Radiation-mediated induction of apoptotic cell death in rat hippocampus

Ionizing radiation is commonly used in the treatment of brain tumors but it can impair cognitive functions, such as learning and memory. Since cognitive dysfunctions are predominantly result of cell death by apoptosis in hippocampal cells, in this study we analyzed acute effects of cranial gamma-irradiation (10 Gy) on expression of proapoptotic molecules (p53, Bax) and antiapoptotic molecule Bcl-2, as well as caspase-3 activation and cytochrome c redistribution in the hippocampus of young rats. The selected regimen of irradiation resembles the established animal model for childhood prophylactic cranial radiotherapy. Our results demonstrated that p53 mRNA expression was unchanged after irradiation, while induction of p53 protein was rapid. In parallel, Bax mRNA and protein levels were also increased following irradiation, whereas Bcl-2 expression was not changed during the examined post-irradiation period. These changes were accompanied with early hallmarks of apoptosis, such as increased cytochrome c release and stimulated activation of caspase-3. Overall, this study demonstrates that cranial irradiation is associated with the augmented apoptotic pathway in the rat hippocampus, which could be related to the cognitive decline observed in patients after prophylactic cranial radiotherapy, but also opens perspective in finding radioprotectors that can mitigate radiation injury of normal brain tissue.Jonizujuće zračenje se često koristi u tretmanu tumora mozga ali ono može da ošteti kognitivne funkcije, kao što su učenje i pamćenje. Pošto je smanjenje kognitivnih funkcija većinom rezultat ćelijske smrti putem apoptoze u hipokampalnim ćelijama u ovoj studiji su analizirani efekti kranijalnog gama-zračenja (10 Gy) na ekspresiju proapoptotskih (p53, Bax) i antiapoptotskih molekula (Bcl-2), kao i na aktivaciju kaspaze-3 i redistribuciju citohroma c u hipokampusu mladih pacova. Odabrani režim zračenja odgovara uspostavljenom životinjskom modelu za dečiju profilaktičku kranijalnu radioterapiju. Naši rezultati pokazuju da je ekspresija p53 i RNK nepromenjena nakon zračenja, dok je indukcija p53 proteina veoma brza. Istovremeno Bax iRNK i protein su povećani nakon zračenja, dok je ekspresija Bcl-2 nepromenjena tokom ispitivanog perioda. Ove promene su praćene ranim znacima apoptoze, kao što su povećano oslobađanje citohroma c i aktivacija kaspaze-3. Generalno, ova studija pokazuje da je kranijalno zračenje povezano sa stimulisanim apoptotskim putem u hipokampusu pacova, što se može povezati sa kognitivnim oštećenjima uočenih kod pacijenata nakon profilaktičke kranijalne radioterapije, ali takođe otvara perspektive u pronalaženju radioprotektora koji smanjuju oštećenje normalnog nervnog tkiva nakon zračenja.nul

Radiation-mediated induction of apoptotic cell death in rat hippocampus

Ionizing radiation is commonly used in the treatment of brain tumors but it can impair cognitive functions, such as learning and memory. Since cognitive dysfunctions are predominantly result of cell death by apoptosis in hippocampal cells, in this study we analyzed acute effects of cranial gamma-irradiation (10 Gy) on expression of proapoptotic molecules (p53, Bax) and antiapoptotic molecule Bcl-2, as well as caspase-3 activation and cytochrome c redistribution in the hippocampus of young rats. The selected regimen of irradiation resembles the established animal model for childhood prophylactic cranial radiotherapy. Our results demonstrated that p53 mRNA expression was unchanged after irradiation, while induction of p53 protein was rapid. In parallel, Bax mRNA and protein levels were also increased following irradiation, whereas Bcl-2 expression was not changed during the examined post-irradiation period. These changes were accompanied with early hallmarks of apoptosis, such as increased cytochrome c release and stimulated activation of caspase-3. Overall, this study demonstrates that cranial irradiation is associated with the augmented apoptotic pathway in the rat hippocampus, which could be related to the cognitive decline observed in patients after prophylactic cranial radiotherapy, but also opens perspective in finding radioprotectors that can mitigate radiation injury of normal brain tissue.Jonizujuće zračenje se često koristi u tretmanu tumora mozga ali ono može da ošteti kognitivne funkcije, kao što su učenje i pamćenje. Pošto je smanjenje kognitivnih funkcija većinom rezultat ćelijske smrti putem apoptoze u hipokampalnim ćelijama u ovoj studiji su analizirani efekti kranijalnog gama-zračenja (10 Gy) na ekspresiju proapoptotskih (p53, Bax) i antiapoptotskih molekula (Bcl-2), kao i na aktivaciju kaspaze-3 i redistribuciju citohroma c u hipokampusu mladih pacova. Odabrani režim zračenja odgovara uspostavljenom životinjskom modelu za dečiju profilaktičku kranijalnu radioterapiju. Naši rezultati pokazuju da je ekspresija p53 i RNK nepromenjena nakon zračenja, dok je indukcija p53 proteina veoma brza. Istovremeno Bax iRNK i protein su povećani nakon zračenja, dok je ekspresija Bcl-2 nepromenjena tokom ispitivanog perioda. Ove promene su praćene ranim znacima apoptoze, kao što su povećano oslobađanje citohroma c i aktivacija kaspaze-3. Generalno, ova studija pokazuje da je kranijalno zračenje povezano sa stimulisanim apoptotskim putem u hipokampusu pacova, što se može povezati sa kognitivnim oštećenjima uočenih kod pacijenata nakon profilaktičke kranijalne radioterapije, ali takođe otvara perspektive u pronalaženju radioprotektora koji smanjuju oštećenje normalnog nervnog tkiva nakon zračenja.nul

Radiation-induced hyposuppression of the hypothalamic-pituitary-adrenal axis is associated with alterations of hippocampal corticosteroid receptor expression

Therapeutic brain irradiation in children can cause a progressive decline in cognitive functions through a diminished capability to learn and memorize. Because of the known involvement of the hippocampus in memory consolidation, this study was aimed at examining the late effects of y radiation on hypothalamic-pituitary-adrenal (HPA) axis activity and hippocampal corticosteroid receptor expression in an animal model of cranial radiotherapy. In the late-response phase, the basal and stress-induced corticosterone levels were not affected by radiation, but the suppression of glucocorticoid negative feedback by dexamethasone was attenuated in irradiated rats. Western blot analyses showed that exposure to radiation led to a decrease of cytosolic glucocorticoid receptor (GR) levels and a concomitant elevation of mineralocorticoid receptor (MR). The results obtained were complemented by those of RT-PCR, since the ratio of GR/MR mRNA was also decreased after radiation exposure. Dexamethasone appeared to be much less effective in shifting GR to the nuclear compartment in irradiated rats than in sham-irradiated animals. However, the expression of chaperones that aid GR intracellular trafficking, Hsp90 and Hsp70, remained unaffected. In conclusion, our data suggest that the hallmark of the late response to y radiation is a hyposuppressive state of the HPA axis that is associated with a decrease in both the GR/MR ratio and the nuclear accumulation of dexamethasone-activated GR in the hippocampus. (c) 2008 by Radiation Research Society.nul

Radiation-induced hyposuppression of the hypothalamic-pituitary-adrenal axis is associated with alterations of hippocampal corticosteroid receptor expression

Therapeutic brain irradiation in children can cause a progressive decline in cognitive functions through a diminished capability to learn and memorize. Because of the known involvement of the hippocampus in memory consolidation, this study was aimed at examining the late effects of y radiation on hypothalamic-pituitary-adrenal (HPA) axis activity and hippocampal corticosteroid receptor expression in an animal model of cranial radiotherapy. In the late-response phase, the basal and stress-induced corticosterone levels were not affected by radiation, but the suppression of glucocorticoid negative feedback by dexamethasone was attenuated in irradiated rats. Western blot analyses showed that exposure to radiation led to a decrease of cytosolic glucocorticoid receptor (GR) levels and a concomitant elevation of mineralocorticoid receptor (MR). The results obtained were complemented by those of RT-PCR, since the ratio of GR/MR mRNA was also decreased after radiation exposure. Dexamethasone appeared to be much less effective in shifting GR to the nuclear compartment in irradiated rats than in sham-irradiated animals. However, the expression of chaperones that aid GR intracellular trafficking, Hsp90 and Hsp70, remained unaffected. In conclusion, our data suggest that the hallmark of the late response to y radiation is a hyposuppressive state of the HPA axis that is associated with a decrease in both the GR/MR ratio and the nuclear accumulation of dexamethasone-activated GR in the hippocampus. (c) 2008 by Radiation Research Society.nul

ATP and ADP hydrolysis in cell membranes from rat myometrium

Extracellular nucleotides affect female reproductive functions, fertilization, and pregnancy. The aim of this study was to investigate biochemical characteristics of ATP and ADP hydrolysis and identify E-NTPDases in myometrial cell membranes from Wistar albino rats. The apparent K (m) values were 506.4 +/- A 62.1 and 638.8 +/- A 31.3 mu M, with a calculated V (max) (app) of 3,973.0 +/- A 279.5 and 2,853.9 +/- A 79.8 nmol/min/mg for ATP and ADP, respectively. The enzyme activity described here has common properties characteristic for NTPDases: divalent cation dependence; alkaline pH optimum for both substrates, insensitivity to some of classical ATPase inhibitors (ouabain, oligomycine, theophylline, levamisole) and significant inhibition by suramine and high concentration of sodium azides (5 mM). According to similar apparent K-m values for both substrates, the ATP/ADP hydrolysis ratio, and Chevillard competition plot, NTPDase1 is dominant ATP/ADP hydrolyzing enzyme in myometrial cell membranes. RT-PCR analysis revealed expression of three members of ectonucleoside triphosphate diphosphohydrolase family (NTPDase 1, 2, and 8) in rat uterus. These findings may further elucidate the role of NTPDases and ATP in reproductive physiology.Serbian Ministry of Education and Science [173044, 41014

Low-Dose Dexamethasone Treatment Promotes the Pro-Survival Signalling Pathway in the Adult Rat Prefrontal Cortex

Synthetic glucocorticoid dexamethasone (DEX), a highly potent anti-inflammatory and immunosuppressive agent, is widely used in the treatment of brain cancer, as well as for inflammatory and autoimmune diseases. The present study aimed to determine whether low-dose subchronic DEX treatment (100g/kg for eight consecutive days) exerts long-term effects on apoptosis in the adult rat prefrontal cortex (PFC) by examining the expression of cell death-promoting molecules [poly(ADP-ribose) polymerase (PARP), p53, procaspase 3, cleaved caspase 3, Bax] and cell-survival molecules (AKT, Bcl-2). The results obtained revealed that body, thymus and adrenal gland weights, as well corticosterone levels, in the serum and PFC were reduced 1day after the last DEX injection. In the PFC, DEX caused activation of AKT, augmentation of pro-survival Bcl-2 protein and an enhanced Bcl-2/Bax protein ratio, as well Bcl-2 translocation to the mitochondria. An unaltered profile with respect to the protein expression of apoptotic molecules PARP, procaspase 3 and Bax was detected, whereas p53 protein was decreased. Reverse transcriptase -polymerase chain reaction analysis showed a decrease of p53 mRNA levels and no significant difference in Bcl-2 and Bax mRNA expression in DEX-treated rats. Finally, a DNA fragmentation assay and Fluoro-Jade staining demonstrated no considerable changes in apoptosis in the rat PFC. Our findings support the concept that low-dose DEX creates a hypocorticoid state in the brain and also indicate that subchronic DEX treatment activates the pro-survival signalling pathway but does not change apoptotic markers in the rat PFC. This mechanism might be relevant for the DEX-induced apoptosis resistance observed during and after chemotherapy of patients with brain tumours

Time Course of Cerebral Hypoperfusion-Induced Neurodegenerative Changes in the Cortex of Male and Female Rats

To study time-dependent and gender-specific intracellular and biochemical mechanisms that lead to neurodegeneration due to moderate but persistent reduction of cerebral blood flow, adult male and female Wistar rats were divided into two main groups controls that underwent sham operation and animals subjected to permanent bilateral occlusion of common carotid arteries. Animals were sacrificed 3, 7 or 90 days following the insult. Expression of several apoptotic proteins in synaptic fractions along with Fluoro-Jade B staining and DNA fragmentation assay were used to estimate the apoptotic processes and potential neurodegeneration in cerebral cortex. Data suggest a time-specific increase of Bax as well as time- and gender-associated down-regulation in protein expression of Bcl-2, up-regulation of procaspase 3, accompanied with increased cleavage of procaspase 3 and PARP in synaptic terminals. Furthermore, time- but not gender-specific neurodegeneration was observed. Our findings support the concept of time- and gender-associated response to permanent bilateral occlusion of common carotid arteries, which would enable better understanding of the mechanisms underlying cerebral hypoperfusion

ATP and ADP hydrolysis in cell membranes from rat myometrium

Extracellular nucleotides affect female reproductive functions, fertilization, and pregnancy. The aim of this study was to investigate biochemical characteristics of ATP and ADP hydrolysis and identify E-NTPDases in myometrial cell membranes from Wistar albino rats. The apparent K (m) values were 506.4 +/- A 62.1 and 638.8 +/- A 31.3 mu M, with a calculated V (max) (app) of 3,973.0 +/- A 279.5 and 2,853.9 +/- A 79.8 nmol/min/mg for ATP and ADP, respectively. The enzyme activity described here has common properties characteristic for NTPDases: divalent cation dependence; alkaline pH optimum for both substrates, insensitivity to some of classical ATPase inhibitors (ouabain, oligomycine, theophylline, levamisole) and significant inhibition by suramine and high concentration of sodium azides (5 mM). According to similar apparent K-m values for both substrates, the ATP/ADP hydrolysis ratio, and Chevillard competition plot, NTPDase1 is dominant ATP/ADP hydrolyzing enzyme in myometrial cell membranes. RT-PCR analysis revealed expression of three members of ectonucleoside triphosphate diphosphohydrolase family (NTPDase 1, 2, and 8) in rat uterus. These findings may further elucidate the role of NTPDases and ATP in reproductive physiology.Serbian Ministry of Education and Science [173044, 41014

Low-Dose Dexamethasone Treatment Promotes the Pro-Survival Signalling Pathway in the Adult Rat Prefrontal Cortex

Synthetic glucocorticoid dexamethasone (DEX), a highly potent anti-inflammatory and immunosuppressive agent, is widely used in the treatment of brain cancer, as well as for inflammatory and autoimmune diseases. The present study aimed to determine whether low-dose subchronic DEX treatment (100g/kg for eight consecutive days) exerts long-term effects on apoptosis in the adult rat prefrontal cortex (PFC) by examining the expression of cell death-promoting molecules [poly(ADP-ribose) polymerase (PARP), p53, procaspase 3, cleaved caspase 3, Bax] and cell-survival molecules (AKT, Bcl-2). The results obtained revealed that body, thymus and adrenal gland weights, as well corticosterone levels, in the serum and PFC were reduced 1day after the last DEX injection. In the PFC, DEX caused activation of AKT, augmentation of pro-survival Bcl-2 protein and an enhanced Bcl-2/Bax protein ratio, as well Bcl-2 translocation to the mitochondria. An unaltered profile with respect to the protein expression of apoptotic molecules PARP, procaspase 3 and Bax was detected, whereas p53 protein was decreased. Reverse transcriptase -polymerase chain reaction analysis showed a decrease of p53 mRNA levels and no significant difference in Bcl-2 and Bax mRNA expression in DEX-treated rats. Finally, a DNA fragmentation assay and Fluoro-Jade staining demonstrated no considerable changes in apoptosis in the rat PFC. Our findings support the concept that low-dose DEX creates a hypocorticoid state in the brain and also indicate that subchronic DEX treatment activates the pro-survival signalling pathway but does not change apoptotic markers in the rat PFC. This mechanism might be relevant for the DEX-induced apoptosis resistance observed during and after chemotherapy of patients with brain tumours.Ministry of Education, Science and Technological Development [173044, 41014

Time Course of Cerebral Hypoperfusion-Induced Neurodegenerative Changes in the Cortex of Male and Female Rats

To study time-dependent and gender-specific intracellular and biochemical mechanisms that lead to neurodegeneration due to moderate but persistent reduction of cerebral blood flow, adult male and female Wistar rats were divided into two main groups controls that underwent sham operation and animals subjected to permanent bilateral occlusion of common carotid arteries. Animals were sacrificed 3, 7 or 90 days following the insult. Expression of several apoptotic proteins in synaptic fractions along with Fluoro-Jade B staining and DNA fragmentation assay were used to estimate the apoptotic processes and potential neurodegeneration in cerebral cortex. Data suggest a time-specific increase of Bax as well as time- and gender-associated down-regulation in protein expression of Bcl-2, up-regulation of procaspase 3, accompanied with increased cleavage of procaspase 3 and PARP in synaptic terminals. Furthermore, time- but not gender-specific neurodegeneration was observed. Our findings support the concept of time- and gender-associated response to permanent bilateral occlusion of common carotid arteries, which would enable better understanding of the mechanisms underlying cerebral hypoperfusion