大鼠肝缺血-再灌流损伤脑组织p38MAPK与脑细胞凋亡的关系

目的观察肝缺血-再灌流损伤过程中大脑皮质层p38有丝分裂素激活蛋白激酶(p38MAPK) 的变化和神经元凋亡,以探讨p38 MAPK与脑组织神经元凋亡的关系。方法建立肝缺血-再灌流损伤动物模型,分为对照组、缺血30 min组(I组)、缺血30 min再灌流组(I／R组)、缺血30 min再灌流后1 h组(I/ R 1h)、缺血30 min再灌流后2 h组(I／R 2h)、缺血30 min再灌流后4 h组(I/R 4h)。应用免疫组化法测定各组肝组织中iNOS的变化和脑皮质层p38MAPK的改变,应用原位细胞凋亡法测定神经元凋亡,同时观察肝和脑组织病理学改变。结果肝缺血-再灌流损伤形成过程中,随着再灌流时间延长肝组织出现iNOS的高表达,同时大脑皮层出现p38MAPK改变和神经元凋亡。肝组织iNOS与p38MAKP呈正相关(r=0．91,P <0．05)。p38MAPK的表达与phospho-p38MAPK的表达呈正相关(r=0．89,P<0．05),phospho-p38MAPK的表达与凋亡指数呈正相关(r=0．95,P<0．05)。HE染色见肝细胞水肿,炎性细胞浸润,甚至细胞坏死。脑皮质层见神经元水肿、坏死。结论肝缺血-再灌流损伤可导致大脑结构和功能的改变。损伤过程中产生 iNOS作为炎性细胞因子导致大脑皮层p38MAKP的改变,从而引起神经元凋亡。     

An antisense oligodeoxynucleotide to p21(Waf1/Cip1) causes apoptosis in human breast cancer cells

Whereas 40% of human breast carcinomas harbor mutations in the tumor suppressor protein p53, the use of tests demonstrating the presence of p53 mutations as a prognostic marker in breast cancer has not altered clinical management. Therefore, the search for new markers, especially among cell cycle-regulatory molecules, is a high priority, both in terms of prognostication and for identification of novel targets. p21 regulates the outcome of the p53 response to DNA damage, as might occur after administration of a chemotherapeutic agent, and we have shown that attenuation of p21 using an antisense oligodeoxynucleotide (ODN) inhibits cell proliferation in vitro and decreases growth of Met-1 mammary carcinomas in mice. In the current study, we extend this work to human cells and tissue. Three of eight human breast tumors that we obtained from a tissue bank show markedly increased p21 levels, variably staining in the nucleus and cytosol. All corresponding normal tissues were p21 negative. In the three p21-positive tumors, the phosphatidylinositol 3'-kinase-relevant signaling proteins p85 and PTEN were also increased. To investigate whether p21 is a feasible target for attenuation in human breast cancer, we investigated two human carcinoma cell lines. When transfected with antisense p21 ODN, both MCF7 and T47D breast cancer cells exhibit dose-dependent attenuation of p21 levels, associated with apoptosis in the absence of an additional apoptotic stimulus. Because p21 regulates the cellular repair response to damaged DNA, our work suggests that attenuation of p21 using our antisense p21 ODN may be effective in modulating the progression of breast cancer in either the presence or absence of combination chemotherapy and sets the stage for future clinical trials.     

p21对缺血-再灌注损伤后肾小管上皮细胞演变的影响

目的 探讨p21对缺血-再灌注损伤（IRI）后肾小管上皮细胞演变的影响。方法 选择低龄（2个月龄）和高龄（12个月龄）p21（＋／＋）和p21（-／-）鼠，建立左肾IRI模型。于IRI后0、1、3、7d及1、3、6个月光镜下观察肾小管组织学变化，采用免疫组化法检测肾小管上皮细胞增殖细胞核抗原（PCNA）表达，组织化学染色观察肾小管上皮细胞衰老相关β-半乳糖苷酶（SA-β-gal）活力，末端脱氧核糖转移酶介导的生物素化脱氧尿嘧啶缺刻标记技术（TUNEL）检测肾小管上皮细胞凋亡。结果 IRI后0d，肾小管以坏死为主，高龄鼠比低龄鼠严重、p21（-／-）鼠比p21（＋／＋）鼠严重（P均〈0．05）。肾小管上皮细胞凋亡在IRI 1d后出现，7d达高峰，且高龄鼠比低龄鼠明显、p21（-／-）鼠比p21（＋／＋）鼠明显（P均d0．05）。低龄鼠IRI后1个月出现SA—β-gal染色阳性的肾小管上皮细胞，而对侧肾此时未见衰老细胞，3和6个月时衰老的肾小管上皮细胞显著增多，且p21（＋／＋）鼠比p21（-／-）鼠明显（P〈0．05）；p21（＋／＋）高龄鼠IRI后0d双肾即可见大量的SA-β-gal染色阳性肾小管上皮细胞，且较p21（-／-）鼠显著增多（P〈O．05），但1d后，p21（＋／＋）和p21（-／-）鼠IRI肾衰老细胞均明显减少（P均〈0．05），1个月后又呈进行性增加，且p21（＋／＋）鼠始终比p21（-／-）鼠严重。高龄和低龄p21（＋／＋）鼠PCNA阳性染色细胞出现的几率差异无显著性（P〉0．05），但低龄鼠细胞增殖能力要强于高龄鼠；而p21（-／-）鼠的细胞增殖能力明显强于p21（＋／＋）鼠，低龄鼠更为显著（P均〈0．05）。对高龄鼠IRI后1d细胞衰老和凋亡进行相关分析显示，二者呈显著负相关Cp21（＋／＋）鼠：r=-0．82，P〈0．001,p21（-／-）鼠：r=-0．76，P〈0．0013。结论 ①IRI可促进正常肾小管上皮细胞衰老的进程；②已经进入衰老状态的肾小管上皮细胞在遭受IRI刺激后，更易走向死亡[坏死和（或）凋亡]；③p21在IRI所致肾小管上皮细胞演变过程中发挥重要的调控作用。     

p53 and the hypoxia-induced apoptosis of cultured neonatal rat cardiac myocytes.

Myocyte cell loss is a prominent and important pathogenic feature of cardiac ischemia. We have used cultured neonatal rat cardiac myocytes exposed to prolonged hypoxia as an experimental system to identify critical factors involved in cardiomyocyte death. Exposure of myocytes to hypoxia for 48 h resulted in intranucleosomal cleavage of genomic DNA characteristic of apoptosis and was accompanied by increased p53 transactivating activity and protein accumulation. Expression of p21/WAF-1/CIP-1, a well-characterized target of p53 transactivation, also increased in response to hypoxia. Hypoxia did not cause DNA laddering or cell loss in cardiac fibroblasts. To determine whether the increase in p53 expression in myocytes was sufficient to induce apoptosis, normoxic cultures were infected with a replication-defective adenovirus expressing wild-type human p53 (AdCMV.p53). Infected cells expressed high intracellular levels of p53 protein and exhibited the morphological changes and genomic DNA fragmentation characteristic of apoptosis. In contrast, no genomic DNA fragmentation was observed in myocytes infected with the control virus lacking an insert (AdCMV.null) or in cardiac fibroblasts infected with AdCMV.p53. These results suggest that the intracellular signaling pathways activated by p53 might play a critical role in the regulation of hypoxia-induced apoptosis of cardiomyocytes.     

Reperfusion injury induces apoptosis in rabbit cardiomyocytes.

The most effective way to limit myocardial ischemic necrosis is reperfusion, but reperfusion itself may result in tissue injury, which has been difficult to separate from ischemic injury. This report identifies elements of apoptosis (programmed cell death) in myocytes as a response to reperfusion but not ischemia. The hallmark of apoptosis, nucleosomal ladders of DNA fragments (approximately 200 base pairs), was detected in ischemic/reperfused rabbit myocardial tissue but not in normal or ischemic-only rabbit hearts. Granulocytopenia did not prevent nucleosomal DNA cleavage. In situ nick end labeling demonstrated DNA fragmentation predominantly in myocytes. The pattern of nuclear chromatin condensation was distinctly different in reperfused than in persistently ischemic tissue by transmission electron microscopy. Apoptosis may be a specific feature of reperfusion injury in cardiac myocytes, leading to late cell death.     

Suppression of p53 activity and p21WAF1/CIP1 expression by vascular cell integrin alphaVbeta3 during angiogenesis.

Induction of p53 activity in cells undergoing DNA synthesis represents a molecular conflict that can lead to apoptosis. During angiogenesis, proliferative endothelial cells become apoptotic in response to antagonists of integrin alphavbeta3 and this leads to the regression of angiogenic blood vessels, thereby blocking the growth of various human tumors. Evidence is presented that administration of alphavbeta3 antagonists during angiogenesis in vivo selectively caused activation of endothelial cell p53 and increased expression of the p53-inducible cell cycle inhibitor p21WAF1/CIP1. In vitro studies revealed that the ligation state of human endothelial cell alphavbeta3 directly influenced p53 activity and the bax cell death pathway. Specifically, agonists of endothelial cell alphavbeta3, but not other integrins, suppressed p53 activity, blocked p21WAF1/CIP1 expression, and increased the bcl-2/bax ratio, thereby promoting cell survival. Thus, ligation of vascular cell integrin alphavbeta3 promotes a critical and specific adhesion-dependent cell survival signal during angiogenesis leading to inhibition of p53 activity, decreased expression of p21WAF1/CIP1, and suppression of the bax cell death pathway.     

Induction of p21WAF1/CIP1/SDI1 in kidney tubule cells affects the course of cisplatin-induced acute renal failure.

The p21 protein is found in the nucleus of most cells at low levels and is induced to elevated levels after DNA damage, causing cell-cycle arrest. We have reported that p21 mRNA is rapidly induced to high levels in murine kidney after acute renal failure. The function(s) in the kidney of p21 induction in cisplatin-induced acute renal failure was studied with mice that are homozygous for a p21 gene deletion. After drug administration, as compared with their wild-type littermates, p21(-/-) mice display a more rapid onset of the physiologic signs of acute renal failure, develop more severe morphologic damage, and have a higher mortality. Therefore, the induction of p21 after cisplatin administration is a protective event for kidney cells. Using both bromodeoxyuridine incorporation and nuclear proliferating cell nuclear antigen detection, we found that cisplatin administration caused kidney cells to start entering the cell-cycle. However, cell-cycle progression is inhibited in wild-type mice, whereas kidney cells in the p21(-/-) mice progress into S-phase. We propose that p21 protects kidneys damaged by cisplatin by preventing DNA-damaged cells from entering the cell-cycle, which would otherwise result in death from either apoptosis or necrosis.     

Posttranscriptional stabilization underlies p53-independent induction of p21WAF1/CIP1/SDI1 in differentiating human leukemic cells.

p21WAF/CIP1/SDI1 is a recently identified gene expressed in cells harboring wild-type but not mutant p53 gene. It encodes a nuclear protein of 21 kD which inhibits cyclin-dependent kinase activity. Constitutive p21WAF1/CIP1/SDI1 mRNA expression was detected in neoplastic cells from patients with various hematological malignancies as well as in normal bone marrow mononuclear cells and in myeloid and lymphoid cell lines independent of their p53 status. Induced differentiation of the p53-deficient promyelocytic HL-60 cells along the monocytic lineage by phorbol ester or 1a,25 dihydroxyvitamin D3 resulted in a marked increase of both p21WAF1/CIP1/SDI1 mRNA and protein expression due to enhanced mRNA stability. Differentiation towards the granulocytic lineage by all-trans retinoic acid or dimethylsulfoxide failed to produce this effect. p21WAF1/CIP1/SDI1 is an immediate early gene since its upregulation occurred independently of de novo protein synthesis. The induction of p21WAF1/CIP1/SDI1 expression and its regulation in p53-deficient differentiating leukemic cells support the idea of an additional, p53-independent role of p21WAF1/CIP1/SDI1 in human hematopoiesis.     

异丙酚对全脑缺血再灌注损伤大鼠的脑保护作用及其机制研究

目的探讨静脉麻醉药异丙酚对全脑缺血再灌注损伤大鼠的脑保护作用及其机制。方法成年雄性Wistar大鼠 19只 ,随机分为缺血组 (n =7)、异丙酚组 (n =7)和假手术对照组 (n =5 ) ,采用Pulsinelli法制备大鼠全脑缺血再灌注模型。异丙酚组再灌注开始后立即静脉输注异丙酚 1.5ml/h ,持续 3 0min。于再灌注 2 4h取脑 ,流式细胞仪检测凋亡率、坏死率、bcl 2、Bax和 p5 3蛋白在大鼠海马神经元中的表达情况。结果异丙酚可以降低大鼠全脑缺血再灌注 2 4h海马神经元的凋亡率和坏死率 (P <0 .0 5 ) ,与缺血组比较 ,异丙酚组Bax、p5 3的蛋白表达均降低 (P <0 .0 5 ) ,而bcl 2的变化无显著性差异 (P >0 .0 5 )。 结论异丙酚能降低大鼠全脑缺血再灌注神经元的凋亡率和坏死率 ,其机制可能与降低促凋亡基因Bax和 p5 3蛋白的表达有关     

Roles of the Tumor Suppressor p53 and the Cyclin-dependent Kinase Inhibitor p21WAF1/CIP1 in Receptor-mediated Apoptosis of WEHI 231 B Lymphoma Cells

Treatment of WEHI 231 immature B lymphoma cells with an antibody against their surface immunoglobulin M (anti-IgM) induces apoptosis and has been studied extensively as a model of self-induced B cell tolerance. Since the tumor suppressor protein p53 has been implicated in apoptosis in a large number of cell types and has been found to be mutated in a variety of B cell tumors, here we sought to determine whether p53 and the p53 target gene cyclin-dependent kinase inhibitor p21^WAF1/CIP1 were involved in anti-IgM–induced cell death. Anti-IgM treatment of WEHI 231 cells increased expression of p53 and p21 protein levels. Ectopic expression of wild-type p53 in WEHI 231 cells induced both p21 expression and apoptosis. Ectopic expression of p21 similarly induced apoptosis. Rescue of WEHI 231 cells from apoptosis by costimulation with CD40 ligand ablated the increase in p21 expression. Lastly, a significant decrease in anti-IgM–mediated apoptosis was seen upon downregulation of endogenous p53 activity by expression of a dominant-negative p53 protein or upon microinjection of an antisense p21 expression vector or antibody. Taken together, the above data demonstrate important roles for p53 and p21 proteins in receptor-mediated apoptosis of WEHI 231 B cells.     

Enhanced expression of p53 and apoptosis induced by blockade of the vacuolar proton ATPase in cardiomyocytes.

Activation of the vacuolar proton ATPase (VPATPase) has been implicated in the prevention of apoptosis in neutrophils and adult cardiac myocytes. To determine the role of the VPATPase in apoptosis of cardiac myocytes, we used a potent and specific inhibitor of the VPATPase, bafilomycin A1. Bafilomycin A1 alone caused increased DNA laddering of genomic DNA and increased nuclear staining for fragmented DNA in neonatal cardiomyocyte apoptosis in a dose- and time-dependent manner. Intracellular acidification in cardiac myocytes was also observed after 18 h of bafilomycin A1 treatment. Accordingly, bafilomycin A1-treated myocytes also showed increased accumulation of p53 protein and p53-dependent transactivation of gene expression, including a persistent upregulation of p21/wild-type p53 activated fragment 1/cyclin kinase inhibitor protein-1 mRNA. The bafilomycin A1-induced increase in p53 protein levels was accompanied by a marked increase in p53 mRNA accumulation. In contrast, cardiac fibroblasts treated with bafilomycin A1 showed no change in p53 protein expression or pHi and did not undergo apoptosis even after 24 h of treatment. Our data suggest that blockade of the VPATPase induces apoptotic cell death of cardiac myocytes and that this may occur through a p53-mediated apoptotic pathway.     

脑缺血再灌注大鼠神经细胞DNA损伤与凋亡的时空关系分析

目的　探讨局灶性脑缺血再灌注大鼠神经细胞DNA损伤与凋亡的时空分布演变过程及两者间的联系。方法　共选取 72只成年Wistar大鼠 ,将其随机分为正常组、假手术组、缺血 3 0min组及缺血 2h组 ;后 2组大鼠又根据再灌注时间 (再灌注 1,6,12 ,2 4及 48h)不同 ,各细分为 5个亚组。制作大鼠大脑中动脉阻塞再灌注模型 (MCAO R) ,应用免疫组化法观察脑缺血组织在不同缺血再灌注时间下 ,其P5 3表达在空间及程度上的改变 ,并结合TUNEL技术观察P5 3表达与细胞凋亡的时空关系。结果　脑缺血再灌注可诱导细胞凋亡及P5 3蛋白表达增强 ,并随着缺血或再灌注时间的延长 ,凋亡细胞数量与P5 3表达均逐渐增加 ,但P5 3蛋白的表达始终早于凋亡细胞的出现 ,且P5 3阳性细胞数量始终多于凋亡细胞数量 (P <0 .0 5 ) ,其分布范围也较凋亡细胞更广。结论　神经细胞缺血可引起DNA损伤 ,DNA损伤后可诱导DNA修复 ,如修复失败则启动细胞凋亡程序。     

银杏叶提取物对肾缺血-再灌注后细胞凋亡的影响

目的:观察银杏叶提取物对大鼠肾缺血-再灌注后细胞凋亡的影响.方法:采用动脉夹闭大鼠双侧肾蒂45 min、再灌注24 h的方法制成急性肾缺血-再灌注模型.光、电镜观察细胞结构改变;采用脱氧核苷酸末端转移酶介导的DNA原位末端标记技术检测细胞凋亡的情况,流式细胞仪定量分析细胞凋亡;测定血浆肌酐、尿素氮,并观察肾功能变化.结果:缺血-再灌注组较假手术组肾小管凋亡细胞数明显增多;银杏叶提取物处理组较缺血-再灌注组凋亡细胞数明显减少,组织损害明显减轻.结论:银杏叶提取物预防给药能减轻肾缺血-再灌注损伤,其机制可能与抑制细胞凋亡有关.     

CP-31398 restores mutant p53 tumor suppressor function and inhibits UVB-induced skin carcinogenesis in mice

Mutations in the tumor suppressor p53 are detectable in over 50% of all human malignancies. Mutant p53 protein is incapable of transactivating its downstream target genes that are required for DNA repair and apoptosis. Chronic exposure to UVB induces p53 mutations and is carcinogenic in both murine and human skin. CP-31398, a styrylquinazoline compound, restores the tumor suppressor functions of mutant forms of p53 in tumor cells. However, its effectiveness in vivo remains unclear. Here, we demonstrate that CP-31398 blocked UVB-induced skin carcinogenesis and was associated with increases in p53, p21, and BclXs. CP-31398 downregulated Bcl2, proliferating nuclear cell antigen, and cyclin D1. Activation of caspase-3 and cleavage of poly (ADP-ribose) polymerase also occurred in both tumor and perilesional skin following treatment. CP-31398 induced the expression of p53-dependent target proteins, and this was followed by apoptosis in UVB-irradiated wild-type mice but not in their p53-deficient littermates. Similar effects were observed in human skin carcinoma A431 cells expressing mutant p53. In addition, CP-31398 induced mitochondrial translocation of p53, leading to changes in mitochondrial membrane permeability pore transition (MPT) and consequent cytochrome c release in these cells. Blocking MPT diminished p53 translocation and apoptosis. These studies indicate that reconstituting p53 tumor suppressor functions in vivo by small molecular weight compounds may block the pathogenesis and progression of skin cancer.