Inhibition of cultured bovine aortic smooth muscle cell proliferation by colominic acid

Colominic acid (CA) is an alpha2,8-linked polymer of sialic acid, originally isolated from capsular Escherichia coli K1. Since inhibition of arterial smooth muscle cell hyperplasia is one of the effective strategies to prevent atherosclerosis, we investigated the effect of CA, purified as an alpha2,8-linked homopolymer of N-acetylneuraminic acid, on the proliferation of bovine aortic smooth muscle cells in culture. The results demonstrate that CA inhibits the proliferation of the cells without nonspecific cell damage. Sulfation did not modify the inhibitory effect of CA. Specifically, the inhibitory effect of sulfated CA was almost equal to that of CA in vascular smooth muscle cell proliferation. On the other hand, it was suggested that the inhibition of the proliferation by CA is in a degree similar to that by heparin but weaker than that by sodium/calcium-spirulans, known sulfated polysaccharides as the potent inhibitor of vascular smooth muscle cells. The present data suggest that CA with or without sulfate groups can be an origin of beneficial agents that prevents atherosclerosis through a moderate inhibition of arterial smooth muscle cell proliferation.     

Inhibition of pig aortic smooth muscle cell DNA synthesis by selective type III and type IV cyclic AMP phosphodiesterase inhibitors.

Foetal calf serum (FCS) and platelet-derived growth factor (PDGF)-stimulated incorporation of [3H]thymidine into pig aortic smooth muscle cell (ASMC) DNA was decreased by agents that either stimulated the synthesis (forskolin) or inhibited the breakdown (3-isobutyl-1-methylxanthine, IBMX) of cAMP. FCS-stimulated incorporation of [3H]thymidine into DNA was also reduced by selective inhibitors of cAMP-specific phosphodiesterase (PDE IV) (Ro-20-1724, rolipram) and cGMP-inhibited cAMP PDE (PDE III) (SK&F 94836). IBMX, Ro-20-1724, rolipram and SK&F 94836 enhanced forskolin inhibition of DNA synthesis. Alone, rolipram was a relatively weak inhibitor of FCS-induced ASMC DNA synthesis (IC25 greater than 20 microM); however, in the presence of a threshold concentration of SK&F 94836 (20 microM), the potency of rolipram increased (IC25 = 4 microM), suggesting synergy in the actions of PDE III and PDE IV inhibitors. SK&F 94836 and rolipram elicited 30% and 37%, respectively, reductions in FCS-induced ASMC proliferation and potentiated the inhibitory actions of forskolin. PDE III and PDE IV inhibitors alone, exerted minimal effects on ASMC cAMP levels after a short term (10 min) or long-term (2 or 24 hr) exposure, but enhanced forskolin-induced accumulation of cAMP. ASMC spontaneously released cAMP into the extracellular medium, a process that was increased by forskolin. PDE III and PDE IV inhibitors had no effect alone on cAMP extrusion but enhanced the effect of forskolin. Exposure of ASMC to forskolin or SK&F 94836 for 15 min increased the activity ratio (AR) of cAMP-dependent protein kinase from 0.05 to 0.17 and 0.23, respectively. Ro-20-1724, alone, did not affect cAMP-dependent protein kinase but enhanced the stimulatory effect of forskolin (AR = 0.37) and SK&F 94836 (AR = 0.27). Agents that increased cGMP synthesis (glycerol trinitrate, atrial natriuretic factor) or decreased its hydrolysis by selectively inhibiting cGMP-specific PDE (PDE V) (zaprinast) exerted no effects on FCS- or PDGF-stimulated [3H]thymidine incorporation into DNA either alone or in combination. The cytosolic fraction of pig ASMC contained four cyclic nucleotide PDEs which were categorized as PDE V, Ca2+/calmodulin-stimulated PDE (PDE I), PDE III and PDE IV. PDE I and III activities were also associated with the particulate fraction. The results demonstrate that inhibitors of PDEs III and IV alone or in combination with forskolin, reduce ASMC DNA synthesis and proliferation, through an action likely to involve elevation of intracellular cAMP. In contrast, inhibition of cGMP hydrolysing PDE subtypes (I and V) exerted no effect on DNA synthesis in this cell type.     

前胡丙素对牛主动脉平滑肌细胞增殖的抑制作用

目的:探讨前胡丙素(pra-C)对牛主动脉平滑肌细胞(SMC)增殖的影响 方法:细胞DNA的合成量由~3H-胸腺嘧啶核苷[~3H]TdR)掺入试验测定,应用流式细胞术测定细胞周期,用乳酸脱氢酶活性测定观察药物的毒性.结果:无论有无血管紧张素Ⅱ(AngⅡ),在0.01μmol/L到10μmol/L浓度范围内,pra-C均可呈浓度依赖性地抑制SMC的增殖,抑制作用主要与阻止细胞进入有丝分裂期有关,而与细胞毒性无关.结论:pra-C能够完全阻断Aug Ⅱ诱导SMC的增殖效应,部分阻止小牛血清诱导的细胞分裂,这对于血管增生性疾病的防治有重要意义.     

Pelargonidin attenuates PDGF-BB-induced aortic smooth muscle cell proliferation and migration by direct inhibition of focal adhesion kinase

Pelargonidin is a natural red pigment found in fruits and vegetables, and has been reported to exhibit various effects potentially beneficial for human health. However, the possible preventive effects of pelargonidin toward atherosclerosis and mechanisms involved have not been investigated to date. Here, we compared the effects of pelargonidin and its glucoside-conjugated form, pelargonidin-3-glucoside (P3G), on proliferation and migration induced by platelet-derived growth factor (PDGF)-BB in human aortic smooth muscle cells (HASMCs). Pelargonidin, but not P3G, exhibited strong inhibitory effects against PDGF-BB-induced HASMC proliferation and migration, while suppressing PDGF-BB-induced ex vivo rat aortic ring sprouting. Immunoblot analysis revealed that pelargonidin inhibited PDGF-BB-induced phosphorylation of focal adhesion kinase (FAK) as well as F-actin reduction, whereas Src, mitogen-activated protein kinases (MAPKs) and Akt phosphorylation status were not altered. We also observed that the anti-proliferative and migratory effects of both pelargonidin and P3G corresponded with the extent of FAK inhibition. Both in vitro and ex vivo pull-down assays revealed that pelargonidin binds directly with FAK in an adenosine triphosphate-competitive manner, suggesting that FAK could be a molecular target of pelargonidin. Interestingly, pelargonidin did not exhibit inhibitory effects on the proliferation, migration or FAK phosphorylation of human umbilical vein endothelial cells (HUVECs). Taken together, our results suggest that pelargonidin exhibits potential preventive effects toward atherosclerosis through the attenuation of HASMC proliferation and migration, as well as aortic sprouting via the direct inhibition of FAK activity.     

RhoA kinase and protein kinase C participate in regulation of rabbit stomach fundus smooth muscle contraction

1. The degree to which the RhoA kinase (ROK) blockers, Y-27632 (1 micro M) and HA-1077 (10 micro M), and the PKC blocker, GF-109203X (1 micro M), reduced force produced by carbachol, a muscarinic receptor agonist, and phenylephrine, an alpha-adrenoceptor agonist, was examined in rabbit stomach fundus smooth muscle. 2. When examining the effect on cumulative carbachol concentration-response curves (CRCs), ROK and PKC blockers shifted the potency EC50 to the right but did not reduce the maximum response. 3. In a single-dose carbachol protocol using moderate ( approximately EC50 and maximum carbachol concentrations, Y-27632 and HA-1077 reduced peak force, but GF-109203X had no effect. By contrast, all three agents inhibited the carbachol contractions of rabbit bladder (detrusor) smooth muscle. 4. Compared to carbachol, phenylephrine produced a weaker maximum response that was not inhibited by phentolamine, atropine nor capsaicin but was inhibited by Y-27632, HA-1077 and GF-109203X. 5. In detrusor, classical down-regulation occurred, but in fundus, up-regulation of responsiveness occurred. This up-regulation in fundus may have been a post-receptor event, because a KCl-induced contraction produced after a carbachol CRC was stronger than one produced before the carbachol stimulus. 6. In conclusion, these data suggest that ROK plays a critical role in the regulation of rabbit fundus smooth muscle contraction, which is distinct from chicken gizzard smooth muscle, where ROK is reported to exist but to not play a role in muscarinic receptor-induced contraction. Additional unique findings are that PKC participates in phenylephrine- but not carbachol-induced contraction in fundus, that carbachol does not activate identical subcellular signalling systems in fundus and detrusor, and that fundus, unlike detrusor, responds to carbachol stimulation with post-receptor up-regulation of contraction.     

Simvastatin inhibits cell cycle progression in glucose-stimulated proliferation of aortic vascular smooth muscle cells by up-regulating cyclin dependent kinase inhibitors and p53

Simvastatin was reported to attenuate platelet-derived growth factor (PDGF)-induced vascular smooth muscle proliferation by up-regulation of cyclin dependent kinase (CDK) inhibitor p27, but had no effect on p16, p21, p53 expression. We investigate the mechanisms by which simvastatin inhibits vascular smooth muscle cell (VSMC) growth in high glucose conditions to mimic diabetes. Simvastatin was added to A7r5 cells cultured in high glucose (25 mM) medium, mimicking diabetes. We used an 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay to evaluate cell viability; flow cytometric analysis for cell counts distribution in the cell cycle; and Western blot, immunoblotting, and immunoprecipitation analyses to evaluate the effects of simvastatin on CDK activity and cell cycle regulatory proteins. Cell counts were significantly increased in G0/G1 phase and significantly decreased in S and G2/M phases. In our study, low dose of simvastatin had no significant inhibitory effect on VSMC growth in normal glucose condition. However, both low and high doses of simvastatin inhibited VSMC growth significantly in a dose-dependent manner in high glucose status. We also found that simvastatin inhibited phosphorylation of Rb, promoted expression of p53, p16, p21, p27 and decreased CDK2/4 activity. In conclusion, simvastatin inhibits VSMC proliferation in high glucose status, mimicking diabetes, inducing a G0/G1 phase cell cycle growth arrest by acting on multiple steps upstream of pRb, including inhibition of CDK2/4 expression and up-regulation of p53, p21, p16, and p27. We propose that statins may be used more extensively in diabetic patients regardless of lipid status for preventing atherosclerosis and restenosis after PCI.     

Inhibition of platelet-derived growth factor-induced mitogenesis by phosphodiesterase 3 inhibitors: role of protein kinase A in vascular smooth muscle cell mitogenesis

Proliferation of vascular smooth muscle cells (SMC) in response to platelet-derived growth factor (PDGF) and other mitogens plays an important role in restenosis following coronary angioplasty. Elevation of adenosine 3',5'-cyclic monophosphate (cAMP) concentration in SMC has been shown to inhibit SMC mitogenesis and could be obtained either directly by stimulation of adenylyl cyclase-coupled receptors or indirectly by inhibition of cAMP-specific phosphodiesterase (PDE4) or the cyclic guanosine 3', 5'-monophosphate-inhibitable phosphodiesterase (PDE3). This study compared the effects of the selective PDE3 inhibitors trequinsin and quazinone with the selective PDE4 inhibitors Ro 20-1724 and rolipram on PDGF-induced DNA synthesis, mitogen-activated protein (MAP) kinase activation, cAMP levels, and protein kinase A (PKA) activation in SMC. Both PDE3 and PDE4 inhibitors stimulated intracellular PKA activation as seen from phosphorylation of vasodilator-stimulated phosphoprotein (VASP). However, only PDE3 inhibitors, and not inhibitors of PDE4, reduced PDGF-induced DNA synthesis and inhibited p42/p44 MAP kinase phosphorylation. At antimitogenic concentrations, the PDE3 inhibitors had only minor effects on cAMP levels. In contrast, PDE4 inhibitors increased the forskolin-induced cellular cAMP concentration 13- to 17-fold above control. These data demonstrate that inhibitors of PDE3 are potent antimitogenic agents and that a general increase in cellular cAMP levels and PKA activation per se are not sufficient to inhibit PDGF-induced SMC mitogenesis.     

阿托品,东莨菪碱和山茛菪碱对家兔主动脉平滑肌细胞增殖的影响

<正> 胞浆钙离子对主动脉平滑肌细胞的增殖是必需的,阻断胞外钙离子的内流对细胞增殖产生抑制作用.阿托品类药物除具有M受体阻断作用外,与维拉帕米一样,具有钙通道阻断作用,但其对细胞增殖的影响尚未见报道.本文以培养的家兔胸主动脉平滑肌细胞(aortic smooth muscle cell,ASMC)为材料,研究了阿托品类药物对细胞增殖的影响.     

丝裂原活化蛋白激酶参与血小板源生长因子刺激的大鼠主动脉平滑肌细胞增殖(英文)

选择大鼠主动脉平滑肌细胞作为细胞模型 ,观察丝裂原活化蛋白激酶 ( MAPK)信号通路在血小板源生长因子 ( PDGF)诱导的血管平滑肌细胞( VSMC)增殖中的作用。用 [3 H]Td R参入率作为衡量 VSMC增殖的指标 ,以 Western-印迹方法 ,用磷酸化一抗测 MAPK磷酸化的程度作为衡量 MAPK活性的指标 ,实验结果发现 ,PDGF( 0 .0 2 - 2 0μg·L-1)诱导 VSMC增殖呈剂量依赖性。 PDGF( 2μg· L-1)能持续性激活 MAPK。用 PD980 59( 1 0 -1 0 0 mol· L-1)预处理 1 5min后 ,MAPK活性较对照组均有明显差别 ( P<0 .0 5) .MAPK反义寡核苷酸能明显抑制 PDGF诱导的 MAPK的激活 ,并明显抑制 VSMC[3 H]Td R参入。上述结果表明 ,MAPK参与 PDGF促细胞增殖的信号途经 ,它的持续性激活与细胞增殖有关 ,针对 p42 /p44MAPK设计的反义寡核苷酸类能有效抑制 PDGF诱导的血管平滑肌细胞增殖。     

Inhibition of muscarinic receptor-induced inositol phospholipid hydrolysis by caffeine, beta-adrenoceptors and protein kinase C in intestinal smooth muscle.

1. The effects of caffeine, isoprenaline, dibutyryl cyclic AMP, isobutylmethylxanthine (IBMX), 12-O-tetradecanoylphorbol-13-acetate (TPA) or 1-oleoyl-2-acetylglycerol (OAG), (protein kinase C (PKC) activators), 2-methoxy verapamil (D600), thapsigargin and ryanodine on muscarinic acetylcholine receptor (AChR)-stimulated inositol phospholipid hydrolysis were studied in smooth muscle fragments from the longitudinal layer of the small intestine of the guinea-pig. 2. Incubation of the fragments with the muscarinic agonist, carbachol (CCh) (100 microM) resulted in rapid increases in the levels of all the inositol phosphate isomers with maximal increases in the [3H]-inositol (1,4,5) trisphosphate ([3H]-Ins(1,4,5)P3) isomer occurring 10 s following incubation. 3. The beta-adrenoceptor agonist, isoprenaline (10 microM) and dibutyryl cyclic AMP (10 microM), a membrane permeant analogue of cyclic AMP both reduced the CCh stimulation, but not the basal levels of [3H]-inositol phosphates. This inhibition by dibutyryl cyclic AMP was enhanced in the presence of the phosphodiesterase inhibitor, IBMX. CCh inhibited the isoprenaline-induced increases in the levels of cyclic AMP and this was via a pertussi toxin (PTX)-sensitive G-protein mechanism. 4. TPA (1 microM) and OAG (100 microM) a 1,2-diacylglycerol (DAG) analogue both reduced the CCh-induced increases in [3H]-inositol phosphates levels but neither affected basal values nor the basal levels of cyclic AMP. 5. D600 (10 microM), which blocks voltage-dependent Ca2+ channels, also reduced the CCh-stimulated levels of [3H]-inositol phosphates suggesting that some of the agonist-induced increases are due to a potentiating effect of Ca2+ entering the cell. 6. Caffeine (0.5-30 mM) significantly inhibited both the basal and CCh-induced increases in all the [3H]-inositol phosphate isomers. Its inhibitory action was not due to increases in cyclic AMP since caffeine had no effect on the levels of cyclic AMP at concentrations up to 30 mM. 7. Incubation with thapsigargin (1 microM) and ryanodine (10 microM) had no effect on either basal or CCh-induced inositol phospholipid hydrolysis or cyclic AMP levels. 8. The results indicate a reciprocal inhibition by beta-adrenoceptors and muscarinic AChRs of their effects on cyclic AMP and inositol phosphate levels respectively. Ca2+ entering the cell (but not the action of ryanodine or thapsigargin) potentiates while caffeine inhibits muscarinic AChR-induced rises in inositol phosphate levels. Diacylglycerols may exert a negative feedback inhibition on inositol phosphate production.     

丝裂原活化蛋白激酶参与血小板源生长因子刺激的大鼠主动脉平滑肌细胞增殖(英文)

选择大鼠主动脉平滑肌细胞作为细胞模型 ,观察丝裂原活化蛋白激酶 ( MAPK)信号通路在血小板源生长因子 ( PDGF)诱导的血管平滑肌细胞( VSMC)增殖中的作用。用 [3 H]Td R参入率作为衡量 VSMC增殖的指标 ,以 Western-印迹方法 ,用磷酸化一抗测 MAPK磷酸化的程度作为衡量 MAPK活性的指标 ,实验结果发现 ,PDGF( 0 .0 2 - 2 0μg·L-1)诱导 VSMC增殖呈剂量依赖性。 PDGF( 2μg· L-1)能持续性激活 MAPK。用 PD980 59( 1 0 -1 0 0 mol· L-1)预处理 1 5min后 ,MAPK活性较对照组均有明显差别 ( P<0 .0 5) .MAPK反义寡核苷酸能明显抑制 PDGF诱导的 MAPK的激活 ,并明显抑制 VSMC[3 H]Td R参入。上述结果表明 ,MAPK参与 PDGF促细胞增殖的信号途经 ,它的持续性激活与细胞增殖有关 ,针对 p42 /p44MAPK设计的反义寡核苷酸类能有效抑制 PDGF诱导的血管平滑肌细胞增殖。     

Inhibition of LIM kinase reduces contraction and proliferation in bladder smooth muscle

Overactive bladder (OAB) is the most bothersome symptom in lower urinary tract symptoms (LUTS). Current pharmacologic treatment aims to inhibit detrusor contraction; however, shows unsatisfied efficacy and high discontinuation rate. LIM kinases (LIMKs) promote smooth muscle contraction in the prostate; however, their function in the bladder smooth muscle remains unclear. Here, we studied effects of the LIMK inhibitors on bladder smooth muscle contraction and proliferation both in vitro and in vivo experiments. Bladder expressions of LIMKs are elevated in OAB rat detrusor tissues. Two LIMK inhibitors, SR7826 and LIMKi3, inhibit contraction of human detrusor strip, and cause actin filament breakdown, as well as cell proliferation reduction in cultured human bladder smooth muscle cells (HBSMCs), paralleled by reduced cofilin phosphorylation. Silencing of LIMK1 and LIMK2 in HBSMCs resulted in breakdown of actin filaments and decreased cell proliferation. Treatment with SR7826 or LIMKi3 decreased micturition frequency and bladder detrusor hypertrophy in rats with bladder outlet obstruction. Our study suggests that LIMKs may promote contraction and proliferation in the bladder smooth muscle, which could be inhibited by small molecule LIMK inhibitors. LIMK inhibitors could be a potential therapeutic strategy for OAB- related LUTS.KEY WORDS: LIMK, Cofilin phosphorylation, Overactive bladder (OAB), Lower urinary tract symptoms (LUTS), Bladder smooth muscle contraction     

Inhibition of rat vascular smooth muscle cell proliferation by taurine and taurine analogues

The growth of rat aorta vascular smooth muscle cells (VSMCs) was measured in the presence and absence of taurine. Concentrations of taurine as low as 0.3 mM in the culture medium inhibited the proliferation of the cells, as monitored by measuring cell count, and also inhibited the rate of DNA synthesis, as examined by measuring [3H]thymidine incorporation into DNA. However, even at the highest concentration of taurine (30 mM), the doubling time of the VSMCs was only increased by 38%. Protein content of the VSMCs was decreased by 30 mM taurine. [3H]Leucine incorporation into newly synthesized protein was not affected by the highest concentration of taurine tested (30 mM), indicating that taurine did not inhibit protein synthesis but rather decreased total protein content by inhibiting cellular proliferation. The effects of other amino acids such as alanine, glycine, and serine and of various taurine analogues such as beta-alanine, guanidinoethanesulfonic acid (GES), and isethionic acid also were tested at a concentration of 20 mM for their effects on the growth of the VSMCs. Alanine, glycine, and serine had only a minimal effect or no effect on cell count, quantity of protein, and incorporation of [3H]thymidine into DNA. GES, beta-alanine, and isethionic acid had a significant effect on cell count, protein content, and incorporation of [3H]thymidine into DNA. Beta-alanine was the only analogue tested that significantly depressed [3H]leucine incorporation into newly synthesized protein. It is concluded that taurine, GES, and isethionic acid inhibited proliferation of VSMCs but did not alter normal protein synthesis or survivability of VSMCs. In contrast, other amino acids, alanine, glycine and serine, had minimal effects on VSMC proliferation and protein synthesis, whereas beta-alanine appeared to be toxic, inhibiting both VSMC synthesis and de novo protein synthesis.     

普洛托品对兔胸主动脉平滑肌细胞增殖的影响

目的　观察普洛托品 (Pro)对正常和内皮素 (ET)诱导的血管平滑肌细胞 (VSMC)增殖的影响。方法　采用组织块贴壁法培养兔胸主动脉VSMC ,应用细胞计数、[3 H] TdR参入量、微量MTT比色测定及电镜法 ,观察Pro对VSMC增殖、DNA合成和细胞超微结构的变化。结果　ET对VSMC的增殖和DNA合成有显著的促进作用 ;1、10、10 0μmol·L-1浓度Pro能够逆转ET所致的 [3 H] TdR参入量、MTT比色的吸光度、细胞计数的增多及电镜下细胞超微结构的改变 ,且随着浓度的增加及时间的延长 ,抑制作用愈显著 ;10、10 0 μmol·L-1浓度Pro对未经ET处理的VSMC有抑制其增殖作用 ,但其抑制作用弱于ET处理组。结论　Pro可显著地抑制正常及ET诱导的VSMC增殖 ,并且对ET诱导的VSMC增殖抑制作用更明显 ,提示Pro可作为临床防治动脉粥样硬化的有效药物。     

3,4-二羟基苯乙酮抑制培养兔主动脉平滑肌细胞的增殖

传代SMC生长d 6加入DHAP(10～80μg/ml)介质。结晶紫染色法和[~3H]TdR参入试验表明SMC的生长受到DHAP的显著抑制,这一作用随剂量增加而加强。在细胞增殖周期的G_1期加药比S期加药产生更为明显的抑制作用,G_1期末加药抑制作用最大。DHAP的这一作用可能和降低SMC膜流动性有关。     

丝裂素活化的蛋白激酶反义寡核苷酸抑制表皮生长因子诱导体外 …

目的：探讨丝裂素活化的蛋白激酶（ＮＡＰＫ）反义寡核苷（ＯＤＮ）对表皮生长因子（ＥＧＦ）诱导的培养大鼠血管平滑肌细胞增生的抑制作用。方法：用脂质体将Ｐ４２－和Ｐ４４－ＭＡＰＫ ＯＤＮ０．２μｍｏｌˉＬ＾－１转染入大鼠血管平滑肌细胞，设正义及随机ＯＤＮ为对照，用Ｗｅｓｔｅｒｎ Ｂｌｏｔ法结合Ｐ－８１滤纸法以髓磷脂碱性蛋白为底物测定ＭＡＰＫ活性。［＾３Ｈ］胸腺嘧啶核苷酸掺入测定平滑肌细胞ＤＮＡ合成。结果     

Inhibition of voltage-gated L-type calcium channels by labedipinedilol-A involves protein kinase C in rat cerebrovascular smooth muscle cells

Labedipinedilol-A, a novel calcium channel blocker with α/β-adrenoceptor blockade properties, inhibits L-type calcium channels (LTCCs) in rat cerebrovascular smooth muscle cells (CSMCs). We used conventional whole cell patch-clamp electrophysiology to investigate Ba²⁺ currents (I_Ba) through LTCCs in rat CSMCs enzymatically dissociated from rat cerebral arteries. Labedipinedilol-A (1, 10 µM) reversibly inhibited I_Ba in a voltage-dependent manner without modifying the I_Ba current–voltage relationship. The I_Ba was also abolished by the LTCC blocker nifedipine (1 µM), but enhanced by the LTCC activator Bay K8644 (100 nM). Labedipinedilol-A shifted the steady-state inactivation curve of I_Ba to more negative potentials. Additionally, labedipinedilol-A had greater inhibitory activity on I_Ba holding at − 40 mV than at − 80 mV. This might contribute to labedipinedilol-A's more selective effect on vascular muscles compared to cardiac muscles. The protein kinase C (PKC) activator phorbol 12-myristate 13-acetate (PMA) and norepinephrine-enhanced I_Ba were also inhibited by labedipinedilol-A. Pretreatment with the PKC inhibitor chelerythrine (5 µM) attenuated labedipinedilol-A-mediated I_Ba inhibition. However, the Rho kinase inhibitor Y-27632 (30 µM) had little effect on labedipinedilol-A inhibition of I_Ba. Labedipinedilol-A inhibition of voltage-dependent LTCCs may be, at least in part, due to its modulation of the PKC pathway.     

Nipradilol inhibits atmospheric pressure-induced cell proliferation in human aortic smooth muscle cells.

Hypertension is a major risk factor for atherosclerosis and the genesis of cardiovascular and cerebrovascular diseases. Therefore, the protection of atherosclerosis progression is one of the purpose of an anti-hypertensive treatment in vascular system.Nitric oxide (NO)-releasing drugs have been reported to have an inhibitory effect on shear stress-induced extracellular signal-regulated kinase (ERK) activation in endothelial cells. For further understanding of the effects of these drugs, the present study focused on the effects on intracellular signal transduction and cell proliferation in cultured human aortic smooth muscle cells (HASMC) under high atmospheric pressure.Three hours of 160-mmHg atmospheric pressure resulted in an approximately 380% increase in cell proliferation compared to non-pressurized controls. Nipradilol (3,4-dihydro-8-(2-hydroxy-3-isopropylaminoproxy)-3-nitroxy-2H-1-benzopyran) (10(-6)M) demonstrated approximately 40% reduction in cell proliferation compared to that shown by pressurized HASMC as a vehicle control. Three hours of 160-mmHg atmospheric pressure resulted in a 25% increase in the amount of activated ERKs. Nipradilol (10(-6)M) demonstrated approximately a 26% reduction in the amount of activated ERKs. NO(x) concentration under the presence of nipradilol (10microM) with HASMC resulted in a 7.2microM of NO production and was 2.4-fold more than that from no dug control (3.0microM). An administration of L-NAME (10(-4)M) supplemented with Nipradilol (10(-6)M) did not show any significant effect on cell proliferation.From these observations, we concluded that nipradilol has an anti-proliferative effect on HASMC under high atmospheric pressure. Nipradilol may act as a nitric oxide inducer from HASMC and suspected to work as a supplement to mitigate the impaired endothelial cell function caused by hypertension.     

MDL 27,032 relaxes vascular smooth muscle and inhibits protein kinase C.

The smooth muscle relaxant effect of MDL 27,032, 4-propyl-5-(4-pyridinyl)-2(3H)-oxazolone, was studied in vitro using strips of femoral arteries and saphenous veins from dogs and trachea from guinea pigs. MDL 27,032 (10(-6)-10(-3) M) produced a concentration-dependent relaxation of arterial and venous strips contracted by carbachol. MDL 27,032 also antagonized contractions of arterial and venous strips produced by phorbol 12,13-dibutyrate (PDB), a protein kinase C activator, both in normal-Ca2+ and zero-Ca2+ medium. The compound inhibited protein kinase C in soluble extracts prepared from saphenous veins of dogs, with an IC50 value of 36.6 microM. MDL 27,032 was more effective against the contractions produced by phenylephrine and serotonin than by KCl in arteries, but no such selectivity was noted in veins. MDL 27,032 (10(-3) M) also inhibited accumulation of inositol phosphates in femoral artery but not in saphenous vein, and this effect may have contributed to the arterial-relaxant effect. Because the vascular smooth muscle relaxant effect of MDL 27,032 was endothelium independent, did not involve blockade of alpha-adrenoceptors or inhibition of cyclic nucleotide phosphodiesterases, stimulation of beta-adrenergic receptors, stimulation of adenosine A2-receptors, or activation of K+ channels, these data suggest that the relaxant effects of MDL 27,032 primarily involve inhibition of protein kinase C.