Pathogenesis Of Radiation-induced Lung Injury Research Articles

METTL3 Mediates Epithelial-Mesenchymal Transition by Modulating FOXO1 mRNA N6 -Methyladenosine-Dependent YTHDF2 Binding: A Novel Mechanism of Radiation-Induced Lung Injury.

The biological roles of epithelial-mesenchymal transition (EMT) in the pathogenesis of radiation-induced lung injury (RILI) have been widely demonstrated, but the mechanisms involved have been incompletely elucidated. N6 -methyladenosine (m6 A) modification, the most abundant reversible methylation modification in eukaryotic mRNAs, plays vital roles in multiple biological processes. Whether and how m6 A modification participates in ionizing radiation (IR)-induced EMT and RILI remain unclear. Here, significantly increased m6 A levels upon IR-induced EMT are detected both in vivo and in vitro. Furthermore, upregulated methyltransferase-like 3 (METTL3) expression and downregulated α-ketoglutarate-dependent dioxygenase AlkB homolog 5 (ALKBH5) expression are detected. In addition, blocking METTL3-mediated m6 A modification suppresses IR-induced EMT both in vivo and in vitro. Mechanistically, forkhead box O1 (FOXO1) is identified as a key target of METTL3 by a methylated RNA immunoprecipitation (MeRIP) assay. FOXO1 expression is downregulated by METTL3-mediated mRNA m6 A modification in a YTH-domain family 2 (YTHDF2)-dependent manner, which subsequently activates the AKT and ERK signaling pathways. Overall, the present study shows that IR-responsive METTL3 is involved in IR-induced EMT, probably by activating the AKT and ERK signaling pathways via YTHDF2-dependent FOXO1 m6 A modification, which may be a novel mechanism involved in the occurrence and development of RILI.

Bibliometric analysis of research relating to radiation-induced lung injury [2001-2020

Radiotherapy is one of the common means of cancer treatment, especially in the treatment of lung cancer. However, radiation therapy can cause lung tissue radiation lung injury. The study of this disease can reduce its incidence and avoid the occurrence of radiation pulmonary fibrosis. In the past 20 years, the study of radiation-induced lung injury (RILI) has attracted more attention. This paper extracts the main text information of RILI-related literature from WOSCC database from 2001 to 2020, uses Citespace and VOSviewer for visual analysis, and presents the results. We found that in the past 20 years, there have been 4,665 articles on RILI, and the number of articles published reached a peak in 2017. The United States is the main leader in this research field, among which UNIV Texas MD Anderson Cancer Center has published many research results in this field. The most active author is Liao Zhongxing, and the most influential journal is Int J Radiat Oncol, which provides a platform for scholars in related fields to publish their articles. Current research focuses mainly on randomized controlled trials related to RILI, the relationship between dose-volume histogram analysis and RILI formation, the protection of normal lung tissue, the effect of stereoscopic radiotherapy on RILI and the pathogenesis of RILI. In the study of the formation mechanism of RILI, the main research directions include the apoptosis mechanism of epithelial and endothelial cells, cytokine cascade theory, immune mechanism regulation process, oxidative stress mechanism, etc.

Research progress on macrophage in radiation induced lung injury

Radiation-induced lung injury (RILI), including acute radiation pneumonitis and chronic radiation-induced pulmonary fibrosis (RIPF), is a side effect of radiotherapy for lung cancer and esophageal cancer. Pulmonary macrophages, as a kind of natural immune cells maintaining lung homeostasis, play a key role in the whole pathological process of RILI. In the early stage of RILI, classically activated M1 macrophages secrete proinflammatory cytokines to induce inflammation and produce massive reactive oxygen species (ROS) through ROS-induced cascade to further impair lung tissue. In the later stage of RILI, alternatively activated M2 macrophages secrete profibrotic cytokines to promote the development of RIPF. The roles of macrophage in the pathogenesis of RILI and the related potential clinical applications are summarized in this review.

Regulatory T Cells: An Emerging Player in Radiation-Induced Lung Injury

Regulatory T cells (Tregs), which have long been recognized as essential regulators of both inflammation and autoimmunity, also impede effective antitumor immune response due to their immunosuppressive properties. Combined radiotherapy and immunotherapeutic interventions focusing on the removal of Tregs have recently garnered interest as a promising strategy to reverse immunosuppression. Meanwhile, Tregs are emerging as a key player in the pathogenesis of radiation-induced lung injury (RILI), a frequent and potentially life-threatening complication of thoracic radiotherapy. Recognition of the critical role of Tregs in RILI raises the important question of whether radiotherapy combined with Treg-targeting immunotherapy offers any beneficial effects in the protection of normal lung tissue. This present review focuses on the contributions of Tregs to RILI, with particular emphasis on the suspected differential role of Tregs in the pneumonitic phase and fibrotic phase of RILI. We also introduce recent progress on the potential mechanisms by which Tregs modulate RILI and the crosstalk among Tregs, other infiltrating T cells, fibrocytes, and resident epithelial cells driving disease pathogenesis. Finally, we discuss whether Tregs also hold promise as a potential target for immunotherapeutic interventions for RILI.

Melatonin Alleviates Radiation-Induced Lung Injury via Regulation of miR-30e/NLRP3 Axis.

Melatonin is a well-known anti-inflammatory and antioxidant molecule, which plays a crucial role in various physiological functions. In this study, mice received a single dose of 15 Gy radiation delivered to the lungs and daily intraperitoneal administration of melatonin. After 7 days, mice were processed to harvest either bronchoalveolar lavage fluid for cytokine assays or lungs for flow cytometry and histopathological studies. Herein, we showed that melatonin markedly alleviated the oxidative stress and injury, especially suppressing the infiltration of macrophages (CD11b+CD11c−) and neutrophils (CD11b+Ly6G+) to the irradiated lungs. Moreover, in the irradiated RAW 264.7 cells, melatonin blocked the NLRP3 inflammasome activation accompanied with the inhibition of the IL-1β release and caspase-1 activity. However, melatonin restored the downregulated miR-30e levels. Quantitative PCR analysis of miR-30e and NLRP3 indicated the negative correlation between them. Notably, immunofluorescence staining showed that overexpression of miR-30e dramatically diminished the increased NLRP3 expression. Luciferase reporter assay confirmed that NLRP3 was a target gene of miR-30e. Western blotting revealed that transfection with miR-30e mimics markedly reduced the expressions of NLRP3 and cleaved caspase-1, whereas this phenomenon was reversed by the miR-30e inhibitor. Consistent with this, the beneficial effect of melatonin under irradiated exposure was blunted in cells transfected with anti-miR-30e. Collectively, our results demonstrate that the NLRP3 inflammasome contributed to the pathogenesis of radiation-induced lung injury. Meanwhile, melatonin exerted its protective effect through negatively regulating the NLRP3 inflammasome in macrophages. The melatonin-mediated miR-30e/NLRP3 signaling may provide novel therapeutic targets for radiation-induced injury.

Pathophysiological mechanisms underlying phenotypic differences in pulmonary radioresponse.

Differences in the pathogenesis of radiation-induced lung injury among murine strains offer a unique opportunity to elucidate the molecular mechanisms driving the divergence in tissue response from repair and recovery to organ failure. Here, we utilized two well-characterized murine models of radiation pneumonitis/fibrosis to compare and contrast differential gene expression in lungs 24 hours after exposure to a single dose of whole thorax lung irradiation sufficient to cause minor to major morbidity/mortality. Expression of 805 genes was altered as a general response to radiation; 42 genes were identified whose expression corresponded to the threshold for lethality. Three genes were discovered whose expression was altered within the lethal, but not the sublethal, dose range. Time-course analysis of the protein product of the most promising gene, resistin-like molecule alpha, demonstrated a significant difference in expression between radiosensitive versus radiotolerant strains, suggesting a unique role for this protein in acute lung injury.

Delayed Administration of WP1066, an STAT3 Inhibitor, Ameliorates Radiation-Induced Lung Injury in Mice.

The present study was designed to investigate the effects of WP1066, a specific inhibitor of STAT3 signaling, on radiation-induced lung injury in mice. C57BL/6J mice were subjected to a single thoracic irradiation of 15 Gy X-ray and WP1066 was administrated through intraperitoneal injection. The early and delayed treatment groups were treated with WP1066 during the first 2 weeks and the second 2 weeks, respectively. The therapeutic effects of WP1066 were evaluated by survival analysis, histological examination, and measurement of inflammatory parameters and collagen deposition. The activation of STAT3 pathway was also estimated by immunohistochemical staining and Western blotting. Delayed treatment of WP1066, but not early treatment, prolonged survival time and prevented the development of radiation pneumonitis and the subsequent lung fibrosis in mice. WP1066 treatment also significantly suppressed the activation of STAT3 signaling in the irradiated lung tissues. The activation of STAT3 pathway might play an important part in the pathogenesis of radiation-induced lung injury. The protective effects of delayed treatment of WP1066 suggested STAT3 signaling could be a therapeutic target for radiation pneumonitis.

Integrating microRNA and mRNA expression profiles in response to radiation-induced injury in rat lung.

PurposeExposure to radiation provokes cellular responses, which are likely regulated by gene expression networks. MicroRNAs are small non-coding RNAs, which regulate gene expression by promoting mRNA degradation or inhibiting protein translation. The expression patterns of both mRNA and miRNA during the radiation-induced lung injury (RILI) remain less characterized and the role of miRNAs in the regulation of this process has not been studied. The present study sought to evaluate miRNA and mRNA expression profiles in the rat lung after irradiation.Methods and materialsMale Wistar rats were subjected to single dose irradiation with 20 Gy using 6 MV x-rays to the right lung. (A dose rate of 5 Gy/min was applied). Rats were sacrificed at 3, 12 and 26 weeks after irradiation, and morphological changes in the lung were examined by haematoxylin and eosin. The miRNA and mRNA expression profiles were evaluated by microarrays and followed by quantitative RT-PCR analysis.ResultsA cDNA microarray analysis found 2183 transcripts being up-regulated and 2917 transcripts down-regulated (P ≤ 0.05, ≥2.0 fold change) in the lung tissues after irradiation. Likewise, a miRNAs microarray analysis indicated 15 miRNA species being up-regulated and 8 down-regulated (P ≤ 0.05). Subsequent bioinformatics anal -yses of the differentially expressed mRNA and miRNAs revealed that alterations in mRNA expression following irradiation were negatively correlated with miRNAs expression.ConclusionsOur results provide evidence indicating that irradiation induces alterations of mRNA and miRNA expression in rat lung and that there is a negative correlation of mRNA and miRNA expression levels after irradiation. These findings significantly advance our understanding of the regulatory mechanisms underlying the pathophysiology of radiation-induced lung injury. In summary, RILI does not develop gradually in a linear process. In fact, different cell types interact via cytokines in a very complex network. Furthermore, this study suggests that microRNAs may serve an important role in the pathogenesis of RILI and that understanding their role in RILI may have a significant effect on patient management and diagnosis in the future.

Paeoniflorin protects human EA.hy926 endothelial cells against gamma-radiation induced oxidative injury by activating the NF-E2-related factor 2/heme oxygenase-1 pathway

Pulmonary endothelial cells have been demonstrated to have a critical role in the pathogenesis of radiation-induced lung injury. Our preliminary experiments indicated that Paeoniflorin protected human EA.hy926 endothelial cells from radiation-induced oxidative injury. This study was designed to confirm the protective effect of Paeoniflorin against radiation-induced endothelial cellular damage and to elucidate the underlying mechanisms. Preincubation of EA.hy926 cells with Paeoniflorin before γ-radiation resulted in significant inhibition of apoptosis, a decrease in mitochondrial membrane potential and enhanced cell viability. In particular, we showed that Paeoniflorin significantly reduced the formation of intracellular reactive oxygen species (ROS), the level of malondialdehyde (MDA) and lactate dehydrogenase (LDH) leakage, and enhanced production of the endogenous antioxidants, glutathione (GSH) and superoxide dismutase (SOD) in EA.hy926 cells. Treatment of these cells with Paeoniflorin significantly induced HO-1 expression. Moreover, Paeoniflorin promoted the nuclear translocation of nuclear factor erythroid 2 related factor-2 (Nrf-2). The Paeoniflorin-induced HO-1 expression was abrogated by Nrf2 siRNA. Furthermore, inhibition of HO-1 with zinc protoporphyrin IX (ZNPP) significantly reversed the protective effect of Paeoniflorin against radiation-induced damage in EA.hy926 cells. Our findings confirmed that Paeoniflorin protected EA.hy926 cells against radiation-induced injury through the Nrf2/HO-1 pathway.

The bronchiolar epithelium as a prominent source of pro-inflammatory cytokines after lung irradiation

The lung is the major dose-limiting organ for radiotherapy of cancer in the thoracic region. The dysregulation of a variety of inflammatory and fibrogenic cytokines has been shown to play an important role in the pathogenesis of radiation-induced lung injury. The present work is a detailed study on the temporal and spatial release of the pro-inflammatory cytokines TNF-alpha, IL-1 alpha and IL-6 in the lung tissue of C57BL/6 mice after thoracic irradiation with 12 Gy.

Potential signaling and attenuation of radiation-induced lung fibrosis

Purpose/Objective: Radiotherapy is a key component in the management of lung cancer. Unfortunately, radiotherapy is particularly toxic to the lung potentially inducing fatal pneumonitis and fibrosis in a radiation dose-dependent manner. The lung is therefore the major dose-limiting organ for radiotherapy of cancer in the thoracic region. The pathogenesis of radiation-induced lung injury at the molecular level is still unclear. Fibrosis is thought to represent the consequence of direct damage to local tissues and/or vascular endothelium by ionizing radiation and the simultaneous expression of proinflammatory and profibrotic cytokines. Studies suggest that growth factors for fibroblasts (including platelet-derived growth factor (PDGF), insulin-like growth factor I (IGF-I)) and cytokines stimulating collagen synthesis (notably transforming growth factor-beta TGF-b) are largely responsible for the fibrotic process. The purpose of this investigation was to evaluate the effects of a specific PDGF signaling inhibitor in vitro and in vivo in a fibrosis-sensitive mouse model for its ability to reduce fibrosis.

Modulation of radiation-induced tumour necrosis factor α (TNF-α) expression in the lung tissue by pentoxifylline

Purpose: The lung is the major dose-limiting organ for radiotherapy of cancer in the thoracic region. Immediate cellular damage after irradiation is supposed to result in cytokine-mediated multicellular interactions with induction and progression of inflammatory and fibrotic tissue reactions. Pentoxifylline (PTX) down-regulates the production of proinflammatory cytokines, particularly TNF-α, in response to noxious stimuli and may therefore provide protection against radiation-induced, cytokine-mediated cellular damage. The purpose of this study was to investigate the temporal and spatial release of TNF-α in the lung tissue after thoracic irradiation with 12 Gy. In addition, we evaluated the ability of PTX to reduce the radiation-induced TNF-α release in this animal model of thoracic irradiation. Materials and methods: C57BL/6J mice were exposed to either sham irradiation or single fraction of 12 Gy delivered to the thorax. Four study groups were defined: those that received neither irradiation nor PTX (NT group), those that received PTX but no irradiation (PTX group), those that underwent irradiation without PTX (XRT group) and those that received both PTX and irradiation (PTX/XRT group). Treated and sham-irradiated mice were sacrificed corresponding to the latent period and the pneumonic phase. The TNF-α mRNA expression in the lung tissue was quantified by ‘real-time’ quantitative reverse transcriptase polymerase chain reaction (RT-PCR). Immunohistochemical detection methods (alkaline phosphatase anti-alkaline phosphatase (APAAP)) and automated image analysis were used for objective quantification of TNF-α protein expression. Results: Following thoracic irradiation with a single dose of 12 Gy (XRT group), radiation-induced TNF-α mRNA release in the lung tissue was significantly increased during the acute phase of pneumonitis ( P<0.05). The elevated levels of TNF-α mRNA during the pneumonic phase correlate with a significant increase of positive inflammatory cells, predominantly macrophages, in the lung parenchyma ( P<0.05). In contrast to the radiation-only group (XRT-group), the lung tissue of the PTX-treated mice (PTX/XRT group) revealed only a minor radiation-mediated TNF-α response on mRNA and protein level. Conclusions: This study demonstrates a significant radiation-induced increase of TNF-α (on mRNA and protein level) in the lung tissue during the pneumonic phase. The predominant localisation of TNF-α in areas of inflammatory cell infiltrates suggests involvement of this cytokine in the pathogenesis of radiation-induced lung injury. In addition, we observed a pronounced reduction of the TNF-α mRNA and protein production in the study group that received both PTX and radiation (PTX/XRT group) as compared to the radiation-only group (XRT group). Therefore our results indicate that PTX down-regulates the TNF-α mRNA and protein production in the lung tissue in response to radiation.

Dose-dependent induction of transforming growth factor β (TGF-β) in the lung tissue of fibrosis-prone mice after thoracic irradiation

Purpose: The lung is the major dose-limiting organ for radiotherapy of cancer in the thoracic region. The pathogenesis of radiation-induced lung injury at the molecular level is still unclear. Immediate cellular damage after irradiation is supposed to result in cytokine-mediated multicellular interactions with induction and progression of fibrotic tissue reactions. The purpose of this investigation was to evaluate the acute and long-term effects of radiation on the gene expression of transforming growth factor beta (TGF-β) in a model of lung injury using fibrosis-sensitive C57BL/6 mice. Methods and Materials: The thoraces of C57BL/6 mice were irradiated with 6 and 12 Gy, respectively. Treated and sham-irradiated control mice were sacrificed at times corresponding to the latent period (1, 3, 6, 12, 24, 48, 72 hours and 1 week postirradiation), the pneumonic phase (2, 4, 8, and 16 weeks postirradiation), and the beginning of the fibrotic phase (24 weeks postirradiation). The lung tissue from three different mice per dosage and time point was analyzed by a combination of polymerase chain reaction (PCR), immunohistochemistry, and light microscopy. The mRNA expression of TGF-β was quantified by competitive reverse transcriptase/polymerase chain reaction (RT-PCR); the cellular origin of the TGF-β protein was identified by immunohistochemical staining (alkaline phosphatase–anti-alkaline phosphatase [APAAP]). The cytokine expression on mRNA and protein level was correlated with the histopathological alterations. Results: Following thoracic irradiation with a single dose of 12 Gy, radiation-induced TGF-β release in lung tissue was appreciable already within the first hours (1, 3, and 6 hours postirradiation) and reached a significant increase after 12 hours; subsequently (48 hours, 72 hours, and 1 week postirradiation) the TGF-β expression declined to basal levels. At the beginning of the pneumonic phase, irradiation-mediated stimulation of TGF-β release reached maximal values at 2 and 4 weeks. The elevated levels of TGF-β mRNA during the latent phase have been found to correlate with immunohistochemical staining of alveolar macrophages. The most striking increase in TGF-β immunoreactivity was seen during the acute phase of pneumonitis. Throughout this observation period, type II pneumocytes and fibroblasts (apart from inflammatory cells) served as important sources of TGF-β expression. Increased TGF-β expression was detected prominently in regions of histopathologic radiation injury. After exposure to a single radiation dose of 6 Gy, the lung tissue revealed only a minor radiation-mediated TGF-β mRNA response. The modest upregulation ranged from 6 hours to 48 hours after irradiation. Corresponding to the only minor histopathologic changes after thoracic irradiation with 6 Gy, measurement of TGF-β mRNA levels during the later time points revealed no significant alterations in comparison to untreated control mice. Conclusions: This study demonstrates an acute and long-lasting increase in the expression of TGF-β in lung tissue following thoracic irradiation with 12 Gy. The predominant localization of TGF-β in areas of inflammatory cell infiltrates and fibrosis suggests involvement of this cytokine in the pathogenesis of radiation-induced pulmonal fibrosis. Further studies should be performed to explore the role of other cytokines in the development of radiation injury. An improved understanding of the underlying mechanisms of pulmonary fibrosis may eventually lead to modulatory intervention at the molecular level to modify the fibrotic process.