Protective effects of tauroursodeoxycholate against radiation-induced intestinal injury in a mouse model.

In patients with high-level radiation exposure, gastrointestinal injury is the main cause of death. Despite the severity of damage to the gastrointestinal tract, no specific therapeutic option is available. Tauroursodeoxycholic acid (TUDCA) is a conjugated form of ursodeoxycholic acid that suppresses endoplasmic reticulum (ER) stress and regulates various cell-signaling pathways. We investigated the effect of TUDCA premedication in alleviating intestinal damage and enhancing the survival of C57BL/6 mice administered a lethal dose (15Gy) of focal abdominal irradiation. TUDCA was administered to mice 1 h before radiation exposure, and reduced apoptosis of the jejunal crypts 12 h after irradiation. At later timepoint (3.5 days), irradiated mice manifested intestinal morphological changes that were detected via histological examination. TUDCA decreased the inflammatory cytokine levels and attenuated the decrease in serum citrulline levels after radiation exposure. Although radiation induced ER stress, TUDCA pretreatment decreased ER stress in the irradiated intestinal cells. The effect of TUDCA indicates the possibility of radiation therapy for cancer in tumor cells. TUDCA did not affect cell proliferation and apoptosis in the intestinal epithelium. TUDCA decreased the invasive ability of the CT26 metastatic colon cancer cell line. Reduced invasion after TUDCA treatment was associated with decreased matrix metalloproteinase (MMP)-7 and MMP-13 expression, which play important roles in invasion and metastasis. This study shows a potential role of TUDCA in protecting against radiation-induced intestinal damage and inhibiting tumor cell migration without any radiation and radiation therapy effect.

Chemical chaperones reduce ionizing radiation-induced endoplasmic reticulum stress and cell death in IEC-6 cells.

Radiotherapy, which is one of the most effective approaches to the treatment of various cancers, plays an important role in malignant cell eradication in the pelvic area and abdomen. However, it also generates some degree of intestinal injury. Apoptosis in the intestinal epithelium is the primary pathological factor that initiates radiation-induced intestinal injury, but the mechanism by which ionizing radiation (IR) induces apoptosis in the intestinal epithelium is not clearly understood. Recently, IR has been shown to induce endoplasmic reticulum (ER) stress, thereby activating the unfolded protein response (UPR) signaling pathway in intestinal epithelial cells. However, the consequences of the IR-induced activation of the UPR signaling pathway on radiosensitivity in intestinal epithelial cells remain to be determined. In this study, we investigated the role of ER stress responses in IR-induced intestinal epithelial cell death. We show that chemical ER stress inducers, such as tunicamycin or thapsigargin, enhanced IR-induced caspase 3 activation and DNA fragmentation in intestinal epithelial cells. Knockdown of Xbp1 or Atf6 with small interfering RNA inhibited IR-induced caspase 3 activation. Treatment with chemical chaperones prevented ER stress and subsequent apoptosis in IR-exposed intestinal epithelial cells. Our results suggest a pro-apoptotic role of ER stress in IR-exposed intestinal epithelial cells. Furthermore, inhibiting ER stress may be an effective strategy to prevent IR-induced intestinal injury.

mTOR inhibitors radiosensitize PTEN-deficient non-small-cell lung cancer cells harboring an EGFR activating mutation by inducing autophagy.

Clinical resistance to gefitinib, an epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI), in patients with lung cancer has been linked to acquisition of the T790M resistance mutation in activated EGFR or amplification of MET. Phosphatase and tensin homolog (PTEN) loss has been recently reported as a gefitinib resistance mechanism in lung cancer. The aim of this study was to evaluate the efficacy of radiotherapy in non-small-cell lung cancer (NSCLC) with acquired gefitinib resistance caused by PTEN deficiency to suggest radiotherapy as an alternative to EGFR TKIs. PTEN deficient-mediated gefitinib resistance was generated in HCC827 cells, an EGFR TKI sensitive NSCLC cell line, by PTEN knockdown with a lentiviral vector expressing short hairpin RNA-targeting PTEN. The impact of PTEN knockdown on sensitivity to radiation in the presence or absence of PTEN downstream signaling inhibitors was investigated. PTEN knockdown conferred acquired resistance not only to gefitinib but also to radiation on HCC827 cells. mTOR inhibitors alone failed to reduce HCC827 cell viability, regardless of PTEN expression, but ameliorated PTEN knockdown-induced radioresistance. PTEN knockdown-mediated radioresistance was accompanied by repression of radiation-induced cytotoxic autophagy, and treatment with mTOR inhibitors released the repression of cytotoxic autophagy to overcome PTEN knockdown-induced radioresistance in HCC827 cells. These results suggest that inhibiting mTOR signaling could be an effective strategy to radiosensitize NSCLC harboring the EGFR activating mutation that acquires resistance to both TKIs and radiotherapy due to PTEN loss or inactivation mutations.

Proteomic identification of radiation response markers in mouse intestine and brain.

Increasing efforts are being made to develop more sensitive and faster molecular methodologies at the genomic and proteomic levels for the identification of protein markers after exposure to ionizing radiation (IR). However, few specific protein markers, especially organ-specific markers, have been identified. In this study, we analyzed altered protein expressions in various tissues, namely, brain, lung, spleen, and intestine, from 1 Gy-irradiated mice by employing 2-DE analysis. MALDI-TOF MS and peptide mapping identified 25 proteins that showed greater than twofold expressional changes. In order to confirm significant differences between control and IR-treated samples, ten identified proteins with available commercial antibodies were selected for immunoblotting. Of these, only five showed protein expression patterns that were similar to 2-DE data. These were heat shock protein 5 (HSP 5), HSP 90 kDa ß, HSP 1, transaldolase 1 (TA1), and phosphoglycerate kinase 1 (PGK1). In particular, PGK1 was specifically upregulated in mouse intestine, and TA1 was specifically downregulated in brain by irradiation. TA1 expression was unaltered in other tissues. Based on these data, we suggest that TA1 and PGK1 can be considered as candidate tissue-specific protein markers of IR exposure.

Ionizing Radiation Regulates Vascular Endothelial Growth Factor-A Transcription in Cultured Human Vascular Endothelial Cells Via the PERK/eIF2α/ATF4 Pathway.

PURPOSE: The delivery of high-dose hypofractionated radiation to a tumor induces vascular damage, but little is known about the responses of vascular endothelial cells to high-dose radiation. We examined whether high-dose irradiation alters vascular endothelial growth factor (VEGF) signaling, which is a critical regulator of the functional integrity and viability of vascular endothelial cells. METHODS AND MATERIALS: Human umbilical vein endothelial cells and human coronary artery endothelial cells were treated with 5, 10, 20, or 30 Gy ionizing radiation (IR). Expression values of VEGFA mRNA were analyzed by real-time polymerase chain reaction at 4 hours after irradiation and normalized to the average value of mock-irradiated human umbilical vein endothelial cell or human coronary artery endothelial cell controls. RESULTS: Irradiation with doses higher than 10 Gy causes an acute increase in VEGFA transcript levels, which was accompanied by activation of the PERK/eIF2α/activating transcription factor 4 (ATF4) pathway in human vascular endothelial cells. ATF4 knockdown with siRNA completely prevented the IR-induced upregulation of VEGFA transcripts, and chromatin immunoprecipitation assays demonstrated that ATF4 binding to the VEGFA locus was enriched in response to IR. Postirradiation treatment with an intracellular inhibitor of VEGF signaling significantly enhances high-dose IR-induced apoptosis in human vascular endothelial cells. CONCLUSIONS: Human vascular endothelial cells activate PERK/eIF2α/ATF4/VEGF signaling in response to high-dose IR to mitigate the apoptotic response. Thus, for cancer treatment, intracellular inhibitors of VEGF signaling could be employed to enhance stereotactic body radiation therapy-induced vascular damage, which would augment tumor cell death.

Dopamine receptor D2 activation suppresses the radiosensitizing effect of aripiprazole via activation of AMPK.

Drug repositioning has garnered attention as an alternative strategy to the discovery and development of novel anticancer drug candidates. In this study, we screened 321 FDA-approved drugs against nonirradiated and irradiated MCF-7 cells, revealing that aripiprazole, a dopamine receptor D2 (D2R) partial agonist, enhances the radiosensitivity of MCF-7 cells. Unexpectedly, D2R-selective antagonist treatment significantly enhanced the radiosensitizing effects of aripiprazole and prevented aripiprazole-induced 5' adenosine monophosphate-activated protein kinase (AMPK) phosphorylation. Direct AMPK activation with A769662 treatment blunted the radiosensitizing effects of aripiprazole. These results indicate that aripiprazole has potential as a radiosensitizing drug. Furthermore, prevention of D2R/AMPK activation might enhance these anticancer effects of aripiprazole in breast cancer cells.

Auranofin, an Anti-rheumatic Gold Drug, Aggravates the Radiation-Induced Acute Intestinal Injury in Mice.

Pelvic and abdominal radiotherapy plays an important role in eradication of malignant cells; however, it also results in slight intestinal injury. The apoptosis of cells in the intestinal epithelium is a primary pathological factor that initiates radiation-induced intestinal injury. Auranofin, a gold-containing triethylphosphine, was approved for the treatment of rheumatoid arthritis, and its therapeutic application has been expanded to a number of other diseases, such as parasitic infections, neurodegenerative disorders, AIDS, and bacterial infections. Recently, a treatment strategy combining the use of auranofin and ionizing radiation aimed at increasing the radiosensitivity of cancer cells was proposed for improving the control of local cancers. In this study, we evaluated the effect of auranofin on the radiosensitivity of intestinal epithelial cells. The treatment with a combination of 1 µM auranofin and 5 Gy ionizing radiation showed clear additive effects on caspase 3 cleavage and apoptotic DNA fragmentation in IEC-6 cells, and auranofin administration significantly aggravated the radiation-induced intestinal injury in mice. Auranofin treatment also resulted in the activation of the unfolded protein response and in the inhibition of thioredoxin reductase, which is a key component of the cellular antioxidant system. Pre-treatment with N-acetyl cysteine, a well-known scavenger of reactive oxygen species, but not with a chemical chaperone, which inhibits endoplasmic reticulum stress and the ensuing unfolded protein response, significantly reduced the radiosensitizing effects of auranofin in the IEC-6 cells. In addition, transfection of IEC-6 cells with a small interfering RNA targeted against thioredoxin reductase significantly enhanced the radiosensitivity of these cells. These results suggest that auranofin-induced radiosensitization of intestinal epithelial cells is mediated through oxidative stress caused by the deregulation of thioredoxin redox system, and auranofin treatment can be an independent risk factor for the development of acute pelvic radiation disease.

Cluh plays a pivotal role during adipogenesis by regulating the activity of mitochondria.

Cluh is a cytosolic protein that is known to specifically bind the mRNAs of nuclear-encoded mitochondrial proteins and play critical roles in mitochondrial biogenesis. Here, we report the role of Cluh in adipogenesis. Our study shows that mRNA expression of Cluh is stimulated during adipogenesis, and that cAMP/Creb signalling increases its transcription. Cluh depletion impaired proper adipocyte differentiation, with reductions seen in lipid droplets and adipogenic marker gene expression. Interestingly, the inductions of the brown adipocyte-specific genes, Ucp1, Cidea and Cox7a1, are severely blocked by Cluh depletion during brown adipogenesis. Mitochondrial respiration and the stability of mRNAs encoding mitochondrial proteins are reduced by Cluh depletion during brown adipogenesis. These results suggest that Cluh, which is induced during adipogenesis, promotes the post-transcriptional regulation of mitochondrial proteins and supports differentiation.

Plasma Fibrinogen-Like 1 as a Potential Biomarker for Radiation-Induced Liver Injury.

Liver damage upon exposure to ionizing radiation, whether accidental or because of therapy can contribute to liver dysfunction. Currently, radiation therapy is used for various cancers including hepatocellular carcinoma; however, the treatment dose is limited by poor liver tolerance to radiation. Furthermore, reliable biomarkers to predict liver damage and associated side-effects are unavailable. Here, we investigated fibrinogen-like 1 (FGL1)-expression in the liver and plasma after radiation exposure. We found that 30 Gy of liver irradiation (IR) induced cell death including apoptosis, necrosis, and autophagy, with fibrotic changes in the liver occurring during the acute and subacute phase in mice. Moreover, FGL1 expression pattern in the liver following IR was associated with liver damage represented by injury-related proteins and oxidative stress markers. We confirmed the association between FGL1 expression and hepatocellular injury by exposing human hepatocytes to radiation. To determine its suitability, as a potential biomarker for radiation-induced liver injury, we measured FGL1 in the liver tissue and the plasma of mice following total body irradiation (TBI) or liver IR. In TBI, FGL1 showed the highest elevation in the liver compared to other major internal organs including the heart, lung, kidney, and intestine. Notably, plasma FGL1 showed good correlation with radiation dose by liver IR. Our data revealed that FGL1 upregulation indicates hepatocellular injury in response to IR. These results suggest that plasma FGL1 may represent a potential biomarker for acute and subacute radiation exposure to the liver.

Sintering Behavior of Spark Plasma Sintered SiC with Si-SiC Composite Nanoparticles Prepared by Thermal DC Plasma Process.

The Si-coated SiC (Si-SiC) composite nanoparticle was prepared by non-transferred arc thermal plasma processing of solid-state synthesized SiC powder and was used as a sintering additive for SiC ceramic formation. Sintered SiC pellet was prepared by spark plasma sintering (SPS) process, and the effect of nano-sized Si-SiC composite particles on the sintering behavior of micron-sized SiC powder was investigated. The mixing ratio of Si-SiC composite nanoparticle to micron-sized SiC was optimized to 10 wt%. Vicker's hardness and relative density was increased with increasing sintering temperature and holding time. The relative density and Vicker's hardness was further increased by reaction bonding using additional activated carbon to the mixture of micron-sized SiC and nano-sized Si-SiC. The maximum relative density (97.1%) and Vicker's hardness (31.4 GPa) were recorded at 1800 °C sintering temperature for 1 min holding time, when 0.2 wt% additional activated carbon was added to the mixture of SiC/Si-SiC.

Inhibitory effects of proton beam irradiation on integrin expression and signaling pathway in human colon carcinoma HT29 cells.

Proton radiotherapy has been established as a highly effective modality used in the local control of tumor growth. Although proton radiotherapy is used worldwide to treat several types of cancer clinically with great success due to superior targeting and energy deposition, the detailed regulatory mechanisms underlying the functions of proton radiation are not yet well understood. Accordingly, in the present study, to assess the effects of proton beam on integrin-mediated signaling pathways, we investigated the expression of integrins related to tumor progression and integrin trafficking, and key molecules related to cell adhesion, as well as examining phosphorylation of signaling molecules involved in integrin-mediated signaling pathways. Proton beam irradiation inhibited the increase in 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced integrin ß1 protein expression and the gene expression of members of the integrin family, such as α5ß1, α6ß4, αvß3, and αvß6 in human colorectal adenocarcinoma HT-29 cells. Simultaneously, the gene expression of cell adhesion molecules, such as FAK and CDH1, and integrin trafficking regulators, such as RAB4, RAB11, and HAX1, was decreased by proton beam irradiation. Moreover, proton beam irradiation decreased the phosphorylation of key molecules involved in integrin signaling, such as FAK, Src, and p130Cas, as well as PKC and MAPK, which are known as promoters of cell migration, while increased the phosphorylation of AMPK and the gene expression of Rab IP4 involved in the inhibition of cell adhesion and cell spreading. Taken together, our findings suggest that proton beam irradiation can inhibit metastatic potential, including cell adhesion and migration, by modulating the gene expression of molecules involved in integrin trafficking and integrin-mediated signaling, which are necessary for tumor progression.

Ionizing radiation activates PERK/eIF2α/ATF4 signaling via ER stress-independent pathway in human vascular endothelial cells.

PURPOSE: Perturbations in protein folding induce endoplasmic reticulum (ER) stress, which elicits coordinated response, namely the unfolded protein response (UPR), to cope with the accumulation of misfolded proteins in ER. In this study, we characterized mechanisms underlying ionizing radiation (IR)-induced UPR signaling pathways. MATERIALS AND METHODS: We analyzed alterations in UPR signaling pathways in human umbilical vein endothelial cells (HUVEC) and human coronary artery endothelial cells (HCAEC) irradiated with 15 Gy IR. RESULTS: IR selectively activated the eIF2α/ATF4 branch of the UPR signaling pathway, with no alterations in the IRE1 and ATF6 branches in HUVEC and HCAEC. Phosphorylation of PERK was enhanced in response to IR, and the IR-induced activation of the eIF2α/ATF4 signaling pathway was completely inhibited by PERK knockdown with siRNA. Surprisingly, chemical chaperones, which inhibit the formation of misfolded proteins and sequential protein aggregates to reduce ER stress, failed to prevent the IR-induced phosphorylation of PERK and the subsequent activation of the eIF2α/ATF4 signaling pathway. CONCLUSIONS: PERK mediates the IR-induced selective activation of the eIF2α/ATF4 signaling pathway, and the IR-induced activation of PERK/eIF2α/ATF4 signaling in human vascular endothelial cells is independent of alterations in protein-folding homeostasis in the ER.

A Case Report of Sweet's Syndrome with Parotitis.

Sweet's syndrome is characterized by clinical symptoms, physical features, and pathologic findings which include fever, neutrophilia, tender erythematous skin lesions, and a diffuse infiltrate of mature neutrophils. This is a report of our experience of Sweet's syndrome with parotitis. A 57-year-old man initially presented with tender swelling on the right cheek similar to parotitis. His symptoms relapsed despite the use of an oral antibiotic agent for 3 weeks. He additionally presented with erythematous papules and plaques on the periocular area and dorsum of both hands. Histiopathologic findings on punch biopsy of the right dorsum of the hand showed superficial perivenular histiocytic infiltration without vasculitis. We confirmed this as histiocytoid Sweet's syndrome and used systemic corticosteroid. After initiation of treatment with systemic corticosteroids, there was a prompt recovery from both the dermatosis-releated symptoms and skin lesions. Sweet's syndrome should be considered in patients with therapy-refractory parotitis and unclear infiltrated nodules. We present a confusing case who initially appeared to have parotitis but turned out to have histiocytoid Sweet's syndrome.

B cell translocation gene 2 enhances susceptibility of HeLa cells to doxorubicin-induced oxidative damage.

BTG2/TIS21/PC3 (B cell translocation gene 2) has been known as a p53 target gene and functions as a tumor suppressor in carcinogenesis of thymus, prostate, kidney, and liver. Although it has been known that the expression of BTG2/TIS21/PC3 is induced during chemotherapy-mediated apoptosis in cancer cells, a role of BTG2/TIS21/PC3 in cell death remains to be elucidated. In this study, the mechanism and role of BTG2 involved in the enhancement of doxorubicin (DOXO)-induced cell death were examined. Treatment of HeLa cells with DOXO revealed apoptotic phenomena, such as chromatin condensation and cleavage of poly(ADP-ribose) polymerase and lamin A/C with concomitant increase of BTG2/TIS21/PC3 expression. Employing infections of Ad-TIS21 virus and lentivirus with short hairpin RNA to BTG2, the effect of BTG2/TIS21/PC3 on the DOXO-induced apoptosis of HeLa cells and liver cancer cells was evaluated. Not only short hairpin RNA-BTG2 but also N-acetyl-L-cysteine significantly reduced the DOXO-induced HeLa cell death and generation of H2O2. Moreover, forced expression of BTG2/TIS21/PC3 using adenoviral vector augmented DOXO-induced cancer cell death concomitantly with increase of manganese-superoxide dismutase but not catalase, CuZnSOD, and glutathione peroxidase 1. The increased apoptosis by forced expression of BTG2/TIS21/PC3 could be inhibited by N-acetyl-L-cysteine and polyethylene glycol-catalase. These results therefore suggest that BTG2/TIS21/PC3 works as an enhancer of DOXO-induced cell death via accumulation of H2O2 by up-regulating manganese-superoxide dismutase without any other antioxidant enzymes. In summary, BTG2/TIS21/PC3 enhances cancer cell death by accumulating H2O2 via imbalance of the antioxidant enzymes in response to chemotherapy.

Chondrogenesis induced by actin cytoskeleton disruption is regulated via protein kinase C-dependent p38 mitogen-activated protein kinase signaling.

Disruption of the actin cytoskeleton in subconfluent mesenchymal cells induces chondrogenic differentiation via protein kinase C (PKC) alpha signaling. In this study, we investigated the role of p38 mitogen-activated protein (MAP) kinase in the chondrogenic differentiation of mesenchymal cells that is induced by depolymerization of the actin cytoskeleton. Treatment of mesenchymal cells derived from chick embryonic limb buds with cytochalasin D (CD) disrupted the actin cytoskeleton with concomitant chondrogenic differentiation. The chondrogenesis was accompanied by an increase in p38 MAP kinase activity and inhibition of p38 MAP kinase with SB203580 blocked chondrogenesis. Together these results suggest an essential role for p38 MAP kinase in chondrogenesis. In addition, inhibition of p38 MAP kinase did not alter CD-induced increased expression and activity of PKC alpha, whereas down-regulation of PKC by prolonged exposure of cells to phorbol ester inhibited CD-induced p38 MAP kinase activation. Our results therefore suggest that PKC is involved in the regulation of chondrogenesis induced by disruption of the actin cytoskeleton via a p38 MAP kinase signaling pathway.

Expression of connective tissue growth factor, a biomarker in senescence of human diploid fibroblasts, is up-regulated by a transforming growth factor-beta-mediated signaling pathway.

Molecular changes associated with cellular senescence in human diploid fibroblasts (HDF), IMR-90, were analyzed by two-dimensional differential proteome analysis. A high percentage of replicative senescent cells were positive for senescence-associated beta-galactosidase activity, and displayed elevated levels of p21 and p53 proteins. Comparison of early population doubling level (PDL) versus replicative senescent cells among the 1000 spots resolved on gels revealed that the signal intensities of six spots were increased fivefold, whereas those of four spots were decreased. Proteome analysis data demonstrated that connective tissue growth factor (CTGF) is an age-associated protein. Up-regulation of CTGF expression in senescent cells was further confirmed by Western blotting and RT-PCR. We postulate that CTGF expression is controlled, in part, by transforming growth factor-beta (TGF-beta), in view of the high levels of TGF-beta isoforms as well as type I and II receptors detected only in late PDL of HDF cells. To verify this hypothesis, we stimulated early PDL cells with TGF-beta1 as well as stress inducing agents such as hydrogen peroxide. As expected, CTGF expression and Smad protein phosphorylation were dramatically increased up to observed levels in normal replicative senescent cells. In vivo experiments disclosed that CTGF, pSmad, and p53 were constitutively expressed at basal levels in up to 18-month-old rat liver, and expression was significantly up-regulated in 24-month-old rat tissue. However, expression patterns were not altered at all periods examined in livers of caloric-restricted rats. In view of both in vitro and in vivo data, we propose that the TGF-beta/Smad pathway functions in the induction of CTGF, a novel biomarker protein of cellular senescence in human fibroblasts.