光敏化促进姜黄素诱导人胃癌MGC-803细胞凋亡

目的: 探讨光敏化促进姜黄素诱导人胃癌MGC-803细胞凋亡及其机制。方法: 用MTT法检测光敏化姜黄素对胃癌MGC-803细胞株的增殖抑制率,Hoechst 33258荧光染色观察细胞核形态的变化,流式细胞术检测细胞的凋亡率、线粒体膜电位、细胞内活性氧和Ca²⁺;比色法检测caspase-3、8和9酶活性;Western blotting分析细胞色素C、Bcl-2、Bax和热休克蛋白70(HSP70)水平。结果: 单纯姜黄素(5.0μmol/L)对MGC-803细胞增殖抑制率为(29.74±2.30)%,在光学显微镜下可见部分凋亡细胞,凋亡率为(12.54±1.75)%。而光敏化姜黄素组细胞增殖抑制率则为(44.93±3.61)%,在光学显微镜下能见明显细胞核形态改变,染色质凝集,凋亡小体形成,凋亡率为(26.58±2.67)%,细胞周期主要阻滞于G₀/G₁期。光敏化姜黄素显著降低线粒体膜电位,显著增加细胞色素C、细胞内活性氧和Ca²⁺以及caspase-3、8和9酶活性,与单纯姜黄素组比较,差异显著(P<0.01)。Western blotting结果显示光敏化姜黄素同时显著抑制Bcl-2和HSP70蛋白表达水平。结论: 光敏化姜黄素通过Bcl-2和线粒体途径增强其诱导胃癌MGC-803细胞凋亡的作用。     

老龄大鼠脑缺血再灌注ATP酶和自由基代谢变化及其意义

目的:从ATP酶活性变化和自由基损伤方面研究老龄大鼠脑缺血再灌注损伤的机制。方法:青年(5月龄)和老龄(20月龄以上)大鼠均分为模型组和正常对照组,观察大鼠全脑缺血30min再灌注60min后ATP酶和SOD活性及MDA、Ca^2＋、Na^＋、K^＋含量。结果:老龄模型组Ca^2＋水平高于青年模型组和老龄对照组。老龄对照组脑组织Na^＋-K^＋-ATP酶低于青年对照组,老龄模型组低于青年模型组。老龄对照组Ca^2＋-ATP酶低于青年对照组,老龄模型组低于青年模型组但高于老龄对照组。老龄对照组血清和脑组织中SOD活性低于青年对照组,老龄模型组低于青年模型组。老龄模型组血清和脑组织MDA/SOD比值高于老龄对照组。结论:脑缺血再灌注损伤与钙超载和自由基损伤有关,但由于老龄大鼠脑组织ATP酶和钙含量及自由基代谢的增龄变化,使脑缺血再灌注后这些病理改变较青年大鼠更为明显并具有一定特点。     

参麦注射液对大鼠急性心肌缺血再灌注损伤的影响

目的:观察参麦注射液对大鼠急性心肌缺血再灌注损伤的影响,并探讨其作用机制。方法:结扎冠状动脉左前降支10min再灌15min复制大鼠急性心肌缺血再灌注损伤模型,描记标准肢体Ⅱ导联心电图,测定心肌组织匀浆中超氧化物歧化酶(SOD)、Na⁺,K⁺-ATP酶和Ca²⁺-ATP酶活性及丙二醛(MDA)含量,电镜观察心肌线粒体改变。结果:参麦注射液使再灌注性心律失常的发生率低于模型组、持续时间较短,心肌组织匀浆中SOD、Na⁺,K⁺-ATP酶和Ca²⁺-ATP酶的活性高于模型组,MDA的含量低于模型组,心肌线粒体损伤轻于模型组。结论:参麦注射液对大鼠急性心肌缺血再灌注损伤有明显的防治作用,其机制与减轻氧自由基及钙超载损伤有关。     

L-精氨酸对兔缺血-再灌注心肌线粒体功能及结构的影响

目的:探讨L-精氨酸对心肌缺血-再灌注(MIR)时心肌细胞线粒体功能及结构的影响。方法:实验兔30只,随机分为正常对照组(control组)、心肌缺血-再灌注组(MIR组)和心肌缺血-再灌注+L-精氨酸治疗组(MRI+L-Arg组);分别观察心肌线粒体呼吸功能、Ca²⁺浓度([Ca²⁺]m)、丙二醛(MDA)浓度、超氧化物歧化酶(SOD)活性及超微结构的改变和心肌组织三磷酸腺苷(ATP)、二磷酸腺苷(ADP)、一磷酸腺苷(AMP)含量、总腺苷酸量(TAN)、能荷(EC)的变化。结果:MIR+L-Arg组线粒体呼吸控制率(RCR)、Ⅲ态呼吸速率(V₃)、SOD、面密度(Sv)、比表面(δ)明显高于MIR组,Ⅳ态呼吸速率(V₄)、[Ca²⁺]m、MDA、体密度(Vv)、横径(Hd)显著低于MIR组,心肌组织ATP、ADP、TAN及EC均明显高于MIR组;且与control组比较,V₃、V₄、SOD、MDA、Vv、Sv、δ、数密度(Nv)、纵径(Vd)及AMP、TAN无明显差异。结论:L-精氨酸可通过降低氧自由基水平和减轻钙超载,而改善缺血-再灌注心肌的线粒体功能及结构。     

灵芝孢子粉对戊四氮活化海马神经细胞bax表达的研究

目的本实验研究灵芝孢子粉对戊四氮活化大鼠海马神经细胞bax表达变化的影响,进一步探讨灵芝孢子粉的作用机制和癫痫与海马神经细胞凋亡调控基因之间的关系。方法通过制备癫痫模型和RT-PCR检测正常对照组、癫痫模型组和灵芝孢子粉用药组bax的表达。结果癫痫模型组和灵芝孢子粉用药组bax的表达较正常对照组(0.17±0.04)均升高;其中癫痫模型组(0.66±0.09)bax的表达水平与对照组(0.17±0.04)比较明显升高(P<0.01),灵芝孢子粉用药组(0.47±0.1)bax的表达水平与癫痫模型组比较明显降低(P<0.01),差异有统计学意义。结论本研究结果证实,在PTZ点燃癫痫后,模型组和治疗组促凋亡基因bax表达较正常对照组显著升高,表明bax基因在细胞凋亡的调控过程中起到促进作用,而给予灵芝孢子粉治疗后,bax的表达与模型组比较显著降低,提示灵芝孢子粉有效成份能充分作用于脑组织,可以调控bax的表达,借以发挥抗凋亡的神经保护作用。     

灵芝孢子粉对戊四氮活化海马神经细胞bad,bcl-xl和p53表达的研究

目的本研究探索灵芝孢子粉对癫痫大鼠海马神经细胞抗凋亡的保护作用及其作用机制,阐述癫痫与海马神经细胞凋亡调控基因之间的关系。方法通过制备癫痫模型和RT-PCR检测正常对照组、癫痫模型组和灵芝孢子粉用药组bad、bcl-xl、p53的m RNA表达。结果癫痫模型组和灵芝孢子粉用药组bad的表达较正常对照组均升高;其中癫痫模型组bad的表达水平与对照组比较明显升高(P0.01),灵芝孢子粉用药组bad的表达水平与癫痫模型组比较明显降低(P0.05),差异有统计学意义。癫痫模型组和灵芝孢子粉用药组bcl-xl的表达较正常对照组均降低;其中癫痫模型组bcl-xl的表达水平与正常对照组比较明显降低(P0.01),灵芝孢子粉用药组bcl-2的表达水平与癫痫模型组比较明显升高(P0.05),差异有统计学意义。癫痫模型组和灵芝孢子粉用药组p53的表达较正常对照组均升高;其中癫痫模型组p53的表达水平与对照组比较明显升高(P0.01),灵芝孢子粉用药组p53的表达水平与癫痫模型组比较明显降低(P0.05),差异有统计学意义。结论说明灵芝孢子粉可以通过对线粒体凋亡途径的调节,发挥抗凋亡的神经保护作用。     

灵芝孢子粉对癫痫大鼠脑组织IL-1β与c-Fos的影响

目的： 观察和探讨灵芝孢子粉对癫痫(EP)大鼠脑组织白细胞介素-1β（IL-1β）和c-Fos含量变化的影响。方法: 用放射免疫学方法检测IL-1β水平，用免疫组织化学方法检测c-Fos的表达。结果: 灵芝孢子粉组脑皮质和海马区c-Fos阳性细胞数明显少于癫痫模型组动物，脑组织中IL-1β明显低于癫痫模型组动物。结论: 灵芝孢子粉能够有效降低癫痫大鼠脑组织IL-1β水平，纠正免疫失调而起到抗癫痫作用；灵芝孢子粉能够抑制癫痫大鼠脑组织c-Fos的表达，阻断迟反应基因（LRG）以达到抗癫痫作用。     

实验性2型糖尿病大鼠心肌线粒体的氧自由基损伤

目的:研究糖尿病大鼠心肌线粒体氧自由基异常的机制。方法:测定正常对照组和链脲佐菌素(STZ)诱导的2型糖尿病大鼠心肌线粒体中一氧化氮(NO)、丙二醛(MDA)、细胞色素C(Cyt-C)和线粒体钙含量及超氧化物歧化酶(SOD)、一氧化氮合酶(NOS)活性,并用透射电镜观察病理学改变。结果:模型组心肌线粒体NO、NOS、MDA、钙和胞浆细胞色素C均显著高于对照组(P0.05);线粒体细胞色素C和SOD均显著低于对照组(P0.05)。电镜下,模型组肌原纤维排列紊乱,部分融解消失,线粒体肿胀变性,数目增多。结论:氧自由基异常及脂质过氧化作用参与糖尿病心肌的线粒体损伤;Cyt-C和线粒体钙的改变也是糖尿病心肌线粒体损伤的因素。     

亚低温缺血预处理对大鼠缺血再灌注肠保护作用的研究

目的:探讨亚低温缺血预处理对缺血再灌注肠的作用及机制。方法: 32只大鼠随机分为4组(每组8只),比较假手术对照组(sham)、缺血再灌注组(I/R)、缺血预处理组(IP)、亚低温预处理组(MHIP)小肠组织湿干重比、Ca²⁺-Mg²⁺-ATPase含量及血清乳酸脱氢酶(LDH)、超氧化物歧化酶(SOD)、丙二醛(MDA)水平、总抗氧化(TAX)能力的变化,并观察各组肠组织超微机构及Bcl-2、Bax蛋白表达。结果: 缺血再灌注后I/R组小肠湿干重比值、LDH、MDA含量、Bcl-2和Bax蛋白表达吸光度(A)值明显高于sham组(P<0.01);Ca²⁺-Mg²⁺-ATPase、SOD活性及TAX能力明显低于sham组(P<0.01)。IP组小肠湿干重比值、LDH、MDA含量、Bax蛋白表达吸光度值明显低于I/R组(P<0.01);Ca²⁺-Mg²⁺-ATPase 、SOD活性及TAX能力、Bcl-2蛋白表达吸光度(A)值明显高于I/R组(P<0.01)。结论: 亚低温缺血预处理通过增加肠组织自身抗氧化能力、抑制脂质过氧化、上调 bcl-2 基因的蛋白表达与下调bax基因的蛋白表达以抑制肠组织细胞凋亡的发生等机制对抗肠缺血再灌注损伤。     

苯那普利对自发性高血压大鼠心肌缺血-再灌注心功能、氧自由基和肌浆网Ca2+-ATP酶的影响

目的:探讨血管紧张素转换酶抑制剂(ACEI)对自发性高血压大鼠(SHR)心肌缺血-再灌注心功能、氧自由基和肌浆网Ca²⁺-ATP酶的影响。方法:30只10周龄雌性SHR分为2组,SHR对照组(SHR)、SHR+B组(每日10mg/kg苯那普利);另15只同周龄、同性别Wistar大鼠作为对照组(Wistar)。治疗12周后,每组大鼠结扎左冠状动脉前降支30min,再灌注30min,观察血流动力学参数,左室心肌丙二醛(MDA)含量、超氧化物岐化酶(SOD)活性及肌浆网(SR)Ca²⁺-ATP酶活性。结果:与Wistar组比较,SHR组血压、左心室重/体重较高,左心功能损害程度较重,心肌MDA含量较高,SOD活性和SRCa²⁺-ATP酶活性较低;SHR+B组血压、左心室重/体重、左心功能损害程度,SRCa²⁺-ATP酶活性无显著性差异,但心肌MDA含量较低,SOD活性较高。结论:苯那普利可逆转SHR左室肥厚,促进缺血-再灌注心肌SRCa²⁺-ATP酶活性的恢复和减少氧自由基损害,从而减轻缺血-再灌注心功能损伤。     

The mechanisms of neuronal death produced by mitochondrial toxin 3-nitropropionic acid: the roles of N-methyl-D-aspartate glutamate receptors and mitochondrial calcium overload

Previous studies showed that 3-nitropropionic acid, an irreversible inhibitor of succinate dehydrogenase, produced neuronal death secondary to perturbed intracellular calcium homeostasis. However, the response of intramitochondrial calcium ([Ca(2+)](m)) to 3-nitropropionic acid remains unknown. In this study, we investigated the roles of and relationships among [Ca(2+)](m) overload, mitochondrial reactive oxygen species, and mitochondrial membrane depolarization in 3-nitropropionic acid-induced neuronal death. Following 1 mM 3-nitropropionic acid treatment on primary rat neuronal cultures, there was a gradual increase of [Ca(2+)](m) beginning at 2-4 h post 3-nitropropionic acid application, and a twofold increase of mitochondrial reactive oxygen species at 4 h. These were followed by mitochondrial membrane depolarization at 6-8 h post-treatment. By inhibiting [Ca(2+)](m) uptake, Ruthenium Red attenuated the production of reactive oxygen species, and prevented the 3-nitropropionic acid-induced mitochondrial membrane depolarization and 70% of apoptotic neuronal death (P<0.001). Inhibition of caspase activation attenuated the elevation of [Ca(2+)](m) (P<0.001), indicating that caspase activation plays a role in the elevation of [Ca(2+)](m). MK-801, an antagonist of N-methyl-D-aspartate (NMDA) glutamate receptors, prevented 3-nitropropionic acid-induced [Ca(2+)](m) elevation, caspase-3 activation, mitochondrial depolarization, and neuronal death.We conclude that the activation of NMDA glutamate receptor contributes to mitochondrial alterations induced by 3-nitropropionic acid. Inhibition of its activation and [Ca(2+)](m) overload with subsequent mitochondrial membrane depolarization can therefore attenuate the neuronal death induced by 3-nitropropionic acid.     

Cytoplasmic and mitochondrial Ca levels in brown adipocytes

AIM: We elucidated the mitochondrial functions of brown adipocytes in intracellular signalling, paying attention to mitochondrial activity and noradrenaline- and forskolin-induced Ca(2+) mobilizations in cold-acclimated rats. METHODS: A confocal laser-scanning microscope of brown adipocytes from warm- or cold-acclimated rats was employed using probes rhodamine 123 which is a mitochondria-specific cationic dye, and the cytoplasmic and mitochondrial Ca(2+) probes fluo-3 and rhod-2. X-ray microanalysis was also studied. RESULTS: The signal of rhodamine 123 in the cells was decreased by antimycin A which effect was less in cold-acclimated cells than warm-acclimated cells. Cytoplasmic and mitochondrial Ca(2+) in cold-acclimated brown adipocytes double-loaded with fluo-3 and rhod-2 were measured. Noradrenaline induced the rise in cytoplasmic Ca(2+) ([Ca(2+)](cyto)) followed by mitochondrial Ca(2+) ([Ca(2+)](mito)), the effect being transformed into an increase in [Ca(2+)](cyto) whereas a decrease in [Ca(2+)](mito) by antimycin A or carbonyl cyanide m-chlorophenylhydrazone (CCCP). Antimycin A induced small Ca(2+) release from mitochondria. CCCP induced Ca(2+) release from mitochondria only after the cells were stimulated with noradrenaline. Further, forskolin also elicited an elevation in [Ca(2+)](cyto) followed by [Ca(2+)](mito) in the cells. The Ca measured by X-ray microanalysis was higher both in the cytoplasm and mitochondria whereas K was higher in the mitochondria of cold-acclimated cells in comparison to warm-acclimated cells. CONCLUSIONS: These results suggest that noradrenaline and forskolin evoked an elevation in [Ca(2+)](cyto) followed by [Ca(2+)](mito), in which H(+) gradient across the inner membrane is responsible for the accumulation of calcium on mitochondria. Moreover, cAMP also plays a role in intracellular and mitochondrial Ca(2+) signalling in cold-acclimated brown adipocytes.     

Analysis of cardiac mitochondrial Na+-Ca2+ exchanger kinetics with a biophysical model of mitochondrial Ca2+ handling suggests a 3:1 stoichiometry

Calcium is a key ion and is known to mediate signalling pathways between cytosol and mitochondria and modulate mitochondrial energy metabolism. To gain a quantitative, biophysical understanding of mitochondrial Ca(2+) regulation, we developed a thermodynamically balanced model of mitochondrial Ca(2+) handling and bioenergetics by integrating kinetic models of mitochondrial Ca(2+) uniporter (CU), Na(+)-Ca(2+) exchanger (NCE), and Na(+)-H(+) exchanger (NHE) into an existing computational model of mitochondrial oxidative phosphorylation. Kinetic flux expressions for the CU, NCE and NHE were developed and individually parameterized based on independent data sets on flux rates measured in purified mitochondria. While available data support a wide range of possible values for the overall activity of the CU in cardiac and liver mitochondria, even at the highest estimated values, the Ca(2+) current through the CU does not have a significant effect on mitochondrial membrane potential. This integrated model was then used to analyse additional data on the dynamics and steady-states of mitochondrial Ca(2+) governed by mitochondrial CU and NCE. Our analysis of the data on the time course of matrix free [Ca(2+)] in respiring mitochondria purified from rabbit heart with addition of different levels of Na(+) to the external buffer medium (with the CU blocked) with two separate models--one with a 2:1 stoichiometry and the other with a 3:1 stoichiometry for the NCE--supports the hypothesis that the NCE is electrogenic with a stoichiometry of 3:1. This hypothesis was further tested by simulating an additional independent data set on the steady-state variations of matrix free [Ca(2+)] with respect to the variations in external free [Ca(2+)] in purified respiring mitochondria from rat heart to show that only the 3:1 stoichiometry model predictions are consistent with the data. Based on these analyses, it is concluded that the mitochondrial NCE is electrogenic with a stoichiometry of 3:1.     

MCU在高糖诱导心肌H9c2细胞凋亡中的作用机制

目的:探讨线粒体钙离子单向转运体(mitochondrial calcium uniporter,MCU)在高糖(high glucose,HG)诱导心肌H9c2细胞凋亡中的作用机制。方法:将心肌H9c2细胞随机分为3组:对照(control)组,5.5 mmol/L葡萄糖处理细胞;HG组,25 mmol/L葡萄糖处理细胞;精胺(spermine,Sp)干预(HG+Sp)组,25 mmol/L葡萄糖和5μmol/L Sp共同处理细胞。Western blot检测H9c2细胞MCU、caspase-9和caspase-3蛋白的表达;RT-qPCR检测H9c2细胞MCU的mRNA水平;Rhod-2 AM探针检测线粒体内Ca2+的荧光强度;吸光度法检测丙酮酸脱氢酶(pyruvate dehydrogenase,PDH)的活性;萤火虫萤光素酶检测细胞裂解液ATP的浓度;JC-1染色法检测线粒体膜电位(mitochondrial membrane potential,Δψm);MitoSOXTM染色法检测线粒体活性氧簇(reactive oxygen species,ROS)水平。结果:与control组相比,HG组MCU mRNA和蛋白水平、线粒体内Ca2+浓度、PDH活性、细胞ATP浓度及Δψm降低(P<0.05),而ROS水平及caspase-9和caspase-3凋亡蛋白表达增加(P<0.05);与HG组相比,HG+Sp组线粒体内Ca2+浓度、PDH活性、细胞ATP浓度和Δψm增加(P<0.05),而ROS水平及caspase-9和caspase-3凋亡蛋白表达降低(P<0.05)。结论:高糖通过降低MCU表达导致其活性下降,从而促进心肌H9c2细胞凋亡,其机制可能与线粒体的钙离子稳态失衡、三羧酸循环障碍和线粒体功能损伤有关。     

胆道梗阻对肝线粒体功能损伤机制的初步研究

目的：初步探讨胆道梗阻对肝线粒体功能损伤的机制。方法：复制犬胆道梗阻模型,观察梗阻的不同时段肝线粒体呼吸功能、钙含量、钙摄取率、丙二醛（MDA）含量及超氧化物歧化酶（SOD）含量的变化。结果：胆道梗阻2周、3周、4周及5周各组（Ⅱ－V组）分别与假手术组（Ⅰ组）比较：①肝线粒体呼吸控制率、钙摄取率及SOD含量均明显下降（Ⅱ组P＜0.05,其余组P＜0．01）②线粒体钙含量均明显升高（Ⅱ组P＜0．05,其余组p＜0．01）③线粒体MDA含量明显升高（各组P＜0.01）。相关分析显示,线粒体钙含量、MDA含量与线粒体呼吸控制率变化之间均呈现显著的负相关（P＜0．01）。结论：胆道梗阻后肝线粒体呼吸功能受到明显损伤,钙超载及脂质过氧化反应是造成线粒体外能损害的可能机制。     

Shifts in calcium in ischemic and reperfused rat hearts: a cytochemical and morphometric study of the effects of diltiazem

Effects of diltiazem upon mitochondrial ultrastructure and distribution of calcium were studied following ischemia (27 minutes) and reperfusion (30 minutes). Hearts receiving no drug recovered low contractile function, while mitochondria nearly doubled in cross-sectional area (0.98 vs 0.56 micron 2) and were structurally damaged (1.88 vs 0.17 score). Mitochondria contained fine calcium deposits (0.029-micron diam) in mildly damaged cells, larger deposits in moderately damaged cells, and a large deposit (0.17-0.29-micron diam) in severely injured cells. Glycocalyx Ca2+ stain, observed in nonischemic hearts, was reduced in moderately and severely damaged cells. Increased mitochondrial Ca2+ may be associated with loss of glycocalyx Ca2+. Diltiazem (7.5 microns), added before ischemia, improved recovery of contractile function and prevented mitochondrial swelling, structural grade change, and increase in mitochondrial Ca2+. Reduction in mitochondrial Ca2+ stain by diltiazem was associated with the maintenance of normal glycocalyx Ca2+.     

Ruthenium red-induced transition from ventricular fibrillation to tachycardia in isolated rat hearts:: possible involvement of changes in mitochondrial calcium uptake

INTRODUCTION: Ventricular tachycardia (VT) is considered to be the most common precursor of ventricular fibrillation (VF) and sudden cardiac death. However, the mechanisms underlying the transition from VT to VF remain unclear despite more than a century of study. Here, we investigated whether perfusion of the heart with blockers of mitochondrial Ca(2+) uniporter changed the macrodynamics of the heart between VT and VF. METHODS: The experiments were performed using Langendorff perfused isolated rat hearts in which left ventricular pressure (LVP) and left ventricular cardiomyogram (LVCMG) were measured. Sustained VT or VF was induced by burst pacing of the left ventricular muscles. RESULTS: During pacing-induced sustained VF, perfusion of the heart with ruthenium red (RR) or Ru 360, blockers of mitochondrial Ca(2+) uniporter, resulted in the reversible conversion of VF to VT. In contrast, during pacing-induced sustained VT, perfusion of the heart with spermine, an activator of mitochondrial Ca(2+) uptake, resulted in the reversible conversion of VT to VF, and the effect was antagonized by cotreatment with RR. In addition, RR-induced conversion of VF to VT was antagonized by cotreatment with S(-)-Bay K8644 (Bay K), an activator of L-type Ca(2+) channels, suggesting that the inactivation of L-type Ca(2+) channels was responsible for the RR-induced effect on the macrodynamics of hearts. In fact, perfusion with verapamil, an antagonist of L-type Ca(2+) channels, during pacing-induced sustained VF, resulted in the conversion of VF to VT. CONCLUSION: This study demonstrated that perfusion of isolated rat hearts with blockers of Ca(2+) uptake by mitochondria resulted in the reversible conversion of pacing-induced sustained VF to VT, suggesting that changes in mitochondrial Ca(2+) uptake were possibly involved in the transition between VT and VF.     

Mitochondrial Ca2+ flux is a critical determinant of the Ca2+ dependence of mast cell degranulation

An increase in intracellular Ca2+ ([Ca2+]i) is necessary for mast cell exocytosis, but there is controversy over the requirement for Ca2+ in the extracellular medium. Here, we demonstrate that mitochondrial function is a critical determinant of Ca2+ dependence. In the presence of extracellular Ca2+, mitochondrial metabolic inhibitors, including rotenone, antimycin A, and the protonophore carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP), significantly reduced degranulation induced by immunoglobulin E (IgE) antigen or by thapsigargin, as measured by beta-hexosaminidase release. In the absence of extracellular Ca2+; however, antimycin A and FCCP, but not rotenone, enhanced, rather than reduced, degranulation to a maximum of 76% of that observed in the presence of extracellular Ca2+. This enhancement of extracellular, Ca2+-independent degranulation was concomitant with a rapid collapse of the mitochondrial transmembrane potential. Mitochondrial depolarization did not enhance degranulation induced by thapsigargin, irrespective of the presence or absence of extracellular Ca2+. IgE antigen was more effective than thapsigargin as an inducer of [Ca2+]i release, and mitochondrial depolarization augmented IgE-mediated but not thapsigargin-induced Ca2+ store release and mitochondrial Ca2+ ([Ca2+]m) release. Finally, atractyloside and bongkrekic acid [an agonist and an antagonist, respectively, of the mitochondrial permeability transition pore (mPTP)], respectively, augmented and reduced IgE-mediated Ca2+ store release, [Ca2+]m release, and/or degranulation, whereas they had no effects on thapsigargin-induced Ca2+ store release. These data suggest that the mPTP is involved in the regulation of Ca2+ signaling, thereby affecting the mode of mast cell degranulation. This finding may shed light on a new role for mitochondria in the regulation of mast cell activation.     

Regucalcin increases Ca2+-ATPase activity in the heart mitochondria of normal and regucalcin transgenic rats

The role of regucalcin, a regulatory protein in intracellular signaling system, in the regulation of Ca2+-ATPase activity in rat heart mitochondria was investigated. Mitochondrial Ca2+-ATPase activity was significantly increased by increasing concentrations of CaCl2 (2.5-50 microM). An increase in the enzyme activity was saturated at 50 microM CaCl2. The addition of regucalcin (10(-11)-10(-8) M) in the enzyme reaction mixture caused a significant increase in Ca2+-ATPase activity in heart mitochondria in the presence of 50 microM CaCl2. Regucalcin did not have a significant effect on mitochondrial Mg2+-ATPase activity. Regucalcin (10(-9) M) did not have a significant effect on Ca2+-ATPase activity in the presence of digitonin (10(-3) or 10(-2) %), which is a solubilization effect on membranous lipids. The effect of regucalcin in increasing mitochondrial Ca2+-ATPase activity was not observed in the presence of ruthenium red (10(-7) M) or lanthanum chloride (10(-7) M), which is an inhibitor of Ca2+ uniporter. The effect of regucalcin (10(-9) M) in increasing mitochondrial Ca2+-ATPase activity was not significantly enhanced in the presence of calmodulin (5 microg/ml) or dibutyryl cyclic AMP (10(-4) M), which is an intracellular signaling factor that can cause a significant increase in the enzyme activity. Mitochondrial regucalcin localization was significantly increased in the heart of regucalcin transgenic rats as compared with that of normal rats using Western blot analysis. Ca2+-ATPase activity was significantly increased in the heart mitochondria of regucalcin transgenic rats. This study demonstrates that regucalcin has an activating effect on Ca2+-ATPase in rat heart mitochondria, suggesting its role in the regulation of heart mitochondrial function.