The broad-spectrum caspase inhibitor Boc-Asp-CMK induces cell death in human leukaemia cells.

Synthetic caspase inhibitors and particularly broad-spectrum caspase inhibitors can prevent cells from death or at least slow down cell death process and abrogate some apoptotic hallmarks [Kitanaka, C., Kuchino, Y., 1999. Caspase-independent programmed cell death with necrotic morphology. Cell Death and Differentiation 6, 508-515]. However, not all synthetic caspase inhibitors diminish cell death. We have found that the broad-spectrum caspase inhibitor Boc-Asp-CMK induced cell death at micromolar concentrations in human leukaemia cells. Interestingly, low concentrations of Boc-Asp-CMK induced cell death with apoptotic hallmarks. Increasing concentrations of Boc-Asp-CMK led to necrotic cell death. The switch between apoptosis and necrosis seemed to depend upon the degree of inhibition of executioner caspases, including caspase-3/7 with Boc-Asp-CMK. Interestingly, caspase-3 processing was not inhibited even for the highest concentration of Boc-Asp-CMK used. We assume, that toxic properties of Boc-Asp-CMK can be attributed to the chloromethylketone residuum in its molecule, as its analogue Boc-Asp-FMK with fluoromethylketone residuum was more than 13 times less toxic. Our results further indicated that toxicity of Boc-Asp-CMK might arise from its interference with mitochondrial metabolism.     

吴茱萸碱诱导人宫颈癌HeLa细胞凋亡过程中非caspase调控因素

目的　研究吴茱萸碱 (evodiamine)诱导人宫颈癌HeLa细胞凋亡机制中非caspase调控因素。方法　MTT法 ,WesternBlot免疫印迹法 ,流式细胞术。结果　虽吴茱萸碱对HeLa细胞杀伤作用介于化疗药物放线菌素D (actino mycineD)、顺铂 (cisplatin)和 5 氟尿嘧啶 (5 fluorouracil,5 Fu)之间 ,但对细胞撤除药物后的继续增殖能力的影响相似。MAP激酶 (MAPK)抑制剂中ERK和p38的抑制剂不影响细胞死亡 ,而JNK抑制剂 (SP6 0 0 12 5 )可协同吴茱萸碱杀死细胞 ,但吴茱萸碱并未影响JNK及磷酸化JNK蛋白表达。吴茱萸碱可将HeLa细胞周期阻滞在G2 /M期 ,发生大量凋亡。结论　对JNK激酶的抑制可协同促进吴茱萸碱对HeLa细胞的杀伤作用 ,而且吴茱萸碱可将细胞周期阻滞在G2 /M期发生凋亡。     

细胞死亡在脓毒症引起的肾损伤中的作用

脓毒症是一种由感染引起的全身炎症反应综合征,伴随着多个器官的急性损伤。脓毒症引起的急性肾损伤（Acute kidney injury, AKI）是与脓毒症相关的最严重的并发症之一,并可能转化为慢性肾病（Chronic kidney disease, CKD）。其病理生理学涉及多种细胞,包括肾血管内皮细胞、肾小管上皮细胞和巨噬细胞等。这些细胞死亡之间的联系与脓毒症引起的肾损伤密切相关。内质网应激、线粒体动力学失衡和氧化应激等都是细胞死亡的主要诱因。     

Estrogen receptors are involved in polychlorinated biphenyl-induced apoptosis on mouse spermatocyte GC-2 cell line

Polychlorinated biphenyls (PCBs) are widespread persistent environmental contaminants which have been shown to have reproductive toxicity and to disturb spermatogenesis. But the precise mechanism is not clear. A mouse pachytene spermatocyte-derived cell line, GC-2 cells were used in the present study to investigate the toxic effect of PCBs (Aroclor 1254) and explore the underlying molecular mechanism. Results showed that Aroclor 1254 inhibited cell proliferation, caused the arrest of cells in G0/G1 phase and induced apoptosis which might be partly explained by the decreased expression of Bcl-2 and cell cycle regulator cyclin D1 together with the activation of caspase-3. Besides, the treatment of Aroclor 1254 decreased the protein expression of estrogen receptor (ER)-α while increasing that of ERβ. Then the administration of selective ERα agonist PPT partly reversed Aroclor 1254-induced alteration in Bcl-2, caspase-3 and cyclin D1 protein expression while selective ERβ agonist DPN accelerated it. These results suggest that Aroclor 1254, working through ERα and ERβ, interferes with the expression of proteins involved in the balance between cellular apoptosis and proliferation.     

Cellular glutathione status modulates polychlorinated biphenyl-induced stress response and apoptosis in vascular endothelial cells

Exposure to environmental contaminants, such as polychlorinated biphenyls (PCBs), may severely compromise normal function of vascular endothelial cells (EC). We have previously shown that PCB 77 (3,3',4,4'-tetrachlorobiphenyl), an arylhydrocarbon receptor (AhR) agonist, can induce oxidative stress in cultured EC. We now show that PCB 77 can activate EC and induce a cellular stress response that is reflected by the activation of c-Jun N-terminal/stress-activated protein kinases (JNK/SAPK). Our data also suggest that this PCB 77-mediated stress response can be modulated by the intracellular glutathione content. EC treated with buthionine-sulphoximine (BSO), an inhibitor of glutathione synthesis, further enhanced PCB-induced JNK/SAPK activity. This stress response was sustained only in the presence of BSO plus PCB 77. Media supplementation with the glutathione precursor N-acetyl-cysteine (NAC) reduced PCB 77-induced JNK/SAPK. Intracellular glutathione also may be implicated in PCB-induced EC apoptosis. Individual treatment with PCB, BSO, or linoleic acid induced activation of caspase 3. Compared to PCB 77 alone, annexin V activity was further amplified during combined treatment with BSO and PCB 77. DNA fragmentation was mostly observed when cells were treated with both BSO and PCB 77. The caspase 3-specific inhibitor DEVD-CHO protected cells against PCB 77/BSO-mediated apoptosis and inhibited the caspase activity without affecting JNK/SAPK activation or cellular glutathione levels. These results suggest that AhR ligands, such as PCB 77, cause vascular EC dysfunction by modulating intracellular glutathione, which subsequently leads to activation of stress-specific kinases. Furthermore, inhibition of glutathione synthesis by BSO can further potentiate the PCB 77-induced stress response and ultimately lead to apoptotic cell death.     

Involvement of caspase on apoptosis in ischemia-induced neuronal cell death: usefulness of caspase inhibitors for stroke therapy

This overviews recent understanding of the mechanisms of apoptosis on ischemia-induced neuronal cell death. Apoptosis is a prominent feature of the developing nervous system. Several lines of evidence suggest that apoptosis is also an important mechanism of cell death in adult brain in acute or chronic diseases such as stroke and Alzheimer's disease. In animal models of stroke, markers of apoptosis such as cytoplasmic and nuclear condensation and DNA fragmentation appear in neurons. A variety of physiological and pathological stimuli can activate signal-transduction pathways that result in the sequential proteolytic activation of caspase family members. The activation of caspases can be inhibited by several molecules, including peptide aldehydes (caspase-1 and or caspase-3 inhibitors) and crmA that target the active-site cysteine of caspase family members, Bcl-2, IAP (inhibitor of apoptosis protein) and NAIP (neuronal apoptosis inhibitory protein). Once activated, caspase-1 protease can activate the caspase family members and hydrolyze a discrete set of cellular targets. Poly (ADP-ribose)polymerase (PARP), which appears to facilitate apoptosis, was recognized as a substrate of activated caspase-3. These results suggest that caspase family, bcl-2 family, IAP family and substrates such PARP contribute to mechanisms of cell death in ischemic brain injury. Inhibition of the caspase family, particularly by non-peptide inhibitors that cross the blood-brain barrier and easily penetrate neurons and glia, could provide novel treatments for stroke and other forms of brain and spinal cord injury in humans.     

Safrole induces cell death in human tongue squamous cancer SCC-4 cells through mitochondria-dependent caspase activation cascade apoptotic signaling pathways

Safrole is one of important food-borne phytotoxin that exhibits in many natural products such as oil of sassafras and spices such as anise, basil, nutmeg, and pepper. This study was performed to elucidate safrole-induced apoptosis in human tongue squamous carcinoma SCC-4 cells. The effect of safrole on apoptosis was measured by flow cytometry and DAPI staining and its regulatory molecules were studied by Western blotting analysis. Safrole-induced apoptosis was accompanied with up-regulation of the protein expression of Bax and Bid and down-regulation of the protein levels of Bcl-2 (up-regulation of the ratio of Bax/Bcl-2), resulting in cytochrome c release, promoted Apaf-1 level and sequential activation of caspase-9 and caspase-3 in a time-dependent manner. We also used real-time PCR to show safrole promoted the mRNA expressions of caspase-3, -8, and -9 in SCC-4 cells. These findings indicate that safrole has a cytotoxic effect in human tongue squamous carcinoma SCC-4 cells by inducing apoptosis. The induction of apoptosis of SCC-4 cells by safrole is involved in mitochondria- and caspase-dependent signal pathways.     

Corosolic acid induces apoptotic cell death in human lung adenocarcinoma A549 cells in vitro

Corosolic acid (CRA), a triterpenoid from medicinal herbs, has been shown to induce apoptosis in several cell lines, with the exception of A549 cells. In this report, we investigated the apoptotic effect and mechanism of CRA in A549 cells. The present study shows that CRA significantly inhibits cell viability in a concentration- and time-dependent manner. Exposure to CRA induces sub-G1 cell cycle arrest and causes apoptotic death in A549 cells. CRA also triggers the activation of caspases and poly(ADP-ribose) polymerase, an effect antagonized by z-vad-fmk. In addition, exposure to CRA leads to a significant increase in the levels of reactive oxygen species (ROS) inA549 cells. Furthermore, exposure to the ROS scavenger N acetylcysteine (NAC)prevents CRA-induced apoptosis, suggesting a role for ROS in CRA-induced apoptosis. ROS are critical regulators of caspase-mediated apoptosis in A549 cells. These results indicate that CRA induces mitochondria-mediated and caspase-dependent apoptosis inA549 cells by altering anti-apoptotic proteins in a ROS-dependent manner.     

Kainic acid-induced neuronal cell death in cerebellar granule cells is not prevented by caspase inhibitors

1. We examined the role of non-NMDA receptors in kainic acid (KA)-induced apoptosis in cultures of rat cerebellar granule cells (CGCs). KA (1 - 500 microM) induced cell death in a concentration-dependent manner, which was prevented by NBQX and GYKI 52466, non-NMDA receptor antagonists. Moreover, AMPA blocked KA-induced excitotoxicity, through desensitization of AMPA receptors. 2. Similarly, KA raised the intracellular calcium concentration of CGCs, which was inhibited by NBQX and GYKI 52466. Again, AMPA (100 microM) abolished the KA (100 microM)-induced increase in intracellular calcium concentration. 3. KA-induced cell death in CGCs had apoptotic features, which were determined morphologically, by DNA fragmentation, and by expression of the prostate apoptosis response-4 protein (Par-4). 5. KA (500 microM) slightly (18%) increased caspase-3 activity, which was strongly enhanced by colchicine (1 microM), an apoptotic stimulus. However, neither Z-VAD.fmk, a pan-caspase inhibitor, nor the more specific caspase-3 inhibitor, Ac-DEVD-CHO, prevented KA-induced cell death or apoptosis. In contrast, both drugs inhibited colchicine-induced apoptosis. 5. The calpain inhibitor ALLN had no effect on KA or colchicine-induced neurotoxicity. 6. Our findings indicate that colchicine-induced apoptosis in CGCs is mediated by caspase-3 activation, unlike KA-induced apoptosis.     

Early loss of mitochondrial inner transmembrane potential in khat-induced cell death of primary normal human oral cells

Previous studies suggest the use of khat, a psychostimulant plant used by millions of people in Middle East and Africa, as risk factor for oral cancer. We previously reported that khat is able to induce adverse affects, as cell cycle arrest and apoptosis, in normal human oral cells cultured in vitro. This study further investigates the more specific role played by mitochondria in khat-induced cell death and the kinetics of the events involved in this process. Exposure of primary normal human oral keratinocytes and fibroblasts to khat extract resulted in a swift and sustained decrease of the mitochondrial inner transmembrane potential occurring within 0.5–1 h. Loss of mitochondrial membrane potential preceded all other biochemical and morphologic changes, and was associated with a significant decrease in cell survival. Subsequently, apoptosis-inducing factor was released from mitochondria into cytosol and relocated to nucleus. Cyclosporine A and bongkrekic acid delayed both the loss of mitochondrial inner transmembrane potential and the onset of cell death. This study describes a novel mechanism of khat-induced cell death in primary normal oral keratinocytes and fibroblasts involving an early pivotal effect on mitochondrial function and integrity.     

Extracellular calcium is required for the polychlorinated biphenyl-induced increase of intracellular free calcium levels in cerebellar granule cell culture.

Recent studies from the laboratory indicate that polychlorinated biphenyl (PCB) congeners can alter signal transduction and calcium homeostasis in neuronal preparations. These effects were more pronounced for the ortho-substituted, non-coplanar congeners, although the mechanisms underlying these effects are not clear. In the present study the time-course and concentration-dependent effects of coplanar and non-coplanar PCBs on intracellular free calcium concentration ([Ca2+]i) in cerebellar granule cell cultures were compared using the fluorescent probe fura-2. The ortho-substituted congeners 2,2'-dichlorobiphenyl (DCB) and 2,2',4,6,6'-pentachlorobiphenyl (PeCB) caused a gradual increase of [Ca2+]i while the non-ortho-substituted congeners 4,4'-DCB and 3,3',4,4',5-PeCB had no effect. The increase of [Ca2+]i produced by 2,2'-DCB was time- and concentration-dependent. Further studies examined possible mechanisms for this rise in [Ca2+]i. In contrast to the muscarinic agonist carbachol, the effects of 2,2'-DCB on [Ca2+]i were not blocked by thapsigargin and required the presence of extracellular calcium. The effects of ortho-substituted PCBs may depend on their ability to inhibit calcium sequestration as 2,2'-DCB significantly inhibited 45Ca2+-uptake by microsomes and mitochondria while 3,3',4,4',5-PeCB had no effect. In addition, 2,2'-DCB significantly increased the binding of [3H]inositol 1,4,5-trisphosphate to receptors on cerebellar microsomes, suggesting another possible mechanism by which ortho-substituted PCBs can mobilize [Ca2+]i. These results show that PCBs increase [Ca2+]i in vitro via a mechanism that requires extracelluar calcium, and support previous structure-activity studies indicating that ortho-substituted PCBs are more potent than non-ortho-substituted PCBs.     

Barium inhibits arsenic-mediated apoptotic cell death in human squamous cell carcinoma cells

Our fieldwork showed more than 1 μM (145.1 μg/L) barium in about 3 μM (210.7 μg/L) arsenic-polluted drinking well water (n = 72) in cancer-prone areas in Bangladesh, while the mean concentrations of nine other elements in the water were less than 3 μg/L. The types of cancer include squamous cell carcinomas (SCC). We hypothesized that barium modulates arsenic-mediated biological effects, and we examined the effect of barium (1 μM) on arsenic (3 μM)-mediated apoptotic cell death of human HSC-5 and A431 SCC cells in vitro. Arsenic promoted SCC apoptosis with increased reactive oxygen species (ROS) production and JNK1/2 and caspase-3 activation (apoptotic pathway). In contrast, arsenic also inhibited SCC apoptosis with increased NF-κB activity and X-linked inhibitor of apoptosis protein (XIAP) expression level and decreased JNK activity (antiapoptotic pathway). These results suggest that arsenic bidirectionally promotes apoptotic and antiapoptotic pathways in SCC cells. Interestingly, barium in the presence of arsenic increased NF-κB activity and XIAP expression and decreased JNK activity without affecting ROS production, resulting in the inhibition of the arsenic-mediated apoptotic pathway. Since the anticancer effect of arsenic is mainly dependent on cancer apoptosis, barium-mediated inhibition of arsenic-induced apoptosis may promote progression of SCC in patients in Bangladesh who keep drinking barium and arsenic-polluted water after the development of cancer. Thus, we newly showed that barium in the presence of arsenic might inhibit arsenic-mediated cancer apoptosis with the modulation of the balance between arsenic-mediated promotive and suppressive apoptotic pathways.     

Effects of the mycotoxin fumonisin B(1) on cell death in human kidney cells and human lung fibroblasts in primary culture

Fumonisins are mycotoxins produced by Fusarium verticillioides. The toxic effects of fumonisin B(1) (FB(1)) at the cellular level consist of a mixture of both necrosis and apoptosis. We studied the effect of FB(1) in human lung fibroblasts (NHLF) and human kidney epithelial cells (RPTEC) in primary culture. Apoptotic and necrotic cell death, collagen and fibronectin secretion were determined mainly after 14 days' exposure. The protein content of NHLF and RPTEC cells was slightly increased after 14 days' exposure to low FB(1) concentrations (0.1 or 1 microm). Caspase-3 activity tended to increase in NHLF and to decrease in RPTEC cells with higher FB(1) concentrations after 14 days' exposure. LDH release was slightly decreased in both cell types after 14 days. Collagen I and III secretion was enhanced in NHLF cells. Collagen III was decreased in RPTEC. Collagen IV was not changed in both cell types. Fibronectin secretion was uninfluenced in RPTEC and interim increased in NHLF. Furthermore LC-MS/MS studies did not give any hints for a metabolism of FB(1). Therefore, the main risk of prolonged FB(1) exposure seems to be altered collagen secretion pattern.     

Irreversible cytoskeletal disarrangement is independent of caspase activation during in vitro azaspiracid toxicity in human neuroblastoma cells

Azaspiracid-1 (AZA-1) is a marine toxin discovered in 1995. Besides damage to several tissues in vivo, AZA-1 has been shown to cause cytotoxicity in a number of cell lines and alterations in actin cytoskeleton and cell morphology. We studied the reversibility of AZA-1-induced morphological changes in human neuroblastoma cells and their dependence on caspases and signaling pathways involved in cytoskeleton regulation. Morphological/cytoskeletal changes were clearly observed by confocal microscopy 24h after the addition of toxin, without recovery upon toxin removal. Interestingly, 2min of incubation with AZA-1 was enough for the cytoskeleton to be altered 24-48h later. The activation of caspases by AZA-1 was studied next using a fluorescent caspase inhibitor. A cell population with activated caspases was observed after 48h of exposure to the toxin, but not at 24h. Two fragments and a stereoisomer of AZA-1 were tested to analyze structure-activity relationship. Only ABCD-epi-AZA-1 was active with a similar effect to AZA-1. Additionally, regarding the involvement of apoptosis/cytoskeleton signaling in AZA-1-induced morphological effects, inhibition of caspases with Z-VAD-FMK did not affect AZA-1-induced cytoskeletal changes, suggesting, together with the activation kinetics, that caspases are not responsible for AZA-1-elicited morphological changes. Modulation of PKA, PKC, PI3K, Erk, p38MAPK, glutathione and microtubules with inhibitors/activators did not inhibit AZA-1-induced actin cytoskeleton rearrangement. The JNK inhibitor SP600125 seemed to slightly diminish AZA-1 effects, however due to the effects of the drug by itself the involvement of JNK in AZA-1 toxicity needs further investigation. The results suggest that AZA-1 binds irreversibly to its cellular target, needing moieties located in the ABCDE and FGHI rings of the molecule. Cytotoxicity of AZA-1 has been previously described without reference to the type of cell death, we report that AZA-1 induces the activation of caspases, commonly used as an early marker of apoptosis, and that these proteases are not responsible for AZA-1-induced cytoskeleton disarragement in human neuroblastoma cells.     

SWCNTs induced autophagic cell death in human bronchial epithelial cells

Carbon nanotubes are being actively introduced in electronics, computer science, aerospace, and other industries. Thus, the urgent need for toxicological studies on CNTs is mounting. In this study, we investigated the alterations in cellular response with morphological changes induced by single-walled carbon nanotubes (SWCNTs) in BEAS-2B cells, a human bronchial epithelial cell line. At 24 h after exposure, SWCNTs rapidly decreased ATP production and cell viability as well a slight increase in the number of cells in the subG1 and G1 phases. In addition, SWCNTs increased the expression of superoxide dismutase (SOD)-1, but not SOD-2, and the number of cells generating ROS. The concentration of Cu and Zn ions also increased in a dose-dependent manner in cells exposed to SWCNTs. SWCNTs significantly enhanced the release of nitric oxide, interleukin (IL)-6, and IL-8 and up-regulated the expression of chemokine- and cytokine-related genes. Furthermore, the levels of autophagy-related genes, especially the DRAM1 gene, and the autophagosome formation-related proteins, were clearly up-regulated together with an increase of autophagosome-like vacuoles. Based on these results, we suggest that SWCNTs induce autophagic cell death through mitochondrial dysfunction and cytosolic damage in human bronchial epithelial cells.     

Hydroxylated polychlorinated biphenyls increase reactive oxygen species formation and induce cell death in cultured cerebellar granule cells

Polychlorinated biphenyls (PCBs) are persistent organic pollutants that bioaccumulate in the body, however, they can be metabolized to more water-soluble products. Although they are more readily excreted than the parent compounds, some of the metabolites are still hydrophobic and may be more available to target tissues, such as the brain. They can also cross the placenta and reach a developing foetus. Much less is known about the toxicity of PCB metabolites than about the parent compounds. In the present study, we have investigated the effects of eight hydroxylated (OH) PCB congeners (2′-OH PCB 3, 4-OH PCB 14, 4-OH PCB 34, 4′-OH PCB 35, 4-OH PCB 36, 4′-OH PCB 36, 4-OH PCB 39, and 4′-OH PCB 68) on reactive oxygen species (ROS) formation and cell viability in rat cerebellar granule cells. We found that, similar to their parent compounds, OH-PCBs are potent ROS inducers with potency 4-OH PCB 14 < 4-OH PCB 36 < 4-OH PCB 34 < 4′-OH PCB 36 < 4′-OH PCB 68 < 4-OH PCB 39 < 4′-OH PCB 35. 4-OH PCB 36 was the most potent cell death inducer, and caused apoptotic or necrotic morphology depending on concentration. Inhibition of ERK1/2 kinase with U0126 reduced both cell death and ROS formation, suggesting that ERK1/2 activation is involved in OH-PCB toxicity. The results indicate that the hydroxylation of PCBs may not constitute a detoxification reaction. Since OH-PCBs like their parent compounds are retained in the body and may be more widely distributed to sensitive tissues, it is important that not only the levels of the parent compounds but also the levels of their metabolites are taken into account during risk assessment of PCBs and related compounds.     

Molecular mechanisms of methylmercury-induced cell death in human HepG2 cells

Methylmercury (MeHg) has been suggested to exert cytotoxicity through multiple mechanisms, but the precise biochemical machinery has not been fully defined. This study was aimed at investigating the time-course (0–24 h) effect of 2 mg/L MeHg on cell death in human HepG2 cells.     

rBTI induces apoptosis in human solid tumor cell lines by loss in mitochondrial transmembrane potential and caspase activation

The molecular mechanisms and the possible effects of a recombinant buckwheat trypsin inhibitor (rBTI) on the induction of apoptosis in the human solid tumor cells (EC9706, HepG2 and HeLa) were investigated. An MTT assay showed that rBTI could specifically inhibit the growth of solid tumor cells in a dose- and time-dependent manner. Analysis by flow cytometry indicated that the apoptosis of several tumor cells increased after treatment with rBTI in range of 6.25–50 μg/ml. DNA electrophoresis analysis showed the ‘DNA ladder’, typical of apoptosis. rBTI-induced apoptosis was shown to involve Bax and Bak up-regulation, Bcl-2 and Bcl-xl down-regulation, release of cytochrome c from the mitochondria to the cytosol, activation of caspase-3 and -9 and disruption of the mitochondrial transmembrane potential (Δψ_m). The z-DEVD-fmk caspase-3 inhibitor significantly inhibited rBTI-induced apoptosis. We concluded that rBTI can induce the apoptosis in several types of human solid tumor cells and promotes apoptosis through the mitochondrial apoptotic pathway.