Intracellular Free Radical Production Research Articles

Mechanism of Anti-Trypanosoma cruzi Action of Gold(I) Compounds: A Theoretical and Experimental Approach

In the search for a more effective chemotherapy for the treatment of Chagas’ disease, caused by Trypanosoma cruzi parasite, the use of gold compounds may be a promising approach. In this work, four gold(I) compounds [AuCl(HL)], (HL = bioactive 5-nitrofuryl containing thiosemicarbazones) were studied. The compounds were theoretically characterized, showing identical chemical structures with the metal ion located in a linear coordination environment and the thiosemicarbazones acting as monodentate ligands. Cyclic voltammetry and Electron Spin Resonance (ESR) studies demonstrated that the complexes could generate the nitro anion radical (NO2−) by reduction of the nitro moiety. The compounds were evaluated in vitro on the trypomastigote form of T. cruzi and human cells of endothelial morphology. The gold compounds studied showed activity in the micromolar range against T. cruzi. The most active compounds (IC50 of around 10 μM) showed an enhancement of the antiparasitic activity compared with their respective bioactive ligands and moderate selectivity. To get insight into the anti-chagasic mechanism of action, the intracellular free radical production capacity of the gold compounds was assessed by ESR and fluorescence measurements. DMPO (5,5-dimethyl-1-pirroline-N-oxide) spin adducts related to the bioreduction of the complexes and redox cycling processes were characterized. The potential oxidative stress mechanism against T. cruzi was confirmed.

Tubermycin B coated on Galactosylated Chitosan Nanoparticles synthesized by eco-friendly method ameliorates intracellular free radical production and reduces oxidative stress, reducing phosphorylation of IKKα/β/pIкBα/NF-кB pathway.

The objective of the current study was to investigate the cytotoxic potentials of Galactosylated Chitosan Nanoparticles. Specifically, the study aimed to develop Tubermycin B coated on Galactosylated Chitosan Nanoparticles using a new green method that replaces sodium borohydride in the reduction process. The study synthesized Tubermycin B coated on Galactosylated Chitosan Nanoparticles through a new green method. The cytotoxicity of these nanoparticles was evaluated in a mice intestinal tract model that had been induced with chlorpyrifos, which causes oxidative stress-related enterotoxicity. Multiple activities, including the apoptosis of intestinal macrophages and the activation of Ikappa α/β kinase (IKKα/β), were examined as indicators of the nanoparticles' efficacy. The stability of the synthesized Chitosan Nanoparticles was also assessed. Additionally, the encapsulation efficiency of Boscia angustifalia and Boscia senegalensis extracts within the nanoparticles was determined. The results of the study showed that Tubermycin B coated on Galactosylated Chitosan Nanoparticles effectively alleviated the oxidative stress-related enterotoxicity in the mice intestinal tract induced by chlorpyrifos. The nanoparticles prevented the apoptosis of intestinal macrophages and inhibited the activation of IKKα/β. The synthesized chitosan nanoparticles exhibited high stability. The encapsulation efficiency of Boscia angustifalia extract was recorded as 46.58%, whereas for Boscia senegalensis extract, it was 9.77%. The nanoparticles showed no cytotoxicity at all tested concentrations and demonstrated a medium-level anticancer effect. Based on the findings, it can be concluded that Tubermycin B coated on Galactosylated Chitosan Nanoparticles has the potential to alleviate oxidative stress-related enterotoxicity in the mice intestinal tract. The nanoparticles showed high stability and exhibited a medium-level anticancer effect. Furthermore, the study demonstrated that Boscia angustifalia extract exhibited higher anti-hepatitis C virus antibodies (anti-HCV) activity compared to Boscia senegalensis extract in an in-vitro system. Therefore, Boscia angustifalia could be considered a promising candidate for the development of an anti-HCV drug for future in-vivo studies.

Host–device interactions: exposure of lung epithelial cells and fibroblasts to nickel, titanium, or nitinol affect proliferation, reactive oxygen species production, and cellular signaling

Endoscopic implantation of medical devices for the treatment of lung diseases, including airway stents, unidirectional valves and coils, is readily used to treat central airway disease and emphysema. However, granulation and fibrotic tissue formation impairs treatment effectiveness. To date little is known about the interaction between implanted devices, often made from metals, such as nickel, titanium or nitinol, and cells in the airways. Here, we study the response of lung epithelial cells and fibroblasts to implant device materials. The adhesion and proliferation of bronchial epithelial cells and lung fibroblasts upon exposure to 10 × 3 × 1 mm pieces of nickel, titanium or nitinol is examined using light and scanning electron microscopy. Pro-inflammatory cytokine mRNA expression and release, signaling kinase activity and intracellular free radical production are assessed. Nitinol, and to a lesser extent nickel and titanium, surfaces support the attachment and growth of lung epithelial cells. Nitinol induces a rapid and significant alteration of kinase activity. Cells directly exposed to nickel or titanium produce free radicals, but those exposed to nitinol do not. The response of lung epithelial cells and fibroblasts depends on the metal type to which they are exposed. Nitinol induces cellular surface growth and the induction of kinase activity, while exposure of lung epithelial cells to nickel and titanium induces free radical production, but nitinol does not.Graphical

Assessment of Cosmetic Properties and Safety of Use of Model Washing Gels with Reishi, Maitake and Lion's Mane Extracts.

Natural cosmetics are becoming more and more popular every day. For this reason, this work investigates the properties of mushroom extracts, which are not as widely used in the cosmetics industry as plant ingredients. Water extracts of Grifolafrondosa (Maitake), Hericiumerinaceus (Lion’s Mane) and Ganoderma lucidum (Reishi) were tested for their antioxidant properties, bioactive substances content, skin cell toxicity, ability to limit TEWL, effect on skin hydration and pH, and skin irritation. Our research showed that Maitake extract contained the highest amount of flavonoids and phenols, and also showed the most effective scavenging of DPPH and ABTS radicals as well as Chelation of Fe2+ and FRAP radicals, which were 39.84% and 82.12% in a concentration of 1000 µg/mL, respectively. All tested extracts did not increase the amount of ROS in fibroblasts and keratinocytes. The addition of mushroom extracts to washing gels reduced the irritating effect on skin, and reduced the intracellular production of free radicals, compared with the cosmetic base. Moreover, it was shown that the analyzedcosmetics had a positive effect on the pH and hydration of the skin, and reduced TEWL.

Novel ruthenium(II) cyclopentadienyl thiosemicarbazone compounds with antiproliferative activity on pathogenic trypanosomatid parasites

Searching for new prospective antitrypanosomal agents, three novel Ru(II)-cyclopentadienyl compounds, [Ru(η5-C5H5)(PPh3)L], with HL=bioactive 5-nitrofuryl containing thiosemicarbazones were synthesized and characterized in the solid state and in solution. The compounds were evaluated in vitro on the blood circulating trypomastigote form of Trypanosoma cruzi (Dm28c strain), the infective form of Trypanosoma brucei brucei (strain 427) and on J774 murine macrophages and human-derived EA.hy926 endothelial cells. The compounds were active against both parasites with IC50 values in the micromolar or submicromolar range. Interestingly, they are much more active on T. cruzi than previously developed Ru(II) classical and organometallic compounds with the same bioactive ligands. The new compounds showed moderate to very good selectivity towards the parasites in respect to mammalian cells. The global results point at [RuCp(PPh3)L2] (L2=N-methyl derivative of 5-nitrofuryl containing thiosemicarbazone and Cp=cyclopentadienyl) as the most promising compound for further developments (IC50T. cruzi=0.41μM; IC50T. brucei brucei=3.5μM). Moreover, this compound shows excellent selectivity towards T. cruzi (SI>49) and good selectivity towards T. brucei brucei (SI>6). In order to get insight into the mechanism of antiparasitic action, the intracellular free radical production capacity of the new compounds was assessed by ESR. DMPO (5,5-dimethyl-1-pirroline-N-oxide) spin adducts related to the bioreduction of the complexes and to redox cycling processes were characterized. In addition, DNA competitive binding studies with ethidium bromide by fluorescence measurements showed that the compounds interact with this biomolecule.

Intracellular free radical production by peripheral blood T lymphocytes from patients with systemic sclerosis: role of NADPH oxidase and ERK1/2.

IntroductionAbnormal oxidative stress has been described in systemic sclerosis (SSc) and previous works from our laboratory demonstrated an increased generation of reactive oxygen species (ROS) by SSc fibroblasts and monocytes. This study investigated the ability of SSc T lymphocytes to produce ROS, the molecular pathway involved, and the biological effects of ROS on SSc phenotype.MethodsPeripheral blood T lymphocytes were isolated from serum of healthy controls or SSc patients by negative selection with magnetic beads and activated either with PMA or with magnetic beads coated with anti-CD3 and anti-CD28 antibodies. Intracellular ROS generation was measured using a DCFH-DA assay in a plate reader fluorimeter or by FACS analysis. CD69 expression and cytokine production were analyzed by FACS analysis. Protein expression was studied using immunoblotting techniques and mRNA levels were quantified by real-time PCR. Cell proliferation was carried out using a BrdU incorporation assay.ResultsPeripheral blood T lymphocytes from SSc patients showed an increased ROS production compared to T cells from healthy subjects. Since NADPH oxidase complex is involved in oxidative stress in SSc and we found high levels of gp91phox in SSc T cells, SSc T cells were incubated with chemical inhibititors or specific siRNAs against gp91phox. Inhibition of NADPH oxidase partially reverted CD69 activation and proliferation rate increase, and significantly influenced cytokine production and ERK1/2 activation.ConclusionsSSc T lymphocityes are characterized by high levels of ROS, generated by NADPH oxidase via ERK1/2 phosphorylation, that are essential for cell activation, proliferation, and cytokine production. These data confirm lymphocytes as key cellular players in the pathogenesis of systemic sclerosis and suggest a crucial link between ROS and T cell activation.Electronic supplementary materialThe online version of this article (doi:10.1186/s13075-015-0591-8) contains supplementary material, which is available to authorized users.

A Review of Animal Models of Nonneoplastic Pancreatic Diseases

The nonneoplastic diseases of the human pancreas generally comprise the inflammatory and degenerative conditions that include acute and chronic pancreatitis, with cystic fibrosis being arguably one of the most important diseases that induce the condition. Both acute and chronic conditions vary in severity, but both can be life threatening; and because of this fact, the study of their progression, and their responsiveness to therapy, is largely conducted by indirect means using serum markers of damage and repair such as amylase and lipase activities that normally occur at very low levels in the circulation but can be significantly increased during inflammatory episodes. Progress in the understanding the pathogenesis of both conditions has therefore been largely due to time course studies in animal models of pancreatitis, and it is in this context that animal model development has been so significant. In general terms, the animal models can be divided into the invasive, surgical procedures, and those induced by the administration of chemical secretagogues that induce hypersecretion of the pancreatic enzymes. The former include ligation and/or cannulation of the biliopancreatic ducts with infusion of solutions of various kinds, or the formation of closed duodenal loops. Secretagogue administration includes administration of caerulein or l-arginine in various protocols. An additional model involves administration of dibutyltin dichloride, which induces a partial blockage of the pancreatic ducts to induce pancreatic disease through enzymic reflux into the gland. The models have been invaluable in generating testable hypotheses for the human diseases. These hypotheses for the production of cellular damage as the initiating events in the disease include (1) intracellular chemical activation, (2) pancreatic secretion reflux, (3) intracellular production of reactive oxygen species, and (4) intracellular production of free radicals.

Autism: Where Genetics Meets the Immune System

Individuals with autism often display immune abnormalities in the form of altered cytokine profiles, autoantibodies, and changes in immune cell function. Are they mere “smoke” or real “fire”? Given what we now know about the cross-talk between the immune and nervous systems, one must ask: are these immune abnormalities simply bystander effects of genetic/genomic variants directly responsible for abnormal neurodevelopment, or is there a sizable subgroup of patients with autism spectrum disorder (ASD), in which a dysfunctional immune system plays a critical mediator role in the pathogenic chain of events leading to the disorder? Is autism one of many genetic/genomic conditions, Down syndrome representing the best-known example, accompanied by immune abnormalities not primarily responsible for changing the trajectory of neurodevelopment? Or could conceivably an unfortunate combination of genetic/genomic susceptibility and environmental factors converging onto the same individual affect neurodevelopment through immune-mediated mechanisms, such as fetomaternal incompatibility, autoimmunity, abnormal neuroinflammation, and so on? This special issue contains six contributions aimed at addressing different aspects of this question. The paper by N. Momeni et al. documents significantly elevated plasma levels of factor I among ASD children compared to controls. Factor I is a plasma enzyme responsible for degrading complement factor 3b, which in turn is the major opsonin in the complement system enabling phagocytosis of microbial agents. Higher factor I levels can be interpreted as either primary (i.e., conferring vulnerability toward microbial infections) or as a secondary event part of a broader immunomodulatory response aiming to blunt an inflammatory process. F1 plasma levels suggest that this process could play a more relevant role in males and in small ASD children. The contribution by S. Rose et al. describes reduced glutathione-mediated redox/antioxidant capacity both inside primary leukocytes and in the plasma of ASD children. Consistently with this intracellular and extracellular imbalance of the glutathione redox status, intracellular production of free radicals is also enhanced, especially in 30% of ASD cases. This and several previous studies provide converging evidence of excessive oxidative stress likely leading to abnormal mitochondrial function in a similar percentage of autistic individuals. Along similar lines, M. I. Waly et al. direct their attention on the complex array of pathophysiological consequences produced by enhanced oxidative stress. In addition to imbalanced glutathione redox status, reduced methionine synthase activity is particularly interesting, as it results in lower availability of S-adenosyl-methionine and consequently blunted DNA methylation. Curiously, a similar abnormality underlies autistic features also in two entirely different contexts, namely, children exposed prenatally to valproic acid and in Rett syndrome girls, carrying MECP2 mutations. The review by S. D. Bilbo et al. presents a stimulating hypothesis, linking ASD to inflammatory, allergic, and autoimmune diseases. These “hyperimmune” disorders are known to share steeply increasing incidence rates over the last decades, as well as significant loading in many families with children with autism. In the authors' view, they also share an inappropriate activation of the immune system due to biome depletion in postindustrial societies, possibly suggesting preventive strategies based on biome reconstitution. The paper by C. Onore et al. reports an impressive threefold decrease in EGF plasma levels among small ASD children compared to controls. EGF is involved in wound healing in the skin, in the gastrointestinal, and respiratory systems, as well as in the central nervous system where this neurotrophic factor supports both adult subventricular zone and midbrain dopaminergic neurons, in addition to stem cell proliferation. A. R. Torres et al. review immune abnormalities in autism, focusing on HLA gene roles as potential contributors to autism pathogenesis through several distinct mechanisms. HLA genes or haplotypes have been found associated with several autoimmune diseases, but strong associations with autism have also been reported. These contributions, while not providing the ultimate answers, do add some new pieces to the autism puzzle, providing further support to the idea that immune abnormalities may play a pathophysiologically relevant role in a subgroup of families with autistic children. Future studies of the interaction of the immune and central nervous system are needed to clarify in more detail how neuroimmune mechanisms influence the enhancement of the neurodevelopmental disarray and disturbances of neurobehavioral trajectories determined by genetic and environmental factors. The heuristic potential of this line of investigation, both in terms of prevention and clinical therapeutics, ensures continued efforts until a more definitive answer can be given to our initial question, so crucial in today's autism field. Antonio M. Persico Judy Van de Water Carlos A. Pardo

Cytotoxic Effects of Lysophosphatidylcholine on Vascular Smooth Muscle Cells

Objectives: To investigate the cytotoxic effects of lysophosphatidylcholine (lysoPC), an active component of oxidized low-density lipoproteins (LDL), on vascular smooth muscle cells (VSMCs). Methods: VSMCs were derived from rat aorta. Cell death was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay, lactic dehydrogenase (LDH) assay, and DNA fragmentation assay. Apoptosis was quantified by propidium iodide staining and fluorescent activated cell sorting (FACS) analysis, and intracellular free radical production was determined using 2',7'-dichlorofluorescin diacetate (DCF-DA). In addition, the changes in caspases, bcl-2 and bax proteins were evaluated by western blot analysis. Results: LysoPC over 25 μM induced more than 50% of the cell death at 10 hours on MTT assay with no change in the level of LDH. The DNA ladder pattern showed that cell death induced by lysoPC was caused by apoptosis, which was associated with increased free radical production. Vitamin E, a potent antioxidant and caffeic acid phenylethyl ester (CAPE), an inhibitor of nuclear factor-kappaB (NF-kB), blocked apoptosis. The casepase-3 precursor decreased and the active form of caspase-8 increased. Total bcl-2 and bax proteins did not change with lysoPC treatment, but translocation of bax from cytosole to the mitochondria membrane was observed. Conclusion: LysoPC induces apoptosis in VSMCs via an oxidant mechanism, dependent on NF-kB. (J Korean Soc Menopause 2012;18:139-146)

Lipoxygenase-mediated pro-radical effect of melatonin via stimulation of arachidonic acid metabolism

We have shown that melatonin immediately and transiently stimulates intracellular free radical production on a set of leukocytes, possibly as a consequence of calmodulin binding. We show here that melatonin-induced ROS are produced by lipoxygenase (LOX), since they are prevented by a set of LOX inhibitors, and are accompanied by increase of the 5-LOX product 5-HETE. LOX activation is accompanied by strong liberation of AA; inhibition of Ca 2+-independent, but not Ca 2+-dependent, phospholipase A2 (PLA2), prevents both melatonin-induced arachidonic acid and ROS production, whereas LOX inhibition only prevents ROS, indicating that PLA2 is upstream with respect to LOX, as occurs in many signaling pathways. Chlorpromazine, an inhibitor of melatonin–calmodulin interaction, inhibits both ROS and arachidonic acid production, thus possibly placing calmodulin at the origin of a melatonin-induced pro-radical pathway. Interestingly, it is known that Ca 2+-independent PLA2 binds to calmodulin: our results are compatible with PLA2 being liberated by melatonin from a steady-state calmodulin sequestration, thus initiating an arachidonate signal transduction. These results delineate a novel molecular pathway through which melatonin may participate to the inflammatory response.

Methylated Bismuth, but Not Bismuth Citrate or Bismuth Glutathione, Induces Cyto- and Genotoxic Effects in Human Cells in Vitro

Bismuth compounds are widely used in industrial processes and products. In medicine, bismuth salts have been applied in combination with antibiotics for the treatment of Helicobacter pylori infections, for the prevention of diarrhea, and in radioimmunotherapy. In the environment, bismuth ions can be biotransformed to the volatile bismuth compound trimethylbismuth (Me3Bi) by methanobacteria. Preliminary in-house studies have indicated that bismuth ions are methylated in the human colon by intestinal microflora following ingestion of bismuth-containing salts. Information concerning cyto- and genotoxicity of these biomethylated products is limited. In the present study, we investigated the cellular uptake of an organic bismuth compound [monomethylbismuth(III), MeBi(III)] and two other bismuth compounds [bismuth citrate (Bi-Cit) and bismuth glutathione (Bi-GS)] in human hepatocytes, lymphocytes, and erythrocytes using ICP-MS. We also analyzed the cyto- and genotoxic effects of these compounds to investigate their toxic potential. Our results show that the methylbismuth compound was better taken up by the cells than Bi-Cit and Bi-GS. All intracellularly detected bismuth compounds were located in the cytosol of the cells. MeBi(III) was best taken up by erythrocytes (36%), followed by lymphocytes (17%) and hepatocytes (0.04%). Erythrocytes and hepatocytes were more susceptible to MeBi(III) exposure than lymphocytes. Cytotoxic effects of MeBi(III) were detectable in erythrocytes at concentrations >4 microM, in hepatocytes at >130 microM, and in lymphocytes at >430 microM after 24 h of exposure. Cytotoxic effects for Bi-Cit and Bi-GS were much lower or not detectable in the used cell lines up to a tested concentration of 500 microM. Exposure of lymphocytes to MeBi(III) (250 microM for 1 h and 25 microM/50 microM for 24 h) resulted in significantly increased frequencies of chromosomal aberrations (CA) and sister chromatid exchanges (SCE), whereas Bi-Cit and Bi-GS induced neither CA nor SCE. Our study also showed an intracellular production of free radicals caused by MeBi(III) in hepatocytes but not in lymphocytes. These data suggest that biomethylation of bismuth ions by the intestinal microflora of the human colon leads to an increase in the toxicity of the primary bismuth salt.

Histidine Inhibits the Degradation of Cells Suspended in Ringer’s Lactate

We previously demonstrated that the degradation of a suspension of Jurkat cells in Ringer's lactate (RL) was inhibited by the addition of a 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid/Tris buffer. Given the ability of histidine to buffer protons in the physiologic range (pKa = 6.0), we hypothesized that this amino acid would have the same effect. RL was made in our laboratory using sodium l-lactate. Jurkat cells were suspended in RL alone or RL with various concentrations of histidine or other test reagents at 37 degrees C for 4 hours or 24 hours in an atmosphere of 95% air and 5% CO2. Using flow cytometry, we measured cell shrinkage, phosphatidylserine translocation, propidium iodide uptake, and intracellular oxygen free radical production. Cell shrinkage was induced by suspension in RL after 4 hours incubation. At 4 hours, cell shrinkage was inhibited by all concentrations of histidine tested, 7.8 mumol/L to 10 mmol/L. There was no statistical difference between cells suspended in medium and cells suspended in 1 mmol/L or 10 mmol/L histidine. After 24 hours incubation, 100% of the cells in RL had undergone cell shrinkage whereas in 10 mmol/L histidine only a mean of 20% of the cells had undergone cell shrinkage. The inhibitory effect of 1 mmol/L histidine at pH 7.4 was compared with that at pH 6.8. After 4 hours incubation, there was no difference. After 24 hours incubation, the inhibitory effect at pH 7.4 was significantly greater that that at pH 6.8. Histidine at 1 mmol/L to 10 mmol/L significantly reduced the percentage of cells that underwent phosphatidylserine translocation and propidium iodide uptake. The effect of the dipeptide buffer, glycylglycine, and the two other positively charged amino acids, arginine and lysine, after 4 hours incubation was compared with histidine at 1 mmol/L. At 1 mmol/L, histidine was superior to arginine and lysine and indistinguishable from glycylglycine. Intracellular free radical production was measured at 0.5 mmol/L, 1.0 mmol/L, and 10 mmol/L histidine concentrations. There was significant inhibition only at 10 mmol/L. Characteristics of apoptotic cell death that occur in cells suspended in RL are inhibited by the addition of histidine, arginine, and lysine as well as the dipeptide glycylglycine, which, with a pKa of 8.25, also buffers in the physiologic range. Histidine is superior to lysine and arginine at 1 mmol/L. The salutary effect of histidine at 0.5 mmol/L and 1 mmol/L is caused by a mechanism other than the inhibition of oxygen free radicals. Moreover, the buffering of protons may play a role at 24 hours but made no difference at 4 hours.

Intracellular free radical production in synovial T lymphocytes from patients with rheumatoid arthritis

To investigate the cellular and molecular sources of oxidative stress in patients with rheumatoid arthritis (RA) through analysis of the production of reactive oxygen species (ROS) in synovium. Cytochemical procedures based on the 3,3'-diaminobenzidine (DAB)-Mn2+ deposition technique were used on unfixed cryostat sections of synovium from RA patients and rheumatic disease controls. For immunophenotyping, sections were incubated, fixed, and stained with fluorescein isothiocyanate-labeled antibodies. Fluorescence-activated cell sorter analysis of the ROS-reactive dye 6-carboxy-2',7'-dichlorodihydrofluorescein diacetate-di(acetoxymethyl ester) was used to measure intracellular ROS in T lymphocytes from peripheral blood and synovial fluid. To determine which enzymes produced ROS, different inhibitors were tested. Large quantities of DAB precipitated in the majority of RA synovial T lymphocytes, indicative of intracellular ROS production. These ROS-producing T lymphocytes were observed throughout the synovium. Polymerization of DAB was observed to a lesser extent in other forms of chronic arthritis, but was absent in osteoarthritis. DAB staining of cytospin preparations of purified RA synovial fluid T cells confirmed the presence of ROS-producing cells. One of the ROS involved appeared to be H2O2, since catalase suppressed intracellular ROS production. Superoxide dismutase, which uses superoxide as a substrate to form H2O2, diphenyleneiodonium (an inhibitor of NADPH oxidase), N(G)-monomethyl-L-arginine (an inhibitor of nitric oxide synthesis), nordihydroguaiaretic acid (an inhibitor of lipoxygenase), and rotenone (an inhibitor of mitochondrial ROS production) failed to suppress ROS production. Our findings show that chronic oxidative stress observed in synovial T lymphocytes is not secondary to exposure to environmental free radicals, but originates from intracellularly produced ROS. Additionally, our data suggest that one of the intracellularly generated ROS is H2O2, although the oxidase(s) involved in its generation remains to be determined.

An Investigation into the Mechanism of Action of Almitrine on Isolated Rat Diaphragm Muscle Fatigue

Background: Previous studies have shown that almitrine bismesylate, a respiratory stimulant which acts on the mitochondrial electron transport chain, enhances recovery of rat diaphragm muscle from fatigue. Objectives: Our aim is to investigate if the enhanced recovery is due to an anti-oxidant property of almitrine, since the electron transport chain is a major site of intracellular free radical production. Methods: A low-frequency fatigue protocol was used (30 Hz; 250 ms; delivered once every 2 s for 5 min), and the effects of almitrine before and after fatigue onset were compared to those of the anti-oxidant compound N-acetylcysteine (NAC). Results: Almitrine (6 and 10 µg/ml) given before fatigue gave better recovery rates than postfatigue application. In contrast, NAC (100 µM) application before fatigue onset was not as effective as NAC given immediately after the cessation of the fatigue protocol. However, almitrine (6 µg/ml) completely reversed the reduction in baseline twitch tension brought about by a free-radical-producing mixture of FeCl₃ + ADP (1 mM + 2.5 mM, respectively). Conclusion: The results of this study confirm that almitrine enhances recovery from fatigue and, in contrast to NAC prefatigue application, is more effective. Also, almitrine was shown to have an anti-oxidant effect, but it does not act like a typical anti-oxidant.

PGE 1 Protection against Apoptosis Induced by d -galactosamine is Not Related to the Modulation of Intracellular Free Radical Production in Primary Culture of Rat Hepatocytes

d -galactosamine ( d -GalN) toxicity is a useful experimental model of liver failure in human. It has been previously observed that PGE 1 treatment reduced necrosis and apoptosis induced by d -GalN in rats. Primary cultured rat hepatocytes were used to evaluate if intracellular oxidative stress was involved during the induction of apoptosis and necrosis by d -GalN (0-40 mM). Also, the present study investigated if PGE 1 (1 w M) was equally potent reducing both types of cell death. The presence of hypodiploid cells, DNA fragmentation and caspase-3 activation were used as a marker of hepatocyte apoptosis. Necrosis was measured by lactate dehydrogenase (LDH) release. Oxidative stress was evaluated by the intracellular production of hydrogen peroxide (H 2 O 2 ), the disturbances on the mitochondrial transmembrane potential (MTP), thiobarbituric-reacting substances (TBARS) release and the GSH/GSSG ratio. Data showed that intermediate range of d -GalN concentrations (2.5-10 mM) induced apoptosis in association with a moderate oxidative stress. High d -GalN concentration (40 mM) induced a reduction of all parameters associated with apoptosis and enhanced all those related to necrosis and intracellular oxidative stress, including a reduction of GSH/GSSG ratio and MTP in comparison with d -GalN (2.5-10 mM)-treated cells. Although PGE 1 reduced apoptosis induced by d -GalN, it was not able to reduce the oxidative stress and cell necrosis induced by the hepatotoxin in spite to its ability to abolish the GSH depletion.

Oxidative stress and glycemic regulation

Oxidative stress is an acknowledged pathogenetic mechanism in diabetic complications. Hyperglycemia is a widely known cause of enhanced free radical concentration, whereas oxidative stress involvement in glycemic regulation is still debated. Glucose transport is a cascade of events starting from the interaction of insulin with its own receptor at the plasma membrane and ending with intracellular glucose metabolism. In this complex series of events, each step plays an important role and can be inhibited by a negative effect of oxidative stress. Several studies show that an acute increase in the blood glucose level may impair the physiological homeostasis of many systems in living organisms. The mechanisms through which acute hyperglycemia exerts these effects may be identified in the production of free radicals. It has been suggested that insulin resistance may be accompanied by intracellular production of free radicals. In adipocytes cultured in vitro, insulin increases the production of hydrogen peroxide, which has been shown to mimic the action of insulin. These data allow us to hypothesize that a vicious circle between hyperinsulinemia and free radicals could be operating: insulin resistance might cause elevated plasma free radical concentrations, which, in turn, might be responsible for a deterioration of insulin action, with hyperglycemia being a contributory factor. Data supporting this hypothesis are available. Vitamin E improves insulin action in healthy, elderly, and non-insulin-dependent diabetic subjects. Similar results can be obtained by vitamin C administration.

FREE RADICAL ACTIVITY FOLLOWING ACUTE MUSCLE STRETCH INJURY IN AN ANIMAL MODEL

189 The present study investigated the changes in the rate of free radical production, antioxidant enzyme activity, and glutathione status immediately and 24hr after acute muscle stretch injury in eighteen male New Zealand white rabbits. A standardized eccentric stretch injury was created under anesthesia to the tibialis anterior muscle using a customized isokinetic test device and electrical stimulator1. Intracellular free radical production, measured with a dichlorofluoroscein (DCF) intracellular probe, was increased in the injured vs. contralateral control leg (p=0.016) and over time (p=0.005). In addition, there was an interaction (time and treatment) effect (p=0.005) for free radical production over the 24hr time period following injury. Antioxidant enzyme activity demonstrated treatment (injured vs control) and interaction effects for both glutathione peroxidase and glutathione reductase. Superoxide dismutase and catalase activity were not effected by the injury. There was no evidence of lipid peroxidation damage, as measured by muscle malondialdehyde content. An interaction effect occurred for both reduced glutathione (p=0.008) and total glutathione (p=0.015). Morphologic analysis (H & E staining) showed fiber tearing and hemorrhage predominantly at the myotendinous junction immediately following injury with significant infiltration of polymorphonuclear leukocytes in the same region 24hr post-injury. We conclude that acute mechanical muscle stretch injury results in increased free radical production within 24hr following injury. Antioxidant enzyme and glutathione systems also appear to be affected during this early post-injury period. Supported by UW Surgical Associates

Hydralazine, but not Captopril, Decreases Free Radical Production and Apoptosis in Neurons and Thymocytes

The effects of captopril and hydralazine, two commonly used antihypertensive drugs, on free radical generation and the onset of apoptosis in neuron and thymocyte preparations from 10–12 day old rats have been studied. Apoptosis was induced in neurons by kainate or N-methyl-D-aspartate and in thymocytes by heat shock. Intracellular free radical production was measured by 2′,7′-dichlorofluorescein fluorescence, and apoptotic cells were detected by cell staining with fluorescein-labelled annexin V. Captopril was found to have no effect on intracellular free radical generation and also had no significant effect on the early stages of apoptosis in neurons and thymocytes. In contrast, hydralazine was found to decrease free radical generation in both neurons and thymocytes, and it also significantly decreased the numbers of apoptotic cells when neurons and thymocytes were stimulated for apoptosis. Hydralazine had a greater effect on decreasing free radical generation in neurons than in thymocytes, but it had a more pronounced effect on decreasing apoptosis in thymocytes compared to neurons, suggesting that apoptosis, under our experimental conditions, may not solely be triggered by free radical generation. These results contrast with earlier reports that captopril is a free radical scavenger and can decrease apoptosis in T-lymphocytes and cardiomyocytes, and the results obtained with hydralazine are in apparent disagreement with earlier reports that this drug is a free radical generator and can cause intracellular damage suggestive of enhanced free radical formation.

Epirubicin-induced oxidative DNA damage and evidence for its repair in lymphocytes of cancer patients who are undergoing chemotherapy.

Anthracycline derivatives have been widely used in the treatment of several types of human malignancies. Cytotoxicity of these drugs has been attributed to inhibition of topoisomerase II as well as intracellular production of free radicals. In our work we used a gas chromatography/mass spectrometry technique to study free radical-induced DNA base modifications in chromatin isolated from lymphocytes of cancer patients who received chemotherapy with epirubicin (one of anthracycline's antitumor derivatives). The anticancer therapy caused significant increases in the amount of all four DNA base modifications over control levels in the lymphocytes of most of the patients. For the majority of the cases the base products returned to the control value 24 hr after the infusion of the drug, which suggests the removal of these lesions by cellular repair processes. However, some of the modified bases escaped repair. Because part of these modifications may possess premutagenic properties, they may be responsible for secondary cancers induced by chemotherapy.

Protease inhibitors (gebexate mesylate and ulinastatin) stimulate intracellular chemiluminescence in human neutrophils.

The effect of protease inhibitors on the intracellular production of free radicals was investigated by measuring chemiluminescence (CL) elicited from phagocytosed luminol-bound microspheres (Lumispheres) in human neutrophils stimulated with formylmethionyl-leucyl-phenylalanine (fMLP), interleukin-8 (IL-8), phorbol 12-myristate 13-acetate, or diacylglycerol. Both gabexate mesylate (Foy) and ulinastatin (Miraclid), urinary trypsin inhibitor, increased intracellular CL in a dose dependent manner. Compared to control buffer without protease inhibitor, gabexate mesylate (322 micrograms/ml) caused about a 10-fold increase in intracellular CL in stimulated neutrophils, and ulinastatin (3100 U/ml) a twofold increase in neutrophils stimulated with fMLP or IL-8. When the protease inhibitors were added to the cell suspension after the phagocytosis of lumispheres, CL responses rapidly increased again to the level which was observed when both protease inhibitors and neutrophil stimulants were incubated simultaneously. In contrast, extracellular release of oxygen metabolites from stimulated neutrophils, assayed by a conventional measurement of luminol-dependent CL, was reduced by the protease inhibitors in a dose dependent fashion. When luminol-unbound microspheres were incubated with neutrophils stimulated by fMLP in luminol solution, extracellular CL was almost completely inhibited by gabexate mesylate. These results indicate that the protease inhibitors enhance the generation of intracellular CL and suppress the extracellular release of free radicals.