Mechanisms for Radioprotection by Melatonin; Can it be Used as a Radiation Countermeasure?

An unmet need for pharmacology: Treatments for radiation-induced gastrointestinal mucositis

Gastrointestinal mucositis (GIM) continues to be a significant issue in the management of abdominal cancer radiation treatments and chemotherapy, causing significant patient discomfort and therapy interruption or even cessation. This review will first focus on radiotherapy induced GIM, providing an understanding of its clinical landscape. Subsequently, the aetiology of GIM will be reviewed, highlighting diverse contributing factors. The cellular and tissue damage and associated molecular responses in GIM will be summarised in the context of the underlying complex biological processes. Finally, available drugs and pharmaceutical therapies will be evaluated, underscoring their insufficiency, and highlighting the need for further research and innovation. This review will emphasize the urgent need for improved pharmacologic therapeutics for GIM, which is a key research priority in oncology.

Rethinking the Role of Biodosimetry to Assess Risks for Acute Radiation Syndrome in Very Large Radiation Events: Reconsidering Legacy Concepts

The development of effective uses of biodosimetry in large-scale events has been hampered by residual, i.e., "legacy" thinking based on strategies that scale up from biodosimetry in small accidents. Consequently, there remain vestiges of unrealistic assumptions about the likely magnitude of victims in "large" radiation events and incomplete analyses of the logistics for making biodosimetry measurements/assessments in the field for primary triage. Elements remain from an unrealistic focus on developing methods to use biodosimetry in the initial stage of triage for a million or more victims. Based on recent events and concomitant increased awareness of the potential for large-scale events as well as increased sophistication in planning and experience in the development of biodosimetry, a more realistic assessment of the most effective roles of biodosimetry in large-scale events is urgently needed. We argue this leads to a conclusion that the most effective utilization of biodosimetry in very large events would occur in a second stage of triage, after initially winnowing the population by identifying those most in need of acute medical attention, based on calculations of geographic sites where significant exposures could have occurred. Understanding the potential roles and limitations of biodosimetry in large-scale events involving significant radiation exposure should lead to development of the most effective and useful biodosimetric techniques for each stage of triage for acute radiation syndrome injuries, i.e., based on more realistic assumptions about the underlying event and the logistics for carrying out biodosimetry for large populations.

The effect of ionizing radiation on the fetal bone development in pregnant rats: Role of melatonin

Radiation has been widely used in many business sectors over the last century. Our study investigated the possible teratogenic effects of radiation on the bones of rat fetuses and the protective effect of melatonin against these effects. In this study, 15 pregnant female Wistar albino rats were used. These rats were divided into four groups: the control group, melatonin group (10 mg/kg/day), radiation group (0.5 gray), radiation (0.5 gray) + melatonin group (10 mg/kg/day), and sham group (1 mm hanks/day). The skeletal system development of fetuses was examined with double skeletal and scanning electron microscope (SEM), histopathological methods. In our study, fetal weight, placental weight, and fetal morphometric values were found to be statistically significantly decreased in the radiation group compared to the control group (p < .05). In immünohistochemistry (IHC) analysis, alkaline phosphatase, and tartrate-resistant acid phosphatase) concentrations were found to be significantly lower in the radiation group compared to the other groups. In the SEM analysis, it was observed that the amount of calcium and sodium decreased when the radiation group was compared with the other groups. As a result, when exposed to ionizing radiation during pregnancy, melatonin has a protective feature against the negative effects of radiation on the bone development of fetuses. RESEARCH HIGHLIGHTS: In our study, fetuses obtained from pregnant rats exposed to ionizing radiation were examined. In this study, the effect of melatonin on bone development in fetuses exposed to gray ionizing radiation was investigated. There are few studies on our subject in the literature. We believe that our findings will contribute to other planned studies.

A Systematic Review of the Chemo/Radioprotective Effects of Melatonin against Ototoxic Adverse Effects Induced by Chemotherapy and Radiotherapy

BACKGROUND

Although chemotherapy and radiotherapy are effective in cancer treatment, different adverse effects induced by these therapeutic modalities (such as ototoxicity) restrict their clinical use. Co-treatment of melatonin may alleviate the chemotherapy/radiotherapy-induced ototoxicity.

OBJECTIVE

In the present study, the otoprotective potentials of melatonin against the ototoxicity induced by chemotherapy and radiotherapy were reviewed.

METHODS

According to the PRISMA guideline, a systematic search was carried out to identify all relevant studies on "the role of melatonin against ototoxic damage associated with chemotherapy and radiotherapy" in the different electronic databases up to September 2022. Sixty-seven articles were screened based on a predefined set of inclusion and exclusion criteria. Seven eligible studies were finally included in this review.

RESULTS

The in vitro findings showed that cisplatin chemotherapy significantly decreased the auditory cell viability compared to the control group; in contrast, the melatonin co-administration increased the cell viability of cisplatin-treated cells. The results obtained from the distortion product otoacoustic emission (DPOAE) and auditory brainstem response (ABR) tests demonstrated a decreased amplitude of DPOAE and increased values of ABR I-IV interval and ABR threshold in mice/rats receiving radiotherapy and cisplatin; nevertheless, melatonin co-treatment indicated an opposite pattern on these evaluated parameters. It was also found that cisplatin and radiotherapy could significantly induce the histological and biochemical changes in the auditory cells/tissue. However, melatonin co-treatment resulted in alleviating the cisplatin/radiotherapy-induced biochemical and histological changes.

CONCLUSION

According to the findings, it was shown that melatonin co-treatment alleviates the ototoxic damage induced by chemotherapy and radiotherapy. Mechanically, melatonin may exert its otoprotective effects via its anti-oxidant, anti-apoptotic, and anti-inflammatory activities and other mechanisms.

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.

Mitotherapy as a Novel Therapeutic Strategy for Mitochondrial Diseases

BACKGROUND

The mitochondrion is a multi-functional organelle that is mainly responsible for energy supply in the mammalian cells. Over 100 human diseases are attributed to mitochondrial dysfunction. Mitochondrial therapy (mitotherapy) aims to transfer functional exogenous mitochondria into mitochondria-defective cells for recovery of the cell viability and consequently, prevention of the disease progress.

OBJECTIVE

The review summarizes the evidence on exogenous mitochondria that can directly enter mammalian cells for disease therapy following local and intravenous administration, and suggests that when healthy cells donate their mitochondria to damaged cells, the mitochondrial transfer between cells serve as a new mode of cell rescue. Then the transferred mitochondria play their roles in recipient cells, including energy production and maintenance of cell function.

CONCLUSION

Mitotherapy makes the of modulation of cell survival possible, and it would be a potential therapeutic strategy for mitochondrial diseases.

Pinus koraiensis polyphenols: structural identification, in vitro antioxidant activity, immune function and inhibition of cancer cell proliferation

Herein, polyphenols were extracted from Pinus koraiensis bark and characterized. Besides, the in vitro antioxidant activity, inhibition effect on cancer cells and the activity of the immune system were investigated. The results showed that the main component of Pinus koraiensis bark was 3,5,7,3',5'-pentahydroxydihydroflavone. PKB polyphenols demonstrated a high antioxidant activity during in vitro investigation. In vivo immunological function studies on oxidatively injured mice revealed that Pinus koraiensis bark polyphenols effectively improved the survival status of irradiated mice. PKBP also increased the spleen and thymus index of mouse immunoregulatory organs. The results indicated that the phagocytic ability of mononuclear macrophages was increased. Comparing the cell distribution of the PKBP administered group and the model group, the PKBP-administered group reduced the cells arrested in the G1 phase, while the number of cells increased in the S and G2 phases. PKBP effectively protected the mouse immune system and reduced the immune suppression caused by radiation. These findings also confirmed that oxidative damaged cells induced by radiation could be repaired. PKBP had the highest inhibitory activity on colon cancer cells HT29, breast cancer cells MFC-7, gastric cancer cells BGC-823 and cervical cancer HeLa and HT29 cancer cells. PKB polyphenols could effectively induce the production of DNA-Ladder fragments and cause DNA damage in cancer cells. PKBP also blocked the cycle of cancer cells in the G2 phase, stopped cell division and induced cancer cell apoptosis. Analysis of cell apoptosis by Annexin V-FTIC/PI double staining indicated that PKBP inhibited HT29 cancer cell proliferation.

Utilization of redox modulating small molecules that selectively act as pro-oxidants in cancer cells to open a therapeutic window for improving cancer therapy

There is a rapidly growing body of literature supporting the notion that differential oxidative metabolism in cancer versus normal cells represents a metabolic frailty that can be exploited to open a therapeutic window into cancer therapy. These cancer cell-specific metabolic frailties may be amenable to manipulation with non-toxic small molecule redox active compounds traditionally thought to be antioxidants. In this review we describe the potential mechanisms and clinical applicability in cancer therapy of four small molecule redox active agents: melatonin, vitamin E, selenium, and vitamin C. Each has shown the potential to have pro-oxidant effects in cancer cells while retaining antioxidant activity in normal cells. This dichotomy can be exploited to improve responses to radiation and chemotherapy by opening a therapeutic window based on a testable biochemical rationale amenable to confirmation with biomarker studies during clinical trials. Thus, the unique pro-oxidant/antioxidant properties of melatonin, vitamin E, selenium, and vitamin C have the potential to act as effective adjuvants to traditional cancer therapies, thereby improving cancer patient outcomes.

Melatonin as an Oncostatic Molecule Based on Its Anti-Aromatase Role in Breast Cancer

Breast cancer is the most common type of cancer. In the developmental stages of breast cancer, estrogens are strongly involved. As estrogen synthesis is regulated by the enzyme aromatase, targeting the activity of this enzyme represents a therapeutic option. The pineal hormone melatonin may exert a suppressive role on aromatase activity, leading to reduced estrogen biosynthesis. A melatonin-mediated decrease in the expression of aromatase promoters and associated genes would provide suitable evidence of this molecule’s efficacy as an aromatase inhibitor. Furthermore, melatonin intensifies radiation-induced anti-aromatase effects and counteracts the unwanted disadvantages of chemotherapeutic agents. In this manner, this review summarizes the inhibitory role of melatonin in aromatase action, suggesting its role as a possible oncostatic molecule in breast cancer.

Radiation protection by Ex-RAD: a systematic review

Protection of normal tissues against ionizing radiation-induced damages is a critical issue in clinical and environmental radiobiology. One of the ways of accomplishing radiation protection is through the use of radioprotectors. In the search for the most effective radioprotective agent, factors such as toxicity, effect on tumors, number of tissues protected, ease of administration, long-term stability, and compatibility with other drugs need to be assessed. Thus, in the present study, we systematically review existing studies on a chemical radioprotector, Ex-RAD, with the aim of examining its efficacy of radiation protection as well as underlying mechanisms. To this end, a systematic search of the electronic databases including Pubmed, Scopus, Embase, and Google Scholar was conducted to retrieve articles investigating the radioprotective effect of Ex-RAD. From an initial search of 268 articles, and after removal of duplicates as well as applying the predetermined inclusion and exclusion criteria, 10 articles were finally included for this systematic review. Findings from the reviewed studies indicated that Ex-RAD showed potentials for effective radioprotection of the studied organs with no side effect. Furthermore, the inhibition of apoptosis through p53 signaling pathway was the main mechanism of radioprotection by Ex-RAD. However, its radioprotective effect would need to be investigated for more organs in future studies.

Mitigation of radiation-induced hematopoietic system injury by melatonin

BACKGROUND

Increased risks of exposure to accidental radiation events are a concern in today's world. Radiation terror, nuclear explosion, as well as accidental exposure to radioactive sources in some industries pose a threat to the life of exposed persons. Studies have been conducted using some low-toxic agents to mitigate radiation toxicity and increase survival probability for exposed people. In the current study, we aimed to show the mitigation of radiation-induced mortality and bone marrow toxicity using postirradiation treatment with melatonin.

METHOD

Mice whole bodies were exposed to 4 or 7 Gy radiation followed by treatment with melatonin after 24 hours. Survival of mice with or without melatonin, the levels of peripheral cells, transforming growth factor (TGF)-β and 8-hydroxy-2' -deoxyguanosine (8-OHdG) in the bone marrow, as well as the expression of NADPH oxidase (NOX)2 and NOX4 in bone marrow cells were evaluated.

RESULTS

Whole body irradiation led to mortality 30 days after irradiation. However, melatonin treatment reduced mortality. Irradiation also showed severe reduction of lymphocytes, platelets, and red blood cells. The expressions of NOX2 and NOX4, in addition to TGF-β level, were increased after exposure to radiation. Melatonin ameliorated the increased levels of these factors and improved the number of blood cells.

CONCLUSIONS

Melatonin showed ability to mitigate radiation-induced hematopoietic system toxicity and also increased survival rate. These results suggest that melatonin could be a potential mitigator for accidental radiation events.

Cardiovascular diseases in survivors of childhood cancer

Over the past few decades, the diagnosis and management of children with various malignancies have improved tremendously. As a result, there are an increasing number of children who are long-term cancer survivors. With improved survival, however, has come an increased risk of treatment-related cardiovascular complications that can appear decades after treatment. These problems are serious enough that all caregivers of childhood cancer survivors, including oncologists, cardiologists, and other health care personnel, must pay close attention to the short- and long-term effects of chemotherapy and radiotherapy on these children. This review discusses the effects of treatment-related cardiovascular complications from anthracyclines and radiotherapy and the methods for preventing, screening, and treating these complications.

Therapeutic effects of kaempferol affecting autophagy and endoplasmic reticulum stress

Regulated cell death (RCD) guarantees to preserve organismal homeostasis. Apoptosis and autophagy are two major arms of RCD, while endoplasmic reticulum (ER) as a crucial organelle involved in proteostasis, promotes cells toward autophagy and apoptosis. Alteration in ER stress and autophagy machinery is responsible for a great number of diseases. Therefore, targeting those pathways appears to be beneficial in the treatment of relevant diseases. Meantime, among the traditional herb medicine, kaempferol as a flavonoid seems to be promising to modulate ER stress and autophagy and exhibits protective effects on malfunctioning cells. There are some reports indicating the capability of kaempferol in affecting autophagy and ER stress. In brief, kaempferol modulates autophagy in noncancerous cells to protect cells against malfunction, while it induces cell mortality derived from autophagy through the elevation of p-AMP-activated protein kinase, light chain-3-II, autophagy-related geness, and Beclin-1 in cancer cells. Noteworthy, kaempferol enhances cell survival through C/EBP homologous protein (CHOP) suppression and GRP78 increment in noncancerous cells, while it enhances cell mortality through the induction of unfolding protein response and CHOP increment in cancer cells. In this review, we discuss how kaempferol modulates autophagy and ER stress in noncancer and cancer cells to expand our knowledge of new pharmacological compounds for the treatment of associated diseases.

The Radioprotective Effect of Combination of Melatonin and Metformin on Rat Duodenum Damage Induced by Ionizing Radiation: A Histological Study

BACKGROUND

Radiation toxicity is one of the major concerns for patients with gastrointestinal cancers that undergo radiotherapy. Duodenum is one of the most radiosensitive parts of gastrointestinal system that may be exposed to a high dose of radiation during radiotherapy for some cancers. The development or identification of appropriate radioprotectors with less toxicity is an interesting aim in radiobiology for clinical radiotherapy applications. In the present study, we aimed to evaluate the radioprotective effect of melatonin and metformin combination in rat's duodenum. In addition, we compared our results with the radioprotective effect of melatonin, when administered alone.

MATERIALS AND METHODS

Thirty male rats were divided into six groups: control, melatonin treatment, melatonin plus metformin treatment, whole-body irradiation, irradiation with melatonin treatment, and irradiation with melatonin plus metformin treatment. Irradiation was performed with 10 Gy cobalt-60 gamma rays, while 100 mg/kg of melatonin and metformin were administered 24 h before to 72 h after irradiation. After 3.5 days, their duodenum tissues were removed for histopathological evaluation.

RESULTS

Irradiation of rats led to mild-to-moderate mucositis signs, infiltration of inflammatory cells, necrosis, and damage to Brunner's glands and reduction of goblet cells. Melatonin was able to alleviate these damages, while melatonin plus metformin could reduce some radiation toxicity signs.

CONCLUSION

Administration of melatonin plus metformin could reduce mucositis in duodenum. However, the administration of melatonin is more effective for mitigation of duodenal injury compared with melatonin plus metformin.

Mechanisms of apoptosis modulation by curcumin: Implications for cancer therapy

Cancer incidences are growing and cause millions of deaths worldwide. Cancer therapy is one of the most important challenges in medicine. Improving therapeutic outcomes from cancer therapy is necessary for increasing patients' survival and quality of life. Adjuvant therapy using various types of antibodies or immunomodulatory agents has suggested modulating tumor response. Resistance to apoptosis is the main reason for radioresistance and chemoresistance of most of the cancers, and also one of the pivotal targets for improving cancer therapy is the modulation of apoptosis signaling pathways. Apoptosis can be induced by intrinsic or extrinsic pathways via stimulation of several targets, such as membrane receptors of tumor necrosis factor-α and transforming growth factor-β, and also mitochondria. Curcumin is a naturally derived agent that induces apoptosis in a variety of different tumor cell lines. Curcumin also activates redox reactions within cells inducing reactive oxygen species (ROS) production that leads to the upregulation of apoptosis receptors on the tumor cell membrane. Curcumin can also upregulate the expression and activity of p53 that inhibits tumor cell proliferation and increases apoptosis. Furthermore, curcumin has a potent inhibitory effect on the activity of NF-κB and COX-2, which are involved in the overexpression of antiapoptosis genes such as Bcl-2. It can also attenuate the regulation of antiapoptosis PI3K signaling and increase the expression of MAPKs to induce endogenous production of ROS. In this paper, we aimed to review the molecular mechanisms of curcumin-induced apoptosis in cancer cells. This action of curcumin could be applicable for use as an adjuvant in combination with other modalities of cancer therapy including radiotherapy and chemotherapy.

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.

Melatonin as an adjuvant in radiotherapy for radioprotection and radiosensitization

It is estimated that more than half of cancer patients undergo radiotherapy during the course of their treatment. Despite its beneficial therapeutic effects on tumor cells, exposure to high doses of ionizing radiation (IR) is associated with several side effects. Although improvements in radiotherapy techniques and instruments could reduce these side effects, there are still important concerns for cancer patients. For several years, scientists have been trying to modulate tumor and normal tissue responses to IR, leading to an increase in therapeutic ratio. So far, several types of radioprotectors and radiosensitizers have been investigated in experimental studies. However, high toxicity of chemical sensitizers or possible tumor protection by radioprotectors creates a doubt for their clinical applications. On the other hand, the protective effects of these radioprotectors or sensitizer effects of radiosensitizers may limit some type of cancers. Hence, the development of some radioprotectors without any protective effect on tumor cells or low toxic radiosensitizers can help improve therapeutic ratio with less side effects. Melatonin as a natural body hormone is a potent antioxidant and anti-inflammatory agent that shows some anti-cancer properties. It is able to neutralize different types of free radicals produced by IR or pro-oxidant enzymes which are activated following exposure to IR and plays a key role in the protection of normal tissues. In addition, melatonin has shown the ability to inhibit long-term changes in inflammatory responses at different levels, thereby ameliorating late side effects of radiotherapy. Fortunately, in contrast to classic antioxidants, some in vitro studies have revealed that melatonin has a potent anti-tumor activity when used alongside irradiation. However, the mechanisms of its radiosensitive effect remain to be elucidated. Studies suggested that the activation of pro-apoptosis gene, such as p53, changes in the metabolism of tumor cells, suppression of DNA repair responses as well as changes in biosynthesis of estrogen in breast cancer cells are involved in this process. In this review, we describe the molecular mechanisms for radioprotection and radiosensitizer effects of melatonin. Furthermore, some other proposed mechanisms that may be involved are presented.