Oxidative damage of rat liver mitochondria during exposure to t-butyl hydroperoxide. Role of Ca²⁺ ions in oxidative processes

Perinatal exposure to a glyphosate pesticide formulation induces offspring liver damage

The present study investigated the effects of perinatal exposure to glyphosate-based herbicide (GBH) in offspring's liver. Pregnant Wistar rats were exposed to GBH (70 mg glyphosate/Kg body weight/day) in drinking water from gestation day 5 to postnatal day 15. The perinatal exposure to GBH increased ⁴⁵Ca²⁺ influx in offspring's liver. Pharmacological tools indicated a role played by oxidative stress, phospholipase C (PLC) and Akt pathways, as well as voltage-dependent Ca²⁺ channel modulation on GBH-induced Ca²⁺ influx in offspring's liver. In addition, changes in the enzymatic antioxidant defense system, decreased GSH content, lipid peroxidation and protein carbonylation suggest a connection between GBH-induced hepatotoxic mechanism and redox imbalance. The perinatal exposure to GBH also increased the enzymatic activities of transaminases and gamma-glutamyl transferase in offspring's liver and blood, suggesting a pesticide-induced liver injury. Moreover, we detected increased iron levels in liver, blood and bone marrow of GBH-exposed rats, which were accompanied by increased transferrin saturation and decreased transferrin levels in blood. The levels of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) were increased in the liver of rats perinatally exposed to GBH, which were associated with. Increased phospho-p65NFκB immunocontent. Therefore, we propose that excessive amounts of iron in offspring's liver, blood and bone marrow induced by perinatal exposure to GBH may account for iron-driven hepatotoxicity, which was associated with Ca²⁺ influx, oxidative damage and inflammation. Further studies will clarify whether these events can ultimately impact on liver function.

[Structural and functional changes in rat liver mitochondria under calcium ion loading in the absence and presence of flavonoids]

The aim of the present work was to elucidate the mechanisms of calcium ion-induced impairments of the ultrastructure and functional activity of isolated rat liver mitochondria in the absence and presence of a number of flavonoids in vitro. In the presence of exogenous Ca²⁺ (20-60 μM), mitochondrial heterogeneity in size and electron density markedly increased: most organelles demonstrated a swollen electron-light matrix, bigger size, elongated cristae and a reduced their number, a damaged native structure of the inner membrane up to its detachment, and some mitochondria showed a more electron-dense matrix (condensed mitochondria). The calcium-induced opening of the mitochondrial permeability transition pores (MPTP) resulted in the ultrastructural disturbances and in the effective inhibition of the respiratory activity of rat liver mitochondria. The flavonoids (10-25 μM) naringenin and catechin, dose-dependently inhibited the respiratory activity of mitochondria and stimulated the MPTP opening in the presence of Ca²⁺ ions. Since Ruthenium red, an inhibitor of the mitochondrial Ca²⁺ uniporter, effectively prevented Ca²⁺-induced MPTP opening both in the absence and presence of flavonoids, we hypothesized that the effect of flavonoids on the MPTP opening could be mediated by stimulation of the Ca²⁺ uniporter.

The mitochondrial copper chaperone COX11 has an additional role in cellular redox homeostasis

Mitochondria are sites of cellular respiration, which is accompanied by the generation of dangerous reactive oxygen species (ROS). Cells have multiple mechanisms to mitigate the dangers of ROS. Here we investigate the involvement of the COX complex assembly chaperone COX11 (cytochrome c oxidase 11) in cellular redox homeostasis, using homologs from the flowering plant Arabidopsis thaliana (AtCOX11) and yeast Saccharomyces cerevisiae (ScCOX11). We found that AtCOX11 is upregulated in Arabidopsis seedlings in response to various oxidative stresses, suggesting a defensive role. In line with this, the overexpression of either AtCOX11 or ScCOX11 reduced ROS levels in yeast cells exposed to the oxidative stressor paraquat. Under normal growth conditions, both Arabidopsis and yeast COX11 overexpressing cells had the same ROS levels as the corresponding WT. In contrast, the COX11 knock-down and knock-out in Arabidopsis and yeast, respectively, significantly reduced ROS levels. In yeast cells, the ScCOX11 appears to be functionally redundant with superoxide dismutase 1 (ScSOD1), a superoxide detoxifying enzyme. The ΔSccox11ΔScsod1 mutants had dramatically reduced growth on paraquat, compared with the WT or single mutants. This growth retardation does not seem to be linked to the status of the COX complex and cellular respiration. Overexpression of putatively soluble COX11 variants substantially improved the resistance of yeast cells to the ROS inducer menadione. This shows that COX11 proteins can provide antioxidative protection likely independently from their COX assembly function. The conserved Cys219 (in AtCOX11) and Cys208 (in ScCOX11) are important for this function. Altogether, these results suggest that COX11 homologs, in addition to participating in COX complex assembly, have a distinct and evolutionary conserved role in protecting cells during heightened oxidative stress.

Role of mitochondrial calcium in hypochlorite induced oxidative damage of cells

Hypochlorite (HOCl) is one of the most important mediators of inflammatory processes. Recent evidence demonstrates that changes in intracellular calcium pool play a significant role in the damaging effects of hypochlorite and other oxidants. Mitochondria are shown to be one of the intracellular targets of hypochlorite. But little is known about the mitochondrial calcium pool changes in HOCl-induced mitochondrial dysfunction. Using isolated rat liver mitochondria, we showed the oxidative damage of mitochondria (GSH oxidation and mixed protein-glutathione formation without membrane lipid peroxidation) and alterations in the mitochondrial functional parameters (decrease of respiratory activity and efficiency of oxidative phosphorylation, NADH and FADH coenzyme levels, and membrane potential) under hypochlorite action (50-300 μM). Simultaneously, the mitochondrial calcium release and swelling were demonstrated. In the presence of EGTA, the damaging effects of HOCl were less pronounced, reflecting direct involvement of mitochondrial Ca²⁺ in mechanisms of oxidant-induced injury. Furthermore, exposure of HeLa cells to hypochlorite resulted in a considerable increase in cytoplasmic calcium concentrations and a decrease in mitochondrial ones. Applying specific inhibitors of calcium transfer systems, we demonstrated that mitochondria play a key role in the redistribution of cytoplasmic Ca²⁺ ions under hypochlorite action and act as mediators of calcium release from the endoplasmic reticulum into the cytoplasm.

Effect of hypothermia on the functional activity of liver mitochondria of grass snake (Natrix natrix): inhibition of succinate-fueled respiration and K+ transport, ROS-induced activation of mitochondrial permeability transition

The article considers the comparative analysis of the functional activity of mitochondria isolated from the liver of grass snakes, Natrix natrix (Linnaeus, 1758) that were kept at different temperatures (23-26 °C and 4-5 °C). It was found that liver mitochondria of hypothermia-exposed grass snakes are characterized by weak coupling of oxidative phosphorylation as compared to mitochondria of active animals which is caused by inhibition of succinate-fuelled respiration in ADP-stimulated state, as well as by activation of basal non-phosphorylating rate. Inhibition of mitochondrial respiration in hibernating animals is associated with a decrease in the activity of the respiratory chain complexes of organelles. A significant decrease in the rate of K⁺ transport in the liver mitochondria of hibernating animals has been established. Under these conditions, a decrease in the calcium capacity of the organelles was also revealed, which indicates a decrease in the resistance of the mitochondria of hibernating animals to the induction of the Ca²⁺-dependent mitochondrial pore. All these changes in the functional activity of mitochondria are observed on the background of increasing H₂O₂ production as well as increasing the proportion of polyunsaturated fatty acids in phospholipid composition of mitochondrial membranes, which are the targets of reactive oxygen species. It can lead to increased formation of lipid peroxides and activation of destructive processes associated with the induction of Ca²⁺-dependent mitochondrial pore.

Fenvalerate induces oxidative hepatic lesions through an overload of intracellular calcium triggered by the ERK/IKK/NF-κB pathway

Fenvalerate (FEN), a mainstream pyrethroid pesticide, was initially recommended as a low-toxicity agent for controlling agricultural and domestic pests. Despite the widespread use of FEN worldwide, little data are available on FEN-induced hepatic lesions and molecular mechanisms. In the present study, we first performed an occupational cross-sectional study on FEN factory workers and found that the levels of serum alanine aminotransferase (ALT) and total antioxidant capacity increased, whereas malondialdehyde decreased in laborers in the working areas where the levels of airborne FEN were much higher compared with the office area. The results were then confirmed by animal experiments that abnormal hepatic histology, increased ALT level, and compromised hepatic oxidative capability were observed in rats exposed to a high concentration of FEN. Furthermore, the bioinformatics analysis of gene microarray in rat liver tissue showed that FEN significantly changed the expressions of genes related to the regulation of intracellular calcium ion homeostasis and the calcium signal pathway. Finally, the functional experiments in Buffalo rat liver (BRL) cells demonstrated that FEN first activated ERK MAPK, followed by IKK and NF-κB, which triggered the transcription of genes responsible for accelerating an overload of intracellular calcium ions, prompted reactive oxygen species generation in the mitochondria, and finally, induced hepatic cellular apoptosis. The calcium signaling pathway and in particular, an overload of intracellular calcium play a critical role in this pathophysiological process via the ERK/IKK/NF-κB pathway. Our study furthers the understanding of the mechanism of FEN-induced hepatic injuries and may have implications in the prevention and control of liver diseases induced by environmental pesticides.-Qiu, L.-L., Wang, C., Yao, S., Li, N., Hu, Y., Yu, Y., Xia, R., Zhu, J., Ji, M., Zhang, Z., Wang S.-L. Fenvalerate induces oxidative hepatic lesions through an overload of intracellular calcium triggered by the ERK/IKK/NF-κB pathway.

Change in Populations of Macrophages Promotes Development of Delayed Gastric Emptying in Mice

BACKGROUND & AIMS

Muscularis propria macrophages lie close to cells that regulate gastrointestinal motor function, including interstitial cells of Cajal (ICC) and myenteric neurons. In animal models of diabetic gastroparesis, development of delayed gastric emptying has been associated with loss of macrophages that express cytoprotective markers and reduced networks of ICC. Mice with long-term diabetes and normal gastric emptying have macrophages that express anti-inflammatory markers and have normal gastric ICC. Mice homozygous for the osteopetrosis spontaneous mutation in the colony-stimulating factor 1 gene (Csf1op/op) do not have macrophages; when they are given streptozotocin to induce diabetes, they do not develop delayed gastric emptying. We investigated whether population of the gastric muscularis propria of diabetic Csf1op/op mice with macrophages is necessary to change gastric emptying, ICC, and myenteric neurons and investigated the macrophage-derived factors that determine whether diabetic mice do or do not develop delayed gastric emptying.

METHODS

Wild-type and Csf1op/op mice were given streptozotocin to induce diabetes. Some Csf1op/op mice were given daily intraperitoneal injections of CSF1 for 7 weeks; gastric tissues were collected and cellular distributions were analyzed by immunohistochemistry. CD45⁺, CD11b⁺, F4/80⁺ macrophages were dissociated from gastric muscularis propria, isolated by flow cytometry and analyzed by quantitative real-time polymerase chain reaction. Cultured gastric muscularis propria from Csf1op/op mice was exposed to medium that was conditioned by culture with bone marrow-derived macrophages from wild-type mice.

RESULTS

Gastric muscularis propria from Csf1op/op mice given CSF1 contained macrophages; 11 of 15 diabetic mice given CSF1 developed delayed gastric emptying and had damaged ICC. In non-diabetic Csf1op/op mice, administration of CSF1 reduced numbers of gastric myenteric neurons but did not affect the proportion of nitrergic neurons or ICC. In diabetic Csf1op/op mice given CSF1 that developed delayed gastric emptying, the proportion of nitrergic neurons was the same as in non-diabetic wild-type controls. Medium conditioned by macrophages previously exposed to oxidative injury caused damage to ICC in cultured gastric muscularis propria from Csf1op/op mice; neutralizing antibodies against IL6R or TNF prevented this damage to ICC. CD45⁺, CD11b⁺, and F4/80⁺ macrophages isolated from diabetic wild-type mice with delayed gastric emptying expressed higher levels of messenger RNAs encoding inflammatory markers (IL6 and inducible nitric oxide synthase) and lower levels of messenger RNAs encoding markers of anti-inflammatory cells (heme oxygenase 1, arginase 1, and FIZZ1) than macrophages isolated from diabetic mice with normal gastric emptying.

CONCLUSIONS

In studies of Csf1op/op and wild-type mice with diabetes, we found delayed gastric emptying to be associated with increased production of inflammatory factors, and reduced production of anti-inflammatory factors, by macrophages, leading to loss of ICC.

Ferutinin Induces Membrane Depolarization, Permeability Transition Pore Formation, and Respiration Uncoupling in Isolated Rat Liver Mitochondria by Stimulation of Ca2+-Permeability

It is well known that the terpenoid ferutinin (4-oxy-6-(4-oxybenzoyloxy) dauc-8,9-en), isolated from the plant Ferula tenuisecta, considerably increases the permeability of artificial and cellular membranes to Ca²⁺-ions and produces apoptotic cell death in different cell lines in a mitochondria-dependent manner. The present study was designed for further evaluation of the mechanism(s) of mitochondrial effects of ferutinin using isolated rat liver mitochondria. Our findings provide evidence for ferutinin at concentrations of 5-27 µM to decrease state 3 respiration and the acceptor control ratio in the case of glutamate/malate as substrates. Ferutinin alone (10-60 µM) also dose-dependently dissipated membrane potential. In the presence of Ca²⁺-ions, ferutinin (10-60 µM) induced considerable depolarization of the inner mitochondrial membrane, which was partially inhibited by EGTA, and permeability transition pore formation, which was diminished partly by cyclosporin A, and did not influence markedly the effect of Ca²⁺ on mitochondrial respiration. Ruthenium Red, a specific inhibitor of mitochondrial calcium uniporter, completely inhibited Ca²⁺-induced mitochondria swelling and membrane depolarization, but did not affect markedly the stimulation of these Ca²⁺-dependent processes by ferutinin. We concluded that the mitochondrial effects of ferutinin might be primarily induced by stimulation of mitochondrial membrane Ca²⁺-permeability, but other mechanisms, such as driving of univalent cations, might be involved.

Loss in PKC Epsilon Causes Downregulation of MnSOD and BDNF Expression in Neurons of Alzheimer's Disease Hippocampus

Oxidative stress and amyloid-β (Aβ) oligomers have been implicated in Alzheimer's disease (AD). The growth and maintenance of neuronal networks are influenced by brain derived neurotrophic factor (BDNF) expression, which is promoted by protein kinase C epsilon (PKCɛ). We investigated the reciprocal interaction among oxidative stress, Aβ, and PKCɛ levels and subsequent PKCɛ-dependent MnSOD and BDNF expression in hippocampal pyramidal neurons. Reduced levels of PKCɛ, MnSOD, and BDNF and an increased level of Aβ were also found in hippocampal neurons from autopsy-confirmed AD patients. In cultured human primary hippocampal neurons, spherical aggregation of Aβ (amylospheroids) decreased PKCɛ and MnSOD. Treatment with t-butyl hydroperoxide (TBHP) increased superoxide, the oxidative DNA/RNA damage marker, 8-OHG, and Aβ levels, but reduced PKCɛ, MnSOD, BDNF, and cultured neuron density. These changes were reversed with the PKCɛ activators, bryostatin and DCPLA-ME. PKCɛ knockdown suppressed PKCɛ, MnSOD, and BDNF but increased Aβ. In cultured neurons, the increase in reactive oxygen species (ROS) associated with reduced PKCɛ during neurodegeneration was inhibited by the SOD mimetic MnTMPyP and the ROS scavenger NAc, indicating that strong oxidative stress suppresses PKCɛ level. Reduction of PKCɛ and MnSOD was prevented with the PKCɛ activator bryostatin in 5-6-month-old Tg2576 AD transgenic mice. In conclusion, oxidative stress and Aβ decrease PKCɛ expression. Reciprocally, a depression of PKCɛ reduces BDNF and MnSOD, resulting in oxidative stress. These changes can be prevented with the PKCɛ-specific activators.

Role of Oxygen Free Radicals, Nitric Oxide and Mitochondria in Mediating Cardiac Alterations During Liver Cirrhosis Induced by Thioacetamide

Thioacetamide (TAA) administration is widely used for induction of liver cirrhosis in rats, where reactive oxygen radicals (ROS) and nitric oxide (NO) participate in development of liver damage. Cardiac dysfunction is an important complication of liver cirrhosis, but the role of ROS or NO in cardiac abnormalities during liver cirrhosis is not well understood. This was investigated in animals after TAA-induced liver cirrhosis and temporal changes in oxidative stress, NO and mitochondrial function in the heart evaluated. TAA induced elevation in cardiac levels of nitrate before development of frank liver cirrhosis, without gross histological alterations. This was accompanied by an early induction of P38 MAP kinase, which is influenced by ROS and plays an important signaling role for induction of iNOS. Increased nitrotyrosine, protein oxidation and lipid peroxidation in the heart and cardiac mitochondria, suggestive of oxidative stress, also preceded frank liver cirrhosis. However, compromised cardiac mitochondrial function with a decrease in respiratory control ratio and increased mitochondrial swelling was seen later, when cirrhosis was evident. In conclusion, TAA induces elevations in ROS and NO in the heart in parallel to early liver damage. This leads to later development of functional deficits in cardiac mitochondria after development of liver cirrhosis.

Mitochondrial dysfunction underlying outer retinal diseases

Dysfunction of photoreceptors, retinal pigment epithelium (RPE) or both contribute to the initiation and progression of several outer retinal disorders. Disrupted Müller glia function might additionally subsidize to these diseases. Mitochondrial malfunctioning is importantly associated with outer retina pathologies, which can be classified as primary and secondary mitochondrial disorders. This review highlights the importance of oxidative stress and mitochondrial DNA damage, underlying outer retinal disorders. Indeed, the metabolically active photoreceptors/RPE are highly prone to these hallmarks of mitochondrial dysfunction, indicating that mitochondria represent a weak link in the antioxidant defenses of outer retinal cells.

Calcium-Induced Mitochondrial Permeability Transitions: Parameters of Ca2+ Ion Interactions with Mitochondria and Effects of Oxidative Agents

We evaluated the parameters of Ca²⁺-induced mitochondrial permeability transition (MPT) pore formations, Ca²⁺ binding constants, stoichiometry, energy of activation, and the effect of oxidative agents, tert-butyl hydroperoxide (tBHP), and hypochlorous acid (HOCl), on Ca²⁺ -mediated process in rat liver mitochondria. From the Hill plot of the dependence of MPT rate on Ca²⁺ concentration, we determined the order of interaction of Ca²⁺ ions with the mitochondrial sites, n = 3, and the apparent K_d = 60 ± 12 µM. We also found the apparent Michaelis-Menten constant, K_m, for Ca²⁺ interactions with mitochondria to be equal to 75 ± 20 µM, whereas that in the presence of 300 µM tBHP was 120 ± 20 µM. Using the Arrhenius plots of the temperature dependences of apparent mitochondrial swelling rate at various Ca²⁺ concentrations, we calculated the activation energy of the MPT process. ΔE_a was 130 ± 20 kJ/mol at temperatures below the break point of the Arrhenius plot (30-34 °C) and 50 ± 9 kJ/mol at higher temperatures. Ca²⁺ ions induced rapid mitochondrial NADH depletion and membrane depolarization. Prevention of the pore formation by cyclosporin A inhibited Ca²⁺-dependent mitochondrial depolarization and Mg²⁺ ions attenuated the potential dissipation. tBHP (10-150 µM) dose-dependently enhanced the rate of MPT opening, whereas the effect of HOCl on MPT depended on the ratio of HOCl/Ca²⁺. The apparent K_m of tBHP interaction with mitochondria in the swelling reaction was found to be K_m = 11 ± 3 µM. The present study provides evidence that three calcium ions interact with mitochondrial site with high affinity during MPT. Ca²⁺-induced MPT pore formations due to mitochondrial membrane protein denaturation resulted in membrane potential dissipation. Oxidants with different mechanisms, tBHP and HOCl, reduced mitochondrial membrane potential and oxidized mitochondrial NADH in EDTA-free medium and had an effect on Ca²⁺-induced MPT onset.

Effects of low-intensity ultrasound on oxidative damage in retinal pigment epithelial cells in vitro

Oxidative stress in retinal pigment epithelium (RPE) is one of the key causative factors of RPE injury in age-related macular degeneration (AMD). Low-intensity ultrasound (LIUS) less than 1 W/cm(2) in intensity has been found to have cytoprotective and anti-inflammatory effects in many cell types and diseases. In this study, we investigated for the first time the feasibility of using LIUS to protect RPE cells from oxidative damage. ARPE-19 cells were treated with H2O2 (an exogenous source of reactive oxygen species) or L-buthionine-(S,R)-sulfoximine (BSO), a glutathione synthase inhibitor, and exposed immediately to LIUS at intensities of 50, 100 and 200 mW/cm(2) and a frequency of 1 MHz for 20 min. Both H2O2 and BSO increased the percentage of cells positive for mitochondrial reactive oxygen species at 1 h, but not at 24 h. Co-treatment with LIUS clearly repressed these cells similarly at all intensities by approximately 34%-43% for H2O2 and 24%-25% for BSO (p < 0.05). The percentage of cells with mitochondrial membrane depolarization also increased with H2O2 and BSO treatment, particularly at 1 h, and decreased by approximately 60% with LIUS at 100 mW/cm(2) (p < 0.05). The amount of intracellular calcium ion ([Ca(2+)]i) was elevated only by BSO at 24 h and was also significantly diminished, by approximately 45%, by LIUS at 100 mW/cm(2) (p < 0.05). Both H2O2 and BSO significantly hampered cell viability at 24 h, but LIUS at 100 mW/cm(2) restored only BSO-induced cell viability by approximately 2.7-fold (p < 0.05). This study illustrated that LIUS has a protective effect on RPE cells against oxidative damage caused by BSO, an endogenous mitochondrial reactive oxygen species generator. We speculate that LIUS has the potential to treat oxidative damage and related pathologic changes in RPE.

Vasoinhibins regulate the inner and outer blood-retinal barrier and limit retinal oxidative stress

Vasoinhibins are prolactin fragments present in the retina, where they have been shown to prevent the hypervasopermeability associated with diabetes. Enhanced bradykinin (BK) production contributes to the increased transport through the blood-retina barrier (BRB) in diabetes. Here, we studied if vasoinhibins regulate BRB permeability by targeting the vascular endothelium and retinal pigment epithelium (RPE) components of this barrier. Intravitreal injection of BK in male rats increased BRB permeability. Vasoinhibins prevented this effect, as did the B2 receptor antagonist Hoe-140. BK induced a transient decrease in mouse retinal and brain capillary endothelial monolayer resistance that was blocked by vasoinhibins. Both vasoinhibins and the nitric oxide (NO) synthase inhibitor L-NAME, but not the antioxidant N-acetyl cysteine (NAC), blocked the transient decrease in bovine umbilical vein endothelial cell (BUVEC) monolayer resistance induced by BK; this block was reversed by the NO donor DETANONOate. Vasoinhibins also prevented the BK-induced actin cytoskeleton redistribution, as did L-NAME. BK transiently decreased human RPE (ARPE-19) cell monolayer resistance, and this effect was blocked by vasoinhibins, L-NAME, and NAC. DETANONOate reverted the blocking effect of vasoinhibins. Similar to BK, the radical initiator Luperox induced a reduction in ARPE-19 cell monolayer resistance, which was prevented by vasoinhibins. These effects on RPE resistance coincided with actin cytoskeleton redistribution. Intravitreal injection of vasoinhibins reduced the levels of reactive oxygen species (ROS) in retinas of streptozotocin-induced diabetic rats, particularly in the RPE and capillary-containing layers. Thus, vasoinhibins reduce BRB permeability by targeting both its main inner and outer components through NO- and ROS-dependent pathways, offering potential treatment strategies against diabetic retinopathies.

The role of calpain in an in vivo model of oxidative stress-induced retinal ganglion cell damage

PURPOSE

In this study, we set out to establish an in vivo animal model of oxidative stress in the retinal ganglion cells (RGCs) and determine whether there is a link between oxidative stress in the RGCs and the activation of calpain, a major part of the apoptotic pathway.

MATERIALS AND METHODS

Oxidative stress was induced in the RGCs of C57BL/6 mice by the intravitreal administration of 2,2'-azobis (2-amidinopropane) dihydrochloride (AAPH, 30mM, 2μl). Control eyes were injected with 2μl of vehicle. Surviving Fluorogold (FG)-labeled RGCs were then counted in retinal flat mounts. Double staining with CellROX and Annexin V was performed to investigate the co-localization of free radical generation and apoptosis. An immunoblot assay was used both to indirectly evaluate calpain activation in the AAPH-treated eyes by confirming α-fodrin cleavage, and also to evaluate the effect of SNJ-1945 (a specific calpain inhibitor: 4% w/v, 100mg/kg, intraperitoneal administration) in these eyes.

RESULTS

Intravitreal administration of AAPH led to a significant decrease in FG-labeled RGCs 7days after treatment (control: 3806.7±575.2RGCs/mm(2), AAPH: 3156.1±371.2RGCs/mm(2), P<0.01). CellROX and Annexin V signals were co-localized in the FG-labeled RGCs 24h after AAPH injection. An immunoblot assay revealed a cleaved α-fodrin band that increased significantly 24h after AAPH administration. Intraperitoneally administered SNJ-1945 prevented the cleavage of α-fodrin and had a neuroprotective effect against AAPH-induced RGC death (AAPH: 3354.0±226.9RGCs/mm(2), AAPH+SNJ-1945: 3717.1±614.6RGCs/mm(2), P<0.01).

CONCLUSION

AAPH administration was an effective model of oxidative stress in the RGCs, showing that oxidative stress directly activated the calpain pathway and induced RGC death. Furthermore, inhibition of the calpain pathway protected the RGCs after AAPH administration.

Sulfite disrupts brain mitochondrial energy homeostasis and induces mitochondrial permeability transition pore opening via thiol group modification

Sulfite oxidase (SO) deficiency is biochemically characterized by the accumulation of sulfite, thiosulfate and S-sulfocysteine in tissues and biological fluids of the affected patients. The main clinical symptoms include severe neurological dysfunction and brain abnormalities, whose pathophysiology is still unknown. The present study investigated the in vitro effects of sulfite and thiosulfate on mitochondrial homeostasis in rat brain mitochondria. It was verified that sulfite per se, but not thiosulfate, decreased state 3, CCCP-stimulated state and respiratory control ratio in mitochondria respiring with glutamate plus malate. In line with this, we found that sulfite inhibited the activities of glutamate and malate (MDH) dehydrogenases. In addition, sulfite decreased the activity of a commercial solution of MDH, that was prevented by antioxidants and dithiothreitol. Sulfite also induced mitochondrial swelling and reduced mitochondrial membrane potential, Ca(2+) retention capacity, NAD(P)H pool and cytochrome c immunocontent when Ca(2+) was present in the medium. These alterations were prevented by ruthenium red, cyclosporine A (CsA) and ADP, supporting the involvement of mitochondrial permeability transition (MPT) in these effects. We further observed that N-ethylmaleimide prevented the sulfite-elicited swelling and that sulfite decreased free thiol group content in brain mitochondria. These findings indicate that sulfite acts directly on MPT pore containing thiol groups. Finally, we verified that sulfite reduced cell viability in cerebral cortex slices and that this effect was prevented by CsA. Therefore, it may be presumed that disturbance of mitochondrial energy homeostasis and MPT induced by sulfite could be involved in the neuronal damage characteristic of SO deficiency.

Antioxidant and antiapoptotic properties of melatonin restore intestinal calcium absorption altered by menadione

The intestinal Ca²⁺ absorption is inhibited by menadione (MEN) through oxidative stress and apoptosis. The aim of this study was to elucidate whether the antioxidant and antiapoptotic properties of melatonin (MEL) could protect the gut against the oxidant MEN. For this purpose, 4-week-old chicks were divided into four groups: (1) controls, (2) treated i.p. with MEN (2.5 μmol/kg of b.w.), (3) treated i.p. with MEL (10 mg/kg of b.w.), and (4) treated with 10 mg MEL/kg of b.w after 2.5 μmol MEN/kg of b.w. Oxidative stress was assessed by determination of glutathione (GSH) and protein carbonyl contents as well as antioxidant enzyme activities. Apoptosis was assayed by the TUNEL technique, protein expression, and activity of caspase 3. The data show that MEL restores the intestinal Ca²⁺ absorption altered by MEN. In addition, MEL reversed the effects caused by MEN such as decrease in GSH levels, increase in the carbonyl content, alteration in mitochondrial membrane permeability, and enhancement of superoxide dismutase and catalase activities. Apoptosis triggered by MEN in the intestinal cells was arrested by MEL, as indicated by normalization of the mitochondrial membrane permeability, caspase 3 activity, and DNA fragmentation. In conclusion, MEL reverses the inhibition of intestinal Ca²⁺ absorption produced by MEN counteracting oxidative stress and apoptosis. These findings suggest that MEL could be a potential drug of choice for the reversal of impaired intestinal Ca²⁺ absorption in certain gut disorders that occur with oxidative stress and apoptosis.