A comprehensive study of the radiobiological response of the murine (BDF1) small intestine

Berberine enhances the function of intestinal stem cells in healthy and radiation-injured mice

Intestinal stem cells (ISCs) are pivotal for the maintenance and regeneration of the intestinal epithelium. Berberine (BBR) exhibits diverse biological activities, but it remains unclear whether BBR can modulate ISCs' function. Therefore, we investigated the effects of BBR on ISCs in healthy and radiation-injured mice and explored the potential underlying mechanisms involved. The results showed that BBR significantly increased the length of the small intestines, the height of the villi, and the depth and density of the crypts, promoted the proliferation of cryptal epithelial cells and increased the number of OLFM4+ ISCs and goblet cells. Crypts from the BBR-treated mice were more capable of growing into enteroids than those from untreated mice. BBR alleviated WAI-induced intestinal injury. BBR suppressed the apoptosis of crypt epithelial cells, increased the quantity of goblet cells, and increased the quantity of OLFM4+ ISCs and tdTomato+ progenies of ISCs after 8 Gy WAI-induced injury. Mechanistically, BBR treatment caused a significant increase in the quantity of p-S6, p-STAT3 and p-ERK1/2 positive cryptal epithelial cells under physiological conditions and after WAI-induced injury. In conclusion, BBR is capable of enhancing the function of ISCs either physiologically or after radiation-induced injury, indicating that BBR has potential value in the treatment of radiation-induced intestinal injury.

Getting clues from nature: the impact of grass hay on suckling piglets' gastrointestinal growth and colonic microbiota

Introduction

The effect of dietary fiber on pig production has been extensively evaluated. Inspired by observations of the diet of wild, young piglets, this study aimed to examine the possibility of feeding grass hay to suckling piglets besides concentrated creep feed.

Methods

The sow-nursed piglets in this study were divided into two groups based on balanced sow parities. The control group (CON, n = 7 sows) only received a regular, concentrated creep feed, while the treatment piglets (GH, n = 8 sows) were also provided with chopped grass hay from 2 days of age until weaning (28 days). At weaning, one piglet with a median weight was selected from each litter for post-mortem evaluation. Subsequently, six pigs around median weight per sow were grouped into nursery pens and monitored for their feed intake and body weight gain until 9 weeks of age.

Results and discussion

Piglets in GH consumed, on average, 57 g of grass hay per piglet during the entire lactation period. The emptied weight of the small and large intestine was significantly greater in GH (280 vs. 228 g, 88.8 vs. 79.3 g, respectively, p < 0.05), and the length of the large intestine was stimulated by the grass hay (164 vs. 150 cm, p < 0.05). Morphologically, the villus height in the jejunum was higher in GH (p < 0.05). In the large intestine, the crypt depth of the mid-colon was lower in GH. Moreover, the short-chain fatty acid (SCFA) concentrations in the cecum were increased in GH compared to CON (1,179 vs. 948 µmol/g dry matter, p < 0.05), whereas in the colon, SCFA concentrations were lower in CON (341 vs. 278 µmol/g dry matter, p < 0.05). There was no major impact of grass hay inclusion on the colonic microbiota composition. Only a trend was observed for a lower inverse of the classical Simpson (InvSimpon) index and a higher abundance of Lactobacillus genera in GH. After weaning, no significant differences in feed intake and body weight gain were observed. In conclusion, supplementing the grass hay to suckling piglets led to alterations in intestinal morphology, increased SCFA fermentation in proximal sections of large intestine, stimulation of gastrointestinal tract growth, and subtle modifications in colonic microbiota.

Anti-ceramide Single-Chain Variable Fragment Mitigates Gastrointestinal-Acute Radiation Syndrome and Improves Marrow Reconstitution, Rendering Near-Normal 90-Day Autopsies

PURPOSE

After September 11, 2001, nuclear threat prompted government agencies to develop medical countermeasures to mitigate two syndromes, the hematopoietic-acute radiation syndrome (H-ARS) and the higher-dose gastrointestinal-acute radiation syndrome (GI-ARS), both lethal within weeks. While repurposing leukemia drugs that enhance bone marrow repopulation successfully treats H-ARS, no mitigator potentially deliverable under mass casualty conditions preserves the GI tract. We recently reported that anti-ceramide single-chain variable fragment (scFv) mitigates GI-ARS lethality, abrogating ongoing small intestinal endothelial apoptosis to rescue Lgr5+ stem cells. Here, we examine long-term consequences of prevention of acute GI-ARS lethality.

METHODS AND MATERIALS

For these studies, C57BL/6J male mice were treated with 15 Gy whole body irradiation, the 90% GI-ARS lethal dose for this mouse strain.

RESULTS

Mice irradiated with 15 Gy alone or with 15 Gy + bone marrow transplantation (BMT) or anti-ceramide scFv, succumb to an ARS within 8 to 10 days. Autopsies reveal only mice receiving anti-ceramide scFv at 24 hours post-whole body irradiation display small intestinal rescue. No marrow reconstitution occurs in any group with attendant undetectable circulating blood elements. Mice receiving 15 Gy + BMT + scFv, however, normalize blood counts by day 12, suggesting that scFv also improves marrow reconstitution, a concept for which we provide experimental support. We show that at 14 Gy, the upper limit dose for H-ARS lethality before transition to GI-ARS lethality, anti-ceramide scFv markedly improves marrow take, reducing the quantity of marrow-conferring survival by more than 3-fold. Consistent with these findings, mice receiving 15 Gy + BMT + scFv exhibit prolonged survival. At day 90, before sacrifice, they display normal appearance, behavior, and serum biochemistries, and surprisingly, at full autopsy, near-normal physiology in all 42 tissues examined.

CONCLUSIONS

Anti-ceramide scFv mitigates GI-ARS lethality and improves marrow reconstitution rendering prolonged survival with near normal autopsies.

Excess Dietary Sugar Alters Colonocyte Metabolism and Impairs the Proliferative Response to Damage

BACKGROUND & AIMS

The colonic epithelium requires continuous renewal by crypt resident intestinal stem cells (ISCs) and transit-amplifying (TA) cells to maintain barrier integrity, especially after inflammatory damage. The diet of high-income countries contains increasing amounts of sugar, such as sucrose. ISCs and TA cells are sensitive to dietary metabolites, but whether excess sugar affects their function directly is unknown.

METHODS

Here, we used a combination of 3-dimensional colonoids and a mouse model of colon damage/repair (dextran sodium sulfate colitis) to show the direct effect of sugar on the transcriptional, metabolic, and regenerative functions of crypt ISCs and TA cells.

RESULTS

We show that high-sugar conditions directly limit murine and human colonoid development, which is associated with a reduction in the expression of proliferative genes, adenosine triphosphate levels, and the accumulation of pyruvate. Treatment of colonoids with dichloroacetate, which forces pyruvate into the tricarboxylic acid cycle, restored their growth. In concert, dextran sodium sulfate treatment of mice fed a high-sugar diet led to massive irreparable damage that was independent of the colonic microbiota and its metabolites. Analyses on crypt cells from high-sucrose-fed mice showed a reduction in the expression of ISC genes, impeded proliferative potential, and increased glycolytic potential without a commensurate increase in aerobic respiration.

CONCLUSIONS

Taken together, our results indicate that short-term, excess dietary sucrose can directly modulate intestinal crypt cell metabolism and inhibit ISC/TA cell regenerative proliferation. This knowledge may inform diets that better support the treatment of acute intestinal injury.

Radiation-induced gastrointestinal (GI) syndrome as a function of age

Previous studies show increased sensitivity of older mice (28-29 months) compared with young adult mice (3 months, possessing a mature immune system) to radiation-induced GI lethality. Age-dependent lethality was associated with higher levels of apoptotic stem cells in small intestinal crypts that correlated with sphingomyelinase activity, a source of pro-apoptotic ceramide. The objective of this study is to determine whether the cycling crypt base columnar cells (CBCs) in aging animals are specifically more sensitive to radiation effects than the CBCs in young adult mice, and to identify factors that contribute to increased radiosensitivity. Mortality induced by subtotal body radiation was assessed at different doses (13 Gy, 14 Gy, and 15 Gy) in young adult mice versus older mice. Each dose was evaluated for the occurrence of lethal GI syndrome. A higher death rate due to radiation-induced GI syndrome was observed in older mice as compared with young adult mice: 30 vs. 0% at 13 Gy, 90 vs. 40% at 14 Gy, and 100 vs. 60% at 15 Gy. Radiation-induced damage to crypts was determined by measuring crypt regeneration (H&E staining, Ki67 expression), CBC biomarkers (lgr5 and ascl2), premature senescence (SA-β-gal activity), and apoptosis of CBCs. At all three doses, crypt microcolony survival assays showed that the older mice had fewer regenerating crypts at 3.5 days post-radiation treatment. Furthermore, in the older animals, baseline CBCs numbers per circumference were significantly decreased, correlating with an elevated apoptotic index. Analysis of tissue damage showed an increased number of senescent CBCs per crypt circumference in older mice relative to younger mice, where the latter was not significantly affected by radiation treatment. It is concluded that enhanced sensitivity to radiation-induced GI syndrome and higher mortality in older mice can be attributed to a decreased capacity to regenerate crypts, presumably due to increased apoptosis and senescence of CBCs.

Gamma-Tocotrienol Modulates Total-Body Irradiation-Induced Hematopoietic Injury in a Nonhuman Primate Model

Radiation exposure causes acute damage to hematopoietic and immune cells. To date, there are no radioprotectors available to mitigate hematopoietic injury after radiation exposure. Gamma-tocotrienol (GT3) has demonstrated promising radioprotective efficacy in the mouse and nonhuman primate (NHP) models. We determined GT3-mediated hematopoietic recovery in total-body irradiated (TBI) NHPs. Sixteen rhesus macaques divided into two groups received either vehicle or GT3, 24 h prior to TBI. Four animals in each treatment group were exposed to either 4 or 5.8 Gy TBI. Flow cytometry was used to immunophenotype the bone marrow (BM) lymphoid cell populations, while clonogenic ability of hematopoietic stem cells (HSCs) was assessed by colony forming unit (CFU) assays on day 8 prior to irradiation and days 2, 7, 14, and 30 post-irradiation. Both radiation doses showed significant changes in the frequencies of B and T-cell subsets, including the self-renewable capacity of HSCs. Importantly, GT3 accelerated the recovery in CD34⁺ cells, increased HSC function as shown by improved recovery of CFU-granulocyte macrophages (CFU-GM) and burst-forming units erythroid (B-FUE), and aided the recovery of circulating neutrophils and platelets. These data elucidate the role of GT3 in hematopoietic recovery, which should be explored as a potential medical countermeasure to mitigate radiation-induced injury to the hematopoietic system.

Cellular Damage in the Target and Out-Of-Field Peripheral Organs during VMAT SBRT Prostate Radiotherapy: An In Vitro Phantom-Based Study

Simple Summary

New developments show that patients with prostate cancer can benefit from radiotherapy delivered with a hypo-fractionated regimen. The aim of our study was to investigate the effect of hypo-fractionated stereotactic body radiation therapy (SBRT) of prostate cancer on out-of-field organs. We used a humanoid phantom to irradiate prostate cells in conditions similar to patient therapy, using SBRT planning. Our results show that radiation doses in the location of the intestine and lung resulted in significantly higher radiation doses than the further locations. We observed a high radiotoxic effect in the cells irradiated in the prostate, and a small increase in DNA damage and cell killing in the intestine location. Gene expression analysis revealed significant enrichment of the biological processes related to the radiation response in the prostate. In the lung and thyroid, the enrichment of several gene groups was revealed, however the processes were not clearly related to the response to radiation. Our study provides extensive data on out-of-field safety of prostate SBRT.

Abstract

Hypo-fractionated stereotactic body radiation therapy (SBRT) is an effective treatment for prostate cancer (PCa). Although many studies have investigated the effects of SBRT on the prostate and adjacent organs, little is known about the effects further out-of-field. The aim of this study was to investigate, both in vitro and in a quasi-humanoid phantom, the biological effects (using a dose-scaling approach) of radiation in the out-of-field peripheral organs delivered by 6 MV volumetric modulated arc therapy (VMAT) SBRT in a prostate cancer model. Healthy prostate cells were irradiated in a phantom at locations corresponding to the prostate, intestine, lung, thyroid, and brain. Seven 10 Gy fractions of VMAT SBRT were delivered to the target in a single session without intermission (scaled-up method). Radiochromic films were used to measure the doses. The radiobiological response was assessed by measuring DNA breaks, the cell survival fraction, and differences in gene expression profile. Our results showed a strong, multiparametric radiobiological response of the cells in the prostate. Outside of the radiation field, the highest doses were observed in the intestine and lung. A small increase (not statistically significant) in DNA damage and cell death was observed in the intestines. Several gene groups (cell cycle, DNA replication) were depleted in the lung and thyroid (DNA replication, endocytosis), but further analysis revealed no changes in the relevant biological processes. This study provides extensive evidence of the types and extent of radiobiological responses during VMAT SBRT in a prostate cancer model. Additional research is needed to determine whether the radiobiological effects observed in the peripheral organs are validated in a clinical context.

Radiomitigation by Melatonin in C57BL/6 Mice: Possible Implications as Adjuvant in Radiotherapy and Chemotherapy

BACKGROUND/AIM

Melatonin (N-acetyl-5-methoxytryptamine), a chief secretory molecule of the pineal gland, has multiple properties, and numerous clinical investigations regarding its actions are in progress. This study investigated the radiomitigative role of melatonin in C57BL/6 mice.

MATERIALS AND METHODS

Melatonin (100 mg/kg) was orally administered once daily starting at 1 h on day 1 and subsequently every 24 h until day 7 after whole-body irradiation (WBI) and survival was monitored for 30 days. The bone marrow, spleen, and intestine were studied to evaluate the mitigative potential of melatonin after radiation-induced damage.

RESULTS

Melatonin significantly improved the survival upto 60% and 90% after 9 Gy (lethal) and 7.5 Gy (sub-lethal) WBI, respectively. Melatonin alleviated WBI-induced myelosuppression and pancytopenia, and increased white blood cell, red blood cell, platelet, and lymphocyte (CD4⁺ and CD8⁺) counts in peripheral blood. Bone marrow and spleen cellularity were restored through enhanced haematopoiesis. Melatonin ameliorated the damage in the small intestine, and promoted recovery of villi length, crypts number, and goblet cell count.

CONCLUSION

Melatonin mitigates the radiation-induced injury in the gastrointestinal and haematopoietic systems. The observed radiomitigative properties of melatonin can also be useful in the context of adjuvant therapy for cancer and radiotherapy.

Effects of Gamma-Tocotrienol on Intestinal Injury in a GI-Specific Acute Radiation Syndrome Model in Nonhuman Primate

The gastrointestinal (GI) system is highly susceptible to irradiation. Currently, there is no Food and Drug Administration (FDA)-approved medical countermeasures for GI radiation injury. The vitamin E analog gamma-tocotrienol (GT3) is a promising radioprotector in mice and nonhuman primates (NHP). We evaluated GT3-mediated GI recovery in total-body irradiated (TBI) NHPs. Sixteen rhesus macaques were divided into two groups; eight received vehicle and eight GT3 24 h prior to 12 Gy TBI. Proximal jejunum was assessed for structural injuries and crypt survival on day 4 and 7. Apoptotic cell death and crypt cell proliferation were assessed with TUNEL and Ki-67 immunostaining. Irradiation induced significant shortening of the villi and reduced mucosal surface area. GT3 induced an increase in crypt depth at day 7, suggesting that more stem cells survived and proliferated after irradiation. GT3 did not influence crypt survival after irradiation. GT3 treatment caused a significant decline in TUNEL-positive cells at both day 4 (p < 0.03) and 7 (p < 0.0003). Importantly, GT3 induced a significant increase in Ki-67-positive cells at day 7 (p < 0.05). These data suggest that GT3 has radioprotective function in intestinal epithelial and crypt cells. GT3 should be further explored as a prophylactic medical countermeasure for radiation-induced GI injury.

Screening of radiation gastrointestinal injury biomarkers in rat plasma by high-coverage targeted lipidomics

INTRODUCTION

In the event of radiological accidents and cancer radiotherapies in clinic, the gastrointestinal (GI) system is vulnerable to ionizing radiation and shows GI injury. Accessible biomarkers may provide means to predict, evaluate, and treat GI tissue damage. The current study investigated radiation GI injury biomarkers in rat plasma.

MATERIAL AND METHODS

High-coverage targeted lipidomics was employed to profile lipidome perturbations at 72 h after 0, 1, 2, 3, 5 and 8 Gy (⁶⁰Co γ-rays at 1 Gy/min) total-body irradiation in male rat jejunum. The results were correlated with previous plasma screening outcomes.

RESULTS

In total, 93 differential metabolites and 28 linear dose-responsive metabolites were screened in the jejunum. Moreover, 52 lipid species with significant differences both in jejunum and plasma were obtained. Three lipid species with linear dose-response relationship both in jejunum and plasma were put forth, which exhibited good to excellent sensitivity and specificity in triaging different exposure levels.

DISCUSSION

The linear dose-effect relationship of lipid metabolites in the jejunum and the triage performance of radiation GI injury biomarkers in plasma were studied for the first time.

CONCLUSION

The present study can provide insights into expanded biomarkers of IR-mediated GI injury and minimally invasive assays for evaluation.

Paeoniflorin Inhibits ASK1-TF Axis by Up-Regulating SOCS3 to Alleviate Radiation Enteritis

Radiation enteritis is one of the main adverse effects of radiotherapy, presenting with a poorly understood etiology and limited options for therapy. Intestinal inflammation and ischemia are the core mechanisms of radiation enteritis. Suppressor of cytokine signaling 3 (SOCS3) is an endogenous “inflammation brake.” We hypothesized that paeoniflorin, a pinane monoterpene bitter glycoside, could increase SOCS3 expression to reduce inflammation and ischemia and improve enteritis in mice. Laser Doppler flowmetry was used to detect changes in intestinal blood flow. RAW264.7 and human umbilical vein endothelial cells were used to investigate the mechanism of action of paeoniflorin. It was observed that radiation caused high mortality, intestinal inflammatory responses, and low blood flow in mice. Paeoniflorin effectively alleviated intestinal atrophy, prevented thrombosis, improved radiation enteritis, and reduced mortality in mice undergoing radiotherapy. In addition, paeoniflorin increased the release of growth arrest-specific gene 6 (Gas6) and phosphorylation of the Axl receptor, subsequently inducing the expression of SOCS3 and inhibiting the expression of p-apoptosis signal-regulating kinase 1 and tissue factor in vivo and in vitro. Based on our findings, we suggest that paeoniflorin is potentially effective in alleviating radiation enteritis via the activation of the Gas6/Axl/SOCS3 axis and subsequent reduction in intestinal inflammation and ischemia.

Incidence and characteristics of death from peptic ulcer among cancer patients in the United States

Most cancer patients die of non-cancer causes, and peptic ulcer is one cause that deserves attention. To characterize the incidence and risk factors of death from peptic ulcer among cancer patients, we extracted the data of cancer patients registered in the Surveillance Epidemiology and End Results (SEER) program from 1975 to 2016. Out of the 8,471,051 patients extracted from SEER, 4,698 died from peptic ulcer, with a mortality rate of 9.08/100,000 person-years. Meanwhile, the mortality rate in the general population was 5.09/100,000 person-years, giving a standardized mortality ratio (SMR) of 1.78 (95% confidence interval, 1.73–1.84). Patients who are female, of other race, unmarried, and with distant tumor stage have greater SMRs. A higher SMR was associated with a younger age at diagnosis. Among those aged < 40 years at diagnosis, the plurality of fatal peptic ulcers occurred in patients with leukemia and lymphoma, while in patients aged > 40 years, the majority occurred in those with prostate, breast, colorectum, and lung cancer. Patients with upper digestive system malignancies had the highest SMRs and hazard ratios (HRs), which could be ascribed to radiotherapy-induced damage to the gastroduodenum. The risk declined rapidly one year after diagnosis. However, the SMRs in the upper digestive system cancer survivors increased significantly over ten years after diagnosis. Upper digestive system cancers adjacent to the gastroduodenum were associated with higher SMRs and HRs compared with other types of cancer, possibly contributing partially to the damage caused by radiotherapy on the radiosensitive gastroduodenum.

CBP/P300 Inhibitors Mitigate Radiation-Induced GI Syndrome by Promoting Intestinal Stem Cell-Mediated Crypt Regeneration

PURPOSE

Radiation-induced gastrointestinal syndrome (RIGS) is currently the main cause of death for people exposed to a high dose of irradiation during nuclear incidents, and there is currently no approved effective therapy. Here, we found that CBP/P300 inhibitors, with high efficacy and low toxicity, might be promising radiation mitigators that can cure RIGS.

METHODS AND MATERIALS

Ex vivo 3D organoid cultures derived from mouse jejunum and human ileum and colon were used to examine the radio-mitigative effects of CBP/P300 inhibitors. The radio-mitigative effect was evaluated by quantifying the survival rate and size of organoids after radiation. SGC-CBP30 (50 mg/kg body weight), an inhibitor of CBP/P300, was intraperitoneally injected into C57B/6J mice 24 hours after subtotal-body irradiation or whole-body irradiation. The regenerated crypts and animal survival were determined by microcolony assay and the Kaplan-Meier method, respectively. Lgr5-lacZ mice were used to evaluate the survival of intestinal stem cells after treatments.

RESULTS

We found that CBP/P300 inhibitors were effective mitigators that could be used to treat RIGS. CBP/P300 inhibition promoted the regeneration of intestinal organoids in vitro and of crypts in vivo. Remarkably, the administration of CBP/P300 inhibitors to mice 24 hours after lethal irradiation promoted Lgr5+ intestinal stem cell and crypt recovery, resulting in improved mouse survival. Moreover, our data show that CBP/P300 inhibitors rescued irradiated mice from RIGS by delaying intestinal epithelial cell cycle progression after radiation.

CONCLUSIONS

These data demonstrate that CBP/P300 inhibitors are effective medical countermeasures to mitigate gastrointestinal toxicity from radiation.

SIRT1 inhibitors mitigate radiation-induced GI syndrome by enhancing intestinal-stem-cell survival

High-dose radiation exposure induces gastrointestinal (GI) stem cell death, resulting in denudation of the intestinal mucosa and lethality from GI syndrome, for which there is currently no effective therapy. Studying an intestinal organoid-based functional model, we found that Sirtuin1(SIRT1) inhibition through genetic knockout or pharmacologic inhibition significantly improved mouse and human intestinal organoid survival after irradiation. Remarkably, mice administered with two doseages of SIRT1 inhibitors at 24 and 96 h after lethal irradiation promoted Lgr5+ intestinal stem cell and crypt recovery, with improved mouse survival (88.89% of mice in the treated group vs. 0% of mice in the control group). Moreover, our data revealed that SIRT1 inhibition increased p53 acetylation, resulting in the stabilization of p53 and likely contributing to the survival of intestinal epithelial cells post-radiation. These results demonstrate that SIRT1 inhibitors are effective clinical countermeasures to mitigate GI toxicity from potentially lethal radiation exposure.

Evaluation of Plasma Biomarker Utility for the Gastrointestinal Acute Radiation Syndrome in Non-human Primates after Partial Body Irradiation with Minimal Bone Marrow Sparing through Correlation with Tissue and Histological Analyses

Exposure to total- and partial-body irradiation following a nuclear or radiological incident result in the potentially lethal acute radiation syndromes of the gastrointestinal and hematopoietic systems in a dose- and time-dependent manner. Radiation-induced damage to the gastrointestinal tract is observed within days to weeks post-irradiation. Our objective in this study was to evaluate plasma biomarker utility for the gastrointestinal acute radiation syndrome in non-human primates after partial body irradiation with minimal bone marrow sparing through correlation with tissue and histological analyses. Plasma and jejunum samples from non-human primates exposed to partial body irradiation of 12 Gy with bone marrow sparing of 2.5% were evaluated at various time points from day 0 to day 21 as part of a natural history study. Additionally, longitudinal plasma samples from non-human primates exposed to 10 Gy partial body irradiation with 2.5% bone marrow sparing were evaluated at timepoints out to 180 d post-irradiation. Plasma and jejunum metabolites were quantified via liquid chromatography-tandem mass spectrometry and histological analysis consisted of corrected crypt number, an established metric to assess radiation-induced gastrointestinal damage. A positive correlation of metabolite levels in jejunum and plasma was observed for citrulline, serotonin, acylcarnitine, and multiple species of phosphatidylcholines. Citrulline levels also correlated with injury and regeneration of crypts in the small intestine. These results expand the characterization of the natural history of gastrointestinal acute radiation syndrome in non-human primates exposed to partial body irradiation with minimal bone marrow sparing and also provide additional data toward the correlation of citrulline with histological endpoints.

LPAR2 receptor activation attenuates radiation-induced disruption of apical junctional complexes and mucosal barrier dysfunction in mouse colon

The tight junction (TJ) and barrier function of colonic epithelium is highly sensitive to ionizing radiation. We evaluated the effect of lysophosphatidic acid (LPA) and its analog, Radioprotein-1, on γ-radiation-induced colonic epithelial barrier dysfunction using Caco-2 and m-IC_C12 cell monolayers in vitro and mice in vivo. Mice were subjected to either total body irradiation (TBI) or partial body irradiation (PBI-BM5). Intestinal barrier function was assessed by analyzing immunofluorescence localization of TJ proteins, mucosal inulin permeability, and plasma lipopolysaccharide (LPS) levels. Oxidative stress was analyzed by measuring protein thiol oxidation and antioxidant mRNA. In Caco-2 and m-IC_C12 cell monolayers, LPA attenuated radiation-induced redistribution of TJ proteins, which was blocked by a Rho-kinase inhibitor. In mice, TBI and PBI-BM5 disrupted colonic epithelial tight junction and adherens junction, increased mucosal permeability, and elevated plasma LPS; TJ disruption by TBI was more severe in Lpar2^-/- mice compared to wild-type mice. RP1, administered before or after irradiation, alleviated TBI and PBI-BM5-induced TJ disruption, barrier dysfunction, and endotoxemia accompanied by protein thiol oxidation and downregulation of antioxidant gene expression, cofilin activation, and remodeling of the actin cytoskeleton. These data demonstrate that LPAR2 receptor activation prevents and mitigates γ-irradiation-induced colonic mucosal barrier dysfunction and endotoxemia.

microRNA and Metabolite Signatures Linked to Early Consequences of Lethal Radiation

Lethal total body irradiation (TBI) triggers multifactorial health issues in a potentially short time frame. Hence, early signatures of TBI would be of great clinical value. Our study aimed to interrogate microRNA (miRNA) and metabolites, two biomolecules available in blood serum, in order to comprehend the immediate impacts of TBI. Mice were exposed to a lethal dose (9.75 Gy) of Cobalt-60 gamma radiation and euthanized at four time points, namely, days 1, 3, 7 and 9 post-TBI. Serum miRNA libraries were sequenced using the Illumina small RNA sequencing protocol, and metabolites were screened using a mass spectrometer. The degree of early impacts of irradiation was underscored by the large number of miRNAs and metabolites that became significantly expressed during the Early phase (day 0 and 1 post-TBI). Radiation-induced inflammatory markers for bone marrow aplasia and pro-sepsis markers showed early elevation with longitudinal increment. Functional analysis integrating miRNA-protein-metabolites revealed inflammation as the overarching host response to lethal TBI. Early activation of the network linked to the synthesis of reactive oxygen species was associated with the escalated regulation of the fatty acid metabolism network. In conclusion, we assembled a list of time-informed critical markers and mechanisms of significant translational potential in the context of a radiation exposure event.

Salmonella infection induced intestinal crypt hyperplasia through Wnt/β-catenin pathway in chicken

S. Pullorum is a causative agent of enteric disease of poultry with serious diarrhea. However, the detailed mechanism behind its injury to intestinal mucosa barrier, especially for intestinal stem cells, is unclear. In this study, S. Pullorum were orally administrated to 3 days old chicken to investigate the pathogenesis of S. Pullorum on intestinal mucosal barrier, especially on the proliferation of epithelial cells. We found that S. Pullorum could colonize in the cecum and invade into the liver through intestinal mucosa damage, which caused obvious pathological changes in liver and intestine and even leaded to death, as well as significant reduction of body weight. We also found that S. Pullorum infection enhanced the mRNA expression of IL-1β and IL-6 through TLR4/MyD88 pathway, which was also further verified by the increased lipopolysaccharide (LPS) levels in serum. Furthermore, S. Pullorum increased the depth of crypt and density of PCNA⁺ cells significantly through the over-activation of Wnt/β-catenin signaling pathway. The expression of intestinal stem cells markers Lgr5 and Bmi1 was also increased after S. Pullorum infection to support the crypt hyperplasia. In addition, we verified that S. Pullorum infection enhanced the mRNA expression of IL-1β, TLR4, Lgr5 and Bmi1. Our study indicated that S. Pullorum infection damaged the intestinal mucosa barrier to induce diarrhea, affected the abnormal proliferation of intestinal stem cells by over-activation of Wnt/β-catenin pathway in chicken.

Organoids Reveal That Inherent Radiosensitivity of Small and Large Intestinal Stem Cells Determines Organ Sensitivity

Tissue survival responses to ionizing radiation are nonlinear with dose, rather yielding tissue-specific descending curves that impede straightforward analysis of biologic effects. Apoptotic cell death often occurs at low doses, while at clinically relevant intermediate doses, double-strand break misrepair yields mitotic death that determines outcome. As researchers frequently use a single low dose for experimentation, such strategies may inaccurately depict inherent tissue responses. Cutting edge radiobiology has adopted full dose survival profiling and devised mathematical algorithms to fit curves to observed data to generate highly reproducible numerical data that accurately define clinically relevant inherent radiosensitivities. Here, we established a protocol for irradiating organoids that delivers radiation profiles simulating the organ of origin. This technique yielded highly similar dose-survival curves of small and large intestinal crypts in vivo and their cognate organoids analyzed by the single-hit multi-target (SHMT) algorithm, outcomes reflecting the inherent radiation profile of their respective Lgr5⁺ stem cell populations. As this technological advance is quantitative, it will be useful for accurate evaluation of intestinal (patho)physiology and drug screening. SIGNIFICANCE: These findings establish standards for irradiating organoids that deliver radiation profiles that phenocopy the organ of origin.See related commentary by Muschel et al., p. 927.

Preclinical murine platform to evaluate therapeutic countermeasures against radiation-induced gastrointestinal syndrome

Currently, there are no therapies available to mitigate intestinal damage after radiation injury. Efforts to study and design new therapies are hampered by a lack of models that can be readily adopted to study therapeutic targets. Here we describe a preclinical platform to evaluate therapeutic countermeasures against intestinal radiation injury in vivo in a mouse model that permits inducible and reversible gene suppression following radiation exposure. We demonstrate that transient intestinal Apc suppression stimulates intestinal regeneration and mitigates lethality after radiation intestinal injury, thus validating pulsed Wnt pathway agonism as a therapeutic strategy. This platform can be readily adopted to study theoretically any gene of interest associated with the biology and treatment of intestinal radiation injury.

Radiation-induced gastrointestinal syndrome (RIGS) is a limiting factor for therapeutic abdominopelvic radiation and is predicted to be a major source of morbidity in the event of a nuclear accident or radiological terrorism. In this study, we developed an in vivo mouse-modeling platform that enables spatial and temporal manipulation of potential RIGS targets in mice following whole-abdomen irradiation without the confounding effects of concomitant hematopoietic syndrome that occur following whole-body irradiation. We then tested the utility of this platform to explore the effects of transient Wnt pathway activation on intestinal regeneration and animal recovery following induction of RIGS. Our results demonstrate that intestinal epithelial suppression of adenomatous polyposis coli (Apc) mitigates RIGS lethality in vivo after lethal ionizing radiation injury-induced intestinal epithelial damage. These results highlight the potential of short-term Wnt agonism as a therapeutic target and establish a platform to evaluate other strategies to stimulate intestinal regeneration after ionizing radiation damage.

Keeping Candida commensal: how lactobacilli antagonize pathogenicity of Candida albicans in an in vitro gut model

The intestine is the primary reservoir of Candida albicans that can cause systemic infections in immunocompromised patients. In this reservoir, the fungus exists as a harmless commensal. However, antibiotic treatment can disturb the bacterial microbiota, facilitating fungal overgrowth and favoring pathogenicity. The current in vitro gut models that are used to study the pathogenesis of C. albicans investigate the state in which C. albicans behaves as a pathogen rather than as a commensal. We present a novel in vitro gut model in which the fungal pathogenicity is reduced to a minimum by increasing the biological complexity. In this model, enterocytes represent the epithelial barrier and goblet cells limit C. albicans adhesion and invasion. Significant protection against C. albicans-induced necrotic damage was achieved by the introduction of a microbiota of antagonistic lactobacilli. We demonstrated a time-, dose- and species-dependent protective effect against C. albicans-induced cytotoxicity. This required bacterial growth, which relied on the presence of host cells, but was not dependent on the competition for adhesion sites. Lactobacillus rhamnosus reduced hyphal elongation, a key virulence attribute. Furthermore, bacterial-driven shedding of hyphae from the epithelial surface, associated with apoptotic epithelial cells, was identified as a main and novel mechanism of damage protection. However, host cell apoptosis was not the driving mechanism behind shedding. Collectively, we established an in vitro gut model that can be used to experimentally dissect commensal-like interactions of C. albicans with a bacterial microbiota and the host epithelial barrier. We also discovered fungal shedding as a novel mechanism by which bacteria contribute to the protection of epithelial surfaces.This article has an associated First Person interview with the joint first authors of the paper.

Glucose-6-phosphate dehydrogenase deficiency reduces susceptibility to cancer of endodermal origin

Background: Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common inherited enzyme defect worldwide. There is a growing scientific evidence for a protective role of G6PD deficiency against carcinogenesis. In this retrospective analysis, we tested the hypothesis that G6PD deficiency may reduce the risk of developing cancer in a tissue-specific manner. Material and methods: The study was conducted using data from 11,708 subjects undergoing gastrointestinal endoscopic procedures between 2002 and 2018 and tested for G6PD status in a teaching hospital of Northern Sardinia, Italy. Results: A 40% reduction of risk for cancer of endodermal origin was observed among G6PD-deficient patients compared with subjects with normal enzyme activity (relative risk (RR) 0.61, 95% confidence interval (CI) 0.47-0.80) in both genders, confirmed by multivariable generalized linear regression after adjusting for age, sex, smoking habits, body mass index, diabetes and socio-economic status. The 'protective' effect of G6PD deficiency was larger for gastric cancer (RR 0.41, 95% CI 0.18-0.99), hepatocellular carcinoma (RR 0.48, 95% CI 0.26-0.92) and colorectal cancer (RR 0.72, 95% CI 0.53-0.98), while a non-significant risk was observed for breast, prostate, lung, hematopoietic and metastases (primary site unknown). Conclusions: Our results suggest a reduced susceptibility to develop cancers, mostly of endodermal origin (stomach, colon and liver), but not of ectodermal/mesodermal origin, in carriers of G6PD deficiency. The effects of G6PD deficiency on carcinogenesis need further studies to better understand how cancer cells originating from different germ layers use pentose phosphate pathway to proliferate.

Non-Invasive Biomarkers for Celiac Disease

Once thought to be uncommon, celiac disease has now become a common disease globally. While avoidance of the gluten-containing diet is the only effective treatment so far, many new targets are being explored for the development of new drugs for its treatment. The endpoints of therapy include not only reversal of symptoms, normalization of immunological abnormalities and healing of mucosa, but also maintenance of remission of the disease by strict adherence of the gluten-free diet (GFD). There is no single gold standard test for the diagnosis of celiac disease and the diagnosis is based on the presence of a combination of characteristics including the presence of a celiac-specific antibody (anti-tissue transglutaminase antibody, anti-endomysial antibody or anti-deamidated gliadin peptide antibody) and demonstration of villous abnormalities. While the demonstration of enteropathy is an important criterion for a definite diagnosis of celiac disease, it requires endoscopic examination which is perceived as an invasive procedure. The capability of prediction of enteropathy by the presence of the high titer of anti-tissue transglutaminase antibody led to an option of making a diagnosis even without obtaining mucosal biopsies. While present day diagnostic tests are great, they, however, have certain limitations. Therefore, there is a need for biomarkers for screening of patients, prediction of enteropathy, and monitoring of patients for adherence of the gluten-free diet. Efforts are now being made to explore various biomarkers which reflect different changes that occur in the intestinal mucosa using modern day tools including transcriptomics, proteomics, and metabolomics. In the present review, we have discussed comprehensively the pros and cons of available biomarkers and also summarized the current status of emerging biomarkers for the screening, diagnosis, and monitoring of celiac disease.

β-Arrestin1-mediated decrease in endoplasmic reticulum stress impairs intestinal stem cell proliferation following radiation

Gastrointestinal toxicity limits the clinical application of abdominal and pelvic radiotherapy and currently has no effective treatment. Intestinal leucine-rich-repeat-containing GPCR 5 (Lgr5)-positive stem cell depletion and loss of proliferative ability due to radiation may be the primary factors causing intestinal injury following radiation. Here, we report the critical role of β-arrestin1 (βarr1) in radiation-induced intestinal injury. Intestinal βarr1 was highly expressed in radiation enteritis and in a radiation model. βarr1 knockout (KO) or knockdown mice exhibited increased proliferation in intestinal Lgr5+ stem cell, crypt reproduction, and survival following radiation. Unexpectedly, the beneficial effects of βarr1 deficiency on intestinal stem cells in response to radiation were compromised when the endoplasmic reticulum stress-related protein kinase RNA-like ER kinase (PERK)/eukaryotic initiation factor-2α (eIF2α) pathway was inhibited, and this result was further supported in vitro. Furthermore, we found that βarr1 knockdown with small interfering RNA significantly enhanced intestinal Lgr5⁺ stem cell proliferation after radiation via directly targeting PERK. βarr1 offers a promising target for mitigating radiation-induced intestinal injury.-Liu, Z., Jiang, J., He, Q., Liu, Z., Yang, Z., Xu, J., Huang, Z., Wu, B. β-Arrestin1-mediated decrease in endoplasmic reticulum stress impairs intestinal stem cell proliferation following radiation.

Lactobacillus rhamnosus GG protects the intestinal epithelium from radiation injury through release of lipoteichoic acid, macrophage activation and the migration of mesenchymal stem cells

OBJECTIVE

Lactobacillus rhamnosus GG (LGG), a probiotic, given by gavage is radioprotective of the mouse intestine. LGG-induced radioprotection is toll-like receptor 2 (TLR2) and cyclooxygenase-2 (COX-2)-dependent and is associated with the migration of COX-2+mesenchymal stem cells (MSCs) from the lamina propria of the villus to the lamina propria near the crypt epithelial stem cells. Our goals were to define the mechanism of LGG radioprotection including identification of the TLR2 agonist, and the mechanism of the MSC migration and to determine the safety and efficacy of this approach in models relevant to clinical radiation therapy.

DESIGN

Intestinal radioprotection was modelled in vitro with cell lines and enteroids as well as in vivo by assaying clinical outcomes and crypt survival. Fractionated abdominal and single dose radiation were used along with syngeneic CT26 colon tumour grafts to assess tumour radioprotection.

RESULTS

LGG with a mutation in the processing of lipoteichoic acid (LTA), a TLR2 agonist, was not radioprotective, while LTA agonist and native LGG were. An agonist of CXCR4 blocked LGG-induced MSC migration and LGG-induced radioprotection. LGG given by gavage induced expression of CXCL12, a CXCR4 agonist, in pericryptal macrophages and depletion of macrophages by clodronate liposomes blocked LGG-induced MSC migration and radioprotection. LTA effectively protected the normal intestinal crypt, but not tumours in fractionated radiation regimens.

CONCLUSIONS

LGG acts as a 'time-release capsule' releasing radioprotective LTA. LTA then primes the epithelial stem cell niche to protect epithelial stem cells by triggering a multicellular, adaptive immune signalling cascade involving macrophages and PGE2 secreting MSCs.

TRIAL REGISTRATION NUMBER

NCT01790035; Pre-results.

Targeted Metabolomics Reveals Metabolomic Signatures Correlating Gastrointestinal Tissue to Plasma in a Mouse Total-body Irradiation Model

High-throughput, targeted metabolomics was used to identify early time-point small intestine and plasma metabolite markers of gastrointestinal acute radiation syndrome. The small intestine metabolite markers were cross correlated to plasma metabolites in order to identify minimally invasive circulating markers. The radiation exposure covered lethal and sublethal gastrointestinal acute radiation syndrome. The small intestine and plasma metabolite profiles were generated at 1 and 3 d postexposure following total-body irradiation. The small intestine and plasma metabolite profiles for mice receiving radiation at day 1 and 3 postexposure were significantly different from sham-irradiated mice. There were 14 metabolite markers identified at day 1 and 18 metabolite markers at day 3 that were small-intestine-specific plasma markers of gastrointestinal acute radiation syndrome. A number of the identified metabolites at day 1 were amino acids. Dysregulation of amino acid metabolism at 24 h post-total-body irradiation provides potential insight into the initial inflammatory response during gastrointestinal acute radiation syndrome.

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.

PERK is essential for proliferation of intestinal stem cells in mice

Protein kinase RNA-like Endoplasmic Reticulum Kinase (PERK) is an endoplasmic reticulum stress sensor that possesses pro-survival capability and contributes to cell homeostasis and survival. Leucine-rich repeat-containing G-protein coupled receptor 5 (Lgr5) has been recognized as a stem cell marker in intestinal epithelial cells. To determine whether PERK modulates the proliferation of intestinal stem cells, we investigated the effects of PERK knock-down on intestinal Lgr5-positive stem cells in mice. Lgr5-EGFP knock-in mice were fed with lentivirus-PERK shRNA twice a day for three days. Isolated intestinal Lgr5-positive stem cells were treated with lentivirus-PERK shRNA. The number of Lgr5-positive cells, the proliferation and apoptotic indices, several biomarkers for proliferation and differentiation, and Akt expression in intestinal stem cells were detected in vivo, in vitro and in two intestinal epithelial injury models caused by radiotherapy and sepsis. PERK knock-down could significantly diminish the number and proliferation of Lgr5-positive cells, induce the low expression of several proliferation markers and the high expression of several differentiation markers in Lgr5-positive cells, enhance the apoptotic Lgr5-positive cells, and reduce the Akt expression in intestinal Lgr5-positive stem cells. Similar results were observed in radiotherapy- and sepsis-induced intestinal injuries. Moreover, PERK inhibition markedly decreased the survival of mice in response to radiation and sepsis. These results suggest a critical role for PERK in the proliferation and survival of intestinal stem cells in mice.

Protective effect of polydatin on radiation-induced injury of intestinal epithelial and endothelial cells

This study aimed to examine the radioprotective effect of polydatin (PD) on crypt and endothelial cells of the small intestines of C57BL/6 mice that received abdominal irradiation (IR). Mice were treated with 6 MV X-ray (20 Gy) abdominal IR at a dose rate of 200 cGy/min. Thirty minutes before or after IR, mice were intraperitoneally injected with PD. The rate of survival of the mice at 30 days after IR was determined. The duodenum (upper small intestine), jejunum (middle small intestine), and ileum (lower small intestine) were collected and subjected to hematoxylin and eosin staining. Tissue sample sections were analyzed through light microscopy, and the lengths of at least 20 intestinal villi were measured in each group; the average number of crypts was obtained from 10 intestinal samples in each group. Microvessel density was assessed using CD31-positive (brown) vascular endothelial cells/cell clusters. FHs74Int cell proliferation was measured using the CCK-8 assay. PD administration (25 mg/kg) before IR was the most effective in prolonging the survival of C57BL/6 mice. PD reduced radiation-induced injury of intestinal villi, prevented loss of crypts, increased intestinal crypt growth, protected against IR-induced intestinal injury, and enhanced the proliferative potential and reduced the apoptosis of FHs74Int cells after IR. Moreover, PD increased small intestinal MVD and reduced the apoptosis of intestinal microvascular endothelial cells in mice after IR. Therefore, PD was found to be able to protect the two types of cells from radiation damage and to thus alleviate radiation-induced injury of small intestine.

A novel morphometry system automatically assessing the growth and regeneration of intestinal organoids

As compared with 2D cell line cultures, 3D intestinal organoids are better at maximally recapitulating the physiological features of stem cells in vivo. However, the complex 3D structure is an obstacle which must be objectively and automatically evaluated to assess colony growth and regeneration. Meanwhile, no internal standard currently exists for evaluating the size of heterogeneities in organoids or defining those regenerating colonies. Herein, we developed a simple morphometry system to image MTT-stained organoids. The growth curve of organoids can be automatically generated based upon analyzing the integrated optical density using software. Referencing the definition standards of in vivo regenerating crypts, the perimeters of crypts cultured 24 h after seeding were selected as an "Organoid Unit" to further evaluate colony survival rate and colony size heterogeneities after exposure to varying doses of irradiation. Moreover, the morphometry-based quantification data collected confirmed other findings associated with radiation sensitizing effects of ataxia telangiectasia mutated (ATM) and ataxia telangiectasia and Rad3-related protein (ATR) inhibitor and the radiation protective effect of IL-22. In summary, the novel organoid morphometry system combined with a new internal reference is a practical means for standardizing assessment of growth, survival and regeneration of intestinal organoid colonies. This method has promise to facilitate drug screens in intestinal and other organoid systems.

Pravastatin Attenuates Acute Radiation-Induced Enteropathy and Improves Epithelial Cell Function

Background and Aim: Radiation-induced enteropathy is frequently observed after radiation therapy for abdominal and pelvic cancer or occurs secondary to accidental radiation exposure. The acute effects of irradiation on the intestine might be attributed to inhibition of mitosis in the crypts, as the loss of proliferative functions impairs development of the small intestinal epithelium and its barrier function. Especially, oxidative damage to intestinal epithelial cells is a key event in the initiation and progression of radiation-induced enteropathy. Pravastatin is widely used clinically to lower serum cholesterol levels and has been reported to have anti-inflammatory effects on endothelial cells. Here, we investigated the therapeutic effects of pravastatin on damaged epithelial cells after radiation-induced enteritis using in vitro and in vivo systems. Materials and Methods: To evaluate the effects of pravastatin on intestinal epithelial cells, we analyzed proliferation and senescence, oxidative damage, and inflammatory cytokine expression in an irradiated human intestinal epithelial cell line (InEpC). In addition, to investigate the therapeutic effects of pravastatin in mice, we performed histological analysis, bacterial translocation assays, and intestinal permeability assays, and also assessed inflammatory cytokine expression, using a radiation-induced enteropathy model. Results: Histological damage such as shortening of villi length and impaired intestinal crypt function was observed in whole abdominal-irradiated mice. However, damage was attenuated in pravastatin-treated animals, in which normalization of intestinal epithelial cell differentiation was also observed. Using in vitro and in vivo systems, we also showed that pravastatin improves the proliferative properties of intestinal epithelial cells and decreases radiation-induced oxidative damage to the intestine. In addition, pravastatin inhibited levels of epithelial-derived inflammatory cytokines including IL-6, IL-1β, and TNF-α in irradiated InEpC cells. We also determined that pravastatin could rescue intestinal barrier dysfunction via anti-inflammatory effects using the mouse model. Conclusion: Pravastatin has a therapeutic effect on intestinal lesions and attenuates radiation-induced epithelial damage by suppressing oxidative stress and the inflammatory response.

Mitochondrial function - gatekeeper of intestinal epithelial cell homeostasis

The intestinal epithelium is a multicellular interface in close proximity to a dense microbial milieu that is completely renewed every 3-5 days. Pluripotent stem cells reside at the crypt, giving rise to transient amplifying cells that go through continuous steps of proliferation, differentiation and finally anoikis (a form of programmed cell death) while migrating upwards to the villus tip. During these cellular transitions, intestinal epithelial cells (IECs) possess distinct metabolic identities reflected by changes in mitochondrial activity. Mitochondrial function emerges as a key player in cell fate decisions and in coordinating cellular metabolism, immunity, stress responses and apoptosis. Mediators of mitochondrial signalling include molecules such as ATP and reactive oxygen species and interrelate with pathways such as the mitochondrial unfolded protein response (MT-UPR) and AMP kinase signalling, in turn affecting cell cycle progression and stemness. Alterations in mitochondrial function and MT-UPR activation are integral aspects of pathologies, including IBD and cancer. Mitochondrial signalling and concomitant changes in metabolism contribute to intestinal homeostasis and regulate IEC dedifferentiation-differentiation programmes in the context of diseases, suggesting that mitochondrial function as a cellular checkpoint critically contributes to disease outcome. This Review highlights mitochondrial function and MT-UPR signalling in epithelial cell stemness, differentiation and lineage commitment and illustrates mitochondrial function in intestinal diseases.

Kaempferol protects against gamma radiation-induced mortality and damage via inhibiting oxidative stress and modulating apoptotic molecules in vivo and vitro

To investigate the potential protective effect of kaempferol, a representative flavonoid, against radiation induced mortality and injury in vivo and vitro.C57BL/6 male mice and human umbilical venous endothelial cells (HUVECs) were pretreated with kaempferol before radiation. We found that kaempferol can effectively increase 30-day survival rate after 8.5 Gy lethal total body irradiation (TBI). Mice were sacrificed at 7th day after 7 Gy TBI, we found kaempferol against radiation-induced tissues damage, by inhibiting the oxidative stress, and attenuating morphological changes and cell apoptosis. In vitro, kaempferol increased HUVECs cell viability and decrease apoptosis. It also mitigated oxidative stress and restored the abnormal expression of prx-5, Cyt-c, Caspase9 and Caspase3 in mRNA and protein level in HUVECs after radiation. Taken together, it suggests kaempferol can protect against gamma-radiation induced tissue damage and mortality. The present study is the first report of the radioprotective role of kaempferol in vivo and vitro.

Bile salt dependent lipase promotes intestinal adaptation in rats with massive small bowel resection

Intestinal adaptation is important for the short bowel syndrome (SBS) patients. Growing evidence has suggested that bile salt dependent lipase (BSDL) not only has the lipolytic activity, but also the immune-modulating and pro-proliferative activities. The purpose of the present study was to investigate the effects of BSDL on intestinal adaptive growth and gut barrier function in a rat model of SBS. Twenty-four male Sprague-Dawley rats were randomly divided into three experimental groups: sham group (rats underwent bowel transection and re-anastomosis), SBS group (rats underwent 80% bowel resection), SBS-BSDL group (SBS rats orally administered BSDL). The animals were weighed daily. The intestinal morpho-histochemical changes and intestinal barrier function were determined 14 days after the operations. Meanwhile, the expressions of Wnt signaling molecules in enterocytes were also analyzed by immunohistochemistry and Western blot. The postoperative weight gain was faster in the SBS rats treated with BSDL than in the SBS/untreated group. The SBS rats treated with BSDL had significantly greater villus height, crypt depth, and enterocyte proliferation in their residual intestines, as compared with the SBS/untreated group. The recovery of intestinal barrier function was promoted and the expressions of tight-junction proteins were increased in the SBS rats treated with BSDL. Additionally, the data indicated that the proadaptive activities of BSDL might be mediated by Wnt signaling activation in the enterocytes. These observations suggested that enteral BSDL administration promoted intestinal adaptive growth and barrier repairing by activating Wnt signaling pathway in SBS rats.

12-O-tetradecanoylphorbol-13-acetate (TPA) increases murine intestinal crypt stem cell survival following radiation injury

Radiation enteropathy is a common complication in cancer patients following radiation therapy. Thus, there is a need for agents that can protect the intestinal epithelium against radiation. 12-O-tetradecanoylphorbol-13-acetate (TPA) has been shown to induce differentiation and/or apoptosis in multiple cell lines and primary cells. In the current report, we studied the function of TPA in radiation induced enteropathy in cultured rat intestinal epithelial cell line IEC-6 after ionizing radiation (IR) and in mice after high dose total-body gamma-IR (TBI). In IEC-6 cells, there were reduced apoptosis and cell cycle arrest in TPA treated cells after IR. We detected a four-fold increase in crypt cell survival and a two-fold increase in animal survival post TBI in TPA treated mice. The beneficial effects of TPA were accompanied by upregulation of stem cells markers and higher level of proteins that are involved in PKC signaling pathway. In addition, TPA also decreased the TBI-augmented levels of the DNA damage indicators. The effects were only observed when TPA was given before irradiation. These results suggest that TPA has the ability to modulate intestinal crypt stem cells survival and this may represent a promising countermeasure against radiation induced enteropathy.

Modeling radiation injury-induced cell death and countermeasure drug responses in a human Gut-on-a-Chip

Studies on human intestinal injury induced by acute exposure to γ-radiation commonly rely on use of animal models because culture systems do not faithfully mimic human intestinal physiology. Here we used a human Gut-on-a-Chip (Gut Chip) microfluidic device lined by human intestinal epithelial cells and vascular endothelial cells to model radiation injury and assess the efficacy of radiation countermeasure drugs in vitro. Exposure of the Gut Chip to γ-radiation resulted in increased generation of reactive oxygen species, cytotoxicity, apoptosis, and DNA fragmentation, as well as villus blunting, disruption of tight junctions, and compromise of intestinal barrier integrity. In contrast, pre-treatment with a potential prophylactic radiation countermeasure drug, dimethyloxaloylglycine (DMOG), significantly suppressed all of these injury responses. Thus, the human Gut Chip may serve as an in vitro platform for studying radiation-induced cell death and associate gastrointestinal acute syndrome, in addition to screening of novel radio-protective medical countermeasure drugs.

A novel mouse model of radiation-induced cancer survivorship diseases of the gut

A deeper understanding of the radiation-induced pathophysiological processes that develop in the gut is imperative to prevent, alleviate, or eliminate cancer survivorship diseases after radiotherapy to the pelvic area. Most rodent models of high-dose gastrointestinal radiation injury are limited by high mortality. We therefore established a model that allows for the delivering of radiation in fractions at high doses while maintaining long-term survival. Adult male C57/BL6 mice were exposed to small-field irradiation, restricted to 1.5 cm of the colorectum using a linear accelerator. Each mouse received 6 or 8 Gy, two times daily in 12-h intervals in two, three, or four fractions. Acute cell death was examined at 4.5 h postirradiation and histological changes at 6 wk postirradiation. Another group was given four fractions of 8 Gy and followed over time for development of visible symptoms. Irradiation caused immediate cell death, mainly limited to the colorectum. At 6 wk postirradiation, several crypts displayed signs of radiation-induced degeneration. The degenerating crypts were seen alongside crypts that appeared perfectly healthy. Crypt survival was reduced after the fourth fraction regardless of dose, whereas the number of macrophages increased. Angiogenesis was induced, likely as a compensatory mechanism for hypoxia. Four months postirradiation, mice began to show radiation-induced symptoms, and histological examination revealed an extensive crypt loss and fibrosis. Our model is uniquely suitable for studying the long-term trajectory and underlying mechanisms of radiation-induced gastrointestinal injury.NEW & NOTEWORTHY A novel mouse model for studying the long-term trajectory of radiation-induced gut injury. The method allows for the use of high doses and multiple fractions, with minor impact on animal health for at least 3 mo. Crypt loss and a slow progression of fibrosis is observed. Crypt degeneration is a process restricted to isolated crypts. Crypt degeneration is presented as a convenient proxy endpoint for long-term radiation-induced gut injury.

MET Signaling Mediates Intestinal Crypt-Villus Development, Regeneration, and Adenoma Formation and Is Promoted by Stem Cell CD44 Isoforms

BACKGROUND & AIMS

Resistance of metastatic human colorectal cancer cells to drugs that block epidermal growth factor (EGF) receptor signaling could be caused by aberrant activity of other receptor tyrosine kinases, activating overlapping signaling pathways. One of these receptor tyrosine kinases could be MET, the receptor for hepatocyte growth factor (HGF). We investigated how MET signaling, and its interaction with CD44 (a putative MET coreceptor regulated by Wnt signaling and highly expressed by intestinal stem cells [ISCs] and adenomas) affects intestinal homeostasis, regeneration, and adenoma formation in mini-gut organoids and mice.

METHODS

We established organoid cultures from ISCs stimulated with HGF or EGF and assessed intestinal differentiation by immunohistochemistry. Mice with total epithelial disruption of MET (Ah^Cre/Met^fl/fl/LacZ) or ISC-specific disruption of MET (Lgr5^Creert2/Met^fl/fl/LacZ) and control mice (Ah^Cre/Met^+/+/LacZ, Lgr5^Creert2/Met^+/+/LacZ) were exposed to 10 Gy total body irradiation; intestinal tissues were collected, and homeostasis and regeneration were assessed by immunohistochemistry. We investigated adenoma organoid expansion stimulated by HGF or EGF using adenomas derived from Lgr5^Creert2/Met^fl/fl/Apc^fl/fl and Lgr5^Creert2/Met^+/+/Apc^fl/fl mice. The same mice were evaluated for adenoma prevalence and size. We also quantified adenomas in Ah^Cre/Met^fl/fl/Apc^fl/+ mice compared with Ah^Cre/Met^+/+/Apc^fl/+ control mice. We studied expansion of organoids generated from crypts and adenomas, stimulated by HGF or EGF, that were derived from mice expressing different CD44 splice variants (Cd44^+/+, Cd44^-/-, Cd44^s/s, or Cd44^v4-10/v4-10 mice).

RESULTS

Crypts incubated with EGF or HGF expanded into self-organizing mini-guts with similar levels of efficacy and contained all differentiated cell lineages. MET-deficient mice did not have defects in intestinal homeostasis. Total body irradiation reduced numbers of proliferating crypts in Ah^Cre/Met^fl/fl/LacZ mice. Lgr5^Creert2/Met^fl/fl/LacZ mice had impaired regeneration of MET-deficient ISCs. Adenoma organoids stimulated with EGF or HGF expanded to almost twice the size of nonstimulated organoids. MET-deficient adenoma organoids did not respond to HGF stimulation, but did respond to EGF. ISC-specific disruption of Met (Lgr5^Creert2/Met^fl/fl/Apc^fl/fl mice) caused a twofold increase in apoptosis in microadenomas, resulting in an approximately 50% reduction of microadenoma numbers and significantly reduced average adenoma size. Total epithelial disruption of Met (Ah^Cre/Met^fl/fl/Apc^fl/+ mice) resulted in an approximate 50% reduction in (micro)adenoma numbers. Intestinal crypts from Cd44^-/- mice did not expand to the same extent as crypts from Cd44^+/+ mice on stimulation with HGF, but had the same response to EGF. The negative effect on HGF-mediated growth was overcome by expression of CD44v4-10, but not by CD44s. Similarly, HGF-mediated expansion of adenoma organoids required CD44v4-10.

CONCLUSIONS

In studies of intestinal organoid cultures and mice with inducible deletion of MET, we found HGF receptor signaling to regulate intestinal homeostasis and regeneration, as well as adenoma formation. These activities of MET are promoted by the stem cell CD44 isoform CD44v4-10. Our findings provide rationale for targeting signaling via MET and CD44 during anti-EGF receptor therapy of patients with colorectal cancer or in patients resistant to EGF receptor inhibitors.

Oral Mucositis: Melatonin Gel an Effective New Treatment

The current treatment for cervico-facial cancer involves radio and/or chemotherapy. Unfortunately, cancer therapies can lead to local and systemic complications such as mucositis, which is the most common dose-dependent complication in the oral cavity and gastrointestinal tract. Mucositis can cause a considerably reduced quality of life in cancer patients already suffering from physical and psychological exhaustion. However, the role of melatonin in the treatment of mucositis has recently been investigated, and offers an effective alternative therapy in the prevention and/or management of radio and/or chemotherapy-induced mucositis. This review focuses on the pathobiology and management of mucositis in order to improve the quality of cancer patients' lives.

Effective chemotherapy of heterogeneous and drug-resistant early colon cancers by intermittent dose schedules: a computer simulation study

PURPOSE

The effectiveness of cancer chemotherapy is limited by intra-tumor heterogeneity, the emergence of spontaneous and induced drug-resistant mutant subclones, and the maximum dose to which normal tissues can be exposed without adverse side effects. The goal of this project was to determine if intermittent schedules of the maximum dose that allows colon crypt maintenance could overcome these limitations, specifically by eliminating mixtures of drug-resistant mutants from heterogeneous early colon adenomas while maintaining colon crypt function.

METHODS

A computer model of cell dynamics in human colon crypts was calibrated with measurements of human biopsy specimens. The model allowed simulation of continuous and intermittent dose schedules of a cytotoxic chemotherapeutic drug, as well as the drug's effect on the elimination of mutant cells and the maintenance of crypt function.

RESULTS

Colon crypts can tolerate a tenfold greater intermittent dose than constant dose. This allows elimination of a mixture of relatively drug-sensitive and drug-resistant mutant subclones from heterogeneous colon crypts. Mutants can be eliminated whether they arise spontaneously or are induced by the cytotoxic drug.

CONCLUSIONS

An intermittent dose, at the maximum that allows colon crypt maintenance, can be effective in eliminating a heterogeneous mixture of mutant subclones before they fill the crypt and form an adenoma.

A PPAR-gamma agonist protects from radiation-induced intestinal toxicity

OBJECTIVE

Because of its anti-inflammatory, anti-fibrotic, anti-apoptotic and anti-neoplastic properties, the PPAR-γ agonist rosiglitazone is an interesting drug for investigating for use in the prevention and treatment of radiation-induced intestinal damage. We aimed to evaluate the radioprotective effect of rosiglitazone in a murine model of acute intestinal damage, assessing whether radioprotection is selective for normal tissues or also occurs in tumour cells.

METHODS

Mice were total-body irradiated (12 Gy), with or without rosiglitazone (5 mg/kg/day). After 24 and 72 hours, mice were sacrificed and the jejunum was collected. HT-29 human colon cancer cells were irradiated with a single dose of 2 (1000 cells), 4 (1500 cells) or 6 (2000 cells) Gy, with or without adding rosiglitazone (20 µM) 1 hour before irradiation. HT-29-xenografted CD1 mice were irradiated (16 Gy) with or without rosiglitazone; tumour volumes were measured for 33 days.

RESULTS

Rosiglitazone markedly reduced histological signs of altered bowel structures, that is, villi shortening, submucosal thickening, necrotic changes in crypts, oedema, apoptosis, and inflammatory infiltrate induced by irradiation. Rosiglitazone significantly decreased p-NF-kB p65 phosphorylation and TGFβ protein expression at 24 and 72 hours post-irradiation and significantly decreased gene expression of Collagen1, Mmp13, Tnfα and Bax at 24 hours and p53 at 72 hours post-irradiation. Rosiglitazone reduced HT-29 clonogenic survival, but only produced a slight reduction of xenograft tumour growth.

CONCLUSION

Rosiglitazone exerts a protective effect on normal tissues and reduces alterations in bowel structures and inflammation in a radiation-induced bowel toxicity model, without interfering with the radiation effect on HT-29 cancer cells. PPAR-γ agonists should be further investigated for their application in abdominal and pelvic irradiation.

Melatonin attenuates 60 Co γ-ray-induced hematopoietic, immunological and gastrointestinal injuries in C57BL/6 male mice

Protection of hematopoietic, immunological, and gastrointestinal injuries from deleterious effects of ionizing radiation is prime rational for developing radioprotector. The objective of this study, therefore, was to evaluate the radioprotective potential of melatonin against damaging effects of radiation-induced hematopoietic, immunological, and gastrointestinal injuries in mice. C57BL/6 male mice were intraperitoneally administered with melatonin (50-150 mg/kg) 30 min prior to whole-body radiation exposure of 5 and 7.5 Gy using ⁶⁰ Co-teletherapy unit. Thirty-day survival against 7.5 Gy was monitored. Melatonin (100 mg/kg) pretreatment showed 100% survival against 7.5 Gy radiation dose. Melatonin pretreatment expanded femoral HPSCs, and inhibited spleenocyte DNA strands breaks and apoptosis in irradiated mice. At this time, it also protected radiation-induced loss of T cell sub-populations in spleen. In addition, melatonin pretreatment enhanced crypts regeneration and increased villi number and length in irradiated mice. Translocation of gut bacteria to spleen, liver and kidney were controlled in irradiated mice pretreated with melatonin. Radiation-induced gastrointestinal DNA strand breaks, lipid peroxidation, and expression of proapoptotic-p53, Bax, and antiapoptotic-Bcl-xL proteins were reversed in melatonin pretreated mice. This increase of Bcl-xL was associated with the decrease of Bax/Bcl-xL ratio. ABTS and DPPH radical assays revealed that melatonin treatment alleviated total antioxidant capacity in hematopoietic and gastrointestinal tissues. Present study demonstrated that melatonin pretreatment was able to prevent hematopoietic, immunological, and gastrointestinal radiation-induced injury, therefore, overcoming lethality in mice. These results suggest potential of melatonin in developing radioprotector for protection of bone marrow, spleen, and gastrointestine in planned radiation exposure scenarios including radiotherapy. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 501-518, 2017.

An amino acid-based oral rehydration solution (AA-ORS) enhanced intestinal epithelial proliferation in mice exposed to radiation

Destruction of clonogenic cells in the crypt following irradiation are thought to cause altered gastrointestinal function. Previously, we found that an amino acid-based oral rehydration solution (AA-ORS) improved gastrointestinal function in irradiated mice. However, the exact mechanisms were unknown. Electrophysiology, immunohistochemistry, qPCR, and Western blot analysis were used to determine that AA-ORS increased proliferation, maturation, and differentiation and improved electrolyte and nutrient absorption in irradiated mice. A single-hit, multi-target crypt survival curve showed a significant increase in crypt progenitors in irradiated mice treated with AA-ORS for six days (8.8 ± 0.4) compared to the saline-treated group (6.1 ± 0.3; P < 0.001) without a change in D₀ (4.8 ± 0.1 Gy). The D_q values increased from 8.8 ± 0.4 Gy to 10.5 ± 0.5 Gy with AA-ORS treatment (P < 0.01), indicating an increased radiation tolerance of 1.7 Gy. We also found that AA-ORS treatment (1) increased Lgr5⁺, without altering Bmi1 positive cells; (2) increased levels of proliferation markers (Ki-67, p-Erk, p-Akt and PCNA); (3) decreased apoptosis markers, such as cleaved caspase-3 and Bcl-2; and (4) increased expression and protein levels of NHE3 and SGLT1 in the brush border membrane. This study shows that AA-ORS increased villus height and improved electrolyte and nutrient absorption.

Neurogenic differentiation factor NeuroD confers protection against radiation-induced intestinal injury in mice

The gastrointestinal tract, especially the small intestine, is particularly sensitive to radiation, and is prone to radiation-induced injury as a result. Neurogenic differentiation factor (NeuroD) is an evolutionarily-conserved basic helix-loop-helix (bHLH) transcription factor. NeuroD contains a protein transduction domain (PTD), which allows it to be exogenously delivered across the membrane of mammalian cells, whereupon its transcription activity can be unleashed. Whether NeuroD has therapeutic effects for radiation-induced injury remains unclear. In the present study, we prepared a NeuroD-EGFP recombinant protein, and explored its protective effects on the survival and intestinal damage induced by ionizing radiation. Our results showed that NeuroD-EGFP could be transduced into small intestine epithelial cells and tissues. NeuroD-EGFP administration significantly increased overall survival of mice exposed to lethal total body irradiation (TBI). This recombinant NeuroD also reduced radiation-induced intestinal mucosal injury and apoptosis, and improved crypt survival. Expression profiling of NeuroD-EGFP-treated mice revealed upregulation of tissue inhibitor of metalloproteinase 1 (TIMP-1), a known inhibitor of apoptosis in mammalian cells. In conclusion, NeuroD confers protection against radiation-induced intestinal injury, and provides a novel therapeutic clinical option for the prevention of intestinal side effects of radiotherapy and the treatment of victims of incidental exposure.

PrP(c) deficiency and dasatinib protect mouse intestines against radiation injury by inhibiting of c-Src

BACKGROUND & AIM

Despite extensive study of the contribution of cell death and apoptosis to radiation-induced acute intestinal injury, our knowledge of the signaling mechanisms involved in epithelial barrier dysfunction remains inadequate. Because PrP(c) plays a key role in intestinal homeostasis by renewing epithelia, we sought to study its role in epithelial barrier function after irradiation.

DESIGN

Histology, morphometry and plasma FD-4 levels were used to examine ileal architecture, wound healing, and intestinal leakage in PrP(c)-deficient (KO) and wild-type (WT) mice after total-body irradiation. Impairment of the PrP(c) Src pathway after irradiation was explored by immunofluorescence and confocal microscopy, with Caco-2/Tc7 cells. Lastly, dasatinib treatment was used to switch off the Src pathway in vitro and in vivo.

RESULTS

The decrease in radiation-induced lethality, improved intestinal wound healing, and reduced intestinal leakage promoted by PrP(c) deficiency demonstrate its involvement in acute intestinal damage. Irradiation of Cacao2/Tc7 cells induced PrP(c) to target the nuclei associated with Src activation. Finally, the protective effect triggered by dasatinib confirmed Src involvement in radiation-induced acute intestinal toxicity.

CONCLUSION

Our data are the first to show a role for the PrP(c)-Src pathway in acute intestinal response to radiation injury and offer a novel therapeutic opportunity.

β-Arrestin-2 modulates radiation-induced intestinal crypt progenitor/stem cell injury

Intestinal crypt progenitor/stem (ICPS) cell apoptosis and vascular endothelial cell apoptosis are responsible for the initiation and development of ionizing radiation (IR)-evoked gastrointestinal syndrome. The signaling mechanisms underlying IR-induced ICPS cell apoptosis remain largely unclear. Our findings provide evidence that β-arrestin-2 (βarr2)-mediated ICPS cell apoptosis is crucial for IR-stimulated intestinal injury. βArr2-deficient mice exhibited decreased ICPS cell and intestinal Lgr5⁺ (leucine-rich repeat-containing G-protein-coupled receptor 5-positive) stem cell apoptosis, promoted crypt proliferation and reproduction, and protracted survival following lethal doses of radiation. Radioprotection in the ICPS cells isolated from βarr2-deficient mice depended on prolonged nuclear factor-κB (NF-κB) activation via direct interaction of βarr2 with IκBα and subsequent inhibition of p53-upregulated modulator of apoptosis (PUMA)-mediated mitochondrial dysfunction. Unexpectedly, βarr2 deficiency had little effect on IR-induced intestinal vascular endothelial cell apoptosis in mice. Consistently, βarr2 knockdown also provided significant radioresistance by manipulating NF-κB/PUMA signaling in Lgr5⁺ cells in vitro. Collectively, these observations show that targeting the βarr2/NF-κB/PUMA novel pathway is a potential radiomitigator for limiting the damaging effect of radiotherapy on the gastrointestinal system. Significance statement: acute injury to the intestinal mucosa is a major dose-limiting complication of abdominal radiotherapy. The issue of whether the critical factor for the initiation of radiation-induced intestinal injury is intestinal stem cell apoptosis or endothelial cell apoptosis remains unresolved. βArrs have recently been found to be multifunctional adaptor of apoptosis. Here, we found that β-arrestin-2 (βarr2) deficiency was associated with decreased radiation-induced ICPS cell apoptosis, which prolonged survival in abdominally irradiated mice. Moreover, βarr2 deficiency-mediated intestinal progenitor/stem cell radioprotection relied on protracted NF-κB activation and subsequent suppression of PUMA induction. Our results suggest that ICPS cell apoptosis is the factor involved in the initiation and development of radiation-induced gastrointestinal syndrome. βArr2 is a potential target for lessening radiation-induced ICPS cell apoptosis.