Cell proliferation and differentiation in the small intestine after irradiation with multiple fractions

Marker Determination for Response Monitoring: Radiotherapy and Disappearance Curves

This paper reports the results of studies on the possible role of biochemical markers in monitoring the effects of ionizing radiations and in the follow-up of cancer patients submitted to radiotherapy.

Three different case series were analyzed: patients with head and neck cancer, prostate carcinoma and residual thyroid tumors or uptaking metastases (131-Iodine therapy).

Serum TPA and amylase were serially determined in patients with head and neck or thyroid cancer to measure the radiation damage to the salivary glands. In the former group a statistically significant correlation between the increase of both molecules and the total dose administered after the first day of treatment (2, 3, 4 or 6 Gy) was observed. In patients treated for thyroid cancer the damage to the salivary glands was revealed by an increase in TPA and amylase serum levels, dependent on the dose of 131-Iodine administered. Moreover, an association was demonstrated between pretreatment values of TPA in patients with head and neck tumors and prognosis: patients with values below the cutoff have significantly higher survival rates than those with higher values.

In patients with prostate carcinoma PSA was confirmed to have better diagnostic and prognostic value than PAP. Patients with metastases show an inversion or lack of negative trend in PSA levels observed in the disease-free patients. This precedes the clinical diagnosis of metastases by 1 to 15 months.

Internal exposure to neutron-activated 56Mn dioxide powder in Wistar rats-Part 2: pathological effects

To fully understand the radiation effects of the atomic bombing of Hiroshima and Nagasaki among the survivors, radiation from neutron-induced radioisotopes in soil and other materials should be considered in addition to the initial radiation directly received from the bombs. This might be important for evaluating the radiation risks to the people who moved to these cities soon after the detonations and probably inhaled activated radioactive "dust." Manganese-56 is known to be one of the dominant radioisotopes produced in soil by neutrons. Due to its short physical half-life, 56Mn emits residual radiation during the first hours after explosion. Hence, the biological effects of internal exposure of Wistar rats to 56Mn were investigated in the present study. MnO2 powder was activated by a neutron beam to produce radioactive 56Mn. Rats were divided into four groups: those exposed to 56Mn, to non-radioactive Mn, to 60Co γ rays (2 Gy, whole body), and those not exposed to any additional radiation (control). On days 3, 14, and 60 after exposure, the animals were killed and major organs were dissected and subjected to histopathological analysis. As described in more detail by an accompanying publication, the highest internal radiation dose was observed in the digestive system of the rats, followed by the lungs. It was found that the number of mitotic cells increased in the small intestine on day 3 after 56Mn and 60Co exposure, and this change persisted only in 56Mn-exposed animals. Lung tissue was severely damaged only by exposure to 56Mn, despite a rather low radiation dose (less than 0.1 Gy). These data suggest that internal exposure to 56Mn has a significant biological impact on the lungs and small intestine.

Marked changes in endogenous antioxidant expression precede vitamin A-, C-, and E-protectable, radiation-induced reductions in small intestinal nutrient transport

Rapidly proliferating epithelial crypt cells of the small intestine are susceptible to radiation-induced oxidative stress, yet there is a dearth of data linking this stress to expression of antioxidant enzymes and to alterations in intestinal nutrient absorption. We previously showed that 5-14 days after acute γ-irradiation, intestinal sugar absorption decreased without change in antioxidant enzyme expression. In the present study, we measured antioxidant mRNA and protein expression in mouse intestines taken at early times postirradiation. Observed changes in antioxidant expression are characterized by a rapid decrease within 1h postirradiation, followed by dramatic upregulation within 4h and then downregulation a few days later. The cell type and location expressing the greatest changes in levels of the oxidative stress marker 4HNE and of antioxidant enzymes are, respectively, epithelial cells responsible for nutrient absorption and the crypt region comprising mainly undifferentiated cells. Consumption of a cocktail of antioxidant vitamins A, C, and E, before irradiation, prevents reductions in transport of intestinal sugars, amino acids, bile acids, and peptides. Ingestion of antioxidants may blunt radiation-induced decreases in nutrient transport, perhaps by reducing acute oxidative stress in crypt cells, thereby allowing the small intestine to retain its absorptive function when those cells migrate to the villus days after the insult.

Radiation-induced reductions in transporter mRNA levels parallel reductions in intestinal sugar transport

More than a century ago, ionizing radiation was observed to damage the radiosensitive small intestine. Although a large number of studies has since shown that radiation reduces rates of intestinal digestion and absorption of nutrients, no study has determined whether radiation affects mRNA expression and dietary regulation of nutrient transporters. Since radiation generates free radicals and disrupts DNA replication, we tested the hypotheses that at doses known to reduce sugar absorption, radiation decreases the mRNA abundance of sugar transporters SGLT1 and GLUT5, prevents substrate regulation of sugar transporter expression, and causes reductions in sugar absorption that can be prevented by consumption of the antioxidant vitamin A, previously shown by us to radioprotect the testes. Mice were acutely irradiated with (137)Cs gamma rays at doses of 0, 7, 8.5, or 10 Gy over the whole body. Mice were fed with vitamin A-supplemented diet (100x the control diet) for 5 days prior to irradiation after which the diet was continued until death. Intestinal sugar transport was studied at days 2, 5, 8, and 14 postirradiation. By day 8, d-glucose uptake decreased by approximately 10-20% and d-fructose uptake by 25-85%. With increasing radiation dose, the quantity of heterogeneous nuclear RNA increased for both transporters, whereas mRNA levels decreased, paralleling reductions in transport. Enterocytes of mice fed the vitamin A supplement had > or = 6-fold retinol concentrations than those of mice fed control diets, confirming considerable intestinal vitamin A uptake. However, vitamin A supplementation had no effect on clinical or transport parameters and afforded no protection against radiation-induced changes in intestinal sugar transport. Radiation markedly reduced GLUT5 activity and mRNA abundance, but high-d-fructose diets enhanced GLUT5 activity and mRNA expression in both unirradiated and irradiated mice. In conclusion, the effect of radiation may be posttranscriptional, and radiation-damaged intestines can still respond to dietary stimuli.

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.

Binding sites for VIP in the reorganizing mucosa of the irradiated bowel

Rats were given radiotherapy (total dose 30 Gy) over the abdomen. Seven days later specimens of the duodenum were prepared for in vitro receptor autoradiography using the radioligand [125I]VIP. The autoradiograms were quantitatively analyzed using a computer system. Histological examination revealed that a very marked reorganization of the mucosa had occurred in response to irradiation. Using receptor autoradiography, we found [125I]VIP-specific binding sites in the reorganizing mucosa, except where denudation had occurred. Such binding sites also occurred in the smooth muscle layer of the duodenal wall. The observations suggest that VIP has profound effects in radiation-induced enteropathy.

Colonic cell proliferation in normal mucosa of patients with colon cancer

Cell kinetics parameters have been analysed in colonic mucosa at different distances from a tumour in patients with colon carcinoma. Total cell number (TCN), 3H thymidine labelling index (TLI), mitotic index (MI), Goblet cell index (GCI) and the distribution of labelled cells along the crypt column (cell position frequency plot) were determined in well-aligned crypts. Total cell number, GCI and the labelled cell position frequency plots were similar in different samples from the same individual. A negative linear correlation between TCN and TLI was observed. The analysis of the cell position plots showed two patterns 1) with a high concentration in the bottom fifth of the crypt and 2) with frequent labelled cells at high positions. Whereas a negative correlation between overall TLI and the percent contribution to the TLI of the lowermost fifth was seen, the correlation was positive for the next 3 fifths and labelling was absent in the last part of the crypt.

Cell kinetics in rat small intestine after exposure to 3 Gy of gamma-rays at different times of the day

Qualitative and quantitative morphological changes in rat jejunum were studied after a whole-body exposure to 3 Gy of gamma rays. Four groups of animals were irradiated at different times of the day, namely midnight, 06.00, 12.00 and 18.00 hours. The number of epithelial cells, labelling and mitotic indices were evaluated in crypt sections and the spatial distribution of S-phase cells was determined. At 12 h after irradiation a marked reduction was observed in all parameters, but the proliferative activity was restored quickly and at 36 h after irradiation the values were significantly higher than the controls. The frequency distribution of labelled cells at different positions in the crypt was reduced at 12 h but a clear expansion of S phase cells to positions near to the crypt villus junction was observed during the recovery phase. The animals irradiated at different times of the day showed a similar general post-irradiation response in the number of cells along the side of the crypt, labelling and mitotic indices and in the distribution of S phase cells along the crypts. It is worth noting that the animals exposed at midnight had a distribution of S phase cells similar to controls at 72 h post-irradiation, i.e. earlier than the other groups.

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

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