FAS/FASL系统介导的生精细胞凋亡在男性生殖中的作用

生精细胞凋亡是机体清除过量及缺陷生精细胞的正常生理机制,其病理状态下的过度凋亡会导致少、弱精子症发生.FAS/FASL系统是介导哺乳动物睾丸生精细胞凋亡的主要途径.FASL特异性的与生精细胞膜上的FAS结合后,通过胞内肽段的死亡结构域激活相关的半胱天冬氨酸酶级联反应,诱导其凋亡.FAS/FASL系统在调节生精细胞凋亡中发挥重要作用,FAS与FASL的结合可触发细胞凋亡,是人体生长发育过程中正常的生理现象,但其过度表达会对精子数量质量产生不利影响.本文综述FAS/FASL系统在生精细胞凋亡中的作用,并讨论与之相关的特发性少、弱精子症所致男性不育.     

睾丸中生殖细胞凋亡通路的调节机制研究进展

细胞凋亡是生物体细胞的主动消亡过程,是多细胞有机体调控机体生长发育、控制细胞衰老,并维持机体内外环境稳定的重要机制,也是当今生命科学领域的热点。而细胞凋亡作为一种维持体内平衡的基本生物学过程,在睾丸中细胞的分化、精子的成熟及存活中也发挥着重要作用。在精子发生的过程中,任何环节的改变都有可能影响凋亡过程的进行,从而破坏生殖细胞存活与死亡之间的平衡。目前研究表明,线粒体通路、细胞死亡受体通路以及内质网通路是睾丸中生殖细胞凋亡的重要途径,且上述3条通路中各因子之间互相影响,从而形成了复杂的生殖细胞凋亡调控网络。本文对近年来国内外关于睾丸生殖细胞凋亡通路研究的相关文献进行回顾与总结,具体阐述3条通路的相关调节机制。     

生精细胞凋亡与激素调控

生精过程中细胞凋亡既可维持正常精子数量又是导致少精无精症的重要机制之一 ,目前越来越多的研究表明 ,激素对生精细胞凋亡的调控有着重要作用。本文就T、FSH、LH、E2、PRL等激素对生精细胞凋亡的影响及机制作一综述。     

雷公藤多甙抑制大鼠精子发生的研究

目的探讨雷公藤多甙对大鼠精子发生的抑制作用及其可能的信号通路。方法成年雄性大鼠给予雷公藤多甙(16 mg/kg)灌胃,每日1次,在2及6周检测血清睾酮(T)、卵泡刺激素(FSH)、黄体生成素(LH)和可的松水平;光镜观察睾丸组织的形态学变化;原位末端标记法(TUNEL)观察睾丸生精细胞凋亡;免疫组织化学法观察凋亡通路相关蛋白Bax/Bcl-2的表达。结果给药组与对照组相比,性激素、肾上腺皮质激素均无显著变化(P均>0.05);给药2周后精子数下降和畸形率上升(P<0.05),给药4和6周精子数下降和畸形率升高更显著(P<0.001);组织学检查给药组大鼠生精小管内各级精母细胞和精子细胞数明显减少,生精细胞排列紊乱,原始精原细胞和支持细胞(Sertoli细胞)未见明显改变。与正常对照组相比,生精小管内生精细胞凋亡显著增加(2周P<0.05,4和6周P<0.001)。凋亡相关蛋白Bax表达明显上调,Bcl-2表达无显著差异。结论雷公藤对大鼠精子发生的抑制作用表现为增加生精细胞凋亡,导致精子计数下降,精子的畸形率升高。雷公藤多甙使睾丸Bax表达增加,与诱导生精细胞凋亡相关,可能是相关的信号通路之一。进一步研究雷公藤多甙作用的分子信号机制有助于今后降低剂量、减少毒副作用,探讨其作为一种安全的男性避孕药可能性。     

生精细胞凋亡与激素调控

生清过程中细胞凋亡既可维持正常精子数量又是导致少精无精症的重要机制之一，目前越来越多的研究表明，激素对生精细胞凋亡的调控有着重要作用。本文就T、FSH、LH、E2、PRL等激素对生精细胞凋亡的影响及机制作一综述。     

睾丸生精细胞体外培养的研究进展

精子的产生是一个高度复杂有序的过程,涉及细胞的增殖和分化。生精细胞体外培养系统包括组织培养和细胞培养两大类,本文对生精细胞体外培养和睾丸组织块培养的研究进展及生精细胞的培养条件作一综述,归纳出各种培养方法的优缺点,旨在寻求生精细胞在体外的最佳分化途径,使精子体外培养成为研究和治疗男性不育的重要手段。     

GABA受体调节精子顶体反应和获能的研究进展

GABA受体广泛分布于哺乳动物生殖系统,包括睾丸生精细胞和精子。研究发现GABA受体在受精过程中精子重要生理变化——顶体反应和获能中起着重要调节作用,其可能是体内激素孕酮和透明带诱发顶体反应的作用靶点之一。GABA受体促进顶体反应和获能作刚可能与其调节细胞膜电位从而介导胞膜电压依赖性钙通道开放有关,其机制可能还涉及多种信号通路。本文就目前GABA受体调节精子顶体反应和获能作用的研究现状作一综述。     

GABA受体调节精子顶体反应和口获能的研究进展

GABA受体广泛分布于哺乳动物生殖系统,包括睾丸生精细胞和精子.研究发现GABA受体在受精过程中精子重要生理变化——顶体反应和获能中起着重要调节作用,其可能是体内激素孕酮和透明带诱发顶体反应的作用靶点之一.GABA受体促进顶体反应和获能作用可能与其调节细胞膜电位从而介导胞膜电压依赖性钙通道开放有关,其机制可能还涉及多种信号通路.本文就目前GABA受体调节精子顶体反应和获能作用的研究现状作一综述.     

雄激素与精子发生的关系

雄激素被认为在精子发生中具有重要作用.近年的动物实验以及临床研究提示,雄激素可以导致严重少精子或者无精子症,内源性睾酮可以引起生精细胞凋亡,与生精细胞阻滞高度相关.本文对近年的材料进行分析后,认为雄激素与精子发生的关系在于,雄激素可以引起生精细胞凋亡,造成细胞重排,对精子发生起到调节作用.     

输精管结扎诱发生精细胞凋亡的研究进展

生精过程是一个精细的调节过程 ,近年生精细胞凋亡的研究进展非常迅速。输精管结扎作为一种刺激因素影响生精细胞凋亡 ,研究表明输精管结扎可使生精细胞凋亡增多。输精管结扎诱导生精细胞凋亡的机制与输精管压力增高、NO作用的影响、基因调控及睾酮水平等有关。本文综述了近年对输精管结扎诱发生精细胞凋亡的研究 ,这对未来男性生殖系统更深入的研究有重要作用     

Mitochondrial involvement in fas-mediated apoptosis of human lumbar disc cells

BACKGROUND: Two main pathways of Fas-mediated apoptosis have been identified: the Type-I (death-inducing signaling complex) pathway and the Type-II (mitochondrial) pathway. While apoptotic cell death has been implicated in lumbar degenerative disc disease, we are not aware of any studies in which surgically removed discs from live humans have been examined to determine which of the two pathways is involved in the apoptosis of disc cells. As an initial step in the development of therapies to inhibit inappropriate or premature apoptosis of disc cells, our objective was to determine which pathway is involved. METHODS: We examined thirty-two samples of herniated lumbar disc tissue with use of immunohistochemical staining and Western blot analysis to determine the presence of several proteins, including caspase-8 (associated with the Type-I pathway); BID (BH3 interacting domain death agonist), cytochrome-c, and caspase-9 (associated with the Type-II pathway); and caspase-3 (an executioner of apoptosis). The TUNEL (terminal deoxynucleotidyl transferase [TDT]-mediated dUTP nick end labeling) assay was performed to confirm the occurrence of apoptosis of the disc cells. RESULTS: The proteins associated with the Type-II pathway (BID, cytochrome-c, and caspase-9) stained positively in all samples. Although the protein associated with the Type-I pathway (caspase-8) was not detected on immunohistochemical analysis, a small amount of caspase-8 was detected on Western blot analysis. However, the expression of Type-II proteins was still higher than the expression of caspase-8 on Western blot analysis. The expression of caspase-3 was identified in all samples with immunohistochemical and Western blot analysis. TUNEL-positive disc cells were identified in all samples. CONCLUSIONS: The results of the present study suggest that human disc cells are Type-II cells, which undergo apoptotic cell death through mitochondrial involvement.     

血管紧张素Ⅱ通过抑制AKT/蛋白激酶B磷酸化诱导肾小管上皮细胞凋亡

目的观察血管紧张素Ⅱ(AngⅡ)在诱导肾小管上皮细胞凋亡的信号传导是否有磷脂酰肌醇3激酶(PI3K)-AKT信号系统的参与,及该系统在诱导细胞凋亡中的作用。方法大鼠肾小管上皮细胞株NRK-52E分别与终浓度为0(对照组)、10-9mol/L、10-8mol/L、10-7mol/L、10-5mol/LAngⅡ共培养24h。用流式细胞仪检测细胞凋亡指数,用免疫组化方法检测增殖细胞核抗原(PCNA)的表达。Western印迹检测PI3K及磷酸化AKT和总AKT蛋白表达,AKT的磷酸化水平用473位丝氨酸磷酸化AKT(AKT-ser473)水平与总AKT水平的比值表示。结果随着AngⅡ浓度的增加,10-6mol/LAngⅡ组与对照组相比,凋亡指数显著增加[(22.7±1.41)%比(3.0±0.75)%,P<0.01]。而10-9mol/LAngⅡ组与对照组相比,PCNA指数显著增强[(47.54±2.6)%比(22.63±2.5)%,P<0.01]。与对照组相比,PI3K-p85蛋白的表达随AngⅡ浓度增加表现为先激活后抑制。AKT的磷酸化具有明显的AngⅡ浓度依赖性,随AngⅡ浓度的增加而逐渐受到抑制,并与细胞凋亡指数呈显著负相关(r=-0.90,P<0.01)。结论AngⅡ可以诱导肾小管上皮细胞凋亡并抑制细胞的增殖,可能部分是通过抑制PI3K-AKT信号传导途径实现的。     

Endoplasmic reticulum stress-induced apoptosis is partly mediated by reduced insulin signaling through phosphatidylinositol 3-kinase/Akt and increased glycogen synthase kinase-3beta in mouse insulinoma cells

An imbalance between the rate of protein synthesis and folding capacity of the endoplasmic reticulum (ER) results in stress that has been increasingly implicated in pancreatic islet beta-cell apoptosis and diabetes. Because insulin/IGF/Akt signaling has been implicated in beta-cell survival, we sought to determine whether this pathway is involved in ER stress-induced apoptosis. Mouse insulinoma cells treated with pharmacological agents commonly used to induce ER stress exhibited apoptosis within 48 h. ER stress-induced apoptosis was inhibited by cotreatment of the cells with IGF-1. Stable cell lines were created by small-interfering RNA (siRNA) with graded reduction of insulin receptor expression, and these cells had enhanced susceptibility to ER stress-induced apoptosis and reduced levels of phospho-glycogen synthase kinase 3beta (GSK3beta). In control cells, ER stress-induced apoptosis was associated with a reduction in phospho-Akt and phospho-GSK3beta. To further assess the role of GSK3beta in ER stress-induced apoptosis, stable cell lines were created by siRNA with up to 80% reduction in GSK3beta expression. These cells were found to resist ER stress-induced apoptosis. These results illustrate that ER stress-induced apoptosis is mediated at least in part by signaling through the phosphatidylinositol 3-kinase/Akt/GSK3beta pathway and that GSK3beta represents a novel target for agents to promote beta-cell survival.     

JAK2-STAT3信号通路在肝细胞癌中的研究进展

近年来发现,JAK2-STAT3信号通路参与肿瘤细胞的生长、增殖、分化、转移、凋亡。在肝细胞癌(HCC)细胞中的JAK蛋白和STAT蛋白过表达,JAK2-STAT3信号通路与HCC发生发展密切相关。笔者就JAK2-STAT3信号通路在HCC的研究进展做一综述。     

Inhibition of c-Jun N-terminal kinase ameliorates apoptosis induced by hydrogen peroxide in the kidney tubule epithelial cells (NRK-52E)

BACKGROUND: Hydrogen peroxide (H2O2)-induced apoptosis has been shown to be involved in ischemic and toxic tubular damage. Recent studies have revealed that oxidative stress can activate c-Jun N-terminal kinase (JNK), and the oxidative stress-JNK pathway is an important apoptotic pathway of cells exposed to various stresses. The present study was designed to investigate JNK activation and the effects of the JNK pathway inhibition during H2O2-induced apoptosis in kidney epithelial tubule cells (NRK-52E). MATERIALS AND METHODS: NRK-52E cells were treated with 0-500 microM H2O2 and/or 100 microM quercetin (an inhibitor of the JNK pathway). Apoptosis was assessed by flow cytometry analysis and DNA ladder. JNK activity was assessed by the GST-c-Jun (1-169) binding/protein kinase assay. RESULTS: H2O2 induced apoptosis in NRK-52E cells in a concentration-dependent manner, which was demonstrated by the reduced DNA PI staining, externalization of phosphatidylserine and DNA ladder. Apoptosis induced by H2O2 was accompanied by JNK activation and up-regulated JNK activity. Quercetin treatment suppressed the JNK activity and ameliorated apoptosis induced by H2O2. CONCLUSIONS: H2O2 induced apoptosis in NRK-52E cells, which was associated with activation and up-regulation of JNK. Quercetin treatment could decrease JNK activity and ameliorate H2O2-induced apoptosis.     

Experimental validation of deuterium oxide-mediated antitumoral activity as it relates to apoptosis in murine malignant astrocytoma cells

OBJECT: Deuterium oxide (D2O), or heavy water, affects a variety of biological activities different from those of water. The authors examined the antitumoral effect of D2O on brain neoplasms and demonstrated D2O-mediated cytotoxicity by using a Rous sarcoma virus-induced murine malignant astrocytoma cell line, RSVM. The mechanism of the observed cytotoxicity may involve D2O-induced apoptosis and cell-cycle modulation. METHODS: The authors performed an assay with methylthiazol tetrazolium bromide and a trypan blue dye exclusion test to confirm in vitro D2O-mediated cytotoxicity for RSVM cells. At D2O concentrations of 10 to 50%, the cytotoxic effect was dose and time dependent. Flow cytometry analysis revealed programmed cell death (apoptosis) and the accumulation of RSVM cells during the G2/M phase. By applying the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling method, fluorescein isothiocyanate-annexin V and propidium iodide double staining, and caspase-family protease activity analysis, the authors demonstrated both DNA fragmentation and enhancement of caspase activity after a 48-hour treatment with D2O, thus indicating that D2O induces apoptosis in RSVM cells. Apoptotic DNA fragmentation was completely abolished by the caspase inhibitor Z-VAD-FMK (benzyloxycarbonil-Val-Ala-Aps-fluoromethylketone). The findings indicate that the caspase activation pathway may be involved in D2Oinduced apoptosis. CONCLUSIONS: The authors found that D2O is cytotoxic to malignant astrocytoma cells. The mechanism of D2O-mediated cytotoxicity involved the induction of apoptosis and cell accumulation during the G2/M phase. This D2O-induced apoptosis is modulated through the caspase activation pathway.     

Oxidant-induced apoptosis of glomerular cells: intracellular signaling and its intervention by bioflavinoid

Oxidant stress plays a crucial role in the generation of a wide range of glomerular disease. In the first part of this article, we describe intracellular signaling pathways involved in the oxidant-initiated apoptosis of mesangial cells, especially highlighting the tyrosine kinase-c-Jun/AP-1 pathway. In the second part, we address a novel potential of bioflavonoid quercetin as an inhibitor of apoptosis in glomerular cells. Possible mechanisms for the antiapoptotic action of quercetin and its therapeutic utility are discussed.     

Lidocaine induces apoptosis via the mitochondrial pathway independently of death receptor signaling

BACKGROUND: Local anesthetics, especially lidocaine, can lead to persistent cauda equina syndrome after spinal anesthesia. Recently, lidocaine has been reported to trigger apoptosis, although the underlying mechanisms remain unknown. To elucidate the pathway of lidocaine-induced apoptosis, the authors used genetically modified cells with overexpression or deficiencies of key regulators of apoptosis. METHODS: Human Jurkat T-lymphoma cells overexpressing the antiapoptotic protein B-cell lymphoma 2 as well as cells deficient of caspase 9, caspase 8, or Fas-associated protein with death domain were exposed to lidocaine and compared with parental cells. The authors evaluated cell viability, mitochondrial alterations, cytochrome c release, caspase activation, and early apoptosis. Apoptosis was in addition investigated in neuroblastoma cells. RESULTS: In Jurkat cells, lidocaine reduced viability, associated with a loss of the mitochondrial membrane potential. At low concentrations (3-6 mm) of lidocaine, caspase 3 was activated and release of cytochrome c was detected, whereas at higher concentrations (10 mm), no caspase activation was found. Apoptosis by lidocaine was strongly reduced by B-cell lymphoma-2 protein overexpression or caspase-9 deficiency, whereas cells lacking the death receptor pathway components caspase 8 and Fas-associated protein with death domain were not protected and displayed similar apoptotic alterations as the parental cells. Lidocaine also induced apoptotic caspase activation in neuroblastoma cells. CONCLUSIONS: Apoptosis is triggered by concentrations of lidocaine occurring intrathecally after spinal anesthesia, whereas higher concentrations induce necrosis. The data indicate that death receptors are not involved in lidocaine-induced apoptosis. In contrast, the observation that B-cell lymphoma-2 protein overexpression or the lack of caspase 9 abolished apoptosis clearly implicates the intrinsic mitochondrial death pathway in lidocaine-induced apoptosis.     

Apoptosis in right-ventricle biopsy is not predictive of graft survival

Myocardial dysfunction is common in grafted hearts from brain-dead donors, but the mechanisms involved remain unclear, although apoptosis has been suggested to play an important role. In this study, we investigated the presence of apoptotic myocardial cells in donor hearts as compared to control hearts to determine whether pre-existing apoptosis can predict donor heart dysfunction. Apoptosis was studied by in situ DNA fragmentation assay and by Western Blotting for caspase-3, the pivotal executive caspase of the apoptotic pathway. We show that brain-death induced myocardial apoptosis was not predictive of myocardial dysfunction in transplanted hearts.     

Induction and mechanism of apoptotic cell death by propofol in HL-60 cells

BACKGROUND: Apoptosis (programmed cell death) occurs in various physiological and pathological conditions, exhibits a characteristic mechanism of intracellular sequential reaction and may be involved in determining clinical outcome. The antioxidant activity of propofol (2,6-diisopropylphenol) together with the stimulating effect of protein kinase C suggests that propofol might have the potential to modulate apoptosis. Thus, it is of both clinical interest and biomedical importance to investigate and clarify the effect and mechanism of propofol upon the intracellular reactions underlying apoptotic cell death. METHODS: The effect of propofol on apoptosis was investigated using cultured human promyelocytic leukemia HL-60 cells. This well-characterized cell line is useful for the study of apoptosis because the various biochemical steps occurring during apoptosis have been well documented. RESULTS: Treatment of HL-60 cells with propofol resulted in growth inhibition with the formation of apoptotic bodies in a concentration-dependent manner. DNA fragmentation and ladder formation was also observed in a concentration-dependent manner. Propofol treatment resulted in activation of caspase-3, -6, -8 and -9, thereby suggesting that cell surface death receptor activation of the caspase cascade mediates propofol-induced apoptosis with consequent formation of the cleaved product of Bid (a pro-apoptotic Bcl-2 family member protein) and activation of the mitochondrial pathway with cytosolic release of cytochrome c. CONCLUSION: Propofol may induce apoptosis, which is dependent on the mechanism that activates both the cell surface death receptor pathway and the mitochondrial pathway.