Radiation enteropathy and leucocyte-endothelial cell reactions in a refined small bowel model

Effect of Lactobacillus Rhamnosus GG for Regulation of Inflammatory Response in Radiation-Induced Enteritis

The purpose of this study was to investigate the role of Lactobacillus rhamnosus GG (LGG) probiotics in radiation enteritis using in vivo mice. A total of 40 mice were randomly assigned to four groups: control, probiotics, radiotherapy (RT), and RT + probiotics. For the group of probiotics, 0.2 mL of solution that contained 1.0 × 108 colony-forming units (CFU) of LGG was used and orally administered daily until sacrifice. For RT, a single dose of 14 Gy was administered using a 6 mega-voltage photon beam to the abdominopelvic area. Mice were sacrifice at day 4 (S1) and day 7 (S2) after RT. Their jejunum, colon, and stool were collected. A multiplex cytokine assay and 16 s ribosomal RNA amplicon sequencing were then performed. Regarding cytokine concentrations in tissues, pro-inflammatory cytokines, such as tumor necrosis factor-α, interleukin-6 and monocyte chemotactic protein-1, showed significantly decreased protein levels in colon tissues of the RT + probiotics group than in the RT alone group (all p < 0.05). As for comparing microbial abundance through alpha-diversity and beta-diversity, no significant differences were observed between the RT + probiotics and RT alone groups, except for an increase in alpha-diversity in the stool of the RT + probiotics group. Upon analysis of differential microbes based on treatment, the dominance of anti-inflammatory-related microbes, such as Porphyromonadaceae, Bacteroides acidifaciens, and Ruminococcus, was observed in the jejunum, colon, and stool of the RT + probiotics group. With regard to predicted metabolic pathway abundances, the pathways associated with anti-inflammatory processes, such as biosynthesis of pyrimidine nucleotides, peptidoglycans, tryptophan, adenosylcobalamin, and propionate, were differentially identified in the RT + probiotics group compared to the RT alone group. Protective effects of probiotics on radiation enteritis were potentially derived from dominant anti-inflammation-related microbes and metabolites.

Application of a derivative of human defensin 5 to treat ionizing radiation-induced enterogenic infection

Enterogenic infection is a common complication for patients with radiation injury and requires efficient therapeutics in the clinic. Herein, we evaluated the promising drug candidate T7E21RHD5, which is a peptide derived from intestinal Paneth cell-secreted human defensin 5. Oral administration of this peptide alleviated the diarrhea symptoms of mice that received total abdominal irradiation (TAI, γ-ray, 12 Gy) and improved survival. Pathologic analysis revealed that T7E21RHD5 elicited an obvious mitigation of ionizing radiation (IR)-induced epithelial damage and ameliorated the reduction in the levels of claudin, zonula occluden 1 and occludin, three tight junction proteins in the ileum. Additionally, T7E21RHD5 regulated the gut microbiota in TAI mice by remodeling β diversity, manifested as a reversal of the inverted proportion of Bacteroidota to Firmicutes caused by IR. T7E21RHD5 treatment also decreased the abundance of pathogenic Escherichia-Shigella but significantly increased the levels of Alloprevotella and Prevotellaceae_NK3B31, two short-chain fatty acid-producing bacterial genera in the gut. Accordingly, the translocation of enterobacteria and lipopolysaccharide to the blood, as well as the infectious inflammatory responses in the intestine after TAI, was all suppressed by T7E21RHD5 administration. Hence, this versatile antimicrobial peptide possesses promising application prospects in the treatment of IR-induced enterogenic infection.

A new perspective in the prevention and treatment of antitumor therapy-related cardiotoxicity: Intestinal microecology

The continuous development of antitumor therapy has significantly reduced the mortality of patients with malignancies. However, the antitumor-related cardiotoxicity has become the leading cause of long-term mortality in patients with malignancies. Besides, the pathogenesis of antitumor-related cardiotoxicity is still unclear, and practical means of prevention and treatment are lacking in clinical practice. Therefore, the major challenge is how to combat the cardiotoxicity of antitumor therapy effectively. More and more studies have shown that antitumor therapy kills tumor cells while causing damage to sensitive tissues such as the intestinal mucosa, leading to the increased permeability of the intestine and the dysbiosis of intestinal microecology. In addition, the dysbiosis of intestinal microecology contributes to the development and progression of cardiovascular diseases through multiple pathways. Thus, the dysbiosis of intestinal microecology may be a potential mechanism and target for antitumor-related cardiotoxicity. We summarized the characteristics of intestinal microecology disorders induced by antitumor therapy and the association between intestinal microecological dysbiosis and CVD. And on this basis, we hypothesized the potential mechanisms of intestinal microecology mediating the occurrence of antitumor-related cardiotoxicity. Then we reviewed the previous studies targeting intestinal microecology against antitumor-associated cardiotoxicity, aiming to provide a reference for future studies on the occurrence and prevention of antitumor-related cardiotoxicity by intestinal microecology.

Research progress and treatment of radiation enteritis and gut microbiota

Radiation enteritis is a kind of intestinal radiation injury in patients with pelvic and retroperitoneal malignancies after radiotherapy, and its occurrence and development process are very complicated. At present, studies have confirmed that intestinal microecological imbalance is an important factor in the formation of this disease. Abdominal radiation causes changes in the composition of the flora and a decrease in its diversity, which is mainly manifested by a decrease in beneficial bacterial species such as Lactobacilli and Bifidobacteria. Intestinal dysbacteriosis aggravates radiation enteritis, weakens the function of the intestinal epithelial barrier, and promotes the expression of inflammatory factors, thereby aggravating the occurrence of enteritis. Given the role of the microbiome in radiation enteritis, we suggest that the gut microbiota may be a potential biomarker for the disease. Treatment methods such as probiotics, antibiotics, and fecal microbiota transplantation are ways to correct the microbiota and may be an effective way to prevent and treat radiation enteritis. Based on a review of the relevant literature, this paper reviews the mechanism and treatment of intestinal microbes in radiation enteritis.

The Effects of Ionizing Radiation on Gut Microbiota: What Can Animal Models Tell Us?-A Systematic Review

BACKGROUND

The gut microbiota is relatively stable; however, various factors can precipitate an imbalance that is known to be associated with various diseases. We aimed to conduct a systematic literature review of studies reporting the effects of ionizing radiation on the composition, richness, and diversity of the gut microbiota of animals.

METHODS

A systematic literature search was performed in PubMed, EMBASE, and Cochrane library databases. The standard methodologies expected by Cochrane were utilized.

RESULTS

We identified 3531 non-duplicated records and selected twenty-nine studies after considering the defined inclusion criteria. The studies were found to be heterogeneous, with significant differences in the chosen populations, methodologies, and outcomes. Overall, we found evidence of an association between ionizing radiation exposure and dysbiosis, with a reduction of microbiota diversity and richness and alterations in the taxonomic composition. Although differences in taxonomic composition varied across studies, Proteobacteria, Verrucomicrobia, Alistipes, and Akkermancia most consistently reported to be relatively more abundant after ionizing radiation exposure, whereas Bacteroidetes, Firmicutes, and Lactobacillus were relatively reduced.

CONCLUSIONS

This review highlights the effect of ionizing exposure on gut microbiota diversity, richness, and composition. It paves the way for further studies on human subjects regarding gastrointestinal side effects in patients submitted to treatments with ionizing radiation and the development of potential preventive, therapeutic approaches.

Ionizing Radiation from Radiopharmaceuticals and the Human Gut Microbiota: An Ex Vivo Approach

This study aimed to determine the effect of three widely used radiopharmaceuticals with intestinal excretion on selected relevant bacteria that are part of the human gut microbiota, using an ex vivo approach. Fecal samples obtained from healthy volunteers were analyzed. Each sample was divided into four smaller aliquots. One served as the non-irradiated control. The other three were homogenized with three radiopharmaceutical solutions ([¹³¹I]NaI, [^99mTc]NaTcO₄, and [²²³Ra]RaCl₂). Relative quantification of each taxa was determined by the 2^−ΔΔC method, using the ribosomal gene 16S as an internal control (primers 534/385). Twelve fecal samples were analysed: three controls and nine irradiated. Our experiment showed fold changes in all analyzed taxa with all radiopharmaceuticals, but results were more significant with I-131, ranging from 1.87–83.58; whereas no relevant differences were found with Tc-99m and Ra-223, ranging from 0.98–1.58 and 0.83–1.97, respectively. This study corroborates limited existing research on how ionizing radiation changes the gut microbiota composition, providing novel data regarding the ex vivo effect of radiopharmaceuticals. Our findings justify the need for future larger scale projects.

Research progress on the mechanism of radiation enteritis

Radiation enteritis (Re) is one of the most common complications of radiation therapy for abdominal tumors. The efficacy of cancer treatment by radiation is often limited by the side effects of Re. Re can be acute or chronic. Treatment of acute Re is essentially symptomatic. However, chronic Re usually requires surgical procedures. The underlying mechanisms of Re are complex and have not yet been elucidated. The purpose of this review is to provide an overview of the pathogenesis of Re. We reviewed the role of intestinal epithelial cells, intestinal stem cells (ISCs), vascular endothelial cells (ECs), intestinal microflora, and other mediators of Re, noting that a better understanding of the pathogenesis of Re may lead to better treatment modalities.

Gut Microbiome and Its Associations With Acute and Chronic Gastrointestinal Toxicities in Cancer Patients With Pelvic Radiation Therapy: A Systematic Review

Aim

Pelvic radiation therapy (RT) can impact the gut microbiome in patients with cancer and result in gastrointestinal (GI) toxicities. The purpose of this systematic review was to describe the effects of RT on the gut microbiome and the associations between the gut microbiome and GI toxicities in patients treated with pelvic RT.

Methods

PubMed, Embase, and Web of Science databases were searched from their earliest records to August 2020. The articles screening process adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The Mixed Method Assessment Tool was used to assess the methodological quality for each included study. All study findings were synthesized and presented in narrative format. Thirteen studies were included. The gut microbiome of fecal samples was analyzed using 16S rRNA sequencing approaches.

Results

There were disparities in alpha and beta diversities that existed across the studies. Divergent results were found among various phyla, including Firmicutes, Bacteroidetes, Proteobacteria, Actinobacteria, Cyanobacteria, Fusobacteria, and Deinococcus-Thermus. Moreover, alteration in the gut microbiome diversity and abundance related to cancer treatment was associated with pelvic toxicities, specifically diarrhea. Following treatment, increases in the abundance of Bacteroides was associated with diarrhea and radiation enteritis.

Conclusions

Pelvic RT can disrupt the diversity and abundance of commensal gut microorganisms. A dysbiotic gut microbiome showed a promising association with radiation enteritis through alterations of the intestinal barrier function, innate immunity, and intestinal repair mechanisms; however, confounders, such as diet, were not thoroughly addressed.

The Impact of Gut Microbiota on Radiation-Induced Enteritis

Radiotherapy is an important treatment for abdominal tumors. A critical side effect for this therapy is enteritis. In this review, we aim to summarize recent findings in radiation enteritis, in particular the role of gut microbiota dysbiosis in the development and therapy of the disease. Gut microbiota dysbiosis plays an important role in the occurrence of various diseases, such as radiation enteritis. Abdominal radiation results in changes in the composition of microbiota and reduces its diversity, which is mainly reflected in the decrease of Lactobacillus spp. and Bifidobacterium spp. and increase of Escherichia coli and Staphylococcus spp. Gut microbiota dysbiosis aggravates radiation enteritis, weakens intestinal epithelial barrier function, and promotes inflammatory factor expression. Pathogenic Escherichia coli induce the rearrangement and redistribution of claudin-1, occludin, and ZO-1 in tight junctions, a critical component in intestinal epithelial barrier. In view of the role that microbiome plays in radiation enteritis, we believe that intestinal flora could be a potential biomarker for the disease. Correction of microbiome by application of probiotics, fecal microbiota transplantation (FMT), and antibiotics could be an effective method for the prevention and treatment of radiation-induced enteritis.

A Minireview on Gastrointestinal Microbiota and Radiosusceptibility

Gastrointestinal (GI) microbiota maintains a symbiotic relationship with the host and plays a key role in modulating many important biological processes and functions of the host, such as metabolism, inflammation, immune and stress response. It is becoming increasingly apparent that GI microbiota is susceptible to a wide range of environmental factors and insults, for examples, geographic location of birth, diet, use of antibiotics, and exposure to radiation. Alterations in GI microbiota link to various diseases, including radiation-induced disorders. In addition, GI microbiota composition could be used as a biomarker to estimate radiosusceptibility and radiation health risk in the host. In this minireview, we summarized the documented studies on radiation-induced alterations in GI microbiota and the relationship between GI microbiota and radiosusceptibility of the host, and mainly discussed the possible mechanisms underlying GI microbiota influencing the outcome of radiation response in humans and animal models. Furthermore, we proposed that GI microbiota manipulation may be used to reduce radiation injury and improve the health of the host.

Bidirectional and dynamic interaction between the microbiota and therapeutic resistance in pancreatic cancer

Pancreatic ductal adenocarcinoma is one of the most lethal malignancies and is known for its high resistance and low response to treatment. Cancer treatments can reshape the microbiota and in turn, the microbiota influences the therapeutic efficacy by regulating immune response and metabolism. This crosstalk is bidirectional, heterogeneous, and dynamic. In this review, we elaborated on the interactions between the microbiota and therapeutic resistance in pancreatic ductal adenocarcinoma. Regulating the microbiota in pancreatic tumor microenvironment may not only generate direct anti-cancer but also synergistic effects with other treatments, providing new directions in cancer therapy.

The role of the gut microbiome on radiation therapy efficacy and gastrointestinal complications: A systematic review

Radiation therapy (RT) is an essential component of therapy either curative or palliative armamentarium in oncology, but its efficacy varies considerably among patients through many extrinsic and intrinsic mechanisms of the tumour, which are beginning to be better understood. Recent studies have shown that the gut microbiome represents a key factor in the modulation of the systemic immune response and consequently on patients' outcome. Moreover, the emergence of biomarkers that are derived from the gut microbiota has fuelled the development of adjuvant strategies for patients treated with immunotherapy in combination or not with RT. Despite progress in development of more precise radiotherapy techniques, almost all patients undergoing RT to the abdomen, pelvis, or rectum develop acute adverse events as a consequence of several dose-limiting parameters such as the location of irradiation that may subsequently damage normal tissue including the intestinal epithelium. Several lines of evidence in preclinical models identified that vancomycin improves RT-induced gastrointestinal toxicities such as diarrhea and oral mucositis. In order to gain further insight into this rapidly evolving field, we have systematically reviewed the studies that have described how the gut microbiome may directly or indirectly modulate RT efficacy and its gastro-intestinal toxicities. Lastly, we outline current knowledge gaps and discuss potentially more satisfactory therapeutic options to restore the functionality of the gut microbiome of patients treated with RT.

Promising role of filgrastim and α-tocopherol succinate in amelioration of gastrointestinal acute radiation syndrome (GI-ARS) in mice

The protective role of α-tocopherol succinate (α-TCS) and the therapeutic efficacy of filgrastim were investigated in gastrointestinal acute radiation syndrome (GI-ARS) induced following 10 Gy whole-body γ-irradiation. Mice were randomly allocated into 5 groups: [1] normal-control, [2] irradiated-control, [3] subcutaneous (s.c.) injection of filgrastim (5 μg/kg/day) for 4 consecutive days given 1 h post-irradiation, [4] s.c. injection with α-TCS (400 mg/kg) 1 day prior to irradiation, [5] s.c. injection with α-TCS (400 mg/kg) 1 day prior to irradiation and filgrastim (5 μg/kg/day) for 4 consecutive days 1 h post-irradiation. Histopathological analysis, serum citrulline level, intestinal interleukin-1β (IL-1β), reduced glutathione (GSH), and malondialdehyde (MDA) contents as well as myeloperoxidase (MPO) activity were measured. Intestinal caspase-3, p53, cyclooxygenase-2 (COX-2), and inducible nitric oxide synthase (iNOS) immunopositivity were examined. In irradiated-control, MDA increased (249%) and GSH decreased (25%) compared to normal and were unaffected by filgrastim. α-TCS alone significantly reduced MDA (84.5%) and normalized GSH. The combination significantly reduced MDA (59%) and dramatically increased GSH (1573%), pointing to a possible synergistic action. In irradiated-control, MPO and IL-1β significantly increased (111% and 613%, respectively) compared to normal-control and both were significantly decreased in all treated groups. Compared to normal-control, citrulline significantly declined (68%) in irradiated-control; a significant elevation was achieved by treatments with α-TCS alone or combined with filgrastim (88% and 94%, respectively). The combination therapy significantly decreased the degree of irradiation-induced injury of the epithelium and cellular infiltration and showed the lowest histopathological scoring compared to the other groups (p ≤ 0.05). In irradiated-control, immune-reactive expressions of iNOS, COX-2, caspase-3, and p53 were remarkable (18.62%, 34.27%, 31.19%, and 27.44%, respectively) and after combination therapy were reduced (1.04%, 22.39%, 8.76%, and 4.91%, respectively). The current findings represent a first-hand strategy in dealing with GI-ARS with a potential preference to using a combined therapy of filgrastim and α-TCS.

Impact of the microbiome on cancer progression and response to anti-cancer therapies

Humans are a colonized with trillions of commensal microorganisms which exert a profound effect on normal host physiology and immune function through an abundance of genetic and metabolic by-products. Although the commensal microbiome has beneficial functions to host physiology, perturbations of the composition of the commensal microbiome or the homeostatic mucosal environment can lead to the induction of immune pathology and systemic inflammation. In the context of cancer progression or response to immune therapy, this inflammation can be detrimental, resulting in tumor growth and the promotion of immune suppression. On the other hand, significant associations have been identified whereby certain commensal microorganisms are able to enhance T cell function or are required for tumor control in cancer patients treated with certain immune therapies and chemotherapies. The focus of this chapter is to highlight the role of the commensal microbiome during tumor progression and in response to immune therapies.

Purified PEGylated human glucagon-like peptide-2 reduces the severity of irradiation-induced acute radiation enteritis in rats

Radiation-induced acute intestinal injury after abdominal and pelvic irradiation is a common and serious problem in the clinical setting. Glucagon-like peptide-2 (GLP-2), a 33-amino acid peptide, exerts diverse effects related to the regulation of gastrointestinal growth and function. However, GLP-2 is relatively unstable in vivo. The aim of the present study was to improve GLP-2 stability in vivo and to evaluate its therapeutic effect on acute radiation enteritis. We generated long-lasting intestinal protection peptides by conjugating human GLP-2 (hGLP-2) peptides to polyethyleneglycol (PEG) to produce mPEGylation hGLP-2 (Mono-PEG-hGLP-2) through an enzymatic site-specific transglutamination reaction. Mono-PEG-hGLP-2 synthesized under optimal reaction conditions and separated by one-step ion-exchange chromatography was found to be resistant to degradation in vitro. Pretreatment with Mono-PEG-hGLP-2 reduced the severity of radiation-induced intestinal injury, oxidative stress, and the expression of NF-κB in rats with irradiation-induced acute radiation enteritis. The enhanced biological potency of Mono-PEG-hGLP-2 highlights its potential as a therapeutic agent for intestinal diseases.

Intestinal probiotics restore the ecological fitness decline of Bactrocera dorsalis by irradiation

The sterile insect technique (SIT) as an eco-friendly and reliable strategy has been used to control populations of insect pests of agricultural, veterinary and human health importance. Successful applications of SIT rely on the high-level ecological fitness of sterile males. A suitable and stable gut microbiome can contribute to the ecological fitness of insect by influencing their physiology, biochemistry and development processes. Here, we show that a shift in the gut bacterial composition and structure by sterilizing irradiation, characterized by a decrease in the major gut microbiota community Enterobacteriaceae, an expansion of the minor members (e.g., Bacillaceae) and a higher richness and diversity, is tightly linked to radiation-induced ecological fitness (male mating competitiveness, flight capacity, survival rate and life span) decline in Bactrocera dorsalis (Hendel) sterile males. Function prediction of gut microbiota indicated that changes in microbiome taxonomy tend to drive microbiome functional shifts. A higher nutrient consumption of the flourishing minor gut microbiota may cause a decline in nutrients and energy metabolic activity of host and then result in the reduced ecological fitness of irradiated flies. Furthermore, we found that a gut bacterial strain Klebsiella oxytoca (BD177) can restore ecological fitness by improving food intake and increasing haemolymph sugar and amino acid levels of irradiated B. dorsalis flies. Our findings suggest that gut symbiont-based probiotics can be used as agents for reversing radiation-induced ecological fitness decrease.

Interleukin 6 Signaling Blockade Exacerbates Acute and Late Injury From Focal Intestinal Irradiation

PURPOSE

To evaluate the acute changes in leukocyte populations after focal irradiation and to assess the role of interleukin 6 (IL-6) in acute and late radiation injury.

METHODS AND MATERIALS

Mice were surgically implanted with a radiopaque marker on the surface of the small intestine. Mice were then imaged with cone beam computed tomography to locate the marker and irradiated with 18 Gy of 5 × 5 mm collimated x-rays onto the marked intestine using the Small Animal Radiation Research Platform. Intestinal sections and blood were harvested 1, 3.5, 7, and 14 days and 2 months postirradiation (post-IR) for histology and complete blood count, respectively. Immune cell populations were assessed by immunofluorescence in the acute phase. Collagen deposition was assessed 2 months post-IR. IL-6^-/- intestinal sections were assessed post-IR for morphology, EdU, Ki67, and TUNEL in comparison to IL-6^+/+ mice. Furthermore, a set of IL-6^+/+ mice were treated with anti-IL-6R to assess the role of IL-6 in late intestinal injury.

RESULTS

Intestinal radiation damage peaked 14 days post-IR, and fibrosis had developed by 60 days post-IR. There was a marked infiltration of immune cells into the irradiated intestine, with increased neutrophils, macrophages, B-cells, and CD4⁺ T cells maintained from 3.5 to 14 days post-IR. CD8⁺ T cells were decreased from days 7 to 14 post-IR. Systemically, leukocytes were increased in the peripheral blood 14 days post-IR with anemia being maintained from 14 days to 2 months. IL-6 was significantly increased in the serum post-IR. IL-6^-/- mice demonstrated worsened intestinal injury acutely post-IR. Moreover, anti-IL-6R-treated mice presented with worsened intestinal fibrosis 2 months post-IR.

CONCLUSIONS

Focal irradiation of the intestine produced a significant increase in immune cells in the irradiated area and systemic inflammation and anemia. Blockade of IL-6 signaling was found to exacerbate acute intestinal injury and late intestinal injury after focal irradiation.

MMP7 Modulation by Short- and Long-term Radiotherapy in Patients with Rectal Cancer

BACKGROUND/AIM

Matrix metalloproteinase 7 (MMP7) expression is highly associated with colorectal cancer and modulates tumour growth and invasion. Radiation injury induces inflammation with increases in MMP7 and in transforming growth factor beta (TGFβ). The aim of this study was to investigate the effect on MMP7 and TGFβ. expression in patients with rectal cancer undergoing different regimens of neoadjuvant radiotherapy (RT).

PATIENTS AND METHODS

We studied 53 patients in three RT treatment groups receiving RT of 25 Gy, long-term RT 50 Gy and controls receiving no RT. Three biopsies were obtained from each patient during the treatments: before RT, after RT and after surgery. Tissue samples were formalin fixed, paraffin embedded and tissue microarrays were constructed and stained for MMP7 and TGFβ. Mann-Whitney U-tests and Wilcoxon Z-tests were used to determine differences between patients before and after RT, and after surgery, as well as between the RT groups.

RESULTS

In all three patient groups, increases of MMP7 and TGFβ expression were observed after surgery. MMP7 expression was significantly increased in patients receiving short-term RT but TGFβ expression was not affected by RT.

CONCLUSION

50 Gy Irradiation of rectal cancer gives less tumour activation of MMP7, whilst it is up-regulated by 25 Gy and surgery regardless of RT.

The synergy between ionizing radiation and immunotherapy in the treatment of prostate cancer

There has been a surge in the use of immunotherapy for genitourinary malignancies. Immunotherapy is an established treatment for metastatic renal cell carcinoma and nonmuscle invasive bladder cancer, but its potential for treating prostate cancer (PCa) remains under investigation. Despite reported survival benefits, no published Phase III PCa trials using immunotherapy only as a treatment has demonstrated direct antitumor effects by reducing prostate-specific antigen levels. Subsequently, the thought of combining immunotherapy with other treatment modalities has gained traction as a way to achieving optimal results. Based on data from other malignancies, it is hypothesized that radiotherapy and immunotherapy can act synergistically to improve outcomes. We will discuss the clinical potential of combining immune-based treatments with radiotherapy as a treatment for advanced PCa.

Application of a Novel Murine Ear Vein Model to Evaluate the Effects of a Vascular Radioprotectant on Radiation-Induced Vascular Permeability and Leukocyte Adhesion

Vascular injury after radiation exposure contributes to multiple types of tissue injury through a cascade of events. Some of the earliest consequences of radiation damage include increased vascular permeability and promotion of inflammation, which is partially manifested by increased leukocyte-endothelial (L/E) interactions. We describe herein a novel intravital imaging method to evaluate L/E interactions, as a function of shear stress, and vascular permeability at multiple time points after local irradiation to the ear. This model permitted analysis of quiescent vasculature that was not perturbed by any surgical manipulation prior to imaging. To evaluate the effects of radiation on vascular integrity, fluorescent dextran was injected intravenously and its extravasation in the extravascular space surrounding the ear vasculature was measured at days 3 and 7 after 6 Gy irradiation. The vascular permeability rate increased approximately twofold at both days 3 and 7 postirradiation ( P < 0.05). Leukocyte rolling, which is indicative of L/E interactions, was significantly increased in mice at 24 h postirradiation compared to that of nonirradiated mice. To assess our model, as a means for assessing vascular radioprotectants, we treated additional cohorts of mice with a thrombopoietin mimetic, TPOm (RWJ-800088). In addition to stimulating platelet formation, thrombopoietin can protect vasculature after several forms of injury. Thus, we hypothesized that TPOm would reduce vascular permeability and L/E adhesion after localized irradiation to the ear vasculature of mice. If TPOm reduced these consequences of radiation, it would validate the utility of our intravital imaging method. TPOm reduced radiation-induced vascular leakage to control levels at day 7. Furthermore, L/E cell interactions were also reduced in irradiated mice treated with TPOm, compared with mice receiving irradiation alone, particularly at high shear stress ( P = 0.03, Kruskal-Wallis). We conclude that the ear model is useful for monitoring quiescent normal tissue vascular injury after radiation exposure. Furthermore, the application of TPOm, for preventing early inflammatory response created by damage to vascular endothelium, suggests that this drug may prove useful in reducing toxicities from radiotherapy, which damage microvasculature that critically important to tissue function.

Determining risk of severe gastrointestinal toxicity based on pretreatment gut microbial community in patients receiving cancer treatment: a new predictive strategy in the quest for personalized cancer medicine

PURPOSE OF REVIEW

Currently, our ability to accurately predict a patient's risk of developing severe gastrointestinal toxicity from their cancer treatment is limited. Risk stratification continues to rely on traditional patient-related and treatment-related factors including age, ethnicity, sex, comorbidities, genetics, agent, dose and schedule. Although informative, these crude measures continue to underestimate toxicity risk, and hence alternative methods of risk prediction must be investigated. Given the increasing focus on the gut microbiome in driving disease, this review will provide an overview of the current literature proposing the gut microbiome as a novel predictive tool for treatment-induced gastrointestinal toxicity.

RECENT FINDINGS

Predictive gut microbial phenotypes have been identified for gastrointestinal toxicity induced by radiation and the checkpoint blocker, Ipilimumab. Each study employed slightly different methods of gut microbiome assessment; however, in all cases, separation of toxic versus nontoxic patients was achieved. No studies have investigated chemotherapy-induced gastrointestinal toxicity.

SUMMARY

The gut microbiome offers an exciting new method of risk stratification for gastrointestinal toxicity. This would enable identification of high-risk patients prior to treatment, enabling tailored treatment regimens based on personalized risk assessment and the proactive provision of supportive care measures. Based on the plasticity of the gut microbiome, methods of risk mitigation may be investigated.

Bowel Radiation Injury: Complexity of the Pathophysiology and Promises of Cell and Tissue Engineering

Ionizing radiation is effective to treat malignant pelvic cancers, but the toxicity to surrounding healthy tissue remains a substantial limitation. Early and late side effects not only limit the escalation of the radiation dose to the tumor but may also be life-threatening in some patients. Numerous preclinical studies determined specific mechanisms induced after irradiation in different compartments of the intestine. This review outlines the complexity of the pathogenesis, highlighting the roles of the epithelial barrier in the vascular network, and the inflammatory microenvironment, which together lead to chronic fibrosis. Despite the large number of pharmacological molecules available, the studies presented in this review provide encouraging proof of concept regarding the use of mesenchymal stromal cell (MSC) therapy to treat radiation-induced intestinal damage. The therapeutic efficacy of MSCs has been demonstrated in animal models and in patients, but an enormous number of cells and multiple injections are needed due to their poor engraftment capacity. Moreover, it has been observed that although MSCs have pleiotropic effects, some intestinal compartments are less restored after a high dose of irradiation. Future research should seek to optimize the efficacy of the injected cells, particularly with regard to extending their life span in the irradiated tissue. Moreover, improving the host microenvironment, combining MSCs with other specific regenerative cells, or introducing new tissue engineering strategies could be tested as methods to treat the severe side effects of pelvic radiotherapy.

Radiation induces proinflammatory dysbiosis: transmission of inflammatory susceptibility by host cytokine induction

OBJECTIVE

Radiation proctitis (RP) is a complication of pelvic radiotherapy which affects both the host and microbiota. Herein we assessed the radiation effect on microbiota and its relationship to tissue damage using a rectal radiation mouse model.

DESIGN

We evaluated luminal and mucosa-associated dysbiosis in irradiated and control mice at two postradiation time points and correlated it with clinical and immunological parameters. Epithelial cytokine response was evaluated using bacterial-epithelial co-cultures. Subsequently, germ-free (GF) mice were colonised with postradiation microbiota and controls and exposed to radiation, or dextran sulfate-sodium (DSS). Interleukin (IL)-1β correlated with tissue damage and was induced by dysbiosis. Therefore, we tested its direct role in radiation-induced damage by IL-1 receptor antagonist administration to irradiated mice.

RESULTS

A postradiation shift in microbiota was observed. A unique microbial signature correlated with histopathology. Increased colonic tumor necrosis factor (TNF)α, IL-1β and IL-6 expression was observed at two different time points. Adherent microbiota from RP differed from those in uninvolved segments and was associated with tissue damage. Using bacterial-epithelial co-cultures, postradiation microbiota enhanced IL-1β and TNFα expression compared with naïve microbiota. GF mice colonisation by irradiated microbiota versus controls predisposed mice to both radiation injury and DSS-induced colitis. IL-1 receptor antagonist administration ameliorated intestinal radiation injury.

CONCLUSIONS

The results demonstrate that rectal radiation induces dysbiosis, which transmits radiation and inflammatory susceptibility and provide evidence that microbial-induced radiation tissue damage is at least in part mediated by IL-1β. Environmental factors may affect the host via modifications of the microbiome and potentially allow for novel interventional approaches via its manipulation.

Inhibition of the Continuum of Radiation-Induced Normal Tissue Injury by a Redox-Active Mn Porphyrin

Normal tissue damage after head and neck radiotherapy involves a continuum of pathologic events to the mucosa, tongue and salivary glands. We examined the radioprotective effects of MnBuOE, a redox-active manganese porphyrin, at three stages of normal tissue damage: immediate (leukocyte endothelial cell [L/E] interactions), early (mucositis) and late (xerostomia and fibrosis) after treatment. In this study, mice received 0 or 9 Gy irradiation to the oral cavity and salivary glands ± MnBuOE treatment. Changes in leukocyte-endothelial cell interactions were measured 24 h postirradiation. At 11 days postirradiation, mucositis was assessed with a cathepsin-sensitive near-infrared optical probe. Stimulated saliva production was quantified at 11 weeks postirradiation. Finally, histological analyses were conducted to assess the extent of long-term effects in salivary glands at 12 weeks postirradiation. MnBuOE reduced oral mucositis, xerostomia and salivary gland fibrosis after irradiation. Additionally, although we have previously shown that MnBuOE does not interfere with tumor control at high doses when administered with radiation alone, most head and neck cancer patients will be treated with the combinations of radiotherapy and cisplatin. Therefore, we also evaluated whether MnBuOE would protect tumors against radiation and cisplatin using tumor growth delay as an endpoint. Using a range of radiation doses, we saw no evidence that MnBuOE protected tumors from radiation and cisplatin. We conclude that MnBuOE radioprotects normal tissue at both early and late time points, without compromising anti-tumor effects of radiation and cisplatin.

An Integrated Multi-Omic Approach to Assess Radiation Injury on the Host-Microbiome Axis

Medical responders to radiological and nuclear disasters currently lack sufficient high-throughput and minimally invasive biodosimetry tools to assess exposure and injury in the affected populations. For this reason, we have focused on developing robust radiation exposure biomarkers in easily accessible biofluids such as urine, serum and feces. While we have previously reported on urine and serum biomarkers, here we assessed perturbations in the fecal metabolome resulting from exposure to external X radiation in vivo. The gastrointestinal (GI) system is of particular importance in radiation biodosimetry due to its constant cell renewal and sensitivity to radiation-induced injury. While the clinical GI symptoms such as pain, bloating, nausea, vomiting and diarrhea are manifested after radiation exposure, no reliable bioindicator has been identified for radiation-induced gastrointestinal injuries. To this end, we focused on determining a fecal metabolomic signature in X-ray irradiated mice. There is overwhelming evidence that the gut microbiota play an essential role in gut homeostasis and overall health. Because the fecal metabolome is tightly correlated with the composition and diversity of the microorganism in the gut, we also performed fecal 16S rRNA sequencing analysis to determine the changes in the microbial composition postirradiation. We used in-house bioinformatics tools to integrate the 16S rRNA sequencing and metabolomic data, and to elucidate the gut integrated ecosystem and its deviations from a stable host-microbiome state that result from irradiation. The 16S rRNA sequencing results indicated that radiation caused remarkable alterations of the microbiome in feces at the family level. Increased abundance of common members of Lactobacillaceae and Staphylococcaceae families, and decreased abundances of Lachnospiraceae, Ruminococcaceae and Clostridiaceae families were found after 5 and 12 Gy irradiation. The metabolomic data revealed statistically significant changes in the microbial-derived products such as pipecolic acid, glutaconic acid, urobilinogen and homogentisic acid. In addition, significant changes were detected in bile acids such as taurocholic acid and 12-ketodeoxycholic acid. These changes may be associated with the observed shifts in the abundance of intestinal microbes, such as R. gnavus , which can transform bile acids.

The potential of mesenchymal stem cells in the management of radiation enteropathy

Although radiotherapy is effective in managing abdominal and pelvic malignant tumors, radiation enteropathy is still unavoidable. This disease severely affects the quality of life of cancer patients due to some refractory lesions, such as intestinal ischemia, mucositis, ulcer, necrosis or even perforation. Current drugs or prevailing therapies are committed to alleviating the symptoms induced by above lesions. But the efficacies achieved by these interventions are still not satisfactory, because the milieus for tissue regeneration are not distinctly improved. In recent years, regenerative therapy for radiation enteropathy by using mesenchymal stem cells is of public interests. Relevant results of preclinical and clinical studies suggest that this regenerative therapy will become an attractive tool in managing radiation enteropathy, because mesenchymal stem cells exhibit their pro-regenerative potentials for healing the injuries in both epithelium and endothelium, minimizing inflammation and protecting irradiated intestine against fibrogenesis through activating intrinsic repair actions. In spite of these encouraging results, whether mesenchymal stem cells promote tumor growth is still an issue of debate. On this basis, we will discuss the advances in anticancer therapy by using mesenchymal stem cells in this review after analyzing the pathogenesis of radiation enteropathy, introducing the advances in managing radiation enteropathy using regenerative therapy and exploring the putative actions by which mesenchymal stem cells repair intestinal injuries. At last, insights gained from the potential risks of mesenchymal stem cell-based therapy for radiation enteropathy patients may provide clinicians with an improved awareness in carrying out their studies.

New model for long-term investigations of cutaneous microcirculatory and inflammatory changes following irradiation

Radiotherapy is used for curative and palliative treatment. However, its negative effect on normal tissue is a limiting factor for the deliverable dose. Microcirculatory breakdown and prolonged inflammation in particular are major features of late side effects. The purpose of this study was to develop a reliable animal model that will allow a long-term in vivo analysis of microcirculation and inflammation following irradiation. A single dose of 90 Gy was delivered to the ears of hairless mice (n = 15). Intravital fluorescent microscopy was used to assess microcirculatory parameters and leukocyte behaviour. Values for the identical (control) areas were obtained before as well as during the following days, weeks and months following irradiation. The arteriolar and venular diameter increased up to Day 14, decreased during the following months, and increased again after one year. The red blood cell velocity increased up to 145% on Day 3, decreased on Day 7 to 115%, and stayed above baseline value the whole year. The integrity loss of the endothelium increased up to Day 7 and continued up to Day 75 after radiation. After one year, the oedema was at the baseline level. Leukocytes showed their maximal activity at one year after trauma. An increase was measured up to Day 25; the lowest values were measured at Day 40 post-irradiation, followed by a repeated increase. The present model allows a certain visualization of microcirculatory disturbances and inflammation over a period of months. This permits the possibility of long-term investigations of the underlying pathophysiology following irradiation, including possible drug interactions.

Intravenous delivery of adipose-derived mesenchymal stromal cells attenuates acute radiation-induced lung injury in rats

BACKGROUND AIMS

Radiation-induced lung injury (RILI) commonly occurs in patients with thoracic cancer. However, an effective treatment option has not yet been established. Adipose-derived mesenchymal stromal cells (Ad-MSCs) have significant potential for clinical use, but their role in RILI is currently unknown. We aimed to evaluate the therapeutic capacity of Ad-MSCs to heal acute RILI in rats.

METHODS

Sprague-Dawley rats were used in this study. Rat Ad-MSCs were delivered through the tail veins of rats 2 h after thorax irradiation. Lung histopathologic findings, pulmonary levels of inflammatory cytokines (interleukin [IL]-1, IL-6, IL-10 and tumor necrosis factor-α), pro-fibrotic factors (transforming growth factor [TGF]-β1, connective tissue growth factor, α-smooth muscle actin and type 1 collagen), pro- or anti-apoptotic mediators (Bcl-2, Bax and caspase-3) and the multifunctional factor hepatocyte growth factor were evaluated after Ad-MSC transplant.

RESULTS

Intravenous delivery of Ad-MSCs attenuated acute RILI. Further studies showed that Ad-MSCs had anti-inflammation and anti-fibrotic effects and maintained lung epithelium integrity, as indicated by reduced serum levels of the pro-inflammatory cytokines IL-1, IL-6 and tumor necrosis factor-α, increased levels of the anti-inflammatory cytokine IL-10, and downregulated transforming growth factor -β1, α-smooth muscle actin and type 1 collagen levels in irradiated lung tissues. Ad-MSCs also regulated the expression of pro- and anti-apoptotic mediators (Bcl-2, Bax and caspase-3) to protect lung cells from apoptosis.

CONCLUSIONS

Intravenous Ad-MSC delivery attenuated acute RILI through anti-inflammation, anti-fibrosis and anti-apoptosis mechanisms.

Systematic review: the role of the gut microbiota in chemotherapy- or radiation-induced gastrointestinal mucositis - current evidence and potential clinical applications

BACKGROUND

Gastrointestinal mucositis is defined as inflammation and/or ulcers of the gastrointestinal tract occurring as a complication of chemotherapy and radiation therapy, and affects about 50% of all cancer patients.

AIM

To assess the role of gut microbiota in the pathogenesis of gastrointestinal mucositis and the potential for manipulations of the microbiota to prevent and to treat mucositis.

METHODS

Search of the literature published in English using Medline, Scopus and the Cochrane Library, with main search terms 'intestinal microbiota', 'bacteremia', 'mucositis', 'chemotherapy-induced diarrhoea', 'chemotherapy-induced mucositis', 'radiotherapy-induced mucositis'.

RESULTS

The gut microbiota plays a major role in the maintenance of intestinal homoeostasis and integrity. Patients receiving cytotoxic and radiation therapy exhibit marked changes in intestinal microbiota, with most frequently, decrease in Bifidobacterium, Clostridium cluster XIVa, Faecalibacterium prausnitzii, and increase in Enterobacteriaceae and Bacteroides. These modifications may contribute to the development of mucositis, particularly diarrhoea and bacteraemia. The prevention of cancer therapy-induced mucositis by probiotics has been investigated in randomised clinical trials with some promising results. Three of six trials reported a significantly decreased incidence of diarrhoea. One trial reported a decrease in infectious complications.

CONCLUSIONS

The gut microbiota may play a major role in the pathogenesis of mucositis through the modification of intestinal barrier function, innate immunity and intestinal repair mechanisms. Better knowledge of these effects may lead to new therapeutic approaches and to the identification of predictive markers of mucositis.

Long-term differential changes in mouse intestinal metabolomics after γ and heavy ion radiation exposure

Tissue consequences of radiation exposure are dependent on radiation quality and high linear energy transfer (high-LET) radiation, such as heavy ions in space is known to deposit higher energy in tissues and cause greater damage than low-LET γ radiation. While radiation exposure has been linked to intestinal pathologies, there are very few studies on long-term effects of radiation, fewer involved a therapeutically relevant γ radiation dose, and none explored persistent tissue metabolomic alterations after heavy ion space radiation exposure. Using a metabolomics approach, we report long-term metabolomic markers of radiation injury and perturbation of signaling pathways linked to metabolic alterations in mice after heavy ion or γ radiation exposure. Intestinal tissues (C57BL/6J, female, 6 to 8 wks) were analyzed using ultra performance liquid chromatography coupled with electrospray quadrupole time-of-flight mass spectrometry (UPLC-QToF-MS) two months after 2 Gy γ radiation and results were compared to an equitoxic ⁵⁶Fe (1.6 Gy) radiation dose. The biological relevance of the metabolites was determined using Ingenuity Pathway Analysis, immunoblots, and immunohistochemistry. Metabolic profile analysis showed radiation-type-dependent spatial separation of the groups. Decreased adenine and guanosine and increased inosine and uridine suggested perturbed nucleotide metabolism. While both the radiation types affected amino acid metabolism, the ⁵⁶Fe radiation preferentially altered dipeptide metabolism. Furthermore, ⁵⁶Fe radiation caused upregulation of ‘prostanoid biosynthesis’ and ‘eicosanoid signaling’, which are interlinked events related to cellular inflammation and have implications for nutrient absorption and inflammatory bowel disease during space missions and after radiotherapy. In conclusion, our data showed for the first time that metabolomics can not only be used to distinguish between heavy ion and γ radiation exposures, but also as a radiation-risk assessment tool for intestinal pathologies through identification of biomarkers persisting long after exposure.

Impact of pelvic radiotherapy on gut microbiota of gynecological cancer patients revealed by massive pyrosequencing

Although pelvic irradiation is effective for the treatment of various cancer types, many patients who receive radiotherapy experience serious complications. Gut microbial dysbiosis was hypothesized to be related to the occurrence of radiation-induced complications in cancer patients. Given the lack of clinical or experimental data on the impact of radiation on gut microbiota, a prospective observational study of gut microbiota was performed in gynecological cancer patients receiving pelvic radiotherapy. In the current study, the overall composition and alteration of gut microbiota in cancer patients receiving radiation were investigated by 454 pyrosequencing. Gut microbial composition showed significant differences (P < 0.001) between cancer patients and healthy individuals. The numbers of species-level taxa were severely reduced after radiotherapy (P < 0.045), and the abundance of each community largely changed. In particular, the phyla Firmicutes and Fusobacterium were significantly decreased by 10% and increased by 3% after radiation therapy, respectively. In addition, overall gut microbial composition was gradually remolded after the full treatment course of pelvic radiotherapy. In this set of cancer patients, dysbiosis of the gut microbiota was linked to health status, and the gut microbiota was influenced by pelvic radiotherapy. Although further studies are needed to elucidate the relationship between dysbiosis and complications induced by pelvic radiotherapy, the current study may offer insights into the treatment of cancer patients suffering from complications after radiation therapy.

Multi-therapeutic effects of human adipose-derived mesenchymal stem cells on radiation-induced intestinal injury

Radiation-induced intestinal injuries (RIII) commonly occur in patients who suffer from pelvic or abdominal cancer. However, current management of these injuries is ineffective. Recently, mesenchymal stem cells (MSCs) have been extensively used in regenerative medicine and have achieved a high level of efficacy. In the present study, we hypothesised that human adipose-derived mesenchymal stem cells (hAd-MSCs) could be used as potential tools to heal RIII. We observed that adult Sprague-Dawley rats that received whole-abdominal irradiation benefitted from hAd-MSC injection. hAd-MSCs had RIII-healing effects, including anti-inflammation, neovascularisation and maintenance of epithelium homeostasis, as indicated by elevated serum IL-10, upregulation of vascular endothelial growth factor, basic fibroblast growth factor and epidermal growth factor in irradiated intestine, mobilisation of CD31-positive haematopoietic stem cells or haematopoietic progenitor cells, and the prolonged presence of Bmi1-positive cells within crypts. Consequently, after hAd-MSC treatment, irradiated rats survived longer than non-treated animals. These results suggest that hAd-MSCs have therapeutic potential for RIII management.

Radiation-induced damage in different segments of the rat intestine after external beam irradiation of the liver

INTRODUCTION

The out-of-field effects on the intestine, caused by radiation treatment of a parenchymatous organ, have not previously been studied.

METHODS

A single dose of 25Gy was administered percutaneously to the liver of male Wistar rats after a planning CT-scan. Sham-irradiated animals served as controls. At 1, 6, 24, 96h, 1.5 and 3months the duodenum, jejunum, ileum and distal colon were removed, washed and deep-frozen or prepared for paraffin staining.

RESULTS

All animals survived the treatment. Epithelial cell damage occurred in all small-intestinal segments. However, prolonged denudation of the villi together with destruction of the crypt lining was only observed in the ileum, resulting in deficient regeneration. In the colon, changes were minor. Radiation mucositis with granulocyte (MP0+) infiltration was seen from 1 to 24h in the duodenum and jejunum, when ED1+ macrophages, CD3+ T-lymphocytes, and CD34+ hematopoietic precursor cells were recruited, accompanied by an increase in the chemokines MCP-1, MIP-1α, MIP3α and Il-8. In the ileum, early granulocyte infiltration was delayed but continuous. Recruitment of macrophages and lymphocytes was deficient and induction of chemokines as of the adhesion molecules PECAM-1, ICAM-1 was lacking.

CONCLUSION

Post-irradiation damage to the ileum was delayed and followed by an altered repair process with structural changes of the villi. The observed changes might result from a higher sensitivity to oxidative stress mechanisms with subsequent damage of the regenerative capacity of the crypt-villus axis, accompanied by a sustained "inflammatory response" and vascular damage with a lack of regeneratory cell recruitment.

Matrilysin expression related to radiation and microflora changes in murine bowel

BACKGROUND

Matrilysin (MMP-7) elevation after radiotherapy is shown in humans. Matrilysin regulates certain cytokines and the production of bactericidal proteins when the mucosa is exposed to bacterial antigens. We investigate the effect of irradiation on matrilysin and microflora in murine bowel, after modulation with antibiotics.

METHODS

Animals were divided into two different groups a radiation group (72 animals) and sham radiation group (36 animals). Animals were divided into smaller groups of six according to radiation dose (19 or 38 Gy or sham). Seven days before radiotherapy ampicillin 500 mg/kg/d was administered intramuscularly, in the antibiotic groups. An exteriorized segment of ileum was subjected to single high dose radiation (19 or 38 Gy). Samples were collected 2, 24, and 48 h and analyzed for microflora, MIP-2, TGF-β, and MMP-7.

RESULTS

The combination of antibiotics and irradiation leads to an early significant reduction of bacteria, down-regulates MIP-2, up-regulates TGF-β and elevation of MMP-7 to levels achieved by antibiotics or irradiation alone. Lactobacilli were reduced to non-existent levels after antibiotics.

CONCLUSIONS

Pretreatment with Ampicillin before irradiation and laparotomy in a murine model leads to Matrilysin over-expression as achieved by radiotherapy alone. Microfloral regulation does not affect MMP-7 stimulation after surgical or radiological trauma. Radiotherapy overrides the effect of antibiotics leading to an up-regulation of MMP-7, TGF-β and MIP-2 expression between 24 h and 48 h.

Rho kinase signalling mediates radiation-induced inflammation and intestinal barrier dysfunction

Background

Radiotherapy is important in the management of pelvic malignancies, but radiation-induced intestinal damage is a dose-limiting factor. Microvascular injury and epithelial barrier dysfunction are considered to be rate-limiting aspects in radiation-induced enteropathy. This study investigated the role of Rho kinase signalling in radiation-induced inflammation and intestinal barrier dysfunction.

Methods

The specific Rho kinase inhibitor Y-27632 (1 and 10 mg/kg) was given to C57BL/6J mice before challenge with 20 Gy radiation. Leucocyte– and platelet–endothelium interactions in the colonic microcirculation were assessed by intravital microscopy. Levels of myeloperoxidase (MPO) and CXC chemokines (macrophage inflammatory protein 2 and cytokine-induced neutrophil chemoattractant), and intestinal leakage were quantified after 16 h.

Results

Radiation increased leucocyte and platelet recruitment, MPO activity, CXC chemokine production and intestinal leakage. Y-27632 significantly reduced radiation-induced leucocyte rolling and abolished adhesion; it also decreased platelet rolling and adhesion by 55 and 74 per cent respectively (P &lt; 0·050). Inhibition of Rho kinase signalling significantly decreased radiation-provoked formation of CXC chemokines, MPO activity by 52 per cent, and intestinal leakage by 67 per cent (P &lt; 0·050).

Conclusion

Rho kinase activity constitutes an important signalling mechanism in radiation-induced inflammation and intestinal barrier dysfunction.

Preventive effect of pentoxifylline on acute radiation damage via antioxidant and anti-inflammatory pathways

PURPOSE

The aim of the present study was to investigate whether pentoxifylline (PTX) treatment could protect against induced acute radiation enteritis.

METHOD

Rats received 100 mg/kg/day PTX for 7 days before irradiation and continued on treatment for 3 days after irradiation. The intestinal myeloperoxidase (MPO) activities and malondialdehyde (MDA), glutathione (GSH), prostaglandin E2, and thromboxane B2 levels were determined. Terminal ileum tissue was evaluated for morphological changes. Also, nuclear factor kappa (NF-kappa), tumor necrosis factor-alpha (TNF-alpha), and intercellular adhesion molecule 1 (ICAM-1) expressions were analyzed with immunohistochemisty methods.

RESULTS

PTX treatment was associated with increased GSH levels and decreased MPO activity and MDA, prostaglandin E2, and thromboxane B2 levels. Histopathologic examination showed that intestinal mucosal structure was preserved in the PTX-treated group while having significant decreases in NF-kappaB, TNF-a, and ICAM-1 expression.

CONCLUSIONS

PTX appears to have a protective effect against radiation damage. This protective effect is mediated in part by decreasing both inflammatory reactions and oxidative stress.

[Radiotherapy: what therapeutic orientations against the digestive aftereffects?]

Despite constant progress in radiotherapy techniques such as tumour imaging and cartography, techniques of radiation delivery or fractionation schedules, damage to normal gastro-intestinal tissues is inevitably associated with radiation therapy of pelvic tumours. Acute radiation enteritis concerns 80% of patients. It is related to stem cell loss, default in epithelial regenerating capacity and inflammation-induced mucosal dystrophy and ulceration. Chronic injury may develop in 5 to 10% of patients and is characterized by intestinal wall fibrosis resulting from an exaggerated scarring process, chronic inflammation and tissue necrosis. Research in mechanistic processes of normal tissue damage paved the way for new therapeutic approaches to emerge. These new targets include mucosal regeneration, reduction of vascular activation, inflammation and thrombosis, and fight against mesenchymal cells sustained activation. Effective strategies are multiple on preclinical models, but numerous efforts have to be made to achieve the complicated goal of protection of normal tissues from the side effects of radiation therapy.

Pravastatin limits radiation-induced vascular dysfunction in the skin

About half of people with cancer are treated with radiation therapy; however, normal tissue toxicity still remains a dose-limiting factor for this treatment. The skin response to ionizing radiation may involve multiple inflammatory outbreaks. The endothelium is known to play a critical role in radiation-induced vascular injury. Furthermore, endothelial dysfunction reflects a decreased availability of nitric oxide. Statins have been reported to preserve endothelial function through their antioxidant and anti-inflammatory activities. In this study, wild type and endothelial nitric oxide synthase (eNOS)(-/-) mice were subjected to dorsal skin irradiation and treated with pravastatin for 28 days. We demonstrated that pravastatin has a therapeutic effect on skin lesions and abolishes radiation-induced vascular functional activation by decreasing interactions between leukocytes and endothelium. Pravastatin limits the radiation-induced increase of blood CCL2 and CXCL1 production expression of inflammatory adhesion molecules such as E-selectin and intercellular adhesion molecule-1, and inflammatory cell migration in tissues. Pravastatin limits the in vivo and in vitro radiation-induced downregulation of eNOS. Moreover, pravastatin has no effect in eNOS(-/-) mice, demonstrating that eNOS plays a key role in the beneficial effect of pravastatin in radiation-induced skin lesions. In conclusion, pravastatin may be a good therapeutic approach to prevent or reduce radiation-induced skin damage.

Local radiotherapy of exposed murine small bowel: apoptosis and inflammation

Background

Preoperative radiotherapy of the pelvic abdomen presents with complications mostly affecting the small bowel. The aim of this study was to define the features of early radiation-induced injury on small bowel.

Methods

54 mice were divided into two groups (36 irradiated and 18 sham irradiated). Animals were placed on a special frame and (in the radiated group) the exteriorized segment of ileum was subjected to a single absorbed dose of 19 or 38 Gy radiation using 6 MV high energy photons. Specimens were collected for histology, immunohistochemistry (IHC) and ELISA analysis after 2, 24 and 48 hours. Venous blood was collected for systemic leucocyte count in a Burker chamber.

Results

Histology demonstrated progressive infiltration of inflammatory cells with cryptitis and increased apoptosis. MIP-2 (macrophage inflammatory protein) concentration was significantly increased in irradiated animals up to 48 hours. No significant differences were observed in IL-10 (interleukin) and TNF-α (tumour necrosis factor) levels. IHC with CD45 showed a significant increase at 2 hours of infiltrating leucocytes and lymphocytes after irradiation followed by progressive decrease with time. Caspase-3 expression increased significantly in a dose dependent trend in both irradiated groups up to 48 hours.

Conclusion

Acute small bowel injury caused by local irradiation is characterised by increased apoptosis of crypt epithelial cells and by lymphocyte infiltration of the underlying tissue. The severity of histological changes tends to be dose dependent and may affect the course of tissue damage.

Local administration of interleukin-11 ameliorates intestinal radiation injury in rats

Intestinal radiation injury is dose limiting during abdominal and pelvic radiotherapy and critical for the outcome after accidental whole-body radiation exposure. The multifunctional cytokine, interleukin-11 (IL-11), ameliorates the intestinal radiation response, but its clinical use is hampered by severe toxicity after systemic administration. This study addressed whether protection against intestinal radiation injury can be achieved by intraluminal administration of IL-11. Male rats underwent surgical transposition of a 4-cm small bowel loop to the scrotum. For repeated intraluminal drug administration, an ileostomy, proximal to the bowel loop in the scrotum, was created. The transposed intestinal loop was exposed to 5 Gy fractions on 9 consecutive days. Recombinant human IL-11 (rhIL-11; 2 mg/kg/d) or vehicle was given through the ileostomy from 2 days before until 2 weeks after irradiation. At 2 weeks, structural, cellular, and molecular aspects of intestinal radiation injury were assessed. rhIL-11 ameliorated structural manifestations of radiation enteropathy, including radiation injury score (6.5 +/- 0.6 in the vehicle group versus 4.0 +/- 0.3 in the IL-11 group; P = 0.001), mucosal surface area loss (0.2 +/- 0.1 versus 0.5 +/- 0.03; P < 0.0001), and intestinal wall thickening (842 +/- 66 microm versus 643 +/- 54 microm; P = 0.02), reduced postradiation transforming growth factor-beta overexpression, and reduced numbers of ED2-positive cells. Postirradiation mucosal mast cell numbers were partially restored by rhIL-11. These data show that local administration of rhIL-11 ameliorates early intestinal radiation injury and support further development of rhIL-11 to reduce manifestations of intestinal radiation injury in the clinic.

Anti-TNFA (TNF-alpha) treatment abrogates radiation-induced changes in vacular density and tissue oxygenation

Ionizing radiation significantly alters the structure and function of microvasculature, which regulates delivery of oxygen to brain tissue. Previous experimental and modeling studies have shown that tissue oxygenation patterns are significantly different in irradiated normal tissue compared to age-matched controls, and the differences are apparent as early as 3 days postirradiation. However, oxygen delivery to irradiated tissue recovers within 6 months postirradiation. Changes in perfusion and oxygenation were studied in a bilaterally (both cerebral hemispheres) and unilaterally (only one hemisphere) irradiated mouse brain model at 6 and 24 h as well as 3, 7, 30, 60 and 120 days postirradiation. The results indicate that significant changes in the number of perfused vessels (as measured by fluorescent DiOC(7) staining) and anatomical vessels (as indicated by CD31 immunohistochemical staining) and tissue oxygenation (by immunohistochemical detection of a fluorescently conjugated monoclonal antibody to EF5) are most pronounced at 3 days postirradiation, while a degree of recovery is observed at later times. However, in the unilaterally irradiated animals, both irradiated and unirradiated (out-of-field) cerebral hemispheres showed similarly significant changes in oxygenation and/or perfusion compared to unirradiated controls. Anti-TNFA treatment inhibited radiation-induced local as well as abscopal effects in the brain tissue.

Radiation-induced up-regulation of adhesion molecules in brain microvasculature and their modulation by dexamethasone

Little is known about the time course and magnitude of the up-regulation of endothelial cell adhesion molecules (ECAMs) in irradiated brain vasculature and the mechanisms by which dexamethasone modulates this up-regulation. We used antibody-conjugated microspheres and a rat closed cranial window model to determine the time course of functional up-regulation of radiation (20 Gy)-induced ICAM1, E-selectin and P-selectin in the pial vasculature of the rat brain and to determine the relationship between suppression of inflammation by dexamethasone and the expression of these ECAMs. The results indicate that ICAM1, E-selectin and P-selectin were up-regulated to a functional level in the microvasculature with distinct time-course patterns. The number of adherent anti-E-selectin and anti-P-selectin microspheres was 5- 12 times greater than that of IgG microspheres 3-6 h postirradiation, and their expression returned to normal at 48 h. The number of adherent anti-ICAM1 microspheres was five and nine times greater than that of IgG at 24 and 48 h, respectively, and returned to baseline by 7 days. Dexamethasone significantly reduced the number of adhering leukocytes and the number of adhering anti-ICAM1, anti-E-selectin and anti-P-selectin microspheres to background levels. Our findings partially identify a key sequence in radiation-induced inflammatory response and provide a potential means to limit radiation-induced inflammatory responses and their potential side effects in the brain.