Prolonged Radiation Damage in Rat Colon and Urokinase Expression in Epithelium

Although radiation therapy plays important role in the treatment of gynecological tumors, it may cause radiation injury as a late effect. Several recent reports show that urokinase such as urokinase type plasminogen activator (uPA) contributes to the repair of ulcerative lesions of the colon epithelium. We studied radiation induced enterocolitis using rat animal models. Seventy-two female Wistar rats were irradiated by a single fraction dose of 36Gy at laparotomy. Histological changes and activity of urokinase system were investigated after irradiation. Ulcers were observed in irradiated field in 12 of 19 animals (63%) even at 60th week after irradiation. Urokinase expressions were observed in the margins of active ulcer. Urokinase was thought to play important role in exacerbation of ulcer formation. Expression of uPA was also observed in submucosal glands. Ischaemic changes were not observed in irradiated colon despite sclerosing vasculitis. It is suggested that uPA played reciprocal roles in radiation induced enterocolitis: healing and aggravation of ulcer

Role of Parathyroid Hormone/Parathyroid Hormone-Related Peptide on Cell Proliferation in the Gastric Mucosa

Parathyroid hormone-related peptide (PTHrP) is widely expressed in normal tissues and elicits various functions through the PTH/PTHrP receptor. Relaxation effects of PTHrP on gastrointestinal smooth muscle cells were well documented, but the physiological role on mucosal growth and differentiation is little known. The purpose of this study was to evaluate the expression of PTHrP and PTHPTHrP receptor in the rat gastric mucosa, and the role of PTHrP on mucosal cell proliferation. Male Wistar rats were used in this study. Localization of PTHrP and PTH/PTHrP receptor were observed by immunohistochemistry and in situ hybridization. Expression of PTH/PTHrP receptor mRNA were examined by RNase protection assay in control and stress condition. Double staining with BrDU incorporation was performed to differentiate cell cycle states. Cell proliferative effect by external PTHrP-(1-34) was evaluated by BrDU incorporation. PTHrP immunopositive cells were encountered in and around the mucosal neck area. PTH/PTHrP receptor immunoreactivity was observed in the gastric mucosa broadly. Cells with stronger expression for PTHrP and its cognate receptor were located in the vicinity of generative zone. But BrDU incorporating cells were negative for both PTHrP and PTH/PTHrP receptor. By RNase protection assay, PTH/PTHrP receptor mRNA expression was weak in a steady state, and the receptor expression increased at stress. External PTHrP-(1-34) did not show cell proliferative effect in a steady state. At stress BrDU incorporation was suppressed significantly, and PTHrP-(1-34) increased BrDU incorporation. These observations suggest that PTHrP and PTH/PTHrP receptor involve maintenance of mucosal growth and differentiation in the stomach

Age-dependent effects on radiation-induced carcinogenesis in the rat thyroid

Childhood radiation exposure is a known thyroid cancer risk factor. This study evaluated the effects of age on radiation-induced thyroid carcinogenesis in rats irradiated with 8 Gy X-rays. We analyzed cell proliferation, cell death, DNA damage response, and autophagy-related markers in 4-week-old (4W) and 7-month-old (7M) rats and the incidence of thyroid tumors in 4W, 4-month-old (4M), and 7M rats 18 months after irradiation. Cell death and DNA damage response were increased in 4W rats compared to those in controls at 1 month post-irradiation. More Ki-67-positive cells were observed in 4W rats at 12 months post-irradiation. Thyroid tumors were confirmed in 61.9% (13/21), 63.6% (7/11), and 33.3% (2/6) of irradiated 4W, 4M, and 7M rats, respectively, compared to 0%, 14.3% (1/7), and 16.7% (1/6) in the respective nonirradiated controls. There were 29, 9, and 2 tumors in irradiated 4W, 4M, and 7M rats, respectively. The expression of several autophagy components was downregulated in the area surrounding radiation-induced thyroid carcinomas in 4W and 7M rats. LC3 and p62 expression levels decreased in radiation-induced follicular carcinoma in 4W rats. Radiosensitive cells causing thyroid tumors may be more prevalent in young rats, and abrogation of autophagy may be associated with radiation-induced thyroid carcinogenesis

Internal radiation exposure from 137Cs and its association with the dietary habits of residents from areas affected by the Chernobyl nuclear accident, Ukraine: 2016-2018.

The total annual effective dose has steadily decreased since the fallout of the Chernobyl Nuclear Power Plant. However, chronic internal exposure to 137Cs still persists and fluctuates in a complex and unpredictable manner. Recently, body contamination was found to primarily occur owing to the intake of forest foodstuffs that contain long-lived 137Cs. Forest foodstuffs may have up to 100 times higher concentration of cesium than does local milk and meat. The present study aimed to investigate the recent dietary habits of residents in the Zhytomyr region of Ukraine, and assess the effect of the intake of forest foodstuffs on the increase in internal radioactivity from 137Cs. We screened 1,612 participants, from July 2016 to February 2018 for internal radioactivity, using whole-body counter at Korosten Medical Center and surveyed their background and intake habits. We analyzed the association among food type, intake frequency, and internal exposure dose. The analysis revealed that nearly 90% of the participants regularly consumed one of the forest foodstuffs (mushrooms, berries, fish) or milk. Nearly 80% of the participants indicated that they consumed mushrooms or berries or both. Internal radioactivity was detected in 30% of the participants. The diet that included mushrooms exhibited the highest internal radioactivity. The lowest Bq/kg concentration was observed in the only-berry group, following the no-intake group. There was a significant correlation between the intake frequency and the magnitude of Bq/kg. Radioactivity detected in the mushroom-berry and only-mushroom group were 8.6 and 9.2 Bq/kg, respectively. The lowest and highest intake frequency showed a radioactivity of 2.4 and 7.5 Bq/kg, respectively. Radioactivity in the winter season was significantly higher than that in other seasons. In conclusion, our study revealed that internal radioactivity varies depending on the type of food, intake frequency, and season