Radiation protection from whole-body gamma irradiation (6.7 Gy): behavioural effects and brain protein-level changes by an aminothiol compound GL2011 in the Wistar rat.

GL2011 is a naturally occurring thiol compound and a series of thiol compounds have been proposed as radioprotectors. Radioprotective efficacy of a triple intraperitoneal dose of GL2011 of 100 mg/kg body weight of Wistar rats, 30 min prior to and 3 and 6 h following irradiation (6.7 Gy) was evaluated. Four groups of animals were used, vehicle-treated non-irradiated (VN), GL2011-treated and irradiated (GI), GL2011-treated and non-irradiated (GN) and vehicle-treated and irradiated (VI) (n = 30 per group). The radioprotective efficacy of GL2011 was determined by measuring 28-day survival and intestinal crypt cell survival. Neuroprotection in terms of behaviour was evaluated using the behavioural observational battery, open field test and elevated plus maze paradigm. An RNA microarray was carried out in order to show differences at the RNA level between VI and VN groups. Brain protein changes were identified using a gel-based proteomics method and major brain receptor complex levels were determined by blue-native gels followed by immunoblotting. 28-Day survival rate in VI was 30 %, in GI survival was 93 %, survival of VN and GN was 100 %. Jejunal crypt cell survival was significantly enhanced in GI. Protein-level changes of peroxiredoxin-5, Mn-superoxide dismutase 2, voltage-dependent anion-selective channel protein 1, septin 5 and dopamine D2 receptor complex levels were paralleling radiation damage and protection. Taken together, the findings demonstrate that GL2011 improves survival rates and jejunal crypt survival, provides partial neuroprotection at the behavioural level and modulates proteins known to be involved in protection against oxidative stress-mediated cell damage.

Increased survival after irradiation followed by regeneration of bone marrow stromal cells with a novel thiol-based radioprotector.

AIM: To investigate the survival of laboratory rats after irradiation and to study the cellularity of their bone marrow and the multipotential mesenchymal stem cells (BM-MSCs) in groups treated with or without a new thiol-based radioprotector (GM2011). METHODS: Animals were irradiated by a Cobalt gamma source at 6.7 Gy. Treated animals were given i.p. GM2011 30 minutes before and 3 and 7 hours after irradiation. Controls consisted of sham irradiated animals without treatment and animals treated without irradiation. After 30 days post-irradiation, animals were sacrificed and bone marrow cells were prepared from isolated femurs. A colony forming unit-fibroblast (CFU-F) assay was performed to obtain the number of BM-MSCs. RESULTS: In the treated group, 87% of animals survived, compared to only 30% in the non-treated irradiated group. Irradiation induced significant changes in the bone marrow of the treated rats (total bone marrow cellularity was reduced by~60%--from 63 to 28 cells × 10(6)/femur and the frequency of the CFU-F per femur by~70% - from 357 to 97), however GL2011 almost completely prevented the suppressive effect observed on day 30 post-irradiation (71 cells × 10(6)/femur and 230 CFU-F/femur). CONCLUSION: Although the irradiation dosage was relatively high, GL2011 acted as a very effective new radioprotector. The recovery of the BN-MSCs and their counts support the effectiveness of the studied radioprotector.

Cranial irradiation modulates hypothalamic-pituitary-adrenal axis activity and corticosteroid receptor expression in the hippocampus of juvenile rat.

Glucocorticoids, essential for normal hypothalamic-pituitary-adrenal (HPA) axis activity, exert their action on the hippocampus through two types of corticosteroid receptors: the glucocorticoid receptor (GR) and the mineralocorticoid receptor (MR). Recent studies report that exposure of juvenile rats to cranial irradiation adversely affects HPA axis stability leading to its activation along with radiation- induced inflammation. This study was aimed to examine the acute effects of radiation on HPA axis activity and hippocampal corticosteroid receptor expression in 18-day-old rats. Since immobilization was part of irradiation procedure, both irradiated and sham-irradiated animals were exposed to this unavoidable stress. Our results demonstrate that the irradiated rats exhibited different pattern of corticosteroid receptor expression and hormone levels compared to respective controls. These differences included upregulation of GR protein in the hippocampus with a concomitant elevation of GR mRNA and an increase in circulating level of corticosterone. In addition, the expression of MR, both at the level of protein and gene expression, was not altered. Taken together, this study demonstrates that cranial irradiation in juvenile rats leads to enhanced HPA axis activity and increased relative GR/MR ratio in hippocampus. The present paper intends to show that neuroendocrine response of normal brain tissue to localized irradiation comprise both activation of HPA axis and altered corticosteroid receptor balance, probably as consequence of innate immune activation.

Spin-trapping of oxygen free radicals in chemical and biological systems: new traps, radicals and possibilities.

The choice of the spin-trap that is to be applied in any EPR study represents the crossroad between a comprehensive investigation and an "ordinary" quantification of production of radicals. So, the scope of our study was to compare the performance of different spin-traps for qualitative analysis of radical-generating systems, and their ability to recognize previously unnoticed radicals. In addition, we present a brief account of the difficulties involved in the detection of oxygen-centered radicals in chemical and biological systems accompanied by the rationale for using the EPR spin-trapping technique in quantitative studies of such reactive species. Certain technical aspects of EPR experiments related to efficient trapping of free radicals in biochemical systems are also discussed. As an example we present here results obtained using EPR spectroscopy and the spin-trap DEPMPO, which show that the Fenton reaction, as well as various biological systems generate a previously unappreciated hydrogen (*H) atom.