大鼠肝星状细胞钙激活钾通道的表达及其意义

活化的肝星状细胞是肝纤维化形成的关键细胞,其收缩是肝纤维化早期门静脉高压形成的基础,而钙激活钾通道是该细胞膜上的离子通道,它与细胞的活化功能有关.我们观察了肝星状细胞膜上该通道的特性,现报道如下.     

SK4通道和BK通道对心脏起搏功能的影响

钙离子激活的钾离子通道根据其电导的大小主要分为三种类型：小电导钙离子激活的钾离子通道SK（SK1-3）,中电导钙离子激活的钾离子通道(IK或SK4)和大电导钙离子激活的钾离子通道(BK)。既往研究已表明SK、SK4和BK在心律失常,高血压,心肌再灌注损伤等的发生发展中发挥重要作用。最近研究提示SK4和BK具有调节心脏起搏的功能。本文旨在综述这两种离子通道在心脏起搏中的作用和机制及构建生物起搏的潜在可能     

Inflammation as a mechanism and therapeutic target for in-stent restenosis

Restenosis following coronary stenting has long been attributed to neointimal proliferation, thrombosis, and negative remodeling. More recently, the important role of inflammation in vascular healing has also been increasingly well understood. From animal models and from clinical experience, we know that endothelial injury, platelet and leukocyte interactions, and subcellular chemoattractant and inflammatory mediators are pivotal in the development of the inflammatory response following stent implantation. By examining the specific mechanisms governing the inflammatory response to percutaneous coronary intervention, we may gain insight into potential therapeutic targets and strategies to prevent restenosis in clinical practice.     

糖尿病大鼠冠状动脉平滑肌细胞大电导钙激活钾通道特性及开放动力学的变化

目的研究糖尿病时冠状动脉平滑肌细胞大电导钙激活钾通道(BK通道)的电压依赖性、钙敏感性及其开放动力学变化,探讨糖尿病时冠状动脉损伤的细胞电生理机制。方法采用链脲霉素腹腔内注射建立糖尿病大鼠模型(糖尿病组,n=30),对照组相应注射生理盐水(n=30);采用酶消化法急性分离大鼠冠状动脉平滑肌细胞;采用膜内向外型单通道膜片钳实验技术记录BK单通道电流;采用Clampfit 10.4软件分析单通道数据。结果在电极外液钙离子浓度为1mmol/L,刺激电位分别为0,20,40,60,80,100,120和140mV时,随着刺激电位增加,正常组BK通道的NPo逐渐增加,其半数有效激活电压(V1/2)为(88.45±1.72)mV;糖尿病组BK通道NPo亦逐渐增加,V1/2为(104.29±1.09)mV,其电压-NPo曲线较正常组向左下移动。在刺激电位60 mV,电极外液钙离子浓度分别为0,0.01,0.1,0.5,1,5,10和50mmol/L时,随着电极外液钙离子浓度增加,正常组BK通道NPo逐渐增加,其半数有效激活浓度(EC50)为(2.26±0.27)mmol/L;糖尿病组BK通道NPo亦逐渐增加,EC50为(3.15±0.20)mmol/L,其浓度-NPo曲线较正常组向左下移动。在电极外液钙离子浓度为1mmol/L,刺激电位60 mV时,与正常组比较,糖尿病组BK通道NPo明显减少,电流幅度与平均开放时间无明显变化,而平均关闭时间显著延长[(451.35±113.71)ms vs(107.58±15.99)ms,P<0.05]。结论糖尿病时冠状动脉平滑肌细胞BK通道电压依赖性与钙敏感性均受损,开放概率减少,通道平均关闭时间延长,这可能是糖尿病冠状动脉功能损伤的重要原因之一。     

Vasoregulation at the molecular level: a role for the beta1 subunit of the calcium-activated potassium (BK) channel

Essential hypertension is among the most common and most costly medical conditions in the United States. Multiple defects in the kidneys, the vasculature, and the neuro-endocrine system may contribute to the development of this disorder. Within the past decade investigators have identified several molecular components of the vasculature that control tone and influence blood pressure. For example, the large conductance BK type calcium-activated potassium channel has recently been shown to play an important role in maintaining the dynamic equilibrium between vasoconstriction and vasodilation of vascular smooth muscle. Activation of vascular smooth muscle BK channels leads to hyperpolarization of the cell membrane, which causes deactivation of voltage-dependent calcium channels and vasodilation. In this review, we will summarize recently published data focusing on the role of the BK channel's accessory beta1 subunit as well as other modulators of BK channel activation that influence vascular tone and blood pressure.     

Blockade of endothelial enzymes: new therapeutic targets

Nitric oxide (NO) is the principal vasoactive substance produced by the vascular endothelium with antitrombotic, antiatherogenic and vasodilator actions. The loss of these functions is now known as endothelial dysfunction (ED) and it has been proposed that it is the final common pathway in cardiovascular disease. At the moment there is an important body of evidence that supports the proposal that ED is a consequence of an imbalance between the free radicals, NO, superoxide (O(-)(2)) and peroxynitrate (ONOO(-)). This imbalance is the result of the actions of well known risk factors associated with an inappropriate diet and infection-inflammation. Angiotensin-converting enzyme (ACE) inhibitors are highly effective against a variety of cardiovascular disorders. Experimental and clinical studies have demonstrated a beneficial effect of ACE inhibition on endothelial function. This action is mainly due to an increase in the concentration of bradykinin, which stimulates NO production. ACE inhibitors also block the formation of angiotensin II that results in a lower production of O(-)(2). These effects lead to improve the imbalance between NO and O(-)(2) observed in cardiovascular disease. This proposal is supported by different clinical trials that have shown that the ACE inhibitors with higher affinity by the tissular ACE, such as quinapril, are the most effective in reversing ED principally by accumulating bradykinin. Recently, the HOPE study conducted in patients at a high risk of cardiovascular events, showed how ramipril, an ACE inhibitor with high affinity by tissular ACE, decreased the mortality rate due to cardiovascular disease independently of changes in blood pressure.     

线粒体钙激活钾通道参与远距缺血预处理心肌保护机制研究

目的:研究线粒体钙激活钾通道在大鼠肢体远距缺血预处理(RPC)对缺血再灌注心肌损伤保护中的作用机制。方法:分离大鼠右下肢股动脉,结扎5min,松开复灌5min,共4个循环。取出心脏悬挂于Langen-dorff灌流装置,全心停灌30min,复灌120min。分离心肌细胞线粒体,电镜观察心肌线粒体结构变化;检测不同处理组线粒体膜电位、线粒体内NOS、Mn-SOD、Ca2+含量的变化。结果:与单纯缺血复灌组相比,RPC组和钙激活钾通道开放剂NS1619组心脏复灌后心肌线粒体损伤减轻,内外膜结构较完整;心肌细胞线粒体膜电位增加(P0.01)、Mn-SOD含量增高(P0.01),NOS含量降低(P0.01)、Ca2+含量下降(P0.01);与RPC组相比,RPC与钙激活钾通道开放阻断剂Paxilline联合组各指标有明显差异(P0.01)。结论:心肌线粒体钙激活钾通道可能通过维持线粒体膜电位,减少心肌复灌期线粒体NO生成和Ca2+含量升高,提高线粒体抗氧化能力而在肢体RPC心肌保护发挥作用。     

Antisenescence as a novel therapeutic strategy for vascular aging

Vascular cells have a finite lifespan when cultured in vitro and eventually enter an irreversible growth arrest state called "cellular senescence." It has been reported that many of the changes in senescent vascular cell behavior are consistent with the changes seen in age-related vascular diseases. Recently, senescent vascular cells have been demonstrated in human atherosclerotic lesions but not non-atherosclerotic lesions. Moreover, these cells express increased levels of proinflammatory molecules and decreased levels of endothelial nitric oxide synthase, suggesting that cellular senescence in vivo contributes to the pathogenesis of human atherosclerosis. One widely discussed hypothesis of senescence is the telomere hypothesis. An increasing body of evidence has established the critical role of the telomere in vascular cell senescence. More recent evidence suggests that telomere-independent mechanisms are implicated in vascular cell senescence. Activation of Ras, an important signaling molecule involved in atherogenic stimuli, induces vascular cell senescence and thereby promotes vascular inflammation in vitro and in vivo. Constitutive activation of Akt also induces vascular cell senescence. This novel role of Akt in regulating the cellular lifespan may contribute to various human diseases including atherosclerosis and diabetes mellitus. Although a causal link between vascular aging and vascular cell senescence remains elusive, a large body of data is consistent with cellular senescence contributing to age-associated vascular disorders. This review considers the clinical relevance of vascular cell senescence in vivo and discusses the potential of antisenescence therapy for human atherosclerosis.     

槲皮素对人肠系膜动脉平滑肌细胞钙激活钾通道的激活作用

目的:观察槲皮素对人肠系膜动脉平滑肌细胞钙激活钾通道(KCa)的影响,以探讨槲皮素在分子水平扩张血管的作用机制.方法:选取需择期行腹部手术并且血压正常的患者14例,取肠系膜动脉小分支,用急性酶消化法获得单个肠系膜动脉平滑肌细胞.然后应用单通道细胞膜片钳技术观察不同浓度槲皮素对肠系膜动脉平滑肌细胞KCa通道开放概率(NPo)、电流幅度值(Am)、平均开放时间(To)、平均关闭时间(Tc)等各指标的影响.结果:在内面向外式方式下,随着浴液中槲皮素浓度的增高,通道NPo明显增高:槲皮素浓度100μmol/L时,NPo由用药前(即0 μmol/L)的0.028 62±0.011 99增高到0.147 03±0.058 17(P＜0.01);通道Am、To变化不大(P＞0.05);而通道Tc明显缩短:由用药前(477.650±376.650)ms缩短到(112.643±114.365)ms(P＜0.01).结论:槲皮素能直接激活人类血管平滑肌细胞KCa通道而实现降血压效应.     

Blockade of the ATP-sensitive potassium channel modulates reactive hyperemia in the canine coronary circulation.

The mechanism of reactive hyperemia remains unknown. We hypothesized that reactive hyperemia was related to the opening of ATP-sensitive potassium channels during coronary occlusion. The resulting hyperpolarization of the smooth muscle cell plasma membrane might reduce calcium influx through voltage-dependent calcium channels and result in relaxation of smooth muscle tone and vasodilation. In eight open-chest, anesthetized dogs, 30-second coronary occlusions resulted in an average flow debt repayment of 200 +/- 41%. After low-dose (0.8 mumol/min) and high-dose (3.7 mumol/min) infusion of intracoronary glibenclamide, flow debt repayment fell to 76 +/- 14% and 50 +/- 8%, respectively (p less than 0.05 compared with control for both). The decline in flow debt repayment was due to a significant reduction both in maximum coronary conductance during reactive hyperemia and in its duration. In addition, there was a significant decline in the sensitivity of the coronary circulation to adenosine-induced vasodilation after glibenclamide. While more variable, there was no overall change in the sensitivity of the coronary vasculature to acetylcholine-induced vasodilation after glibenclamide. We conclude that reactive hyperemia is determined in a large part by the ATP-sensitive potassium channel, probably through its effect on membrane potential and voltage-sensitive calcium channels. Because reactive hyperemia was never fully abolished at the highest doses of glibenclamide tested, it is possible that additional mechanisms are involved in the genesis of this complex phenomenon.     

Targeting hydrogen sulfide as a promising therapeutic strategy for atherosclerosis

Physiological concentrations of nitric oxide (NO) and carbon monoxide (CO) have multiple protective effects in the cardiovascular system. Recent studies have implicated hydrogen sulfide (H₂S) as a new member of vasculoprotective gasotransmitter family, behaving similarly to NO and CO. H₂S has been demonstrated to inhibit multiple key aspects of atherosclerosis, including atherogenic modification of LDL, monocytes adhesion to the endothelial cells, macrophage-derived foam cell formation and inflammation, smooth muscle cell proliferation, neointimal hyperplasia, vascular calcification, and thrombogenesis. H₂S also decreases plasma homocysteine levels in experimental animal models. In the human body, H₂S production is predominantly catalyzed by cystathionine-β-synthase (CBS) and cystathionine γ-lyase (CSE). CSE is the primary H₂S-producing enzyme in the vasculature. Growing evidence suggests that atherosclerosis is associated with vascular CSE/H₂S deficiency and that H₂S supplementation by exogenous H₂S donors (such as NaHS and GYY4137) attenuates, and H₂S synthesis suppression by inhibitors (such as D, L-propargylglycine) aggravates the development of atherosclerotic plaques. However, it remains elusive whether CSE deficiency plays a causative role in atherosclerosis. A recent study (Circulation. 2013; 127: 2523–2534) demonstrates that decreased endogenous H₂S production by CSE genetic deletion accelerates atherosclerosis in athero-prone ApoE^−/− mice, pinpointing that endogenously produced H₂S by CSE activation may be of benefit in the prevention and treatment of atherosclerosis. This study will facilitate the development of H₂S-based pharmaceuticals with therapeutic applications in atherosclerosis-related cardiovascular diseases.     

Phosphocitrate as a potential therapeutic strategy for crystal deposition disease

The deposition of basic calcium phosphate and calcium pyrophosphate dihydrate crystals in articular tissues is probably an underrecognized event. Clinical observations indicate that exaggerated and uniquely distributed cartilage degeneration is associated with these deposits. Measurements of putative markers of cartilage breakdown suggest that these crystals magnify the degenerative process. In vitro studies reveal two potential mechanisms by which crystals cause degeneration. These involve the stimulation of mitogenesis in synovial fibroblasts and the secretion of metalloproteinases by cells that phagocytose these crystals. Approaches that may ameliorate the degenerative process may ensue from new information about how crystals form and how they exert their biologic effects.     

Single channel recordings of calcium-activated potassium channels in the apical membrane of rabbit cortical collecting tubules.

Recordings of single potassium channels from the apical membrane of rabbit cortical collecting tubule have been achieved using the patch-clamp technique. The conductive properties of the channel have been studied in inside-out patches. The slope conductance of the open channel is approximately equal to 90 pS. The channel is selective to potassium over sodium, with a selectivity ratio of 9:1. Decreasing the calcium concentration of the solution bathing the cytoplasmic face of the patch results in a decrease of the open-channel probability. Decreasing the calcium concentration to 10 nM or less completely inhibited channel activity. The channel is also inhibited by barium in a dose-dependent fashion.     

Ibandronate as a new therapeutic agent for osteoporosis

Ibandronate, a second generation amino-bisphosphonate has a high potency as much as the third generation bisphosphonates. Therefore this compound can be characteristically administrated by means of bolus intravenous injection. Moreover it is the first bisphosphonate prospectively shown antifracture efficacy for the intermittent administration in a randomized, controlled clinical trial.     

左心耳封堵策略选择

心房颤动是临床上最常见的心律失常之一,血栓栓塞并发症是其致残、致死的主要原因。经食管超声检查发现,非瓣膜性房颤患者心房内血栓90%位于左心耳。因此,预防左心耳血栓形成可能会减少血栓栓塞事件的发生。口服抗凝药是预防房颤血栓栓塞并发症的有效方法,但是很多患者不能耐受口服抗凝药药物治疗。随着心血管介入治疗和器械研发的进展,经皮左心耳封堵预防卒中越来越受到关注,已经成为一种替代华法林预防房颤并发卒中的有效方法。     

Aiming at minimal invasiveness as a therapeutic strategy for Budd-Chiari syndrome

The 1-year spontaneous mortality rate in patients with Budd-Chiari syndrome (BCS) approaches 70%. No prospective assessment of indications and impact on survival of current therapeutic procedures has been performed. We evaluated a therapeutic strategy uniformly applied during the last 8 years in a single referral center. Fifty-one consecutive patients first received anticoagulation and were treated for associated diseases. Symptomatic patients were considered for hepatic vein recanalization; then for transjugular intrahepatic portosystemic shunt (TIPS), and finally for liver transplantation. The absence of a complete response led to the next procedure. Assessment was according to the strategy, whether procedures were technically applicable and successful. At entry, median (range) Child-Pugh score and Clichy prognostic index were 8 (5-12), and 5.4 (3.1-7.7), respectively. A complete response was achieved on medical therapy alone in 9 patients; after recanalization in 6, TIPS in 20, liver transplantation in 9, and retransplantation in 1. Of the 41 patients considered for recanalization, the procedure was not feasible in 27 and technically unsuccessful in 3. Of the 34 patients considered for TIPS, the procedure was considered not feasible in 9 and technically unsuccessful in 4. At 1 year of follow-up, a complete response to TIPS was achieved in 84%. One- and 5-year survival from starting anticoagulation were 96% (95% CI, 90-100) and 89% (95% CI, 79-100), respectively. In conclusion, excellent survival can be achieved in BCS patients when therapeutic procedures are introduced by order of increasing invasiveness, based on the response to previous therapy rather than on the severity of the patient's condition.     

The potassium channel openers: a new class of vasorelaxants.

Cromakalim, pinacidil, nicorandil, diazoxide and RP-49356 belong to the class of drugs termed potassium channel openers. In rat portal vein diazoxide, like cromakalim, abolished spontaneous mechanical and electrical activity and in rat aorta caused an increase in 86Rb efflux and inhibited KCl(20 mM)-induced contractions. However, in contrast to cromakalim, diazoxide (greater than 100 microM) also inhibited mechanical responses evoked by 80 mM KCl in rat aorta suggesting that it possesses pharmacological properties in addition to K channel opening. Since glibenclamide can attenuate the effects of cromakalim and diazoxide in vascular tissues, it is possible that a channel resembling the ATP-sensitive K channel found in pancreatic beta-cells may be involved in the vasorelaxant effects of these agents. However, differences exist in the order of potency of cromakalim and diazoxide for producing smooth muscle relaxation and for decreasing insulin secretion in pancreatic beta-cells. Furthermore galanin (which opens ATP-sensitive K channels in beta-cells) increases mechanical activity in rat portal vein. It is anticipated that new chemical developments will produce K channel opening molecules with greater potency and tissue selectivity.