Proinflammatory effects of local abdominal irradiation on rat gastrointestinal tract

Parallel increase in substance P and VIP in rat duodenum in response to irradiation

Irradiation was administered to the upper abdomen of rats, whereupon the duodenum was examined. Numerous vasoactive intestinal peptide (VIP)- and substance P (SP)-like immunoreactive nerve fibers were seen in the damaged mucosa, often in close association to each other. The intensity of the SP- and VIP-like immunoreaction was increased in several of the tissue compartments and, as measured with radioimmunoassay, the contents of SP- and VIP-like materials were increased after 30 Gray. The results show that SP and VIP levels increase after irradiation and suggest that SP and VIP are involved in interactive reactions in the reorganization and inflammatory processes in the gut after abdominal irradiation.

Ionizing radiation induces iNOS-mediated epithelial dysfunction in the absence of an inflammatory response

Ionizing radiation induces intestinal epithelial hyporesponsiveness to secretagogues through an unknown mechanism. We investigated the role of the inducible isoform of nitric oxide (NO) synthase (iNOS)-derived NO in radiation-induced hyporesponsiveness. C57BL/6 mice were sham treated or exposed to 10-Gy gamma-radiation and were studied 3 days later. Tissues were mounted in Ussing-type diffusion chambers to assess chloride secretion in response to electrical field stimulation (EFS) and forskolin (10 microM). Transport studies were also repeated in iNOS-deficient mice. White blood cell counts were significantly lower in irradiated mice, and there was no inflammatory response as shown by myeloperoxidase activity and histological assessment. iNOS mRNA levels and nitrate/nitrite concentrations were significantly elevated in irradiated colons. iNOS immunoreactivity localized to the epithelium. Colons from irradiated wild-type, but not iNOS-deficient, mice exhibited a significant reduction in the responsiveness of the tissue to EFS and forskolin. The hyporesponsiveness was reversed by L-N(6)-(1-iminoethyl)lysine, 1400W, and dexamethasone treatments. iNOS-derived NO mediates colonic hyporesponsiveness 3 days after irradiation in the mouse in the absence of an inflammatory response.

Influence of dose-rate on inflammatory damage and adhesion molecule expression after abdominal radiation in the rat

PURPOSE

The goal of this study was to assess the effects of two clinically relevant radiation dose-rates on endothelial adhesion molecule expression, inflammatory response, and microvascular dysfunction.

METHODS AND MATERIALS

Rats were irradiated with 10 Gy at low (0.9 Gy/min) or high (3 Gy/min) dose-rates. Control animals received sham irradiation. Leukocyte rolling, adhesion, emigration, and microvascular permeability were assessed in mesenteric venules by intravital microscopy 6 hours after irradiation. P-selectin and intercellular adhesion molecule-1 (ICAM-1) expression were measured using radiolabeled monoclonal antibodies.

RESULTS

Low dose-rate (LDR) abdominal irradiation increased leukocyte adhesion compared with sham-irradiated animals, whereas high dose-rate (HDR) irradiation resulted in enhanced leukocyte rolling, adhesion, and emigration, compared with the LDR or with sham-irradiated rats. Both dose-rates increased microvascular permeability, although this effect was significantly greater after radiation with the high (8-fold) than the low (5-fold) dose-rate. HDR radiation induced significantly larger increments in P-selectin expression in splanchnic organs than LDR, whereas in most organs ICAM-1 expression was only upregulated by the HDR. Blockade of ICAM-1, but not P-selectin, abrogated leukocyte adhesion at both dose-rates.

CONCLUSIONS

The magnitude of upregulation of endothelial adhesion molecules, leukocyte recruitment, and endothelial barrier dysfunction elicited by radiation therapy is dependent on the dose-rate at which the radiation is delivered.

Differential regulation by IL-4 and IL-10 of radiation-induced IL-6 and IL-8 production and ICAM-1 expression by human endothelial cells

Radiation exposure results in an inflammatory reaction with acute as well as subacute consequences. Leukocyte infiltration is one of the predominant early histological changes and involves both cytokines and adhesion molecules. Endothelial cells play a key role in this reaction. We have previously shown the increased production of interleukin 6 (IL-6) and IL-8 and the upregulation in intercellular adhesion molecule 1 (ICAM-1) expression by HUVEC following gamma ray exposure. In the present study, we used the cytokines IL-4 and IL-10 to regulate these radiation-induced manifestations. Human umbilical vascular endothelial cells (HUVEC) were treated with IL-4 and IL-10 (50 pg/ml) either before or after 10- Gy irradiation. Three and seven days after irradiation, IL-6 and IL-8 production by HUVEC (either treated or non-treated) was assessed by enzyme-linked immunosorbent assay (ELISA). Our results show that IL-4, when added after irradiation, reversed the radiation-induced increase in IL-8 production, although slightly increased IL-6 production. IL-10 decreased both IL-8 and IL-6 production when added after irradiation. ICAM-1 expression was evaluated 3 days after irradiation by flow cytometry. The radiation-induced upregulation in ICAM-1 expression remained unaffected by the use of IL-4. Altogether, our results show that radiation-induced endothelial cell activation may be ameliorated by IL-4 and/or IL-10, which is of significance in designing strategies for cytokine-mediated intervention and/or therapy of radiation damage.

Gynecologic laparoscopic surgery is not associated with an increase of serotonin metabolites excretion

Gynecologic laparoscopic surgery is associated with a high incidence of postoperative nausea and vomiting (PONV). The specific antagonists of the 5-hydroxytryptamine-3 (5-HT3) receptor have been progressively introduced in anesthesiology to prevent or treat PONV. Although a large increase of serotonin has been documented after cisplatin treatment, the link between serotonin and PONV in surgery/anesthesiology is unknown. In a prospective study, we compared the excretion of the serotonin metabolite 5-hydroxyindoacetic acid (5-HIAA) in 40 women undergoing either gynecologic laparoscopic surgery (laparoscopy group) or traditional open laparotomy surgery (laparotomy group). Premedication, anesthetic technique, and postoperative pain treatment were standardized. The excretion of 5-H IAA corrected to creatinine was measured in all patients immediately after the induction of anesthesia and was repeated regularly until 9 h after induction. The excretion of 5-HIAA/creatinine was similar in the two groups; no increase was observed in either group. The incidence of nausea and vomiting was 40% and 35%, respectively, in the laparoscopy group versus 60% and 15%, respectively, in the laparotomy group (not significantly different). The excretion of 5-HIAA/creatinine was comparable in patients of both groups among those who vomited and those who did not. We conclude that the creation of a pneumoperitoneum during gynecologic laparoscopic surgery is not associated with an increase of 5-HIAA excretion. PONV after gynecologic laparoscopic surgery is not explained by an increase of serotonin secretion.

IMPLICATIONS

The mechanism leading to the high incidence of postoperative nausea and vomiting after gynecologic laparoscopic surgery is unknown. The excretion of the serotonin metabolite 5-hydroxyindoacetic acid did not increase during the creation of the pneumoperitoneum and the first 9 h postoperatively. Increase of serotonin secretion from the gut may not explain postoperative nausea and vomiting associated with this surgery.

Effects of GR203040, an NK1 antagonist, on radiation- and cisplatin-induced tissue damage in the ferret

1. The effects of GR203040, a tachykinin neurokinin1 receptor antagonist, on tissue damage induced by X-irradiation (Rad) or cisplatin (Cisp) were investigated in ferrets. 2. GR203040 (0.3 mg/kg SC) reduced the Rad-induced plasma protein extravasation (PPE) in the duodenum and kidney by 25% in each tissue. 3. GR203040 (3 mg/kg SC, 5-min pretreatment and every 8 hr for 48 hr after Cisp) reduced the Cisp-induced PPE in the duodenum, jejunum and lung by 59, 52 and 60%, respectively. 4. Histological examination showed that GR203040 also ameliorated the Rad- and Cisp-induced tissue damage.

Expression, activity and cellular localization of inducible nitric oxide synthase in rat ileum and colon post-irradiation

PURPOSE

Studies were conducted to determine the acute effect of exposure to ionizing radiation on inducible nitric oxide synthase (iNOS) activity and expression in the rat ileum and colon.

MATERIALS AND METHODS

Rats received whole body exposure to 10 Gy gamma-radiation and were studied 0.5-48 h later. Segments of ileum and colon were taken from anaesthetized rats for determination of myeloperoxidase activity (a marker of acute inflammation), and iNOS mRNA expression, enzyme activity and localization.

RESULTS

Myeloperoxidase activity in ileum was not increased compared with shams until 48 h post-irradiation. In colon, myeloperoxidase activity was lower than shams at 48 h post-irradiation. Irradiation resulted in a dexamethasone-sensitive expression of iNOS mRNA in both the ileum and colon within 2h. Inducible NOS activity was significantly elevated in the ileum, but not in the colon. The elevated ileal nitric oxide synthase activity was significantly reduced by pretreatment with the iNOS inhibitor, aminoguanidine. Immunoreactivity for iNOS protein was localized to the epithelium and was apparent at 2-6 h post-irradiation in the ileum, but not the colon.

CONCLUSIONS

Exposure to ionizing radiation results in the expression of iNOS in ileum and colon, but only significantly increases iNOS activity in the ileum. Inducible NOS-derived NO may participate in acute, whole body radiation-induced ileal dysfunction, independently of the development of an inflammatory response.

Exposure to ionizing radiation increases responsiveness to neural secretory stimuli in the ferret jejunum in vitro

Experiments were designed to determine the effects of ionizing radiation on jejunal epithelial function in the ferret in vitro. Basal and stimulated electrolyte transport were determined in Ussing chambers at 0.5, 2, 24 and 48 h post-irradiation. Tissue histamine and 5-hydroxytryptamine levels were measured. Myeloperoxidase activity was also measured as an index of inflammation. Basal short circuit current was reduced at 2 h post-irradiation, but was elevated at 48 h. Basal conductance was significantly increased by 24 and 48 h. Responsiveness to electrical field stimulation was depressed at 0.5 h, and was greater than control by 24 and 48 h post-irradiation. Similarly, short circuit current responses to prostaglandin E2 were depressed at 0.5 h and elevated at 24 h. No significant change was observed in the response to carbachol post-irradiation, indicating that alterations in responsiveness were not likely at the level of the enterocyte. Changes in responsiveness to electrical field stimulation correlated significantly with increases in mucosal mast cell numbers. Myeloperoxidase activity, indicative of neutrophil infiltration, did not increase post-irradiation, nor was there histological evidence of an inflammatory cell infiltrate. There were no changes in tissue histamine or 5-hydroxytryptamine. Histology also revealed little microscopic morphological change from shams in tissue from irradiated ferrets. The results of this study demonstrate effects of irradiation on electrolyte transport in the ferret jejunum. The enhanced neurally evoked electrolyte transport observed at 24-48 h post-irradiation was not correlated with the development of inflammation, but was correlated with changes in mast cell numbers.

Modulation of gut substance P after whole-body irradiation. A new pathological feature

Exposure to ionizing radiation induces gastrointestinal dysfunction and inflammatory reactions. The present study carried out in the rat, focuses on substance P, an inflammatory mediator implicated in the control of intestinal motility. We have investigated the effects of gamma irradiation on plasma and tissue substance P levels, ileal smooth muscle activity, and properties of specific receptors. Plasma and ileal (mucosa and muscle) substance P concentrations were measured by radioimmunoassay. At doses ranging from 1 to 8 Gy, plasma substance P levels increased in a dose-dependent manner up to four days after irradiation. Ileal mucosal concentration decreased rapidly 1 hr after a 6-Gy irradiation as compared to controls. A second class of binding sites appeared three days after 6 Gy irradiation. In addition, substance P contractile effects measured on isolated ileum showed a fourfold decrease of EC50, three days after 6 Gy irradiation. These results indicated that gamma irradiation induced an increase of plasma levels concomitant with a modification of gastro-intestinal substance P specific binding sites and contractile activity.

Gastrointestinal and nutritional sequelae of bone marrow transplantation

The nature of the gastrointestinal injury following bone marrow transplantation and its clinical and nutritional sequelae are poorly defined. Prospective assessments of gastrointestinal function, nutritional status, and wellbeing were therefore carried out in 47 consecutive patients (28 males, 19 females; mean age 8.4 years) undergoing bone marrow transplant. 31 diarrhoeal episodes (median duration 9.5 days) occurred in 27 patients at a median of 10 days after transplantation. Ninety one per cent of episodes were associated with protein losing enteropathy. Protein losing enteropathy was more severe in graft-versus-host disease (GVHD) comparing with other causes. It led to a substantial fall in serum albumin and there was a negative correlation between faecal alpha 1-antitrypsin concentrations and serum albumin. Transient pancreatic insufficiency developed in 18 patients, and pancreatitis in one. Intestinal permeability was normal in 12 patients who had no diarrhoea during the conditioning treatments. Diarrhoeal patients had a significantly greater decrease in nutritional status and wellbeing than patients without diarrhoea. Gastrointestinal injury following bone marrow transplantation is thus complex. Severe protein losing enteropathy in this context suggests the presence of GVHD.

Role of leukocyte-endothelial cell adhesion in radiation-induced microvascular dysfunction in rats

BACKGROUND/AIMS

Recent evidence suggests an active role of endothelial cells and inflammatory cells in radiation-induced vascular dysfunction and organ damage. The aim of this study was to characterize the endothelial cell-leukocyte interactions, their molecular mechanisms, and the associated microvascular dysfunction in postcapillary venules exposed to ionizing radiation.

METHODS

Leukocyte rolling, adherence, and emigration and leakage of fluorescein isothiocyanate albumin in rat mesenteric venules were measured in control conditions and at 2, 4, and 6 hours after abdominal irradiation. Some animals were treated with monoclonal antibodies against leukocyte (CD18) or endothelial cell (intercellular adhesion molecule 1, P-selectin) adhesion molecules before radiation and 5 hours thereafter.

RESULTS

In comparison with controls, irradiated animals had a marked increase in the number of rolling leukocytes at 2 hours after radiation. In animals studied 6 hours after radiation, a significant increment in the number of adherent and emigrated leukocytes was observed. This was associated with an increased permeability to fluorescein isothiocyanate albumin. Treatment with antibodies against either CD18 or intercellular adhesion molecule 1, but not P-selectin, significantly attenuated leukocyte adherence, emigration, and the increase in permeability induced by radiation.

CONCLUSIONS

Radiation-induced leukocyte adherence and emigration involves an interaction between CD11/CD18 on leukocytes and intercellular adhesion molecule 1 on vascular endothelium. These interactions are implicated in the early increase in vascular permeability after irradiation.

Cellular blebbing in superficial colonic epithelial cells occurring with murine graft-versus-host disease

Subnuclear blebbing of the superficial colonic epithelium, a rarely described light and electron microscopic change in graft-versus-host disease (GVHD), was studied in a murine model of GVHD. Severity of changes induced by transfer of various donor T cell subsets to irradiated, allogeneic recipients, and association with more severe alterations such as erosions and ulceration were evaluated. By light microscopy the basal region of the superficial enterocytes was greatly expanded by eosinophilic to amphophilic, flocculent, sometimes vacuolated material. By electron microscopy these changes were found to be organelle-poor, cytoplasm-filled protrusions from the basal surface of the epithelium. In this model, helper T cells (CD(4+)-enriched, CD(8+)-depleted T cells) transplanted after high dose irradiation were capable of causing the change suggesting cytokine responses may be involved in mediating the cellular injury seen histologically. Close association of blebbing and erosions suggest the blebbing may be the precursor to epithelial erosion or denudation seen in severe intestinal GVHD.

Ionizing radiation reduces neurally evoked electrolyte transport in rat ileum through a mast cell-dependent mechanism

BACKGROUND/AIMS

Mechanisms of neuroimmune regulation of intestinal electrolyte transport under pathophysiological conditions are unclear. This study investigated the effect of ionizing radiation on ileal electrolyte transport.

METHODS

Rats were exposed to 10 Gy gamma-radiation and were killed 2, 24, and 48 hours later. Ileal segments were either mounted in Ussing chambers and exposed to electrical field stimulation, prostaglandin E2, leukotriene D4, or theophylline, or they were assayed for biochemical indices of inflammation. Other segments were processed for routine histological screening, mast cell counts, or immunohistochemical analysis of the distribution of vasoactive intestinal polypeptide or substance P immunoreactivity.

RESULTS

Basal short-circuit current was unchanged 2, 24, or 48 hours postirradiation. However, there was a reduction of tissue responsiveness to electrical field stimulation, prostaglandin E2, and theophylline but not to leukotriene D4. Decreased responsiveness at 2-hours postirradiation was blocked by pretreatment with the H1 antagonist pyrilamine. Tissue myeloperoxidase activity and 5-hydroxytryptamine content were not altered postirradiation, but tissue histamine and mucosal mast cells were significantly reduced at 24 and 48 hours. There were no significant changes in villus-crypt architecture until 48 hours postirradiation. There was no significant alteration in the distribution of immunoreactive vasoactive intestinal polypeptide or substance P.

CONCLUSIONS

Ionizing radiation reduced the transport response to neural stimulation. The effect correlated temporally with decreased mast cells and histamine, suggesting a functional role for previously reported mast cell-nerve interactions.

Prostaglandin E2 localization in the rat ileum

The application of anti-prostaglandin E2 immunoglobulin to plastic-embedded thin sections of the rat ileum has permitted the localization of prostaglandin E2 in this tissue. In agreement with the published data (Chock & Schmauder-Chock (1988), Schmauder-Chock & Chock (1989)), the results also suggest the presence of an arachidonic acid cascade in the granules of various secretory cells of the gut. Since antibody labelling was found within the secretory granules of connective tissue mast cells, goblet cells, and Paneth cells, the presence of the arachidonic acid cascade in these granules is implied. The appearance of prostaglandin E2 over the non-cellular internal elastic lamina of arterioles suggests that it may have been secreted along with the elastin. The even distribution of prostaglandin throughout the cytoplasm of the erythrocyte is consistent with the concept that this cell scavenges the eicosanoid from the circulation. These data further link the secretory granule to the production of eicosanoids and therefore illustrate the potential sources of prostaglandins in the rat ileum.

Fractionated doses of ionizing radiation alter postprandial small intestinal motor activity

We investigated the effects of total abdominal fractionated irradiation on postprandial small intestinal motor activity in five dogs. Five strain-gauge transducers were attached to the seromuscular layer of the duodenum, jejunum, and ileum of each dog to record circular muscle contractions. Radiation (250 cGy) was administered three times a week on alternate days for three successive weeks (total dose, 2250 cGy). Postprandial 4-hr recordings were made once each week during radiation and at one and three weeks following completion of radiation. Duodenal mean amplitude and area under contractions did not change during or following the radiation schedule, but the mean frequency and duration of duodenal contractions decreased during the radiation schedule. Both parameters returned to baseline values postirradiation. Jejunal mean duration, amplitude, area, and frequency of contractions decreased during radiation; mean amplitude and area returned to baseline values postirradiation but not the duration and frequency of contractions. All parameters of ileal contractions decreased during radiation, and all but area and amplitudes remained depressed postirradiation. Significantly decreased strength and frequency of contractions, particularly in the jejunum and ileum occur during and following irradiation. These changes may potentially alter transit time.