Tso Lin

KMUP-1, a xanthine derivative, induces relaxation of guinea-pig isolated trachea: the role of the epithelium, cyclic nucleotides and K+ channels.

7‐[2‐[4‐(2‐chlorophenyl)piperazinyl]ethyl]‐1,3‐dimethylxanthine (KMUP‐1) produces tracheal relaxation, intracellular accumulation of cyclic nucleotides, inhibition of phosphodiesterases (PDEs) and activation of K+ channels. KMUP‐1 (0.01–100 μM) induced concentration‐dependent relaxation responses in guinea‐pig epithelium‐intact trachea precontracted with carbachol. Relaxation responses were also elicited by the PDE inhibitors theophylline, 3‐isobutyl‐1‐methylxanthine (IBMX), milrinone, rolipram and zaprinast (100 μM), and a KATP channel opener, levcromakalim. Tracheal relaxation induced by KMUP‐1 was attenuated by epithelium removal and by pretreatment with inhibitors of soluble guanylate cyclase (sGC) (1H‐[1,2,4]oxadiazolo[4,3‐a]quinoxalin‐1‐one (ODQ), 1 μM), nitric oxide synthase (Nω‐nitro‐L‐arginine methyl ester, 100 μM), K+ channels (tetraethylammonium, 10 mM), KATP channels (glibenclamide, 1 μM), voltage‐dependent K+ channels (4‐aminopyridine, 100 μM) and Ca2+‐dependent K+ channels (charybdotoxin, 0.1 μM or apamin, 1 μM). Both KMUP‐1 (10 μM) and theophylline nonselectively and slightly inhibited the enzyme activity of PDE3, 4 and 5, suggesting that they are able to inhibit the metabolism of adenosine 3′,5′‐cyclic monophosphate (cyclic AMP) and guanosine 3′,5′‐cyclic monophosphate (cyclic GMP). Likewise, the effects of IBMX were also measured and its IC50 values for PDE3, 4 and 5 were 6.5±1.2, 26.3±3.9 and 31.7±5.3 μM, respectively. KMUP‐1 (0.01–10 μM) augmented intracellular cyclic AMP and cyclic GMP levels in guinea‐pig cultured tracheal smooth muscle cells. These increases in cyclic AMP and cyclic GMP were abolished in the presence of an adenylate cyclase inhibitor SQ 22536 (100 μM) and an sGC inhibitor ODQ (10 μM), respectively. KMUP‐1 (10 μM) increased the expression of protein kinase A (PKARI) and protein kinase G (PKG1α1β) in a time‐dependent manner, but this was only significant for PKG after 9 h. Intratracheal administration of tumour necrosis factor‐α (TNF‐α, 0.01 mg kg−1) induced bronchoconstriction and exhibited a time‐dependent increase in lung resistance (RL) and decrease in dynamic lung compliance (Cdyn). KMUP‐1 (1.0 mg kg−1), injected intravenously for 10 min before the intratracheal TNF‐α, reversed these changes in RL and Cdyn. These data indicate that KMUP‐1 activates sGC, produces relaxation that was partly dependent on an intact epithelium, inhibits PDEs and increases intracellular cyclic AMP and cyclic GMP, which then increases PKA and PKG, leading to the opening of K+ channels and resulting tracheal relaxation.

KMUP‐1 relaxes rabbit corpus cavernosum smooth muscle in vitro and in vivo: involvement of cyclic GMP and K+ channels

In isolated endothelium‐intact or denuded rabbit corpus cavernosum preconstricted with phenylephrine, KMUP‐1 (0.001 – 10 μM) caused a concentration‐dependent relaxation. This relaxation of KMUP‐1 was attenuated by endothelium removed, high K+ and pretreatments with a soluble guanylyl cyclase (sGC) inhibitor ODQ (1 μM), a NOS inhibitor L‐NAME (100 μM), a K+ channel blocker TEA (10 mM), a KATP channel blocker glibenclamide (1 μM), a voltage‐dependent K+ channel blocker 4‐AP (100 μM) and Ca2+‐dependent K+ channel blockers apamin (1 μM) and charybdotoxin (ChTX, 0.1 μM). The relaxant responses of KMUP‐1 (0.01, 0.05, 0.1 μM) together with a PDE inhibitor IBMX (0.5 μM) had additive actions on rabbit corpus cavernosum smooth muscle (CCSM). KMUP‐1 (0.01 – 10 μM) induced increase of intracellular cyclic GMP level in the primary cell culture of rabbit CCSM. This increase in cyclic GMP content was abolished in the presence of ODQ (10 μM). Both KMUP‐1 and sildenafil at 0.2, 0.4, 0.6 mg kg−1 caused increases of intracavernous pressure (ICP) and duration of tumescene (DT) in a dose‐dependent manner. These in vivo activities of ICP for sildenafil and KMUP‐1 are consistent with those of in vitro effects of cyclic GMP. KMUP‐1 has the following merits: (1) inhibition of PDE or cyclic GMP breakdown, (2) stimulation of NO/sGC/cyclic GMP pathway, and (3) subsequent stimulation of K+ channels, in rabbit CCSM. We suggest that these merits play prominent roles in KMUP‐1‐induced CCSM relaxation‐associated increases of ICP and penile erection.

Vanidipinedilol : A vanilloid-based β-adrenoceptor blocker displaying Calcium entry blocking and vasorelaxant activities

Calcium channel and beta-adrenoceptor blockade have proved highly useful in antihypertensive therapy. Studies of the mechanisms of action of vanidipinedilol that combine these effects within a single molecule are described here. Intravenous injection of vanidipinedilol (0.1, 0.25, 0.5, 1.0, and 2.0 mg/kg) produced dose-dependent hypotensive and bradycardic responses, significantly different from nifedipine-induced (0.5 mg/kg, i.v.) hypotensive and reflex tachycardic effects in pentobarbital-anesthetized Wistar rats. A single oral administration of vanidipinedilol at doses of 10, 25, and 50 mg/kg dose-dependently reduced blood pressure with a decrease in heart rate in conscious spontaneously hypertensive rats (SHRs). In the isolated Wistar rat atrium, vanidipinedilol (10(-7), 10(-6), and 10(-5) M) competitively antagonized the (-)isoproterenol-induced positive chronotropic and inotropic effects and inhibited the increase in heart rate induced by Ca2+ (3.0-9.0 mM) in a concentration-dependent manner. The parallel shift to the right of the concentration-response curve of (-)isoproterenol and CaCl2 suggested that vanidipinedilol possessed beta-adrenoceptor-blocking and calcium entry-blocking activities. On tracheal strips of reserpinized guinea pig, cumulative doses of vanidipinedilol (10(-10) to 3x10(-6) M) produced dose-dependent relaxant responses. Preincubating the preparation with ICI 118,551 (10(-10), 10(-9), 10(-8) M), a beta2-adrenoceptor antagonist, shifted the vanidipinedilol concentration-relaxation curve significantly to a region of higher concentrations. These results implied that vanidipinedilol had a partial beta2-agonist activity. In the isolated thoracic aorta of rat, vanidipinedilol had a potent effect inhibiting high-K+-induced contractions. KCI-induced intracellular calcium changes of blood vessel smooth muscle cell (A7r5 cell lines) determined by laser cytometry also was decreased after administration of vanidipinedilol (10(-8), 10(-7), 10(-6) M). Furthermore, the binding characteristics of vanidipinedilol and various antagonists were evaluated in [3H]CGP-12177 binding to ventricle and lung and [3H]nitrendipine binding to cerebral cortex membranes in rats. The order of potency of beta1- and beta2-adrenoceptor antagonist activity against [3H]CGP-12177 binding was (-)propranolol (pKi, 8.59 for beta1 and 8.09 for beta2) > vanidipinedilol (pKi, 7.09 for beta1 and 6.64 for beta2) > atenolol (pKi, 6.58 for beta1 and 5.12 for beta2). The order of potency of calcium channel antagonist activity against [3H]nitrendipine binding was nifedipine (pKi, 9.36) > vanidipinedilol (pKi, 8.07). The ratio of beta1-adrenergic-blocking/calcium entry-blocking selectivity is 0.1 and indicated that vanidipinedilol revealed more in calcium entry-blocking than in beta-adrenergic-blocking activities. It has been suggested that vanidipinedilol-induced smooth muscle relaxation may involve decreased entry of Ca2+ and partial beta2-agonist activities. In conclusion, vanidipinedilol is a nonselective beta-adrenoceptor antagonist with calcium channel blocking and partial beta2-agonist associated vasorelaxant and tracheal relaxant activities. Particularly, the vasodilator effects of vanidipinedilol are attributed to a synergism of its calcium entry blocking and partial beta2-agonist activities in the blood vessel. A sustained bradycardic effect results from beta-adrenoceptor blocking and calcium entry blocking, which blunts the sympathetic activation-associated reflex tachycardia in the heart.

(-)-Epigallocatechin-3-gallate improves bone microarchitecture in ovariectomized rats

ObjectivePreviously, we reported that (−)-epigallocatechin-3-gallate (EGCG), a green tea polyphenol, increased the osteogenic differentiation of murine bone marrow mesenchymal stem cells by increasing the messenger RNA expression of osteogenesis-related genes, alkaline phosphatase activity, and, eventually, mineralization. The present study further investigated the effects of EGCG on bone microstructure change and possible mechanisms in ovariectomy (OVX)–induced osteopenic rats. MethodsRats subjected to OVX were administered EGCG systemically for 12 weeks. Proximal tibial bone mineral densities before and after treatment were compared between groups. Changes in the microarchitecture of both the proximal tibia and the third lumbar spine were compared between EGCG-treated and nontreated groups using micro-CT (&mgr;CT). Bone histology and immunohistochemistry in the proximal tibia were evaluated. ResultsResults showed that EGCG 3.4 mg/kg/day (estimated peak serum concentration, 10 &mgr;mol/L) hampered the decrease in bone mineral density (from 7.97% to 3.96%) and improved the parameters of &mgr;CT measurements, including bone volume (from 18% to 27%), trabecular thickness (from 0.17 to 0.22 mm), trabecular number (from 1.13 to 1.37 mm−1), and trabecular separation (from 0.91 to 0.69 mm), compared with nontreated ovariectomized rats. Similar improvements in bone volume (from 30% to 49%) and trabecular thickness (from 0.14 to 0.26 mm) were also found in the third lumbar spine. Bone volume in the tibial cortex also increased after EGCG treatment (from 9% to 28%). A higher trabecular number and greater trabecular volume were also seen in histology, further confirming the results of &mgr;CT. The immunolocalized bone morphogenetic protein 2 brown-stained area increased from 31% in the OVX group to 53% in the OVX + 10 EGCG group (P < 0.01). Serial biochemistry data revealed no significant systemic toxic effect of EGCG. ConclusionsIntraperitoneal treatment with EGCG 3.4 mg/kg/day for 3 months can mitigate bone loss and improve bone microarchitecture in ovariectomized rats, and increased expression of bone morphogenetic protein 2 may contribute to this effect.

Vasomolol : An ultra short-acting and vasorelaxant vanilloid type β1-adrenoceptor antagonist

The ultra-short-acting and vasorelaxant beta 1-adrenoceptor blocking activities of vasomolol, a guaiacoxypropanolamine derivative of vanillic acid ethyl ester, were studied. Vasomolol (0.5, 1.0, 3.0 mg/kg intravenously, i.v.) produced a dose-dependent bradycardia response and demonstrated particularly a hypotensive action with an ultra-short-acting property in pentobarbital-anesthetized normotensive rats. Vasomolols steady state of beta-blockade was attained < or = 10 min after initial infusion, and a rapid recovery from blockade occurred after discontinuation of the infusion, although intravenous infusion of vasomolol (300 micrograms/kg/min) could not inhibit pressor responses induced by (-)phenylephrine (10 micrograms/kg i.v.). In isolated rat thoracic aorta, vasomolol (1-10 microM) inhibited vascular smooth muscle contractions induced by both (-)phenylephrine (10(-5) M) and high K+ (75 mM) concentration dependently. This inhibitory effect of vasomolol was more sensitive on K(+)-induced than on (-)phenylephrine-induced contractions, suggesting that the block of Ca2+ influx may involve the major mechanism of vasorelaxation. In isolated guinea pig tissues, vasomolol (0.01-10 microM) antagonized the (-)isoproterenol (ISO)-induced positive inotropic and chronotropic effects of the atria and tracheal relaxation responses in a concentration-dependent manner. The parallel shift to the right of the concentration-response curve of (-)ISO suggested that vasomolol was a beta-adrenoceptor competitive antagonist. The effect of vasomolol was more potent on atria than on tracheal tissues, indicating that it possesses beta 1-adrenoceptor selectivity. In addition, vasomolol did not show intrinsic sympathomimetic activity (ISA). Moreover, the binding characteristics of vasomolol were evaluated in [3H]dihydroalprenolol ([3H]DHA) binding to porcine ventricular membranes. Vasomolol was an ultra-short-acting and highly selective beta 1-adrenoceptor antagonist with vasorelaxant activity and is devoid of ISA.

Inhibition of mitogen-mediated proliferation of rat vascular smooth muscle cells by labedipinedilol-A through PKC and ERK 1/2 pathway.

Labedipinedilol-A is a novel 1, 4-dihydropyridine type calcium antagonist with alpha-receptor blocking activity. This study investigates the effects of labedipinedilol-A on mitogen-induced proliferation of rat vascular smooth muscle cells (VSMCs). Labedipinedilol-As inhibition on cell proliferation was measured by the tetrazolium salt (XTT) test. Labedipinedilol-A dose-dependently inhibited mitogen-induced DNA synthesis, determined by the incorporation of 5-bromo-2′-deoxyuridine (BrdU). Labedipinedilol-A was also found capable of inhibiting the migration of VSMCs induced by PDGF-BB with an IC50 value of 5.6 μM. In accordance with these findings, labedipinedilol-A revealed blocking of the FBS-inducible progression through G0/G1 to S phase of the cell cycle in synchronized cells. Labedipinedilol-A appeared to cause inhibition of mitogens-induced PKC translocation, suggesting the probable involvement of protein kinase C (PKC) in this cellular response. Labedipinedilol-A reduced both intracellular Ca2+ and the phosphorylation of extracellular signal-regulated protein kinase 1/2 in PDGF-BB-stimulated VSMCs. It also suppressed the levels of proliferative cell nuclear antigen (PCNA) in VSMCs both time- and dose-dependently. These results indicate that labedipinedilol-A may inhibit cell proliferation by attenuating activation of the ERK 1/2 pathway, which is regulated by PKC and Ca2+, suggesting that it may have great potential in the prevention of progressive atherosclerosis.

Eugenodilol : A third-generation β-adrenoceptor blocker, derived from eugenol, with α-adrenoceptor blocking and β2-Adrenoceptor agonist-associated vasorelaxant activities

: Eugenodilol, derived from natural eugenol, was first investigated with in vivo and in vitro models. In our in vivo study, eugenodilol (0.5, 1.0, and 1.5 mg/kg, i.v.) produced dose-dependent hypotensive and bradycardic responses in pentobarbital-anesthetized Wistar rats. Eugenodilol also inhibited the tachycardia and arterial pressor effects induced by (-)isoproterenol and phenylephrine, respectively. In our in vitro study, eugenodilol competitively antagonized (-)isoproterenol-induced positive inotropic and chronotropic effects and tracheal-relaxation responses on isolated guinea pig tissues in a concentration-dependent manner. The apparent pA2 values were 7.88+/-0.12 for right atria, 7.52+/-0.05 for left atria, and 7.33+/-0.15 for trachea, indicating that eugenodilol was a nonselective beta-adrenoceptor blocker. In thoracic aorta experiments, the apparent pA2 values of alpha-adrenoceptor blockade were 7.05+/-0.25 and 6.87+/-0.08 for eugenodilol and labetalol, respectively. In addition, eugenodilol produced cumulative relaxation responses on isolated guinea pig tracheal strips. The effects were competitively antagonized by ICI 118,551 (10(-8)-10(-6) M), a relatively selective beta2-adrenoceptor antagonist. In the radioligand-binding assay, the Ki values of [3H]CGP-12177 binding to rat ventricle and lung membranes were 9.72 and 48.29 nM, respectively, and the value of [3H]prazosin binding to rat brain membrane was 38.72 nM. These results further confirmed the alpha/beta-adrenoceptors-blocking activities of eugenodilol reported in the functional studies. We conclude that eugenodilol is a novel third-generation beta-adrenoceptor blocker with ancillary blocking activity at alpha-adrenoceptors and weak sympathomimetic activity at beta2-adrenoceptors.

Predictors of Shoulder Subluxation in Stroke Patients

Shoulder subluxation has been recognized as a major and frequent complication in patients with hemiplegia. It may worsen and may be associated with shoulder and extremity pain, nerve damage, and interfere with functional activities. The overall goal of this study was to examine the significant predictors of shoulder subluxation in stroke patients and to suggest a way of early prevention and management of hemiplegic shoulder subluxation. A retrospective study was performed and backward stepwise logistic regression analysis was used to analyze the available collected data. The result showed that significant predictors of hemiplegic shoulder subluxation were Brunnstroms arm motor stage (beta = -2.480, the Wald statistic = 10.03, p = 0.0015) and arm sensory (tactile) status (beta = 1.0283, the Wald statistic = 3.93, p = 0.0474). This study supports that sensory (tactile) impairment may be a precipitating factor for hemiplegic shoulder subluxation and it may highlight the importance of both motor and sensory preventive strategies in early prevention and management of shoulder subluxation. The preventive strategies for shoulder subluxation during the acute/flaccid phase of neural recovery are also discussed in this study.

Pharmacological effects of an aldehyde type α/β-adrenoceptor blocking agent with vasodilating properties

Abstract KMUP 880723 (0.5, 1.0, and 3.0 mg/kg, iv) produced dose-dependent hypotensive and bradycardia responses in pentobarbital-anesthetized Wistar rats. KMUP 880723 (1.0 mg/kg, iv) also markedly inhibited both the tachycardia effects induced by (−)isoproterenol and arterial pressor responses induced by phenylephrine. In the isolated Wistar rat right atria, left atria, and guinea pig tracheal strips, KMUP 880723 competitively antagonized the (−)isoproterenol-induced positive chronotropic effects, inotropic effects, and tracheal relaxation effects in a concentration-dependent manner. The parallel shift to the right of the concentration–response curve of (−)isoproterenol suggested that KMUP 880723 was a β1/β2-adrenoceptor competitive antagonist. The apparent pA2 values were 6.89±0.10 in the right atria, 7.02±0.09 in the left atria, and 6.59±0.11 in the trachea, indicating that KMUP 880723 was a nonselective β-adrenoceptor blocker. In thoracic aorta experiments, KMUP 880723 also produced a competitive antagonism of norepinephrine-induced contraction with a pA2 value of 7.14±0.06. In isolated rat thoracic aorta, KMUP 880723 more potently relaxed the contractions induced by norepinephrine (3×10−6 M) than those by high K+ (75 mM). In the radioligand-binding assay, the pKi values of [3H]CGP-12177 binding to rat ventricle and lung membranes were 6.56 and 6.40, respectively, and the value of [3H]prazosin binding to rat brain membranes was 6.66. These results further confirmed the α/β-adrenoceptor blocking activities of KMUP 880723 reported in the functional studies. We conclude that KMUP 880723 is a nonselective β-adrenoceptor antagonist with α-adrenoceptor blocking-associated vasorelaxant activity.

Promising antimicrobial capability of thin film metallic glasses

Thin film metallic glasses (TFMGs) are demonstrated to exhibit excellent surface flatness, high corrosion resistance and satisfactory hydrophobic properties. Moreover, the antimicrobial and biocompatibility abilities of TFMGs are examined and the results are compared with the behavior of pure Ag and 316L stainless steel. Three TFMGs, Al48Ag37Ti15, Zr54Ti35Si11, and Zr59Ti22Ag19, are prepared by sputtering to assess the antimicrobial performance against Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa, which are the most common nosocomial infection pathogens. Experimental results show that the antimicrobial effect of the Al- or Ag-containing AlAgTi and ZrTiAg TFMGs is similar to that of the pure Ag coating. The ZrTiSi TFMG with no Ag or Al shows poor antimicrobial capability. The physical properties of highly smooth surface and hydrophobic nature alone are not sufficient to result in promising antimicrobial ability. The chemical metal ion release still plays a major role, which should be born in mind in designing biomedical devices.