结核分枝杆菌对人急性白血病单核细胞株THP-1凋亡和死亡水平的影响

目的通过对不同毒力的结核分枝杆菌感染细胞后的细胞凋亡和死亡程度的检测,以期发现结核分枝杆菌和细胞相互作用的新的方向和观点,以及对结核病免疫学发病机制的新认识。方法选用不同毒力的结核分枝杆菌H37Ra、H37Rv及北京基因型敏感菌株(BJTB)分别感染人的巨噬细胞THP-1细胞株,模拟细胞体外感染的过程。以流式细胞仪检测细胞凋亡水平,免疫荧光检测细胞的凋亡蛋白的分布,末端脱氧核糖核酸转移酶介导的dUTP缺口末端标记染色检测细胞晚期凋亡的变化,台盼兰染色检测细胞死亡水平的变化。结果H37Ra引起THP-1细胞的凋亡水平最高,H37Rv次之,BJTB引起的凋亡水平最低。BJTB引起的死亡水平最高,H37Rv次之,H37Ra最低。结论毒力不同的结核分枝杆菌刺激细胞后和细胞的相互作用不同,毒力越高引起的凋亡水平越低,毒力越低引起的凋亡水平越高;对死亡水平的影响是毒力越高的结核分枝杆菌引起的死亡水平越高,毒力越低引起的死亡水平越低。

结核分枝杆菌对人急性白血病单核细胞株THP-1凋亡和死亡水平的影响

目的通过对不同毒力的结核分枝杆菌感染细胞后的细胞凋亡和死亡程度的检测，以期发现结核分枝杆菌和细胞相互作用的新的方向和观点，以及对结核病免疫学发病机制的新认识。方法选用不同毒力的结核分枝杆菌H37Ra、H37Rv及北京基因型敏感菌株（BJTB）分别感染人的巨噬细胞THP-1细胞株，模拟细胞体外感染的过程。以流式细胞仪检测细胞凋亡水平，免疫荧光检测细胞的凋亡蛋白的分布，末端脱氧核糖核酸转移酶介导的dUTP缺口末端标记染色检测细胞晚期凋亡的变化，台盼兰染色检测细胞死亡水平的变化。结果H37Ra引起THP-1细胞的凋亡水平最高，H37Rv次之，北京基因型敏感菌株（BJTB）引起的凋亡水平最低。北京基因型敏感菌株（BJTB）引起的死亡水平最高，H37Rv次之，H37Ra最低。结论毒力不同的结核分枝杆菌刺激细胞后和细胞的相互作用不同，毒力越高引起的凋亡水平越低，毒力越低引起的凋亡水平越高；对死亡水平的影响是毒力越高的结核分枝杆菌引起的死亡水平越高，毒力越低引起的死亡水平越低。

NT4(Si)-p53(N15)-antennapedia induces cell death in a human hepatocellular carcinoma cell line

AIM： To construct the recombinant lentivirus expression plasmid, pLenti6/V5-NT4 p53（N 15）-antennapedia （Ant）, and study its effect on HepG2 cells. METHODS： Plasmid pLenti6/V5-NT4 p53（N15）-Ant was constructed incorporating the following functional regions, including signal peptide sequence and proregion of neurotrophin 4, N-terminal residues 12-26 of p53 and 17 amino acid drosophila carrier protein, Ant. Hepatocellular carcinoma （HepG2） cells were used for transfection. 3-[4,5-climethyl-thiazol-2yl]-2,5 diphenyl tetrazolium bromide （MI-I） assay, lactate dehydrogenase （LDH） release assay, transmission electron microscopy （TEM） and flow cytometric analysis （FCM） were employed to investigate the effects of LV-NT4（Si）- p53（N15）-Ant in vitro on HepG2 cells. In vivo experiment was also performed to investigate the inhibitory effect of LV-NT4（Si）-p53（N15）-Ant on tumor growth in nude mice.RESULTS： LV-NT4（Si）-p53（N15）-Ant significantly suppressed the growth of HepG2 cells. MTT assay showed that the growth of HepG2 cells was mucj more significantly inhibited by LV-NT4（Si）-p53（N15）-Ant than by LV-EGFP. The inhibition rate for HepG2 cell growth in the two groups was 46.9% and 94.5%, respectively, 48 h after infection with LV-NT4（Si）-p53（N15）-Ant, and was 33.9% and 95.8%, respectively, 72 h after infection with LV-NT4（Si）-p53（N15）-Ant （P 〈 0.01）. Light microscopy and TEM showed morphological changes in HepG2 cells infected with LV-NT4（Si）-p53（N15）-Ant, but no significant changes in HepG2 cells infected with LV-EGFR Changes were observed in ultra-structure of HepG2 cells infected with LV-NT4（Si）-p53（N15）-Ant, with degraded membranes, resulting in necrosis. LDH release from HepG2 cells was analyzed at 24, 48, 72 and 96 h after infection with LV-NT4（Si）-p53（N15）-Ant and LV-EGFP, which showed that LDH release was significantly higher in LV-NT4（Si）-p53（N15）-Ant treatment group （682 IU/L） than in control group （45 IU/L, P 〈 0.01）. The longer the time was after infection, the bigger the difference was in LDH release. FCM analysis showed that LV-NT4（Si）- p53（N15）-Ant could induce two different kinds of cell death： necrosis and apoptosis, with apoptosis being the minor type and necrosis being the main type, suggesting that LV-NT4（Si）-p53（N15）-Ant exerts its anticancer effect on HepG2 cells by inducing necrosis. The in vivo study showed that LV-NT4（Si）-p53（N15）-Ant significantly inhibited tumor growth with an inhibition rate of 66.14% in terms of tumor size and weight. CONCLUSION： LV-NT4（Si）-p53（N15）-Ant is a novel recombinant lentivirus expression plasmid and can be used in gene therapy for cancer.

Apoptosis signaling pathways and lymphocyte homeostasis

It has been almost three decades since the term ＂apoptosis＂ was first coined to describe a unique form of cell death that involves orderly, gene-dependent cell disintegration. It is now well accepted that apoptosis is an essential life process for metazoan animals and is critical for the formation and function of tissues and organs. In the adult mammalian body, apoptosis is especially important for proper functioning of the immune system. In recent years, along with the rapid advancement of molecular and cellular biology, great progress has been made in understanding the mechanisms leading to apoptosis. It is generally accepted that there are two major pathways ofapoptotic cell death induction： extrin- sic signaling through death receptors that leads to the formation of the death-inducing signaling complex （DISC）, and intrinsic signaling mainly through mitochondria which leads to the formation of the apoptosome. Formation of the DISC or apoptosome, respectively, activates initiator and common effector caspases that execute the apoptosis process. In the immune system, both pathways operate; however, it is not known whether they are sufficient to maintain lymphocyte homeostasis. Recently, new apoptotic mechanisms including caspase-independent pathways and granzyme-initiated pathways have been shown to exist in lymphocytes. This review will summarize our understanding of the mechanisms that control the homeostasis of various lymphocyte populations.

Casticin-induced apoptosis involves death receptor 5 upregulation in hepatocellular carcinoma cells

AIM:To investigate the apoptotic activities of casticin in hepatocellular carcinoma(HCC) cells and its molecular mechanisms.METHODS:PLC/PRF/5 and Hep G2 cell lines were cultured in vitro and the inhibitory effect of casticin on the growth of cells was detected by 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolim bromide(MTT) assay.The apoptotic cell death was examined using the cell apoptosis enzyme linked immunosorbent assay(ELISA) detection kit,flow cytometry(FCM) after propidium iodide(PI) staining and DNA agarose gel electrophoresis.The caspase activities were measured using ELISA.Reactive oxygen species(ROS) production was evaluated by FCM after dichlorodihydrofluorescein diacetate(DCFH-DA) probe labeling.Intracellular glutathione(GSH) content was measured using a glutathione assay kit.The expression of death receptor(DR)4 and DR5 proteins was analyzed by Western blotting and FCM.RESULTS:Casticin significantly inhibited the growth of human HCC(PLC/PRF/5 and Hep G2) cells in a dosedependent manner(P < 0.05).Casticin increased the percentage of the sub-G1 population in HCC cells in a concentration-dependent manner.The potency of casticin to PLC/PRF/5 cells was higher than that of 5-flurouracil(26.8% ± 4.8% vs 17.4% ± 5.1%) at 10 μmol/L for 24 h.Casticin increased the levels of Histone/DNA fragmentation and the levels of active caspase-3,-8 and-9 in a concentration-dependent manner(P < 0.05).Treatment with 30 μmol/L casticin for 24 h resulted in the formation of a DNA ladder.Casticin reduced the GSH content(P < 0.05),but did not affect the level of intracellular ROS in PLC/PRF/5 and Hep G2 cells.The thiol antioxidants,acetylcysteine(NAC) and GSH restored GSH content and attenuated casticin-induced apoptosis.In contrast,the nonthiol antioxidants,butylated hydroxyanisole and mannitol failed to do so.In the HCC cells treated with casticin for 24 h,DR5 protein level was increased.The expression of DR5 protein induced by casticin was inhibited by NAC.Pretreatment with DR5/Fc chimera protein,a blocking antibody,effectively attenuated the induction of apoptosis by casticin.CONCLUSION:Casticin-induced apoptosis of HCC cells is involved in GSH depletion and DR5 upregulation.

Early apoptosis and cell death induced by ATX-S10Na(Ⅱ)-mediated photodynamic therapy are Bax- and p53-dependent in human colon cancer cells

AIM： To investigate the roles of Bax and p53 proteins in photosensitivity of human colon cancer cells by using lysosome-localizing photosensitizer, ATX-S10Na （Ⅱ）. METHODS： HCT116 human colon cancer cells and Bax-null or p53-null isogenic derivatives were irradiated with a diode laser. Early apoptosis and cell death in response to photodynamic therapy were determined by MTT assays, annexin Ⅴ assays, transmission electron microscopy assays, caspase assays and western blotting. RESULTS： Induction of early apoptosis and cell death was Bax- and p53-dependent. Bax and p53 were required for caspase-dependent apoptosis. The levels of anti-apoptotic Bcl-2 family proteins, Bcl-2 and Bcl-xL, were decreased in Bax- and p53-independent manner. CONCLUSION： Our results indicate that eady apoptosis and cell death of human colon cancer cells induced by photodynamic therapy with lysosome-localizing photosensitizer ATX-S10Na （Ⅱ） are mediated by p53- Bax network and low levels of Bcl-2 and Bcl-xL proteins. Our results might help in formulating new therapeutic approaches in photodynamic therapy.

Apoptosis in oncology

Apoptosis is a complex process involving a large array of genes and mutation of any of these genes may lead to malignancy formation. Re-acquirement of FasL by tumor cells may enable them to evade the surveillance of immune system and thus contributes to the growth of tumor. Apart from traditional therapies, inducing apoptosis of tumor cell by new methods employing death receptor ligands and making use of Fas counterattack is also being developed.

Signal transduction mediated by Bid,a pro-death Bcl-2 family proteins, connects the death receptor and mitochondria apoptosis pathways

Two major apoptosis pathways have been defined in mammalian cells, the Fas/TNF-R1 death receptor pathway and the mitochondria pathway. The Bcl-2 family proteins consist of both anti-apoptosis and pro- apoptosis members that regulate apoptosis, mainly by controlling the release of cytochrome c and other mitochondrial apoptotic events. However, death signals mediated by Fas/TNF-R1 receptors can usually activate caspases directly, bypassing the need for mitochondria and escaping the regulation by Bcl-2 family proteins. Bid is a novel pro-apoptosis Bcl-2 family protein that is activated by caspase 8 in response to Fas/TNF-R1 death receptor signals. Activated Bid is translocated to mitochondria and induces cytochrome c release, which in turn activates downstream caspases. Such a connection between the two apoptosis pathways could be important for induction of apoptosis in certain types of cells and responsible for the pathogenesis of a number of human diseases.

S100A8/A9 induces autophagy and apoptosis via ROS-mediated cross-talk between mitochondria and lysosomes that involves BNIP3

The complex formed by two members of the S100 calcium-binding protein family, S100A8/A9, exerts apoptosisinducing activity in various cells of different origins. Here, we present evidence that the underlying molecular mechanisms involve both programmed cell death I （PCD I, apoptosis） and PCD II （autophagy）-like death. Treatment of cells with S100A8/A9 caused the increase of Beclin-1 expression as well as Atgl2-Atg5 formation. S100A8/A9-induced cell death was partially inhibited by the specific PI3-kinase class Ⅲ inhibitor, 3-methyladenine （3-MA）, and by the vacuole H＋-ATPase inhibitor, bafilomycin-A1 （Baf-A1）. S100A8/A9 provoked the translocation of BNIP3, a BH3 only pro-apoptotic Bcl2 family member, to mitochondria. Consistent with this finding, ATM-BNIP3 overexpression partially inhibited S100A8/A9-induced cell death, decreased reactive oxygen species （ROS） generation, and partially pro- tected against the decrease in mitochondrial transmembrane potential in S100A8/A9-treated ceils. In addition, either ATM-BNIP3 overexpression or N-acetyl-L-cysteine co-treatment decreased lysosomal activation in cells treated with S100A8/A9. Our data indicate that S100A8/A9-promoted cell death occurs through the cross-talk of mitochondria and lysosomes via ROS and the process involves BNIP3.

Detachment of esophageal carcinoma cells from extracellular matrix causes relocalization of death receptor 5 and apoptosis

AIM： To investigate the effect of detachment of esophageal cancer cells from extracellular matrix on the localization of death receptor 5 （DR5） and apoptosis. METHODS： Anchorage-dependent EC9706 cells of esophageal squamous cell carcinoma were pretreated or not treated with brefeldin A. Detached cells were harvested by ethylenediaminetetraacetic acid digestion. Expression and localization of DR5 in these cells were determined by immunocytochemical and immunofluorescence assays, as well as flow cytometry analysis. Apoptosis of EC9706 cells was detected by flow cytometry after stained with fluorescein isothiocyanate-labeled annexin V/propidium iodide. Activation of caspase 8 was detected by Western blot analysis. RESULTS： Immunocytochemical assay indicated that DR5 was predominantly perinuclear in adherent cells but was mainly localized in cell membrane in detached cells. In addition, immunofluorescence assay also confirmed the above-mentioned results, and further demonstrated that DR5 was present in the form of coarse granules in detached cells, but in the form of fine granules in adherent cells. Cytometry analysis revealed higher levels of DR5 expression on the surfaces of brefeldin-A-untreated cells than on the surfaces of brefeldin-A-treated cells, but brefeldin A treatment did not affect the total DR5 expression levels. Moreover, nocodazole did not influence the extracelluar DR5 expression levels in EC9706 cells. Apoptosis assay revealed that detached cells were more sensitive to DR5 antibody-induced apoptosis than adherent ceils. Western blotting showed that caspase 8 was activated in temporarily detached cells 4 h earlier than in adherent cells. CONCLUSION： Progress from adhesion to detachment of EC9706 cells causes DR5 relocalization, and promotes cytoplasmic translocation of DR5 to cell surfaces via a Golgi-dependent pathway. Moreover, it might also result in DR5 aggregation to render apoptosis of detached cells.

Downregulation of cyclooxygenase-1 is involved in gastric mucosal apoptosis via death signaling in portal hypertensive rats

Portal hypertension （PHT） gastropathy is a frequent complication of fiver cirrhosis and one of the leading causes of death from cirrhosis. Apoptosis is widely considered to be an active energy-dependent mode of cell death and a distinct entity from necrotic cell death. It is unclear whether gastric mucosal apoptosis is involved in PHT gastropa- thy. Prostaglandins （PGs） produced through cyclooxygenase （COX） are thought to play a key role in protection of the gastrointestinal mucosa from injury and apoptosis. However, the role of COX in PHT gastropathy is still not clearly understood. The aims of this study were to investigate whether （1） gastric mucosal apoptosis is involved in PHT gas- tropathy and （2） downregulation of COX contributes to this apoptosis. In this study, we show that gastric mucosal apoptosis was remarkably increased while mucosal proliferation was inhibited in PHT rats. Gastric mucosal COX- 1 was significantly suppressed at both the mRNA and protein levels, and PGE2 was reduced in PHT rats. Further, PGE2 treatment suppressed gastric mucosal apoptosis in PHT rats. However, gastric mucosal COX-2 levels did not differ between sham-operated rats and PHT rats. Gastric mucosal levels of tumor necrosis factor-α （TNF-α） and Fas ligand, but not TNF-related apoptosis-inducing ligand, were increased, and activated caspase-8 and caspase-3 levels were upregulated in PHT rats. The release of cytochrome c from the mitochondria to the cytosol was not observed in PHT rats. Our data indicate that downregulation of COX-1 is involved in gastric mucosal apoptosis via death signal- ing-mediated type-I cell death in PHT rats.

Inhibition of methionine adenosyltransferase II induces FasL expression, Fas-DISC formation and caspase-8-dependent apoptotic death in T leukemic cells

Methionine adenosyltransferase Ⅱ（MAT Ⅱ） is a key enzyme in cellular metabolism and catalyzes the formation of S-adenosylmethionine （SAMe） from L-methionine and ATE Normal resting T lymphocytes have minimal MAT Ⅱ activity, whereas activated proliferating T lymphocytes and transformed T leukemic cells show significantly enhanced MAT Ⅱ activity. This work was carried out to examine the role of MAT Ⅱ activity and SAMe biosynthesis in the survival of leukemic T cells. Inhibition of MAT Ⅱ and the resultant decrease in SAMe levels enhanced expression of FasL mRNA and protein, and induced DISC （Death Inducing Signaling Complex） formation with FADD （Fasassociated Death Domain） and procaspase-8 recruitment, as well as concomitant increase in caspase-8 activation and decrease in c-FLIPs levels. Fas-initiated signaling induced by MAT Ⅱ inhibition was observed to link to the mitochondrial pathway via Bid cleavage and to ultimately lead to increased caspase-3 activation and DNA fragmentation in these cells. Furthermore, blocking MAT 2A mRNA expression, which encodes the catalytic subunits of MAT Ⅱ, using a small-interfering RNA approach enhanced FasL expression and cell death, validating the essential nature of MAT Ⅱ activity in the survival of T leukemic cells.

The molecular cell death machinery in the simple cnidarian Hydra includes an expanded caspase family and pro-and anti-apoptotic Bcl-2 proteins

The fresh water polyp Hydra belongs to the phylum Cnidaria, which diverged from the metazoan lineage before the appearance of bilaterians. In order to understand the evolution of apoptosis in metazoans, we have begun to elucidate the molecular cell death machinery in this model organism. Based on ESTs and the whole Hydra genome assembly, we have identified 15 caspases. We show that one is activated during apoptosis, four have characteristics of initiator caspases with N-terminal DED, CARD or DD domain and two undergo autoprocessing in vitro. In addition, we describe seven Bcl-2-1ike and two Bak-like proteins. For most of the Bcl-2 family proteins, we have observed mitochondrial localization. When expressed in mammalian cells, HyBak-like 1 and 2 strongly induced apoptosis. Six of the Bcl-2 family members inhibited apoptosis induced by camptothecin in mammalian ceils with HyBcl-2-1ike 4 showing an especially strong protective effect. This protein also interacted with HyBak-like 1 in a yeast two-hybrid assay. Mutation of the conserved leucine in its BH3 domain abolished both the interaction with HyBak-like 1 and the anti-apoptotic effect. Moreover, we describe novel Hydra BH-3-only proteins. One of these interacted with Bcl-2-1ike 4 and induced apoptosis in mammalian cells. Our data indicate that the evolution of a complex network for cell death regulation arose at the earliest and simplest level of multicellular organization, where it exhibited a substantially higher level of complexity than in the protostome model organisms Caenorhabditis and Drosophila.

Dynamic process of phagocytosis and forms of macrophage cell death induced by ingestion of apoptotic neutrophils

Clearance of apoptotic neutrophils by macrophages is important for both the successful resolution of acute inflammation and homeostasis.However,the dynamic process of phagocytosis of apoptotic neutrophils by macrophages and the fate of macrophages after the ingestion of apoptotic neutrophils has not been well documented.In the present study,we staged the recognition and tethering,internalization,digestion and exocytosis steps of phagocytosis of apoptotic neutrophils.Furthermore,we found that after the ingestion of apoptotic cells,a subset of macrophages underwent cell death by autophagy,apoptosis or oncosis as revealed by transmission electron microscopy and confocal microscopy combined with specific dyes.The percentage of autophagic,apoptotic and oncotic macrophages were 8.00%±2.00%,12.33%±2.08%,and 3.66%±1.50%,respectively.These results indicated that after ingestion of apoptotic neutrophils,a subset of macrophages undergoes autophagy and apoptosis.We propose that autophagy of macrophages after the ingestion of apoptotic cells may be a new mechanism present in the resolution of inflammation.