Evidence for humoral effects on the radiation response of rat foot skin

NORMAL TISSUE REACTIONS TO CHRONIC RADIATION EXPOSURE IN MAN

This paper presents an overview of radiobiological dependences governing the occurrence of tissue (organ) reactions that determine the outcomes of chronic exposure to low-LET ionizing radiation (IR) in humans. The mechanisms involved in the development of tissue reactions (TRs) to long-term exposures to IR and radioadaptation are considered. The overview describes the reactions of the haematopoietic, immune, nervous, reproductive and endocrine systems, lungs, skin and crystalline lens to chronic radiation exposure, which are of fundamental importance in view of radiation protection. It is shown that the individual's physiological tissue (organ) reserve, and also that induced by radiation exposure at low-dose rates are of great significance in the context of TR development.

[Stem cell derived therapy for cutaneous radiation exposure]

Radiation injury to skin results in a variety of deterministic effects including inflammatory reactions and cell depletion leading to distinct clinical symptoms following a defined time pattern. Therapeutic approaches are still limited, a complete restitution of affected areas is so far impossible. In the last few years increasing experimental knowledge about acquisition and administration of autologous stem cells also in the field of radiation injuries has been obtained. Evidence reviewed in this article shows that the beneficial effects of stem cell transplantation are not necessarily due to the replacement of damaged cells by transplanted cells but most probably due in the most part to a paracrine effect. Transplanted cells secrete bioactive factors that initiate the stimulation of the host stem cells to regenerate the damaged tissues. Transplanted stem cells produce trophic factors which aid the systemic healing of the victims. Furthermore, administration of stem cell secretomes in the form of conditioned media containing microvesicles or exosomes can be as effective as administering the stem cells. This hypothesis is supported by findings that cell-free derivatives from hMSCs were useful for wound healing purposes and could circumvent the need for intact cells. Furthermore, the beneficial effect of MSC injection on reperfusion and tissue damage in a mouse model of hind limb ischemia could be attributed to paracrine mechanisms with local release of arteriogenic cytokines. Further evaluation of the paracrine potential of autologous stem cells may open new means for treatment of acute as well as chronic sequelae of cutaneous radiation injuries.

Effect of grape seed extract on lipid peroxidation, antioxidant activity and peripheral blood lymphocytes in rats exposed to x-radiation

The present studies were designed to evaluate supplemental grape seed extract (GSE) and vitamin E supplements on lipid peroxidation, on antioxidant systems and peripheral blood lymphocytes in rats exposed to x-rays. Three groups of rats were investigated: a control group (CG) received intraperitoneal (i.p.) physiological serum 1 mL/day (n=10), i.p.; a vitamin E group (VG) received 50 mg/kg/day (n=10); an i.p. grape seed extract group received 50 mg/kg/day (n=10). Four weeks later, a 6 Gy radiation dose was given to the rats. Blood samples were taken 24 h later after irradiation and lymphocyte, malondialdehyde (MDA), reduced glutathione (GSH), nitrate, nitrite, reduced ascorbic acid, retinol, beta-carotene and ceruloplasmin concentrations were analysed. The levels of GSH (p<0.05), retinol (p<0.001), beta-carotene (p<0.05) and ceruloplasmin concentration (p<0.001) in the GSE group were found to be higher than in the control group but the level of MDA (p<0.001) and nitrite concentration (p<0.05) in rats supplemented with GSE were found to be lower than in the control group. The results indicate that GSE enhanced the antioxidant status and decreased the incidence of free radical-induced lipid peroxidation in blood samples of rats exposed to x-radiation. The antioxidant effect of GSE given to animals was more effective than vitamin E administered before whole-body irradiation in rats.