Bleb formation in hepatocytes during drug metabolism is caused by disturbances in thiol and calcium ion homeostasis

Ferroptosis in plant immunity

Plant cell death is mediated by calcium, iron, and reactive oxygen species (ROS) signaling in plant immunity. The reconstruction of a nucleotide-binding leucine-rich-repeat receptor (NLR) supramolecular structure, called the resistosome, is intimately involved in the hypersensitive response (HR), a type of cell death involved in effector-triggered immunity (ETI). Iron is a crucial redox catalyst in various cellular reactions. Ferroptosis is a regulated, non-apoptotic form of iron- and ROS-dependent cell death in plants. Pathogen infections trigger iron accumulation and ROS bursts in plant cells, leading to lipid peroxidation via the Fenton reaction and subsequent ferroptosis in plant cells similar to that in mammalian cells. The small-molecule inducer erastin triggers iron-dependent lipid ROS accumulation and glutathione depletion, leading to HR cell death in plant immunity. Calcium (Ca2+) is another major mediator of plant immunity. Cytoplasmic Ca2+ influx through calcium-permeable channels, the resistosomes, mediates iron- and ROS-dependent ferroptotic cell death under reduced glutathione reductase (GR) expression levels in the ETI response. Acibenzolar-S-methyl (ASM), a plant defense activator, enhances Ca2+ influx, ROS and iron accumulation, and lipid peroxidation to trigger ferroptotic cell death. These breakthroughs suggest a potential role for Ca2+ signaling in ferroptosis and its coordination with iron and ROS signaling in plant immunity. In this review, we highlight the essential roles of calcium, iron, and ROS signaling in ferroptosis during plant immunity and discuss advances in the understanding of how Ca2+-mediated ferroptotic cell death orchestrates effective plant immune responses against invading pathogens.

Cytoplasmic Ca2+ influx mediates iron- and reactive oxygen species-dependent ferroptotic cell death in rice immunity

Iron- and reactive oxygen species (ROS)-dependent ferroptosis occurs in plant cells. Ca2+ acts as a conserved key mediator to control plant immune responses. Here, we report a novel role of cytoplasmic Ca2+ influx regulating ferroptotic cell death in rice immunity using pharmacological approaches. High Ca2+ influx triggered iron-dependent ROS accumulation, lipid peroxidation, and subsequent hypersensitive response (HR) cell death in rice (Oryza sativa). During Magnaporthe oryzae infection, 14 different Ca2+ influx regulators altered Ca2+, ROS and Fe2+ accumulation, glutathione reductase (GR) expression, glutathione (GSH) depletion and lipid peroxidation, leading to ferroptotic cell death in rice. High Ca2+ levels inhibited the reduction of glutathione isulphide (GSSG) to GSH in vitro. Ca2+ chelation by ethylene glycol-bis (2-aminoethylether)-N, N, N', N'-tetra-acetic acid (EGTA) suppressed apoplastic Ca2+ influx in rice leaf sheaths during infection. Blocking apoplastic Ca2+ influx into the cytoplasm by Ca2+ chelation effectively suppressed Ca2+-mediated iron-dependent ROS accumulation and ferroptotic cell death. By contrast, acibenzolar-S-methyl (ASM), a plant defense activator, significantly enhanced Ca2+ influx, as well as ROS and iron accumulation to trigger ferroptotic cell death in rice. The cytoplasmic Ca2+ influx through calcium-permeable cation channels, including the putative resistosomes, could mediate iron- and ROS-dependent ferroptotic cell death under reduced GR expression levels in rice immune responses.

Scanning Ion Conductance Microscopy Study Reveals the Disruption of the Integrity of the Human Cell Membrane Structure by Oxidative DNA Damage

Oxidative stress can damage organs, tissues, and cells through reactive oxygen species (ROS) by oxidizing DNA, proteins, and lipids, thereby resulting in diseases. However, the underlying molecular mechanisms remain to be elucidated. In this study, employing scanning ion conductance microscopy (SICM), we explored the early responses of human embryonic kidney (HEK293H) cells to oxidative DNA damage induced by potassium chromate (K₂CrO₄). We found that the short term (1-2 h) exposure to a low concentration (10 μM) of K₂CrO₄ damaged the lipid membrane of HEK293H cells, resulting in structural defects and depolarization of the cell membrane and reducing cellular secretion activity shortly after the treatment. We further demonstrated that the K₂CrO₄ treatment decreased the expression of the cytoskeleton protein, β-actin, by inducing oxidative DNA damage in the exon 4 of the β-actin gene. These results suggest that K₂CrO₄ caused oxidative DNA damage in cytoskeleton genes such as β-actin and reduced their expression, thereby disrupting the organization of the cytoskeleton beneath the cell membrane and inducing cell membrane damages. Our study provides direct evidence that oxidative DNA damage disrupted human cell membrane integrity by deregulating cytoskeleton gene expression.

A history of the roles of cytochrome P450 enzymes in the toxicity of drugs

The history of drug metabolism began in the 19th Century and developed slowly. In the mid-20th Century the relationship between drug metabolism and toxicity became appreciated, and the roles of cytochrome P450 (P450) enzymes began to be defined in the 1960s. Today we understand much about the metabolism of drugs and many aspects of safety assessment in the context of a relatively small number of human P450s. P450s affect drug toxicity mainly by either reducing exposure to the parent molecule or, in some cases, by converting the drug into a toxic entity. Some of the factors involved are enzyme induction, enzyme inhibition (both reversible and irreversible), and pharmacogenetics. Issues related to drug toxicity include drug-drug interactions, drug-food interactions, and the roles of chemical moieties of drug candidates in drug discovery and development. The maturation of the field of P450 and drug toxicity has been facilitated by advances in analytical chemistry, computational capability, biochemistry and enzymology, and molecular and cell biology. Problems still arise with P450s and drug toxicity in drug discovery and development, and in the pharmaceutical industry the interaction of scientists in medicinal chemistry, drug metabolism, and safety assessment is critical for success.

Studies on Mechanisms of the Toxic Effects of Cadmium in Mouse Tracheal Organ Culture

Exposure of tracheal organ cultures to 10μM cadmium acetate resulted in a reduction of ciliary activity by 89% and a profound swelling of the epithelial cells within 4 hours. Substances with specific effects on ion transport systems did not interact with these cadmium induced effects. The swelling took place without any significant alterations of the intracellular electrolyte content (Na+, K+). Trifluoperazine (0.1mM), a calmodulin-specific drug, resulted in a reduction of ciliary activity similar to that induced by 10μM cadmium acetate, and induced a prominent swelling in part of the epithelial cell layer. A possible mechanism for the toxicity of cadmium could thus be binding of Cd2+ to the Ca2+ sites on calmodulin, causing dysfunctions of its normal regulatory role in both ciliary activity and volume control.

Gold alloy-based nanozyme sensor arrays for biothiol detection

Biothiols play an important role in living cells and are associated with many diseases. Thus, it is necessary to develop a facile, cost-effective, and convenient analytical method for the detection of biothiols. Nanozymes are functional nanomaterials with enzymatic activities. Due to their unique advantages (e.g., low cost, high stability, and multifunctionality), nanozymes have been extensively used to construct sensing systems. Previous studies demonstrated colorimetric assays for biothiol detection because they could competitively inhibit the peroxidase-like activities of nanozymes. However, few studies were able to differentiate biothiols from each other. To address these challenges, herein, we first synthesized Au alloy nanozymes with better peroxidase-like activities than gold nanoparticles (AuNPs). Then, cross-reactive sensor arrays were constructed with three alloy nanozymes. Six typical biothiols (i.e., glutathione, cysteine, dithiothreitol, mercaptoacetic acid, mercaptoethanol, and mercaptosuccinic acid) were successfully detected and discriminated by the as-prepared nanozyme sensor arrays. Moreover, the practical application of the nanozyme sensor arrays was demonstrated by discriminating biothiols in serum successfully.

Cell-cell contacts protect against t-BuOOH-induced cellular damage and ferroptosis in vitro

Ferroptosis is a recently discovered pathway of regulated necrosis dependent on iron and lipid peroxidation. It has gained broad attention since it is a promising approach to overcome resistance to apoptosis in cancer chemotherapy. We have recently identified tertiary-butyl hydroperoxide (t-BuOOH) as a novel inducer of ferroptosis. t-BuOOH is a widely used compound to induce oxidative stress in vitro. t-BuOOH induces lipid peroxidation and consequently ferroptosis in murine and human cell lines. t-BuOOH additionally results in a loss of mitochondrial membrane potential, formation of DNA double-strand breaks, and replication block. Here, we specifically address the question whether cell-cell contacts regulate t-BuOOH-induced ferroptosis and cellular damage. To this end, murine NIH3T3 or human HaCaT cells were seeded to confluence, but below their saturation density to allow the establishment of cell-cell contacts without inducing quiescence. Cells were then treated with t-BuOOH (50 or 200 µM, respectively). We revealed that cell-cell contacts reduce basal and t-BuOOH-triggered lipid peroxidation and consequently block ferroptosis. Similar results were obtained with the specific ferroptosis inducer erastin. Cell-cell contacts further protect against t-BuOOH-induced loss of mitochondrial membrane potential, and formation of DNA double-strand breaks. Interestingly, cell-cell contacts failed to prevent t-BuOOH-mediated replication block or formation of the oxidative base lesion 8-oxo-dG. Since evidence of protection against cell death was both (i) observed after treatment with hydrogen peroxide, methyl methanesulfonate or UV-C, and (ii) seen in several cell lines, we conclude that protection by cell-cell contacts is a widespread phenomenon. The impact of cell-cell contacts on toxicity might have important implications in cancer chemotherapy.

Mitochondrial calcium transport and the redox nature of the calcium-induced membrane permeability transition

Mitochondria possess a Ca²⁺ transport system composed of separate Ca²⁺ influx and efflux pathways. Intramitochondrial Ca²⁺ concentrations regulate oxidative phosphorylation, required for cell function and survival, and mitochondrial redox balance, that participates in a myriad of signaling and damaging pathways. The interaction between Ca²⁺ accumulation and redox imbalance regulates opening and closing of a highly regulated inner membrane pore, the membrane permeability transition pore (PTP). In this review, we discuss the regulation of the PTP by mitochondrial oxidants, reactive nitrogen species, and the interactions between these species and other PTP inducers. In addition, we discuss the involvement of mitochondrial redox imbalance and PTP in metabolic conditions such as atherogenesis, diabetes, obesity and in mtDNA stability.

Role of Cell Death in Toxicology: Does It Matter How Cells Die?

My research activity started with studies on drug metabolism in rat liver microsomes in the early 1960s. The CO-binding pigment (cytochrome P450) had been discovered a few years earlier and was subsequently found to be involved in steroid hydroxylation in adrenal cortex microsomes. Our early studies suggested that it also participated in the oxidative demethylation of drugs catalyzed by liver microsomes, and that prior treatment of the animals with phenobarbital caused increased levels of the hemoprotein in the liver, and similarly enhanced rates of drug metabolism. Subsequent studies of cytochrome P450-mediated metabolism of toxic drugs in freshly isolated rat hepatocytes characterized critical cellular defense systems and identified mechanisms by which accumulating toxic metabolites could damage and kill the cells. These studies revealed that multiple types of cell death could result from the toxic injury, and that it is important to know which type of cell death results from the toxic injury.

Anti-proliferative and cytotoxic activities of Allium autumnale P. H. Davis (Amaryllidaceae) on human breast cancer cell lines MCF-7 and MDA-MB-231

BACKGROUND

Natural products obtained from plants can be potent sources for developing a variety of pharmaceutical products. Allium species have been widely studied for their anti-cancer effects and presented promising results as potential anti-cancer agents. Breast cancer (BCa) is one of the most commonly diagnosed types of cancer in women. In this study, we aimed to investigate the anti-proliferative, cytotoxic and anti-metastatic effects of bulb and stem extracts from Allium autumnale P. H. Davis (Amaryllidaceae), an endemic Allium species to the island of Cyprus, in a comparative approach to weakly metastatic MCF-7 and strongly metastatic MDA-MB-231 breast cancer (BCa) cell lines.

METHODS

Possible cytotoxic, anti-proliferative and anti-metastatic effects of the Allium extracts on MCF-7 and MDA-MB-231 cells were tested using trypan blue exclusion, MTT and wound heal assays, respectively. Gas Chromatography Mass Spectroscopy (GC-MS) analysis was performed to determine the prominent medically important compounds in Allium autumnale bulb (AAB) and Allium autumnale stem (AAS) extracts. Student unpaired t-test or ANOVA followed by Newman-Keuls post hoc analysis (INSTAT Software) was used where appropriate.

RESULTS

Our results demonstrate that AAB extract (24, 48 and 72 h) exerts significant anti-proliferative effect on both MCF-7 and MDA-MB-231 cells where this effect for AAS extract was observed only at high (5000 and 10,000 μg/mL) concentrations. Cell viability experiments revealed that AAB extract incubations caused more cytotoxicity on both BCa cell lines compared to the AAS. In contrast, there was no effect on lateral motilities of either cell line.

CONCLUSION

Overall, our studies demonstrated the anti-cancer activities associated with Allium autumnale, revealing it's cytotoxic and anti-proliferative potential to be further utilized in in vivo studies.

Activation of the phospholipid scramblase TMEM16F by nanosecond pulsed electric fields (nsPEF) facilitates its diverse cytophysiological effects

Nanosecond pulsed electric fields (nsPEF) are emerging as a novel modality for cell stimulation and tissue ablation. However, the downstream protein effectors responsible for nsPEF bioeffects remain to be established. Here we demonstrate that nsPEF activate TMEM16F (or Anoctamin 6), a protein functioning as a Ca2+-dependent phospholipid scramblase and Ca2+-activated chloride channel. Using confocal microscopy and patch clamp recordings, we investigated the relevance of TMEM16F activation for several bioeffects triggered by nsPEF, including phosphatidylserine (PS) externalization, nanopore-conducted currents, membrane blebbing, and cell death. In HEK 293 cells treated with a single 300-ns pulse of 25.5 kV/cm, Tmem16f expression knockdown and TMEM16F-specific inhibition decreased nsPEF-induced PS exposure by 49 and 42%, respectively. Moreover, the Tmem16f silencing significantly decreased Ca2+-dependent chloride channel currents activated in response to the nanoporation. Tmem16f expression also affected nsPEF-induced cell blebbing, with only 20% of the silenced cells developing blebs compared with 53% of the control cells. This inhibition of cellular blebbing correlated with a 25% decrease in cytosolic free Ca2+ transient at 30 s after nanoporation. Finally, in TMEM16F-overexpressing cells, a train of 120 pulses (300 ns, 20 Hz, 6 kV/cm) decreased cell survival to 34% compared with 51% in control cells (*, p < 0.01). Taken together, these results indicate that TMEM16F activation by nanoporation mediates and enhances the diverse cellular effects of nsPEF.

Carbon Nanodots-Based Fluorescent Turn-On Sensor Array for Biothiols

Biothiols play important roles in biological processes. In this study, a novel sensor array-based method was proposed to detect and differentiate biothiols. The sensor array was constructed using three kinds of Ag⁺-sensitive carbon nanodots (CDs). The CDs were synthesized with amino acids and urea as carbon sources via a simple microwave method. Results revealed that Ag⁺ can bind with CDs and depress the fluorescence of CDs, while the subsequently joined biothiols can take Ag⁺ away from CDs and recover the fluorescence of CDs. Due to the different binding ability between Ag⁺ and various CDs, as well as Ag⁺ and various biothiols, the CD-Ag⁺ array exhibits a unique pattern of fluorescence variations when interacting with six biothiol samples (cysteamine, dithiothreitol, mercaptosuccinic acid, glutathione, mercaptoacetic acid, and mercaptoethanol). Principal component analysis (PCA) was applied to analyze the pattern and generate a clustering map for a clearer identification of these biothiols. PCA can also be employed to simplify the established three-sensor array into a two-sensor array. Both the three- and two-sensor arrays can identify these biothiols in a wide biothiol concentration range (>10 μM).

Effects of colored and noncolored phenolics of Echium plantagineum L. bee pollen in Caco-2 cells under oxidative stress induced by tert-butyl hydroperoxide

Bee pollen is used as a dietary supplement, being promoted as a health food. Echium plantagineum L. bee pollen fractions enriched in flavonols (fraction I) or anthocyanins (fraction II) and the whole extract were characterized by HPLC-DAD. Both in the whole extract and in fraction II seven flavonols and five anthocyanins were identified, while fraction I contained six flavonols (in higher levels than fraction II) and small amounts of petunidin-3-O-rutinoside. Antioxidant capacity was evaluated in Caco-2 cells under oxidative stress induced by tert-butyl hydroperoxide (t-BHP). Fraction I pre-exposure imparted a tendency to protect cells, while fraction II and the whole extract aggravated t-BHP toxicity at some concentrations. The protective effects seem to be correlated with the levels of total glutathione, while no correlation between cellular viability and reactive species was seen. The extracts displayed no significant effect on antioxidant enzymes activity. Overall, anthocyanins seem to abrogate the antioxidant potential of flavonoid-rich extracts.

Revealing the binding structure of the protein corona on gold nanorods using synchrotron radiation-based techniques: understanding the reduced damage in cell membranes

Regarding the importance of the biological effects of nanomaterials, there is still limited knowledge about the binding structure and stability of the protein corona on nanomaterials and the subsequent impacts. Here we designed a hard serum albumin protein corona (BSA) on CTAB-coated gold nanorods (AuNRs) and captured the structure of protein adsorption using synchrotron radiation X-ray absorption spectroscopy, microbeam X-ray fluorescent spectroscopy, and circular dichroism in combination with molecular dynamics simulations. The protein adsorption is attributed to at least 12 Au-S bonds and the stable corona reduced the cytotoxicity of CTAB/AuNRs. These combined strategies using physical, chemical, and biological approaches will improve our understanding of the protective effects of protein coronas against the toxicity of nanomaterials. These findings have shed light on a new strategy for studying interactions between proteins and nanomaterials, and this information will help further guide the rational design of nanomaterials for safe and effective biomedical applications.

Computer simulation of cytoskeleton-induced blebbing in lipid membranes

Blebs are balloon-shaped membrane protrusions that form during many physiological processes. Using computer simulation of a particle-based model for self-assembled lipid bilayers coupled to an elastic meshwork, we investigated the phase behavior and kinetics of blebbing. We found that blebs form for large values of the ratio between the areas of the bilayer and the cytoskeleton. We also found that blebbing can be induced when the cytoskeleton is subject to a localized ablation or a uniform compression. The results obtained are qualitatively in agreement with the experimental evidence and the model opens up the possibility to study the kinetics of bleb formation in detail.

Mitochondrial membrane potential is a suitable candidate for assessing pollution toxicity in fish

Fish inhabiting polluted estuaries are highly exposed to severe stress characterized by an oxidant-antioxidant imbalance. The aim of the study was to explore the use of stress parameters such as adenosine triphosphate/adenosine diphosphate (ATP/ADP) ratio, mitochondrial membrane potential (∆ψm) and total protein expression patterns as biomarkers against oxidant exposures in hepatocytes of Mugil cephalus living in either a contaminated (Test; Ennore) or uncontaminated (Control; Kovalam) estuary. Earlier, the pollutant stress impact was determined through light and electron microscopy studies. The ATP/ADP ratio was measured using high performance liquid chromatography; ∆ψm by fluorescent probe 5, 5', 6, 6'-tetrachloro-1, 1', 3, 3'-tetraethyl benzimidazolcarbocyanine iodide (JC-1) dye and total protein expression patterns by protein profiling. The preponderance of stress impact was confirmed through microscopy studies that featured cytological alterations, disturbances in the surface morphology and in the cell organelles at the ultrastructural levels. Hepatocytes of test fish demonstrated a decrease in ATP and an increase in ADP and thereby alteration in ATP/ADP ratio (p<0.05; 20.75%). A significant disturbance (p<0.05; 26.57%) in ∆ψm with a ratio of J-aggregates/JC-1 monomer of 1 was observed for test fish hepatocytes compared to control group with a J-aggregates/JC-1 monomer ratio of 1.5. Quantitative assessment of protein expression levels also revealed enhanced induction of both low and high molecular weight proteins in test fish hepatocytes. The findings highlight the use of these parameters as the highly sensitive biomarkers in response to contaminant exposure compared to the routinely used antioxidant and oxidant stress parameters in biomonitoring programs. Among the measured parameters, the determination of ∆ψm may be suggested as a novel candidate as a biomarker because of its greater specificity and rapid quantitative risk assessment of pollutant exposures.

Zingiber officinale acts as a nutraceutical agent against liver fibrosis

Background/objective

Zingiber officinale Roscoe (ginger) (Zingiberaceae) has been cultivated for thousands of years both as a spice and for medicinal purposes. Ginger rhizomes successive extracts (petroleum ether, chloroform and ethanol) were examined against liver fibrosis induced by carbon tetrachloride in rats.

Results

The evaluation was done through measuring antioxidant parameters; glutathione (GSH), total superoxide dismutase (SOD) and malondialdehyde (MDA). Liver marker enzymes; succinate and lactate dehydrogenases (SDH and LDH), glucose-6-phosphatase (G-6-Pase), acid phosphatase (AP), 5'- nucleotidase (5'NT) and liver function enzymes; aspartate and alanine aminotransferases (AST and ALT) as well as cholestatic markers; alkaline phosphatase (ALP), gamma glutamyl transferase (GGT), total bilirubin were estimated. Liver histopathological analysis and collagen content were also evaluated. Treatments with the selected extracts significantly increased GSH, SOD, SDH, LDH, G-6-Pase, AP and 5'NT. However, MDA, AST, ALT ALP, GGT and total bilirubin were significantly decreased.

Conclusions

Extracts of ginger, particularly the ethanol one resulted in an attractive candidate for the treatment of liver fibrosis induced by CCl₄. Further studies are required in order to identify the molecules responsible of the pharmacological activity.

A new possible function for placental pericytes

The pericyte is a multifunctional cell closely associated with endothelial cells and may play a role in angiogenesis and vessel stabilisation. Re-examination of over 1,100 micrographs from archival material used to investigate ultrastructural changes in placental development and pathology has identified previously undescribed structures associated with the pericyte of the human placental terminal villus. These structures take the form of outgrowths from the main body of the cell, with a narrow neck rich in cytoplasmic filaments, terminating in swollen tips which appear to bleb off the pericyte and form electron lucent stromal vesicles. Semi-quantitative analysis indicated that these features are present in some placentae from normal, term pregnancies but are increasingly found where capillaries show abnormalities such as a failure to form sinusoids, as in pregnancies complicated by diabetes, postmaturity, rhesus incompatibility and pre-eclampsia. This blebbing is compared with similar phenomena associated with apoptosis and zeiosis and it is suggested that it may contribute to fluid homeostasis where normal mechanisms are impaired by thickening or damage to endothelial cells.

γ-Glutamylcysteine ameliorates oxidative injury in neurons and astrocytes in vitro and increases brain glutathione in vivo

γ-Glutamylcysteine (γ-GC) is an intermediate molecule of the glutathione (GSH) synthesis pathway. In the present study, we tested the hypothesis that γ-GC pretreatment in cultured astrocytes and neurons protects against hydrogen peroxide (H(2)O(2))-induced oxidative injury. We demonstrate that pretreatment with γ-GC increases the ratio of reduced:oxidized GSH levels in both neurons and astrocytes and increases total GSH levels in neurons. In addition, γ-GC pretreatment decreases isoprostane formation both in neurons and astrocytes, as well as nuclear factor erythroid 2-related factor 2 (Nrf2) nuclear translocation in astrocytes in response to H(2)O(2)-induced oxidative stress. Furthermore, GSH and isoprostane levels significantly correlate with increased neuron and astrocyte viability in cells pretreated with γ-GC. Finally, we demonstrate that administration of a single intravenous injection of γ-GC to mice significantly increases GSH levels in the brain, heart, lungs, liver, and in muscle tissues in vivo. These results support a potential therapeutic role for γ-GC in the reduction of oxidant stress-induced damage in tissues including the brain.

Montelukast, a selective cysteinyl leukotriene receptor 1 antagonist, reduces cerulein-induced pancreatic injury in rats

OBJECTIVES

This study was designed to evaluate the protective effect of the cysteinyl leukotriene receptor antagonist montelukast against pancreatic injury during acute pancreatitis.

METHODS

Acute pancreatitis was induced in rats by 20-μg/kg (intraperitoneal) cerulein given at 1-hour intervals within 4 hours. Montelukast was administered intraperitoneally at a dose of 10 mg/kg 15 minutes before the first cerulein injection. Six hours after the cerulein or saline injections, the animals were killed by decapitation. Blood samples were collected to analyze amylase, lipase, and the proinflammatory cytokines tumor necrosis factor α and interleukin 1β. Pancreas tissues were taken for the determination of tissue glutathione and malondialdehyde levels and Na,K-adenosine triphosphatase and myeloperoxidase activities. The extent of tissue injury was analyzed microscopically.

RESULTS

Acute pancreatitis caused significant decreases in tissue glutathione level and Na,K-adenosine triphosphatase activity, which were accompanied with significant increases in the pancreatic malondialdehyde level, myeloperoxidase activity, and plasma cytokine level. On the other hand, montelukast treatment reversed all these biochemical indices and histopathological alterations that were induced by cerulein.

CONCLUSIONS

These results suggest that cysteinyl leukotrienes may be involved in the pathogenesis of acute pancreatitis and that the cysteinyl leukotriene receptor antagonist, montelukast, might be of therapeutic value for treatment of acute pancreatitis.

The protection of hepatocyte cells from the effects of oxidative stress by treatment with vitamin E in conjunction with DTT

We investigated the effect of vitamin E on membrane protein thiols under oxidative stress, which we induced by treating hepatocytes with tert-butyl hydroperoxide (TBH) for 60 mins. Those cells which we pretreated with vitamin E formed fewer blebs (22.3% compared to 60.0% in nonvitamin E-treated cells) and maintained cytosolic calcium concentration and the number of membrane protein thiols instead of showing the usual symptoms in cells undergoing oxidative stress. Dithiothreitol (DTT) also commonly reduces bleb formation in hepatocytes affected by TBH. However, our experiments clearly demonstrate that DTT does not prevent the changes in cytosolic calcium and membrane protein thiols in the blebbing cells. Consequently, we decided to pretreat cells with both DTT and vitamin E and found that the influence of TBH was entirely prevented. These findings may provide us with a new aspect for investigating the mechanism of bleb formation under oxidative stress.

Leukocyte membrane bleb and pseudopod formation in hypertension

Leukocyte activation, including adhesion molecule expression, oxygen radical generation and, in animal studies, pseudopod formation, is a hallmark of hypertension. This study examined pseudopod and bleb formation and demonstrates that leukocytes from hypertensive individuals are more susceptible to produce membrane blebs than leukocytes from normotensive individuals. Bleb formation is likely indicative of apoptosis, thus this observation adds to previous observations of increased apoptosis in various tissues in hypertension.

Protective Effects of Proanthocyanidin on Cerulein-induced Acute Pancreatic Inflammation in Rats

Background

The aim of this study was to assess the possible protective effect of proanthocyanidin against cerulein-induced acute pancreatic inflammation (AP) and oxidative injury.

Methods

Sprague-Dawley rats were pretreated with proanthocyanidine (100 mg/kg, orally) or saline 15 min before cerulein was given by 20 µg/kg subcutaneously at 1-h intervals within 4 hours. Six hours after cerulein or saline injections, the animals were killed by decapitation. Blood samples were collected to analyze amylase, lipase, and proinflammatory cytokines (TNF-α and IL-1b). Pancreas tissues were taken for the determination of tissue glutathione (GSH) and malondialdehyde (MDA) levels, Na⁺, K⁺-ATPase and myeloperoxidase (MPO) activities. Formation of reactive oxygen species in pancreatic tissue samples was monitored by using chemiluminescence (CL) technique with luminol and lucigenin probes, while the extent of tissue injury was analyzed microscopically.

Results

Acute pancreatitis caused a significant decrease in tissue GSH level and Na⁺, K⁺-ATPase activity, which was accompanied with significant increases in the pancreatic MDA, luminol and lucigenin chemiluminescences (CL) levels and MPO activity. Similarly TNF-α and IL-1β levels were elevated in the pancreatic group as compared to control group. On the other hand, proanthocyanidin treatment reversed all these biochemical indices, as well as histopathological alterations that were induced by cerulein.

Conclusions

Proanthocyanidine can ameliorate pancreatic injury induced by cerulein in rats, this result suggests that proanthocyanidin may have utility in treating acute pancreatititis.

Genetic disruption of calpain correlates with loss of membrane blebbing and differential expression of RhoGDI-1, cofilin and tropomyosin

Dynamic regulation of the actin cytoskeleton is important for cell motility, spreading and the formation of membrane surface extensions such as lamellipodia, ruffles and blebs. The ubiquitous calpains contribute to integrin-mediated cytoskeletal remodelling during cell migration and spreading, by cleavage of focal adhesion components and signalling molecules. In the present study, the live-cell morphology of calpain-knockout and wild-type cells was examined by time-lapse fluorescence microscopy, and a role of calpain in mediating the formation of sporadic membrane blebs was established. Membrane blebbing was significantly reduced in calpain-knockout cells, and genetic rescue fully restored the wild-type phenotype in knockout cells. Proteomic comparison of wild-type and knockout cells identified decreased levels of RhoGDI-1 (Rho GDP-dissociation inhibitor) and cofilin 1, and increased levels of tropomyosin in calpain-knockout cells, suggesting a role of calpain in regulating membrane extensions involving these proteins. RhoGDI, cofilin and tropomyosin are known regulators of actin filament dynamics and membrane extensions. The reduced levels of RhoGDI-1 in calpain-knockout cells observed by proteome analysis were confirmed by immunoblotting. Genetic rescue of the calpain-knockout cells enhanced RhoGDI-1-expression 2-fold above that normally present in wild-type cells. These results suggest a regulatory connection between calpain and RhoGDI-1 in promoting formation of membrane blebs.

Effects of hepatic zonal oxygen levels on hepatocyte stress responses

BACKGROUND

Hepatocytes spend their lifetimes in a gradient of oxygen, hormones, and enzymes. We used a three-dimensional Matrigel model to determine whether hepatocytes cultured at perivenous (zone 3) oxygen levels differed in susceptibility to anoxia-induced cell injury compared with hepatocytes cultured at periportal (zone 1) oxygen levels.

MATERIALS AND METHODS

Hepatocytes were harvested from Sprague Dawley rats and cultured at 9% oxygen (hepatic zone 1) or 5% oxygen (hepatic zone 3) and stressed at 0% oxygen. Microscopy, real-time reverse transcriptase-polymerase chain reaction, and enzyme-linked immunosorbent assay were used to assess cell viability, mitochondrial potential, acute phase responses, and membrane blebbing.

RESULTS

Hepatocytes cultured in Matrigel with HepatoZyme medium at zone 1 and zone 3 oxygen conditions were viable for 1 wk and showed acute phase responses as measured by interleukin-6-induced fibrinogen production. In response to 3 h anoxia, cells maintained at the perivenous oxygen level showed increased membrane blebbing and increased loss of mitochondrial membrane potential in comparison to the periportal oxygen cultured cells. Cells at perivenous oxygen also showed a reduced ability to recover following reoxygenation.

CONCLUSIONS

Hepatocytes can remain viable and functional for extended periods in culture at low oxygen levels that mimic the hepatic perivenous environment, yet these cells are more susceptible to anoxia-induced damage than hepatocytes cultured at the periportal oxygen level. The small population of perivenous hepatocytes may be critical in determining the fate of the liver during ischemia/reperfusion since hepatocytes cultured at that concentration appear to be more labile in response to anoxia.

Allicin inhibits cell growth and induces apoptosis through the mitochondrial pathway in HL60 and U937 cells

In this article, the effects of allicin, a biological active compound of garlic, on HL60 and U937 cell lines were examined. Allicin induced growth inhibition and elicited apoptotic events such as blebbing, mitochondrial membrane depolarization, cytochrome c release into the cytosol, activation of caspase 9 and caspase 3 and DNA fragmentation. Pretreatment of HL60 cells with cyclosporine A, an inhibitor of the mitochondrial permeability transition pore (mPTP), inhibited allicin-treated cell death. HL60 cell survival after 1 h pretreatment with cyclosporine A, followed by 16 h in presence of allicin (5 microM) was approximately 80% compared to allicin treatment alone (approximately 50%). Also N-acetyl cysteine, a reduced glutathione (GSH) precursor, prevented cell death. The effects of cyclosporine A and N-acetyl cysteine suggest the involvement of mPTP and intracellular GSH level in the cytotoxicity. Indeed, allicin depleted GSH in the cytosol and mitochondria, and buthionine sulfoximine, a specific inhibitor of GSH synthesis, significantly augmented allicin-induced apoptosis. In HL60 cells treated with allicin (5 microM, 30 min) the redox state for 2GSH/oxidized glutathione shifted from EGSH -240 to -170 mV. The same shift was observed in U937 cells treated with allicin at a higher concentration for a longer period of incubation (20 microM, 2 h). The apoptotic events induced by various concentrations of allicin correlate to intracellular GSH levels in the two cell types tested (HL60: 3.7 nmol/10(6) cells; U937: 7.7 nmol/10(6) cells). The emerging mechanistic basis for the antiproliferative function of allicin, therefore, involves the activation of the mitochondrial apoptotic pathway by GSH depletion and by changes in the intracellular redox status.

Membrane reserves and hypotonic cell swelling

To accommodate expanding volume (V) during hyposmotic swelling, animal cells change their shape and increase surface area (SA) by drawing extra membrane from surface and intracellular reserves. The relative contributions of these processes, sources and extent of membrane reserves are not well defined. In this study, the SA and V of single substrate-attached A549, 16HBE14o(-), CHO and NIH 3T3 cells were evaluated by reconstructing cell three-dimensional topology based on conventional light microscopic images acquired simultaneously from two perpendicular directions. The size of SA reserves was determined by swelling cells in extreme 98% hypotonic (approximately 6 mOsm) solution until membrane rupture; all cell types examined demonstrated surprisingly large membrane reserves and could increase their SA 3.6 +/- 0.2-fold and V 10.7 +/- 1.5-fold. Blocking exocytosis (by N-ethylmaleimide or 10 degrees C) reduced SA and V increases of A549 cells to 1.7 +/- 0.3-fold and 4.4 +/- 0.9-fold, respectively. Interestingly, blocking exocytosis did not affect SA and V changes during moderate swelling in 50% hypotonicity. Thus, mammalian cells accommodate moderate (<2-fold) V increases mainly by shape changes and by drawing membrane from preexisting surface reserves, while significant endomembrane insertion is observed only during extreme swelling. Large membrane reserves may provide a simple mechanism to maintain membrane tension below the lytic level during various cellular processes or acute mechanical perturbations and may explain the difficulty in activating mechanogated channels in mammalian cells.

The cleavage mode of apoptotic nuclear vesiculation is related to plasma membrane blebbing and depends on actin reorganization

In U937 monocytic cells induced to apoptosis, plasma membrane blebbing of different intensities appears, before the development of nuclear alterations; this latter phenomenon can occur through two major pathways, namely the cleavage and the budding mode (Dini et al., 1996). Strongly blebbing cells develop deep nuclear constrictions leading to nuclear fragmentation according to the cleavage mode, while cells with milder forms of blebbing, or no blebbing at all, undergo nuclear fragmentation along the budding mode. Compounds interfering with different cytoskeletal components affect blebbing, which is completely inhibited by the actin polymerization inhibitors, cytochalasins, while disturbance of tubulin network with taxol limits blebbing to milder forms. At the same time, the cytoskeletal poisons affect the type of nuclear fragmentation, abolishing the cleavage mode, shifting all events into the budding pathway. Adherent cells, which possess a more structured cytoskeleton, do not develop strong blebs and undergo nuclear fragmentation via budding. These observations suggest that the deep cytoskeletal movements that cause the strongest forms of plasma membrane blebbing strangle the nucleus, leading to the constrictions that later evolve into nuclear fragmentation by cleavage. The trigger for the cytoskeletal movements, known to be redox-sensitive, is probably the apoptotic GSH extrusion.

Different fates of intracellular glutathione determine different modalities of apoptotic nuclear vesiculation

U937 monocytic cells show two main apoptotic nuclear morphologies, budding and cleavage, that are the result of two independent morphological routes, since they never interconvert one into the other, and are differently modulated by stressing or physiological apoptogenic agents [Exp Cell Res 1996; 223:340-347]. With the aim of understanding which biochemical alterations are at the basis of these alternative apoptotic morphologies, we performed an in situ analysis that showed that in U937 cells intracellular glutathione (GSH) is lost in cells undergoing apoptosis by cleavage, whereas it is maintained in apoptotic budding cells. Lymphoma cells BL41 lose GSH in apoptosis, and show the cleavage nuclear morphology; the same cells latently infected with Epstein Barr Virus (E2r line) undergo apoptosis without GSH depletion and show the budding nuclear morphology. GSH depletion is not only concomitant to, but is the determinant of the cleavage route, since the inhibition of apoptotic GSH efflux with cystathionine or methionine shifts the apoptotic morphology from cleavage to budding. Accordingly, cystathionine or methionine antagonizes apoptosis in the all-cleavage BL41, without affecting the all-budding E2r.

Common mechanisms in nephropathy induced by toxic metals

Various metals of unknown function in the body (Cd, Cr, Hg, Pb, U), trace elements in excessive concentrations (Co, Cu, Fe, Zn), or metals used in cancer therapy (Pt, V), accumulate in the mammalian kidney, largely in the proximal tubule (PT) cells, and cause functional and structural damage that results in reabsorptive and secretory defects. The intracellular mechanisms of their toxicity in the PT cells are not well known. Recent studies have indicated an oxidative stress with associated lipid peroxidation, apoptosis, and necrosis as common phenomena in the course of nephrotoxicity of these metals. However, a number of other phenomena, such as the selective inhibition and/or loss of various membrane transporters, enhancement of ion conductances, increased cytoplasmic concentration of calcium, deranged cytoskeleton and cell polarity, impaired endocytosis, swelling and fragmentation of mitochondria, increased expression of metallothionein, heat-shock and multidrug resistance proteins, loss of cell membrane integrity, as well as the damage of mitochondrial and genomic DNAs have been fragmentarily demonstrated for the action of some toxic metals, but their importance for the course of nephrotoxicity and the sequence of events in relation to oxidative stress, apoptosis, and necrosis have not been clearly established. Recent studies of metal toxicity in various tissues and cells of non-renal and renal origin enable us to estimate 'causes and consequences' of various phenomena in the metal-induced nephrotoxicity, and to assemble them in a possible common, time-related sequence.

Aggregates of ultrafine particles impair phagocytosis of microorganisms by human alveolar macrophages

We investigated whether exposure of alveolar macrophages to aggregates of ultrafine carbon particles affected subsequent phagocytosis of microorganisms. Human alveolar macrophages were obtained by bronchoalveolar lavage and exposed to aggregates of ultrafine carbon particles or diesel exhaust particles (DEP) for 20 h before measurements of phagocytosis. The particle loads were estimated to be comparable to those of air pollution exposure with established health effects in humans. Phagocytotic activity was measured as attachment and ingestion of four different test particles (amorphous silica particles, yeast cells from Candida albicans, and Cryptococcus neoformans opsonized with specific IgG or fresh serum) that bind to scavenger, mannose, Fc, and complement receptors, respectively. Carbon preloading significantly impaired the attachment and ingestion process (P<0.01) for all particles, except for yeast cells from C. neoformans opsonized with specific IgG. On the average, the accumulated attachment decreased by 30% and the ingested fraction decreased by 10%. Loading of alveolar macrophages with either aggregates of ultrafine DEP or carbon particles impaired the phagocytosis of silica test particles in a similar way. Exposure of human alveolar macrophages to aggregates of carbon or DEP, in concentrations relevant to human environmental exposures, caused significant impairment of phagocytosis of silica particles and microorganisms. The inhibitory effect on particle phagocytosis mediated by four different receptors suggests that air pollution particles cause a general inhibition of macrophage phagocytosis. Such an effect may contribute to increased susceptibility to infections and, for example, result in more exacerbations of asthma and chronic obstructive pulmonary disease.

Consequences of abrupt glutathione depletion in murine Clara cells: ultrastructural and biochemical investigations into the role of glutathione loss in naphthalene cytotoxicity

Glutathione plays many critical roles within the cell, including offering protection from reactive chemicals. The bioactivated toxicant naphthalene forms chemically reactive intermediates that can deplete glutathione and covalently bind to cellular proteins. Naphthalene selectively injures the nonciliated epithelial cells of the intrapulmonary airways (i.e., Clara cells). This study attempted to define what role glutathione loss plays in naphthalene cytotoxicity by comparing Swiss-Webster mice treated with naphthalene with those treated with the glutathione depletor diethylmaleate. High-resolution imaging techniques were used to evaluate acute changes in Clara cell ultrastructure, membrane permeability, and cytoskeleton structure. A single dose of either diethylmaleate (1000 mg/kg) or naphthalene (200 mg/kg) caused similar glutathione losses in intrapulmonary airways (< 20% of control). Diethylmaleate did not increase membrane permeability, disrupt mitochondria, or lead to cell death--hallmark features of naphthalene cytotoxicity. However, diethylmaleate treatment did cause Clara cell swelling, plasma membrane blebs, and actin cytoskeleton disruptions similar to naphthalene treatment. Structural changes in mitochondria and Golgi bodies also were noted. Changes in ATP levels were measured as an indication of overall cell function, in isolated airway explants incubated with diethylmaleate, naphthalene, or naphthalene metabolites in vitro. Only the reactive metabolites of naphthalene caused significant ATP losses. Unlike the lethal injury caused by naphthalene, the disruptive cellular changes associated with glutathione loss from diethylmaleate seemed to be reversible after recovery of glutathione levels. This suggests that glutathione depletion may be responsible for some aspects of naphthalene cytotoxicity, but it is not sufficient to cause cell death without further stresses.

Curcumin inhibits cell motility and alters microfilament organization and function in prostate cancer cells

Curcumin is a dietary phytochemical associated with anti-tumorigenic effects, but the mechanisms by which it inhibits cancer cell growth and metastasis are not completely understood. For example, little information is available regarding the effects of curcumin on cytoskeletal organization and function. In this study, time-lapse video and immunofluorescence labeling methods were used to demonstrate that curcumin significantly alters microfilament organization and cell motility in PC-3 and LNCaP human prostate cancer cells in vitro. Curcumin rapidly arrests cell movements and subsequently alters cell shape in the highly motile PC-3 cell line, but has a less noticeable effect on the relatively immobile LNCaP cell line. Stress fibers are augmented, and the overall quantity of f-actin appears to increase in both types of cells following curcumin treatment. Cytochalasin B (CB) disrupts microfilament organization in both cell lines, and causes vigorous membrane blebbing in PC-3 cells, but not LNCaP cells. Pre-treatment of cells with curcumin suppresses changes in microfilament organization caused by CB, and blocks PC-3 membrane blebbing. At least some of the effects of curcumin appear to be mediated by protein kinase C (PKC), as treatment with the PKC inhibitor bisindolylmaleimide inhibits the ability of curcumin to block CB-induced membrane blebbing. These findings demonstrate that curcumin exerts significant effects on the actin cytoskeleton in prostate cancer cells, including altering microfilament organization and function. This is a novel observation that may represent an important mechanism by which curcumin functions as a chemopreventative agent, and as an inhibitor of angiogenesis and metastasis.

Prevention of naphthalene-induced pulmonary toxicity by glutathione prodrugs: Roles for glutathione depletion in adduct formation and cell injury

Naphthalene is metabolized in the lung and liver to reactive intermediates by cytochrome P450 enzymes. These reactive species deplete glutathione, covalently bind to proteins, and cause necrosis in Clara cells of the lung. The importance of glutathione loss in naphthalene toxicity was investigated by using the glutathione prodrugs (glutathione monoethylester or cysteine-glutathione mixed disulfide) to maintain glutathione pools during naphthalene exposure. Mice given a single intraperitoneal injection of naphthalene (1.5 mmol/kg) were treated with either prodrug (2.5 mmol/kg) 30 min later. Both compounds effectively maintained glutathione levels and decreased naphthalene-protein adducts in the lung and liver. However, cysteine-glutathione mixed disulfide was more effective at preventing Clara cell injury. To study the prodrugs in Clara cells without the influence of hepatic naphthalene metabolism and circulating glutathione, dose-response and time-course studies were conducted with intrapulmonary airway explant cultures. Only the ester of glutathione raised GSH in vitro; however, both compounds limited protein adducts and cell necrosis. In vitro protection was not associated with decreased naphthalene metabolism. We conclude that (1) glutathione prodrugs can prevent naphthalene toxicity in Clara cells, (2) the prodrugs effectively prevent glutathione loss in vivo, and (3) cysteine-glutathione mixed disulfide prevents naphthalene injury in vitro without raising glutathione levels.

Melatonin protects against pancreaticobiliary inflammation and associated remote organ injury in rats: role of neutrophils

Although the role of oxidative stress in acute pancreatitis (AP) has been studied in several animal models, little data are available regarding AP induced by pancreatic duct obstruction. We characterized the protective effects of melatonin on pancreaticobiliary inflammation and associated remote organ injury. In Sprague-Dawley rats, either the common pancreaticobiliary duct (PBDL; n = 28) or bile duct (BDL; n = 28) was ligated or a sham operation was applied (n = 14). Either melatonin (10 mg/kg) or vehicle (saline; 1 mL/kg) was administered intraperitoneally (i.p.) immediately before the surgery and twice a day until the rats were decapitated at 6 or 72 h. The pancreas, liver, kidneys and lungs were removed and tissue samples were stored for the determination of malondialdehyde (MDA) and glutathione (GSH) levels and myelopreoxidase activity. The results demonstrate that pathogenesis of acute obstructive pancreatitis involves not only the oxidative damage of the pancreatic and hepatic tissues, as assessed by increased MDA and reduced GSH levels, but the lungs and kidneys are also challenged by oxidant injury. Similarly, hepatic oxidative injury caused by cholestasis was also accompanied by pulmonary, renal and even pancreatic damage. The biochemical findings were also verified histologically. Melatonin, probably because of its free-radical scavenging and antioxidant activity, which involves an inhibitory effect on tissue neutrophil infiltration, protected all the affected tissues.

Tributyltin-sulfhydryl interaction as a cause of immunotoxicity in phagocytes of tunicates

We reported elsewhere that tributyltin (TBT) has detrimental effects on the immune system of the colonial ascidian Botryllus schlosseri, through interaction with calmodulin and alteration of Ca2+ homeostasis. Here, we studied the capability of TBT to react with intracellular thiols. After exposure to 0.1 microM TBT, a significant decrease in B. schlosseri hemocytes stained for total thiols and reduced glutathione (GSH) was detected. Exogenous sulfhydryl and sulfide compounds can prevent TBT-induced cell morphology alterations and decrease the percentage of tin-containing hemocytes, indicating the scavenging ability of thiol peptides. No effects were observed with disulfides, N-acetylcysteine, or the GSH fragment Cys-Gly. No interactions were observed with TBT and carmustine, whereas TBT and N-ethylmaleimide (NEM) showed a combined antagonistic action, suggesting direct interaction of TBT with thiol-containing compounds. Regulation of Ca2+ efflux from internal stores seems to depend on stimulation of the inositol 1,4,5-trisphosphate (InsP3) receptor by oxidized glutathione (GSSG), which results from interactions of both TBT-GSH and TBT-GSH reductase.

Hypoxic stress stably alters apoptotic parameters on U937 cells

Tumor promonocytic U937 cells cultured under a low O(2)/high CO(2) atmosphere display altered characteristics after restoration of normal atmosphere: increased resistance to apoptosis induced by different treatments; apoptotic morphology; lack of glutathione (GSH) extrusion in apoptosis; lack of protection by antioxidants; and lack of Ca(2+) mobilization with thapsigargin. These alterations were stably maintained for many months of culture in normal conditions, originating the stable U937-HX variant. Since the hypoxic treatment did not produce a great selective pressure, the alterations are conceivably the result of stable adaptative response.

Role of Ca2+ in radiation-induced damage in murine splenocytes

PURPOSE

To address the links between calcium, peroxidation, cell damage and death and the response of the enzymes involved in free radical metabolism, in splenocytes of mice irradiated with gamma-rays.

MATERIALS AND METHODS

Splenocytes of Swiss albino mice were irradiated with various doses (0-7 Gy) of gamma-rays (60Co) at a dose-rate of 0.0575 Gy s(-1). Membrane peroxidation and fluidity were determined by the thiobarbituric acid-reactive substances (TBARS) method, and fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene (DPH), respectively. Apoptosis was analysed by nucleosomal ladder formation and activity of NF-kappaB by electrophoretic mobility shift assay (EMSA). The specific activities of the antioxidant enzymes, lactate dehydrogenase (LDH), levels of nitric oxide (NO*) and glutathione were determined spectrophotometrically. Modulatory effects of Ca2+ were examined at 3 Gy using different concentrations (1, 3 and 5 mM) in the presence or absence of the ionophore A23187.

RESULTS

Irradiation of splenocytes resulted in enhanced peroxidative damage. membrane fluidity, apoptosis and DNA binding activity of NF-kappaB. The specific activities of LDH and antioxidant enzymes superoxide dismutase (SOD), DT-diaphorase (DTD), glutathione S-transferase (GST) and levels of glutathione (GSH) and NO* were increased with radiation dose up to 4Gy. Ca2+ augmented the radiation-induced responses. The presence of ionophore A23187 potentiated the modulatory effects of Ca2+.

CONCLUSIONS

These findings show that Ca2+ augments radiation damage and is more effective intracellularly. Ca2+, peroxidation, cellular damage and apoptosis are possibly interlinked through signals, as is evident from the increased activity of NF-kappaB and generation of NO*. The enhanced antioxidant status suggests an attempt made by the irradiated cells to maintain their normal functions.