Intestinal Radiation Research Articles

Mast Cells Are an Essential Component of Human Radiation Proctitis and Contribute to Experimental Colorectal Damage in Mice

Radiation proctitis is characterized by mucosal inflammation followed by adverse chronic tissue remodeling and is associated with substantial morbidity and mortality. Mast cell hyperplasia has been associated with diseases characterized by pathological tissue remodeling and fibrosis. Rectal tissue from patients treated with radiotherapy shows mast cell hyperplasia and activation, suggesting that these cells play a role in the development of radiation-induced sequelae. To investigate the role of mast cells in radiation damage, experimental radiation proctitis was induced in a mast cell-deficient (W(sh)/W(sh)) mouse model. The colon and rectum of W(sh)/W(sh) and wild-type mice were exposed to 27-Gy single-dose irradiation and studied after 2 and 14 weeks. Irradiated rodent rectum showed mast cell hyperplasia. W(sh)/W(sh) mice developed less acute and chronic rectal radiation damage than their control littermates. Tissue protection was associated with increased tissue neutrophil influx and expression of several inflammatory mediators immediately after radiation exposure. It was further demonstrated that mast cell chymase, tryptase, and histamine could change human muscularis propria smooth muscle cells into a migrating/proliferating and proinflammatory phenotype. These data show that mast cells have deleterious effects on both acute and chronic radiation proctitis, possibly by limiting acute tissue neutrophil influx and by favoring phenotypic orientation of smooth muscle cells, thus making them active participants in the radiation-induced inflammatory process and dystrophy of the rectal wall.

Practical approaches to effective management of intestinal radiation injury: Benefit of resectional surgery

To study the outcome of patients undergoing surgical resection of the bowel for sustained radiation-induced damage intractable to conservative management. During a 7-year period we operated on 17 cases (5 male, 12 female) admitted to our surgical department with intestinal radiation injury (IRI). They were originally treated for a pelvic malignancy by surgical resection followed by postoperative radiotherapy. During follow-up, they developed radiation enteritis requiring surgical treatment due to failure of conservative management. IRI was located in the terminal ileum in 12 patients, in the rectum in 2 patients, in the descending colon in 2 patients, and in the cecum in one patient. All patients had resection of the affected region(s). There were no postoperative deaths, while 3 cases presented with postoperative complications (17.7%). All patients remained free of symptoms without evidence of recurrence of IRI for a median follow-up period of 42 mo (range, 6-96 mo). We report a favorable outcome without IRI recurrence of 17 patients treated by resection of the diseased bowel segment.

Effect of actovegin on intestinal mucosa and expression of bcl-2/bax genes in rats with acute radiation enteritis

To evaluate the effect of actovegin (Nycomed, deproteinized hemoderivative of calf blood injection) on intestinal mucosa in rats with acute radiation enteritis, and observe the changes of expression of apoptosis-related bcl-2/bax genes. An abdominal irradiation in a dose of 9.0 Gy X-ray of linear accelerator was performed once on a group of Wistar rats to establish a model of acute intestinal radiation enteritis. The experimental rats were randomly divided into five groups. Group 1 was normal control group; group 2 was model control group; groups 3, 4 and 5 were treated with low, middle and high dose of actovegin, respectively. After the model was established, actovegin injection was given intraperitoneally for successive 4 days. Corresponding intestinal tissues were taken for morphological examination with an image analysis system. The expression of apoptosis related bax and bcl-2 protein in the intestinal mucosal epithelial cells was determined by immunohistochemistry. The groups 4 and 5 had significantly higher height of intestinal villi, the depth of crypt, the thickness of the mucosa and entire wall (254.66/261.71 microm, 166.47/165.41 microm, 510.44/511.71 microm, 610.38/608.98 microm), compared with those of the model control group (239.12 microm, 151.45 microm, 420.27 microm and 579.32 microm), respectively (P < 0.05). Treatment with middle and high doses of actovegin also significantly down-regulated the expression of activating apoptosis protein bax (24.54/23.24) compared with that of model control group (59.32) (P < 0.05) and up-regulated the expression of inhibiting apoptosis protein bcl-2 (55.54/52.21) compared with that of model control group (20.32) (P < 0.05). The ratio of bcl-2/bax was significantly higher in the groups 4 and 5 (2.2632, 2.1275) compared with that in the model control group (0.3425) (P < 0.01). Actovegin accelerates the recovery of the acute radiation-injured intestinal mucosal epithelium by decreasing apoptosis via down-regulation of the expression of activating apoptosis protein bax and up-regulation of inhibiting apoptosis protein bcl-2.

The Somatostatin Analog SOM230 (Pasireotide) Ameliorates Injury of the Intestinal Mucosa and Increases Survival after Total-Body Irradiation by Inhibiting Exocrine Pancreatic Secretion

Somatostatin analogs ameliorate intestinal injury after localized irradiation. This study investigated whether SOM230, a novel, metabolically stable analog with broad receptor affinity, reduces intestinal injury and lethality in mice exposed to total-body irradiation (TBI). Male CD2F1 mice were exposed to 7-15 Gy TBI. Twice-daily administration of SOM230 (1, 4 or 10 mg/kg per day) or vehicle was started either 2 days before or 4 h after TBI and continued for either 14 or 21 days. Parameters of intestinal and hematopoietic radiation injury, bacterial translocation, and circulating cytokine levels were assessed. Animal survival was monitored for up to 30 days. SOM230 increased survival (P < 0.001) and prolonged survival time (P < 0.001) whether administration was initiated before or after TBI. There was no benefit from administration for 21 compared to 14 days. The survival benefit of SOM230 was completely reversed by co-administration of pancreatic enzymes (P = 0.009). Consistent with the presumed non-cytoprotective mechanism of action, SOM230 did not influence hematopoietic injury or intestinal crypt lethality. However, SOM230 preserved mucosal surface area (P < 0.001) and reduced bacterial translocation in a dose-dependent manner (P < 0.001). Circulating IL-12 levels were reduced in SOM230-treated mice (P = 0.007). No toxicity from SOM230 was observed. SOM230 enhances animal survival whether administration begins before or after TBI; i.e., it is effective both as a protector and as a mitigator. The mechanism likely involves reduction of intraluminal pancreatic enzymes. Because of its efficacy and favorable safety profile, SOM230 is a promising countermeasure against radiation and should undergo further development.

Gamma-Tocotrienol ameliorates intestinal radiation injury and reduces vascular oxidative stress after total-body irradiation by an HMG-CoA reductase-dependent mechanism.

Analogs of vitamin E (tocols) are under development as radioprophylactic agents because of their high efficacy and lack of toxicity. Gamma-tocotrienol (GT3) is of particular interest because, in addition to being an antioxidant, it also inhibits 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase and accumulates to greater extent in endothelial cells than other tocols. We addressed in vivo whether HMG-CoA reductase inhibition contributes to the radioprotection conferred by GT3. Groups of mice were treated with vehicle, mevalonate (the product of the reaction catalyzed by HMG-CoA reductase), GT3 alone or GT3 in combination with mevalonate. Lethality and standard parameters of injury to the hematopoietic, intestinal and vascular/endothelial systems were assessed after exposure to total-body irradiation. GT3 improved postirradiation survival and decreased radiation-induced vascular oxidative stress, an effect that was reversible by mevalonate. GT3 also enhanced hematopoietic recovery, reduced intestinal radiation injury, and accelerated the recovery of soluble markers of endothelial function. These parameters were not reversed by mevalonate co-administration. Our data confirm GT3's radioprophylactic properties against hematopoietic injury and, for the first time, demonstrate benefits in terms of protection against gastrointestinal and vascular injury. The radioprotective efficacy of GT3 against vascular injury is related to its properties as an HMG-CoA reductase inhibitor.

Tumor Recovery by Angiogenic Switch from Sprouting to Intussusceptive Angiogenesis after Treatment with PTK787/ZK222584 or Ionizing Radiation

Inhibitors of angiogenesis and radiation induce compensatory changes in the tumor vasculature both during and after treatment cessation. To assess the responses to irradiation and vascular endothelial growth factor-receptor tyrosine kinase inhibition (by the vascular endothelial growth factor tyrosine kinase inhibitor PTK787/ZK222854), mammary carcinoma allografts were investigated by vascular casting; electron, light, and confocal microscopy; and immunoblotting. Irradiation and anti-angiogenic therapy had similar effects on the tumor vasculature. Both treatments reduced tumor vascularization, particularly in the tumor medulla. After cessation of therapy, the tumor vasculature expanded predominantly by intussusception with a plexus composed of enlarged sinusoidal-like vessels containing multiple transluminal tissue pillars. Tumor revascularization originated from preserved alpha-smooth muscle actin-positive vessels in the tumor cortex. Quantification revealed that recovery was characterized by an angiogenic switch from sprouting to intussusception. Up-regulated alpha-smooth muscle actin-expression during recovery reflected the recruitment of alpha-smooth muscle actin-positive cells for intussusception as part of the angio-adaptive mechanism. Tumor recovery was associated with a dramatic decrease (by 30% to 40%) in the intratumoral microvascular density, probably as a result of intussusceptive pruning and, surprisingly, with only a minimal reduction of the total microvascular (exchange) area. Therefore, the vascular supply to the tumor was not severely compromised, as demonstrated by hypoxia-inducible factor-1alpha expression. Both irradiation and anti-angiogenic therapy cause a switch from sprouting to intussusceptive angiogenesis, representing an escape mechanism and accounting for the development of resistance, as well as rapid recovery, after cessation of therapy.

Acid Sphingomyelinase Overexpression Enhances the Antineoplastic Effects of Irradiation In Vitro and In Vivo

Exposure of cells or animals to stress frequently induces acid sphingomyelinase (ASM)-mediated ceramide production that leads to cell death. Consistent with this, overexpression of ASM in subcutaneous B16-F10 mouse melanomas, in combination with irradiation, resulted in tumors that were up to 12-fold smaller than irradiated control melanomas. Similarly, when irradiated melanomas were pretreated with a single, peritumoral injection of recombinant ASM (rhASM), the tumors were up to threefold smaller. The in vivo effect of ASM was likely due to enhanced cell death of the tumor cells themselves, as well as the surrounding microvascular endothelial cells. In vitro, rhASM had little or no effect on the growth of tumor cells, even in combination with irradiation. However, when the culture media was acidified to mimic the acidic microenvironment of solid tumors, rhASM-mediated cell death was markedly enhanced when combined with irradiation. Microscopic analysis suggested that this was associated with an increase in autophagy. rhASM has been produced for the treatment of the lysosomal storage disorder, type B Niemann-Pick disease, and is currently being evaluated in a phase-1 clinical trial. Based on the data presented in this article, we propose that further investigation of this protein and gene as antineoplastic agents also is warranted.

Imaging in Intestinal Ischemic Disorders

Intestinal ischemia and infarction are a heterogeneous group of diseases that have as their unifying theme hypoxia of the small bowel and/or colon. The incidence of bowel ischemia is increasing for a number of reasons: the aging of the population, the ability of intensive care units to salvage critically ill patients, and heightened clinical awareness of these disorders. Improvements in diagnostic imaging techniques have contributed greatly to the earlier diagnosis of intestinal ischemia, which can have a positive influence on patient outcomes. In this review, advances in multidetector computerized tomography, magnetic resonance, and ultrasound in the detection of intestinal ischemia are highlighted and placed in the context of expeditious patient management.

Essential Role of Plasminogen Activator Inhibitor Type-1 in Radiation Enteropathy

Intestinal radiation injury is a dose-limiting factor in radiation therapy for abdominal and pelvic cancers. Because transforming growth factor-beta1 is a key mediator involved in radiation-induced damage, we hypothesized that its target gene, plasminogen activator inhibitor type 1 (PAI-1), is an essential mediator of intestinal radiation toxicity. In a model of radiation enteropathy, survival was monitored and intestinal radiation injury was assessed in both wild-type (Wt) and PAI-1 knockout mice. Immunohistochemical labeling of PAI-1 was also assessed in patients treated with preoperative radiotherapy for rectal adenocarcinoma. Finally, the molecular mechanisms involved in radiation-induced PAI-1 expression were investigated. We found that PAI-1 -/- mice exhibited increased survival and better intestinal function compared with Wt mice. Intestinal radiation injury was attenuated in irradiated PAI-1 -/- mice compared with irradiated Wt mice, and irradiation increased blood cell-endothelial cell interactions in Wt but not PAI-1 -/- mice. In vivo, radiation-induced intestinal damage in mice, as well as in patients treated with radiotherapy, was associated with the up-regulation of PAI-1 in the endothelium. In vitro, irradiation increased PAI-1 expression in endothelial cells by a p53/Smad3-dependent mechanism. Together, these data demonstrate that PAI-1 plays a critical role in radiation-induced intestinal damage, suggesting that PAI-1 is an attractive target for preventing or reducing the side effects of radiation therapy.

Role of plasminogen activator inhibitor type-1 in radiation-induced endothelial cell apoptosis.

Normal tissue toxicity still remains a dose-limiting factor in clinical radiation therapy. Intestinal radiation toxicity is characterized by mucosal injury, inflammation, vascular activation followed by development of progressive vascular fibrosis/sclerosis and radiation enteritis. The endothelium is known to play a critical role in radiation-induced intestinal injury. Previous studies showed that endothelial cell (EC) apoptosis plays a central role in early radiation-induced intestinal injury. Recently, we demonstrated that plasminogen activator inhibitor type 1 (PAI-1) is an essential mediator of late intestinal radiation toxicity. PAI-1 knockout mice (PAI-1 -/-) are protected against intestinal radiation-induced damage with increased survival and better intestinal function compared with wild type mice (Wt). However, it is not clear whether PAI-1 plays a role in acute radiation-induced intestinal damages. We hypothesized that PAI-1 could contribute to the radiosensitivity of the endothelium in acute phases of radiation enteropathy. In vitro, irradiation stimulates PAI-1 expression (mRNA and protein) in EC 4 hours to 48 hours after irradiation. Moreover, FACS analyses (Sub-G1 and AnnexinV) and caspase assay showed that apoptosis is rapidly induced 4h to 24h after irradiation. These results suggest that PAI-1 could play a key role in radiation-induced EC cell death. To prove that PAI-1 is involved, molecular modulation of PAI-1 expression was performed using an expression vector and a RNA interference strategy. In EC overexpressing PAI-1 (pCMV PAI-1), radiation-induced apoptosis is increased 6h after 10Gy irradiation compared with EC transfected with a control vector. 48 hours after PAI-1 siRNA transfection, PAI-1 mRNA and protein levels are decreased by 85%. Sub-G1 and Annexin V flow cytometry analyses showed that radiation-induced apoptosis is decreased in siRNA-PAI-1 transfected EC. These preliminary results show that PAI-1 plays a role in the radiosensitivity of EC. To prove the relevance of our in vitro results, radiation-induced EC apoptosis in vivo was monitored in a model radiation enteropathy. After exposure of an intestinal segment to 19 Gy radiation, acute intestinal radiation injury are assessed in Wt and PAI-1 -/- mice 4 hours to 3 days after irradiation. Radiation injury score (RIS) is monitored and radiation-induced EC apoptosis is followed by double immunolabelling TUNEL or caspase-3 / CD31. RIS is reduced in PAI-1 -/- mice compared to Wt mice suggesting that acute EC apoptosis is reduced in PAI-1 -/- mice. This current and ongoing work should allow to determine the putative role of PAI-1 in radiation-induced endothelial cells apoptosis and consequently in intestinal radiation injury.

Differential diagnosis of Acute Radiation Syndromes by Enzyme Immune-Assay (EIA)

Differential diagnosis of Acute Radiation Syndromes by the method of immune enzyme assay is a very efficient tool of biological dosimetry and evaluation of acute radiation disease. We use as biological markers the group of essential Radiotoxins - high molecular weight glycoproteins with specific antigenic properties. A molecular weight of radiation toxins was 200-250 kDa. High doses of radiation induce the formation of radiation toxins in the organs and tissues of irradiated animals. After whole body irradiation, cellular macromolecules and cells and mitochondrial outer and inner wall membranes are damaged by long-lived radiation-induced free radicals, reactive oxygen species and fast, charged particles of radiation. High doses of radiation induce breaks in the chemicals bonds of macromolecules (proteins,lipids,carbohydrates,DNA molecules) and cross-linking reactions via chemically active processes. These processes result in creation of novel modified macromolecules that possess specific toxic and antigenic properties defined by the type and doses of irradiation by which they are generated. After formation, Radiation toxins migrate from irradiated tissues to interstitial fluid and accumulate in the lymphatic and blood transportation system. Radiation toxins isolated from the lymph of irradiated animals are classified as hematotoxic, neurotoxic, and enteric non-bacterial(GI) Radiation Toxins, and they play an important role in development of Hematopoietic, Cerebrovascular, Cardiovascular and Gastro- Intestinal Acute Radiation Syndromes(ARS). Four Groups and Seven distinct Toxins derived from post-irradiated animals have been designated as Specific Radiation Determinants (SRD): SRD-1(Neuro-toxic radiation toxin generated by Cerebrovascular ARS), SRD-2(Vascular-toxic radiation toxin generated by Cardiovascular ARS), SRD-3(Enteric non-bacterial radiation toxins generated by the Gastrointestinal form of ARS), and SRD-4(Hematotoxic radiation toxins generated by hematological, bone marrow form of ARS ). SRD-4 is further subdivided into four groups depending on the severity of the ARS induced: SRD-4/1, mild ARS; SRD-4/2, moderate ARS; SRD-4/3, severe ARS and SRD-4/4, extremely severe ARS. We postulate that the SRD-1 and the SRD-2 radiation toxins produce toxicity for central and peripheral nervous system. Determination of high levels of SRD-1, SRD-2,SRD-3 and SRD-4 in the periferal blood allowed to recognize early periods of Cerebrovascular, Cardiovascular, Gastrointestinal and Hematopoietic forms of ARS. The important goal of an early assessment with Enzyme Immune Assay is the accurate description of the Acute Radiation Syndromes at initial phases. Early and precise differential diagnosis allow doctors to provide an effective medical management of ARS.

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.

Neuroimmune interactions: potential target for mitigating or treating intestinal radiation injury

Intestinal radiation injury is characterized by breakdown of the epithelial barrier and mucosal inflammation. In addition to replicative and apoptotic cell death, radiation also induces changes in cellular function, as well as alterations secondary to tissue injury. The recognition of these "non-cytocidal" radiation effects has enhanced the understanding of normal tissue radiation toxicity, thus allowing an integrated systems biology-based approach to modulating radiation responses and providing a mechanistic rationale for interventions to mitigate or treat radiation injuries. The enteric nervous system regulates intestinal motility, blood flow and enterocyte function. The enteric nervous system also plays a central role in maintaining the physiological state of the intestinal mucosa and in coordinating inflammatory and fibroproliferative processes. The afferent component of the enteric nervous system, in addition to relaying sensory information, also exerts important effector functions and contributes critically to preserving mucosal integrity. Interactions between afferent nerves, mast cells as well as other cells of the resident mucosal immune system serve to maintain mucosal homeostasis and to ensure an appropriate response to injury. Notably, enteric sensory neurons regulate the activation threshold of mast cells by secreting substance P, calcitonin gene-related peptide and other neuropeptides, whereas mast cells signal to enteric nerves by the release of histamine, nerve growth factor and other mediators. This article reviews how enteric neurons interact with mast cells and other immune cells to regulate the intestinal radiation response and how these interactions may be modified to mitigate intestinal radiation toxicity. These data are not only applicable to radiation therapy, but also to intestinal injury in a radiological terrorism scenario.

Simvastatin Ameliorates Radiation Enteropathy Development After Localized, Fractionated Irradiation by a Protein C-Independent Mechanism

Microvascular injury plays a key role in normal tissue radiation responses. Statins, in addition to their lipid-lowering effects, have vasculoprotective properties that may counteract some effects of radiation on normal tissues. We examined whether administration of simvastatin ameliorates intestinal radiation injury, and whether the effect depends on protein C activation. Rats received localized, fractionated small bowel irradiation. The animals were fed either regular chow or chow containing simvastatin from 2 weeks before irradiation until termination of the experiment. Groups of rats were euthanized at 2 weeks and 26 weeks for assessment of early and delayed radiation injury by quantitative histology, morphometry, and quantitative immunohistochemistry. Dependency on protein C activation was examined in thrombomodulin (TM) mutant mice with deficient ability to activate protein C. Simvastatin administration was associated with lower radiation injury scores (p < 0.0001), improved mucosal preservation (p = 0.0009), and reduced thickening of the intestinal wall and subserosa (p = 0.008 and p = 0.004), neutrophil infiltration (p = 0.04), and accumulation of collagen I (p = 0.0003). The effect of simvastatin was consistently more pronounced for delayed than for early injury. Surprisingly, simvastatin reduced intestinal radiation injury in TM mutant mice, indicating that the enteroprotective effect of simvastatin after localized irradiation is unrelated to protein C activation. Simvastatin ameliorates the intestinal radiation response. The radioprotective effect of simvastatin after localized small bowel irradiation does not appear to be related to protein C activation. Statins should undergo clinical testing as a strategy to minimize side effects of radiation on the intestine and other normal tissues.

Successful Mitigation of Delayed Intestinal Radiation Injury Using Pravastatin is not Associated with Acute Injury Improvement or Tumor Protection

To investigate whether pravastatin mitigates delayed radiation-induced enteropathy in rats, by focusing on the effects of pravastatin on acute cell death and fibrosis according to connective tissue growth factor (CTGF) expression and collagen inhibition. Mitigation of delayed radiation-induced enteropathy was investigated in rats using pravastatin administered in drinking water (30 mg/kg/day) 3 days before and 14 days after irradiation. The ileum was irradiated locally after surgical exteriorization (X-rays, 19 Gy). Acute apoptosis, acute and late histologic alterations, and late CTGF and collagen deposition were monitored by semiquantitative immunohistochemistry and colorimetric staining (6 h, 3 days, 14 days, 15 weeks, and 26 weeks after irradiation). Pravastatin antitumor action was studied in HT-29, HeLa, and PC-3 cells by clonogenic cell survival assays and tumor growth delay experiments. Pravastatin improved delayed radiation enteropathy in rats, whereas its benefit in acute and subacute injury remained limited (6 h, 3 days, and 14 days after irradiation). Delayed structural improvement was associated with decreased CTGF and collagen deposition but seemed unrelated to acute damage. Indeed, the early apoptotic index increased, and severe subacute structural damage occurred. Pravastatin elicited a differential effect, protecting normal intestine but not tumors from radiation injury. Pravastatin provides effective protection against delayed radiation enteropathy without interfering with the primary antitumor action of radiotherapy, suggesting that clinical transfer is feasible.

Twenty‐five consecutive isolated intestinal transplants in adult patients: a five‐yr clinical experience

Between December 2000 and December 2005, 25 isolated intestinal transplants from cadaveric donors have been performed for short gut syndrome (short bowel syndrome, 52%), chronic intestinal pseudo-obstruction (24%), Gardner syndrome (16%), radiation enteritis (4%) and massive intestinal angiomatosis (4%). Indications for transplantation were: loss of venous access, recurrent sepsis due to central line infection, major electrolyte and fluid imbalance. Liver dysfunction was present in 13 cases. All patients were adult; median age was 36.3 yr and mean weight at transplantation 61.6 kg. All recipients were on life-threatening parenteral nutrition for a mean time of 23.7 months. Mean donor/recipient body weight ratio was 1.08. Rejection monitoring was accomplished by graft ileoendoscopies and intestinal biopsies through the temporary ileostomy. Our immunosuppressive regimen was based on induction therapy with three different protocols: daclizumab for induction, tacrolimus and steroids as maintenance therapy; alemtuzumab for induction and low-dose tacrolimus as maintenance; thymoglobulin for induction and maintenance based on low-dose tacrolimus. Closure of the abdomen at the end of transplantation represented a technical problem with several options performed: graft reduction, only skin closure, prothesic meshes, abdominal closure in two steps, cutaneous flaps and abdominal wall transplant in one case. The mean hospital stay was 37 days. The mean follow-up 27 months. Twenty patients are alive (80%) with two- and five-yr patient survival rate of 80% and 66%; mortality rate was 20% due to sepsis in all cases. Our two- and five-yr graft survival rate is 76% and 64%, graftectomy rate was 16%. Sixteen grafts are working properly, with no need of parenteral nutrition. We diagnosed 35 mild acute cellular rejection (ACRs), seven moderate ACRs and three severe ACRs (two needed graftectomy). We experienced two episodes of chronic rejection biopsy-proven. Rapamicine was added in case of renal failure or biopsy-proven intestinal rejection. Graft-vs.-host disease was not seen in our series while post-transplant lymphoproliferative disease in two cases. After discharge, the most common indication for medical support was dehydration. The abdominal wall transplant did not experience any rejection. Induction therapy has reduced the amount of postoperative immunosuppressive agents, especially in the first period, lowering the risk of renal failure and sepsis and the mucosal surveillance protocol for early detection of rejection dramatically reduced the number of severe ACR.

Significance of endothelial dysfunction in the pathogenesis of early and delayed radiation enteropathy.

This review summarizes the current state of knowledge regarding the role of endothelial dysfunction in the pathogenesis of early and delayed intestinal radiation toxicity and discusses various endothelial-oriented interventions aimed at reducing the risk of radiation enteropathy. Studies published in the biomedical literature during the past four decades and cited in PubMed, as well as clinical and laboratory data from our own research program are reviewed. The risk of injury to normal tissues limits the cancer cure rates that can be achieved with radiation therapy. During treatment of abdominal and pelvic tumors, the intestine is frequently a major dose-limiting factor. Microvascular injury is a prominent feature of both early (inflammatory), as well as delayed (fibroproliferative) radiation injuries in the intestine and in many other normal tissues. Evidence from our and other laboratories suggests that endothelial dysfunction, notably a deficiency of endothelial thrombomodulin, plays a key role in the pathogenesis of these radiation responses. Deficient levels of thrombomodulin cause loss of vascular thromboresistance, excessive activation of cellular thrombin receptors by thrombin, and insufficient activation of protein C, a plasma protein with anticoagulant, anti-inflammatory, and cytoprotective properties. These changes are presumed to be critically involved in many aspects of early intestinal radiation toxicity and may sustain the fibroproliferative processes that lead to delayed intestinal dysfunction, fibrosis, and clinical complications. In conclusion, injury of vascular endothelium is important in the pathogenesis of the intestinal radiation response. Endothelial-oriented interventions are appealing strategies to prevent or treat normal tissue toxicity associated with radiation treatment of cancer.

Orazipone, a locally acting immunomodulator, ameliorates intestinal radiation injury: A preclinical study in a novel rat model

Intestinal radiation injury (radiation enteropathy) is relevant to cancer treatment, as well as to radiation accidents and radiation terrorism scenarios. This study assessed the protective efficacy of orazipone, a locally-acting small molecule immunomodulator. Male rats were orchiectomized, a 4-cm segment of small bowel was sutured to the inside of the scrotum, a proximal anteperistaltic ileostomy was created for intraluminal drug administration, and intestinal continuity was re-established by end-to-side anastomosis. After three weeks postoperative recovery, the intestine in the "scrotal hernia" was exposed locally to single-dose or fractionated X-radiation. Orazipone (30 mg/kg/day) or vehicle was administered daily through the ileostomy, either during and after irradiation, or only after irradiation. Structural, cellular, and molecular aspects of intestinal radiation toxicity were assessed two weeks after irradiation. Orazipone significantly ameliorated histologic injury and transforming growth factor-beta immunoreactivity levels, both after single-dose and fractionated irradiation. Intestinal wall thickness was significantly reduced after single-dose and nonsignificantly after fractionated irradiation. Mucosal surface area and numbers of mast cells were partially restored by orazipone after single-dose irradiation. This work (1) demonstrates the utility of the ileostomy rat model for intraluminal administration of response modifiers in single-dose and fractionated radiation studies; (2) shows that mucosal immunomodulation during and/or after irradiation ameliorates intestinal toxicity; and (3) highlights important differences between single-dose and fractionated radiation regimens.

Calcitonin Gene-Related Peptide and Substance P Regulate the Intestinal Radiation Response

Intestinal toxicity is important in the therapeutic use of radiation as well as in nontherapeutic radiation exposure scenarios. Enteric sensory nerves are critical for mucosal homeostasis and for an appropriate response to injury. This study assessed the role of the two major neuropeptides released by sensory nerves, calcitonin gene-related peptide (CGRP) and substance P, in the intestinal radiation response. Male rats received full-length CGRP, CGRP antagonist (CGRP(8-37)), a modified substance P peptide (GR73632), a small-molecule substance P receptor antagonist (neurokinin-1 receptor antagonist, SR140333), or vehicle for 2 weeks after localized X irradiation of a 4-cm loop of small bowel. Structural, cellular, and molecular aspects of the intestinal radiation response were assessed. Intestinal CGRP and substance P transcript levels increased after irradiation. Multivariate analysis showed that CGRP and SR140333 ameliorated and CGRP(8-37) and GR73632 exacerbated intestinal radiation injury. Univariate analysis revealed increased radiation injury score, bowel wall thickening, and collagen III deposition after treatment with CGRP(8-37), whereas SR140333 ameliorated radiation injury score, loss of mucosal surface area, collagen III deposition, and mucosal inflammation. The two major neuropeptides released by sensory neurons, CGRP and substance P, are overexpressed after irradiation and have opposing effects during development of intestinal radiation injury. Systematic studies to assess CGRP agonists and/or neurokinin-1 receptor blockers as protectors against intestinal toxicity during radiation therapy and after nontherapeutic radiation exposure are warranted.

Regulation of early and delayed radiation responses in rat small intestine by capsaicin-sensitive nerves

Mast cells protect against the early manifestations of intestinal radiation toxicity, but promote chronic intestinal wall fibrosis. Intestinal sensory nerves are closely associated with mast cells, both anatomically and functionally, and serve an important role in the regulation of mucosal homeostasis. This study examined the effect of sensory nerve ablation on the intestinal radiation response in an established rat model. Rats underwent sensory nerve ablation with capsaicin or sham ablation. Two weeks later, a localized segment of ileum was X-irradiated or sham irradiated. Structural, cellular, and molecular changes were examined 2 weeks (early injury) and 26 weeks (chronic injury) after irradiation. The mast cell dependence of the effect of sensory nerve ablation on intestinal radiation injury was assessed using c-kit mutant (Ws/Ws) mast cell-deficient rats. Capsaicin treatment caused a baseline reduction in mucosal mast cell density, crypt cell proliferation, and expression of substance P and calcitonin gene-related peptide, two neuropeptides released by sensory neurons. Sensory nerve ablation strikingly exacerbated early intestinal radiation toxicity (loss of mucosal surface area, inflammation, intestinal wall thickening), but attenuated the development of chronic intestinal radiation fibrosis (collagen I accumulation and transforming growth factor beta immunoreactivity). In mast cell-deficient rats, capsaicin treatment exacerbated postradiation epithelial injury (loss of mucosal surface area), but none of the other aspects of radiation injury were affected by capsaicin treatment. Ablation of capsaicin-sensitive enteric neurons exacerbates early intestinal radiation toxicity, but attenuates development of chronic fibroproliferative changes. The effect of capsaicin treatment on the intestinal radiation response is partly mast cell dependent.