非酒精性脂肪性肝病的病理生理机制研究进展

随着非酒精性脂肪性肝病(NAFLD)的发病率持续增加,逐渐成为引起终末肝硬化、肝癌的主要病因.NAFLD的发生、发展涉及的病因学极其复杂,包括高脂饮食、缺乏运动、胰岛素抵抗、内质网应激、线粒体功能异常、星状细胞活化等.研究显示,内质网应激贯穿肝细胞脂肪样变到肝硬化全过程,在NAFLD中发挥重要作用.此外,线粒体功能异常...     

毒物所致肝细胞钙稳态失调规律探讨

毒物所致肝细胞钙稳态失调规律探讨周炯亮符立梧廖肇浩李芳红石世华李胜联（中山医科大学公共卫生学院，广州５１００８９）细胞钙稳态是实现细胞生理功能和保持细胞结构完整的必要条件．钙稳态依赖于钙移位酶Ｃａ２＋，Ｍｇ２＋－ＡＴＰ酶，细胞内储库（内质网，线粒体）...     

细胞自噬：糖尿病发生发展中的积极参与者

糖尿病病因复杂,涉及自身免疫、环境及遗传等多种因素。细胞自噬是一种细胞内分解代谢过程,在维持胰岛细胞内环境稳态中发挥重要作用。自噬通过参与内质网应激、线粒体功能障碍以及炎症反应等过程,影响糖尿病的发生发展。本文就糖尿病中自噬和内质网应激、线粒体功能障碍以及炎症的相互作用作一综述,旨在探讨糖尿病的发病机制,寻找防治糖尿病的新策略。     

β-肾上腺素能受体通过内质网应激诱导心肌细胞凋亡

交感神经系统活性增强是心室血流动力学功能障碍的早期反应之一,刺激β-肾上腺素能受体（β-AR）可以诱导心肌细胞凋亡。内质网应激反应是新近发现的一条重要的细胞凋亡途径,主要是指未折叠或错误折叠蛋白的积累或细胞内钙离子稳态失衡,引起内质网功能紊乱的病理状态。在内质网应激早期,细胞本身会激活未折叠蛋白反应（UPR）促进细胞功能的恢复,PERK-eIF2α通路是重要的途径之一,可以从翻译水平抑制蛋白质的合成,减轻内质网负荷,促进细胞存活。如果应激过强或长时间不缓解,会触发内质网应激诱导的凋亡通路（主要包括GADD153和caspase-12途径）,消除受损的细胞。本实验主要是探讨β-AR诱导的细胞凋亡是否与内质网应激反应有关。     

钙离子在急性高原脑水肿中的作用

钙离子对神经细胞的损害起决定性作用,当脑组织缺血、缺氧或中毒时,钙离子迅速进入细胞内,而且细胞内线粒体和内质网的钙也被释放,使细胞内钙离子的增加达正常浓度的200倍,病理学称此为钙超载现象,细胞内钙离子的增多导致蛋白质和脂肪的破坏,最后细胞死亡。钙离子还可进人脑的小动脉壁内,引起小动脉痉挛而加重缺血与缺氧,是脑水肿发病机制的一种学说t‘］。本文主要复习钙离子的基本概念、生物学意义及钙离子学说,并对钙离子在急性高原脑水肿发生发展过程中的病理生理作用以及钙离子括抗剂的作用进行探讨。钙离子的基本概念及生物…     

内质网应激与代谢性疾病

内质网是真核细胞内合成代谢的重要场所,细胞内稳态改变可引起内质网应激.适宜的内质网应激有利于细胞内环境的恢复,过度的应激则导致代谢障碍.内质网应激介导的炎症通路及细胞凋亡通路改变与细胞的生长、分化、存活及凋亡有密切联系,在代谢性疾病发生发展过程中起重要作用.维持适当的应激状态,减少过度应激有利于代谢性疾病的恢复,内质网应激为进一步认识和治疗代谢性疾病提供了新的视野和思路.     

钙通道阻滞剂在心血管疾病中的应用

钙离子在人体的组织细胞及亚细器正常的生理功能中发挥着重要作用。如平滑肌的收缩 ,某些细胞的分泌、代谢等 ,都有赖于钙离子的参与。当由于各种病理生理因素 ,引起局部组织或细胞内钙离子超载或对钙离子敏感性增高时 ,则可引起它们的功能异常或发生疾病。钙通道阻滞剂 (CCB)能阻止细胞外钙离子内流或亚细器 (线粒体 ,肌浆网等 )钙离子的释放 ,降低细胞浆钙离子含量等 ,故可广泛用于钙离子超载等与钙离子有关的许多疾病的防治。本文着重介绍了钙通道阻滞剂在心血管疾病中的应用 ,概述如下 :1 常用钙通道阻滞剂及其特点　临床常用的钙通道…     

内质网应激在纳米材料毒性效应中的作用研究进展

活性氧生成和氧化应激是纳米材料引发细胞毒性的主要作用机制之一。内质网作为细胞内蛋白质合成、加工以及钙储存的重要场所,对细胞应激十分敏感并参与氧化应激诱导的细胞损伤。氧化应激、钙稳态失衡等可诱导内质网应激(ERS),激活未折叠蛋白反应,从而促进细胞内稳态的恢复。但持续或严重的ERS可触发细胞凋亡信号通路,导致细胞死亡。已有研究表明,ERS是纳米材料毒性效应的早期、敏感指标。这一发现为纳米材料毒作用机制研究提供了新角度。此外,纳米材料诱导ERS的水平与颗粒理化性质、作用模式、细胞类型等有关。本文对ERS在纳米材料毒性效应中的作用及其机制进行简要综述。     

钙通道阻滞剂的临床应用

钙离子在人体的组织细胞及亚细胞器正常的生理功能中发挥着重要作用。如平滑肌的收缩,某些细胞的分泌、代谢等,都有赖于钙离子的参与。当由于各种病理生理原因,引起局部组织或细胞内钙     

细胞内钙的调节机制与临床应用

钙离子参与细胞多种反应 ,对维持机体功能十分重要。该文简要介绍了细胞内钙离子通道及调节机制 ,脑血管疾病、心血管疾病钙离子分布的变化及一些药物对细胞内钙的调节机制。     

Influence of the carcinogenic oestrogen diethylstilboestrol on the intracellular calcium level in C6 rat glioma cells

The synthetic oestrogen diethylstilboestrol (DES) causes a dose-dependent elevation of the cytoplasmic Ca²⁺ concentration in C6 rat glioma cells. This Ca²⁺ rise is caused neither by Ca²⁺ influx nor by release from the Ca²⁺ stores of the endoplasmic reticulum. Therefore it seems likely that DES mobilizes Ca²⁺ from a mitochondrial source. The DES-induced Ca²⁺ signal is remarkably similar to the one induced by the tumour promotor thapsigargin. As this compound causes leakage of calcium from the endoplasmic reticulum it seems possible that DES induces a similar leakage from mitochondrial Ca²⁺ stores. It remains to be established whether the DES-mediated rise in intracellular calcium is causally related to the tumour-promoting properties of this compound.     

Tetrabromobisphenol A (TBBPA), induces cell death in TM4 Sertoli cells by modulating Ca transport proteins and causing dysregulation of Ca homeostasis

Tetrabromobisphenol A (TBBPA) is a commonly used brominated flame retardant (BFR) utilized to reduce the flammability of a variety of products. Studies have indicated that a number of BFRs are becoming widely distributed within the environment and are bio-accumulating within organisms. There has been much speculation that a variety of phenolic pollutants (including compounds chemically related to TBBPA, such as bisphenol A) may cause endocrine disruption and Ca²⁺ dysregulation in cells involved in spermatogenesis. In this study we therefore investigate the effects of TBBPA on mouse TM4 Sertoli cells (essential for sperm development). Results show that TBBPA increases Ca²⁺ within these cells in the 5–60 μM concentration range (EC₅₀, 21 μM). TBBPA also causes cell death (LC₅₀, 18 μM) partly via apoptosis, involving Ca²⁺-dependent mitochondrial depolarisation. Studies on intracellular Ca²⁺ transporters shows that TBBPA can inhibit sarcoplasmic/endoplasmic reticulum Ca²⁺-ATPases (SERCA) at low concentrations (IC₅₀, 0.4 to 1.2 μM) and also activate the Ryanodine receptor Ca²⁺ channel within the 0.4–4 μM concentration range. Therefore these studies suggest that the cytotoxic effects of TBBPA on cells is partly due to dysregulation of Ca²⁺ signalling, by directly affecting Ca²⁺ transport proteins.     

Heptachlor epoxide induces a non-capacitative type of Ca2+ entry and immediate early gene expression in mouse hepatoma cells

The effects of the organochlorine (OC) liver tumor promoter heptachlor epoxide (HE) and a related non-tumor promoting OC, delta-hexachlorocyclohexane (δ-HCH), on the dynamics of intracellular calcium (Ca²⁺) were investigated in mouse 1c1c7 hepatoma cells. HE induced a non-capacitative, Ca²⁺ entry-like phenomenon, which was transient and concentration-dependent with 10 and 50 μM HE. The plasma membrane Ca²⁺ channel blocker SKF-96365 antagonized this HE-induced Ca²⁺ entry. δ-HCH failed to induce Ca²⁺ entry, rather it antagonized the HE-induced Ca²⁺ entry. Both HE and δ-HCH induced Ca²⁺ release from endoplasmic reticulum (ER) at treatment concentrations as low as 10 μM; at 50 μM, the former induced 5× as much Ca²⁺ release as the latter. The HE-induced Ca²⁺ release from the ER was antagonized using the IP₃ receptor/channel blocker xestospongin C, suggesting that HE induces ER Ca²⁺ release through the IP₃ receptor/channel pore. These results show that the effect of HE on cellular Ca²⁺ mimics that of mitogens such as epidermal and hepatocyte growth factors. They also provide insight into the similarities and differences between tumorigenic and non-tumorigenic OCs, in terms of the mechanisms and the extent of the [Ca²⁺]_i increased by these agents.     

Methapyrilene hepatotoxicity is associated with oxidative stress, mitochondrial disfunction and is prevented by the Ca channel blocker verapamil

Methapyrilene (MP) is an unusual hepatotoxin in that it causes periportal necrosis in rats. The mechanism of acute methapyrilene hepatotoxicity has, therefore, been investigated in cultured male rat hepatocytes. Addition of methapyrilene to rat hepatocytes resulted in a time- and dose-dependent loss in cell viability between 4 and 8 h of incubation as judged by cellular enzyme leakage. The cytochrome P450 (CYP) inhibitor metyrapone protected against methapyrilene-mediated toxicity suggesting that MP is metabolised by CYP for toxicity. The concentration-dependent protection from methapyrilene toxicity afforded by metyrapone correlated with an inhibition of microsomal CYP2C11-associated androstenedione 16 hydroxylase activity, and hepatocytes prepared from hypophysectomised rats (containing reduced levels of microsomal immunodetectable CYP2C11 and associated androstenedione 16 hydroxylase activity) showed resistance to the toxic effects of methapyrilene. These data suggest that the toxicity of methapyrilene is predominantly dependent on the CYP2C11 isoform. Treatment of hepatocytes with a toxic concentration of MP caused oxidative stress as indicated by increases in NADP⁺ levels within 2 h and cellular thiol oxidation as evidenced by a reduction—but not complete loss—in glutathione levels. Methapyrilene hepatotoxicity was associated with an early loss in mitochondrial function, as indicated by mitochondrial swelling and significant losses in cellular ATP within 2 h. Co-incubation of methapyrilene-treated hepatocytes with inhibitors of inner mitochondrial transition permeability pore opening—cyclosporin A or the thiol reductant dithiothreitol—abrogated cell death suggesting that pore opening and loss of mitochondrial Ca²⁺ homeostasis play a significant role in methapyrilene-mediated cell death. Co-incubation of methapyrilene-treated hepatocytes with the phenylalkylamine calcium channel blocker verapamil—but not by treating cells in a nominally calcium-free medium—also abrogated cell death, suggesting that if Ca²⁺ is involved in cell killing then it is dependent on an intracellular Ca²⁺ pool. Pre-treatment of hepatocytes for 1 h with verapamil—to inhibit intracellular Ca²⁺ pool filling—increased the potency of verapamil protection against methapyrilene toxicity by approximately 100-fold. Taken together, these data indicate that methapyrilene intoxication leads to mitochondrial disfunction and suggest a critical role for a loss of mitochondrial Ca²⁺ homeostasis in this model of hepatocyte death.     

Inhibition of aftercontractions and phasic calcium release by yohimbine in ferret papillary muscle

Phasic release of calcium from the sarcoplasmic reticulum occurs in all mammalian cardiac preparations when the intracellular calcium concentration is sufficiently high. The phasic calcium release is often sufficient to trigger electrophysiological responses and aftercontractions. These can be detrimental to normal cardiac function. We induced phasic calcium release in ferret papillary muscles loaded with the calcium indicator aequorin. Development of phasic calcium release was associated with an increase in resting and peak [Ca²⁺]_i. Inhibiting sodium channels with yohimbine reduced resting [Ca²⁺]_i and prevented phasic calcium release. We propose a mechasism where by reduced [Na⁺]_i, and the subsequent increased efflux of calcium via sodium/calcium exchange reduced [Ca²⁺]_i.     

Tributyltin induces apoptotic signaling in hepatocytes through pathways involving the endoplasmic reticulum and mitochondria

Tri-n-butyltin is a widespread environmental toxicant, which accumulates in the liver. This study investigates whether tri-n-butyltin induces pro-apoptotic signaling in rat liver hepatocytes through pathways involving the endoplasmic reticulum and mitochondria. Tri-n-butyltin activated the endoplasmic reticulum pathway of apoptosis, which was demonstrated by the activation of the protease calpain, its translocation to the plasma membrane, followed by cleavage of the calpain substrates, cytoskeletal protein vinculin, and caspase-12. Caspase-12 is localized to the cytoplasmic side of the endoplasmic reticulum and is involved in apoptosis mediated by the endoplasmic reticulum. Tri-n-butyltin also caused translocation of the pro-apoptotic proteins Bax and Bad from the cytosol to mitochondria, as well as changes in mitochondrial membrane permeability, events which can activate the mitochondrial death pathway. Tri-n-butyltin induced downstream apoptotic events in rat hepatocytes at the nuclear level, detected by chromatin condensation and by confocal microscopy using acridine orange. We investigated whether the tri-n-butyltin-induced pro-apoptotic events in hepatocytes could be linked to perturbation of intracellular calcium homeostasis, using confocal microscopy. Tri-n-butyltin caused changes in intracellular calcium distribution, which were similar to those induced by thapsigargin. Calcium was released from a subcellular compartment, which is likely to be the endoplasmic reticulum, into the cytosol. Cytosolic acidification, which is known to trigger apoptosis, also occurred and involved the Cl(-)/HCO(3)(-) exchanger. Pro-apoptotic events in hepatocytes were inhibited by the calcium chelator, Bapta-AM, and by a calpain inhibitor, which suggests that changes in intracellular calcium homeostasis are involved in tri-n-butyltin-induced apoptotic signaling in rat hepatocytes.     

Intracellular calcium and neurotoxic events

Calcium is important in many intracellular regulatory processes. However, the maintenance of low levels of this cation within the cytosol is essential for maintenance of cell viability, in view of the large concentration gradient of ionic calcium across the plasma membrane. The expenditure of energy is needed to maintain intracellular calcium concentration [Ca²⁺]_i at normal levels. In addition, the integrity of the limiting membrane is also vital for this function. Thus, any disruption of membrane characteristics or of mitochondrial anabolic processes may lead to deleterious levels of [Ca²⁺]_i. The toxicity of a wide range of unrelated agents may, therefore, be in part due to elevation of cytosolic calcium. This general event may synergize with the more selective harmful properties of a compound, thus adversely affecting cell metabolism. The capacity now exists to measure levels of [Ca²⁺]_i in isolated cells or organelles such as synaptosomes. The use of such in vitro models can be of value in the evaluation of the neurotoxic potential of compounds. This method, in conjunction with the use of pharmacological agents known to act at specific sites, and with the use of radioactive calcium in translocation studies, also has utility in the delineation of the biochemical mode of action of neurotoxic agents.     

Mitochondrial dysfunction in bipolar disorder]

Phosphorus magnetic resonance spectroscopic studies in bipolar disorder revealed altered brain energy metabolism resembling that of chronic progressive external ophthalmoplegia (CPEO). Mood disorder is one characteristic symptom in several families of CPEO caused by mutations of three genes, ANT1, Twinkle, and POLG. Molecular genetic analysis revealed association of bipolar disorder with mitochondrial DNA (mtDNA) 10398A polymorphism, 3644C mutation, and FDUFV2. In the postmortem brains, increased levels of mtDNA 4977bp deletion and 3243G mutation, and altered expression of mitochondria-related genes were reported. Mitochondria play an important role in neuroplasticity and apoptotic signaling via regulating intracellular calcium homeostasis. Thus, mitochondrial dysfunction may cause altered calcium homeostasis and neuroplasticity, resulting in bipolar disorder. Most molecular genetic findings in bipolar disorder regarding mitochondria and endoplasmic reticulum stress signaling are common to Parkinson's disease and diabetes mellitus. Thus, it is possible that bipolar disorder is also a disease caused by the progressive loss of some neuronal cells.     

内质网应激与心房颤动研究进展

心房颤动（AF）是临床常见的持续性心律失常,是卒中和心力衰竭的独立危险因素,然而其具体发病机制尚不完全清楚。内质网是调控蛋白质合成、细胞内Ca2+浓度、氧化应激水平、诱导细胞凋亡信号通路的主要细胞器,在心律失常发生和发展中的作用日益受到重视。多种致病因素可导致内质网应激（ERS）,其主要通过未折叠蛋白反应（UPR）来恢复内质网稳态。ERS的过度激活可导致心房肌细胞Ca2+超载、氧化应激失衡和细胞凋亡,在AF的发病机制中发挥重要作用。本文对ERS和AF研究进展进行了综述。