The cell cycle related apoptotic susceptibility to arsenic trioxide is associated with the level of reactive oxygen species

Cold-Responsive Hyaluronated Upconversion Nanoplatform for Transdermal Cryo-Photodynamic Cancer Therapy

Cryotherapy leverages controlled freezing temperature interventions to engender a cascade of tumor-suppressing effects. However, its bottleneck lies in the standalone ineffectiveness. A promising strategy is using nanoparticle therapeutics to augment the efficacy of cryotherapy. Here, a cold-responsive nanoplatform composed of upconversion nanoparticles coated with silica - chlorin e6 - hyaluronic acid (UCNPs@SiO2-Ce6-HA) is designed. This nanoplatform is employed to integrate cryotherapy with photodynamic therapy (PDT) in order to improve skin cancer treatment efficacy in a synergistic manner. The cryotherapy appeared to enhance the upconversion brightness by suppressing the thermal quenching. The low-temperature treatment afforded a 2.45-fold enhancement in the luminescence of UCNPs and a 3.15-fold increase in the photodynamic efficacy of UCNPs@SiO2-Ce6-HA nanoplatforms. Ex vivo tests with porcine skins and the subsequent validation in mouse tumor tissues revealed the effective HA-mediated transdermal delivery of designed nanoplatforms to deep tumor tissues. After transdermal delivery, in vivo photodynamic therapy using the UCNPs@SiO2-Ce6-HA nanoplatforms resulted in the optimized efficacy of 79% in combination with cryotherapy. These findings underscore the Cryo-PDT as a truly promising integrated treatment paradigm and warrant further exploring the synergistic interplay between cryotherapy and PDT with bright upconversion to unlock their full potential in cancer therapy.

Bradykinin/bradykinin 1 receptor promotes brain microvascular endothelial cell permeability and proinflammatory cytokine release by downregulating Wnt3a

Stroke is a life-threatening disease with limited therapeutic options. Damage to the blood-brain barrier (BBB) is the key pathological feature of ischemic stroke. This study explored the role of the bradykinin (BK)/bradykinin 1 receptor (B1R) and its mechanism of action in the BBB. Human brain microvascular endothelial cells (BMECs) were used to test for cellular responses to BK by using the Cell Counting Kit-8 assay, 5-ethynyl-2'-deoxyuridine staining, enzyme-linked immunosorbent assay, flow cytometry, immunofluorescence, cellular permeability assays, and western blotting to evaluate cell viability, cytokine production, and reactive oxygen species (ROS) levels in vitro. A BBB induced by middle cerebral artery occlusion was used to evaluate BBB injuries, and the role played by BK/B1R in ischemic/reperfusion (I/R) was explored in a rat model. Results showed that BK reduced the viability of BMECs and increased the levels of proinflammatory cytokines (interleukin 6 [IL-6], IL-18, and monocyte chemoattractant protein-1) and ROS. Additionally, cellular permeability was increased by BK treatment, and the expression of tight junction proteins (claudin-5 and occludin) was decreased. Interestingly, Wnt3a expression was inhibited by BK and exogenous Wnt3a restored the effects of BK on BMECs. In an in vivo I/R rat model, knockdown of B1R significantly decreased infarct volume and inflammation in I/R rats. Our results suggest that BK might be a key inducer of BBB injury and B1R knockdown might provide a beneficial effect by upregulating Wnt3a.

Convection enhanced delivery of light responsive antigen capturing oxygen generators for chemo-phototherapy triggered adaptive immunity

In recent years, combination therapy has emerged as the cornerstone of clinical practice in treating glioblastoma multiforme. However, their ability to trigger and leverage the body's adaptive immunity has rarely been studied. Tumour heterogeneity, the presence of the blood-brain barrier, and an immunosuppressive tumor microenvironment play a crucial role in the 90% local tumor recurrence post-treatment. Herein, we report an improved combination therapy approach capable of stimulating an immune response that utilizes Light responsive antigen-capturing oxygen generators (LAGs). The engineered LAGs loaded with a non-genotoxic molecule, Nutlin-3a, and a photosensitizer, Protoporphyrin IX, can release the payload on-demand when exposed to light of a specific wavelength. The in-situ oxygen generation capability of LAGs enables tumor oxygenation enhancement, thereby alleviating the tumor hypoxia and enhancing the efficacy of chemo-photodynamic therapy. Furthermore, by modulating the surface properties of LAGs, we demonstrated that the tumor-derived protein antigens released can be captured and retained in-situ, which improves antigen uptake and presentation by the antigen-presenting cells. Dual drug-loaded LAGs (DD-LAGs) upregulated the expression of cell surface CD83 maturation and CD86 costimulatory markers on monocyte-derived-dendritic cells, suggesting intrinsic immune adjuvancy. In the presence of 3D printed hypoxic U87 spheroids (h-U87), DD-LAGs induced cancer cell death, upregulated IL-1β, and downregulated IL-10 resulting in CD3⁺, helper CD4⁺, and cytotoxic CD8⁺ proliferation. Finally, we have investigated convection-enhanced delivery as a potential route of administration for DD-LAGs. Our work presents a novel strategy to induce tumor cell death both during and post-treatment, thereby reducing the possibility of recurrence.

Full-Process Radiosensitization Based on Nanoscale Metal-Organic Frameworks

Full-process radiosensitization, that is, pre-increasing radiation sensitivity of cancer cells, magnifying •OH formation during ionizing irradiation, and intervention on the resultant DNA repair for final cells death, could enhance the overall radiotherapeutic effects, but has not yet been achieved. Herein, Hf-nMOFs with Fe³⁺ ions uniformly dispersed (Hf-BPY-Fe) were constructed to integratedly improve radiotherapeutic effects via a multifaceted mechanism. The in vitro experiments demonstrated that persistent reactive oxygen species stress from Hf-BPY-Fe-activated in situ Fenton reaction reassorted cell cycle distribution, consequently contributing to increased tumoral radiosensitivity to photon radiation. Upon irradiation during the course of radiation therapy, Hf⁴⁺ in Hf-BPY-Fe gave substantial amounts of high-energy electrons, which partially converted H₂O to •OH and, meanwhile, relaxed to a low-energy state in nMOF pores, leading to an electron-rich environment. These aggregated electrons facilitated the reduction from Fe³⁺ to Fe²⁺ and further promoted the production of •OH in the Fenton process to attack DNA. The Hf-BPY-Fe postponed the DNA damage response process by interfering with certain proteins involved in the DNA repair signaling pathway. The in vivo experiments showed improved radiotherapeutic effects from integrated contributions from Fe³⁺-based Fenton reaction and Hf⁴⁺-induced X-ray energy conversion in tumors. This work provides a nMOFs-based full-process radiosensitizing approach for better radiotherapeutic efficacy.

Proteomics and phosphoproteomics study of LCMT1 overexpression and oxidative stress: overexpression of LCMT1 arrests H2O2-induced lose of cells viability

Objectives: Protein phosphatase 2A (PP2A), a major serine/threonine phosphatase, is also known to be a target of ROS. The methylation of PP2A can be catalyzed by leucine carboxyl methyltransferase-1 (LCMT1), which regulates PP2A activity and substrate specificity.

Methods: In the previous study, we have showed that LCMT1-dependent PP2Ac methylation arrests H₂O₂-induced cell oxidative stress damage. To explore the possible protective mechanism, we performed iTRAQ-based comparative quantitative proteomics and phosphoproteomics studies of H₂O₂-treated vector control and LCMT1-overexpressing cells.

Results: A total of 4480 non-redundant proteins and 3801 unique phosphopeptides were identified by this means. By comparing the H₂O₂-regulated proteins in LCMT1-overexpressing and vector control cells, we found that these differences were mainly related to protein phosphorylation, gene expression, protein maturation, the cytoskeleton and cell division. Further investigation of LCMT1 overexpression-specific regulated proteins under H₂O₂ treatment supported the idea that LCMT1 overexpression induced ageneral dephosphorylation of proteins and indicated increased expression of non-erythrocytic hemoglobin, inactivation of MAPK3 and regulation of proteins related to Rho signal transduction, which were known to be linked to the regulation of the cytoskeleton.

Discussion: These data provide proteomics and phosphoproteomics insights into the association of LCMT1-dependent PP2Ac methylation and oxidative stress and indirectly indicate that the methylation of PP2A plays an important role against oxidative stress.

Functionalization of iron oxide nanoparticles with clove extract to induce apoptosis in MCF-7 breast cancer cells

It has been reported that iron oxide nanoparticles have various biomedical applications, including cancer diagnosis and treatment. Iron oxide nanoparticles were known to exert cytotoxicity against MCF-7 breast cancer cell lines and in this present study, we have investigated for their apoptosis-inducing potential in the same cell line. The flow cytometry analysis of the MCF-7 breast cancer cell lines treated with functionalized iron oxide nanoparticles showed an increased percentage of cells in terms of viable, early, and late apoptosis. The cell cycle analysis of the MCF-7 cell lines treated with Syzygium aromaticum extract coated with polyvinylpyrrolidone (PVP) + iron oxide nanoparticles and PVP + iron oxide nanoparticles showed substantial accumulation of nanoparticles in the sub-G1 phase, confirming induction of apoptosis. The activities of caspase-3, caspase-8, and caspase-9 increased with increasing concentration of the nanoparticles indicating that activities of caspase can be activated by iron nanoparticles. Further, functionalized nanoparticles induced oxidative stress through reactive oxygen species (ROS) formation. Therefore, it is concluded that the functionalized iron nanoparticles induce apoptosis in MCF-7 breast cancer cell lines and further provides an opportunity to explore the iron nanoparticles for apoptosis in cancer treatment.

Capsaicin induces cytotoxicity in human osteosarcoma MG63 cells through TRPV1-dependent and -independent pathways

An accumulating body of evidence has shown that capsaicin induces apoptosis in various tumor cells as a mechanism of its anti-tumor activity. However, the effects of capsaicin on osteosarcoma have not been studied extensively. In the current study, we explore the molecular mechanism of capsaicin-mediated tumor suppressive function in osteosarcoma. We found that capsaicin-induced apoptosis and the activation of transient receptor potential receptor vanilloid 1 (TRPV1) in a dose- and time-dependent manner in human osteosarcoma MG63 cells in vitro. Blocking TRPV1 using capsazepine attenuated the capsaicin-induced cytotoxicity, mitochondrial dysfunction, overproduction of reactive oxygen species (ROS) and decrease in superoxide dismutase (SOD) activity. In addition, the results demonstrated that capsaicin induced the activation of adenosine 5'-monophosphate-activated protein kinase (AMPK), p53 and C-jun N-terminal kinase (JNK). In addition, Compound C (antagonist of AMPK) attenuated the activation of p53, which appeared to be TRPV1 independent. Taken together, the present study suggests that capsaicin effectively causes cell death in human osteosarcoma MG63 cells via the activation of TRPV1-dependent (mitochondrial dysfunction, and overproduction of ROS and JNK) and TRPV1-independent (AMPK-p53) pathways. Thus, capsaicin may be a potential anti-osteosarcoma agent.

Ethanol-induced DNA repair in neural stem cells is transforming growth factor β1-dependent

Following neurotoxic damage, cells repair their DNA, and survive or undergo apoptosis. This study tests the hypothesis that ethanol induces a DNA damage response (DDR) in neural stem cells (NSCs) that promotes excision repair (ER) and this repair is influenced by the growth factor environment. Non-immortalized NSCs treated with fibroblast growth factor 2 or transforming growth factor (TGF) β1 were exposed to ethanol. Ethanol increased total DNA damage, reactive oxygen species, and oxidized DNA bases. TGFβ1 potentiated these toxic effects. Transcriptional analyses of cultured NSCs revealed ethanol-induced increases in transcripts related to the DDR (e.g., Hus1 and p53), base ER (e.g., Mutyh and Nthl1), and nucleotide ER (e.g., Xpc), particularly in the presence of TGFβ1. Expression and activity of ER proteins were affected by ethanol. Similar changes occurred in proliferating cells of ethanol-treated mouse fetuses. Ethanol-induced DNA repair in NSCs depends on the ambient growth factors. Gene products for DNA repair in stem cells are among the first biomarkers identifying fetal alcohol-induced damage.

Modulation of reactive oxygen species production, apoptosis and cell cycle in pleural exudate cells of carrageenan-induced acute inflammation in rats by rutin

The present study seeks to investigate the effect of rutin, a flavonoid compound in rat models of acute inflammation induced by carrageenan (CAR). Twenty-four female Wistar rats weighing 222-247 g received saline or 2% λ-carrageenan in the pleural cavity and treatment with rutin (80 mg kg^-1) or saline by oral gavage for 21 days prior to the intrapleural induction of CAR. After 4 h of induction, the rats were euthanized, the plasma was prepared from the blood for the analysis of haematological parameters and the pleural exudate was obtained for the analysis of the total cell count, cell viability, reactive oxygen species (ROS) production, apoptosis and cell cycle. The result revealed that rutin exhibited anti-inflammatory effects by modulating the ROS level, apoptosis and cell cycle. This study indicates that rutin may exert a protective effect against ROS-mediated oxidative damage associated with an anti-inflammatory activity in rat models of acute inflammation.

Auranofin radiosensitizes tumor cells through targeting thioredoxin reductase and resulting overproduction of reactive oxygen species

Auranofin (AF) is an anti-arthritic drug considered for combined chemotherapy due to its ability to impair the redox homeostasis in tumor cells. In this study, we asked whether AF may in addition radiosensitize tumor cells by targeting thioredoxin reductase (TrxR), a critical enzyme in the antioxidant defense system operating through the reductive protein thioredoxin. Our principal findings in murine 4T1 and EMT6 tumor cells are that AF at 3-10 μM is a potent radiosensitizer in vitro, and that at least two mechanisms are involved in TrxR-mediated radiosensitization. The first one is linked to an oxidative stress, as scavenging of reactive oxygen species (ROS) by N-acetyl cysteine counteracted radiosensitization. We also observed a decrease in mitochondrial oxygen consumption with spared oxygen acting as a radiosensitizer under hypoxic conditions. Overall, radiosensitization was accompanied by ROS overproduction, mitochondrial dysfunction, DNA damage and apoptosis, a common mechanism underlying both cytotoxic and antitumor effects of AF. In tumor-bearing mice, a simultaneous disruption of the thioredoxin and glutathione systems by the combination of AF and buthionine sulfoximine was shown to significantly improve tumor radioresponse. In conclusion, our findings illuminate TrxR in cancer cells as an exploitable radiobiological target and warrant further validation of AF in combination with radiotherapy.

The consequence of NAC on sodium arsenite-induced uterine oxidative stress

Arsenic consumption through drinking water is a worldwide major health problem. Management of arsenic intoxication with invasive, painful therapy using metal chelators is usually used as a conventional treatment strategy in human. In this present study, we examined the efficacy of oral administration of N-acetyl l-cysteine (NAC) in limiting arsenic-mediated female reproductive disorders and oxidative stress in female Wistar rats. The treatment was continued for 8 days (2 estrus cycles) on rats with sodium arsenite (10 mg/Kg body weight) orally. We examined the electrozymographic imprint of three different enzymatic antioxidants in uterine tissue. Rats fed with sodium arsenite exhibited a significant lessening in the activities of superoxide dismutase (SOD), catalase and glutathione peroxidase (GPx). Uterine DNA breakage, necrosis, ovarian and uterine tissue damage, disruption in steroidogenesis were also found in arsenic treated rats. Co-administration of NAC at different doses (50 mg/kg body weight, 100 mg/kg body weight, respectively) significantly reversed the action of uterine oxidative stress markers like malondialdehyde (MDA), conjugated dienes (CD) and non protein soluble thiol (NPSH); and noticeably improved antioxidant status of the arsenic fed rats. This ultimately resulted in the uterine tissue repairing followed by improvement of ovarian steroidogenesis. However, this effective function of NAC might be crucial for the restoration of arsenic-induced female reproductive organ damage in rats.

Demethylation and alterations in the expression level of the cell cycle-related genes as possible mechanisms in arsenic trioxide-induced cell cycle arrest in human breast cancer cells

Arsenic trioxide (As₂O₃) has been used clinically as an anti-tumor agent. Its mechanisms are mostly considered to be the induction of apoptosis and cell cycle arrest. However, the detailed molecular mechanisms of its anti-cancer action through cell cycle arrest are poorly known. Furthermore, As₂O₃ has been shown to be a potential DNA methylation inhibitor, inducing DNA hypomethylation. We hypothesize that As₂O₃ may affect the expression of cell cycle regulatory genes by interfering with DNA methylation patterns. To explore this, we examined promoter methylation status of 24 cell cycle genes in breast cancer cell lines and in a normal breast tissue sample by methylation-specific polymerase chain reaction and/or restriction enzyme-based methods. Gene expression level and cell cycle distribution were quantified by real-time polymerase chain reaction and flow cytometric analyses, respectively. Our methylation analysis indicates that only promoters of RBL1 (p107), RASSF1A, and cyclin D2 were aberrantly methylated in studied breast cancer cell lines. As₂O₃ induced CpG island demethylation in promoter regions of these genes and restores their expression correlated with DNA methyltransferase inhibition. As₂O₃ also induced alterations in messenger RNA expression of several cell cycle-related genes independent of demethylation. Flow cytometric analysis revealed that the cell cycle arrest induced by As₂O₃ varied depending on cell lines, MCF-7 at G1 phase and both MDA-MB-231 and MDA-MB-468 cells at G2/M phase. These changes at transcriptional level of the cell cycle genes by the molecular mechanisms dependent and independent of demethylation are likely to represent the mechanisms of cell cycle redistribution in breast cancer cells, in response to As₂O₃ treatment.

Arsenic trioxide induces ROS activity and DNA damage, leading to G0/G1 extension in skin fibroblasts through the ATM-ATR-associated Chk pathway

Arsenic (As) toxicity is a global health problem, affecting millions of people. Exposure to arsenic, mostly via drinking water, has been associated with cancer of skin, lungs, and blood, in addition to several kinds of skin lesions. The present study focused on the effect of arsenic trioxide (As₂O₃) on normal skin fibroblast cells. Specifically, the effect of As₂O₃ on ROS generation and oxidative stress was investigated. Proteins involved in the DNA damage signaling pathway and cell cycle were also studied. As₂O₃ induced the generation of intracellular ROS. Immunohistochemistry analysis revealed a dose-dependent increase in the number of 8-OHdG-positive cells, an indication of oxidative stress. Cell cycle analysis by flow cytometry demonstrated that As₂O₃ caused a significant percentage of cells to accumulate in the G0/G1 phase with a concomitant reduction in the S phase. Increases in the activated forms of DNA damage signaling proteins, ATM and ATR, and their effector molecules, Chk2 and p53, were also observed. In addition, expression of oncogene p21 was also increased. The study shows that exposure of normal skin fibroblast cells to As₂O₃ could lead to cell cycle arrest through ATM/ATR and DNA damage signaling pathways. In conclusion, we report here that arsenic trioxide increases cellular oxidative stress leading to shift in cell cycle and leads to DNA damage through ATM/ATR and the CHK-dependent signaling pathway.

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.

Hijacking microglial glutathione by inorganic arsenic impels bystander death of immature neurons through extracellular cystine/glutamate imbalance

Arsenic-induced altered microglial activity leads to neuronal death, but the causative mechanism remains unclear. The present study showed, arsenic-exposed (10 μM) microglial (N9) culture supernatant induced bystander death of neuro-2a (N2a), which was further validated with primary microglia and immature neuronal cultures. Results indicated that arsenic-induced GSH synthesis by N9 unfavorably modified the extracellular milieu for N2a by lowering cystine and increasing glutamate concentration. Similar result was observed in N9-N2a co-culture. Co-exposure of arsenic and 250 μM glutamate, less than the level (265 μM) detected in arsenic-exposed N9 culture supernatant, compromised N2a viability which was rescued by cystine supplementation. Therefore, microglia executes bystander N2a death by competitive inhibition of system Xc^- (xCT) through extracellular cystine/glutamate imbalance. We confirmed the role of xCT in mediating bystander N2a death by siRNA inhibition studies. Ex-vivo primary microglia culture supernatant from gestationally exposed mice measured to contain lower cystine and higher glutamate compared to control and N-acetyl cysteine co-treated group. Immunofluorescence staining of brain cryosections from treated group showed more dead immature neurons with no such effect on microglia. Collectively, we showed, in presence of arsenic microglia alters cystine/glutamate balance through xCT in extracellular milieu leading to bystander death of immature neurons.

The Coadministration of N-Acetylcysteine Ameliorates the Effects of Arsenic Trioxide on the Male Mouse Genital System

Arsenic trioxide (As2O3) has shown effectiveness in treatment of leukemia but is also associated with reproductive toxicity. Since remediation with N-acetylcysteine (NAC) may mitigate the adverse effects caused by exposure, we assessed the effects of As2O3 and its potential reversibility after exposure cessation or coadministration of NAC. Animals received 0.3 or 3.0 mg/Kg/day of As2O3 subcutaneously and 40 mM of NAC in tap water. As2O3 treatment impaired spermatogenesis and sperm motility and decreased seminal vesicle weight and testosterone serum levels; after suspension of treatment, these parameters remained altered. When NAC was administered, animals showed improvement in sperm parameters and seminal vesicle weight. In vitro epididymal contractility was increased in As2O3-treated animals. We concluded that As2O3 is toxic to the male mouse genital system by compromising sperm quality and quantity; these effects persisted even after suspension of the treatment. However, the coadministration of NAC ameliorates the harmful effects of the drug on the male genital system.

Amentoflavone acts as a radioprotector for irradiated v79 cells by regulating reactive oxygen species (ROS), cell cycle and mitochondrial mass

Radioprotective effects of amentoflavone were investigated by examining cell viability, apoptosis, cell cycling concentrations of intracellular ROS (reactive oxygen species), and relative mitochondrial mass by flow cytometry after 60Co irradiation. Pretreatment with amentoflavone 24 hours prior to 8 Gy 60Co γ-ray irradiation significantly inhibited apoptosis, promoted the G2 phase, decreased the concentration of ROS and mitochondrial mass. These results collectively indicate that amentoflavone is an effective radioprotective agent.

Arsenic trioxide and resveratrol show synergistic anti-leukemia activity and neutralized cardiotoxicity

Cardiotoxicity is an aggravating side effect of many clinical antineoplastic agents such as arsenic trioxide (As2O3), which is the first-line treatment for acute promyelocytic leukemia (APL). Clinically, drug combination strategies are widely applied for complex disease management. Here, an optimized, cardiac-friendly therapeutic strategy for APL was investigated using a combination of As2O3 and genistein or resveratrol. Potential combinations were explored with respect to their effects on mitochondrial membrane potential, reactive oxygen species, superoxide dismutase activity, autophagy, and apoptosis in both NB4 cells and neonatal rat left ventricular myocytes. All experiments consistently suggested that 5 µM resveratrol remarkably alleviates As2O3-induced cardiotoxicity. To achieve an equivalent effect, a 10-fold dosage of genistein was required, thus highlighting the dose advantage of resveratrol, as poor bioavailability is a common concern for its clinical application. Co-administration of resveratrol substantially amplified the anticancer effect of As2O3 in NB4 cells. Furthermore, resveratrol exacerbated oxidative stress, mitochondrial damage, and apoptosis, thereby reflecting its full range of synergism with As2O3. Addition of 5 µM resveratrol to the single drug formula of As2O3 also further increased the expression of LC3, a marker of cellular autophagy activity, indicating an involvement of autophagy-mediated tumor cell death in the synergistic action. Our results suggest a possible application of an As2O3 and resveratrol combination to treat APL in order to achieve superior therapeutics effects and prevent cardiotoxicity.

Capsaicin induces apoptosis in MG63 human osteosarcoma cells via the caspase cascade and the antioxidant enzyme system

Osteosarcoma is the most common malignant bone tumor in children and adolescents. This aggressive cancer mostly occurs in the long bones. Therefore, novel therapeutic approaches, such as biological therapies and gene therapy, are required to efficiently treat osteosarcoma. Capsaicin (trans-8-methyl-N-vanillyl-6-nonenamide) has been demonstrated to inhibit the growth of several types of cancer cells and a number of studies have shown that osteosarcoma may be vulnerable to biological therapies. However, little is known regarding the therapeutic effects of capsaicin on osteosarcoma. This study investigated the effects of capsaicin on MG63 human osteosarcoma cells, in addition to elucidating the regulatory signaling pathways underlying the effects of capsaicin, the caspase cascade and the antioxidant enzyme system. The MG63 cell line was treated with various concentrations of capsaicin. Cells were analyzed using MTT and flow cytometry, and the presence of DNA fragmentation was evaluated using TUNEL assay. Results showed capsaicin induced apoptosis in MG63 cells. Thus, capsaicin exhibited an anticancer effect in osteosarcoma cells.

Arsenic trioxide induced endoplasmic reticulum stress in laryngeal squamous cell line Hep-2 cells

Arsenic trioxide (As2O3) has been used in the treatment of acute promyelocytic leukemia (APL) and many malignant solid tumors. Recently, endoplasmic reticulum (ER) stress plays an important role in As2O3-treated laryngeal squamous cell line Hep-2 cells. In the present work, the expression of ER stress-related proteins was investigated in As2O3-treated Hep-2 cells. The results showed that As2O3 increased the expression of GRP78, CHOP, phosphorylated eIF2α and ATF4, all of which are the molecule of ER stress. Therefore, As2O3 induced ER stress in Hep-2 cells.

Oxidative DNA damage and inflammatory responses in cultured human cells and in humans exposed to traffic-related particles

Particulate pollution is a major public health concern because epidemiological studies have demonstrated that exposure to particles is associated with respiratory diseases and lung cancer. Diesel exhaust particles (DEP), which is classified as a human carcinogen (IARC, 2012), are considered a major contributor to traffic-related particulate matter (PM) in urban areas. DEP consists of various compounds, including PAHs and metals which are the principal components that contribute to the toxicity of PM. The present study aimed to investigate effects of PM on induction of oxidative DNA damage and inflammation by using lymphocytes in vitro and in human exposed to PM in the environment. Human lymphoblasts (RPMI 1788) were treated with DEP (SRM 2975) at various concentrations (25-100 μg/ml) to compare the extent of responses with alveolar epithelial cells (A549). ROS generation was determined in each cell cycle phase of DEP-treated cells in order to investigate the influence of the cell cycle stage on induction of oxidative stress. The oxidative DNA damage was determined by measurement of 8-hydroxy-deoxyguanosine (8-OHdG) whereas the inflammatory responses were determined by mRNA expression of interleukin-6 and -8 (IL-6 and IL-8), Clara cell protein (CC16), and lung surfactant protein-A (SP-A). The results showed that RPMI 1788 and A549 cells had a similar pattern of dose-dependent responses to DEP in terms of particle uptake, ROS generation with highest level found in G2/M phase, 8-OHdG formation, and induction of IL-6 and IL-8 expression. The human study was conducted in 51 healthy subjects residing in traffic-congested areas. The effects of exposure to PM2.5 and particle-bound PAHs and toxic metals on the levels of 8-OHdG in lymphocyte DNA, IL-8 expression in lymphocytes, and serum CC16 were evaluated. 8-OHdG levels correlated with the exposure levels of PM2.5 (P<0.01) and PAHs (P<0.05), but this was not the case with IL-8. Serum CC16 showed significantly negative correlations with B[a]P equivalent (P<0.05) levels, but positive correlation with Pb (P<0.05). In conclusion, a similar pattern of the dose-dependent responses to DEP in the lymphoblasts and lung cells suggests that circulating lymphocytes could be used as a surrogate for assessing PM-induced oxidative DNA damage and inflammatory responses in the lung. Human exposure to PM leads to oxidative DNA damage whereas PM-induced inflammation was not conclusive and should be further investigated.

Neuroprotective effects of L-carnitine against oxygen-glucose deprivation in rat primary cortical neurons

Purpose

Hypoxic-ischemic encephalopathy is an important cause of neonatal mortality, as this brain injury disrupts normal mitochondrial respiratory activity. Carnitine plays an essential role in mitochondrial fatty acid transport and modulates excess acyl coenzyme A levels. In this study, we investigated whether treatment of primary cultures of rat cortical neurons with L-carnitine was able to prevent neurotoxicity resulting from oxygen-glucose deprivation (OGD).

Methods

Cortical neurons were prepared from Sprague-Dawley rat embryos. L-Carnitine was applied to cultures just prior to OGD and subsequent reoxygenation. The numbers of cells that stained with acridine orange (AO) and propidium iodide (PI) were counted, and lactate dehydrogenase (LDH) activity and reactive oxygen species (ROS) levels were measured. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and the terminal uridine deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling assay were performed to evaluate the effect of L-carnitine (1 µM, 10 µM, and 100 µM) on OGD-induced neurotoxicity.

Results

Treatment of primary cultures of rat cortical neurons with L-carnitine significantly reduced cell necrosis and prevented apoptosis after OGD. L-Carnitine application significantly reduced the number of cells that died, as assessed by the PI/AO ratio, and also reduced ROS release in the OGD groups treated with 10 µM and 100 µM of L-carnitine compared with the untreated OGD group (P<0.05). The application of L-carnitine at 100 µM significantly decreased cytotoxicity, LDH release, and inhibited apoptosis compared to the untreated OGD group (P<0.05).

Conclusion

L-Carnitine has neuroprotective benefits against OGD in rat primary cortical neurons in vitro.

Oxidative stress adaptation in aggressive prostate cancer may be counteracted by the reduction of glutathione reductase

Oxidative stress has been associated with prostate cancer development and progression due to an increase of reactive oxygen species (ROS). However, the mechanisms whereby ROS and the antioxidant system participate in cancer progression remain unclear.

In order to clarify the influence of oxidative stress in prostate cancer progression, we performed this study in two human prostate cancer cell lines, PC3 and HPV10 (from metastasis and from localized cancer, respectively) and RWPE1 cells derived from normal prostate epithelium. Cells were treated with hydrogen peroxide (H₂O₂) and PC3 cells were also treated with diethyl maleate (DEM). The effect on cell growth, viability, mitochondria membrane potential and oxidative stress was analysed. Oxidative stress was evaluated based on ROS production, oxidative lesion of lipids (MDA) and on determination of antioxidants, including enzyme activity of glutathione peroxidase (Gl-Px), glutathione reductase (Gl-Red) and on the quantification of glutathione (GSH), glutathione-s-transferase (GST) and total antioxidant status (TAS).

PC3 shows higher ROS production but also the highest GSH levels and Gl-Red activity, possibly contributing to oxidative stress resistance. This is also associated with higher mitochondrial membrane potential, TAS and lower lipid peroxidation. On the other hand, we identified Gl-Red activity reduction as a new strategy in overcoming oxidative stress resistance, by inducing H₂O₂ cytotoxicity. Therefore these results suggest Gl-Red activity reduction as a new potential therapeutic approach, in prostate cancer.

Conditioned medium from actinomycin D-treated apoptotic cells induces mitochondria-dependent apoptosis in bystander cells

Chemical-induced bystander effects have been known for several years, but the underlying mechanism is still seldom investigated. Previous researchers have found that mitomycin C and phleomycin induced micronuclei in bystander cells the same as in exposed cells. We previously demonstrated the ability of actinomycin D (ACTD) to induce bystander effects in normal Chinese hamster fibroblast V79 cells and found that conditioned medium (CM) obtained from ACTD-exposed apoptotic cells induced apoptosis in bystander cells. The present study further explores the probable mechanism of apoptosis in bystander cells. The main findings of this study are: (1) ACTD-treated CM induced apoptosis in bystander cells in a time-dependent manner, which was confirmed with morphological changes. (2) ACTD-treated CM increased the mRNA and protein levels of pro-apoptotic p53 and Bax, whereas it decreased those of anti-apoptotic Bcl-2 in bystander cells; these were all time-dependent effects. Reactive oxygen species (ROS) were also involved in apoptosis of bystander cells. (3) ACTD-treated CM reduced mitochondria membrane potential and induced cytochrome c release. (4) ACTD-treated CM induced G1 cell phase arrest, which may be another response in bystander cells when cultured with CM. These results suggest that chemical-treated CM induces p53-Bcl-2/Bax-cytochrome c signaling (i.e., mitochondria pathway)-dependent apoptosis in bystander cells, which is a kinetic response.

Dequalinium induces human leukemia cell death by affecting the redox balance

Dequalinium, an amphiphilic quinolinium derivative, selectively accumulates in mitochondria and displays anticancer activity in cells from different malignancies. Previous studies indicate a differential DQA-induced cytotoxicity in NB4 and K562 human leukemia cells as a consequence of an early disturbance in mitochondrial function. Results in this paper show that DQA induces a concentration-dependent oxidative stress by decreasing GSH level and increasing ROS in a cell type specific way. Inhibitors of the JNK and p38 stress regulated kinases potentiate DQA-induced NB4 cell death suggesting a protective function for these enzymes. K562 cells with relatively high GSH levels remained resistant to DQA action.

Artesunate induces oncosis-like cell death in vitro and has antitumor activity against pancreatic cancer xenografts in vivo

Pancreatic cancer is highly resistant to the currently available chemotherapeutic agents. Less than 5% of patients diagnosed with this disease could survive beyond 5 years. Thus, there is an urgent need for the development of novel, efficacious drugs that can treat pancreatic cancer. Herein we report the identification of artesunate (ART), a derivative of artemisinin, as a potent and selective antitumor agent against human pancreatic cancer cells in vitro and in vivo. ART exhibits selective cytotoxic activity against Panc-1, BxPC-3 and CFPAC-1 pancreatic cancer cells with IC(50) values that are 2.3- to 24-fold less than that of the normal human hepatic cells (HL-7702). The pan caspase inhibitor zVAD-fmk did not inhibit the cytotoxic activity of ART. Electron microscopy of ART-treated cells revealed severe cytoplasmic swelling and vacuolization, swollen and internally disorganized mitochondria, dilation (but not fragmentation) of the nuclei without chromatin condensation, and cell lysis, yielding a morphotype that is typical of oncosis. The ART-treated cells exhibited a loss of mitochondrial membrane potential (DeltaPsim) and ART-induced cell death was inhibited in the presence of the reactive oxygen species (ROS) scavenger N-acetyl-cysteine (NAC). Importantly, ART produced a dose-dependent tumor regression in an in vivo pancreatic cancer xenografts model. The in vivo antitumor activity of ART was similar to that of gemcitabine. Taken together, our study suggests that ART exhibits antitumor activity against human pancreatic cancer via a novel form of oncosis-like cell death, and that ART should be considered a potential therapeutic candidate for treating pancreatic cancer.

Immunotoxicity and biodistribution analysis of arsenic trioxide in C57Bl/6 mice following a 2-week inhalation exposure

In these studies the immunotoxicity of arsenic trioxide (ATO, As(2)O(3)) was evaluated in mice following 14 days of inhalation exposures (nose only, 3 h per day) at concentrations of 50 microg/m(3) and 1 mg/m(3). A biodistribution analysis performed immediately after inhalation exposures revealed highest levels of arsenic in the kidneys, bladder, liver, and lung. Spleen cell levels were comparable to those found in the blood, with the highest concentration of arsenic detected in the spleen being 150 microg/g tissue following the 1 mg/m(3) exposures. No spleen cell cytotoxicity was observed at either of the two exposure levels. There were no changes in spleen cell surface marker expression for B cells, T cells, macrophages, and natural killer (NK) cells. There were also no changes detected in the B cell (LPS-stimulated) and T cell (Con A-stimulated) proliferative responses of spleen cells, and no changes were found in the NK-mediated lysis of Yac-1 target cells. The primary T-dependent antibody response was, however, found to be highly susceptible to ATO suppression. Both the 50 microg/m(3) and 1 mg/m(3) exposures produced greater than 70% suppression of the humoral immune response to sheep red blood cells. Thus, the primary finding of this study is that the T-dependent humoral immune response is extremely sensitive to suppression by ATO and assessment of humoral immune responses should be considered in evaluating the health effects of arsenic containing agents.

Overexpression of catalase delays G0/G1- to S-phase transition during cell cycle progression in mouse aortic endothelial cells

Although it is understood that hydrogen peroxide (H(2)O(2)) promotes cellular proliferation, little is known about its role in endothelial cell cycle progression. To assess the regulatory role of endogenously produced H(2)O(2) in cell cycle progression, we studied the cell cycle progression in mouse aortic endothelial cells (MAECs) obtained from mice overexpressing a human catalase transgene (hCatTg), which destroys H(2)O(2). The hCatTg MAECs displayed a prolonged doubling time compared to wild-type controls (44.0 +/- 4.7 h versus 28.6 +/- 0.8 h, p<0.05), consistent with a diminished growth rate and H(2)O(2) release. Incubation with aminotriazole, a catalase inhibitor, prevented the observed diminished growth rate in hCatTg MAECs. Inhibition of catalase activity with aminotriazole abrogated catalase overexpression-induced antiproliferative action. Flow cytometry analysis indicated that the prolonged doubling time was principally due to an extended G(0)/G(1) phase in hCatTg MAECs compared to the wild-type cells (25.0 +/- 0.9 h versus 15.9 +/- 1.4 h, p< 0.05). The hCatTg MAECs also exhibited decreased activities of the cyclin-dependent kinase (Cdk) complexes responsible for G(0)/G(1)- to S-phase transition in the cell cycle, including the cyclin D-Cdk4 and cyclin E-Cdk2 complexes. Moreover, the reduction in cyclin-Cdk activities in hCatTg MAECs was accompanied by increased protein levels of two Cdk inhibitors, p21 and p27, which inhibit the Cdk activity required for the G(0)/G(1)- to S-phase transition. Knockdown of p21 and/or p27 attenuated the antiproliferative effect of catalase overexpression in MAECs. These results, together with the fact that catalase is an H(2)O(2) scavenger, suggest that endogenously produced H(2)O(2) mediates MAEC proliferation by fostering the transition from G(0)/G(1) to S phase.

MER1, a novel organic arsenic derivative, has potent PML-RARalpha-independent cytotoxic activity against leukemia cells

Arsenic trioxide (ATO) is an inorganic arsenic derivative that is highly effective against PML-RARalpha-positive leukemia but much less against other hematological malignancies. We synthesized an organic arsenic derivative (OAD), S-dimethylarsino-thiosuccinic acid (MER1), which offers a superior toxicity profile and comparable in vitro activity relative to ATO. In Swiss Webster mice, maximally-tolerated cumulative dose of MER1 when given i.v. for 5 days was 100 mg/kg/d. We demonstrated that MER1 induced apoptosis and dose- and time-dependent inhibition of survival and growth in a panel of myeloid leukemia cell lines. Unlike ATO, this activity was independent of PML-RARalpha status and was not associated with induction of myeloid maturation. In NB4 and HL60 cells, MER1 and ATO induced caspase activation and dissipation of mitochondrial transmembrane potential. At the same time, MER1 induced generation of reactive oxygen species (ROS) and cell cycle arrest in G2/M phase and proved to be more potent than ATO at inducing apoptosis. ROS generation and intracellular glutathione levels were key modulators of MER1-induced cytotoxicity as evidenced by abrogation of apoptosis in myeloid leukemia cell lines pretreated with the disulfide bond-reducing agent dithiothreitol or the radical scavenger N-acetyl-L-cysteine. Collectively, these data indicate that MER1 induces apoptosis in PML-RARalpha-positive and -negative myeloid leukemia cells by enhancing oxidative stress. This agent, therefore, combines low in vivo toxicity with formidable in vitro pro-apoptotic ROS-mediated activity, and may represent a novel OAD suitable for clinical development against a variety of hematological malignancies.

Antiapoptotic role for ornithine decarboxylase during oocyte maturation

Ornithine decarboxylase (ODC), the rate-limiting enzyme in polyamine biosynthesis, is a nonredundant and essential gene in all eukaryotes. During the mitotic cell cycle, ODC exhibits two activity peaks: one at the G(1)/S transition and one during the G(2)/M transition. The physiological role of this cell cycle-dependent ODC activity dynamic is not clear. Previous studies have reported a significant elevation of ODC activity during Xenopus oocyte maturation, which resembles mitotic G(2)/M transition. In order to study the roles of ODC activity in the oocytes, we utilized antisense morpholino (xODC mo) oligonucleotides to inhibit ODC translation. We report here that xODC mo abolished ODC activity increase during oocyte maturation. xODC mo-injected oocytes underwent germinal vesicle breakdown, emitted the first polar body, and reached metaphase II, thus completing nuclear maturation. However, the metaphase II oocytes exhibited high levels of reactive oxygen species and became apoptotic. When transferred to host frogs and subsequently ovulated, these eggs were fertilized but exhibited embryo fragmentation. Translation of ODC is therefore integral to cytoplasmic maturation, protecting metaphase II oocytes from reactive oxygen species-induced apoptosis.

Assessing methods for blood cell cytotoxic responses to inorganic nanoparticles and nanoparticle aggregates

Inorganic nanoparticles (NPs) show great potential for medicinal therapy. However, biocompatibility studies are essential to determine if they are safe. Here, five different NPs are compared for their cytotoxicity, internalization, aggregation in medium, and reactive oxygen species (ROS) production, using tumoral and normal human blood cells. Differences depending on the cell type are analyzed, and no direct correlation between ROS production and cell toxicity is found. Results are discussed with the aim of standardizing the procedures for the evaluation of the toxicity.

PML/RARalpha fusion protein mediates the unique sensitivity to arsenic cytotoxicity in acute promyelocytic leukemia cells: Mechanisms involve the impairment of cAMP signaling and the aberrant regulation of NADPH oxidase

Acute promyelocytic leukemia (APL) cells are characterized by PML/RARalpha fusion protein, high responsiveness to arsenic trioxide (ATO)-induced cytotoxicity and an abundant generation of reactive oxygen species (ROS). In this study we investigated the association among these three features in APL-derived NB4 cells. We found that NADPH oxidase-derived ROS generation was more abundant in NB4 cells compared with monocytic leukemia U937 cells. By using PR9, a sub-line of U937 stably transduced with the inducible PML/RARalpha expression vectors, we attributed disparities on ROS generation and ATO sensitivity to the occurrence of PML/RARalpha fusion protein, since PML/RARalpha-expressing cells appeared higher NADPH oxidase activity, higher ROS level and higher sensitivity to ATO. On the other hand, the basal intensity of cAMP signaling pathway was compared between NB4 and U937 as well as between PR9 cells with or without PML/RARalpha, demonstrating that PML/RARalpha-expressing cells had an impaired cAMP signaling pathway which relieved its inhibitory effect on NADPH oxidase derived ROS generation. In summary, the present study demonstrated the correlation of PML/RARalpha with cAMP signaling pathway, NADPH oxidase and ROS generation in APL cells. PML/RARalpha that bestows NB4 cells various pathological features, paradoxically also endows these cells with the basis for susceptibility to ATO-induced cytotoxcity.

NADPH oxidase-derived reactive oxygen species are responsible for the high susceptibility to arsenic cytotoxicity in acute promyelocytic leukemia cells

We have previously demonstrated that an acute promyelocytic leukemia (APL)-derived cell line NB4 exhibited a relatively higher basal level of reactive oxygen species (ROS) than other leukemia cell lines, which is one of the mechanisms determining a higher apoptotic susceptibility of NB4 cells to arsenic trioxide (ATO)-induced apoptosis. Here we identified the source of the basal ROS generation in NB4 cells. We demonstrated the existence of all the components of phagocytic NADPH oxidase in NB4 cells and found that this oxidase could be effectively activated. The basal ROS generation in NB4 cells could be blocked by diphenyleneiodonium (DPI), an inhibitor of NADPH oxidase, but not by inhibitors of mitochondria respiratory chain, implying that NADPH oxidase played an essential role in maintaining the basal ROS level in NB4 cells. Furthermore, ATO-induced cytotoxicity was reduced by pre-treatment with DPI in NB4 cells, suggesting the involvement of NADPH oxidase in ATO-induced cytotoxicity. Therefore, increasing the NADPH oxidase activity may be a novel mechanism to enhance cytotoxicity induced by anticancer agents.

Novel glycoconjugates of diospyrin, a quinonoid plant product: synthesis and evaluation of cytotoxicity against human malignant melanoma (A375) and laryngeal carcinoma (Hep2)

Glycoside derivatives of diospyrin (1) were synthesized for the first time, and the cytotoxicity of the novel compounds vis-à-vis their precursors were evaluated against two human cancer cell lines, viz. malignant melanoma (A375) and laryngeal carcinoma (Hep2). The IC(50) values were in the low micromolar range for all the compounds tested, and A375 cells showed comparatively greater sensitivity than Hep2. Most of the compounds exhibited enhanced activity as compared to the plant-derived quinonoid precursor of the series (1), while the aminophenyl mannosyl (6) was found to be the most effective derivative. In A375 cells, 6 (IC(50) = 0.02 microM) showed the maximum increase in cytotoxicity (approximately 35-fold) over that of 1 (IC(50) = 0.82 microM). Again, when the glycosides were evaluated at a given concentration (0.1 microM) for their relative capacity to generate ROS from A375 cells, the compound 6 could produce the highest amount of ROS. Incidentally, this derivative also showed a comparatively lower toxicity (IC(50) approximately 41 microM) when tested against normal human peripheral blood mononuclear cells, indicating a fair prospect of its development as a novel chemotherapeutic agent for the treatment of malignant melanoma.

Alteration of subcellular redox equilibrium and the consequent oxidative modification of nuclear factor kappaB are critical for anticancer cytotoxicity by emodin, a reactive oxygen species-producing agent

We previously found that emodin produced reactive oxygen species (ROS) intracellularly. In various tumor cells at low doses it enhances the cytotoxicity of As(2)O(3), and at higher doses it renders cytotoxicity independently in vitro and in vivo. The effects involve redox-mediated inhibition of NF-kappaB activation. In this study, we focus on the mechanisms by which emodin inhibits NF-kappaB activation. Results in HeLa cells demonstrated that emodin at high doses or in combination with As(2)O(3), via generation of ROS especially in the nucleus, altered subcellular redox equilibrium and thus oxidized the redox-sensitive site on NF-kappaB and prevented its binding to the target DNA. In vivo study showed that tumors exposed to the arsenic/emodin cotreatment had dramatically smaller sizes and weaker antioxidant capacity, compared with arsenic alone. NF-kappaB binding and transactivation were inhibited in these tumors. These data help in the understanding of the mechanisms by which manipulation of cellular redox and NF-kappaB activation may enhance chemotherapy.

Role of GSTP1-1 in mediating the effect of As2O3 in the Acute Promyelocytic Leukemia cell line NB4

Arsenic trioxide (As2O3) is a highly effective agent in the treatment of acute promyelocytic leukemia (APL), whereas other hematopoietic tumors are less responsive to this agent and mechanisms underlying As2O3,-resistance are poorly understood. To better understand the complex network of GSH-related pathways in As2O3 sensitivity, we investigated the role of GSH and GSH-relevant enzymes in an APL cell line sensitive to As2O3 (NB4) and in a resistant subclone (AsR). Cell proliferation, viability, and apoptosis were investigated in NB4 cells before and after treatment with 1 muM As2O3 and in AsR cells. In these experimental cell models, GSTP1-1, JNK1 and JNK2 proteins were analyzed by immunoblotting, and a kinase assay for JNK1 was performed. GSH levels as well as the activities of the enzymes glutathione peroxidase, glutathione transferase, gamma-Glutamylcysteynilsinthetase and superoxide dismutase were measured. NB4 cells treated with As2O3 showed a high level of oxidative stress and an increase of GSH levels. GSTP1-1 polymerization and JNK1 activation were detectable after 24 h and were followed by an increase of the apoptotic rate starting at 72 h. Neither GSTP1-1 polymerization nor JNK activation was found in AsR cells that showed a very low apoptotic rate. Our results suggest that APL sensitivity to As2O3 might be, at least in part, mediated by the balance between association and dissociation of JNK from GSTP1-1, depending on the redox status of the cell. Further investigation is warranted to find a way to interfere with this balance, whenever it might represent a mechanism of drug resistance.

Arsenic trioxide inhibits cell growth in SH-SY5Y and SK-N-AS neuroblastoma cell lines by a different mechanism

Neuroblastoma, characterized by heterogeneous cell population, is a common solid tumor in childhood and some malignant neuroblastomas are refractory to conventional chemotherapy. Recently, treatment with arsenic trioxide (As2O3) was found effective in the treatment of acute promyelocytic leukemia as well as neuroblastoma cells by inducing apoptosis. To define the mechanism contributing to cell death in those heterogenous cell populations, the authors used two different types of neuroblastoma cells, SH-SY5Y and SK-N-AS, to compare the pathways that mediate death response to arsenic trioxide. With arsenic trioxide exposure, both cell lines were arrested at the S-G2/M phase with the increase of cyclin B expression and CDK1 activity. Although caspase 3 was activated in both cell lines, the NF-kappaB activity and the expression of cyclin D1, cyclin E, and p27 were different. Therefore, arsenic trioxide could be an effective cytotoxic drug for the treatment of heterogeneous cellular population of neuroblastoma.

Flow-cytometric analysis of reactive oxygen species in peripheral blood mononuclear cells of patients with thyroid dysfunction

BACKGROUND

Thyroid hormones are major regulators of energy metabolism and increased levels of the hormones (hyperthyroidism) results in an increase in the metabolic rate. Thyroid dysfunction causing alteration in hormone secretion leads to perturbations in the metabolic status. The hypermetabolic state may cause increased generation of reactive oxygen species (ROS), leading to oxidative stress in these patients. This study was carried out to verify our proposition by measuring the ROS in the terminally differentiated cells like the peripheral blood mononuclear cells of the patients.

METHODS

Flow-cytometric analysis of the ROS was carried out using 2',7' dichlorofluorescein diacetate in the isolated peripheral blood mononuclear cells of the subjects.

RESULTS

ROS generation was found to be 3-folds higher in hyperthyroids as compared with euthyroids and hypothyroids and this was not found to be gender specific.

CONCLUSIONS

Hyperthyroidism results in ROS generation in patients, which can be detected flow cytometrically in the peripheral blood mononuclear cells. Hence, this could complement the other thyroid function tests facilitating the diagnosis and design of appropriate therapy.

Dihydroartemisinin Is Cytotoxic to Papillomavirus-Expressing Epithelial Cells In vitro and In vivo

Nearly all cervical cancers are etiologically attributable to human papillomavirus (HPV) infection and pharmaceutical treatments targeting HPV-infected cells would be of great medical benefit. Because many neoplastic cells (including cervical cancer cells) overexpress the transferrin receptor to increase their iron uptake, we hypothesized that iron-dependent, antimalarial drugs such as artemisinin might prove useful in treating HPV-infected or transformed cells. We tested three different artemisinin compounds and found that dihydroartemisinin (DHA) and artesunate displayed strong cytotoxic effects on HPV-immortalized and transformed cervical cells in vitro with little effect on normal cervical epithelial cells. DHA-induced cell death involved activation of the mitochondrial caspase pathway with resultant apoptosis. Apoptosis was p53 independent and was not the consequence of drug-induced reductions in viral oncogene expression. Due to its selective cytotoxicity, hydrophobicity, and known ability to penetrate epithelial surfaces, we postulated that DHA might be useful for the topical treatment of mucosal papillomavirus lesions. To test this hypothesis, we applied DHA to the oral mucosa of dogs that had been challenged with the canine oral papillomavirus. Although applied only intermittently, DHA strongly inhibited viral-induced tumor formation. Interestingly, the DHA-treated, tumor-negative dogs developed antibodies against the viral L1 capsid protein, suggesting that DHA had inhibited tumor growth but not early rounds of papillomavirus replication. These findings indicate that DHA and other artemisinin derivatives may be useful for the topical treatment of epithelial papillomavirus lesions, including those that have progressed to the neoplastic state.

Co-mutagenic activity of arsenic and benzo[a]pyrene in mouse skin

Exposure to inorganic arsenic in drinking water is linked to skin, lung and bladder cancer in humans. The mechanism of arsenic-induced cancer is not clear, but exposure to arsenic and polycyclic arylhydrocarbons (PAH) is more carcinogenic than exposure to either type of carcinogen alone. Arsenic can also generate reactive oxygen species, suggesting that oxidation of DNA may play a role in carcinogenesis. Oxidization of guanosines in polyG tracts is known to cause frameshift mutations, and such events can be detected in situ using the G11 placental alkaline phosphatase (PLAP) transgenic mouse model, which reports frameshift mutations in a run of 11 G:C basepairs by generating cells containing heat-resistant alkaline phosphatase activity. PAH can also induce frameshift mutations. In the study described here, FVB/N mice carrying the G11 PLAP transgene were crossed to C57Bl/6 mice. Half of the hybrid mice were given drinking water with sodium arsenite (10 mg/L) for 10 weeks. Half of the arsenic treated mice were also exposed to benzo[a]pyrene (BaP) by skin painting (500 nmol/week) for 8 weeks. Another group of mice was exposed to BaP but not arsenic. The effect on frameshift mutation was assessed by staining sections of skin tissue to detect cells with PLAP activity. Arsenic alone had no significant effect. On average, mice given BaP alone had approximately three times more PLAP-positive (PLAP+) cells. By contrast, mice exposed to both arsenic and BaP exhibited 10-fold more PLAP+ cells in the skin, and these cells were often arranged in large clusters, suggesting derivation from stem cells. Whereas combined treatment produced more PLAP+ cells, stable BaP adduct levels and arsenic burdens were not higher in mice exposed to both agents compared to mice exposed to either one agent or the other.

Gene expression alteration during redox-dependent enhancement of arsenic cytotoxicity by emodin in HeLa cells

Emodin (1,3,8-trihydroxy-6-methylanthraquinone) could enhance the sensitivity of tumor cells to arsenic trioxide (As2O3)-induced apoptosis via generation of ROS, but the molecular mechanism has not been elucidated. Here, we carried out cDNA microarray-based global transcription profiling of HeLa cells in response to As2O3/emodin cotreatment, comparing with As2O3-only treatment. The results showed that the expression of a number of genes was substantially altered at two time points. These genes are involved in different aspects of cell function. In addition to redox regulation and apoptosis, ROS affect genes encoding proteins associated with cell signaling, organelle functions, cell cycle, cytoskeleton, etc. These data suggest that based on the cytotoxicity of As2O3, emodin mobilize every genomic resource through which the As2O3-induced apoptosis is facilitated.

NO restores HIF-1alpha hydroxylation during hypoxia: role of reactive oxygen species

The activity of hypoxia-inducible factor 1 (HIF-1) is primarily determined by stability regulation of its alpha subunit, which is stabilized under hypoxia but degraded during normoxia. Hydroxylation of HIF-1alpha by prolyl hydroxylases (PHDs) recruits the von Hippel-Lindau (pVHL) E3 ubiquitin ligase complex to initiate proteolytic destruction of the alpha subunit. Hypoxic stabilization of HIF-1alpha has been reported to be antagonized by nitric oxide (NO). By using a HIF-1alpha-pVHL binding assay, we show that NO released from DETA-NO restored prolyl hydroxylase activity under hypoxia. Destabilization of HIF-1alpha by DETA-NO was reversed by free radical scavengers such as NAC and Tiron, thus pointing to the involvement of reactive oxygen species (ROS). Therefore, we examined the effects of ROS on HIF-1alpha stabilization. Treatment of cells under hypoxia with low concentrations of the superoxide generator 2,3-dimethoxy-1,4-naphthoquinone lowered HIF-1alpha protein stabilization. In vitro HIF-1alpha-pVHL interaction assays demonstrated that low-level ROS formation increased prolyl hydroxylase activity, an effect antagonized by ROS scavengers. While determining intracellular ROS formation we noticed that reduced ROS production under hypoxia was restored by the addition of DETA-NO. We propose that an increase in ROS formation contributes to HIF-1alpha destabilization by NO donors under hypoxia via modulation of PHD activity.

Phosphoinositide 3-kinase/Akt inhibition increases arsenic trioxide-induced apoptosis of acute promyelocytic and T-cell leukaemias

Recent studies suggest that the prosurvival signal transduction pathway involving phosphoinositide 3-kinase (PI3K)/Akt can confer an aggressive, apoptosis-resistant phenotype to acute leukaemia cells. We have investigated the effect of modulating this signalling pathway on the sensitivity of leukaemic cell lines (NB-4, CEM, Jurkat, MOLT-4) and acute promyelocytic primary blasts to apoptosis induced by 1 micromol/l As2O3. Whereas parental NB-4 cells did not display any phosphorylated (active) Akt, CEM, Jurkat and MOLT-4 cells exhibited high levels of Akt activation. Consistently, treatment of NB-4 cells with pharmacological inhibitors of the PI3K/Akt pathway (LY294002, wortmannin) did not increase sensitivity of these cells to arsenic trioxide (As2O3), whereas siRNA knock-down of Akt enhanced As2O3-induced apoptosis of CEM, Jurkat and MOLT-4 cells. Overexpression of a constitutively active Akt cDNA rendered NB-4 cells less susceptible to As2O3. Upon prolonged exposure to As2O3, we isolated a NB-4 cell clone that was resistant to As2O3 and displayed high levels of active Akt. LY294002 treatment of acute promyelocytic primary blasts with elevated Akt phosphorylation levels resulted in an increased sensitivity to As2O3. These results may provide a rationale for the development of combined or sequential treatment with PI3K/Akt inhibitors to improve the efficacy of As2O3 on acute leukaemias and also to overcome As2O3 resistance.