PPARα Is Necessary for Radiation-Induced Activation of Noncanonical TGFβ Signaling in the Heart

Changes in the Proteome of the Circle of Willis during Aging Reveal Signatures of Vascular Disease

Approximately 70% of all strokes occur in patients over 65 years old, and stroke increases the risk of developing dementia. The circle of Willis (CoW), the ring of arteries at the base of the brain, links the intracerebral arteries to one another to maintain adequate cerebral perfusion. The CoW proteome is affected in cerebrovascular and neurodegenerative diseases, but changes related to aging have not been described. Here, we report on a quantitative proteomics analysis comparing the CoW from five young (2-3-month-old) and five aged male (18-20-month-old) mice using gene ontology (GO) enrichment, ingenuity pathway analysis (IPA), and iPathwayGuide tools. This revealed 242 proteins that were significantly dysregulated with aging, among which 189 were upregulated and 53 downregulated. GO enrichment-based analysis identified blood coagulation as the top biological function that changed with age and integrin binding and extracellular matrix constituents as the top molecular functions. Consistent with these findings, iPathwayGuide-based impact analysis revealed associations between aging and the complement and coagulation, platelet activation, ECM-receptor interaction, and metabolic process pathways. Furthermore, IPA analysis revealed the enrichment of 97 canonical pathways that contribute to inflammatory responses, as well as 59 inflammation-associated upstream regulators including 39 transcription factors and 20 cytokines. Thus, aging-associated changes in the CoW proteome in male mice demonstrate increases in metabolic, thrombotic, and inflammatory processes.

Epigenetic regulation of TGF-β pathway and its role in radiation response

PURPOSE

Transforming growth factor (TGF-β) plays a dual role in tumor progression as well as a pivotal role in radiation response. TGF-β-related epigenetic regulations, including DNA methylation, histone modifications (including methylation, acetylation, phosphorylation, ubiquitination), chromatin remodeling and non-coding RNA regulation, have been found to affect the occurrence and development of tumors as well as their radiation response in multiple dimensions. Due to the significance of radiotherapy in tumor treatment and the essential roles of TGF-β signaling in radiation response, it is important to better understand the role of epigenetic regulation mechanisms mediated by TGF-β signaling pathways in radiation-induced targeted and non-targeted effects.

CONCLUSIONS

By revealing the epigenetic mechanism related to TGF-β-mediated radiation response, summarizing the existing relevant adjuvant strategies for radiotherapy based on TGF-β signaling, and discovering potential therapeutic targets, we hope to provide a new perspective for improving clinical treatment.

Oncostatin M/Oncostatin M Receptor Signal Induces Radiation-Induced Heart Fibrosis by Regulating SMAD4 in Fibroblast

PURPOSE

Radiation-induced heart fibrosis (RIHF) is a severe consequence of radiation-induced heart damage (RIHD) leading to impaired cardiac function. The involvement of oncostatin M (OSM) and its receptor (OSMR) in RIHD remains unclear. This study aimed to investigate the specific mechanism of OSM/OSMR in RIHF/RIHD.

METHODS AND MATERIALS

RNA sequencing was performed on heart tissues from a RIHD mouse model. OSM levels were assessed in serum samples obtained from patients receiving thoracic radiation therapy (RT), as well as in RIHF mouse heart tissues and serum using enzyme-linked immunosorbent assay. Fiber activation was evaluated through costimulation of primary cardiac fibroblasts and NIH3T3 cells with RT and OSM, using Western blotting, immunofluorescence, and quantitative Polymerase Chain Reaction (qPCR). Adeno-associated virus serotype 9-mediated overexpression or silencing of OSM specifically in the heart was performed in vivo to assess cardiac fibrosis levels by transthoracic echocardiography and pathologic examination. The regulatory mechanism of OSM on the transcription level of SMAD4 was further explored in vitro using mass spectrometric analysis, chromatin immunoprecipitation-qPCR, and DNA pull-down.

RESULTS

OSM levels were elevated in the serum of patients after thoracic RT as well as in RIHF mouse cardiac endothelial cells and mouse serum. The OSM rate (post-RT/pre-RT) and the heart exposure dose in RT patients showed a positive correlation. Silencing OSMR in RIHF mice reduced fibrosis, while OSMR overexpression increased fibrotic responses. Furthermore, increased OSM promoted histone acetylation (H3K27ac) in the SMAD4 promoter region, influencing SMAD4 transcription and subsequently enhancing fibrotic response.

CONCLUSIONS

The findings demonstrated that OSM/OSMR signaling promotes SMAD4 transcription in cardiac fibroblasts through H3K27 hyperacetylation, thereby promoting radiation-induced cardiac fibrosis and manifestations of RIHD.

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.

Late Effects of Chronic Low Dose Rate Total Body Irradiation on the Heart Proteome of ApoE-/- Mice Resemble Premature Cardiac Ageing

Recent epidemiologic studies support an association between chronic low-dose radiation exposure and the development of cardiovascular disease (CVD). The molecular mechanisms underlying the adverse effect of chronic low dose exposure are not fully understood. To address this issue, we have investigated changes in the heart proteome of ApoE deficient (ApoE^-/-) C57Bl/6 female mice chronically irradiated for 300 days at a very low dose rate (1 mGy/day) or at a low dose rate (20 mGy/day), resulting in cumulative whole-body doses of 0.3 Gy or 6.0 Gy, respectively. The heart proteomes were compared to those of age-matched sham-irradiated ApoE^-/- mice using label-free quantitative proteomics. Radiation-induced proteome changes were further validated using immunoblotting, enzyme activity assays, immunohistochemistry or targeted transcriptomics. The analyses showed persistent alterations in the cardiac proteome at both dose rates; however, the effect was more pronounced following higher dose rates. The altered proteins were involved in cardiac energy metabolism, ECM remodelling, oxidative stress, and ageing signalling pathways. The changes in PPARα, SIRT, AMPK, and mTOR signalling pathways were found at both dose rates and in a dose-dependent manner, whereas more changes in glycolysis and ECM remodelling were detected at the lower dose rate. These data provide strong evidence for the possible risk of cardiac injury following chronic low dose irradiation and show that several affected pathways following chronic irradiation overlap with those of ageing-associated heart pathology.

Long term toxicities following developmental exposure to perfluorooctanoic acid: Roles of peroxisome proliferation activated receptor alpha

Perfluorooctanoic acid (PFOA) is a widespread persistent organic pollutant. Fertile chicken eggs were exposed to PFOA and incubated to hatch. At three time points post hatch (0-, 1- and 3-months old), chickens were subjected to electrocardiography and sacrificed. Serum was subjected to LC-MS/MS for PFOA concentration, and organs were subjected to histopathological assessments. Additionally, PPARα-silencing lentivirus was co-applied with PFOA exposure, and the corresponding phenotypes were evaluated. Western blotting was performed to assess expressions of FABPs and pSMAD2 in heart and liver samples. Considerable amount of PFOA were detected in hatchling chicken serum, but not in one-month-old or three-month-old chicken serum. PFOA exposure resulted in developmental cardiotoxicity and hepatotoxicity in hatchling chickens. Meanwhile, one-month-old chickens still exhibited elevated heart rate, but classical cardiac remodeling (thicker right ventricular wall) were observed in exposed animals. Three-month-old chickens exhibited similar results as one-month-old ones. PPARα silencing only had partial protective effects in hatchling chickens, but the protective effects seemed to increase as chickens aged. Western blotting results indicated that L-FABP was involved in PFOA-induced hepatotoxicity, while pSMAD2 was involved in PFOA-induced cardiotoxicity. In summary, developmental exposure to PFOA resulted in persistent cardiotoxicity, but not hepatotoxicity. PPARα participates in both cardiotoxicity and hepatotoxicity.

Application of radiation omics in the development of adverse outcome pathway networks: an example of radiation-induced cardiovascular disease

BACKGROUND

Epidemiological studies have indicated that exposure of the heart to doses of ionizing radiation as low as 0.5 Gy increases the risk of cardiac morbidity and mortality with a latency period of decades. The damaging effects of radiation to myocardial and endothelial structures and functions have been confirmed radiobiologically at high dose, but much less is known at low dose. Integration of radiation biology and epidemiology data is a recommended approach to improve the radiation risk assessment process. The adverse outcome pathway (AOP) framework offers a comprehensive tool to compile and translate mechanistic information into pathological endpoints which may be relevant for risk assessment at the different levels of a biological system. Omics technologies enable the generation of large volumes of biological data at various levels of complexity, from molecular pathways to functional organisms. Given the quality and quantity of available data across levels of biology, omics data can be attractive sources of information for use within the AOP framework. It is anticipated that radiation omics studies could improve our understanding of the molecular mechanisms behind the adverse effects of radiation on the cardiovascular system. In this review, we explored the available omics studies on radiation-induced cardiovascular disease (CVD) and their applicability to the proposed AOP for CVD.

RESULTS

The results of 80 omics studies published on radiation-induced CVD over the past 20 years have been discussed in the context of the AOP of CVD proposed by Chauhan et al. Most of the available omics data on radiation-induced CVD are from proteomics, transcriptomics, and metabolomics, whereas few datasets were available from epigenomics and multi-omics. The omics data presented here show great promise in providing information for several key events of the proposed AOP of CVD, particularly oxidative stress, alterations of energy metabolism, extracellular matrix and vascular remodeling.

CONCLUSIONS

The omics data presented here shows promise to inform the various levels of the proposed AOP of CVD. However, the data highlight the urgent need of designing omics studies to address the knowledge gap concerning different radiation scenarios, time after exposure and experimental models. This review presents the evidence to build a qualitative omics-informed AOP and provides views on the potential benefits and challenges in using omics data to assess risk-related outcomes.

Activation of PPARα by Fenofibrate Attenuates the Effect of Local Heart High Dose Irradiation on the Mouse Cardiac Proteome

Radiation-induced cardiovascular disease is associated with metabolic remodeling in the heart, mainly due to the inactivation of the transcription factor peroxisome proliferator-activated receptor alpha (PPARα), thereby inhibiting lipid metabolic enzymes. The objective of the present study was to investigate the potential protective effect of fenofibrate, a known agonist of PPARα on radiation-induced cardiac toxicity. To this end, we compared, for the first time, the cardiac proteome of fenofibrate- and placebo-treated mice 20 weeks after local heart irradiation (16 Gy) using label-free proteomics. The observations were further validated using immunoblotting, enzyme activity assays, and ELISA. The analysis showed that fenofibrate restored signalling pathways that were negatively affected by irradiation, including lipid metabolism, mitochondrial respiratory chain, redox response, tissue homeostasis, endothelial NO signalling and the inflammatory status. The results presented here indicate that PPARα activation by fenofibrate attenuates the cardiac proteome alterations induced by irradiation. These findings suggest a potential benefit of fenofibrate administration in the prevention of cardiovascular diseases, following radiation exposure.

Expert consultation is vital for adverse outcome pathway development: a case example of cardiovascular effects of ionizing radiation

BACKGROUND

The circulatory system distributes nutrients, signaling molecules, and immune cells to vital organs and soft tissues. Epidemiological, animal, and in vitro cellular mechanistic studies have highlighted that exposure to ionizing radiation (IR) can induce molecular changes in cellular and subcellular milieus leading to long-term health impacts, particularly on the circulatory system. Although the mechanisms for the pathologies are not fully elucidated, endothelial dysfunction is proven to be a critical event via radiation-induced oxidative stress mediators. To delineate connectivities of events specifically to cardiovascular disease (CVD) initiation and progression, the adverse outcome pathway (AOP) approach was used with consultation from field experts. AOPs are a means to organize information around a disease of interest to a regulatory question. An AOP begins with a molecular initiating event and ends in an adverse outcome via sequential linkages of key event relationships that are supported by evidence in the form of the modified Bradford-Hill criteria. Detailed guidelines on building AOPs are provided by the Organisation for Economic Cooperation and Development (OECD) AOP program. Here, we report on the questions and discussions needed to develop an AOP for CVD resulting from IR exposure. A recent workshop jointly organized by the MELODI (Multidisciplinary European Low Dose Initiative) and the ALLIANCE (European Radioecology Alliance) associations brought together experts from the OECD to present the AOP approach and tools with examples from the toxicology field. As part of this workshop, four working groups were formed to discuss the identification of adverse outcomes relevant to radiation exposures and development of potential AOPs, one of which was focused on IR-induced cardiovascular effects. Each working group comprised subject matter experts and radiation researchers interested in the specific disease area and included an AOP coach.

CONCLUSION

The CVD working group identified the critical questions of interest for AOP development, including the exposure scenario that would inform the evidence, the mechanisms of toxicity, the initiating event, intermediate key events/relationships, and the type of data currently available. This commentary describes the four-day discussion of the CVD working group, its outcomes, and demonstrates how collaboration and expert consultation is vital to informing AOP construction.

Data-Independent Acquisition Proteomics Reveals Long-Term Biomarkers in the Serum of C57BL/6J Mice Following Local High-Dose Heart Irradiation

Background and Purpose: Cardiotoxicity is a well-known adverse effect of radiation therapy. Measurable abnormalities in the heart function indicate advanced and often irreversible heart damage. Therefore, early detection of cardiac toxicity is necessary to delay and alleviate the development of the disease. The present study investigated long-term serum proteome alterations following local heart irradiation using a mouse model with the aim to detect biomarkers of radiation-induced cardiac toxicity.

Materials and Methods: Serum samples from C57BL/6J mice were collected 20 weeks after local heart irradiation with 8 or 16 Gy X-ray; the controls were sham-irradiated. The samples were analyzed by quantitative proteomics based on data-independent acquisition mass spectrometry. The proteomics data were further investigated using bioinformatics and ELISA.

Results: The analysis showed radiation-induced changes in the level of several serum proteins involved in the acute phase response, inflammation, and cholesterol metabolism. We found significantly enhanced expression of proinflammatory cytokines (TNF-α, TGF-β, IL-1, and IL-6) in the serum of the irradiated mice. The level of free fatty acids, total cholesterol, low-density lipoprotein (LDL), and oxidized LDL was increased, whereas that of high-density lipoprotein was decreased by irradiation.

Conclusions: This study provides information on systemic effects of heart irradiation. It elucidates a radiation fingerprint in the serum that may be used to elucidate adverse cardiac effects after radiation therapy.

Chronic Occupational Exposure to Ionizing Radiation Induces Alterations in the Structure and Metabolism of the Heart: A Proteomic Analysis of Human Formalin-Fixed Paraffin-Embedded (FFPE) Cardiac Tissue

Epidemiological studies on workers employed at the Mayak plutonium enrichment plant have demonstrated an association between external gamma ray exposure and an elevated risk of ischemic heart disease (IHD). In a previous study using fresh-frozen post mortem samples of the cardiac left ventricle of Mayak workers and non-irradiated controls, we observed radiation-induced alterations in the heart proteome, mainly downregulation of mitochondrial and structural proteins. As the control group available at that time was younger than the irradiated group, we could not exclude age as a confounding factor. To address this issue, we have now expanded our study to investigate additional samples using archival formalin-fixed paraffin-embedded (FFPE) tissue. Importantly, the control group studied here is older than the occupationally exposed (>500 mGy) group. Label-free quantitative proteomics analysis showed that proteins involved in the lipid metabolism, sirtuin signaling, mitochondrial function, cytoskeletal organization, and antioxidant defense were the most affected. A histopathological analysis elucidated large foci of fibrotic tissue, myocardial lipomatosis and lymphocytic infiltrations in the irradiated samples. These data highlight the suitability of FFPE material for proteomics analysis. The study confirms the previous results emphasizing the role of adverse metabolic changes in the radiation-associated IHD. Most importantly, it excludes age at the time of death as a confounding factor.

Critical biomarkers for myocardial damage by fine particulate matter: Focused on PPARα-regulated energy metabolism

Fine particulate matter is one of the leading threats to cardiovascular health worldwide. The exploration of novel and sensitive biomarkers to detect damaging effect of fine particulate matter on cardiac tissues is of great importance in the better understanding of haze-caused myocardial injury. A link between heart failure and PPARα-regulated energy metabolism has been confirmed previously. Herein, the study intends to reveal the critical biomarkers of fine particulate matter induced myocardial damage from the PPARα-regulated energy metabolism. Ambient fine particulate matter induced severe pathological alterations in cultured cells, accompanied by the decrease in ATP content. Additionally, the expressions of CPT1/CPT2 and levels of CS and MDH, crucial members in β-oxidation and the TCA cycle, were significantly decreased. In direct contrast, fine particulate matter increased the biomarkers of glycolysis, as measured by the accumulation of pyruvate and lactate contents, and the enhanced activities of HK and PKM1/2. Importantly, fine particulate matter-exposed cardiomyocytes exhibited the reduced PPARα level, that increased when cardiomyocytes were co-incubation with WY-14643 and fine particulate matter. Simultaneously, the adverse impact of fine particulate matter on critical biomarkers were observed in β-oxidation, TCA cycle and glycolysis, associated with WY-14643 additional complement. Fine particulate matter caused the myocardial energy metabolism transformation through the regulation of PPARα expression and translation, which provided novel and critical biomarkers for haze particles-caused myocardial damage.

NRP1 regulates radiation-induced EMT via TGF-β/Smad signaling in lung adenocarcinoma cells

PURPOSE

Radiation has been shown to promote the epithelial-mesenchymal transition (EMT) in tumor cells, and TGF-β/Smad and PI3K-Akt signaling pathways play an important role in the EMT. In this study, we investigated the effects of neuropilin-1 (NRP1) on radiation-induced TGF-β/Smad and non-classical Smad signaling pathways in lung cancer cells, as well as the effects of NRP1 on invasion and migration.

MATERIALS AND METHODS

Changes in the expression levels of EMT markers (β-catenin, N-cadherin, and vimentin) and related transcription factors (Twist and ZEB1) in stably transfected cells were detected by Western blotting and qPCR, and changes were assessed by TGF-β/Smad and non-classical Smad signaling. Immunofluorescence was used to detect the expression of the cytoskeletal protein F-actin. Expression of TGF-β1 and CXCL-12 was detected by ELISA. Transwell and scratch assays were used to detect the invasive ability and migration of lung cancer cells, respectively.

RESULTS

Our results showed that ionizing radiation could induce the EMT as well as morphological changes in lung adenocarcinoma cells (A549); however, the effects were not significant in lung squamous carcinoma cells (SK-MES-1). Moreover, we showed that NRP1 promotes the EMT induced by ionizing radiation in A549 cells, which may be related to the increased expression of EMT-related transcription factors. NRP1 may promote the radiation-induced EMT of A549 cells mainly through TGF-β1/Smad2/3 signaling. NRP1 also enhanced radiation-induced invasion, migration, and CXCL-12 expression in A549 cells.

CONCLUSIONS

We conclude that NRP1 promotes radiation-induced EMT in lung adenocarcinoma cells via TGF-β1/Smad signaling and not non-classical Smad signaling, and enhances the invasion and migration of lung adenocarcinoma cells.

Radiotherapy-induced heart disease: a review of the literature

Radiotherapy as one of the four pillars of cancer therapy plays a critical role in the multimodal treatment of thoracic cancers. Due to significant improvements in overall cancer survival, radiotherapy-induced heart disease (RIHD) has become an increasingly recognized adverse reaction which contributes to major radiation-associated toxicities including non-malignant death. This is especially relevant for patients suffering from diseases with excellent prognosis such as breast cancer or Hodgkin’s lymphoma, since RIHD may occur decades after radiotherapy. Preclinical studies have enriched our knowledge of many potential mechanisms by which thoracic radiotherapy induces heart injury. Epidemiological findings in humans reveal that irradiation might increase the risk of cardiac disease at even lower doses than previously assumed. Recent preclinical studies have identified non-invasive methods for evaluation of RIHD. Furthermore, potential options preventing or at least attenuating RIHD have been developed. Ongoing research may enrich our limited knowledge about biological mechanisms of RIHD, identify non-invasive early detection biomarkers and investigate potential treatment options that might attenuate or prevent these unwanted side effects. Here, we present a comprehensive review about the published literature regarding clinical manifestation and pathological alterations in RIHD. Biological mechanisms and treatment options are outlined, and challenges in RIHD treatment are summarized.

Co‑culturing with hypoxia pre‑conditioned mesenchymal stem cells as a new strategy for the prevention of irradiation‑induced fibroblast‑to‑myofibroblast transition

Cardiac fibrosis is a pathological consequence of radiation-induced fibroblast proliferation and fibroblast-to-myofibroblast transition (FMT). Mesenchymal stem cell (MSC) transplantation has been revealed to be an effective treatment strategy to inhibit cardiac fibrosis. We identified a novel MSC-driven mechanism that inhibited cardiac fibrosis, via the regulation of multiple fibrogenic pathways. Hypoxia pre-conditioned MSCs (MSCs^Hypoxia) were co-cultured with fibroblasts using a Transwell system. Radiation-induced fibroblast proliferation was assessed using an MTT assay, and FMT was confirmed by assessing the mRNA levels of various markers of fibrosis, including type I collagen (Col1) and alpha smooth muscle actin (α-SMA). α-SMA expression was also confirmed via immunocytochemistry. The expression levels of Smad7 and Smad3 were detected by western blotting, and Smad7 was silenced using small interfering RNAs. The levels of oxidative stress following radiation were assessed by the detection of reactive oxygen species (ROS) and the activity of superoxide dismutase (SOD), malondialdehyde (MDA), and 4-hydroxynonenal (HNE). It was revealed that co-culturing with MSCs^Hypoxia could inhibit fibroblast proliferation and FMT. In addition, the present results indicated that MSCs are necessary and sufficient for the inhibition of fibroblast proliferation and FMT by functionally targeting TGF-β1/Smad7/Smad3 signaling via the release of hepatocyte growth factor (HGF). Furthermore, it was observed that MSCs inhibited fibrosis by modulating oxidative stress. Co-culturing with MSCs^Hypoxia alleviated fibroblast proliferation and FMT via the TGF-β1/Smad7/Smad3 pathway. MSCs may represent a novel therapeutic approach for the treatment of radiation-related cardiac fibrosis.

Mechanistic approach of the inhibitory effect of chrysin on inflammatory and apoptotic events implicated in radiation-induced premature ovarian failure: Emphasis on TGF-β/MAPKs signaling pathway

Radiotherapy is one of the most relevant treatment modalities for various types of malignancies. However, it causes premature ovarian failure (POF) and subsequent infertility in women of reproductive age; hence urging the development of effective radioprotective agents. Chrysin, a natural flavone, possesses several pharmacological activities owing to its antioxidant, anti-inflammatory and anti-apoptotic properties. Therefore, the aim of this study was to investigate the efficacy of chrysin in limiting γ-radiation-mediated POF and to elucidate the underlying molecular mechanisms. Immature female Sprague-Dawley rats were subjected to a single dose of γ-radiation (3.2 Gy) and/or treated with chrysin (50 mg/kg) once daily for two weeks before and three days post-irradiation. Chrysin prevented the radiation-induced ovarian dysfunction by restoring estradiol levels, preserving the normal ovarian histoarchitecture and combating the follicular loss. Eelectron microscopic analysis showed that the disruption of ultrastructure components due to radiation exposure was hampered by chrysin administration. Mechanistically, chrsyin was able to reduce the levels of the inflammatory markers NF-κB, TNF-α, iNOS and COX-2 in radiation-induced ovarian damage. Chrysin also exhibited potent anti-apoptotic effects against radiation-induced cell death by downregulating the expression of cytochrome c and caspase 3. Radiation obviously induced upregulation of TGF-β protein with subsequent phospholyration and hence activation of downstream mitogen-activated protein kinases (MAPKs); p38 and JNK. Notably, administration of chrysin successfully counteracted these effects. These findings revealed that chrysin may be beneficial in ameliorating radiation-induced POF, predominantly via downregulating TGF-β/MAPK signaling pathways leading subsequently to hindering inflammatory and apoptotic signal transduction pathways implicated in POF.

Proteomic Changes in Mouse Spleen after Radiation-Induced Injury and its Modulation by Gamma-Tocotrienol

Gamma-tocotrienol (GT3), a naturally occurring vitamin E isomer, a promising radioprotector, has been shown to protect mice against radiation-induced hematopoietic and gastrointestinal injuries. We analyzed changes in protein expression profiles of spleen tissue after GT3 treatment in mice exposed to gamma radiation to gain insights into the molecular mechanism of radioprotective efficacy. Male CD2F1 mice, 12-to-14 weeks old, were treated with either vehicle or GT3 at 24 h prior to 7 Gy total-body irradiation. Nonirradiated vehicle, nonirradiated GT3 and age-matched naïve animals were used as controls. Blood and tissues were harvested on days 0, 1, 2, 4, 7, 10 and 14 postirradiation. High-resolution mass-spectrometry-based radioproteomics was used to identify differentially expressed proteins in spleen tissue with or without drug treatment. Subsequent bioinformatic analyses helped delineate molecular markers of biological pathways and networks regulating the cellular radiation responses in spleen. Our results show a robust alteration in spleen proteomic profiles including upregulation of the Wnt signaling pathway and actin-cytoskeleton linked proteins in mediating the radiation injury response in spleen. Furthermore, we show that 24 h pretreatment with GT3 attenuates radiation-induced hematopoietic injury in the spleen by modulating various cell signaling proteins. Taken together, our results show that the radioprotective effects of GT3 are mediated, via alleviation of radiation-induced alterations in biochemical pathways, with wide implications on overall hematopoietic injury.