Molecular and Biochemical Basis of Fluoroquinolones-Induced Phototoxicity-The Study of Antioxidant System in Human Melanocytes Exposed to UV-A Radiation.

Phototoxicity of fluoroquinolones is connected with oxidative stress induction. Lomefloxacin (8-halogenated derivative) is considered the most phototoxic fluoroquinolone and moxifloxacin (8-methoxy derivative) the least. Melanin pigment may protect cells from oxidative damage. On the other hand, fluoroquinolone-melanin binding may lead to accumulation of drugs and increase their toxicity to skin. The study aimed to examine the antioxidant defense system status in normal melanocytes treated with lomefloxacin and moxifloxacin and exposed to UV-A radiation. The obtained results demonstrated that UV-A radiation enhanced only the lomefloxacin-induced cytotoxic effect in tested cells. It was found that fluoroquinolones alone and with UV-A radiation decreased superoxide dismutase (SOD) activity and SOD1 expression. UV-A radiation enhanced the impact of moxifloxacin on hydrogen peroxide-scavenging enzymes. In turn, lomefloxacin alone increased the activity and the expression of catalase (CAT) and glutathione peroxidase (GPx), whereas UV-A radiation significantly modified the effects of drugs on these enzymes. Taken together, both analyzed fluoroquinolones induced oxidative stress in melanocytes, however, the molecular and biochemical studies indicated the miscellaneous mechanisms for the tested drugs. The variability in phototoxic potential between lomefloxacin and moxifloxacin may result from different effects on the antioxidant enzymes.

Repeated exposure to far infrared ray attenuates acute restraint stress in mice via inhibition of JAK2/STAT3 signaling pathway by induction of glutathione peroxidase-1.

Exposure to far-infrared ray (FIR) has been shown to exert beneficial effects on cardiovascular and emotional disorders. However, the precise underlying mechanism mediated by FIR remains undetermined. Since restraint stress induces cardiovascular and emotional disorders, the present study investigated whether exposure to FIR affects acute restraint stress (ARS) in mice. c-Fos-immunoreactivity (IR) was significantly increased in the paraventricular hypothalamic nucleus (PVN) and dorsomedial hypothalamic nucleus (DMH) in response to ARS. The increase in c-Fos-IR parallels that in oxidative burdens in the hypothalamus against ARS. Exposure to FIR significantly attenuated increases in the c-Fos-IR, oxidative burdens and corticosterone level. ARS elicited decreases in GSH/GSSG ratio, cytosolic Cu/Zn-superoxide dismutase (SOD-1), glutathione peroxidase (GPx), and glutathione reductase (GR) activities. FIR-mediated attenuation was particularly observed in ARS-induced decrease in GPx, but not in SOD-1 or GR activity. Consistently, ARS-induced decreases in GPx-1-immunoreactivity in PVN and DMH, and decreases in GPx-1 expression in the hypothalamus were significantly attenuated by FIR. ARS-induced significant increases in phosphorylation of JAK2/STAT3, and nuclear translocation and DNA-binding activity of NFκB were observed in the hypothalamus. Exposure to FIR selectively attenuated phosphorylation of JAK2/STAT3, but did not diminish nuclear translocation and DNA-binding activity of NFκB, suggesting that JAK2/STAT3 constitutes a critical target for FIR-mediated pharmacological potential. ARS-induced increase in c-Fos-IR in the PVN and DMH of non-transgenic mice was significantly attenuated by FIR exposure or JAK2/STAT3 inhibitor AG490. GPx-1 overexpressing transgenic mice significantly protected increases in the c-Fos-IR and corticosterone level induced by ARS. However, neither FIR exposure nor AG490 significantly affected attenuations by genetic overexpression of GPx-1. Moreover, AG490 did not exhibit any additional positive effects against the attenuation by genetic overexpression of GPx-1 or FIR exposure. Our results indicate that exposure to FIR significantly protects ARS-induced increases in c-Fos-IR and oxidative burdens via inhibition of JAK2/STAT3 signaling by induction of GPx-1.

[The antioxidant enzyme activity in mouse liver mitochondria after nanosecond pulsed periodic X-ray exposure].

The effect of repetitive pulsed X-ray (4 ns pulse duration, 300 kV accelerating voltage; 2.5 kA electron beam current) on the antioxidant enzyme activity in mouse liver mitochondria has been investigated. The mitochondrial suspension was exposed to single 4000 pulse X-ray radiation with repetition rates ranging between 10 and 22 pps (pulsed dose was 0.3-1.8 x 10(-6) Gy/pulse, the total absorbed dose following a single exposure was 7.2 x 10(-3) Gy). It was shown that a short-time exposure to X-ray radiation changes the antioxidant enzyme activity in mouse liver mitochondria. The greatest effect was observed in the changes of the activity of the metal-containing enzymes: superoxide dismutase and glutathione peroxidase. The effect depends on the pulse repetition frequency and radiation dose.

Modulation of wireless (2.45 GHz)-induced oxidative toxicity in laryngotracheal mucosa of rat by melatonin.

It is well known that oxidative stress induces larynx cancer, although antioxidants induce modulator role on etiology of the cancer. It is well known that electromagnetic radiation (EMR) induces oxidative stress in different cell systems. The aim of this study was to investigate the possible protective role of melatonin on oxidative stress induced by Wi-Fi (2.45 GHz) EMR in laryngotracheal mucosa of rat. For this purpose, 32 male rats were equally categorized into four groups, namely controls, sham controls, EMR-exposed rats, EMR-exposed rats treated with melatonin at a dose of 10 mg/kg/day. Except for the controls and sham controls, the animals were exposed to 2.45 GHz radiation during 60 min/day for 28 days. The lipid peroxidation levels were significantly (p < 0.05) higher in the radiation-exposed groups than in the control and sham control groups. The lipid peroxidation level in the irradiated animals treated with melatonin was significantly (p < 0.01) lower than in those that were only exposed to Wi-Fi radiation. The activity of glutathione peroxidase was lower in the irradiated-only group relative to control and sham control groups but its activity was significantly (p < 0.05) increased in the groups treated with melatonin. The reduced glutathione levels in the mucosa of rat did not change in the four groups. There is an apparent protective effect of melatonin on the Wi-Fi-induced oxidative stress in the laryngotracheal mucosa of rats by inhibition of free radical formation and support of the glutathione peroxidase antioxidant system.

Activation of de novo GSH synthesis pathway in mouse spleen after long term low-dose γ-ray irradiation.

Glutathione (GSH) is an important cellular antioxidant and has a critical role in maintaining the balance of cellular redox. In this study, we investigated the GSH biosynthesis genes involved in the elevation of endogenous GSH levels using an irradiation system with an irradiation dose rate of 1.78 mGy/h, which was about 40,000 times less than the dose rates used in other studies. The results showed that GSH levels were significantly increased in the low-dose (0.02 and 0.2 Gy) irradiated group compared to those in the non-irradiated group, but enzymatic antioxidants such as superoxide dismutase and catalase were not induced at any doses tested. The elevation in GSH was accompanied by elevated expression of glutamate-cysteine ligase modifier subunit, but no changes were observed in the expression of glutamate-cysteine ligase catalytic subunit and thioredoxin in de novo GSH synthesis. In the case of genes involved in the GSH regeneration cycle, the expression of glutathione reductase was not changed after irradiation, whereas glutathione peroxidase was only increased in the 0.2 Gy irradiated group. Collectively, our results suggest that the de novo pathway, rather than the regeneration cycle, may be mainly switched on in response to stimulation with long-term low-dose radiation in the spleen.

900-MHz microwave radiation promotes oxidation in rat brain.

Recently, there have been several reports referring to detrimental effects due to radio frequency electromagnetic fields (RF-EMF) exposure. Special attention was given to investigate the effect of mobile phone exposure on the rat brain. Since the integrative mechanism of the entire body lies in the brain, it is suggestive to analyze its biochemical aspects. For this, 35-day old Wistar rats were exposed to a mobile phone for 2 h per day for a duration of 45 days where specific absorption rate (SAR) was 0.9 W/Kg. Animals were divided in two groups: sham exposed (n = 6) and exposed group (n = 6). Our observations indicate a significant decrease (P < 0.05) in the level of glutathione peroxidase, superoxide dismutase, and an increase in catalase activity. Moreover, protein kinase shows a significant decrease in exposed group (P < 0.05) of hippocampus and whole brain. Also, a significant decrease (P < 0.05) in the level of pineal melatonin and a significant increase (P < 0.05) in creatine kinase and caspase 3 was observed in exposed group of whole brain as compared with sham exposed. Finally, a significant increase in the level of ROS (reactive oxygen species) (P < 0.05) was also recorded. The study concludes that a reduction or an increase in antioxidative enzyme activities, protein kinase C, melatonin, caspase 3, and creatine kinase are related to overproduction of reactive oxygen species (ROS) in animals under mobile phone radiation exposure. Our findings on these biomarkers are clear indications of possible health implications.

Mutagenic response of 2.45 GHz radiation exposure on rat brain.

PURPOSE: To investigate the effect of 2.45 GHz microwave radiation on rat brain of male wistar strain. MATERIAL AND METHODS: Male rats of wistar strain (35 days old with 130 +/- 10 g body weight) were selected for this study. Animals were divided into two groups: Sham exposed and experimental. Animals were exposed for 2 h a day for 35 days to 2.45 GHz frequency at 0.34 mW/cm(2) power density. The whole body specific absorption rate (SAR) was estimated to be 0.11 W/Kg. Exposure took place in a ventilated Plexiglas cage and kept in anechoic chamber in a far field configuration from the horn antenna. After the completion of exposure period, rats were sacrificed and the whole brain tissue was dissected and used for study of double strand DNA (Deoxyribonucleic acid) breaks by micro gel electrophoresis and the statistical analysis was carried out using comet assay (IV-2 version software). Thereafter, antioxidant enzymes and histone kinase estimation was also performed. RESULTS: A significant increase was observed in comet head (P < 0.002), tail length (P < 0.0002) and in tail movement (P < 0.0001) in exposed brain cells. An analysis of antioxidant enzymes glutathione peroxidase (P < 0.005), and superoxide dismutase (P < 0.006) showed a decrease while an increase in catalase (P < 0.006) was observed. A significant decrease (P < 0.023) in histone kinase was also recorded in the exposed group as compared to the control (sham-exposed) ones. One-way analysis of variance (ANOVA) method was adopted for statistical analysis. CONCLUSION: The study concludes that the chronic exposure to these radiations may cause significant damage to brain, which may be an indication of possible tumour promotion (Behari and Paulraj 2007).

Lycopene: An antioxidant and radioprotector against gamma-radiation-induced cellular damages in cultured human lymphocytes.

The present study aimed to evaluate the radioprotective effect of lycopene, a naturally occurring dietary carotenoid on gamma-radiation-induced toxicity. The cellular changes were estimated by using lipid peroxidative indices like thiobarbituric acid reactive substances (TBARS), hydroperoxides (HP), the antioxidants superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and reduced glutathione (GSH). The DNA damage was analyzed by cytokinesis blocked micronucleus assay (CBMN), dicentric aberration (DC) and translocation frequency. The gamma-radiation at different doses (1, 2 and 4Gy) resulted in a significant increase in the number of micronuclei (MN), DC, translocation frequency, TBARS and HP level, whereas the levels of GSH and antioxidant enzymes were significantly decreased when compared with normal control. The maximum damage to lymphocytes was observed at 4Gy irradiation. Lycopene pretreatment (1, 5 and 10microg/ml) significantly decreased the frequency of MN, DC and translocation when compared with gamma-radiation control. The levels of TBARS, HP were also decreased and activities of SOD, CAT and GPx were significantly increased along with GSH levels when compared with gamma-radiation control. The dose of 5microg/ml of lycopene was found to be more effective than the other two doses. Thus, our result shows that pretreatment with lycopene offers protection to normal lymphocytes against gamma-radiation-induced cellular damage.

Selenoprotein deficiency enhances radiation-induced micronuclei formation.

The availability of selenium and the levels of specific selenoproteins might affect cancer risk by influencing the ability of DNA damaging agents to cause genomic instability and mutations. Transgenic mice that express reduced levels of selenoproteins and previously shown to be more susceptible to pathology associated with cancer development were used to study this possibility. These mice were exposed to X-rays and DNA damage assessed in the erythrocytes, where micronuclei formation was higher compared to the same cells obtained from irradiated wild-type controls. To determine whether the selenoprotein glutathione peroxidase-1 (GPx-1) might be involved in this protection, its levels were reduced by siRNA targeting in LNCaP human prostate cells. UV-induced micronuclei frequency was higher in these cells compared to control-transfected cells. These results indicate a role for selenoproteins in protecting DNA from damage and support human data implicating GPx-1 as a possible target of the chemoprotective effect of selenium.

Effect of alpha-tocopherol on pro-oxidant and antioxidant enzyme status in radiation-treated oral squamous cell carcinoma.

OBJECTIVES: The relationships between alpha-tocopherol, pro-oxidant and antioxidant enzyme status, and radiation toxicity were studied in stage II, III, and IVA oral squamous cell carcinoma patients. The low levels of malondialdehyde and increased activities of antioxidant enzymes were correlated with decreased oxidative stress by alpha-tocopherol in oral cancer patients treated with radiotherapy. The objective of the present study was to evaluate the effect of alpha-tocopherol on oxidant-antioxidant enzyme status in oral squamous cell carcinoma patients treated with radiotherapy. MATERIALS AND METHODS: The study included three groups with histologically confirmed oral squamous cell carcinoma patients (untreated), and they were further divided into two groups, viz., one consisting of patients who underwent radiotherapy alone (radiotherapy was given at the dosage of 6000 cGy in five fractions per week for a period of 6 weeks); and the other group treated with radiotherapy plus alpha-tocopherol supplementation (alpha-tocopherol was supplemented at a dosage of 400 IU/day) for the entire period of radiotherapy. RESULTS: A significant decrease ( P < 0.001) in malondialdehyde levels and increase in activities of antioxidant enzymes ( P < 0.001) in hemolysate were noticed in patients treated with radiotherapy and simultaneously supplemented with alpha-tocopherol when compared to radiation-treated patients. CONCLUSION: It was seen that alpha-tocopherol played a role in protecting against the damage caused by irradiation in oral squamous cell carcinoma patients treated with radiotherapy, by enhancing the antioxidant enzyme status and reducing the pro-oxidant status.

Cell culture conditions potentiate differences in the response to ionising radiation of peripheral blood leukocytes isolated from breast cancer patients and healthy subjects.

To compare the effects of ionising radiation on leukocytes from breast cancer patients and healthy subjects ex vivo, the level of NF-kappaB and the antioxidant enzymes manganese-containing superoxide dismutase (Mn-SOD), copper/zinc-containing superoxide dismutase (CuZn-SOD) and catalase (CAT) in combination with flow cytometric analysis of CD4+ lymphocytes was performed. The level of Mn-SOD protein was significantly increased in the breast cancer study group both before (P < 0.001) and after (P < 0.001) irradiation when compared with healthy subjects. Measurements in parallel indicated that the level of CAT protein was significantly higher in the breast cancer study group after irradiation (2 Gy [P < 0.001] and 9 Gy [P < 0.05]) when compared with healthy subjects. Although the initial number of lymphocytes in the blood of breast cancer patients was not different from healthy subjects, the percentage of apoptotic CD4+ cells was significantly (P < 0.001) lower both before and after irradiation indicating that cell culture conditions induced radioresistance of CD4+ cells in the blood of breast cancer patients. The data presented in this current study indicate that brief ex vivo culture of peripheral blood leukocytes potentiates oxidative stress imposed by a breast cancer tumour.

Obesity increases the risk of UV radiation-induced oxidative stress and activation of MAPK and NF-kappaB signaling.

Obesity has been implicated in several diseases, including cancer; however, the relationship of obesity and susceptibility to ultraviolet (UV) radiation-caused skin diseases has not been investigated. As UV-induced oxidative stress has been implicated in several skin diseases, we assessed the role of obesity on UVB-induced oxidative stress in genetically obese Lep(ob)/Lep(ob) (leptin-deficient) mice. Here, we report that chronic exposure to UVB (120 mJ/cm(2)) resulted in greater oxidative stress in the skin of obese mice in terms of higher levels of H(2)O(2) and NO production, photo-oxidative damage of lipids and proteins, and greater depletion of antioxidant defense enzymes, like glutathione, glutathione peroxidase, and catalase. As UV-induced oxidative stress mediates activation of MAPK and NF-kappaB signaling pathways, we determined the effects of UVB on these pathways in obese mice. Exposure of obese mice to UVB resulted in phosphorylation of ERK1/2, JNK, and p38 proteins of the MAPK family. Compared to wild-type mice, the obese mice exhibited higher levels of phosphorylation of these proteins, greater activation of NF-kappaB/p65, and higher levels of circulating proinflammatory cytokines, including TNF-alpha, IL-1beta and IL-6, on UVB irradiation. Taking these results together, our study suggests for the first time that obesity in mice is associated with greater susceptibility to UVB-induced oxidative stress and therefore may be a risk factor for skin diseases associated with UVB-induced oxidative stress.

Apoptotic index as predictive marker for radiosensitivity of cervical carcinoma: evaluation of membrane fluidity, biochemical parameters and apoptosis after the first dose of fractionated radiotherapy to patients.

BACKGROUND: This study was aimed to develop possible predictive response of cervical carcinoma in stage IIIA and B patients by evaluating the changes in physical parameter, such as, membrane fluidity, biochemical parameters, such as, intracellular calcium, antioxidant enzymes [superoxide dismutase (SOD), catalase, glutathione peroxidase (GPx)] and apoptotic cell death in cervical cancer cells from patients after treating with the first fractionated dose of 2 Gy in radiation therapy protocol. METHODS: Biopsies of cervical carcinoma patients were collected before and 24h after first fractionated radiation dose of 2 Gy. Cell suspensions and tissue of cervix cancer biopsies were used to measure various physical and biochemical parameters. RESULTS AND CONCLUSIONS: A negative correlation was found to exist between observed fluidity of membrane/SOD level with the degree of apoptosis in cervical cells. On the other hand, a positive correlation was observed between intracellular calcium level and percent cellular apoptosis. These results suggest that changes in membrane fluidity, SOD and calcium level were involved in the mechanism of radiation induced cervical apoptosis as measured by TUNEL assay. Moreover, apoptotic sensitivity of these cells after the first dose of radiation treatment showed a direct correlation with the radiation treatment outcome in patients after completion of radiotherapy protocol (70 Gy) in the clinic suggesting that apoptotic index may form a basis for prognosis in radiotherapy in stage III cervix cancer patients.

Radioprotective mechanism of Podophyllum hexandrum during spermatogenesis.

RP-1, a herbal preparation of Podophyllum hexandrum has already been reported to provide protection against whole body lethal gamma irradiation (10 Gy). It has also been reported to render radioprotection to germ cells during spermatogenesis. Present study was undertaken to unravel the cellular and molecular mechanism of action of RP-1 on testicular system in strain 'A' mice. Various antioxidant parameters such as thiol content, glutathione peroxidase (GPx), glutathione reductase (GR), glutathione-S-transferase (GST) enzyme activity, lipid peroxidation (LPO) and total protein levels were investigated. Thiol content was seen to increase significantly (p < 0.05) in both RP-1 alone and RP-1 pretreated irradiated groups over the irradiated groups at 8, 16 and 24 h. Irradiation (10 Gy) significantly decreased GPx, GST and GR activity in comparison to untreated control but RP-1 treatment before irradiation significantly (p < 0.05) countered radiation-induced decrease in the activity of these enzymes. Radiation-induced LPO was also found to be reduced at all time intervals by RP-1 treatment before irradiation. As compared to irradiated group the protein content in testicular tissue was increased in RP-1 pretreated irradiated group at 4 and 16 h significantly (p < 0.05). Comets revealed by single-cell gel electrophoresis were significantly longer (p < 0.001) in irradiated mice than in unirradiated control. RP-1 treatment before irradiation, however, rendered significant increase (p < 0.05) in comet length over the corresponding control and irradiated group initially at 4 h but at later time points, this was reduced significantly (p < 0.01) as compared to the irradiated group. RP-1 treatment alone rendered shorter comets at 8, 16 and 24 h than irradiated groups (p < 0.001). This study implies that RP-1 offers radioprotection at biochemical and cytogenetic level by protecting antioxidant enzymes, reducing LPO and increasing thiol content.

Effects of infrared and low-power laser irradiation on cell viability, glutathione and glutathione-related enzyme activities in primary rat hepatocytes.

BACKGROUND AND PURPOSE: Both infrared and low-power laser have been applied to improve circulation, wound repair, and pain control. Infrared and low-power laser therapies have the potential for stimulating enzyme activities which might contribute to increased glutathione (GSH) concentration and provide protection against oxidative damage. This study investigated cell viability, and GSH and its related enzyme activities in rat hepatocytes after irradiation. METHODS: Hepatocytes were isolated from 8-week-old male Sprague-Dawley rats and the cultures were divided into infrared, laser, and control groups. The cells were treated with infrared and low-power laser at a distance of 35 cm for 20 minutes. The cell morphology, lactate dehydrogenase (LDH) leakage, lipid peroxidation, GSH concentration, GSH peroxidase, GSH reductase (GRd), and GSH S-transferase activities were measured after irradiation. RESULTS: The morphology and LDH leakage of hepatocytes in the irradiation groups did not differ significantly from those of the control group. After infrared irradiation, a significant decrease in thiobarbituric acid-reactive substances and an increase in GSH concentration were found after 48 hours of incubation compared to the control group (p < 0.05). Furthermore, laser irradiation resulted in a significant increase in GRd activity after 48 hours of incubation compared to the control group (p < 0.05). A 48-hour incubation period produced greater GRd activity in all groups compared to a 24-hour period (p < 0.05). CONCLUSIONS: Irradiation did not damage rat hepatocytes in this study. Infrared was shown to stimulate GSH production, while laser irradiation increased GRd activity.

Antioxidantes y envejecimiento cutáneo / Antioxodants and cutaneous aging

Las formulaciones disponibles actualmente para uso dermatológico, basadas en sustancias antioxidantes tales como vitaminas C y E, entre otras, abundan con promesas de revertir el envejecimiento cutáneo. En el presente trabajo se realiza una revisión de los sistemas antioxidantes cutáneos, de la relación entre envejecimiento y daño oxidativo, así como de la evidencia disponible en cuanto al tratamiento con antioxidantes. La intención de este artículo es que el dermatólogo comprenda las bases fisiológicas de acción de los antioxidantes, para poder juzgar su utilidad con una mirada crítica

Antioxidantes y envejecimiento cutáneo / Antioxodants and cutaneous aging

Las formulaciones disponibles actualmente para uso dermatológico, basadas en sustancias antioxidantes tales como vitaminas C y E, entre otras, abundan con promesas de revertir el envejecimiento cutáneo. En el presente trabajo se realiza una revisión de los sistemas antioxidantes cutáneos, de la relación entre envejecimiento y daño oxidativo, así como de la evidencia disponible en cuanto al tratamiento con antioxidantes. La intención de este artículo es que el dermatólogo comprenda las bases fisiológicas de acción de los antioxidantes, para poder juzgar su utilidad con una mirada crítica (AU)

Antioxidant adaptive response of human mononuclear cells to UV-B: effect of lipoic acid.

Supplementation of human mononuclear cells with 3 and 6 mM of lipoic acid produces an inhibition of the antioxidant adaptive response triggered by treatment with UV-B light (0.30 W/m2 for 15 min). Supplementation with 1.5 mM of lipoic acid gives no conclusive results. The adaptive response is characterized by an increase in the activities of superoxide dismutase, catalase, glutathione peroxidase and DT-diaphorase. Catalase (5.5 +/- 0.6 pmol/mg prot) increases its activity by up to 22 +/- 3 pmol/mg prot, after irradiation with UV-B. Supplementation with 3 and 6 mM of lipoic acid completely inhibits the adaptive response. The activities of the membrane-bound mitochondrial enzymes succinate dehydrogenase and cytochrome oxidase do not increase after UV-B exposure. Moreover, their activities are found to decrease and the addition of lipoic acid does not prevent this effect. The inhibition of the antioxidant response by lipoic acid in human cells appears as indirect evidence of the existence of oxidative stress in the development of this response. As lipoic acid behaves as an effective antioxidant, it seems that its action decreases the intracellular oxidative signals necessary to develop the adaptive response in human mononuclear cells.

[The systemic response of antioxidant enzymes to the oxidative stress induced by irradiation at low doses]. / Sistemnyi otvet antioksidantnykh fermentov na okislitel'nyi stress, vyzvannyi oblucheniem v malykh dozakh.

As a result of total chronic gamma irradiation of mice (137Cs, 0.6 cGy/day, 9 days) the functioning of superoxide generation and utilisation systems in liver were disturbed. The regulatory links between the activities of superoxide dismutase and glutathione peroxidase are found to be maintained. Postradiation effects were more expressed for a total dose of 1.2 cGy than for a dose of 5.4 cGy, providing support for the hypothesis of delayed reparation as a reason of harmful action of low-dose irradiation.

Studies of methyl 2-nitroimidazole-1-acetohydroxamate (KIN-804) 1: effect on free radical scavenging system in mice bearing Ehrlich ascites carcinoma.

Methyl 2-nitroimidazole-1-acetohydroxamate (KIN-804) is a 2-nitroimidazole derivative containing a hydroxamate side chain designed to enhance the radiosensitization response of hypoxic cells. The possible sensitization of tumor tissue by KIN-804 can be evaluated through investigation of the levels of the free radical scavengers; namely, glutathione (GSH) and its complex enzyme system including glutathione reductase (GR) and glutathione peroxidase (GSH-Px), as well as glucose-6-phosphate dehydrogenase (G-6-PD). Female albino mice were inoculated with Ehrlich carcinoma in the thigh. Administration of KIN-804 (i.p. 80 mg/kg body weight) was carried out 20 min before localized irradiation of 10 Gy. The data revealed that KIN-804 administration, followed or not by gamma irradiation, resulted in a significant decrease in GSH content in tumor tissues associated with inhibition in GR and G-6-PD activities. Blood GSH-Px was enhanced in tumor inoculated mice and the administration of KIN-804 returned it to the normal value. These changes were more noticeable in tumor bearing mice exposed to both KIN-804 and irradiation.