Cell death by apoptosis and its protective role against disease

Cancer initiation by fumonisin B(1) in rat liver--role of cell proliferation

Fumonisin B(1) (FB(1)), a carcinogenic mycotoxin produced by the fungus Fusarium verticillioides in corn, causes cancer initiation in rat liver in a similar manner to genotoxic carcinogens although apparently with different kinetics. The present experiment was designed to evaluate the role of regenerative cell proliferation, effected by partial hepatectomy (PH) and carbontetrachloride (CCl(4)) and direct mitogen-induced hyperplasia, induced by lead nitrate (PbNO(3)), on FB(1)-induced cancer initiation. Initiation was effected over a period of 14 days by gavage administration of FB(1) at different daily doses ranging from 0.14 to 3.5 mg FB(1)/100 g body weight while the stimuli for cell proliferation were introduced 7 days after the start of the FB(1) treatment. Based on the proliferative stimulus used, cancer promotion was effected 3 weeks after completion of the initiating treatment by 2-acetylaminofluorene (2-AAF) treatment followed by PH or carbon tetrachloride CCl(4) on day 4. Cancer initiation by FB(1) was associated with a hepatotoxic effect and an increase in lipid peroxidation. In contrast to compensatory liver cell proliferation induced by PH and CCl(4), mitogen-induced hyperplasia (PbNO(3)) failed to enhance the cancer initiating potential of FB(1) suggesting that cancer induction by a non-genotoxic carcinogen is supported by regenerative cell proliferation. Cognizance of the enhancing role of cell proliferation during cancer initiation by FB(1) is required in assessing the risks posed by this mycotoxin to humans.

Marijuana smoke and Delta(9)-tetrahydrocannabinol promote necrotic cell death but inhibit Fas-mediated apoptosis

Marijuana smoke shares many components in common with tobacco smoke except for the presence of Delta(9)-tetrahydrocannabinol (Delta(9)-THC), the psychotropic compound found only in Cannibis sativa. Delta(9)-THC has been shown to potentiate smoke-induced oxidative stress and necrotic cell death. In the present study, our objective was to determine the effects of Delta(9)-THC on the balance between Fas-induced apoptosis and necrosis in A549 lung tumor cells. We found that Fas-induced activation of caspase-3 was inhibited by whole smoke from both tobacco and marijuana cigarettes. Gas-phase smoke, which generates high levels of intracellular reactive oxygen species, had no effect on caspase-3 activity. However, particulate-phase smoke (tar) was a potent inhibitor of Fas-induced caspase-3 activity, with marijuana tar being more potent than either tobacco or placebo marijuana tar (lacking Delta(9)-THC). Delta(9)-THC also inhibited Fas-induced caspase-3 activity in A549 cells. In contrast, no inhibition was observed when Delta(9)-THC was incubated with activated caspase-3 enzyme, suggesting that Delta(9)-THC acts on the cell pathway(s) leading to caspase-3 activation and not directly on enzyme function. Flow cytometry was used to measure the percentage of cells undergoing apoptosis (staining for annexin V) versus necrosis (staining for propidium iodide) and confirmed that both marijuana tar extract and synthetic Delta(9)-THC inhibit Fas-induced apoptosis while promoting necrosis. These observations suggest that the Delta(9)-THC contained in marijuana smoke disrupts elements of the apoptotic pathway, thereby shifting the balance between apoptotic and necrotic cell death. This shift may affect both the carcinogenic and immunologic consequences of marijuana smoke exposure.

Oxidative stress and liver toxicity in rats and human hepatoma cell line induced by pentachlorophenol and its major metabolite tetrachlorohydroquinone

Pentachlorophenol (PCP) is a pesticide used worldwide in industrial and domestic applications. It is used extensively as biocide and wood preservatives. Metabolic studies carried out in rodents and human liver homogenates have indicated that PCP undergoes oxidative dechlorination to form tetrachlorohydroquinone (TCHQ). Free radical catalyzed tissue injury is thought to play a fundamental role in human disease. In the present study, we examined the effects of PCP and TCHQ on the induction of lipid peroxidation and liver injury in rats. In addition, the cytotoxic dose, cell death mechanisms and related gene expressions induced by PCP and TCHQ were also determined for human hepatoma cell line (Hep G2). The results indicated that more toxic effects could be observed both in rats and human hepatoma cell line treated with TCHQ than its parent compound, PCP. Oxygen species may be involved in the mechanism of TCHQ intoxication since the urinary 8-epi-PGF2alpha and AST, ALT activities can be induced by TCHQ and attenuated by vitamin E treatment. Apoptosis features were found in cells treated with TCHQ but not PCP. TCHQ-induced cell damage may issue signals for the induction of HSPs, the decrease of the bcl/bax protein ratio and the decrease of CAS gene, whereas the PCP-induced damage may not.

The autophagosomal-lysosomal compartment in programmed cell death

In the last decade a tremendous progress has been achieved in understanding the control of apoptosis by survival and death factors as well as the molecular mechanisms of preparation and execution of the cell's suicide. However, accumulating evidence suggests that programmed cell death (PCD) is not confined to apoptosis but that cells use different pathways for active self-destruction as reflected by different morphology: condensation prominent, type I or apoptosis; autophagy prominent, type II; etc. Autophagic PCD appears to be a phylogenetically old phenomenon, it may occur in physiological and disease states. Recently, distinct biochemical and molecular features have been be assigned to this type of PCD. However, autophagic and apoptotic PCD should not be considered as mutually exclusive phenomena. Rather, they appear to reflect a high degree of flexibility in a cell's response to changes of environmental conditions, both physiological or pathological. Furthermore, recent data suggest that diverse or relatively unspecific signals such as photodamage or lysosomotropic agents may be mediated by lysosomal cysteine proteases (cathepsins) to caspases and thus, apoptosis. The present paper reviews morphological, functional and biochemical/molecular data suggesting the participation of the autophagosomal-lysosomal compartment in programmed cell death.

Suppression of cell transformation and induction of apoptosis by caffeic acid phenethyl ester

Caffeic acid phenethyl ester (CAPE), which is derived from the propolis of honeybee hives, has been shown to block tumor promotion and to have toxic effects on several cancer cells. The mechanism of the anti-tumor promotion activity of CAPE is unclear, however. In this study, we found that CAPE suppressed 12-O-tetradecanoylphorbol-13-acetate-induced cell transformation and induced apoptosis in mouse epidermal JB6 Cl 41 cells. No difference in induction of apoptosis was observed between normal lymphoblasts and sphingomyelinase-deficient cell lines. Although CAPE treatment of two p53 mutant tumor cell lines, NCI-H358 and SK-OV-3, and p53-deficient (p53(-/-)) cells caused the cleavage of caspase-3 as well as DNA fragmentation, caspase-3 cleavage was seen early (at 6 h) only in cells expressing wild-type p53 (p53(+/+)) and Cl 41 cells. These results suggested that p53 may be involved in the early stage of CAPE-induced apoptosis. The p53-dependent transcription activation occurred 2 h after treatment with CAPE and reached a maximum at 6 h in Cl 41 p53 DNA-binding sequence stable transfectant cells. In addition, phosphorylation of p53 at serine 15 and serine 392 was induced in Cl 41 cells within 6 h after treatment with CAPE. Therefore, CAPE may induce apoptosis through p53-dependent and p53-independent pathways and its anti-tumor promotion activity may have occurred through the induction of apoptosis.

Delayed re-endothelialization and T-cell infiltration following intracoronary radiation therapy in the porcine model

PURPOSE

To evaluate the late induction of apoptosis following intracoronary radiation (IR) and the effects of IR on inflammatory cells.

METHODS AND MATERIALS

Porcine coronaries were injured by balloon overstretch followed by either 0 or 15 Gy of 192Ir prescribed to 2 mm from the center of the source. Swine were euthanized at 3, 7, and 14 days posttreatment, and arteries were stained for markers of smooth muscle cells (SMCs alpha-actin), T cells (CD3), macrophages, endothelial cells, and apoptotic nuclei (terminal uridine nick end labeling, TUNEL). Intimal area (IA) and IA corrected for medial fracture length (IA/FL) were quantified by digital image analysis, which was also used to quantify the distribution of immunostain-positive cells in the adventitia, media, and neointima, respectively.

RESULTS

IA/FL was significantly reduced following treatment with 15 Gy, in association with decreased SMC density. Following injury and IR, TUNEL- and CD3-positive cell density increased significantly, and density of macrophages was increased in the adventitia and neointima. Staining for endothelial cells revealed a delay of re-endothelialization after radiation treatment.

CONCLUSION

Increased T-cell infiltration at the medial tear following IR, perhaps due to incomplete re-endothelialization, may indicate incomplete healing. The elevated apoptosis of these infiltrating T cells may indicate a mechanism for the resolution of inflammation.

Peroxisome proliferators: their biological and toxicological effects

One of the most rapidly developing areas of organelle biology, which has a major involvement in biochemical pharmacology, is the research into the peroxisomal function. There is a large group of compounds that are capable of inducing liver enlargement, proliferation of peroxisomal structures, and induction of peroxisomal and extraperoxisomal fatty acid-oxidizing enzymes in rodent liver, called peroxisome proliferators. This list includes hypolipidemic drugs, analgesics, uricosuric drugs, environmental pollutants, phthalates, etc. Some peroxisome proliferators have also been shown to increase the incidence of liver tumors. This review describes the characteristics of peroxisome proliferation in rodent liver and gives examples of different classes of chemicals that produce this effect. Mechanisms of initiation of peroxisome proliferation in rodent hepatocytes, including peroxisome proliferator-activated receptors, are also described. Rodent peroxisome proliferators are not considered to be genotoxic agents. Proposed mechanisms of liver tumor formation include induction of sustained oxidative stress, enhanced cell replication, promotion of spontaneous preneoplastic lesions, and inhibition of apoptosis. In addition, the absence of effects of peroxisome proliferators on peroxisome proliferator-associated parameters supports the hypothesis that human liver cells are refractory to peroxisome proliferator-induced hepatic carcinogenesis.

Expression of apoptosis on rat liver by hepatic vagus hyperactivity after ventromedial hypothalamic lesioning

We examined whether the Fas (APO-1/CD95)/Fas ligand system mediates apoptosis in rats with ventromedial hypothalamus (VMH) lesions. Northern and Western blotting indicated that VMH lesions lead to a significant increase in Fas mRNA and protein expression from day 1 to day 7 and in Fas ligand mRNA and protein expression from day 2 to day 7. Immunohistochemistry indicated that the region of strongest Fas expression shifted from acinar zone 1 to zones 2 and 3 by day 7 after VMH lesioning and that at days 2-7 Fas-ligand-positive hepatocyte cell membranes and cytoplasm were randomly distributed in acinar zones 1-3. We also analyzed activation of caspase 3-like proteases in hepatocytes, Kupffer cells, and sinusoidal endothelial cells. Spectrofluorometric assay demonstrated that caspase 3-like activity significantly increased only in hepatocytes after VMH lesioning. Moreover, electron microscopy and TUNEL assay showed that VMH lesions induced apoptosis. All of these effects were completely inhibited by hepatic vagotomy and administration of atropine. Vagal firing after VMH lesioning may stimulate Fas/Fas ligand system-mediated apoptosis through the cholinergic system in the rat liver.

Apoptosis and cell death channels in prostate cancer

Apoptosis, a type of programmed cell death, is a decisive mechanism in cell processes such as homeostasis, development, and many diseases including cancer. In mammals, the mechanisms that trigger and control the process of apoptosis are complex, because it has been observed that many molecules might be involved, acting in distinct ways and depending on the cellular type. The process of apoptosis is characterized by specific biochemical and morphologic changes. However, important specific messengers such as Ca(2)+ act in active proliferation as well as in apoptosis. At present, there is convincing evidence that a sustained increase in intracellular Ca(2)+ can activate cytotoxic mechanisms in various cells and tissues. Several ionic channels located in the cytoplasmic membrane might participate in the entry of calcium into the cytosol during apoptosis. Among these ionic channels, the purinoreceptors P2X and the channels of capacitative entry of calcium have been described. Pro- and anti-apoptotic molecules such as bax and bcl-2, respectively, have also been shown to participate in the process. We have recently found the activation of a Ca(2)+-permeable, nonselective cation channel of 23 pS conductance in prostatic cancer (LNCaP) exclusively in cells previously induced to apoptosis. Our findings are discussed taking into account the different ion channels that might participate in programmed cell death in prostate cancer.

Capsaicin-induced apoptosis in SK-Hep-1 hepatocarcinoma cells involves Bcl-2 downregulation and caspase-3 activation

Hepatocellular carcinoma is one of the most lethal malignancies and there is no effective preventive measure in this highly malignant disease to date. In the present study, we investigated the chemopreventive potential of capsaicin (8-methyl-N- vanillyl-6-nonenamide), the principal pungent ingredient found in hot red pepper, in SK-Hep-1 hepatocellular carcinoma cells. Treatment of capsaicin inhibited growth of SK-Hep-1 cells in a concentration-dependent manner while 4-methoxy capsaicin (Met-capsaicin) was less potent. This inhibitory effect of capsaicin on SK-Hep-1 cell growth was mainly due to the induction of apoptosis as evidenced by DNA fragmentation and nuclear condensation. Furthermore, capsaicin prominently reduced the ratio of anti-apoptotic Bcl-2 to pro-apoptotic Bax and consequently increased caspase-3 activity. These results demonstrate that capsaicin efficiently induced apoptosis in SK-Hep-1 cells through a caspase-3-dependent mechanism, which may contribute to its chemopreventive function.

Detection of Drug-induced Apoptosis by Flow Cytometry after Alkaline Extraction of Ethanol Fixed Cells

A new flow cytometric method was developed to detect apoptotic cells with fragmented DNA and to determine cell cycle distribution of viable cells, in the same sample, by propidium iodide staining. Apoptosis, in HT58 human B lymphoma cells, was induced by etoposide and/or by staurosporine. Using appropriate alkaline solutions (between 1-10 mN NaOH in 150 mM saline) followed by neutralization with buffer solution, the fragmented DNA can be extracted quantitatively from ethanol fixed cells. Further, good resolution of the cell cycle distribution can be obtained in unimpaired cells without RNase treatment. Furthermore, unlike the widely used hypotonic-detergent extraction of unfixed cells, the suggested extraction method can prevent drug-induced disintegration of dead cells when karyorrhexis occurs.

The role of apoptotic cell death in cardiovascular disease

BACKGROUND

Programmed cell death, or apoptosis, is a distinct, managed form of cell death. It is fundamentally different from necrosis. It is a genetically controlled, energy-dependent method of cellular deletion without inflammation. In the cardiovascular system, apoptosis occurs as a primary and secondary event in disease pathogenesis. This review addresses our current understanding of the initiation, propagation and significance of apoptosis in the cardiovascular system, as well as assessing therapeutic potentials arising therefrom.

METHODS

A Medline search was performed and relevant publications reviewed. Further articles were obtained from the references of these publications.

RESULTS

and conclusions Apoptotic cell death is a key element in the pathogenesis and progression of ischaemia-reperfusion (IR) injury, cardiac failure, myocardial infarction, atherosclerosis, endothelial dysfunction and the clinical syndromes which these situations produce. Our increased understanding of the role of apoptosis in the pathogenesis of cardiovascular disease offers potential to develop new therapeutic strategies.

Role of stem cells and gap junctional intercellular communication in human carcinogenesis

Epidemiological data, experimental animal bioassays, studies of in vitro neoplastic transformation, and molecular oncology studies have implicated a multistage, multimechanism process in human carcinogenesis. From animal carcinogenesis studies, the operational concept of a single normal cell being irreversibly altered during the first step in carcinogenesis is called initiation. The subsequent interruptible or reversible clonal expansion of these initiated cells by non-cytotoxic mitogenic stimuli, compensatory hyperplasia due to cell death by necrosis, or inhibition of apoptosis is referred to as the promotion phase. Last, when one of these clonally expanded, initiated cells acquires sufficient genetic/epigenetic alterations to become neoplastically transformed and acquire the phenotypes of promoter independence, invasiveness and metastasis, it is referred to as the progression step of carcinogenesis. This report hypothesizes that the single normal cell that is initiated is a pluripotent stem cell. By assuming that the normal pluripotent stem cell is immortal and becomes mortal when induced to terminally differentiate, initiation would be viewed as the irreversible process by which a stable alteration in a finite number of proto-oncogenes and/or tumor suppressor genes could block terminal differentiation or "mortalization". Promotion would involve the reversible inhibition of gap junctional intercellular communication (GJIC) and while progression occurs with the stable down-regulation of GJIC.

Thymosin alpha1 is a time and dose-dependent antagonist of dexamethasone-induced apoptosis of murine thymocytes in vitro

It is well established that glucocorticoid hormones induce apoptosis in immature developing thymocytes. Thymocyte apoptosis can be modulated by growth factors, anti-oxidants and adhesion receptors. We have previously demonstrated that thymosin alpha1 (Talpha1) antagonizes dexamethasone-induced apoptosis of CD4+CD8+ thymocytes. In the present study, we further characterize the dose and time dependence of Talpha1's antagonism of dexamethasone-induced thymocyte apoptosis. Talpha1 is effective at concentrations ranging from 2 to 100 microg/10(6) thymocytes. Talpha1 pre-treatment is necessary to achieve its anti-apoptotic activity. Talpha1 provides temporary protection to thymocytes by slowing dexamethasone's apoptotic activity up to 12 h post dexamethasone treatment. Additionally, Talpha1's activity is not sensitive to cycloheximide treatment, suggesting Talpha1's activity is independent of protein synthesis. Finally, Talpha1 is unable to antagonize apoptosis induced by the reactive oxygen species, H2O2, suggesting Talpha1's antagonism of dexamethasone occurs at the early stages of dexamethasone-induced apoptosis, prior to the production of reactive oxygen species. This evidence suggests that Talpha1 may provide a mechanism to transiently extend the life of a thymocyte during thymic selection.

Different cell death mechanisms and gene expression in human cells induced by pentachlorophenol and its major metabolite, tetrachlorohydroquinone

Pentachlorophenol (PCP) and its salt are used extensively as biocide and wood preservative. Due to improper disposal, PCP has become an environmental pollutant and is now considered to be ubiquitos. Metabolic studies carried out in rodents or human liver homogenate have indicated that PCP undergoes oxidative dechlorination to form tetrachlorohydroquinone (TCHQ). The cytotoxicity, cell death mechanisms and gene expression of PCP and TCHQ are investigated in human liver and bladder cells and show that TCHQ induces apoptosis and DNA genomic fragmentation in bladder cells but not liver cells. No apoptotic features could be induced by treatment of PCP in both cell lines. The concentrations of PCP required to cause 50% cell death in T-24 and Chang liver cells were 5-10-fold greater than the concentrations of TCHQ. Several gene products are important in controlling the apoptotic and necrotic processes. Of these, hsp 70, CAS, bcl-2 and bax were studied. The expression of the hsp70 gene increased significantly (2-3-fold) in cells treated with TCHQ. However, no significant change was found in the cells treated with PCP. The expression of CAS gene decreased significantly in T-24 cells treated with both TCHQ and PCP. Whereas, no significant change was found in Chang liver cells with the same treatment. In addition, the expression of the bcl-2/bax protein decreased significantly in these two cell lines treated with TCHQ but not PCP.

Vascular repair after balloon overstretch injury in porcine model effects of intracoronary radiation

OBJECTIVES

The purpose of this study was to evaluate the effect of IR on thrombus formation and dissection repair following overstretch balloon injury in porcine coronary arteries.

BACKGROUND

Exposure of blood to the injured arterial wall after percutaneous transluminal coronary angioplasty (PTCA) induces thrombus formation and inflammation in the dissection plane. Neointima formation is related to smooth muscle cell (SMC) proliferation and migration into the preformed thrombus. Intracoronary radiation (IR) with doses of 10 to 25 Gy using either beta or gamma emitters can prevent neointima accumulation by reducing SMC proliferation. However, there are some indications that IR may delay the process of dissection repair after PTCA. The purpose of this study was to evaluate the effect of IR on thrombus formation and dissection repair after overstretch balloon injury in porcine coronary arteries.

METHODS

Forty porcine coronaries were injured by balloon overstretch followed by either 0 or 18 Gy of 90Y prescribed to 1.2 mm from the balloon center. The animals were euthanized 14 days after treatment, and intimal area (IA) and IA corrected for medial fracture length (IA/FL) were quantified by digital image analysis. Dissections were quantified by tracing the length, thickness and area behind the dissection flap. The rate of dissections was calculated for each group. Thrombi were identified and designated as intraluminal thrombus or thrombus within dissection planes (mural thrombus), and area measurements were obtained.

RESULTS

The irradiated group showed a significant reduction of IA/FL (0.55 +/- 0.29 vs. 0.05 +/- 0.09; p < 0.001). No difference was observed in the rate of dissection between control and irradiated arteries (77% vs. 88%, respectively). The control group showed a smaller dissection area (0.19 +/- 0.28 mm2 vs. 0.32 +/- 0.29 mm2; p < 0.05) with smaller mural thrombi (0.03 +/-0.01 mm2 vs. 0.29 +/- 0.30 mm2; p < 0.001). A strong correlation between dissection area and neointima area was observed only in the control group (R2 = 0.474; p < 0.003; alpha0.05 = 0.862). A positive correlation between mural thrombus and dissection area was observed only in the irradiated group (R2 = 0.889; p < 0.001; alpha0.05 = 1.00).

CONCLUSIONS

These results suggest that the dissection area may be a useful parameter by which to quantify the extent of injury and repair after IR and may indicate an incomplete healing process after IR at this time point.

Interrelationship of apoptosis, mutation, and cell proliferation in N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced medaka carcinogenesis model

The present study examined the interrelationship of GSH depletion, apoptosis, mutation, and cell proliferation following carcinogen exposure. Medaka (Oryzias latipes) were investigated following a 28 day, three times/week pulse exposure to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Fish (5 weeks old) were exposed to MNNG at concentrations of 0, 0.5, and 1 mg l(-1) and reared for 3, 5 and 7 more months after the last day of exposure. GSH levels were decreased in the higher concentration groups and longer-reared groups. Flow cytometric analysis revealed that fish from the groups reared 3 and 5 months showed active apoptotic changes in the dose- and time-dependent manner, but the group reared 7 months had fewer apoptotic, rather showed more necrotic and carcinogenic alterations. Mutational responses were detected by an arbitrarily primed polymerase chain reaction (AP-PCR) fingerprinting method using whole body DNA samples as templates and pBR primer. A mutational change was expressed by a loss or gain of a band. There was a time-dependent mutational change, but no distinctive concentration-dependent one. A band from normal fish sample that disappeared after treatment of MNNG was excised and sequenced. The band had an 869 base pair-long sequence, however, there was no putative protein-coding region based on an analysis by DNAsis. Spindle cell sarcomas invading muscle were detected on the whole body sections from three of ten fish examined, and immunohistochemical analysis with PCNA showed that tumor cells were actively proliferating. However, terminal deoxynucleotidyl transferase (TdT) assay showed that tumored fish still had active apoptotic cell changes in the tissues without tumor. This study shows not only the interrelationship of GSH depletion, apoptosis, mutation and cell proliferation, but also indicates that medaka is appropriate as a fish model for research on the passage of carcinogenesis.

Immune modulatory potentials of antineoplaston A-10 in breast cancer patients

Antineoplastons are naturally occurring cytodifferentiating agents. Chemically, they are medium and small sized peptides, amino acid derivatives and organic acids, which exist in blood, tissues and urine. Antineoplaston A-10 (3-phenylacetylamino-2,6-piperidinedione) is the first chemically identified antineoplaston. Previously we have shown a strong inverse association of urinary antineoplaston A-10 with breast cancer. This study is designed to evaluate neutrophil apoptosis in patients with breast cancer at time of diagnosis and to correlate urinary antineoplaston A-10 levels with neutrophil apoptosis and to describe the direct effect of A-10 in vitro on neutrophil apoptosis in breast cancer patients. The participants were patients with a histologically confirmed diagnosis of breast cancer. Only those cases without previous treatment for breast cancer were included. Neutrophil apoptosis was assessed in breast cancer patients both morphologically and by DNA fragmentation and studied relative to healthy controls. Antineoplaston A-10 was measured using high performance liquid chromatography in urine samples collected from the patients. Urine samples from normal women served as controls. Direct effect of antineoplaston A-10 on neutrophil apoptosis was tested in vitro after adding A-10 at a concentration of 10 ng/ml to the cellular suspensions of breast cancer patients. Non-treated samples served as controls. Significantly higher neutrophil apoptosis levels were detected among patients with breast cancer with a P value <0.001. Urinary antineoplaston A-10 level is significantly negatively correlated with high apoptosis levels (P<0.0001). In vitro, antineoplaston A-10 was found to inhibit significantly the neutrophil apoptosis with a P value <0.0001. These findings confirm the presence of immune defects among patients with breast cancer and such results should stimulate the development of new strategies to induce and augment immunity for the treatment of breast cancer. Antineoplaston A-10 may provide rational basis for designing trials to employ its immune modulatory potentials as adjuvant therapy in breast cancer patients.

Fas-mediated apoptosis in adriamycin-induced cardiomyopathy in rats: In vivo study

BACKGROUND

The precise molecular mechanism of Adriamycin-induced cardiomyopathy (ADR-CM) is still unknown. We address the demonstration of apoptotic myocardial cell death and the apoptosis-inducing molecules in ADR-CM induced in rats.

METHODS AND RESULTS

Until 8 weeks after the first administration of ADR, there was no increase in the number of labeled cells by terminal deoxynucleotidyl transferase assay (TUNEL method). Apoptotic indices increased significantly at weeks 9 and 10 in hearts of the ADR-treated group but not in those of the control group (0.42+/-0.12% versus 0.10+/-0.02% and 0.86+/-0.11% versus 0.09+/-0.04% at weeks 9 and 10, respectively). DNA ladder formation was also observed in the myocardial tissues during the late stages of the ADR-CM of rats. There was no significant difference in expression of p53 gene between the ADR group and the control group at either the message or the protein level. An overexpression of Fas antigen was shown in myocardial cells of ADR-treated hearts at weeks 9 and 10 by both Western blotting and immunofluorescent staining. Furthermore, we confirmed that neutralization of anti-Fas ligand antibody inhibited ADR-induced apoptosis.

CONCLUSIONS

Apoptotic cell death was observed in the hearts of ADR-CM rats, and the number of apoptotic myocardial cells increased with the deterioration of morphological findings and cardiac function, indicating that apoptosis may be an important mechanism of loss of myocardial cells and cardiac dysfunction in ADR-CM. Apoptosis in ADR-CM rats is not p53-dependent but rather is executed through a Fas-mediated pathway.

Reciprocal control of apoptosis and proliferation in cultured rat hepatoma arl-6 cells: roles of nutrient supply, serum, and oxidative stress

In order to understand how cancer cells accumulate, rat hepatoma ARL-6 cells were cultured for 8 d to identify factors involved in spontaneous cell proliferation and apoptosis. With increasing time in culture, the proportion of cells in the proliferative phases of the cell cycle and the rate of deoxyribonucleic acid (DNA) synthesis decreased. The waning of proliferation was associated with a gradual reduction of cell viability, and this was temporally related to the appearance of typical apoptotic morphology and DNA laddering. Medium replacement or supplementation with fetal calf serum (FCS) suppressed apoptosis, while medium change, but not fetal calf serum alone, enhanced cell proliferation. Apoptosis was also suppressed by dimethyl sulfoxide (DMSO), but supplementary glutathione was without effect. Expression of poly(adenosine diphosphate[ADP]-ribose)polymerase peaked on days 34 of culture, and was followed by a progressive decrease thereafter, consistent with proteolytic cleavage. This decrease was prevented to varying extents by complete medium replacement, FCS and DMSO, indicating a close temporal relationship between poly(ADP-ribose)polymerase activation and apoptosis. Expression of Fas and Bcl-2 did not change appreciably over the 8-d culture, but there was a gradual increase in Bax expression; medium change, FCS and DMSO all partly inhibited Bax expression. These data indicate that spontaneous apoptosis in cultured ARL-6 cells is inversely related to cell proliferation, and that nutrient supply, and to a lesser extent, serum-derived factors and oxidative stress modulate apoptosis in this system. Proteolytic cleavage of poly(ADP-ribose)polymerase and expression of Bax are likely to be mechanistically involved with the control of spontaneous apoptosis in ARL-6 cells, whereas changes in the levels of Fas and Bcl-2 do not play a role.

Apoptosis, PCNA, and p53 in Fundulus grandis fish liver after in vivo exposure to N-methyl-N'-nitro-N-nitrosoguanidine and 2-aminofluorene

Dysfunction in homeostatic mechanisms of cell death and proliferation are considered to be important in the pathogenesis of chemically induced neoplasia. p53 has been implicated in the regulation of cell death and proliferation. To determine whether expression of apoptosis, proliferating cell nuclear antigen (PCNA), and p53 differ between an alkylating agent and a polycyclic aromatic hydrocarbon, host response was measured through sequential immunohistochemical detection of apoptosis (terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling method), PCNA PC-10, and p53 (PAb 240) in livers of the fish Fundulus grandis. Nine hundred fish were randomly assigned to 3 groups of 300 fish each and kept in separate aquarium tanks. One group of fish was exposed to 6.7 microM N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), 1 group was exposed to 6.9 mM 2-aminofluorene (2-AF), and the remaining group served as a control. A significant decrease (p = 0.005) in the level of apoptosis and a significant increase (p < 0.0001) in the level of p53 were found on experimental day 180 in the livers of MNNG-exposed fish. PCNA was significantly increased (p < 0.005) by day 9 of the experiment in both MNNG and 2-AF fish when compared with controls, but no significant differences existed between the 2 groups of treated fish. Response of fish liver cells to MNNG-mediated and 2-AF-mediated injury differs, at least initially, in the expression of p53, inhibition of apoptosis, and increased net cell proliferation. Concurrent use of a marker for cell death with a marker of proliferation greatly enhances the assessment of the effect of these compounds on liver cells.

Induction of apoptosis in caco-2 cells by wheat gliadin peptides

Recent experimental evidence suggests that enterocyte apoptosis is greater than hitherto assumed and may be responsible for villous atrophy in coeliac disease. We have previously demonstrated that a small peptide (M.W. 1157.5 Da), identified as the sequence H(2)N-gln-gln-pro-gln-asp-ala-val-gln-pro-phe-COOH from durum wheat gliadin, is able to prevent K 562 (S) cell agglutination induced by the peptic-tryptic digests (PT) of prolamin fractions from the cereals which are not tolerated in coeliac disease (i.e. bread wheat, rye, barley and possibly oats), and toxic A-gliadin peptides in coeliac disease. In the present study we have investigated the effects of the bread wheat gliadin digest (PT) on apoptosis of Caco-2 cells and whether the '1157.5' Da peptide may in any way interfere with them. We evaluated both earlier biochemical and later morphological nuclear apoptotic events in the human colon adenocarcinoma cell line Caco-2. After 48 h exposure to the PT gliadin digest and the '1157.5' Da peptide, apoptosis was detected both for the early-stage apoptotic cells (adherent cells) and the late-stage apoptotic ones (detached cells which were floating in the culture medium). Exposure to the PT gliadin digest resulted in a high percentage of adherent cells that underwent cell death by apoptosis (about 30%), independent of the concentration range used; while the presence in the culture medium of peptide '1157.5' Da determined complete inhibition of cell death. On the other hand, morphological nuclear modifications observed in the floating cells showed a difference in the rate of the apoptosis dependent on the PT concentration, with partial protection in the presence of the peptide. These findings show an action of bread wheat gliadin peptides leading to cell death by apoptosis in the Caco-2 cell line and that the '1157.5' Da peptide is capable of preventing such an effect.

Species differences in peroxisome proliferation; mechanisms and relevance

Peroxisome proliferators are a class of structurally diverse chemicals, which induce liver carcinogenesis in rodents through interaction and activation of the Peroxisome Proliferator-Activated Receptor alpha (PPARalpha). PPARalpha agonists elicit a powerful pleiotropic response, which include hypolipidaemia. We have examined the response of species that are classically unresponsive to peroxisome proliferators. Whereas hamster responds to PPARalpha agonists by hepatomegaly and induction of marker genes, the guinea pig does not undergo hepatomegaly or induction of marker genes, such as CYP4A13. Both the hamster and the guinea pig have PPARalpha, and the guinea pig receptor has been characterised to be fully functional, as demonstrated in reporter gene expression assays. However, the guinea pig PPARalpha is expressed at low levels in liver, and the currently favoured hypothesis to explain species differences in hepatic peroxisome proliferation invokes the low level of PPARalpha as the principal determinant of species responsiveness. However, the demonstration that guinea pigs and humans undergo hypolipidaemia induced by PPARalpha-agonists calls into question the mode of action of PPARalpha agonists in "non-responsive" species.

Demonstration of testicular apoptosis in human male infertility states using a DNA laddering technique

DNA laddering, morphometric analysis, and in-situ end labelling of testis biopsy tissue obtained from azoospermic or severely oligozoospermic men revealed increased apoptosis frequency, implicating a possible role of apoptosis in the pathogenesis of human male infertility.

Cell population dynamics (apoptosis, mitosis, and cell-cell communication) during disruption of homeostasis

The sequence of events involved in maintenance of homeostasis must encompass mechanisms within single cells as well as interactions between cells within a population. To investigate the interaction among these inter- and intracellular mechanisms, disruption of homeostasis by serum deprivation was performed in WB-F344, a normal diploid epithelial cell line. Changes in cell-cell communication (gap junction function) at the population level and in individual cells were monitored using the scrape load/dye transfer and fluorescence redistribution after photobleaching assays. Apoptosis and mitosis were measured using internucleosomal DNA ladder assays and fluorescence-activated cell sorting. The results indicate that a common element in early apoptosis and early mitosis is sustained gap junction function. As cell life (mitosis) and cell death (apoptosis) progressed, a common process of change in gap junction function occurred. A transient stimulation of mitosis concomitant with increased apoptosis was also observed during serum deprivation. Gap junctions may play a regulatory role during initiation of these opposite yet equally important mechanisms of maintaining homeostasis. This model system is useful for further studies on the relationships among inter- and intracellular mechanisms of homeostasis.

Subcellular alterations induced by UV-oxidized low-density lipoproteins in epithelial cells can be counteracted by alpha-tocopherol

Oxidized LDL (ox-LDL) have been involved in the pathogenesis of several human diseases including dermatological pathologies. Oxidative modification of low-density lipoproteins (LDL) is accompanied by both extensive degradation of its polyunsaturated fatty acids and production of lipoperoxides. These highly reactive products induce an intracellular oxidative stress with a variety of cytotoxic effects. In order to evaluate cellular damage induced by oxidative stress in epidermal cells, a human epidermoid carcinoma cell line in culture (A 431) was used as experimental model. Cell treatment with UV-oxidized LDL resulted in cytostatic and cytotoxic effects characterized by morphological and functional alterations: inhibition of cell proliferation, modifications of cytoskeleton network, microtubular derangement, loss of cell-cell and cell-substrate contacts, cell detachment and cell death by apoptosis. The ox-LDL-induced alterations were almost completely prevented by pre-incubating cells with alpha-tocopherol. The results presented here could be of relevance for a better comprehension of the pathogenic mechanisms of several human diseases, including dermatological pathologies, and could indicate that antioxidants such as alpha-tocopherol could represent an important therapeutic challenge in the maintenance of cell and tissue homeostasis in the long run.

Apoptosis and cell proliferation in rat hepatocytes induced by barbiturates

To examine the effect on cell population in hepatocytes of phenobarbital (PB) and other barbiturates, PB, allobarbital (ALB), barbital sodium (BS) and barbituric acid (BA) were given orally to male rats for 7 consecutive days. Although there was no apparent change in non-promoting BA, hepatomegaly was induced by PB, BS and ALB, which are promoters of hepatocarcinogenesis. In PB- and BS-treated livers, hepatomegaly was attributable to hepatocyte proliferation and enzyme induction. In ALB-treated liver, it was attributable to enzyme induction. The level of cell proliferation was reduced to less than the control values following withdrawal of PB, ALB and BS. It seemed that the degree of suppression of cell proliferation following withdrawal of these compounds correlated to the degree of cell proliferation (PB>BS>ALB) during treatment. In PB-treated liver, apoptosis was induced during treatment, serving to eliminate the excess of hepatocytes. This suggests that short-term administration of PB neither induced suppression of apoptosis nor disturbed homeostasis of hepatocyte populations.

Impact of burn injury on hepatic TGF-beta1 expression and plasma TGF-beta1 levels

BACKGROUND

The liver plays a critical regulatory role in the acute inflammatory response to injury, although the mechanisms of this regulation are not well understood. transforming growth factor-beta1 (TGF-beta1) is induced after burn injury and may contribute to an inhibitory or fatal effect on hepatocytes. We investigated the association over time between plasma concentration of TGF-beta1, expression of TGF-beta1 m-RNA in liver tissue, and histologic analysis of liver apoptosis after burn injury.

METHODS

Male BALB/c mice were anesthetized and randomized to receive 0% (sham), moderate (approximately 25%) (M), or large (approximately 50%) (L) body surface area full-thickness contact burn, followed by resuscitation and analgesia. Animals were killed over a time course from 15 minutes to 24 hours after burn injury, and liver tissue and peripheral blood were collected. Plasma levels of TGF-beta1 (nanograms per milliliter) were measured by enzyme-linked immunosorbent assay. TGF-beta1 m-RNA was extracted from liver and measured by reverse transcription-polymerase chain reaction. Histology of liver apoptosis was examined after fixation and staining with TdT-mediated dUTP nick-end labeling (TUNEL) method.

RESULTS

The plasma concentration of TGF-beta in burn group L was significantly increased at 4 hours after burn when compared with sham and M burn groups. This rise in plasma TGF-beta1 was preceded by an increase in hepatic TGF-beta1 m-RNA expression at 30 minutes, 1, 2, and 4 hours after burn in the L group. Histologic analysis found greater hepatocyte death in the L group than in the M group at 8 hours after burn.

CONCLUSION

The levels of induced TGF-beta1 and TGF-beta1 m-RNA after L burn injury are higher and peak earlier than after M burn injury. Elevated TGF-beta1 may be associated with cell death in hepatocytes. The TGF-beta1 rise may be associated with hepatocyte injury and systemic response to massive burn.

Vegan proteins may reduce risk of cancer, obesity, and cardiovascular disease by promoting increased glucagon activity

Amino acids modulate the secretion of both insulin and glucagon; the composition of dietary protein therefore has the potential to influence the balance of glucagon and insulin activity. Soy protein, as well as many other vegan proteins, are higher in non-essential amino acids than most animal-derived food proteins, and as a result should preferentially favor glucagon production. Acting on hepatocytes, glucagon promotes (and insulin inhibits) cAMP-dependent mechanisms that down-regulate lipogenic enzymes and cholesterol synthesis, while up-regulating hepatic LDL receptors and production of the IGF-I antagonist IGFBP-1. The insulin-sensitizing properties of many vegan diets--high in fiber, low in saturated fat--should amplify these effects by down-regulating insulin secretion. Additionally, the relatively low essential amino acid content of some vegan diets may decrease hepatic IGF-I synthesis. Thus, diets featuring vegan proteins can be expected to lower elevated serum lipid levels, promote weight loss, and decrease circulating IGF-I activity. The latter effect should impede cancer induction (as is seen in animal studies with soy protein), lessen neutrophil-mediated inflammatory damage, and slow growth and maturation in children. In fact, vegans tend to have low serum lipids, lean physiques, shorter stature, later puberty, and decreased risk for certain prominent 'Western' cancers; a vegan diet has documented clinical efficacy in rheumatoid arthritis. Low-fat vegan diets may be especially protective in regard to cancers linked to insulin resistance--namely, breast and colon cancer--as well as prostate cancer; conversely, the high IGF-I activity associated with heavy ingestion of animal products may be largely responsible for the epidemic of 'Western' cancers in wealthy societies. Increased phytochemical intake is also likely to contribute to the reduction of cancer risk in vegans. Regression of coronary stenoses has been documented during low-fat vegan diets coupled with exercise training; such regimens also tend to markedly improve diabetic control and lower elevated blood pressure. Risk of many other degenerative disorders may be decreased in vegans, although reduced growth factor activity may be responsible for an increased risk of hemorrhagic stroke. By altering the glucagon/insulin balance, it is conceivable that supplemental intakes of key non-essential amino acids could enable omnivores to enjoy some of the health advantages of a vegan diet. An unnecessarily high intake of essential amino acids--either in the absolute sense or relative to total dietary protein--may prove to be as grave a risk factor for 'Western' degenerative diseases as is excessive fat intake.

Apoptosis, Bcl-2, and proliferating cell nuclear antigen in the failing human heart: observations made after implantation of left ventricular assist device

BACKGROUND

Heart failure is characterized by progressive left ventricular remodeling, a complex process that results from cell growth and cell death. The quantitative contribution of apoptotic cells toward left ventricular remodeling has varied widely in tissue removed from cardiomyopathic hearts. Apoptosis has been responsive to angiotensin-converting enzyme inhibition in experimental heart failure, but the dynamics and responsiveness to chronic left ventricular unloading have not been studied.

METHODS AND RESULTS

We studied 8 patients with severe heart failure before and after chronic left ventricular unloading with a left ventricular assist device (LVAD). Tissue from the left ventricular apex removed at the time of LVAD implantation was examined for apoptosis using the technique of terminal deoxynucleotidyl transferase deoxyuridine triphosphate-biotin nick end-labeling (TUNEL) in 10 patients. These same hearts explanted at the time of cardiac transplantation were then examined for apoptosis after patients had been on the LVAD for 99 +/- 20 (SEM) days. An additional 10 patients with equally severe heart failure who underwent heart transplantation without the use of an LVAD served as controls. Eight hearts obtained at autopsy approximately 6 hours after death from patients who died of non-cardiovascular disease causes served as non-heart failure controls. Additionally, 6 hearts were examined by immunohistochemistry for the antiapoptotic protein, Bcl-2, and for the repair and/or proliferation marker, proliferating cell nuclear antigen (PCNA), before and after LVAD. Apoptosis was not detected in the tissue sections from the hearts of 8 patients at the time of LVAD implantation. Only 1 of these patients had limited apoptosis (< 1 apoptotic cell/1,000 myocytes) after LVAD insertion. Three of 10 patients with severe heart failure who did not receive an LVAD but underwent transplantation showed limited apoptosis (< 1 apoptotic cell/1,000 myocytes). Likewise, none of the control hearts from patients who died of noncardiovascular disease manifested apoptosis. Six of 6 patients overexpressed Bcl-2 at the time of LVAD insertion. In all these patients, Bcl-2 returned to negligible levels after chronic unloading of the heart. Likewise, PCNA was abundantly expressed in 5 of 6 failing hearts at the time of LVAD implantation and was reduced in 4 of 5 hearts after chronic unloading by LVAD.

CONCLUSION

Apoptosis is a rare or inconsistent finding in the failing human heart. Overexpression of such indicators of cellular stress and DNA replication and/or repair as Bcl-2 and PNCA in heart failure may be altered by optimizing left ventricular loading conditions by such mechanical devices as the LVAD.

Downregulation of apoptosis-related genes in keloid tissues

BACKGROUND

Physiologically programmed cell death or apoptosis occurs during the natural balance between cellular proliferation and demise.

MATERIALS AND METHODS

We compared the expression of 64 apoptosis-related genes in keloids and normal scars to investigate the potential role of apoptosis in keloid formation. Two sets of mRNA were isolated from keloids excised from four previously untreated patients and four normal scar patients separately. Human cDNA arrayed hybridization was performed to compare the apoptosis-related gene expression between these two groups. In addition, TUNEL assays were performed to evaluate the percentage of apoptotic cells in keloids (center and periphery) versus normal scars.

RESULTS

Eight of the sixty-four apoptosis-related genes studied were significantly underexpressed in keloid tissue. The underexpressed genes and their relative expression compared with normal scar were defender against cell death 1 (DAD-1) (34.1% of normal scar); nucleoside diphosphate kinase B (c-myc transcription factor) (24.7%); glutathione S-transferase (17.9%); glutathione S-transferase microsomal (28.1%); glutathione peroxidase (47.2%); tumor necrosis factor receptor 1-associated protein (TRADD) (51.0%); 19-kDa interacting protein 3 (NIP3) (36.0%); and cytoplasmic dynein light chain 1 (HDLC1) (47.7%). Spatial analysis of apoptosis using TUNEL assays revealed apoptosis indices of 0.83 for keloid periphery and 0.63 for keloid center.

CONCLUSIONS

In this study we demonstrated underexpression of apoptosis-related genes in human keloid tissue and decreased apoptotic activity in fibroblasts derived from keloids versus normal scars. We hypothesized that keloid fibroblasts fail to undergo physiologically programmed cell death and, thus, continue to produce and secrete connective tissue beyond the period expected in normal scar formation, accounting for the progressive and hypertrophic nature of keloids. This mechanism leads to new possibilities for treatment of keloids through induction of apoptosis.

Role of nitric oxide in the induction of apoptosis by smokeless tobacco extract

Smokeless tobacco usage is a growing public health concern in the United States. Lesions of the oral cavity have been clearly linked to smokeless tobacco use. The objective of this study was to determine the biochemical effects of smokeless tobacco extract (STE) exposure upon hamster cheek pouch cell (HCPC-1) cultures. HCPC-1 cells were exposed to a 5 -fold dose-range of STE (0.5, 1.0 and 2.5%) over a time-course of 24-96 h. Following each exposure we measured various biochemical parameters of cell proliferation and cell death. Cell viability, cell cycle progression and S-phase DNA synthesis were measured as markers of cell proliferation. We measured lactate dehydrogenase leakage as a marker of cell membrane damage and cell death due to necrosis. No significant alterations were observed in cell cycle progression and cell proliferation as a result of exposure to STE. LDH measured colorimetrically indicated no significant effect with the lower doses(0.5, 1.0 and 2.5% STE). Apoptosis measured as the A0 peak and by the TUNEL procedure revealed that STE caused significant rates of apoptosis. Maximal apoptosis was noted between 48-96 h. In order to probe the mechanism further we measured the levels of nitrites as an indicator of nitric oxide (NO) in the media. NO levels were significantly elevated at the doses that caused an induction of apoptosis. The results from this study indicate that STE causes a dose-dependent induction of apoptosis and that this is mediated by nitric oxide.

Inhibition of mitogen-activated kinase signaling sensitizes HeLa cells to Fas receptor-mediated apoptosis

The Fas receptor (FasR) is an important physiological mediator of apoptosis in various tissues and cells. However, there are also many FasR-expressing cell types that are normally resistant to apoptotic signaling through this receptor. The mitogen-activated protein kinase (MAPK) signaling cascade has, apart from being a growth-stimulating factor, lately received attention as an inhibitory factor in apoptosis. In this study, we examined whether MAPK signaling could be involved in protecting FasR-insensitive cells. To this end, we used different approaches to inhibit MAPK signaling in HeLa cells, including treatment with the MAPK kinase inhibitor PD 98059, serum withdrawal, and expression of dominant-interfering MAPK kinase mutant protein. All of these treatments were effective in sensitizing the cells to FasR-induced apoptosis, demonstrating that MAPK indeed is involved in the control of FasR responses. The MAPK-mediated control seemed to occur at or upstream of caspase 8, the initiator caspase in apoptotic FasR responses. Transfection with the constitutively active MAPK kinase abrogated FasR-induced apoptosis also in the presence of cycloheximide, indicating that the MAPK-generated suppression of FasR-mediated apoptotic signaling is protein synthesis independent. In cells insensitive to FasR-induced apoptosis, stimulation of the FasR with an agonistic antibody resulted in significant MAPK activation, which was inhibited by PD 98059. When different cell types were compared, the FasR-mediated MAPK activation seemed proportional to the degree of FasR insensitivity. These results suggest that the FasR insensitivity is likely to be a consequence of FasR-induced MAPK activation, which in turn interferes with caspase activation.

Report of a fatal case of dengue infection with hepatitis: demonstration of dengue antigens in hepatocytes and liver apoptosis

A fatal case of dengue (DEN) infection associated with a spleen rupture and with hepatitis is reported here. Microscopic studies showed numerous areas of spleen rupture with hematomas and revealed necrotic foci in liver samples obtained at autopsy. Although hepatitis was reported in several cases of DEN fever, the mechanism of liver injury remains poorly understood. In this case, immunohistochemistry showed that DEN viral antigens were mostly detected in hepatocytes surrounding the necrotic foci. By in situ detection of DNA fragmentation, apoptotic hepatocytes were found to be colocated with DEN virus-infected hepatocytes. These findings suggest that hepatocytes are the major sites of DEN virus replication in the liver and that DEN virus induces apoptosis of hepatocytes in vivo.

Role of poly(ADP-ribose) polymerase (PARP) cleavage in apoptosis. Caspase 3-resistant PARP mutant increases rates of apoptosis in transfected cells

An early transient burst of poly(ADP-ribosyl)ation of nuclear proteins was recently shown to be required for apoptosis to proceed in various cell lines (Simbulan-Rosenthal, C., Rosenthal, D., Iyer, S., Boulares, H., and Smulson, M. (1998) J. Biol. Chem. 273, 13703-13712) followed by cleavage of poly(ADP-ribose) polymerase (PARP), catalyzed by caspase-3. This inactivation of PARP has been proposed to prevent depletion of NAD (a PARP substrate) and ATP, which are thought to be required for later events in apoptosis. The role of PARP cleavage in apoptosis has now been investigated in human osteosarcoma cells and PARP -/- fibroblasts stably transfected with a vector encoding a caspase-3-resistant PARP mutant. Expression of this mutant PARP increased the rate of staurosporine and tumor necrosis factor-alpha-induced apoptosis, at least in part by reducing the time interval required for the onset of caspase-3 activation and internucleosomal DNA fragmentation, as well as the generation of 50-kilobase pair DNA breaks, thought to be associated with early chromatin unfolding. Overexpression of wild-type PARP in osteosarcoma cells also accelerated the apoptotic process, although not to the same extent as that apparent in cells expressing the mutant PARP. These effects of the mutant and wild-type enzymes might be due to the early and transient poly(ADP-ribose) synthesis in response to DNA breaks, and the accompanying depletion of NAD apparent in the transfected cells. The accelerated NAD depletion did not seem to interfere with the later stages of apoptosis. These results indicate that PARP activation and subsequent cleavage have active and complex roles in apoptosis.

C3-fullero-tris-methanodicarboxylic acid protects epithelial cells from radiation-induced anoikia by influencing cell adhesion ability

Anoikia is a type of apoptotic cell death that occurs in cells that are substrate-restricted in their growth. Buckminsterfullerenes represent a new class of chemical compounds with wide potential pharmacological antioxidant activity. In this report we provide the first demonstration that a water-soluble fullerene derivative, C3-fullero-tris-methanodicarboxylic acid, synthesized in our laboratories, is capable of inducing anoikia resistance in epithelial cells by a mechanism involving a 'trophic' effect on cell spreading-associated cytoskeletal components, i.e. on actin microfilaments.

Tyrosol, the major olive oil biophenol, protects against oxidized-LDL-induced injury in Caco-2 cells

Experimental and clinical evidence suggest that oxidative stress causes cellular damage, leading to functional alterations of the tissue. Free radicals may thus play an important role in the pathogenesis of a number of human diseases. Among pro-oxidant agents, oxidized LDL lead to the production of cytotoxic reactive species, e.g., lipoperoxides, causing tissue injury and various subsequent pathologies including intestinal diseases. Thus, to analyze the oxidative damage induced by oxidized LDL to intestinal mucosa, we evaluated morphological and functional changes induced in the human colon adenocarcinoma cell line, Caco-2. In addition, we examined the protective effects exerted by tyrosol, 2-(4-hydroxyphenyl)ethanol, the major phenolic compound present in olive oil. Caco-2 cell treatment (24 and/or 48 h) with oxidized LDL (0.2 g/L) resulted in cytostatic and cytotoxic effects characterized by a series of morphological and functional alterations: membrane damage, modifications of cytoskeleton network, microtubular disorganization, loss of cell-cell and cell-substrate contacts, cell detachment and cell death. The oxidized LDL-induced alterations in Caco-2 cells were almost completely prevented by tyrosol which was added 2 h before and present during the treatments. Our results suggest that some biophenols, such as those contained in olive oil, may counteract the reactive oxygen metabolite-mediated cellular damage and related diseases, by improving in vivo antioxidant defenses.

The effects of cell density, attachment substratum and dexamethasone on spontaneous apoptosis of rat hepatocytes in primary culture

The rates of spontaneous cell detachment, cell viability, and apoptosis in primary cultures of rat hepatocytes plated at high and low density were compared. Apoptosis was frequent in detached cells, and the rates of cell detachment and apoptosis were greater in high-density than in low-density cultures. Among attached cells, more cells had condensed or fragmented nuclei in high-density than in low-density cultures. Further, ladder-like DNA fragmentation was not seen in low-cell-density cultures but was clearly evident in high-density cultures. Bax was more highly expressed in cells cultured at high density, and on collagen vs. matrigel, whereas changes of Bcl-2 and Fas expression observed in culture appeared unrelated to the rate of apoptosis. The rate of hepatocyte apoptosis appeared to be identical in low-density cultures on collagen 1 and matrigel, but when cells were cultured at high density, matrigel suppressed apoptosis by more than 50% at 36 h. In hepatocytes cultured on collagen 1, dexamethasone (0.1 microM) suppressed apoptosis in both low- and high-density cultures; higher doses had no further effects. In high density cultures, aurintricarboxylic acid (10 microM) suppressed apoptosis and this improved cell attachment at 48 h. It is concluded that cell viability in primary cultures of rat hepatocytes grown on collagen I is dependent on optimal culture density and that the cell population is regulated, at least in part, by apoptosis. Corticosteroids suppress spontaneous apoptosis of cultured hepatocytes in a non-dose-dependent manner, whereas matrigel abolishes apoptosis induced by increasing cell density. Bax may be an important protein in the cell density and cell matrix-dependent regulation of apoptosis in cultured hepatocytes.

Growth arrest and induction of apoptosis in breast cancer cells by antisense depletion of protein kinase A-RI alpha subunit: p53-independent mechanism of action

The enhanced expression of the RI alpha subunit of cyclic AMP-dependent protein kinase type 1 (PKA-1) has been correlated with cancer cell growth. We have investigated the effects of sequence-specific inhibition of RI alpha gene expression on the growth of MCF-7 human breast cancer cells. We report that RI alpha antisense treatment results in a reduction in RI alpha expression at both mRNA and protein levels and inhibition of cell growth. The growth inhibition was accompanied by changes in cell morphology, cleavage of poly(ADP-ribose) polymerase (PARP) and appearance of apoptotic nuclei. In addition, bcl-2 protein level was reduced and p53 expression increased in growth arrested cells. Interestingly, RI alpha antisense inhibited cell viability and induced apoptosis in the absence of p53, suggesting that these actions of RI alpha antisense are exerted independent of p53. In contrast, two- and four-base mismatched control oligonucleotides had no effect on either cell growth or morphology. These results demonstrate that the RI alpha antisense, which efficiently depletes the growth stimulatory molecule RI alpha, induces cell differentiation and apoptosis, providing a new approach to combat breast cancer cell growth.

Cleavage of poly(ADP-ribose) transferase during p53-independent apoptosis in rat liver after treatment with N-nitrosomorpholine and cyproterone acetate

The aim of this work was to study the role of the tumor suppressor p53 and of poly(ADP-ribose) transferase (pADPRT) in the control of hepatocyte apoptosis in two different in vivo models, i.e., during the process of tumor initiation by the genotoxin and cytotoxin N-nitrosomorpholine (NNM) and after withdrawal of the hepatomitogen cyproterone acetate (CPA). Treatment with NNM induces apoptosis followed by necrosis and regenerative DNA synthesis. At the first wave of apoptosis 12 h after NNM application, no p53 expression could be detected by immunohistochemical analysis and immunoblotting. However, 24 h after treatment, numerous p53-positive hepatocyte nuclei were detected, whereas hepatocytes in early and later stages of apoptosis were always negative. Simultaneously with the increased p53 levels, p21 protein was induced. This was accompanied by a block in replicative DNA synthesis, as detected by proliferating-cell nuclear antigen immunostaining. Concomitantly with the increase in apoptosis, dramatic degradation of the nuclear enzyme pADPRT was observed, as evidenced by immunoblotting and activity blotting. The decrease in pADPRT enzymatic activity observed 12 h after treatment coincided with the greatest extent of pADPRT cleavage. One prominent cleavage product was 64 kDa, suggesting that granzyme B was involved in pADPRT degradation. In the second in vivo model we used, i.e., withdrawal of treatment with the hepatomitogen CPA, apoptosis of excessive hepatocytes but no necrosis occurs. Again, no induction of p53 expression could be detected in the liver even at the maximum level of apoptosis, whereas a strong correlation between induction of apoptosis and cleavage of pADPRT to a 64-kDa fragment was observed. These results from whole-animal experiments strongly suggest that the induction of apoptosis in rat liver after genotoxic and cytotoxic damage and during regression of hyperplasia is driven by a p53-independent pathway but is accompanied by cleavage of pADPRT.

Incidence of cancer in postmyocardial infarction patients treated with short-acting nifedipine and diltiazem. Secondary Prevention Group

BACKGROUND

Recent reports suggest a possible link between nifedipine (but not diltiazem) and an increased risk of cancer in patients being treated with calcium antagonists.

METHODS

A total of 1054 postmyocardial infarction patients were divided randomly into those being treated with calcium antagonists (n = 566 [nifedipine, 425 patients and diltiazem, 141 patients]) and controls (no calcium antagonist; n = 488). The patients were followed for 26.3 months, and the incidences of cardiac events as well as cancer were compared among the 3 groups.

RESULTS

Thirteen patients (2.7%) in the control group developed cancer, whereas 15 patients in the nifedipine group (3.5%; odds ratio, 1.34; 95% confidence interval [95% CI], 0.63-2.85) and 3 patients in the diltiazem group (2.1%; odds ratio, 0.89; 95% CI, 0.27-2.93) developed cancer.

CONCLUSIONS

Diltiazem appears to present no increased risk of cancer. The incidence of cancer was slightly higher in the patients receiving nifedipine than in those not being treated with a calcium antagonist, which is consistent with earlier reports; however, this increase was not statistically significant.

Interleukin-2-activated natural killer cells can induce both apoptosis and necrosis in rat hepatocytes

Natural killer (NK) cells play a crucial role in the elimination of virus-infected or transformed cells in the liver. In this article, we describe the mechanism by which liver cells are killed by NK cells. Interleukin-2-activated natural killer (A-NK) cells from the rat induced apoptotic cell death in 30% of freshly isolated rat hepatocytes within 60 minutes. Recognition by the A-NK cells of the hepatocytes as nonself was established by masking the major histocompatibility complex (MHC) class I molecules on the hepatocytes with the OX18 antibody. During the killing process, a decrease of the mitochondrial membrane potential (MMP), formation of blebs, phosphatidyl serine (PS) externalization, chromatin condensation, and nuclear fragmentation were observed. The hepatocytes became apoptotic before permeabilization of the plasma membrane occurred, suggesting that the observed cytolysis was caused by secondary necrosis. The apoptotic process was completely abolished by the caspase inhibitors, Z-Val-Ala-DL-Asp fluormethylketone (zVAD-fmk) and Ac-Asp-Glu-Val-aldehyde (DEVD-cho). However, under these conditions, A-NK cells killed a smaller fraction of the hepatocytes by (primary) necrosis. These results indicate that apoptosis is the major cytotoxic process induced by A-NK cells in hepatocytes. If apoptosis is prevented, a more limited necrotic effect is induced. Therefore, this study shows that NK cells are fully equipped to induce both apoptosis and necrosis in hepatocytes, but appear to prefer the apoptotic route.

Abnormalities of protein kinases in neurodegenerative diseases

In neurodegenerative diseases such as ALS and AD there is evidence for abnormal regulation of protein kinases. In these diseases, altered activities and protein levels of several specific kinases suggest that abnormal phosphorylation is present and this aberrant phosphorylation may be involved in the pathogenesis of these diseases. The observation that regulation of the NMDA receptor ion channel is altered in tissue from ALS patients may arise from the abnormal phosphorylation state of the protein kinase regulating NMDA receptor function. Whether the abnormalities of these protein kinases is a primary event leading to altered receptor regulation or vice versa is still poorly understood. The seemingly multiple pathogenic mechanisms of ALS and AD create complexity in assessing a primary cause that may lead to cell death. The mechanisms causing cell death (apoptosis or necrosis) may be overlapping with integrated events among the components interacting and contributing to a final pathway for neuron death. Thus, evidence of impairment in protein kinase signalling in these diseases may be a primary cause, a secondary event, or a compensatory mechanism. To further study this issue, different model systems could be beneficial to obtain a better understanding of these diseases.

Pit cells (Hepatic natural killer cells) of the rat induce apoptosis in colon carcinoma cells by the perforin/granzyme pathway

The high mortality of colon cancer is to a large extent caused by the frequent occurrence of liver metastasis. This is remarkable, because the liver harbors two distinct cell populations that can eliminate invading cancer cells, namely hepatic natural killer (NK) cells and Kupffer cells. These hepatic NK cells, known as pit cells, are the most cytotoxic cells of the naturally occurring NK cells. However, the mechanism by which pit cells eliminate tumor cells is largely unknown. Because we recently found an indication that apoptosis is involved, we tried to assess the role of this mode of cell death using an in vitro system with isolated pure pit cells (>90%) and CC531s cells, a rat colon carcinoma (CC) cell line. Pit cells induced apoptosis in CC531s cells as shown by quantitative DNA fragmentation, agarose gel electrophoresis, and different modes of microscopy. When extracellular Ca2+ was chelated by ethylene glycol-bis(beta-aminoethyl ether)-N,N,-tetraacetic acid (EGTA) during coincubation or when the pit cells were preincubated with the granzyme inhibitor 3,4-dichloroisocoumarin (DCI), the induction of apoptosis was abolished. These results show that pit cells use the Ca2+-dependent perforin/granzyme pathway to induce apoptosis in the CC531s cells, and not the alternative Ca2+-independent Fas pathway. To further exclude the possibility of the involvement of the Fas pathway, we treated CC531s cells with recombinant Fas ligand. This treatment did not result in the induction of apoptosis, indicating that CC531s cells are resistant to Fas-mediated apoptosis. We conclude therefore that pit cells induce apoptosis in CC cells in vitro by the perforin/granzyme pathway.

Peroxisome proliferator-activated receptor (PPAR) alpha-regulated growth responses and their importance to hepatocarcinogenesis

Peroxisome proliferators (PPs) are a class of non-genotoxic rodent hepatocarcinogens that act by perturbing liver growth regulation. We have demonstrated previously that PPs suppress both spontaneous rat hepatocyte apoptosis and that induced by exogenous stimuli such as transforming growth factor-beta1 (TGF beta1). More recently, we have demonstrated that PPs can suppress apoptosis induced by more diverse stimuli such as DNA damage or ligation of Fas, a receptor related to the tumour necrosis factor alpha (TNF alpha) family of cell surface receptors. PPs transcriptionally activate the peroxisome proliferator activated receptor-alpha, PPAR alpha, a member of the nuclear hormone receptor superfamily. We investigated whether activation of PPAR alpha mediates the suppression of rat hepatocyte apoptosis induced by PPs. We isolated a naturally occurring variant form of PPAR alpha (hPPAR alpha-6/29) from human liver by PCR cloning. hPPAR alpha-6/29 shared the ability of mPPAR alpha to bind to DNA but, unlike mPPAR alpha, could not be activated by PPs. Furthermore, hPPAR alpha-6/29 could act as a dominant negative regulator of PPAR-mediated gene transcription. When introduced into primary rat liver cell cultures by transient transfection, hPPAR alpha-6/29 prevented the suppression of hepatocyte apoptosis by the PP nafenopin, but not that seen in response to phenobarbitone (PB), a non-genotoxic carcinogen whose action does not involve PPAR alpha. The suppression of hepatocyte apoptosis was abrogated completely even though only 30% of hepatocytes were transfected, suggesting the involvement of a soluble factor. Recent data have suggested that TNF alpha, perhaps released by liver Kupffer cells in response to PPs, may play a key role in mediating the effects of PPs on hepatocyte growth regulation.