Almira Georgieva

Effects of proteasome inhibitor, MG132, on proteasome activity and oxidative status of rat liver.

In vivo effects of N‐benzyloxycarbonyl (Cbz)‐Leu–Leu‐leucinal (MG132) on chymotryptic‐like (ChT‐L), tryptic‐like, and post‐glutamyl peptide hydrolytic‐like proteasome activities, protein oxidation, lipid peroxidation (LP), glutathione (GSH) level, as well as on the activity of antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH‐Px), and glutathione‐reductase) in the rat liver were studied. The possibility of MG132 provoking the formation of free oxygen radicals was also assayed in primary hepatocytes. The following results were obtained: (1) In vivo, MG132 did not change the spontaneous LP, but increased Fe‐induced LP and the amount of oxidized proteins; it decreased the GSH level in liver. From the proteasome activities studied in liver cytosol only ChT‐L activity was significantly decreased after MG132 administration. Furthermore, MG132 increased antioxidant enzyme activities of SOD, CAT, and GSH‐Px. (2) In vitro, MG132 increased free radical oxygen species in hepatocytes; this effect disappeared in the presence of CAT or mannitol. In conclusion, since nowadays proteasome inhibitors are entering into the swing of laboratory and clinical practice, the present data could provide useful information for MG132 action. Consequently, future in vivo experiments with MG132 could highlight the possibility of its use at different pathological conditions. Copyright

In vivo effects of pentoxifylline on enzyme and non-enzyme antioxidant levels in rat liver after carrageenan-induced paw inflammation

The present study aimed to investigate the effects of pentoxifylline (PTX) on the carrageenan (CG)‐induced paw oedema and on the endogenous levels of cell enzyme and non‐enzyme antioxidants in rat liver, 4 and 24 h after CG injection. PTX (50 mg kg−1, i.p.), administered 30 min before CG, decreased the paw oedema, 2–4 h after CG administration. The drug protected CG‐induced decrease of glutathione (non‐enzyme antioxidant) and had no effect on CG‐unchanged activities of superoxide dismutase, glutathione peroxidase (enzyme antioxidants) and glucose‐6‐phosphate dehydrogenase (enzyme, important for the activity of GSH‐conjugated antioxidant enzymes). The drug showed a good antioxidant capacity in chemical systems, generating reactive oxygen species. The present results suggest that the antioxidant activity of PTX might contribute to its beneficial effects in liver injuries. Copyright

Effect of MG132 on proteasome activity and prooxidant/antioxidant status of rat liver subjected to ischemia/reperfusion injury.

Aim:  Previous studies have shown that proteasome inhibitors exerted protective effects against ischemia/reperfusion injury (IRI) of brain, heart, kidney and intestine. The aim of the present study was to investigate: (i) whether the proteasome inhibitor MG132 protects rat liver against IRI; and (ii) whether MG132 modulates prooxidant/antioxidant status of rat liver subjected to warm IRI.

Effects of desipramine on the antioxidant status in rat tissues at carrageenan-induced paw inflammation

The pathogenesis of many diseases and different pathological conditions, including inflammation, is associated with excess production of reactive oxygen species (ROS). The present study aimed to investigate the effects of the antidepressant desipramine (DES) on carrageenan (CG)‐induced inflammation, as well as on the endogenous levels of cell enzyme and non‐enzyme antioxidants in rat liver and spleen, 4 and 24 h after CG injection. The intra‐plantar CG injection into the right hind paw resulted in a time‐dependent increase in the paw volume; the maximum of CG‐induced edema peak was in 2–4 h. A single DES dose of 20 mg·kg−1, administered 30 min before CG, had no effect on paw edema, whereas the higher drug dose used (50 mg·kg−1) suppressed the edematous response to CG. The latter drug dose protected CG‐induced decrease of glutathione (non‐enzyme antioxidant) in the liver; it did not affect CG‐unchanged activities of superoxide dismutase, glutathione peroxidase (enzyme antioxidants) and glucose‐6‐phosphate dehydrogenase (enzyme, important for the activity of glutathione‐conjugated antioxidant enzymes) in both liver and spleen. The drug showed an efficient antioxidant capacity in ROS‐generating chemical systems; it was higher than that of fluoxetine (another type of antidepressant). The present results suggest that the good antioxidant activity of DES might contribute to its beneficial effects in liver injuries. Copyright

Effect of copper intoxication on rat liver proteasome activity: relationship with oxidative stress.

Copper toxicity is associated with formation of reactive oxygen species, which are capable to oxidize proteins. The selective removal of the latter by the 20S proteasome is considered an essential part of the cell antioxidant defense system. The aim of the present study was to investigate whether peptidase activities of rat liver proteasomes were affected by chronic (40 mg CuSO4/rat/daily with the drinking water for 2 weeks) and acute (20 mg/kg CuSO4, s.c.) copper treatment. To evaluate the role of proteasome, its inhibitor MG132 was also used. The degree of copper‐induced oxidative stress (OS), established by measuring lipid peroxidation, protein oxidation, and cellular glutathione level, as well as activities of antioxidant enzymes—catalase, superoxide dismutase, and gultathionine peroxidase, depended on the mode of copper administration. Chronic copper administration (mild oxidative stress) did not affect proteasome activities, whereas acute copper treatment (severe oxidative stress) caused a decline in chymotryptic‐ and tryptic‐like activities. The treatment of copper‐loaded animals with MG132 did not change copper‐induced alterations in the tested indices, except an additional increase in protein oxidation and inhibition of glutathionine peroxidase activity. The results suggested that the in vivo copper‐induced oxidative stress was associated with changes in the catalytic activity of proteasome.

Effects of structural analogues of nociceptin(1–13)NH2 on brain antioxidant status in kainic acid‐treated rats

The in vivo effects of nociceptin (N/OFQ(1–13)NH2) and its structural analogues ([Dab9]N/OFQ(1–13)NH2, [Dap9]N/OFQ(1–13)NH2 and [Cav9]N/OFQ(1–13)NH2) on the levels of lipid peroxidation and cell antioxidants (enzyme and non‐enzyme) in brain of control and kainic acid (KA)‐treated rats were studied. In control animals, [Dab9]N/OFQ(1–13)NH2 and [Dap9]N/OFQ(1–13)NH2, unlike N/OFQ(1–13)NH2 and [Cav9]N/OFQ(1–13)NH2, slightly increased the brain lipid peroxidation; the rest of the parameters were unchanged by all neuropeptides tested. KA (0.25 µg in 0.5 µl, i.c.v) increased the lipid peroxidation (4 and 24 h after KA‐injection) and decreased the glutathione level (1 h after KA‐administration). One hour after KA‐administration, the neuropeptides (2 µg in 0.5 µl, injected 30 min before KA) showed the following effects: a slight decrease in the KA‐induced lipid peroxidation by all nociceptin analogues and an enhancement of the KA‐decreased GSH level, but by [Cav9]N/OFQ(1–13)NH2 only. The brain antioxidant enzyme activities were unchanged in all used experimental groups. In addition, the nociceptin analogues, especially [Can9]N/OFQ(1–13)NH2, showed a good antioxidant capacity in chemical systems, generating reactive oxygen species. In conclusion, the substitution of lysin (Lys) in N/OFQ(1–13)NH2 molecule with other amino acids might contribute to changes in its antioxidant properties. Copyright

Cytotoxic and genotoxic potential of Bulgarian Rosa alba L. essential oil – in vitro model study

ABSTRACT Rosa alba L., also known as the white oil-bearing rose, has been cultivated in relatively small areas of Europe – predominantly in the Rose Valley of Bulgaria. An increasing number of studies in vitro and in vivo, including clinical studies, have demonstrated the therapeutic efficacy of rose oils in recent years. However, little is known about the cytotoxic and genotoxic potential of the phytocomplex oil extract derived from Rosa alba L. The aim of the present work was to investigate the cytotoxicity and clastogenic effects of Rosa alba L. essential oil and its main constituent – geraniol, as well as citral A, associated with allergies and contact dermatitis. We used classical cytogenetic methods and comet assay. 1-Methyl-3-nitro-1-nitrosoguanidine was used as a standard mutagen. The data showed that R. alba L. essential oil (in concentrations up to 1000 μg/mL) did not exhibit a statistically significant cytotoxic effect. The essential oil did not significantly increase the level of mitotic disturbances (micronuclei and aneuploidy effects) and had no significant effect on the induction of chromatid aberrations, compared to the untreated control sample. Only geraniol and citral A (in the concentrations used) increased significantly the percentage of migrated DNA in the comet tail, compared to the whole oil extract. This study gives a reason to believe that R. alba L. oil has potential as a supplementary component in some therapeutic strategies. It would be harmless to normal cells and tissues, but with potential for additive or synergistic cytotoxicity against cancer cells.

Comparative study of alloxan effects in copper-loaded and iron-loaded rats: lipid peroxidation, protein oxidation, proteasome and antioxidant enzyme activities

The in-vivo effects of alloxan on protein oxidation and lipid peroxidation, as well as on proteasome and antioxidant enzyme activities in liver and kidney of copper-loaded and iron-loaded rats, were studied. In control animals, a single alloxan dose (120 mg/kg, i.p.) increased blood-glucose concentration at the 24th hr and 48th hr and, especially, on the 5th day. For these periods of alloxan action, no changes in lipid peroxidation and antioxidant enzyme activities were found; only a slight increase of carbonyl content and strong increase of trypsin-like proteasome activity in rat liver on the 5th day was observed. Five days after alloxan injection, the blood-glucose concentration in iron-pretreated rats was similar to that of the controls. However, it was significantly lower in copper-pretreated animals; hence, insulin-mimetic action of copper might be suggested. The lower proteasome activity, measured in liver of copper-pretreated diabetic rats is probably due to a potential copper-chelating ability of alloxan. The present results showed that the action of alloxan was different in copper-and iron-pretreated rats. Analogous studies, using pretreatment with other metals, would contribute to a further elucidation of the role of different metals in diabetes development, especially in regions with environmental metal contamination.