Lipid Peroxidation By-products Research Articles

Differential response to acrylonitrile toxicity in rat primary astrocytes and microglia

Acrylonitrile (ACN) is a widely used chemical in the production of plastics, resins, nitriles, acrylic fibers, synthetic rubber and acrylamide. While acute high level exposures to ACN are known to be lethal, chronic low dose exposures causes glial cell tumors in rats. Recently, these glial tumors have been characterized as microglial in origin. While effects of ACN on astrocytes, the more numerous glial cell, have been investigated, the effects on microglia are unknown. This study was conducted to compare the responses of astrocytes and microglia to ACN treatment in vitro to address differential sensitivities and adaptive responses to this toxic chemical. Cell viability, ACN uptake, lipid peroxidation byproducts (F2-isoprostanes), glutathione (GSH) levels and expression of NF-E2-related factor 2 (Nrf2) were evaluated in primary rat microglia and astrocytes following ACN treatment. Results indicate that microglia are more sensitive to ACN than astrocytes, accumulating less ACN while demonstrating higher F2-isoprostane levels. GSH levels were up-regulated in both cell types, as a protective mechanism against ACN-induced oxidative stress, while Nrf2 levels were only induced in microglia. Our data suggest that microglia and astrocytes exhibit different sensitivities and responses to ACN, which are linked to the intracellular thiol status inherent to each of these cell types.

Abstract 1344: Glutathione S-transferase alpha 4 is a potential biomarker for Enterococcus faecalis-induced inflammation and colon cancer.

Abstract Enterococcus faecalis is a human colonic commensal that induces colon inflammation and cancer in several mouse models. We have shown that E. faecalis-infected macrophages produce 4-hydroxy-2-nonenal (4-HNE), a lipid peroxidation byproduct of ω-6 polyunsaturated fatty acids, and that this reactive aldehyde is genotoxic and mediates bystander effects (BSE). To further investigate mechanisms for 4-HNE-mediated BSE, we treated primary murine colonic epithelial cells (YAMC) with 4-HNE and studied Wnt/β-catenin signaling. Western blotting showed activation of β-catenin after 1 hr exposure of YAMC cells to 1 μM 4-HNE. Immunofluorescence staining confirmed nuclear translocation of activated β-catenin 5 hrs following treatment. These findings suggested that 4-HNE as an endogenous carcinogen that potentially contributes to colorectal carcinogenesis. Because glutathione S-transferase alpha 4 (Gsta4) is a detoxifying enzyme for this reactive aldehyde, we determined whether exposure of YAMC cells to 4-HNE increased the production of Gsta4. Indeed, Gsta4 was significantly increased at 24-72 hrs following 4-HNE treatment, suggesting upregulation of Gsta4 in response to 4-HNE-induced genotoxicity. In addition, we measured Gsta4 in 6 human colon cancer cell lines and compared these results to normal human colonic epithelial cells (FHC). Our findings showed that Gsta4 was strongly produced by all cancer cell lines compared to FHC. Finally, we colonized interleukin (IL)-10 knockout mice with E. faecalis for short- (2 weeks), intermediate- (3 months), and long-term (9 months) periods of time. Gsta4 levels in serum significantly increased for Il10−/− mice colonized with E. faecalis at 2 weeks compared to no change for colonized wildtype mice. Immunohistochemical staining for Gsta4 was apparent in tissue macrophages from colon biopsies for colonized mice, implying macrophage activation. Gsta4-positivity significantly increased in colon macrophages after 3 and 9 months of colonization in areas of increased inflammation. Of note, although Gsta4-positive staining was not seen in epithelial cells in areas of inflammation, intense staining was noted in neoplastic epithelial cells. These results suggest that activation of Gsta4 may be an early event in macrophage activation and associated with neoplasia. In summary, in the IL-10 knockout model, E. faecalis-infected macrophages produce 4-HNE and this lipid peroxidation breakdown product induces Wnt/β-catenin signaling and Gsta4 production. These findings implicate Gsta4 as a potential surrogate biomarker for colon cancer and should permit the development of new chemopreventive strategies. Citation Format: Xingmin Wang, Yonghong Yang, Mark Huycke, Department of Veterans Affairs Medical Center. Glutathione S-transferase alpha 4 is a potential biomarker for Enterococcus faecalis-induced inflammation and colon cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1344. doi:10.1158/1538-7445.AM2013-1344

Modulation of antioxidant and detoxifying capacity in fish Cyprinus carpio (Cyprinidae) after treatment with nanocapsules containing lipoic acid

Lipoic acid (LA) is a water- and lipid-soluble molecule with capacity to pass through cell membranes and with several antioxidant properties. Previous studies have shown that polymeric nanocapsules with LA favor the protection of this antioxidant, increasing their physical and chemical stability compared to formulations containing free LA. The aim of this study was to evaluate and compare the effect of free LA and LA-nanocapsules on antioxidant enzymes, the concentration of reduced glutathione (GSH) and a by-product of lipid peroxidation (malondialdehyde), as well as the expression of gene coding for different forms of glutathione-S-transferase (GST) in model fish. For this, carp Cyprinus carpio (Cyprinidae) were exposed (i.p.) to different forms of LA (free and in nanocapsules) for different times (48h, 96h and 1week) and the brain, liver and muscle were analyzed. Results indicated that the organs respond differently depending on the time and form in which LA was delivered. After 96h and 1week, a better antioxidant response was found generally in the formulation with nanocapsules. The nanocapsule composition showed to be a factor to be considered in future studies, because in some organs and exposure times empty nanocapsules promoted an antioxidant effect and in others a pro-oxidant effect.

Study on Mechanism of Soy Protein Oxidation Induced by Lipid Peroxidation Products

Oxidative modification of soy protein by lipid peroxidation products, which was potentially present in a lipoxygenase-catalyzed polyunsaturated fatty acid peroxidation system, was investigated in this study. 13S-Hydroperoxy-9Z, 11E-Octadecadienoic acid (HPODE), malondialdehyde and acrolein were selected as representative primary product and secondary byproducts of lipid peroxidation and 2, 2’-azobis-(2-amidinopropane) dihydrochloride (AAPH) -derived peroxyl radical peroxyl radicals were chosen to simulate lipid peroxidation- derived free radical. Incubation of soy protein with increasing concentration of AAPH, HPODE, malondialdehyde and acrolein resulted in gradual generation of protein carbonyl derivatives, loss of free sulphydryl groups, total sulphydryl groups, free amine, available lysine, surface hydrophobicity and formation of oxidation aggregates. The average distribution model of protein accessible groups could explain majority mechanism of lipid peroxidation products-mediated soy protein oxidation. Primary oxidation aggregates further developed into insoluble aggregates by covalent cross-linking also may provide a partial mechanism of lipid peroxidation products-mediated soy protein oxidation.

Effect of Cd(ii) and Se(iv) exposure on cellular distribution of both elements and concentration levels of glyoxal and methylglyoxal in Lepidium sativum

In this work, the effect of cadmium (0-5.0 mg L(-1) as cadmium chloride, Cd(II)) and selenium (0-2.0 mg L(-1) as sodium selenite, Se(IV)) was studied in Lepidium sativum with specific focus on glyoxal (GO) and methylglyoxal (MGO) and on the cellular distribution of both elements under different exposure conditions. The concentrations of two reactive α-ketoaldehydes present as natural metabolites and as by-products of lipid peroxidation, were increased in plants treated with Cd(II), providng complementary experimental evidence on element phytotoxicity in garden cress, in terms of oxidative damage. Even though for higher than 1.0 mg L(-1) Se in medium similar adverse effect was found, under simultaneous exposure to both elements the changes in GO and MGO concentrations were clearly attenuated as compared to a single stressor treatment. This effect was accompanied by lower uptake of the two elements, significant decrease of their relative distribution in the fraction containing polar compounds and their increase in fraction corresponding to insoluble cell fragments/components, suggesting that the direct in vivo interaction between two element forms might be involved in the favorable effects of simultaneous treatment with Cd(II) + Se(IV). The fluorescence spectra obtained for biomass extracts corresponding to different exposure conditions suggested possible in vivo formation of CdSe quantum dots; however further studies are needed for ultimate identification and characterization of such nanoparticulate species.

Oxidative stress and lipid peroxidation by-products at the crossroad between adipose organ dysregulation and obesity-linked insulin resistance

Obesity has been proposed as an energy balance disorder in which the expansion of adipose tissue (AT) leads to unfavorable health outcomes. Even though adiposity represents the most powerful driving force for the development of insulin resistance (IR) and type 2 diabetes, mounting evidence points to "adipose dysregulation", rather than fat mass accrual per se, as a key pathophysiological trigger of the obesity-linked metabolic complications. The dysfunctional fat, besides hypertrophic adipose cells and inflammatory cues, displays a reduced ability to form new adipocytes from the undifferentiated precursor cells (ie, the preadipocytes). The failure of adipogenesis poses a "diabetogenic" milieu either by promoting the ectopic overflow/deposition of lipids in non-adipose targets (lipotoxicity) or by inducing a dysregulated secretion of different adipose-derived hormones (ie, adipokines and lipokines). This novel and provocative paradigm ("expandability hypothesis") further extends current "adipocentric view" implicating a reduced adipogenic capacity as a missing link between "unhealthy" fat expansion and impairment of metabolic homeostasis. Hitherto, reactive oxygen species have been implicated in multiple forms of IR. However, the effects of stress on adipogenesis remain controversial. Compelling circumstantial data indicate that lipid peroxidation by-products (ie, oxysterols and 4-hydrononenal) may detrimentally affect adipose homeostasis partly by impairing (pre)adipocyte differentiation. In this scenario, it is tempting to speculate that a fine tuning of the adipose redox status may provide new mechanistic insights at the interface between fat dysregulation and development of metabolic dysfunctions. Yet, in humans, the molecular "signatures" of oxidative stress in the dysregulated fat as well as the pathophysiological effects of adipose (per)oxidation on glucose homeostasis remain poorly investigated. In this review we will summarize the potential mechanisms by which increased oxidative stress in fat may impair (pre)adipocyte differentiation and promote the adipose dysfunction. We will also attempt to highlight the conundrum with the adipose redox changes and the regulation of glucose homeostasis. Finally, we will briefly discuss the scientific rationale for proposing the adipose redox state as a potential target for novel therapeutic strategies to curb/prevent adiposity-linked insulin resistance.

Fibroblast protective effect of Royal Jelly against deleterious lipid peroxidation by-products

Fibroblast protective effect of Royal Jelly against deleterious lipid peroxidation by-products

Temperature-induced changes of malondialdehyde, heat-shock proteins in relation to chlorophyll fluorescence and photosynthesis in Conocarpus lancifolius (Engl.)

The effect of variable temperatures (10–50 °C) on photosynthesis and chlorophyll fluorescence in Conocarpus lancifolius was evaluated. Additionally, the ability of the species to synthesize heat-shock proteins (HSPs) to protect against high temperatures, and malondialdehyde (MDA) as a by-product of lipid peroxidation was investigated. Plants at 10 °C showed virtually no measurable growth, leaf discoloration and a few brown lesions, while high temperatures (40 and 50 °C) promoted growth and lateral branch development. Chlorophyll content index, photochemical efficiency (F v/F m) of PS II, electron transport rate and photosynthetic rate declined with decreasing temperature but increased significantly at higher temperatures. Heat-shock protein (HSP 70 kDa) was produced at temperatures 30–50 °C and an additional 90 kDa protein was also produced at 50 °C. Increase in the efficiency of excitation energy captured by the open PS II reaction centers (F v/F m) increased linearly (P ≤ 0.05) with the accumulation of HSP 70 at higher temperatures. However, at low temperatures the concentration of MDA increased significantly, indicating lipid peroxidation due to oxidative stress. The production and accumulation of HSP 70 and 90 kDa coupled with increased electron transport rate and photochemical efficiency can be used to assess survival, growth capacity and to some extent the tolerance of C. lancifolius to elevated temperatures.

Protective Effects of d‐Limonene on Lipid Peroxidation and Antioxidant Enzymes in Streptozotocin‐Induced Diabetic Rats

The aim of this study was to evaluate the protective effects of D-limonene on the levels of lipid peroxidation by-products and antioxidant defence systems in the plasma and tissues of normal and streptozotocin (STZ)-induced diabetes rats. The experimental diabetes was induced in rats by a single dose of STZ (40 mg/kg i.p.) injection, and treatment with D-limonene was continued for 45 days. After the treatment period, oxidative stress parameters such as lipid peroxidation by-products; enzymatic antioxidants such as superoxide dismutase, catalase, glutathione peroxidase and glutathione-S-transferase; non-enzymic antioxidants including reduced glutathione, Vitamins C and E were measured in the plasma and tissues of experimental rats. An increase in the levels of lipid peroxidation by-products and significant decrease in antioxidant enzymes were observed in untreated diabetic rats. Administration of D-limonene to diabetic rats for 45 days caused a significant reduction in the levels of lipid peroxidation by-products and an increase in the activities of antioxidant enzymes, when compared with the untreated diabetic group. There was no significant difference in normal treated groups, when compared with normal rats. Biochemical observations were substantiated with the help of histopathological examinations through its antioxidant properties and thereby conferred protection against STZ-induced diabetic rats. The result of this study indicates that D-limonene has antioxidant potential in addition to its antidiabetic effect in experimental diabetes.

Anticlastogenic effect of diosgenin on 7,12-dimethylbenz(a)anthracene treated experimental animals

The present investigation explores the anticlastogenic effect of diosgenin on 7,12-dimethylbenz(a)anthracene (DMBA) treated clastogenesis. The frequency of bone marrow micronucleated polychromatic erythrocytes (MnPCEs), chromosomal aberrations (CA), deoxyribonucleic acid (DNA) damage as cytogenetic markers and the levels of lipid peroxidation by-products, activities of enzymatic antioxidant and the status of detoxification agents were performed to assess the anticlastogenic effects of diosgenin on DMBA treated hamsters. Intraperitoneal injection of DMBA (30 mg/kg bw) leads to clastogenesis in hamster. Elevated MnPCEs frequencies, CA, DNA damage, enhanced lipid peroxidation by products, declined antioxidant activities and detoxification cascade were observed in DMBA treated hamsters. Oral pretreatment with diosgenin (80 mg/kg bw) daily for a period of five days significantly reduced the frequency of MnPCEs, CA, DNA damage and normalized the levels of lipid peroxidation by products with increased activities of antioxidants and detoxification agents in DMBA alone treated hamsters. Outcome of the present study revealed that diosgenin has potent anticlastogenic effects on DMBA treated hamsters.

The Peroxisome Proliferator-activated Receptor γ (PPARγ) Controls Natural Protective Mechanisms against Lipid Peroxidation in Amyotrophic Lateral Sclerosis

Recent evidence highlights the peroxisome proliferator-activated receptors (PPARs) as critical neuroprotective factors in several neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS). To gain new mechanistic insights into the role of these receptors in the context of ALS, here we investigated how PPAR transcriptional activity varies in hSOD1(G93A) ALS transgenic mice. We demonstrate that PPARγ-driven transcription selectively increases in the spinal cord of symptomatic hSOD1(G93A) mice. This phenomenon correlates with the up-regulation of target genes, such as lipoprotein lipase and glutathione S-transferase α-2, which are implicated in scavenging lipid peroxidation by-products. Such events are associated with enhanced PPARγ immunoreactivity within motor neuronal nuclei. This observation, and the fact that PPARγ displays increased responsiveness in cultured hSOD1(G93A) motor neurons, points to a role for this receptor in neutralizing deleterious lipoperoxidation derivatives within the motor cells. Consistently, in both motor neuron-like cultures and animal models, we report that PPARγ is activated by lipid peroxidation end products, such as 4-hydroxynonenal, whose levels are elevated in the cerebrospinal fluid and spinal cord from ALS patients. We propose that the accumulation of critical concentrations of lipid peroxidation adducts during ALS progression leads to the activation of PPARγ in motor neurons. This in turn triggers self-protective mechanisms that involve the up-regulation of lipid detoxification enzymes, such as lipoprotein lipase and glutathione S-transferase α-2. Our findings indicate that anticipating natural protective reactions by pharmacologically modulating PPARγ transcriptional activity may attenuate neurodegeneration by limiting the damage induced by lipid peroxidation derivatives.

Lipid peroxidation product 4-hydroxy-2-nonenal promotes seeding-capable oligomer formation and cell-to-cell transfer of α-synuclein.

Abnormal accumulation of α-synuclein aggregates is one of the key pathological features of many neurodegenerative movement disorders and dementias. These pathological aggregates propagate into larger brain regions as the disease progresses, with the associated clinical symptoms becoming increasingly severe and complex. However, the factors that induce α-synuclein aggregation and spreading of the aggregates remain elusive. Herein, we have evaluated the effects of the major lipid peroxidation byproduct 4-hydroxy-2-nonenal (HNE) on α-synuclein oligomerization and cell-to-cell transmission of this protein. Incubation with HNE promoted the oligomerization of recombinant human α-synuclein via adduct formation at the lysine and histidine residues. HNE-induced α-synuclein oligomers evidence a little β-sheet structure and are distinct from amyloid fibrils at both conformation and ultrastructure levels. Nevertheless, the HNE-induced oligomers are capable of seeding the amyloidogenesis of monomeric α-synuclein under in vitro conditions. When neuronal cells were treated with HNE, both the translocation of α-synuclein into vesicles and the release of this protein from cells were increased. Neuronal cells can internalize HNE-modified α-synuclein oligomers, and HNE treatment increased the cell-to-cell transfer of α-synuclein proteins. These results indicate that HNE induces the oligomerization of α-synuclein through covalent modification and promotes the cell-to-cell transfer of seeding-capable oligomers, thereby contributing to both the initiation and spread of α-synuclein aggregates.

4-Hydroxyhexenal (HHE) Impairs Glutamate Transport in Astrocyte Cultures

Multiple studies show elevations of α,β-unsaturated aldehydic by-products of lipid peroxidation including 4-hydroxynonenal and acrolein in vulnerable brain regions of subjects throughout the progression of Alzheimer's disease (AD). More recently 4-hydroxyhexenal (HHE), a diffusible α,β-unsaturated aldehyde resulting from peroxidation of ω-3 polyunsaturated fatty acids, was shown to be elevated in the hippocampus/parahippocampal gyrus (HPG) of subjects with preclinical AD (PCAD) and in late stage AD (LAD). HHE treatment of primary rat cortical neuron cultures led to a time- and concentration-dependent decrease in survival and glucose uptake. To determine if HHE also impairs glutamate uptake, primary rat astrocyte cultures were exposed to HHE for 4 hours and glutamate transport measured. Results show subtoxic (2.5 μM) HHE concentrations significantly (p < 0.05) impair glutamate uptake in primary astrocytes. Immunoprecipitation of excitatory amino acid transporter-2 (EAAT-2), the primary glutamate transporter in brain, from normal control, mild cognitive impairment (MCI), PCAD, and LAD HPG followed by quantification of HHE immunolabeling showed a significant increase in HHE positive EAAT-2 in MCI and LAD HPG. Together these data suggest HHE can significantly impair glutamate uptake and may play a role in the pathogenesis of AD.

Naturally Occurring Variation in the Glutathione-S-Transferase 4 Gene Determines Neurodegeneration After Traumatic Brain Injury

Genetic factors are important for outcome after traumatic brain injury (TBI), although exact knowledge of relevant genes/pathways is still lacking. We here used an unbiased approach to define differentially activated pathways between the inbred DA and PVG rat strains. The results prompted us to study further if a naturally occurring genetic variation in glutathione-S-transferase alpha 4 (Gsta4) affects the outcome after TBI. Survival of neurons after experimental TBI is increased in PVG compared to the DA strain. Global expression profiling analysis shows the glutathione metabolism pathway to be the most regulated between the strains, with increased Gsta4 in PVG among top regulated transcripts. A congenic strain (R5) with a PVG genomic insert containing the Gsta4 gene on DA background displays a reversal of the strain pattern for Gsta4 expression and increased survival of neurons compared to DA. Gsta4 is known to effectively reduce 4-hydroxynonenal (4-HNE), a noxious by-product of lipid peroxidation. Immunostaining of 4-HNE was evident in both rat and human TBI. Intracerebral injection of 4-HNE resulted in neurodegeneration with increased levels of a marker for nerve injury in cerebrospinal fluid of DA compared to R5. These findings provide strong support for the notion that the inherent capability of coping with increased 4-HNE after TBI affects outcome in terms of nerve cell loss. A naturally occurring variation in Gsta4 expression in rats affects neurodegeneration after TBI. Further studies are needed to explore if genetic variability in Gsta4 can be associated to outcome also in human TBI.

Total thiol redox status as a potent biomarker of PAH-mediated effects on mussels

This laboratory study describes phenanthrene (Ph) and/or anthracene (An) ability to alter the total thiol redox status (TRS), via depletion of protein free thiols (PSH) and glutathione (GSH) levels, in gills of mussel Mytilus galloprovincialis, after a short-term (7 days) exposure period to each contaminant (at a final concentration of 0.1 mg L−1) or in a mixture (ration 1:1, at a final concentration of 0.2 mg L−1). A number of observable changes, like lysosomal membrane impairment (as detected via the neutral red retention time assay, primarily performed in haemocytes), enhancement of lipid peroxidation byproducts, increased nuclear abnormalities, inhibition of AChE and ALP activity, as well as a significant depletion of PSH and GSH were detected in gills of exposed mussels, in any case. Significant relationships occurred among TRS parameters with each change/stress indices measured in tissues of mussels, could reinforce the use of PSH as a potent biomarker.

English

The implications of diet on health sustainability have assumed a major importance. Microcystis are able to enhance the nutritional content of conventional food and feed preparation and hence to positively affect humans and animal health due to their original chemical compositions, protein contents, antioxidant properties, vitamins and other biologically active compounds. Butylated hydroxytoluene ‘BHT’ is one of the synthetic antioxidant agents commonly used for food additives. Cyanobactria like Oscillatoria sp. and Microcystis aerungionosa, those are commonly available in the coastal zone of Puri District of Odisha State were capable of producing this compound. Extracts from these two species exhibited various degrees of antioxidant properties when they were tested with free radical scavenging assay. The highest antioxidant activity was observed in the extracts of Microcystic aerungionosa, which displayed a similar activity to synthetic BHT. Gas chromatography and mass spectroscopy analysis concluded that the compounds are very similar to the synthetic BHT. This synthetic antioxidant was produced in the cells irradiated with higher light intensity. More BHT was produced in the cells irradiated with a higher light intensity and its production was irradiance dependent. The quantity of cellular BHT displayed a positive correlation with antioxidant activity of the tested species. The present study confirms the production of natural antioxidant like BHT from these two species of Puri District of Odisha State which constitute a potential source for producing natural antioxidant. KeywordsButylated hydroxytoluene, cyanobacteria, green alga, irradiance, natural antioxidant. International Journal of Microbiology Research ISSN: 0975-5276 & E-ISSN:0975-9174, Volume 4, Issue 6, 2012 Introduction Lipid peroxidation is mostly an undesirable deteriorative reaction in food materials, which can produce rancid odors and flavors during storage and processing. Moreover the nutritional quality and safety of foods also can easily change due to their toxic compound formation [1,2].These lipid peroxidation by-products, called free radicals, give damage to healthy cells and thereby create harmful molecules. Free radicals and other reactive oxygen species (ROS) are generated continuously not only via normal physiological processes but also by external stimulations. Normal physiological processes need oxygen in order to carry out their operations as a resultant by-product like ROS are produced within the human body. If these harmful factors accumulate in cell, tissue and other vital organs of the body, then our body exposed to dangerous circumstances of the external stimulation, ROS can be induced by tobacco smoke, ionizing radiation, certain pollutants, organic solvents and pesticides [3,4]. ROS including superoxide (O2 hydroxyl radical (HO·) and hydrogen peroxide (H2O2), have the ability to react with a large variety of easily oxidizable cellular components, such as proteins, lipids, nucleic acids and carbohydrates. Their oxidative damages cause aging and many other diseases, including arthritis, strokes, heart diseases, atherosclerosis, diabetes, cancers and neurodegenerative disorders [5,6]. Reactive oxygen species (ROS), such as the superoxide anion, Citation: Pradyuti Dash and Padhi S.B. (2012) Natural Antioxidant Production by Oscillatoria Sp. and Microcystis Sp. From Ponds of Puri District, Odisha. International Journal of Microbiology Research, ISSN: 0975-5276 & E-ISSN:0975-9174, Volume 4, Issue 6, pp.-249-252. Copyright: Copyright©2012 Pradyuti Dash and Padhi S.B. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution and reproduction in any medium, provided the original author and source are credited.

Protective effects of α-tocopherol against oxidative stress related to nephrotoxicity by monosodium glutamate in rats

Context: Chronic oral intake of high doses of monosodium glutamate (MSG) could be harmful to tissues and organs. Oxidative stress enhances membrane damage by lipid peroxidation and alterations of antioxidant enzymes, which affects the functional activity of organs. Antioxidant vitamins have the capacity to regulate the oxidative stress related functional and pathological processes.Objective: In this study, the protective role of α-tocopherol against MSG-induced nephrotoxicity was analyzed. Materials and methods: MSG (4 g/kg) was given orally to female wistar rats for a period of 180 days. Renal function parameters (urea, uric acid, and creatinine), lipid peroxidation markers (malondialdehyde and conjugated dienes), antioxidant system (superoxide dismutase, catalase, glutathione peroxidase, glutathione transferase, and reduced glutathione), and histopathology were investigated. All tests were done in rats treated with MSG and at two different doses of α-tocopherol (100 and 200 mg/kg).Results: Oral exposure of MSG significantly increased renal function markers, lipid peroxidation byproducts, and altered antioxidant system. Moreover, the kidney showed congested glomeruli, tubular swelling, capillary congestion and microhemorrhages in stromal areas of the tubules. Co-administration of MSG and α-tocopherol (200 mg/kg) significantly reduced the oxidative damage compared with MSG-treated group and also restored the normal renal function.Discussion: The results indicated that oxidative stress was involved in MSG-induced functional and pathological changes in the kidney. α-tocopherol modulates the functional disorder and maintains the normal architecture of renal tissue by reducing oxidative stress.Conclusion: The α-tocopherol may be a potent protective agent in combating MSG-induced renal toxicity.

Abstracts from the 2012 Annual Meeting of the International Society for Heart Research North American Section

Cardiovascular stress, such as that due to the synthetic catecholamine, isoprenaline (iso), can induce myocardial infarction (MI). Ethanolamine (etn) is a biogenic amine, found in certain food types, that protects the isolated rat heart against ischemiareperfusion injury. The aim of this study was to investigate the cardioprotective effects of acute etn on iso-induced MI. Male Wistar rats (250-350 g) were divided into four groups: Control (saline injections only), iso + etn (iso 67 mg/kg, s.c. and etn 10 mg/ kg i.p.), iso (67 mg/kg, s.c. and a saline injection), and etn (saline injection and 10 mg/kg i.p.). Rats were anaesthetised with sodium pentobarbitone (60 mg/kg, i.p.) and mechanically ventilated with room air. Arterial blood pressure wasmeasured from the right carotid artery and electrocardiogram (ECG) was recorded from surface leads. Infarct size was measured using triphenyltetrazolium chloride (TTC) staining and the by-products of lipid peroxidation were quantified. Iso administration significantly increased the infarct size (62.0±3.9%, Pb0.001) (mean±SEM) compared to control rats (23.7±2.7%). The heart weight/body weight (HW/BW) ratio was also significantly raised in iso rats (4.6±0.1, Pb0.001) compared to control rats (3.4±0.02). Iso + etn (5.0±0.2 Pb0.05) treated rats displayed significantly greater HW/BW ratio compared to iso treated rats. However, there was no significant difference in infarct size between iso and iso + etn. Iso + etn treated rats had a lower death rate (1.9%) compared to iso rats (11.3%). There was a significant increase in the amount of conjugated dienes (CD) in iso rats (59.56±2.6 μmol/L) compared to control rats (39.9±4.0 μmol/L, Pb0.05). There was no significant difference in the generation of CDs between control and iso + etn rats. In summary, etn seems to protect the rat from iso-induced MI; however the possibility of increased cardiac hypertrophy needs further investigation.

Preeclampsia, Placenta, Oxidative Stress, and PMCA

Objective: The aim of this study is to summarize the reported evidence on the possible relationship between preeclampsia, placenta, oxidative stress and plasma membrane Ca-ATPase (PMCA) activity, responsible for fine control of intracellular calcium concentration. Methods: Literature search was conducted in MEDLINE/PubMed and several unpublished results from our laboratory were included. Results: Lipid peroxidation in placental and red blood cell plasma membranes during preeclampsia and a concomitant diminution of their PMCA activity are described. Conclusions: Uteroplacental hypoperfusion raises lipid peroxidation by-products in the blood plasma that could alter structure and functionality of the cell membranes of the endothelium and several tissues.

An Unconventional Hexacoordinated Flavohemoglobin from Mycobacterium tuberculosis

Being an obligate aerobe, Mycobacterium tuberculosis faces a number of energetic challenges when it encounters hypoxia and environmental stress during intracellular infection. Consequently, it has evolved innovative strategies to cope with these unfavorable conditions. Here, we report a novel flavohemoglobin (MtbFHb) from M. tuberculosis that exhibits unique features within its heme and reductase domains distinct from conventional FHbs, including the absence of the characteristic hydrogen bonding interactions within the proximal heme pocket and mutations in the FAD and NADH binding regions of the reductase domain. In contrast to conventional FHbs, it has a hexacoordinate low-spin heme with a proximal histidine ligand lacking imidazolate character and a distal heme pocket with a relatively low electrostatic potential. Additionally, MtbFHb carries a new FAD binding site in its reductase domain similar to that of D-lactate dehydrogenase (D-LDH). When overexpressed in Escherichia coli or Mycobacterium smegmatis, MtbFHb remained associated with the cell membrane and exhibited D-lactate:phenazine methosulfate reductase activity and oxidized D-lactate into pyruvate by converting the heme iron from Fe(3+) to Fe(2+) in a FAD-dependent manner, indicating electron transfer from D-lactate to the heme via FAD cofactor. Under oxidative stress, MtbFHb-expressing cells exhibited growth advantage with reduced levels of lipid peroxidation. Given the fact that D-lactate is a byproduct of lipid peroxidation and that M. tuberculosis lacks the gene encoding D-LDH, we propose that the novel D-lactate metabolizing activity of MtbFHb uniquely equips M. tuberculosis to balance the stress level by protecting the cell membrane from oxidative damage via cycling between the Fe(3+)/Fe(2+) redox states.