Menadione induces both necrosis and apoptosis in rat pancreatic acinar AR4-2J cells

Apoptotic Effects of a Thioether Analog of Vitamin K3 in a Human Leukemia Cell Line

Research suggests that thioether analogs of vitamin K₃ (VK₃) can act to preserve the phosphorylation of epidermal growth factor receptors by blocking enzymes (phosphatases) responsible for their dephosphorylation. Additionally, these derivatives can induce apoptosis via mitogen-activated protein kinase and caspase-3 activation, inducing reactive oxygen species (ROS) production, and apoptosis. However, vitamin K₁ exhibits only weak inhibition of phosphatase activity, while the ability of VK₃ to cause oxidative DNA damage has raised concerns about carcinogenicity. Hence, in the current study, we designed, synthesized, and screened a number of VK₃ analogs for their ability to enhance phosphorylation activity, without inducing off-target effects, such as DNA damage. 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) assay revealed that each analog produced a different level of cytotoxicity in the Jurkat human leukemia cell line; however, none elicited a cytotoxic effect that differed significantly from that of the control. Of the VK₃ analogs, CPD5 exhibited the lowest EC₅₀, and flow cytometry results showed that apoptosis was induced at final concentrations of ≥10 μM; hence, only 0.1, 1, and 10 μM were evaluated in subsequent assays. Furthermore, CPD5 did not cause vitamin K-attributed ROS generation and was found to be associated with a significant increase in caspase 3 expression, indicating that, of the synthesized thioether VK₃ analogs, CPD5 was a more potent inducer of apoptosis than VK₃. Hence, further elucidation of the apoptosis-inducing effect of CPD5 may reveal its efficacy in other neoplastic cells and its potential as a medication.

The Efficacy of Vitamin K, A Member Of Naphthoquinones in the Treatment of Cancer: A Systematic Review and Meta-Analysis

BACKGROUND

Redox dysregulation originating from metabolic alterations in cancer cells contributes to their proliferation, invasion, and resistance to therapy. Conversely, these features represent a specific vulnerability of malignant cells that can be selectively targeted by redox chemotherapeutics. Amongst them, Vitamin K (VitK) carries the potential against cancer stem cells, in addition to the rest of tumor mass.

OBJECTIVES

To assess the possible benefits and safety of VitK for cancer treatment using a systematic review and meta-analysis with a mixed-methods approach.

METHODS

We performed a systematic search on several electronic databases for studies comparing VitK treatment with and without combination to the control groups. For quantitative studies, fully or partially reported clinical outcomes such as recurrence rates, survival, overall response and adverse reactions were assessed. For qualitative studies, a narrative synthesis was accomplished.

RESULTS

Our analysis suggested that the clinical outcome of efficacy, the pooled hazard ratio for progression-free survival, and the pooled relative risk for overall survival, and overall response were significantly higher in the VitK therapy group compared to the placebo group (p<0.05). We did not observe any significant difference in the occurrence of adverse events between groups. Among qualitative studies, VitK treatment targeting myelodysplastic syndrome and advanced solid tumors resulted in 24.1% and 10% of clinical response, respectively.

CONCLUSION

VitK not only exerts antitumor effects against a wide range of tumor types, but it also has excellent synergism with other therapeutic agents.

Nicotine and modafinil combination protects against the neurotoxicity induced by 3,4-Methylenedioxymethamphetamine in hippocampal neurons of male rats

MDMA (3,4-Methylenedioxymethamphetamine) is a common recreational drug of abuse which causes neurodegeneration. Nicotine and modafinil provide antioxidant and neuroprotective properties and may be beneficial in the management of MDMA-induced neurotoxicity. The purpose of this study was to characterize how acute and chronic administration of nicotine and/or modafinil exert protective effects against the MDMA-induced impaired cognitive performance, oxidative stress, and neuronal loss. Adult male rats were divided into three groups, namely control, MDMA and treatment (modafinil and/or nicotine). MDMA (10 mg/kg) was administered intraperitoneally during a three-week schedule (two times/day for two consecutive days/week). The treated-groups were classified based on the acute or chronic status of treatment. In the groups which underwent acute treatments, nicotine (0.5 mg/kg) and/or modafinil (100 mg/kg) were injected just prior to the MDMA administration (acute nicotine (NA), acute modafinil (MA), and acute nicotine and modafinil (NMA)). In the rats which received chronic treatments, nicotine (0.5 mg/kg) and/or modafinil (100 mg/kg) were injected every day during the three week-schedule administration of MDMA (chronic nicotine (NC), chronic modafinil (MC), and chronic nicotine and modafinil (NMC)). Learning and memory performance, as well as avoidance response, were assessed by Morris water maze and Shuttle box, respectively. Our findings indicate enhanced learning and memory and avoidance response in the NMC group. By TUNEL test and Cresyl Violet staining we evaluated neuronal loss and apoptosis in the hippocampal CA1 and found increased neuronal viability in the NMC group. On the other hand, chronic administration of modafinil and nicotine significantly down-regulated the caspase 3 and up-regulated both BDNF and TrkB levels in the MDMA-received rats. The serum levels of glutathione peroxidase (GPx) and total antioxidant capacity (TAC) were evaluated and we found that the alterations of serum levels of GPx and TAC were considerably prevented in the NMC group. The overall results indicate that nicotine and modafinil co-administration rescued brain from MDMA-induced neurotoxicity. We suggest that nicotine and modafinil combination therapy could be considered as a possible treatment to reduce the neurological disorders induced by MDMA.

Cytotoxic effects of menadione on normal and cytochrome c-deficient yeast cells cultivated aerobically or anaerobically

Cytotoxic effects of menadione on normal and cytochrome c-deficient yeast cells were examined on the basis of the cell growth rate, NAD(P)H concentration, reactive oxygen production, plasma membrane H⁺-ATPase activity, and ethanol production. In aerobically or anaerobically cultured yeast cells, NAD(P)H concentration decreased with increasing concentration of menadione, and the recovery of NAD(P)H concentration was proportional to the cell growth rate. However, there was no relationship among the inhibition of the cell growth and reactive oxygen production, plasma membrane H⁺-ATPase activity, and ethanol production. Among them, ethanol production showed resistance to the cytotoxicity of menadione, suggesting the resistance of glycolysis to menadione. The growth inhibitory effect of menadione depended on the rapid decrease and the recovery of NAD(P)H rather than production of reactive oxygen species regardless of aerobic culture or anaerobic culture and presence or absence of mitochondrial function. The recovery of NAD(P)H concentration after the addition of menadione might depend on menadione-resistant glycolytic enzymes.

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The rapid decrease in NAD(P)H concentration in yeast cells was observed after the addition of menadione.

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The recovery of NAD(P)H concentration after addition of menadione was proportional to the cell growth rate.

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The above phenomena were observed in suspension of aerobically or anaerobically cultured yeast cells.

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The above phenomena were observed in suspension of normal or cytochrome c-deficient yeast cells.

Current trends in pharmacological approaches for treatment and management of acute pancreatitis – a review

Objectives

Acute pancreatitis (AP) is an inimical disorder associated with overall mortality rates between 10-15%. It is a disorder of the exocrine pancreas which is characterized by local and systemic inflammatory responses primarily driven by oxidative stress and death of pancreatic acinar cells. The severity of AP ranges from mild pancreatic edema with complete recuperative possibilities to serious systemic inflammatory response resulting in peripancreatic/pancreatic necrosis, multiple organ failure, and death.

Key findings

We have retrieved the potential alternative approaches that are developed lately for efficacious treatment of AP from the currently available literature and recently reported experimental studies. This review summarizes the need for alternative approaches and combinatorial treatment strategies to deal with AP based on literature search using specific key words in PubMed and ScienceDirect databases.

Summary

Since AP results from perturbations of multiple signaling pathways, the so called “monotargeted smart drugs” of the past decade is highly unlikely to be effective. Also, the conventional treatment approaches were mainly involved in providing palliative care instead of curing the disease. Hence, many researchers are beginning to focus on developing alternate therapies to treat AP effectively. This review also summarizes the recent trends in the combinatorial approaches available for AP treatment.

Menadione reduces CDC25B expression and promotes tumor shrinkage in gastric cancer

BACKGROUND

Gastric cancer is one of the most incident types of cancer worldwide and presents high mortality rates and poor prognosis. MYC oncogene overexpression is a key event in gastric carcinogenesis and it is known that its protein positively regulates CDC25B expression which, in turn, plays an essential role in the cell division cycle progression. Menadione is a synthetic form of vitamin K that acts as a specific inhibitor of the CDC25 family of phosphatases.

METHODS

To better understand the menadione mechanism of action in gastric cancer, we evaluated its molecular and cellular effects in cell lines and in Sapajus apella, nonhuman primates from the new world which had gastric carcinogenesis induced by N-Methyl-N-nitrosourea. We tested CDC25B expression by western blot and RT-qPCR. In-vitro assays include proliferation, migration, invasion and flow cytometry to analyze cell cycle arrest. In in-vivo experiments, in addition to the expression analyses, we followed the preneoplastic lesions and the tumor progression by ultrasonography, endoscopy, biopsies, histopathology and immunohistochemistry.

RESULTS

Our tests demonstrated menadione reducing CDC25B expression in vivo and in vitro. It was able to reduce migration, invasion and proliferation rates, and induce cell cycle arrest in gastric cancer cell lines. Moreover, our in-vivo experiments demonstrated menadione inhibiting tumor development and progression.

CONCLUSIONS

We suggest this compound may be an important ally of chemotherapeutics in the treatment of gastric cancer. In addition, CDC25B has proven to be an effective target for investigation and development of new therapeutic strategies for this malignancy.

Oxidative stress alters mitochondrial bioenergetics and modifies pancreatic cell death independently of cyclophilin D, resulting in an apoptosis-to-necrosis shift

Mitochondrial dysfunction lies at the core of acute pancreatitis (AP). Diverse AP stimuli induce Ca2+-dependent formation of the mitochondrial permeability transition pore (MPTP), a solute channel modulated by cyclophilin D (CypD), the formation of which causes ATP depletion and necrosis. Oxidative stress reportedly triggers MPTP formation and is elevated in clinical AP, but how reactive oxygen species influence cell death is unclear. Here, we assessed potential MPTP involvement in oxidant-induced effects on pancreatic acinar cell bioenergetics and fate. H2O2 application promoted acinar cell apoptosis at low concentrations (1-10 μm), whereas higher levels (0.5-1 mm) elicited rapid necrosis. H2O2 also decreased the mitochondrial NADH/FAD+ redox ratio and ΔΨm in a concentration-dependent manner (10 μm to 1 mm H2O2), with maximal effects at 500 μm H2O2 H2O2 decreased the basal O2 consumption rate of acinar cells, with no alteration of ATP turnover at <50 μm H2O2 However, higher H2O2 levels (≥50 μm) diminished spare respiratory capacity and ATP turnover, and bioenergetic collapse, ATP depletion, and cell death ensued. Menadione exerted detrimental bioenergetic effects similar to those of H2O2, which were inhibited by the antioxidant N-acetylcysteine. Oxidant-induced bioenergetic changes, loss of ΔΨm, and cell death were not ameliorated by genetic deletion of CypD or by its acute inhibition with cyclosporine A. These results indicate that oxidative stress alters mitochondrial bioenergetics and modifies pancreatic acinar cell death. A shift from apoptosis to necrosis appears to be associated with decreased mitochondrial spare respiratory capacity and ATP production, effects that are independent of CypD-sensitive MPTP formation.

Disruption of mitochondrial function as mechanism for anti-cancer activity of a novel mitochondriotropic menadione derivative

Menadione, also known as vitamin K₃, is a 2-methyl-1,4 naphthoquinone with a potent cytotoxic activity mainly resulting from its quinone redox-cycling with production of reactive oxygen species (ROS). Although increased ROS generation is considered a relevant mechanism in cancer cell death, it may not be sufficiently effective to kill cancer cells due to phenotypic adaptations. Therefore, combining ROS-generating agents with other molecules targeting important cancer cell phenotypes can be an effective therapeutic strategy. As mitochondrial dysfunction has been implicated in many human diseases, including cancer, we describe here the discovery of a mitochondrial-directed agent (MitoK₃), which was developed by conjugating a TPP cation to the C3 position of the menadione's naphthoquinone ring, increasing its selective accumulation in mitochondria, as well as led to alterations of its redox properties and consequent biological outcome. MitoK₃ disturbed the mitochondrial bioenergetic apparatus, with subsequent loss of mitochondrial ATP production. The combinatory strategy of MitoK₃ with anticancer agent doxorubicin (DOX) resulted in a degree of cytotoxicity higher than those of the individual molecules, as the combination triggered tumour apoptotic cell death evident by caspase 3/9 activities, probably through mitochondrial destabilization or by interference with mitochondrial redox processes. The results of this investigation support the importance of drug discovery process in developing molecules that can be use as adjuvant therapy in patients with specific cancer subtypes.

Vitamin K and its analogs: Potential avenues for prostate cancer management

Epidemiological studies have demonstrated a relationship between cancer incidence and dietary habits. Especially intake of certain essential nutrients like vitamins has been shown to be beneficial in experimental studies and some clinical trials. Vitamin K (VK) is an essential nutrient involved in the blood clotting cascade, and there are considerable experimental data demonstrating its potential anticancer activity in several cancer types including prostate cancer. Previous in vitro and in vivo studies have focused mainly on anti-oxidative effects as the underlying anticancer mechanism of VK. However, recent studies reveal that VK inhibits the growth of cancer cells through other mechanisms, including apoptosis, cell cycle arrest, autophagy, and modulation of various transcription factors such as Myc and Fos. In the present review, we focus on the anticancer effect of dietary VK and its analogs on prostate cancer, with an emphasis on the signaling pathways that are activated following exposure to these compounds. This review also highlights the potential of VK and its derivatives as an adjuvant treatment in combination with other vitamins or with chemotherapeutic drugs. Based on our recent results and a review of the existing literature, we present evidence that VK and its derivatives can potentially be explored as cancer therapy, especially for prostate cancer.

Anticancer copper(II) phosphorus dendrimers are potent proapoptotic Bax activators

A multivalent phosphorus dendrimer 1G₃ and its corresponding Cu-complex, 1G₃-Cu have been recently identified as agents retaining high antiproliferative potency. This antiproliferative capacity was preserved in cell lines overexpressing the efflux pump ABC B1, whereas cross-resistance was observed in ovarian cancer cell lines resistant to cisplatin. Theoretical 3D models were constructed: the dendrimers appear as irregularly shaped disk-like nano-objects of about 22 Å thickness and 49 Å diameter, which accumulated in cells after penetration by endocytosis. To get insight in their mode of action, cell death pathways have been examined in human cancer cell lines: early apoptosis was followed by secondary necrosis after multivalent phosphorus dendrimers exposure. The multivalent plain phosphorus dendrimer 1G₃ moderately activated caspase-3 activity, in contrast with the multivalent Cu-conjugated phosphorus dendrimer 1G₃-Cu which strikingly reduced the caspase-3 content and activity. This decrease of caspase activity is not related to the presence of copper, since inorganic copper has no or little effect on caspase-3. Conversely the potent apoptosis activation could be related to a noticeable translocation of Bax to the mitochondria, resulting in the release of AIF into the cytosol, its translocation to the nucleus and a severe DNA fragmentation, without alteration of the cell cycle. The multivalent Cu-conjugated phosphorus dendrimer is more efficient than its non-complexed analog to activate this pathway in close relationship with the higher antiproliferative potency. Therefore, this multivalent Cu-conjugated phosphorus dendrimer 1G₃-Cu can be considered as a new and promising first-in-class antiproliferative agent with a distinctive mode of action, inducing apoptosis tumor cell death through Bax activation pathway.

Cytotoxicity, hemolysis and in vivo acute toxicity of 2-hydroxy-3-anilino-1,4-naphthoquinone derivatives

The 1,4-naphthoquinones, important members of the family of quinones are used as both crude extracts and as compound manipulated by the pharmaceutical industry. They have gained great emphasis by presenting different pharmacological properties as antibacterial, antiviral, antiprotozoal and anthelmintic, and has antitumor activity. Our aim was to evaluate the cytotoxicity, hemolytic activity and in vivo acute toxicity of three derivatives of 2-hydroxy-1,4-naphthoquinones. The cell viability in vitro against RAW Cell Line displayed IC₅₀ ranging of 483.5–2044.8 μM, whereas in primary culture tests using murine macrophages, IC₅₀ were 315.8–1408.0 μM for naphthoquinones derivatives 4a and 4c respectively, besides no hemolysis was observed at the dose tested. The in vivo acute toxicity assays exhibited a significant safety margin indicated by a lack of systemic and behavioral toxicity up to 300 mg/kg, and at a dose of 1000 mg/kg the derivatives not triggering signs of toxicity although the compound 4a have promoted hepatic steatosis and hyperemia in kidney tissue. Thereby, these modifications decrease the toxicity of the tested derivatives naphthoquinones, providing a high potential for the development of news drugs.

A synopsis on aging-Theories, mechanisms and future prospects

Answering the question as to why we age is tantamount to answering the question of what is life itself. There are countless theories as to why and how we age, but, until recently, the very definition of aging - senescence - was still uncertain. Here, we summarize the main views of the different models of senescence, with a special emphasis on the biochemical processes that accompany aging. Though inherently complex, aging is characterized by numerous changes that take place at different levels of the biological hierarchy. We therefore explore some of the most relevant changes that take place during aging and, finally, we overview the current status of emergent aging therapies and what the future holds for this field of research. From this multi-dimensional approach, it becomes clear that an integrative approach that couples aging research with systems biology, capable of providing novel insights into how and why we age, is necessary.

Redox Homeostasis and Cellular Antioxidant Systems: Crucial Players in Cancer Growth and Therapy

Reactive oxygen species (ROS) and their products are components of cell signaling pathways and play important roles in cellular physiology and pathophysiology. Under physiological conditions, cells control ROS levels by the use of scavenging systems such as superoxide dismutases, peroxiredoxins, and glutathione that balance ROS generation and elimination. Under oxidative stress conditions, excessive ROS can damage cellular proteins, lipids, and DNA, leading to cell damage that may contribute to carcinogenesis. Several studies have shown that cancer cells display an adaptive response to oxidative stress by increasing expression of antioxidant enzymes and molecules. As a double-edged sword, ROS influence signaling pathways determining beneficial or detrimental outcomes in cancer therapy. In this review, we address the role of redox homeostasis in cancer growth and therapy and examine the current literature regarding the redox regulatory systems that become upregulated in cancer and their role in promoting tumor progression and resistance to chemotherapy.

Cyanobacterial Metabolite Calothrixins: Recent Advances in Synthesis and Biological Evaluation

The marine environment is host to unparalleled biological and chemical diversity, making it an attractive resource for the discovery of new therapeutics for a plethora of diseases. Compounds that are extracted from cyanobacteria are of special interest due to their unique structural scaffolds and capacity to produce potent pharmaceutical and biotechnological traits. Calothrixins A and B are two cyanobacterial metabolites with a structural assembly of quinoline, quinone, and indole pharmacophores. This review surveys recent advances in the synthesis and evaluation of the biological activities of calothrixins. Due to the low isolation yields from the marine source and the promise this scaffold holds for anticancer and antimicrobial drugs, organic and medicinal chemists around the world have embarked on developing efficient synthetic routes to produce calothrixins. Since the first review appeared in 2009, 11 novel syntheses of calothrixins have been published in the efforts to develop methods that contain fewer steps and higher-yielding reactions. Calothrixins have shown their potential as topoisomerase I poisons for their cytotoxicity in cancer. They have also been observed to target various aspects of RNA synthesis in bacteria. Further investigation into the exact mechanism for their bioactivity is still required for many of its analogs.

PRX1 knockdown potentiates vitamin K3 toxicity in cancer cells: a potential new therapeutic perspective for an old drug

Background

Many promising anticancer molecules are abandoned during the course from bench to bedside due to lack of clear-cut efficiency and/or severe side effects. Vitamin K3 (vitK3) is a synthetic naphthoquinone exhibiting significant in vitro and in vivo anticancer activity against multiple human cancers, and has therapeutic potential when combined with other anticancer molecules. The major mechanism for the anticancer activity of vitK3 is the generation of cytotoxic reactive oxygen species (ROS). We thus reasoned that a rational redox modulation of cancer cells could enhance vitK3 anticancer efficiency.

Methods

Cancer cell lines with peroxiredoxin 1 (PRX1) gene transiently or stably knocked-down and corresponding controls were exposed to vitK3 as well as a set of anticancer molecules, including vinblastine, taxol, doxorubicin, daunorubicin, actinomycin D and 5-fluorouracil. Cytotoxic effects and cell death events were evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT)-based assay, cell clonogenic assay, measurement of mitochondrial membrane potential and annexin V/propidium iodide double staining. Global ROS accumulation and compartment-specific H₂O₂ generation were determined respectively by a redox-sensitive chemical probe and H₂O₂-sensitive sensor HyPer. Oxidation of endogenous antioxidant proteins including TRX1, TRX2 and PRX3 was monitored by redox western blot.

Results

We observed that the PRX1 knockdown in HeLa and A549 cells conferred enhanced sensitivity to vitK3, reducing substantially the necessary doses to kill cancer cells. The same conditions (combination of vitK3 and PRX1 knockdown) caused little cytotoxicity in non-cancerous cells, suggesting a cancer-cell-selective property. Increased ROS accumulation had a crucial role in vitK3-induced cell death in PRX1 knockdown cells. The use of H₂O₂-specific sensors HyPer revealed that vitK3 lead to immediate accumulation of H₂O₂ in the cytosol, nucleus, and mitochondrial matrix. PRX1 silencing significantly up-regulated mRNA and protein levels of NRH:quinone oxidoreductase 2, which was partially responsible for vitK3-induced ROS accumulation and consequent cell death.

Conclusion

Our data suggest that PRX1 inactivation could represent an interesting strategy to enhance cancer cell sensitivity to vitK3, providing a potential new therapeutic perspective for this old molecule. Conceptually, a combination of drugs that modulate intracellular redox states and drugs that operate through the generation of ROS could be a new therapeutic strategy for cancer treatment.

Vitamins in pancreatic cancer: a review of underlying mechanisms and future applications

Although there is increasing evidence that vitamins influence pancreatic adenocarcinoma biology and carcinogenesis, a comprehensive review is lacking. In this study, we performed a PubMed literature search to review the anticancer mechanisms and the preclinical and clinical studies that support the development of the bioactive vitamins A, C, D, E, and K in pancreatic cancer intervention. Preclinical studies have shown promising results for vitamin A in pancreatic cancer prevention, with clinical trials showing intriguing responses in combination with immunotherapy. For vitamin C, preclinical studies have shown slower tumor growth rates and/or increased survival when used alone or in combination with gemcitabine, with clinical trials with this combination revealing decreased primary tumor sizes and improved performance status. Preclinical studies with vitamin D analogues have shown potent antiproliferative effects and repression of migration and invasion of pancreatic cancer cells, with a clinical trial showing increased time to progression when calciferol was added to docetaxel. For vitamin E, preclinical studies have shown that δ-tocotrienol and γ-tocotrienol inhibited tumor cell growth and survival and augmented gemcitabine activity. Early-phase clinical trials with δ-tocotrienol are ongoing. Vitamin K demonstrates activation of apoptosis and inhibition of cellular growth in pancreatic tumor cells; however, there are no clinical studies available for further evaluation. Although preclinical and clinical studies are encouraging, randomized controlled trials with endpoints based on insights gained from mechanistic and preclinical studies and early-phase clinical trials are required to determine the efficacy of bioactive vitamin interventions in pancreatic cancer.

Dietary and pharmacological compounds altering intestinal calcium absorption in humans and animals

The intestine is the only gate for the entry of Ca to the body in humans and mammals. The entrance of Ca occurs via paracellular and intracellular pathways. All steps of the latter pathway are regulated by calcitriol and by other hormones. Dietary and pharmacological compounds also modulate the intestinal Ca absorption process. Among them, dietary Ca and P are known to alter the lipid and protein composition of the brush-border and basolateral membranes and, consequently, Ca transport. Ca intakes are below the requirements recommended by health professionals in most countries, triggering important health problems. Chronic low Ca intake has been related to illness conditions such as osteoporosis, hypertension, renal lithiasis and incidences of human cancer. Carbohydrates, mainly lactose, and prebiotics have been described as positive modulators of intestinal Ca absorption. Apparently, high meat proteins increase intestinal Ca absorption while the effect of dietary lipids remains unclear. Pharmacological compounds such as menadione, dl-butionine-S,R-sulfoximine and ursodeoxycholic acid also modify intestinal Ca absorption as a consequence of altering the redox state of the epithelial cells. The paracellular pathway of intestinal Ca absorption is poorly known and is under present study in some laboratories. Another field that needs to be explored more intensively is the influence of the gene × diet interaction on intestinal Ca absorption. Health professionals should be aware of this knowledge in order to develop nutritional or medical strategies to stimulate the efficiency of intestinal Ca absorption and to prevent diseases.

Long-term heat exposure prevents hypoxia-induced apoptosis in mouse fibroblast cells

Long-term continuous exposure to high ambient temperatures induces complete heat acclimation in humans and animals. However, to date, the effects of long-term exposure to heat stress on cells have not been fully evaluated. In this study, we investigated an adaptive physiological process induced in culture cells by continuous exposure to mild heat stress for 60 days. The results of this investigation provide evidence that after long-term heat acclimation in cells, (1) heat shock protein levels are increased, (2) hypoxia inducible factor-1α (HIF-1α) expression is upregulated, and (3) heat shock-induced and hypoxia-induced apoptoses are attenuated. These results suggest that the hypoxia response pathway is an intrinsic part of the heat acclimation repertoire and that the HIF-1 pathway following long-term heat acclimation induces cells with cross tolerance against hypoxia.

Advances in revealing the molecular targets downstream of oxidative stress-induced proapoptotic kinase signaling in diabetic embryopathy

Preexisting maternal diabetes is a high-risk factor of diabetic embryopathy, such as neural tube defects and congenital heart defects. Maternal diabetes significantly increases the production of reactive oxygen species, resulting in oxidative stress and diabetic embryopathy. Multiple cellular and metabolic factors contribute to these processes. Forkhead box O (FoxO)-3a has been demonstrated as a key transcription factor in the signaling transduction pathways responsible for maternal diabetes-induced birth defects. Apoptosis signal-regulating kinase 1 (ASK1) activated by oxidative stress stimulates nuclear translocation of FoxO3a, resulting in the overexpression of tumor necrosis factor receptor 1-associated death domain protein, which, in turn, leads to caspase-8 activation and apoptosis. Maternal diabetes-activated c-Jun N-terminal kinase (JNK)-1/2, downstream effectors of ASK1, can be blocked by superoxide dismutase-1 overexpression, suggesting that oxidative stress is responsible for JNK1/2 signaling activation. Deletion of JNK1/2 significantly suppressed the activity of FoxO3a. These observations indicate that maternal diabetes-induced oxidative stress stimulates the activation of ASK1, JNK1/2, FoxO3a, tumor necrosis factor receptor 1-associated death domain protein, caspase-8 cleavage, and finally, apoptosis and diabetic embryopathy.

Menadione-induced caspase-dependent programmed cell death in the green chlorophyte Chlamydomonas reinhardtii

Menadione, a quinone that undergoes redox cycles leading to the formation of superoxide radicals, induces programmed cell death (PCD) in animals and plants. In this study, we investigated whether the unicellular green alga Chlamydomonas reinhardtii P.A.Dangeard is capable of executing PCD upon exposure to menadione stress. We report here, the morphological, molecular, and biochemical changes after menadione exposure of C. reinhardtii cells. The effect of menadione on cell death has been shown to be dose-dependent; 5-100 μM menadione causes 20%-46% cell death, respectively. It appears that growth is inhibited with the concomitant degradation of the photosynthetic pigments and by a decrease in the photosynthetic capacity. Being an oxidative stress, we found an H2 O2 burst within 15 min of menadione exposure, followed by an increase in antioxidant enzyme (superoxide dismutase [SOD], catalase [CAT], and ascorbate peroxidase [APX]) activities. In parallel, RT-PCR was performed for transcript analyses of Mn-SOD, CAT, and APX. Our results clearly revealed that expression of these genes were up-regulated upon menadione exposure. Furthermore, classical hallmarks of PCD such as alteration of mitochondrial membrane potential, significant increase in caspase-3-like DEVDase activity, cleavage of poly (ADP) ribose polymerase (PARP)-1-like enzyme, and DNA fragmentation as detected by terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) assay and oligosomal DNA fragmentation were observed. Moreover, antibodies against a mammalian active caspase-3 shared epitopes with a caspase-3-like protein of ~17 kDa; its pattern of expression and activity correlated with the onset of cell death. To the best of our knowledge, this is the first report on menadione-induced PCD through a mitochondrian-caspase protease pathway in an algal species.

Molecular mechanisms of leptin and pro-apoptotic signals induced by menadione in HepG2 cells

Apoptosis is a significant physiological function in the cell. P(53) is known as tumor suppressor cellular factor, executive caspases are also the most involved pathway for apoptosis. Menadione (VK3) has apoptotic action on many harmful cells, but the molecular role of adipokines is not studied enough in this regard, so the ability of menadione to modify the adipokine (leptin hormone), caspase-3 and P(53) signals to induce its apoptotic action on HepG2 cells was studied. The study revealed that menadione has anti-viability and apoptotic effect at sub-G1 phase of HepG2 cell cycle. Its cytotoxic effect is mediated by molecular mechanisms included: inhibiting leptin expression and level, activating caspase-3 pathway and up-regulating the expression of P(53). Menadione exerts its apoptotic mechanisms in a concentration and time dependent way through ROS generation. In addition to the known apoptotic pathways, the results indicate that suppressing leptin pathway is a significant mechanism for menadione apoptotic effect which made it as a potential therapeutic vitamin in preventing hepatocyte survival and proliferation.

Study on cytotoxicity and structure-activity relationship of HL-7702 cell exposed to naphthoquinones

The acute cytotoxicities of six naphthoquinone compounds, including Atovaquone, Buparvaquone, Menadione, 2-acetoxy-1,4-naphthoquinone and 2-ethoxy-1,4-naphthoquinone, to HL-7702 cells were determined. The results showed that the toxicities of these naphthoquinones were characterized by a steep response pattern except for 2-hydroxy-1,4-naphthoquinone. Meanwhile, the cellular injuries were unrecoverable. Several molecular descriptors, such as the octanol-water partition coefficients (LogP), diameter (Dia) and topological index (TIndx), played an important role in the toxicity of naphthoquinones to HL-7702 cell. Our results provide a foundation for further investigation using 3D-QSAR and HQSAR to evaluate the aquatic ecological risk and the possible mechanisms of toxicity of naphthoquinones.

Sorafenib combined vitamin K induces apoptosis in human pancreatic cancer cell lines through RAF/MEK/ERK and c-Jun NH2-terminal kinase pathways

Apoptosis has been shown to be induced by many agents, including the clinically useful Sorafenib and K vitamins (VKs). Since few agents have activity against pancreas cancer cell growth, we evaluated the role of naturally occurring K vitamins and Sorafenib both independently and together on the growth in culture of pancreas adenocarcinoma cell lines, including PL-5, PANC-1, and MIA PaCa-2. We found that when a K vitamin was combined with Sorafenib, the dose of Sorafenib required for growth inhibition was substantially reduced. Furthermore, growth could be inhibited at doses of each VK plus Sorafenib in combination that were ineffective when used alone. This effect was seen using vitamins K1, K2, and K5. The combination of VK1 plus Sorafenib-induced apoptosis, as determined by both FACS and TUNEL staining. Phospho-ERK and Bcl-2 levels were decreased, but not levels of other bcl-2 family members. Cleavage of caspases 3 and 8, PARP and Bid were all induced by this combination. Vitamin K1 plus Sorafenib combination also resulted in elevated levels of activated c-Jun N-terminal kinase (JNK) and its substrates c-Jun and FasL. JNK inhibition partly antagonized the induction of apoptosis. Thus, combination VK1 plus Sorafenib strongly induced growth inhibition and apoptosis in pancreas cancer cells, involving both inhibition of the RAF/MEK/ERK pathway as well as activation of the JNK, c-Jun and FasL apoptotic pathway. Since both agents are available for human use, the combination is attractive for evaluation against pancreas cancer growth in vivo.

Calcium elevation in mitochondria is the main Ca2+ requirement for mitochondrial permeability transition pore (mPTP) opening

We have investigated in detail the role of intra-organelle Ca2+ content during induction of apoptosis by the oxidant menadione while changing and monitoring the Ca2+ load of endoplasmic reticulum (ER), mitochondria, and acidic organelles. Menadione causes production of reactive oxygen species, induction of oxidative stress, and subsequently apoptosis. In both pancreatic acinar and pancreatic tumor AR42J cells, menadione was found to induce repetitive cytosolic Ca2+ responses because of the release of Ca2+ from both ER and acidic stores. Ca2+ responses to menadione were accompanied by elevation of Ca2+ in mitochondria, mitochondrial depolarization, and mitochondrial permeability transition pore (mPTP) opening. Emptying of both the ER and acidic Ca2+ stores did not necessarily prevent menadione-induced apoptosis. High mitochondrial Ca2+ at the time of menadione application was the major factor determining cell fate. However, if mitochondria were prevented from loading with Ca2+ with 10 mum RU360, then caspase-9 activation did not occur irrespective of the content of other Ca2+ stores. These results were confirmed by ratiometric measurements of intramitochondrial Ca2+ with pericam. We conclude that elevated Ca2+ in mitochondria is the crucial factor in determining whether cells undergo oxidative stress-induced apoptosis.

Prevention of TNF-induced necrotic cell death by rottlerin through a Nox1 NADPH oxidase

Previous studies have demonstrated that rottlerin, a specific PKCdelta inhibitor, potentiates death receptor- mediated apoptosis through a cytochrome c-dependent or -independent pathway. However, its ability to regulate necrotic cell death, as well as the underlying mechanism, remains unknown. We found that in murine fibrosarcoma L929 cells, treatment with rottlerin protected the cells against TNF-induced necrosis, whereas it sensitized the cells to apoptosis induced by co-treatment with Hsp90 inhibitor geldanamycin and TNF, in a manner independent of its ability to inhibit PKC-delta. TNF treatment induced rapid accumulation of mitochondrial superoxide (O2-) through the Nox1 NADPH oxidase when cells undergo necrosis. Moreover, pretreatment with rottlerin failed to induce the GTP-bound form of small GTPase Rac1 by TNF treatment, and subsequently suppressed mitochondrial O2- production and poly(ADP-ribose) polymerase activation, thus inhibiting necrotic cell death. Therefore, our study suggests that Nox1 NADPH oxidase is a new molecular target for anti-necrotic activity of rottlerin upon death-receptor ligation.

A possible role of oxidative stress in the switch mechanism of the cell death mode from apoptosis to necrosis--studies on rho0 cells

Apoptosis is induced not only during morphogenesis and embryogenesis but also under various pathological conditions, especially related to oxidative stress. Apoptotic cells are phagocytized by neighboring cells while necrotic cells cause local and general reactions sometimes lethal to our bodies. Data have been accumulated to demonstrate that the switch of the cell death mode from apoptosis to necrosis does occur. However, detailed mechanisms involved in the switch mechanism remain unsolved although decreases in the intracellular level of ATP and a burst in the cellular level of reactive oxygen species (ROS) have been proposed. Recently, we have shown that the population of apoptotic cells reaches maximum in human osteosarcoma 143B cells treated for 6h with menadione (MEN) while necrotic cells become predominant at 9h of the treatment. In the present study we have attempted to clarify the role of cellular ATP in the switch mechanism using rho(0) cells derived from human osteosarcoma rho+ cells. Results are summarized as follows: (1) Apoptotic and necrotic changes in rho(0) cells are much faster than rho+ cells after the treatment with MEN. (2) Cellular level of ATP in rho(0) cells remains essentially in the same level before and after the MEN-treatment while intracellular levels of superoxide continuously increase after the MEN-treatment. (3) rho+ cells treated with MEN in the presence of antimycin A plus oligomycin show similar changes to those of MEN-treated rho(0) cells. (4) MEN-induced increases in the cellular level of superoxide are distinctly suppressed by inhibitors of NADPH oxidase. These results suggest that the intracellular level of superoxide may be a key factor directly related to the switch mechanism from apoptosis to necrosis, and that decreases in cellular level of ATP accelerate both apoptotic and necrotic changes of the cells.

Inhibition of apoptosis by menadione on exposure to UVA

Quinones are widely distributed in the environment, both as natural products and as pollutants. This paper reports that one of the simplest quinones, 2-methyl-1,4-naphthoquinone (menadione), effectively inhibited apoptosis in the presence of UVA. Menadione suppressed the apoptosis induced by serum depletion and cell detachment. This effect was significantly enhanced by UVA irradiation. An antioxidant, N-acetylcysteine, completely inhibited the antiapoptotic effects of both menadione itself and menadione plus UVA, and peroxidation of the cells after treatment was observed using a probe to detect the intracellular production of peroxides. By contrast, 2-hydroxy-1,4-naphtoquinone (lawsone) showed no antiapoptotic effect in the presence or absence of UVA. Lawsone is reported not to undergo the redox process that produces reactive oxygen species. These results indicated that intracellular peroxidation contributed to the antiapoptotic effects of both menadione itself and menadione plus UVA. Dysregulation of the apoptotic process is critical to carcinogenesis. The photosensitization of quinone compounds as it relates to the inhibition of apoptosis should be examined in the future.

Oxidative metabolism, apoptosis and perinatal brain injury

Perinatal hypoxic-ischaemic injury (HII) is a significant cause of neurodevelopmental impairment and disability. Studies employing 31P magnetic resonance spectroscopy to measure phosphorus metabolites in situ in the brains of newborn infants and animals have demonstrated that transient hypoxia-ischaemia leads to a delayed disruption in cerebral energy metabolism, the magnitude of which correlates with the subsequent neurodevelopmental impairment. Prominent among the biochemical features of HII is the loss of cellular ATP, resulting in increased intracellular Na+ and Ca2+, and decreased intracellular K+. These ionic imbalances, together with a breakdown in cellular defence systems following HII, can contribute to oxidative stress with a net increase in reactive oxygen species. Subsequent damage to lipids, proteins, and DNA and inactivation of key cellular enzymes leads ultimately to cell death. Although the precise mechanisms of neuronal loss are unclear, it is now clear both apoptosis and necrosis are the significant components of cell death following HII. A number of different factors influence whether a cell will undergo apoptosis or necrosis, including the stage of development, cell type, severity of mitochondrial injury and the availability of ATP for apoptotic execution. This review will focus on some pathological mechanisms of cell death in which there is a disruption to oxidative metabolism. The first sections will discuss the process of damage to oxidative metabolism, covering the data collected both from human infants and from animal models. Following sections will deal with the molecular mechanisms that may underlie cerebral energy failure and cell death in this form of brain injury, with a particular emphasis on the role of apoptosis and mitochondria.

JNK signaling pathway is a key modulator in cell death mediated by reactive oxygen and nitrogen species

c-Jun N-terminal kinase (JNK), or stress-activated protein kinase, is an important member of the mitogen-activated protein kinase superfamily, the members of which are readily activated by many environmental stimuli. Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are important groups of free radicals that are capable of eliciting direct damaging effects or acting as critical intermediate signaling molecules, leading to oxidative and nitrosative stress and a series of biological consequences. Recently there has been an increasing amount of research interest focusing on the regulatory role of JNK activation in ROS-and RNS-induced cellular responses. In this review we will first summarize and discuss some recent findings regarding the signaling mechanisms of ROS-or RNS-mediated JNK activation. Second, we will talk about the role of JNK in ROS-or RNS-mediated cell death (both apoptosis and necrosis). Finally, we will analyze the emerging evidence for the involvement of ROS and RNS as mediators in tumor necrosis factor alpha-induced apoptosis. Taken together, the accumulating knowledge about the ROS/RNS-induced JNK signaling pathway has greatly advanced our understanding of the complex processes deciding the cellular responses to environmental stress.

Apoptosis vs. necrosis: glutathione-mediated cell death during rewarming of rat hepatocytes

Hypothermia induces injury in its own right, but the mechanisms involved in the cell damage are still unclear. The aim of this study was to test the effects that glutathione (GSH) depletion induces on cell death in isolated rat hepatocytes, kept at 4 degrees C for 20 h, by modulating intracellular GSH concentration with diethylmaleate and buthionine sulfoximine (DEM and BSO). Untreated hepatocytes showed Annexin V stained cells (AnxV(+)), scarce propidium iodide stained cells (PI(+)) and presented a low level of lactate dehydrogenase (LDH) leakage after 20 h at 4 degrees C and rewarming at 37 degrees C. When DEM and BSO were added before cold storage, we observed a few AnXV(+) cells and an increase in PI(+) cells associated with LDH release in the incubation medium. Conversely, the addition of DEM and BSO only during rewarming caused a marked increase in cell death by apoptosis. Production of reactive oxygen species (ROS) and thiobarbituric acid species (TBARS), associated with a decrease in GSH concentrations, was higher when DEM and BSO were added before cold storage. Cells treated with DEM and BSO before cold storage showed lower ATP energy stores than hepatocytes treated with DEM and BSO only during rewarming. Pretreatment of hepatocytes with deferoxamine protected against apoptotic and necrotic morphology in conditions of GSH depletion. These results suggest that pretreatment of hepatocytes with DEM and BSO before cold storage induces necrosis, while the treatment of hepatocytes only during rewarming increases apoptosis. In both conditions, iron represents a crucial mediator of cell death.

The switch mechanism of the cell death mode from apoptosis to necrosis in menadione-treated human osteosarcoma cell line 143B cells

Time-dependent changes in the cell death mode from apoptosis to necrosis were studied in cultured 143B cells treated with menadione, an anti-cancerous drug, excluding a possible involvement of "secondary necrosis." The population of apoptotic cells judged by FITC-Annexin V and propidium iodide (PI) double staining reached its maximum at 6 hours after 100 microM menadione treatment followed by an abrupt decrease thereafter, while that of necrotic cells continuously increased reaching 90% at 24 hours. Electron microscopically, cells attached to the culture dish at 6 hours after the treatment consisted of two different types of cells: cells with typical apoptotic features occupying the major population and those with condensed nuclei and swollen cytoplasm. Cells attached to the culture dish at 8 hours after the treatment consisted exclusively of those with condensed nuclei and swollen cytoplasm. Mitochondria in these cells showed various structural changes: those swollen to various degrees with deposition of flocculent densities, or those with highly condensed matrix. Distinct decreases both in intracellular levels of ATP and caspase-3-like activities and remarkable elevations of intracellular levels of superoxide, which were partly suppressed by NAD(P)H oxidase inhibitors, occurred at 6 hours after the treatment. These results may suggest that distinct increases of the intracellular level of superoxide derived from plasma membrane NAD(P)H oxidase besides that from mitochondria have triggered the transition of cell death mode from apoptosis to necrosis. Transition of highly condensed mitochondria to extremely swollen ones may reflect necrotic processes in menadione-treated cells. The present study strongly suggests that time-dependent study is essential using the electron microscopic technique to analyze detailed processes in the changes of the cell death mode.

Vitamins A and D but not E and K decreased the cell number in human pancreatic cancer cell lines

BACKGROUND

The four fat-soluble vitamins A, D, E and K have been tested in experimental and human studies to assess their influence on the growth of cancer cells of different origins. Receptors for vitamin A and D have been detected on pancreatic cancer cells, and analogues of these reduced the cell number in vitro. The aim of the present study was to evaluate the effect of fat-soluble vitamins on the growth of pancreatic cancer cells.

METHODS

The seven cell lines used were established from patients operated on for pancreatic adenocarcinoma. The effect of incubation with the vitamin A analogues all-trans-retinoic acid (atRA;tretinoin) and 9-cis-retinoic acid (9-cis-RA), the synthetic vitamin D analogue EB 1089, vitamin E succinate and K on the cell number was examined by the XTT method.

RESULTS

The vitamin A and D analogues decreased the pancreatic cancer cell number when high concentrations of 10 - 10 M were administered. A combination of retinoids and the vitamin D analogue EB 1089 did not enhance the effect. Vitamin E succinate inhibited cell growth to a small extent (maximal 26%) in 3 out of 7 cell lines, whereas vitamin K increased the pancreatic cancer cell number in 3 out of 7 cell lines.

CONCLUSION

High concentrations of vitamin A and D analogues decreased the cell number in pancreatic cancer cell lines. Vitamin E succinate and K did not have this effect. In the treatment of pancreatic cancer, further exploration of vitamin D analogues could be fruitful.

Essential roles of receptor-interacting protein and TRAF2 in oxidative stress-induced cell death

Oxidative stress and reactive oxygen species (ROS) can elicit and modulate various physiological and pathological processes, including cell death. However, the mechanisms controlling ROS-induced cell death are largely unknown. Data from this study suggest that receptor-interacting protein (RIP) and tumor necrosis factor receptor (TNFR)-associated factor 2 (TRAF2), two key effector molecules of TNF signaling, are essential for ROS-induced cell death. We found that RIP(-/-) or TRAF2(-/-) mouse embryonic fibroblasts (MEF) are resistant to ROS-induced cell death when compared to wild-type cells, and reconstitution of RIP and TRAF2 gene expression in their respective deficient MEF cells restored their sensitivity to H(2)O(2)-induced cell death. We also found that RIP and TRAF2 form a complex upon H(2)O(2) exposure, but without the participation of TNFR1. The colocalization of RIP with a membrane lipid raft marker revealed a possible role of lipid rafts in the transduction of cell death signal initiated by H(2)O(2). Finally, our results demonstrate that activation of c-Jun NH(2)-terminal kinase 1 is a critical event downstream of RIP and TRAF2 in mediating ROS-induced cell death. Therefore, our study uncovers a novel signaling pathway regulating oxidative stress-induced cell death.

Effects of genotoxic compounds on DNA and development of early and late grass shrimp embryo stages

Early and late developmental stages of grass shrimp embryos were exposed to different concentrations of two genotoxicants, 2-methyl-1,4-naphthoquinone (MNQ) and 4-nitroquinoline-N-oxide (NQO). DNA strand breaks were assessed by the comet assay while embryo development effects were determined by % of embryos hatching. Early embryo stage embryos were significantly more sensitive to genotoxicants than late stages. For example, all stage 4 embryos failed to hatch at 1 microM NQO while 95% of stage 8 hatched at this concentration. High DNA tail moments, which are a measure of the number of DNA strand breaks, were found in late stage embryos exposed to genotoxicants. Early stage embryo development was effected by low concentrations of genotoxicants but no changes were observed in DNA tail moments. We suggest that high DNA moments in late embryo stages reflect high DNA repair activity, while early stages may lack a fully developed DNA repair system.

Anti-estrogenic activity of fifty chemicals evaluated by in vitro assays

We examined the anti-estrogenic activity of 50 chemicals by the yeast two-hybrid assay and detected the activity of hexachlorophene, pentachlorophenol, and vitamin K3 (menadione), in that order. These chemicals were also observed to inhibit the transcriptional activity of 17beta-estradiol in a reporter gene assay system using MCF-7 cells, estrogen receptor-positive breast cancer cells, and to bind directly to estrogen receptor alpha in a competitive binding assay system, although the order of the activity was slightly different among the 3 assays. These findings suggested that three of fifty chemicals could inhibit estrogen activity by competitive binding with 17beta-estradiol to the estrogen receptor.

Role of reactive oxygen species, glutathione and NF-kappaB in apoptosis induced by 3,4-methylenedioxymethamphetamine ("Ecstasy") on hepatic stellate cells

"Ecstasy" (3,4-methylenedioxymethamphetamine, MDMA), is a derivative of amphetamine with hepatotoxic effects that has been shown to induce apoptosis of cultured liver cells. In the present work, we studied the role played by oxidative stress in the apoptotic response caused by MDMA on a cell line of hepatic stellate cells (HSC). MDMA-treatment provoked oxidative stress determined as reactive oxygen species (ROS) accumulation and decrease of intracellular reduced glutathione levels. Pre-treatment with the antioxidant pyrrolidine dithiocarbamate blocked ROS production but did not prevent MDMA-induced apoptosis of HSC. The pro-oxidant menadione induced in HSC ROS production and apoptosis that were prevented by pyrrolidine dithiocarbamate, showing HSC to be susceptible to oxidative stress-induced apoptosis. Addition of exogenous GSH or its precursor NAC potentiated the apoptotic action of MDMA but blocked apoptosis induced by menadione. Pre-treatment of HSC with the cytochrome P450 inhibitor quinine diminished the extent of apoptosis caused by MDMA, suggesting the involvement of a metabolic derivative of MDMA on its apoptotic effect. Nuclear factor NF-kappaB was activated by MDMA in a oxidative stress independent fashion and played a protective role in the apoptotic response, since inhibition of NF-kappaB by treatment with parthenolide or by viral infection with a dominant-negative form of NIK (Ad5dnNIK) resulted in an increase of MDMA-induced cell death. In summary, MDMA-induced apoptosis of HSC is accompanied, but not caused by oxidative stress; a metabolic derivative of the drug is responsible for the apoptotic effect of MDMA, which is partially blocked by NF-kappaB activation.

Cell cycle arrest and autoschizis in a human bladder carcinoma cell line following Vitamin C and Vitamin K3 treatment

Exponentially growing cultures of human bladder tumor cells (T24) were treated with Vitamin C (VC) alone, Vitamin K(3) (VK(3)) alone, or with a VC:VK(3) combination for 1, 2, or 4hr. Flow cytometry of T24 cells exposed to the vitamins for 1h revealed a growth arrested population and a population undergoing cell death. Cells in G(1) during vitamin treatment arrested in G(1) while those in S phase progressed through S phase and arrested in G(2)/M. DNA synthesis decreased to 14 to 21% of control levels which agreed with the percent of cells in S phase during treatment. Annexin V labeling demonstrated the majority of the cells died by autoschizis, but necrosis and apoptosis also were observed. Catalase treatment abrogated both cell cycle arrest and cell death which implicated hydrogen peroxide (H(2)O(2)) in these processes. Redox cycling of VC and VK(3) increased H(2)O(2) production and decreased cellular thiol levels and DNA content, while increasing intracellular Ca(2+) levels and lipid peroxidation. Feulgen staining of treated cells revealed a time-dependent decrease in tumor cell DNA, while electrophoresis revealed a spread pattern. These results suggest that Ca(2+) disregulation activates at least one DNase which degrades tumor cell DNA and induces tumor cell death.

Use of the single cell gel electrophoresis/comet assay for detecting DNA damage in aquatic (marine and freshwater) animals

The comet assay is a rapid, sensitive and inexpensive method for measuring DNA strand breaks. The comet assay has advantages over other DNA damage methods, such as sister chromatid exchange, alkali elution and micronucleus assay, because of its high sensitivity and that DNA strand breaks are determined in individual cells. This review describes a number of studies that used the comet assay to determine DNA strand breaks in aquatic animals exposed to genotoxicants both in vitro and in vivo, including assessment of DNA damage in aquatic animals collected from contaminated sites. One difficulty of using the comet assay in environmental work is that of comparing results from studies that used different methods, such as empirical scoring or comet tail lengths. There seems to be a consensus in more recent studies to use both the intensity of the tail and the length of the tail, i.e. DNA tail moment, percentage of DNA in the tail. The comet assay has been used to assess DNA repair and apoptosis in aquatic animals and modifications of the comet assay have allowed the detection of specific DNA lesions. There have been some recent studies to link DNA strand breaks in aquatic animals to effects on the immune system, reproduction, growth, and population dynamics. Further work is required before the comet assay can be used as a standard bio-indicator in aquatic environments, including standardization of methods (such as ASTM method E2186-02a) and measurements.

Effects of a single dose of menadione on the intestinal calcium absorption and associated variables

The effect of a single large dose of menadione on intestinal calcium absorption and associated variables was investigated in chicks fed a normal diet. The data show that 2.5 micro mol of menadione/kg of b.w. causes inhibition of calcium transfer from lumen-to-blood within 30 min. This effect seems to be related to oxidative stress provoked by menadione as judged by glutathione depletion and an increment in the total carbonyl group content produced at the same time. Two enzymes presumably involved in calcium transcellular movement, such as alkaline phosphatase, located in the brush border membrane, and Ca(2+)- pump ATPase, which sits in the basolateral membrane, were also inhibited. The enzyme inhibition could be due to alterations caused by the appearance of free hydroxyl groups, which are triggered by glutathione depletion. Addition of glutathione monoester to the duodenal loop caused reversion of the menadione effect on both intestinal calcium absorption and alkaline phosphatase activity. In conclusion, menadione shifts the balance of oxidative and reductive processes in the enterocyte towards oxidation causing deleterious effects on intestinal Ca(2+) absorption and associated variables, which could be prevented by administration of oral glutathione monoester.

Menadione biphasically controls JNK-linked cell death in leukemia Jurkat T cells

Signals for cell-death induction by menadione were studied in Jurkat T cells. Low concentrations of menadione (10-20 microM) and H(2)O(2) (10-50 microM) induced cell death accompanying low (menadione: <5%) or moderate (H(2)O(2): 10-15%) levels of DNA fragmentation in Jurkat cells. These concentrations of menadione (10 microM) and H(2)O(2) also caused membrane (necrotic) cell death at unproportionally high (80%) and proportional (10-30%) levels, respectively. Higher concentrations (100-5,000 microM) of H(2)O(2) exclusively induced membrane cell death. Unexpectedly, 30-300 microM menadione induced ever-decreasing levels of necrotic cell death in a concentration-dependent manner. An in vitro kinase assay showed that 20-50 microM, but not >100 microM, menadione induced activation of c-Jun NH(2)-terminal kinase (JNK), whereas a striking activation of JNK was induced by 500-5,000 microM H(2)O(2). Induction of cell death by a low concentration of menadione was partially inhibited in dominant negative JNK gene-transfected Jurkat/VPF cells. A high concentration (300 microM) of menadione was found to inhibit cell-death induction by high concentrations (200-5,000 microM) of H(2)O(2). The JNK inhibitory activity of menadione was also demonstrated in a cell-free system. However, menadione did not activate JNK in vitro. These results suggest that JNK is required for induction of not only apoptotic cell death, but also necrotic cell death in Jurkat T cells and that menadione biphasically controls this JNK-linked signal for inducing cell death.

Autoschizis: a novel cell death

Vitamin C (VC) and vitamin K(3) (VK(3)) administered in a VC:VK(3) ratio of 100:1 exhibit synergistic antitumor activity and preferentially kill tumor cells by autoschizis, a novel type of necrosis characterized by exaggerated membrane damage and progressive loss of organelle-free cytoplasm through a series of self-excisions. During this process, the nucleus becomes smaller, cell size decreases one-half to one-third of its original size, and most organelles surround an intact nucleus in a narrow rim of cytoplasm. While the mitochondria are condensed, tumor cell death does not result from ATP depletion. However, vitamin treatment induces a G(1)/S block, diminishes DNA synthesis, increases H(2)O(2) production, and decreases cellular thiol levels. These effects can be prevented by the addition of catalase to scavenge the H(2)O(2). There is a concurrent 8- to 10-fold increase in intracellular Ca(2+) levels. Electrophoretic analysis of DNA reveals degradation due to the caspase-3-independent reactivation of deoxyribonuclease I and II (DNase I, DNase II). Redox cycling of the vitamins is believed to increase oxidative stress until it surpasses the reducing ability of cellular thiols and induces Ca(2+) release, which triggers activation of Ca(2+)-dependent DNase and leads to degradation of DNA. Recent experiments indicate that oral VC:VK(3) increases the life-span of tumor-bearing nude mice and significantly reduces the growth rate of solid tumors without any significant toxicity by reactivating DNase I and II and inducing autoschizis. This report discusses the mechanisms of action employed by these vitamins to induce tumor-specific death by autoschizis.