Glutathione depletion and the production of reactive oxygen species in isolated hepatocyte suspensions

Allium sativum Essential Oil Supplementation Reverses the Hepatic Inflammation, Genotoxicity and Apoptotic Effects in Swiss Albino Mice Intoxicated with the Lead Nitrate

Prolonged lead (Pb) exposure impairs human health due to its interference with physiological and biochemical processes. Therefore, it is necessary to investigate natural therapeutics to alleviate Pb-induced intoxication. In the current investigation, essential oil extracted from the fresh bulbs of Allium sativum was considered as a natural remedy. Initially, in vitro antioxidant and anti-inflammatory activity of A. sativum essential oil (ASEO) were explored. The results reported that ASEO exhibits potent antioxidant and anti-inflammatory potential. Additionally, an in vivo study was conducted to elucidate its preventive role against Lead-nitrate (LN)-induced hepatic damage in Swiss albino mice. The experimental mice were allocated into six groups: Control, LN-intoxicated group (50 mg/kg), LN + ASEO (50 mg/kg), LN + ASEO (80 mg/kg), LN + Silymarin (25 mg/kg), and LN + vehicle oil control group. The entire duration of the study was of 30 days. From the results, it was determined that LN exposure elevated the Pb content in hepatic tissues which subsequently increased the serum biomarkers, inflammatory cytokines (NF-kB, TNF-α, IL-6) as well as apoptotic factors (caspase-3, BAX), all of which contribute to DNA damage. Meanwhile, it reduced anti-inflammatory (IFN-γ and IL-10) and anti-apoptotic factors (Bcl-2). Furthermore, Pb accumulation in hepatic tissues changed the histological architecture, which was linked to necrosis, central vein dilation, inflammatory cell infiltration and Kupffer cell activation. In contrast to this, ASEO administration decreased the Pb content, which in turn reduced the level of serum biomarkers, inflammatory and apoptotic factors. At the same time, it increased the anti-inflammatory and anti-apoptotic factors, thereby reduced DNA damage and restored the hepatic histology. In conclusion, exhaustive research is of the utmost demand to elucidate the precise defense mechanisms of ASEO against LN-induced hepatotoxicity.

Contribution of Autophagy to Cellular Iron Homeostasis and Stress Adaptation in Alternaria alternata

The tangerine pathotype of Alternaria alternata produces the Alternaria citri toxin (ACT), which elicits a host immune response characterized by the increase in harmful reactive oxygen species (ROS) production. ROS detoxification in A. alternata relies on the degradation of peroxisomes through autophagy and iron acquisition using siderophores. In this study, we investigated the role of autophagy in regulating siderophore and iron homeostasis in A. alternata. Our results showed that autophagy positively influences siderophore production and iron uptake. The A. alternata strains deficient in autophagy-related genes 1 and 8 (ΔAaatg1 and ΔAaatg8) could not thrive without iron, and their adaptability to high-iron environments was also reduced. Furthermore, the ability of autophagy-deficient strains to withstand ROS was compromised. Notably, autophagy deficiency significantly reduced the production of dimerumic acid (DMA), a siderophore in A. alternata, which may contribute to ROS detoxification. Compared to the wild-type strain, ΔAaatg8 was defective in cellular iron balances. We also observed iron-induced autophagy and lipid peroxidation in A. alternata. To summarize, our study indicates that autophagy and maintaining iron homeostasis are interconnected and contribute to the stress resistance and the virulence of A. alternata. These results provide new insights into the complex interplay connecting autophagy, iron metabolism, and fungal pathogenesis in A. alternata.

AOP Report: Glutathione Conjugation Leading to Reproductive Dysfunction via Oxidative Stress

We propose an adverse outcome pathway (AOP) for reproductive dysfunction via oxidative stress (OS). The AOP was developed based on Organisation for Economic Co-operation and Development (OECD) Guidance Document 184 and on the specific considerations of the OECD users' handbook supplement to the guidance document for developing and assessing AOPs (no. 233). According to the qualitative and quantitative experimental data evaluation, glutathione (GSH) conjugation is the first upstream key event (KE) of this AOP to reproductive dysfunction triggering OS. This event causes depletion of GSH basal levels (KE2 ). Consequently, this drop of free GSH induces an increase of reactive oxygen species (KE3 ) generated by the natural cellular metabolic processes (cellular respiration) of the organism. Increased levels of these reactive species, in turn, induce an increase of lipid peroxidation (KE4 ). This KE consequently leads to a rise in the amount of toxic substances, such as malondialdehyde and hydroxynonenal, which are associated with decreased quality and competence of gamete cell division, consequently impairing fertility (KE5 and adverse outcome). The overall assessment of the general biological plausibility, the empirical support, and the essentiality of KE relationships was considered as high for this AOP. We conclude that GSH conjugation is able to lead to reproductive disorder in fishes and mammals, via OS, but that the amount of stressor needed to trigger the AOP differs between stressors. Environ Toxicol Chem 2023;42:2519-2528. © 2023 SETAC.

Lupeol attenuated the NAFLD and PCOS-induced metabolic, oxidative, hormonal, histopathological, and molecular injuries in mice

Background and purpose

The current study aimed to study the therapeutic effects of lupeol as a nutritional triterpene on non-alcoholic fatty liver disease (NAFLD) and polycystic ovarian syndrome (PCOS) disorders in separate and concurrent models.

Experimental approach

This study was performed in three sets and each set contained 4 groups of female mice (n = 6), including control, NAFLD or PCOS and/or NAFLD/PCOS, lupeol, and metformin (MET). The treatment groups following the induction of disorders were treated with lupeol (40 mg/kg, orally) or MET (500 mg/kg, orally) for 28 days. The insulin resistance index and hormonal assessments were conducted on the collected serum samples. Moreover, oxidative stress biomarkers were measured in the liver and ovaries. Histopathological studies and ultimately any changes in the expression of androgen receptors, toll-like receptor (TLR)-2 and TLR-4 were analyzed.

Findings/Results

Results revealed that lupeol reduced significantly the insulin resistance index in NAFLD and NAFLD/PCOS-positive animals. Lupeol attenuated remarkably the PCOS and PCOS/NAFLD-elevated concentration of testosterone. lupeol recovered the metabolic disorders-induced oxidative stress and restored the disorders-depleted glutathione. The NAFLD/PCOS-induced hepatic damages such as microvesicular or macrovesicular steatosis and atretic follicles number in the ovary were attenuated in the lupeol-treated mice. Serum level of TNF-α was reduced and the expression of androgen receptors, TLR-4 and TLR-2 were downregulated in the lupeol-treated NAFLD/PCOS-positive animals.

Conclusions and implication

The results suggest that lupeol could be a novel nutraceutical for the treatment of metabolic disorders. Lupeol's anti-metabolic disorders effects attribute to its anti-dyslipidemia, antioxidant, and anti-inflammatory properties.

Targeted Combination of Antioxidative and Anti-Inflammatory Therapy of Rheumatoid Arthritis using Multifunctional Dendrimer-Entrapped Gold Nanoparticles as a Platform

Abundant reactive oxygen species and tumor necrosis factor-α (TNF-α) cytokine supply of M1-type macrophages boost rheumatoid arthritis (RA) pathological process. For efficient RA therapy, here a multifunctional nanoplatform is presented based on generation 5 (G5) poly(amidoamine) dendrimer-entrapped gold nanoparticles (Au DENPs) to achieve co-delivery of antioxidant alpha-tocopheryl succinate (α-TOS) and anti-inflammatory anti-TNF-α siRNA to macrophage cells. G5 dendrimers with amine termini are sequentially functionalized with 1,3-propane sultone (1,3-PS), α-TOS through a polyethylene glycol (PEG) spacer, and PEGylated folic acid (FA), and subsequently entrapped with Au NPs. The generated functional Au DENPs exhibit desired cytocompatibility, zwitterion-rendered antifouling property, and FA-mediated targeting specificity, enabling serum-enhanced siRNA delivery to M1-type macrophage cells. Meanwhile, the attached α-TOS affords enhanced oxidation resistance of macrophage cells. In vivo investigation shows that the treatment of a collagen-induced arthritis mouse model using α-TOS-modified Au DENPs/TNF-α siRNA polyplexes can achieve excellent combination therapy effect in inflammatory cytokines downregulation of RA lesion and bone erosions. The therapeutic efficacy is also supported by 3D micro-computed tomography analysis and TNF-α cytokine reduction of RA lesion joints in the mRNA, protein, and histology levels. The created multifunctional nanoplatform may be employed in antioxidative and anti-inflammatory combination therapy of RA.

Quantitative phosphoproteomics to unravel the cellular response to chemical stressors with different modes of action

Damage to cellular macromolecules and organelles by chemical exposure evokes activation of various stress response pathways. To what extent different chemical stressors activate common and stressor-specific pathways is largely unknown. Here, we used quantitative phosphoproteomics to compare the signaling events induced by four stressors with different modes of action: the DNA damaging agent: cisplatin (CDDP), the topoisomerase II inhibitor: etoposide (ETO), the pro-oxidant: diethyl maleate (DEM) and the immunosuppressant: cyclosporine A (CsA) administered at an equitoxic dose to mouse embryonic stem cells. We observed major differences between the stressors in the number and identity of responsive phosphosites and the amplitude of phosphorylation. Kinase motif and pathway analyses indicated that the DNA damage response (DDR) activation by CDDP occurs predominantly through the replication-stress-related Atr kinase, whereas ETO triggers the DDR through Atr as well as the DNA double-strand-break-associated Atm kinase. CsA shares with ETO activation of CK2 kinase. Congruent with their known modes of action, CsA-mediated signaling is related to down-regulation of pathways that control hematopoietic differentiation and immunity, whereas oxidative stress is the most prominent initiator of DEM-modulated stress signaling. This study shows that even at equitoxic doses, different stressors induce distinctive and complex phosphorylation signaling cascades.

Evaluating biological activity of compounds by transcription factor activity profiling

Assessing the biological activity of compounds is an essential objective of biomedical research. We show that one can infer the bioactivity of compounds by assessing the activity of transcription factors (TFs) that regulate gene expression. Using a multiplex reporter system, the FACTORIAL, we characterized cell response to a compound by a quantitative signature, the TF activity profile (TFAP). We found that perturbagens of biological pathways elicited distinct TFAP signatures in human cells. Unexpectedly, perturbagens of the same pathway all produced identical TFAPs, regardless of where or how they interfered. We found invariant TFAPs for mitochondrial, histone deacetylase, and ubiquitin/proteasome pathway inhibitors; cytoskeleton disruptors; and DNA-damaging agents. Using these invariant signatures permitted straightforward identification of compounds with specified bioactivities among uncharacterized chemicals. Furthermore, this approach allowed us to assess the multiple bioactivities of polypharmacological drugs. Thus, TF activity profiling affords straightforward assessment of the bioactivity of compounds through the identification of perturbed biological pathways.

Elevation in and persistence of multiple urinary biomarkers indicative of oxidative DNA stress and inflammation: Toxicological implications of maleic acid consumption using a rat model

Maleic acid (MA), an intermediate reagent used in many industrial products, instigated public health concerns in Taiwan when it was used to adulterate an array of starch-based delicacies to improve texture and storage time. Established studies reported that exposure to high concentrations of MA induce renal injury; little is known whether oxidative stress is induced at a relative low dose. This study aims to investigate the effect of oral single dose exposure of MA on the status of oxidative stress and inflammation. Single dose of MA at 0, 6 and 60 mg/kg (control, low- and high-dose groups, respectively) were orally administered to adult male and female rats. Urine samples were collected and analyzed to measure 8-hydroxy-2’-deoxyguanosine (8-OHdG), 8-iso-prostaglandin F_2α (8-IsoPGF_2α), 8-nitroguanine (8-NO₂Gua) and N-acetyl-S-(tetrahydro-5-hydroxy-2-pentyl-3-furanyl)-L-cysteine (HNE-MA) using LC-MS/MS. Results revealed that oral consumption of MA induced oxidative DNA damage and lipid peroxidation, as demonstrated by the statistically significant increases in urinary levels of 8-NO₂Gua, 8-OHdG, and 8-isoPGF_2α, in high-dosed male rats within 12 h of oral gavage (p < 0.05). Additionally, increases in concentration of these biomarkers persist for days after consumption; male rats appear to be more sensitive to oxidative burden compared to their counterparts. The aforementioned findings could help elucidate the mechanisms through which nephrotoxicity occur.

Nuclear magnetic resonance- and mass spectrometry-based metabolomics to study maleic acid toxicity from repeated dose exposure in rats

Maleic acid (MA), a chemical intermediate used in many consumer and industrial products, was intentionally adulterated in a variety of starch-based foods and instigated food safety incidents in Asia. We aim to elucidate possible mechanisms of MA toxicity after repeated exposure by (1) determining the changes of metabolic profile using ¹ H nuclear magnetic resonance spectroscopy and multivariate analysis, and (2) investigating the occurrence of oxidative stress using liquid chromatography tandem mass spectrometry by using Sprague-Dawley rat urine samples. Adult male rats were subjected to a 28 day subchronic study (0, 6, 20 and 60 mg kg^-1 ) via oral gavage. Urine was collected twice a day on days 0, 7, 14, 21 and 28; organs underwent histopathological examination. Changes in body weight and relative kidney weights in medium- and high-dose groups were significantly different compared to controls. Morphological alterations were evident in the kidneys and liver. Metabolomic results demonstrated that MA exposure increases the urinary concentrations of 8-hydroxy-2'-deoxyguanosine, 8-nitroguanine and 8-iso-prostaglandin F_2α ; levels of acetoacetate, hippurate, alanine and acetate demonstrated time- and dose-dependent variations in the treatment groups. Findings suggest that MA consumption escalates oxidative damage, membrane lipid destruction and disrupt energy metabolism. These aforementioned changes in biomarkers and endogenous metabolites elucidate and assist in characterizing the possible mechanisms by which MA induces nephro- and hepatotoxicity.

Designing greener plasticizers: Effects of alkyl chain length and branching on the biodegradation of maleate based plasticizers

The ubiquitous presence of the plasticizer di (2-ethylhexyl) phthalate (DEHP) in the environment is of concern due to negative biological effects associated with it and its metabolites. In particular, the metabolite mono (2-ethylhexyl) phthalate (MEHP) is a potential endocrine disruptor. Earlier work had identified the diester di (2-ethylhexyl) maleate (DEHM) as a potential greener candidate plasticizer to replace DEHP, yet its biodegradation rate was reported to be slow. In this study, we modified the side chains of maleate diesters to be linear (i.e., unbranched) alkyl chains that varied in length from ethyl to n-octyl. The plasticization efficiency of these compounds blended into PVC at 29 wt.% increased with the overall length of the molecule, but all compounds performed as well as or better than comparable samples with DEHP. Tests conducted with the equally long DEHM and dihexyl maleate (DHM) showed that branching has no effect on glass transition temperature (Tg) reduction efficiency. Biodegradation experiments with the common soil bacterium Rhodococcus rhodocrous in the presence of the plasticizer showed acceptable hydrolysis rates of maleates with unbranched side chains, while the branched DEHM showed almost no degradation. The addition of hexadecane as auxiliary carbon source improved hydrolysis rates. Temporary buildup of the respective monoester of the compounds were observed, but only in the case of the longest molecule, dioctyl maleate (DOM), did this buildup lead to growth inhibition of the bacteria. Maleates with linear side chains, if designed and tested properly, show promise as potential candidate plasticizers as replacements for DEHP.

Comparative effects of sulfhydryl compounds on target organellae, nuclei and mitochondria, of hydroxylated fullerene-induced cytotoxicity in isolated rat hepatocytes

DNA damage and cytotoxicity induced by a hydroxylated fullerene [C60 (OH)24 ], which is a spherical nanomaterial and/or a water-soluble fullerene derivative, and their protection by sulfhydryl compounds were studied in freshly isolated rat hepatocytes. The exposure of hepatocytes to C60 (OH)24 at a concentration of 50 μM caused time (0 to 3 h)-dependent cell death accompanied by the formation of cell surface blebs, the loss of cellular levels of ATP and reduced glutathione, accumulation of glutathione disulfide, and induction of DNA fragmentation assayed using alkali single-cell agarose-gel electrophoresis. C60 (OH)24 -induced cytotoxicity was effectively prevented by pretreatment with sulfhydryl compounds. N-acetyl-L-cysteine (NAC), L-cysteine and L-methionine, at a concentration of 2.5 mM, ameliorated cell death, accompanied by a decrease in cellular ATP levels, formation of cell surface blebs, induction of reactive oxygen species (ROS) and loss of mitochondrial membrane potential caused by C60 (OH)24 . In addition, DNA fragmentation caused by C60 (OH)24 was also inhibited by NAC, whereas an antioxidant ascorbic acid did not affect C60 (OH)24 -induced cell death and DNA damage in rat hepatocytes. Taken collectively, these results indicate that incubation of rat hepatocytes with C60 (OH)24 elicits DNA damage, suggesting that nuclei as well as mitochondria are target sites of the hydroxylated fullerene; and induction of DNA damage and oxidative stress is ameliorated by an increase in cellular GSH levels, suggesting that the onset of toxic effects may be partially attributable to a thiol redox-state imbalance caused by C60 (OH)24 .

Hierarchical coated metal hydroxide nanoconstructs as potential controlled release carriers of photosensitizer for skin melanoma

Inorganic nanostructured ensembles containing an anionic clay matrix with layered double hydroxide (LDH) were designed in nanooncology for photosensitizer delivery.

A structurally simplified analogue of geldanamycin exhibits neuroprotective activity

The syntheses of a structurally simplified geldanamycin analogue 2 and two related compounds are described. Compound 2 conferred cytoprotection and quenched ROS and lipid peroxidation in a dose-dependent manner in Friedreich's ataxia (FRDA) lymphocytes at low micromolar concentrations. It also prevented ROS-induced damage of cellular lipid membranes and maintained the mitochondrial membrane potential of FRDA lymphocytes. In addition, 2 did not inhibit Hsp90 when tested at micromolar concentrations, exhibited no cytotoxicity, and afforded neuroprotection to differentiated SH-SY5Y cells under conditions of Aβ-induced cell toxicity.

Effects of N-acetyl-L-cysteine on target sites of hydroxylated fullerene-induced cytotoxicity in isolated rat hepatocytes

The effects of N-acetyl-L-cysteine (NAC) on cytotoxicity caused by a hydroxylated fullerene [C60(OH)24], which is known a nanomaterial and/or a water-soluble fullerene derivative, were studied in freshly isolated rat hepatocytes. The exposure of hepatocytes to C60(OH)24 at a concentration of 0.1 mM caused time (0-3 h)-dependent cell death accompanied by the formation of cell blebs, loss of cellular ATP, and reduced glutathione (GSH) and protein thiol levels, as well as the accumulation of glutathione disulfide and malondialdehyde (MDA), indicating lipid peroxidation. Despite this, C60(OH)24-induced cytotoxicity was effectively prevented by NAC pretreatment ranging in concentrations from 1 to 5 mM. Further, the loss of mitochondrial membrane potential (MMP) and generation of oxygen radical species in hepatocytes incubated with C60(OH)24 were inhibited by pretreatment with NAC, which caused increases in cellular and/or mitochondrial levels of GSH, accompanied by increased levels of cysteine via enzymatic deacetylation of NAC. On the other hand, severe depletion of cellular GSH levels caused by diethyl maleate at a concentration of 1.25 mM led to the enhancement of C60(OH)24-induced cell death accompanied by a rapid loss of ATP. Taken collectively, these results indicate that pretreatment with NAC ameliorates (a) mitochondrial dysfunction linked to the depletion of ATP, MMP, and mitochondrial GSH level and (b) induction of oxidative stress assessed by reactive oxygen species generation, losses of intracellular GSH and protein thiol levels, and MDA formation caused by C60(OH)24, suggesting that the onset of toxic effects is at least partially attributable to a thiol redox-state imbalance as well as mitochondrial dysfunction related to oxidative phosphorylation.

Determination of the antigenotoxic potencies of some luteolin derivatives by using a eukaryotic cell system, Saccharomyces cerevisiae

In this study, we aimed to examine the mutagenic and antimutagenic potencies of three luteolin derivatives (luteolin-7-O-glucoside, luteolin-7-O-rutinoside and luteolin-7-O-glucuronide) by using a eukaryotic cell system, Saccharomyces cerevisiae (RS112). In the antimutagenicity assays, these luteolin derivatives showed antimutagenic effects in deletion and intrachromosomal recombination events against ethyl methanesulfonate and acridine mutagen agents. In deletion events, the highest inhibition rates for luteolin-7-O-glucoside, luteolin-7-O-rutinoside and luteolin-7-O-glucuronide against ethyl methanesulfonate were 57.6%, 58.3% and 62.5%, respectively. Likewise, the highest inhibition rates for luteolin-7-O-glucoside, luteolin-7-O-rutinoside and luteolin-7-O-glucuronide against acridin were 21.8%, 22.4% and 23.6%, respectively. Our findings showed that these luteolin derivatives have stronger antimutagenic properties against ethyl methanesulfonate compared to the acridine mutagen agent.

Protective effect of naringenin on hepatic and renal dysfunction and oxidative stress in arsenic intoxicated rats

Arsenic has a long history as a potent human poison, chronic exposure over a period of time may result in the manifestation of toxicity in practically all systems of the body. In the present investigation the efficacy of naringenin (NRG), a naturally occurring citrus flavanone against arsenic-induced hepatotoxic and nephrotoxic manifestations have been studied in rats. Arsenic trioxide was administered orally at the dose of 2 mg/kg/day with or without combination of NRG (20 or 50 mg/kg/day) for 28 days. At the end of the experimental period the hepatic and renal dysfunction was evaluated by histological examination, serum biomarkers and markers of oxidative stress; lipid peroxidation (LPO), reduced glutathione (GSH) and antioxidant enzymes. Arsenic intoxication increased serum bilirubin, urea, uric acid and creatinine levels, additionally enhanced the activities of hepatic marker enzymes aspartate transaminase, alanine transaminase and alkaline phosphatase. Also, the hepatic and renal tissues showed a marked elevation in LPO levels with a decrease in GSH content and the activities of antioxidant enzymes such as superoxide dismutase, catalase, glutathione peroxidase and glutathione-S-transferase on arsenic treatment. Simultaneous treatment with NRG restored the activities of serum biomarkers and antioxidant enzymes in the tissues in a dose-dependent manner. Furthermore, the histopathological studies confirmed the protective effect of NRG co-treatment by reducing the pathological changes due to arsenic intoxication in both liver and kidney. Thus, our present study demonstrates that NRG has a potential to protect arsenic-induced oxidative hepatic and renal dysfunction.

The presence of p47phox in liver parenchymal cells is a key mediator in the pathogenesis of alcoholic liver steatosis

BACKGROUND

Reactive oxygen species contribute to steatosis and inflammation in alcoholic liver disease (ALD). Here, we evaluated the selective contribution of p47phox, a critical subunit of nicotinamide adenine dinucleotide phosphate oxidase (NADPH) oxidase complex, in liver parenchymal cells and in bone marrow (BM)-derived cells.

METHODS

Female C57Bl/6 wild type [WT], total body p47phox-deficient knockout [KO] or p47phox chimera mice generated by BM transplantation of p47phox-KO-BM into irradiated WT mice (WT/p47phox-KO-BM mice) received 5% Lieber-DeCarli alcohol or control (pair feeding) diet for 4 weeks.

RESULTS

Alcohol-induced liver steatosis as measured by Oil Red O staining and serum triglyceride up-regulation were prevented in p47phox-KO mice but not in WT/p47phox-KO-BM chimeras compared to WT controls. Serum alanine aminotransferase (ALT) was significantly increased in alcohol-fed WT mice but not in p47phox-KO mice compared to pair-fed controls. There was no protection from alcohol-induced increase in ALT and liver damage in the WT/p47phox-KO-BM mice. Alcohol-induced liver steatosis was accompanied by up-regulation of the lipid droplet-stabilizing protein, adipocyte differentiation-related protein (ADRP), and the fatty acid synthesis-associated genes, fatty acid synthase (FASN) and acetyl-CoA carboxylase (ACACA). Total body deficiency in p47phox but not selective absence of p47phox in BM-derived cells prevented alcohol-induced up-regulation of ADRP, FASN, and ACACA in the liver. Finally, alcohol-induced activation and DNA binding of nuclear factor κB (NF-κB), a master regulator of inflammation, were significantly increased after alcohol feeding in WT but not in p47phox-KO mice. Selective deficiency of p47phox in BM-derived cells (WT/p47phox-KO-BM chimera) failed to prevent NF-κB induction after alcohol feeding.

CONCLUSIONS

Total body deficiency in p47phox subunit of NADPH oxidase complex protects mice from alcohol-induced liver steatosis via mechanisms involving ADRP, FASN, and ACACA as well as from alcohol-induced NF-κB activation. In contrast, selective absence of p47phox in BM-derived cells fails to provide protection via these mechanisms. These results suggest that p47phox in parenchymal cells plays a critical role in the pathogenesis of ALD.

In vivo and in vitro antioxidant effects of three Veronica species

The aim of the present study was to examine the antioxidant activity of three Veronica species (Plantaginaceae). The antioxidant potential of various extracts obtained from aerial flowering parts was evaluated by DPPH-free (1,1-diphenyl-2-picrylhydrazyl-free) radical scavenging activity and ferric-reducing antioxidant power assays. Considerable antioxidant activity was observed in the plant samples (FRAP values ranged from 0.97 to 4.85 mmol Fe2+/g, and DPPH IC50 values from 12.58 to 66.34 µg/ml); however, these levels were lower than the activity of the control compound butylated hydroxytoluene (BHT) (FRAP: 10.58 mmol Fe2+/g; DPPH IC50: 9.57 µg/ml). Also, the in vivo antioxidant effects were evaluated in several hepatic antioxidant systems in rats (activities of glutathione peroxidase, glutathione reductase, peroxidase, catalase, xanthine oxidase, glutathione content and level of thiobarbituric acid reactive substances) after treatment with different Veronica extracts, or in combination with carbon tetrachloride (CCl4). Pretreatment with 100 mg/kg b.w. of Veronica extracts inhibited CCl4-induced liver injury by decreasing TBA-RS level, increasing GSH content, and bringing the activities of CAT and Px to control levels. The present study suggests that the extracts analyzed could protect the liver cells from CCl4-induced liver damage by their antioxidative effect on hepatocytes.

Oxidative stress is involved in Dasatinib-induced apoptosis in rat primary hepatocytes

Dasatinib, a multitargeted inhibitor of BCR-ABL and SRC kinases, exhibits antitumor activity and extends the survival of patients with chronic myeloid leukemia (CML) and Philadelphia chromosome-positive acute lymphoblastic leukemia (ALL). However, some patients suffer from hepatotoxicity, which occurs through an unknown mechanism. In the present study, we found that Dasatinib could induce hepatotoxicity both in vitro and in vivo. Dasatinib reduced the cell viability of rat primary hepatocytes, induced the release of alanine aminotransferase (ALT) and lactate dehydrogenase (LDH) in vitro, and triggered the ballooning degeneration of hepatocytes in Sprague-Dawley rats in vivo. Apoptotic markers (chromatin condensation, cleaved caspase-3 and cleaved PARP) were detected to indicate that the injury induced by Dasatinib in hepatocytes in vitro was mediated by apoptosis. This result was further validated in vivo using terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assays. Here we found that Dasatinib dramatically increased the level of reactive oxygen species (ROS) in hepatocytes, reduced the intracellular glutathione (GSH) content, attenuated the activity of superoxide dismutase (SOD), generated malondialdehyde (MDA), a product of lipid peroxidation, decreased the mitochondrial membrane potential, and activated nuclear factor erythroid 2-related factor 2 (Nrf2) and mitogen-activated protein kinases (MAPK) related to oxidative stress and survival. These results confirm that oxidative stress plays a pivotal role in Dasatinib-mediated hepatotoxicity. N-acetylcysteine (NAC), a typical antioxidant, can scavenge free radicals, attenuate oxidative stress, and protect hepatocytes against Dasatinib-induced injury. Thus, relieving oxidative stress is a viable strategy for reducing Dasatinib-induced hepatotoxicity.

Determination of antimutagenic properties of apigenin-7-O-rutinoside, a flavonoid isolated from Mentha longifolia (L.) Huds. ssp. longifolia with yeast DEL assay

Lamiaceae is an important plant family that has been investigated for its medicinal properties due to its large amounts of phenolic acids and flavonoids. Flavonoids have been shown to have antioxidant and antimutagenic activities in different test systems, but their certain mechanisms are still unclear. This study was designed to evaluate the mutagenic and antimutagenic activities of apigenin 7-O-rutinoside, a flavonoid isolated from Mentha longifolia (L.) Huds. ssp. longifolia. The possible antimutagenic potential of apigenin 7-O-rutinoside (A7R) was examined against mutagens ethyl methanesulfonate (EMS) and acridine (AC) in a eukaryotic cell system Saccharomyces cerevisiae RS112. The results showed that A7R has different inhibition rates against EMS and AC-induced mutagenicity. Thus, the properties of A7R are of great pharmacological importance and might be beneficial for reducing the risk of reactive oxygen species-related diseases.

Biochemical and pathological toxic effects induced by the cyanotoxin Cylindrospermopsin on the human cell line Caco-2

Cylindrospermopsin (CYN), a cyanotoxin produced by several freshwater cyanobacteria, causes human intoxications and animal mortalities. The present study focuses on the cytotoxic effects of CYN on Caco-2 cells at 24 and 48 h. The basal cytotoxicity endpoints studied were total protein content (TP), neutral red uptake (NR) and reduction of the tetrazolium salt (MTS). The effect of non-cytotoxic concentrations of CYN on the generation of intracellular reactive oxygen species (ROS), γ-glutamylcysteine synthetase (GCS) activity and glutathione (GSH) content was also studied and the morphological alterations in the Caco-2 cells subsequent to CYN exposure were recorded. The most sensitive endpoint - the reduction of MTS - showed that the viability of Caco-2 cells after exposure to the highest concentration assayed (40 μg/mL CYN) was reduced by about 90%. Intracellular ROS production increased only when exposed to a concentration of 1.25 μg/mL CYN, while GSH content and GCS activity increased when exposed to 2.5 μg/mL CYN. The main insights provided by the present study are the ultrastructural alterations, which reveal lipid degeneration, mitochondrial damage and nucleolar segregation with altered nuclei. Therefore, it has been demonstrated that CYN can induce toxic effects in Caco-2 cells in a time-concentration dependent manner. Moreover, unlike the cytotoxic and biochemical alterations, which were only evident at higher concentrations, morphological damage at the ultrastructural level was noticeable even at the lowest concentration used.

Ameliorative effects of dimetylthiourea and N-acetylcysteine on nanoparticles induced cyto-genotoxicity in human lung cancer cells-A549

We study the ameliorative potential of dimetylthiourea (DMTU), an OH^• radical trapper and N-acetylcysteine (NAC), a glutathione precursor/H₂O₂ scavenger against titanium dioxide nanoparticles (TiO₂-NPs) and multi-walled carbon nanotubes (MWCNTs) induced cyto-genotoxicity in cultured human lung cancer cells-A549. Cytogenotoxicity was induced by exposing the cells to selected concentrations (10 and 50 µg/ml) of either of TiO₂-NPs or MWCNTs for 24 h. Anti-cytogenotoxicity effects of DMTU and NAC were studied in two groups, i.e., treatment of 30 minutes prior to toxic insult (short term exposure), while the other group received DMTU and NAC treatment during nanoparticles exposure, i.e., 24 h (long term exposure). Investigations were carried out for cell viability, generation of reactive oxygen species (ROS), micronuclei (MN), and expression of markers of oxidative stress (HSP27, CYP2E1), genotoxicity (P⁵³) and CYP2E1 dependent n- nitrosodimethylamine-demethylase (NDMA-d) activity. In general, the treatment of both DMTU and NAC was found to be effective significantly against TiO₂-NPs and MWCNTs induced cytogenotoxicity in A549 cells. Long-term treatment of DMTU and NAC during toxic insults has shown better prevention than short-term pretreatment. Although, cells responded significantly to both DMTU and NAC, but responses were chemical specific. In part, TiO_2-NPs induced toxic responses were mediated through OH^• radicals generation and reduction in the antioxidant defense system. While in the case of MWCNTs, adverse effects were primarily due to altering/hampering the enzymatic antioxidant system. Data indicate the applicability of human lung cancer cells-A549 as a pre-screening tool to identify the target specific prophylactic and therapeutic potential of drugs candidate molecules against nanoparticles induced cellular damages.

A Strategy for Suppressing Redox Stress within Mitochondria

An aza analogue (1) of the experimental neuroprotective drug idebenone has been prepared and evaluated. The compound quenches lipid peroxidation more effectively than α-tocopherol and potently suppresses reactive oxygen species in cells under oxidative stress. It is thought to do so via a catalytic cycle in which both forms of oxidative stress are suppressed simultaneously. Consequently, the compound effectively protects cultured CEM leukemia cells and Friedreich's ataxia fibroblasts from oxidative stress more effectively than idebenone or idebenol.

Real-time measurement of cytosolic free calcium concentration in DEM-treated HL-60 cells during static magnetic field exposure and activation by ATP

This study investigated whether glutathione depletion affected the sensitivity of HL-60 cells to static magnetic fields. The effect of Diethylmaleate (DEM) on static magnetic field induced changes in cytosolic free calcium concentration ([Ca(2+)](c)) was examined. Cells were loaded with a fluorescent dye and exposed to a uniform static magnetic field at a strength of 0 mT (sham) or 100 mT. [Ca(2+)](c) was monitored during field and sham exposure using a ratiometric fluorescence spectroscopy system. Cells were activated by the addition of ATP. Metrics extracted from the [Ca(2+)](c) time series included: average [Ca(2+)](c) during the Pre-Field and Field Conditions, peak [Ca(2+)](c) following ATP activation and the full width at half maximum (FWHM) of the peak ATP response. Comparison of each calcium metric between the sham and 100 mT experiments revealed the following results: average [Ca(2+)](c) measured during the Field condition was 53 +/- 2 nM and 58 +/- 2 nM for sham and 100 mT groups, respectively. Average FWHM was 51 +/- 3 s and 54 +/- 3 s for sham and 100 mT groups, respectively. An effect of experimental order on the peak [Ca(2+)](c) response to ATP in sham/sham experiments complicated the statistical analysis and did not allow pooling of the first and second order experiments. No statistically significant difference between the sham and 100 mT groups was observed for any of the calcium metrics. These data suggested that manipulation of free radical buffering capacity in HL-60 cells did not affect the sensitivity of the cells to a 100 mT static magnetic field.

Molecular mechanisms involved in NAFLD progression

Non-alcoholic fatty liver disease (NAFLD) is an emerging metabolic-related disorder characterized by fatty infiltration of the liver in the absence of alcohol consumption. NAFLD ranges from simple steatosis to non-alcoholic steatohepatitis (NASH), which might progress to end-stage liver disease. This progression is related to the insulin resistance, which is strongly linked to the metabolic syndrome consisting of central obesity, diabetes mellitus, and hypertension. Earlier, the increased concentration of intracellular fatty acids within hepatocytes leads to steatosis. Subsequently, multifactorial complex interactions between nutritional factors, lifestyle, and genetic determinants promote necrosis, inflammation, fibrosis, and hepatocellular damage. Up to now, many studies have revealed the mechanism associated with insulin resistance, whereas the mechanisms related to the molecular components have been incompletely characterized. This review aims to assess the potential molecular mediators initiating and supporting the progression of NASH to establish precocious diagnosis and to plan more specific treatment for this disease.

MTBITC mediates cell cycle arrest and apoptosis induction in human HepG2 cells despite its rapid degradation kinetics in the in vitro model

Despite the great variety of structure homologous, experimental research on the cancer preventive properties of isothiocyanates (ITCs) is limited to only a fractional amount thereof so far. Especially the degradation of these compounds in the experimental system has not been investigated so far. In this study, we investigated the effect of 4-methylthiobutyl isothiocyante (MTBITC) on the proliferation of human hepatoma (HepG2) cells and underlying mechanisms. A concentration and time-dependent reduction in proliferation activity could be observed in cells treated with MTBITC exceeding 10 microM. At these concentrations MTBITC-induced apoptosis in HepG2 cells could be observed by internucleosomal DNA fragmentation, flow cytometry analysis, and the detection of single-stranded apoptotic DNA. In all the three assays, clear apoptotic events were present after 6-hr exposure to MTBITC. Apoptosis induction was accompanied by a time-dependent arrest of HepG2 cells at the G2/M phase of the cell cycle. This study shows for the first time the inhibitory potency of MTBITC on metabolically competent hepatoma cells, whereas the loss of reduced glutathione and its impact on mitochondria seem to be the major processes involved in the initiation and execution of the apoptotic cell death. The results of this study also showed that irrespective of the intense degradation kinetics of MTBITC, the strong cytostatic effect of the ITC was not markedly affected by it and suggests that although ITCs are only present at maximum concentrations in a living system for a rather short time, this might be sufficient to exert their therapeutic effects.

Oxidized low-density-lipoprotein accumulation is associated with liver fibrosis in experimental cholestasis

OBJECTIVE

The aim of the present study was to examine the probable relationship between the accumulation of oxLDL and hepatic fibrogenesis in cholestatic rats.

INTRODUCTION

There is growing evidence to support the current theories on how oxidative stress that results in lipid peroxidation is involved in the pathogenesis of cholestatic liver injury and fibrogenesis. One of the major and early lipid peroxidation products, OxLDL, is thought to play complex roles in various immuno-inflammatory mechanisms.

METHODS

A prolonged (21-day) experimental bile duct ligation was performed on Wistar-albino rats. Biochemical analysis of blood, histopathologic evaluation of liver, measurement of the concentration of malondialdehyde (MDA) and superoxide-dismutase (SOD) in liver tissue homogenates, and immunofluorescent staining for oxLDL in liver tissue was conducted in bile-duct ligated (n=8) and sham-operated rats (n=8).

RESULTS

Significantly higher levels of MDA and lower concentrations of SOD were detected in jaundiced rats than in the sham-operated rats. Positive oxLDL staining was also observed in liver tissue sections of jaundiced rats. Histopathological examination demonstrated that neither fibrosis nor other indications of hepatocellular injury were found in the sham-operated group, while features of severe hepatocellular injury, particularly fibrosis, were found in jaundiced rats.

CONCLUSION

Our results support the finding that either oxLDLs are produced as an intermediate agent during exacerbated oxidative stress or they otherwise contribute to the various pathomechanisms underlying the process of liver fibrosis. Whatever the mechanism, it is clear that an association exists between elevated oxLDL levels and hepatocellular injury, particularly with fibrosis. Further studies are needed to evaluate the potential effects of oxLDLs on the progression of secondary biliary cirrhosis.

Activating transcription factor 3 is a novel repressor of the nuclear factor erythroid-derived 2-related factor 2 (Nrf2)-regulated stress pathway

The transcription factor nuclear factor erythroid-derived 2-related factor 2 (Nrf2) regulates induction of an extensive cellular stress response network when complexed with the cAMP-responsive element binding protein (CBP) at antioxidant response elements (ARE) located in the promoter region of target genes. Activating transcription factor 3 (ATF3) can repress Nrf2-mediated signaling in a manner that is not well understood. Here, we show that ATF3-mediated suppression is a consequence of direct ATF3-Nrf2 protein-protein interactions that result in displacement of CBP from the ARE. This work establishes ATF3 as a novel repressor of the Nrf2-directed stress response pathway.

Mechanisms of chloroform-induced hepatotoxicity: oxidative stress and mitochondrial permeability transition in freshly isolated mouse hepatocytes

The role of mitochondrial permeability transition (MPT) and oxidative stress in chloroform toxicity was determined in freshly isolated female B6C3F1 mouse hepatocytes. Incubation of chloroform (12 mM) with hepatocytes resulted in cell death (alanine aminotransferase release and propidium iodide fluorescence). Chloroform had volatilized from the incubation and glutathione was depleted by 1 h; however, toxicity was not significantly different between control and chloroform-incubated cells. Hepatocytes were washed and reincubated in fresh media at 1 h. Subsequent reincubation of chloroform-treated hepatocytes resulted in significant toxicity at 3-5 h. Inclusion of the MPT inhibitor cyclosporine A or the antioxidant N-acetylcysteine (NAC) in the reincubation media at 1 h prevented toxicity. Confocal microscopy studies with the dye calcein AM indicated MPT that was blocked by cyclosporine A or NAC. Fluorescence microscopy studies utilizing JC-1 indicated loss of mitochondrial membrane potential, which was also blocked by cyclosporine A or NAC. Dichlorofluorescein fluorescence increased during the reincubation phase, indicating increased oxidative stress, and the increase was blocked by cyclosporine A. Since oxidative stress may occur by peroxynitrite, its role in toxicity was examined. Either of the nitric oxide synthase inhibitors N(G)-methyl-L-arginine (L-NMMA) and 7-nitroindazole (7-NI) at 1 h blocked toxicity. Western blot analysis of hepatocytes for 3-nitrotyrosine in proteins, a biomarker of peroxynitrite, indicated one major nitrated protein at 81 kD. Nitration of this protein was inhibited by cyclosporine A, L-NMMA, 7-NI, or NAC. The data indicate that chloroform-induced cell death occurs in two phases: a metabolic phase characterized by glutathione depletion, and an oxidative phase characterized by MPT and protein nitration.

Maleate nephrotoxicity: mechanisms of injury and correlates with ischemic/hypoxic tubular cell death

Maleate injection causes dose-dependent injury in proximal tubular cells. This study sought to better define underlying pathogenic mechanisms and to test whether maleate toxicity recapitulates critical components of the hypoxic/ischemic renal injury cascade. CD-1 mice were injected with maleate or used as a source for proximal tubule segments (PTS) for in vitro studies. Maleate induced dose-dependent PTS injury [lactate deydrogenase (LDH) release, ATP reductions, nonesterified fatty acid (NEFA) accumulation]. These changes were partially dependent on maleate metabolism (protection conferred by metabolic inhibitors: succinate, acetoacetate). Maleate toxicity reproduced critical characteristics of the hypoxia/ATP depletion-induced injury cascade: 1) glutathione (GSH) conferred protection, but due to its glycine, not cysteine (antioxidant), content; 2) ATP reductions reflected decreased production, not Na-K-ATPase-driven increased consumption; 3) cell death was completely blocked by extracellular acidosis (pH 6.6); 4) intracellular Ca(2+) chelation (BAPTA) mitigated cell death; 5) maleate and hypoxia each caused plasma membrane cholesterol shedding and in both instances, this was completely glycine suppressible; 6) maleate + hypoxia caused neither additive NEFA accumulation nor LDH release, implying shared pathogenic pathways; and 7) maleate, like ischemia, induced renal cortical cholesterol loading; increased HMG CoA reductase (HMGCR) activity (statin inhibitable), increased HMGCR mRNA levels, and increased RNA polymerase II recruitment to the HMGCR locus (chromatin immunoprecipitation, ChIP, assay) were involved. These results further define critical determinants of maleate nephrotoxicity and suggest that it can serve as a useful adjunct for studies of ischemia/ATP depletion-induced, proximal tubule-specific, cell death.

Copper-induced stimulation of extracellular signal-regulated kinase in trout hepatocytes: the role of reactive oxygen species, Ca2+, and cell energetics and the impact of extracellular signal-regulated kinase signaling on apoptosis and necrosis

The present study investigated if copper (Cu) exposure of trout hepatocytes, which stimulates formation of reactive oxygen species (ROS) and increases intracellular free Ca(2+) (Ca(2+)i), leads to an activation of extracellular signal-regulated kinase (ERK), the mechanisms underlying this activation, and the role of ERK signaling in cell death. Cu stimulated a time- and dose-dependent increase of phosphorylated extracellular signal-regulated kinase (pERK), and preventing the associated Ca(2+) influx or radical formation diminished or inhibited ERK activation, respectively. Furthermore, Cu enhanced caspase 3/7 activity and necrosis, and both effects were inhibited by treatments diminishing radical production and by chelating extracellular Ca(2+). In addition, ERK activity, and to a lesser extent caspase activity, was reduced by inhibiting mitochondrial ATP production, suggesting ATP dependence of the process. Inhibition of the ERK activator MEK, as well as of p38, significantly reduced caspase activation and necrosis, whereas c-Jun N-terminal kinase (JNK) inhibition diminished only caspase activity. Likewise, inhibition of MEK and p38, but not of JNK, prevented Cu-induced ROS production. In summary, we found that stimulation of ERK by Cu exposure of trout hepatocytes is dependent on radical formation and ATP, whereas Ca(2+) only modulates ERK activity. At the same time, activated ERK, as well as p38, contributes to enhanced ROS formation, whereas JNK did not. All three mitogen-activated protein kinases appear to promote apoptotic cell death upon Cu exposure, and ERK and p38 also stimulate necrosis.

Differential metabolomics reveals ophthalmic acid as an oxidative stress biomarker indicating hepatic glutathione consumption

Metabolomics is an emerging tool that can be used to gain insights into cellular and physiological responses. Here we present a metabolome differential display method based on capillary electrophoresis time-of-flight mass spectrometry to profile liver metabolites following acetaminophen-induced hepatotoxicity. We globally detected 1,859 peaks in mouse liver extracts and highlighted multiple changes in metabolite levels, including an activation of the ophthalmate biosynthesis pathway. We confirmed that ophthalmate was synthesized from 2-aminobutyrate through consecutive reactions with gamma-glutamylcysteine and glutathione synthetase. Changes in ophthalmate level in mouse serum and liver extracts were closely correlated and ophthalmate levels increased significantly in conjunction with glutathione consumption. Overall, our results provide a broad picture of hepatic metabolite changes following acetaminophen treatment. In addition, we specifically found that serum ophthalmate is a sensitive indicator of hepatic GSH depletion, and may be a new biomarker for oxidative stress. Our method can thus pinpoint specific metabolite changes and provide insights into the perturbation of metabolic pathways on a large scale and serve as a powerful new tool for discovering low molecular weight biomarkers.

TEGDMA induces mitochondrial damage and oxidative stress in human gingival fibroblasts

Free monomers including triethylene glycol dimethacrylate (TEGDMA) are released by resin composite. Recent studies in vitro have demonstrated that TEGDMA induced GSH depletion and production of radical oxygen species (ROS) in human gingival fibroblasts (HGF) but the exact mechanism of these events remains unclear. Our purpose is to investigate the origin of ROS production. TEGDMA induces a rapid (within 30 min) and drastic depletion of ATP concomitant with the GSH depletion. After 3h incubation, TEGDMA induced an increase of lipid peroxidation associated with LDH leakage. Our data also showed that TEGDMA produced damage at mitochondrial level. This is demonstrated by the collapse of mitochondrial membrane potential (MMP) in HGF treated with TEGDMA. The protective effect of carbonylcyanide m-chlorophenylhydrazone (CCCP), an uncoupler of oxidative phosphorylation on lipid peroxidation and LDH leakage suggests that mitochondria can be implicated in these events. Trolox, a soluble derivative of Tocopherol, weakly prevents ATP but not GSH depletion and totally protects the cells against lipid peroxidation, MMP collapse and cell death. Thus, the present results suggest that TEGDMA induces lipid peroxidation and mitochondrial damage, which contribute to cell death.

Apoptosis vs. necrosis: glutathione-mediated cell death during rewarming of rat hepatocytes

Hypothermia induces injury in its own right, but the mechanisms involved in the cell damage are still unclear. The aim of this study was to test the effects that glutathione (GSH) depletion induces on cell death in isolated rat hepatocytes, kept at 4 degrees C for 20 h, by modulating intracellular GSH concentration with diethylmaleate and buthionine sulfoximine (DEM and BSO). Untreated hepatocytes showed Annexin V stained cells (AnxV(+)), scarce propidium iodide stained cells (PI(+)) and presented a low level of lactate dehydrogenase (LDH) leakage after 20 h at 4 degrees C and rewarming at 37 degrees C. When DEM and BSO were added before cold storage, we observed a few AnXV(+) cells and an increase in PI(+) cells associated with LDH release in the incubation medium. Conversely, the addition of DEM and BSO only during rewarming caused a marked increase in cell death by apoptosis. Production of reactive oxygen species (ROS) and thiobarbituric acid species (TBARS), associated with a decrease in GSH concentrations, was higher when DEM and BSO were added before cold storage. Cells treated with DEM and BSO before cold storage showed lower ATP energy stores than hepatocytes treated with DEM and BSO only during rewarming. Pretreatment of hepatocytes with deferoxamine protected against apoptotic and necrotic morphology in conditions of GSH depletion. These results suggest that pretreatment of hepatocytes with DEM and BSO before cold storage induces necrosis, while the treatment of hepatocytes only during rewarming increases apoptosis. In both conditions, iron represents a crucial mediator of cell death.

Inhibitors arrest myofibrillogenesis in skeletal muscle cells at early stages of assembly

A three-step model for myofibrillogenesis has been proposed for the formation of myofibrils [Rhee et al., 1994: Cell Motil. Cytoskeleton 28:1-24; Sanger et al., 2002: Adv. Exp. Med. 481:89-105]: premyofibril to nascent myofibril to mature myofibril. We have found two chemically related inhibitors that will arrest development at both the first and second step. Cultured quail embryonic skeletal myoblasts were treated with ethyl methane sulfonate (EMS) or 2-aminoethyl-methanesulfonate (MTSEA+). When the myoblasts fused in the presence of either of these compounds, myosheets rather than myotubes formed. Treated cells were fixed and immunostained against multiple proteins commonly found in muscle cells. Protein expression and localization throughout the myosheet were similar to that of developing myotube tips. Cells treated with high concentrations of EMS (10 mM) stained for non-muscle myosin II, sarcomeric alpha-actinin, and tropomyosin. No zeugmatin (Z-band region of titin) or muscle myosin II antibody staining was detected in fibers in this treatment group. These fibers are comparable to premyofibrils in control myotubes. At lower concentrations of EMS (7.5 to 5 mM), fibers that formed stained for muscle myosin II and titin as well as for non-muscle myosin IIB, sarcomeric alpha-actinin, and tropomyosin. Muscle myosin II was in an unbanded pattern. These fibers are comparable to nascent myofibrils observed during normal myofibrillogenesis. Similar effects to those obtained by treating cells with EMS were obtained when we treated cultured cells with MTSEA+ (5 mM) and stained them with sarcomeric alpha-actinin. MTSEA+ is chemically related to EMS, and is a well-known inhibitor of ryanodine receptors in skeletal muscle cells. Some abnormalities such as nemaline-like rods and other protein aggregates also appear within the myosheet during EMS and MTSEA+ treatment. Removal of these two inhibitors of myofibrillogenesis allows the premyofibrils and nascent myofibrils to form mature myofibrils.

Experimental bile-duct ligation resulted in accumulation of oxidized low-density lipoproteins in BALB/c mice liver

BACKGROUND AND AIM

Oxidized low-density lipoproteins (LDL), which are produced during oxidative stress by the process of lipid peroxidation, have also been proposed to have complex roles in many other immuno-inflammatory mechanisms. It has been shown that bile-duct ligation results in oxidative stress in the liver of animals. The aim of this study was to investigate if oxidized LDL are produced in the liver tissues of bile-duct-ligated mice.

METHODS

Obstructive jaundice was induced in BALB/c mice by the ligation and division of the common bile duct. Liver concentrations of glutathione and malondialdehyde were measured in the sham-operated (n = 10) and bile-duct-ligated (n = 10) mice on the 10th day of obstructive jaundice. The presence of oxidized LDL in the liver tissue sections was evaluated using a special, novel immunofluorescent staining method. The final step was to explore the existence of oxidized LDL under fluorescent microscopy.

RESULTS

Compared with sham-operated mice, jaundiced mice showed significantly higher levels of malondialdehyde and lower concentrations of reduced glutathione in the liver. While there was no staining in the sham-operated group, bile-duct ligation resulted in positive oxidized LDL staining in the liver tissues of mice. The present study testifies that bile-duct ligation results in oxidative stress and enhanced lipid peroxidation in the hepatic tissues of BALB/c mice and moreover, that oxidized LDL accumulate in the liver of mice with experimental obstructive jaundice.

CONCLUSION

Oxidized LDL may be an important and direct indicator of ongoing oxidative stress and enhanced lipid peroxidation in obstructive jaundice. The potential roles of this finding were also discussed, briefly.

Glutathione depletion increases nitric oxide-induced oxidative stress in primary rat hepatocyte cultures: involvement of low-molecular-weight iron

Various drugs and chemicals can cause a glutathione (GSH) depletion in the liver. Moreover, nitric oxide (NO) can be generated in response to physiological and pathological situations such as inflammation. The aim of this study was to estimate oxidative stress when primary rat hepatocytes were exposed to GSH depletion after NO production. For this purpose, cells were preincubated with lipopolysaccharide (LPS) and gamma-interferon (IFN) for 18 h in order to induce NO production by NO synthase and then L-buthionine sulfoximine (BSO), an inhibitor of GSH synthesis, was added for 5 h. In hepatocyte cultures preincubated with LPS and IFN before BSO addition, an increase in lipid peroxidation was noted. In those cells, an elevation of iron-bound NO and a decrease in free NO led us to suggest the involvement of low-molecular-weight iron (LMW iron) in the enhancement of oxidative stress. Indeed, addition of deferiprone, a chelator of LMW iron, reduced iron-bound NO levels and the extent of oxidative stress. Moreover, an important elevation of LMW iron levels was also observed. As both, N-acetylcysteine, a GSH precursor, and N(G)-monomethyl-L-arginine, a NO synthase inhibitor, totally inhibited the elevation of LMW iron and oxidative stress, a cooperative role could be attributed to NO production and GSH depletion.

Phenolic antioxidants attenuate hippocampal neuronal cell damage against kainic acid induced excitotoxicity

Increasing evidence supports the role of excitotoxicity in neuronal cell injury. Thus, it is extremely important to explore methods to retard or reverse excitotoxic neuronal injury. In this regard, certain dietary compounds are beginning to receive increased attention, in particular those involving phytochemicals found in medicinal plants in alleviating neuronal injury. In the present study, we examined whether medicinal plant extracts protect neurons against excitotoxic lesions induced by kainic acid (KA) in female Swiss albino mice. Mice were anesthetized with ketamine and xylazine (200 mg and 2 mg/kg body wt. respectively) and KA (0.25 microg in a volume of 0.5 microl) was administered to mice by intra hippocampal injections. The results showed an impairment of the hippocampus region of brain after KA injection. The lipid peroxidation and protein carbonyl content were significantly (P < 0.05) increased in comparison to controls. Glutathione peroxidase (GPx) activity (EC 1.11.1.9) and reduced glutathione (GSH) content declined after appearance of excitotoxic lesions. As GPx and GSH represent a major pathway in the cell for metabolizing hydrogen peroxide (H2O2), their depletion would be expected to allow H2O2 to accumulate to toxic levels. Dried ethanolic plant extracts of Withania somnifera (WS), Convolvulus pleuricauas (CP) and Aloe vera (AV) dissolved in distilled water were tested for their total antioxidant activity. The diet was prepared in terms of total antioxidant activity of plant extracts. The iron (Fe3+) reducing activity of plant extracts was also tested and it was found that WS and AV were potent reductants of Fe3+ at pH 5 5. CP had lower Fe3+ reducing activity in comparison to WS and AV. Plant extracts given singly and in combination 3 weeks prior to KA injections resulted in a decrease in neurotoxicity. Measures of lipid peroxidation and protein carbonyl declined. GPx activity and GSH content were elevated in hippocampus supplemented with WS and combination of WS + CP + AV. However, when CP and AV were given alone, the changes in the GPx activity and GSH content were not significant. Although the major factors involved in these properties of phytochemicals remain to be specified, the finding of this study has suggested that phytochemicals present in plant extracts mitigate the effects of excitotoxicity and oxidative damage in hippocampus and this might be accomplished by their antioxidative properties.

Determination of mitochondrial reactive oxygen species: methodological aspects

The generation of Reactive Oxygen Species (ROS) as by-products in mitochondria Electron Transport Chain (ETC) has long been admitted as the cost of aerobic energy metabolism with oxidative damages as consequence. The purpose of this methodological review is to present some of the most widespread methods of ROS generation and to underline the limitations as well as some problems, identified with some experiments as examples, in the interpretation of such results. There is now no doubt that besides their pejorative role, ROS are involved in a variety of cellular processes for the continuous adaptation of the cell to its environment. Because ROS metabolism is a complex area (low production, instability of species, efficient antioxidant defense system, several places of production...) bias, variances and limitations in ROS measurements must be recognized in order to avoid artefactual conclusions, and especially to improve our understanding of physiological and pathophysiological mechanisms of such phenomenon.