Arsenic trioxide inhibits the growth of Calu-6 cells via inducing a G2 arrest of the cell cycle and apoptosis accompanied with the depletion of GSH

Propyl gallate induces human pulmonary fibroblast cell death through the regulation of Bax and caspase-3

Propyl gallate (PG) has been found to exert an inhibitory effect on the growth of different cell types, including lung cancer cells. However, little is known about the cytotoxicological effects of PG specifically on normal primary lung cells. The current study examined the cellular effects and cell death resulting from PG treatment in human pulmonary fibroblast (HPF) cells. DNA flow cytometry results demonstrated that PG (100-1,600 μM) had a significant impact on the cell cycle, leading to G1 phase arrest. Notably, 1,600 μM PG slightly increased the number of sub-G1 cells. Additionally, PG (400-1,600 μM) resulted in the initiation of cell death, a process that coincided with a loss of mitochondrial membrane potential (MMP; ΔΨm). This loss of MMP (ΔΨm) was evaluated using a FACS cytometer. In PG-treated HPF cells, inhibitors targeting pan-caspase, caspase-3, caspase-8, and caspase-9 showed no significant impact on the quantity of annexin V-positive and MMP (ΔΨm) loss cells. The administration of siRNA targeting Bax or caspase-3 demonstrated a significant attenuation of PG-induced cell death in HPF cells. However, the use of siRNAs targeting p53, Bcl-2, or caspase-8 did not exhibit any notable effect on cell death. Furthermore, none of the tested MAPK inhibitors, including MEK, c-Jun N-terminal kinase (JNK), and p38, showed any impact on PG-induced cell death or the loss of MMP (ΔΨm) in HPF cells. In conclusion, PG induces G1 phase arrest of the cell cycle and cell death in HPF cells through apoptosis and/or necrosis. The observed HPF cell death is mediated by the modulation of Bax and caspase-3. These findings offer insights into the cytotoxic and molecular effects of PG on normal HPF cells.

Cyanidin-3-O-glucoside alleviates ethanol-induced liver injury by promoting mitophagy in a Gao-binge mouse model of alcohol-associated liver disease

BACKGROUND

Alcohol-associated liver disease (ALD) is a leading cause of liver disease-related deaths worldwide. Unfortunately, approved medications for the treatment of this condition are quite limited. One promising candidate is the anthocyanin, Cyanidin-3-O-glucoside (C3G), which has been reported to protect mice against hepatic lipid accumulation, as well as fibrosis in different animal models. However, the specific effects and mechanisms of C3G on ALD remain to be investigated.

EXPERIMENTAL APPROACH

In this report, a Gao-binge mouse model of ALD was used to investigate the effects of C3G on ethanol-induced liver injury. The mechanisms of these C3G effects were assessed using AML12 hepatocytes.

RESULTS

C3G administration ameliorated ethanol-induced liver injury by suppressing hepatic oxidative stress, as well as through reducing hepatic lipid accumulation and inflammation. Mechanistically, C3G activated the AMPK pathway and enhanced mitophagy to eliminate damaged mitochondria, thus reducing mitochondria-derived reactive oxidative species in ethanol-challenged hepatocytes.

CONCLUSIONS

The results of this study indicate that mitophagy plays a potentially important role underlying the hepatoprotective action of C3G, as demonstrated in a Gao-binge mouse model of ALD. Accordingly, C3G may serve as a promising, new therapeutic drug candidate for use in ALD.

Oxidative cell death in cancer: mechanisms and therapeutic opportunities

Reactive oxygen species (ROS) are highly reactive oxygen-containing molecules generated as natural byproducts during cellular processes, including metabolism. Under normal conditions, ROS play crucial roles in diverse cellular functions, including cell signaling and immune responses. However, a disturbance in the balance between ROS production and cellular antioxidant defenses can lead to an excessive ROS buildup, causing oxidative stress. This stress damages essential cellular components, including lipids, proteins, and DNA, potentially culminating in oxidative cell death. This form of cell death can take various forms, such as ferroptosis, apoptosis, necroptosis, pyroptosis, paraptosis, parthanatos, and oxeiptosis, each displaying distinct genetic, biochemical, and signaling characteristics. The investigation of oxidative cell death holds promise for the development of pharmacological agents that are used to prevent tumorigenesis or treat established cancer. Specifically, targeting key antioxidant proteins, such as SLC7A11, GCLC, GPX4, TXN, and TXNRD, represents an emerging approach for inducing oxidative cell death in cancer cells. This review provides a comprehensive summary of recent progress, opportunities, and challenges in targeting oxidative cell death for cancer therapy.

Propyl gallate induces cell death in human pulmonary fibroblast through increasing reactive oxygen species levels and depleting glutathione

Propyl gallate (PG) exhibits an anti-growth effect on various cell types. The present study investigated the impact of PG on the levels of reactive oxygen species (ROS) and glutathione (GSH) in primary human pulmonary fibroblast (HPF) cells. Moreover, the effects of N-acetyl cysteine (NAC, an antioxidant), L-buthionine sulfoximine (BSO, a GSH synthesis inhibitor), and small interfering RNA (siRNAs) against various antioxidant genes on ROS and GSH levels and cell death were examined in PG-treated HPF cells. PG (100-800 μM) increased the levels of total ROS and O2·- at early time points of 30-180 min and 24 h, whereas PG (800-1600 μM) increased GSH-depleted cell number at 24 h and reduced GSH levels at 30-180 min. PG downregulated the activity of superoxide dismutase (SOD) and upregulated the activity of catalase in HPF cells. Treatment with 800 μM PG increased the number of apoptotic cells and cells that lost mitochondrial membrane potential (MMP; ΔΨm). NAC treatment attenuated HPF cell death and MMP (ΔΨm) loss induced by PG, accompanied by a decrease in GSH depletion, whereas BSO exacerbated the cell death and MMP (ΔΨm) loss without altering ROS and GSH depletion levels. Furthermore, siRNA against SOD1, SOD2, or catalase attenuated cell death in PG-treated HPF cells, whereas siRNA against GSH peroxidase enhanced cell death. In conclusion, PG induced cell death in HPF cells by increasing ROS levels and depleting GSH. NAC was found to decrease HPF cell death induced by PG, while BSO enhanced cell death. The findings shed light on how manipulating the antioxidant system influence the cytotoxic effects of PG in HPF cells.

Tempol Inhibits the Growth of Lung Cancer and Normal Cells through Apoptosis Accompanied by Increased O2•- Levels and Glutathione Depletion

Tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl) is a stable, cell-permeable redox-cycling nitroxide water-soluble superoxide dismutase (SOD) mimetic agent. However, little is known about its cytotoxic effects on lung-related cells. Thus, the present study investigated the effects of Tempol on cell growth and death as well as changes in reactive oxygen species (ROS) and glutathione (GSH) levels in Calu-6 and A549 lung cancer cells, normal lung WI-38 VA-13 cells, and primary pulmonary fibroblast cells. Results showed that Tempol (0.5~4 mM) dose-dependently inhibited the growth of lung cancer and normal cells with an IC50 of approximately 1~2 mM at 48 h. Tempol induced apoptosis in lung cells with loss of mitochondrial membrane potential (MMP; ∆Ψm) and activation of caspase-3. There was no significant difference in susceptibility to Tempol between lung cancer and normal cells. Z-VAD, a pan-caspase inhibitor, significantly decreased the number of annexin V-positive cells in Tempol-treated Calu-6, A549, and WI-38 VA-13 cells. A 2 mM concentration of Tempol increased ROS levels, including O2•- in A549 and WI-38 VA-13 cells after 48 h, and specifically increased O2•- levels in Calu-6 cells. In addition, Tempol increased the number of GSH-depleted cells in Calu-6, A549, and WI-38 VA-13 cells at 48 h. Z-VAD partially downregulated O2•- levels and GSH depletion in Tempol-treated these cells. In conclusion, treatment with Tempol inhibited the growth of both lung cancer and normal cells via apoptosis and/or necrosis, which was correlated with increased O2•- levels and GSH depletion.

The Anti-Apoptotic Effects of Caspase Inhibitors in Propyl Gallate-Treated Lung Cancer Cells Are Related to Changes in Reactive Oxygen Species and Glutathione Levels

Propyl gallate [3,4,5-trihydroxybenzoic acid propyl ester; PG] exhibits an anti-growth effect in various cells. In this study, the anti-apoptotic effects of various caspase inhibitors were evaluated in PG-treated Calu-6 and A549 lung cancer cells in relation to reactive oxygen species (ROS) and glutathione (GSH) levels. Treatment with 800 μM PG inhibited the proliferation and induced the cell death of both Calu-6 and A549 cells at 24 h. Each inhibitor of pan-caspase, caspase-3, caspase-8, and caspase-9 reduced the number of dead and sub-G1 cells in both PG-treated cells at 24 h. PG increased ROS levels, including O₂^∙−, in both lung cancer cell lines at 24 h. Generally, caspase inhibitors appeared to decrease ROS levels in PG-treated lung cancer cells at 24 h and somewhat reduced O₂^∙− levels. PG augmented the number of GSH-depleted Calu-6 and A549 cells at 24 h. Caspase inhibitors did not affect the level of GSH depletion in PG-treated A549 cells but differently and partially altered the depletion level in PG-treated Calu-6 cells. In conclusion, PG exhibits an anti-proliferative effect in Calu-6 and A549 lung cancer cells and induced their cell death. PG-induced lung cancer death was accompanied by increases in ROS levels and GSH depletion. Therefore, the anti-apoptotic effects of caspase inhibitors were, at least in part, related to changes in ROS and GSH levels.

Mitochondrial Dysfunction in Arsenic-Induced Hepatotoxicity: Pathogenic and Therapeutic Implications

Mitochondria are vital cellular organelles associated with energy production as well as cell signaling pathways. These organelles, responsible for metabolism, are highly abundant in hepatocytes that make them key players in hepatotoxicity. The literature suggests that mitochondria are targeted by various environmental pollutants. Arsenic, a toxic metalloid known as an environmental pollutant, readily contaminates drinking water and exerts toxic effects. It is toxic to various cellular organs; among them, the liver seems to be most affected. A growing body of evidence suggests that within cells, arsenic is highly toxic to mitochondria and reported to cause oxidative stress and alter an array of signaling pathways and functions. Hence, it is imperative to highlight the mechanisms associated with altered mitochondrial functions and integrity in arsenic-induced liver toxicity. This review provides the details of mechanistic aspects of mitochondrial dysfunction in arsenic-induced hepatotoxicity as well as various ameliorative measures undertaken concerning mitochondrial functions.

Imbalanced GSH/ROS and sequential cell death

Reactive oxygen species (ROS) are produced in cells during metabolic processes. Excessive intracellular ROS may react with large biomolecules, such as DNA, RNA, proteins, and small biomolecules, that is, glutathione (GSH) and unsaturated fatty acids. GSH has physiological functions, including free radical scavenging, anti-oxidation, and electrophile elimination. The disruption of ROS/GSH balance results in the deleterious oxidation and chemical modification of biomacromolecules, which eventually leads to cell-cycle arrest and proliferation inhibition, and even induces cell death. Imbalanced ROS/GSH may result from a direct increase of ROS, consumption of GSH, intracellular oxidoreductase interference, or thioredoxin activity reduction. Some chemicals including arsenic trioxide (ATO), pyrogallol (PG), and carbobenzoxy-Leu-Leu-leucinal (MG132) could also disrupt the balance of GSH and ROS. This article reviews the occurrence and consequences of the imbalance between GSH and ROS and introduces factors responsible for the disruption of cellular ROS and GSH balance, resulting in cell death. "GSH" and "ROS" were used as keywords to search the relevant literaturess.

Seed oil of Brucea javanica induces apoptosis through the PI3K/Akt signaling pathway in acute lymphocytic leukemia Jurkat cells

Brucea javanica oil emulsion (BJOE) has been used to treat tumor in China for more than 40 years. However, its components and effectiveness in the treatment of acute lymphocytic leukemia (ALL) and its mechanism of anti-cancer activity remain unknown. In the current study, high-performance liquid chromatography-evaporative light scattering detector (HPLC-ELSD) was used to analyze the components of BJOE. Then, the anti-leukemia effects of BJOE were examined both in vitro and in vivo using ALL Jurkat cells and the p388 mouse leukemia transplant model, respectively. The primary ALL leukemia cells were also used to confirm the anti-leukemia effects of BJOE. The apoptotic-related results indicated that BJOE induced apoptosis in Jurkat cells and were suggestive of intrinsic apoptotic induction. Moreover, BJOE inhibited Akt (protein kinase B) activation and upregulated its downstream targets p53 and FoxO1 (forkhead box gene, group O-1) to initiate apoptosis. The activation of GSK3β was also involved. Our findings demonstrate that BJOE has anti-leukemia effects on ALL cells and can induce apoptosis in Jurkat cells through the phosphoinositide3-kinase (PI3K) /Akt signaling pathway.

Paradoxical effects of arsenic in the lungs

High levels (> 100 ug/L) of arsenic are known to cause lung cancer; however, whether low (≤ 10 ug/L) and medium (10 to 100 ug/L) doses of arsenic will cause lung cancer or other lung diseases, and whether arsenic has dose-dependent or threshold effects, remains unknown. Summarizing the results of previous studies, we infer that low- and medium-concentration arsenic cause lung diseases in a dose-dependent manner. Arsenic trioxide (ATO) is recognized as a chemotherapeutic drug for acute promyelocytic leukemia (APL), also having a significant effect on lung cancer. The anti-lung cancer mechanisms of ATO include inhibition of proliferation, promotion of apoptosis, anti-angiogenesis, and inhibition of tumor metastasis. In this review, we summarized the role of arsenic in lung disease from both pathogenic and therapeutic perspectives. Understanding the paradoxical effects of arsenic in the lungs may provide some ideas for further research on the occurrence and treatment of lung diseases.

Emerging Role and Clinicopathological Significance of AEG-1 in Different Cancer Types: A Concise Review

Tumor breakthrough is driven by genetic or epigenetic variations which assist in initiation, migration, invasion and metastasis of tumors. Astrocyte elevated gene-1 (AEG-1) protein has risen recently as the crucial factor in malignancies and plays a potential role in diverse complex oncogenic signaling cascades. AEG-1 has multiple roles in tumor growth and development and is found to be involved in various signaling pathways of: (i) Ha-ras and PI3K/AKT; (ii) the NF-κB; (iii) the ERK or mitogen-activated protein kinase and Wnt or β-catenin and (iv) the Aurora-A kinase. Recent studies have confirmed that in all the hallmarks of cancers, AEG-1 plays a key functionality including progression, transformation, sustained angiogenesis, evading apoptosis, and invasion and metastasis. Clinical studies have supported that AEG-1 is actively intricated in tumor growth and progression which includes esophageal squamous cell, gastric, colorectal, hepatocellular, gallbladder, breast, prostate and non-small cell lung cancers, as well as renal cell carcinomas, melanoma, glioma, neuroblastoma and osteosarcoma. Existing studies have reported that AEG-1 expression has been induced by Ha-ras through intrication of PI3K/AKT signaling. Conversely, AEG-1 also activates PI3K/AKT pathway and modulates the defined subset of downstream target proteins via crosstalk between the PI3K/AKT/mTOR and Hedgehog signaling cascade which further plays a crucial role in metastasis. Thus, AEG-1 may be employed as a biomarker to discern the patients of those who are likely to get aid from AEG-1-targeted medication. AEG-1 may play as an effective target to repress tumor development, occlude metastasis, and magnify the effectiveness of treatments. In this review, we focus on the molecular mechanism of AEG-1 in the process of carcinogenesis and its involvement in regulation of crosstalk between the PI3K/AKT/mTOR and Hedgehog signaling. We also highlight the multifaceted functions, expression, clinicopathological significance and molecular inhibitors of AEG-1 in various cancer types.

Enhanced cell death effects of MAP kinase inhibitors in propyl gallate-treated lung cancer cells are related to increased ROS levels and GSH depletion

Propyl gallate (PG) has an anti-growth effect in lung cancer cells. The present study investigated the effects of mitogen-activated protein kinase (MAPK; MEK, JNK, and p38) inhibitors on PG-treated Calu-6 and A549 lung cancer cells in relation to cell death as well as reactive oxygen species (ROS) and glutathione (GSH) levels. PG induced cell death in both Calu-6 and A549 lung cancer cells at 24 h, which was accompanied by loss of mitochondrial membrane potential (MMP; ΔΨ_m). All of the tested MAPK inhibitors increased cell death in both PG-treated lung cancer cell lines. In particular, MEK inhibitor strongly enhanced cell death and MMP (ΔΨ_m) loss in PG-treated Calu-6 cells and p38 inhibitor had the same effects in A549 cells as well. PG increased ROS levels and caused GSH depletion in both cell lines at 24 h. MAPK inhibitors increased O₂^•- levels and GSH depletion in PG-treated Calu-6 cells, and JNK and p38 inhibitors increased ROS levels and GSH depletion in PG-treated A549 cells. In conclusion, MAPK inhibitors increased cell death in PG-treated Calu-6 and A549 lung cancer cells. Enhanced cell death and GSH depletion in Calu-6 cells caused by the MEK inhibitor were related to increased O₂^•- levels, and the effects of the p38 inhibitor in A549 cells were correlated with increased general ROS levels.

Arsenic trioxide disturbs the LIS1/NDEL1/dynein microtubule dynamic complex by disrupting the CLIP170 zinc finger in head and neck cancer

Cancer mortality is mainly caused by metastasis, which requires dynamic remodeling of cytoskeletal components such as microtubules. Targeting microtubules presents a promising antimetastatic strategy that could prevent cancer spreading and recurrence. It is known that arsenic trioxide (ATO) is able to inhibit the migration and invasion of solid malignant tumors, but its exact molecular mechanism remains unclear. Here, we report a novel molecular target and antimetastatic mechanism of ATO in head and neck squamous cell carcinoma (HNSCC). We found that cytoplasmic linker protein 170 (CLIP170) was overexpressed in HNSCC tissues and cells compared to normal controls. ATO at non-cytotoxic level (1 μM) inhibited the migration and invasion of HNSCC cells by displacing zinc in the zinc finger motif of CLIP170, which is a key protein that controls microtubule dynamics. The antimetastatic effects of ATO were equivalent to those of siRNA-mediated CLIP170 knockdown. Furthermore, ATO dysregulated microtubule polymerization via the CLIP170/LIS1/NDEL1/dynein signaling pathway in Cal27 cells as a functional consequence of CLIP170 zinc finger disruption. The effect was partially reversed by zinc supplementation. Taken together, these findings reveal that CLIP170 is a novel molecular target of ATO and demonstrate the capability and underlying mechanisms of ATO as a potential antimetastatic agent for HNSCC treatment.

Combination of Arsenic Trioxide and Valproic Acid Efficiently Inhibits Growth of Lung Cancer Cells via G2/M-Phase Arrest and Apoptotic Cell Death

Arsenic trioxide (ATO; As₂O₃) has anti-cancer effects in various solid tumors as well as hematological malignancy. Valproic acid (VPA), which is known to be a histone deacetylase inhibitor, has also anti-cancer properties in several cancer cells including lung cancer cells. Combined treatment of ATO and VPA (ATO/VPA) could synergistically enhance anti-cancer effects and reduce ATO toxicity ATO. In this study, the combined anti-cancer effects of ATO and VPA (ATO/VPA) was investigated in NCI-H460 and NCI-H1299 lung cancer cells in vitro and in vivo. A combination of 3 μM ATO and 3 mM VPA (ATO/VPA) strongly inhibited the growths of both lung cancer cell types. DNA flow cytometry indicated that ATO/VPA significantly induced G2/M-phase arrest in both cell lines. In addition, ATO/VPA strongly increased the percentages of sub-G1 cells and annexin V-FITC positive cells in both cells. However, lactate dehydrogenase (LDH) release from cells was not increased in ATO/VPA-treated cells. In addition, ATO/VPA increased apoptosis in both cell types, accompanied by loss of mitochondrial membrane potential (MMP, ∆Ψm), activation of caspases, and cleavage of anti-poly ADP ribose polymerase-1. Moreover, a pan-caspase inhibitor, Z-VAD, significantly reduced apoptotic cell death induced by ATO/VPA. In the xenograft model, ATO/VPA synergistically inhibited growth of NCI-H460-derived xenograft tumors. In conclusion, the combination of ATO/VPA effectively inhibited the growth of lung cancer cells through G2/M-phase arrest and apoptotic cell death, and had a synergistic antitumor effect in vivo.

A simple model of a growing tumour

This paper presents the CellCycler, a model of a growing tumour which aims to simulate and predict the effect of treatment on xenograft studies or in the clinic. The model, which is freely available as a web application, uses ordinary differential equations (ODEs) to simulate cells as they pass through the phases of the cell cycle. However the guiding philosophy of the model is that it should only use parameters that can be observed or reasonably well approximated. There is no representation of the complex internal dynamics of each cell; instead the level of analysis is limited to cell state observables such as cell phase, apoptosis, and damage. We show that this approach, while limited in many respects, still naturally accounts for a heteregenous cell population with varying doubling time, and closely captures the dynamics of a growing tumour as it is exposed to treatment. The program is demonstrated using three case studies.

A candidate for lung cancer treatment: arsenic trioxide

Arsenic trioxide (ATO), a highly effective drug in treating acute promyelocytic leukemia with low toxicity, demonstrates a significant effect on lung cancer. The anti-cancer mechanisms of ATO include inhibition of cancer stem-like cells, induction of apoptosis, anti-angiogenesis, sensitization of chemotherapy and radiotherapy, anti-cancer effects of hypoxia, and immunoregulation properties. In addition, some studies have reported that different lung cancers respond differently to ATO. It was concluded on numerous studies that the rational combination of administration and encapsulation of ATO have promising potentials in increasing drug efficacy and decreasing adverse drug effects. We reviewed the efficacy of ATO in the treatment of lung cancer in recent years to provide some views for further study.

Ellagic and ferulic acids protect arsenic-induced male reproductive toxicity via regulating Nfe2l2, Ppargc1a and StAR expressions in testis

Arsenic (As) - induced oxidative stress causes male reproductive toxicity apart from its other generalized systemic effects. Some phytochemicals through their antioxidant properties might help to overcome such toxic effects. The aim of the study was to elucidate the protective role of the selected phytochemicals, ellagic and ferulic acids against the As-induced reproductive toxicity. Forty two healthy male Swiss albino mice were randomly assigned to six groups (each @ n = 7). Group A served as the control, while group B received 200 ppm of As through drinking water. The group C and D mice were administered Per os (P.O) with 50 mg/kg BW of ellagic and ferulic acids, respectively on alternate days. Group E or F received 50 mg of ellagic or ferulic acid + 200 ppm of As for forty days. Ellagic and/ ferulic acid significantly reduced the accumulation of As, protein carbonylation (PC), lipid peroxidation (LPO) in addition to altering the antioxidant enzymes (CAT and SOD) activities, reduced glutathione (GSH) and total antioxidant capacity (TAC) in the testicular tissues. A significantly (p < 0.05) altered sperm functions (viability, functional membrane integrity, Δψ_m and sperm kinematics like total motility, rapid, progressive motile and type-A (STR > 80%, ALH > 2.5 μm) and testicular damage induced by the As were ameliorated (p < 0.05) by the phytochemical treatments. These phytochemicals due to their antioxidant activities were found to attenuate the As-induced oxidative stress, testicular damage, and sperm abnormalities via regulating the expressions of Nfe2l2, StAR and Ppargc1a. The study revealed that ellagic and ferulic acids might be potential therapeutic options to protect the male reproductive system from As-poisoning.

Dehydroepiandrosterone reduced lipid droplet accumulation via inhibiting cell proliferation and improving mitochondrial function in primary chicken hepatocytes

Dehydroepiandrosterone (DHEA) possesses fat-reducing effect, while little information is available on whether DHEA regulates cell proliferation and mitochondrial function, which would, in turn, affect lipid droplet accumulation in the broiler. In the present study, the lipid droplet accumulation, cell proliferation, cell cycle and mitochondrial membrane potential were analysis in primary chicken hepatocytes after DHEA treated. The results showed that total area and counts of lipid droplets were significantly decreased in hepatocytes treated with DHEA. The cell viability was significantly increased, while cell proliferation was significantly inhibited in a dose dependent manner in primary chicken hepatocytes after DHEA treated. DHEA treatment significantly increased the cell population in S phase and decreased the population in G2/M in primary chicken hepatocytes. Meanwhile, the cyclin A and cyclin-dependent kinases 2 (CDK2) mRNA abundance were significantly decreased in hepatocytes after DHEA treated. No significant differences were observed in the number of mitochondria, while the mitochondrial membrane permeability and succinate dehydrogenase (SDH) activity were significantly increased in hepatocytes after DHEA treated. In conclusion, our results demonstrated that DHEA reduced lipid droplet accumulation by inhibiting hepatocytes proliferation and enhancing mitochondrial function in primary chicken hepatocytes.

Antioxidants Protect against Arsenic Induced Mitochondrial Cardio-Toxicity

Arsenic is a potent cardiovascular toxicant associated with numerous biomarkers of cardiovascular diseases in exposed human populations. Arsenic is also a carcinogen, yet arsenic trioxide is used as a therapeutic agent in the treatment of acute promyelotic leukemia (APL). The therapeutic use of arsenic is limited due to its severe cardiovascular side effects. Many of the toxic effects of arsenic are mediated by mitochondrial dysfunction and related to arsenic's effect on oxidative stress. Therefore, we investigated the effectiveness of antioxidants against arsenic induced cardiovascular dysfunction. A growing body of evidence suggests that antioxidant phytonutrients may ameliorate the toxic effects of arsenic on mitochondria by scavenging free radicals. This review identifies 21 antioxidants that can effectively reverse mitochondrial dysfunction and oxidative stress in cardiovascular cells and tissues. In addition, we propose that antioxidants have the potential to improve the cardiovascular health of millions of people chronically exposed to elevated arsenic concentrations through contaminated water supplies or used to treat certain types of leukemias. Importantly, we identify conceptual gaps in research and development of new mito-protective antioxidants and suggest avenues for future research to improve bioavailability of antioxidants and distribution to target tissues in order reduce arsenic-induced cardiovascular toxicity in a real-world context.

Protective role of epigallocatechin-3-gallate on arsenic induced testicular toxicity in Swiss albino mice

Arsenic, often referred to as the king of poisons is carcinogenic in humans and animals. It affects multiorgan systems including reproduction. The present study was undertaken to explore the protective role of green tea compound, epigallocatechin-3-gallate (EGCG) on arsenic induced testicular toxicity in Swiss albino mice. Thirty two adult male mice were randomly assigned to four groups (n=8). Group I served as control without test chemical. The group II received arsenic (200ppm) through drinking water, group III received only EGCG (20mg/kgb.wt., intraperitoneally, alternate days) and group IV was administered arsenic+EGCG for 40days. Factorial experimental design was employed to assess the treatment effect. The EGCG restored arsenic induced decrements in epididymal sperm concentration, kinematic attributes (total motility, rapid, progressive motile, fast progressive, VSL, VAP, VCL, BCF, LIN, WOB, STR and Type A), structutal membrane integrity, functional membrane integrity and mitochondrial membrane potential. As evidenced by the histoarchitectural studies, the EGCG reversed the deleterious effects of arsenic on testicular malondialdehyde (p<0.05) levels, reduced glutathione, antioxidative enzymes and spermatogenesis. Overall, the results suggest that EGCG reduces the testicular oxidative stress induced by arsenic poisoning and thereby protect the reproductive system.

Genome-wide transcriptome profiling of genes associated with arsenate toxicity in an arsenic-tolerant rice mutant

The presence of arsenic (As) in polluted environments, such as ground water, affects the accumulation of As in rice grains and causes a serious threat to human health. However, the precise molecular regulations related to As toxicity and tolerance in rice remain largely unknown. In the present study, we developed an arsenic-tolerant type 1 (ATT1) rice mutant by γ-irradiation mutagenesis and performed genome-wide transcriptome analysis for the characterization of As-responsive genes. Toxicity inhibited transcriptional regulation of putative genes involved in photosynthesis, mitochondrial electron transport, and lipid biosynthesis metabolism in wild-type (WT) and ATT1 rice mutant. However, many cysteine biosynthesis-related genes were significantly upregulated in both plants. We also attempted to elucidate the putative genes associated with As tolerance by comparing transcriptomes and identified ATT1-specific transcriptional regulation of genes involved in stress and RNA-protein synthesis. This analysis identified 50 genes that had DNA polymorphisms in upstream regions that differed from those in the exon regions, which suggested that genetic variations in the upstream regions might enhance As tolerance in the mutants. Therefore, the expression profiles of the genes evaluated in this study may improve understanding of the functional roles of As-related genes in response to As tolerance mechanisms and could potentially be used in molecular breeding to limit As accumulation in rice grains.

Plasma metabolomics study of the hepatoprotective effect of glycyrrhetinic acid on realgar-induced sub-chronic hepatotoxicity in mice via 1H NMR analysis

ETHNOPHARMACOLOGICAL RELEVANCE

Realgar, a type of mineral drug that contains arsenic, is concurrently used with Glycyrrhizae Radx et Rhizoma to reduce its toxicity in many Chinese herbal formulations. Glycyrrhetinic acid (GA) is the bioactive ingredient in Glycyrrhizae Radx et Rhizoma. In this study, the protective effects of GA on realgar-induced hepatotoxicity was investigated using ¹H nuclear magnetic resonance (¹H NMR)-based metabolomic approaches.

MATERIALS AND METHODS

Mice were divided into control, GA, realgar, and GA and realgar co-administration groups. Their plasma samples were used for a metabolomics study.

RESULTS

GA can protect the mice against realgar-induced hepatotoxicity to some extent by relieving alterations in the clinical biochemical parameters and the damage to hepatocytes. Metabolic profiling via principal components analysis (PCA) and partial least squares-discriminant analysis (PLS-DA) indicated that the metabolic perturbation caused by realgar was reduced by GA. Six metabolites, including 3-hydroxybutyrate (3-HB), very low density/low density lipoprotein (VLDL/LDL), N-acetylglycoprotein (NAc), lactate, choline and D-glucose, were considered as potential biomarkers that are involved in the toxicity reduction effect of GA on realgar-induced hepatotoxicity. The correlation analysis showed that these potential biomarkers were all positively correlated with ALT and AST activities (correlation coefficient > 0.5). Lipid and energy metabolism pathways were found to be primarily associated with the hepatoprotective effect of GA.

CONCLUSIONS

GA has an effective protection function by regulating the lipid and energy metabolism to liver injuries that are induced by realgar.

Tumour growth-suppressive effect of arsenic trioxide in squamous cell lung carcinoma

Lung squamous cell carcinoma (SCC) is the second most common subtype of non-small cell lung carcinoma. The anticancer effects of arsenic trioxide (ATO) in lung adenocarcinoma and small-cell lung cancer have previously been reported; however its effects in SCC remain unclear. An MTT assay and western blot analysis were performed to determine cell viability and protein expression, respectively, in the SK-MES-1 and SW900 SCC cell lines following treatment with ATO. Phosphatidylserine externalization, mitochondrial membrane depolarization and cell cycle distribution were studied using flow cytometry and the in vivo effects of ATO on tumour growth were investigated with a xenograft model. The results demonstrated that SK-MES-1 and SW900 SCC cells were sensitive to clinically relevant concentrations of ATO. ATO induced apoptosis, mitochondrial membrane depolarization and G₂/M arrest. In addition, treatment with ATO resulted in the downregulation of X-linked inhibitor of apoptosis, B-cell lymphoma-2 (Bcl-2), E2F transcription factor 1 (E2F1), thymidylate synthase and ribonucleotide reductase M1 in addition to the upregulation of Bcl-2 antagonist/killer protein, cleaved poly ADP-ribose polymerase and cleaved caspase 3 in a cell-line specific manner. In the SW900 xenograft model, tumour growth was inhibited by ATO with the formation of apoptotic bodies and downregulation of Bcl-2 and E2F1. In conclusion, ATO suppresses the growth of SCC in vitro and in vivo.

Low dose of arsenic trioxide inhibits multidrug resistant-related P-glycoprotein expression in human neuroblastoma cell line

This study investigated arsenic trioxide (As2O3), cisplatin (DDP) and etoposide (Vp16) on the anticancer effects and P-glycoprotein (P-gp) expression in neuroblastoma (NB) SK-N-SH cells. The potential influence of As2O3, DDP and Vp16 currently included in NB routine treatment protocols on cytotoxicity in SK-N-SH cells was measured by flow cytometry and drug half-maximal inhibitory concentration (IC50) was established. Moreover, chemotherapeutic agent-mediated changes of cellular expression levels of resistant-related P-gp, was monitored using western blotting. The data showed that As2O3, DDP and Vp16 significantly inhibited the growth and survival of the SK-N-SH cells at different concentration. Notably, the levels of apoptosis were upregulated in SK-N-SH cells with an acceleration of the exposure time and the concentration of As2O3, DDP and Vp16. As2O3, DDP and Vp16 were observed with their IC50 values on SK-N-SH cells being 3 µM, 8 and 100 µg/ml, respectively. Flow cytometry analysis showed that As2O3 at low concentrations in SK-N-SH cells led to enhanced accumulation of cell populations in G2/M phase with increasing the exposure time, and increased levels of apoptosis. In contrast, we observed that SK-N-SH cell populations arrested in S phase by DDP and Vp16. In vitro examination revealed that following pretreatment of SK-N-SH cells with As2O3, the expression of P-gp was not increased. The expression of P-gp downregulation were noted following the group treated by As2O3 at 2 and 3 µM. Exposed to As2O3 at 3 µM for 72 h, SK-N-SH cells exhibited lower expression of P-gp than 2 µM As2O3 for 72 h. In contrast, the expression of P-gp was upregulated by DDP and VP16. In summary, SK-N-SH cells were responsive to chemotherapeutic agent-induced apoptosis in a dose-dependent and time-dependent manner. In particular, ours findings showed that low dose of As2O3 markedly reduced the P-gp expression and increased apoptotic cell death in human NB cell line.

Arsenic trioxide induces cell cycle arrest and alters DNA methylation patterns of cell cycle regulatory genes in colorectal cancer cells

AIMS

Cell cycle dysregulation is important in tumorigenesis. Transcriptional silencing of cell cycle regulatory genes, due to DNA methylation, is a common epigenetic event in malignancies. As₂O₃ has been shown to induce cell cycle arrest and also to be a potential hypomethylating agent. Our study aimed to investigate DNA methylation patterns of cell cycle regulatory genes promoters, the effects of Arsenic trioxide (As₂O₃) on the methylated genes and cell cycle distribution in colorectal cancer (CRC) cell lines.

MAIN METHODS

The methylation-specific PCR (MSP) and/or restriction enzyme-based methods were used to study the promoter methylation patterns of 24 cell cycle regulatory genes in CRC cell lines. Gene expression level and cell cycle distribution were determined by Real-time PCR and flow cytometric analyses, respectively.

KEY FINDINGS

Our methylation analysis indicated that only promoters of RBL1 (p107), CHFR and p16 genes were aberrantly methylated in three cell lines. As₂O₃ significantly decreased DNA methylation in promoter regions of these genes and restored their expression. We found that As₂O₃ significantly reduced the expression of DNA methyltransferase 1 (DNMT1) and increased arsenic methyltransferase (AS3MT). Furthermore, As₂O₃ altered transcriptional activity of several unmethylated cell cycle regulatory genes including cyclin B1, E1, D1, GADD45A and p21. Cell cycle flow cytometry analysis showed As₂O₃ induced G2/M arrest in all three cell lines.

SIGNIFICANCE

These data suggest that demethylation and alteration in the expression level of the cell cycle-related genes may be possible mechanisms in As₂O₃-induced cell cycle arrest in colorectal cancer cells.

Impact of arsenic(V) on testicular oxidative stress and sperm functional attributes in Swiss albino mice

The arsenic (As) is a multi system effector including reproduction. The present study examined the association of graded doses of As(V) on testicular microenvironment and sperm function in mice. Thirty-six adult male mice were randomly assigned to six groups (n = 6). Group A served as control without test chemical. The groups B, C, D, E, and F were administered graded doses of 10, 25, 50, 100, and 200 ppm As(V), respectively, through drinking water for 40 days. A dose-dependant significant (P < 0.05) decrements were observed in epididymal sperm kinematic attributes (progressive motility, rapid, fast progressive, VCL, VSL, VAP, LIN, STR, WOB and TYPE A (STR >80 %, ALH 2.5 μm) by CASA), viability, plasma membrane functional integrity, and mitochondrial membrane potential which were associated with insignificant decrease in serum testosterone levels. The histoarchitectural studies of testes showed progressive loss of spermatozoa concentration in the seminiferous tubules as the As(V) dose increased. The mice exposed to As(V) had an increase in the As accumulation, protein carbonylation, and lipid peroxidation levels associated with alterations in SOD, CAT, and GST activities in the testes. In conclusion, higher doses of As(V) (more than 50 ppm) were found to be testicular toxicants which impaired semen quality by inducing oxidative stress in the testicular microenvironment.

Monomethylarsonous acid, but not inorganic arsenic, is a mitochondria-specific toxicant in vascular smooth muscle cells

Arsenic exposure has been implicated as a risk factor for cardiovascular diseases, metabolic disorders, and cancer, yet the role mitochondrial dysfunction plays in the cellular mechanisms of pathology is largely unknown. To investigate arsenic-induced mitochondrial dysfunction in vascular smooth muscle cells (VSMCs), we exposed rat aortic smooth muscle cells (A7r5) to inorganic arsenic (iAs(III)) and its metabolite monomethylarsonous acid (MMA(III)) and compared their effects on mitochondrial function and oxidative stress. Our results indicate that MMA(III) is significantly more toxic to mitochondria than iAs(III). Exposure of VSMCs to MMA(III), but not iAs(III), significantly decreased basal and maximal oxygen consumption rates and concomitantly increased compensatory extracellular acidification rates, a proxy for glycolysis. Treatment with MMA(III) significantly increased hydrogen peroxide and superoxide levels compared to iAs(III). Exposure to MMA(III) resulted in significant decreases in mitochondrial ATP, aberrant perinuclear clustering of mitochondria, and decreased mitochondrial content. Mechanistically, we observed that mitochondrial superoxide and hydrogen peroxide contribute to mitochondrial toxicity, as treatment of cells with MnTBAP (a mitochondrial superoxide dismutase mimetic) and catalase significantly reduced mitochondrial respiration deficits and cell death induced by both arsenic compounds. Overall, our data demonstrates that MMA(III) is a mitochondria-specific toxicant that elevates mitochondrial and non-mitochondrial sources of ROS.

Dehydroepiandrosterone inhibits cell proliferation and improves viability by regulating S phase and mitochondrial permeability in primary rat Leydig cells

Dehydroepiandrosterone (DHEA) is widely used as a nutritional supplement and exhibits putative anti-aging properties. However, the molecular basis of the actions of DHEA, particularly on the biological characteristics of target cells, remain unclear. The aim of the current study was to investigate the effects of DHEA on cell viability, cell proliferation, cell cycle and mitochondrial function in primary rat Leydig cells. Adult Leydig cells were purified by Percoll gradient centrifugation, and cell proliferation was detected using a Click-iT^® EdU Assay kit and cell cycle assessment performed using flow cytometry. Mitochondrial membrane potential was detected using JC-1 staining assay. The results of the current study demonstrate that DHEA decreased cell proliferation in a dose-dependent manner, whereas it improved cell viability in a time-dependent and dose-dependent manner. Flow cytometry analysis demonstrated that DHEA treatment increased the S phase cell population and decreased the G2/M cell population. Cyclin A and CDK2 mRNA levels were decreased in primary rat Leydig cells following DHEA treatment. DHEA treatment decreased the transmembrane electrical gradient in primary Leydig cells, whereas treatment significantly increased succinate dehydrogenase activity. These results indicated that DHEA inhibits primary rat Leydig cell proliferation by decreasing cyclin mRNA level, whereas it improves cells viability by modulating the permeability of the mitochondrial membrane and succinate dehydrogenase activity. These findings may demonstrate an important molecular mechanism by which DHEA activity is mediated.

Targeting hedgehog signalling by arsenic trioxide reduces cell growth and induces apoptosis in rhabdomyosarcoma

Rhabdomyosarcomas (RMS) are soft tissue tumours treated with a combination of surgery and chemotherapy. However, mortality rates remain high in case of recurrences and metastatic disease due to drug resistance and failure to undergo apoptosis. Therefore, innovative approaches targeting specific signalling pathways are urgently needed. We analysed the impact of different hedgehog (Hh) pathway inhibitors on growth and survival of six RMS cell lines using MTS assay, colony formation assay, 3D spheroid cultures, flow cytometry and western blotting. Especially the glioma-associated oncogene family (GLI) inhibitor arsenic trioxide (ATO) effectively reduced viability as well as clonal growth and induced cell death in RMS cell lines of embryonal, alveolar and sclerosing, spindle cell subtype, whereas normal skeletal muscle cells were hardly compromised by ATO. Combination of ATO with itraconazole potentiated the reduction of colony formation and spheroid size. These results show that ATO is a promising substance for treatment of relapsed and refractory RMS by directly targeting GLI transcription factors. The combination with itraconazole or other chemotherapeutic drugs has the opportunity to enforce the treatment efficiency of resistant and recurrent RMS.

Rat Liver Mitochondrial Dysfunction Induced by an Organic Arsenical Compound 4-(2-Nitrobenzaliminyl) Phenyl Arsenoxide

Arsenic is successfully used in cancer chemotherapy and several cancer treatments on account of its apoptogenic effects. However, it is environmentally hazardous with potential for toxicity when distributed in the soil, water, and food, and long exposure to water contaminated with Arsenic may induce cancers. Some research studies have reported that liver is the storage site and an important target organ for Arsenic toxicity. In the present work, a new kind of organic arsenic compound, 4-(2-nitrobenzaliminyl) phenyl arsenoxide (NPA), was synthesized, and its potential involvement of mitochondria was explored. The results presented that the toxicology of NPA, at least in part, mediated mitochondrial function and may thoroughly destroy mitochondrial membrane physiological functions. NPA induced mitochondrial permeability transition pore (mtPTP) opening that induces mitochondrial biochemical abnormalities as evidenced by mitochondrial swelling, mitochondrial membrane potential breakdown, membrane fluidity alterations, and the strikingly remarkable protection of CsA. Meanwhile, both the decreased respiration rate of state 4 and the increased inner membrane H(+) permeabilization revealed that the inner membrane function regarding important energy production chain was destroyed. The toxicity of NPA is due to its interaction with mitochondrial membrane thiol protein. This conclusion is based on the protective effects of RR, DTT, and MBM(+).

ANXA1 silencing increases the sensitivity of cancer cells to low-concentration arsenic trioxide treatment by inhibiting ERK MAPK activation

AIMS AND BACKGROUND

Arsenic trioxide (ATO), an antitumor agent, is widely used for treating acute promyelocytic leukemia (APL), in which it induces apoptosis. In most solid tumors, ATO disturbs the cell cycle instead of inducing apoptosis. We aimed to determine the exact mechanism underlying the different response of APL to ATO compared with the response of solid tumors.

METHODS

A proteomics-based screening was used to identify the ATO-associated proteins in the human esophageal squamous cell carcinoma cell line, Eca109. The expression levels of Annexin A1 (ANXA1) in 4 different types of cancer cells were determined by quantitative reverse transcription polymerase chain reaction and Western blotting. Human esophageal squamous cell carcinoma cell line Eca109 and pancreatic carcinoma cell line BxPC3 cells were transfected with siRNAs targeting ANXA1 and scrambled control siRNA. Cell proliferation was evaluated by methyl thiazolyl tetrazolium assay.

RESULTS

After verification of the mRNA and protein levels in 4 cancer cell lines, ANXA1 and lamin A/B were validated to have increased expression levels after low-concentration ATO treatment. Lower concentrations of ATO, which has no effect on proliferation of cancer cells, induced apoptosis after ANXA1 silencing. Furthermore, overexpression of ANXA1 induced by ATO resulted in activation of extracellular signal-regulated kinase (ERK) mitogen-activated protein kinases (MAPKs), rendering cancer cells resistant to the agent. In addition, PD98059, a specific ERK inhibitor, increased the sensitivity of cancer cells to a lower concentration of ATO treatment.

CONCLUSIONS

Taken together, these data indicate that overexpression of ANXA1 induced by low-concentration ATO makes cancer cells more resistant to the agent via activated ERK MAPKs. Specific silencing of ANXA1 increased the sensitivity of cancer cells to ATO treatment.

Fibroblast growth factor (FGF21) protects mouse liver against D-galactose-induced oxidative stress and apoptosis via activating Nrf2 and PI3K/Akt pathways

FGF21 is recently discovered with pleiotropic effects on glucose and lipid metabolism. However, the potential protective effect of FGF21 against D-gal-induced injury in the liver has not been demonstrated. The aim of this study is to investigate the pathophysiological role of FGF21 on hepatic oxidative injury and apoptosis in mice induced by D-gal. The 3-month-old Kunming mice were subcutaneously injected with D-gal (180 mg kg(-1) d(-1)) for 8 weeks and administered simultaneously with FGF21 (5 or 1 mg kg(-1) d(-1)). Our results showed that the administration of FGF21 significantly alleviated histological lesion including structure damage, degeneration, and necrosis of hepatocytes induced by D-gal, and attenuated the elevation of liver injury markers, serum AST, and ALP in a dose-dependent manner. FGF21 treatment also suppressed D-gal-induced profound elevation of ROS production and oxidative stress, as evidenced by an increase of the MDA level and depletion of the intracellular GSH level in the liver, and restored the activities of antioxidant enzymes SOD, CAT, GSH-Px, and T-AOC. Moreover, FGF21 treatment increased the nuclear abundance of Nrf2 and subsequent up regulation of several antioxidant genes. Furthermore, a TUNEL assay showed that D-gal-induced apoptosis in the mouse liver was significantly inhibited by FGF21. The expression of caspase-3 was markedly inhibited by the treatment of FGF21 in the liver of D-gal-treated mice. The levels of PI3K and PBK/Akt were also largely enhanced, which in turn inactivated pro-apoptotic signaling events, restoring the balance between pro- and anti-apoptotic Bcl-2 and Bax proteins in the liver of D-gal-treated mice. In conclusion, these results suggest that FGF21 protects the mouse liver against D-gal-induced hepatocyte oxidative stress via enhancing Nrf2-mediated antioxidant capacity and apoptosis via activating PI3K/Akt pathway.

Radioprotective activity of neutral polysaccharides isolated from the fruiting bodies of Hohenbuehelia serotina

In this study, the radioprotective effect of neutral polysaccharides from Hohenbuehelia serotina (NTHSP) against the damages induced by (60)Co-γ radiation was investigated. The results showed that NTHSP could significantly improve the activity of glutathione peroxidase (GSH-Px) and increase the contents of glutathione (GSH) and ceruloplasmin in plasma after treated with 6 Gy-radiation compared with the radiation controls (p < 0.05). Furthermore, administration with NTHSP could effectively increase the quantity of marrow DNA (p < 0.05) and reduce the rates of chromosome aberration and micronuclei (p < 0.01) in bone marrows of mice. In addition, NTHSP could markedly inhibit the expressions of Bax protein and promote the expressions of Bcl-2 protein, accordingly inhibit the releases of cytochrome c and expressions of activated Caspase-3, and therefore block the mitochondrial apoptotic pathway of splenocytes in mice induced by (60)Co-γ radiation. These results suggested that NTHSP might be a natural radioprotective agent against the injuries induced by radiation.

E2F1 downregulation by arsenic trioxide in lung adenocarcinoma

Lung cancer is one of the most common cancers worldwide. Arsenic trioxide (ATO) has been approved by the US Food and Drug Administration for the treatment of acute promyelocytic leukemia. Nonetheless preliminary data have suggested potential activity of ATO in solid tumors including lung cancer. This study aimed to examine the underlying mechanisms of ATO in the treatment of lung adenocarcinoma. Using a panel of 7 lung adenocarcinoma cell lines, the effects of ATO treatment on cell viability, expression of E2F1 and its downstream targets, phosphatidylserine externalization, mitochondrial membrane depolarization and alteration of apoptotic/anti-apoptotic factors were studied. Tumor growth inhibition in vivo was investigated using a nude mouse xenograft model. ATO decreased cell viability with clinically achievable concentrations (8 µM) in all cell lines investigated. This was accompanied by reduced expression of E2F1, cyclin A2, skp2, c-myc, thymidine kinase and ribonucleotide reductase M1, while p-c-Jun was upregulated. Cell viability was significantly decreased with E2F1 knockdown. Treatment with ATO resulted in phosphatidylserine externalization in H23 cells and mitochondrial membrane depolarization in all cell lines, associated with truncation of Bid, downregulation of Bcl-2, upregulation of Bax and Bak, caspase-9 and -3 activation and PARP cleavage. Using the H358 xenograft model, the tumor growth was suppressed in the ATO treatment group during 8 days of treatment, associated with downregulation of E2F1 and upregulation of truncated Bid and cleaved caspase-3. In conclusion, ATO has potent in vitro and in vivo activity in lung adenocarcinoma, partially mediated through E2F1 downregulation and apoptosis.

Inactivation of Akt by arsenic trioxide induces cell death via mitochondrial-mediated apoptotic signaling in SGC-7901 human gastric cancer cells

Arsenic trioxide (As2O3) has been recognized as a potential chemotherapeutic agent, yet the details concerning its mechanism of action in solid cancers remain undetermined. The present study assessed the role of Akt in the cell death induced by As2O3. The MTT assay showed that As2O3 suppressed the proliferation of SGC-7901 cells in a dose- and time-dependent manner. Characteristic apoptotic changes were observed in the As2O3‑treated cells by Hoechst 33342 staining, and FACS analysis showed that As2O3 caused dose-dependent apoptotic cell death. As2O3 activated caspase-3 and -9, and PARP cleavage in a dose-dependent manner. Compromised mitochondrial membrane potential and an increased protein level of Bax indicated involvement of mitochondia. As2O3 decreased the levels of p-Akt (Ser473), p-Akt (Thr308) and p-GSK-3β (Ser9), suggesting that As2O3 inactivated Akt kinase. In addition, LY294002 (a PI3 kinase inhibitor) augmented the apoptosis induced by As2O3. These results demonstrated that inhibition of PI3K/Akt signaling was involved in As2O3-induced apoptosis of gastric cancer SGC-7901 cells.

Endoplasmic reticulum stress-mediated apoptosis in imatinib-resistant leukemic K562-r cells triggered by AMN107 combined with arsenic trioxide

The first tyrosine kinase inhibitor (TKI) imatinib mesylate (imatinib) targets the kinase domain of BCR-ABL and induces apoptosis in newly diagnosed chronic myeloid leukaemia (CML). However, resistant and relapse are common problems in imatinib-treated patients. Although second-generation TKI such as AMN107 appears to improve the treatment of CML, TKI resistance and relapse are also frequently occurred in the patients. To test whether arsenic trioxide (ATO) could potentiate the efficacy of AMN107 in imatinib-resistant cells, we conducted a series of assays in TKI-resistant K562-r cells treated with AMN107 and ATO. Based on a time-course cDNA microarray analysis, we found many genes typically involved in the endoplasmic reticulum (ER) stress signalling were significantly up-regulated, implicating the occurrence of ER stress-mediated apoptosis in K562-r cells treated with the combination of ATO and AMN107. Such implication was also supported by the data showing the activation of members in the JNK pathway, which are known to be characteristic markers bridging ER-stress and apoptosis. Partial knock-down of the JNK activities alleviated the effects of apoptosis (p < 0.05) triggered by combining AMN107 with ATO. In conclusion, this study for the first time demonstrates a synergistic effect of AMN107 with ATO, allowing insights into the possible mechanisms underlying imatinib-induced resistance in CML. Our data also suggest that combination of AMN107 with ATO may represent a new strategy for the treatment of imatinib-resistant CML patients.

Asperolide A, a marine-derived tetranorditerpenoid, induces G2/M arrest in human NCI-H460 lung carcinoma cells, is mediated by p53-p21 stabilization and modulated by Ras/Raf/MEK/ERK signaling pathway

Here we first demonstrate that asperolide A, a very recently reported marine-derived tetranorditerpenoid, leads to the inhibition of NCI-H460 lung carcinoma cell proliferation by G2/M arrest with the activation of the Ras/Raf/MEK/ERK signaling and p53-dependent p21 pathway. Treatment with 35 μM asperolide A (2 × IC₅₀) resulted in a significant increase in the proportion of G2/M phase cells, about a 2.9-fold increase during 48 h. Immunoblot assays demonstrated time-dependent inhibition of G2/M regulatory proteins. Moreover, asperolide A significantly activated MAP kinases (ERK1/2, JNK and p38 MAP kinase) by phosphorylation, and only the inhibition of ERK activation by PD98059 reversed downregulation of G2/M regulatory proteins CDC2, and suppressed upregulation of p21 and p-p53 levels. Transfection of cells with dominant-negative Ras (RasN17) mutant genes up-regulated asperolide A-induced the decrease of cyclin B1 and CDC2, suppressed Raf, ERK activity and p53-p21 expression, and at last, abolished G2/M arrest. This study indicates that asperolide A-induced G2/M arrest in human NCI-H460 lung carcinoma cells relys on the participation of the Ras/Raf/MEK/ERK signaling pathway in p53-p21 stabilization. An in vivo study with asperolide A illustrated a marked inhibition of tumor growth, and little toxcity compared to Cisplatin therapy. Overall, these findings provide potential effectiveness and a theoretical basis for the therapeutic use of asperolide A in the treatment of malignancies.

AEG-1 expression characteristics in human non-small cell lung cancer and its relationship with apoptosis

Expression of astrocyte-elevated gene-1 (AEG-1), a novel oncoprotein, has been shown to promote cell growth and inhibit apoptosis, but the underlying molecular mechanisms and its functional significance in non-small cell lung cancer (NSCLC) remain to be elucidated. In the present study, statistical analysis displayed a significant correlation of AEG-1 expression with clinical staging (P = 0.048), differentiation (P = 0.019) and lymph node metastasis (P = 0.032). Simultaneously, the overall survival time in patients with higher AEG-1 expression was obviously shorter than that in patients with lower expression of AEG-1 (P < 0.001). Furthermore, we found that AEG-1 could inhibit apoptotic cell death in L-78 cells, as assessed by MTT, TUNEL and flow cytometry assay. After treating L-78 cells with AEG-1 siRNA, caspase-3 protein was significantly up-regulated and Bcl-2 protein was markedly decreased in L-78 cells, which was verified by the immunohistochemistry results about AEG-1, caspase-3 and Bcl-2. Furthermore, PI3K p110 protein and phosphorylated Akt were also largely attenuated by the treatment of AEG-1 siRNA. In conclusion, our results indicated that AEG-1 played a crucial role in the carcinogenesis of NSCLC and could inhibit apoptosis via activating cell survival signaling (enhancing the level of anti-apoptotic protein Bcl-2 and the activation of PI3K/Akt pathway).

Effect of dehydroepiandrosterone on cell growth and mitochondrial function in TM-3 cells

Dehydroepiandrosterone (DHEA), a major steroid hormone, decreases with age, and this reduction has been shown to be associated with physical health. In the present study, the effect of DHEA on cell growth and mitochondrial function was investigated using TM-3 cells, a Leydig cell line. The growth of TM-3 cells exposed to 100 μM DHEA for 24h was inhibited due to cell cycle arrest, primarily in the S and G2/M phases, and this effect was caused by decreased activity of glucose-6-phosphate dehydrogenase (G6PD) and reduced expression of cyclinA and cyclinB mRNA. A novel finding was that DHEA improved TM-3 cell viability in a markedly time-dependent manner. Although no differences were observed in the configuration or number of TM-3 cell mitochondria following DHEA treatment, mitochondrial membrane permeability and the activity of succinate dehydrogenase (SDH) increased subsequent to 24h treatment of cells with 100 μM DHEA. Overall, the data demonstrate that DHEA inhibited TM-3 cell growth by decreasing G6PD activity and the expression of cyclin mRNAs, whereas it improved TM-3 cell viability by increasing mitochondrial membrane permeability and the activity of SDH. This could be one of mechanisms of DHEA exerts its biological function.

Oridonin nanosuspension was more effective than free oridonin on G2/M cell cycle arrest and apoptosis in the human pancreatic cancer PANC-1 cell line

Oridonin, a diterpenoid isolated from Rabdosia rubescencs, has been reported to have antitumor effects. However, low solubility has limited its clinical applications. Preparation of drugs in the form of nanosuspensions is an extensively utilized protocol. In this study, we investigated the anticancer activity of oridonin and oridonin nanosuspension on human pancreatic carcinoma PANC-1 cells. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was performed to investigate the effect of oridonin on cell growth. Propidium iodide and Hoechst 33342 staining were used to detect morphologic changes. The percentage of apoptosis and cell cycle progression was determined by flow cytometric method staining with propidium iodide. Annexin V-fluorescein isothiocyanate (FITC)/PI staining was used to evaluate cell apoptosis by flow cytometry. Caspase-3 activity was measured by spectrophotometry. The apoptotic and cell cycle protein expression were determined by Western blot analysis. Both oridonin and oridonin nanosuspension induced apoptosis and G₂/M phase cell cycle arrest, and the latter had a more significant cytotoxic effect. The ratio of Bcl-2/Bax protein expression was decreased and caspase- 3 activity was stimulated. The expression of cyclin B1 and p-cdc2 (T161) was suppressed. Our results showed that oridonin nanosuspension was more effective than free oridonin on G₂/M cell cycle arrest and apoptosis in the human pancreatic cancer PANC-1 cell line.

Enhanced suppression of tumor growth by concomitant treatment of human lung cancer cells with suberoylanilide hydroxamic acid and arsenic trioxide

The efficacy of arsenic trioxide (ATO) against acute promyelocytic leukemia (APL) and relapsed APL has been well documented. ATO may cause DNA damage by generating reactive oxygen intermediates. Suberoylanilide hydroxamic acid (SAHA), a histone deacetylase inhibitor, modulates gene and protein expression via histone-dependent or -independent pathways that may result in chromatin decondensation, cell cycle arrest, differentiation, and apoptosis. We investigated whether ATO and SAHA act synergistically to enhance the death of cancer cells. Our current findings showed that combined treatment with ATO and SAHA resulted in enhanced suppression of non-small-cell lung carcinoma in vitro in H1299 cells and in vivo in a xenograft mouse model. Flow cytometric analysis of annexin V+ cells showed that apoptotic cell death was significantly enhanced after combined treatment with ATO and SAHA. At the doses used, ATO did not interfere with cell cycle progression, but SAHA induced p21 expression and led to G1 arrest. A Comet assay demonstrated that ATO, but not SAHA, induced DNA strand breaks in H1299 cells; however, co-treatment with SAHA significantly increased ATO-induced DNA damage. Moreover, SAHA enhanced acetylation of histone H3 and sensitized genomic DNA to DNase I digestion. Our results suggest that SAHA may cause chromatin relaxation and increase cellular susceptibility to ATO-induced DNA damage. Combined administration of SAHA and ATO may be an effective approach to the treatment of lung cancer.

Anticancer activity of metal complexes: involvement of redox processes

Cells require tight regulation of the intracellular redox balance and consequently of reactive oxygen species for proper redox signaling and maintenance of metal (e.g., of iron and copper) homeostasis. In several diseases, including cancer, this balance is disturbed. Therefore, anticancer drugs targeting the redox systems, for example, glutathione and thioredoxin, have entered focus of interest. Anticancer metal complexes (platinum, gold, arsenic, ruthenium, rhodium, copper, vanadium, cobalt, manganese, gadolinium, and molybdenum) have been shown to strongly interact with or even disturb cellular redox homeostasis. In this context, especially the hypothesis of "activation by reduction" as well as the "hard and soft acids and bases" theory with respect to coordination of metal ions to cellular ligands represent important concepts to understand the molecular modes of action of anticancer metal drugs. The aim of this review is to highlight specific interactions of metal-based anticancer drugs with the cellular redox homeostasis and to explain this behavior by considering chemical properties of the respective anticancer metal complexes currently either in (pre)clinical development or in daily clinical routine in oncology.

Arsenic trioxide induces human pulmonary fibroblast cell death via the regulation of Bcl-2 family and caspase-8

Arsenic trioxide (ATO; As(2)O(3)) can induce apoptotic cell death in various cancer cells including lung cancer cells. However, little is known about the toxicological effects of ATO on normal primary lung cells. In this study, we investigated the cellular effects of ATO on human pulmonary fibroblast (HPF) cells in relation to cell growth inhibition and death. ATO inhibited HPF cell growth with an IC(50) of approximately 30-40 μM at 24 h and induced cell death accompanied by the loss of mitochondrial membrane potential (MMP; ΔΨ(m)). Thus, HPF cells were considered to be very resistant to ATO insults. ATO increased the expression of p53 protein and decreased that of Bcl-2 protein. This agent activated caspase-8 but not caspase-3 in HPF cells. Z-VAD (a pan-caspase inhibitor; 15 μM) did not significantly decrease cell growth inhibition, death and MMP (ΔΨ(m)) loss by ATO. Moreover, administration of Bax or casase-8 siRNA attenuated HPF cell death by ATO whereas p53 or caspase-3 siRNAs did not affect cell death. In conclusion, HPF cells were resistant to ATO and higher doses of ATO induced the growth inhibition and death in HPF cells via the regulation of Bcl-2 family and caspase-8.

Arsenic-induced oxidative stress and its reversibility

This review summarizes the literature describing the molecular mechanisms of arsenic-induced oxidative stress, its relevant biomarkers, and its relation to various diseases, including preventive and therapeutic strategies. Arsenic alters multiple cellular pathways including expression of growth factors, suppression of cell cycle checkpoint proteins, promotion of and resistance to apoptosis, inhibition of DNA repair, alterations in DNA methylation, decreased immunosurveillance, and increased oxidative stress, by disturbing the pro/antioxidant balance. These alterations play prominent roles in disease manifestation, such as carcinogenicity, genotoxicity, diabetes, cardiovascular and nervous systems disorders. The exact molecular and cellular mechanisms involved in arsenic toxicity are rather unrevealed. Arsenic alters cellular glutathione levels either by utilizing this electron donor for the conversion of pentavalent to trivalent arsenicals or directly binding with it or by oxidizing glutathione via arsenic-induced free radical generation. Arsenic forms oxygen-based radicals (OH(•), O(2)(•-)) under physiological conditions by directly binding with critical thiols. As a carcinogen, it acts through epigenetic mechanisms rather than as a classical mutagen. The carcinogenic potential of arsenic may be attributed to activation of redox-sensitive transcription factors and other signaling pathways involving nuclear factor κB, activator protein-1, and p53. Modulation of cellular thiols for protection against reactive oxygen species has been used as a therapeutic strategy against arsenic. N-acetylcysteine, α-lipoic acid, vitamin E, quercetin, and a few herbal extracts show prophylactic activity against the majority of arsenic-mediated injuries in both in vitro and in vivo models. This review also updates the reader on recent advances in chelation therapy and newer therapeutic strategies suggested to treat arsenic-induced oxidative damage.