Apoptosis of bile duct epithelial cells in hepatic allograft rejection

Liver biopsy remains the 'gold standard' for monitoring rejection in liver transplant patients. Portal inflammation, bile duct damage and endothelialitis are recognized features of hepatic allograft rejection. The pathogenesis of the bile duct injury during rejection, however, remains unclear. To define the mechanism of bile duct damage, we studied the light- and electronmicroscopic appearance of hepatic tissue from selected patients in whom allograft failure was solely due to rejection. Of the 25 orthotopic liver transplant rejection cases examined, 17 were mild, seven were moderate and one was severe rejection. Light microscopy examination of the damaged bile duct epithelium revealed evidence of apoptosis which was confirmed by electronmicroscopy. Furthermore, there appeared to be a positive correlation between the grade of rejection and the number of apoptotic cells. Also included in the study were 13 cases of chronic active hepatitis and 10 normal livers which showed the least apoptotic cells. We conclude that the identification of apoptotic cells in damaged bile ducts in allograft biopsies might be helpful in the diagnosis of rejection and in assessment of the severity of rejection.     

Gliotoxin non-selectively induces apoptosis in fibrotic and normal livers.

BACKGROUND: Liver fibrosis is the common response to chronic liver injury, ultimately leading to cirrhosis. Several lines of evidence indicate that inducing apoptosis of hepatic stellate cells (HSC) may lead to regression of liver fibrosis. Recently, it was shown that gliotoxin (GTX) induces apoptosis of HSC. However, the clinical use of GTX may be limited because of the lack of cell and tissue specificity, causing a high risk of potentially severe adverse effects. The aim of this study, therefore, was to study the effect of GTX on different cells of the liver. METHODS: We used normal and fibrotic precision-cut rat liver slices to study the effect of GTX on the various resident liver cell types. In these slices, the complex cell-cell interactions are preserved, which closely mimics the in vivo situation. RESULTS: GTX exhibited a potent apoptosis-inducing activity in these slices. Both immunohistochemical stainings and real-time mRNA techniques showed that this apoptosis-inducing effect was seen in HSC. However, Kupffer cells and liver endothelial cells were also affected by GTX, whereas hepatocytes were only mildly affected. CONCLUSIONS: This study indicates that the apoptosis-inducing strategy to treat liver fibrosis has high potential, but it will be necessary to develop an HSC-specific therapy to prevent adverse effects.     

PGE1 abolishes the mitochondrial-independent cell death pathway induced by D-galactosamine in primary culture of rat hepatocytes

Background and Aim:  PGE₁ reduces in vivo and in vitro D-galactosamine (D-GalN)-induced cell death in hepatocytes. The present study was undertaken to elucidate the intracellular pathway by which D-GalN induces cell death in cultured hepatocytes. In addition, we evaluated if PGE₁ was able to modulate different parameters related to D-GalN-induced apoptosis in cultured rat hepatocytes.
Methods:  Hepatocytes were isolated from male Wistar rats (225–275 g) by the classical collagenase procedure. PGE₁ (1 µM) was administered 2 h before D-GalN (5 mM) in primary culture of rat hepatocytes. Apoptosis was determined by DNA fragmentation and caspase-3, -6, -8 and -9 activation in hepatocytes. Caspase activation was evaluated by the detection of the related cleaved product and its associated activity. Cell necrosis was determined by the measurement of lactate dehydrogenase (LDH) activity in culture medium. To elucidate the role of mitochondria, we measured neutral (nSMase) and acid (aSMase) sphingomyelinase, as well as the expression of cytochrome c in mitochondria and cytoplasm fractions from D-GalN treated hepatocytes.
Results:  D-GalN induced caspase-3 activation and DNA fragmentation in hepatocytes. This apoptotic response was not associated with the activation of caspase-6, -8 or -9. The use of specific inhibitors confirmed that only caspase-3 was involved in D-GalN-induced apoptosis. D-GalN did not modify nSMase and aSMase activities, nor mitochondrial cytochrome c release in hepatocytes.
Conclusions:  D-GalN induced apoptosis through caspase-3 activation but without modification of the activity of caspase-6, -8, -9, SMases or cytochrome c release. PGE₁ appears to prevent D-GalN-induced apoptosis by a mitochondria-independent mechanism.     

不同浓度的富马毒素B1对肝癌细胞凋亡的影响

目的探讨不同浓度富马毒素对肝癌细胞凋亡的影响,为进一步研究富马毒素诱导凋亡的机制打下基础。方法利用PI标记的流式细胞术测定不同浓度下富马毒素对体外培养肝癌细胞凋亡率的影响。结果在1.25nmol/ml的富马毒素作用下凋亡率与空白没有差异,在2.5～40nmol/mlFB1的浓度范围内出现了明显的凋亡,随着富马毒素浓度的增加,体外培养的肝细胞凋亡率增加,且凋亡率在15nmol/ml达到高峰。结论富马毒素可导致肝癌细胞凋亡,随着浓度的递增,其凋亡率也随之递增。     

一氧化氮诱导肝癌细胞凋亡过程bcl-2和bax mRNA表达水平的变化

目的 探讨在一氧化氮(NO)诱导肝癌细胞凋亡过程bcl-2和bax mRNA表达水平的动态变化。方法 用NO供体硝普钠(SNP)诱导SMMC-7721和HepG2肝癌细胞株凋亡，RT-PCR的方法检测bcl-2、ba xmRNA表达水平，并采用凝胶分析系统进行半定量分析。结果 1．0mmol/L可降低SMMC-7721和HepG2细胞bcL2、bax mRNA的表达水平，提高bax/bc1-2 mRNA的比值并呈时间依赖性。HepG2细胞bcl-2和bax mRNA降低的幅度较SMMC-7721细胞小(P＜0．05)，开始变化的时间也较SMMC-7721细胞迟。结论 NO诱导肝癌细胞株的凋亡，可能与其bcl-2、bax mRNA表达水平变化导致bax/bc1-2 mRNA比值上升有关。     

灯盏花素对大鼠心肌缺血再灌注损伤诱导细胞凋亡的影响

目的观察灯盏花素（BRE）对大鼠心肌缺血再灌注（I/R）诱导细胞凋亡及凋亡相关基因Bcl-2、Bax表达的影响,并对其作用机制进行初步探讨。方法30只SD大鼠随机分为3组（n=10）:①假手术（Sham）组:前降支穿线不结扎,观察1.5 h;②缺血再灌注（I/R）组:结扎前降支30 m in,再灌注前5 m in生理盐水（4 mg/kg）iv,再灌注1h;③BRE组:再灌注前5 m in应用BRE（4 mg/kg）iv,余同I/R组。常规方法检测丙二醛（MDA）含量、超氧化物歧化酶（SOD）活性,免疫组化法测定Bc l-2、Bax蛋白的表达,通过细胞图像分析系统测量细胞阳性染色面积百分率,应用透射电镜观察心肌超微结构的变化。结果同I/R组相比,BRE组心肌组织MDA含量显著降低[（7.56±1.67）μmol/gvs（16.58±2.59）μmol/g,P<0.05],SOD活性显著升高[（2.37±0.22）mkat/gvs1.38±0.14 mkat/g,P<0.05],Bax蛋白表达显著降低（5.02±1.01vs18.59±5.68,P<0.01）,而Bc l-2蛋白表达显著增高（17.48±4.72vs7.32±2.05,P<0.01）,Bax/Bc l-2显著降低（0.29±0.57vs3.32±0.10,P<0.01）,细胞阳性染色面积百分率显著减少（0.42±0.06vs13.84±1.97,P<0.01）,细胞超微结构损伤明显减轻。结论BRE通过调控Bax/Bc l-2表达抑制心肌I/R诱导的细胞凋亡,对缺血再灌注心肌具有保护作用。     

褪黑素对大鼠脑缺血再灌注损伤及胞浆型磷脂酶A_2蛋白表达的影响

目的观察褪黑素在脑损伤时对脑细胞凋亡和胞浆型磷脂酶A2(cPLA2)蛋白的表达及相关介质的影响。方法采用线栓法制作大脑中动脉缺血再灌注模型,将78只雄性Wister大鼠随机分为假手术组(6只)、模型组(36只)、治疗组(36只)。用HE染色和TUNEL法检测各组海马CA1区神经细胞凋亡;用免疫组织化学法检测海马CA1区神经细胞中cPLA2蛋白表达;用ELISA法检测血清中TNF-α和前列腺素E2(PGE2)水平。结果与假手术组比较,模型组不同时间点凋亡细胞及cPLA2蛋白表达增强,且血清中TNF-α和PGE2水平也显著增高(P<0.01)。与模型组比较,治疗组能明显降低海马CA1区细胞凋亡数和cPLA2蛋白表达,同时也能降低血清中TNF-α和PGE2水平(P<0.01)。结论褪黑素对大鼠大脑中动脉缺血再灌注脑损伤有良好的保护作用:降低缺血再灌注后血清中TNF-α和PGE2水平,抑制缺血再灌注后海马CA1区cPLA2蛋白表达。     

595nm激光对兔耳瘢痕成纤维细胞增殖与凋亡的影响

目的：探讨595nmVbeam激光照射对增生性瘢痕动物模型伤口愈合过程中成纤维细胞增殖与凋亡的影响。方法：成年大耳白兔20只,建立兔耳腹侧面增生性瘢痕模型,对比研究在瘢痕形成过程中595nmVbeam激光照射对兔耳瘢痕成纤维细胞的影响,采用免疫组化方法检测增殖细胞核抗原（PCNA）蛋白表达和细胞凋亡的原位检测。结果：兔耳增生性瘢痕经595nmVbeam激光照射后,按不同时间段取材进行免疫组化染色并与对照组比较,高倍镜下观察结果,显示PCNA蛋白表达明显减弱,细胞凋亡增加。结论：595nmVbeam激光照射可抑制兔耳增生性瘢痕成纤维细胞的增殖过程,诱导细胞凋亡。应用595nmVbeam激光预防和治疗瘢痕是可行的。     

JNK通路可能介导MPTP诱导的黑质神经元凋亡

目的 探讨氧化应激激活的c-jun NH2-terminal kinase(JNK)细胞凋亡通路在1-甲基-4-苯基-1，2，3，6-四氢吡啶(MPTP)诱导帕金森病(PD)小鼠黑质神经元凋亡中的可能作用。方法 采用MPTP制备PD小鼠模型，应用生化技术检测黑质区域谷胱甘肽(GSH)浓度及超氧化物歧化酶(SOD)活力，尼氏体染色和酪氨酸羟化酶(TH)免疫组织化学染色观察黑质神经元的损害情况，原位缺口末端标记(TUNEL)染色和活化型Caspase 3免疫组织化学染色观察黑质神经元的凋亡情况，同时采用蛋白兔疫印迹法检测磷酸化JNK及磷酸化c-jun蛋白表达水平。结果 MPTP诱导的PD小鼠黑质区域GSH浓度明显降低，SOD活力明显升高，黑质致密带尼氏体阳性神经元和TH阳性神经元显著脱失，磷酸化JNK及磷酸化c-jun蛋白表达水平上升，同时活化型Caspase 3表达阳性细胞增多，黑质神经元TUNEL染色的阳性率增高。结论 MPTP可诱导小鼠黑质神经元凋亡，机制与增强氧化应激并激活JNK细胞凋亡通路有关。     

NGF对小脑皮质细胞凋亡影响的实验研究

目的　探讨神经生长因子 (NGF)对小脑皮质神经细胞凋亡的影响 ,为临床治疗小脑变性疾病提供新的措施。方法　以原代培养的新生SD乳鼠小脑皮质细胞建立谷氨酸诱导的神经细胞凋亡模型。为观察NGF对受损细胞的保护作用 ,应用MTT法测定细胞的存活率和细胞代谢情况 ;利用光学显微镜技术观察细胞凋亡的形态学改变。结果　Glu (5 0 0 μmol/L)作用 5min可诱导小脑神经细胞凋亡。MTT法计数结果显示 ,NGF高剂量治疗组细胞存活率显著高于模型组 (P <0 0 1) ,光学显微镜观察发现受损细胞的形态学变化也得到明显改善。结论　外源性NGF能够减轻大鼠小脑皮质神经细胞凋亡。