Mitochondrial Effects in the Liver of C57BL/6 Mice by Low Dose, High Energy, High Charge Irradiation

Galactic cosmic rays are primarily composed of protons (85%), helium (14%), and high charge/high energy ions (HZEs) such as ⁵⁶Fe, ²⁸Si, and ¹⁶O. HZE exposure is a major risk factor for astronauts during deep-space travel due to the possibility of HZE-induced cancer. A systems biology integrated omics approach encompassing transcriptomics, proteomics, lipidomics, and functional biochemical assays was used to identify microenvironmental changes induced by HZE exposure. C57BL/6 mice were placed into six treatment groups and received the following irradiation treatments: 600 MeV/n ⁵⁶Fe (0.2 Gy), 1 GeV/n ¹⁶O (0.2 Gy), 350 MeV/n ²⁸Si (0.2 Gy), ¹³⁷Cs (1.0 Gy) gamma rays, ¹³⁷Cs (3.0 Gy) gamma rays, and sham irradiation. Left liver lobes were collected at 30, 60, 120, 270, and 360 days post-irradiation. Analysis of transcriptomic and proteomic data utilizing ingenuity pathway analysis identified multiple pathways involved in mitochondrial function that were altered after HZE irradiation. Lipids also exhibited changes that were linked to mitochondrial function. Molecular assays for mitochondrial Complex I activity showed significant decreases in activity after HZE exposure. HZE-induced mitochondrial dysfunction suggests an increased risk for deep space travel. Microenvironmental and pathway analysis as performed in this research identified possible targets for countermeasures to mitigate risk.

[RADIOPROTECTIVE ACTIVITY OF POLYMETOXY-LATED FLAVONOIDS OF CITRUS EXTRACT]

The aim of the study was to establish the radioprotective activity of citrus polymetoxylated flavonoids extract (CPMFE) on the X-irradiated rats. The experiments were carried out on white Wistar rats. Animals were irradiated with X rays in doses of 5 Gy and 7 Gy. The control group consisted the sham-irradiated rats. Part of animals of each group were treated with intramusculary injections of CPMFE (dose 30 mg/kg) during 7 days; blood was taken from the tail vein (0.5 ml) for detection of lipoperoxides (LOO.) content. On the 3rd day after irradiation 3 animals from each group were sacrificed (under ether anesthesia) and blood samples were taken for the study of antioxidant status. The activity of antioxidant enzymes (catalase (CAT) and superoxidedismutase (SOD)) was determined by the spectrophotometric method; the content of LOO.in the blood was determined by electron paramagnetic resonance (EPR) mrthod. In group of irradiated rats a sharp dose-dependent inactivation of blood antioxidant enzymes (SOD, CAT) and intensification of the lipid peroxidation were detected. The direct and feedback mechanism in the regulation of CAT and SOD activity, ensuring the implementation of antioxidant protection in the body was revealed. Under irradiation with 7Gy rapid death of animals (on 3-d day after irradiation the mortality of animals was 70%, and on the 5th day all died) were detected. During irradiation with dose 5 Gy the survival of animals increased (on the 8-th day after irradiation - 50% survival rate). CPMFE in dose-dependent manner supported the reduce the intensity of lipid peroxidation processes - at relatively low doses of radiation (5Gy) during the first 3 days the content of LOO.in the blood decreased insignificantly compared with indices in untreated animals, whereas with an increase in the dose of irradiation (7Gy) a statistically significant antiradical effect of CPMFE (a statistically significant decrease in the LOO. content) was detected. Under the effect of CPMFE in the blood of rats irradiated with a dose of 5 Gy and 7 Gy, the activity of CAT and SOD, not statistically significant tends to increase (more significant with a dose of 7 Gy). CPMFE did not affect the cumulative survival of animals irradiated with a dose of 5 Gy, but reduced the mortality of rats by 20% (on the 3rd day of irradiation), and contributed to an increase in the life expectancy of animals by 2 times (up to 7 days) in the case of dose 7 Gr. Based on the analysis of the research results, it can be assumed that under conditions of radiation damage, exogenous antioxidants synergistically with a dose-dependently activated endogenous non-enzymatic antioxidant system of the body (especially at 7Gy) contribute to the effective suppression of chain reactions of peroxidation, reduction of mortality and increase in life expectancy of animals.

GUCY2C Signaling Opposes the Acute Radiation-Induced GI Syndrome

High doses of ionizing radiation induce acute damage to epithelial cells of the gastrointestinal (GI) tract, mediating toxicities restricting the therapeutic efficacy of radiation in cancer and morbidity and mortality in nuclear disasters. No approved prophylaxis or therapy exists for these toxicities, in part reflecting an incomplete understanding of mechanisms contributing to the acute radiation-induced GI syndrome (RIGS). Guanylate cyclase C (GUCY2C) and its hormones guanylin and uroguanylin have recently emerged as one paracrine axis defending intestinal mucosal integrity against mutational, chemical, and inflammatory injury. Here, we reveal a role for the GUCY2C paracrine axis in compensatory mechanisms opposing RIGS. Eliminating GUCY2C signaling exacerbated RIGS, amplifying radiation-induced mortality, weight loss, mucosal bleeding, debilitation, and intestinal dysfunction. Durable expression of GUCY2C, guanylin, and uroguanylin mRNA and protein by intestinal epithelial cells was preserved following lethal irradiation inducing RIGS. Oral delivery of the heat-stable enterotoxin (ST), an exogenous GUCY2C ligand, opposed RIGS, a process requiring p53 activation mediated by dissociation from MDM2. In turn, p53 activation prevented cell death by selectively limiting mitotic catastrophe, but not apoptosis. These studies reveal a role for the GUCY2C paracrine hormone axis as a novel compensatory mechanism opposing RIGS, and they highlight the potential of oral GUCY2C agonists (Linzess; Trulance) to prevent and treat RIGS in cancer therapy and nuclear disasters. Cancer Res; 77(18); 5095-106. ©2017 AACR.

Sam68 Is Required for DNA Damage Responses via Regulating Poly(ADP-ribosyl)ation

The rapid and robust synthesis of polymers of adenosine diphosphate (ADP)-ribose (PAR) chains, primarily catalyzed by poly(ADP-ribose) polymerase 1 (PARP1), is crucial for cellular responses to DNA damage. However, the precise mechanisms through which PARP1 is activated and PAR is robustly synthesized are not fully understood. Here, we identified Src-associated substrate during mitosis of 68 kDa (Sam68) as a novel signaling molecule in DNA damage responses (DDRs). In the absence of Sam68, DNA damage-triggered PAR production and PAR-dependent DNA repair signaling were dramatically diminished. With serial cellular and biochemical assays, we demonstrated that Sam68 is recruited to and significantly overlaps with PARP1 at DNA lesions and that the interaction between Sam68 and PARP1 is crucial for DNA damage-initiated and PARP1-conferred PAR production. Utilizing cell lines and knockout mice, we illustrated that Sam68-deleted cells and animals are hypersensitive to genotoxicity caused by DNA-damaging agents. Together, our findings suggest that Sam68 plays a crucial role in DDR via regulating DNA damage-initiated PAR production.

The RNA-binding protein Sam68 has unexpected function in the early signaling of DNA damage, and is critical for the activation and regulation of poly(ADP-ribose) polymerase 1 in response to DNA damage.

Maintaining genome integrity is crucial for all organisms, and failure to do so can lead to fatal diseases such as cancer. Exposure to challenging environments can induce DNA strand breaks or other lesions; thus, rapid and appropriate DNA damage responses (DDRs) need to be in place to detect and repair the damage. Cellular networks use a variety of signaling molecules and post-translational modifications that are crucial for the signaling of DNA breaks to repair machineries. Poly(adenosine diphosphate [ADP]-ribosyl)ation (PARylation) and activation of the enzyme poly(ADP-ribose) polymerase 1 (PARP1) is a post-translational modification that occurs within seconds upon DNA damage detection and triggers downstream DDR signaling; however, it remains obscure whether other molecules, beyond DNA strand breaks, stimulate or control PARP1 activity. We report here that a novel DDR signaling molecule, Src-associated substrate during mitosis of 68 kDa (Sam68), has a crucial function in governing the DNA damage-initiated PARP1 activation and polymers of ADP-ribose (PAR) production. We show that Sam68 is recruited to and significantly overlaps with PARP1 at DNA lesions and that the Sam68-PARP1 interaction is critical for DNA damage-initiated PARP1 activation and PAR production both in vitro and in vivo. Sam68-deleted cells and animals have a diminished PAR-dependent DNA repair signaling and are hypersensitive to genotoxicity caused by DNA-damaging agents. Hence, our data reveal an unexpected function for Sam68 in DNA damage-initiated early signaling and provide a novel mechanism on the activation and regulation of PARP1 in DDR.

Multiple parametric approaches to assess acute radiation lung injury of rats radiation lung injury of rats

The effect of whole body gamma irradiation (WBI) in single fraction was studied, as well as its influence on the secretion of various biochemical markers and cellular component that could be used as acute radiation lung injury marker. Sprague dawley rats were treated with WBI (60Co) of radiation dose from 1 Gy to 5 Gy (dose rate - 0.95 Gy/min). Bronchoalveolar lavage fluid was retrieved from all animals in control and radiation treated groups up to 72 h post radiation. Bronchoalveolar lavage fluid (BALF) was analyzed for lactate dehydrogenase (LDH ), acid phosphatase (AP ), alkaline phosphatase (ALP ), cell count and total protein. Intragroup and intergroup comparison of BALF parameters at different radiation doses showed significant difference. LDH was significantly increased as the dose increased from 1Gy to 5Gy (P = 0.00) after 2 h with effect size of difference (r > 0.3). ALP was significantly altered after 3Gy and 4Gy (P < 0.05). AP was significantly altered at 2Gy-5Gy (p < 0.05). Total protein level changed significantly from 1Gy to 5Gy (P < 0.00). Cellular content of BALF showed significant changes after radiation exposure. BALF parameters like LDH, AP, ALP, neutrophils, lymphocytes, total leukocyte count and total protein were sensitive to radiation exposure and their levels vary significantly up to 72 h after single whole body radiation exposure in Sprague dawley rats. It can be concluded that the biochemical indices in BALF have more wide application in evaluation of acute radiation induced lung injury.

Modulation of radiation injury response in retinal endothelial cells by quinic acid derivative KZ-41 involves p38 MAPK

Radiation-induced damage to the retina triggers leukostasis, retinal endothelial cell (REC) death, and subsequent hypoxia. Resultant ischemia leads to visual loss and compensatory retinal neovascularization (RNV). Using human RECs, we demonstrated that radiation induced leukocyte adhesion through mechanisms involving p38MAPK, p53, and ICAM-1 activation. Additional phenotypic changes included p38MAPK-dependent tyrosine phosphorylation of the focal adhesion scaffolding protein, paxillin (Tyr118). The quinic acid derivative KZ-41 lessened leukocyte adhesion and paxillin-dependent proliferation via inhibition of p38MAPK-p53-ICAM-1 signaling. Using the murine oxygen-induced retinopathy (OIR) model, we examined the effect of KZ-41 on pathologic RNV. Daily ocular application of a KZ-41-loaded nanoemulsion significantly reduced both the avascular and neovascular areas in harvested retinal flat mounts when compared to the contralateral eye receiving vehicle alone. Our data highlight the potential benefit of KZ-41 in reducing both the retinal ischemia and neovascularization provoked by genotoxic insults. Further research into how quinic acid derivatives target and mitigate inflammation is needed to fully appreciate their therapeutic potential for the treatment of inflammatory retinal vasculopathies.

Low-dose radiation modifies skin response to acute gamma-rays and protons

The goal of the present study was to obtain pilot data on the effects of protracted low-dose/low-dose-rate (LDR) γ-rays on the skin, both with and without acute gamma or proton irradiation (IR). Six groups of C57BL/6 mice were examined: a) 0 Gy control, b) LDR, c) Gamma, d) LDR+Gamma, e) Proton, and f) LDR+Proton. LDR radiation was delivered to a total dose of 0.01 Gy (0.03 cGy/h), whereas the Gamma and Proton groups received 2 Gy (0.9 Gy/min and 1.0 Gy/min, respectively). Assays were performed 56 days after exposure. Skin samples from all irradiated groups had activated caspase-3, indicative of apoptosis. The significant (p<0.05) increases in immunoreactivity in the Gamma and Proton groups were not present when LDR pre-exposure was included. However, the terminal deoxynucleotidyl transferase dUTP nick-end labeling assay for DNA fragmentation and histological examination of hematoxylin and eosin-stained sections revealed no significant differences among groups, regardless of radiation regimen. The data demonstrate that caspase-3 activation initially triggered by both forms of acute radiation was greatly elevated in the skin nearly two months after whole-body exposure. In addition, LDR γ-ray priming ameliorated this response.

Semiquinone derivative isolated from Bacillus sp. INM-1 protects cellular antioxidant enzymes from γ-radiation-induced renal toxicity

This study was focused to evaluate protection of indigenous antioxidant system of mice against gamma radiation-induced oxidative stress using a semiquinone (SQGD)-rich fraction isolated from Bacillus sp. INM-1. Male C57bl/6 mice were administered SQGD (50 mg/kgb.w.i.p.) 2 h before irradiation (10 Gy) and modulation in antioxidant enzymes activities was estimated at different time intervals and compared with irradiated mice which were not pretreated by SQGD. Compared to untreated controls, SQGD pretreatment significantly (p < 0.05) accelerates superoxide dismutase, catalase, GSH, and glutathione-S-transferase activities. Similarly, significant (p < 0.05) increase in the expression of superoxide dismutase, catalase, GSH, and glutathione-S-transferase was observed in irradiated mice pretreated by SQGD, compared to only irradiated groups. Total antioxidant status equivalent to trolox was estimated in renal tissue of the mice after SQGD administration. Significant ABTS(+) radical formation was observed in H2O2-treated kidney homogenate, due to oxidative stress in the tissue. However, significant decrease in the levels of ABTS(+) radical was observed in kidney homogenate of the mice pretreated with SQGD. Therefore, it can be concluded that SQGD neutralizes oxidative stress by induction of antioxidant enzymes activities and thus improved total antioxidant status in cellular system and hence contributes to radioprotection.

Radiation-induced c-Jun activation depends on MEK1-ERK1/2 signaling pathway in microglial cells

Radiation-induced normal brain injury is associated with acute and/or chronic inflammatory responses, and has been a major concern in radiotherapy. Recent studies suggest that microglial activation is a potential contributor to chronic inflammatory responses following irradiation; however, the molecular mechanism underlying the response of microglia to radiation is poorly understood. c-Jun, a component of AP-1 transcription factors, potentially regulates neural cell death and neuroinflammation. We observed a rapid increase in phosphorylation of N-terminal c-Jun (on serine 63 and 73) and MAPK kinases ERK1/2, but not JNKs, in irradiated murine microglial BV2 cells. Radiation-induced c-Jun phosphorylation is dependent on the canonical MEK-ERK signaling pathway and required for both ERK1 and ERK2 function. ERK1/2 directly interact with c-Jun in vitro and in cells; meanwhile, the JNK binding domain on c-Jun is not required for its interaction with ERK kinases. Radiation-induced reactive oxygen species (ROS) potentially contribute to c-Jun phosphorylation through activating the ERK pathway. Radiation stimulates c-Jun transcriptional activity and upregulates c-Jun-regulated proinflammatory genes, such as tumor necrosis factor-α, interleukin-1β, and cyclooxygenase-2. Pharmacologic blockade of the ERK signaling pathway interferes with c-Jun activity and inhibits radiation-stimulated expression of c-Jun target genes. Overall, our study reveals that the MEK-ERK1/2 signaling pathway, but not the JNK pathway, contributes to the c-Jun-dependent microglial inflammatory response following irradiation.

Effect of irradiation on microvascular endothelial cells of parotid glands in the miniature pig

PURPOSE

To evaluate the effect of irradiation on microvascular endothelial cells in miniature pig parotid glands.

METHODS AND MATERIALS

A single 25-Gy dose of irradiation (IR) was delivered to parotid glands of 6 miniature pigs. Three other animals served as non-IR controls. Local blood flow rate in glands was measured pre- and post-IR with an ultrasonic Doppler analyzer. Samples of parotid gland tissue were taken at 4 h, 24 h, 1 week, and 2 weeks after IR for microvascular density (MVD) analysis and sphingomyelinase (SMase) assay. Histopathology and immunohistochemical staining (anti-CD31 and anti-AQP1) were used to assess morphological changes. MVD was determined by calculating the number of CD31- or AQP1-stained cells per field. A terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) apoptosis assay was used to detect apoptotic cells. The activity of acid and neutral Mg(2+)-dependent SMase (ASMase and NSMase, respectively) was also assayed.

RESULTS

Local parotid gland blood flow rate decreased rapidly at 4 h post-IR and remained below control levels throughout the 14-day observation period. Parotid MVD also declined from 4 to 24 hours and remained below control levels thereafter. The activity levels of ASMase and NSMase in parotid glands increased rapidly from 4 to 24 h post-IR and then declined gradually. The frequency of detecting apoptotic nuclei in the glands followed similar kinetics.

CONCLUSIONS

Single-dose IR led to a significant reduction of MVD and local blood flow rate, indicating marked damage to microvascular endothelial cells in miniature pig parotid glands. The significant and rapid increases of ASMase and NSMase activity levels may be important in this IR-induced damage.

[Changes of caspase-9 in rat retina caused by Nd:YAG laser injury]

OBJECTIVE

To investigate the changes of caspase-9 in the retina of Long Evans rats caused by Nd: YAG laser injury.

METHODS

A model of retina injury in rats caused by Nd:YAG laser was established. The activity and the expression of mRNA and protein of caspase-9 were detected at Oh, 3h, 6h, 24h, 3d and 7d after laser irradiation. RESULTS; No conspicuous change of caspase-9 mRNA in retina was observed just after laser irradiation, but the activity of caspase-9 and the expression of caspase-9 mRNA and protein increased significantly at 6h and 12h after irradiation (P < 0.05).

CONCLUSION

Caspase-9 in the retina of LE rat was activated by Nd:YAG laser irradiation.

[Effect of radiation on the activity and expression of Ca(2+)-Mg(2+)-ATPase in rat masseter muscle]

OBJECTIVE

To investigate the activity and expression of Ca(2+)-Mg(2+)-ATPase in irradiated rat masseter muscle.

METHODS

The rats were irradiated locally with a single dose of 20 Gy X-ray. The activities of Ca(2+)-Mg(2+)-ATPase were measured with colorimetric method. The protein expression of Ca(2+)-Mg(2+)-ATPase was determined by Western blotting and immunohistochemistry.

RESULTS

The activities of Ca(2+)-Mg(2+)-ATPase in masseter muscle decreased by approximately 20% and 40% in irradiated rats on days 3 and 30 postirradiation. There was significant difference in the expression of Ca(2+)-Mg(2+)-ATPase protein between irradiated and nonirradiated rats on day 30 postirradiation. Ca(2+)-Mg(2+)-ATPase protein was found in the cytoplasm of masseter muscle.

CONCLUSIONS

The decrease of ATPase activity played an important role in the cause of radiation-induced skeletal muscle injury, while there was no significant reduction in the expression of Ca(2+)-Mg(2+)-ATPase protein in irradiated rat masseter muscle.

[Mechanisms of detoxification efficiency of new enterosorbent in combined radiation pathology]

Studies with rats and white mice demonstrated that combined radiation injury (CRI) comes to reducing protease activity in small intestine tissues. In liver tissue the activity of cathepsine D increased under the action of new enterosorbent--clay of Kaluga deposit ("CKD"). In blood serum of the damaged animals the amount of histogenic toxins--middle mass molecules (MMM) and oligopeptides decreased after "CKD" administration. An effective fixation and withdrawal of bacteria from the bowl of the affected animals took place. The survival level of mice in 30 days after CRI comprised 20% as compared with 60% in the case of "CK D" administration. It is supposed that the increase of survival after "CKD" administration is the result of enhancement of macrophage detoxification in liver, determined on the increase of activity of cathepsine D (lysosomal protease), elimination of MMM and normalization of gut microflora.

Matrix-Metallo-Proteinases and their tissue inhibitors in radiation-induced lung injury

PURPOSE

Remodeling of extracellular matrix (ECM) after lung damage depends on collagen degrading Matrix-Metallo-Proteinases (MMP) and their endogenous inhibitors (Tissue-Inhibitors of Metallo-Proteinases, TIMP). Transforming growth factor (TGF)-beta1 has been implicated in the pathogenesis of radiation-induced lung fibrosis upon its effects on fibroblast proliferation and collagen synthesis. Lung cancer patients have often elevated TGF-beta1 plasma levels as a result of increased TGF-beta1 expression in their tumours. On this background, we investigated the effect of irradiation on the MMP/TIMP system in the lung tissue of normal and transgenic TGF-beta1 mice, in which TGF-beta1 is overexpressed in the liver resulting in high TGF-beta1 plasma levels.

MATERIAL AND METHODS

Transgenic (TG) and wild-type (WT) mice underwent thoracic irradiation with 12 Gy or sham-irradiation. For each study group (TG 12 Gy; TG 0 Gy; WT 12 Gy; WT 0 Gy) 8 mice were sacrificed at 4 and 8 weeks after (sham-) irradiation. The TGF-beta1, TIMP-1/-2/-3 expression in the lung tissue was quantified by Western blot; the MMP-2 and MMP-9 activity was analysed by zymography. The cellular origin of the MMP and TIMP was localised by immunohistochemistry.

RESULTS

Irradiation had no influence on the TIMP-1/-2/-3, but increased significantly the MMP-2 /-9 expression. In the lung tissue of TG mice the TIMP-1/-2/-3 expression was elevated, the MMP-9 activity was decreased. The immunhistochemical study showed that parenchymal and inflammatory cells express these MMP/TIMP.

CONCLUSION

Our results provide evidence that the overexpression of MMP-2 and MMP-9 is involved in the inflammatory response of radiation-induced lung injury. MMP-2 and MMP-9 are known to degrade collagen IV of basement membranes, therefore affecting the structural integrity of lung tissue. In contrast, in lung tissue of TG mice the TIMP-1/-2/-3 expression was up-regulated and the MMP-9 activity was diminished, thereby decreasing possibly the ECM degradation leading to lung fibrosis.

Free radical scavenging and radioprotective activity of dehydrozingerone against whole body gamma irradiation in Swiss albino mice

Dehydrozingerone (DZ) was explored for in vitro-in vivo antioxidant potential and in vivo radioprotective activity against whole body gamma irradiation in Swiss albino mice. DZ scavenged the ABTS (2, 2'-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) and DPPH (1, 1-dipehnyl-2-picrylhydrazyl) free radicals at room temp. DZ reduced Fe (III) to Fe (II) at pH 7.4 and scavenged the NADH/phenazine methosulfate generated superoxide radical in cell free system. DZ also scavenged the nitric oxide radical generated by sodium nitroprusside. To evaluate the radioprotective activity, mice were exposed to whole body gamma irradiation 30 min after the drug treatment at a dose rate of 1.66 Gy/min. Pretreatment with DZ 75, 100 and 125 mg/kg, i.p. reduced the radiation induced mortality and increased the mean survival times (MSTs). An i.p. dose of DZ 100 mg/kg was found the most effective dose in preventing radiation sickness and increasing the MST. Pretreatment DZ100 mg/kg maintained the spleen index (spleen weight/body weight x 100) and stimulates the endogenous spleen colony forming units (CFU). Pretreatment with DZ100 mg/kg maintained the villus height close to normal, prevents mucosal erosion and basement membrane damage in irradiated mice jejunum. However, no significant reductions in dead, inflammatory and mitotic cells were observed in DZ pretreated mice, but there was an increased in crypt cells proliferation and regeneration. Pretreatment with DZ100 mg/kg significantly elevated the endogenous antioxidant enzymes (GSH, GST and SOD) in mice at 2, 4 and 8 h post sham irradiation. Radiation induced fall in endogenous antioxidant enzymes was significantly prevented by DZ pretreatment. Pretreatment with DZ 75 and 100 mg/kg reduced the radiation induced micronucleated polychromatic erythrocytes (MPCE) and normochromatic erythrocytes (MNCE) in mice bone marrow. DZ also maintained the polychromatic erythrocytes (PCE) and normochromatic erythrocytes (NCE) ratio (P/N ratio) in irradiated mice. Dose modifying factor (DMF) was calculated by using the graded radiation dose (8.0, 9.0, 9.5 and 10 Gy). DZ 100 mg/kg elevated radiation LD(50) from 9.1 to 10.0 Gy, indicating the DMF of 1.09.

Caspase-Dependent Apoptosis in Light-Induced Retinal Degeneration

PURPOSE

To study the apoptotic mechanism involved in our model of light-induced retinal degeneration.

METHODS

Rats were injected intravitreally with PBS, 2% dimethyl sulfoxide (DMSO), caspase inhibitor Z-VAD-FMK (1.06 mM), Z-YVAD-FMK (0.16 mM), or Z-DEVD-FMK (2 mM) before they were placed in constant light (3400 lux) for 24 hours. Additional controls included rats that were uninjected or were punctured with a dry needle. Electroretinograms were recorded before injection and 1 day after the cessation of exposure to constant light. A group of rats was killed for apoptotic cell detection in the outer nuclear layer. Fifteen days later, the remaining rats were killed for histology, and the outer nuclear layer (ONL) thickness was measured. Caspase-1, caspase-3, and calpain activities were measured before and 1 day after exposure to the damaging light.

RESULTS

ZVAD, YVAD, and DEVD inhibited caspase-1 and -3 activities, but not calpain activity, from the beginning and up to 1 day after light exposure. In untreated, dry needle-punctured, PBS, DMSO, and YVAD groups, light exposure significantly reduced retinal function and ONL thickness and increased by 51-fold the number of apoptotic cells. ZVAD and DEVD preserved retinal function to 86% and 78%, respectively, and reduced by three times the number of apoptotic photoreceptors. ONL thickness was more preserved in ZVAD (to 72%) than in DEVD (to 56%).

CONCLUSIONS

In the authors' model of retinal degeneration, photoreceptor cells die through a caspase-dependent mechanism. However, the molecular events involved during and after light exposure seemed to implicate different proteases.

A novel isoform of acetylcholinesterase exacerbates photoreceptors death after photic stress

PURPOSE

To study the involvement of stress-induced acetylcholinesterase (AChE) expression in light-induced retinal damage in albino rats.

METHODS

Adult albino rats were exposed for 24 hours to bright, damaging light. AChE expression was monitored by in situ hybridization, by histochemistry for AChE activity, and by immunocytochemistry. An orphan antisense agent (Monarsen; Ester Neurosciences, Ltd., Herzlia Pituach, Israel) was administered intraperitoneally to minimize light-induced AChE expression. The electroretinogram (ERG) was recorded to assess retinal function.

RESULTS

Twenty-four-hour exposure to bright light caused severe reduction in the ERG responses and augmented expression of mRNA for the "read-through" variant of AChE (AChE-R) in photoreceptor inner segments (IS), bipolar cells, and ganglion cells. AChE activity increased in IS. The expressed AChE protein was a novel variant, characterized by an extended N terminus (N-AChE). Systemic administration of the orphan antisense agent, Monarsen, reduced the photic induction of mRNA for AChE-R, and of the N-AChE protein. Rats exposed to bright, damaging light and treated daily with Monarsen exhibited larger ERG responses, relatively thicker outer nuclear layer (ONL), and more ONL nuclei than did rats exposed to the same damaging light but treated daily with saline.

CONCLUSIONS

The findings indicate that the photic-induced novel variant of AChE (N-AChE-R) may be causally involved with retinal light damage and suggest the use of RNA targeting for limiting such damage.

The effect of L-carnitine in the prevention of ionizing radiation-induced cataracts: a rat model

BACKGROUND

The objective was to determine the antioxidant role of L-carnitine (LC) against ionizing radiation-induced cataracts in lens after total cranium irradiation of rats with a single dose of 5 Gy.

METHODS

Sprague-Dawley rats were used in this experiment and were divided into three groups. Group 1 did not receive LC or irradiation (control group). Group 2 received a 5 Gy gamma irradiation as a single dose to the total cranium (RT group). Group 3 received total cranium irradiation plus 100 mg/kg body weight/day LC (RT+LC group). The rats were irradiated using a cobalt-60 teletherapy unit. At the end of the 10th day, the rats were sacrificed and their eyes were enucleated. The lenticular activity of the antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) were measured. Furthermore, the lenticular content of an indicator of lipid peroxidation, malondialdehyde (MDA), was measured.

RESULTS

Irradiation significantly increased the MDA level as an end product of lipid peroxidation. Irradiation also significantly decreased SOD activity and increased GSH-Px activity, indicating the generation of oxidative stress and an early protective response to oxidative damage. Irradiation with 5 Gy to the total cranium as a single fraction formed cataracts in the rat lenses. Cataract development was detectable in 9 rats in the RT group, and in only 4 rats in the RT+LC group 10 days after irradiation. LC administration plus irradiation significantly decreased the MDA level and increased the activity of SOD and GSH-Px enzymes, which might indicate the protection of the lenses from gamma radiation-induced cataracts.

CONCLUSIONS

L-carnitine may protect against the damage produced by gamma radiation by increasing the activity of the SOD enzyme and by scavenging free radicals generated by ionizing radiation. As a result of this process, MDA as an indicator of lipid peroxidation may decrease.

Retinal Light Damage: Structural and Functional Effects of the Antioxidant Glutathione Peroxidase-1

PURPOSE

The role of the antioxidant enzyme glutathione peroxidase-1 (GPx1) in protecting the retina against photo-oxidative damage was investigated in GPx1-deficient and wild-type mice.

METHOD

Albino GPx1-deficient and age-matched wild-type mice were examined. Baseline electroretinograms (ERGs) were recorded. Thereafter, mice were exposed to intense light for 12 hours. After a 24-hour recovery in darkness, post-light-insult ERGs were recorded and compared with baseline. Structural effects of light insult were evaluated by retinal histology. Antioxidant expression was investigated by quantitative reverse transcription-PCR (qRT-PCR).

RESULTS

Light insult significantly affected ERG responses, with reduced a- and b-wave amplitudes. Structurally, photoreceptor layers were predominantly affected. As expected, GPx1 expression was negligible in GPx1-deficient mice but was upregulated in wild-type mice in response to light insult. Similarly, hemeoxygenase-1 and thioredoxin-1 expression increased significantly in wild-type retinas after light exposure. Catalase, GPx isoforms (GPx2 to -4), peroxiredoxin-6, glutaredoxin-1, and thioredoxin-2 expression was unaffected by GPx1 deficiency and light insult, whereas significant increases in glutaredoxin-2 occurred in non-light-exposed (baseline) GPx1-deficient retinas. Compared with baseline wild-type retinas, lipid peroxidation (TBARS assay), an indicator of oxidative stress, was elevated in baseline GPx1-deficient retinas. Unexpectedly, the light insult induced diminution of retinal function, in terms of ERG amplitude, and structural damage was significantly greater in wild-type than in with GPx1-deficient retinas.

CONCLUSIONS

The data showing increased oxidative damage in baseline GPx-deficient retina give rise to the hypothesis that increased oxidative stress provides a "preconditioning" environment in which protective mechanisms paradoxically render GPx1-deficient retinas less vulnerable to light-induced oxidative damage. This study identified glutaredoxin-2 as a potential candidate.

TGF-beta1 transgenic mouse model of thoracic irradiation: Modulation of MMP-2 and MMP-9 in the lung tissue

To investigate the effects of TGF-beta1 on the two gelatinases (MMP-2 and MMP-9), and their roles in lung remodeling after irradiation-induced lung injury. Expressions of TGF-beta1 were measured with western blot, and expressions of MMP-2 and MMP-9 were analyzed with zymography in a -TGF-beta1 transgenic mouse model after thoracic irradiation with 12 Gy. We found expressions of TGF-beta1 in the lung from the transgenic mice were three folds as compared to those from control mice. With densitometrical analysis, we found a significant decrease in MMP-9 activity in lung homogenates from the transgenic mice as compared with those from non-transgenic control mice 8 weeks after sham-irradiation (relative MMP-9 activity: C: 1.000 0.1091; TG: 0.4772 +/- 0.470 (n = 8, P < 0.05). But MMP-2 was constitutively expressed in the lung homogenates from the transgenic mice as compared to those from control mice 8 weeks after sham-irradiation (relative MMP-2 activity 8 weeks after sham-irradiation: C: 1.000 +/- 0.1556, TG: 1.0075 +/- 0.1472). Eight weeks after thoracic irradiation with 12 Gy, we observed a significant increase of MMP-2 and MMP-9 activity in lung homogenates from both transgenic and normal mice. In TGF-beta1 transgenic mice relative MMP-9 activity was increased to 1.5321 +/- 0.2217 folds 8 weeks after thoracic irradiation with 12 Gy as compared to those after sham-irradiation (1.000 +/- 0.2153), and relative MMP-2 activity was increased to 1.7142 +/- 0.4231 folds. Our results show that TGF-beta1 itself down-regulates activity of MMP-9, thereby decreases ECM degradation in lungs of TGF-beta1 transgenic mice. Also we find that ionizing irradiation upregulates both MMP-2 and MMP-9 activity. Over-expressions of MMP-9 and MMP-2 after lung irradiation are involved in the inflammatory response associated with radiation-induced lung injury, and maybe further in radiation-induced lung fibrosis.

Light-Induced photoreceptor degeneration in the mouse involves activation of the small GTPase Rac1

PURPOSE

Rho GTPases play a central role in actin-based cytoskeleton reorganization, and they participate in signaling pathways that regulate gene transcription, cell cycle entry, and cell survival. This study verifies the role of Rac1 during light-induced retinal degeneration.

METHODS

BALB/c mice were exposed to degenerative light stimulus, and their eyes were enucleated immediately or after the mice were kept in the dark for 6, 24, and 48 hours. Retinas were fixed and processed for immunohistochemical analysis. The distribution of Rac1 and its effectors-p21-activated kinases (PAKs) 1, 2, and 3-was studied by immunohistochemistry, whereas the expression of PAKs 3, 4, and 5 mRNA was analyzed by real-time PCR. Rac1 activity was measured using a pull-down assay.

RESULTS

In control retinas, Rac1 was mostly observed in photoreceptors, plexiform layers, and Müller glial cells. In light-damaged retinas, some TUNEL-positive photoreceptors upregulated Rac1 expression. Conversely, most of the Rac1-positive cells were TUNEL-positive, mainly in early stages of retinal degeneration. The increase in Rac1 expression was preceded by enhanced Rac1 activity, detectable at the end of the light stimulus and still present 48 hours later. The distribution patterns of PAK1, PAK2, and PAK3 did not change in light-damaged retinas. However, there was a marked increase in PAK3 and PAK4 gene expression, whereas that of PAK5 mRNA remained the same.

CONCLUSIONS

Rac1 may play a role in the apoptosis of light-damaged photoreceptors. The increased expression of PAK4 after light stimulus possibly functions as a protective mechanism against apoptosis.

Altered nitric oxide synthase and PKC activities in cerebellum of gamma-irradiated neonatal rats

In this study, we show that one single dose of gamma-irradiation at birth induces an inhibition of the cerebellar calcium dependent nitric oxide synthase (NOS) activity, probably correlated to the motor abnormalities and the disarrangement in the cerebellar cytoarchitecture observed in adult rats. This decrease in calcium dependent NOS activity could be associated with an increased protein kinase C (PKC) activity. PKC inhibition partially restores calcium dependent NOS activity, indicating that PKC activity could be negatively modulating the catalytic activity of calcium dependent NOS. These findings suggest that a decrease in nitric oxide (NO) production and the related increase in PKC activity could be intracellular events that participate in the onset of motor and cerebellar abnormalities induced by postnatal gamma-irradiation at early stages of life.

Minocycline partially inhibits caspase-3 activation and photoreceptor degeneration after photic injury

PURPOSE

To evaluate the possible role of caspase-3 in retinal photic injury, and to investigate whether minocycline can ameliorate light-induced photoreceptor degeneration.

METHODS

Retinal photic injury was induced in rats by exposure to intense light. Expression of caspase-3 was studied using Western blot analysis, immunohistochemical staining and enzyme activity assay. Apoptotic photoreceptor cells were detected by the TdT-dUTP terminal nick-end labeling (TUNEL) method. Minocycline (15, 30 or 45 mg/kg) was administered before or after photic injury in rats randomly assigned to pretreatment and posttreatment groups. Minocycline and vehicle-treated retinas subjected to photic injury were compared with respect to Western blotting, enzyme activity assay, quantitative counts of TUNEL stains, morphometry of the outer nuclear layer (ONL) thickness and histopathological examination.

RESULTS

After light exposure, active caspase-3 and poly-adenosine diphosphate-ribose-polymerase were upregulated in the retinas and increased caspase-3 immunoreactivity was observed in the ONL. Caspase-3 enzyme activity increased in the retinas that underwent photic injury, and this increase was significantly reduced in minocycline pretreated (30 and 45 mg/kg) and posttreated (45 mg/kg) groups. Intraperitoneal administration of minocycline before or after photic injury in rats also resulted in less TUNEL-positive photoreceptors, as assessed by the quantitative TUNEL counts. The degree of retinal degeneration, measured by the ONL thickness 14 days after photic injury, was significantly improved in minocycline pretreatment (45 mg/kg) rats.

CONCLUSIONS

We demonstrate that increased caspase-3 activities localize specifically within the ONL after photic injury, and that minocycline partially inhibits caspase-3 activation and photoreceptor degeneration in this animal model.

[The estimation of the nitric oxide role in the aggravation of combined radiation-thermal injuries]

The influence of specific inhibitor of inducible NO synthase S-ethil-isothiourea (as "Difetur" preparation) on liver NO production level, and 30-days survival, mean survival time and probability of mortality within animals under combined radiation/thermal injury (CRTI) were evaluated. Experiments were carrying out on mice (whole body gamma-irradiation at the dose of 7 Gy + 10% body surface full-thickness thermal burn). It was shown, that CRTI induce 2-fold statistical significant increase of NO production in liver of experimental animals. Mice pretreatment with Difetur preparation lead to practically full inhibition of NO production. In the group of animals, with Difetur administration during first two days after CRTI 60% mice survived as compared 15% survive in control group. In pair with data on probability of mortality it was suggested that growth of NO production in the early period of CRTI increase sensitivity of animals to pathological processes leading to death on 10-12 days.

Ciliary neurotrophic factor protects rat retina cells in vitro and in vivo via PI3 kinase

PURPOSE

Neurotrophic factors and neurotrophins are well-known to have neuroprotective efficacy against retinal injury. The aim of this experiment is to investigate the signal transduction pathway of ciliary neurotrophic factor (CNTF) on the upregulation of viability of retinal primary culture and retinal protection against constant light damage in vivo. CNTF is known to enhance the viability of retinal culture and provide protection under constant light exposure conditions, but little is known about how the signal transduction pathways of CNTF affect retina function.

METHODS

Primary retinal cultures were prepared from 7-day-old Wistar rats. Brain-derived neurotrophic factor (BDNF) (0.1, 1, 10 ng/ml), CNTF (0.1, 1, 10 ng/ml), PD98059 (10, 100, 1000 nM), or LY294002 (10, 100, 1000 nM) was added to these cultures at the time of cell preparation. After 3 days, the percentage of cells surviving was assessed using alamarBlue. For the in vivo experiment, inhibitors for the MAPKK (PD98059, 10 microg/eye) or PI3K (LY294002, 10 microg/eye) pathways were injected into the vitreous together with CNTF (1 microg/eye) 2 days before constant light exposure. Electroretinogram (ERG) analysis was performed to investigate which pathway was used by CNTF.

RESULTS

CNTF at 1, 10, or 100 ng/ml enhanced cell viability in retinal cultures. The cell-survival activity of CNTF was blocked by 10 ng/ml LY294002 (Dunnet's test, p < 0.05). In vivo, the neuroprotective activity of CNTF in constant-light conditions was attenuated by 10 microg/eye LY294002 (Dunnet's test, p < 0.05).

CONCLUSIONS

These data suggest that CNTF promotes cell survival via the PI3K signaling pathway in vitro and in vivo.

The protective effect of alpha-lipoic acid against oxidative damage in rabbit conjunctiva and cornea exposed to ultraviolet radiation

PURPOSE

The purpose of this study was to determine the protective effect of alpha-lipoic acid against oxidative damage in rabbit conjunctiva and cornea exposed to ultraviolet radiation.

METHODS

20 rabbits weighing 2,500- 3,000 g were used, and we divided them into 4 groups with 5 randomly selected rabbits. The rabbits were exposed to 2 J/cm(2)/h of ultraviolet A radiation (UVA) in the range of 320-405 nm for 12 h per day within 90 days. The control group did not undergo any procedure, the UVA group was only exposed to UVA radiation. The PUVA group was treated with 8-methoxypsoralen and UVA. The alpha-lipoic acid group was administered 8-methoxypsoralen + UVA + alpha-lipoic acid. At the end of 90 days, the rabbits were killed by decapitation, and the eyes were enucleated. Both eyes of each rabbit were used for biochemical evaluation. Conjunctival and corneal free malondialdehyde (MDA), glutathione peroxidase (GSH-PX) and superoxide dismutase (SOD) levels were compared among the groups.

RESULTS

Conjunctival free MDA levels were lower in the alpha-lipoic acid group compared with the UVA and PUVA groups (p < 0.05, p < 0.001, respectively). Both conjunctival SOD levels (p < 0.05, p < 0.01, respectively) and conjunctival GSH-PX levels (p < 0.01, p < 0.001, respectively) were higher in the alpha-lipoic acid group compared with other groups. Corneal free MDA levels were lower in the alpha-lipoic acid group compared with the UVA and PUVA groups (p < 0.01, p < 0.001, respectively). Both corneal SOD levels (p < 0.01, p < 0.01, respectively) and corneal GSH-PX levels (p < 0.01, p < 0.01, respectively) were higher in the alpha-lipoic acid group compared with the other groups.

CONCLUSION

alpha-Lipoic acid which is considered as potent antioxidant protects the eye from the damaging effect of ultraviolet exposure.

Effects of oral Ginkgo biloba supplementation on cataract formation and oxidative stress occurring in lenses of rats exposed to total cranium radiotherapy

PURPOSE

To determine the antioxidant role of Ginkgo biloba (GB) in preventing radiation-induced cataracts in the lens after total-cranium irradiation of rats with a single radiation dose of 5 Gy.

METHODS

Sprague-Dawley rats were randomly divided into three groups. Group 1 received neither GB nor irradiation (control group). Group 2 was exposed to total-cranium irradiation of 5 Gy in a single dose [radiation therapy (RT) Group], and group 3 received total cranium irradiation from a cobalt-60 teletherapy unit, plus 40 mg/kg per day GB (RT+GB group). At the end of the tenth day, the rats were killed and their eyes were enucleated to measure the antioxidant enzymes, the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), and the lipid peroxidation level [malondialdehyde (MDA)].

RESULTS

Irradiation significantly increased both the MDA level and the activity of GSH-Px, and significantly decreased the activity of SOD in the rat lenses. GB supplementation significantly increased the activities of SOD and GSH-Px enzymes and significantly decreased the MDA level. Total cranium irradiation of 5 Gy in a single dose promoted cataract formation, and GB supplementation protected the lenses from radiation-induced cataracts.

CONCLUSIONS

We suggest that Ginkgo biloba is an antioxidant that protects the rat lens from radiation-induced cataracts.

Protective role of intramuscularly administered vitamin E on the levels of lipid peroxidation and the activities of antioxidant enzymes in the lens of rats made cataractous with gamma-irradiation

PURPOSE

To determine the antioxidant role of vitamin E (VE) (10 mg/kg/day) against radiation-induced cataract in lens after total-cranium irradiation of rats with a single dose of 5 Gy.

METHODS

Sprague-Dawley rats were divided into three groups. Group 1 did not receive VE or irradiation but received both 0.1 ml physiologic saline intraperitoneally and sham irradiation (control group). Group 2 received to total cranium 5 Gy of gamma irradiation as a single dose (RT group) plus 0.1 ml physiologic saline intraperitoneally. Group 3 received irradiation to total cranium plus 10 mg/kg/day VE (RT+VE group). The rats were irradiated using a cobalt-60 teletherapy unit. Chylack's cataract classification (1) was used in this study. At the end of 10 days, the rats were killed and their eyes were enucleated to measure the antioxidant enzymes (the activity of superoxide dismutase [SOD], glutathione peroxidase [GSH-Px]) and lipid peroxidation level (malondialdehyde [MDA]).

RESULTS

While grade 1 cataract development was detectable in seven rats in the RT group, it was detectable only in two rats in the RT+VE group, whereas none of the rats in the control group exhibited any biomicroscopic change in their lenses. MDA level and GSH-Px activity in the rat lens in the RT group was significantly higher than in the control group. SOD activity in the RT group was lower than in the control group. The activity of SOD and GSH-Px enzymes was higher in the RT+VE group, but MDA level was lower in the RT+VE group when compared with the RT group.

CONCLUSIONS

Vitamin E has a protective effect on radiation-induced cataract by decreasing oxidative stress.

The relationship between mucosal cyclooxygenase-2 (COX-2) expression and experimental radiation-induced mucositis

Although cycloooxygenase-2 (COX-2) is upregulated by factors associated with oral mucositis, its role in the pathogenesis of mucositis has not been studied. We investigated the kinetics of mucosal COX-2 expression following radiation exposure, and assessed its relationship to the development of oral mucositis in an established animal model using immunohistochemical endpoints. While little or no COX-2 expression was observed in unirradiated mucosa or in tissue taken 2 days after radiation, COX-2 expression was dramatic on days 10 and 16, especially in submucosal fibroblasts and endothelium. The kinetics of COX-2 expression paralleled mucositis severity. A burst of angiogenic activity was seen on day 21 following peak COX-2 expression. The kinetics of COX-2 expression relative to mucositis progression suggests that COX-2 is not a primary driver of radiation injury, but instead plays an amplifying role.

Radiation-induced edema is dependent on cyclooxygenase 2 activity in mouse brain

Cerebrovascular dysfunction, characterized by compromise of the blood-brain barrier and formation of cerebral edema, is common during the acute period after brain irradiation and may contribute to delayed pathology (e.g. vascular collapse, white matter necrosis) that leads to functional deficits. Another response of normal brain tissue to radiation is the induction of inflammatory markers, such as cytokine expression and glial activation. In particular, radiation-induced neuroinflammation is associated with an elevation in cyclooxygenase 2 (COX2), one of two isoforms of the obligate enzyme in prostanoid synthesis and the principal target of non-steroid anti-inflammatory drugs. Since prostanoids serve as autocrine and paracrine mediators in numerous physiological and pathological processes, including vasoregulation, we investigated COX2 protein expression and COX2-mediated prostanoid production in radiation-induced cerebral edema in male C57/BL6 mice. We found that radiation induces COX2 protein that is accompanied by specific increases in prostaglandin E(2) and thromboxane A(2) within 4 and 24 h after brain irradiation. Furthermore, we showed that treatment with NS-398, a selective COX2 inhibitor, attenuated prostanoid induction and edema formation. These results suggest that radiation-induced changes in vascular permeability are dependent on COX2 activity, implicating this enzyme and its products as targets for potential therapeutic treatment/protection from the effects of radiation on normal brain tissue.

[Activity of antioxidant enzymes in enterocytes of the small intestine and blood cells after ionizing irradiation and administration of vitamin E in rats]

The long-term influence of low X-ray irradiation increases lipid peroxidation (LP) in radiosensitive (bone marrow, enterocytes of small intenstine) and in relatively radioresistant blood cells (erythrocytes). The activation of antioxidant system enzymes in observed cells does not decrease LP intensity. We concluded that additional administration of alpha-tocopherol provided the decrease of the first and end products of LP in the observed tissues mostly in the beginning of the experiment. Antioxidant effect of the preparation is more significant in cells with high proliferative activity but normal activity of enzymes was not determined.

The effect of N-acetyl serotonin on ultraviolet-radiation-induced cataracts in rats

AIMS

To investigate the effects of ultraviolet radiation (UVR) on cataract development in rat lenses and whether or not N-acetyl serotonin has an effect on changes in these lenses.

MATERIAL AND METHODS

The study was performed using 5 groups of Sprague-Dawley albino rats, with each group consisting of 15 rats. The 5th group being the control group did not receive any applications, whilst the other 4 groups received a daily dose of 0.2 J/cm(2)/day UVR (305 nm wavelength) for 60 days. A dose of 4 mg/kg/0.1 ml N-acetyl serotonin was injected intraperitoneally to group 1 and group 2 every day and on alternate days, respectively. Group 3 received an intraperitoneal injection of 0.1 ml phosphate buffer solution every day, whilst group 4 received no injection. On the 60th day, an intracardiac withdrawal of blood was performed, after the rats had been anesthetized with ether. Following the withdrawal of blood, the rats were killed using a high dose of ether and their eyes were enucleated. The lens fresh weights, plasma malondialdehyde (P-MDA), erythrocyte glutathione peroxidase (E-GSHPx), erythrocyte glutathione reductase, blood reduced glutathione (B-RGSH), erythrocyte catalase (E-CAT), lenticular malondialdehyde, lenticular superoxide dismutase (L-SOD), lenticular glutathione peroxidase (L-GSHPx) and lenticular glutathione (L-GSH) levels were all assessed.

RESULTS

The lens fresh weights were determined to be lower in group 1 and in the control group in comparison with the other groups (p < 0.01). Whilst the P-MDA level was found to be lower (p < 0.001), the E-GSHPx level was higher (p < 0.01) in the control group than in the other groups. The E-GSHPx level was higher in groups 1 and 2 than in groups 3 and 4 (p < 0.01). The B-RGSH level was higher in the control group than in the other groups (p < 0.001). The E-CAT level was higher in both the control group and group 1 than in groups 2, 3 and 4 (p < 0.01), whilst it was higher in group 2 when compared to groups 3 and 4 (p < 0.01). The L-SOD levels were found to be higher in the control group and group 1 than in groups 2, 3 and 4 (p < 0.001). Whilst the L-GSHPx levels were determined to be higher only in the control group (p < 0.001), the L-GSH levels were higher in the control group and group 1 than in the other groups (p < 0.001).

CONCLUSIONS

In recent years, the depletion of the atmospheric ozone layer has resulted in the penetration of more UVR to the earth, which causes various effects on different tissues of organisms. N-acetyl serotonin, a melatonin precursor, may well be effective in the prevention of the negative effects induced by the UVR upon the lens tissue, in which case the capability of melatonin to capture free radicals as well as its antioxidative properties should be taken into consideration.

Glutathione peroxidase induced in rat retinas to counteract photic injury

PURPOSE

To examine the hypothesis that glutathione peroxidase (GPX) is induced at different time points after retinal exposure to light and localizes in different retinal cells.

METHODS

The rats were kept in cyclic light for 2 weeks before the experiments. The animals were maintained in 12-hour light-dark cycles, before and after exposure to intense white fluorescent light, for as long as 24 hours and then returned to cyclic light. Expression of GPX was measured by immunohistocytochemistry and Western and Northern blot analyses. Light-induced retinal damage was determined by the thickness of the outer nuclear layer (ONL) thickness in relation to total retinal thickness.

RESULTS

GPX labeling did not appear in the photoreceptor inner segments, and slight labeling was observed in the photoreceptor outer segments or the retinal pigment epithelial (RPE) cells in the normal retina kept in cyclic light. In retinal specimens maintained in light for 12 and 24 hours, GPX labeling was induced in the photoreceptor outer segments and RPE cells. High expression of GPX in the RPE was sustained until day 7 after challenge. In contrast, GPX expression in the photoreceptor outer segments decreased on day 1 and disappeared on days 3 and 7 after exposure. Intense GPX labeling was seen from the internal limiting membrane to the ganglion cell layer. GPX labeling was constantly localized in both high-intensity white light and cyclic conditions, suggesting no induction of GPX in those areas. In addition, GPX labeling was apparent at the posterior retinal pole but not at the peripheral retina. We observed marked upregulation of GPX mRNA in rats kept in high-intensity white light. One, 3, and 7 days after exposure to high-intensity white light, there was a significant difference (P < 0.0001) between the control and experimental groups in the ratio of the outer nuclear layer thickness to the entire retina.

CONCLUSIONS

GPX was induced at different time points after exposure to high-intensity white light and localized in different retinal cells. Changes in expression of GPX after exposure to light may be related to the difference in susceptibility of the retina to damage by light.

Cell phenotype specific kinetics of expression of intratracheally injected manganese superoxide dismutase-plasmid/liposomes (MnSOD-PL) during lung radioprotective gene therapy

Intratracheal (IT) injection of manganese superoxide dismutase-plasmid/liposome (MnSOD-PL) complexes prior to whole lung irradiation of C57BL/6J mice provides significant protection from acute and chronic irradiation damage. We determined the duration of increased MnSOD biochemical activity and differential expression of a hemagglutinin (HA) epitope-tagged MnSOD transgene. HA-MnSOD-PL was IT injected at doses of 0-1000 microg, and mice were killed 1,2,3 or 4 days later. Other groups of mice were irradiated to 20 Gy to the pulmonary cavity 24 h after injection and killed at the same time points as non-irradiated mice. Both non-irradiated and irradiated groups of mice showed increased MnSOD biochemical activity with plasmid dose that plateaued at 100 microg of MnSOD plasmid DNA. In control mice, MnSOD biochemical activity decreased at 2, 3 or 4 days after injection. In irradiated mice, MnSOD biochemical activity decreased at day 2 but increased on days 3 and 4. HA-MnSOD expression decreased in broncheoalveolar macrophages and alveolar type-II cells 3 days after injection in non-irradiated and irradiated mice, but remained elevated in endothelial and epithelial cells past 4 days. The data provide a rationale for every second-day administration of intrapulmonary MnSOD-PL in clinical trials of radioprotective gene therapy. This should be sufficient to provide radioprotection during radiation treatments.

Ultraviolet light-induced changes in the glucose-6-phosphate dehydrogenase activity of porcine corneas

PURPOSE

Corneas have the high activity of the pentose phosphate pathway. To clarify the relevance of the pentose phosphate pathway to their antioxidant defense, we examined the activity of glucose-6-phosphate dehydrogenase (G6PDH), the rate-determining enzyme of the pathway, in corneas exposed to ultraviolet light (UV).

METHODS

Fresh porcine eye globes were exposed to ultraviolet light A (UVA) or ultraviolet light C (UVC), and the tear film-removed eye globes to UVA. After UV exposure, the corneas were dissected from the eye globes and extracted with a saline solution, and the G6PDH activity in the extract was assayed. The G6PDH activity of unilateral opaque corneas, their paired, transparent corneas, and normal corneas, all of which were obtained from fresh, UV-unexposed eye globes, and the L-lactate dehydrogenase (LDH) activity of these opaque and normal corneas also were assayed.

RESULTS

The G6PDH activity of corneas increased with UVA exposure, and decreased with long-term UVC exposure, although it increased with short-term UVC exposure. A UV-blocking contact lens screened corneas from the UVA-induced increase. Removal of the tear film enhanced the UVC-induced decrease. The G6PDH activity of unilateral opaque corneas was lower than that of paired, transparent corneas or normal corneas, all of which were obtained from fresh, UV-unexposed eye globes. The LDH activity of the opaque corneas was much higher than that of the normal corneas.

CONCLUSION

Exposure of corneas to UVA or a small dose of UVC enhances the G6PDH activity, i.e., the pentose phosphate pathway. This activity enhancement may play an important role in corneal antioxidant defense against UV-induced oxidative stress. However, exposure of corneas to large doses of UVC appears to damage the pathway.

Radioprotective effect of silymarin against radiation induced hepatotoxicity

The radioprotective effect of silymarin using different modes of treatment against radiation (3 or 6 Gy) induced hepatotoxicity 1, 3 and 7 days post-irradiation was studied. Whole-body gamma-irradiation revealed an increase in serum alkaline phosphatase (AP) activity as well as liver glutathione reductase (GR) and glutathione peroxidase (GSH-PX) activities on the first post-exposure day with respect to the control value. However, 3 days after radiation exposure, these parameters showed a significant decrease below the control level which persisted till the end of the experimental time except for serum AP activity that showed another increase on the seventh post-exposure day at 3 Gy dose of radiation. A gradual increase in serum alanine and aspartate aminotransferase (ALT&AST) as well as gamma glutamyl transpeptidase activities were observed due to irradiation throughout the experimental time. Administration of silymarin as single (70 mg kg (-1)), fractionated (490 mg kg (-1)) oral doses or as intravenous (i.v.) injection (50 mg kg (-1)), caused significant protection. Intravenous treatment showed the most pronounced protection. The protective effect of silymarin was attributed to its antioxidant and free radicals scavenging properties.

Dimensional variations induced by local irradiation in cheek skin and oral mucous membrane

The present study was undertaken to characterize and quantitatively analyze an easily reproducible experimental model of rat oral mucosa subjected to a sequence of radiation doses and post-irradiation times using epithelial and connective tissue thickness and cytochrome oxidase activity as end-pints. The radiobiological behaviour of oral mucosa was compared to that of skin subjected to the same experimental conditions.

Role of CD13/aminopeptidase N in rat lymphocytic alveolitis caused by thoracic irradiation

CD13/aminopeptidase N is a cell surface glycoprotein that is widely distributed in a variety of mammalian cells. It was recently shown to have chemotactic activity for T lymphocytes. This study examined the role of CD13/aminopeptidase N in lymphocytic alveolitis in radiation-induced lung injury caused by a single-dose thoracic irradiation (15 Gy) in rats. Significantly increased aminopeptidase activity was detected in bronchoalveolar lavage fluid obtained from irradiated rats at 4 weeks after irradiation compared to the activity in unirradiated rats. Significantly higher aminopeptidase activity was detected on alveolar macrophages from irradiated rats at 2 and 4 weeks than on those from unirradiated rats. Western blot analysis showed an increased expression of CD13/aminopeptidase N protein in alveolar macrophages from irradiated rats at 4 weeks. Chemotactic activity for normal rat lymphocytes was detected in bronchoalveolar lavage fluid from irradiated rats at 4 weeks, and approximately 60% of the activity was inhibited by pretreatment of bronchoalveolar lavage fluid with bestatin, a specific aminopeptidase inhibitor. This study suggests that CD13/aminopeptidase N may play an important role as a lymphocyte chemoattractant in lymphocyte-mediated alveolitis in experimental radiation-induced lung injury.

Lens lactate dehydrogenase inactivation after UV-B irradiation: an in vivo measure of UVR-B penetration

PURPOSE

To elucidate the spatial distribution of inactivation of lactate dehydrogenase (LDH) in ultraviolet-B radiation (UVR-B)-exposed eyes. To determine the in vivo penetration depth of UVR-B in the lens.

METHODS

LDH activity in cornea and lens was investigated with an enzyme histochemical technique. Thirty rats were exposed in vivo to UVR-B of approximately 300 nm, and the eyes were enucleated and frozen at 0, 2, and 6 hours after exposure. LDH activity in frozen sections was determined quantitatively in the corneal epithelium and four different regions in the lens. UVR-B penetration depth was estimated by using a calculated Lambertian absorption coefficient.

RESULTS

The LDH activity was decreased in the cornea and the outer anterior lens cortex at all three time points. The average decrease in enzyme activity in the time range was 35% in the cornea and 20% in the outer anterior lens cortex. UVR-B inhibition of LDH was immediate and not dependent on an inflammatory reaction within the eye. Penetration depth, corresponding to 1/e(2) ( approximately 14%) residual UVR-B intensity, was 0.45 mm.

CONCLUSIONS

UVR-B does not exhibit any significant effect on LDH activity in the major part of the lens, and this is attributed to the shallow penetration (0.45 mm) of UVR-B into the anterior parts of the lens.

[Mechanisms of cerebral radiation syndrome]

Postradiation DNA breaks activate the repair enzyme, Adenosine diphosphoribosil transferase, which consumes NAD as a substrate and causes neuronal NAD and then ATP pool depletion; here this is considered to be the crucial links of the cerebral radiation syndrome (CRS) mechanism. Two ways of its metabolic correction were examined: (a) prevention of postradiation NAD depletion by administration of the enzyme inhibitor and (b) shunting NAD-dependent oxidative phosphorilation path of ATP resynthesis by administration of substrate of NAD-independent oxidation.

Disruption of cyclooxygenase-1 gene results in an impaired response to radiation injury

Prostaglandins may play an important role in regulating normal renewal of gastrointestinal epithelium, epithelial injury repair, and initiation or progression of intestinal neoplasia. Synthesis of prostaglandins is catalyzed by either of two cyclooxygenase isoforms, Cox-1 and Cox-2. Cox-1 is the predominant cyclooxygenase isoform found in the normal intestine. In contrast, Cox-2 is present at low levels in normal intestine but is elevated at sites of inflammation and in adenomas and carcinomas. To determine directly whether prostaglandins synthesized by Cox-1 or Cox-2 regulate crypt epithelial cell fate after genotoxic or cytotoxic injury, we examined apoptosis, prostaglandin synthesis, and crypt stem cell survival after gamma-irradiation in Cox-1(-/-) and Cox-2(-/-) mice. Cox-1(-/-) mice had increased crypt epithelial cell apoptosis and decreased clonogenic stem cell survival compared with wild-type littermates. PGE(2) synthesis was also diminished in Cox-1(-/-) mice compared with wild-type controls in unstressed intestine and after radiation injury. In contrast, apoptosis, stem cell survival, and intestinal PGE(2) synthesis in Cox-2(-/-) mice after irradiation were the same as in wild-type littermates. Crypt stem cell survival after irradiation was inhibited by a highly specific neutralizing antibody to PGE(2), suggesting that this prostaglandin mediates stem cell fate in vivo. These data suggest that prostaglandins synthesized by Cox-1 regulate multiple steps that determine the fate of crypt epithelial cell after genotoxic or cytotoxic injury.

Reduction of high-energy shock-wave-induced renal tubular injury by selenium

In shock-wave-induced renal injury cavitation-generated free radicals play an important role. Using an in vitro model with Madin-Darby canine kidney (MDCK) cells, we investigated the influence of selenium, a free radical scavenger, in shock-wave-induced tubular cell injury. Suspensions of MDCK cells (33 x 10(6) cells/ml) were placed in small containers (volume 1.1 ml) for shock wave exposure. Two groups of 12 containers each were examined: (1) control (no medication), (2) selenium (0.4 microg/ml nutrient medium). Six containers in each group were exposed to shock waves (impulse rate 256, frequency 60 Hz, generator voltage 18 kV), while the other six containers in each group served as a control. After shock wave exposure, the concentration of cellular enzymes such as lactate dehydrogenase (LDH), N-acetyl-beta-glucosaminidase (NAG), glutamate oxaloacetate transaminase (GOT) and glutamate lactate dehydrogenase (GLDH) in the nutrient medium was examined. Following shock wave exposure there was a significant rise in LDH, NAG, GOT and GLDH concentrations. Selenium reduced this enzyme leakage significantly. Thus we conclude that selenium protects renal tubular cells against shock-wave-induced injury. Since selenium is an essential part of glutathione peroxidase, this effect seems to be mediated by a reduction in reactive oxygen species.

Prevention of irradiation-induced esophagitis by plasmid/liposome delivery of the human manganese superoxide dismutase transgene

Esophagitis is a major toxicity of radiation therapy for nonsmall-cell lung cancer. Intraesophageal injection of manganese superoxide dismutase (MnSOD) plasmid/liposome complexes (1 mg of the pRK5-MnSOD plasmid containing the human MnSOD transgene in a 0.15 ml volume of lipofectin) before irradiation was carried out to attempt to prevent irradiation esophagitis. In control noninjected male C3H/HeNsd mice, esophagitis was induced by single fraction 3,500 cGy irradiation. Histopathology at 4 days revealed vacuole formation in squamous lining cells, separation of the squamous layer from the underlying muscle layer, ulceration at 7 days, and dehydration and death by 30 days. MnSOD plasmid/liposome complex-injected mice showed transcription of the human MnSOD transgene message in esophageal squamous lining cells by nested reverse transcriptase-polymerase chain reaction (RT-PCR) increased MnSOD biochemical activity 24 h after injection, decreased vacuole formation at day 4 (P < 0.001) after 3,500 cGy thoracic irradiation, and improved survival (P = 0.0009). In contrast, groups of mice receiving LacZ (bacterial beta-galactosidase gene) plasmid/liposome complexes or liposomes containing no DNA before 3,500 cGy irradiation showed an unaltered irradiation histopathology and decreased survival. Mice receiving intraesophageal MnSOD plasmid/liposomes followed 8 h later by human equivalent doses of Taxol (1.4 mg/kg) and carboplatin (2.5 mg/kg), then 15 h later 3,300 cGy irradiation, showed increased survival, compared with irradiated control or LacZ plasmid/liposome groups. Thus, overexpression of the human MnSOD transgene in the esophagus can prevent irradiation-induced esophagitis in the mouse model.

Biochemical indicators of whole-body gamma-radiation effects in the pig

PURPOSE

Validation of the pig as an experimental animal model for dose assessment after ionizing irradiation.

MATERIALS AND METHODS

The evolution of haematological and biochemical parameters was followed for up to 7 days after irradiation in pigs exposed to whole-body 60Co gamma-radiation at doses between O and 6 Gy.

RESULTS

Some biochemical indicators showed significant variations: amylase, LDH, alkaline and acid phosphatases, ALT and iron. None of the studied parameters alone presents a reliable dose-effect relationship; however, there was evidence that the combination of lymphocyte and neutrophil counts and the determination of LDH, ALT, AST and urea levels allowed some dose determination, independent of time, if blood samples were taken within 7 days post-irradiation.

CONCLUSION

The results confirm the main problems of biochemical dosimetry. However, the pig model could represent a useful alternative to the non-human primate in radiobiology research, especially in the case of partial-body exposure. A multiparametric approach to dose assessment seems to be possible in the pig model. Confirmation should be carried out using blood samples from patients undergoing radiotherapy treatment.

[The effect of the parenteral administration of alpha-ketoglutarate on the resistance of rats to ionizing radiation and on their cholinergic systems]

We have investigate the effect of sodium ketoglutarate intraperitoneal injection (20 mg/100 g body weight) made 0.5 hour before and 1, 2 and 3 hours after total X-ray treatment (259 mKl/kg) on the survival of rats. Simultaneously we have define changes in cholinesterase-acetylcholine system and content of adrenaline and noradrenaline in liver and pancreas tissues, small intestines mucous and in blood. All the data were taking at 1, 2, 5, 4, 24 and 72 hours after treatment and sodium ketoglutarate injection. We have found that sodium ketoglutarate injection made 0.5 hour before the treatment results in increasing of percentage death rate and injection made 1 and 2 hours after treatment results in increase in survival of rats. The effect of alpha-ketoglutarate injection made 1 hour after treatment in more pronounced. It is accompanied with increase of cholinergic status of organism on the catecholamine deficit background, decrease in the cholinesterase activity and increase of acetylcholine content in tissues of treated organism.

[Post-irradiation changes in blood 5'-nucleotidase activity of rats after chronic exposure to gamma irradiation]

Kinetics of 5'-AMP hydrolysis by rat's blood serum was studied at 3, 10, 30, 90 and 180 days after prolonged gamma-irradiation at 0.1-1 Gy doses (60Co source, dose rate 4.4 x 10(-6) Gy/h). It was shown that more expressed kinetic anticooperativity of nucleotidase reaction in irradiated animals, as compare to control ones, was conditioned by composition predominance of low-affinity 5'-nucleotidases forms over their high-affinity patterns. The ratio of maximal velocities of high- to low-affinity 5'-nucleotidases was ranged from 2 in the control to 7 in irradiated rats at different postirradiation periods during the first 90 days of observation. It was suggested that appearance of new kinetic 5'-nucleotidases forms in blood stream of irradiated animals, predominantly with low-affinity, was attributed to impairment in the integrity of cellular membranes and may testify to postirradiation development of tissues injury.

[New approaches in clinical ophthalmology: UV absorbers and hindered amines covalently bound to contact lenses. Importance of enzyme histochemistry in studying their effectiveness in vivo]

UV absorbers developed by us are covalently bound in hydrophilic contact lenses. This is great advantage because UV absorbers cannot be diluted from contact lenses. In laboratory investigations and "in vivo" experiments it was found that contact lenses containing UV absorbents prevent the eye against the damaging effect of UV irradiation (UVA, UVB, UVC rays). The second new approach (mentioned in this paper) is the use of Hindered Amine Light Stabilizer (4-methakryloylamino-2,2,6,6-tetramethylpiperidine) covalently bound in the hydrophilic contact or therapeutic lenses--for the healing of the damaged eye. In laboratory measurements the cleavage of hydrogen peroxide (of various concentrations) by hindered amine light stabilizer was confirmed. In "in vivo" experiments it was examined histochemically and morphologically that Hindered Amines Light Stabilizer bound in contact lenses favourable influenced the healing of the damaged anterior eye segment of rabbits. The amount as well as enzyme activation (lysosomal hydrolases) of inflammatory cells was significantly reduced in the anterior eye segment. It is suggested that Hindered Amine Light Stabilizer reacts with reactive oxygen species (oxyradicals and hydrogen peroxide) present in the damaged anterior eye segment (e.g. released from inflammatory cells). During this reaction intermediate products appear and the resulting product is a nitroxide radical. All reaction products as well as resulting product are covalently bound in hydrophilic material. For the development and also evaluation of the efficacy of both new approaches perspective for the use in clinical ophthalmology, biochemical investigations and histochemical methods are employed. Enzyme histochemistry is very important for the evaluation of the efficacy of new therapeutic approaches "in vivo" and therefore the particular attention is devoted to it in this communication.

Increased synthesis of high-molecular-weight cPLA2 mediates early UV-induced PGE2 in human skin

Ultraviolet light (UV) B-induced inflammation is characterized by dramatic increases in prostaglandin E2 (PGE2) synthesis due to enhanced arachidonate deacylation from the membrane. Therefore, the effect of UV on sythesis, mass, and distribution of the high-molecular-weight phospholipase A2 (cPLA2) in cultured human keratinocytes and human skin was studied. The 105-kDa cPLA2 was demonstrated to be the critical enzyme in UV-induced PGE2 synthesis and erythema in the first 6 h postirradiation. Immunoprecipitation of 35S-labeled protein showed cPLA2 synthesis increased three- to fourfold 6 h after irradiation. Immunoprecipitated 32P-labeled cPLA2 demonstrated phosphorylation of cPLA2 was concurrently induced, suggesting that UV also activates cPLA2. This increase in cPLA2 synthesis and activation also closely correlated with increased PGE2 synthesis and [3H]arachidonic acid release and was effectively blocked by both an S-oligonucleotide antisense to cPLA2 and methyl arachidonate fluorophosphate, a specific inhibitor of cPLA2. Biopsy and histochemical examination of erythematous sites expressed increased amounts of cPLA2 whereas nonerythematous irradiated sites did not. In contrast, cyclooxygenase-1 and -2 in cultures and skin explants were unaffected 6 h post-UV, and no change in cyclooxygenase activity was observed at this time. These results suggest that increased cPLA2 synthesis occurs only when skin is exposed to UV doses that are sufficient to cause erythema and indicate expression of cPLA2 participates in acute UV inflammation.

Immunohistological detection of the beta subunit of prolyl 4-hydroxylase in rat and mini pig lungs with radiation-induced pulmonary fibrosis

Polyclonal and monoclonal antibodies to the beta subunit of prolyl 4-hydroxylase, the protein disulphide isomerase, were used to compare the pulmonary cells in 13 normal and in 20 fibrotic rat and mini-pig lungs made fibrotic by X-ray irradiation, using the ABC immunoperoxidase technique. In normal lungs, prominent staining of Clara cells and type II pneumocytes and weaker reactivity with alveolar macrophages, fibroblasts, endothelial and smooth muscle cells were detectable. In pulmonary disease, in which interstitial fibrosis was the characteristic feature, the immunoreactivity was increased in both the epithelial and interstitial cells. Type I pneumocytes remained negative. In the early stages of disease (3 to 4 weeks after irradiation) when little morphological alteration was seen, capillary endothelial cells had already become immunoreactive. These results underline the complex involvement and interaction of different lung cell populations in the process of pulmonary fibrogenesis.