Proinflammatory effects of local abdominal irradiation on rat gastrointestinal tract

Protective effects of tauroursodeoxycholate against radiation-induced intestinal injury in a mouse model

In patients with high-level radiation exposure, gastrointestinal injury is the main cause of death. Despite the severity of damage to the gastrointestinal tract, no specific therapeutic option is available. Tauroursodeoxycholic acid (TUDCA) is a conjugated form of ursodeoxycholic acid that suppresses endoplasmic reticulum (ER) stress and regulates various cell-signaling pathways. We investigated the effect of TUDCA premedication in alleviating intestinal damage and enhancing the survival of C57BL/6 mice administered a lethal dose (15Gy) of focal abdominal irradiation. TUDCA was administered to mice 1 h before radiation exposure, and reduced apoptosis of the jejunal crypts 12 h after irradiation. At later timepoint (3.5 days), irradiated mice manifested intestinal morphological changes that were detected via histological examination. TUDCA decreased the inflammatory cytokine levels and attenuated the decrease in serum citrulline levels after radiation exposure. Although radiation induced ER stress, TUDCA pretreatment decreased ER stress in the irradiated intestinal cells. The effect of TUDCA indicates the possibility of radiation therapy for cancer in tumor cells. TUDCA did not affect cell proliferation and apoptosis in the intestinal epithelium. TUDCA decreased the invasive ability of the CT26 metastatic colon cancer cell line. Reduced invasion after TUDCA treatment was associated with decreased matrix metalloproteinase (MMP)-7 and MMP-13 expression, which play important roles in invasion and metastasis. This study shows a potential role of TUDCA in protecting against radiation-induced intestinal damage and inhibiting tumor cell migration without any radiation and radiation therapy effect.

Investigation of Gastrointestinal Toxicities Associated with Concurrent Abdominal Radiation Therapy and the Tyrosine Kinase Inhibitor Sunitinib in a Mouse Model

Tyrosine kinase inhibitors (TKIs) may be combined with radiation therapy (RT) to enhance tumor control; however, increased incidences of gastrointestinal (GI) toxicity have been reported with this combination. We hypothesize that toxicity is due to compromised intestinal healing caused by inhibition of vascular repair and proliferation pathways. This study explores underlying tissue toxicity associated with abdominal RT and concurrent sunitinib in a mouse model. Four groups of CD-1 mice were treated with 12 Gy abdominal RT, oral sunitinib, abdominal RT + sunitinib, or sham treatment. Mice received oral sunitinib or the vehicle via gavage for 14 days. On day 7, mice were irradiated with 12 Gy abdominal RT or sham treated. Mice were euthanized on day 14 and intestinal tract was harvested for semiquantitative histopathologic evaluation and immunohistochemical quantification of proliferation (Ki67) and vascular density (CD31). Non-irradiated groups had stable weights while abdominal irradiation resulted in weight loss, with mice receiving RT + SUN having greater weight loss than mice receiving RT alone. Semiquantitative analysis showed significant increases in inflammation in irradiated groups. The difference in the density of CD31+ cells was significantly increased in RT alone compared to SUN alone. Ki67+ density was not significant. In summary, we identify a lack of angiogenic response in irradiated GI tissues when abdominal RT is combined with a TKI, which may correlate with clinical toxicities seen in canine and human patients receiving combined treatment.

Involved-field irradiation or elective-nodal irradiation in neoadjuvant chemo-radiotherapy for locally-advanced esophageal cancer: comprehensive analysis for dosimetry, treatment-related complications, impact on lymphocyte, patterns of failure and survival

Purpose

To compare the differences between involved-field irradiation (IFI) and elective nodal irradiation (ENI) in selecting the optimal target area for neoadjuvant chemoradiotherapy (nCRT) in patients with locally advanced esophageal squamous cell carcinoma (LA-ESCC).

Materials and methods

We retrospectively analyzed 267 patients with LA-ESCC, of whom 165 underwent ENI and 102 underwent IFI. Dosimetry, treatment-related complications, pathological responses, recurrence/metastasis patterns, and survival were compared between the two groups.

Results

The median follow-up duration was 27.9 months. The R0 resection rates in the IFI and ENI groups were 95.1% and 92.7%, respectively (p=0.441), while the pathological complete response (pCR) rates were 42.2% and 34.5%, respectively (p=0.12). The ENI group received higher radiation doses to the heart (HV30:23.9% vs. 18%, p=0.033) and lungs (LV30:7.7% vs. 4.9%, p<0.001) than the IFI group. Consequently, the ENI group showed a higher incidence of grade 2 or higher radiation pneumonitis (30.3% vs. 17.6%, p=0.004) and pericardial effusion (26.7% vs. 11.8%, p=0.021) than the IFI group. Post-operation fistulas were observed in 3 (2.9%) and 17 cases (10.3%) in the IFI and ENI groups, respectively (p=0.026). In the multivariate analysis, smoking, positive lymph node involvement (pN+), and anastomotic fistula were independent predictors of overall survival (OS). The pN+ patients exhibited a greater propensity for recurrence compared to pN- patients, especially in the first year of follow-up (6.67% vs. 0.56%, p=0.003).

Conclusion

The ENI group had a higher incidence of radiation-induced adverse events compared to the IFI group, likely due to the higher radiation doses to normal tissues. Considering the similar disease-free survival (DFS) and OS rates in the two groups, IFI may be suitable for nCRT in patients with LA-ESCC, although further prospective studies are warranted.

PrC-210 Protects against Radiation-Induced Hematopoietic and Intestinal Injury in Mice and Reduces Oxidative Stress

The development of safe, orally available, and effective prophylactic countermeasures to protect our warfighters is an unmet need because there is no such FDA-approved countermeasure available for use. Th 1-Propanethiol, 3-(methylamino)-2-((methylamino)methyl) (PrC-210), a synthetic small molecule, is a member of a new family of aminothiols designed to reduce toxicity while scavenging reactive oxygen species (ROS). Our study investigated the protective role of a single oral administration of PrC-210 against radiation-induced hematopoietic and intestinal injury in mice. Pre-treatment with PrC-210 significantly improved the survival of mice exposed to a lethal dose of radiation. Our findings indicated that the radioprotective properties of PrC-210 are achieved by accelerating the recovery of the hematopoietic system, stimulating bone marrow progenitor cells, and ameliorating additional biomarkers of hematopoietic injury. PrC-210 pre-treatment reduced intestinal injury in mice exposed to a lethal dose of radiation by restoring jejunal crypts and villi, reducing translocation of bacteria to the spleen, maintaining citrulline levels, and reducing the sepsis marker serum amyloid A (SAA) in serum. Finally, PrC-210 pre-treatment led to a significant reduction (~10 fold) of Nos2 expression (inducible nitric oxide) in the spleen and decreased oxidative stress by enhancing the antioxidant defense system. These data support the further development of PrC-210 to receive approval from the FDA to protect warfighters and first responders from exposure to the harmful effects of ionizing radiation.

Dichotomous effects of in vivo and in vitro ionizing radiation exposure on lymphatic function

On the one hand, lymphatic dysfunction induces interstitial edema and inflammation. On the other hand, the formation of edema and inflammation induce lymphatic dysfunction. However, informed by the earlier reports of undetected apoptosis of irradiated lymphatic endothelial cells (LECs) in vivo, lymphatic vessels are commonly considered inconsequential to ionizing radiation (IR)-induced inflammatory injury to normal tissues. Primarily because of the lack of understanding of the acute effects of IR exposure on lymphatic function, acute edema and inflammation, common sequelae of IR exposure, have been ascribed solely to blood vessel damage. Therefore, in the present study, the lymphatic acute responses to IR exposure were quantified to evaluate the hypothesis that IR exposure impairs lymphatic pumping. Rat mesenteric lymphatic vessels were irradiated in vivo or in vitro, and changes in pumping were quantified in isolated vessels in vitro. Compared with sham-treated vessels, pumping was lowered in lymphatic vessels irradiated in vivo but increased in vessels irradiated in vitro. Furthermore, unlike in blood vessels, the acute effects of IR exposure in lymphatic vessels were not mediated by nitric oxide-dependent pathways in either in vivo or in vitro irradiated vessels. After cyclooxygenase blockade, pumping was partially restored in lymphatic vessels irradiated in vitro but not in vessels irradiated in vivo. Taken together, these findings demonstrated that lymphatic vessels are radiosensitive and LEC apoptosis alone may not account for all the effects of IR exposure on the lymphatic system.NEW & NOTEWORTHY Earlier studies leading to the common belief that lymphatic vessels are radioresistant either did not characterize lymphatic pumping, deemed necessary for the resolution of edema and inflammation, or did it in vivo. By characterizing pumping in vitro, the present study, for the first time, demonstrated that lymphatic pumping was impaired in vessels irradiated in vivo and enhanced in vessels irradiated in vitro. Furthermore, the pathways implicated in ionizing radiation-induced blood vessel damage did not mediate lymphatic responses.

Roles of Simvastatin and Sildenafil in Modulation of Cranial Irradiation-Induced Bystander Multiple Organs Injury in Rats

In radiobiology and radiation oncology fields, the observation of a phenomenon called radiation-induced bystander effect (RIBE) has introduced the prospect of remotely located tissues' affection. This phenomenon has been broadly developed to involve the concept of RIBE, which are relevant to the radiation-induced response of a distant tissue other than the irradiated one. The current study aimed at investigating each of the RIBE of cranial irradiation on oxidative and inflammatory status in different organs such as liver, kidney, heart, lung, and spleen. Being a vital target of the cholinergic anti-inflammatory response to an inflammatory stimulus, the splenic α-7-nicotinic acetylcholine receptor (α-7nAchR) was evaluated and the hepatic contents of thioredoxin, peroxisome proliferator-activated receptor-alpha and paraoxinase-1 (Trx/PPAR-α/PON) were also assessed as indicators for the liver oxidative stress and inflammatory responses. Being reported to act as antioxidant and anti-inflammatory agents, simvastatin (SV) and/or sildenafil (SD) were investigated for their effects against RIBE on these organs. These objectives were achieved via the biochemical assessments and the histopathological tissues examinations. Five experimental groups, one sham irradiated and four irradiated groups, were exposed to cranial irradiation at dose level of 25 Gy using an experimental irradiator with a Cobalt (Co60) source, RIBE, RIBE + SV (20 mg.(kg.bw)-1 day-1), RIBE + SD (75 mg.(kg.bw)-1 day-1), and RIBE + SV + SD. Cranial irradiation induced structural, biochemical, and functional dys-regulations in non-targeted organs. RIBE-induced organs' injuries have been significantly corrected by the administration of SV and/or SD. Our results suggest the possibility of a potentiated interaction between SV and SD in the modulation of the RIBE associated with head and neck radiotherapy.

Tailoring of chitosan/diacrylated pluronic system as a versatile nanoplatform for the amelioration of radiation-induced cognitive dysfunction

Rutin (RUT) is a biologically active flavonoid that is reported to modulate radiation-induced brain dysfunctions. However, RUT's poor water solubility and low brain bioavailability limit its clinical use. To increase its brain bioavailability, RUT was loaded onto nanoplatforms based on chitosan/diacrylated pluronic (CS/DA-PLUR) nanogels synthesized by gamma radiation. The optimized formulation was investigated as a carrier system for RUT. Based on pilot experiments' results, the cranial radiation (CR) dose that induced cognitive dysfunction was selected. In the main experiment, rats were pre-treated orally with either free RUT or RUT-CS/DA-PLUR. Rats' cognitive and motor functions were assessed; 24 h later, rats were sacrificed, and the whole brain was separated for histopathological examination and biochemical estimation of brain content of acetylcholine esterase (AChE), neurotransmitters, oxidative stress markers, and interleukin-1β. CR produced prominent impairment in spatial and non-spatial learning memory, motor coordination, and muscular strength. Moreover, histopathological and biochemical alterations in brain contents of neurotransmitters, oxidative stress, and interleukin-1β were induced by CR. Conversely, RUT-CS/DA-PLUR, but not free RUT, successfully guarded against all the detrimental effects induced by CR. Based on the current findings, loading of RUT enhanced its bioavailability and therapeutic effectiveness by restoring the cognitive functions impaired by CR.

Modulation of the Nitric Oxide/BH4 Pathway Protects Against Irradiation-Induced Neuronal Damage

The kynurenine pathway (KP, IDO/Kyn pathway) is an important metabolic pathway related to many diseases. Although cranial radiotherapy is the mainstay in metastatic tumors management, its efficacy is limited owing to the associated neuropsychiatric disorders. Sildenafil (SD) and simvastatin (SV) were reported to have antioxidant/anti-inflammatory effects and to serve as NO donor/BH4 regulator, respectively. Fluoxetine (Fx) is an FDA-approved anti-depressant agent and one of the selective serotonin reuptake inhibitor drugs (SSRI), used in neurological disorder treatment. The study objective was to investigate the role of cranial irradiation (C-IR) on KP signaling impairment and the possible intervention by SD and/or SV (as nitric oxide (NO) donor/Tetrahydrobiopterin (BH4) regulatory) on KP following C-IR-induced disruption compared with Fx (as standard drug).Herein, rats were exposed to C-IR at a single dose level of 25 Gy, then treated with sildenafil (SD) and/or simvastatin (SV), and fluoxetine (Fx) at doses of 75, 20, 10 mg/kg/day, respectively. The body weight gain and forced swimming test (FST) were used for evaluation along with the biochemical quantifications of KP intermediates and histopathological examination of cortex and hippocampus. The results indicated a significant activation of KP following C-IR as manifested by decreased Trp content and increased activities of indoleamine 2,3-dioxygenase (IDO) and tryptophan 2,3-dioxygenase (TDO) with a rise in kynurenine (KYN) and quinolinic acid (QA) hippocampal contents. In addition, a state of C-IR-induced oxidative stress, inflammation, NO-pathway dysregulation and neuronal apoptosis were observed as compared to the control group. However, significant modulations were recorded after the combined administration of SD and SV than those offered by each of them alone and by Fx. The biochemical assessment results were supported by the histopathological tissue examination. It could be concluded that the co-administration of SV and SD offers a neuroprotective effect against irradiation-induced brain injury due to its NO donor/BH4 regulatory activities, anti-inflammatory and antioxidant properties that modulate IDO/KYN pathway.

Amelioration of thioacetamide-induced hepatic encephalopathy in rats by low-dose gamma irradiation

Brain affection is a common symptom of liver insufficiency. This study aimed to evaluate the role of low-dose γ irradiation (LDR) as a potential therapeutic agent in thioacetamide (TAA)-induced hepatic encephalopathy (HE) in rats. Effects of local and whole-body irradiation (0.5 Gy) on rat brain/liver were evaluated following the induction of HE by TAA (200 mg/kg/day/for 3 successive days). Serum activities of aspartate transaminase (AST) and alanine transaminase (ALT) and ammonia level were assessed. The effect of HE on brain was evaluated through the determination of brain contents of malondialdehyde (MDA), reduced glutathione (GSH), tumor necrosis factor-alpha (TNF-α), and interleukin-1beta (IL-1β) and glutathione peroxidase (GPx) activity. Moreover, apoptotic and inflammatory changes in brain and liver tissues were assessed together with alpha-smooth muscle actin (α-SMA); fibrosis marker. Results showed correction of the biochemical parameters which was supported by the results of the immunohistochemical examinations. LDR is a promising hepato- and neurotherapy against HE.

Platelet-rich plasma-induced feedback inhibition of activin A/follistatin signaling: A mechanism for tumor-low risk skin rejuvenation in irradiated rats

BACKGROUND

Platelet-rich plasma (PRP) is a source of natural growth factors and is emerging as a treatment modality to mitigate radiotherapy- induced adverse effects. Activin A (ACTA) is a member of the transforming growth factor-β (TGF-β) superfamily, which has been shown to modulate the inflammatory response and macrophages polarization between different phenotypes. The aim of this study is to determine the value of PRP in preventing radiation-induced malignancies in light of the cross-talk between PRP and activin A type II receptors (ActR-IIA)/follistatin (FST) signaling pathways where the inflammatory responses at 2 different time points were evaluated.

MATERIAL AND METHODS

Male albino rats were exposed to radiation and given PRP over the course of 6 days. Rats were sacrificed on day 7 or day 28 post radiation.

RESULTS

Quantitative real-time reverse transcriptase polymerase chain reaction (QRT-PCR) and western-blot showed that after 7 days of administrating of PRP, ActR-IIA/FST signaling was markedly induced and was associated with the expressions of inflammatory, natural killer and M1 macrophages markers, TNF-α, IL-1β, IFN-γ and IL-12. By contrast, on day 28 of PRP administration, ActR-IIA/FST signaling and the expressions of proinflammatory cytokines were downregulated in parallel with inducing M2 macrophages phenotype as indicated by arginase-1, IL-10 and dectin-1.

CONCLUSION

The suppression of inflammation and induction of M2 macrophages phenotype in response to PRP administration were found significantly linked to ActR-IIA/FST signaling downregulation. Furthermore, the specific M2 macrophage subtype was found to express dectin-1 receptors which have high affinity for tumor cells thereby is expected to reduce the potential for developing tumors after radiotherapy.

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

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

Segmental Differences in Radiation-Induced Alterations of Tight Junction-Related Proteins in Non-Human Primate Jejunum, Ileum and Colon

Dysfunction of the intestinal epithelial barrier and leakage of luminal antigens and bacteria across the barrier have been linked to various human diseases. Intestinal permeability is regulated by intercellular structures, termed "tight junction" (Tj), which are disrupted after total-body irradiation (TBI). In this study, we investigated radiation-induced alterations in Tj-related proteins in the jejunum, ileum and colon of a non-human primate (NHP) model. NHPs were total-body irradiated with 6.7 and 7.4 Gy and intestines were procured at day 4, 7 and 12. Radiation exposure was found to induce significant increases in claudin-10 mRNA early (day 4) in all three gut segments and claudin-4 mRNA levels were repressed through day 12. TNF-alpha was highly induced in the jejunum and colon at early time points, but little induction was found in the ileum. Claudin-1 was induced only in the colon on day 4 postirradiation. Unlike the colon and jejunum, the ileum levels of claudin-7 were significantly downregulated through day 12 postirradiation. Western blot analysis revealed increased levels of claudin-2 on day 4 and of JAM-1 on day 7 postirradiation in all three gut segments. E-cadherin was downregulated on day 4 postirradiation in all segments, but remained reduced in the jejunum only until day 12. Taken together, these data suggest that exposure to radiation causes segment-specific alterations in the expression of Tj-related proteins. Interruption of Tjs may be a key factor contributing to injury to the intestinal mucosal barrier and increased intestinal permeability.

Gamma tocotrienol, a potent radioprotector, preferentially upregulates expression of anti-apoptotic genes to promote intestinal cell survival

Gamma tocotrienol (GT3) has been reported as a potent ameliorator of radiation-induced gastrointestinal (GI) toxicity when administered prophylactically. This study aimed to evaluate the role of GT3 mediated pro- and anti-apoptotic gene regulation in protecting mice from radiation-induced GI damage. Male 10- to 12-weeks-old CD2F1 mice were administered with a single dose of 200 mg/kg of GT3 or equal volume of vehicle (5% Tween-80) 24 h before exposure to 11 Gy of whole-body γ-radiation. Mouse jejunum was surgically removed 4 and 24h after radiation exposure, and was used for PCR array, histology, immunohistochemistry, and immunoblot analysis. Results were compared among vehicle pre-treated no radiation, vehicle pre-treated irradiated, and GT3 pre-treated irradiated groups. GT3 pretreated irradiated groups, both 4h and 24h after radiation, showed greater upregulation of anti-apoptotic gene expression than vehicle pretreated irradiated groups. TUNEL staining and intestinal crypt analysis showed protection of jejunum after GT3 pre-treatment and immunoblot results were supportive of PCR data. Our study demonstrated that GT3-mediated protection of intestinal cells from a GI-toxic dose of radiation occurred via upregulation of antiapoptotic and downregulation of pro-apoptotic factors, both at the transcript as well as at the protein levels.

Protection by L-carnitine against radiation-induced ileal mucosal injury in the rat: pattern of oxidative stress, apoptosis and cytokines

PURPOSE

In this study, we tested the effects of L-carnitine (LC) on radiation-induced ileal mucosal damage.

MATERIALS AND METHODS

Thirty Wistar albino rats were divided into five groups. The control group received physiological saline intraperitoneally (i.p.). Radiation-1 and radiation-2 groups received whole-body X-irradiation of 8.3 Gy as a single dose. These groups were sacrificed at the 6th hour and 4th day after irradiation, respectively. The Radiation-1 + LC and the radiation-2 + LC groups received the same dose irradiation plus a daily dose of 200 mg/kg LC. LC was applied one day before and for four days after irradiation.

RESULTS

The levels of serum monocyte chemotactic protein-1 (MCP-1) and interferon gamma (IFN-γ) were significantly higher in the radiation groups when compared with the control. Treatment with LC decreased the serum MCP-1 and IFN-γ levels considerably. In the radiations groups, the Chiu score was significantly elevated compared with that of the control group. However, LC administered prior to the irradiation reduced the severity of mucosal damage. The number of apoptotic cells of the ileal crypt in the irradiated rats increased from the 6th hour after irradiation and then decreased at 4th day.

CONCLUSIONS

Our data demonstrated that LC may be beneficial to radiation enteritis.

Ionizing radiation enhances IL-6 and IL-8 production by human endothelial cells

Irradiation exposure is known to induce an inflammatory reaction. Endothelial cells play a crucial role both in the inflammatory process and in radiation damage. Therefore, supernatants and cell lysates of (60)Co-irradiated human umbilical vein endothelial cells (HUVEC) have been assessed for the presence of pro-inflammatory cytokines. After gamma irradiation, interleukin (IL)-1alpha, IL-1beta and tumor necrosis factor (TNF)-alpha remained undetectable in both cell supernatants and cell lysates. However, a dose-dependent increase in the production of IL-6 and IL-8 has been demonstrated up to 6 days after exposure. These data indicate that the pro-inflammatory cytokines IL-6 and IL-8 may be involved in the inflammatory response of vascular endothelium induced by exposure to ionizing radiation.

Amelioration of radiation-induced hematopoietic and gastrointestinal damage by Ex-RAD(R) in mice

The aim of the present study was to assess recovery from hematopoietic and gastrointestinal damage by Ex-RAD(®), also known as ON01210.Na (4-carboxystyryl-4-chlorobenzylsulfone, sodium salt), after total body radiation. In our previous study, we reported that Ex-RAD, a small-molecule radioprotectant, enhances survival of mice exposed to gamma radiation, and prevents radiation-induced apoptosis as measured by the inhibition of radiation-induced protein 53 (p53) expression in cultured cells. We have expanded this study to determine best effective dose, dose-reduction factor (DRF), hematological and gastrointestinal protection, and in vivo inhibition of p53 signaling. A total of 500 mg/kg of Ex-RAD administered at 24 h and 15 min before radiation resulted in a DRF of 1.16. Ex-RAD ameliorated radiation-induced hematopoietic damage as monitored by the accelerated recovery of peripheral blood cells, and protection of granulocyte macrophage colony-forming units (GM-CFU) in bone marrow. Western blot analysis on spleen indicated that Ex-RAD treatment inhibited p53 phosphorylation. Ex-RAD treatment reduces terminal deoxynucleotidyl transferase mediated dUTP nick end labeling assay (TUNEL)-positive cells in jejunum compared with vehicle-treated mice after radiation injury. Finally, Ex-RAD preserved intestinal crypt cells compared with the vehicle control at 13 and 14 Gy. The results demonstrated that Ex-RAD ameliorates radiation-induced peripheral blood cell depletion, promotes bone marrow recovery, reduces p53 signaling in spleen and protects intestine from radiation injury.

Pulp vitality in patients with intraoral and oropharyngeal malignant tumors undergoing radiation therapy assessed by pulse oximetry

INTRODUCTION

The aim of this study was to evaluate pulp oxygenation levels (%SpO(2)) in patients with malignant intraoral and oropharyngeal tumors treated by radiotherapy (RT).

METHODS

Pulp oxygenation levels were measured by pulse oximetry. Twenty patients were selected, and two teeth of each participant (n = 40) were analyzed, regardless of the quadrant and the area irradiated, at four different time points: TP1, before RT; TP2, at the beginning of RT with radiation doses between 30 and 35 Gy; TP3, at the end of RT with radiation doses between 60 and 70 Gy; and TP4, 4 to 5 months after the beginning of cancer treatment.

RESULTS

Mean %SpO(2) at the different time points were 93% (TP1), 83% (TP2), 77% (TP3), and 85% (TP4). The Student's t test showed statistically significant differences between TP1 and TP2 (P < .01), TP3 (P < .01), and TP4 (P < .01). TP3 was also statistically significantly different when compared with TP2 (P < .01) and TP4 (P < .01). No statistically significant difference could be observed between TP2 and TP4.

CONCLUSIONS

Because the mean %SpO(2) before RT was greater than during and after therapy and values obtained 4 to 5 months after the beginning of RT were close to the initiation of RT, pulp tissue may be able to regain normal blood flow after RT. If the changes in the microcirculation of the dental pulp were indeed transitory, preventive endodontic treatment or extraction in patients who are currently undergoing or recently received RT and who show negative signs of pulp sensitivity may not be necessary for pulpal reasons.

Persistence of altered 5-hydroxytryptamine turnover following hemibody X-irradiation in the rat distal colon

PURPOSE

Acute gastrointestinal responses to ionizing radiation exposure include a role for 5-hydroxytryptamine (5-HT), but it is not known whether involvement of 5-HT persists and contributes to late effects. The aim was to investigate the acute and later effects of lower hemibody irradiation on 5-HT turnover and the biological effect in the rat distal colon.

MATERIALS AND METHODS

Rats were exposed to 10 Gy lower hemibody X-radiation. 5-HT and 5-hydroxyindole acetic acid tissue levels were measured in the distal colon along with the serotonin re-uptake transporter and tryptophan hydroxylase mRNA. 5-HT-containing cells and crypt cell numbers were estimated in addition to 5-HT-stimulated short-circuit current responses in isolated mucosa. Studies were performed from 3 days to 3 months post-exposure.

RESULTS

During the acute phase, at 3 days post-irradiation, reductions in cell number, tissue resistance, serotonin re-uptake transporter expression and secretory responses to 5-HT were observed. However, at later times when secretory responses were normal, 5-HT tissue levels and enterochromaffin cell numbers were increased.

CONCLUSIONS

The results provide evidence that after 10 Gy hemibody irradiation, modifications persist past the acute phase. In particular, 5-HT turnover in the distal colon is altered during a longer period.

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.

Effects of radiotherapy and chemotherapy on angiogenesis and leukocyte infiltration in rectal cancer

BACKGROUND

We and others have shown that angiogenesis and leukocyte infiltration are important prognostic factors in rectal cancer. However, little is known about its possible changes in response to radiotherapy (RTX), which is frequently given to rectal tumors as a neoadjuvant treatment to improve the prognosis. We therefore investigated the biologic effects of RTX on these parameters using fresh-frozen biopsy samples of tumor and normal mucosa tissue before and after RTX.

METHODS

Biopsy samples were taken from a total of 34 patients before and after either a short course or long course of RTX combined with chemotherapy. The following parameters were analyzed by immunohistochemistry, flow cytometry, or quantitative real-time polymerase chain reaction: Microvessel density, leukocyte infiltration, proliferating epithelial and tumor cells, proliferating endothelial cells, adhesion molecule expression on endothelial cells, and the angiogenic mRNA profile.

RESULTS

The tumor biopsy samples taken after RTX treatment demonstrated a significant decrease in microvessel density and the number of proliferating tumor cells and proliferating endothelial cells (p < 0.001). In contrast, the leukocyte infiltration, the levels of basic fibroblast growth factor in carcinoma tissue, and the adhesion molecule expression on endothelial cells in normal as well as carcinoma tissue increased significantly (p < 0.05).

CONCLUSION

Our data show that together with an overall decrease in tumor cell and endothelial cell proliferation, RTX results in an increase in the expression of adhesion molecules that stimulate leukocyte infiltration. This suggests the possibility that, in addition to its direct cytotoxic effect, radiation may also stimulate an immunologic tumor response that could contribute to the documented improvement in local tumor control and distal failure rate of rectal cancers.

Melatonin prevents inflammation and oxidative stress caused by abdominopelvic and total body irradiation of rat small intestine

We investigated the day-night differences in intestinal oxidative-injury and the inflammatory response following total body (TB) or abdominopelvic (AP) irradiation, and the influence of melatonin administration on tissue injury induced by radiation. Rats (male Wistar, weighing 220-280 g) in the irradiated groups were exposed to a dose of 8 Gy to the TB or AP region in the morning (resting period - 1 h after light onset) or evening (activity span - 13 h after light onset). Vehicle or melatonin was administered immediately before, immediately after and 24 h after irradiation (10, 2.0 and 10 mg/kg, ip, respectively) to the irradiated rats. AP (P < 0.05) and TB (P < 0.05) irradiation applied in the morning caused a significant increase in thiobarbituric acid reactive substance (TBARS) levels. Melatonin treatment in the morning (P < 0.05) or evening (P < 0.05) decreased TBARS levels after TB irradiation. After AP irradiation, melatonin treatment only in the morning caused a significant decrease in TBARS levels (P < 0.05). Although we have confirmed the development of inflammation after radiotherapy by histological findings, neither AP nor TB irradiation caused any marked changes in myeloperoxidase activity in the morning or evening. Our results indicate that oxidative damage is more prominent in rats receiving TB and AP irradiation in the morning and melatonin appears to have beneficial effects on oxidative damage irrespective of the time of administration. Increased neutrophil accumulation indicates that melatonin administration exerts a protective effect on AP irradiation-induced tissue oxidative injury, especially in the morning.

Effects of chronic 137Cs ingestion on barrier properties of jejunal epithelium in rats

Environmental contamination by 137Cs is of particular public health interest because of the various sources of fallout originating from nuclear weapons, radiological source disruptions, and the Chernobyl disaster. This dispersion may lead to a chronic ecosystem contamination and subsequent ingestion of contaminated foodstuffs. The aim of this study was to thus determine the impact of a chronic ingestion of low-dose 137Cs on small intestine functions in rats. The animals received 150 Bq per day in drinking water over 3 mo. At these environmental doses, 137Cs contamination did not modify the crypt and villus architecture. In addition, epithelial integrity was maintained following the chronic ingestion of 137Cs, as demonstrated by histological analyses (no breakdown of the surface mucosa) and electrical transepithelial parameters (no change in potential difference and tissue conductance). Furthermore, cesium contamination seemed to induce contradictory effects on the apoptosis pathway, with an increase in the gene expression of Fas/FasL and a decrease in the apoptotic cell number present in intestinal mucosa. No marked inflammation was observed following chronic ingestion of 137Cs, as indicated by neutrophil infiltration and gene expression of cytokines and chemokines. Results indicated no imbalance in the Th1/Th2 response induced by cesium at low doses. Finally, evaluation of the functionality of the jejunal epithelium in rats contaminated chronically with 137Cs did not demonstrate changes in the maximal response to carbachol, nor in the cholinergic sensitivity of rat jejunal epithelium. In conclusion, this study shows that chronic ingestion of 137Cs over 3 mo at postaccidental doses exerts few biological effects on the epithelium of rat jejunum with regard to morphology, inflammation status, apoptosis/proliferation processes, and secretory functions.

Radiation Induced Inflammatory Changes in the Mouse Bladder: The Role of Cyclooxygenase-2

PURPOSE

We assessed the effect of irradiation on COX-2 expression in blood vessels of the mouse bladder wall during the early and late radiation response phases. Vasodilatation was quantified as an additional marker of inflammation related to COX-2 activity.

MATERIALS AND METHODS

Female C3H/Neu mice were irradiated with a single dose of 20 Gy. The intensity of the COX-2 immunohistochemical staining signal was assessed using an arbitrary semiquantitative score of 0 to 3. To evaluate vasodilatation the percent of the bladder wall covered by the lumen of the blood vessels, depicted as vascular area, was determined.

RESULTS

Constitutive COX-2 expression was found in the tunica intima and media of bladder blood vessels. During the early response significant biphasic changes were detected in the COX-2 staining signal as well as in the vascular area with peak values on days 4 and 16 after irradiation. A significant association was found between vascular area and COX-2 expression in blood vessels during the early radiation response (p <0.0001). No changes in COX-2 expression were observed during the late phase, that is between days 90 and 360 after irradiation. Minor vasodilatation seen during the late phase did not correlate with COX-2 activity.

CONCLUSIONS

Irradiation resulted in pronounced COX-2 dependent inflammatory changes in the bladder wall during the early but not during the late radiation reaction. Therefore, a potential effect of COX-2 inhibition on early radiation side effects in the bladder can be proposed.

Maintenance of differentiation capacity of HT-29 cells after radiation exposure

PURPOSE

Following ionizing radiation exposure, intestinal crypt regeneration is possible but it is still not known if regenerating crypts give rise to differentiated functional epithelial cells on villi. The aim of this study was to demonstrate that irradiated progeny of enterocytic precursor cells are capable of proliferation and subsequent differentiation using the HT-29?cell line.

MATERIALS AND METHODS

Cells were cultured, irradiated (5 Gy or 10 Gy) and incubated in the presence or absence of butyrate (5 mM). Cell numbers, cell cycle parameters, alkaline phosphatase (ALP) activity, occludin labelling and gene expression were determined at different times post-exposure.

RESULTS

Butyrate-induced inhibition of cell growth and arrest in G0 phase was comparable in both sham and irradiated cells in addition to similar development of ALP activity and expression. Cells also formed a monolayer with tight junctions post-irradiation. Butyrate-stimulated modulation of integrin expression during differentiation was unchanged after radiation exposure. Genes known to be implicated in differentiation mechanisms, i.e., growth and transcription factors (vascular Epidermal Growth Factor, v-EGF ; Activating Transcription Factor 4, ATF4), cell cycle genes (Cyclin-Dependent Kinase Inhibitor 1A, CDKN1A/p21(Cip1/waf1)), were studied. Most responded similarly to the differentiation stimulus whether irradiated or not.

CONCLUSION

These results demonstrate that irradiated HT-29 cells still respond to butyrate to form a differentiated, functional epithelium.

Abdominal radiation exposure elicits inflammatory responses and abscopal effects in the lungs of mice

An inflammatory reaction is a classical feature of radiation exposure and appears to be a key event in the development of the acute radiation syndrome. We have investigated the radiation-induced inflammatory response in C57BL6/J mice after total abdominal or total-body irradiation at a dose of 15 Gy. Our goal was to determine the radiation-induced inflammatory response of the gut and to study the consequences of abdominal irradiation for the intestine and for the lungs as a distant organ. A comparison with total-body irradiation was used to take into account the hematopoietic response in the inflammatory process. For both irradiation regimens, systemic and intestinal responses were evaluated. A systemic inflammatory reaction was found after abdominal and total-body irradiation, concomitant with increased cytokine and chemokine production in the jejunum of irradiated mice. In the lungs, the radiation-induced changes in the production of cytokines and chemokines and in the expression of adhesion molecules after both abdominal and total-body irradiation indicate a possible abscopal effect of radiation in our model. The effects observed in the lungs after irradiation of the abdomino-pelvic region may be caused by circulating inflammatory mediators consequent to the gut inflammatory response.

Role of the intestinal tight junction modulator zonulin in the pathogenesis of type I diabetes in BB diabetic-prone rats

Increased intestinal permeability has been observed in numerous human autoimmune diseases, including type-1 diabetes (T1D) and its' animal model, the BB-wor diabetic prone rat. We have recently described zonulin, a protein that regulates intercellular tight junctions. The objective of this study was to establish whether zonulin-dependent increased intestinal permeability plays a role in the pathogenesis of T1D. In the BB diabetic-prone rat model of T1D, intestinal intraluminal zonulin levels were elevated 35-fold compared to control BB diabetic-resistant rats. Zonulin up-regulation was coincident with decreased small intestinal transepithelial electrical resistance, and was followed by the production of autoantibodies against pancreatic beta cells, which preceded the onset of clinically evident T1D by approximately 25 days. In those diabetic prone rats that did not progress to diabetes, both intraluminal zonulin and transepithelial electrical resistance were similar to those detected in diabetic-resistant animal controls. Blockade of the zonulin receptor reduced the cumulative incidence of T1D by 70%, despite the persistence of intraluminal zonulin up-regulation. Moreover, treatment responders did not seroconvert to islet cell antibodies. Combined together, these findings suggest that the zonulin-induced loss in small intestinal barrier function is involved in the pathogenesis of T1D in the BB diabetic-prone animal model.

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

BACKGROUND

Leucocyte recruitment and inflammation are key features of high dose radiation-induced tissue injury. The inflammatory response in the gut may be more pronounced following radiotherapy due to its high bacterial load in comparison to the response in other organs. We designed a model to enable us to study the effects of radiation on leucocyte-endothelium interactions and on intestinal microflora in the murine ileum. This model enables us to study specifically the local effects of radiation therapy.

METHOD

A midline laparotomy was performed in male C57/Bl6 mice and a five-centimetre segment of ileum is irradiated using the chamber. Leucocyte responses (rolling and adhesion) were then analysed in ileal venules 2 - 48 hours after high dose irradiation, made possible by an inverted approach using intravital fluorescence microscopy. Furthermore, intestinal microflora, myeloperoxidase (MPO) and cell histology were analysed.

RESULTS

The highest and most reproducible increase in leucocyte rolling was exhibited 2 hours after high dose irradiation whereas leucocyte adhesion was greatest after 16 hours. Radiation reduced the intestinal microflora count compared to sham animals with a significant decrease in the aerobic count after 2 hours of radiation. Further, the total aerobic counts, Enterobacteriaceae and Lactobacillus decreased significantly after 16 hours. In the radiation groups, the bacterial count showed a progressive increase from 2 to 24 hours after radiation.

CONCLUSION

This study presents a refinement of a previous method of examining mechanisms of radiation enteropathy, and a new approach at investigating radiation induced leucocyte responses in the ileal microcirculation. Radiation induced maximum leucocyte rolling at 2 hours and adhesion peaked at 16 hours. It also reduces the microflora count, which then starts to increase steadily afterwards. This model may be instrumental in developing strategies against pathological recruitment of leucocytes and changes in intestinal microflora in the small bowel after radiotherapy.

Inflammatory reaction and changes in expression of coagulation proteins on lung endothelial cells after total-body irradiation in mice

Inflammatory reaction is a classical feature of radiation exposure, and pneumonitis is a dose-limiting complication in the handling of hematological disorders treated with total-body irradiation. In the present study, we first evaluated the inflammatory response in C57BL6/J mice exposed to lethal doses of gamma rays treated with antibiotics or not. Both interleukin 6 and KC (also known as Gro1) were increased in the plasma 10 to 18 days after radiation exposure, independent of bacterial infection, whereas fibrinogen release was linked to a bacterial infection. Furthermore, both Il6 and KC were increased in the lungs of irradiated mice. Our second objective was to characterize the endothelial cell changes in the lungs of total-body-irradiated mice. For this purpose, a quantitative RT-PCR was used to determine the expression of genes involved in inflammatory and coagulation processes. We found that the adhesion molecules P-selectin and platelet endothelial cell adhesion molecule 1 were up-regulated, whereas E-selectin remained unchanged. Tissue factor expression was up-regulated as well, and thrombomodulin gene expression was down-regulated. The investigation by immunohistochemistry of adhesion molecules confirmed the increase in the basal expression of both P-selectin and platelet endothelial cell adhesion molecule 1 on pulmonary endothelial cells. All together, our results suggest the involvement of endothelial cells in the development of radiation-induced inflammatory and thrombotic processes.

Different radiogenic effects on microcirculation in healthy pancreas and in pancreatic carcinoma of the rat

OBJECTIVE

To compare the radiogenic effects on microcirculation in healthy and malignant pancreatic tissue.

SUMMARY BACKGROUND DATA

Vascular injury is an important effect of radiotherapy, which has been suggested for antiangiogenic tumor therapy.

METHODS

An established model of duct-like pancreatic cancer (DSL6A) was used. Investigation was performed in 12 healthy and 24 tumor-bearing Lewis rats. The tumors were locally irradiated with 15 Gy in 12 animals 4 weeks after intraperitoneal inoculation. Additionally, local radiation of the normal pancreas was performed in six healthy animals. Intravital microscopy of tumor and normal pancreatic microcirculation was performed 5 days after radiation. Relevant parameters were erythrocyte velocity and functional vessel density. Tumor apoptosis and the fraction of vital tumor cells were estimated histologically 5 and 12 days after radiation.

RESULTS

Local radiation with 15 Gy caused a pronounced impairment of blood flow and functional capillary density in the normal pancreas 5 days after radiation, while the tumor blood flow was not significantly changed. A significant reduction in the fraction of vital tumor cells and a significant increase in tumor apoptosis were observed 12 days after radiation.

CONCLUSIONS

Local radiation impairs blood flow in healthy pancreas but not in pancreatic cancer tissue. Tumor cell death is the leading consequence of radiation injury in malignant pancreatic tissue without affecting the vascular system of the tumor. The authors conclude that external beam radiation does not appear to be a useful adjunct for a vascular-targeted therapy in pancreatic carcinoma but causes distinct hypoperfusion in the healthy pancreas.

Prophylactic antiemetic efficacy of granisetron or ramosetron in patients undergoing thyroidectomy

OBJECTIVE

Thyroidectomy is associated with a high incidence of postoperative nausea and vomiting (PONV), ranging from 60% to 84%. We conducted this study to compare the antiemetic effects and safety of granisetron 20 micro g/kg and ramosetron 4 micro g/kg in patients undergoing elective thyroidectomy under standard anaesthetic technique.

METHODS

One hundred and thirteen patients were randomized to receive placebo (n = 41), granisetron 20 nug/kg (n = 36) or ramosetron 4 micro g/kg (n = 36) intravenously over 2-5 minutes immediately before the induction of anaesthesia. The incidence of PONV, nausea severity score (NSS), adverse events and the need for rescue antiemetics were assessed during the first 1 hour (0-1 h) and following 23 hours (1-24 h) after anaesthesia.

RESULTS

During the first hour after anaesthesia, the incidence of PONV was 36.6% for placebo, 11.1% for granisetron (p = 0.012 vs placebo) and 25.0% for ramosetron. During 1 hour to 23 hours after anaesthesia, the incidence of PONV was 51.2% for placebo, 30.6% for granisetron and 41.7% for ramosetron. There were no significant differences between the three groups. Overall (0-24 h), the corresponding incidence of PONV were 61.0%, 30.6% and 50.0%, respectively, showing a significantly lower value in the granisetron group than in the placebo group (p = 0.008). The incidence of vomiting and rescue antiemetic requirement during the first 24 hours after anaesthesia was significantly lower with the granisetron group than with placebo (p = 0.021 and 0.030, respectively). The most common adverse events in the three groups were headache and dizziness.

CONCLUSION

Only granisetron 20 micro g/kg was superior to placebo for the prevention of PONV after thyroidectomy.

Alterations of the VIP-stimulated cAMP pathway in rat distal colon after abdominal irradiation

Ionizing radiation induces hyporesponsiveness of rat colonic mucosa to vasoactive intestinal peptide (VIP). Possible mechanisms responsible for this hyporesponsiveness of the cAMP communication pathway in rat colon were investigated. VIP- and forskolin-stimulated short-circuit current (I(sc)) responses were studied after a 10-Gy abdominal irradiation in Ussing chambers as well as in single, isolated crypts. Adenylyl cyclase (AC) activity and VIP receptor characteristics were determined in mucosal membrane preparations. In addition, alterations in crypt morphology were studied. Impaired secretory responses to VIP and forskolin were observed 4 days after irradiation (decrease of 80%). cAMP analog-stimulated I(sc) responses were unchanged. In isolated crypts, VIP- and forskolin-stimulated cAMP accumulation was markedly reduced by 80 and 50%, respectively. VIP-stimulated AC activity and VIP receptor number were decreased in membrane preparations. No major change of cellularity was associated with these functional alterations. In conclusion, the decreased secretory responses to VIP of rat colon are associated with reduced cAMP accumulation, decreased AC activity, and diminution of VIP receptor numbers without a marked decrease of crypt cell number.

Tight junctional changes upon microwave and x-ray irradiation

Tight junctions (zonulae occludentes, ZO) are cellularly regulated dynamic structures sensitive to environmental stress agents including ionizing radiation. Radiation induced pathological alterations of the small intestine (gastrointestinal radiation syndrome) are related to altered ZO-mediated paracellular transport. We carried out a quantitative morphological evaluation of the murine jejunal epithelial tight junctional structure in freeze fracture replicas as changed upon whole body X-ray irradiation and low energy microwave exposition. X-ray treatment (4 Gy, 1, 24 h) brought about a partial dearrangement of the ZO strand network which regenerated only partially by 24 h. This observation is in line with data on paracellular permeability increases and ZO-bound calcium drop caused by X-ray irradiation. On the other hand, microwave treatment (16 Hz-modulated 2.45 GHz wave, 1 mW/cm2 power density, I h exposition, samples at I and 3 h after exposition) did not cause dearrangement but, rather an increase in the integration of thight junctional structure, which is in agreement with an increase in cytochemically detectable ZO-bound calcium.

Morphological aspects of ionizing radiation response of small intestine

Knowledge of the acute and late ionizing radiation exposure damage to the gastrointestinal tract, particularly injury of the small intestine, is of great significance in radiotherapy, as is management of accidental radiation exposure. Irradiation (X-ray, neutron, cobalt gamma) induces a series of events in this rapidly renewing tissue resulting in the well-known symptoms of the gastrointestinal (GI) radiation syndrome, such as GI haemorrhage, endotoxemia, bacterial infection, anorexia, nausea, vomiting, diarrhoea, and loss of electrolytes and fluid. In spite of the significant advances that have occurred in research on underlying mechanisms over the last two decades, the overall etiology and pathogenesis of the GI-syndrome still remains unclear. Currently, to our knowledge, these symptoms are probably due to a rapid modification of the intestinal motility and to the structural alteration of the intestinal mucosa (cell loss and altered crypt integrity). Several evidences suggest that radiation-induced dysfunctions and structural changes of this organ (either changes in subcellular, cellular, and histological structure) are mediated by concerted and interrelated changes of a plethora of various extracellular mediators and their intracellular messengers. The aim of this review is to summarize our current knowledge about the pathomorphology and cell biology of the ionizing radiation response of the GI tract with a focus on the small intestine.

Effects of radiation damage on intestinal morphology

The current flow of papers on intestinal structure, radiation science, and intestinal radiation response is reflected in the contents of this review. Multiparameter findings and changes in compartments, cells, or subcellular structure all contribute to the overall profile of the response. The well-recognized changes in proliferation, vessels, and fibrogenesis are accompanied by alterations in other compartments, such as neuroendocrine or immune components of the intestinal wall. The responses at the molecular level, such as in levels of hormones, cytokines, or neurotransmitters, are of fundamental importance. The intestine responds to localized radiation, or to changes in other organs that influence its structure or function: some structural parameters respond differently to different radiation schedules. Apart from radiation conditions, factors affecting the outcome include the pathophysiology of the irradiated subject and accompanying treatment or intervention. More progress in understanding the overall responses is expected in the next few years.

Characterization of the acute inflammatory response after irradiation in mice and its regulation by interleukin 4 (Il4)

The aim of this study was to determine the effects of total-body irradiation of mice on the acute release of a panel of several mediators of inflammation and to evaluate the efficacy of Il4 in regulating these radiation-induced modifications. We studied the effects of exposure of C57BL6/J mice to 8 Gy gamma rays on the early release of cytokines, chemokines, acute-phase proteins, prostaglandins and corticosterone in either plasma or tissues compared to those observed after intraperitoneal injection of lipopolysaccharide from 1 h to 3 days after stimulation. During the characterization of the acute inflammatory response induced by radiation or lipopolysaccharide, we observed differences both in the type of mediators produced and in the time course of release. We next determined the anti-inflammatory potential of Il4 in this model of total-body irradiation. We found that Il4 was able to down-regulate the radiation-induced production of mediators of inflammation such as Gro1 (also known as KC, N51) in plasma and lung, corticosterone in blood, Il1b in lung, and prostaglandin E(2) in colon, suggesting the anti-inflammatory potential of Il4 in regulating the radiation-induced response.

Role of P-selectin in radiation-induced intestinal inflammatory damage

The aims of our study were to characterize the dose- and time-dependent changes in endothelial P-selectin expression and the role of this adhesion molecule as a mediator of radiation-induced inflammation. For that purpose, endothelial P-selectin expression was measured by the radiolabeled antibody technique in control and irradiated mice at 2, 6, and 24 hr following abdominal irradiation with 4 or 10 Gy; leukocyte endothelial cell interactions were assessed using intravital microscopy in intestinal venules following irradiation at the aforementioned doses and times in C57BL/6 and P-selectin-deficient mice. In wild-type mice, radiation induced a time- and dose-dependent up-regulation of P-selectin and a significant increase in the flux of rolling leukocytes 2 hr after irradiation. Irradiation induced a significant increase in leukocyte adhesion that was dose-dependent. Following irradiation, P-selectin-deficient mice did not show any increase in leukocyte rolling but did demonstrate a response in leukocyte adhesion similar to that of the wild-type mice. Radiation-induced dose-dependent histological inflammatory damage that did not differ between P-selectin-deficient and wild-type mice. We conclude that P-selectin is up-regulated following irradiation and is a key molecular determinant of leukocyte rolling but not leukocyte adhesion in this inflammatory condition. Therefore, isolated neutralization of this adhesion molecule is not an effective means for preventing radiation-induced inflammation.

Substance P (NK1) receptor in relation to substance P innervation in rat duodenum after irradiation

It has previously been shown that high dose of irradiation to the rat abdomen leads to an increased level of substance P (SP) in the duodenum. In the present study the pattern of distribution of NK1 receptors (NK1-R) in rat duodenum after irradiation (5-30 Gy), was examined at the same time-point (7 days) after irradiation, comparisons being made with the distribution of SP-innervation. Immunohistochemical methods were used. In controls, NK1-R-like immunoreactivity (-LI) was detected in epithelial cells, in cells in the region of the intestinal cells of Cajal within the deep muscular plexus (ICC-DMP), in neuronal cells in the myenteric plexus, and variably in granulocytes in the mucosa. Irradiation with 5-10 Gy did not lead to obvious changes in the pattern of NK1-R-LI. After irradiation with the highest doses (25-30 Gy), the mucosa was often gravely damaged, displaying granulation tissue. No epithelial NK1-R-LI was detected in this tissue, but was present in less affected mucosa after these doses. In the region of the ICC-DMP, in the myenteric plexus, and in granulocytes, NK1-R-LI was detected also after high dose irradiation. However, the degree of NK1-R-LI in the region of the ICC-DMP was somewhat lower than seen in controls and after low doses. SP-immunoreactive nerve fibers were present in the regions where NK1-R-LI was detected. These findings support a suggestion that an increased level of SP after irradiation may contribute to the dose-dependent gastrointestinal adverse effects that occur after radiotherapy.

Intestinal and colonic motor alterations associated with irradiation-induced diarrhoea in rats

Localized application of ionizing radiation to the gastrointestinal tract frequently elicits responses, which include diarrhoea. The origin of this symptom is not clear but has been attributed to loss of epithelial integrity, together with alterations in motility and increased secretion. The purpose of this study was to examine whether a 10 Gy abdominal gamma irradiation leads to an inflammatory reaction, and to compare intestinal and colonic motility in controls and abdominally irradiated rats 1, 3 and 7 days after irradiation, using an electromyographic technique. The motility parameters analysed were the frequency and velocity of propagation of migrating myoelectric complexes (MMC) in the jejunum and colonic spike activity (long spike bursts; LSB) per 10 min in fasted rats. The MMC frequency was significantly reduced on days 1 and 7 after irradiation and the MMC pattern was markedly disrupted on day 3. The frequency of colonic LSB was significantly reduced on days 1, 3 and 7. Mouth to anus transit was significantly accelerated on day 3 only and diarrhoea was observed at this time. Myeloperoxidase activity in the jejunum and colon was also increased on this day only. It is concluded that irradiation-induced diarrhoea occurs contemporaneously with disruption of MMC in the small intestine.

Intestinal permeability in humans is increased after radiation therapy

PURPOSE

Irradiation inflicts acute injuries to the intestinal mucosa with rapid apoptosis induction and subsequent reduction in epithelial surface area. It may therefore be assumed that the intestinal barrier function is affected. The aim of this study was to compare the mucosal permeability in irradiated rectum and nonirradiated sigmoid colon from patients subjected to radiation therapy before surgical treatment for rectal cancer.

METHODS

Segments from sigmoid colon and rectum obtained from irradiated and nonirradiated patients were stripped from the serosa-muscle layer and mounted in Ussing diffusion chambers. The mucosa-to-serosa passage of the marker molecules 14C-mannitol, fluorescein isothiocyanate-dextran 4,400, and ovalbumin was followed for 120 minutes.

RESULTS

The permeability to the markers was size-dependent and increased linearly across time in all specimens. The passage of all markers was increased in irradiated rectum compared with nonirradiated sigmoid colon, whereas in specimens from nonirradiated patients there were no differences between rectum and sigmoid colon. Histologic signs of crypt and mucosal atrophy were found in the irradiated rectal specimens.

CONCLUSIONS

Early gastrointestinal complications after radiation therapy may be the result of mucosal atrophy in addition to mucosal damage, with a loss of barrier integrity.

Tepoxalin inhibits inflammation and microvascular dysfunction induced by abdominal irradiation in rats

BACKGROUND

Inflammatory cells contribute to the acute and sub-acute sequelae of radiation therapy. Tepoxalin, an inhibitor of cyclooxygenase and 5-lipoxygenase that suppresses NF-kappaB activation, has potent anti-inflammatory activity.

AIMS

To assess the effects of tepoxalin on radiation-induced inflammatory damage, and determine its mechanisms of action.

METHODS

Leucocyte rolling, adhesion and emigration, and albumin leakage were determined by intra-vital microscopy in rat mesenteric venules. NF-kappaB activation was measured by electrophoretic mobility shift assays, and endothelial intercellular adhesion molecule-1 expression by the radiolabelled antibody technique. Groups of irradiated rats were treated with tepoxalin, N-acetyl-L-cysteine, zileuton (lipoxygenase inhibitor), or vehicle.

RESULTS

Irradiated animals had a marked increase in the number of rolling, adherent and emigrated leucocytes in mesenteric venules, and in microvascular permeability. Tepoxalin prevented leucocyte adhesion and the increase in permeability after radiation. Tepoxalin did not inhibit radiation-induced NF-kappaB activation or intercellular adhesion molecule-1 up-regulation, while N-acetyl-L-cysteine, which attenuated NF-kappaB activation, had no effect on leucocyte recruitment. In contrast, tepoxalin inhibited the increase in leukotriene B4 levels after radiation, and the anti-inflammatory effects of the drug were mimicked by zileuton.

CONCLUSIONS

Tepoxalin affords significant protection against radiation-induced inflammation and microvascular dysfunction in splanchnic organs through a mechanism dependent on leukotriene synthesis inhibition.

Impact of hetastarch on the intestinal microvascular barrier during ECLS

The effects of hetastarch on microvascular fluid flux were determined in anesthetized dogs undergoing extracorporeal life support (ECLS) with a roller pump and membrane oxygenator. ECLS with a lactated Ringer priming solution resulted in a decrease in microvascular protein reflection coefficient and an increase in transvascular protein clearance. Use of a 6% hetastarch priming solution attenuated the decrease in microvascular protein reflection coefficient and blunted the increase in transvascular protein clearance. Ileal tissue water increased in the group treated with the lactated Ringer priming solution compared with the group treated with 6% hetastarch. The effective plasma-to-interstitial colloid osmotic pressure gradient was greater in the group treated with hetastarch than in the group treated with lactated Ringer solution. Hetastarch decreases the edema associated with ECLS. The reduction in edema is due to the maintenance of the plasma-to-interstitial colloid osmotic pressure gradient and the reduction in the microvascular permeability to protein.