Radiation and the small intestine. Future perspectives for preventive therapy

The Protection Effect of Resveratrol Against Radiation-Induced Inflammatory Bowel Disease via NLRP-3 Inflammasome Repression in Mice

With the extensive application of radiotherapy in various cancers, its side effects in tissues adjacent to cancers are garnering much attention. Intestines are sensitive to irradiation due to its rapid proliferation, and irradiation-induced enteric inflammation is common in patients with pelvic peritoneal tumors. Sirt1, class III protein deacetylase, could lead to transcriptional repression of various inflammation-associated genes, and our previous study has proved its relationship with interleukin (IL)-1β. Here we show that resveratrol, the activator of Sirt1, could alleviate the bowel inflammation induced by irradiation and the expression of Sirt1 is consistent with the inflammation level. We further identified in vivo that Sirt1 repress the expression of IL-1β by the repression of NLR Family, Pyrin Domain Containing protein 3 (NLRP3) expression. In conclusion, this study confirms resveratrol acts against radiation-induced inflammatory bowel disease via NLRP-3 inflammasome repression in mice and supports Sirt1 as a potential biomarker and therapy target in intestinal radiation protection.

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.

Unraveling intestinal stem cell behavior with models of crypt dynamics

The definition, regulation and function of intestinal stem cells (ISCs) has been hotly debated. Recent discoveries have started to clarify the nature of ISCs, but many questions remain. This review discusses the current advances and controversies of ISC biology as well as theoretical compartmental models that have been coupled with in vivo experimentation to investigate the mechanisms of ISC dynamics during homeostasis, tumorigenesis, repair and development. We conclude our review by discussing the key lingering questions in the field and proposing how many of these questions can be addressed using both compartmental models and experimental techniques.

Pelvic Ewing sarcomas. Three-dimensional conformal vs. intensity-modulated radiotherapy

PURPOSE

The goal of the present work was to assess the potential advantage of intensity-modulated radiotherapy (IMRT) over three-dimensional conformal radiotherapy (3D-CRT) planning in pelvic Ewing's sarcoma.

PATIENTS AND METHODS

A total of 8 patients with Ewing sarcoma of the pelvis undergoing radiotherapy were analyzed. Plans for 3D-CRT and IMRT were calculated for each patient. Dose coverage of the planning target volume (PTV), conformity and homogeneity indices, as well as further parameters were evaluated.

RESULTS

The average dose coverage values for PTV were comparable in 3D-CRT and IMRT plans. Both techniques had a PTV coverage of V95 > 98 % in all patients. Whereas the IMRT plans achieved a higher conformity index compared to the 3D-CRT plans (conformity index 0.79 ± 0.12 vs. 0.54 ± 0.19, p = 0.012), the dose distribution across the target volumes was less homogeneous with IMRT planning than with 3D-CRT planning. This difference was statistically significant (homogeneity index 0.11 ± 0.03 vs. 0.07 ± 0.0, p = 0.035). For the bowel, Dmean and D1%, as well as V2 to V60 were reduced in IMRT plans. For the bladder and the rectum, there was no significant difference in Dmean. However, the percentages of volumes receiving at least doses of 30, 40, 45, and 50 Gy (V30 to V50) were lower for the rectum in IMRT plans. The volume of normal tissue receiving at least 2 Gy (V2) was significantly higher in IMRT plans compared with 3D-CRT, whereas at high dose levels (V30) it was significantly lower.

CONCLUSION

Compared to 3D-CRT, IMRT showed significantly better results regarding dose conformity (p = 0.012) and bowel sparing at dose levels above 30 Gy (p = 0.012). Thus, dose escalation in the radiotherapy of pelvic Ewing's sarcoma can be more easily achieved using IMRT.

Validation of a surgical technique for rat intestinal irradiation: potential side effects prevention by dietary grape phenolics

AIMS

This study evaluates and defines the histological and biochemical consequences of irradiation on the Hauer-Jensen intestinal model and investigates the potential effects of dietary polyphenols.

MAIN METHODS

Sprague-Dawley rats were orchiectomized, and an ileal loop was transposed to the left part of the scrotum, then irradiated 2 weeks after surgery with a single dose of 21 Gy (4.49 Gy/min). Four groups of rats received either phenolic extracts from grape seeds (EGS) and from red wine (ACYS, EGT), or pure quercetin 3-O-β-glucoside (Q3G), for 5 days before the irradiation and were sacrificed 2 weeks after. Antioxidant enzyme activities, i.e. superoxide dismutase (SOD) and glutathione peroxidase activity (GSHPx), and oxidative markers such as myeloperoxidase activity (MPO) and thiobarbituric acid reactive substances (MDA) were measured as well as cytokine-induced neutrophil chemoattractant level (CINC-1), a chemokine involved in inflammation.

KEY FINDINGS

Irradiated rats exhibited a high radiation injury score (RIS) with a thickened serosa, mucosal loss and ulceration, and epithelial atypicality. Intestinal MPO activity and CINC-1 concentration were significantly increased in irradiated animals (60 and 66 %, respectively). Higher plasma MDA levels (58 %) and SOD activity (32 %) were accompanied by a reduced GSHPx activity (79 %). However, feeding phenolic extracts remarkably reduced levels of blood SOD activity (34 % on average), intestinal CINC-1 (25-75 % range) and MPO activity (36-84 %). Except for Q3G, phenolics preserved the intestinal structure.

SIGNIFICANCE

These findings show that irradiation triggers an inflammation, and an oxidative stress by disturbing the pro-oxidant/antioxidant balance and indicate that phenolics supply exerts preventive effects against radio-induced intestinal impairment.

Biochemical signs of impaired cobalamin status during and after radiotherapy for rectal cancer

PURPOSE

The aim of the study was to investigate whether pelvic radiotherapy for rectal cancer had a negative impact on cobalamin status.

METHODS AND MATERIALS

Consecutive patients receiving pelvic radiotherapy (50 Gy) for rectal cancer were evaluated prospectively (n = 54). Serum cobalamin, holotranscobalamin (holoTC), methylmalonic acid (MMA), and total homocysteine (tHcy) were measured at start and end of radiotherapy, at follow-up 4-6 weeks and 1 year (n = 23) after radiotherapy.

RESULTS

Mean serum cobalamin decreased from 306 pmol/L before treatment to 267 pmol/L at the end of radiotherapy (p < 0.001), 247 pmol/L 4-6 weeks after radiotherapy (p < 0.001), and 249 pmol/L 1 year after radiotherapy (p = 0.02). Mean serum MMA was 0.16 micromol/L pretreatment, 0.17 micromol/L at the end of radiotherapy (n.s.), and increased to 0.19 micromol/L after 4-6 weeks (p = 0.007), and to 0.21 micromol/L after 1 year (p < 0.001). There was no change in serum tHcy. Mean serum holoTC was reduced from 111 pmol/L pretreatment to 93 pmol/L 4-6 weeks after radiotherapy (p = 0.002).

CONCLUSIONS

The data suggest rapid and persistent decrease in cobalamin status after radiotherapy for rectal cancer, as reflected by reduced serum cobalamin combined with increased serum MMA. This observation, though modest, may motivate routine monitoring of cobalamin status at follow-up after radiotherapy.

The preclinical basis for broad-spectrum selective cytoprotection of normal tissues from cytotoxic therapies by amifostine (Ethyol)

Administered prior to cytotoxic chemotherapy or radiation, the aminothiol amifostine provides broad-spectrum cytoprotection of various normal tissues without attenuating antitumour response. The basis for the selectivity of action resides in the anabolism of amifostine at the normal tissue site by membrane-bound alkaline phosphatase. Dephosphorylation to the free thiol, WR-1065, is followed by rapid uptake into normal tissues by a carrier mediated, facilitated diffusion process; in contrast, uptake into tumour tissue is slow to negligible. Preclinical studies have shown that pretreatment with amifostine provides protection of normal tissues from the cytotoxic effects of alkylating agents, organoplatinums, anthracyclines, taxanes and radiation. Normal tissues protected include bone marrow, kidney, neural tissues, the heart, intestinal crypt cells and pulmonary tissues. Additionally, the mutagenic and carcinogenic effects of these modalities are also attenuated. With respect to bone marrow, preclinical studies have shown significant protection of progenitor cells that give rise to the red and white cells and platelets. Comparative in vitro and in vivo studies using murine and human tumour xenografts show no decrease of antitumour effects of these same therapies despite the protection of normal organs. The unique preclinical profile of amifostine serves as a model for the clinical development programme for this important new broad-spectrum cytoprotective agent.

Intestinal complications of radiotherapy in gynecologic malignancy--clinical presentation and management

Radiation therapy is an effective treatment modality for various gynecologic malignancies. In spite of advances in radiotherapy equipment and techniques over the years, the gastrointestinal and urinary tracts have remained a considerable problem with radiotherapy of the pelvis and abdomen. Clinical presentation of intestinal complications, current concepts of pathophysiology and principles of medical and surgical management are reviewed.

Severe late radiation enteropathy is characterized by impaired motility of proximal small intestine

Late radiation enteropathy (LRE) is a serious disorder, and therapeutic progress has thus far been hampered by insufficient understanding of the pathogenesis. This prospective study addresses whether alterations in proximal intestinal motility can predict the clinical severity of this disorder. Forty-one consecutive patients with chronic abdominal complaints after radiotherapy for gynecological cancer were examined by prolonged ambulatory manometry. Twenty-seven healthy adults served as controls. Impaired fasting motility was found in 12 of 41 patients (29%), and attenuated postprandial motor response after a liquid-solid meal was seen in 10 of 41 patients (24%). Postprandial delay of the migrating motor complex (MMC) was a good predictor of the degree of malnutrition (Cox regression, P < 0.01), and intensity of the MMC and postprandial motility index explained 69% (P < 0.001, multiple regression) of the variability in degree of malnutrition, assessed by weight loss and serum albumin level. The typical presentation of severe LRE was clinical symptoms suggesting intestinal pseudoobstruction, malnutrition, failure of a liquid-solid meal to induce postprandial motility, and delayed initiation and reduced intensity of MMC during nocturnal fasting. Prolonged ambulatory manometry was useful for detection of dysmotility in patients with symptoms of LRE and impaired motility of proximal small intestine seems to be a key factor in the pathogenesis of severe LRE.