Protective Role of Nuclear Factor-Erythroid 2-Related Factor 2 Against Radiation-Induced Lung Injury and Inflammation

Nrf-2 as a novel target in radiation induced lung injury

Radiation-induced lung injury (RILI) is a common and fatal complication of chest radiotherapy. The underlying mechanisms include radiation-induced oxidative stress caused by damage to the deoxyribonucleic acid (DNA) and production of reactive oxygen species (ROS), resulting in apoptosis of lung and endothelial cells and recruitment of inflammatory cells and myofibroblasts expressing NADPH oxidase to the site of injury, which in turn contribute to oxidative stress and cytokine production. Nuclear factor erythroid 2-related factor 2 (Nrf-2) is a vital transcription factor that regulates oxidative stress and inhibits inflammation. Studies have shown that Nrf-2 protects against radiation-induced lung inflammation and fibrosis. This review discusses the protective role of Nrf-2 in RILI and its possible mechanisms.

Radiation injury and gut microbiota-based treatment

The exposure to either medical sources or accidental radiation can cause varying degrees of radiation injury (RI). RI is a common disease involving multiple human body parts and organs, yet effective treatments are currently limited. Accumulating evidence suggests gut microbiota are closely associated with the development and prevention of various RI. This article summarizes 10 common types of RI and their possible mechanisms. It also highlights the changes and potential microbiota-based treatments for RI, including probiotics, metabolites, and microbiota transplantation. Additionally, a 5P-Framework is proposed to provide a comprehensive strategy for managing RI.

Amomum subulatum fruits protect against radiation-induced esophagitis by regulating antioxidant status and inflammatory responses

Radiation esophagitis (RE) is an inimical event that requires proper management while carrying out radiotherapy for thoracic cancers. The present study investigates the protective effect of dry fruits of the culinary and folkloric spice Amomum subulatum against experimental thoracic radiation-induced esophagitis. C57BL/6 mice were subjected to 25 Gy whole thorax irradiation and administered with 250 mg/kg body weight of methanolic extract of A. subulatum dry fruits (MEAS) orally for four consecutive weeks. Changes in tissue antioxidant activities, oxidative stress parameters, expression of antioxidant, inflammation, and fibrosis-related genes were observed. Administration of MEAS boosted antioxidant status, thereby reducing radiation-induced oxidative stress in the esophagus. PCR (polymerase chain reaction) results showed decreased expression of apoptosis, inflammation, and fibrosis-associated genes as well as increased expression of vital cytoprotective and antioxidant genes in MEAS-treated mice, manifesting its protective effect against radiation-induced oxidative stress, inflammatory responses, and fibrosis in the esophagus. Further, histopathology, immunohistochemistry (Cyclooxygenase-2), and Masson's Trichrome staining ascertained the protective effect of MEAS in alleviating radiation-induced esophageal injury. The synergistic effect of bioactive phytochemicals in MEAS with potent antioxidant and anti-inflammatory efficacies might have contributed to its mitigating effect against RE. Taken together, our results ascertained the radioprotective potential of MEAS, suggesting its possible nutraceutical application as a radiation countermeasure.

Activation of Nrf2/ARE pathway by Anisodamine (654-2) for Inhibition of cellular aging and alleviation of Radiation-Induced lung injury

BACKGROUND

Radiation-induced lung injury (RILI) is a common side effect of thoracic tumor radiotherapy, including early-stage radiation-induced lung injury (RP) and late-stage radiation-induced pulmonary fibrosis (RIPF). Currently, it is urgently needed to clarify the pathogenesis of RILI and find safe and effective RILI treatment methods. Irradiation causes DNA damage and oxidative stress in tissues and cells, induces cellular senescence, and promotes the occurrence and development of RILI. In recent years, Anisodamine (654-2) has shown potential therapeutic value in acute lung injury, acute kidney injury, chlamydial pneumonia, and COVID-19. However, there is currently no research on the mechanism of 654-2-mediated cellular senescence and its preventive and therapeutic effects on RILI.

PURPOSE

This study aimed to investigate the protective effect and mechanism of 654-2 on X-ray-induced RILI.

METHODS

In vivo experiments involved a mouse RILI model with 18 Gy X-ray irradiation. Mice were divided into control, model, medication (control + 654-2), and treatment (model + 654-2) groups. And mice in medication and treatment groups were intraperitoneal injection of 5 mg/kg 654-2 every other day until being sacrificed at week 6. In vitro experiments used MLE-12 cells irradiated with 16 Gy and divided into control, model, and model + 654-2（2 μM and 10 μM） groups. Various assays were performed to evaluate lung tissue morphology, fibrosis, apoptosis, cytokine expression, cellular senescence, protein expression, and antioxidant capacity.

RESULTS

654-2 mitigated pulmonary pathological damage, inflammation, DNA damage, cellular senescence, and apoptosis in RILI mice and MLE-12 cells. It restored epithelial cell proliferation ability and enhanced antioxidant capacity. Additionally, 654-2 activated the Nrf2/ARE pathway, increased Nrf2 phosphorylation, and upregulated antioxidant gene expression. Inhibition of Nrf2 reversed the effects of 654-2 on ROS production, antioxidant capacity, and cell senescence.

CONCLUSION

654-2 can activate the Nrf2/ARE pathway, enhance cellular antioxidant capacity, and inhibit cellular senescence, thereby exerting a protective effect against RILI.

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.

Febuxostat, an inhibitor of xanthine oxidase, ameliorates ionizing radiation-induced lung injury by suppressing caspase-3, oxidative stress and NF-κB

Febuxostat (FBX), a selective inhibitor of xanthine oxidase, has several biological properties such as antioxidant, anti-inflammatory and anti-apoptosis activities. The purpose of this study was to evaluate the protective effect of FBX against ionizing radiation (IR)-induced lung injury through mitigation of oxidative stress, inflammation and apoptosis. Sixty-four mice were randomized into eight groups as control, FBX (5, 10, and 15 mg/kg), IR (6 Gy), and IR + FBX (IR + FBX in three doses). Mice were received FBX for 8 consecutive days and then were exposed to IR at a single dose (6 Gy) of X-ray. At 1 and 7 days after irradiation, the biochemical parameters were analyzed in lung tissue, while histological and immunohistochemical examinations were evaluated 1 week after irradiation. Irradiation led to elevate of oxidative stress parameters (an increase of MDA, PC, NO, and decrease of GSH), inflammation and apoptosis in lung of mice. Furthermore, IR resulted in histopathological changes in the lung tissues. These changes were significantly mitigated by FBX treatment. FBX also inhibited immunoreactivity of caspase-3, NF-κB, and reduced oxidative stress. This study showed that FBX is able to protect lung injury induced by IR through inhibiting apoptosis (caspase-3), oxidative stress and inflammation (NF-κB).

Near-infrared Nrf2 activator IR-61 dye alleviates radiation-induced lung injury

Oxidative stress injury and subsequent inflammatory response are considered to play critical roles in radiation-induced lung injury (RILI). Nuclear factor erythroid 2-related factor 2 (Nrf2) is a key transcription factor that regulates oxidative stress response and represses inflammation, but its therapeutic value in RILI remains elusive. Our previous studies have shown that the near-infrared (NIR) IR-61 dye evokes intracellular antioxidant defence by enhancing Nrf2 signalling and promoting anti-inflammatory effects. We established a model of RILI in mice exposed to whole-thoracic irradiation. The results showed that IR-61 treatment notably improved pulmonary functions by decreasing lung density and diminishing airway resistance. In addition, IR-61 significantly ameliorated radiation-induced inflammatory cell infiltration and proinflammatory cytokine (IL-1β, IL-6 and TNF-α) release, thereby mitigating inflammatory response. Furthermore, IR-61 mitigated radiation-induced lung fibrosis by decreasing the collagen deposition and the levels of fibrogenesis-related factors (collagen I, collagen III, α-SMA, and fibronectin). More importantly, IR-61 was found to accumulate in the mitochondria of macrophages in irradiated lung tissues. Therefore, the functions of IR-61 in macrophages were further studied in irradiated macrophage cell lines, MH-s and RAW 264.7 in vitro. The results indicated that IR-61 upregulated the expression of Nrf2 and haem oxygenase-1(HO-1) and decreased the levels of reactive oxygen species (ROS) and pro-inflammatory cytokines (IL-1β and IL-6) in macrophages after radiation. In summary, our study suggests that IR-61 effectively mitigates RILI by activating Nrf2 signalling in irradiated lung tissues. In particular, Nrf2-mediated anti-inflammatory and antioxidant effects in irradiated lung tissue macrophages play critical roles in protecting against RILI.

Electroacupuncture pretreatment protects septic rats from acute lung injury by relieving inflammation and regulating macrophage polarization

BACKGROUND

Macrophage polarization toward the M2 phenotype may attenuate inflammation and have a therapeutic effect in acute lung injury (ALI).

OBJECTIVE

To investigate the role of electroacupuncture (EA) pretreatment on the inflammatory response and macrophage polarization in a septic rat model of lipopolysaccharide (LPS)-induced ALI.

METHODS

Male Sprague Dawley rats (n = 24) were randomly divided into three groups (n = 8 each): control (Ctrl), ALI (LPS) and pre-EA (LPS + EA pretreatment). ALI and pre-EA rats were injected with LPS via the caudal vein. Pulmonary edema was assessed by left upper pulmonary lobe wet-to-dry (W/D) ratios. Lung injury scores were obtained from paraffin-embedded and hematoxylin and eosin-stained sections of the left lower pulmonary lobe. Inflammatory activation was quantified using serum tumor necrosis factor (TNF)-α, interleukin (IL)-1β, transforming growth factor (TGF)-β and IL-10 levels measured by enzyme linked immunosorbent assay (ELISA). Macrophage phenotype was determined by real-time quantitative polymerase chain reaction (RT-qPCR) and Western blotting.

RESULTS

Mean lung W/D ratio was significantly lower and serum IL-1β levels were decreased in pre-EA rats compared to ALI rats (P < 0.05). TNF-α mRNA expression was decreased and mannose receptor (MR) and Arg1 mRNA expression was increased in the lung tissues of pre-EA rats compared to ALI rats (P < 0.01). Arg1 protein expression was similarly increased in the lung tissues of pre-EA rats compared to ALI rats (P < 0.05).

CONCLUSION

EA pretreatment may play a protective role by promoting macrophage polarization to the M2 phenotype in a septic rat model of LPS-induced ALI.

Radiation affects glutathione redox reaction by reduced glutathione peroxidase activity in human fibroblasts

The glutathione (GSH) redox control is critical to maintain redox balance in the body's internal environment, and its perturbation leads to a dramatic increase in reactive oxygen species (ROS) levels and oxidative stress which have negative impacts on human health. Although ionizing radiation increases mitochondrial ROS generation, the mechanisms underlying radiation-induced late ROS accumulation are not fully understood. Here we investigated the radiation effect on GSH redox reactions in normal human diploid lung fibroblasts TIG-3 and MRC-5. Superoxide anion probe MitoSOX-red staining and measurement of GSH peroxidase (GPx) activity revealed that high dose single-radiation (SR) exposure (10 Gy) increased mitochondrial ROS generation and overall oxidative stress in parallel with decrease in GSH peroxidase (GPx) activity, while GSH redox control was effective after exposure to moderate doses under standard serum conditions. We used different serum conditions to elucidate the role of serum on GSH redox reaction. Serum starvation, serum deprivation and DNA damage response (DDR) inhibitors-treatment reduced the GPx activity and increased mitochondrial ROS generation regardless of radiation exposure. Fractionated-radiation was used to evaluate the radiation effect on GSH reactions. Repeated fractionated-radiation induced prolonged oxidative stress by down-regulation of GPx activity. In conclusion, radiation affects GSH usage according to radiation dose, irradiation methods and serum concentration. Radiation affected the GPx activity to disrupt fibroblast redox homeostasis.

Crossed Pathways for Radiation-Induced and Immunotherapy-Related Lung Injury

Radiation-induced lung injury (RILI) is a form of radiation damage to normal lung tissue caused by radiotherapy (RT) for thoracic cancers, which is most commonly comprised of radiation pneumonitis (RP) and radiation pulmonary fibrosis (RPF). Moreover, with the widespread utilization of immunotherapies such as immune checkpoint inhibitors as first- and second-line treatments for various cancers, the incidence of immunotherapy-related lung injury (IRLI), a severe immune-related adverse event (irAE), has rapidly increased. To date, we know relatively little about the underlying mechanisms and signaling pathways of these complications. A better understanding of the signaling pathways may facilitate the prevention of lung injury and exploration of potential therapeutic targets. Therefore, this review provides an overview of the signaling pathways of RILI and IRLI and focuses on their crosstalk in diverse signaling pathways as well as on possible mechanisms of adverse events resulting from combined radiotherapy and immunotherapy. Furthermore, this review proposes potential therapeutic targets and avenues of further research based on signaling pathways. Many new studies on pyroptosis have renewed appreciation for the value and importance of pyroptosis in lung injury. Therefore, the authors posit that pyroptosis may be the common downstream pathway of RILI and IRLI; discussion is also conducted regarding further perspectives on pyroptosis as a crucial signaling pathway in lung injury treatment.

ATF3 regulates oxidative stress and extracellular matrix degradation via p38/Nrf2 signaling pathway in pelvic organ prolapse

Pelvic organ prolapse (POP) is a common disorder in women, and it is characterized by weakening of pelvic supportive structure with extracellular matrix (ECM) degradation. Activating transcription factor 3 (ATF3) was upregulated in anterior vaginal wall tissues of POP patients. We hypothesized that upregulation of ATF3 might contribute to POP development. This study aims to unveil the role of ATF3 in the pathogenesis of POP using a H₂O₂-induced in vitro model. Vaginal fibroblasts were isolated from woman with POP-Q stage greater than II and asymptomatic women with normal pelvic floor support. Knockdown of ATF3 enhanced cell viability and decreased cell apoptosis. Flow cytometry and immunnofluorescence showed that ATF3 deficiency inhibited H₂O₂-induced ROS production and the expression of 8 OHdG and 4-HNE. Western blot and Real-time PCR analysis revealed that ATF3 deficiency attenuated ECM component degradation (increasing collagen I, collagen III and elastin) and MMPs/TIMPs imbalance (decreasing MMP2 and MMP9 and increasing TIMP2). Moreover, knockdown of ATF3 induced the activation of p38/Nrf2/HO-1 signaling pathway. Further treatment with p38 inhibitor SB203580 abolished the protection of ATF3 deficiency against H₂O₂-induced cell damage, which was reverted by Nrf2 activator TBHQ. Thus, ATF3 likely contributes to POP progression by inducing cell apoptosis, oxidative stress and ECM degradation via regulating p38/Nrf2 pathway, which provides a potential therapeutic target for POP.

All for one, though not one for all: team players in normal tissue radiobiology

PURPOSE

As part of the special issue on 'Women in Science', this review offers a perspective on past and ongoing work in the field of normal (non-cancer) tissue radiation biology, highlighting the work of many of the leading contributors to this field of research. We discuss some of the hypotheses that have guided investigations, with a focus on some of the critical organs considered dose-limiting with respect to radiation therapy, and speculate on where the field needs to go in the future.

CONCLUSIONS

The scope of work that makes up normal tissue radiation biology has and continues to play a pivotal role in the radiation sciences, ensuring the most effective application of radiation in imaging and therapy, as well as contributing to radiation protection efforts. However, despite the proven historical value of preclinical findings, recent decades have seen clinical practice move ahead with altered fractionation scheduling based on empirical observations, with little to no (or even negative) supporting scientific data. Given our current appreciation of the complexity of normal tissue radiation responses and their temporal variability, with tissue- and/or organ-specific mechanisms that include intra-, inter- and extracellular messaging, as well as contributions from systemic compartments, such as the immune system, the need to maintain a positive therapeutic ratio has never been more urgent. Importantly, mitigation and treatment strategies, whether for the clinic, emergency use following accidental or deliberate releases, or reducing occupational risk, will likely require multi-targeted approaches that involve both local and systemic intervention. From our personal perspective as five 'Women in Science', we would like to acknowledge and applaud the role that many female scientists have played in this field. We stand on the shoulders of those who have gone before, some of whom are fellow contributors to this special issue.

Asparaginyl endopeptidase (AEP) regulates myocardial apoptosis in response to radiation exposure via alterations in NRF2 activation

Radiation-induced heart disease (RIHD) leads to myocardial dysfunction and metabolic abnormalities in patients treated with thoracic irradiation which restricts the long-term survival benefits of radiotherapy. There is no specific or effective manner of intervention currently available. Asparaginyl endopeptidase (AEP) plays a pivotal role in the maintenance of cellular functions through regulating proteolytic cleavage as peptidase enzyme. We aimed to investigate the role of unique cardiac AEP in cardiac function by modulating key signaling elements in the myocardium. The murine heart was exposed to a single dose of 14 Gy radiation. Cellular signaling and apoptosis was analyzed in human and rat cardiomyocytes treated with various doses of radiation, we observed expression of AEP was increased by immunohistochemical staining in murine heart exposed to radiation. The AEP production along with its increased level of mRNA expression was associated with increased doses of radiation (0, 2, 5, 10 Gy) in cardiomyocytes. The myocardial cells transfected with AEP overexpression showed overall cellular viability enhancement, DNA damage inhibition, the foci formation of γ-H2AX suppressed and DNA repair enhancement significantly after radiation exposure. Small interfering RNA-mediated AEP knockdown was with reduced cardiomyocyte viability, elevated apoptotic rate, increased γ-H2AX foci formation and inhibited DNA repair as well after irradiation. After radiation exposure of 10 Gy, the expression of AEP increased in P53 overexpressing cardiomyocytes and decreased in the P53 knockdown cells, indicates that radiation-induced expression of AEP might be regulated by P53. Moreover, treatments with either AEP overexpression or knockdown showed enhanced NRF2 activity in the nuclear or suppressed NRF2 expression in the cytoplasm of myocardial cells after irradiation, respectively, defined a possible regulatory effect of AEP associated with diminished NRF2 translocation and activation by radiation exposure, including impair myocardium and myocardial apoptosis. These findings suggest that increased levels of AEP in failing myocardium after irradiation is mediated by P53 and regulate a novel pathway that involves NRF2 activation. AEP is essential for maintaining cellular redox homeostasis of cardiac function.

Nrf2 alleviates radiation-induced rectal injury by inhibiting of necroptosis

Radiation-induced rectal injury is one of the common side effects of pelvic radiation therapy. This study aimed to explore the role of nuclear factor erythroid 2-related factor 2 (Nrf2) in this process. In vivo, knockout (KO) of Nrf2 led to aggravated radiation-induced histological changes in the rectums. In vitro, interference or overexpression of Nrf2 resulted in enhanced or reduced radiosensitivity in human intestinal epithelial crypts (HIEC) cells, respectively. A potential relationship between Nrf2 and necroptosis was identified using RNA sequencing (RNA-seq) and western blotting (WB), which showed that necroptosis-related proteins were negatively correlated with Nrf2. Upon treatment with necrostatin-1 (Nec-1), the increased radiosensitivity, decreased cell viability, increased γH2AX foci formation, and decreased mitochondrial membrane potential (MMP) in Nrf2-interfered HIEC cells were alleviated. A significant recovery in morphological alterations was also observed in Nrf2 KO mice administered with Nec-1. Taken together, our results highlight the important protective effect of Nrf2 in radiation-induced rectal injury through the inhibition of necroptosis, and the physiological significance of necroptosis in radiation-induced rectal injury.

Age-related alteration in HNE elimination enzymes

4-hydroxynonenal (HNE, 4-hydroxy-2-nonenal) is a primary α,β-unsaturated aldehyde product of lipid peroxidation. The accumulation of HNE increases with aging and the mechanisms are mainly attributable to increased oxidative stress and decreased capacity of HNE elimination. In this review article, we summarize the studies on age-related change of HNE concentration and alteration of HNE metabolizing enzymes (GCL, GST, ALDHs, aldose reductase, and 20S-proteasome), and discuss potential mechanism of age-related decrease in HNE-elimination capacity by focusing on Nrf2 redox signaling.

Oxidative Stress and Cancer Development: Are Noncoding RNAs the Missing Links?

Significance: It is now clear that genetic changes underlie the basis of cancer, and alterations in functions of multiple genes are responsible for the process of tumorigenesis. Besides the classical genes that are usually implicated in cancer, the role of noncoding RNAs (ncRNAs) and reactive oxygen species (ROS) as independent entitites has also been investigated. Recent Advances: The microRNAs and long noncoding RNAs (lncRNAs), two main classes of ncRNAs, are known to regulate many aspects of tumor development. ROS, generated during oxidative stress and pathological conditions, are known to regulate every step of tumor development. Conversely, oxidative stress and ROS producing agents can suppress tumor development. The malignant cells normally produce high levels of ROS compared with normal cells. The interaction between ROS and ncRNAs regulates the expression of multiple genes and pathways implicated in cancer, suggesting a unique mechanistic relationship among ncRNA-ROS-cancer. The mechanistic relationship has been reported in hepatocellular carcinoma, glioma, and malignancies of blood, breast, colorectum, esophagus, kidney, lung, mouth, ovary, pancreas, prostate, and stomach. The ncRNA-ROS regulate several cancer-related cell signaling pathways, namely, protein kinase B (AKT), epidermal growth factor receptor (EGFR), forkhead box O3 (FOXO3), kelch-like ECH-associated protein 1 (Keap1), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), nuclear factor erythroid 2-related factor 2 (Nrf2), p53, phosphatase and tensin homologue (PTEN), and wingless-related integration site (Wnt)/glycogen synthase kinase-3 beta (GSK3β). Critical Issues: To date, most of the reports about ncRNA-oxidative stress-carcinogenesis relationships are based on cell lines. The mechanistic basis for this relationship has not been completely elucidated. Future Directions: Attempts should be made to explore the association of lncRNAs with ROS. The significance of the ncRNA-oxidative stress-carcinogenesis interplay should also be explored through studies in animal models.

The role of Nrf2/PIWIL2/purine metabolism axis in controlling radiation-induced lung fibrosis

NF-E2-related factor 2 (Nrf2) is a key transcription factor recently implicated in the control of radiation-induced lung fibrosis (RILF). However, the molecular mechanism of Nrf2 in the pathogenesis of RILF is still unclear. The purpose of this study was to evaluate the regulatory effect and mechanism of Nrf2 in the pathogenesis of RILF. The effects of different Nrf2 expression levels on RILF were explored in vitro and in vivo. The RILF model of Nrf2 knockout mice was established for in vivo study. In the study of the mechanism of action, ChIP-seq assay and metabolomics analysis were performed. The discovered mechanism of Nrf2-mediated RILF alleviation was further validated in vitro and in vivo. We found that overexpression of Nrf2 significantly alleviated the fibrosis caused by irradiation in vivo and in vitro. Conversely, Nrf2 silencing strongly aggravated the development of RILF. Mechanistically, Nrf2 signaling increased the expression of piwi-like RNA-mediated gene silencing 2 (PIWIL2), leading to the alteration of purine metabolism and contributing to the relief of RILF. These results suggest that Nrf2 promotes the attenuation of RILF in vivo and in vitro by directly targeting PIWIL2 and activating purine metabolism.

Cellular senescence: A pathogenic mechanism of pelvic organ prolapse (Review)

Pelvic organ prolapse (POP) is a common symptom of pelvic floor disorders which is characterized by the descent of the uterus, bladder or bowel from their normal anatomical position towards or through the vagina. Among the older population, the incidence of POP increases with age. It is becoming necessary to recognize that POP is a degenerative disease that is correlated with age. In recent years, studies have been performed to improve understanding of the cellular and molecular mechanisms concerning senescent fibroblasts in pelvic tissues, which contribute to the loss of structure supporting the pelvic organs. These mechanisms can be classified into gene and mitochondrial dysfunctions, intrinsic senescence processes, protein imbalance and alterations in stem cells. The present review provides an integrated overview of the current research and concepts regarding POP, in addition to discussing how fibroblasts can be targeted to evade the negative impact of senescence on POP. However, it is probable that other mechanisms that can also cause POP exist during cell senescence, which necessitates further research and provides new directions in the development of novel medical treatment, stem cell therapy and non-surgical interventions for POP.

Manganese porphyrin, MnTE-2-PyP, treatment protects the prostate from radiation-induced fibrosis (RIF) by activating the NRF2 signaling pathway and enhancing SOD2 and sirtuin activity

Radiation therapy is a frequently used treatment for prostate cancer patients. Manganese (III) meso-tetrakis (N-ethylpyridinium-2-yl) porphyrin (MnTE-2-PyP or T2E or BMX-010) and other similar manganese porphyrin compounds that scavenge superoxide molecules have been demonstrated to be effective radioprotectors and prevent the development of radiation-induced fibrosis (RIF). However, understanding the molecular pathway changes associated with these compounds remains limited for radioprotection. Recent RNA-sequencing data from our laboratory revealed that MnTE-2-PyP treatment activated the nuclear factor erythroid 2-related factor 2 (NRF2) signaling pathway. Therefore, we hypothesize that MnTE-2-PyP protects the prostate from RIF by activating the NRF2 signaling pathway. We identified that MnTE-2-PyP is a post-translational activator of NRF2 signaling in prostate fibroblast cells, which plays a major role in fibroblast activation and myofibroblast differentiation. The mechanism of NRF2 activation involves an increase in hydrogen peroxide and a corresponding decrease in kelch-like ECH-associated protein 1 (KEAP1) levels. Activation of NRF2 signaling leads to an increase in expression of NAD(P)H dehydrogenase [quinone] 1 (NQO1), nicotinamide adenine dinucleotide (NAD+) levels, sirtuin activity (nuclear and mitochondrial), and superoxide dismutase 2 (SOD2) expression/activity. Increase in mitochondrial sirtuin activity correlates with a decrease in SOD2 (K122) acetylation. This decrease in SOD2 K122 acetylation correlates with an increase in SOD2 activity and mitochondrial superoxide scavenging capacity. Further, in human primary prostate fibroblast cells, the NRF2 pathway plays a major role in the fibroblast to myofibroblast transformation, which is responsible for the fibrotic phenotype. In the context of radiation protection, MnTE-2-PyP fails to prevent fibroblast to myofibroblast transformation in the absence of NRF2 signaling. Collectively, our results indicate that the activation of the NRF2 signaling pathway by MnTE-2-PyP is at least a partial mechanism of radioprotection in prostate fibroblast cells.

MicroRNA-21 mediates bone marrow mesenchymal stem cells protection of radiation-induced lung injury during the acute phase by regulating polarization of alveolar macrophages

Background

Radiation-induced lung injury (RILI) often occurs in patients with non-small cell lung cancer (NSCLC) after radiotherapy, and the prognosis of patients with RILI is usually poor. This work plan to investigate the expression patterns of microRNA-21(miR-21) in NSCLC patients with RILI and the protective effects of miR-21 over-expressed bone marrow mesenchymal stem cells (BMSCs) against RILI in rat model.

Methods

MiR-21 expressions were determined in both serum samples and bronchoalveolar lavage fluid (BALF) samples from NSCLC patients after radiation therapy. The correlation between miR-21 expression and the follow-up clinical characterizations were determined. Further, miR-21 over-expressed BMSCs were transplanted into RILI rats and the protective effects were evaluated. BMSCs and alveolar macrophages (AMs) were co-cultured in vitro and the macrophage M1 polarization markers were determined by ELISA and qRT-PCR assays.

Results

Expression of miR-21 was significantly increased in NSCLC patients with RILI compared with control group, especially before or at 4 weeks after radiation therapy commenced. The miR-21 levels were highly correlated with IL-12, TNF-α, and IL-6 expressions and the severity of RILI. Animal based experiments demonstrated that BMSCs treatment had a remarkable effect on alleviating alveolitis in RILI rats, and miR-21 over-expression could enhance this effect significantly. Cell based experiments demonstrated that BMSCs notably inhibited M1 polarization of AMs and this inhibition is in a miR-21 dependent manner.

Conclusions

These results indicated that BMSCs could blocked the proinflammatory pathway of macrophage through miR-21 over-expression, thus could be a potential therapeutic strategy for RILI.

The Role of Nrf2 Activity in Cancer Development and Progression

Nrf2 is a transcription factor that stimulates the expression of genes which have antioxidant response element-like sequences in their promoter. Nrf2 is a cellular protector, and this principle applies to both normal cells and malignant cells. While healthy cells are protected from DNA damage induced by reactive oxygen species, malignant cells are defended against chemo- or radiotherapy. Through our literature search, we found that Nrf2 activates several oncogenes unrelated to the antioxidant activity, such as Matrix metallopeptidase 9 (MMP-9), B-cell lymphoma 2 (BCL-2), B-cell lymphoma-extra large (BCL-xL), Tumour Necrosis Factor α (TNF-α), and Vascular endothelial growth factor A (VEGF-A). We also did a brief analysis of The Cancer Genome Atlas (TCGA) data of lung adenocarcinoma concerning the effects of radiation therapy and found that the therapy-induced Nrf2 activation is not universal. For instance, in the case of recurrent disease and radiotherapy, we observed that, for the majority of Nrf2-targeted genes, there is no change in expression level. This proves that the universal, axiomatic rationale that Nrf2 is activated as a response to chemo- and radiation therapy is wrong, and that each scenario should be carefully evaluated with the help of Nrf2-targeted genes. Moreover, there were nine genes involved in lipid peroxidation, which showed underexpression in the case of new radiation therapy: ADH1A, ALDH3A1, ALDH3A2, ADH1B, GPX2, ADH1C, ALDH6A1, AKR1C3, and NQO1. This may relate to the fact that, while some studies reported the co-activation of Nrf2 and other oncogenic signaling pathways such as Phosphoinositide 3-kinases (PI3K), mitogen-activated protein kinase (MAPK), and Notch1, other reported the inverse correlation between Nrf2 and the tumor-promoter Transcription Factor (TF), Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). Lastly, Nrf2 establishes its activity through interactions at multiple levels with various microRNAs. MiR-155, miR-144, miR-28, miR-365-1, miR-93, miR-153, miR-27a, miR-142, miR-29-b1, miR-340, and miR-34a, either through direct repression of Nrf2 messenger RNA (mRNA) in a Kelch-like ECH-associated protein 1 (Keap1)-independent manner or by enhancing the Keap1 cellular level, inhibit the Nrf2 activity. Keap1–Nrf2 interaction leads to the repression of miR-181c, which is involved in the Nuclear factor kappa light chain enhancer of activated B cells (NF-κB) signaling pathway. Nrf2’s role in cancer prevention, diagnosis, prognosis, and therapy is still in its infancy, and the future strategic planning of Nrf2-based oncological approaches should also consider the complex interaction between Nrf2 and its various activators and inhibitors.

Pituitary adenylate cyclase-activating polypeptide ameliorates radiation-induced cardiac injury

Radiation-induced heart disease (RIHD) is a common sequelae of thoracic irradiation. Currently, there is no effective prevention and treatment strategy. Oxidative stress is associated with the development of RIHD. Pituitary adenylate cyclase-activating polypeptide 38 (PACAP38) has been defined as the multipotent properties of cytoprotective effect on its anti-apoptotic and antioxidant activities. Here, we set to investigate whether PACAP38 plays a role in attenuating RIHD. We established radiation-related cardiac injury models using 6MV X-ray based on H9C2 cardiomyocytes and male C57/BL6 mice which were pre-treated with PACAP38 prior to radiation exposure. PACAP38 protected mice from radiation-induced histological damage including myocardial apoptosis and fibrosis. Also, cell viability and colony-forming efficiency were enhanced and intracellular ROS generation was reduced in PACAP38 treated H9C2 cardiomyocytes exposed to radiation. Moreover, PACAP38 suppressed myocardial apoptosis and G2/M arrest through blunting the radiation-induced down-regulation of Bcl-2, CyclinB1 and CDC2, and inhibiting the up-regulation of Bax. Furthermore, irradiation resulted in activating of NRF2 and HO-1 expressions were further enhanced by PACAP38 in H9C2 cells and the protective effect of PACAP38 was partially blocked by NRF2 siRNA silencing. In summary, PACAP38 has the potential to effectively protect against acute radiation-induced cardiac injury and its cardioprotective effect involves upregulation of NRF2/HO-1-dependent signaling activation.

Ferroptosis inhibitor alleviates Radiation-induced lung fibrosis (RILF) via down-regulation of TGF-β1

Background

Radiation-induced lung fibrosis (RILF) is a severe and life-threatening complication of thoracic radiotherapy. Cell death is the key issue in RILF. Ferroptosis is a form programmed cell death implicated in the pathologies of inflammation. This study aimed to investigate the role of ferroptosis in RILF, and the effectiveness and the potential underlying mechanism of ferroptosis inhibitor on RILF.

Methods

Immunofluorescence, western blot and RT-PCR assays were performed to examine the ferroptosis maker glutathione peroxidase 4 (GPX4) in a mice RILF model. The lung tissue sections were stained with hematoxylin and eosin (H&E), Masson trichrome staining and Sirius-Red staining to evaluate the histopathological changes in RILF mice. Reactive oxygen species (ROS) and hydroxyproline (HYP) in lungs were measured by the relevant kits. The serum levels of inflammatory cytokines (TNF-α, IL-6, IL-10, and TGF-β1) were measured with Elisa. The protein and mRNA levels of GPX4, nuclear factor (erythroid-derived 2)-like 2 (Nrf2), hemeoxygenase-1 (HO1) and quinone oxidoreductase 1 (NQO1) in lungs were examined by western blot and RT-PCR.

Results

GPX4 levels of the irradiated lungs were significantly down-regulated than the groups with no irradiation, and the ferroptosis inhibitor, liproxstatin-1, increased GPX4 levels significantly in RILF mice. Treatment with liproxstatin-1 lowered the Szapiel and Ashcroft scores significantly, down-regulated the levels of ROS and HYP in lungs and reduced the serum inflammatory cytokines levels in RILF mice. The protein and the mRNA levels of Nrf2, HO1 and NQO1 were up-regulated by liproxsratin-1 in RILF.

Conclusions

Our data suggested that ferroptosis played a critical role in RILF, ferroptosis inhibitor liproxstatin-1 alleviated RILF via down-regulation of TGF-β1 by the activation of Nrf2 pathway. The effectiveness of ferroptosis inhibition on RILF provides a novel therapeutic target for RILF.