Effects of dual-action genistein derivatives on relaxation in rat aorta.

Protein tyrosine kinases and nitric oxide (NO) play important roles in several cardiovascular diseases. In this study, we examined the actions of two compounds, each has structure of genistein (a tyrosine kinase inhibitor) and an NO donor, on endothelium-independent relaxation responses in the isolated rat aorta. By rational drug design, genistein was modified to acquire an NO donor, and we synthesized two such compounds (G-II, G-VI). These compounds and genistein induced dose-dependent relaxation responses in endothelium-denuded aortic strips, the rank order of potencies being G-VI > G-II > genistein. Incubation of endothelium-denuded strips with 1H-[1,2,4] oxadiazolo[4,3-a]-quinoxalin-1-one (ODQ, 10 microM), a guanylyl cyclase inhibitor, inhibited both the G-II- and G-VI-induced relaxations, but not the genistein-induced relaxation. The residual relaxations induced by these two compounds were similar to the genistein-induced relaxation. Incubation of endothelium-denuded strips with lysophosphatidylcholine (LPC, 20 microM)-which is a major atherogenic lysophospholipid component of oxidized low-density lipoprotein and is known to activate tyrosine kinase-caused a significant rightward shift in the dose-response curve for genistein. LPC also shifted the G-II- and G-VI-induced relaxation curves to the right; however, these relaxations in the presence of LPC were greater than that induced by genistein. The sodium nitroprusside-induced relaxation in endothelium-denuded strips was similar between in the absence and presence of LPC. These results suggest that each of our newly developed G-II and G-VI compounds has a dual action, as an NO donor and a tyrosine kinase inhibitor. These compounds may be useful against certain cardiovascular diseases.     

Characterization of histamine-induced relaxation in pre-contracted rat aorta

Inflammation Research -     

Superoxide dismutase reduces the impairment of endothelium-dependent relaxation in the spontaneously hypertensive rat aorta.

The involvement of the superoxide anion in endothelium-dependent relaxation (EDR) was examined in noradrenaline-contracted aortic smooth muscle preparations isolated from normotensive Wistar Kyoto rats (WKY) and stroke-prone spontaneously hypertensive rats (SHRSP). Acetylcholine (ACh, 10(-9)-10(-5) M) induced EDR in both WKY and SHRSP preparations in a concentration-dependent manner, but with a significantly smaller amplitude in those from SHRSP than in those from WKY. The ACh-induced EDR was inhibited by N(omega)-nitro-L-arginine (L-NOARG), in a concentration-dependent manner, both in WKY and SHRSP. The EDR produced in WKY in the presence of 3 x 10(-6) M L-NOARG was similar in magnitude to that produced in SHRSP in the absence of L-NOARG. Superoxide dismutase (SOD, 300 units/ml) increased the amplitude of EDR in SHRSP but not in WKY, with no alteration of the threshold or of the maximal amplitude. The maximal amplitude of EDR produced in SHRSP in the presence of SOD was still smaller than that in WKY. In WKY, a possible involvement of superoxide in the EDR was examined in aortae whose EDR was partially inhibited by treatment with a subthreshold concentration (3 x 10 (-6) M) of L-NOARG. In the L-NOARG-conditioned aorta, the reduced EDR was partially but significantly recovered by SOD. These results suggest that the impaired EDR in aortae of SHRSP may be causally related to a higher production of superoxide. The L-NOARG-induced inhibition of EDR in WKY may be produced, in part, by the reduction of effective NO due to its destruction by superoxide.     

Cortical mechanisms underlying acquisition of latch-box problems in the white rat

Adult rats, previously subjected to bilateral frontal, parietal, occipital, frontocingulate or posterior cingulate ablations, were required to learn two discrete latch-box tasks (sliding a barrel-bolt to the right and elevating a hook). Those groups showing significant learning impairments had lesions to either the frontal cortex or frontocingulate cortex. The data suggest that the neocortical focus for latch-box deficits lies rostral to Level 8 on the Lashley brain diagram, while the frontocingulate focus for latch-box deficits lies within the prelimbic area.     

Matrix biology of abdominal aortic aneurysms in diabetes: mechanisms underlying the negative association

Several case-control studies have shown a significant negative association between diabetes and abdominal aortic aneurysm (AAA). This interaction has the potential to further our understanding of these two diseases but has attracted little research. The changes seen in the walls of aneurysmal aortas include inflammation and the activation of proteolytic pathways resulting in loss of elastin and other structural proteins. In contrast, diabetes is associated with increased synthesis and reduced degradation of matrix. The deposition of advanced glycation end products also renders vascular matrix resistant to proteolysis in diabetic patients. The aim of our present minireview is to compare the changes in matrix biology seen in diabetes and AAA and to explore molecular mechanisms that may explain the negative association and identify possible therapeutic implications.     

染料木素对对氧磷损伤大鼠胸主动脉内皮依赖性舒张功能的保护作用

目的:探讨染料木素( genistein,GST)对对氧磷(paraoxon,PO)损伤血管功能的保护作用.方法:取雄性SD大鼠胸主动脉制备离体血管环,测量并记录血管环张力.实验分组如下:1)溶媒对照组,用0.1％的二甲基亚砜(dimethyl sulfoxide,DMSO)预孵育血管环30 min后,检测大鼠胸主动脉...     

梓醇对糖尿病大鼠主动脉的保护作用与抗氧化机制研究*

 目的：研究梓醇对Goto-Kakizaki(GK)大鼠主动脉的保护作用并探讨其抗氧化机制。方法：6月龄GK大鼠45只随机分为糖尿病模型组、二甲双胍(100 mg·kg-1·d-1)组以及梓醇高剂量（100 mg·kg-1·d-1）组、中剂量（50 mg·kg-1·d-1）组、低剂量(10 mg·kg-1·d-1)组,10只雄性Wistar大鼠作为对照组。各组灌胃给药12周,对照组和模型组给予等量的生理盐水。检测大鼠空腹血糖(FBG)和血脂;检测血清活性氧（ROS）、丙二醛（MDA）、超氧化物歧化酶（SOD）和总抗氧化力（T-AOC）水平;Western blotting检测胸主动脉组织核因子E2相关因子2（Nrf2）和血红素加氧酶1(HO-1)表达;HE染色观察胸主动脉病理变化;透射电镜观察胸主动脉组织超微结构变化。结果：梓醇治疗后,血糖和血脂显著下降;血清ROS和MDA水平明显降低,SOD活性和T-AOC显著增强;胸主动脉组织Nrf2和HO-1蛋白表达明显增强;HE染色显示胸主动脉病变程度明显减轻,透射电镜观察胸主动脉超微结构损伤明显减轻。结论：梓醇能够有效保护GK大鼠胸主动脉,其机制可能与降低血糖和血脂,减轻氧化应激反应,激活Nrf2/ARE/HO-1信号通路有关。     

Ionic mechanisms underlying the firing properties of rat neonatal motoneurons studied in vitro

Ionic mechanisms underlying the firing properties of spinal motoneurons of neonatal rats (postnatal days 3-10) have been investigated using a hemisected, in vitro spinal cord preparation. These results demonstrate the presence of a high-threshold voltage-dependent calcium response and partial sodium-dependent spikes. The calcium current is evident during the falling phase of the action potential and is the major component of the after-depolarizing potential. The subsequent increase in intracellular calcium concentration activates a calcium-dependent potassium conductance (gK-Ca), the major component of the after-hyperpolarizing potential. The gCa, by activating gK-Ca, is the primary determinant of firing rate in neonatal motoneurons. For, when gCa was blocked by Cd2+, the interspike interval decreased, the maximum firing rate and the slope of the firing frequency-injected current relation increased. The calcium current is particularly robust during the first few postnatal days; during this period, tetrodotoxin resistant action potentials can be elicited by direct stimulation under control conditions. In animals older than 5 days such calcium spikes could be elicited only after decreasing gK with intracellular Cs+ or extracellular tetraethylammonium. This was the case even when 1 mM of the bath CaCl2 was replaced with BaCl2. The rising phases of calcium spikes recorded from neurons in both age groups demonstrate several components suggesting the calcium spikes comprise several discrete events, which probably originate across the dendritic membrane. When gK was decreased by bath application of tetraethylammonium+ and Cs+, neonatal motoneurons generated prolonged Ca-dependent spikes lasting for up to 6 s. Repolarization of Ca spikes occurred in two stages, the first was rapid (-2.11 +/- 0.8 V/s, n = 6) but incomplete. The second, was slower (-0.01 +/- 0.003 V/s, n = 5) and returned the membrane potential to the resting level after about 1-2 s. It is suggested that accumulation of extracellular potassium may contribute to the slow phase of repolarization. Motoneurons from the younger age group (3-5 days old) demonstrate all-or-none partial spikes rising from the after-depolarization of directly elicited sodium-dependent action potentials. Similar partial spikes were elicited from neurons from older animals during intracellular Cs+ loading. The partial spikes had faster rates of rise than the tetrodotoxin-resistant spikes and were not seen after tetrodotoxin treatment, suggesting that they are sodium-dependent.(ABSTRACT TRUNCATED AT 400 WORDS)     

Mechanisms of relaxation of rat aorta in response to progesterone and synthetic progestins

Objective: To compare the acute effects of progesterone, chlormadinone acetate (CMA), norethisterone acetate (NETA) and dienogest (DNG) with those of 17β-estradiol (17β-E₂) on the vascular reactivity of male rat thoracic aorta. Methods: Aortic rings with or without endothelium were placed in an organ bath for isometric tension recording. The integrity of the endothelium was assessed by the relaxant response of precontracted rings to acetylcholine (1 and 10 μM), which was diminished after mechanical removal of the endothelium. The concentrations of the steroid hormones were 0.01–10 μM. Results: In vessels precontracted with phenylephrine (1 μM), CaCl₂ (3 mM) or KCl (30 mM), progesterone, CMA and NETA (10 μM each) an endothelium-independent relaxation of 20–35% resulted, with a maximum response after 20–30 min, while DNG had a negligible effect in all experiments. The same concentration of 17β-E₂ was twice as potent as the progestins. Indomethacin, the cyclooxygenase inhibitor and glibenclamide, an inhibitor of the ATP-sensitive potassium channels, did not affect the relaxant responses. The antagonists of progesterone receptors J 867 (1 μM) as well as of estrogen receptors ICI 182780 (1μM) did not counteract the relaxation induced by progesterone and 17β-E₂, respectively. Progesterone (10 μM) did not interfere with endothelium-dependent acetylcholine-induced relaxation of precontracted aortic rings. Pretreatment of the vessels with the hormones attenuated the maximal contractile response to phenylephrine. In the presence of verapamil (1 μM) or progesterone (10 μM) or 17β-E₂ (1 and 10 μM) the concentration-response curves for calcium-induced contractions in K⁺-depolarized vessels were shifted to the right, with suppression of the maximum response. Conclusions: These studies suggest that in addition to 17β-E₂ the progestins, progesterone, CMA and NETA caused a reduction of vascular tone, probably due to blockade of voltage-dependent and/or receptor-operated calcium channels.     

Endothelial factors involved in the bradykinin-induced relaxation of the guinea-pig aorta.

Endothelial factors involved in the bradykinin (BK)-induced relaxation of the guinea-pig aorta were investigated using isolated aortic rings. In intact aortic rings, higher concentrations of BK (> or = 10(-7) M) produced contraction, possibly as a direct action on smooth muscle. This BK-induced contraction was enhanced either by Nw-nitro-L-arginine (NOLA), an inhibitor of the production of nitric oxide or by indomethacin (IND), an inhibitor of cyclooxygenase, but not by carbenoxolone (CX), a known inhibitor of gap junctions. In aortic rings contracted with noradrenaline, BK elicited a relaxation with two components; an initial fast relaxation followed by a gradually diminishing slow relaxation, both in an endothelium-dependent manner. The BK-induced relaxation was inhibited in a drug specific manner by either NOLA, IND or CX. NOLA either abolished the fast relaxation, or sometimes converted it into a contractile response. IND reduced the amplitude and duration of the relaxation, by inhibiting the fast relaxation and abolishing the following slow relaxation. CX reduced both components of the relaxation. In the presence of both NOLA and CX, the BK-induced relaxation was converted to a contractile response followed by an IND-sensitive slow relaxation. In the presence of NOLA and IND together, BK stimulation caused a contraction with no following relaxation. These results indicate that in aortic rings of the guinea-pig, BK stimulates endothelial cells to release nitric oxide and prostanoids that produce the fast and slow components of the relaxation respectively. The effects of CX suggest that the contribution of EDHF to the BK-induced relaxation is weak.     

Ionic mechanisms underlying excitatory effects of serotonin on embryonic rat motoneurons in long-term culture

The actions of serotonin were investigated on motoneurons isolated from embryonic day 14 rat spinal cord and enriched by metrizamide density gradient centrifugation. Trophic support was provided by a spinal cord glial monolayer, ciliary neurotrophic factor and heat-inactivated serum. Cultures were maintained for 17–83 days and investigated using whole-cell patch-clamp recording. Serotonin evoked slow depolarizations (6.2±0.7 or 9.3±1.3 mV in the presence of 6-cyano-7-nitroquinoxaline-2,3-dione and strychnine, ₅₀ 8.2 nM), which were reversibly blocked by 0.1 μM ketanserin. Serotonin generated synaptic potentials in motoneurons, lowered the threshold for repetitive firing and changed the slope of the current intensity–firing frequency relationship. The inward current evoked by serotonin (−147±15.2 pA) was ascribed to a complex ionic mechanism, which varied amongst neurons in the sampled population. It was due to closure of barium-sensitive potassium channels, effects on I_h and increase in a separate mixed cation current which comprised both transient voltage-sensitive and sustained components.

We conclude that serotonergic responses develop in motoneurons cultured under these conditions in the absence of serotonergic input, sensory neurons or many interneurons.     

The role of alpha1-adrenoceptors in the clonidine-induced contraction and relaxation of rat aorta

Clonidine causes dilatation of the aorta in the presence of endothelium, while it causes contraction of the aorta in the absence of endothelium. The present study was carried out to clarify the role of alpha-1-adrenoceptors in the vascular action of clonidine. The aortic rings were suspended in Krebs-Henseleit (K-H) medium, and the effects of alpha-1- and alpha-2-adrenoceptor antagonists on the clonidine-induced contractions were measured. Moreover, the role of the phosphatidylinositol (PI) response was examined. The aortic slices were incubated in K-H medium containing, [3H]myo-inositol and clonidine. The formation of [3H]inositol monophosphate (IP1) was measured with a liquid scintillation counter. Clonidine caused contraction of the aorta in the absence of endothelium, in a dose-dependent manner. This contraction was inhibited by antagonists in the following order of the potency: prazosin > phentolamine > spiperone > urapidil = yohimbine > L-659066 > atipamezole. On the other hand, clonidine inhibited norepinephrine (NE)-induced contraction in the aorta in the absence and in the presence of endothelium. Clonidine enhanced IP1 accumulation in the aorta in the absence of endothelium, whereas it inhibited NE-induced IP1 accumulation in the aorta. The present results show that alpha-1-adrenoceptors are probably involved in the clonidine-induced contraction and relaxation of the rat aorta.     

Measurements of the diameter of the abdominal aorta using C.T

The purpose of this study was to verify the difference between diameters of abdominal aorta obtained on corpses and on living bodies, using C.T. The Authors focused the attention on abdominal aorta, beneath kidney veins. Moreover, a linear relationship was found between height and diameter of abdominal aorta. A careful examination of the literature has shown discordance among the values of the abdominal aorta. The Authors conclude that improved techniques of radiological anatomy may offer an important support to obtain important data for clinical practice.     

Hepatocellular carcinoma and the underlying mechanisms

The incidence of hepatocellular carcinoma is increasing worldwide as well as the associated risk factors, some of which include exposure to aflatoxin B1, Hepatitis B (HBV) virus and hepatitis C (HCV) virus. Mutation of tumour suppressor gene p53 at codon 249^ser at exon 7 has been found to contribute significantly to replication of damaged DNA and subsequent tumour progression. The x gene of HBV (HBx) is the most common open reading frame integrated into the host genome in hepatocellular carcinoma and the integrated HBx is frequently mutated in hepatocellular carcinoma. Mutant HBx proteins still retain their ability to bind to p53 thereby attenuating DNA repair and p53-mediated apoptosis.