Identification of differentially expressed proteins of gamma-ray irradiated rat intestinal epithelial IEC-6 cells by two-dimensional gel electrophoresis and matrix-assisted laser desorption/ionisation-time of flight mass spectrometry

N-acetyl-L-tryptophan (NAT) provides protection to intestinal epithelial cells (IEC-6) against radiation-induced apoptosis via modulation of oxidative stress and mitochondrial membrane integrity

BACKGROUND

Ionizing radiation generates oxidative stress in biological systems via inducing free radicals. Gastro-intestinal system has been known for its high radiosensitivity. Therefore, to develop an effective radiation countermeasure for gastrointestinal system, N-acetyl L-tryptophan was evaluated for its radioprotective efficacy using intestinal epithelial cells-6 (IEC-6) cells as the experimental model.

METHODS AND RESULTS

Cellular metabolic and lysosomal activity of L-NAT and L-NAT treated irradiated IEC-6 cells were assessed by MTT and NRU staining, respectively. ROS and mitochondrial superoxide levels along with mitochondrial disruption were detected using specific fluorescent probes.  Endogenous antioxidants (CAT, SOD, GST, GPx) activities were determined using calorimetric assay.  Apoptosis and DNA damage were assessed using flow cytometery and Comet assay, respectively. Results of the study were demonstrated that L-NAT pre-treatment (- 1 h) to irradiated IEC-6 cells significantly contribute to ensuring 84.36% to 87.68% (p < 0.0001) survival at 0.1 μg/mL concentration against LD50 radiation dose (LD50; 20 Gy). Similar level of radioprotection was observed with a clonogenic assay against γ radiation (LD50; 5 Gy). L-NAT was found to provide radioprotection by neutralizing radiation-induced oxidative stress, enhancing antioxidant enzymes (CAT, SOD, GST, and GPx), and protecting DNA from radiation-induced damage. Further, significant restoration of mitochondrial membrane integrity along with apoptosis inhibition was observed with irradiated IEC-6 cells upon L-NAT pretreatment.

Radiation-Induced Intestinal Normal Tissue Toxicity: Implications for Altered Proteome Profile

Radiation-induced toxicity to healthy/normal intestinal tissues, especially during radiotherapy, limits the radiation dose necessary to effectively eradicate tumors of the abdomen and pelvis. Although the pathogenesis of intestinal radiation toxicity is highly complex, understanding post-irradiation alterations in protein profiles can provide crucial insights that make radiotherapy safer and more efficient and allow for increasing the radiation dose during cancer treatment. Recent preclinical and clinical studies have advanced our current understanding of the molecular changes associated with radiation-induced intestinal damage by assessing changes in protein expression with mass spectrometry-based approaches and 2-dimensional difference gel electrophoresis. Studies by various groups have demonstrated that proteins that are involved in the inflammatory response, the apoptotic pathway, reactive oxygen species scavenging, and cell proliferation can be targeted to develop effective radiation countermeasures. Moreover, altered protein profiles serve as a crucial biomarkers for intestinal radiation damage. In this review, we present alterations in protein signatures following intestinal radiation damage as detected by proteomics approaches in preclinical and clinical models with the aim of providing a better understanding of how to accomplish intestinal protection against radiation damage.

Polysaccharides extracted from Rheum tanguticum ameliorate radiation-induced enteritis via activation of Nrf2/HO-1

Radiation-induced enteritis is a major side effect in cancer patients undergoing abdominopelvic radiotherapy. The Nrf2/HO-1 pathway is a critical endogenous antioxidant stress pathway, but its precise role in radiation-induced enteritis remains to be clarified. Polysaccharides extracted from Rheum tanguticum (RTP) can protect the intestinal cells from radiation-induced damage, but the underlying mechanism is unknown. SD rats and IEC-6 cells were exposed to 12 or 10 Gy X-ray radiation. Rat survival, and histopathological and immunohistochemical profiles were analyzed at different time points. Indicators of oxidative stress and inflammatory response were also assessed. Cell viability, apoptosis and Nrf2/HO-1 expression were evaluated at multiple time points. Significant changes were observed in the physiological and biochemical indexes of rats after radiation, accompanied by significant oxidative stress response. The mRNA and protein expression of Nrf2 peaked at 12 h after irradiation, and HO-1 expression peaked at 48 h after irradiation. RTP administration reduced radiation-induced intestinal damage, upregulated Nrf2/HO-1, improved physiological indexes, significantly decreased apoptosis and inflammatory factors, and upregulated HO-1, particularly at 48 h after irradiation. In conclusion, Nrf2 is activated in the early stage of radiation-induced intestinal injury and plays a protective role. RTP significantly ameliorates radiation-induced intestinal injury via the regulation of Nrf2 and its downstream protein HO-1.

Proteomic Evaluation of the Natural History of the Acute Radiation Syndrome of the Gastrointestinal Tract in a Non-human Primate Model of Partial-body Irradiation with Minimal Bone Marrow Sparing Includes Dysregulation of the Retinoid Pathway

Exposure to ionizing radiation results in injuries of the hematopoietic, gastrointestinal, and respiratory systems, which are the leading causes responsible for morbidity and mortality. Gastrointestinal injury occurs as an acute radiation syndrome. To help inform on the natural history of the radiation-induced injury of the partial body irradiation model, we quantitatively profiled the proteome of jejunum from non-human primates following 12 Gy partial body irradiation with 2.5% bone marrow sparing over a time period of 3 wk. Jejunum was analyzed by liquid chromatography-tandem mass spectrometry, and pathway and gene ontology analysis were performed. A total of 3,245 unique proteins were quantified out of more than 3,700 proteins identified in this study. Also a total of 289 proteins of the quantified proteins showed significant and consistent responses across at least three time points post-irradiation, of which 263 proteins showed strong upregulations while 26 proteins showed downregulations. Bioinformatic analysis suggests significant pathway and upstream regulator perturbations post-high dose irradiation and shed light on underlying mechanisms of radiation damage. Canonical pathways altered by radiation included GP6 signaling pathway, acute phase response signaling, LXR/RXR activation, and intrinsic prothrombin activation pathway. Additionally, we observed dysregulation of proteins of the retinoid pathway and retinoic acid, an active metabolite of vitamin A, as quantified by liquid chromatography-tandem mass spectrometry. Correlation of changes in protein abundance with a well-characterized histological endpoint, corrected crypt number, was used to evaluate biomarker potential. These data further define the natural history of the gastrointestinal acute radiation syndrome in a non-human primate model of partial body irradiation with minimal bone marrow sparing.

Proteomic Evaluation of the Acute Radiation Syndrome of the Gastrointestinal Tract in a Murine Total-body Irradiation Model

Radiation exposure to the gastrointestinal system contributes to the acute radiation syndrome in a dose- and time-dependent manner. Molecular mechanisms that lead to the gastrointestinal acute radiation syndrome remain incompletely understood. Using a murine model of total-body irradiation, C57BL/6J male mice were irradiated at 8, 10, 12, and 14 Gy and assayed at day 1, 3, and 6 after exposure and compared to nonirradiated (sham) controls. Tryptic digests of gastrointestinal tissues (upper ileum) were analyzed by liquid chromatography-tandem mass spectrometry on a Waters nanoLC coupled to a Thermo Scientific Q Exactive hybrid quadrupole-orbitrap mass spectrometer. Pathway and gene ontology analysis were performed with Qiagen Ingenuity, Panther GO, and DAVID databases. A number of trends were identified in our proteomic data including pronounced protein changes as well as protein changes that were consistently up regulated or down regulated at all time points and dose levels interrogated. Time- and dose-dependent protein changes, canonical pathways affected by irradiation, and changes in proteins that serve as upstream regulators were also identified. Additionally, proteins involved in key processes including inflammation, radiation, and retinoic acid signaling were identified. The proteomic profiling conducted here represents an untargeted systems biology approach to identify acute molecular events that will be useful for a greater understanding of animal models and may be potentially useful toward the development of medical countermeasures and/or biomarkers.

Proteomic analysis of irradiated lung tissue of mice using gel-based proteomic approach

PURPOSE

Exposure to radiation causes severe alterations of protein expression level inside the cell, thus it may influence the biological events and stress response. In the present investigation, we have demonstrated the effect of radiation on mice lung tissues.

MATERIALS AND METHODS

Two-dimensional gel electrophoresis (2-DE) coupled with MALDI-TOF/TOF was used to check the expression changes in lung proteome profile of strain 'A' female mice after exposure to lethal doses of gamma irradiation at different time periods (24 and 48 h). Identified proteins were analysed for their altered expression and were further validated by Western blotting and enzyme-linked immunosorbent assay (ELISA).

RESULTS

Nine significant differentially expressed proteins were identified from irradiated lungs tissues. The expression level of zinc finger protein was found to be up regulated at 24 h irradiation in comparison to 48 h irradiation.

CONCLUSIONS

Zinc finger protein may be considered as a radiation responsive protein. Alteration in its expression pattern may primarily affect binding specificity of the protein that can further result in the interference in transcriptional control of multiple stress responsive genes.

Erp29 Attenuates Cigarette Smoke Extract-Induced Endoplasmic Reticulum Stress and Mitigates Tight Junction Damage in Retinal Pigment Epithelial Cells

PURPOSE

Endoplasmic reticulum protein 29 (ERp29) is a novel chaperone that was recently found decreased in human retinas with AMD. Herein, we examined the effect of ERp29 on cigarette smoke-induced RPE apoptosis and tight junction disruption.

METHODS

Cultured human RPE (HRPE) cells (ARPE-19) or mouse RPE eyecup explants were exposed to cigarette smoke extract (CSE) for short (up to 24 hours) or long (up to 3 weeks) periods. Expression of ERp29 was up- and downregulated by adenovirus and siRNA, respectively. Endoplasmic reticulum stress markers, apoptosis, and cell death, the expression and distribution of tight junction protein ZO-1, transepithelial electrical resistance (TEER), and F-actin expression were examined.

RESULTS

Endoplasmic reticulum protein 29 was significantly increased by short-term exposure to CSE in ARPE-19 cells or eyecup explants but was reduced after 3-week exposure. Overexpression of ERp29 increased the levels of GRP78, p58(IPK), and Nrf-2, while reducing p-eIF2α and C/EBP homologous protein (CHOP), and protected RPE cells from CSE-induced apoptosis. In contrast, knockdown of ERp29 decreased the levels of p58(IPK) and Nrf2, but increased p-eIF2α and CHOP and exacerbated CSE-triggered cell death. In addition, overexpression of ERp29 attenuated CSE-induced reduction in ZO-1 and enhanced the RPE barrier function, as measured by TEER. Knockdown of ERp29 decreased the level of ZO-1 protein. These effects were associated with changes in the expression of cytoskeleton F-actin.

CONCLUSIONS

Endoplasmic reticulum protein 29 attenuates CSE-induced ER stress and enhances cell viability and barrier integrity of RPE cells, and therefore may act as a protective mechanism for RPE survival and activity.

The endoplasmic reticulum protein folding factory and its chaperones: new targets for drug discovery?

Cytosolic heat shock proteins have received significant attention as emerging therapeutic targets. Much of this excitement has been triggered by the discovery that HSP90 plays a central role in the maintenance and stability of multifarious oncogenic membrane receptors and their resultant tyrosine kinase activity. Numerous studies have dealt with the effects of small molecules on chaperone- and stress-related pathways of the endoplasmic reticulum (ER). However, unlike cytosolic chaperones, relatively little emphasis has been placed upon translational avenues towards targeting of the ER for inhibition of folding/secretion of disease-promoting proteins. Here, we summarise existing small molecule inhibitors and potential future targets of ER chaperone-mediated inhibition. Client proteins of translational relevance in disease treatment are outlined, alongside putative future disease treatment modalities based on ER-centric targeted therapies. Particular attention is paid to cancer and autoimmune disorders via the effects of the GRP94 inhibitor geldanamycin and its population of client proteins, overloading of the unfolded protein response, and inhibition of members of the IL-12 family of cytokines by celecoxib and non-coxib analogues.

Proteomic and genomic modulations induced by &#x03B3;-irradiation of human blood lymphocytes

PURPOSE

Quantitative evaluation of early response proteins (ERPRO) and early response genes (ERG) following γ-irradiation of human lymphocytes; identification of specific proteins and genes as candidate biomarkers for the development of a novel biodosimeter.

MATERIALS AND METHODS

Human peripheral blood lymphocytes were exposed to clinically relevant doses (1, 2 and 4 Gy) of γ-radiation ex-vivo. Analyses of protein and gene expression modulation were conducted 2 h post-irradiation. Global modulations were monitored using two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) and DNA microarray analyses of the samples originating from one human donor. On the proteome level, both phosphorylated and non-phosphorylated proteins were considered. Proteins and genes of specific interest were further targeted using Western blot (WB) and real-time quantitative polymerase chain reaction (RT-qPCR) techniques, employing samples from several human donors (n=3).

RESULTS

A set of ERPRO and ERG showing significant alterations 2 h post-γ-irradiation have been identified in human lymphocytes. The most radiation responsive genes and proteins indicated alterations of cellular structure (ß-actin, talin-1 [TLN1], talin-2, zyxin-2), immune and defence reactions (major histocompatibility complex binding protein-2 [MBP2], interleukin-17E and interferon-γ), cell cycle control (cyclin-dependent kinase inhibitor-1A [CDKN1A], mouse double minute-2, annexin-A6 [ANXA6], growth arrest and DNA-damage-inducible protein-α [GADD45A], proliferating cell nuclear antigen [PCNA], dual specificity phosphatase-2 and 8 [DUSP8]) as well as detoxification processes (peroxin-1) and apoptosis (B-cell lymphoma-2 binding component-3 [BBC3]).

SUMMARY

The estimations of protein concentration modulation of TLN1 and CDKN1A, phosphorylation status of ANXA6 (dose range 0-2 Gy) and MBP2 as well as the alterations in the level of gene expressions of BBC3, DUSP8, GADD45A and PCNA appears to be of potential value for future biodosimetric applications.

Candidate protein biodosimeters of human exposure to ionizing radiation

PURPOSE

To conduct a literature review of candidate protein biomarkers for individual radiation biodosimetry of exposure to ionizing radiation.

MATERIALS AND METHODS

Reviewed approximately 300 publications (1973 - April 2006) that reported protein effects in mammalian systems after either in vivo or in vitro radiation exposure.

RESULTS

We found 261 radiation-responsive proteins including 173 human proteins. Most of the studies used high doses of ionizing radiation (>4 Gy) and had no information on dose- or time-responses. The majority of the proteins showed increased amounts or changes in phosphorylation states within 24 h after exposure (range: 1.5- to 10-fold). Of the 47 proteins that are responsive at doses of 1 Gy and below, 6 showed phosphorylation changes at doses below 10 cGy. Proteins were assigned to 9 groups based on consistency of response across species, dose- and time-response information and known role in the radiation damage response.

CONCLUSIONS

ATM (Ataxia telengiectasia mutated), H2AX (histone 2AX), CDKN1A (Cyclin-dependent kinase inhibitor 1A), and TP53 (tumor protein 53) are top candidate radiation protein biomarkers. Furthermore, we recommend a panel of protein biomarkers, each with different dose and time optima, to improve individual radiation biodosimetry for discriminating between low-, moderate-, and high-dose exposures. Our findings have applications for early triage and follow-up medical assessments.

ERp29 is a radiation-responsive gene in IEC-6 cell

ERp29 is a resident protein of the endoplasmic reticulum (ER) lumen, which is thought to be involved in the folding of secretory proteins. In our previous work, it was found that, when treated with ionizing radiation (IR), the ERp29 expression was increased in mouse intestinal epithelia and cultured IEC-6 cells, which suggested that ERp29 might be a radiation-induced gene. The current work is to confirm the induction of ERp29 by IR and to analyze its role in irradiated IEC-6 cells. Our results showed that ERp29 expression was elevated by IR in IEC-6 cells at mRNA and protein levels in a time-dependent manner. IEC-6 cells with different exogenous ERp29 expression were obtained by transfection with sense and antisense expression vectors of ERp29 coding region. As ERp29 expression was inhibited, these cells exhibited more serious radiation injury and more sensitivity to IR-induced apoptosis. To further elucidate the induction of ERp29, we analyzed the XBP1 expression after IR. Results showed that the spliced form of XBP1 mRNA rapidly reached a peak at 3 hours after irradiation, which indicated that UPR sensor was involved in radiation and might be a reason to induce ERp29 expression. Our results demonstrate that ERp29 is a radiation associated protein and plays an important role in protecting cells from IR.

Progress in research on radiation combined injury in China

The significant feature of radiation combined injury is the occurrence of a combined effect. For decades our institute has focused on studying the key complications of radiation-burn injury, including shock, suppression of hematopoiesis and immunity, gastrointestinal damage and local refractory wound healing. Here we summarize recent advancements in elucidating the mechanisms of and potential treatments for radiation combined injury. Concerning the suppression and regeneration of hematopoiesis in radiation combined injury, mechanisms of megakaryocyte damage have been elucidated and a new type of fusion protein stimulating thrombopoiesis has been developed and is being tested in animals. With regard to the damage and repair of intestinal epithelium, the important molecular mechanisms of radiation combined injury have been clarified, and new measures to prevent and treat gastrointestinal tract injury are proposed. With respect to the difficulties encountered in wound healing, the underlying causes of radiation combined injury have been proposed, and some potential methods to accelerate wound closure are under study. Systemic experiments have been done to determine the appropriate time for eschar excision and skin grafting, and the results provided significant insight into clinical treatment of the injury. In the search for early therapeutic regimens for severe burns and radiation combined injury to prevent deterioration of injuries and to improve survival, cervical sympathetic ganglion block was used for the treatment of animals with radiation combined injury and had significant benefits. These research advancements have potential for application in on-site emergency rescue and in-hospital treatment of radiation combined injury.

Proteomic analysis of glutamine-treated human intestinal epithelial HCT-8 cells under basal and inflammatory conditions

Glutamine (Gln) promotes intestinal growth and maintains gut structure and function, especially in situations of injury and during inflammation. Several mechanisms could contribute to Gln protective effects on gut. Proteomics enable us to characterize differentially expressed proteins in tissues in response to modifications of the biological or nutritional environment. Gln effects on the human intestinal epithelial HCT-8 cell line proteome were assessed under basal and proinflammatory conditions. The 2-DE gels were obtained and compared. Proteins were identified by MS and using databases. About 1200 spots were detected in both 2- and 10-mM Gln concentrations. Under basal conditions, 24 proteins were differentially expressed in response to Gln. Half of these proteins were implicated in protein biosynthesis or proteolysis and 20% in membrane trafficking. Under proinflammatory conditions, 27 proteins were up- or down-regulated by Gln 10 mM. From these proteins, 40% were involved in protein biosynthesis or proteolysis, 16% in membrane trafficking, 8% in cell cycle and apoptosis mechanisms and 8% in nucleic acid metabolism. This study provides the first holistic picture of proteome modulation by Gln in a human enterocytic cell line under basal and proinflammatory conditions, and supports further evaluation of nutritional modulation of intestinal proteome in humans.

Involvement of peroxiredoxin I in protecting cells from radiation-induced death

Peroxiredoxin I (Prx-I), a key member of the peroxiredoxin family, reduces peroxides and equivalents through the thioredoxin system. Our previous work has shown that expression of Prx-I in mammalian cells increases following ionizing radiation (IR), indicating that Prx-I actively responds to IR-induced reactive oxygen species (ROS) and suggesting that Prx-I plays an important role in protecting cells from IR-induced death. To test this hypothesis, we suppressed the expression of Prx-I in SW480 cells by RNA interference. Our results show that IR induces the expression of Prx-I in SW480 cells in a dose- and time-dependent manner. The recombinant siRNA vector targeting Prx-I dramatically reduced the expression of Prx-I in SW480 cells. When Prx-I was knocked down in SW480 cells, the cells exhibited a decreased growth rate, a reduced antioxidant capability following IR and became more sensitive to IR-induced apoptosis. Together, our results demonstrate that Prx-I plays an important role in protecting cells from IR-induced cell death, which might be through scavenging IR-induced ROS in the cells.

Dansylation of tryptic peptides for increased sequence coverage in protein identification by matrix-assisted laser desorption/ionization time-of-flight mass spectrometric peptide mass fingerprinting

A database search using peptide mass fingerprints obtained by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry leads to protein identification with incomplete sequence coverage, because certain peptides are preferentially desorbed/ionized and some are not detected at all. We show that certain tryptic peptides mainly with C-terminal arginine not detected before derivatization become detectable upon dansylation. Others, mainly with C-terminal lysine, are suppressed. An increase in protein sequence coverage and protein identification score by combined data from underivatized and dansylated peptides in database search is demonstrated using human amnion proteins (human serum albumin precursor, calmodulin, collagen alpha 2(VI) chain precursor, galectin-3) separated by two-dimensional gel electrophoresis as well as femtomole amounts of BSA in solution.