An alternative mechanism for radioprotection by dimethyl sulfoxide; possible facilitation of DNA double-strand break repair

Metabolic disruptions induced by low concentrations of DMSO in RTgill-W1 fish cells: The importance of solvent controls in in vitro studies

Dimethyl sulfoxide (DMSO) is a widely used solvent in biological research due to its ability to enhance membrane permeability, facilitating drug delivery and molecular transport across cellular membranes. However, its effects on cellular metabolism, especially at low concentrations, remain insufficiently understood. This study investigated the metabolic disruptions induced by 0.1-10 % DMSO in the RTgill-W1 fish cell line, focusing on changes in cell viability, oxidative stress, and key metabolic pathways. Results revealed that DMSO exposure caused dose-dependent declines in cell viability at 0.5 % DMSO and increases in reactive oxygen species (ROS) at 4 % and higher, indicating elevated oxidative stress. Metabolomic profiling revealed altered levels of numerous metabolites and significant impacts on 41 metabolic pathways belonging to five major functional groups: amino acid metabolism, carbohydrate metabolism, lipid metabolism, vitamin and co-factor metabolism, and nucleotide metabolism. The effects were observed across all exposure concentrations (0.1, 0.5, 1, 4, and 8 %), with more pronounced impacts at higher concentrations. These findings highlight that DMSO, even at low concentrations (≤ 0.5 %), can have widespread effects on cellular metabolism, impacting experimental outcomes in in vitro studies. This study provides valuable insights into the biochemical impacts of DMSO on fish cell lines and emphasizes a caution in using DMSO in biological research to minimize unintended cellular effects. Additionally, it highlights the critical need to include solvent controls at matching concentrations to accurately distinguish solvent-induced effects from those caused by experimental treatments.

Insecticide chlorfenapyr confers induced toxicity in human cells through mitochondria-dependent pathways of apoptosis

Pesticides are always used in the environment, the unexpected effects of pesticides on the environment and non-target organisms need to be continuously studied. Insecticide chlorfenapyr (Chl) is widely used in agriculture and also recommended for public health use (e.g., providing protection from malaria). Here we study toxic effects of Chl on human alveolar carcinoma cells (A549) and human normal liver cells (L02) in vitro. Chl's ability to induce DNA damage and apoptosis in human cells was confirmed through alkaline comet assay, immunofluorescence assay, and flow cytometric analysis. Further research showed that Chl induced mitochondrial damage (the collapse of mitochondrial membrane potential and the opening of mitochondrial permeability transition pore) with up-regulated expression of Bax/Bcl-2 leads to the release of cytochrome c from mitochondria which in turn activated the apoptotic pathway. Meanwhile, the key protein PARP is cleaved during apoptosis, resulting in the inhibition of DNA damage repair. In short, human A549 and L02 cells exposed to Chl were experiencing DNA damage and apoptosis linked to mitochondria. The results of this study supply theoretical understanding of Chl's toxicity on human cells, and can attract attention on the potential threat of insecticide Chl to human health.

Induction of Chromosomal Aberrations after Exposure to the Auger Electron Emitter Iodine-125, the β--emitter Tritium and Cesium-137 γ rays

High-LET-type cell survival curves have been observed in cells that were allowed to incorporate 125I-UdR into their DNA. Incorporation of tritiated thymidine into the DNA of cells has also been shown to result in an increase in relative biological effectiveness in cell survival experiments, but the increase is smaller than observed after incorporation of 125I-UdR. These findings are explained in the literature by the overall complexity of the induced DNA damage resulting from energies of the ejected electron(s) during the decay of 3H and 125I. Chromosomal aberrations (CA) are defined as morphological or structural changes of one or more chromosomes, and can be induced by ionizing radiation. Whether the number of CA is associated with the linear energy transfer (LET) of the radiation and/or the actual complexity of the induced DNA double-strand breaks (DSB) remains elusive. In this study, we investigated whether DNA lesions induced at different cell cycle stages and by different radiation types [Auger-electrons (125I), β- particles (3H), or γ radiation (137Cs)] have an impact on the number of CA induced after induction of the same number of DSB as determined by the γ-H2AX foci assay. Cells were synchronized and pulse-labeled in S phase with low activities of 125I-UdR or tritiated thymidine. For decay accumulation, cells were cryopreserved either after pulse-labeling in S phase or after progression to G2/M or G1 phase. Experiments with γ irradiation (137Cs) were performed with synchronized and cryopreserved cells in S, G2/M or G1 phase. After thawing, a CA assay was performed. All experiments were performed after a similar number of DSB were induced. CA induction after 125I-UdR was incorporated was 2.9-fold and 1.7-fold greater compared to exposure to γ radiation and radiation from incorporated tritiated thymidine, respectively, when measured in G2/M cells. In addition, measurement of CA in G2/M cells after incorporation of 125I-UdR was 2.5-fold greater when compared to cells in G1 phase. In contrast, no differences were observed between the three radiation qualities with respect to exposure after cryopreservation in S or G1 phase. The data indicate that the 3D organization of replicated DNA in G2/M cells seems to be more sensitive to induction of more complex DNA lesions compared to the DNA architecture in S or G1 cells. Whether this is due to the DNA organization itself or differences in DNA repair capability remains unclear.

Dimethyl Sulfoxide Attenuates Radiation-Induced Testicular Injury through Facilitating DNA Double-Strand Break Repair

The testis is susceptible to ionizing radiation, and male infertility and sexual dysfunction are prevalent problems after whole-body or local radiation exposure. Currently, there is no approved agent for the prevention or treatment of radiation-induced testicular injury. Herein, we investigated the radioprotective effect of dimethyl sulfoxide (DMSO), an organosulfur compound that acts as a free radical scavenger, on testicular injury. Treatment of mice with a single dose of DMSO prior to 5 Gy irradiation restored sex hormones and attenuated the reduction in testis weight. Histological analyses revealed that DMSO alleviated the distorted architecture of seminiferous tubules and promoted seminiferous epithelium regeneration following irradiation. Moreover, DMSO provided quantitative and qualitative protection for sperm and preserved spermatogenesis and fertility in male mice. Mechanistically, DMSO treatment enhanced GFRα-1⁺ spermatogonial stem cell and c-Kit⁺ spermatogonial survival and regeneration after radiation. DMSO also alleviated radiation-induced oxidative stress and suppressed radiation-induced germ cell apoptosis in vivo and in vitro. Additionally, DMSO efficiently reduced DNA damage accumulation and induced the expression of phosph-BRCA1, BRCA1, and RAD51 proteins, indicating that DMSO facilitates DNA damage repair with a bias toward homologous recombination. In summary, our findings demonstrate the radioprotective efficacy of DMSO on the male reproductive system, which warrants further studies for future application in the preservation of male fertility during conventional radiotherapy and nuclear accidents.

The incipient denaturation mechanism of DNA

DNA denaturation is related to many important biological phenomena, such as its replication, transcription and the interaction with some specific proteins for single-stranded DNA. Dimethyl sulfoxide (DMSO) is a common chemical agent for DNA denaturation. In the present study, we investigate quantitatively the effects of different concentrations of DMSO on plasmid and linear DNA denaturation by atomic force microscopy (AFM) and UV spectrophotometry. We found that persistent length of DNA decreases significantly by adding a small amount of DMSO before ensemble DNA denaturation occurs; the persistence length of DNA in 3% DMSO solution decreases to 12 nm from about 50 nm without DMSO in solution. And local DNA denaturation occurs even at very low DMSO concentration (such as 0.1%), which can be directly observed in AFM imaging. Meanwhile, we observed the forming process of DNA contacts between different parts for plasmid DNA with increasing DMSO concentration. We suggest the initial mechanism of DNA denaturation as follows: DNA becomes more flexible due to the partial hydrogen bond braking in the presence of DMSO before local separation of the two complementary nucleotide chains.

The persistent length of DNA decreases significantly by adding small amount of DMSO. Local DNA denaturation occurs even at very low DMSO concentration, which can be observed by atomic force microscopy directly.

Evaluation of Calyculin A Effect on γH2AX/53BP1 Focus Formation and Apoptosis in Human Umbilical Cord Blood Lymphocytes

Dephosphorylation inhibitor calyculin A (cal A) has been reported to inhibit the disappearance of radiation-induced γH2AX DNA repair foci in human lymphocytes. However, other studies reported no change in the kinetics of γH2AX focus induction and loss in irradiated cells. While apoptosis might interplay with the kinetics of focus formation, it was not followed in irradiated cells along with DNA repair foci. Thus, to validate plausible explanations for significant variability in outputs of these studies, we evaluated the effect of cal A (1 and 10 nM) on γH2AX/53BP1 DNA repair foci and apoptosis in irradiated (1, 5, 10, and 100 cGy) human umbilical cord blood lymphocytes (UCBL) using automated fluorescence microscopy and annexin V-FITC/propidium iodide assay/γH2AX pan-staining, respectively. No effect of cal A on γH2AX and colocalized γH2AX/53BP1 foci induced by low doses (≤10 cGy) of γ-rays was observed. Moreover, 10 nM cal A treatment decreased the number of all types of DNA repair foci induced by 100 cGy irradiation. 10 nM cal A treatment induced apoptosis already at 2 h of treatment, independently from the delivered dose. Apoptosis was also detected in UCBL treated with lower cal A concentration, 1 nM, at longer cell incubation, 20 and 44 h. Our data suggest that apoptosis triggered by cal A in UCBL may underlie the failure of cal A to maintain radiation-induced γH2AX foci. All DSB molecular markers used in this study responded linearly to low-dose irradiation. Therefore, their combination may represent a strong biodosimetry tool for estimation of radiation response to low doses. Assessment of colocalized γH2AX/53BP1 improved the threshold of low dose detection.

The Effects of Dimethylsulfoxide and Oxygen on DNA Damage Induction and Repair Outcomes for Cells Irradiated by 62 MeV Proton and 3.31 MeV Helium Ions

Reactive oxygen species (ROS) play an essential role in radiation-induced indirect actions. In terms of DNA damage, double strand breaks (DSBs) have the greatest effects on the repair of DNA damage, cell survival and transformation. This study evaluated the biological effects of the presence of ROS and oxygen on DSB induction and mutation frequency. The relative biological effectiveness (RBE) and oxygen enhancement ratio (OER) of 62 MeV therapeutic proton beams and 3.31 MeV helium ions were calculated using Monte Carlo damage simulation (MCDS) software. Monte Carlo excision repair (MCER) simulations were used to calculate the repair outcomes (mutation frequency). The RBE values of proton beams decreased to 0.75 in the presence of 0.4 M dimethylsulfoxide (DMSO) and then increases to 0.9 in the presence of 2 M DMSO while the RBE values of 3.31 MeV helium ions increased from 2.9 to 5.7 (0–2 M). The mutation frequency of proton beams also decreased from 0.008–0.065 to 0.004–0.034 per cell per Gy by the addition of 2 M DMSO, indicating that ROS affects both DSB induction and repair outcomes. These results show that the combined use of DMSO in normal tissues and an increased dose in tumor regions increases treatment efficiency.

5-Nitro-2,4-Dichloropyrimidine as an Universal Model for Low-Energy Electron Processes Relevant for Radiosensitization

We report experimental results of low-energy electron interactions with.

Modeling Direct and Indirect Action on Cell Survival After Photon Irradiation under Normoxia and Hypoxia

The demand for personalized medicine in radiotherapy has been met by a surge of mechanistic models offering predictions of the biological effect of ionizing radiation under consideration of a growing number of parameters. We present an extension of our existing model of cell survival after photon irradiation to explicitly differentiate between the damage inflicted by the direct and indirect (radicals-mediated) action of ionizing radiation. Within our approach, we assume that the oxygenation status affects the indirect action. The effect of different concentrations of dimethyl sulfoxide (DMSO), an effective radical scavenger, has been simulated at different dose levels in normoxic and hypoxic conditions for various cell lines. Our model is found to accurately predict experimental data available in literature, validating the assumptions made in our approach. The presented extension adds further flexibility to our model and could act as basis for further developments of our model.

Radiation Chemical Investigation of Antioxidant Activity of Biologically Important Compounds from Plant Materials

Radiation chemical modeling of redox reactions of biologically active compounds from plant materials showed that coumarins possess strong antiradical properties. Data confirming the radioprotective properties of these compounds were obtained. Antioxidant activity has been shown for specific medicinal plant extracts-Melilotus officinalis and Ledum palustre cormus. The radiation chemical transformations of coumarins revealed that an unsubstituted coumarin has greater radioprotective activity.

Roundup® confers cytotoxicity through DNA damage and Mitochondria-Associated apoptosis induction

Glyphosate-based herbicides (GBH) are the most widely used pesticides in the world. The extensive use of them increases the potential human health risk, including the human inhalation toxicity risk. We studied the effect of the most famous GBH Roundup® (RDP) in the concentration range from 50 to 125 μg/mL on Mitochondria-Associated apoptosis and DNA damage in Human alveolar carcinoma cells (A549 cells). Alkaline comet assay, immunofluorescence assay and Flow Cytometric Analysis assay were employed to detect DNA damages and apoptosis of A549 cells. We found RDP caused concentration-dependent increases in DNA damages and proportion of apoptotic cells in A549 cells. RDP induced the DNA single-strand breaks and double-strand breaks; the collapse of mitochondrial membrane by increasing Bax/Bcl-2, resulting in the release of cytochrome c into cytosol and then activated caspase-9/-3, cleaved poly (ADP-ribose) polymerase (PARP) in human lung tissue cells. The results demonstrate that RDP can induce A549 cells cytotoxic effects in vitro at the concentration lower than the occupational exposures level of workers, which means RDP has a potential threat to human health.

Impact of dimethyl sulfoxide on irradiation-related DNA double-strand-break induction, -repair and cell survival

Dimethyl sulfoxide (DMSO) is an effective radical scavenger and, when added to cells, reduces the initial number of radiation-induced DNA double-strand breaks (DSB). The aim of this study was to investigate modification by DMSO of both DSB induction and DSB repair by means of pulsed-field gel electrophoresis (PFGE) as well as gamma-H2AX immunofluorescence staining. WiDr cells (human colon carcinoma provided by DKFZ) were incubated with 2% DMSO for 2 h (or mock-treated) prior to irradiation with varying X-ray doses and subsequent incubation for repair. Sample processing for PFGE analysis or counting of γ-H2AX foci was performed according to standard protocols. Effects on apoptosis induction and cell survival were investigated additionally by standard protocols. DMSO reduced DSB yield after 20-80 Gy measured by PFGE. A qualitatively similar result was found after low-dose irradiation (1 Gy) using γ-H2AX immunofluorescence staining. During incubation for repair, both DNA fragment rejoining (PFGE) as well as γ-H2AX foci removal occurred at a reduced rate when cells had been pre-treated with DMSO. But this effect was clearly more pronounced for the PFGE-analyzed double-strand breakage, particularly at early repair times. WiDr cells treated with DMSO (2%) showed a significantly increased clonogenic survival after irradiation doses above 8 Gy. Apoptosis rates were not changed by DMSO. The radio-protective effect of DMSO, well known from other PFGE studies, could be confirmed for the formation of γ-H2AX foci. DSB generated in the presence of DMSO were less rapidly repaired. DMSO showed radio-protective effects on clonogenic survival but not on apoptosis.

Biological outcomes of γ-radiation induced DNA damages in breast and lung cancer cells pretreated with free radical scavengers

PURPOSE

Investigation of effects on DNA of γ-irradiated human cancer cells pretreated with free radical scavengers is aimed to create reference data which would enable assessment of the relative efficiency of high linear energy transfer (LET) radiations used in hadron therapy, i.e. protons and carbon ions.

MATERIALS AND METHODS

MCF-7 breast and HTB177 lung cancer cells are irradiated with γ-rays. To minimize indirect effects of irradiation, dimethyl sulfoxide (DMSO) or glycerol are applied as free radical scavengers. Biological response to irradiation is evaluated through clonogenic cell survival, immunocytochemical and cell cycle analysis, as well as expression of proteins involved in DNA damage response.

RESULTS

Examined cell lines reveal similar level of radioresistance. Application of scavengers leads to the rise of cell survival and decreases the number of DNA double strand breaks in irradiated cells. Differences in cell cycle and protein expression between the two cell lines are probably caused by different DNA damage repair mechanisms that are activated.

CONCLUSION

The obtained results show that DMSO and glycerol have good scavenging capacity, and may be used to minimize DNA damage induced by free radicals. Therefore, they will be used as the reference for comparison with high LET irradiations, as well as good experimental data suitable for validation of numerical simulations.

Low dose dimethyl sulfoxide driven gross molecular changes have the potential to interfere with various cellular processes

Dimethyl sulfoxide (DMSO) is a small molecule with polar, aprotic and amphiphilic properties. It serves as a solvent for many polar and nonpolar molecules and continues to be one of the most used solvents (vehicle) in medical applications and scientific research. To better understand the cellular effects of DMSO within the concentration range commonly used as a vehicle (0.1-1.5%, v/v) for cellular treatments, we applied Attenuated Total Reflectance (ATR) Fourier Transform Infrared (FT-IR) spectroscopy to DMSO treated and untreated epithelial colon cancer cells. Both unsupervised (Principal Component Analysis-PCA) and supervised (Linear Discriminant Analysis-LDA) pattern recognition/modelling algorithms applied to the IR data revealed total segregation and prominent differences between DMSO treated and untreated cells at whole, lipid and nucleic acid regions. Several of these data were supported by other independent techniques. Further IR data analyses of macromolecular profile indicated comprehensive alterations especially in proteins and nucleic acids. Protein secondary structure analysis showed predominance of β-sheet over α-helix in DMSO treated cells. We also observed for the first time, a reduction in nucleic acid level upon DMSO treatment accompanied by the formation of Z-DNA. Molecular docking and binding free energy studies indicated a stabilization of Z-DNA in the presence of DMSO. This alternate DNA form may be related with the specific actions of DMSO on gene expression, differentiation, and epigenetic alterations. Using analytical tools combined with molecular and cellular biology techniques, our data indicate that even at very low concentrations, DMSO induces a number of changes in all macromolecules, which may affect experimental outcomes where DMSO is used as a solvent.

Dimethyl Sulfoxide Prevents Radiation-Induced Oral Mucositis Through Facilitating DNA Double-Strand Break Repair in Epithelial Stem Cells

PURPOSE

Oral mucositis is one of the most prevalent side effects in patients undergoing radiation therapy for head and neck cancers. Current therapeutic agents such as palifermin recombinant human keratinocyte growth factor and amifostine do not efficiently or fully prevent mucositis. Dimethyl sulfoxide (DMSO), a free-radical scavenger, has shown therapeutic benefits in many preclinical and clinical studies. This study aimed to investigate the efficacy of DMSO in a clinically relevant mouse model of acute, radiation-induced oral mucositis.

METHODS AND MATERIALS

Oral mucositis was induced by a high single and fractioned irradiation of the head and neck area in C57BL/6J mice, and the effects of DMSO (by intraperitoneal injection) were assessed by macroscopic and histopathological examination. Epithelial stem and progenitor cells were analyzed by immunohistochemical staining of p63 and Ki-67, and DNA double-strand breaks (DSBs) were visualized by immunofluorescence detection of γ-H2AX. Tumor xenograft was obtained using CAL-27 cells.

RESULTS

Pretreatment with DMSO protected the oral mucosa from severe acute radiation injury, reduced the extent of radiation-induced weight loss, and had no significant effects on tumor weight in irradiated or nonirradiated xenograft mice. Furthermore, the efficacy of DMSO was superior to that of recombinant human keratinocyte growth factor and amifostine. DMSO treatment prevented the loss of proliferative lingual epithelial stem and progenitor cells upon irradiation. More interestingly, the average levels of γ-H2AX foci were significantly decreased in p63-positive epithelial stem cells at 6 hours, but not at 2 hours, after irradiation, indicating that DMSO facilitated DNA DSB repair rather than suppressing the indirect action of irradiation.

CONCLUSIONS

DMSO prevents the loss of proliferative lingual epithelial stem and progenitor cells upon irradiation by facilitating DNA DSB repair, thereby protecting against radiation-induced mucositis without tumor protection. Given its high efficacy and low toxicity, DMSO could be a potential treatment option to prevent radiation-induced oral mucositis.

A single-molecule assessment of the protective effect of DMSO against DNA double-strand breaks induced by photo-and γ-ray-irradiation, and freezing

Dimethyl sulfoxide (DMSO) is widely used as a cryoprotectant for organs, tissues, and cell suspension in storage. In addition, DMSO is known to be a useful free radical scavenger and a radio-protectant. To date, many in vitro assays using cultured cells have been performed for analysing the protective effect of DMSO against genomic DNA damage; however, currently it has been rather difficult to detect DNA double strand breaks (DSBs) in a quantitative manner. In the present study, we aimed to observe the extent of DNA damage by use of single molecular observation with a fluorescence microscope to evaluate DSBs induced by photo- and γ-ray-irradiation, or freeze/thawing in variable concentrations of DMSO. As a result, we found that 2% DMSO conferred the maximum protective effect against all of the injury sources tested, and these effects were maintained at higher concentrations. Further, DMSO showed a significantly higher protective effect against freezing-induced damage than against photo- and γ-ray-irradiation-induced damage. Our study provides significant data for the optimization of DNA cryopreservation with DMSO, as well as for the usage of DNA as the protective agent against the injuries caused by active oxygen and radiations.

Suppression Of β-catenin Nuclear Translocation By CGP57380 Decelerates Poor Progression And Potentiates Radiation-Induced Apoptosis in Nasopharyngeal Carcinoma

Nuclear localization of β-catenin is essential for the progression of various human cancers via transcriptional upregulation of downstream genes. The MAP kinase interacting serine/threonine kinase (MNK)-eukaryotic translation initiation factor 4E (eIF4E) axis has been reported to activate Wnt/β-catenin signaling, and CGP57380, an inhibitor of MNK kinases, inhibits the proliferation of multiple cancers. In this study, we showed that β-catenin signaling (including β-catenin, cyclin D1, c-Myc, and MMP-7) and p-eIF4E expression were elevated in nasopharyngeal carcinoma (NPC) compared with non-cancerous nasopharyngeal epithelial tissues, and was associated with clinical characteristics of NPC patients. Lymph node metastasis, gender, aberrant β-catenin expression, and elevated levels of MMP-7 and cyclin D1 were independent prognostic factors. Significantly, expression of p-eIF4E was positively correlated with β-catenin, and targeting the MNK-eIF4E axis with CGP57380 downregulated β-catenin in the nucleus, which in turn decreased proliferation, cell cycle progression, migration, invasion, and metastasis of NPC in vitro and in vivo. CGP57380 also potentiated radiation-induced apoptosis in NPC. Moreover, CGP57380 upregulated β-catenin in the cytoplasm thus blocking epithelial-mesenchymal transition (EMT), a key mechanism in cancer cell invasiveness and metastasis. Mechanistically, inhibition of β-catenin nuclear translocation by CGP57380 was dependent on AKT activation. Notably, identification of the MNK/eIF4E/β-catenin axis might provide a potential target for overcoming the poor prognosis mediated by β-catenin in NPC.

Omeprazole induces heme oxygenase-1 in fetal human pulmonary microvascular endothelial cells via hydrogen peroxide-independent Nrf2 signaling pathway

Omeprazole (OM) is an aryl hydrocarbon receptor (AhR) agonist and a proton pump inhibitor that is used to treat humans with gastric acid related disorders. Recently, we showed that OM induces NAD (P) H quinone oxidoreductase-1 (NQO1) via nuclear factor erythroid 2-related factor 2 (Nrf2)-dependent mechanism. Heme oxygenase-1 (HO-1) is another cytoprotective and antioxidant enzyme that is regulated by Nrf2. Whether OM induces HO-1 in fetal human pulmonary microvascular endothelial cells (HPMEC) is unknown. Therefore, we tested the hypothesis that OM will induce HO-1 expression via Nrf2 in HPMEC. OM induced HO-1 mRNA and protein expression in a dose-dependent manner. siRNA-mediated knockdown of AhR failed to abrogate, whereas knockdown of Nrf2 abrogated HO-1 induction by OM. To identify the underlying molecular mechanisms, we determined the effects of OM on cellular hydrogen peroxide (H2O2) levels since oxidative stress mediated by the latter is known to activate Nrf2. Interestingly, the concentration at which OM induced HO-1 also increased H2O2 levels. Furthermore, H2O2 independently augmented HO-1 expression. Although N-acetyl cysteine (NAC) significantly decreased H2O2 levels in OM-treated cells, we observed that OM further increased HO-1 mRNA and protein expression in NAC-pretreated compared to vehicle-pretreated cells, suggesting that OM induces HO-1 via H2O2-independent mechanisms. In conclusion, we provide evidence that OM transcriptionally induces HO-1 via AhR - and H2O2 - independent, but Nrf2 - dependent mechanisms. These results have important implications for human disorders where Nrf2 and HO-1 play a beneficial role.

Bystander effects and compartmental stress response to X-ray irradiation in L929 cells

Bystander effects are indirect consequences of radiation and many other stress factors. They occur in cells that are not directly exposed to these factors, but receive signals from affected cells either by gap junctions or by molecules released in the medium. Characterizing these effects and deciphering the underlying mechanisms involved in radiation-induced bystander effects are relevant for cancer radiotherapy and radioprotection. At doses of X-ray radiation 0.5 and 1 Gy, we detected bystander effects as increased numbers of micronuclei shortly after the treatment, through medium transfer and by co-cultures. Interestingly, bystander cells did not exhibit long-term adverse changes in viability. Evaluation of several compartmental stress markers (CHOP, BiP, mtHsp60, cytHsp70) by qRT-PCR did not reveal expression changes at transcriptional level. We investigated the involvement of ROS and NO in this process by addition of specific scavengers of these molecules, DMSO or c-PTIO in the transferred medium. This approach proved that ROS but not NO is involved in the induction of lesions in the acceptor cells. These results indicate that L929 cells are susceptible to stress effects of radiation-induced bystander signaling.

Photodynamic therapy of melanoma using new, synthetic porphyrins and phthalocyanines as photosensitisers - a comparative study

Melanoma, a cancer that arises from melanocytes, is one of the most unresponsive cancers to known therapies and has a tendency to produce early metastases. Several studies showed encouraging results of the efficacy of photodynamic therapy (PDT) in melanoma, in different experimental settings in vitro and in vivo, as well as several clinical reports.

Dimethyl sulfoxide attenuates hydrogen peroxide-induced injury in cardiomyocytes via heme oxygenase-1

The antioxidant property of dimethyl sulfoxide (DMSO) was formerly attributed to its direct effects. Our former study showed that DMSO is able to induce heme oxygenase-1 (HO-1) expression in endothelial cells, which is a potent antioxidant enzyme. In this study, we hypothesized that the antioxidant effects of DMSO in cardiomyocytes are mediated or partially mediated by increased HO-1 expression. Therefore, we investigated whether DMSO exerts protective effects against H2 O2 -induced oxidative damage in cardiomyocytes, and whether HO-1 is involved in DMSO-imparted protective effects, and we also explore the underlying mechanism of DMSO-induced HO-1 expression. Our study demonstrated that DMSO pretreatment showed a cytoprotective effect against H2 O2 -induced oxidative damage (impaired cell viability, increased apopototic cells rate and caspase-3 level, and increased release of LDH and CK) and this process is partially mediated by HO-1 upregulation. Furthermore, our data showed that the activation of p38 MAPK and Nrf2 translocation are involved in the HO-1 upregulation induced by DMSO. This study reports for the first time that the cytoprotective effect of DMSO in cardiomyocytes is partially mediated by HO-1, which may further explain the mechanisms by which DMSO exerts cardioprotection on H2 O2 injury. J. Cell. Biochem. 115: 1159-1165, 2014. © 2013 Wiley Periodicals, Inc.

Optimization of upcyte® human hepatocytes for the in vitro micronucleus assay

"Upcyte(®) human hepatocytes" have the unique property of combining proliferation with the expression of drug metabolising activities. In our current study, we evaluated whether these cells would be suitable for early in vitro micronucleus (MN) tests. A treatment period of 96 h without a recovery period was most reliable for detecting MN formation in upcyte(®) hepatocytes from Donor 740. The basal MN rate in upcyte(®) hepatocytes varied considerably between donors (7-28%); therefore, modifications to the assay medium were tested to determine whether they could decrease inherent MN formation. Optimal medium supplements were 10 ng/ml oncostatin M for the pre-culture and recovery periods and 25 ng/ml epidermal growth factor and 10 ng/ml oncostatin M for the treatment period. Using the optimised conditions and outcome criteria, the upcyte(®) hepatocyte MN assay could correctly identify directly acting (e.g. mitomycin C, etoposide) and metabolically activated genotoxins (e.g. benzo[a]pyrene, cyclophosphamide). "True negative" and "false positive" compounds were also correctly identified as negative. The basal %MN in upcyte(®) hepatocytes from Donor 740 treated with DMSO, cyclophosphamide or MMC, was essentially unaffected by the growth stage ranging from population doublings of 14-61, suggesting that billions of cells could be produced from a single donor for standardised drug toxicity testing. In conclusion, we have established and optimised an in vitro MN test by using upcyte(®) hepatocytes to correctly identify known direct and metabolically activated genotoxicants as well as "false positives" and true negative compounds. The almost unlimited supply of cells from a single donor and optimised test conditions increase reproducibility in early and more predictive in vitro MN tests.

Dimethyl sulfoxide induces oxidative stress in the yeast Saccharomyces cerevisiae

Dimethyl sulfoxide (DMSO) is used as a cryoprotectant for the preservation of cells, including yeast, and as a solvent for chemical compounds. We report that DMSO induces oxidative stress in the yeast. Saccharomyces cerevisiae wt strain EG-103 and its mutants Δsod1, Δsod2, and Δsod1 Δsod2 were used. Yeast were subjected to the action of 1-14% DMSO for 1 h at 28 °C. DMSO induced a concentration-dependent inhibition of yeast growth, the effect being more pronounced for mutants devoid of SOD (especially Δsod1 Δsod2). Cell viability was compromised. DMSO-concentration-dependent activity loss of succinate dehydrogenase, a FeS enzyme sensitive to oxidative stress, was observed. DMSO enhanced formation of reactive oxygen species, estimated with dihydroethidine in a concentration-dependent manner, the effect being again more pronounced in mutants devoid of superoxide dismutases. The content of cellular glutathione was increased with increasing DMSO concentrations, which may represent a compensatory response. Membrane fluidity, estimated by fluorescence polarization of DPH, was decreased by DMSO. These results demonstrate that DMSO, although generally considered to be antioxidant, induces oxidative stress in yeast cells.

Biphasic pro-melanogenic and pro-apoptotic effects of all-trans-retinoic acid (ATRA) on human melanocytes: time-course study

BACKGROUND

The effects of retinoids on melanogenesis and their mechanism as depigmenting agents in topical therapy have not been fully elucidated. Conflicting data about their impact on melanogenic pathways have been reported.

OBJECTIVE

To investigate the effects of all-trans-retinoic acid (ATRA) on normal human melanocytes from Caucasian subjects.

METHODS

We assessed ATRA's cytotoxicity by measuring viability with a cell proliferation assay, and apoptotic effects using Annexin V and γ-H2AX markers. ATRA's melanogenic activity was investigated based on spectrophotometric measurement of melanin content and tyrosinase enzymatic activity. Tyrosinase expression was assessed by Western blotting. We tested the antioxidant activity of superoxide dismutase (SOD) and catalase (CAT) in melanocytes using a spectrophotometric assay.

RESULTS

Of the concentrations tested in this 72h time-course study, the 1.0μM ATRA had a well-defined two-stage pro-melanogenic and pro-apoptotic effect on melanocytes. In the first 6h, treated cells showed significant increase (p≤0.01) of melanin content, tyrosinase, SOD, and CAT activities compared to the controls. While overall tyrosinase expression was not affected by ATRA, all other tested parameters decreased progressively beyond the short-term point of 6h. ATRA treatment of over 6h induced melanocyte apoptosis, as shown by the time-dependent decrease in cell viability, coupled with significant increase in Annexin V positive cells and nuclear accumulation of γ-H2AX foci.

CONCLUSION

The results obtained using this testing platform show a biphasic ATRA action: immediate pro-melanogenic effect and longer-term exposure pro-apoptotic activity. These data qualify ATRA as a potent tool to better understand the mechanisms that regulate the pigmentary system.