In vivo radioprotection by 5-aminosalicylic acid

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.

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.

Chemoprevention of Colitis-Associated Dysplasia or Cancer in Inflammatory Bowel Disease

The association between inflammatory bowel disease and colorectal cancer is well known. Although the overall incidence of inflammatory bowel disease has declined recently, patients with this disease still have a 1.7-fold increased risk of colorectal cancer. The risk factors for developing colorectal cancer include extensive colitis, young age at diagnosis, disease duration, primary sclerosing cholangitis, chronic colonic mucosal inflammation, dysplasia lesion, and post-inflammatory polyps. In patients with inflammatory bowel disease, control of chronic inflammation and surveillance colonoscopies are important for the prevention of colorectal cancer. The 2017 guidelines from the European Crohn's and Colitis Organisation suggest that colonoscopies to screen for colorectal cancer should be performed when inflammatory bowel disease symptoms have lasted for 8 years. Current evidence supports the use of chemoprevention therapy with mesalamine to reduce the risk of colorectal cancer in patients with ulcerative colitis. Other compounds, including thiopurine, folic acid, statin, and tumor necrosis factor-α inhibitor, are controversial. Large surveillance cohort studies with longer follow-up duration are needed to evaluate the impact of drugs on colorectal cancer risks.

Correlations between Risk Factors for Breast Cancer and Genetic Instability in Cancer Patients-A Clinical Perspective Study

Molecular epidemiological studies have identified several risk factors linking to the genes and external factors in the pathogenesis of breast cancer. In this sense, genetic instability caused by DNA damage and DNA repair inefficiencies are important molecular events for the diagnosis and prognosis of therapies. Therefore, the objective of this study was to analyze correlation between sociocultural, occupational, and lifestyle risk factors with levels of genetic instability in non-neoplastic cells of breast cancer patients. Total 150 individuals were included in the study that included 50 breast cancer patients submitted to chemotherapy (QT), 50 breast cancer patients submitted to radiotherapy (RT), and 50 healthy women without any cancer. Cytogenetic biomarkers for apoptosis and DNA damage were evaluated in samples of buccal epithelial and peripheral blood cells through micronuclei and comet assay tests. Elder age patients (61-80 years) had higher levels of apoptosis (catriolysis by karyolysis) and DNA damage at the diagnosis (baseline damage) with increased cell damage during QT and especially during RT. We also reported the increased frequencies of cytogenetic biomarkers in patients who were exposed to ionizing radiation as well as for alcoholism and smoking. QT and RT induced high levels of fragmentation (karyorrhexis) and nuclear dissolution (karyolysis) and DNA damage. Correlations were observed between age and karyorrhexis at diagnosis; smoking and karyolysis during RT; and radiation and karyolysis during QT. These correlations indicate that risk factors may also influence the genetic instability in non-neoplastic cells caused to the patients during cancer therapies.

Antitumor and radiosensitizing synergistic effects of apigenin and cryptotanshinone against solid Ehrlich carcinoma in female mice

Considerable attention has been paid to the introduction of novel naturally occurring plant-derived radiosensitizer compounds in order to augment the radiation efficacy and improve the treatment outcome of different tumors. This study was therefore undertaken to evaluate the antitumor, antiangiogeneic, and synergistic radiosensitizing effects of apigenin, a dietary flavonoid, and/or cryptotanshinone, a terpenoid isolated from the roots of Salvia miltiorrhiza, against the growth of solid Ehrlich carcinoma in female mice. Apigenin (50 mg/kg body weight) and/or cryptotanshinone (40 mg/kg body weight) was intraperitoneally (i.p.) injected into non-irradiated or γ-irradiated (6.5 Gy whole-body γ-irradiation) solid Ehrlich carcinoma-bearing mice for 30 consecutive days. Investigations included molecular targets involved in proliferation, inflammation, angiogenesis, and tumor invasiveness. Treatment with apigenin and/or cryptotanshinone significantly suppressed the growth of solid Ehrlich carcinoma tumors and demonstrated a synergistic radiosensitizing efficacy together with γ-irradiation. These effects were achieved through downregulating the expression of angiogenic and lymphangiogenic regulators, including signal transducer and activator of transcription 3, vascular endothelial growth factor C, and tumor necrosis factor alpha, suppressing matrix metalloproteinase-2 and -9 activities, which play a key role in tumor invasion and metastasis, and enhancing apoptosis via inducing cleaved caspase-3 and granzyme B levels. Histological findings of solid Ehrlich carcinoma tumors verified the recorded data. In conclusion, a synergistic radiosensitizing efficacy for apigenin and cryptotanshinone was demonstrated against Ehrlich carcinoma in the current in vivo murine model, representing therefore a potential therapeutic strategy for increasing the radiation response of solid tumors.

Preclinical Evaluation of DMA, a Bisbenzimidazole, as Radioprotector: Toxicity, Pharmacokinetics, and Biodistribution Studies in Balb/c Mice

Radiotherapy, a therapeutic modality of cancer treatment, nonselectively damages normal tissues as well as tumor tissues. The search is ongoing for therapeutic agents that selectively reduce radiation-induced normal tissue injury without reducing tumoricidal effect, thereby increasing the therapeutic ratio of radiation therapy. Our laboratory established 5-(4-methylpiperazin-1-yl)-2-[2'-(3,4-dimethoxyphenyl)-5'benzimidazolyl] benzimidazole (DMA) as noncytotoxic radioprotector in mammalian cells. DMA showed an excellent radioprotection in mice at single nontoxic oral dose by a dose-reduction factor of 1.28. An oxygen radical absorbing capacity assay confirmed its free-radical quenching ability. Single bolus dose and 28-days of repeated administration of DMA in mice for toxicity studies determined an LD50 of >2000 mg/kg body weight (bw) and 225 mg/kg bw, respectively, suggesting DMA is safe. Histopathology, biochemical parameters, and relative organ weight analysis revealed insignificant changes in the DMA-treated animals. The pharmacokinetic study of DMA at oral and intravenous doses showed its C(max) = 1 hour, bioavailability of 8.84%, elimination half-life of 4 hours, and an enterohepatic recirculation. Biodistribution study in mice with Ehrlich ascites tumors showed that (99m)Tc-DMA achieved its highest concentration in 1 hour and was retained up to 4 hours in the lungs, liver, kidneys, and spleen, and in a low concentration in the tumor, a solicited property of any radioprotector to protect normal cells over cancerous cells. We observed that the single-dose treatment of tumor-bearing mice with DMA 2 hours before 8 Gy total body irradiation showed an impressive rescue of radiation-induced morbidity in terms of weight loss and mortality without a change in tumor response.

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

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

Polyphenolic fraction of Pilea microphylla (L.) protects Chinese hamster lung fibroblasts against γ-radiation-induced cytotoxicity and genotoxicity

Present study was designed to compare cytoprotective and antigenotoxic activity of the polyphenolic fraction of Pilea microphylla (PM1) with that of its active polyphenolic constituents against γ-radiation in V79 cells. PM1 was standardized with respect to the polyphenols present by RP-HPLC. It was evaluated for its free radical scavenging potential using Fenton reaction-induced DNA damage and lipid peroxidation. Further, PM1 was subjected against γ-radiation-induced cytotoxicity and genotoxicity in V79 cells. PM1 significantly reduced free radical-mediated calf thymus DNA damage and lipid peroxidation. Among the concentrations tested (12.5, 25 and 50 μg/ml) for radioprotection, PM1 at 25 μg/ml exhibited maximum protection. Further, when compared with constituent polyphenols viz., rutin, quercetin and chlorogenic acid (concentrations equivalent to that present in PM1-25 μg/ml), a combination of polyphenols was found most effective in preventing γ-radiation-induced cytotoxicity and genotoxicity. To conclude, radioprotection is possibly a synergistic effect of the phytochemicals present in the herbal extract, rather than any single component.

Whole body radioprotective activity of an acetone-water extract from the seedpod of Nelumbo nucifera Gaertn. seedpod

Procyanidins extracted with acetone-water from lotus (Nelumbo nucifera Gaertn.) seedpod (LSPCs) were evaluated for in vivo radioprotective activity against whole body gamma irradiation in Swiss albino mice. Pretreated with LSPCs 200 mg/kg by intragastric (i.g.) for 15 days was found to be the most effective dose in preventing radiation sickness, reducing radiation-induced mortality, increasing mean survival time and elevating radiation median lethal dose (LD(50)) from 8.9 to 10.5 Gy, indicating a dose modifying factor (DMF) of 1.18. Further, administered LSPCs at a dose of 200 mg/kg could effectively maintain spleen index close to normal, stimulate endogenous spleen colony forming units, promote the levels of red blood cells (RBC), white blood cells (WBC), platelets and hemoglobin in peripheral blood, and prevent spleen and skin damage in irradiated mice, reduce the level of radiation-induced micronucleated polychromatic erythrocytes in bone marrow, maintain the polychromatic erythrocytes (PCE) and normochromatic erythrocytes (NCE) ratio (P/N ratio) and significantly decrease bone marrow chromosomal damage. Alternatively, pretreated with LSPCs (200 mg/kg) significantly decreased the lipid peroxidation (LPO) level, and elevated the activities of endogenous antioxidant enzymes in liver after irradiation. Thus LSPCs possess a strong whole body radioprotective activity, and it may be used as a radioprotector.

Sodium orthovanadate inhibits p53-mediated apoptosis

Sodium orthovanadate (vanadate) inhibits the DNA-binding activity of p53, but its precise effects on p53 function have not been examined. Here, we show that vanadate exerts a potent antiapoptotic activity through both transcription-dependent and transcription-independent mechanisms relative to other p53 inhibitors, including pifithrin (PFT) alpha. We compared the effects of vanadate to PFTalpha and PFTmicro, an inhibitor of transcription-independent apoptosis by p53. Vanadate suppressed p53-associated apoptotic events at the mitochondria, including the loss of mitochondrial membrane potential, the conformational change of Bax and Bak, the mitochondrial translocation of p53, and the interaction of p53 with Bcl-2. Similarly, vanadate suppressed the apoptosis-inducing activity of a mitochondrially targeted temperature-sensitive p53 in stable transfectants of SaOS-2 cells. In radioprotection assays, which rely on p53, vanadate completely protected mice from a sublethal dose of 8 Gy and partially from a lethal dose of 12 Gy. Together, our findings indicated that vanadate effectively suppresses p53-mediated apoptosis by both transcription-dependent and transcription-independent pathways, and suggested that both pathways must be inhibited to completely block p53-mediated apoptosis.