Regulation of microRNAs by molecular hydrogen contributes to the prevention of radiation-induced damage in the rat myocardium

The Molecular Mechanisms in Senescent Cells Induced by Natural Aging and Ionizing Radiation

This review discusses the relationship between cellular senescence and radiation exposure. Given the wide range of ionizing radiation sources encountered by people in professional and medical spheres, as well as the influence of natural background radiation, the question of the effect of radiation on biological processes, particularly on aging processes, remains highly relevant. The parallel relationship between natural and radiation-induced cellular senescence reveals the common aspects underlying these processes. Based on recent scientific data, the key points of the effects of ionizing radiation on cellular processes associated with aging, such as genome instability, mitochondrial dysfunction, altered expression of miRNAs, epigenetic profile, and manifestation of the senescence-associated secretory phenotype (SASP), are discussed. Unraveling the molecular mechanisms of cellular senescence can make a valuable contribution to the understanding of the molecular genetic basis of age-associated diseases in the context of environmental exposure.

Tissue fibrosis induced by radiotherapy: current understanding of the molecular mechanisms, diagnosis and therapeutic advances

Cancer remains the leading cause of death around the world. In cancer treatment, over 50% of cancer patients receive radiotherapy alone or in multimodal combinations with other therapies. One of the adverse consequences after radiation exposure is the occurrence of radiation-induced tissue fibrosis (RIF), which is characterized by the abnormal activation of myofibroblasts and the excessive accumulation of extracellular matrix. This phenotype can manifest in multiple organs, such as lung, skin, liver and kidney. In-depth studies on the mechanisms of radiation-induced fibrosis have shown that a variety of extracellular signals such as immune cells and abnormal release of cytokines, and intracellular signals such as cGAS/STING, oxidative stress response, metabolic reprogramming and proteasome pathway activation are involved in the activation of myofibroblasts. Tissue fibrosis is extremely harmful to patients' health and requires early diagnosis. In addition to traditional serum markers, histologic and imaging tests, the diagnostic potential of nuclear medicine techniques is emerging. Anti-inflammatory and antioxidant therapies are the traditional treatments for radiation-induced fibrosis. Recently, some promising therapeutic strategies have emerged, such as stem cell therapy and targeted therapies. However, incomplete knowledge of the mechanisms hinders the treatment of this disease. Here, we also highlight the potential mechanistic, diagnostic and therapeutic directions of radiation-induced fibrosis.

Biological Effects of Hydrogen Water on Subjects with NAFLD: A Randomized, Placebo-Controlled Trial

Non-alcoholic fatty liver disease (NAFLD) is a liver pathology affecting around 25% of the population worldwide. Excess oxidative stress, inflammation and aberrant cellular signaling can lead to this hepatic dysfunction and eventual carcinoma. Molecular hydrogen has been recognized for its selective antioxidant properties and ability to attenuate inflammation and regulate cellular function. We administered hydrogen-rich water (HRW) to 30 subjects with NAFLD in a randomized, double-blinded, placebo-controlled manner for eight weeks. Phenotypically, we observed beneficial trends (p > 0.05) in decreased weight (≈1 kg) and body mass index in the HRW group. HRW was well-tolerated, with no significant changes in liver enzymes and a trend of improved lipid profile and reduced lactate dehydrogenase levels. HRW tended to non-significantly decrease levels of nuclear factor kappa B, heat shock protein 70 and matrix metalloproteinase-9. Interestingly, there was a mild, albeit non-significant, tendency of increased levels of 8-hydroxy-2’-deoxyguanosine and malondialdehyde in the HRW group. This mild increase may be indicative of the hormetic effects of molecular hydrogen that occurred prior to the significant clinical improvements reported in previous longer-term studies. The favorable trends in this study in conjunction with previous animal and clinical findings suggest that HRW may serve as an important adjuvant therapy for promoting and maintaining optimal health and wellness. Longer term studies focused on prevention, maintenance, or treatment of NAFLD and early stages of NASH are warranted.

Adropin Improves Radiation-Induced Myocardial Injury via VEGFR2/PI3K/Akt Pathway

Mediastinal cancer radiotherapy exposes the heart and causes myocardial injury. It is of utmost importance to identify effective prevention and treatment targets. In this study, the regulatory role of adropin (Ad) in radiation-induced myocardial injury (RIMI) was explored in mice. After C57BL/6 mice were administered E0771 cells and received radiotherapy, the effects of exogenous Ad intervention on myocardial fibrosis, apoptosis, microvessel density, oxidative stress, and protein expression levels were observed. The results showed that exogenous Ad effectively improved cardiac function, suppressed oxidative stress, inhibited myocardial fibrosis, reduced myocardial apoptosis, and promoted microangiogenesis in RIMI mice. Ad also downregulated the expression levels of transforming growth factor β1 (TGF-β1), NADPH oxidase 4 (NOX4), and cleaved caspase 3 and upregulated the expression of phosphor-endothelial nitric oxide synthase (p-eNOS). However, the above-mentioned effects of Ad were significantly reversed in Ad^−/− mice. Radiotherapy resulted in the downregulation of phosphor-vascular endothelial growth factor receptor (p-VEGFR2) and p-Akt in myocardial tissue, which were upregulated by Ad. However, after targeted inhibition of VEGFR2 with apatinib, the effect of Ad on improving RIMI was significantly reversed. Taken together, exogenous Ad significantly ameliorated RIMI by reducing oxidative stress, promoting microangiogenesis, and inhibiting myocardial fibrosis and apoptosis. The underlying molecular mechanism involved may be elucidated by activation of the VEGFR2/PI3K/Akt pathway.

Histone deacetylase HDAC4 participates in the pathological process of myocardial ischemia-reperfusion injury via MEKK1/JNK pathway by binding to miR-206

Histone deacetylases (HDACs) and microRNAs (miRs) have been reported to exert pivotal roles on the pathogenesis of myocardial ischemia-reperfusion injury (MIRI). Therefore, the present study was performed to define the underlying role of HDAC4 and miR-206 in the pathological process of MIRI. An IRI rat model was established. The interaction between HDAC4 and the promoter region of miR-206 was determined using ChIP, and that between miR-206 and mitogen-activated protein kinase kinase kinase 1 (MEKK1) was determined using dual luciferase reporter gene assay. After the loss- or gain-of-function assay in cardiomyocytes, western blot analysis, RT-qPCR, TUNEL, and ELISA assay were performed to define the roles of HDAC4, miR-206, and MEKK1. Up-regulation of HDAC4 and down-regulation of miR-206 occurred in rat myocardial tissues and cardiomyocytes in MIRI. HDAC4 down-regulation or miR-206 up-regulation contributed to reduced cell apoptosis and the levels of tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and malondialdehyde (MDA), while elevating the superoxide dismutase (SOD) and glutathione (GSH) contents. Meanwhile, HDAC4 silencing promoted the expression of miR-206, which targeted and negatively regulated MEKK1. Then inhibition of JNK phosphorylation reduced the cardiomyocyte apoptosis to alleviate MIRI. Coherently, HDAC4 silencing could up-regulate the expression of miR-206 to reduce cardiomyocyte apoptosis and inhibit oxidative stress, and exerting a protective effect on MIRI via the MEKK1/JNK pathway.

The cardiac toxicity of radiotherapy - a review of characteristics, mechanisms, diagnosis, and prevention

PURPOSE

Radiation-induced heart disease (RIHD) is one of the most serious complications of radiotherapy. The purpose of this paper is to review recent researches about cardiac toxicity of radiotherapy in clinical characteristics, mechanisms, diagnosis, and prevention.

CONCLUSIONS

Powered by the rapid development of medicine, the overall survival (OS) of cancer has been improved significantly. Surgery, chemotherapy, and radiotherapy (RT) are three critical ways in the comprehensive treatments of cancer. There is a consensus that early diagnosis and interventions for the prevention of RIHD are crucial. This review concludes recent clinical and experimental studies on RIHD. RIHD, a heterogeneous and serious disease, is a spectrum of heart disease including myocardial disease, pericarditis, coronary artery disease, valvular heart disease, and conduction system dysfunction. Mean heart dose, biomarkers, and detecting techniques are important components in detecting heart injury. Improvements in radiotherapy regimens remain the primary goal of prevention. Further investigation is needed beyond the observation period of most of these studies.

Molecular Hydrogen as a Potential Clinically Applicable Radioprotective Agent

Although ionizing radiation (radiation) is commonly used for medical diagnosis and cancer treatment, radiation-induced damages cannot be avoided. Such damages can be classified into direct and indirect damages, caused by the direct absorption of radiation energy into DNA and by free radicals, such as hydroxyl radicals (•OH), generated in the process of water radiolysis. More specifically, radiation damage concerns not only direct damages to DNA, but also secondary damages to non-DNA targets, because low-dose radiation damage is mainly caused by these indirect effects. Molecular hydrogen (H₂) has the potential to be a radioprotective agent because it can selectively scavenge •OH, a reactive oxygen species with strong oxidizing power. Animal experiments and clinical trials have reported that H₂ exhibits a highly safe radioprotective effect. This paper reviews previously reported radioprotective effects of H₂ and discusses the mechanisms of H₂, not only as an antioxidant, but also in intracellular responses including anti-inflammation, anti-apoptosis, and the regulation of gene expression. In doing so, we demonstrate the prospects of H₂ as a novel and clinically applicable radioprotective agent.

Protective Effects of Hydrogen against Irradiation

Radiation-induced lung injury is characterized by an acute pneumonia phase followed by a fibrotic phase. At the time of irradiation, a rapid, short-lived burst of reactive oxygen species (ROS) such as hydroxyl radicals (•OH) occurs, but chronic radiation-induced lung injury may occur due to excess ROS such as H₂O₂, O2•-, ONOO-, and •OH. Molecular hydrogen (H₂) is an efficient antioxidant that quickly diffuses cell membranes, reduces ROS such as •OH and ONOO-, and suppresses damage caused by oxidative stress in various organs. In 2011, through the evaluation of electron-spin resonance and fluorescent indicator signals, we had reported that H₂ can eliminate •OH and can protect against oxidative stress-related apoptotic damage induced by irradiation of cultured lung epithelial cells. We had explored for the first time the radioprotective effects of H₂ treatment on acute and chronic radiation-induced lung damage in mice by inhaled H2 gas (for acute) and imbibed H₂-enriched water (for chronic). Thus, we had proposed that H₂ be considered a potential radioprotective agent. Recent publications have shown that H₂ directly neutralizes highly reactive oxidants and indirectly reduces oxidative stress by regulating the expression of various genes. By regulating gene expression, H₂ functions as an anti-inflammatory and anti-apoptotic molecule and promotes energy metabolism. The increased evidence obtained from cultured cells or animal experiments reveal a putative place for H₂ treatment and its radioprotective effect clinically. This review focuses on major scientific advances in the treatment of H₂ as a new class of radioprotective agents.

Oxidative Stress and Pathways of Molecular Hydrogen Effects in Medicine

There are many situations of excessive production of reactive oxygen species (ROS) such as radiation, ischemia/reperfusion (I/R), and inflammation. ROS contribute to and arises from numerous cellular pathologies, diseases, and aging. ROS can cause direct deleterious effects by damaging proteins, lipids, and nucleic acids as well as exert detrimental effects on several cell signaling pathways. However, ROS are important in many cellular functions. The injurious effect of excessive ROS can hypothetically be mitigated by exogenous antioxidants, but clinically this intervention is often not favorable. In contrast, molecular hydrogen provides a variety of advantages for mitigating oxidative stress due to its unique physical and chemical properties. H₂ may be superior to conventional antioxidants, since it can selectively reduce ●OH radicals while preserving important ROS that are otherwise used for normal cellular signaling. Additionally, H₂ exerts many biological effects, including antioxidation, anti-inflammation, anti-apoptosis, and anti-shock. H₂ accomplishes these effects by indirectly regulating signal transduction and gene expression, each of which involves multiple signaling pathways and crosstalk. The Keap1-Nrf2-ARE signaling pathway, which can be activated by H₂, plays a critical role in regulating cellular redox balance, metabolism, and inducing adaptive responses against cellular stress. H₂ also influences the crosstalk among the regulatory mechanisms of autophagy and apoptosis, which involve MAPKs, p53, Nrf2, NF-κB, p38 MAPK, mTOR, etc. The pleiotropic effects of molecular hydrogen on various proteins, molecules and signaling pathways can at least partly explain its almost universal pluripotent therapeutic potential.

The effect of selected drugs on the mitigation of myocardial injury caused by gamma radiation

Radiation damage of healthy tissues represents one of the complications of radiotherapy effectiveness. This study is focused on the screening of potentially effective drugs routinely used in medical practice and involved in the mechanism of radiation injury, namely for radiation-induced production of free radicals in the body. Experiments in rats revealed significant reduction of oxidative stress (malondialdehyde) and inflammatory marker (tumor necrosis factor α) in 10 Gy irradiated groups after administration of atorvastatin and a slight decrease after tadalafil administration, which indicates that one of the possible mechanisms for mitigation of radiation-induced cardiac damage could be the modulation of nitric oxide (NO) in endothelium and phosphodiesterase 5. In addition, miRNAs were analyzed as potential markers and therapeutically effective molecules. Expression of miRNA-21 and miRNA-15b showed the most significant changes after irradiation. Atorvastatin and tadalafil normalized changes of miRNA (miRNA-1, miRNA-15b, miRNA-21) expression levels in irradiated hearts. This screening study concludes that administration of specific drugs could mitigate the negative impact of radiation on the heart, but more detailed experiments oriented to other aspects of drug effectiveness and their exact mechanisms are still needed.

Hydrogen-rich water attenuates the radiotoxicity induced by tritium exposure in vitro and in vivo

Radionuclide tritium is widely used in the nuclear energy production industry and creates a threat to human health through radiation exposure. Herein, the radioactive elimination and radioprotective effect of hydrogen-rich water (HRW), a potential antioxidant with various medical applications, on tritiated water (HTO) exposure, was studied in vitro and in vivo. Results showed that intragastric administration of HRW effectively promoted the elimination of urinary tritium, decreased the level of serum tritium and tissue-bound tritium (OBT), and attenuated the genetic damage of blood cells in mice exposed to HTO (18.5 MBq/kg). Pretreatment with HRW effectively reduces tritium accumulation in HTO-treated human blood B lymphocyte AHH-1 cells. In addition, the anti-oxidative properties of HRW could attenuate the increased intracellular ROS (such as O2•-, •OH and ONOO-), resulting in reversing the exhaustion of cellular endogenous antioxidants (reduced GSH and SOD), decreasing lipid peroxidation (MDA), relieving DNA oxidative damage, and depressing cell apoptosis and cytotoxicity induced by HTO exposure. In conclusion, HRW is expected to be an effective radioactive elimination agent through the competition effect of isotope exchange or a radioprotective agent by scavenging free radicals induced by HTO exposure.

Exosomal MiR-769-5p Exacerbates Ultraviolet-Induced Bystander Effect by Targeting TGFBR1

Exosomal microRNAs have been investigated in bystander effect, but it is unclear whether microRNA works in ultraviolet radiation-induced bystander effects (UV-RIBEs) and what the underlying mechanism could be. Exosomes from ultraviolet (UV)-irradiated human skin fibroblasts (HSFs) were isolated and transferred to normal HSFs, followed by the detection of proliferation rate, oxidative damage level, and apoptosis rate. Exosomal miRNAs were evaluated and screened with miRNA sequencing and quantitative reverse transcriptase-polymerase chain reaction method. MiRNA shuttle and bystander photodamage reactions were observed after transfection of miR-769-5p. MiR-769-5p targeting gene transforming growth factor-β1 (TGFBR1), and TGFBR1 mRNA 3'-untranslated region (UTR) was assessed and identified by Western blotting and dual-luciferase reporter assay. Bystander effects were induced after being treated with isolated exosomes from UV-irradiated HSFs. Exosomal miR-769-5p expression was significantly upregulated. Human skin fibroblasts showed lower proliferation, increasing oxidative damage, and faster occurrence of apoptosis after transfection. Exosome-mediated transfer of miR-769-5p was observed. Upregulation of miR-769-5p induced bystander effects, whereas downregulation of miR-769-5p can suppress UV-RIBEs. In addition, miR-769-5p was found to downregulate TGFBR1 gene expression by directly targeting its 3'-UTR. Our results demonstrate that exosome-mediated miR-769-5p transfer could function as an intercellular messenger and exacerbate UV-RIBEs. MiR-769-5p inhibits the expression of TGFBR1 by targeting TGFBR1 mRNA 3'-UTR.

MicroRNA-548ac induces apoptosis in laryngeal squamous cell carcinoma cells by targeting transmembrane protein 158

Laryngeal cancer is a common head and neck cancer that effects the quality of life of those affected. Early diagnosis and treatment are vital to minimize the harmful effects of laryngeal cancer, which can improve the survival rate of patients following surgery and retain the voice function of the larynx. The purpose of the present study was to explore the molecular mechanism of the development of laryngeal cancer and to determine the biomarker for the diagnosis and treatment of laryngeal cancer. Reverse transcription-quantitative PCR (RT-qPCR) and The Cancer Genome Atlas database analysis were used to confirm high expression of TMEM158 in laryngeal cancer. The effects of TMEM158 and miR-548ac was investigated through in vitro and in vivo assays (MTT assay, colony-formation assay, flow cytometry assay, western blotting and tumor xenograft assay). Luciferase reporter assay, western blotting and RTq-PCR were used to confirm that miR-548 directly targeted the 3'-untranslated region of TMEM158 and inhibited TMEM158 expression. Taken together, the present results suggest that miR-548ac functions as a crucial cancer suppressor in laryngeal cancer, which induces apoptosis in laryngeal cancer cells by suppressing TMEM158. Thus, miR-548ac may be a potential target for the treatment of laryngeal cancer.

Targets for protection and mitigation of radiation injury

Protection of normal tissues against toxic effects of ionizing radiation is a critical issue in clinical and environmental radiobiology. Investigations in recent decades have suggested potential targets that are involved in the protection against radiation-induced damages to normal tissues and can be proposed for mitigation of radiation injury. Emerging evidences have been shown to be in contrast to an old dogma in radiation biology; a major amount of reactive oxygen species (ROS) production and cell toxicity occur during some hours to years after exposure to ionizing radiation. This can be attributed to upregulation of inflammatory and fibrosis mediators, epigenetic changes and disruption of the normal metabolism of oxygen. In the current review, we explain the cellular and molecular changes following exposure of normal tissues to ionizing radiation. Furthermore, we review potential targets that can be proposed for protection and mitigation of radiation toxicity.

Morphological and molecular analysis of apoptosis in the corpus cavernosum of rats submitted to a chronic alcoholism model

Purpose

To evaluate the effect of chronic alcoholism on morphometry and apoptosis mechanism and correlate with miRNA-21 expression in the corpus cavernosum of rats.

Methods

Twenty-four rats were divided into two experimental groups: Control (C) and Alcoholic group (A). After two weeks of an adaptive phase, rats from group A received only ethanol solution (20%) during 7 weeks. The morphometric and caspase-3 immunohistochemistry analysis were performed in the corpus cavernosum. The miRNA-21 expression was analyzed in blood and cavernous tissue.

Results

Chronic ethanol consumption decreased cavernosal smooth muscle area of alcoholic rats. The protein expression of caspase 3 in the corpus cavernosum was higher in A compared to the C group. There was no difference in the expression of miRNA-21 in serum and cavernous tissue between the groups.

Conclusion

Chronic ethanol consumption reduced smooth muscle area and increased caspase 3 in the corpus cavernosum of rats, without altered serum and cavernosal miR-21 gene expression.

Citrate pretreatment attenuates hypoxia/reoxygenation-induced cardiomyocyte injury via regulating microRNA-142-3p/Rac1 aix

Purpose: Citrate has a positive effect on improving the pathophysiological changes of cardiomyocytes such as cardiac failure and auricular fibrillation. However, the underlying mechanism remains still unclear.Methods: Rat cardiomyocytes were used to establish hypoxia/reoxygenation (H/R) cell model. Citrate was conduct to pretreat with cardiomyocytes, and microRNA-142-3p (miR-142-3p) knockdown and overexpression were used to determine the underlying mechanism of their functions in cardiomyocytes. Cell viability and apoptosis were respectively detected by CCK-8 and flow cytometry. Protein and mRNA levels were determined by Western blot and qRT-PCR. Luciferase reporter assay and Targetscan were performed to study the regulation of miR-142-3p and Rac1.Results: The level of miR-142-3p was down-regulated in H/R model, but up-regulated in cardiomyocytes following citrate treatment. Citrates attenuated H/R injury induced miR-142-3p level and cell viability, and also inhibited H/R injury induced apoptosis, LDH, MDA and autophagy. Cell viability was improved, and autophagy was suppressed by miR-142-3p mimic, while inhibitor had opposite results. Compared with H/R + miR-142-3p inhibitor group, cell viability was higher, and apoptosis and autophagy were lower in Cit + H/R + miR-142-3p inhibitor group. Furthermore, Rac1 was target gene of miR-142-3p, and decreased by citrate, in comparison with H/R + miR-142-3p inhibitor group.Conclusion: Taken together, our findings indicated that citrate ameliorates H/R injury-induced cardiomyocytes autophagy by regulating miR-142-3p/Rac1 aix.

Hydrogen attenuates radiation-induced intestinal damage by reducing oxidative stress and inflammatory response

The small intestine is known to be particularly sensitive to radiation, and the major limiting factor of radiotherapy is the gastrointestinal syndrome that subsequently develops after its administration. The detrimental effects of radiation are mostly mediated via the overproduction of reactive oxygen species (ROS), especially the hydroxyl radical (·OH). Because hydrogen is a selective ·OH scavenger, we hypothesized that hydrogen might exert a protective effect against radiation-induced intestinal damage. Herein, radiation models were built both in mice and in an intestinal crypt epithelial cell (IEC-6) line. In the animal experiment, we demonstrated that hydrogen-rich saline significantly reduced radiation-induced intestinal mucosal damage, improved intestinal function, and increased the survival rate. In addition, radiation-induced oxidative stress damage and systemic inflammatory response were also mitigated by hydrogen treatment. Moreover, hydrogen treatment decreased cell apoptosis and maintained intestinal epithelial cell proliferation in mice. In vitro experiments using the IEC-6 cell line showed that hydrogen-rich medium significantly inhibited ROS formation, maintained cell viability, and inhibited cell apoptosis. Importantly, hydrogen treatment prevented mitochondrial depolarization, cytochrome c release, and activity of caspase-3, caspase-9, and PARP. Moreover, the decreased expression of Bcl-xl and Bcl-2 and the increased expression of Bax protein were also blocked by hydrogen treatment. In conclusion, our study concurrently demonstrated that hydrogen provides an obviously protective effect on radiation-induced intestinal and cell injuries. Our work demonstrated that this protective effect might be due to the blockage of the mitochondrial apoptotic pathway.

Molecular hydrogen attenuates methamphetamine-induced behavioral sensitization and activation of ERK-ΔFosB signaling in the mouse nucleus accumbens

Methamphetamine (METH) is one of the most prevalently used illegal psychostimulants in many countries. Continuous exposure to METH leads to behavioral sensitization in animals, which can be used as a behavioral model with many mechanisms in common with relapse in humans. Molecular hydrogen has recently gained attention for its potential as a novel healthcare product with preventive and therapeutic applicability to a wide range of pathological conditions. However, it remains unclear whether and, if so, how hydrogen regulates METH-induced behavioral abnormalities. In the present study, we investigated the roles of molecular hydrogen on the acquisition and transfer of METH-induced behavioral sensitization and the accompanying changes in ERK phosphorylation and ΔFosB activation in the nucleus accumbens (NAc) of mice. To this end, male C57BL/6 mice received METH (0.1, 0.5 and 1.0 mg/kg, i.p.) injections for 7 days followed by a METH challenge (0.1, 0.5 and 1.0 mg/kg, i.p.) after a 7-day transfer period. Molecular hydrogen, delivered through a hydrogen-rich saline (HRS) injection (10 mL/kg, i.p., 3-h interval), was administered during the acquisition and transfer periods. We found that HRS administration was able to inhibit the acquisition and transfer of 0.1 and 0.5 mg/kg METH-induced behavioral sensitization to a certain extent, thereby attenuating the expression of behavioral sensitization. The HRS injections alone did not induce any obvious changes in locomotor activity in mice. Intriguingly, the increases in pERK and ΔFosB in the NAc, which accompanied the METH-induced behavioral sensitization, were also attenuated by the HRS treatments. Due to the anti-oxidative function of molecular hydrogen, the HRS injections reduced METH-induced reactive oxygen species and malondialdehyde generation in the NAc. These results suggest that molecular hydrogen serves as an anti-oxidative agent with potentially therapeutic applicability to the treatment of METH addicts.

Emerging Challenges of Radiation-Associated Cardiovascular Dysfunction (RACVD) in Modern Radiation Oncology: Clinical Practice, Bench Investigation, and Multidisciplinary Care

Radiotherapy (RT) is a crucial treatment modality in managing cancer patients. However, irradiation dose sprinkling to tumor-adjacent normal tissues is unavoidable, generating treatment toxicities, such as radiation-associated cardiovascular dysfunction (RACVD), particularly for those patients with combined therapies or pre-existing adverse features/comorbidities. Radiation oncologists implement several efforts to decrease heart dose for reducing the risk of RACVD. Even applying the deep-inspiration breath-hold (DIBH) technique, the risk of RACVD is though reduced but still substantial. Besides, available clinical methods are limited for early detecting and managing RACVD. The present study reviewed emerging challenges of RACVD in modern radiation oncology, in terms of clinical practice, bench investigation, and multidisciplinary care. Several molecules are potential for serving as biomarkers and therapeutic targets. Of these, miRNAs, endogenous small non-coding RNAs that function in regulating gene expression, are of particular interest because low-dose irradiation, i.e., 200 mGy (one-tenth of conventional RT daily dose) induces early changes of pro-RACVD miRNA expression. Moreover, several miRNAs, e.g., miR-15b and miR21, involve in the development of RACVD, further demonstrating the potential bio-application in RACVD. Remarkably, many RACVDs are late RT sequelae, characterizing highly irreversible and progressively worse. Thus, multidisciplinary care from oncologists and cardiologists is crucial. Combined managements with commodities control (such as hypertension, hypercholesterolemia, and diabetes), smoking cessation, and close monitoring are recommended. Some agents show abilities for preventing and managing RACVD, such as statins and angiotensin-converting enzyme inhibitors (ACEIs); however, their real roles should be confirmed by further prospective trials.

Potential Clinical Implications of miR-1 and miR-21 in Heart Disease and Cardioprotection

The interest in non-coding RNAs, which started more than a decade ago, has still not weakened. A wealth of experimental and clinical studies has suggested the potential of non-coding RNAs, especially the short-sized microRNAs (miRs), to be used as the new generation of therapeutic targets and biomarkers of cardiovascular disease, an ever-growing public health issue in the modern world. Among the hundreds of miRs characterized so far, microRNA-1 (miR-1) and microRNA-21 (miR-21) have received some attention and have been associated with cardiac injury and cardioprotection. In this review article, we summarize the current knowledge of the function of these two miRs in the heart, their association with cardiac injury, and their potential cardioprotective roles and biomarker value. While this field has already been extensively studied, much remains to be done before research findings can be translated into clinical application for patient’s benefit.

New therapeutic insights into radiation-induced myocardial fibrosis

Radiation therapy (RT) for the treatment of thoracic tumors causes radiation-induced heart disease (RIHD). Radiation-induced myocardial fibrosis (RIMF) is both an acute and chronic stage of RIHD, depending on the specific pathology, and is thought to be a major risk factor for adverse myocardial remodeling and vascular changes. With the use of more three-dimensional conformal radiation regimens and early screenings and diagnoses for RIMF, the incidence of RIHD is declining, but it still must be carefully investigated to minimize the mortality and morbidity of patients with thoracic malignancies after RT treatment. Effective methods for preventing RIMF involve a decrease in the direct radiation dose in the heart, and early screening and diagnosis. Medications remain as a useful adjunct for preventing or treating RIMF. This review mainly discusses the cellular and molecular mechanisms underlying RIMF, and new therapeutic drugs that can potentially be developed from this knowledge.

A New Approach for the Prevention and Treatment of Cardiovascular Disorders. Molecular Hydrogen Significantly Reduces the Effects of Oxidative Stress

Cardiovascular diseases are the most common causes of morbidity and mortality worldwide. Redox dysregulation and a dyshomeostasis of inflammation arise from, and result in, cellular aberrations and pathological conditions, which lead to cardiovascular diseases. Despite years of intensive research, there is still no safe and effective method for their prevention and treatment. Recently, molecular hydrogen has been investigated in preclinical and clinical studies on various diseases associated with oxidative and inflammatory stress such as radiation-induced heart disease, ischemia-reperfusion injury, myocardial and brain infarction, storage of the heart, heart transplantation, etc. Hydrogen is primarily administered via inhalation, drinking hydrogen-rich water, or injection of hydrogen-rich saline. It favorably modulates signal transduction and gene expression resulting in suppression of proinflammatory cytokines, excess ROS production, and in the activation of the Nrf2 antioxidant transcription factor. Although H₂ appears to be an important biological molecule with anti-oxidant, anti-inflammatory, and anti-apoptotic effects, the exact mechanisms of action remain elusive. There is no reported clinical toxicity; however, some data suggests that H₂ has a mild hormetic-like effect, which likely mediate some of its benefits. The mechanistic data, coupled with the pre-clinical and clinical studies, suggest that H₂ may be useful for ROS/inflammation-induced cardiotoxicity and other conditions.

Hydrogen gas: from clinical medicine to an emerging ergogenic molecule for sports athletes 1

H₂ has been clinically demonstrated to provide antioxidant and anti-inflammatory effects, which makes it an attractive agent in exercise medicine. Although exercise provides a multiplicity of benefits including decreased risk of disease, it can also have detrimental effects. For example, chronic high-intensity exercise in elite athletes, or sporadic bouts of exercise (i.e., noxious exercise) in untrained individuals, result in similar pathological factors such as inflammation, oxidation, and cellular damage that arise from and result in disease. Paradoxically, exercise-induced pro-inflammatory cytokines and reactive oxygen species largely mediate the benefits of exercise. Ingestion of conventional antioxidants and anti-inflammatories often impairs exercise-induced training adaptations. Disease and noxious forms of exercise promote redox dysregulation and chronic inflammation, changes that are mitigated by H₂ administration. Beneficial exercise and H₂ administration promote cytoprotective hormesis, mitochondrial biogenesis, ATP production, increased NAD⁺/NADH ratio, cytoprotective phase II enzymes, heat-shock proteins, sirtuins, etc. We review the biomedical effects of exercise and those of H₂, and we propose that hydrogen may act as an exercise mimetic and redox adaptogen, potentiate the benefits from beneficial exercise, and reduce the harm from noxious exercise. However, more research is warranted to elucidate the potential ergogenic and therapeutic effects of H₂ in exercise medicine.