The radioprotective effect of metformin against cytotoxicity and genotoxicity induced by ionizing radiation in cultured human blood lymphocytes

Metformin as anticancer agent and adjuvant in cancer combination therapy: Current progress and future prospect

Metformin, as the preferred antihyperglycemic drug for type 2 diabetes, has been found to have a significant effect in inhibiting tumor growth in recent years. However, metformin alone in cancer treatment has the disadvantages of high dose concentrations and few targeted cancer types. Increasing studies have confirmed that metformin can be used in combination with conventional anticancer therapy to obtain more promising clinical benefits, which is expected to be rapidly transformed and applied in clinic. Some combination therapy strategies including metformin combined with chemotherapy, radiotherapy, targeted therapy and immunotherapy have been proven to have more significant antitumor effects and longer survival time than monotherapy. In this review, we summarize the synergistic antitumor effects and mechanisms of metformin in combination with other current conventional anticancer therapies. In addition, we update the research progress and the latest prospect of the metformin-combined application in the cancer treatment. This work could provide more evidence and future direction for the clinical application of metformin in antitumor.

Targeting Neutrophil Extracellular Trap Formation: Exploring Promising Pharmacological Strategies for the Treatment of Preeclampsia

Neutrophils, which constitute the most abundant leukocytes in human blood, emerge as crucial players in the induction of endothelial cell death and the modulation of endothelial cell responses under both physiological and pathological conditions. The hallmark of preeclampsia is endothelial dysfunction induced by systemic inflammation, in which neutrophils, particularly through the formation of neutrophil extracellular traps (NETs), play a pivotal role in the development and perpetuation of endothelial dysfunction and the hypertensive state. Considering the potential of numerous pharmaceutical agents to attenuate NET formation (NETosis) in preeclampsia, a comprehensive assessment of the extensively studied candidates becomes imperative. This review aims to identify mechanisms associated with the induction and negative regulation of NETs in the context of preeclampsia. We discuss potential drugs to modulate NETosis, such as NF-κβ inhibitors, vitamin D, and aspirin, and their association with mutagenicity and genotoxicity. Strong evidence supports the notion that molecules involved in the activation of NETs could serve as promising targets for the treatment of preeclampsia.

Crosstalk between Oxidative Stress and Inflammation Induced by Ionizing Radiation in Healthy and Cancerous Cells

Radiotherapy (RT) is a unique modality in cancer treatment with no replacement in many cases and uses a tumoricidal dose of various ionizing radiation (IR) types to kill cancer cells. It causes oxidative stress through reactive oxygen species (ROS) production or the destruction of antioxidant systems. On the other hand, RT stimulates the immune system both directly and indirectly by releasing danger signals from stress-exposed and dying cells. Oxidative stress and inflammation are two reciprocal and closely related mechanisms, one induced and involved by the other. ROS regulates the intracellular signal transduction pathways, which participate in the activation and expression of pro-inflammatory genes. Reciprocally, inflammatory cells release ROS and immune system mediators during the inflammation process, which drive the induction of oxidative stress. Oxidative stress or inflammation-induced damages can result in cell death (CD) or survival mechanisms that may be destructive for normal cells or beneficial for cancerous cells. The present study has focused on the radioprotection of those agents with binary effects of antioxidant and anti-inflammatory mechanisms IR-induced CD.

Iron Deposition in the Bone Marrow and Spleen of Nonhuman Primates with Acute Radiation Syndrome

The risk of exposure to high levels of ionizing radiation from nuclear weapons or radiological accidents is an increasing world concern. Partial- or total-body exposure to high doses of radiation is potentially lethal through the induction of acute radiation syndrome (ARS). Hematopoietic cells are sensitive to radiation exposure; white blood cells primarily undergo apoptosis while red blood cells (RBCs) undergo hemolysis. Several laboratories demonstrated that the rapid hemolysis of RBCs results in the release of acellular iron into the blood. We recently demonstrated using a murine model of ARS after total-body irradiation (TBI) and the loss of RBCs, iron accumulated in the bone marrow and spleen, notably between 4-21 days postirradiation. Here, we investigated iron accumulation in the bone marrow and spleens from TBI nonhuman primates (NHPs) using histological stains. We observed trends in increased intracellular and extracellular brown pigmentation in the bone marrow after various doses of radiation, especially after 4-15 days postirradiation, but these differences did not reach significance. We observed a significant increase in Prussian blue-staining intracellular iron deposition in the spleen 13-15 days after 5.8-8.5 Gy of TBI. We observed trends of increased iron in the spleen after 30-60 days postirradiation, with varying doses of radiation, but these differences did not reach significance. The NHP model of ARS confirms our earlier findings in the murine model, showing iron deposition in the bone marrow and spleen after TBI.

Radioproteomics modeling of metformin-enhanced radiosensitivity: an animal study

PURPOSE

Metformin is considered as radiation modulator in both tumors and healthy tissues. Radiomics has the potential to decode biological mechanisms of radiotherapy response. The aim of this study was to apply radiomics analysis in metformin-induced radiosensitivity and finding radioproteomics associations of computed tomography (CT) imaging features and proteins involved in metformin radiosensitivity signaling pathways.

MATERIALS AND METHODS

A total of 32 female BALB/c mice were used in this study and were subjected to injection of breast cancer cells. When tumors reached a mean volume of 150 mm3, mice were randomly divided into the four groups including Control, Metformin, Radiation, and Radiation + Metformin. Western blot analysis was performed after treatment to measure expression of proteins including AMPK-alpha, phospho-AMPK-alpha (Thr172), mTOR, phospho-mTOR (Ser2448), phospho-4EBP1 (Thr37/46), phospho-ACC (Ser79), and β-actin. CT imaging was performed before treatment and at the end of treatment in all groups. Radiomics features extracted from segmented tumors were selected using Elastic-net regression and were assessed in terms of correlation with expression of the proteins.

RESULTS

It was observed that proteins including phospho-mTOR, phospho-4EBP1, and mTOR had positive correlations with changes in tumor volumes in days 28, 24, 20, 16, and 12, while tumor volume changes at these days had negative correlations with AMPK-alpha, phospho-AMPK-alpha, and phospho-ACC proteins. Furthermore, median feature had a positive correlation with AMPK-alpha, phospho-ACC, and phospho-AMPK-alpha proteins. Also, Cluster shade feature had positive correlations with mTOR and p-mTOR. On the other hand, LGLZE feature had negative correlations with AMPK-alpha and phospho-AMPK-alpha.

CONCLUSION

Radiomics features can decode proteins that involved in response to metformin and radiation, although further studies are warranted to investigate the optimal way to integrate radiomics into biological experiments.

Metformin mitigates radiation toxicity exerting antioxidant and genoprotective properties

The antidiabetic drug metformin (MF) exhibits redox-modulating effects in various pathologies associated with oxidative stress and mitigates ionizing radiation-induced toxicity, but the underlying mechanisms remain to be elucidated. Thus, we studied some radiomitigatory effects of MF and explored the possible mechanisms behind them. Highly sensitive luminescence methods and non-competitive enzyme-linked immunosorbent assay (ELISA) were used in in vitro studies, and in vivo the damage to bone marrow cells and its repair were assessed by the micronucleus test. In a solution, MF at concentrations exceeding 0.1 µM effectively intercepts •OH upon X-ray-irradiation, but does not react directly with H2O2. MF accelerates the decomposition of H2O2 catalyzed by copper ions. MF does not affect the radiation-induced formation of H2O2 in the solution of bovine gamma-globulin (BGG), but has a modulating effect on the generation of H2O2 in the solution of bovine serum albumin (BSA). MF at 0.05-1 mM decreases the radiation-induced formation of 8-oxoguanine in a DNA solution depending on the concentration of MF with a maximum at 0.25 mM. MF at doses of 3 mg/kg body weight (bw) and 30 mg/kg bw administered to mice after irradiation, but not before irradiation, reduces the frequency of micronucleus formation in polychromatophilic erythrocytes of mouse red bone marrow. Our work has shown that the radiomitigatory properties of MF are mediated by antioxidant mechanisms of action, possibly including its ability to chelate polyvalent metal ions.

Metformin beyond an anti-diabetic agent: A comprehensive and mechanistic review on its effects against natural and chemical toxins

In addition to the anti-diabetic effect of metformin, a growing number of studies have shown that metformin has some exciting properties, such as anti-oxidative capabilities, anticancer, genomic stability, anti-inflammation, and anti-fibrosis, which have potent, that can treat other disorders other than diabetes mellitus. We aimed to describe and review the protective and antidotal efficacy of metformin against biologicals, chemicals, natural, medications, pesticides, and radiation-induced toxicities. A comprehensive search has been performed from Scopus, Web of Science, PubMed, and Google Scholar databases from inception to March 8, 2023. All in vitro, in vivo, and clinical studies were considered. Many studies suggest that metformin affects diseases other than diabetes. It is a radioprotective and chemoprotective drug that also affects viral and bacterial diseases. It can be used against inflammation-related and apoptosis-related abnormalities and against toxins to lower their effects. Besides lowering blood sugar, metformin can attenuate the effects of toxins on body weight, inflammation, apoptosis, necrosis, caspase-3 activation, cell viability and survival rate, reactive oxygen species (ROS), NF-κB, TNF-α, many interleukins, lipid profile, and many enzymes activity such as catalase and superoxide dismutase. It also can reduce the histopathological damages induced by many toxins on the kidneys, liver, and colon. However, clinical trials and human studies are needed before using metformin as a therapeutic agent against other diseases.

Metformin derivatives - Researchers' friends or foes?

Metformin has been used for ages to treat diabetes mellitus due to its safety profile and low cost. However, metformin has variable pharmacokinetics in patients, and due to its poor oral absorption, the therapeutic doses are relatively high, causing unpleasant gastrointestinal adverse effects. Therefore, novel derivatives of metformin have been synthesized during the past decades. Particularly, after the mid-2000 s, when organic cation transporters were identified as the main metformin carriers, metformin derivatives have been under intensive investigation. Nevertheless, due to the biguanide structure, derivatives of metformin have been challenging to synthesize. Moreover, the mechanisms of metformin's action are not fully understood to date, and since it has multifunctional properties, the interests have switched to re-purposing for other diseases. Indeed, metformin derivatives have been demonstrated in many cases to be more effective than metformin itself and have the potential to be used in different diseases, including several types of cancers and neurodegenerative diseases. On the other hand, the pleiotropic nature of metformin and its derivatives can also create challenges. Not all properties are fit for all diseases. In this review, the history of the development of metformin-like compounds is summarized, and insights into their potential for future drug discovery are discussed.

Predicting acute radiation dermatitis in breast cancer: a prospective cohort study

BACKGROUND

Acute radiation dermatitis (ARD) is one of the most common acute adverse reactions in breast cancer patients during and immediately after radiotherapy. As ARD affects patient quality of life, it is important to conduct individualized risk assessments of patients in order to identify those patients most at risk of developing severe ARD.

METHODS

The data of breast cancer patients who received radiotherapy were prospectively collected and analyzed. Serum ferritin, high-sensitivity C-reactive protein (hs-CRP) levels, and percentages of lymphocyte subsets were measured before radiotherapy. ARD was graded (0-6 grade), according to the Oncology Nursing Society Skin Toxicity Scale. Univariate and multivariate logistic regression analyses were used and the odds ratio (OR) and 95% confidence interval (CI) of each factor were calculated.

RESULTS

This study included 455 breast cancer patients. After radiotherapy, 59.6% and 17.8% of patients developed at least 3 (3+) grade and at least 4 (4+) grade ARD, respectively. Multivariate logistic regression analysis found that body mass index (OR: 1.11, 95% CI: 1.01-1.22), diabetes (OR: 2.70, 95% CI: 1.11-6.60), smoking (OR: 3.04, 95% CI: 1.15-8.02), higher ferritin (OR: 3.31, 95% CI: 1.78-6.17), higher hs-CRP (OR: 1.96, 95% CI: 1.02-3.77), and higher CD3 + T cells (OR: 2.99, 95% CI: 1.10-3.58) were independent risk factors for 4 + grade ARD. Based on these findings, a nomogram model of 4 + grade ARD was further established. The nomogram AUC was 0.80 (95% CI: 0.75-0.86), making it more discriminative than any single factor.

CONCLUSION

BMI, diabetes, smoking history, higher ferritin, higher hs-CRP, and higher CD3 + T cells prior to radiotherapy for breast cancer are all independent risk factors for 4 + grade ARD. The results can provide evidence for clinicians to screen out high-risk patients, take precautions and carefully follow up on these patients before and during radiotherapy.

Metformin Protects Radiation-Induced Early Brain Injury by Reducing Inflammation and DNA Damage

Radiation-induced brain injury (RIBI) is one of the most common and fatal complications of cranial radiation therapy (CRT); however, no effective intervention is available currently. Metformin has been reported to have anti-RIBI activity as a first-line anti-diabetic drug. However, the mechanism of action is unclear. An RIBI mice model and an in vitro cell model under 30 and 10 Gy ⁶⁰Co γ-rays exposure were established to investigate the mechanism of metformin in RIBI. The results showed that pre-treatment with metformin protects hippocampal neurogenesis in the brain of mice and improves learning and memory ability after irradiation. Further investigations revealed that metformin pretreatment reduces inflammation and decreases DNA damage in the in vitro BV2 cell line. In addition, we observed that metformin inhibits the activation of IκB and IRF-3, which are downstream components of the cGAS-STING pathway. These findings suggest that metformin might protect the brain from RIBI, at least partly, through the cGAS pathway, making it a potential therapeutic drug for RIBI.

The first peptide derivatives of dioxybiphenyl-bridged spiro cyclotriphosphazenes: In vitro cytotoxicity activities and DNA damage studies

In this study, we aimed to synthesize new peptide-substituted cyclotriphosphazenes from a series of tyrosine-based peptides and dioxyphenyl-substituted spirocyclotriphosphazenes, and to evaluate their in vitro cytotoxicity and genotoxicity activities. Genotoxicity studies were conducted to understand whether the cytotoxic compounds cause cell death through DNA damage. The structures of the novel series of phosphazenes were characterized by FT-IR, elemental analysis, MS, 1D (³¹P, ¹H, and ¹³C-APT NMR), and 2D (HETCOR) NMR spectroscopic techniques. In vitro cytotoxic activities were carried out against human breast (MCF-7), ovarian (A2780), prostate (PC-3), colon (Caco-2) cancer cell lines and human normal epithelial cell line (MCF-10A) at different concentrations by using an MTT assay. The compounds showed considerable reductions in cell viability against all human cancer cell lines. Especially, the compounds exhibited notable effects in A2780 cell lines (p < 0.05). The IC₅₀ values of the compounds in the A2780 cell line were calculated to be 1.914 µM for TG, 20.21 µM for TV, 20.45 µM for TA, 4.643 µM for TP, 5.615 µM for BTG, 1.047 µM for BTV, 27.02 µM for BTA, 0.7734 µM for BTP, 21.5 µM for DTG, 1.65 µM for DTV, 2.89 µM for DTA and 4.599 µM for DTP. DNA damage studies of the compounds were conducted by the comet assay method using tail length, tail density, olive tail moment, head length, and head density parameters, and the results showed that the cell death occurred through DNA damage mechanism. In a nutshell, these compounds show promising cytotoxic effects and can be considered powerful candidate molecules for pharmaceutical applications.

Metformin counters oxidative stress and mitigates adverse effects of radiation exposure: An overview

Metformin (1,1-dimethylbiguanidine hydrochloride) (MF) is a drug that has long been in use for the treatment of type 2 diabetes mellitus and recently is coming into use in the radiation therapy of cancer and other conditions. Exposure to ionizing radiation disturbs the redox homeostasis of cells and causes damage to proteins, membranes, and mitochondria, destroying a number of biological processes. After irradiation, MF activates cellular antioxidant and repair systems by signaling to eliminate the harmful consequences of disruption of redox homeostasis. The use of MF in the treatment of the negative effects of irradiation has great potential in medical patients after radiotherapy and in victims of nuclear accidents or radiologic terrorism.

Review of compounds that exhibit radioprotective and/or mitigatory effects after application of diagnostic or therapeutic ionizing radiation

PURPOSE

Exposure to ionizing radiation can be accidental or for medical purposes. Analyzes of the frequency of radiation damage in the general population, it has been determined that by far the most common are those that occur as a result of diagnostic or therapeutic procedures. Damage caused by radiation, either accidentally or for therapeutic purposes, can be reduced by the use of radioprotectors, mitigators or other therapeutic agents. A detailed research of the available literature shows that there is little systematized data of potentially radioprotective and/or mitigating effects of drugs from the personal therapy of patients during the application of therapeutic ionizing radiation. The aim of this paper is to present review of compounds, especially personal therapy drugs, that exhibit radioprotective and/or mitigating effects after the application of diagnostic or therapeutic ionizing radiation.

CONCLUSIONS

Given the widespread use of ionizing radiation for diagnostic and therapeutic purposes, there is a clear need to create a strategy and recommendations of relevant institutions for the use of radioprotectors and mitigators in everyday clinical practice, with individual evaluation of the patient's condition and selection of the compounds that will show the greatest benefit in terms of radioprotection.

The effects of medical linear accelerator X-rays on human peripheral blood lymphocytes in the presence of glucosamine

Glucosamine is widely prescribed as a dietary supplement used to treat arthritis. In this study, the radioprotective ability of glucosamine was evaluated against radiation-induced genotoxicity and cytotoxicity in human peripheral blood lymphocytes. Blood samples were collected from five healthy male donors and were divided into four groups. Isolated lymphocytes and blood samples were treated with 10 µM of glucosamine for 2 h before exposure to 2 Gy radiation. The radioprotective potential of glucosamine was assessed by micronucleus assay, reactive oxygen species (ROS) level analysis, and flow cytometry. Irradiation significantly increased the micronuclei frequency as compared to the control group. Contrary to that pretreatment with glucosamine before irradiation significantly reduced the frequency of micronuclei. Furthermore, pretreatment with glucosamine significantly prevented the percentage of apoptotic lymphocytes. Also, glucosamine pretreatment significantly reduced the production of ROS in irradiated lymphocytes. This study shows glucosamine to be a potent radioprotector against radiation that induces DNA damage and apoptosis in human lymphocytes. Several additional in vivo and in vitro studies are needed before glucosamine can be considered as a radioprotective candidate in patients undergoing radiation therapy.

Reversing radiation-induced immunosuppression using a new therapeutic modality

Radiation-induced immune suppression poses significant health challenges for millions of patients undergoing cancer chemotherapy and radiotherapy treatment, and astronauts and space tourists travelling to outer space. While a limited number of recombinant protein therapies, such a Sargramostim, are approved for accelerating hematologic recovery, the pronounced role of granulocyte-macrophage colony-stimulating factor (GM-CSF or CSF2) as a proinflammatory cytokine poses additional challenges in creating immune dysfunction towards pathogenic autoimmune diseases. Here we present an approach to high-throughput drug-discovery, target validation, and lead molecule identification using nucleic acid-based molecules. These Nanoligomer™ molecules are rationally designed using a bioinformatics and an artificial intelligence (AI)-based ranking method and synthesized as a single-modality combining 6-different design elements to up- or downregulate gene expression of target gene, resulting in elevated or diminished protein expression of intended target. This method additionally alters related gene network targets ultimately resulting in pathway modulation. This approach was used to perturb and identify the most effective upstream regulators and canonical pathways for therapeutic intervention to reverse radiation-induced immunosuppression. The lead Nanoligomer™ identified in a screen of human donor derived peripheral blood mononuclear cells (PBMCs) upregulated Erythropoietin (EPO) and showed the greatest reversal of radiation induced cytokine changes. It was further tested in vivo in a mouse radiation-model with low-dose (3 mg/kg) intraperitoneal administration and was shown to regulate gene expression of epo in lung tissue as well as counter immune suppression. These results point to the broader applicability of our approach towards drug-discovery, and potential for further investigation of our lead molecule as reversible gene therapy to treat adverse health outcomes induced by radiation exposure.

Iron Deposition and Ferroptosis in the Spleen in a Murine Model of Acute Radiation Syndrome

Total body irradiation (TBI) can result in death associated with hematopoietic insufficiency. Although radiation causes apoptosis of white blood cells, red blood cells (RBC) undergo hemolysis due to hemoglobin denaturation. RBC lysis post-irradiation results in the release of iron into the plasma, producing a secondary toxic event. We investigated radiation-induced iron in the spleens of mice following TBI and the effects of the radiation mitigator captopril. RBC and hematocrit were reduced ~7 days (nadir ~14 days) post-TBI. Prussian blue staining revealed increased splenic Fe3+ and altered expression of iron binding and transport proteins, determined by qPCR, western blotting, and immunohistochemistry. Captopril did not affect iron deposition in the spleen or modulate iron-binding proteins. Caspase-3 was activated after ~7–14 days, indicating apoptosis had occurred. We also identified markers of iron-dependent apoptosis known as ferroptosis. The p21/Waf1 accelerated senescence marker was not upregulated. Macrophage inflammation is an effect of TBI. We investigated the effects of radiation and Fe3+ on the J774A.1 murine macrophage cell line. Radiation induced p21/Waf1 and ferritin, but not caspase-3, after ~24 h. Radiation ± iron upregulated several markers of pro-inflammatory M1 polarization; radiation with iron also upregulated a marker of anti-inflammatory M2 polarization. Our data indicate that following TBI, iron accumulates in the spleen where it regulates iron-binding proteins and triggers apoptosis and possible ferroptosis.

Breast Cancer Treatment Decreases Serum Levels of TGF-β1, VEGFR2, and TIMP-2 Compared to Healthy Volunteers: Significance for Therapeutic Outcomes?

Various complications from a breast cancer treatment, in the pathogenesis of which excessive tissue fibrosis plays a leading role, are a common pathology. In this study, the levels of TGF-β1, VEGFR-2, and TIMP-2 were determined by the immuno-enzyme serum analysis for patients during the long-term period after breast cancer treatment as potential markers of fibrosis. The single-center study enrolled 92 participants, which were divided into two age-matched groups: (1) 67 patients following breast cancer treatment, and (2) 25 healthy female volunteers. The intergroup analysis demonstrated that the patients after breast cancer treatment showed a decrease in the serum levels of TGF-β1 (U = 666, p < 0.001) and TIMP-2 (U = 637, p < 0.001) as compared to the group of healthy volunteers. The levels of VEGFR-2 in these groups were comparable (U = 1345, p = 0.082). It was also found that the type of treatment, the presence of lymphedema, shoulder joint contracture, and changes in lymphoscintigraphy did not affect the levels of TGF-β1, VEGFR-2, and TIMP-2 within the group of patients after breast cancer treatment. These results may indicate that these biomarkers do not play a leading role in the maintenance and progression of fibrosis in the long-term period after breast cancer treatment. The reduced levels of TGF-β1 and TIMP-2 may reflect endothelial dysfunction caused by the antitumor therapy.

Metformin for treatment of cytopenias in children and young adults with Fanconi anemia

Fanconi anemia (FA), a genetic DNA repair disorder characterized by marrow failure and cancer susceptibility. In FA mice, metformin improves blood counts and delays tumor development. We conducted a single institution study of metformin in nondiabetic patients with FA to determine feasibility and tolerability of metformin treatment and to assess for improvement in blood counts. Fourteen of 15 patients with at least 1 cytopenia (hemoglobin < 10 g/dL; platelet count < 100 000 cells/µL; or an absolute neutrophil count < 1000 cells/µL) were eligible to receive metformin for 6 months. Median patient age was 9.4 years (range 6.0-26.5 ). Thirteen of 14 subjects (93%) tolerated maximal dosing for age; 1 subject had dose reduction for grade 2 gastrointestinal symptoms. No subjects developed hypoglycemia or metabolic acidosis. No subjects had dose interruptions caused by toxicity, and no grade 3 or higher adverse events attributed to metformin were observed. Hematologic response based on modified Myelodysplastic Syndrome International Working Group criteria was observed in 4 of 13 evaluable patients (30.8%; 90% confidence interval, 11.3-57.3). Median time to response was 84.5 days (range 71-128 days). Responses were noted in neutrophils (n = 3), platelets (n = 1), and red blood cells (n = 1). No subjects met criteria for disease progression or relapse during treatment. Correlative studies explored potential mechanisms of metformin activity in FA. Plasma proteomics showed reduction in inflammatory pathways with metformin. Metformin is safe and tolerable in nondiabetic patients with FA and may provide therapeutic benefit. This trial was registered at as #NCT03398824.

Interruptin C, a Radioprotective Agent, Derived from Cyclosorus terminans Protect Normal Breast MCF-10A and Human Keratinocyte HaCaT Cells against Radiation-Induced Damage

Radiotherapy is a common method to treat cancers, with the goal of maximizing the dose to tumors while minimizing the dose to normal tissues. Radioprotectors can reduce the toxicity to normal tissues during radiotherapy. Several plant-derived compounds can function as radioprotectors by scavenging free radicals. We investigated the radioprotective activity of interruptin C from the fern Cyclosorus terminans. The molecular mechanism of interruptin C’s activity in X-ray-irradiated cells was evaluated. Superoxide dismutase activity was examined to investigate the antioxidant enzyme activity. Clonogenic cell survival was also investigated following radiation exposure. DNA damage and cell cycle progression were detected using micronuclei formation assays. DNA repair after irradiation was analyzed in a γH2AX assay. The levels of the proteins related to the radioprotective responses were analyzed by Western blotting. Interruptin C increased the antioxidant enzyme activity and significantly decreased the DNA damage by reducing the γH2AX foci and micronucleus formation in irradiated MCF-10A normal breast and HaCaT human keratinocyte cells. The apoptotic protein levels decreased, whereas the antiapoptotic protein levels increased. Interruptin C pretreatment increased the survival rate of irradiated MCF-10A and HaCaT cells. Moreover, the compound did not promote the survival of MDA-MB-231 and Hs578T breast cancer cells. Therefore, interruptin C may exert radioprotective activity without enhancing cancer cell proliferation.

High-dose metformin induces a low-glucose dependent genotoxic stress

Epidemiological studies have demonstrated that metformin (a cornerstone of diabetes treatment) has anticancer activity, but the underlying mechanism remains elusive. We aimed to investigate whether metformin elicits anticancer activity via increasing genotoxic stress, a state of increased genome damage that becomes tumor-suppressing if it goes beyond an intolerable threshold. We found that metformin (1-16 mM) suppressed proliferation and colony formation in a panel of cancer cell lines (HeLa, A375, A549 and QGY). Metformin induced a dose-dependent increase of genotoxic stress (including micronucleus, nucleoplasmic bridge and nuclear bud) and the increase of genotoxic stress correlated well with metformin's anticancer potential. Metformin deregulated the expression of BUBR1 and MAD2, two core genes of spindle assembly checkpoint (SAC) that surveillances chromosome segregation. Metformin had weakened antiproliferative effect and a corresponding attenuated genotoxic effect in HeLa cells cultured in high glucose (16 mg/ml). Meanwhile, metformin significantly increased genotoxicity in non-cancer cells (NCM460 and HUVECs). Metformin became non-genotoxic to HUVECs in high-glucose (8 and 16 mg/ml) conditions and reduced the genotoxicity of high glucose. Overall, these results infer a new mechanism of high-dose metformin, whereby low-glucose dependent genotoxic stress derived from SAC dysfunction might mediate some of the anticancer effect of this drug.

Metformin effects on brain development following cranial irradiation in a mouse model

BACKGROUND

Cranial radiation therapy (CRT) is a mainstay of treatment for malignant pediatric brain tumors and high-risk leukemia. Although CRT improves survival, it has been shown to disrupt normal brain development and result in cognitive impairments in cancer survivors. Animal studies suggest that there is potential to promote brain recovery after injury using metformin. Our aim was to evaluate whether metformin can restore brain volume outcomes in a mouse model of CRT.

METHODS

C57BL/6J mice were irradiated with a whole-brain radiation dose of 7 Gy during infancy. Two weeks of metformin treatment started either on the day of or 3 days after irradiation. In vivo magnetic resonance imaging was performed prior to irradiation and at 3 subsequent time points to evaluate the effects of radiation and metformin on brain development.

RESULTS

Widespread volume loss in the irradiated brain appeared within 1 week of irradiation with limited subsequent recovery in volume outcomes. In many structures, metformin administration starting on the day of irradiation exacerbated radiation-induced injury, particularly in male mice. Metformin treatment starting 3 days after irradiation improved brain volume outcomes in subcortical regions, the olfactory bulbs, and structures of the brainstem and cerebellum.

CONCLUSIONS

Our results show that metformin treatment has the potential to improve neuroanatomical outcomes after CRT. However, both timing of metformin administration and subject sex affect structure outcomes, and metformin may also be deleterious. Our results highlight important considerations in determining the potential benefits of metformin treatment after CRT and emphasize the need for caution in repurposing metformin in clinical studies.

Pretreatment with metformin protects mice from whole-body irradiation

Metformin, a first-line oral drug for type II diabetes mellitus, not only reduces blood glucose levels, but also has many other biological effects. Recent studies have been conducted to determine the protective effect of metformin in irradiation injuries. However, the results are controversial and mainly focus on the time of metformin administration. In this study, we aimed to investigate the protective effect of metformin in BALB/c mice exposed to 6 Gy or 8 Gy of a 60Co source of γ-rays for total body irradiation (TBI). Survival outcomes were assessed following exposure to 8 Gy or 6 Gy TBI, and hematopoietic damage and intestinal injury were assessed after exposure to 6 Gy TBI. Metformin prolonged the survival of mice exposed to 8 Gy TBI and improved the survival rate of mice exposed to 6 Gy TBI only when administered before exposure to irradiation. Moreover, pretreatment with metformin reduced the frequency of micronuclei (MN) in the bone marrow of mice exposed to 6 Gy TBI. Pretreatment of metformin also protected the intestinal morphology of mice, reduced inflammatory response and decreased the number of apoptotic cells in intestine. In conclusion, we demonstrated that pretreatment with metformin could alleviate irradiation injury.

Metformin Protects against Radiation-Induced Acute Effects by Limiting Senescence of Bronchial-Epithelial Cells

Radiation-induced damage to normal lung parenchyma remains a dose-limiting factor in thorax-associated radiotherapy (RT). Severe early and late complications with lungs can increase the risk of morbidity in cancer patients after RT. Herein, senescence of lung epithelial cells following RT-induced cellular stress, or more precisely the respective altered secretory profile, the senescence-associated secretory phenotype (SASP), was suggested as a central process for the initiation and progression of pneumonitis and pulmonary fibrosis. We previously reported that abrogation of certain aspects of the secretome of senescent lung cells, in particular, signaling inhibition of the SASP-factor Ccl2/Mcp1 mediated radioprotection especially by limiting endothelial dysfunction. Here, we investigated the therapeutic potential of a combined metformin treatment to protect normal lung tissue from RT-induced senescence and associated lung injury using a preclinical mouse model of radiation-induced pneumopathy. Metformin treatment efficiently limited RT-induced senescence and SASP expression levels, thereby limiting vascular dysfunctions, namely increased vascular permeability associated with increased extravasation of circulating immune and tumor cells early after irradiation (acute effects). Complementary in vitro studies using normal lung epithelial cell lines confirmed the senescence-limiting effect of metformin following RT finally resulting in radioprotection, while fostering RT-induced cellular stress of cultured malignant epithelial cells accounting for radiosensitization. The radioprotective action of metformin for normal lung tissue without simultaneous protection or preferable radiosensitization of tumor tissue might increase tumor control probabilities and survival because higher radiation doses could be used.

Radioprotective Role of Natural Polyphenols: From Sources to Mechanisms

The identification and development of radioprotective agents has emerged as a subject matter of research during recent years due to the growing usage of ionizing radiation in different areas of human life. Previous work on synthetic radioprotectors has achieved limited progress because of the numerous issues associated with toxicity. Compounds extracted from plants have potential to serve as lead candidates for developing ideal radioprotectors due to their low cost, safety and selectivity. Polyphenols are the most abundant and commonly dispersed group of biologically active molecules possessing broad range of pharmacological activities. Polyphenols have displayed efficacy for radioprotection during various investigations and can be administered at high doses with lesser toxicity. Detoxification of free radicals, modulating inflammatory responses, DNA repair, stimulation of hematopoietic recovery, and immune functions are the main mechanisms for radiation protection with polyphenols. Epicatechin, epigallocatechin-3-gallate, apigenin, caffeic acid phenylethylester, and silibinin provide cytoprotection together with the suppression of many pro-inflammatory cytokines owing to their free radical scavenging, anti-oxidant, and anti-inflammatory properties. Curcumin, resveratrol, quercetin, gallic acid, and rutin's radioprotective properties are regulated primarily by direct or indirect decline in cellular stress. Thus, polyphenols may serve as potential candidates for radioprotection in the near future, however, extensive investigations are still required to better understand their protection mechanisms.

Chemical and biological characteristics of propolis from Apis mellifera caucasica from the Ardahan and Erzurum provinces of Turkey: a comparative study

The aim of this study was to compare the biological activities of ethanolic propolis extracts of Apis mellifera caucasica obtained from Ardahan and Erzurum provinces of Turkey. Samples were tested for antioxidant, anticytotoxic, anticarcinogenic, antibacterial, and antifungal potentials using different techniques. Propolis samples from the two provinces had different mineral and organic compositions related to their geographical origin. The ferric reducing antioxidant power (FRAP) test showed superiority of Ardahan propolis over the Erzurum. Regardless of origin and the presence of mitomycin C in the culture medium, propolis enhanced human peripheral lymphocyte viability, which depended on the duration and propolis concentration. Antiperoxidative activity on MCF-7 breast cancer cells was concentration-dependent. Erzurum propolis showed the highest anticarcinogenic activity at the concentrations of 62.5 μg/mL and 125 μg/ mL, which dropped at higher concentrations. All propolis samples also showed antibacterial activity against the tested human pathogens similar to ampicillin and penicillin controls, except for Pseudomonas aeruginosa. However, they did not exert any antifungal activity against Candida albicans and Yarrowia lipolytica. In conclusion, propolis samples from both provinces showed promising biological activities, but further research should focus on finding the right concentrations for optimal effect and include the cell necrosis pathway to get a better idea of the anticarcinogenic effects.

Protection from Radiation-induced Damage in Rat's Ileum and Colon by Combined Regimens of Melatonin and Metformin: A Histopathological Study

Background: Radiation-induced enteritis and proctitis are common side effects of abdominopelvic cancers among patients that undergo radiotherapy for prostate, colorectal or urinary cancers. Exposure of these tissues to high doses of radiation leads to damage to villous, inflammation, pain, ulcer and bleeding, which may cause malabsorption and gastrointestinal disorders. To date, several procedures such as pharmaceutical treatment have been proposed for protection and mitigation of gastrointestinal toxicity following radiotherapy.

Aims: In the current study, we aimed to investigate the possible radioprotection of ileum and colon in rats using a combination of melatonin and metformin.

Methods: In this experimental study, 30 male Wistar rats were randomly assigned to six groups: control, melatonin (100 mg/kg) treatment, melatonin (100 mg/kg) plus metformin (100 mg/kg) treatment, radiation (10 Gy to whole body) group, radiation + melatonin (100 mg/kg) treatment, and radiation + melatonin (100 mg/kg) plus metformin (100 mg/kg) treatment. After 3.5 days, rats were sacrificed and their ileum and colon tissues carefully removed. Histopathological evaluations were conducted on these tissue samples.

Results: Histological evaluations reported moderate to severe damages to ileum and colon following whole body irradiation. Melatonin administration was able to protect the ileum remarkably, while the combination of melatonin and metformin was less effective. Interestingly, for the colon, melatonin was less effective while its combination with metformin was able to protect against radiation toxicity completely.

Conclusion: For the ileum, melatonin was a more effective radioprotector compared to its combination with metformin. However, the combination of melatonin and metformin can be proposed as an ideal radioprotector for the colon.

External Validation of a Predictive Model for Acute Skin Radiation Toxicity in the REQUITE Breast Cohort

Background: Acute skin toxicity is a common and usually transient side-effect of breast radiotherapy although, if sufficiently severe, it can affect breast cosmesis, aftercare costs and the patient's quality-of-life. The aim of this study was to develop predictive models for acute skin toxicity using published risk factors and externally validate the models in patients recruited into the prospective multi-center REQUITE (validating pREdictive models and biomarkers of radiotherapy toxicity to reduce side-effects and improve QUalITy of lifE in cancer survivors) study.

Methods: Patient and treatment-related risk factors significantly associated with acute breast radiation toxicity on multivariate analysis were identified in the literature. These predictors were used to develop risk models for acute erythema and acute desquamation (skin loss) in three Radiogenomics Consortium cohorts of patients treated by breast-conserving surgery and whole breast external beam radiotherapy (n = 2,031). The models were externally validated in the REQUITE breast cancer cohort (n = 2,057).

Results: The final risk model for acute erythema included BMI, breast size, hypo-fractionation, boost, tamoxifen use and smoking status. This model was validated in REQUITE with moderate discrimination (AUC 0.65), calibration and agreement between predicted and observed toxicity (Brier score 0.17). The risk model for acute desquamation, excluding the predictor tamoxifen use, failed to validate in the REQUITE cohort.

Conclusions: While most published prediction research in the field has focused on model development, this study reports successful external validation of a predictive model using clinical risk factors for acute erythema following radiotherapy after breast-conserving surgery. This model retained discriminatory power but will benefit from further re-calibration. A similar model to predict acute desquamation failed to validate in the REQUITE cohort. Future improvements and more accurate predictions are expected through the addition of genetic markers and application of other modeling and machine learning techniques.

The protective effect of oleuropein against radiation-induced cytotoxicity, apoptosis, and genetic damage in cultured human lymphocytes

PURPOSE

The aim of this study was to evaluate the effects of oleuropein radiation protection and to find an effective radioprotector.

MATERIALS AND METHOD

Human mononuclear cells were treated with oleuropein at the concentration of 100 μM (optimum concentration), incubated for 24 h, and then exposed to 2 Gy gamma-rays. The anti-radiation effect of oleuropein was assessed by MTT assay, flow cytometry, comet assay, and micronucleus (MN) assay.

RESULTS

It was found that pretreatment with oleuropein (25, 50, 75, 100, 200, 400, and 800 nM, and 1, 5, 10, 15, 20, 25, 30, 40, 50, 75, 100, 125, 150, 175, and 200 µM) significantly increased the percentage of cell viability compared to the irradiated group (p < .001). Moreover, oleuropein treatment with the above concentrations defined without gamma-ray did not show any cytotoxicity effect in human mononuclear cells. The LD_50/24h dose was calculated as 2.9 Gy, whereas by 200, 150, 50, and 100 µM oleuropein prior to radiation (1, 2,and 4 Gy), radiation LD_50/24h increased to 3.36, 3.54, 3.81, and >4 Gy, in that order. A very noticeable dose-modifying factor (DMF) of 1.16, 1.23, 1.31, and 1.72 was observed for 200, 150, 50, and 100 µM, in order. Therefore, 100 µM of oleuropein was selected as the desirable dose for radio-protection trial, and 2 Gy gamma-rays were used for further research. Human mononuclear cells treatment with oleuropein (100 µM) prior to 2 Gy gamma-rays significantly decreased apoptosis, genomic damage, and MN occurrence in human mononuclear caused by gamma-radiation (p < .001). Furthermore, treatment with oleuropein (100 µM) without radiation did not lead to apoptosis, genotoxicity, or clastogenic effects caused by oleuropein in human mononuclear cells.

CONCLUSION

The results revealed that oleuropein is able to significantly reduce cytotoxicity, apoptosis, genotoxic, and clastogenic effects of gamma-rays.

Cytogenetic effects of antidiabetic drug metformin

Metformin (MET) is the first-choice antidiabetic drug for type 2 diabetes mellitus treatment. In this study, the genotoxic potential of MET was evaluated by using chromosome aberrations (CAs), sister chromatid exchanges (SCEs), and micronucleus (MN) assays in human peripheral lymphocytes as well as comet assay in isolated lymphocytes. Human lymphocytes were treated with different concentrations of MET (12.5, 25, 50, 75, 100, and 125 µg/mL) for 24 h and 48 h. A negative and a positive control (Mitomycin-C-MMC, 0.20 μg/mL, for CA, SCE, and MN tests; hydrogen peroxide-H₂O₂, 100 µM, for comet assay) were also maintained. MET significantly increased the frequency of CAs at 48 h exposure (except 12.5 µg/mL) compared to the negative control. MET increased SCEs/cells in both treatment periods (except 12.5 µg/mL at 24 h). MET only increased the frequency of MN at 125 µg/mL. While MET significantly increased the comet tail length (CTL) at four concentrations (25, 75, 100, and 125 µg/mL), it did not affect comet tail intensity (CTI) (except 125 µg/mL) and comet tail moment (CTM) at all the treatments. All these data showed that MET had a mild genotoxic effect, especially at a long treatment period and higher concentrations in human lymphocytes in vitro. However, further in vitro and especially in vivo studies should be conducted to understand the detailed genotoxic potential of MET.HighlightsMetformin increased the frequency of CAs and SCEs, especially at 48-h exposure time in human lymphocytes.This antidiabetic drug increased the frequency of MN only at the highest concentration tested (125 µg/mL).Metformin significantly increased the comet tail length in all treatments (except 50 µg/mL).The drug did not significantly affect the comet tail intensity (except 125 µg/mL) and comet tail moment in all treatments.

Comparison of the effects of osmotic pump implantation with subcutaneous injection for administration of drugs after total body irradiation in mice

The increasing potential for radiation exposure from nuclear accidents or terrorist activities has intensified the need to develop pharmacologic countermeasures against injury from total body irradiation (TBI). Many initial experiments to develop and test these countermeasures utilize murine irradiation models. Yet, the route of drug administration can alter the response to irradiation injury. Studies have demonstrated that cutaneous injuries can exacerbate damage from radiation, and thus surgical implantation of osmotic pumps for drug delivery could adversely affect the survival of mice following TBI. However, daily handling and injections to administer drugs could also have negative consequences. This study compared the effects of subcutaneous needlesticks with surgical implantation of osmotic pumps on morbidity and mortality in a murine model of hematopoietic acute radiation syndrome (H-ARS). C57BL/6 mice were sham irradiated or exposed to a single dose of 7.7 Gy ⁶⁰Co TBI. Mice were implanted with osmotic pumps containing sterile saline seven days prior to irradiation or received needlesticks for 14 days following irradiation or received no treatment. All irradiated groups exhibited weight loss. Fewer mice with osmotic pumps survived to 30 days post irradiation (37.5%) than mice receiving needlesticks or no treatment (70% and 80%, respectively), although this difference was not statistically significant. However, mice implanted with the pump lost significantly more weight than mice that received needlesticks or no treatment. These data suggest that surgical implantation of a drug-delivery device can adversely affect the outcome in a murine model of H-ARS.

Benefits of Metformin in Attenuating the Hallmarks of Aging

Biological aging involves an interplay of conserved and targetable molecular mechanisms, summarized as the hallmarks of aging. Metformin, a biguanide that combats age-related disorders and improves health span, is the first drug to be tested for its age-targeting effects in the large clinical trial-TAME (targeting aging by metformin). This review focuses on metformin's mechanisms in attenuating hallmarks of aging and their interconnectivity, by improving nutrient sensing, enhancing autophagy and intercellular communication, protecting against macromolecular damage, delaying stem cell aging, modulating mitochondrial function, regulating transcription, and lowering telomere attrition and senescence. These characteristics make metformin an attractive gerotherapeutic to translate to human trials.

Fluoxetine as an antidepressant medicine improves the effects of ionizing radiation for the treatment of glioma

Radiotherapy is a cancer treatment protocol which delivers high dose of ionizing radiation (IR) to tumor. Tumor resistance and side effects induced by IR still are the major challenges in radiotherapy. The purpose of this study was to evaluate the synergistic killing effect of fluoxetine (FL) with IR on glioma cancer cell (U-87 MG), as well as radioprotective effect of FL against cellular toxicity induced by IR on non-malignant human fibroblast cell (HFFF2). Firstly, the inhibitory effects of FL on cell proliferations were evaluated in U-87 MG and HFFF2 cells. The clonogenic and MTT assays were used to evaluate the radiosensitivity and radioprotective effects of FL on cancer and non-malignant cells. The frequencies of apoptotic cells were evaluated by flow cytometry on both cancer and normal cells. Results showed that FL exhibited anti-cancer effect on glioma cells, while cellular toxicity was low in HFFF2 cells treated with FL. FL decreased the viable colonies and enhanced apoptotic cells when U-87 cells were treated with FL prior irradiation. For comparison, FL exhibited radioprotective effect through increasing cellular proliferation rate and reducing apoptosis in HFFF2 cells against IR. The results showed that FL enhanced the IR-induced glioma cancer cell death and apoptosis, whereas it exhibited a radioprotective effect on normal fibroblast cells suggesting that FL administration may improve glioma radiotherapy.

Deposition of Iron in the Bone Marrow of a Murine Model of Hematopoietic Acute Radiation Syndrome

Exposure to high-dose total body irradiation (TBI) can result in hematopoietic acute radiation syndrome (H-ARS), characterized by leukopenia, anemia, and coagulopathy. Death from H-ARS occurs from hematopoietic insufficiency and opportunistic infections. Following radiation exposure, red blood cells (RBCs) undergo hemolysis from radiation-induced hemoglobin denaturation, causing the release of iron. Free iron can have multiple detrimental biological effects, including suppression of hematopoiesis. We investigated the impact of radiation-induced iron release on the bone marrow following TBI and the potential impact of the ACE inhibitor captopril, which improves survival from H-ARS. C57BL/6J mice were exposed to 7.9 Gy, ⁶⁰Co irradiation, 0.6 Gy/min (LD_70-90/30). RBCs and reticulocytes were significantly reduced within 7 days of TBI, with the RBC nadir at 14-21 days. Iron accumulation in the bone marrow correlated with the time course of RBC hemolysis, with an ∼10-fold increase in bone marrow iron at 14-21 days post-irradiation, primarily within the cytoplasm of macrophages. Iron accumulation in the bone marrow was associated with increased expression of genes for iron binding and transport proteins, including transferrin, transferrin receptor 1, ferroportin, and integrin αMβ2. Expression of the gene encoding Nrf2, a transcription factor activated by oxidative stress, also increased at 21 days post-irradiation. Captopril did not alter iron accumulation in the bone marrow or expression of iron storage genes, but did suppress Nrf2 expression. Our study suggests that following TBI, iron is deposited in tissues not normally associated with iron storage, which may be a secondary mechanism of radiation-induced tissue injury.

Targeting of cellular redox metabolism for mitigation of radiation injury

Accidental exposure to ionizing radiation is a serious concern to human life. Studies on the mitigation of side effects following exposure to accidental radiation events are ongoing. Recent studies have shown that radiation can activate several signaling pathways, leading to changes in the metabolism of free radicals including reactive oxygen species (ROS) and nitric oxide (NO). Cellular and molecular mechanisms show that radiation can cause disruption of normal reduction/oxidation (redox) system. Mitochondria malfunction following exposure to radiation and mutations in mitochondria DNA (mtDNA) have a key role in chronic oxidative stress. Furthermore, exposure to radiation leads to infiltration of inflammatory cells such as macrophages, lymphocytes and mast cells, which are important sources of ROS and NO. These cells generate free radicals via upregulation of some pro-oxidant enzymes such as NADPH oxidases, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Epigenetic changes also have a key role in a similar way. Other mediators such as mammalian target of rapamycin (mTOR) and peroxisome proliferator-activated receptor (PPAR), which are involved in the normal metabolism of cells have also been shown to regulate cell death following exposure to radiation. These mechanisms are tissue specific. Inhibition or activation of each of these targets can be suggested for mitigation of radiation injury in a specific tissue. In the current paper, we review the cellular and molecular changes in the metabolism of cells and ROS/NO following exposure to radiation. Furthermore, the possible strategies for mitigation of radiation injury through modulation of cellular metabolism in irradiated organs will be discussed.

Pterostilbene Inhibits FcεRI Signaling through Activation of the LKB1/AMPK Pathway in Allergic Response

In this study, the role and mechanism of pterostilbene (Pts) in mast cell degranulation in vitro and in vivo were investigated. The results showed that Pts inhibited mast cell-mediated local passive allergic reactions in mice. In addition, treatment with Pts reduced both histamine release and calcium influx in rat peritoneal mast cells and RBL-2H3 cells and reduced IgE-mediated mast cell activation. Furthermore, the mechanism underlying Pts inhibition of mast cell signaling was probed via studying the effects of Pts on liver kinase B1 (LKB1), including the use of the LKB1 activator metformin and siRNA knockdown of LKB1. The data showed that Pts reduced the release of inflammatory mediators such as tumor necrosis factor-α, interleukin-6, leukotriene C4, and prostaglandin D2 in mast cells by activating the LKB1/adenosine monophosphate (AMP)-activated protein kinase (AMPK) signaling pathway. Furthermore, Pts inhibited phosphorylation of FcεRI and FcεRI-mediated degranulation in RBL-2H3 cells. These effects were attenuated after LKB1 knockdown. Taken together, Pts could inhibit FcεRI signaling through activation of the LKB1/AMPK signaling pathway in IgE-mediated mast cell activation. Thus, Pts might be an effective therapeutic agent for mast cell-mediated allergic diseases.

Genistein Enhances Radiosensitivity of Human Hepatocellular Carcinoma Cells by Inducing G2/M Arrest and Apoptosis

New radiosensitizers are urgently needed for radiation therapy patients with localized hepatocellular carcinoma (HCC) that is refractory to radical surgery. We previously found that genistein, a major soy isoflavone, exerts radioprotective effects on L-02 normal liver cells at low concentrations. Here, we report that 5 µM genistein shows less harm to L-02 cells than HCC cells and that it significantly enhances the radiosensitivity of HCC cells by enhancing DNA damage, chromosomal aberrations and cell cycle arrest at G₂/M phase and by exacerbating apoptosis. Mechanistically, genistein aggravates X-ray-induced decreases in the levels of phospho-Bad (Ser136) but enhances the levels of phospho-Chk2 (Thr68), phospho-ATM (Ser1981) and γ-H2AX. Micro-array analysis indicated that downregulation of POU6F and CCNE2 expression and upregulation of FBXO32 and cyclin B1 expression might play vital roles in genistein-induced radiosensitivity. These findings suggest genistein as an interesting candidate for adjuvant radiotherapy for HCC and indicate that genistein causes less harm to normal cells than HCC cells by inducing G₂/M arrest and apoptosis.

Radioprotective effect of olanzapine as an anti-psychotic drug against genotoxicity and apoptosis induced by ionizing radiation on human lymphocytes

Olanzapine (OLA), is prescribed as an anti-psychotic medicine in schizophrenia patients. In this study, the protective effect of OLA against genotoxicity and apoptosis induced by ionizing radiation in human healthy lymphocytes was evaluated. At first, the antioxidant activities of OLA were assayed by two different methods as free radical scavenging with DPPH (2,2-diphenyl-1-picryl-hydrazyl) and ferric reducing power methods. In in vitro experiment, human blood samples were treated with OLA at various concentrations (0.25-20 μM) for 3 h and then were exposed to X-ray at a dose of 150 cGy. The genotoxicity was assessed in binucleated human lymphocytes with micronuclei assay. The apoptotic lymphocytes were assessed by flow cytometry in OLA treated and/or irradiated lymphocytes. OLA exhibited free radical scavenging and reducing power activities more than ascorbic acid. The results showed that the lymphocytes treated with OLA and later exposed to IR presented lower frequencies of micronuclei and apoptosis compared to the control sample which was irradiated and not treated to OLA. The maximum radioprotection was observed at 20 μM of OLA with 83% of efficacy. The present study suggested the protective role for OLA in protection radiation-induced genetic damage and apoptosis induced by ionizing irradiation in human normal cells.

Protection from ionizing radiation-induced genotoxicity and apoptosis in rat bone marrow cells by HESA-A: a new herbal-marine compound

HESA-A is an herbal-marine compound which improves the quality of life of end-stage cancer patients. The aim of the present study was to evaluate the possible protective effect of HESA-A against IR-induced genotoxicity and apoptosis in rat bone marrow. Rats were given HESA-A orally at doses of 150 and 300 mg/kg body weight for seven consecutive days. On the seventh day, the rats were irradiated with 4 Gy X-rays at 1 h after the last oral administration. The micronucleus assay, reactive oxygen species (ROS) level analysis, hematological analysis and flow cytometry were used to assess radiation antagonistic potential of HESA-A. Administration of 150 and 300 mg/kg of HESA-A to irradiated rats significantly reduced the frequencies of micronucleated polychromatic erythrocytes (MnPCEs) and micronucleated normochromatic erythrocytes (MnNCEs), and also increased PCE/(PCE + NCE) ratio in bone marrow cells. Moreover, pretreatment of irradiated rats with HESA-A (150 and 300 mg/kg) significantly decreased ROS level and apoptosis in bone marrow cells, and also increased white blood cells count in peripheral blood. For the first time in this study, it was observed that HESA-A can have protective effects against radiation-induced genotoxicity and apoptosis in bone marrow cells. Therefore, HESA-A can be considered as a candidate for future studies to reduce the side effects induced by radiotherapy in cancer patients.

Mitigation of Radiation-Induced Lung Pneumonitis and Fibrosis Using Metformin and Melatonin: A Histopathological Study

Background and objectives: Pneumonitis and fibrosis are the most common consequences of lung exposure to a high dose of ionizing radiation during an accidental radiological or nuclear event, and may lead to death, after some months to years. So far, some anti-inflammatory and antioxidant agents have been used for mitigation of lung injury. In the present study, we aimed to detect possible mitigatory effects of melatonin and metformin on radiation-induced pneumonitis and lung fibrosis. Materials and methods: 40 male mice were divided into 4 groups (10 mice in each). For control group, mice did not receive radiation or drugs. In group 2, mice were irradiated to chest area with 18 Gy gamma rays. In groups 3 and 4, mice were first irradiated similar to group 2. After 24 h, treatment with melatonin as well as metformin began. Mice were sacrificed after 100 days for determination of mitigation of lung pneumonitis and fibrosis by melatonin or metformin. Results: Results showed that both melatonin and metformin are able to mitigate pneumonitis and fibrosis markers such as infiltration of inflammatory cells, edema, vascular and alveolar thickening, as well as collagen deposition. Conclusion: Melatonin and metformin may have some interesting properties for mitigation of radiation pneumonitis and fibrosis after an accidental radiation event.

Radiosensitizing effects of Cyclocarya paliurus polysaccharide on hypoxic A549 and H520 human non-small cell lung carcinoma cells

Cyclocarya paliurus (CP) polysaccharide (CPP) is a chemical component contained in CP, which has been reported to possess significant hypoglycemic activity. The present study aimed to investigate the radiosensitizing effect and underlying mechanisms of CPP on hypoxic A549 and H520 human non-small cell lung carcinoma cells. Cell viability, apoptosis and proliferation were determined using Cell Counting kit-8 assay, flow cytometry and colony formation assay, respectively. mRNA and protein expression levels were determined by reverse transcription-quantitative PCR and western blot analysis, respectively. The results suggested that CPP markedly inhibited the viability of hypoxic A549 and H520 cells. In response to combined treatment with CPP and radiation, hypoxic A549 and H520 cells exhibited enhanced apoptosis; in addition, cell proliferation was suppressed and the expression levels of hypoxia-inducible factor-1α, survivin and cleaved caspase-3 were modified. Furthermore, CPP in combination with radiation affected the mammalian target of rapamycin (mTOR)/Akt/phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K) pathway. These findings indicated that CPP may enhance the radiosensitivity of hypoxic A549 and H520 cells; this effect may be associated with inhibition of the mTOR/Akt/PI3K pathway. The potential radiosensitizing effects of CPP on hypoxic A549 and H520 cells suggested that CPP may be an effective target for treatment of non-small cell lung carcinoma.

Metformin attenuates cisplatin-induced genotoxicity and apoptosis in rat bone marrow cells

Metformin is widely used as an oral hypoglycemic drug in the management of type 2 diabetes mellitus. This study evaluated the possible protective effects of metformin against cisplatin-induced genotoxicity and apoptosis in rat bone marrow cells. Two different doses of metformin (50 and 100 mg/kg b.w.) were administered orally to experimental animals for seven consecutive days. On the seventh day, the rats were exposed to cisplatin (5 mg/kg, i.p.) 1 h after the last oral metformin administration. Rats in the control group were treated orally with 10 ml/kg PBS for 7 consecutive days and a single intraperitoneal injection of saline (0.9%) on the 7th day. The antagonistic effects of metformin against cisplatin were evaluated using micronucleus assay, reactive oxygen species (ROS) level analysis, hematological analysis, and flow cytometry. Treatment with 50 and 100 mg/kg metformin before cisplatin injection produced a significant reduction in the frequencies of micronucleated polychromatic erythrocytes (MnPCEs) and micronucleated normochromatic erythrocytes (MnNCEs) 24 h after cisplatin treatment with a corresponding increase in the PCE/(PCE + NCE) ratio. Moreover, metformin markedly elevated the levels of both red and white blood cells in peripheral blood and decreased the percentage of apoptotic cells and the ROS level in bone marrow cells of rats treated with cisplatin. The data suggest that metformin has potential chemoprotective properties in rat bone marrow after cisplatin treatment, which support its candidature as a potential chemoprotective agent for cancer patients undergoing chemotherapy.

Senolytics and senostatics as adjuvant tumour therapy

Cell senescence is a driver of ageing, frailty, age-associated disease and functional decline. In oncology, tumour cell senescence may contribute to the effect of adjuvant therapies, as it blocks tumour growth. However, this is frequently incomplete, and tumour cells that recover from senescence may gain a more stem-like state with increased proliferative potential. This might be exaggerated by the induction of senescence in the surrounding niche cells. Finally, senescence will spread through bystander effects, possibly overwhelming the capacity of the immune system to ablate senescent cells. This induces a persistent system-wide senescent cell accumulation, which we hypothesize is the cause for the premature frailty, multi-morbidity and increased mortality in cancer survivors. Senolytics, drugs that selectively kill senescent cells, have been developed recently and have been proposed as second-line adjuvant tumour therapy. Similarly, by blocking accelerated senescence following therapy, senolytics might prevent and potentially even revert premature frailty in cancer survivors. Adjuvant senostatic interventions, which suppress senescence-associated bystander signalling, might also have therapeutic potential. This becomes pertinent because treatments that are senostatic in vitro (e.g. dietary restriction mimetics) persistently reduce numbers of senescent cells in vivo, i.e. act as net senolytics in immunocompetent hosts.

Metformin as a Radiation Modifier; Implications to Normal Tissue Protection and Tumor Sensitization

BACKGROUND

Nowadays, ionizing radiation is used for several applications in medicine, industry, agriculture, and nuclear power generation. Besides the beneficial roles of ionizing radiation, there are some concerns about accidental exposure to radioactive sources. The threat posed by its use in terrorism is of global concern. Furthermore, there are several side effects to normal organs for patients who had undergone radiation treatment for cancer. Hence, the modulation of radiation response in normal tissues was one of the most important aims of radiobiology. Although, so far, several agents have been investigated for protection and mitigation of radiation injury. Agents such as amifostine may lead to severe toxicity, while others may interfere with radiation therapy outcomes as a result of tumor protection. Metformin is a natural agent that is well known as an antidiabetic drug. It has shown some antioxidant effects and enhances DNA repair capacity, thereby ameliorating cell death following exposure to radiation. Moreover, through targeting endogenous ROS production within cells, it can mitigate radiation injury. This could potentially make it an effective radiation countermeasure. In contrast to other radioprotectors, metformin has shown modulatory effects through induction of several genes such as AMPK, which suppresses reduction/ oxidation (redox) reactions, protects cells from accumulation of unrepaired DNA, and attenuates initiation of inflammation as well as fibrotic pathways. Interestingly, these properties of metformin can sensitize cancer cells to radiotherapy.

CONCLUSION

In this article, we aimed to review the interesting properties of metformin such as radioprotection, radiomitigation and radiosensitization, which could make it an interesting adjuvant for clinical radiotherapy, as well as an interesting candidate for mitigation of radiation injury after a radiation disaster.

Metformin Protects Against Radiation-Induced Pneumonitis and Fibrosis and Attenuates Upregulation of Dual Oxidase Genes Expression

Purpose: Lung tissue is one of the most sensitive organs to ionizing radiation (IR). Early and late side effects of exposure to IR can limit the radiation doses delivered to tumors that are within or adjacent to this organ. Pneumonitis and fibrosis are the main side effects of radiotherapy for this organ. IL-4 and IL-13 have a key role in the development of pneumonitis and fibrosis. Metformin is a potent anti-fibrosis and redox modulatory agent that has shown radioprotective effects. In this study, we aimed to evaluate possible upregulation of these cytokines and subsequent cascades such as IL4-R1, IL-13R1, Dual oxidase 1 (DUOX1) and DUOX2. In addition, we examined the potential protective effect of metformin in these cytokines and genes, as well as histopathological changes in rat’s lung tissues.

Methods: 20 rats were divided into 4 groups: control; metformin treated; radiation + metformin; and radiation. Irradiation was performed with a ⁶⁰Co source delivering 15 Gray (Gy) to the chest area. After 10 weeks, rats were sacrificed and their lung tissues were removed for histopathological, real-time PCR and ELISA assays.

Results: Irradiation of lung was associated with an increase in IL-4 cytokine level, as well as the expression of IL-4 receptor-a1 (IL4ra1) and DUOX2 genes. However, there was no change in the level of IL-13 and its downstream gene including IL-13 receptor-a2 (IL13ra2). Moreover, histopathological evaluations showed significant infiltration of lymphocytes and macrophages, fibrosis, as well as vascular and alveolar damages. Treatment with metformin caused suppression of upregulated genes and IL-4 cytokine level, associated with amelioration of pathological changes.

Conclusion: Results of this study showed remarkable pathological damages, an increase in the levels of IL-4, IL4Ra1 and Duox2, while that of IL-13 decreased. Treatment with metformin showed ability to attenuate upregulation of IL-4–DUOX2 pathway and other pathological damages to the lung after exposure to a high dose of IR.

Metformin Protects Against Radiation-Induced Heart Injury and Attenuates the Upregulation of Dual Oxidase Genes Following Rat's Chest Irradiation

Radiation-induced heart toxicity is one of the serious side effects after a radiation disaster or radiotherapy for patients with chest cancers, leading to a reduction in the quality of life of the patients. Evidence has shown that infiltration of inflammatory cells plays a key role in the development of functional damages to the heart via chronic upregulation of some pro-fibrotic and pro-inflammatory cytokines. These changes are associated with continuous free radical production and increased stiffness of heart muscle. IL-4 and IL-13 are two important pro-fibrotic cytokines which contribute to the side effects of ionizing radiation exposure. Recent studies have proposed that IL-4 through upregulation of DUOX2, and IL-13 via stimulation of DUOX1 gene expression, are involved in the development of radiation late effects. In the present study, we aimed to detect changes in the expression of these pathways following irradiation of rat’s heart. Furthermore, we evaluated the possible protective effect of metformin on the development of these abnormal changes. 20 male rats were divided into 4 groups (control, radiation, metformin treated, metformin + radiation). These rats were irradiated with 15 Gy ⁶⁰Co gamma rays, and sacrificed after 10 weeks for evaluation of the changes in the expression of IL4R1, IL-13R2a, DUOX1 and DUOX2. In addition, the levels of IL-4 and IL-13 cytokines, as well as infiltration of macrophages and lymphocytes were detected. Results showed an upregulation of both DUOX1 and DUOX2 pathways in the presence of metformin, while the level of IL-13 did not show any significant change. This was associated with infiltration of macrophages and lymphocytes. Also, treatment with metformin could significantly attenuate accumulation of inflammatory cells, and upregulate these pathways. Therefore, suppression of dual oxidase genes by metformin may be a contributory factor to its protective effect.

Metformin: Prevention of genomic instability and cancer: A review

The diabetes drug metformin can mitigate the genotoxic effects of cytotoxic agents and has been proposed to prevent or even cure certain cancers. Metformin reduces DNA damage by mechanisms that are only incompletely understood. Metformin scavenges free radicals, including reactive oxygen species and nitric oxide, which are produced by genotoxicants such as ionizing or non-ionizing radiation, heavy metals, and chemotherapeutic agents. The drug may also increase the activities of antioxidant enzymes and inhibit NADPH oxidase, cyclooxygenase-2, and inducible nitric oxide synthase, thereby limiting macrophage recruitment and inflammatory responses. Metformin stimulates the DNA damage response (DDR) in the homologous end-joining, homologous recombination, and nucleotide excision repair pathways. This review focuses on the protective properties of metformin against genomic instability.