Up-regulation of autophagy in small intestine Paneth cells in response to total-body gamma-irradiation

Loss of Mist1 alters the characteristics of Paneth cells and impacts the function of intestinal stem cells in physiological conditions and after radiation injury

Intestinal stem cells (ISCs) and Paneth cells (PCs) reside at the bottom of the crypts of Lieberkühn in the small intestine. Recent studies have shown that the transcription factor Mist1, also named BHLHA15, plays an important role in the maturation of PCs. Since there is an intimate interaction between PCs and ISCs, we speculated that the loss of Mist1 could impact these two neighboring cell types. Here, we report that mice lacking Mist1 had fewer but larger PCs with shrunken secretory granules, accompanied by an increase in goblet cells and tuft cells. Mist1 loss significantly decreased the number of proliferative crypt cells, especially columnar basal cells (CBCs). In addition, Mist1-deficient enteroids needed supplemental Wnt3a to support their growth. Results from RNA sequencing (RNA-seq) demonstrated an apparent deficiency of innate immunity in Mist1-knockout mice. Intriguingly, Mist1 loss increased the survival rate of mice subjected to whole abdominal irradiation (WAI). Moreover, radiation injury was ameliorated in Mist1-knockout mice compared with their wild-type littermates based on histological analysis and enteroid culture, which might be a consequence of increased contents of the endoplasmic reticulum (ER) and the increased activity of mTORC1 in Paneth cells. In summary, our data uncover that Mist1 plays an important functional role in PCs and regulates the maintenance of ISCs and their response to radiation injury. © 2025 The Pathological Society of Great Britain and Ireland.

Morphological and biochemical characteristics associated with autophagy in gastrointestinal diseases

Autophagy is a cellular catabolic process characterized by the formation of double-membrane autophagosomes. Transmission electron microscopy is the most rigorous method to clearly visualize autophagic engulfment and degradation. A large number of studies have shown that autophagy is closely related to the digestion, secretion, and regeneration of gastrointestinal (GI) cells. However, the role of autophagy in GI diseases remains controversial. This article focuses on the morphological and biochemical characteristics of autophagy in GI diseases, in order to provide new ideas for their diagnosis and treatment.

Reg3α concentrations at day of allogeneic stem cell transplantation predict outcome and correlate with early antibiotic use

Intestinal microbiome diversity plays an important role in the pathophysiology of acute gastrointestinal (GI) graft-versus-host disease (GVHD) and influences the outcome of patients after allogeneic stem cell transplantation (ASCT). We analyzed clinical data and blood samples taken preconditioning and on the day of ASCT from 587 patients from 7 German centers of the Mount Sinai Acute GVHD International Consortium, dividing them into single-center test (n = 371) and multicenter validation (n = 216) cohorts. Regenerating islet-derived 3α (Reg3α) serum concentration of day 0 correlated with clinical data as well as urinary 3-indoxylsulfate (3-IS) and Clostridiales group XIVa, indicators of intestinal microbiome diversity. High Reg3α concentration at day 0 of ASCT was associated with higher 1-year transplant-related mortality (TRM) in both cohorts (P < .001). Cox regression analysis revealed high Reg3α at day 0 as an independent prognostic factor for 1-year TRM. Multivariable analysis showed an independent correlation of high Reg3α concentrations at day 0 with early systemic antibiotic (AB) treatment. Urinary 3-IS (P = .04) and Clostridiales group XIVa (P = .004) were lower in patients with high vs those with low day 0 Reg3α concentrations. In contrast, Reg3α concentrations before conditioning therapy correlated neither with TRM nor disease or treatment-related parameters. Reg3α, a known biomarker of acute GI GVHD correlates with intestinal dysbiosis, induced by early AB treatment in the period of pretransplant conditioning. Serum concentrations of Reg3α measured on the day of graft infusion are predictive of the risk for TRM of ASCT recipients.

From birth to death: The hardworking life of Paneth cell in the small intestine

Paneth cells are a group of unique intestinal epithelial cells, and they play an important role in host-microbiota interactions. At the origin of Paneth cell life, several pathways such as Wnt, Notch, and BMP signaling, affect the differentiation of Paneth cells. After lineage commitment, Paneth cells migrate downward and reside in the base of crypts, and they possess abundant granules in their apical cytoplasm. These granules contain some important substances such as antimicrobial peptides and growth factors. Antimicrobial peptides can regulate the composition of microbiota and defend against mucosal penetration by commensal and pathogenic bacteria to protect the intestinal epithelia. The growth factors derived from Paneth cells contribute to the maintenance of the normal functions of intestinal stem cells. The presence of Paneth cells ensures the sterile environment and clearance of apoptotic cells from crypts to maintain the intestinal homeostasis. At the end of their lives, Paneth cells experience different types of programmed cell death such as apoptosis and necroptosis. During intestinal injury, Paneth cells can acquire stem cell features to restore the intestinal epithelial integrity. In view of the crucial roles of Paneth cells in the intestinal homeostasis, research on Paneth cells has rapidly developed in recent years, and the existing reviews on Paneth cells have mainly focused on their functions of antimicrobial peptide secretion and intestinal stem cell support. This review aims to summarize the approaches to studying Paneth cells and introduce the whole life experience of Paneth cells from birth to death.

Radiation-induced Cell Death and Its Mechanisms

ABSTRACT

With rapid technical advances, ionizing radiation has been put into wider application in ordinary living, with the worst cytological effect on the human body being cell death. Moreover, according to the Nomenclature Committee on Cell Death, the method of radiation-induced cell death, usually classified as interphase and proliferative death, undergoes more detailed classifications oriented by its molecular mechanism. Elaborating its mode and molecular mechanism is crucial for the protection and treatment of radiation injury, as well as the radiotherapy and recovery of tumors. Varying with the changes of the radiation dose and the environment, the diverse targets and pathways of ionizing radiation result in various cell deaths. This review focuses on classifications of radiation-induced cell death and its molecular mechanism. We also examine the main characteristics of ionizing radiation-induced cell death. The modes of radiation-induced cell death can be classified as apoptosis, necrosis, autophagy-dependent cell death, pyroptosis, ferroptosis, immunogenic cell death, and non-lethal processes. Once the dose is high enough, radiation effects mostly appear as destructiveness ("destructiveness" is used to describe a situation in which cells do not have the opportunity to undergo a routine death process, in which case high-dose radiation works like a physical attack). This breaks up or even shatters cells, making it difficult to find responses of the cell itself. Due to diversities concerning cell phenotypes, phases of cell cycle, radiation dose, and even cellular subregions, various methods of cell death occur, which are difficult to identify and classify. Additionally, the existence of common initial activation and signaling molecules among all kinds of cell deaths, as well as sophisticated crossways in cellular molecules, makes it more laborious to distinguish and classify various cell deaths.

SUMO2-mediated SUMOylation of SH3GLB1 promotes ionizing radiation-induced hypertrophic cardiomyopathy through mitophagy activation

Hypertrophic cardiomyopathy (HC) is characterized by the enlargement of individual cardiomyocytes, which is a typical pathophysiological process that occurs in various cardiovascular diseases. Ionizing radiation (IR) is an important independent risk factor for hypertrophic cardiomyopathy, but the underlying molecular mechanism is still unclear. In the present study, we aimed to clarify the role of IR in promoting cardiac hypertrophy and investigate the mechanism by which the SUMO2-mediated SUMOylation of SH3GLB1 affects mitophagy in IR-induced cardiac hypertrophy. In vivo, IR promoted cardiac hypertrophy by activating mitophagy. In vitro, IR upregulated PINK1 and Parkin protein expression and damaged mitochondrial morphological structure. We further demonstrated that SH3GLB1 deficiency inhibited mitophagy activation and restored mitochondrial cristae, revealing a regulatory role of SH3GLB1 in cardiac hypertrophy. IR promoted interactions between SH3GLB1 and mitochondrial membrane proteins, such as MFN1/2, TOM20 and Drp1, further indicating that the mechanism by which SH3GLB1 functions in cardiac hypertrophy might involve mitophagy. A bioinformatics prediction found that SUMO2 could SUMOylate SH3GLB1 at position K82. Consistent with this finding, both co-IP assays and laser confocal microscopy showed that IR promoted the interaction and colocalization of SUMO2 and SH3GLB1. In summary, our study identifies IR as an important factor that promotes hypertrophic cardiomyopathy by accelerating the activation of mitophagy through the SUMO2-mediated SUMOylation of SH3GLB1; thus, IR exerts dual therapeutic effects in the treatment of thoracic tumours with long-term radiotherapy. Additionally, this study provides novel treatment strategies and targets for preventing the hypertrophic cardiomyopathy caused by thoracic tumour radiotherapy. Furthermore, SH3GLB1 may be a promising experimental target for the development of strategies for treating cardiovascular diseases caused by IR.

Cell Signaling Pathways That Promote Radioresistance of Cancer Cells

Radiation therapy (RT) is a standard treatment for solid tumors and about 50% of patients with cancer, including pediatric cancer, receive RT. While RT has significantly improved the overall survival and quality of life of cancer patients, its efficacy has still been markedly limited by radioresistance in a significant number of cancer patients (intrinsic or acquired), resulting in failure of the RT control of the disease. Radiation eradicates cancer cells mainly by causing DNA damage. However, radiation also concomitantly activates multiple prosurvival signaling pathways, which include those mediated by ATM, ATR, AKT, ERK, and NF-κB that promote DNA damage checkpoint activation/DNA repair, autophagy induction, and/or inhibition of apoptosis. Furthermore, emerging data support the role of YAP signaling in promoting the intrinsic radioresistance of cancer cells, which occurs through its activation of the transcription of many essential genes that support cell survival, DNA repair, proliferation, and the stemness of cancer stem cells. Together, these signaling pathways protect cancer cells by reducing the magnitude of radiation-induced cytotoxicity and promoting radioresistance. Thus, targeting these prosurvival signaling pathways could potentially improve the radiosensitivity of cancer cells. In this review, we summarize the contribution of these pathways to the radioresistance of cancer cells.

Ionizing Radiation-Induced Brain Cell Aging and the Potential Underlying Molecular Mechanisms

Population aging is occurring rapidly worldwide, challenging the global economy and healthcare services. Brain aging is a significant contributor to various age-related neurological and neuropsychological disorders, including Alzheimer's disease and Parkinson's disease. Several extrinsic factors, such as exposure to ionizing radiation, can accelerate senescence. Multiple human and animal studies have reported that exposure to ionizing radiation can have varied effects on organ aging and lead to the prolongation or shortening of life span depending on the radiation dose or dose rate. This paper reviews the effects of radiation on the aging of different types of brain cells, including neurons, microglia, astrocytes, and cerebral endothelial cells. Further, the relevant molecular mechanisms are discussed. Overall, this review highlights how radiation-induced senescence in different cell types may lead to brain aging, which could result in the development of various neurological and neuropsychological disorders. Therefore, treatment targeting radiation-induced oxidative stress and neuroinflammation may prevent radiation-induced brain aging and the neurological and neuropsychological disorders it may cause.

Gut commensal bacteria, Paneth cells and their relations to radiation enteropathy

In steady state, the intestinal epithelium forms an important part of the gut barrier to defend against luminal bacterial attack. However, the intestinal epithelium is compromised by ionizing irradiation due to its inherent self-renewing capacity. In this process, small intestinal bacterial overgrowth is a critical event that reciprocally alters the immune milieu. In other words, intestinal bacterial dysbiosis induces inflammation in response to intestinal injuries, thus influencing the repair process of irradiated lesions. In fact, it is accepted that commensal bacteria can generally enhance the host radiation sensitivity. To address the determination of radiation sensitivity, we hypothesize that Paneth cells press a critical "button" because these cells are central to intestinal health and disease by using their peptides, which are responsible for controlling stem cell development in the small intestine and luminal bacterial diversity. Herein, the most important question is whether Paneth cells alter their secretion profiles in the situation of ionizing irradiation. On this basis, the tolerance of Paneth cells to ionizing radiation and related mechanisms by which radiation affects Paneth cell survival and death will be discussed in this review. We hope that the relevant results will be helpful in developing new approaches against radiation enteropathy.

Radiation induces EIF2AK3/PERK and ERN1/IRE1 mediated pro-survival autophagy

Cellular effects of ionizing radiation include oxidative damage to macromolecules, unfolded protein response (UPR) and metabolic imbalances. Oxidative stress and UPR have been shown to induce macroautophagy/autophagy in a context-dependent manner and are crucial factors in determining the fate of irradiated cells. However, an in-depth analysis of the relationship between radiation-induced damage and autophagy has not been explored. In the present study, we investigated the relationship between radiation-induced oxidative stress, UPR and autophagy in murine macrophage cells. A close association was observed between radiation-induced oxidative burst, UPR and induction of autophagy, with the possible involvement of EIF2AK3/PERK (eukaryotic translation initiation factor 2 alpha kinase 3) and ERN1/IRE1 (endoplasmic reticulum [ER] to nucleus signaling 1). Inhibitors of either UPR or autophagy reduced the cell survival indicating the importance of these processes after radiation exposure. Moreover, modulation of autophagy affected lethality in the whole body irradiated C57BL/6 mouse. These findings indicate that radiation-induced autophagy is a pro-survival response initiated by oxidative stress and mediated by EIF2AK3 and ERN1. Abbreviations: ACTB: actin, beta; ATF6: activating transcription factor 6; ATG: autophagy-related; BafA1: bafilomycin A1; CQ: chloroquine; DBSA: 3,5-dibromosalicylaldehyde; EIF2AK3: eukaryotic translation initiation factor 2 alpha kinase 3; ERN1: endoplasmic reticulum (ER) to nucleus signaling 1; IR: ionizing radiation; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; 3-MA: 3-methyladenine; MTOR: mechanistic target of rapamycin kinase; NAC: N-acetyl-L-cysteine; PARP1: poly (ADP-ribose) polymerase family, member 1; 4-PBA: 4-phenylbutyrate; Rap: rapamycin; ROS: reactive oxygen species; UPR: unfolded protein response; XBP1: x-box binding protein 1.

TLR4 Agonist Monophosphoryl Lipid A Alleviated Radiation-Induced Intestinal Injury

The small intestine is one of the most sensitive organs to irradiation injury, and the development of high effective radioprotectants especially with low toxicity for intestinal radiation sickness is urgently needed. Monophosphoryl lipid A (MPLA) was found to be radioprotective in our previous study, while its effect against the intestinal radiation injury remained unknown. In the present study, we firstly determined the intestinal apoptosis after irradiation injury according to the TUNEL assay. Subsequently, we adopted the immunofluorescence technique to assess the expression levels of different biomarkers including Ki67, γ-H2AX, and defensin 1 in vivo. Additionally, the inflammatory cytokines were detected by RT-PCR. Our data indicated that MPLA could protect the intestine from ionizing radiation (IR) damage through activating TLR4 signal pathway and regulating the inflammatory cytokines. This research shed new light on the protective effect of the novel TLR4 agonist MPLA against intestine detriment induced by IR.

Radiation: a poly-traumatic hit leading to multi-organ injury

The range of radiation threats we face today includes everything from individual radiation exposures to mass casualties resulting from a terrorist incident, and many of these exposure scenarios include the likelihood of additional traumatic injury as well. Radiation injury is defined as an ionizing radiation exposure inducing a series of organ injury within a specified time. Severity of organ injury depends on the radiation dose and the duration of radiation exposure. Organs and cells with high sensitivity to radiation injury are the skin, the hematopoietic system, the gastrointestinal (GI) tract, spermatogenic cells, and the vascular system. In general, acute radiation syndrome (ARS) includes DNA double strand breaks (DSB), hematopoietic syndrome (bone marrow cells and circulatory cells depletion), cutaneous injury, GI death, brain hemorrhage, and splenomegaly within 30 days after radiation exposure. Radiation injury sensitizes target organs and cells resulting in ARS. Among its many effects on tissue integrity at various levels, radiation exposure results in activation of the iNOS/NF-kB/NF-IL6 and p53/Bax pathways; and increases DNA single and double strand breaks, TLR signaling, cytokine concentrations, bacterial infection, cytochrome c release from mitochondria to cytoplasm, and possible PARP-dependent NAD and ATP-pool depletion. These alterations lead to apoptosis and autophagy and, as a result, increased mortality. In this review, we summarize what is known about how radiation exposure leads to the radiation response with time. We also describe current and prospective countermeasures relevant to the treatment and prevention of radiation injury.

Autophagy Promotes the Repair of Radiation-Induced DNA Damage in Bone Marrow Hematopoietic Cells via Enhanced STAT3 Signaling

Autophagy protects hematopoietic cells from radiation damage in part by promoting DNA damage repair. However, the molecular mechanisms by which autophagy regulates DNA damage repair remain largely elusive. Here, we report that this radioprotective effect of autophagy depends on STAT3 signaling in murine bone marrow mononuclear cells (BM-MNCs). Specifically, we found that STAT3 activation and nuclear translocation in BM-MNCs were increased by activation of autophagy with an mTOR inhibitor and decreased by knockout of the autophagy gene Atg7. The autophagic regulation of STAT3 activation is likely mediated by induction of KAP1 degradation, because we showed that KAP1 directly interacted with STAT3 in the cytoplasm and knockdown of KAP1 increased the phosphorylation and nuclear translocation of STAT3. Subsequently, activated STAT3 transcriptionally upregulated the expression of BRCA1, which increased the ability of BM-MNCs to repair radiation-induced DNA damage. This novel finding that activation of autophagy can promote DNA damage repair in BM-MNCs via the ATG-KAP1-STAT3-BRCA1 pathway suggests that autophagy plays an important role in maintaining genomic integrity of BM-MNCs and its activation may confer protection of BM-MNCs against radiation-induced genotoxic stress.

Synergistic effect of aluminum and ionizing radiation upon ultrastructure, oxidative stress and apoptotic alterations in Paneth cells of rat intestine

Environmental and occupational exposure to aluminum along with ionizing radiation results in serious health problems. This study was planned to investigate the impact of oxidative stress provoked by exposure to ionizing radiation with aluminum administration upon cellular ultra structure and apoptotic changes in Paneth cells of rat small intestine . Animals received daily aluminum chloride by gastric gavage at a dose 0.5 mg/Kg BW for 4 weeks. Whole body gamma irradiation was applied at a dose 2 Gy/week up to 8 Gy. Ileum malondialdehyde, advanced oxidative protein products, protein carbonyl and tumor necrosis factor-alpha were assessed as biomarkers of lipid peroxidation, protein oxidation and inflammation respectively along with superoxide dismutase, catalase, and glutathione peroxidase activities as enzymatic antioxidants. Moreover, analyses of cell cycle division and apoptotic changes were evaluated by flow cytometry. Intestinal cellular ultra structure was investigated using transmission electron microscope.Oxidative and inflammatory stresses assessment in the ileum of rats revealed that aluminum and ionizing radiation exposures exhibited a significant effect upon the increase in oxidative stress biomarkers along with the inflammatory marker tumor necrosis factor-α accompanied by a significant decreases in the antioxidant enzyme activities. Flow cytometric analyses showed significant alterations in the percentage of cells during cell cycle division phases along with significant increase in apoptotic cells. Ultra structurally, intestinal cellular alterations with marked injury in Paneth cells at the sites of bacterial translocation in the crypt of lumens were recorded. The results of this study have clearly showed that aluminum and ionizing radiation exposures induced apoptosis with oxidative and inflammatory disturbance in the Paneth cells of rat intestine, which appeared to play a major role in the pathogenesis of cellular damage. Furthermore, the interaction of these two intestinal toxic routes was found to be synergistic.

Increase in the radioresistance of normal skin fibroblasts but not tumor cells by mechanical injury

The timing of radiation after mechanical injury such as in the case of surgery is considered a clinical challenge because radiation is assumed to impair wound healing. However, the physiological responses and underlying mechanisms of this healing impairment are still unclear. Here, we show that mechanical injury occurring before ionizing radiation decreases radiation-induced cell damage and increases cell repair in normal fibroblasts but not tumor cells in vitro and in vivo. At the molecular level, mechanical injury interrupts focal adhesion complexes and cell–cell cadherin interactions, transducing mechanical signals into intracellular chemical signals via activation of the phosphatidylinositol 3-kinase (PI3K), Akt, and glycogen synthase kinase 3 beta (GSK-3β) pathways. We show that subsequent nuclear translocation of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) and β-catenin strengthen the stemness, antioxidant capabilities, and DNA double-strand break repair abilities of fibroblasts, ultimately contributing to increased radioresistance. Our findings demonstrate that mechanical injury to normal fibroblasts enhances radioresistance and may therefore question conventional wisdom surrounding the timing of radiation after surgery.

Unraveling Fungal Radiation Resistance Regulatory Networks through the Genome-Wide Transcriptome and Genetic Analyses of Cryptococcus neoformans

The basidiomycetous fungus Cryptococcus neoformans has been known to be highly radiation resistant and has been found in fatal radioactive environments such as the damaged nuclear reactor at Chernobyl. To elucidate the mechanisms underlying the radiation resistance phenotype of C. neoformans, we identified genes affected by gamma radiation through genome-wide transcriptome analysis and characterized their functions. We found that genes involved in DNA damage repair systems were upregulated in response to gamma radiation. Particularly, deletion of recombinase RAD51 and two DNA-dependent ATPase genes, RAD54 and RDH54, increased cellular susceptibility to both gamma radiation and DNA-damaging agents. A variety of oxidative stress response genes were also upregulated. Among them, sulfiredoxin contributed to gamma radiation resistance in a peroxiredoxin/thioredoxin-independent manner. Furthermore, we found that genes involved in molecular chaperone expression, ubiquitination systems, and autophagy were induced, whereas genes involved in the biosynthesis of proteins and fatty acids/sterols were downregulated. Most importantly, we discovered a number of novel C. neoformans genes, the expression of which was modulated by gamma radiation exposure, and their deletion rendered cells susceptible to gamma radiation exposure, as well as DNA damage insults. Among these genes, we found that a unique transcription factor containing the basic leucine zipper domain, named Bdr1, served as a regulator of the gamma radiation resistance of C. neoformans by controlling expression of DNA repair genes, and its expression was regulated by the evolutionarily conserved DNA damage response protein kinase Rad53. Taken together, the current transcriptome and functional analyses contribute to the understanding of the unique molecular mechanism of the radiation-resistant fungus C. neoformans.

Although there are no natural environments under intense radiation, some living organisms have been found to show high radiation resistance. Organisms harboring the ability of radiation resistance have unique regulatory networks to overcome this stress. Cryptococcus neoformans is one of the radiation-resistant fungi and is found in highly radioactive environments. However, it remains elusive how radiation-resistant eukaryotic microorganisms work differentially from radiation-sensitive ones. Here, we performed transcriptome analysis of C. neoformans to explore gene expression profiles after gamma radiation exposure and functionally characterized some of identified radiation resistance genes. Notably, we identified a novel regulator of radiation resistance, named Bdr1 (a bZIP TF for DNA damage response 1), which is a transcription factor (TF) that is not closely homologous to any known TF and is transcriptionally controlled by the Rad53 kinase. Therefore, our work could shed light on understanding not only the radiation response but also the radiation resistance mechanism of C. neoformans.

Repression of the autophagic response sensitises lung cancer cells to radiation and chemotherapy

Background:

The cellular autophagic response to radiation is complex. Various cells and tissues respond differentially to radiation, depending on both the dose of exposure and the time post irradiation. In the current study, we determined the autophagosomal and lysosomal response to radiation in lung cancer cell lines by evaluating the expression of the associated proteins, as well as the effect of relevant gene silencing in radio and chemosensitisation. Furthermore, tumour sensitisation was evaluated in in vivo autophagic gene silencing model after irradiation.

Methods:

A549 and H1299 cell lines were utilised as in vitro cancer models. Both cell lines were transfected with various small-interfering RNAs, silencing auto-lysosomal genes, and irradiated with 4 Gy. Cell growth response was evaluated with AlamarBlue assay. Western blot and confocal microscopy were utilised for the characterisation of the auto-lysosomal flux. Also, the H1299 cell line was stable transfected with small-hairpin RNA of the MAP1LC3A gene, and the tumour radiosensitisation in Athymic Nude-Foxn1^nu was evaluated.

Results:

Following exposure to 4 Gy of radiation, A549 cells exhibited a significant induction of the autophagic flux, which was not supported by transcriptional activation of auto-lysosomal genes (LC3A, LC3B, p62, TFEB and LAMP2a), resulting in aggresome accumulation. Recovery of transcriptional activity and autophagy efficacy occurred 7 days post irradiation. Alternatively, H1299 cells, a relatively radio-resistant cell line, sharply responded with an early (at 2 days) transcriptional activation of auto-lysosomal genes that sustained an effective autophagosomal flux, resulting in adequate aggresome clearance. Subsequently, we tested the silencing of four genes (LC3A, LC3B, TFEB and LAMP2a), confirming a significant radiosensitisation and chemosensitisation to various chemotherapeutic agents, including cisplatin and taxanes. In mouse xenografts, exposure to radiation significantly reduced tumour growth (P<0.001), which was exacerbated among shLC3A-H1299 transfected tumours.

Conclusions:

The ability of lung cancer cells to survive after irradiation at 4 Gy depends on their ability to sustain a functional autophagic flux. Abrogation of such ability results in increased radiosensitivity and susceptibility to various chemotherapy agents. Selective inhibitors of cancer cell autophagic function may prove important for the eradication of lung cancer.

Ciprofloxacin Therapy Results in Mitigation of ATP Loss after Irradiation Combined with Wound Trauma: Preservation of Pyruvate Dehydrogenase and Inhibition of Pyruvate Dehydrogenase Kinase 1

Ionizing radiation exposure combined with wound injury increases animal mortalities than ionizing radiation exposure alone. Ciprofloxacin (CIP) is in the fluroquinolone family of synthetic antibiotic that are available from the strategic national stockpile for emergency use and is known to inhibit bacterial sepsis. The purpose of this study was to evaluate the efficacy of ciprofloxacin as a countermeasure to combined injury mortality and determine the signaling proteins involved in energy machinery. B6D2F1/J female mice were randomly assigned to receive either 9.75 Gy irradiation with Co-60 gamma rays followed by skin wounding (combined injury; CI) or sham procedure (sham). Either ciprofloxacin (90 mg/kg/day) or vehicle (VEH) (water) was administered orally to these mice 2 h after wounding and thereafter daily for 10 days. Determination of tissue adenosine triphosphate (ATP) was conducted, and immunoblotting for signaling proteins involved in ATP machinery was performed. Combined injury resulted in 60% survival after 10 days compared to 100% survival in the sham group. Furthermore, combined injury caused significant reductions of ATP concentrations in ileum, pancreas, brain, spleen, kidney and lung (-25% to -95%) compared to the sham group. Ciprofloxacin administration after combined injury resulted in 100% survival and inhibited reductions in ileum and kidney ATP production. Ileum protein levels of heat-shock protein 70 kDa (HSP-70, a chaperone protein involved in ATP synthesis) and pyruvate dehydrogenase (PDH, an enzyme complex crucial to conversion of pyruvate to acetyl CoA for entrance into TCA cycle) were significantly lower in the CI group (vs. sham group). Using immunoprecipitation and immunoblotting, HSP-70-PDH complex was found to be present in the ileum tissue of CI mice treated with ciprofloxacin. Furthermore, phosphorylation of serine residues of PDH resulting in inactivating PDH enzymatic activity, which occurred after combined injury, was inhibited with ciprofloxacin treatment, thus enabling PDH to increase ATP production. Increased ileum levels of pyruvate dehydrogenase kinase 1 protein (PDK1, an enzyme responsible for PDH phosphorylation) after combined injury were also prevented by ciprofloxacin treatment. Taken together, these data suggest that ciprofloxacin oral administration after combined injury had a role in sustained ileum ATP levels, and may have acted through preservation of PDH by HSP-70 and inhibition of PDK1. These molecular changes in the ileum are simply one of a host of mechanisms working in concert with one another by which ciprofloxacin treatment mitigates body weight loss and drastically enhances subsequent survival after combined injury. To this end, our findings indicate that oral treatment of ciprofloxacin is a valuable therapeutic treatment after irradiation with combined injury and warrants further analyses to elucidate the precise mechanisms involved.

NF-kB as a key player in regulation of cellular radiation responses and identification of radiation countermeasures

Nuclear factor (NF)-κB is a transcription factor that plays significant role in immunity, cellular survival and inhibition of apoptosis, through the induction of genetic networks. Depending on the stimulus and the cell type, the members of NF-κB related family (RelA, c-Rel, RelB, p50, and p52), forms different combinations of homo and hetero-dimers. The activated complexes (Es) translocate into the nucleus and bind to the 10bp κB site of promoter region of target genes in stimulus specific manner. In response to radiation, NF-κB is known to reduce cell death by promoting the expression of anti-apoptotic proteins and activation of cellular antioxidant defense system. Constitutive activation of NF-κB associated genes in tumour cells are known to enhance radiation resistance, whereas deletion in mice results in hypersensitivity to IR-induced GI damage. NF-κB is also known to regulate the production of a wide variety of cytokines and chemokines, which contribute in enhancing cell proliferation and tissue regeneration in various organs, such as the GI crypts stem cells, bone marrow etc., following exposure to IR. Several other cytokines are also known to exert potent pro-inflammatory effects that may contribute to the increase of tissue damage following exposure to ionizing radiation. Till date there are a series of molecules or group of compounds that have been evaluated for their radio-protective potential, and very few have reached clinical trials. The failure or less success of identified agents in humans could be due to their reduced radiation protection efficacy. In this review we have considered activation of NF-κB as a potential marker in screening of radiation countermeasure agents (RCAs) and cellular radiation responses. Moreover, we have also focused on associated mechanisms of activation of NF-κB signaling and their specified family member activation with respect to stimuli. Furthermore, we have categorized their regulated gene expressions and their function in radiation response or modulation. In addition, we have discussed some recently developed radiation countermeasures in relation to NF-κB activation

Innate immune activation by tissue injury and cell death in the setting of hematopoietic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation (Allo-HSCT) with donor lymphocyte infusion is the mainstay of treatment for many types of hematological malignancies, but the therapeutic effect and prevention of relapse is complicated by donor T-cell recognition and attack of host tissue in a process known as graft-versus-host disease (GvHD). Cytotoxic myeloablative conditioning regimens used prior to Allo-HSCT result in the release of endogenous innate immune activators that are increasingly recognized for their role in creating a pro-inflammatory milieu. This increased inflammatory state promotes allogeneic T-cell activation and the induction and perpetuation of GvHD. Here, we review the processes of cellular response to injury and cell death that are relevant following Allo-HSCT and present the current evidence for a causative role of a variety of endogenous innate immune activators in the mediation of sterile inflammation following Allo-HSCT. Finally, we discuss the potential therapeutic strategies that target the endogenous pathways of innate immune activation to decrease the incidence and severity of GvHD following Allo-HSCT.

Protracted Oxidative Alterations in the Mechanism of Hematopoietic Acute Radiation Syndrome

The biological effects of high-dose total body ionizing irradiation [(thereafter, irradiation (IR)] are attributed to primary oxidative breakage of biomolecule targets, mitotic, apoptotic and necrotic cell death in the dose-limiting tissues, clastogenic and epigenetic effects, and cascades of functional and reactive responses leading to radiation sickness defined as the acute radiation syndrome (ARS). The range of remaining and protracted injuries at any given radiation dose as well as the dynamics of post-IR alterations is tissue-specific. Therefore, functional integrity of the homeostatic tissue barriers may decline gradually within weeks in the post-IR period culminating with sepsis and failure of organs and systems. Multiple organ failure (MOF) leading to moribundity is a common sequela of the hemotapoietic form of ARS (hARS). Onset of MOF in hARS can be presented as “two-hit phenomenon” where the “first hit” is the underlying consequences of the IR-induced radiolysis in cells and biofluids, non-septic inflammation, metabolic up-regulation of pro-oxidative metabolic reactions, suppression of the radiosensitive hematopoietic and lymphoid tissues and the damage to gut mucosa and vascular endothelium. While the “second hit” derives from bacterial translocation and spread of the bacterial pathogens and inflammagens through the vascular system leading to septic inflammatory, metabolic responses and a cascade of redox pro-oxidative and adaptive reactions. This sequence of events can create a ground for development of prolonged metabolic, inflammatory, oxidative, nitrative, and carbonyl, electrophilic stress in crucial tissues and thus exacerbate the hARS outcomes. With this perspective, the redox mechanisms, which can mediate the IR-induced protracted oxidative post-translational modification of proteins, oxidation of lipids and carbohydrates and their countermeasures in hARS are subjects of the current review. Potential role of ubiquitous, radioresistant mesenchymal stromal cells in the protracted responses to IR and IR-related septicemia is also discussed.

Krüppel-like factor 4 is a radioprotective factor for the intestine following γ-radiation-induced gut injury in mice

Gut radiation-induced injury is a concern during treatment of patients with cancer. Krüppel-like factor 4 (KLF4) is expressed in differentiated villous epithelial cells of the small intestine. We previously showed that KLF4 protects cells from apoptosis following γ-irradiation in vitro. We sought to determine whether KLF4 mediates the small intestinal response to γ-irradiation in vivo. Mice with intestinal epithelium-specific deletion of Klf4 (Klf4(ΔIS)) and control (Klf4(fl/fl)) mice were irradiated with total-body γ-radiation. Following irradiation, the Klf4(ΔIS) mice had significantly increased mortality compared with irradiated Klf4(fl/fl) mice. Immunohistochemistry and immunofluorescence staining were used to assess the morphological changes, levels of proliferation, and apoptosis in the intestinal epithelium. At 96 h following irradiation, there was a regenerative response manifested by an expansion of the proliferative zone in both mouse groups, with the control mice having a higher proliferative activity than the Klf4(ΔIS) group. In addition, there was a significant increase in the number of Klf4/Ki67-copositive cells in the irradiated control mice compared with unirradiated mice. Also, the irradiated Klf4(ΔIS) mice had a significantly higher number of crypt cells positive for apoptosis, p53, and p21 compared with irradiated Klf4(fl/fl) mice. Taken together, our data suggest that Klf4 may function as a radioprotective factor against gastrointestinal syndrome in mice following γ-irradiation by inhibiting apoptosis in the acute response to irradiation and contributing to crypt regeneration.

Important role of autophagy in endothelial cell response to ionizing radiation

Objectives

Vasculature damage is an important contributor to the side-effects of radiotherapy. The aim of this study is to provide insights into the radiobiology of the autophagic response of endothelial cells.

Methods and Materials

Human umbilical vascular endothelial cells (HUVEC) were exposed to 2 Gy of ionizing radiation (IR) and studied using confocal microscopy and western blot analysis, at 4 and 8 days post-irradiation. The role of autophagy flux in HUVEC radio-sensitivity was also examined.

Results

IR-induced accumulation of LC3A+, LC3B+ and p62 cytoplasmic vacuoles, while in double immunostaining with lysosomal markers (LAMP2a and CathepsinD) repression of the autophagolysosomal flux was evident. Autophagy-related proteins (ATF4, HIF1α., HIF2α, Beclin1) were, however, induced excluding an eventual repressive effect of radiation on autophagy initiating protein expression. Exposure of HUVEC to SMER28, an mTOR-independent inducer of autophagy, enhanced proLC3 and LC3A, B-I protein expression and accelerated the autophagic flux. Pre-treatment of HUVEC with SMER28 protected against the blockage of autophagic flux induced by IR and conferred radio-resistance. Suppression of LC3A/LC3B proteins with siRNAs resulted in radio-sensitization.

Conclusions

The current data provide a rationale for the development of novel radioprotection policies targeting the autophagic pathway.

Paneth cells: maestros of the small intestinal crypts

Paneth cells are highly specialized epithelial cells of the small intestine, where they coordinate many physiological functions. First identified more than a century ago on the basis of their readily discernible secretory granules by routine histology, these cells are located at the base of the crypts of Lieberkühn, tiny invaginations that line the mucosal surface all along the small intestine. Investigations over the past several decades determined that these cells synthesize and secrete substantial quantities of antimicrobial peptides and proteins. More recent studies have determined that these antimicrobial molecules are key mediators of host-microbe interactions, including homeostatic balance with colonizing microbiota and innate immune protection from enteric pathogens. Perhaps more intriguing, Paneth cells secrete factors that help sustain and modulate the epithelial stem and progenitor cells that cohabitate in the crypts and rejuvenate the small intestinal epithelium. Dysfunction of Paneth cell biology contributes to the pathogenesis of chronic inflammatory bowel disease.

Ciprofloxacin modulates cytokine/chemokine profile in serum, improves bone marrow repopulation, and limits apoptosis and autophagy in ileum after whole body ionizing irradiation combined with skin-wound trauma

Radiation combined injury (CI) is a radiation injury (RI) combined with other types of injury, which generally leads to greater mortality than RI alone. A spectrum of specific, time-dependent pathophysiological changes is associated with CI. Of these changes, the massive release of pro-inflammatory cytokines, severe hematopoietic and gastrointestinal losses and bacterial sepsis are important treatment targets to improve survival. Ciprofloxacin (CIP) is known to have immunomodulatory effect besides the antimicrobial activity. The present study reports that CIP ameliorated pathophysiological changes unique to CI that later led to major mortality. B6D2F1/J mice received CI on day 0, by RI followed by wound trauma, and were treated with CIP (90 mg/kg p.o., q.d. within 2 h after CI through day 10). At day 10, CIP treatment not only significantly reduced pro-inflammatory cytokine and chemokine concentrations, including interleukin-6 (IL-6) and KC (i.e., IL-8 in human), but it also enhanced IL-3 production compared to vehicle-treated controls. Mice treated with CIP displayed a greater repopulation of bone marrow cells. CIP also limited CI-induced apoptosis and autophagy in ileal villi, systemic bacterial infection, and IgA production. CIP treatment led to LD_0/10 compared to LD_20/10 for vehicle-treated group after CI. Given the multiple beneficial activities of CIP shown in our experiments, CIP may prove to be a useful therapeutic drug for CI.

Enhanced mitophagy in Sertoli cells of ethanol-treated rats: morphological evidence and clinical relevance

Although chronic ethanol consumption results in Sertoli cell vacuolization and augmented testicular germ cell apoptosis via death receptor and mitochondrial pathways, Sertoli cells are resistant to apoptosis. The aim of this study was to examine whether the activation of autophagy in the Sertoli cells of ethanol-treated rats (ETR) may have a role in their survival. Adult Wistar rats were fed either 5% ethanol in Lieber-DeCarli liquid diet or an isocaloric control diet for 12 weeks. The TUNEL method demonstrated that Sertoli cells were always TUNEL-negative despite the presence of many apoptotic germ cells in ETR, supporting our previous studies. Electron microscopy revealed the presence of large numbers of autophagic vacuoles (AVs) in Sertoli cells of ETR compared to few AVs in control testes. Most of the AVs in Sertoli cells of ETR enveloped and sequestered damaged and abnormally shaped mitochondria, without cytoplasm, indicating mitochondrial autophagy (mitophagy). Immuno-electron microscopy showed the localization of LC3, a specific marker of early AVs (autophagosomes), around AVs sequestering mitochondria in Sertoli cells of ETR. Immunohistochemical staining of LC3 demonstrated a punctate pattern in Sertoli cells of ETR, confirming the formation of autophagosomes, while LC3 puncta were almost absent in control testes. Moreover, increased immunoreactivity of LAMP-2, a lysosomal membrane protein and marker of late AVs (autolysosomes), was mainly observed in Sertoli cells of ETR, with weaker expression in control testes. Via the deletion of pro-apoptotic damaged mitochondria, enhanced Sertoli cell mitophagy in ETR may be an anti-apoptotic mechanism that is essential for spermatogenesis.

Response of crypt paneth cells in the small intestine following total-body gamma-irradiation

Ionizing irradiation causes damage and functional failure of irradiation-sensitive systems and tissues such as small intestine. The molecular mechanisms underlying inflammatory and adaptive responses to acute irradiation damage are poorly understood. Using a mouse model of total-body γ-irradiation, we assessed the irradiation response of crypt host-defense Paneth cells by measuring alpha-defensin 4 (AD4) expression and correlated the gathered data with activation of the caspase-1/IL-1β inflammatory signaling cascade. The irradiation injury was produced in CD2F1 mice exposed to 9.25 Gy γ-radiation. This dose resulted in 85-100 percent mortality at the 15(th) day post-irradiation. Small intestine tissue samples were collected at the 7th day post-irradiation. Assessment of irradiation-associated pro-inflammatory alterations in small intestine tissue and expression of AD4 in Paneth cells was conducted using confocal immunofluorescence imaging, transmission electron microscopy (TEM), light microscopy, and immunoblotting techniques. The small intestine analysis revealed an increase in the precursor form of IL-1β, the activated form of IL-1β, and the activated form of caspase-1 (p10 CASP-1) at the 7(th) day post-irradiation. Immunoprecipitation analysis showed increased interaction between IL-1β and p10 CASP-1 after irradiation. This effect was observed in the irradiated small intestine and CD15-positive Paneth cells using confocal imaging techniques. The pro-inflammatory alterations in Paneth cells were accompanied by increases in AD4 mRNA and its 8 kD peptide product. Paneth cell secretory activity was observed at the sites of bacterial translocation in the crypt lumens. These data suggest that Paneth cells can contribute to small intestine inflammatory remodeling during the post-irradiation period.

Lung autophagic response following exposure of mice to whole body irradiation, with and without amifostine

PURPOSE

The effect of ionizing irradiation on the autophagic response of normal tissues is largely unexplored. Abnormal autophagic function may interfere the protein quality control leading to cell degeneration and dysfunction. This study investigates its effect on the autophagic machinery of normal mouse lung.

METHODS AND MATERIALS

Mice were exposed to 6 Gy of whole body γ-radiation and sacrificed at various time points. The expression of MAP1LC3A/LC3A/Atg8, beclin-1, p62/sequestosome-1 and of the Bnip3 proteins was analyzed.

RESULTS

Following irradiation, the LC3A-I and LC3A-II protein levels increased significantly at 72 h and 7 days. Strikingly, LC3A-II protein was increased (5.6-fold at 7 days; p<0.001) only in the cytosolic fraction, but remained unchanged in the membrane fraction. The p62 protein, was significantly increased in both supernatant and pellet fraction (p<0.001), suggesting an autophagosome turnover deregulation. These findings contrast the patterns of starvation-induced autophagy up-regulation. Beclin-1 levels remained unchanged. The Bnip3 protein was significantly increased at 8 h, but it sharply decreased at 72 h (p<0.05). Administration of amifostine (200 mg/kg), 30 min before irradiation, reversed all the LC3A and p62 findings on blots, suggesting restoration of the normal autophagic function. The LC3A and Beclin1 mRNA levels significantly declined following irradiation (p<0.01), whereas Bnip3 levels increased.

CONCLUSIONS

It is suggested that irradiation induces dysfunction of the autophagic machinery in normal lung, characterized by decreased transcription of the LC3A/Beclin-1 mRNA and accumulation of the LC3A, and p62 proteins. Whether this is due to defective maturation or to aberrant degradation of the autophagosomes requires further investigation.

Radiation Combined Injury: DNA Damage, Apoptosis, and Autophagy

Radiation combined injury is defined as an ionizing radiation exposure received in combination with other trauma or physiological insults. The range of radiation threats we face today includes everything from individual radiation exposures to mass casualties resulting from a terrorist nuclear incident, and many of these exposure scenarios include the likelihood of additional traumatic injury. Radiation combined injury sensitizes target organs and cells and exacerbates acute radiation syndrome. Organs and cells with high sensitivity to combined injury are the skin, the hematopoietic system, the gastrointestinal tract, spermatogenic cells, and the vascular system. Among its many effects, radiation combined injury results in decreases in lymphocytes, macrophages, neutrophils, platelets, stem cells, and tissue integrity; activation of the iNOS/NF-κB/NF-IL6 and p53/Bax pathways; and increases in DNA single and double strand breaks, TLR signaling, cytokine concentrations, bacterial infection, and cytochrome c release from mitochondria to cytoplasm. These alterations lead to apoptosis and autophagy and, as a result, increased mortality. There is a pressing need to understand more about the body's response to combined injury in order to be able to develop effective countermeasures, since few currently exist. In this review, we summarize what is known about how combined injury modifies the radiation response, with a special emphasis on DNA damage/repair, signal transduction pathways, apoptosis, and autophagy. We also describe current and prospective countermeasures relevant to the treatment and prevention of combined injury.

Wound trauma increases radiation-induced mortality by activation of iNOS pathway and elevation of cytokine concentrations and bacterial infection

Abstract Although it is documented that concurrent wounding increases mortality from radiation injury, the molecular mechanism of combined injury is unknown. In this study, mice were exposed to gamma radiation followed by skin wounding. Wound trauma exacerbated radiation-induced mortality, reducing the LD(50/30) from 9.65 Gy to 8.95 Gy. Analyses of histopathology, inducible nitric oxide synthase (iNOS), and serum cytokines were performed on mouse ileum and skin at various times after 9.75 Gy and/or wounding. In the ileum, the villi were significantly shortened 3 days postirradiation but not after wounding; combined injury resulted in decreased villus width and tunica muscularis thickness. The skin of mice subjected to combined injury was less cellular and had a smaller healing bud than the skin of mice subjected to wounding alone. Combined injury significantly delayed wound closure times; it also prolonged the increased levels of iNOS protein in the skin and ileum. iNOS up-regulation was correlated with increases in transcription factors, including NF-kappaB and NF-IL6. The increase in NF-IL6 may be due to increases in cytokines, including IL-1beta, -6, -8, -9, -10 and -13, G-CSF, eotaxin, INF-gamma, MCP-1, MIP-1alpha and MIP-1beta. Combined injury resulted in early detection of bacteria in the blood of the heart and liver, whereas radiation alone resulted in later detection of bacteria; only a transient bacteremia occurred after wounding alone. Results suggest that enhancement of iNOS, cytokines and bacterial infection triggered by combined injury may contribute to mortality. Agents that inhibit these responses may prove to be therapeutic for combined injury and may reduce related mortality.

The role of autophagy in Paneth cell differentiation and secretion

Paneth cells are a small intestinal epithelial cell lineage that is considered to have a role in innate immune function. Recent studies on mice with diminished and/or loss of autophagy have suggested that Paneth cells are a primary target in vivo. Interestingly, loss of autophagy affects the secretion of antimicrobial proteins from Paneth cells. Understanding the intersection of the autophagy pathway with the secretory apparatus, which is a key feature of differentiation of Paneth cells, is a key unanswered question.