Cell death by apoptosis and its protective role against disease

[Molecular and parametric imaging with iron oxides]

Superparamagnetic iron oxide (SPIO) contrast agents, clinically established for high resolution magnetic resonance imaging of reticuloendothelial system containing anatomical structures, can additionally be exploited for the non-invasive characterization and quantification of pathology down to the molecular level. In this context, SPIOs can be applied for non-invasive cell tracking, quantification of tissue perfusion and target specific imaging, as well as for the detection of gene expression. This article provides an overview of new applications for clinically approved iron oxides as well of new, modified SPIO contrast agents for parametric and molecular imaging.

Different mechanisms of modulation of gap junction communication by non-genotoxic carcinogens in rat liver in vivo

This is a comparative study of the mechanisms by which three different rodent non-genotoxic carcinogens modulate connexin-mediated gap junction intercellular communication in male rat liver in vivo. In the case of the peroxisome proliferating agent Wy-14,643, a non-hepatotoxic dose of 50mg/kg led to a marked loss of inter-hepatocyte dye transfer associated with a loss of both Cx32 and Cx26 protein expression. In contrast, p,p'-dichlorodiphenyltrichloroethane (DDT) at a non-hepatotoxic dose (25mg/kg) was not found to alter Cx32 or Cx26 expression or to produce a measurable Cx32 serine phosphorylation but did give a small, significant reduction of cell communication. Carbon tetrachloride (CCl(4)) did not affect cell communication (despite a small significant reduction of Cx32 content) at a non-hepatotoxic dose. Both loss of communication and Cx32 expression was observed only at a dose that caused hepatocyte toxicity as evidenced by increased serum alanine aminotransferase activity. Overall, the findings emphasise that loss of gap junctional communication in vivo can contribute to carcinogenesis by non-genotoxic carcinogens through different primary mechanism. In contrast to Wy-14,643 and DDT, the results with CCl(4) are consistent with a requirement for hepatotoxicity in its carcinogenic action.

From adult stem cells to cancer stem cells: Oct-4 Gene, cell-cell communication, and hormones during tumor promotion

Carcinogenesis is characterized by "initiation," "promotion," and "progression" phases. The "stem cell theory" and "de-differentiation" theories are used to explain the origin of cancer. Growth control for stem cells, which lack functional gap junctional intercellular communication (GJIC), involves negative soluble or niche factors, while for progenitor cells, it involves GJIC. Tumor promoters, hormones, and growth factors inhibit GJIC reversibly. Oncogenes stably inhibit GJIC. Cancer cells, which lack growth control and the ability to terminally differentiate and to apoptose, lack GJIC. The Oct3/4 gene, a POU (Pit-Oct-Unc) family of transcription factors was thought to be expressed only in embryonic stem cells and in tumor cells. With the availability of normal adult human stem cells, tests for the expression of Oct3/4 gene and the stem cell theory in human carcinogenesis became possible. Human breast, liver, pancreas, kidney, mesenchyme, and gastric stem cells, HeLa and MCF-7 cells, and canine tumors were tested with antibodies and polymerase chain reaction (PCR) primers for Oct3/4. Adult human breast stem cells, immortalized nontumorigenic and tumor cell lines, but not the normal differentiated cells, expressed Oct3/4. Adult human differentiated cells lose their Oct-4 expression. Oct3/4 is expressed in a few cells found in the basal layer of human skin epidermis. The data demonstrate that normal adult stem cells and cancer stem cells maintain expression of Oct3/4, consistent with the stem cell hypothesis of carcinogenesis. These Oct-4 positive cells might represent the "cancer stem cells." A strategy to target "cancer stem cells" is to suppress the Oct-4 gene in order to cause the cells to differentiate.

In vitro apoptotic activity of 2,2-diphenyl-1,3,2-oxazaborolidin-5-ones in L5178Y cells

Compounds containing B-N bonds have shown interesting biological activity. One class of such molecules is the 2,2-diphenyl-1,3,2-oxazaborolidin-5-ones (3a-j), which contain a B-N bond, have an alpha-amino acid moiety in the heterocycle, and have an exocyclic moiety related to an amino acid. The purpose of this work was to determine the inhibitory effects of 3a-j on the proliferation of murine L5178Y lymphoma cells. A new five-membered heterocyclic nucleus with apoptotic activity was found. The target products showed potent cytotoxicity in the L5178Y cell line. Among them, 3a exhibited the highest antineoplastic activity in L5178Y cells with an IC(50) value of 22.5+/-0.2 microM.

Morphological changes in mouse embryos cryopreserved by different techniques

Cryopreservation of mammalian embryos is an important tool for the application of reproductive biotechnologies. Subjective evaluation to determine embryo viability is often used. The determination of the best cryopreservation protocol depends on morphological and molecular analysis of cellular injuries. The main objective of this study was to compare two methods of cryopreservation by assessing morphological alterations of frozen embryos using light, fluorescence, and transmission electron microscope. Fresh (control), slow frozen, and vitrified mouse embryos were composed. To evaluate the viability of the embryos, the cell membrane integrity was assessed using Hoechst33342 and propidium iodide (H/PI) staining. Morphological analyses using hematoxylin and eosin (HE) staining were performed to test different techniques (in situ, paraffin, and historesin) by both light and fluorescence microscopy. Transmission electron microscope was used to detect ultrastructural alterations in Spurr- and Araldite-embedded samples. H/PI staining detected more membrane permeability in the vitrification (69.8%) than in the slow freezing (48.4%) or control (13.8%) groups (P < 0.001). Historesin-embedded samples showed to be more suitable for morphological analyses because cellular structures were better identified. Nuclear evaluation in historesin sections showed the induction of pycnosis in slow freezing and vitrification groups. Cytoplasm evaluation revealed a condensation and an increase in eosinophilic intensity (indicating apoptosis) in the slow freezing group, and weakly eosinophilic structures and degenerated cells (indicating oncosis) in the vitrification group (P < 0.05). Ultrastructural analyses confirmed HE morphological findings. It was concluded that both cryopreservation techniques resulted in oncosis and apoptosis injuries. However, vitrification caused more severe cellular alterations and reduced embryonic viability compared to slow freezing.

Nickel Compounds Render Anti-apoptotic Effect to Human Bronchial Epithelial Beas-2B Cells by Induction of Cyclooxygenase-2 through an IKKβ/p65-dependent and IKKα- and p50-independent Pathway

The carcinogenicity of nickel compounds has been well documented both in vitro and in vivo; however, the molecular mechanisms by which nickel compounds cause cancers are far from understood. Because suppression of apoptosis is thought to contribute to carcinogenesis, we investigated the mechanisms implicated in nickel-induced anti-apoptotic effect in human bronchial epithelial (Beas-2B) cells. We found that exposure of Beas-2B cells to nickel compounds resulted in increased cyclooxygenase-2 (COX-2) expression and that small interfering RNA (siCOX-2) knockdown of COX-2 expression resulted in increased cell sensitivity to nickel-triggered cell apoptosis, demonstrating that COX-2 induction has an anti-apoptotic effect on Beas-2B cells. Overexpression of IKKbeta-KM, a kinase inactive mutant of IKKbeta, blocked NF-kappaB activation and COX-2 induction by nickel compounds, indicating that activated NF-kappaB may be a mediator for COX-2 induction. To further explore the contribution of the NF-kappaB pathway in COX-2 induction and in protection from nickel exposure, mouse embryonic fibroblasts deficient in IKKbeta, IKKalpha, p65, and p50 were analyzed. Loss of IKKbeta impaired COX-2 induction by nickel exposure, whereas knockout of IKKalpha had a marginal effect. Moreover, the NF-kappaB p65, and not the p50 subunit, was critical for nickel-induced COX-2 expression. In addition, a deficiency of IKKbeta or p65 rendered cells more sensitive to nickel-induced apoptosis as compared with those in wild type cells. Finally, it was shown that reactive oxygen species H(2)O(2) were involved in both NF-kappaB activation and COX-2 expression. Collectively, our results demonstrate that COX-2 induction by nickel compounds occurs via an IKKbeta/p65 NF-kappaB-dependent but IKKalpha- and p50-independent pathway and plays a crucial role in antagonizing nickel-induced cell apoptosis in Beas-2B cells.

Dietary modulation of the multistage, multimechanisms of human carcinogenesis: effects on initiated stem cells and cell-cell communication

Diet can influence the risk to cancer in both negative and positive ways. Worldwide, more than 10 million persons develop cancer annually. Diet could prevent many cancers. Carcinogenesis is a multistage, multimechanism process, consisting of "initiation," "promotion," and "progression" phases. Although diet could affect each phase, an efficacious strategy for dietary chemoprevention would be intervention during the promotion phase. The tumor-promotion process requires sustained exposure to agents that stimulate the growth and inhibition of apoptosis of initiated cells in the absence of antipromoters. Chronic inflammation has been associated with the promotion process. The mechanism affecting the promotion process appears to be the inhibition of cell-cell communication between normal and initiated cells. Most, if not all, tumor-promoting agents and conditions, reversibly, inhibit cell-cell communication, whereas antipromoters, antioxidants, and anti-inflammatory agents have been shown to ameliorate the effects of tumor promoters on cell-cell communication. Additionally, adult stem cells are hypothesized to be the target cells for initiating the carcinogenic process. A new paradigm has been presented that postulates the first function of the carcinogenic process is to block the "mortalization" of a normal, "immortal" adult stem cell rather than the induction of "immortalization" of a normal mortal cell.

Fragment 31–35 of β-amyloid peptide induces neurodegeneration in rat cerebellar granule cells via bax gene expression and caspase-3 activation

The amyloid beta-peptide (AbetaP) is the major protein component of brain senile plaques in Alzheimer's disease. The redox state of methionine-35 residue plays a critical role in peptide neurotoxic actions. We used the fragment 31-35 of AbetaP [AbetaP(31-35)], containing a single methionine-35 residue (Met-35), to investigate the relationship between the oxidative state of Met-35 and neurotoxic and pro-apoptotic actions induced by the peptide; in rat cerebellar granule cells (CGC), we compared the effects of AbetaP(31-35), in which the Met-35 is present in the reduced state, with those of a modified peptide with oxidized Met-35 [AbetaP(31-35)Met-35(OX)](,) as well as an AbetaP-derivative with Met-35 substituted by norleucine [AbetaP(31-35)Nle-35]. AbetaP(31-35) induced a time-dependent decrease in cell viability. AbetaP(31-35)Met-35(OX) was significantly less potent, but still induced a significant decrease in cell viability compared to control. No toxic effects were observed after treatment with AbetaP(31-35)Nle-35. AbetaP(31-35) induced a 2-fold increase in bax mRNA levels after 4h, whereas AbetaP(31-35)Met-35(OX) raised bax mRNA levels by 41% and AbetaP(31-35)Nle-35 had no effect. Finally, AbetaP(31-35) caused a 43% increase in caspase-3 activity after 24h; AbetaP(31-35)Met-35(OX) caused only a 18% increase, and AbetaP(31-35)Nle-35 had no effect. These findings suggest that AbetaP(31-35)-induced neurodegeneration in CGC is mediated by a selective early increase in bax mRNA levels followed by delayed caspase-3 activation; the redox state of the single Met-35 residue is crucial in the occurrence and extent of the above phenomena.

Effects of a high-fiber diet on hepatocyte apoptosis and liver regeneration after partial hepatectomy in rats with fatty liver

BACKGROUND

The morbidity and mortality that accompany fatty liver may occur as a result of increased apoptosis of hepatocytes and decreased liver regeneration. We determined the effects of a high-fiber diet on hepatocyte apoptosis and liver regeneration after partial hepatectomy in rats with fatty liver.

METHODS

Fatty liver was induced in male Wistar rats weighing around 200 g through feeding of a high-fat diet for 4 weeks. The rats were then randomly assigned to 3 groups that received a high-fat diet, a normal diet, or a high-fiber diet for another 4 weeks. Partial hepatectomy (around 70%) was performed, and rats were killed 6, 24, 48, or 72 hours after hepatectomy. We then measured (1) the ratio of remnant liver weight to body weight and assessed the histology of the remnant liver as indicators of fatty liver, (2) caspase-3 activity and in situ cell death detection of DNA fragmentation as indicators of apoptosis, and (3) 5-bromo-2-deoxyuridine (BrdU) activity and (4) ornithine decarboxylase (ODC) contents in remnant livers as markers of regeneration.

RESULTS

We found that (1) a high-fat diet for 4 weeks can markedly induce fatty liver, (2) apoptosis of hepatocytes is greater in fatty liver than in normal liver (98 +/- 19 vs 36 +/- 7) at 6 hours after partial hepatectomy (p < .05), (3) the capacity of liver regeneration decreases significantly (BrdU index: 30 +/- 5 vs 12 +/- 3, and ODC contents: 604 +/- 48 vs 390 +/- 42 mg/dL) in fatty liver 24 hours after partial hepatectomy (p < .05), (4) a normal diet can partially reverse the effects of fatty liver; (5) a high-fiber diet can significantly reverse the effects of fatty liver (p < .05).

CONCLUSIONS

A high-fiber diet can reverse the negative effects of fatty liver on apoptosis and regenerative capacity after partial hepatectomy.

Inhibition of telomerase activity and induction of apoptosis by curcumin in K-562 cells

Telomerase, a reverse transcriptase that maintains telomere length, is highly activated in tumor cells and practically absent in somatic cells and hence considered a potential marker for tumorigenesis. A connection between telomerase activity and resistance to apoptosis has been established. Telomerase, therefore, has been proposed to represent a novel and potentially selective target for cancer therapy. Several synthetic compounds have been developed in recent years with a view to inhibit telomerase activity with telomere shortening below a critical length resulting in apoptosis. Such compounds are always highly toxic. Many plant-derived products act through the induction of apoptosis as a mechanism to suppress carcinogenesis. Curcumin, a phenolic compound isolated from the rhizome of the plant Curcuma longa Linn., has been reported to possess anti-tumor, apoptotic and anti-angiogenic properties. Apoptosis has emerged as the major mechanism by which anti-tumor agents eliminate pre-neoplastic cells or cells progressed to malignancy. The present study was undertaken to examine the mechanism of curcumin-induced apoptosis in human leukemia cell line K-562 with particular emphasis on the role of curcumin on telomerase activity. Induction of apoptosis by curcumin is initiated by the release of cytochrome c from mitochondria into the cytosol, and evidenced by the increase in DNA content in the sub-G1 region as obtained from FACS analysis. Apoptosis is mediated by the activation of caspases 3 and 8, up-regulation of the apoptotic gene bax with concomitant down-regulation of the anti-apoptotic gene bcl-2. Using TRAP assay it has been observed that curcumin inhibits telomerase activity in a dose and time-dependent manner, the inhibition being due to suppression of translocation of telomerase reverse transcriptase (TERT), a catalytic subunit, from cytosol to nucleus. Most significantly, the inhibition of telomerase activity by curcumin correlates with several parameters of apoptosis. The results suggest that telomerase status plays an important role in the induction of apoptosis in K-562 cells by curcumin.

Amarogentin can reduce hyperproliferation by downregulation of Cox-II and upregulation of apoptosis in mouse skin carcinogenesis model

Swertia chirata, is a bitter plant, used in the Indian system of medicine (Ayurveda) for various human ailments. Our laboratory was the first to report the chemopreventive effect of this plant. The antiproliferative and pro-apoptotic action of amarogentin rich fraction of S. chirata is now demonstrated on a mouse skin carcinogenesis model. Immunohistochemical localization revealed a reduction in proliferating and increase in apoptotic cells in skin lesion following treatment, also reflected in the expression of molecular markers--Cox-II and caspase-3 proteins. It may be possible to calculate relative risk, relative protection and attributable risk from the action of test agents on proliferation and apoptosis.

Modulating apoptosis as a target for effective therapy

Alterations in cell proliferation and cell death are essential determinants in the pathogenesis and progression of several diseases such as cancer, neurodegenerative disorders or autoimmune diseases among others. Complex networks of regulatory factors determine whether cells proliferate or die. Recent progress in understanding the molecular changes offer the possibility of specifically targeting molecules and pathways to achieve more effective and rational therapies. Drugs that target molecules involved in apoptosis are used as treatment against several diseases. Candidates such as TNF death receptor family, caspase inhibitors, antagonists of the p53-MDM2 interaction, NF-kappaB and PI3K pathways and Bcl-2 family members have been targeted as cancer cell killing agents. Moreover, apoptosis of tumor cells can also be achieved by targeting the inhibitor of apoptosis proteins, IAPs, in addition to the classical antiproliferative approach. Disruption of STAT activation and interferon beta therapy have been used as a treatment to prevent the progression of some autoimmune diseases. In models of Parkinson's, Alzheimer's and amyotrophic lateral sclerosis, blocking of Par-4 expression or function, as well as caspase activation, prevents neuronal cell death. Finally, it has been shown that gene therapy may be an encouraging approach for treatment of neurodegenerative disorders.

Nitric oxide and peroxynitrite induce cellular death in bovine chromaffin cells: Evidence for a mixed necrotic and apoptotic mechanism with caspases activation

Treatment of chromaffin cells with nitric oxide (NO) donors (SNP and SNAP) and peroxynitrite produces a time- and dose-dependent necrotic and apoptotic cell death. Necrotic cell death was characterized by both an increase in lactate dehydrogenase and ATP release and changes in nuclei and cell morphology (as seen with fluorescence microscopy analysis with propidium iodide and Hoechst 33342). Apoptotic cell death was characterized by nuclear fragmentation and presence of apoptotic cell bodies, by a decrease in DNA content, and by an increase in DNA fragmentation. Treatment of chromaffin cells with lipopolysaccharide (LPS) or cytokines (interferon-gamma, tumor necrosis factor-alpha) resulted only in apoptotic cell death. Apoptotic effects of NO-inducing compounds were specifically reversed, depending on the stimuli, by the NO scavenger carboxy-PTIO (CPTio) or by the NOS inhibitors L-NMA and thiocitrulline. NO-induced apoptotic death in chromaffin cells was concomitant to a cell cycle arrest in G0G1 phase and a decrease in the number of chromaffin cells in the G2M and S phases of cell cycle. All NO-producing compounds were able to induce activation of caspase 3 and cytochrome c release, and specific inhibitors of caspase 3 and 9, such as Ac-DEVD-CHO (CPP32) and Ac-Z-LEHD-FMK, respectively, prevented NO-induced apoptosis in chromaffin cells. These results suggest that chromaffin cells could be good models for investigating the molecular basis of degeneration in diseases showing death of catecholaminergic neurons, phenomenon in which NO plays an important role.

Cannabinoid agonist WIN55,212-2 induces apoptosis in cerebellar granule cells via activation of the CB1 receptor and downregulation of bcl-xL gene expression

The endogenous cannabinoid system is involved in the regulation of a number of physiologic effects in both the central and peripheral nervous systems. Its role in the control of neuronal cell proliferation has attracted major attention because of its potential implications for new therapeutic strategies. In the present study, we demonstrated that treatment of cultured cerebellar granule cells with the synthetic cannabinoid WIN55,212-2, causes cell-body and nuclear shrinkage, which are hallmarks of neuronal apoptosis, as well as concentration-dependent decrease in cell viability. Staining with the fluorescent nuclear dye, Hoechst 33258, revealed apoptosis in 27.1% and 58.5% of cells exposed to 1 and 10 microM of WIN55,212-2, respectively (P < 0.01 and P < 0.001 vs. control respectively) after 36 hr. After 24 hr of exposure to WIN55,212-2, mRNA levels for the anti-apoptotic gene bcl-xL were reduced to 45.6% of those found in control (P < 0.01). These effects were completely reverted when cells were exposed to the synthetic cannabinoid in the presence of the specific CB1-receptor antagonist, SR141716A (1 microM). Moreover, the pro-apoptotic effect of 10 microM WIN55,212-2 could be reduced by the addition to the incubation medium of a cell-permeant inhibitor of caspase-1 (50 nM). Finally, WIN55,212-2 significantly increased caspase-1 activity after 24 hr. These findings show that the activation of CB1 receptors on cerebellar granule cells induces apoptotic cell death, which is associated with downregulation of the anti-apoptotic gene, bcl-xL, and at least in part, activation of caspase-1.

Mechanisms of Neuroprotective Effects of Therapeutic Acetylcholinesterase Inhibitors Used in Treatment of Alzheimer's Disease

Donepezil, galanthamine, and tacrine are therapeutic acetylcholinesterase (AChE) inhibitors used for the treatment of Alzheimer's disease. The aim of this paper is to review recent findings on their neuroprotective properties and the mechanisms of neuroprotection against glutamate neurotoxicity in rat cortical neurons. First, the hallmark of neurotoxicity induced by two different glutamate treatment conditions was examined, revealing that acute glutamate treatment (1 mM, 10 min) induces necrotic neuronal death and that moderate glutamate treatment (100 microM, 24 hr) induces apoptotic neuronal death. Next, we showed that therapeutic AChE inhibitors protect cortical neurons from glutamate neurotoxicity in a time- and concentration-dependent manner. We examined the mechanism of this neuroprotective effect and found that the neuroprotective effects against both acute and moderate glutamate treatments are mediated through nicotinic acetylcholine receptors (nAChRs), or more specifically, the effects of donepezil and galanthamine are mediated through alpha4- and alpha7-nAChR. We also showed that donepezil and galanthamine protect cortical neurons against acute glutamate treatment-induced neurotoxicity at steps before, and that tacrine protects at steps after, nitric oxide radical formation. On the other hand, the neuroprotective effects of donepezil and galanthamine, but not of tacrine, against neurotoxicity induced by moderate glutamate treatment were mediated through the phosphatidylinositol 3-kinase-Akt pathway. These findings unveiled the hitherto unknown neuroprotective effects of therapeutic AChE inhibitors and provided valuable insights into its neuroprotective mechanisms. They may very likely form the basis for a novel treatment strategy against Alzheimer's disease.

Apoptotic death of Listeria monocytogenes-infected human macrophages induced by lactoferricin B, a bovine lactoferrin-derived peptide

Listeria monocytogenes, an intracellular facultative food-borne pathogen, was reported to induce apoptosis in vitro and in vivo in a variety of cell types with the exception of murine macrophages. These cells represent the predominant compartment of bacterial multiplication and die as a result of necrosis. In this study we showed that human non-activated and IFN-gamma-activated macrophagic-like (THP-1) cells infected with L. monocytogenes, mainly die by necrosis rather than by an apoptotic process. Two natural products derived from bovine milk, lactoferrin and its derivative peptide lactoferricin B, are capable of regulating the fate of infected human macrophages. Bovine lactoferrin treatment of macrophages protects them from L. monocytogenes-induced death whereas lactoferricin B, its derivative peptide, determines a shifting of the equilibrium from necrosis to apoptosis.

Paclitaxel induces apoptosis via caspase-3 activation in human osteogenic sarcoma cells (U-2 OS)

Paclitaxel has been found to exhibit cytotoxic and antitumor activity. There is little information regarding the mechanisms of apoptotic-inducing effect of paclitaxel on human osteogenic sarcoma U-2 OS cells. Several key regulatory proteins are involved in the initiation of apoptosis. Caspase-3 plays a direct role in proteolytic cleavage of cellular proteins responsible for progression to apoptosis. We examined the effect of paclitaxel on the cell cycle arrest and apoptosis in U-2 OS cells using flow cytometric analysis and Western blotting. We also measured the inhibition of paclitaxel-induced apoptosis and the caspase-3 activity by the broad-spectrum caspase inhibitor z-VAD-fmk on U-2 OS cells. The increased levels of casapse-3 were also confirmed by cDNA microarray. Our observations were: (1) paclitaxel treatment resulted in G2/M-cycle arrest in U-2 OS cells; (2) time and dose dependent apoptosis of U-2 OS cells was induced by paclitaxel; (3) in U-2 OS cells, z-VAD-fmk blocked the paclitaxel-induced apoptosis and caspase-3 activation. These results suggest that paclitaxel-induced G2/M-cycle arrest of the G2/M phase and apoptosis via a caspase-3 pathway in U-2 OS cells.

Induction of cytochrome P450 2E1 increases hepatotoxicity caused by Fas agonistic Jo2 antibody in mice

Cytochrome P450 2E1 (CYP2E1) may be a central pathway in generating oxidative stress, reactive oxygen species, and causing hepatotoxic injury by alcohol and various hepatotoxins. This study evaluated the ability of CYP2E1 to potentiate or synergize the hepatotoxicity of Fas in vivo. C57BL/6 mice were injected intraperitoneally with pyrazole (Pyr) to induce CYP2E1. Then, 16-hour fasted mice were administered agonistic Jo2 anti-Fas antibody ip. Other mice were treated with Pyr or Jo2 alone. Levels of serum aminotransferase were 8.3- and 6.3-fold higher in the Pyr/Jo2 group compared with Jo2 alone, respectively. Histological evaluation of liver showed more extensive acidophilic necrosis and severe pathological changes in the Pyr/Jo2-treated mice. DNA fragmentation and caspase-8 and -3 activities were more elevated in the Pyr/Jo2 group compared with Jo2 alone. CYP2E1 activity and protein levels were higher in the Pyr/Jo2 group than in Jo2 alone. Levels of inducible nitric oxide synthase, 3-nitrotyrosine protein adducts, malondialdehyde, and protein carbonyls were also higher in the Pyr/Jo2 group compared with Jo2 alone. Glutathione and activities of catalase and Cu-Zn superoxide dismutase were decreased in the Pyr/Jo2 group. Administration of chlormethiazole, an inhibitor of CYP2E1, to the Pyr/Jo2-treated mice caused a significant decrease of alanine aminotransferase and liver pathological changes in association with a decrease in CYP2E1 protein and activity. In conclusion, enhanced hepatotoxicity of Fas was found in mice with elevated levels of CYP2E1. We speculate that overexpression of CYP2E1 might synergize and increase the susceptibility to Fas induced-liver injury.

Hydroxyurea (HU)-induced apoptosis in the mouse fetal lung

In this study, the cytotoxicologic effects of HU on the fetal lung were assessed by exposing pregnant mice to HU on day 13 of gestation. The number of TUNEL-positive cells, i.e., apoptotic cells, in the fetal lung began to increase at 3 h after treatment (h), peaked at 6 h, and decreased thereafter, and the sequence of the number of cleaved caspase 3-positive cells corresponded to that of TUNEL-positive cells. Such positive reactivity for TUNEL and cleaved caspase 3 was mainly seen in pulmonary mesenchymal cells. Prior to the induction of apoptosis, the number of p53-positive cells in the fetal lung prominently increased at 1 and 3 h, and decreased thereafter. Among p53 transcriptional target genes (p21, fas, bax, apaf1, cyclin G, mdm2, and gad 45) examined, the expression levels of p21, bax, and cyclin G mRNAs were significantly elevated. In addition, the expression of fas mRNA tended to show higher levels compared with controls until 24 h. In addition, the results of flow cytometric analysis suggested that cell cycle arrest might be induced in S phase at 3 h. The present results suggest that HU-induced apoptosis in the mouse fetal lung may be closely related with the induction of p53.

Induction of caspase-3-dependent apoptosis in human leukemia HL-60 cells by paclitaxel

BACKGROUND

Paclitaxel, an antineoplastic drug, inhibits cell growth and cell cycle progression and induces apoptosis in human leukemia HL-60 cells. Caspase-3 plays a direct role in proteolytic cleavage of cellular proteins responsible for progression to apoptosis.

METHODS

We examined the cell morphology and apoptosis in HL-60 cells after exposure to paclitaxel and measured caspase-3 activities with or without z-VAD-fmk (a broad-spectrum caspase inhibitor) pretreatment by flow cytometric analysis and Western blotting.

RESULTS

Together, our results were (1) paclitaxel mainly induced G2/M cell cycle arrest in HL-60 cells (p<0.001); (2) time (p<0.001)- and dose-dependent (p<0.001) apoptosis of HL-60 cells was induced by paclitaxel; (3) in HL-60 cells, z-VAD-fmk blocked paclitaxel-induced apoptosis (12 h: p<0.001; 24 h: p<0.01; 48 h: p<0.01; 72 h: p<0.001) and caspase-3 activation (12 h: p<0.05; 24 h: p<0.01; 48 h: p<0.01; 72 h: p<0.01).

CONCLUSIONS

These results suggest that paclitaxel can induce G2/M cell cycle transition and apoptosis via caspase-3 activity in HL-60 cells.

Adenosine triphosphate induces activation of caspase-3 in apoptosis of human granulosa-luteal cells

Adenosine triphosphate (ATP) has been shown to induce programmed cell death in various systems. However, little is known about the effect of ATP on human granulosa-luteal cells (hGLCs). The present study was designed to examine the effect of ATP on the activation of the caspase signaling pathway and its role in inducing programmed cell death. Human GLCs were collected from patients undergoing in vitro fertilization programs, and then were cultured in FBS-supplemented DMEM for 3 days prior to our studies. To examine the dose-response relationship, hGLCs were treated with increasing concentrations of ATP (10 microM, 100 microM, 1 mM or 10 mM) for 24 hours. For time-course experiments, hGLCs were treated with 10 mM ATP for 6, 12, or 24 hours. Western blot analysis was performed using antibodies against the pro- and active forms of caspase-3, -9, or PARP. To quantify the induction of apoptosis, DNA fragmentation was measured using the cell death detection enzyme-linked immunosorbent assay. To examine the effect of human chorionic gonadotropin (hCG) in protecting cells from apoptosis, hGLCs were treated with 10 IU hCG in the presence of 10 mM ATP for 12 hours. It was demonstrated that ATP was capable of inducing DNA fragmentation in a dose- and time-dependent manner. Furthermore, Western blot analysis, which detected the pro- and active forms of caspase-3, or PARP, demonstrated that ATP activated the caspase-signaling pathway, leading to the proteolytic conversion of pro-caspase-3 to active caspase-3, and the subsequent cleavage of the caspase substrate PARP. Based on our observation, caspase-9 was not triggered by ATP. Interestingly, hCG attenuated the effect of ATP in activating the caspase signaling pathway. To our knowledge, this is the first demonstration of the ATP-induced activation of the caspase signaling pathway in the human ovary. These results support the notion that the caspase-signaling pathway is involved in mediating ATP actions in the human ovary.

Apoptosis in stages of mouse hepatocarcinogenesis: failure to counterbalance cell proliferation and to account for strain differences in tumor susceptibility

C3H/He and B6C3F1 show much higher liver cancer susceptibility than C57BL/6J mice. We studied the hypothesis that this difference might result from failure of apoptosis. Hepatocarcinogenesis was induced by a single dose of N-nitrosodiethylamine (NDEA), followed by phenobarbital (PB) for up to 90 weeks. We observed (1) earlier appearance of putative preneoplastic foci (PPF), hepatocellular adenoma (HCA), and carcinoma (HCC) in C3H/He than in C57Bl/6J mice and (2) an increase of hepatocellular DNA synthesis in C3H/He and C57Bl/6J mice, compared to normal liver, via PPF and HCA to HCC. PB enhanced DNA synthesis and growth of PPF, in the C3H/He strain only, and of HCA and HCC of both strains. Apoptoses were rare in unaltered livers as well as in preneoplastic lesions, but tended to increase in HCA and HCC of both strains. PB lowered apoptotic activity in PPF of C3H/He mice, but enhanced it in HCA and HCC of C57Bl/6J mice at late stages. In conclusion, the strain difference in growth rates of PPF and tumors is largely determined by higher rates of cell proliferation in C3H/He mice, with and without promotion by PB. Moreover, in C57Bl/6J mice the promoting effect of PB was restricted to HCA and HCC and was not seen in PPF. Apoptosis was generally low and was not a major cause of the strain difference in tumor susceptibility. In contrast with rat liver, inhibition of apoptosis appears to be a minor determinant of tumor promotion in mice.

Grape seed proanthocyanidins induce apoptosis through p53, Bax, and caspase 3 pathways

Grape seed proanthocyanidins (GSP) have been shown to inhibit skin chemical carcinogenesis and photocarcinogenesis in mice. The mechanisms responsible for the anticarcinogenic effects of GSP are not clearly understood. Here, we report that treatment of JB6 C141 cells (a well-developed cell culture model for studying tumor promotion in keratinocytes) and p53+/+ fibroblasts with GSP resulted in a dose-dependent induction of apoptosis. GSP-induced (20-80 g/ml) apoptosis was observed by using immunofluorescence (27-90% apoptosis) and flow cytometry (18-87% apoptosis). The induction of apoptosis by GSP was p53-dependent because it occurred mainly in cells expressing wild-type p53 (p53+/+; 15-80%) to a much greater extent than in p53-deficient cells (p53-/-; 6-20%). GSP-induced apoptosis in JB6 C141 cells was associated with increased expression of the tumor-suppressor protein, p53, and its phosphorylation at Ser15. The antiapoptotic proteins, Bcl-2 and Bcl-xl, were downregulated by GSP, whereas the expression of the pro-apoptotic protein, Bax, and the levels of cytochrome c release, Apaf-1, caspase-9, and cleaved caspase 3 (p19 and p17) were markedly increased in JB6 C141 cells. The downregulation of Bcl-2 and upregulation of Bax were also observed in wild-type p53 (p53+/+) fibroblasts but was not observed in their p53-deficient counterparts. These data clearly demonstrate that GSP-induced apoptosis is p53-dependent and mediated through the Bcl-2, Bax, and caspase 3 pathways.

Epigallocatechin-3-gallate induces apoptosis in estrogen receptor–negative human breast carcinoma cells via modulation in protein expression of p53 and Bax and caspase-3 activation

Epigallocatechin-3-gallate (EGCG) has been shown to have anticarcinogenic effects in in vitro and in vivo models, and this effect is mediated at least in part by its ability to induce apoptosis in cancer cells without affecting normal cells. It has been recognized that estrogen receptor (ER)–dependent breast cancers generally have a better prognosis and are often responsive to antiestrogen therapy; however, ER-independent breast cancers are more aggressive and unresponsive to antiestrogens. Using the MDA-MB-468 human breast cancer cell line as an in vitro model of ER-negative breast cancers, we found that treatment of EGCG resulted in dose-dependent (5-80 μg/mL) and time-dependent (24-72 hours) inhibition of cellular proliferation (15-100%) and cell viability (3-78%) in MDA-MB-468 cells. Decrease in cell viability was associated with the induction of apoptosis (18-66%) which was analyzed by DNA ladder assay, fluorescence staining, and flow cytometry. Induction of apoptosis by EGCG could be corroborated to the increased expression of tumor suppressor protein p53 and its phosphorylation at Ser 15 residue. EGCG decreased the expression of antiapoptotic protein Bcl-2 but increased proapoptotic protein Bax in these cells. The increased ratio of Bax/Bcl-2 proteins after EGCG treatment may have resulted in increased release of cytochrome c from mitochondria into cytosols, increased expression of Apaf-1, and activation of caspase-3 and poly(ADP-ribose) polymerase, which may lead to apoptosis in MDA-MB-468 cells. Together, the results of this study provide evidence that EGCG possesses anticarcinogenic effect against ER-negative breast cancer cells and thus provide the molecular basis for the future development of EGCG as a novel and pharmacologically safe chemopreventive agent for breast cancer prevention.

Marine Alkaloid Polycarpine and Its Synthetic Derivative Dimethylpolycarpine Induce Apoptosis in JB6 Cells Through p53- and Caspase 3-Dependent Pathways

PURPOSE

Polycarpine from ascidian Polycarpa aurata was previously found to be active against different human tumor cells. In this study, we investigated the antitumor mechanisms of polycarpine and its synthetic derivative, desmethoxyethoxy-polycarpine (dimethylpolycarpine), through the induction of apoptosis. This new knowledge regarding the proapoptotic action of polycarpine and dimethylpolycarpine should lead to a better understanding of their effects and development of a new class of anticancer drugs.

METHODS

Apoptosis was clearly observed by flow cytometry and Western blotting using an antibody against cleaved caspase-3 as an apoptotic marker.

RESULTS

Polycarpines differentially activated p38 kinase, JNKs, and ERKs in JB6 Cl 41 cells. The polycarpines-induced apoptosis was decreased in cells expressing a dominant-negative mutant of JNK. Both compounds stimulated p53-dependent transcriptional activity and phosphorylation. Induction of p53-phosphorylation at serine 15 was suppressed in JNKI and JNK2 knockout cells. Furthermore, polycarpines were unable to induce apoptosis in p53-deficient MEFs in contrast to a strong induction of apoptosis in wild type MEFs, suggesting that p53 is involved in apoptosis induced by polycarpines. The p53 phosphorylation in turn was mediated by activated JNKs.

CONCLUSIONS

These results indicate that all three MAPK signaling pathways are involved in the response of JB6 cells to treatment with polycarpines. Evidence also supports a proapoptotic role of the JNKs signaling pathway in vivo and clearly indicates that JNKs are required for phosphorylation of c-Jun, activation of p53, and subsequent apoptosis induced by polycarpines.

Insulin and dexamethasone inhibit TGF-beta-induced apoptosis of hepatoma cells upstream of the caspase activation cascade

Insulin and dexamethasone are potent inhibitors of apoptosis induced by transforming growth factor-beta1 (TGF-beta) in hepatoma cells. Using FTO-2B rat hepatoma cells, we determined whether the anti-apoptotic effects of these agents result from interference within or upstream of the TGF-beta-induced caspase cascade. Activation of different initiator and effector caspases, Bax and Bcl-xL expression, mitochondrial cytochrome c release and activation of PKB/Akt were analyzed by use of synthetic caspase substrates and Western blotting, respectively. TGF-beta-induced apoptosis was characterized by release of cytochrome c from mitochondria and activation of caspases-3, -7, -8 and -9. These effects were observable as early as 8-12 h after start of treatment and increased with time of observation. Inhibition of TGF-beta-induced apoptosis by insulin and dexamethasone was paralleled by a strong reduction of caspase-3-like activity. Caspase-8 activation was almost completely suppressed by these agents, and caspase-9 activity was decreased to levels within or slightly above unstimulated control cells. In addition, cytochrome c release from mitochondria was efficiently repressed, which was associated with upregulation of Bcl-xL by dexamethasone and activation of PKB/Akt by insulin. Thus, both anti-apoptotic compounds exert their inhibitory effects through modulation of anti-apoptotic signalling pathways involved in regulation of cytochrome c release and activation of the caspase machinery.

Assessment of the genotoxic and cytotoxic potential of an anti-epileptic drug, phenobarbital, in mice: a time course study

To examine if chronic oral administration of phenobarbital (PB), a widely used anti-epileptic drug, has any genotoxic and cytotoxic potential in mice, a mammalian model, cytogenetic assays through several endpoints such as chromosome aberrations, induction of micronuclei, mitotic index of bone marrow cells, sperm-head anomaly in testis and enzymatic assays of several toxicity marker enzymes have been conducted by use of standard techniques. Mice of both treated (chronically receiving an oral dose of PB at 1.2 mg/kg bw) and control (without receiving PB) groups were sacrificed at 7, 15, 30, 60, 90 and 120 days for the study with all the above-mentioned protocols. Further, total protein profiles in liver of both control and treated mice were analyzed through the SDS-PAGE technique at day 60. The results of all these studies, when compared with controls, showed that PB has both genotoxic and cytotoxic potential in apparently increasing intensity at longer periods of chronic feeding in mice, which would warrant due consideration in its long-term use on human subjects.

Rapid clearance of fetal cells from maternal circulation after delivery

We previously reported increased apoptosis in the maternal circulation during pregnancy, partly accounting for the presence of cell-free fetal DNA in maternal plasma. In the current study, apoptosis was quantitated in 60 peripheral blood samples obtained from 15 women sequentially tested postpartum using the binding of annexin V. FISH with X/Y probes was performed on annexin V-positive cells isolated by MACS in patients with male fetuses to estimate the proportion of fetal cells among the apoptotic cell population. Twenty-four women at the thirty-seventh to thirty-eighth week of gestation and 35 nonpregnant females were used as controls. Apoptosis rate in the thirty-seventh to thirty-eighth week was 12.5% (9.2-14.7%). At 30 minutes, 12 hours, 24 hours, and 48 hours postpartum, it was 25.1% (16.8-28.5%), 12.5% (10.9-14.1%), 6.1% (4.8-7.1%), and 2.3% (1.3-3.0%), respectively. Male apoptotic cells were identified in all cases with male fetuses at 37 to 38 weeks of gestation, and the mean proportion was 9.9% (5.9-13.2%). The proportion of fetal cells 30 minutes after delivery was 14.8% (12.5-25.5%) and 12 hours postpartum 2.1% (0.8-4.1%). Male fetal apoptotic cells were detected in three of eight samples collected 24 hours after delivery from women who delivered males, at frequencies of 0.10%, 0.15%, and 0.25% (mean 0.16%). There were no fetal apoptotic cells 48 hours after delivery. Apoptosis partly accounts for the clearance of fetal cells from the maternal circulation. Because it is a rapid reaction, completed within 2-3 hours, persistence of fetal cells is possibly due to apoptosis-resistant progenitors or to defective regulation of apoptosis, leading to fetal cell microchimerism associated with autoimmune diseases.

Involvement of histone hypoacetylation in Ni2+-induced bcl- 2 down-regulation and human hepatoma cell apoptosis

Although induction of cell apoptosis is known to be involved in the cytotoxicity of Ni(2+), little research has been aimed at the mechanism of Ni(2+)-induced apoptosis. Recent studies showed that Ni(2+) induces histone hypoacetylation in different cell lines. Since histone hypoacetylation plays important roles in the control of cell cycle progress and apoptosis, we hypothesized that histone hypoacetylation may be an unrevealed pathway in Ni(2+)-induced apoptosis. To address this, effects of Ni(2+) on cell apoptosis, bcl- 2 gene expression and histone acetylation were examined in human hepatoma Hep3B cells. We found that Ni(2+) treatment resulted in cell proliferation arrest, the appearance of detached cells, condensed chromatin, apoptotic bodies and specific DNA fragmentation, indicating the occurrence of cell apoptosis. At the same time, Ni(2+) induced a significant decrease in bcl- 2 expression and histone acetylation; the decrease of histone H4 acetylation in nucleosomes associated with the bcl- 2 promoter region was also proven by a chromatin immunoprecipitation assay, indicating the involvement of histone hypoacetylation in Ni(2+)-induced bcl- 2 down-regulation. Further studies showed that increasing histone acetylation by either 100 nM of trichostatin A or over-expressing histone acetyltranferase p300 in Hep3B cells obviously attenuated the bcl- 2 down-regulation and cell apoptosis caused by Ni(2+). Considering the importance of bcl- 2 in determining cell survival and apoptosis, the data presented here suggest that histone hypoacetylation may represent one unrevealed pathway in Ni(2+)-induced cell apoptosis, where bcl- 2 is one of its targets.

Bcl-2 overexpression inhibits tetrachlorohydroquinone-induced apoptosis in NIH3T3 cells: A possible mechanism for tumor promotion

TCHQ is a major carcinogenic metabolite of the widely used wood preservative PCP. Recently, we found that TCHQ was a promoter in a mouse skin carcinogenesis model. However, the mechanism is still not clear. In this study, we showed that overexpression of Bcl-2 effectively suppressed TCHQ-induced apoptosis in NIH3T3 cells, as evidenced by morphological changes and DNA fragmentation. Although production of ROS contributes to TCHQ-induced apoptosis, Bcl-2 failed to attenuate TCHQ-elicited increase of intracellular ROS level. In addition, overexpressed Bcl-2 provides only partial protection against TCHQ-induced cellular DNA damage. We also found that TCHQ induced a change in mitochondrial transmembrane potential, and that caspase-9 and subsequent caspase-3 can be activated during TCHQ-induced acute apoptosis. Interestingly, TCHQ induced a significant upregulation of Bcl-2 expression, and over-expressed Bcl-2 can dramatically inhibit the change of mitochondria membrane potential and activation of both caspase-9 and -3. Thus, our results suggest TCHQ-induced tumor promotion may be through a mechanism of upregulation of Bcl-2 protein and subsequent apoptosis inhibition.

Kupffer cells promote lead nitrate-induced hepatocyte apoptosis via oxidative stress

BACKGROUND: Apoptosis and its modulation are crucial factors for the maintenance of liver health, allowing hepatocytes to die without provoking a potential harmful inflammatory response through a tightly controlled and regulated process. Since Kupffer cells play a key role in the maintenance of liver function, the aim of this study was to verify whether Kupffer cells are involved in the induction of liver apoptosis after i.v. injection of Pb(NO3)2 likely by secretion mechanisms. RESULTS: The in vivo hepatic apoptosis, induced by Pb(NO3)2 was prevented by a pre-treatment with gadolinium chloride (GdCl3), a Kupffer cells toxicant, that suppresses Kupffer cell activity and reduces to a half the apoptotic rate. In addition, in vivo Pb(NO3)2 administration deprives hepatocytes of reduced glutathione, whereas the loss of this important oxidation-preventing agent is considerably mitigated or abolished by pre-treatment with GdCl3. However, incubation of isolated hepatocytes and Kupffer cells and HepG2 cells with Pb(NO3)2 for 24 hours induced necrotic but not apoptotic cells. Apoptosis of hepatocytes and HepG2 cells was observed only after the addition of conditioned medium obtained from Kupffer cells cultured for 24 hours with Pb(NO3)2, thus indicating the secretion of soluble mediators of apoptosis by Kupffer cells. Apoptosis in the HepG2 cells was observed upon 24-hours incubation of HepG2 cells with 1 mM buthionine sulfoximine, a glutathione depleting agent, thus showing that there is an oxidative apoptogenic pathway in HepG2 cells. CONCLUSION: Pb(NO3)2 has, at most, a direct necrotic (but not apoptogenic) effect on hepatocytes and HepG2 cells, giving a clue about the regulatory role of Kupffer cells in the induction of liver apoptosis after a single Pb(NO3)2 injection without pre-treatment with GdCl3, probably via secreting soluble factors that trigger oxidative stress in target cells.

Role of superoxide in poly(ADP-ribose) polymerase upregulation after transient cerebral ischemia

Oxidative stress plays a pivotal role in ischemic-reperfusion cell injury. Oxygen-derived free radicals trigger DNA strand damage, which is responsible for the activation of poly(ADP-ribose) polymerase (PARP). Recent studies have shown that peroxynitrite is the primary mediator of DNA damage and, hence, PARP activation after ischemia. PARP activation depletes NAD and ATP pools, ultimately resulting in necrotic cell death by loss of energy stores. Our study shows that PARP is upregulated as early as 15 min after 1 h of transient focal cerebral ischemia and remains for 8 h. We also examined the role of superoxide in PARP induction using copper/zinc-superoxide dismutase transgenic mice. Immunohistochemical and Western blotting data showed that there was no increased induction in PARP expression in these mice, suggesting that one of the mechanisms by which ischemic injury is attenuated in these mice might be by the inhibition of PARP induction. Furthermore, double staining of ischemic tissue with a PARP antibody and terminal deoxynucleotidyl transferase-mediated uridine 5'-triphosphate-biotin nick end labeling (TUNEL) indicated that most cells that are positive for TUNEL do not stain for the PARP antibody, confirming recent reports that PARP activation is involved in necrotic cell death rather than apoptosis during ischemic-reperfusion injury.

Oxysterol-induced apoptosis of vascular smooth muscle cells is reduced by HMG-CoA reductase inhibitor, pravastatin

We investigated the mechanism by which 7-ketocholesterol damages vascular smooth muscle cells and the protective effect of the hydroxymethyl glutary CoA reductase inhibitor, pravastatin on it. When 7-ketocholesterol (50 micromol/L) was added to cultured human vascular smooth muscle cells, the extent of cell detachment increased and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling was positive. DNA extracted from the smooth muscle cells exposed to 7-ketocholesterol showed a ladder pattern on agarose electrophoresis. The fragmented DNA also increased in smooth muscle cells incubated with 7-ketocholesterol dose-dependently. In the presence of pravastatin, the cell detachment induced by 7-ketocholesterol was inhibited and the amount of fragmented DNA decreased significantly. These effects of pravastatin were inhibited by mevalonate. The results suggest that 7-ketocholesterol-induced apoptosis of vascular smooth muscle cells is inhibited by pravastatin, and mevalonate acts as a trigger of the apoptosis.

Intracellular glutathione depletion and reactive oxygen species generation are important in alpha-hederin-induced apoptosis of P388 cells

alpha-Hederin, a pentacyclic triterpene saponin isolated from the seeds of Nigella sativa, was recently reported to have potent in vivo antitumor activity against LL/2 (Lewis Lung carcinoma) in BDF1 mice. In this study we observed that alpha-hederin caused a dose- and time-dependent increase in apoptosis of murine leukemia P388 cells. In order to evaluate the possible mechanisms for apoptosis, the effects of alpha-hederin on intracellular thiol concentration, including reduced glutathione (GSH), and protein thiols, and the effects of pretreatment with N-acetlycysteine (NAC), a precursor of intracellular GSH synthesis, or buthionine sulfoxime (BSO), a specific inhibitor of intracellular GSH synthesis, on alpha-hederin-induced apoptosis were investigated. It was found that alpha-hederin rapidly depleted intracellular GSH and protein thiols prior to the occurrence of apoptosis. NAC significantly alleviated alpha-hederin-induced apoptosis, while BSO augmented alpha-hederin-induced apoptosis significantly. The depletion of cellular thiols observed after alpha-hederin treatment caused disruption of mitochondrial membrane potential (deltapsi(m)) and subsequently increased the production of reactive oxygen species (ROS) in P388 cells at an early time point. Bongkrekic acid (BA), a ligand of the mitochondrial adenine nucleotide translocator, and cyclosporin (CsA) attenuated the alpha-hederin-induced loss of deltapsi(m), and ROS production. Thus, oxidative stress after alpha-hederin treatment is an important event in alpha-hederin-induced apoptosis. As observed in this study, permeability transition of mitochondrial membrane occurs after depletion of GSH and precedes a state of reactive oxygen species (ROS) generation. Further, we observed that alpha-hederin caused the release of cytochrome c from the mitochondria to cytosol, leading to caspase-3 activation. Our findings thus demonstrate that changes in intracellular thiols and redox status leading to perturbance of mitochondrial functions are important components in the mechanism of alpha-hederin-induced cell death.

Apoptosis: its importance in spermatogenic dysfunction

Apoptosis, spontaneous programmed cell death, has recently generated great interest in several areas of investigation, including infertility. Selective sperm cell death also seems to be a component of normal spermatogenesis. A better understanding of this process may lead to the development of new strategies to treat intrinsic testicular failure.

Phagocytosis of apoptotic cells by liver: a morphological study

The present review deals with the morphological features of the removal of apoptotic cells by liver. The engulfment of cells undergoing apoptosis can be considered a specialized form of phagocytosis, playing a major role in the general tissue homeostasis in physiological and pathological conditions. In fact, defects of phagocytosis of apoptotic cells might have deleterious consequences for neighboring healthy cells, i.e., pathogenesis of inflammatory disease or dysregulation of the immune system. Phagocytosis of apoptotic cells by liver is a complex phenomenon, involving multiple molecular mechanisms of recognition (i.e., lectin-like receptors and receptors for externalized phosphatydilserine) of both parenchymal (hepatocytes) and nonparenchymal (Kupffer and endothelial cells) liver cells, often operating in cooperation. The data discussed in the present review are drawn from studies of phagocytosis of apoptotic cells in the liver, carried out with in vivo and in situ adhesion experiments as well as in vitro assays. Our results indicate that the three main liver cell types (hepatocytes, Kupffer, and endothelial cells) are able to recognize and internalize apoptotic cells by means of specific receptors (galactose and mannose-specific receptor; receptor for phosphatydilserine) and by cytoskeletal reorganization that favors the engulfment of the apoptotic cells. The "flags" for the identification of apoptotic cells by the liver are modifications of the surface of dead cells, i.e., sugar residues and phosphatydilserine exposition. Vitronectin receptor is not involved in such a recognition. The adhesions between modified cell surfaces of apoptotic cells and phagocytes generate cytoplasmatic signaling pathways that drive apoptotic cells to their final fate within the phagocytes (i.e., lysosomal digestion).

Determination of the epigenetic effects of ochratoxin in a human kidney and a rat liver epithelial cell line

Epidemiological studies have implicated ochratoxin A (OTA), a fungal metabolic-contaminant of animal and human food sources, in Balkan Endemic Nephropathy and renal tumors. Many environmental toxicants operate through nongenotoxic mechanisms that epigenetically control gene expression leading to a diseased state. Gap junctional intercellular communication (GJIC) plays a central role in the epigenetic control of genes in which alteration of normal GJIC has been implicated in many human pathologies, including cancer, teratogenesis, reproductive dysfunction and peripheral neuropathies. The cell proliferative stages of human diseases, such as cancer, also involves the induction of signal transduction pathways controlling the mitogenic steps, in which the mitogen activated protein kinases (MAPK), such as extracellular receptor kinase (ERK) and p38, are central to mitogenesis. We therefore determined the effects of OTA on GJIC and MAPK in a human kidney and rat liver epithelial cell line. OTA reversibly inhibited GJIC at noncytotoxic doses in the rat liver but not the human kidney cell line. Similarly, OTA was also a strong activator of MAPK, ERK and p38, in the rat liver cells but only weakly activated ERK and had no affect on p38 in the human kidney cell line. Another hallmark of human diseases is an abnormal alteration of apoptosis, also known as programmed cell death. We used our myc-transfected cell line, which exhibits higher levels of apoptosis, to test the effects of OTA on apoptosis. OTA greatly induced apoptosis in this cell line, which is contrary to the effects of most tumor promoters. In summary, OTA exhibits tumor promoting properties in the liver, but the effects of OTA on the human kidney epithelial cells suggested a lack of tumorigenic activity assuming that these epithelial cells, like the rat liver epithelial cells, are a primary target for carcinogens. These results also indicate that the nephrotoxicity of OTA either does not involve GJIC, assuming these epithelial cells play a vital role in kidney physiology, or that a more differentiated kidney cell type is the target for OTA toxicity, of which the role of GJIC remains unknown.

DI-(2-ethylhexyl) phthalate-induced cell proliferation is involved in the inhibition of gap junctional intercellular communication and blockage of apoptosis in mouse Sertoli cells

Di-(2-ethylhexyl) phthalate (DEHP) has been studied on gap junctional intercellular communication (GJIC) and apoptosis in cultured normal mouse Sertoli cells. Since the inhibition of GJIC and programmed cell death or apoptosis play important roles in tumor promotion and developmental toxicity, it has been hypothesized that tumor promoters may inhibit apoptosis by blocking GJIC. The results showed that the most significant downregulation of GJIC was detected at 9 h after DEHP treatment. However, a significant concentration-dependent pattern was not observed at concentrations of 100 and 500 microM, but there was a time-dependent recovery of GJIC. DEHP inhibited the apoptotic changes in the cells such as chromatin condensation, nuclear fragmentation, and the cleavage of poly(ADP-ribose) polymerase. Morphological changes related to apoptosis appeared in the nontreated cells after 12 h of serum deprivation. These morphological changes were significantly reduced in the TM5 Sertoli cells treated with 500 microM DEHP for 24 h. These results suggest that DEHP inhibited apoptosis in this cell line, preceded by the downregulation of GJIC. It was also found that DEHP reduced the phosphorylation of Cx43, which might partly explain the mechanism of inhibition of GJIC.

In vitro models of brain ischemia: the peptidergic drug cerebrolysin protects cultured chick cortical neurons from cell death

Glutamate (1 mM), iodoacetate (0.01 mM) and ionomycin (0.25 micro M) are reported to induce several characteristics of ischemia and neuronal degeneration in vitro, e.g. glutamate and ionomycin lesion result in a disturbance of Ca(2+) homeostasis, iodoacetate impairment leads to an inhibition of energy metabolism, suppression of protein synthesis and generation of oxygen free radicals. In this study these three lesion models were used to investigate the effects of the nootropic drug Cerebrolysin (Cere) on the survival of cortical neurons in culture and on the occurrence of apoptosis. The viability of the cells was evaluated with the colorimetric MTT-reduction assay. Apoptosis was detected with Bisbenzimide (Hoechst:33258), a fluorescent DNA stain. Administration of Cere resulted in dose dependent neuroprotection independent from the kind of lesion. In the glutamate model the drug almost doubled neuronal viability compared to lesioned controls. After acute glutamate exposure Cere reduced the number of apoptotic cells significantly. In spite of the protective efficacy after cytotoxic hypoxia induced by iodoacetate, the drug significantly increased the number of apoptotic neurons, indicating a shift from necrosis to apoptosis. In contrast to previous studies investigating acute ionomycin lesions, the chronic Ca(2+)-overload used here did not increase the abundance of apoptosis compared to the unlesioned control. Summarizing the findings it can be suggested that Cere is able to stabilize Ca(2+) homeostasis, to protect protein synthesis and to counteract neuronal death in different in vitro medels of ischemia.

Influence of transfection with connexin 26 gene on malignant potential of human hepatoma cells

We investigated the effect of transfection with connexin (Cx) 26 gene on the malignant potential of PLC/PRF/5 hepatoma cells, observing changes in their morphological features, alpha-fetoprotein (AFP) expression, cell proliferation and apoptosis in vitro, and their tumor growth in vivo. Fluorescence-activated cell sorting (FACS) analysis showed that 10.6% of PLC/PRF/5 hepatoma cells transfected with Cx26 cDNA expressed excessive Cx26, and the spread of lucifer yellow was wider in the colony of stable transfectants (PLC/Cx26) after its microinjection than in control. Nucleo-cytoplasmic (N/C) ratio was significantly lower in PLC/Cx26 (P < 0.0001). Cell proliferation assay showed significantly lower numbers in PLC/Cx26 on day 10 after seeding than in control (P = 0.0039), and AFP level /10(5) cells was significantly lower in medium of PLC/Cx26 (P = 0.0039). The number of proliferating cell nuclear antigen (PCNA)-positive cells was less in PLC/Cx26 in vitro than in control (P = 0.0039), and single-stranded DNA (ssDNA)-positive cells were more abundant in the colony of PLC/Cx26 (P = 0.029). Tumor volume in SCID mice was significantly smaller in the group of PLC/Cx26 than in the control (P < 0.01) throughout the observation period, and tumor weight of PLC/Cx26 was significantly lower (P = 0.0019) week 9 after inoculation. Transfection with Cx26 cDNA inhibited dedifferentiation, suppressed cell proliferation, and apoptosis was induced. Tumor growth of PLC/Cx26 was retarded. These findings suggest that transfection with Cx26 gene into human hepatoma cells reduces their malignant potential.

Wogonin and fisetin induce apoptosis in human promyeloleukemic cells, accompanied by a decrease of reactive oxygen species, and activation of caspase 3 and Ca(2+)-dependent endonuclease

Seven structurally related flavonoids including luteolin, nobiletin, wogonin, baicalein, apigenin, myricetin and fisetin were used to study their biological activities on the human leukemia cell line, HL-60. On MTT assay, wogonin, baicalein, apigenin, myricetin and fisetin showed obvious cytotoxic effects on HL-60 cells, with wogonin and fisetin being the most-potent apoptotic inducers among them. The cytotoxic effects of wogonin and fisetin were accompanied by the dose- and time-dependent appearance of characteristics of apoptosis including DNA fragmentation, apoptotic bodies and the sub-G1 ratio. Treatment with an apoptosis-inducing concentration of wogonin or fisetin causes rapid and transient induction of caspase 3/CPP32 activity, but not caspase 1 activity. Further, cleavage of poly(ADP-ribose) polymerase (PARP) and decrease of pro-caspase 3 protein were detected in wogonin- and fisetin-treated HL-60 cells. An increase in the pro-apoptotic protein, bax, and a decrease in the anti-apoptotic protein, Mcl-1, were detected in fisetin- and wogonin-treated HL-60 cells. However, Bcl-2, Bcl-XL, and Bad all remained unchanged in wogonin- and fisetin-treated HL-60 cells. In vitro chromatin digestion revealed that endonuclease activity was profoundly enhanced in wogonin- and fisetin-treated HL-60 cells, and the addition of ethylenediaminetetraacetic acid (EDTA) or ethyleneglycoltetraacetic acid (EGTA) into the reaction blocked endonuclease activation and at an optimum pH of 7.5. The caspase 3 inhibitor, Ac-DEVD-CHO, but not the caspase 1 inhibitor, Ac-YVAD-CHO, attenuated wogonin- and fisetin-induced DNA ladders, PARP cleavage, and endonuclease activation. Pretreatment of HL-60 cells with N-acetyl-cysteine or catalase efficiently inhibited H(2)O(2) (200 microM)-induced apoptosis, but showed no inhibitory effect on wogonin- and fisetin-induced DNA ladders, caspase 3 activation, or bax protein induction. Decrease in endogenous ROS production was detected in wogonin- and fisetin-treated HL-60 cells by DCHF-DA assay. In conclusion, our experiments indicate that a decrease in intracellular peroxide level was involved in wogonin- and fisetin-induced apoptosis; activation of caspase 3 and endonuclease, induction of bax protein and suppression of Mcl-1 protein were detected in the process.

Evaluation of the neurotoxic activity of typical and atypical neuroleptics: relevance to iatrogenic extrapyramidal symptoms

Typical neuroleptic therapy often results in extrapyramidal symptoms (EPS) and tardive dyskinesia (TD). Recent reports reveal neurotoxic activity in some neuroleptics. We hypothesized that neurotoxicity might be implicated in EPS. This study aims to evaluate the neurotoxic activity of typical and atypical neuroleptics and to determine the possible role of neurotoxicity in neuroleptic-induced EPS. Perphenazine, haloperidol, clozapine, sulpiride, and risperidone (10-100 microM) were administered, either alone or combined with dopamine, to primary mouse neuronal or intact brain culture and to a human neuroblastoma (NB) cell line (SK-N-SH). Cell viability (measured by neutral red and alamar blue), DNA fragmentation (flow cytometry-NB) were determined. Neuroblastoma: perphenazine, clozapine, and haloperidol (100 microM) decreased viability by 87, 43, and 34% respectively. Sulpiride and risperidone were not toxic. At 10 microM, toxicity decreased markedly. Dopamine (125 microM) potentiated the perphenazine-induced toxicity. Flow cytometry of NB cells treated with perphenazine (2.5-40 microM) showed an increase (perphenazine 20 microM, 40 microM, 48 h) in fragmented DNA (74.7% and 95.0% vs. 8.7% in controls). Lower concentrations increased the G1 phase and decreased S phase in the cell cycle. In primary neurons, perphenazine, haloperidol, and clozapine, but not risperidone and sulpiride, induced a significant neurotoxic effect, which, in intact brain culture, was absent (haloperidol and clozapine) or lowered (perphenazine). Dopamine (0.5 mM) did not modify the effect of the drugs in the primary cultures. Neuroleptics possess differential neurotoxic activity with higher sensitivity of neoplasm tissue (NB compared to primary cultures). The order of toxicity was perphenazine > haloperidol = clozapine:sulpiride and risperidone were not toxic. Neurotoxicity is independent of dopamine and is associated with cell cycle arrest and apoptosis. With the exception of clozapine, neurotoxicity seems relevant to neuroleptic-induced EPS and TD.

Inhibition of apoptosis by pentachlorophenol in v-myc-transfected rat liver epithelial cells: relation to down-regulation of gap junctional intercellular communication

Pentachlorophenol (PCP), a promoter of murine hepatocarcinogenesis, inhibits gap junctional intercellular communication (GJIC) in rat liver epithelial cells in vitro. To test the hypothesis that both inhibition of GJIC and apoptosis contribute to tumor promotion, we investigated the effect of PCP on both GJIC and serum deprivation-induced apoptosis in v-myc-transfected rat liver epithelial cells. The results showed that PCP inhibited apoptosis, as measured by the TUNEL assay and DNA ladder formation. Inhibition of apoptosis was associated with a decrease in GJIC. The study demonstrated that PCP has a potential for inhibiting apoptosis and GJIC, supporting the hypothesis.

Apoptosis in diseases of the liver

Apoptosis, or programmed cell death, and the elimination of apoptotic cells are crucial factors in the maintenance of liver health Apoptosis allows hepatocytes to die without provoking a potentially harmful inflammatory response In contrast to necrosis, apoptosis is tightly controlled and regulated via several mechanisms, including Fas/Fas ligand interactions, the effects of cytokines such as tumor necrosis factor alpha (TNF-alpha) and transforming growth factor beta (TGF-beta), and the influence of pro- and antiapoptotic mitochondria-associated proteins of the B-cell lymphoma-2 (Bcl-2) family. Efficient elimination of apoptotic cells in the liver relies on Kupffer cells and endothelial cells and is thought to be regulated by the expression of certain cell surface receptors. Liver disease is often associated with enhanced hepatocyte apoptosis, which is the case in viral and autoimmune hepatitis, cholestatic diseases, and metabolic disorders. Disruption of apoptosis is responsible for other diseases, for example, hepatocellular carcinoma. Use and abuse of certain drugs, especially alcohol, chemotherapeutic agents, and acetaminophen, have been associated with increased apoptosis and liver damage. Apoptosis also plays a role in transplantation-associated liver damage, both in ischemia/reperfusion injury and graft rejection. The role of apoptosis in various liver diseases and the mechanisms by which apoptosis occurs in the liver may provide insight into these diseases and suggest possible treatments.

Mechanism of up-regulated gap junctional intercellular communication during chemoprevention and chemotherapy of cancer

To develop a strategy for efficacious intervention in order to prevent or treat various cancers, one must understand the basic mechanism(s) by which various anticancer dietary factors prevent or reverse the tumor promotion or progression phases. Carcinogenesis is a multistage, multimechanism process, involving the irreversible alteration of a stem cell (the "initiation" phase), followed by the clonal proliferation of the initiated stem cell (the "promotion" phase), from which the acquisition of the invasive and metastatic phenotypes are generated (the "progression" phase). While intervention to prevent or treat cancer could occur at each step, the objective of this presentation will focus on the rate limiting step, the promotion phase.Gap junctional intercellular communication (GJIC) has been hypothesized to regulate growth control, differentiation and apoptosis. Most normal, contact-inhibited cells have functional GJIC, while most, if not all, tumor cells have dysfunctional homologous or heterologous GJIC. Cancer cells are characterized by the lack of growth control, by the inability to terminally differentiate and by resistance to apoptosis. Chemical tumor promoters (phorbol esters, DDT, phenobarbital, unsaturated fatty acids, saccharin, etc.) inhibit GJIC in a reversible fashion and at doses above particular chemical thresholds. Various oncogenes (e.g. ras, raf, neu, src, mos) down-regulate GJIC while several tumor suppressor genes can up-regulate GJIC. Antitumor promoters (retinoids, carotenoids, green tea components) and antioncogene drugs (i.e. lovastatin) can up-regulate GJIC. Transfection of gap junction genes ("connexins") into GJIC-deficient tumor cells can restore GJIC, growth control and reduce tumorigenicity. On the other hand, antisense gap junction genes can convert the phenotype of a non-tumorigenic cell to that of a tumorigenic one. Recently, a specific connexin knockout mouse was shown to have a higher frequency of spontaneous and induced liver cancers. Evidence from these studies clearly suggests that dietary factors can modulate GJIC by inducing various signal transducing systems. The modulation can either down-regulate GJIC and lead to tumor promotion or it can up-regulate GJIC and lead to suppression of the initiated cells. Multiple mechanisms of up- or down-regulation of GJIC exist, as well as multiple types of pre-malignant and malignant tumor cells that are unable able to have functional GJIC. GJIC can be down-regulated by mutations and by epigenetic means. Alteration of gene expression at the transcriptional, translational or post-translational levels would require specific dietary prevention or treatment of cancer. In conclusion, if dietary prevention or treatment of cancer is to occur, it must ameliorate the growth-stimulatory effects, above threshold levels, of chemicals, growth factors or hormones, that trigger various mitogenic/antiapoptotic signal transducing systems that block GJIC.