To Tert-butyl Hydroperoxide Research Articles

Anti-Apoptotic and Anti-Inflammatory Properties of Grapefruit IntegroPectin on Human Microglial HMC3 Cell Line.

In this study, we investigated the beneficial effects of grapefruit IntegroPectin, derived from industrial waste grapefruit peels via hydrodynamic cavitation, on microglia cells exposed to oxidative stress conditions. Grapefruit IntegroPectin fully counteracted cell death and the apoptotic process induced by cell exposure to tert-butyl hydroperoxide (TBH), a powerful hydroperoxide. The protective effects of the grapefruit IntegroPectin were accompanied with a decrease in the amount of ROS, and were strictly dependent on the activation of the phosphoinositide 3-kinase (PI3K)/Akt cascade. Finally, IntegroPectin treatment inhibited the neuroinflammatory response and the basal microglia activation by down-regulating the PI3K- nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kB)- inducible nitric oxide synthase (iNOS) cascade. These data strongly support further investigations aimed at exploring IntegroPectin's therapeutic role in in vivo models of neurodegenerative disorders, characterized by a combination of chronic neurodegeneration, oxidative stress and neuroinflammation.

Tert‐butanol and hydrogen peroxide react over Amberlyst‐15 to form tert‐butyl hydroperoxide

AbstractOrganic peroxides are explosive compounds that are applied as disinfectants, bleaching agents, and as initiators for polymer synthesis because of their high reactivity. Traditional homogeneous processes with H2SO4 catalyst produce salts, either in the neturalization step after reaction or due to the foramtion of tert‐butyl hydrogen sulphate, that must be disposed of, which introduces cost and represents an environmental burden. Here, we devised a flow chemistry approach to oxidize tert‐butyl alcohol (TBA) to tert‐butyl hydroperoxide (TBHP) over various heterogeneous catalysts. Under acidic conditions, TBHP is the main product and di‐tert‐butyl peroxide (DTBP) and peroxy‐ketal are by‐products. The most active catalyst was Amberlyst‐15, while yield of Nafion, activated carbon, and heteropoly acids (HPA) on carbon and silica matrices was less than 1% at 70°C. In in the range of 30 to 50°C, a first order kinetic expression characterizes the tert‐butyl alcohol conversion well (). The reaction rate is slow and the rate constant, , was 0.003 min−1. Above 50°C, by‐products reacted further to acetone, methane, ethane, and other compounds.

Transition metal Schiff base complexes supported on layered double hydroxide: synthesis, characterization and catalytic activity for the oxidation of toluene

The catalytic oxidation of toluene was studied over Mn(III) and Fe(III) Schiff base complexes supported layered double hydroxide catalysts. The supported catalysts were synthesized by intercalation method and abbreviated as LDH-[NAPABA-M], {where M = Mn(III) and Fe(III)}. The obtained material was characterized by various physical techniques such as ICP-AES, EDX, XRD, FTIR, SEM, TEM, BET surface area, EPR, and TGA. The liquid-phase catalytic oxidation of toluene was studied using LDH-[NAPABA-M]/TBHP system. A maximum conversion of toluene (55.3%) and selectivity of benzaldehyde (86.1%) was observed with LDH-[NAPABA-Mn(Cl)]/TBHP system, when the reaction is carried out at toluene to tert-butylhydroperoxide (TBHP) molar ratio 1:3, temperature 373 K, and catalyst amount, 100 mg. The catalyst, LDH-[NAPABA-Mn(Cl)] gave excellent; conversion of toluene and selectivity of benzaldehyde in comparison to LDH-[NAPABA-Fe(Cl)] catalyst. The catalyst, LDH-[NAPABA-Mn(Cl)] showed good stability and reusability up to five cycles without significant loss of catalytic activity.

PGC-1α acts as an mediator of Sirtuin2 to protect annulus fibrosus from apoptosis induced by oxidative stress through restraining mitophagy

Apoptosis of annulus fibrosus (AF) is observed widely in intervertebral disc degeneration (IVDD) which causes weaken of tension in the annulus of intervertebral disc. Previous studies reported that apoptosis of AF is induced mainly by oxidative stress. SIRT2 is a major regulator of mitochondria to mediate ROS production. However, the mechanism of SIRT2 in IVDD remains unclear. Here, the expression of SIRT2 was detected in AF cells exposed to tert-Butyl hydroperoxide (TBHP) by western blotting. Autophagic flux and apoptosis were assessed by western blotting, flow cytometry and immunofluorescence respectively. Safranin O staining, HE, and immunohistochemical were used to assess the IVDD after 3, 6 and 9 months of surgical procedure in vivo. The expression of SIRT2 was decreased in AF cells treated with TBHP. Repression of mitophagy alleviated the apoptosis of AF cells caused by TBHP. Overexpression of PGC-1α prevented AF cells from apoptosis and mitophagy after applying Lenti-PGC-1α to transfect AF cells. These protections of PGC-1α were reduced by FCCP. Furthermore, the expression of PGC-1α was reduced and the level of mitophagy was increased in IVDD models. In conclusion, this study indicates that the regulation of PGC-1α expression provide a new theoretical basis for the mechanism of IVDD.

Ag nanoparticles supported on UiO-66 for selective oxidation of styrene

By immobilizing Ag nanoparticles to UiO-66, a series of nanocatalysts (Ag/UiO-66) were synthesized and used as catalysts for oxidation of styrene. The catalytic efficiency could be optimized by altering Ag loadings of Ag/UiO-66, solvents, the molar ratios of styrene to tert-butyl hydroperoxide (TBHP) and reaction temperatures. Interestingly, the Ag loadings 1.86wt% of Ag/UiO-66 exhibited high conversion, selectivity and recyclability in the selective oxidation of styrene.

Blvrb Mutation Induces Thrombocytosis Via Redox Dysregulation in the Heme Degradation Pathway

Known genetic loci influencing blood cell production account for <10% of platelet and red blood cell variability, and thrombopoietin (Tpo)/c-MPL liganding is dispensable for definitive thrombopoiesis establishing that fundamentally important modifier loci remain unelucidated. We completed RNASeq of highly-purified platelets from 7 essential thrombocythemia (ET) subjects [4 harbored the JAK2V617F mutation and 3 were genotypically normal] and 5 healthy controls, and developed an iterative algorithm to identify 33 non-synonymous SNVs that are putatively linked to the ET phenotype. Transcripts possessing these candidate SNVs were enriched on average in early-stage megakaryocyte/erythroid progenitors (MEPs), and became more restricted in terminally-differentiating megakaryocytes and erythroblasts. Genotypic studies using an expanded ET cohort (N = 36), followed by statistical association analyses using controls from the 1000 Human Genomes Project and an independently-genotyped cohort of healthy controls (N = 208), established that 5 SNVs (excluding JAK2V617F) were associated with ET. A single mutation (BLVRBS111L; p = 0.0006) retained its significance as a thrombocytosis risk allele using genotypic data from a secondary cohort with reactive (non-clonal) thrombocytosis (RT, N = 53), suggesting a function as an independent driver mutation of enhanced thrombopoiesis. TheBLVRB (biliverdin IXβ reductase) gene functions downstream of heme oxygenase(s)-1 (inducible HMOX1) and -2 (constitutive HMOX2) within the heme degradation pathway to catalyze reduction of biliverdin (BV) tetrapyrrole(s) as an intermediary redox substrate in Bilirubin (BR) generation. Bacterially-expressed and purified recombinant BLVRBS111L showed defective enzymatic activity [compared to BLVRBWT (wild-type)] using flavin mononucleotide [flavin reductase (FR) activity; p <0.0001] and BV IXβ dimethyl esters (biliverdin reductase (BVR) activity; p <0.0001), the latter specifically generated by coupled heme oxidation as verdin-restricted BLVRB activity probes. The loss-of-mutation BLVRBS111L NAD(P)H-dependent redox coupling caused higher baseline ROS (reactive oxygen species) accumulation in lentivirus-transduced CD34+-derived induced pluripotent stem cells (iPSC/BLVRBS111L), results sharply contrasting with ROS neutralization in iPSC/BLVRBWT exposed to tert-butyl hydroperoxide (TBHP) as the oxidant stress source (p < 0.00001). Disparate redox coupling/ROS handling in genetically-modified primary CD34+ multipotential progenitor cultures established disproportionate expansion of primitive CFU-GEMMs in CD34+/BLVRBS111L (p = 0.001), and an absolute increase of BFU-E in CD34+/BLVRBWT (p = 0.001). Collagen-based progenitor cultures demonstrated a statistically-significant increase of CD41+ CFU-MKs in CD34+/BLVRBS111L cells (p <0.01) with no increased CFU-MKs in CD34+/BLVRBWT cells. Cumulative distribution plots of parallel Tpo-suspension cultures confirmed divergent ROS accumulation between MK/BLVRBWT and MK/BLVRBS111L, differences that were identifiable pre-terminal differentiation (Day 0, p = 0.0007), most pronounced at Day 5 corresponding to peak MK BLVRB expression across genotypes (p = 8 x 10-7), and persistent at terminal differentiation (Day 10; p = 0.05). Maximally disparate ROS accumulation (Day 5) corresponded to greatest size disparity and temporally-earlier (and sustained at Day 10) CD41 expression in MK/BLVRBS111L (p = 0.03). A bilineage (Tpo/Epo) differentiation model, designed to characterize erythroid/megakaryocyte (E/Meg) progenitor balance arising from common MEPs demonstrated no evidence for differential Mk (CD41+/Glycophorin A-) lineage balance, suggesting that BLVRBS111L ROS-promoting effects accelerate post-commitment expansion downstream of MEP lineage fate decisions. These data provide the first evidence linking redox coupling to MK lineage fate and expansion in humans, either via activity as a flavin reductase, in partnered electron exchange with an unidentified protein, or as a verdin-regulated redox coupler regulated by heme degradation and isomer-restricted BV IXβ (or IXδ, IXγ) generation; in principle, development of BLVRB-specific redox inhibitors represent innovative approaches to selectively alter a regulatory pathway controlling MK lineage expansion and human platelet counts. DisclosuresNo relevant conflicts of interest to declare.

LC-MS/MS Determination of Isoprostanes in Plasma Samples Collected from Mice Exposed to Doxorubicin or Tert-Butyl Hydroperoxide

Isoprostanes are stable products of arachidonic acid peroxidation and are regarded as the most reliable markers of oxidative stress in vivo. Here we describe the LC-MS/MS procedure enabling simultaneous determination of four regioisomers (8-iso prostaglandin F2α, 8-iso-15(R)-prostaglandin F2α, 11β-prostaglandin F2α, 15(R)-prostaglandin F2α) in plasma samples collected from mice. The four plasma isoprostanes are determined by LC–ESI-MS/MS with deuterated 8-iso-PGF2α-d4 as an internal standard (I.S.). For plasma samples spiked with the isoprostanes at a level of 200 pg/mL each, the method imprecision has been below 7.1% and mean inaccuracy equaled 8.7%. The applicability of the proposed approach has been verified by the assessment of changes in isoprostane levels in plasma samples derived from mice exposed to tert-butyl hydroperoxide (TBHP), a model inducer of oxidative stress, or to antitumor drug doxorubicin (DOX) known for potent stimulation of redox cycling. Compared to the control group of mice, both oxidative stress inducers tested increased the levels of three out of four isoprostanes in exposed animals; 11β-prostaglandin F2α being the exception. The greatest rise was observed in the case of 15(R)-prostaglandin F2α, by about 50% and 70% in plasma samples derived from mice exposed to DOX and TBHP, respectively.

The effect of oxidative stress upon the intestinal uptake of folic acid: in vitro studies with Caco-2 cells

Folic acid (FA) is a vitamin essential for normal cellular functions, growth, and development. Because humans cannot synthesize this micronutrient, it must be obtained from dietary sources through intestinal absorption. The intestinal tract is a major target for oxidative stress. Our aim was to investigate the effect of oxidative stress upon the uptake of FA by Caco-2 cells. Oxidative stress was induced by exposure of the cells to tert-butyl hydroperoxide (TBH) for 1h. TBH (3,000μM) induced an increase in biomarkers of oxidative stress, while maintaining cell viability and proliferation. In relation to the apical uptake of (3)H-FA, TBH (3,000μM) reduced the cellular accumulation of (3)H-FA (10nM), although the characteristics (kinetics, pH dependence, and inhibitory profile) of (3)H-FA uptake were not changed. This effect was associated with a decrease in the mRNA steady-state levels of proton-coupled folate transporter and folate receptor alpha and of the efflux transporter multidrug resistance protein 2. Moreover, TBH (3,000μM) did not affect the noncarrier-mediated apical uptake of (3)H-FA. Finally, the effect of TBH upon (3)H-FA apical uptake was not dependent on protein kinase A, protein kinase C, mitogen-activated protein kinases, phosphoinositide 3-kinase, nuclear factor kappa B, and protein tyrosine kinases, but was completely prevented by dietary polyphenols (resveratrol, quercetin, and EGCG). These results suggest that oxidative stress at the intestinal level may result in a reduction in the intestinal absorption of dietary FA and that polyphenolic dietary components may offer protection against oxidative stress-induced inhibition of intestinal FA absorption.

Testing Predictions of the Oxidative Stress Hypothesis of Aging Using a Novel Invertebrate Model of Longevity: The Giant Clam (Tridacna Derasa)

Bivalve species with exceptional longevity are newly introduced model systems in biogerontology to test evolutionarily conserved mechanisms of aging. Here, we tested predictions based on the oxidative stress hypothesis of aging using one of the tropical long-lived sessile giant clam species, the smooth giant clam (Tridacna derasa; predicted maximum life span: >100 years) and the short-lived Atlantic bay scallop (Argopecten irradians irradians; maximum life span: 2 years). The warm water-dwelling giant clams warrant attention because they challenge the commonly held view that the exceptional longevity of bivalves is a consequence of the cold water they reside in. No significant interspecific differences in production of H2O2 and O2- in the gills, heart, or adductor muscle were observed. Protein carbonyl content in gill and muscle tissues were similar in T derasa and A i irradians. In tissues of T derasa, neither basal antioxidant capacities nor superoxide dismutase and catalase activities were consistently greater than in A i irradians. We observed a positive association between longevity and resistance to mortality induced by exposure to tert-butyl hydroperoxide (TBHP). This finding is consistent with the prediction based on the oxidative stress hypothesis of aging. The findings that in tissues of T derasa, proteasome activities are significantly increased as compared with those in tissues of A i irradians warrant further studies to test the role of enhanced protein recycling activities in longevity of bivalves.

Preconditioning and Acute Effects of Flavonoids in Protecting Cardiomyocytes from Oxidative Cell Death

While flavonoids can reportedly protect against cardiac ischemia-reperfusion injury, the relative effectiveness of different flavonoids and the mechanisms involved are unclear. We compared protection by different flavonoids using rat embryonic ventricular H9c2 cells subjected to simulated ischemia-reperfusion (IR) and to tert-butyl hydroperoxide (t-buOOH). Characterization of the IR model showed the relative contributions of glucose, serum, and oxygen deprivation to cell death. With long-term (2-3 day) pretreatment before IR the best protection was given by catechin, epigallocatechin gallate, proanthocyanidins, and ascorbate, which protected at all doses. Quercetin protected (34%) at 5 μM but was cytotoxic at higher doses. Cyanidin protected mildly (10–15%) at 5 and 20 μM, while delphinidin had no effect at 5 μM and was cytotoxic at higher doses. Comparing long-term and acute protection by catechin, a higher concentration was needed for benefit with acute (1 hr) pretreatment. With a pure oxidative stress (t-buOOH) only quercetin significantly protected with 3-day pretreatment, while with short-term (1 h) pretreatments protection was best with quercetin and epigallocatechin gallate. The results suggest catechins to be especially useful as IR preconditioning agents, while quercetin and epigallocatechin gallate may be the most protective acutely in situations of oxidative stress.

CztR, a LysR-Type Transcriptional Regulator Involved in Zinc Homeostasis and Oxidative Stress Defense in Caulobacter crescentus

Caulobacter crescentus is a free-living alphaproteobacterium that has 11 predicted LysR-type transcriptional regulators (LTTRs). Previously, a C. crescentus mutant strain with a mini-Tn5lacZ transposon inserted into a gene encoding an LTTR was isolated; this mutant was sensitive to cadmium. In this work, a mutant strain with a deletion was obtained, and the role of this LTTR (called CztR here) was evaluated. The transcriptional start site of this gene was determined by primer extension analysis, and its promoter was cloned in front of a lacZ reporter gene. β-galactosidase activity assays, performed with the wild-type and mutant strains, indicated that this gene is 2-fold induced when cells enter stationary phase and that it is negatively autoregulated. Moreover, this regulator is essential for the expression of the divergent cztA gene at stationary phase, in minimal medium, and in response to zinc depletion. This gene encodes a hypothetical protein containing 10 predicted transmembrane segments, and its expression pattern suggests that it encodes a putative zinc transporter. The cztR strain was also shown to be sensitive to superoxide (generated by paraquat) and to hydrogen peroxide but not to tert-butyl hydroperoxide. The expression of katG and ahpC, but not that of the superoxide dismutase genes, was increased in the cztR mutant. A model is proposed to explain how CztR binding to the divergent regulatory regions could activate cztA expression and repress its own transcription.

A novel hemin-based organic phase artificial enzyme electrode and its application in different hydrophobicity organic solvents

Based on the newly discovered artificial enzyme formed by mixing hemin with supramolecular hydrogels via the self-assembly of amphiphilic oligopeptides, we prepared a novel organic phase artificial enzyme electrode by coating the artificial enzyme on an electrode which was then covered with sodium alginate for protection. Scanning electron micrograph showed that the supramolecular hydrogel kept its nanofibers structure on the electrode surface. Hemin dispersed in the supermolecular hydrogel as monomer greatly promotes its direct electrochemistry behavior in organic solvents. At the same time, this electrode exhibited higher electrocatalytic ability to tert-butyl hydroperoxide (TBHP) than free hemin modified electrode (free hemin mainly present as dimer). As low as 27μM TBHP could be detected with a linear range from 6.6×10−5 to 1.27×10−2M via amperometric method. The biosensor can reach 95% of the steady-state current in about 10±2s. More importantly, it can be applied in both hydrophilic and hydrophobic solvents without adding extra buffer or mediators to them that cannot be received by most traditional organic phase enzyme electrodes. This unique property greatly promotes the development of the organic phase enzyme electrodes by facilitating the detection of different kinds of substrates of the hemin-based artificial enzyme soluble in hydrophilic and hydrophobic solvents. The artificial enzyme electrode was successfully used to determine organic peroxides in body lotion samples.

Cytosolic Thioredoxin Peroxidase I and II Are Important Defenses of Yeast against Organic Hydroperoxide Insult: CATALASES AND PEROXIREDOXINS COOPERATE IN THE DECOMPOSITION OF H2O2 BY YEAST

The cytosolic thioredoxin peroxidase II (cTPxII/Tsa2p) from Saccharomyces cerevisiae shares 86% identity with the relatively well characterized cytosolic thioredoxin peroxidase I (cTPxI/Tsa1p). In contrast to cTPxI protein, cTPxII is not abundant and is highly inducible by peroxides. Here, we describe a unique phenotype for DeltacTPxII strain; these cells were highly sensitive to tert-butylhydroperoxide (TBHP) but presented resistance to H(2)O(2) in fermentative and respiratory conditions. In contrast, DeltacTPxI strain was very sensitive to both TBHP and H(2)O(2), whatever the carbon source present in the media. These differences in the response of mutant cells to the different kinds of peroxide insult could not be attributed to enzymatic properties of cTPxI and cTPxII since the recombinant proteins showed similar in vitro efficiencies (K(cat) /K(m)) in the removals of both kinds of peroxide. This specific sensitivity of DeltacTPxII cells to TBHP could not be related to the expression pattern of TSA2 (cytosolic thioredoxin peroxidase II gene) either, since this gene is highly inducible by both H(2)O(2) and TBHP when cells were grown in different conditions. Finally, peroxide-removing assays were performed and showed that catalase activity increased significantly only in DeltacTPxII cells, which appear to be related with the resistance of this strain to H(2)O(2). Taken together, present data indicate that cTPxII and cTPxI are key components of the yeast defense system against organic peroxide insult. In regard to the stress induced by H(2)O(2), catalases (peroxisomal and/or cytosolic) and cTPxII seemed to cooperate with cTPxI in the defense of yeast against this oxidant.

Lack of molecular relationships between lipid peroxidation and mitochondrial DNA single strand breaks in isolated rat hepatocytes and mitochondria

We investigated the molecular relationships between lipid peroxidation and mitochondrial DNA (mtDNA) single strand breaks (ssb) in isolated rat hepatocytes and mitochondria exposed to tert-butylhydroperoxide (TBH). Our results show that mtDNA ssb induced by TBH are independent of lipid peroxidation and dependent on the presence of iron and of hydroxyl free radicals. These data contribute to the definition of the mechanisms whereby mtDNA ssb are induced and provide possible molecular targets for the prevention of this kind of damage in vivo.

Analysis of molecular species of peroxide adducts of triacylglycerols following treatment of corn oil with tert-butyl hydroperoxide.

We recently demonstrated that exposure of synthetic mono- and diunsaturated triacylglycerols to tert-butylhydroperoxide (TBHP) leads to formation of stable adducts of the oxidizing agent and the unsaturated esters (Sjövall, O., Kuksis, A., and Kallio, H., Reversed Phase High-Performance Liquid Chromatographic Separation of tert-Butyl Hydroperoxide Oxidation Products of Unsaturated Triacylglycerols, J. Chromatogr. A 905, 119-132, 2001). In the present study we isolated and identified the TBHP adducts of corn oil triacylglycerols. The much wider range of molecular species available in the corn oil permitted us to demonstrate that the yield of the adducts varies with the degree of unsaturation of the triacylglycerol. The highest yields were obtained for the linoleate (20%, of linoleoyl-containing residual triacylglycerols) and the lowest ones for the oleate (5% of oleoyl-containing residual triacylglycerols) triacylglycerols, whereas the saturated triacylglycerols did not give TBHP adducts in readily detectable amounts. Normal-phase thin-layer chromatography along with reversed-phase high-performance liquid chromatography/mass spectrometry (LC/MS) with electrospray ionization was used to isolate and separate the major molecular species of polyunsaturated triacylglycerols and corresponding TBHP adducts. As an extreme example, the dilinoleoylmonooleoylglycerol was identified as the mono-, di-, tri-, tetra-, and penta-TBHP adduct. LC/MS with electrospray ionization at elevated capillary exit voltage (pseudo tandem mass spectrometry) was used to confirm structures of the [M-RCOOH]+ ions and the absence of TBHP adducts of [M-RCOOH]+. It is concluded that stable adduct formation is an unavoidable complication of preparation of oxotriacylglycerols by oxidation with concentrated TBHP solutions and care must be taken to resolve the adducts from the desired oxidation product.

Effects of G6PD Overexpression in NIH3T3 Cells Treated with Tert-Butyl Hydroperoxide or Paraquat

The major physiological role of glucose-6-phosphate dehydrogenase (G6PD) is to provide NADPH, which is required for reductive biosynthesis and for detoxification of free radicals and peroxides in mature red blood cells. To study the function of G6PD in non-erythroid cells, we examined the sensitivity of NIH3T3 cells transfected with a plasmid containing human G6PD cDNA to tert-butyl hydroperoxide (TBH) and paraquat. Two transfected clones which had a sixteen-fold (H7 clone) and six-fold (H6 clone) increase in their intracellular G6PD activity were compared with control cells transfected with a vector alone. Cells with high-level expression of human G6PD were 2.3 (H6) to 3.7 (H7) times more resistant to TBH than control cells. The antioxidant (anti-TBH) abilities in H6 and H7 cells were revealed by (1) a significant increase in the intracellular level of NADPH and glutathione, (2) a reduction of fluorescent intensity of the oxidant-sensitive dye, 2′,7′-dichlorofluorescin diacetate, and (3) a significant reduction in the production of oxidized adducts generated by lipid peroxidation. In contrast, cells overexpressing G6PD were very sensitive to paraquat, a superoxide-producing herbicide. The concentrations of paraquat required to produce a 50% decrease in cell viability of H7, H6 and control cells were 0.80 mM, 1.14 mM, and 2.19 mM, respectively. The cytotoxicity of paraquat correlated with the expression level of NADPH in the cells. In this study, overexpression of human G6PD in NIH3T3 cells had different effects on the toxicity of TBH vs. paraquat. Reduction of NADP + to NADPH by G6PD protects cells from oxidative damage by TBH, but appears to enhance the toxicity of paraquat.

Gender-related response to a tert-butyl hydroperoxide-induced oxidation in human neonatal tissue

Reports of gender-related differences in the activity of enzymes involved in the metabolism of intracellular antioxidants, led us to verify whether the prostaglandins response to tert-butyl hydroperoxide (TBH) differed according to the sex of infants. Segments of human umbilical veins were perfused in the presence or absence of TBH (0.25 mmol/l, and 1.0mmol/l). Because TBH is quenched in the cell by glutathion peroxidase, total glutathione concentrations and the production of glutathione-dependent prostaglandins (PGE 2 and PGF 2α as well as membrane-derived eicosanoids (PGI 2 and thromboxane) were measured in the eluate. In veins from boys, TBH induced a sustained response for glutathione only, which was increased ( p<0.05). In female-derived tissue, the hydroperoxide induced a different response according to the dose of TBH. At 0.25 mmol/l, a drop ( p<0.005) in PGF 2α was associated with a rise ( p< 0.001) in thromboxane. At 1.0 mmol/l, TBH had an opposite effect—there was a rise ( p<0.01) in PGE 2 and PGI 2. The prostaglandins concentrations were not proportional to the oxidative stimulus, suggesting a critical level of TBH at which the oxidative state differes in tissues derived from boys or girls.

Protective action of putrescine against rat liver injury.

The hepatoprotective action of orally dosed putrescine was investigated using rat models of liver injury. When rats received putrescine orally soon after a dose of carbon tetrachloride or D-galactosamine, deranged serum alanine aminotransferase values and prothrombin times were significantly attenuated compared with control levels, with improved histologic extent of liver injury. Putrescine addition to the medium of rat hepatocytes in primary culture reduced cell killing induced by D-galactosamine or the membrane detergents chenodeoxycholic acid and Triton X-100. Similar reduction was seen in cells exposed to tert-butyl hydroperoxide (TBHP), an agent producing cell death through lipid peroxidation, with attenuation of cellular malondialdehyde content. Putrescine also significantly attenuated the extent of increased plasma membrane microviscosity as assessed with 1-[4-(trimethylammonio)phenyl]-6-phenyl-1,3,5-hexatriene in TBHP-treated cells. These results suggest that orally given putrescine protects against liver injury. Plasma membrane stabilization and reduction of lipid peroxidation may contribute to this hepatoprotection.

Postanoxic oxidative injury in rat hepatocytes: Lactate-dependent protection against tert-butylhydroperoxide

Previous studies in this laboratory showed that hypoxia and anoxia enhance the susceptibility of hepatocytes to tert-butylhydroperoxide (TBH)-induced oxidative injury. To determine whether preceding exposure to anoxia affects postanoxic sensitivity to oxidative injury, viability was studied in hepatocytes incubated under anoxic conditions followed by reoxygenation without or with tert-butylhydroperoxide addition. Results showed that a preceding exposure to 60 min of anoxia substantially increased the vulnerability of cells to injury by the oxidant. Because substantial tissue lacta can accumulate during anoxia, the effect of increased lactate on postanoxic injury due to TBH was determined. Results showed that added lactate protected in a concentration-dependent manner. The TBH elimination rate was stimulated by lactate, and the pyruvate production rate approached the rate of TBH elimination. Thus, lactate protects against postanoxic oxidative injury by supplying reducing equivalents for peroxide reduction. This suggests that lactate accumulation during ischemia may be beneficial and that supplementation with lactate could be considered as a means to protect against postischemic injury.