KB-R7943对造影剂诱导NRK52E细胞凋亡及p38MAPK信号通路的影响

目的 探讨经钠钙离子交换体介导的细胞内钙超载及p38MAPK信号通路是否参与了造影剂诱导的肾小管上皮细胞损伤及反向模式钠钙离子交换体抑制剂KB-R7943对造影剂诱导的肾小管上皮细胞凋亡及p38MAPK信号通路的影响.方法 鼠肾小管上皮细胞(NRK52E)被分成6组:A正常对照组;B造影剂组;C甘露醇组;D CCB(1×10-5mol/L);E KB-R7943(1×10-5mol/L);F KB-R7943(1×10-6mol/L).造影剂作用1 h后,细胞损伤采用LDH检测,细胞形态变化及细胞凋亡分别由倒置显微镜和流式细胞仪检测;细胞内钙通过Fluo-4染色共聚焦微镜测定;钠钙离子交换体mRNA表达采用RT-PCR测定;p38蛋白的表达采用Western blot测定.结果 造影剂作用1 h后,细胞损伤、细胞凋亡、细胞内钙明显增加,显著高于相同渗透压甘露醇组;p-p38表达30min时增加、60 min时下降.KB-R7943显著降低细胞损伤、细胞凋亡、细胞内钙水平、抑制p-p38的高表达述并显示出剂量效应;钠钙离子交换体mRNA表达没有变化.结论 经反向模式钠钙离子交换体导致的细胞内钙超载诱导了造影剂诱导的肾小管上皮细胞凋亡及p-p38蛋白的高表达;KB-R7943以呈剂量方式降低造影剂诱导的.肾小管上皮细胞凋亡及p-p38蛋白的表达.     

细胞内Ca^2＋及Na^＋/Ca^2＋交换体在对比剂急性肾损伤中的作用

对比剂急性肾损伤（contrast induced-acute kidney injury,CI-AKI）的发病机制到目前为止尚未完全明确.有观点认为,细胞内Ca^2＋超载是CI-AKI发生的一个关键因素,在病理条件下电压依赖性钙离子通道（voltage dependence calcium channel,VDC）和Na^＋/Ca^2＋交换体（Na^＋/Ca^2＋ exchange,NCX）是引起细胞内Ca^2＋超载的主要途径.本文将对细胞内NCX介导的Ca^2＋超载引起肾小管上皮细胞损伤及血流动力学改变在CI-AKI发病机制中的作用做一综述.     

1-6二磷酸果糖抗肝脏缺血再灌注损伤的作用

肝脏缺血再灌注损伤的确切机制尚不十分清楚。目前认为细胞能量不足或缺乏为始动机制，细胞内钙超载、氧自由基等因素参与其中。现已知１６二磷酸果糖（ＦＢＰ）为糖酵解中高能中间代谢产物，能改善细胞能量代谢，降低细胞外钙离子，抑制氧自由基的产生。１．材料与方法...     

钙离子在疼痛和抗伤害性感受中的作用

1钙通道的结构与分类钙离子广泛地参与各种生命活动的调节。通过细胞膜上的钙通道、离子泵的转运或细胞内钙库释放钙离子使胞浆钙离子浓度急剧升高,促使突触囊泡释放神经递质,引起膜兴奋性的改变。钙离子内流主要经由3种不同类型的钙通道:电压依从型钙通道(VOCC)、配体门控非特     

冬虫夏草对体外线粒体钙离子负荷和缺血性急性肾功能衰竭大…

本文观察了冬虫夏草对体外大鼠肾皮质线粒体钙离子负荷和缺血性急性肾功能衰竭大鼠肾皮质线粒体钙离子，及其对线粒体ＡＴＰ酶的影响。实验结果证实，冬虫夏草可减轻实验性缺血性急性肾功能衰竭大鼠皮质线粒体钙离子内流和保护ＡＴＰ酶的活性，从而改善了肾功能，冬虫夏草减轻线粒体钙离子内流的机制与钌红选择性抑制线粒体膜钙离子通道不同，可能与其保护线粒体膜ＡＴＰ酶，改善线粒体能量代谢有关。     

钙离子超载对低温保存人肝细胞的损伤作用的研究

目的：研究分离培养的成人肝细胞在低温保存状态下（0-4℃）的钙离子代谢特点和钙离子超载的损伤作用机制。方法：胶原酶消化法制备分离的成人肝细胞,钙离子荧光探针Flou-3标记,流式细胞仪检测。结果：低温保存下,细胞内游离钙迅速升高,逐渐达到稳态水平,随细胞内钙离子的升高,细胞的存活率也逐渐下降,但在含0.5mmol/L CaCl2的保存液组,保存效果明显好于其它两组;在含1.5mmol/L CaCl2的保存液组,继发的钙离子超载峰值出现早,而且要高于原发的钙超载峰。结论：低温保存可以引起成人肝细胞的钙超载,细胞外钙是细胞钙超载的主要来源,继发超载是缺血再灌注损伤的主要原因。     

激光共聚焦显微镜技术在研究肠上皮细胞内钙超载中的应用

细胞内钙稳态的维持对生命活动至关重要。病理状态下细胞内钙超负荷将造成一系列代谢紊乱，致细胞坏死和凋亡。目前有关肠上皮细胞（IEC）缺血缺氧损伤导致IEC细胞内钙超载是否确切，钙离子阻断剂是否有防治作用，目前尚无这方面的研究报道。     

钙通道阻断剂与肝缺血再灌注损伤（文献综述）

除氧自由基的作用外，近期又发现细胞内钙超载是脏器缺血再灌注损伤的一个重要机制。本文对肝细胞内外自由钙的稳定和调节、钙超载在肝缺血再灌注损伤中的作用以及钙通道阻断剂对肝脏的保护作了重点介绍。     

肾缺血预处理对膜脂质过氧化损伤的保护作用

研究证实,肾缺血预处理可以减轻缺血-再灌注损伤。本研究通过观察大鼠肾缺血预处理后血清超氧化物歧化酶(SOD)、丙二醛(MDA)及肾小管上皮细胞内游离钙离子浓度([Ca2 ]i)的变化来判断肾缺血预处理对膜脂质过氧化损伤及细胞内钙超载的影响,以及脂质过氧化损伤与细胞内钙超载的关系。     

山莨菪碱对急性肾缺血—再灌注损伤的保护机制

目的:观察山莨菪碱(645-2)对急性肾缺血-再灌注损伤的保护机制.方法:用新西兰大白兔制作急性肾缺血及再灌注损伤动物模型、观察肾组织细胞内游离钙(Ca~(?)i)、第二信使三磷酸肌醇(IP_3)含量的浓度变化及再灌注前2分钟给于654-2后肾组织细胞内Ca~(?)i、IP_3含量的浓度变化.结果:缺血60分钟及再灌注60分钟.肾组织细胞内游离钙及IP_3明显增高,而给于654-2后,肾组织细胞内Ca~(?)i及第二信使三磷酸肌醇(IP_3)的含量明显下降.结论:642—2能减轻急性肾缺血-再灌注损伤时细胞内钙超载.其保护肾组织细胞的作用与细胞内IP_3的降低有密切关系.     

Ca2+ signaling mediated by IP3-dependent Ca2+ releasing and store-operated Ca2+ channels in rat odontoblasts.

In the phospholipase-C (PLC) signaling system, Ca2+ is mobilized from intracellular Ca2+ stores by an action of inositol 1,4,5-trisphosphate (IP3). The depletion of IP3-sensitive Ca2+ stores activates a store-operated Ca2+ entry (SOCE). However, no direct evidence has been obtained about these signaling pathways in odontoblasts. In this study, we investigate the characteristics of the SOCE and IP3-mediated Ca2+ mobilizations in rat odontoblasts using fura-2 microfluorometry and a nystatin-perforated patch-clamp technique. In the absence of extracellular Ca2+ ([Ca2+]o), thapsigargin (TG) evoked a transient rise in intracellular Ca2+ concentration ([Ca2+]i). After TG treatment to deplete the store, the subsequent application of Ca2+ resulted in a rapid rise in [Ca2+]i caused by SOCE. In the absence of TG treatment, no SOCE was evoked. The Ca2+ influx was dependent on [Ca2+]o (KD = 1.29 mM) and was blocked by an IP3 receptor inhibitor, 2-aminoethoxydiphenyl borate (2-APB), as well as La3+ in a concentration-dependent manner (IC50 = 26 microM). In TG-treated cells, an elevation of [Ca2+]o from 0 to 2.5 mM elicited an inwardly rectifying current at hyperpolarizing potentials with a positive reversal potential. The currents were selective for Ca2+ over the other divalent cations (Ca2+ > Ba2+ > Sr2+ > Mn2+). In the absence of [Ca2+]o, carbachol, bradykinin, and 2-methylthioadenosine 5'triphosphate activated Ca2+ release from the store; these were inhibited by 2-APB. These results indicate that odontoblasts possessed Ca2+ signaling pathways through the activation of store-operated Ca2+ channels by the depletion of intracellular Ca2+ stores and through the IP3-induced Ca2+ release activated by PLC-coupled receptors.     

Regulation of intracellular Ca2+ stores by multiple Ca2+-releasing messengers

Although glucose-elicited insulin secretion depends on Ca(2+) entry through voltage-gated Ca(2+) channels in the surface cell membrane of the pancreatic beta-cell, there is also ample evidence for an important role of intracellular Ca(2+) stores, particularly in relation to hormone- or neurotransmitter-induced insulin secretion. There is now direct evidence for Ca(2+) entry-induced release of Ca(2+) from the endoplasmic reticulum in neurons, but with regard to glucose stimulation of beta-cells, there is conflicting evidence about the operation of such a process. This finding suggests that the sensitivity of the Ca(2+) release channels in the endoplasmic reticulum membrane varies under different conditions and therefore is regulated. Recent evidence from studies of pancreatic acinar cells has revealed combinatorial roles of multiple messengers in setting the sensitivity of the endoplasmic reticulum for Ca(2+) release. Here we focus on the possible combinatorial roles of inositol 1,4,5-trisphosphate, cyclic ADP-ribose, and nicotinic acid adenine dinucleotide phosphate in beta-cell function.     

钙离子与精子功能

钙离子是生物体内重要的阳离子,虽然钙离子在精子中的调控作用还不清楚,但近些年来有关钙离子在精子中的功能不断有新的报道,如钙离子参与精子的发生,是精子运动的调控者,精子获能的参与者,还是顶体反应的第二信使。现对钙离子与精子功能间的关系进行综述。     

Extracellular Ca2+ increases cytosolic free Ca2+ in freshly isolated rat odontoblasts.

Recent evidence suggests that extracellular Ca2+ may modulate cell function in mineralized tissue. To determine whether dentinogenic cells, in particular, are sensitive to extracellular Ca2+, fura-2 microfluorometry was used to monitor intracellular calcium levels in odontoblasts freshly isolated from rat incisor. In response to applications of 0.5-4.0 mM extracellular calcium (CaCl2), most odontoblasts (84%; 107/128) showed an increase in intracellular calcium. For the majority of these cells (70%; 75/107), the typical response was biphasic; there was an initial, transient increase in intracellular calcium which reached peak levels within 30-50 s and decayed rapidly, followed by a slower (> 300 s) recovery toward basal levels. In general, the response of these cells to calcium was repeatable and the mean calcium concentration for the half-maximal response was approximately 1.3 mM. This effect could be partially blocked by either 200 microM lanthanum, a nonspecific blocker of Ca2+ channels, or 20 microM dantrolene, a potent inhibitor of Ca2+ release from internal stores. Used in combination, lanthanum, and dantrolene nearly abolished the calcium response completely. In addition, this response was sensitive to the dihydropyridine-sensitive calcium channel blocking agent nicardipine (60 microM), indicating a role for voltage-gated calcium channels during these events. These results show that odontoblasts respond to external calcium through mechanisms involving both influx of external calcium as well as release of calcium from internal stores and suggest a role for extracellular calcium in regulating the function of these cells.     

Epithelial Ca2+ and Mg2+ channels in kidney disease

Many physiological functions rely on the precise maintenance of body calcium (Ca2+) and magnesium (Mg2+) balance, which is tightly regulated by the concerted actions of intestinal absorption, renal reabsorption, and exchange with bone. The kidney plays an important role in the homeostasis of divalent ions. Most Ca2+ and Mg2+ reabsorption occurs in the proximal tubules and the thick ascending limb of Henle's loop via a passive paracellular pathway. At the level of the distal convoluted tubule (DCT) and the connecting tubule (CNT), Ca2+ and Mg2+ are reabsorbed via an active transcellular route. Reabsorption of divalents in these latter segments is regulated in a Ca2+ and Mg2+-specific manner and determines the final excretion in the urine. Importantly, genetic studies, as well as molecular cloning strategies, recently identified epithelial ion channels as the gatekeepers of active Ca2+ and Mg2+ reabsorption. These channels are members of the transient receptor potential (TRP) superfamily. TRP vanilloid 5 (TRPV5) is responsible for the rate-limiting Ca2+ entry, and TRP melastatin 6 (TRPM6) constitutes the apical entry step in Mg2+ reabsorption. Dysregulation or malfunction of these influx pathways has been associated with renal Ca2+ and Mg2+ wasting. This review updates the current knowledge and the recent advances of Ca2+ and Mg2+ reabsorption and related disorders.     

Propofol attenuates angiotensin II-induced vasoconstriction by inhibiting Ca2+-dependent and PKC-mediated Ca2+ sensitization mechanisms

Purpose

Angiotensin II (Ang II)-induced vascular contraction is mediated by Ca²⁺-dependent mechanisms and Ca²⁺ sensitization mechanisms. The phosphorylation of protein kinase C (PKC) regulates myofilament Ca²⁺ sensitivity. We have previously demonstrated that sevoflurane inhibits Ang II-induced vasoconstriction by inhibiting PKC phosphorylation, whereas isoflurane inhibits Ang II-induced vasoconstriction by decreasing intracellular Ca²⁺ concentration ([Ca²⁺]_i) in vascular smooth muscle. Propofol also induces vasodilation; however, the effect of propofol on PKC-mediated myofilament Ca²⁺ sensitivity is poorly understood. The aim of this study is to determine the mechanisms by which propofol inhibits Ang II-induced vascular contraction in rat aortic smooth muscle.

Methods

An isometric force transducer was used to investigate the effect of propofol on vasoconstriction, a fluorometer was used to investigate the change in [Ca²⁺]_i, and Western blot testing was used to analyze Ang II-induced PKC phosphorylation.

Results

Ang II (10^?7?M) elicited a transient contraction of rat aortic smooth muscle, which was associated with an elevation of [Ca²⁺]_i. Propofol (10^?6?M) inhibited Ang II-induced vascular contraction (P?<?0.01) and increase in [Ca²⁺]_i (P?<?0.05) in rat aortic smooth muscle. Ang II also induced a rapid increase in [Ca²⁺]_i in cultured vascular smooth muscle cells, which was suppressed by propofol (P?<?0.05). Propofol (10^?6?M) attenuated Ang II-stimulated PKC phosphorylation (P?<?0.05).

Conclusion

These results suggest that the inhibitory effect of propofol on Ang II-induced vascular contraction is mediated by the attenuation of a Ca²⁺-dependent pathway and Ca²⁺ sensitivity through the PKC signaling pathway.     

Essential role of Ca2+ release channels in angiotensin II-induced Ca2+ oscillations and mesangial cell contraction

The increased resistance of the glomerulus as a result of contractile dysfunction of mesangial cells (MCs) is associated with reduction of glomerular filtration rate and development of glomerulosclerosis. Evidences show MCs contraction changes with intracellular Ca(2+) concentration ([Ca(2+)](i)). Here, we explore the mechanism of angiotensin II (AngII)-induced Ca(2+) oscillations and MCs contraction. Primary MCs from 3-month-old and 28-month-old rats were used for detection of Ca(2+) oscillations and MC planar area with confocal microscopy. AngII could induce typical Ca(2+) oscillations and contraction of MCs. This process was abolished by thapsigargin, 2-aminoethoxydiphenyl borate, or 1-O-octadecyl-2-O-methyl-sn-glycero-3-phosphorylcholine, and partially inhibited by ryanodine, but could not be inhibited in the absence of extracellular Ca(2+). Ryanodine receptors (RyRs) and inositol 1,4,5-trisphosphate (InsP(3)) receptors displayed a strong colocalization, which may contribute to the amplification of Ca(2+) response. MLC(20) phosphorylation and MC planar area were associated with AngII-induced Ca(2+) oscillations. The frequency of Ca(2+) oscillations was dependent on the AngII concentration and correlated with the MCs' contractive extent, which could be attenuated by KN-93. The amplitude reduction of oscillations correlated with the decrease in aging-related contraction. In conclusion, [Ca(2+)](i) response of MCs to AngII is characterized by repetitive spikes through the following repetitive cycles: Ca(2+) release by phospholipase C -InsP(3) pathway, Ca(2+) amplification by Ca(2+)-activated RyRs and Ca(2+) reuptake by the endoplasmic reticulum. MCs contraction can be modulated by oscillations not only in an AngII-induced frequency-dependent mode but also in an aging-related, amplitude-dependent mode.     

Epithelial Ca2+ and Mg2+ channels in health and disease

A near constancy of the extracellular Ca(2+) and Mg(2+) concentration is required for numerous physiologic functions at the organ, tissue, and cellular levels. This suggests that minor changes in the extracellular concentration of these divalents must be detected to allow the appropriate correction by the homeostatic systems. The maintenance of the Ca(2+) and Mg(2+) balance is controlled by the concerted action of intestinal absorption, renal excretion, and exchange with bone. After years of research, rapid progress was made recently in identification and characterization of the Ca(2+) and Mg(2+) transport proteins that contribute to the delicate balance of divalent cations. Expression-cloning approaches in combination with knockout mice models and genetic studies in families with a disturbed Mg(2+) balance revealed novel Ca(2+) and Mg(2+) gatekeeper proteins that belong to the super family of the transient receptor potential (TRP) channels. These epithelial Ca(2+) (TRPV5 and TRPV6) and Mg(2+) channels (TRPM6 and TRPM7) form prime targets for hormonal control of the active Ca(2+) and Mg(2+) flux from the urine space or intestinal lumen to the blood compartment. This review describes the characteristics of epithelial Ca(2+) and Mg(2+) transport in general and highlights in particular the distinctive features and the physiologic relevance of these new epithelial Ca(2+) and Mg(2+) channels in (patho)physiologic situations.     

大电导钙激活钾通道与心血管保护

背景 大电导钙激活钾通道(large conductance Ca2+-activated K+ channels,BKCa)可能是各类心脏疾病的重要治疗靶点. 目的 主要阐述如何通过调节心肌及血管平滑肌的BKCa通道而发挥保护心肌作用及其相关机制. 内容 在心肌细胞的线粒体上,BKCa通道能够有效地调节线粒体的活性氧、Ca2+和呼吸作用.在血管平滑肌细胞,BKCa通道能调节血管紧张度,促进血管扩张. 趋向 BKCa通道在心肌缺血/再灌注(ischemia/reperfusion,I/R)损伤中有着重要的作用,包括改善心肌功能和减少梗死面积.     

Ca2+ uptake and Ca2+ release by skeletal muscle sarcoplasmic reticulum: differing sensitivity to inhalational anesthetics

The effects of halothane, enflurane, and isoflurane were measured on two different mechanisms of Ca2+ regulation by isolated skeletal muscle sarcoplasmic reticulum (SR) membranes. A 100,000-dalton Ca2+-ATPase protein transports Ca2+ from outside to inside the SR membrane. At concentration ranges representing anesthetic levels of 0.06 to 2.3 times MAC, halothane, enflurane, and isoflurane each increased rate of Ca2+ uptake by SR. Each concentration of isoflurane produced a greater rate of Ca2+ uptake, whereas halothane and enflurane produced maximum stimulation of Ca2+ uptake at 1 and 1.6 times MAC, respectively. The second Ca2+ regulation mechanism studied was a Ca2+ release channel in the SR membrane. The release of Ca2+ via this mechanism requires a critical threshold Ca2+ load (nmol Ca2+/mg SR protein) for Ca2+-induced Ca2+ release to occur. Each anesthetic tested effectively lowered the critical Ca2+ load threshold for Ca2+ release, i.e., the Ca2+ channel was more readily induced to an open state in the presence of anesthetic. The concentrations of anesthetics having this effect on the putative Ca2+ channel were between 0.0026 and 0.078 MAC equivalents for each agent, and these concentrations are much lower than the anesthetic concentrations affecting Ca2+ uptake. These data show that in isolated skeletal muscle SR membranes a Ca2+ channel release function is altered at anesthetic concentrations far below those that change Ca2+ uptake function by a Ca2+-ATPase and below concentrations of the volatile agents producing clinical anesthesia. The Ca2+ channel effect may represent protein-anesthetic interaction, whereas the Ca2+-ATPase effect may occur by a generalized SR membrane perturbation by the anesthetics.