Comparison of the degradation mechanisms of diclofenac in the presence of iron octacarboxyphthalocyanine and myeloperoxidase

The degradation process of diclofenac (DCF) by hematoprotein myeloperoxidase (MPO) and iron octacarboxyphthalocyanine (FePcOC) in the presence of hydrogen peroxide was compared. During the oxidation of diclofenac, in the presence of iron octacarboxyphthalocyanine (FePcOC) and hydroxyl radicals (HO^•) (from H₂O₂), an intermediate product (dimer with an m/z value of 587) with the characteristic yellow colouration and an intense band at λ_max = 451 nm is formed. Iron octacarboxyphthalocyanine oxidises in the presence of hydrogen peroxide, following the first-order reaction kinetics for FePcOC and H₂O₂. The concentration of diclofenac does not affect the initial reaction rate. For comparison, the oxidation of DCF in the presence of myeloperoxidase and hydrogen peroxide also provided yellow-coloured solutions with an absorption maximum at λ_max = 451 nm. However, LC-MS/MS analysis indicates the presence of at least seven main products of the diclofenac oxidation process in the final reaction mixture, including two dimers with the ion mass [M-H]^¯ = 587.01. The mechanism of the diclofenac degradation with hematoprotein myeloperoxidase is more complex than with iron octacarboxyphthalocyanine. Furthermore, the biological activity of diclofenac and DCF dimer (iron octacarboxyphthalocyanine and hydroxyl radicals degradation product) was tested. In this case, the long-term assayed in vitro against E. coli, colorectal HCT116 and melanoma Me45 cancer cells were performed.

Involvement of miRNAs in cellular responses to radiation

PURPOSE

Exposure of living cells to ionizing radiation has different consequences, depending on the dose and cell type. Changes of gene expression at the level of transcription and translation, including those regulated by microRNAs (miRNAs), play a role in intrinsic radiosensitivity of different cells and define their fate, survival or death. The aim of our work was to examine how ionizing radiation may influence the expression of genes regulated by different miRNAs and miRNA biogenesis.

MATERIALS AND METHODS

The work was performed on cultured human melanoma Me45 cells, transiently transfected with plasmids containing Renilla luciferase reporter gene targeted by miRNAs Let-7, miR-21 or miR-24. The levels of reporter mRNAs and mRNAs coding for proteins participating in miRNA biogenesis were assayed at different time points in irradiated and non-irradiated cells using RT-qPCR, and reporter protein by luciferase activity assays. MiRNA-targeted motifs in mRNAs coding for proteins engaged in miRNA biogenesis were extracted from the miRTarBase database.

RESULTS

Messenger RNA and protein levels of transfected luciferase genes fluctuated in time in patterns which depended on the type of miRNA regulation and changed upon irradiation of the cells. The average levels of reporter mRNAs were higher in irradiated cells, whereas the levels of proteins changed in either direction. Radiation also influenced the levels of miRNAs and the expression of genes engaged in their biogenesis suggesting that the changes in gene expression following ionizing radiation result mainly from these changes in expression of genes regulating miRNA biogenesis and the influence of miRNA on mRNA translation.

CONCLUSIONS

Currently, the responses of cells to ionizing radiation are mainly ascribed to changes of their redox conditions and increased intracellular levels of ROS, but the experiments described here suggest that a further important factor is modulation of translation through changes in biogenesis and levels of miRNAs.

Irradiation of platelets in Transfusion Medicine: risk and benefit judgments

Irradiation of platelet products is generally used to prevent transfusion-associated graft-versus-host disease (TA-GvHD) as well as transfusion-transmitted infections. As an essential prerequisite, gamma-irradiation of blood products prior to transfusion is required in patients who may develop TA-GVHD. Most studies suggest that gamma irradiation has no significant effect on the quality of platelet products; however, more recent studies have shown that the oxidative effects of gamma irradiation can lead to the induction of platelet storage lesion (PSL) and to some extent reduce the efficiency of transfused platelets. As the second widely used irradiation technique, UV-illumination was primarily introduced to reduce the growth of infectious agents during platelet storage, with the advantage that this method can also prevent TA-GvHD. However, the induction of oxidative conditions and platelet pre-activation that lead to PSL is more pronounced after UV-based methods of pathogen reduction. Since these lesions are large enough to clearly affect the post-transfusion platelet recovery and survival, more studies are needed to improve the safety and effectiveness of pathogen reduction technologies (PRTs). Therefore, pointing to other benefits of PRTs, such as preventing TA-GvHD or prolonging the shelf life of products by eliminating the possibility of pathogen growth during storage, does not yet seem to justify their widespread use due to above-mentioned effects. Even for gamma-irradiated platelets, some researchers have suggested that due to decreased 1-hour post-transfusion increments and increased risk of platelet refractoriness, their use should be limited to the patients who may develop TA-GVHD. It is noteworthy that due to the effect of X-rays in preventing TA-GvHD, some recent studies are underway to examine its effects on the quality and effectiveness of platelet products and determine whether X-rays can be used as a more appropriate and cost-effective alternative to gamma radiation. The review presented here provides a detailed description about irradiation-based technologies for platelet products, including their applications, mechanistic features, advantages, and disadvantages.

Role of Mitochondria in Radiation Responses: Epigenetic, Metabolic, and Signaling Impacts

Until recently, radiation effects have been considered to be mainly due to nuclear DNA damage and their management by repair mechanisms. However, molecular biology studies reveal that the outcomes of exposures to ionizing radiation (IR) highly depend on activation and regulation through other molecular components of organelles that determine cell survival and proliferation capacities. As typical epigenetic-regulated organelles and central power stations of cells, mitochondria play an important pivotal role in those responses. They direct cellular metabolism, energy supply and homeostasis as well as radiation-induced signaling, cell death, and immunological responses. This review is focused on how energy, dose and quality of IR affect mitochondria-dependent epigenetic and functional control at the cellular and tissue level. Low-dose radiation effects on mitochondria appear to be associated with epigenetic and non-targeted effects involved in genomic instability and adaptive responses, whereas high-dose radiation effects (>1 Gy) concern therapeutic effects of radiation and long-term outcomes involving mitochondria-mediated innate and adaptive immune responses. Both effects depend on radiation quality. For example, the increased efficacy of high linear energy transfer particle radiotherapy, e.g., C-ion radiotherapy, relies on the reduction of anastasis, enhanced mitochondria-mediated apoptosis and immunogenic (antitumor) responses.

Fatty Acids Metabolism: The Bridge Between Ferroptosis and Ionizing Radiation

Exposure of tumor cells to ionizing radiation (IR) alters the microenvironment, particularly the fatty acid (FA) profile and activity. Moreover, abnormal FA metabolism, either catabolism or anabolism, is essential for synthesizing biological membranes and delivering molecular signals to induce ferroptotic cell death. The current review focuses on the bistable regulation characteristics of FA metabolism and explains how FA catabolism and anabolism pathway crosstalk harmonize different ionizing radiation-regulated ferroptosis responses, resulting in pivotal cell fate decisions. In summary, targeting key molecules involved in lipid metabolism and ferroptosis may amplify the tumor response to IR.

The effect of gamma irradiation on platelet redox state during storage

BACKGROUND

As a method with insignificant adverse effects on in vitro quality of platelet concentrates (PCs), gamma irradiation is applied to abrogate the risk of transfusion-associated graft-vs-host disease in vulnerable recipients. However, there is some evidence of lower posttransfusion responses and proteomic alterations in gamma-irradiated platelets (PLTs), which raises some questions about their quality, safety, and efficacy. Since reactive oxygen species (ROS) are considered as markers of PLT storage lesion (PSL), the study presented here investigated oxidant state in gamma-irradiated PCs.

STUDY DESIGN AND METHODS

PLT-rich plasma PC was split into two bags, one kept as control while other was subjected to gamma irradiation. Within 7 days of storage, the levels of intra-PLT superoxide, H₂ O₂ , mitochondrial ROS, P-selectin expression, and phosphatidylserine (PS) exposure were detected by flow cytometry while intracellular reduced glutathione (GSH), glucose concentration, and lactate dehydrogenase (LDH) activity were measured by enzymocolorimetric method.

RESULTS

GSH decreased, while ROS generation and LDH activity increased, during storage. Gamma irradiation significantly attenuated GSH whereas increased ROS generation in earlier and later stages of storage associated with either P-selectin or PS exposure increments.

CONCLUSION

Gamma irradiation can significantly increase cytosolic ROS generation in two distinct phases, one upon irradiation and another later in longer-stored PCs. While earlier ROS influx seems to be governed by direct effect of irradiation, the second phase of oxidant stress is presumably due to the storage-dependent PLT activation. Intriguingly, these observations were also in line with early P-selectin increments and increased PS exposure in longer-stored PLTs. Given the mutual link between ROS generation and PLT activation, further investigation is required to explore the effect of gamma irradiation on the induction of PSL.

Live Impedance Measurements and Time-lapse Microscopy Observations of Cellular Adhesion, Proliferation and Migration after Ionizing Radiation

BACKGROUND

Changes in the cellular behavior depend on environmental and intracellular interactions. Cancer treatments force the changes, first on the molecular level, but the main visible changes are macroscopic. During radiotherapy, cancer cell's adhesion, proliferation and migration should be well monitored. In over 60% of diagnosed cancers cases, patients are given treatments with different protocols of radiotherapy, which result in possible metastasis and acute whole body response to toxic radiation.

OBJECTIVE

Effectiveness of the therapy used depends on the sensitivity/resistance of irradiated cancer cells. Cellular mechanisms of cancer protection, such as the activation of DNA damage and repair pathways, antioxidants production and oxidative stress suppression during treatments are not desirable. Cancer cells monitoring require the development of novel techniques, and the best techniques are non-invasive and long-term live observation methods, which are shown in this study.

METHODS

In cancers, invasive and metastatic phenotypes could be enhanced by stimulation of proliferation rate, decreased adhesion with simultaneous increase of motility and migration potential. For such reasons, the Ionizing Radiation (IR) stimulated proliferation; migration with lowered adhesiveness of cancer Me45 and normal fibroblasts NHDF were studied. Using impedance measurements technique for live cells, the adhesion of cells after IR exposition was assessed. Additionally proliferation and migration potential, based on standard Wound Healing assay were evaluated by timelapse microscopic observations.

RESULTS

We found simulative IR dose-ranges (0.2-2 Gy) for Me45 and NHDF cells, with higher proliferation and adhesion rates. On the other hand, lethal impact of IR (10-12 Gy) on both the cell lines was indicated.

CONCLUSION

Over-confluence cell populations, characterized with high crowd and contact inhibition could modulate invasiveness of individual cells, convert them to display migration phenotype and advance motility, especially after radiotherapy treatments.

Adverse outcome pathways for ionizing radiation and breast cancer involve direct and indirect DNA damage, oxidative stress, inflammation, genomic instability, and interaction with hormonal regulation of the breast

Knowledge about established breast carcinogens can support improved and modernized toxicological testing methods by identifying key mechanistic events. Ionizing radiation (IR) increases the risk of breast cancer, especially for women and for exposure at younger ages, and evidence overall supports a linear dose-response relationship. We used the Adverse Outcome Pathway (AOP) framework to outline and evaluate the evidence linking ionizing radiation with breast cancer from molecular initiating events to the adverse outcome through intermediate key events, creating a qualitative AOP. We identified key events based on review articles, searched PubMed for recent literature on key events and IR, and identified additional papers using references. We manually curated publications and evaluated data quality. Ionizing radiation directly and indirectly causes DNA damage and increases production of reactive oxygen and nitrogen species (RONS). RONS lead to DNA damage and epigenetic changes leading to mutations and genomic instability (GI). Proliferation amplifies the effects of DNA damage and mutations leading to the AO of breast cancer. Separately, RONS and DNA damage also increase inflammation. Inflammation contributes to direct and indirect effects (effects in cells not directly reached by IR) via positive feedback to RONS and DNA damage, and separately increases proliferation and breast cancer through pro-carcinogenic effects on cells and tissue. For example, gene expression changes alter inflammatory mediators, resulting in improved survival and growth of cancer cells and a more hospitable tissue environment. All of these events overlap at multiple points with events characteristic of "background" induction of breast carcinogenesis, including hormone-responsive proliferation, oxidative activity, and DNA damage. These overlaps make the breast particularly susceptible to ionizing radiation and reinforce that these biological activities are important characteristics of carcinogens. Agents that increase these biological processes should be considered potential breast carcinogens, and predictive methods are needed to identify chemicals that increase these processes. Techniques are available to measure RONS, DNA damage and mutation, cell proliferation, and some inflammatory proteins or processes. Improved assays are needed to measure GI and chronic inflammation, as well as the interaction with hormonally driven development and proliferation. Several methods measure diverse epigenetic changes, but it is not clear which changes are relevant to breast cancer. In addition, most toxicological assays are not conducted in mammary tissue, and so it is a priority to evaluate if results from other tissues are generalizable to breast, or to conduct assays in breast tissue. Developing and applying these assays to identify exposures of concern will facilitate efforts to reduce subsequent breast cancer risk.

Adverse outcome pathways for ionizing radiation and breast cancer involve direct and indirect DNA damage, oxidative stress, inflammation, genomic instability, and interaction with hormonal regulation of the breast

Knowledge about established breast carcinogens can support improved and modernized toxicological testing methods by identifying key mechanistic events. Ionizing radiation (IR) increases the risk of breast cancer, especially for women and for exposure at younger ages, and evidence overall supports a linear dose-response relationship. We used the Adverse Outcome Pathway (AOP) framework to outline and evaluate the evidence linking ionizing radiation with breast cancer from molecular initiating events to the adverse outcome through intermediate key events, creating a qualitative AOP. We identified key events based on review articles, searched PubMed for recent literature on key events and IR, and identified additional papers using references. We manually curated publications and evaluated data quality. Ionizing radiation directly and indirectly causes DNA damage and increases production of reactive oxygen and nitrogen species (RONS). RONS lead to DNA damage and epigenetic changes leading to mutations and genomic instability (GI). Proliferation amplifies the effects of DNA damage and mutations leading to the AO of breast cancer. Separately, RONS and DNA damage also increase inflammation. Inflammation contributes to direct and indirect effects (effects in cells not directly reached by IR) via positive feedback to RONS and DNA damage, and separately increases proliferation and breast cancer through pro-carcinogenic effects on cells and tissue. For example, gene expression changes alter inflammatory mediators, resulting in improved survival and growth of cancer cells and a more hospitable tissue environment. All of these events overlap at multiple points with events characteristic of "background" induction of breast carcinogenesis, including hormone-responsive proliferation, oxidative activity, and DNA damage. These overlaps make the breast particularly susceptible to ionizing radiation and reinforce that these biological activities are important characteristics of carcinogens. Agents that increase these biological processes should be considered potential breast carcinogens, and predictive methods are needed to identify chemicals that increase these processes. Techniques are available to measure RONS, DNA damage and mutation, cell proliferation, and some inflammatory proteins or processes. Improved assays are needed to measure GI and chronic inflammation, as well as the interaction with hormonally driven development and proliferation. Several methods measure diverse epigenetic changes, but it is not clear which changes are relevant to breast cancer. In addition, most toxicological assays are not conducted in mammary tissue, and so it is a priority to evaluate if results from other tissues are generalizable to breast, or to conduct assays in breast tissue. Developing and applying these assays to identify exposures of concern will facilitate efforts to reduce subsequent breast cancer risk.

Oxidation resistance 1 prevents genome instability through maintenance of G2/M arrest in gamma-ray-irradiated cells

Human oxidation resistance 1 (OXR1) was identified as a protein that decreases genomic mutations in Escherichia coli caused by oxidative DNA damage. However, the mechanism by which OXR1 defends against genome instability has not been elucidated. To clarify how OXR1 maintains genome stability, the effects of OXR1-depletion on genome stability were investigated in OXR1-depleted HeLa cells using gamma-rays (γ-rays). The OXR1-depleted cells had higher levels of superoxide and micronucleus (MN) formation than control cells after irradiation. OXR1-overexpression alleviated the increases in reactive oxygen species (ROS) level and MN formation after irradiation. The increased MN formation in irradiated OXR1-depleted cells was partially attenuated by the ROS inhibitor N-acetyl-L-cysteine, suggesting that OXR1-depeletion increases ROS-dependent genome instability. We also found that OXR1-depletion shortened the duration of γ-ray-induced G2/M arrest. In the presence of the cell cycle checkpoint inhibitor caffeine, the level of MN formed after irradiation was similar between control and OXR1-depleted cells, demonstrating that OXR1-depletion accelerates MN formation through abrogation of G2/M arrest. In OXR1-depleted cells, the level of cyclin D1 protein expression was increased. Here we report that OXR1 prevents genome instability by cell cycle regulation as well as oxidative stress defense.

A comparison of the radiosensitisation ability of 22 different element metal oxide nanoparticles using clinical megavoltage X-rays

Background

A wide range of nanoparticles (NPs), composed of different elements and their compounds, are being developed by several groups as possible radiosensitisers, with some already in clinical trials. However, no systematic experimental survey of the clinical X-ray radiosensitising potential of different element nanoparticles has been made. Here, we directly compare the irradiation-induced (10 Gy of 6-MV X-ray photon) production of hydroxyl radicals, superoxide anion radicals and singlet oxygen in aqueous solutions of the following metal oxide nanoparticles: Al2O3, SiO2, Sc2O3, TiO2, V2O5, Cr2O3, MnO2, Fe3O4, CoO, NiO, CuO, ZnO, ZrO2, MoO3, Nd2O3, Sm2O3, Eu2O3, Gd2O3, Tb4O7, Dy2O3, Er2O3 and HfO2. We also examine DNA damage due to these NPs in unirradiated and irradiated conditions.

Results

Without any X-rays, several NPs produced more radicals than water alone. Thus, V2O5 NPs produced around 5-times more hydroxyl radicals and superoxide radicals. MnO2 NPs produced around 10-times more superoxide anions and Tb4O7 produced around 3-times more singlet oxygen. Lanthanides produce fewer hydroxyl radicals than water. Following irradiation, V2O5 NPs produced nearly 10-times more hydroxyl radicals than water. Changes in radical concentrations were determined by subtracting unirradiated values from irradiated values. These were then compared with irradiation-induced changes in water only. Irradiation-specific increases in hydroxyl radical were seen with most NPs, but these were only significantly above the values of water for V2O5, while the Lanthanides showed irradiation-specific decreases in hydroxyl radical, compared to water. Only TiO2 showed a trend of irradiation-specific increase in superoxides, while V2O5, MnO2, CoO, CuO, MoO3 and Tb4O7 all demonstrated significant irradiation-specific decreases in superoxide, compared to water. No irradiation-specific increases in singlet oxygen were seen, but V2O5, NiO, CuO, MoO3 and the lanthanides demonstrated irradiation-specific decreases in singlet oxygen, compared to water. MoO3 and CuO produced DNA damage in the absence of radiation, while the highest irradiation-specific DNA damage was observed with CuO. In contrast, MnO2, Fe3O4 and CoO were slightly protective against irradiation-induced DNA damage.

Conclusions

Beyond identifying promising metal oxide NP radiosensitisers and radioprotectors, our broad comparisons reveal unexpected differences that suggest the surface chemistry of NP radiosensitisers is an important criterion for their success.

Effects of Resveratrol, Berberine and Their Combinations on Reactive Oxygen Species, Survival and Apoptosis in Human Squamous Carcinoma (SCC-25) Cells

Background:

Levels of cellular Reactive Oxygen Species (ROS) influence the oxidized/reduced states of cellular proteins, and create redox-signaling pathways that can activate transcription factors, kinases, and phosphatases. ROS levels can be increased radically by external factors, including ionizing and UV radiation or exposure to chemical compounds. These increased ROS levels can, in turn, lead to oxidative damage of DNA. Natural plant treatments against cancer can modulate these processes by inducing or decreasing ROS production.

Methods:

Here we report new observations that squamous carcinoma (SCC-25) cells, exposed to 24 hours of combined resveratrol and berberine treatment, contain increased ROS levels. Using flow cytometry, for drug activity characteristics, an accumulation of ROS was observed. A combination of different dyes, CellROX Green (Life Technologies) and DCFH-DA (Sigma), allowed for flow cytometric estimation of levels of cellular ROS as well as cellular localization.

Results:

Live staining and microscopic observations confirmed the accumulation of ROS in SCC-25 cells following a combination treatment at concentrations of 10μg/ml. Additionally, the cytotoxicity of the compounds was significantly improved after their combined application. Additive effects were observed for doses lower than the calculated IC50 of berberine [IC50=23µg/ml] and resveratrol [IC50=9µg/ml]. Viability (MTS) assays and analysis of isobolograms revealed a significant impact on cell viability upon combination treatment.

Conclusion:

These results suggest that administration of berberine, in the presence of resveratrol, could be decreased even to 50% (half the IC50 for berberine) for cancer treatment.

S-Glutathionylated Serine Proteinase Inhibitors as Biomarkers for Radiation Exposure in Prostate Cancer Patients

In biological tissues, radiation causes the formation of reactive oxygen species (ROS), some of which lead to sequential oxidation of certain protein cysteine residues. Resultant cysteinyl radicals are subject to post-translational modification through S-glutathionylation. The present clinical trial was designed to determine if S-glutathionylated serine protease inhibitors (serpins) in blood could be used as biomarkers of exposure to radiation. 56 male prostate cancer patients treated with radiotherapy were enrolled in the trial and levels of S-glutathionylated serpins A1 and A3 were assessed by immunoblotting. Patients were classified into three groups: (1) external beam radiation therapy (EBRT); (2) brachytherapy (BT); (3) both EBRT and BT. Prior to treatment, baseline plasma levels of both unmodified and S-glutathionylated serpins were similar in each group. We identified elevated plasma levels of S-glutathionylated serpin A1 monomer, trimer and serpin A3 monomer in patient blood following radiation. Maximal increased levels of these S-glutathionylated serpins were correlated with increased duration of radiotherapy treatments. We conclude that it is practical to quantify patient plasma S-glutathionylated serpins and that these post-translationally modified proteins are candidate biomarkers for measuring radiation exposure. This provides a platform for use of such biomarkers in trials with the range of drugs that, like radiation, produce ROS.

The adipokine vaspin reduces apoptosis in human hepatocellular carcinoma (Hep-3B) cells, associated with lower levels of NO and superoxide anion

BACKGROUND

Among adipose-derived factors, adipocytokines play roles as hormones and signaling mediators for apoptotic pathway. Among of them, vaspin, regulates the metabolism of adipose tissue itself as an endocrine organ, and stimulates adipocytes to maturation, differentiation, etc. Damaged adipocytes, present in obesity and hepatocellular carcinoma (HCC) respond with over-production of inflammatory cytokines. Such pro-inflammatory stimulation remains under adipokine control. Pro-inflammatory pathways are connected to oxidative stress and apoptosis, reported as co-existing with an elevated level of some adipokines in cancer cell lines. However, some hormones, such as vaspin, reduce apoptosis, have anti-inflammatory and anti-oxidative roles in cancer cell lines.

METHODS

Hep-3B cells were cytometrically evaluated under vaspin treatment for reactive oxygen species (ROS) and apoptosiss induction. The statistical significant changes to the untreated controls was calculated by T-tests (indicated at value p < 0.05).

RESULTS

Here we studied the production of reactive oxygen and nitrogen species in cells of HCC line Hep-3B after vaspin treatment. A decreased level of nitric oxide and superoxide anion 24 h after vaspin addition at 5 ng/ml was correlated with restricted, to the physiological level, apoptosis. A protective role of vaspin was displayed as enhanced cell viability and proliferation, which could be a poor prognostic in liver cancer.

CONCLUSIONS

Apoptosis was suppressed after vaspin treatment, together with low levels of nitric oxide and superoxide anions.

Radiosensitizing effect of 5-aminolevulinic acid in colorectal cancer in vitro and in vivo

The radiosensitizing effect of 5-aminolevulinic acid (5-ALA) has been demonstrated in glioma and melanoma in a number of studies. Enhancing the radiosensitivity of colorectal cancer may improve survival rates and lessen adverse effects. The present study assessed the radiosensitizing effect of 5-ALA in colorectal cancer using the human colon cancer cell line HT29 in vitro and in vivo. In vitro, cells were pretreated with 5-ALA and exposed to ionizing radiation. Cells pretreated with or without 5-ALA were compared using a colony formation assay. In vivo, HT29 cells were implanted into mice subcutaneously and subsequently exposed to ionizing radiation. 5-ALA was administrated by intraperitoneal injection. Subcutaneous tumors treated with or without 5-ALA were compared. Single-dose and multi-dose irradiations were applied both in vitro and in vivo. Cells exposed to multi-dose irradiation and pretreated with 5-ALA in vitro had a significantly lower surviving fraction compared with cells without 5-ALA pretreatment. Following multi-dose irradiation in vivo, the volume of the subcutaneous tumors treated with 5-ALA was significantly lower compared with that of tumors without treatment. These results suggest that radiotherapy with 5-ALA may enhance the therapeutic effect in colon cancer.

ROS Reduction Does Not Decrease the Anticancer Efficacy of X-Ray in Two Breast Cancer Cell Lines

Radiotherapy is effective on a large number of cancer types and is one of the most frequently administrated treatments for cancer patients. The anticancer efficacy of X-ray radiotherapy has been frequently correlated with reactive oxygen species (ROS) elevation, which is also a limiting factor for its toxicity on normal tissues. Here, we found that although 4-10 Gy X-rays could significantly reduce cell numbers in both MDA-MB-231 and MCF-7 breast cancer cells, the ROS level changes are less in MCF-7 cells than in MDA-MB-231 cells. Moreover, although both the ROS scavenger N-acetyl-L-cysteine (NAC) and 1 T static magnetic field (SMF) could reduce X-ray-induced ROS elevation, they did not prevent X-ray-induced cell number reduction or cell death increase, which is significantly different from cisplatin. These results demonstrate that although the anticancer efficacy of cisplatin on two breast cancer cell lines is dependent on ROS, the anticancer efficacy of X-ray is not. Moreover, by testing 19 different cell lines, we found that 1 T SMF could effectively reduce ROS levels in multiple cell lines by 10-20%, which encourages further studies to investigate whether SMF could be used as a potential "physical antioxidant" in the future.

A novel pro-apoptotic role of zinc octacarboxyphthalocyanine in melanoma me45 cancer cell's photodynamic therapy (PDT)

Zn-based phthalocyanine acts as drug or photosensitizer in photodynamic therapy (PDT) for the treatment of cancer cells. The activated zinc octacarboxyphthalocyanine (ZnPcOC) reacts with oxygen, to generate reactive oxygen species for the damage of melanoma cancer cells, Me45. This in vitro study aimed at investigating the cytotoxic effects of different concentrations of ZnPcOC activated with a diode laser (λ = 685 nm) on Me45, and normal human fibroblast cells, NHDF. To perform this study 10⁴ cells/ml were seeded in 96-well plates and allowed to attach overnight, after which cells were treated with different concentrations of ZnPcOC (10, 20 and 30 μM). After 4 h, cells were irradiated with a constant light dose of 2.5; 4.5 and 7.5 J/cm². Post-irradiated cells were incubated for 24 h before cell viability was measured using the MTT viability assay. Data indicated that high concentrations of ZnPcOC (30 μM) in its inactive state are not cytotoxic to the melanoma cancer cells and normal fibroblasts. Moreover, the results showed that photoactivated ZnPcOC (30 μM) was able to reduce the cell viability of melanoma and fibroblast to about 50%, respectively. At this photosensitizing concentration the efficacy the treatment light dose of 2.5; 4.5 and 7.5 J/cm² was evaluated against Me45 cells. ZnPcOC at a concentration of 30 μM activated with a light dose of 2.5; 4.5 and 7.5 J/cm² was the most efficient for the killing of melanoma cancer cells. Melanoma cancer cells after PDT with a photosensitizing concentration of 30 μM ZnPcOC and a treatment light dose of 2.5; 4.5 and 7.5 J/cm² showed certain pro-apoptotic characteristics, such as direct inducer (early apoptosis) and long-term inducer, also (late apoptosis). This concludes that low concentrations of ZnPcOC, activated with the appropriate light dose, can be used to induce cell death in melanoma cells via ROS-induces apoptosis pathway, what was confirmed with cytometric ROS measurements. Our in vitro study showed that ZnPcOC mediated photodynamic therapy is an effective treatment option for melanoma Me45 cancer cells. 30 μM of ZnPcOC with the treatment light dose of 2.5 J/cm² from a LED diode laser source, with a wavelength of 685 nm, was adequate to destroy melanoma cancer cells via ROS-induced apoptosis pathway, with low killing effects on healthy NHDF normal fibroblasts.

Evaluation of mitochondrial redox status and energy metabolism of X-irradiated HeLa cells by LC/UV, LC/MS/MS and ESR

To evaluate the metabolic responses in tumour cells exposed to ionizing radiation, oxygen consumption rate (OCR), cellular lipid peroxidation, cellular energy status (intracellular nucleotide pool and ATP production), and mitochondrial reactive oxygen species (ROS), semiquinone (SQ), and iron-sulphur (Fe-S) cluster levels were evaluated in human cervical carcinoma HeLa cells at 12 and 24 h after X-irradiation. LC/MS/MS analysis showed that levels of 8-iso PGF_2α and 5-iPF_2α-VI, lipid peroxidation products of membrane arachidonic acids, were not altered significantly in X-irradiated cells, although mitochondrial ROS levels and OCR significantly increased in the cells at 24 h after irradiation. LC/UV analysis revealed that intracellular AMP, ADP, and ATP levels increased significantly after X-irradiation, but adenylate energy charge (adenylate energy charge (AEC) = [ATP + 0.5 × ADP]/[ATP + ADP + AMP]) remained unchanged after X-irradiation. In low-temperature electron spin resonance (ESR) spectra of HeLa cells, the presence of mitochondrial SQ at g = 2.004 and Fe-S cluster at g = 1.941 was observed and X-irradiation enhanced the signal intensity of SQ but not of the Fe-S cluster. Furthermore, this radiation-induced increase in SQ signal intensity disappeared on treatment with rotenone, which inhibits electron transfer from Fe-S cluster to SQ in complex I. From these results, it was suggested that an increase in OCR and imbalance in SQ and Fe-S cluster levels, which play a critical role in the mitochondrial electron transport chain (ETC), occur after X-irradiation, resulting in an increase in ATP production and ROS leakage from the activated mitochondrial ETC.

N-Acetyl-L-cysteine protects thyroid cells against DNA damage induced by external and internal irradiation

We evaluated the effect of the antioxidant N-acetyl-L-cysteine (NAC) on the levels of reactive oxygen species (ROS), DNA double strand breaks (DSB) and micronuclei (MN) induced by internal and external irradiation using a rat thyroid cell line PCCL3. In internal irradiation experiments, ROS and DSB levels increased immediately after ¹³¹I addition and then gradually declined, resulting in very high levels of MN at 24 and 48 h. NAC administration both pre- and also post-¹³¹I addition suppressed ROS, DSB and MN. In external irradiation experiments with a low dose (0.5 Gy), ROS and DSB increased shortly and could be prevented by NAC administration pre-, but not post-irradiation. In contrast, external irradiation with a high dose (5 Gy) increased ROS and DSB in a bimodal way: ROS and DSB levels increased immediately after irradiation, quickly returned to the basal levels and gradually rose again after >24 h. The second phase was in parallel with an increase in 4-hydroxy-2-nonenal. The number of MN induced by the second wave of ROS/DSB elevations was much higher than that by the first peak. In this situation, NAC administered pre- and post-irradiation comparably suppressed MN induced by a delayed ROS elevation. In conclusion, a prolonged ROS increase during internal irradiation and a delayed ROS increase after external irradiation with a high dose caused serious DNA damage, which were efficiently prevented by NAC. Thus, NAC administration even both after internal or external irradiation prevents ROS increase and eventual DNA damage.

Synthesis and Radioprotective Activity of Mitochondria Targeted Dihydropyridines In Vitro

The radiation-induced damage to mitochondrial oxidative respiratory chain could lead to generating of superoxide anions (O²⁻) and secondary reactive oxygen species (ROS), which are the major resources of continuous ROS production after radiation. Scavenging radiation-induced ROS effectively can help mitochondria to maintain their physiological function and relief cells from oxidative stress. Dihydropyridines (DHPs) are biomimetic hydrogen sources that could protect cells against radiation damage. In this study, we designed and synthetized three novel mitochondrial-targeted dihydropyridines (Mito-DHPs) that utilize the mitochondrial membrane potential to enter the organelle and scavenge ROS. MitoTracker confirmed Mito-DHPs accumulation in mitochondria, and the DCFH-DA assay demonstrated effective ROS scavenging activity. In addition, the γ-H2AX and comet assay demonstrated the ability of Mito-DHPs to protect against both radiation and ROS-induced DNA strand breaks. Furthermore, Mito-DHP1 proved to be non-toxic and displayed significant radioprotection activity (p < 0.05) in vitro. Mito-DHPs are therefore promising antioxidants that could penetrate the membrane of mitochondria, scavenge excessive ROS, and protect cells against radiation-induced oxidative damage.

Selective ATP hydrolysis inhibition in F1Fo ATP synthase enhances radiosensitivity in non-small-cell lung cancer cells (A549)

Background

F1Fo-ATP synthase (F1Fo-ATPase) is a reversibly rotary molecular machine whose dual functions of synthesizing or hydrolyzing ATP switch upon the condition of cell physiology. The robust ATP-hydrolyzing activity occurs in ischemia for maintaining the transmembrane proton motive force of mitochondria inner membrane, but the effect of F1Fo-ATPase on X-ray response of non-small-cell lung cancer (NSCLC) cells is unknown.

Methods and Findings

We studied whether ATP hydrolysis affected X-ray radiation induced cell death. NSCLC cells (A549) were pretreated with BTB06584 (BTB), an elective ATP hydrolysis inhibitor, followed by X-ray radiation. Cell viability and clonogenic survival were markedly decreased, clear indications of enhanced radiosensitivity through BTB incubation. Additionally, ATP5α1 was upregulated in parallel with elevated ATP hydrolytic activity after X-ray radiation, showing an increased mitochondrial membrane potential (ΔΨm). ATP hydrolysis inhibition led to collapse of ΔΨm suggesting ATP hydrolytic activity could enhance ΔΨm after X-ray radiation. Furthermore, we also demonstrated that apoptosis was pronounced with the prolonged collapse of ΔΨm due to hydrolysis inhibition by BTB incubation.

Conclusion

Overall, these findings supported that ATP hydrolysis inhibition could enhance the radiosensitivity in NSCLC cells (A549) after X-ray radiation, which was due to the collapse of ΔΨm.

Spatio-temporal changes in glutathione and thioredoxin redox couples during ionizing radiation-induced oxidative stress regulate tumor radio-resistance

Ionizing radiation (IR)-induced oxidative stress in tumor cells is effectively managed by constitutive and inducible antioxidant defense systems. This study was initiated to understand the relative contribution of different redox regulatory systems in determining the tumor radio-resistance. In this study, human T-cell lymphoma (Jurkat) cells were exposed to IR (4 Gy) and monitored for the spatio-temporal changes in cellular redox regulatory parameters. We monitored the changes in the levels of reactive oxygen species (ROS) (total, mitochondrial, primary, and secondary), thiols (total, surface, and intracellular), GSH/GSSG ratio, antioxidant enzyme activity viz. thioredoxin (Trx), Trx reductase (TrxR), glutathione peroxidase, and glutathione reductase with respect to time. We have also measured protein glutathionylation. We observed that tumor cells mount a biphasic response after IR exposure which can be divided into early (0-6 h) and late (16-48 h) responses in terms of changes in cellular redox parameters. During early response, constitutively active GSH and Trx systems respond to restore cellular redox balance to pre-exposure levels and help in activation of redox-sensitive transcription factor Nrf-2. During late response, increase in the levels of antioxidants GSH and Trx rescue cells against IR-mediated damage. We observed that disruption of either glutathione or thioredoxin metabolism led to partial impairment of ability of cells to survive against IR-induced damage. But simultaneous disruption of both the pathways significantly increased radio sensitivity of Jurkat cells. This highlighted the importance of these two antioxidant pathways in regulating redox homeostasis under conditions of IR-induced oxidative stress.

Modeling cell response to low doses of photon irradiation: Part 2--application to radiation-induced chromosomal aberrations in human carcinoma cells

The biological phenomena observed at low doses of ionizing radiation (adaptive response, bystander effects, genomic instability, etc.) are still not well understood. While at high irradiation doses, cellular death may be directly linked to DNA damage, at low doses, other cellular structures may be involved in what are known as non-(DNA)-targeted effects. Mitochondria, in particular, may play a crucial role through their participation in a signaling network involving oxygen/nitrogen radical species. According to the size of the implicated organelles, the fluctuations in the energy deposited into these target structures may impact considerably the response of cells to low doses of ionizing irradiation. Based on a recent simulation of these fluctuations, a theoretical framework was established to have further insight into cell responses to low doses of photon irradiation, namely the triggering of radioresistance mechanisms by energy deposition into specific targets. Three versions of a model are considered depending on the target size and on the number of targets that need to be activated by energy deposition to trigger radioresistance mechanisms. These model versions are applied to the fraction of radiation-induced chromosomal aberrations measured at low doses in human carcinoma cells (CAL51). For this cell line, it was found in the present study that the mechanisms of radioresistance could not be triggered by the activation of a single small target (nanometric size, 100 nm), but could instead be triggered by the activation of a large target (micrometric, 10 μm) or by the activation of a great number of small targets. The mitochondria network, viewed either as a large target or as a set of small units, might be concerned by these low-dose effects.

Ionizing radiation-induced cell death is partly caused by increase of mitochondrial reactive oxygen species in normal human fibroblast cells

Radiation-induced cell death is thought to be caused by nuclear DNA damage that cannot be repaired. However, in this study we found that a delayed increase of mitochondrial reactive oxygen species (ROS) is responsible for some of the radiation-induced cell death in normal human fibroblast cells. We have previously reported that there is a delayed increase of mitochondrial (·)O2(-), measured using MitoSOX™ Red reagent, due to gamma irradiation. This is dependent on Drp1 localization to mitochondria. Here, we show that knockdown of Drp1 expression reduces the level of DNA double-strand breaks (DSBs) remaining 3 days after 6 Gy irradiation. Furthermore, cells with knockdown of Drp1 expression are more resistant to gamma radiation. We then tested whether the delayed increase of ROS causes DNA damage. The antioxidant, 2-glucopyranoside ascorbic acid (AA-2G), was applied before or after irradiation to inhibit ROS production during irradiation or to inhibit delayed ROS production from mitochondria. Interestingly, 1 h after exposure, the AA-2G treatment reduced the level of DSBs remaining 3 days after 6 Gy irradiation. In addition, irradiated AA-2G-treated cells were more resistant to radiation than the untreated cells. These results indicate that delayed mitochondrial ROS production may cause some of the cell death after irradiation.

Understanding cancer development processes after HZE-particle exposure: roles of ROS, DNA damage repair and inflammation

During space travel astronauts are exposed to a variety of radiations, including galactic cosmic rays composed of high-energy protons and high-energy charged (HZE) nuclei, and solar particle events containing low- to medium-energy protons. Risks from these exposures include carcinogenesis, central nervous system damage and degenerative tissue effects. Currently, career radiation limits are based on estimates of fatal cancer risks calculated using a model that incorporates human epidemiological data from exposed populations, estimates of relative biological effectiveness and dose-response data from relevant mammalian experimental models. A major goal of space radiation risk assessment is to link mechanistic data from biological studies at NASA Space Radiation Laboratory and other particle accelerators with risk models. Early phenotypes of HZE exposure, such as the induction of reactive oxygen species, DNA damage signaling and inflammation, are sensitive to HZE damage complexity. This review summarizes our current understanding of critical areas within the DNA damage and oxidative stress arena and provides insight into their mechanistic interdependence and their usefulness in accurately modeling cancer and other risks in astronauts exposed to space radiation. Our ultimate goals are to examine potential links and crosstalk between early response modules activated by charged particle exposure, to identify critical areas that require further research and to use these data to reduced uncertainties in modeling cancer risk for astronauts. A clearer understanding of the links between early mechanistic aspects of high-LET response and later surrogate cancer end points could reveal key nodes that can be therapeutically targeted to mitigate the health effects from charged particle exposures.

Increased effectiveness of carbon ions in the production of reactive oxygen species in normal human fibroblasts

The production of reactive oxygen species (ROS), especially superoxide anions (O2 (·-)), is enhanced in many normal and tumor cell types in response to ionizing radiation. The influence of ionizing radiation on the regulation of ROS production is considered as an important factor in the long-term effects of irradiation (such as genomic instability) that might contribute to the development of secondary cancers. In view of the increasing application of carbon ions in radiation therapy, we aimed to study the potential impact of ionizing density on the intracellular production of ROS, comparing photons (X-rays) with carbon ions. For this purpose, we used normal human cells as a model for irradiated tissue surrounding a tumor. By quantifying the oxidization of Dihydroethidium (DHE), a fluorescent probe sensitive to superoxide anions, we assessed the intracellular ROS status after radiation exposure in normal human fibroblasts, which do not show radiation-induced chromosomal instability. After 3-5 days post exposure to X-rays and carbon ions, the level of ROS increased to a maximum that was dose dependent. The maximum ROS level reached after irradiation was specific for the fibroblast type. However, carbon ions induced this maximum level at a lower dose compared with X-rays. Within ∼1 week, ROS decreased to control levels. The time-course of decreasing ROS coincides with an increase in cell number and decreasing p21 protein levels, indicating a release from radiation-induced growth arrest. Interestingly, radiation did not act as a trigger for chronically enhanced levels of ROS months after radiation exposure.

Radioprotective effects of mitochondria-targeted antioxidant SkQR1

We show here that mitochondria-targeted antioxidant composed of plastoquinone conjugated through hydrocarbon linker with cationic rhodamine 19 (SkQR1) protected against nuclear DNA damage induced by gamma radiation in K562 erythroleukemia cells. We also demonstrate that SkQR1 prevented the early (1 h postirradiation) accumulation of phosphorylated histone H2AX (γ-H2AX) an indicator of DNA double-strand break formation, as well as the radiation-induced increase in chromosomal aberrations. These data suggested that nuclear DNA damage induced by gamma radiation may be mediated by mitochondrial reactive oxygen species (ROS) production. We show that SkQR1 suppressed delayed accumulation of ROS 32 h after irradiation probably by inhibiting mitochondrial ROS-induced ROS release mechanisms. This suggests that mitochondria-targeted antioxidants may protect cells from the late consequences of radiation exposure related to delayed oxidative stress. We have previously reported that SkQRl is the substrate of multidrug resistance pump P-glycoproten (Pgp 170) and selectively protects Pgp 170-negative cells against oxidative stress. In line with this finding, we demonstrate here that SkQR1 did not protect Pgp170-positive K562 subline against DNA damage induced by gamma radiation. The selective radioprotection of normal Pgp 170-negative cells by mitochondria-targeted antioxidants could be a promising strategy to increase the efficiency of radiotherapy for multidrug-resistant tumors.

Induction of bystander effects by UVA, UVB, and UVC radiation in human fibroblasts and the implication of reactive oxygen species

Radiation-induced bystander effects are various types of responses displayed by nonirradiated cells induced by signals transmitted from neighboring irradiated cells. This phenomenon has been well studied after ionizing radiation, but data on bystander effects after UV radiation are limited and so far have been reported mainly after UVA and UVB radiation. The studies described here were aimed at comparing the responses of human dermal fibroblasts exposed directly to UV (A, B, or C wavelength range) and searching for bystander effects induced in unexposed cells using a transwell co-incubation system. Cell survival and apoptosis were used as a measure of radiation effects. Additionally, induction of senescence in UV-exposed and bystander cells was evaluated. Reactive oxygen species (ROS), superoxide radical anions, and nitric oxide inside the cells and secretion of interleukins 6 and 8 (IL-6 and IL-8) into the medium were assayed and evaluated as potential mediators of bystander effects. All three regions of ultraviolet radiation induced bystander effects in unexposed cells, as shown by a diminution of survival and an increase in apoptosis, but the pattern of response to direct exposure and the bystander effects differed depending on the UV spectrum. Although UVA and UVB were more effective than UVC in generation of apoptosis in bystander cells, UVC induced senescence both in irradiated cells and in neighbors. The level of cellular ROS increased significantly shortly after UVA and UVB exposure, suggesting that the bystander effects may be mediated by ROS generated in cells by UV radiation. Interestingly, UVC was more effective at generation of ROS in bystanders than in directly exposed cells and induced a high yield of superoxide in exposed and bystander cells, which, however, was only weakly associated with impairment of mitochondrial membrane potential. Increasing concentration of IL-6 but not IL-8 after exposure to each of the three bands of UV points to its role as a mediator in the bystander effect. Nitric oxide appeared to play a minor role as a mediator of bystander effects in our experiments. The results demonstrating an increase in intracellular oxidation, not only in directly UV-exposed but also in neighboring cells, and generation of proinflammatory cytokines, processes entailing cell damage (decreased viability, apoptosis, senescence), suggest that all bands of UV radiation carry a potential hazard for human health, not only due to direct mechanisms, but also due to bystander effects.