Anserine is expressed in human cardiac and skeletal muscles

We evaluated whether anserine, a methylated analog of the dipeptide carnosine, is present in the cardiac and skeletal muscles of humans and whether the CARNMT1 gene, which encodes the anserine synthesizing enzyme carnosine-N-methyltransferase, is expressed in human skeletal muscle. We found that anserine is present at low concentrations (low micromolar range) in both cardiac and skeletal muscles, and that anserine content in skeletal muscle is ~15 times higher than in cardiac muscle (cardiac muscle: 10.1 ± 13.4 μmol·kg-1 of dry muscle, n = 12; skeletal muscle: 158.1 ± 68.5 μmol·kg-1 of dry muscle, n = 11, p < 0.0001). Anserine content in the heart was highly variable between individuals, ranging from 1.4 to 45.4 μmol·kg-1 of dry muscle, but anserine content was not associated with sex, age, or body mass. We also showed that CARNMT1 gene is poorly expressed in skeletal muscle (n = 10). This is the first study to demonstrate that anserine is present in the ventricle of the human heart. The presence of anserine in human heart and the confirmation of its expression in human skeletal muscle open new avenues of investigation on the specific and differential physiological functions of histidine dipeptides in striated muscles.

Singlet Molecular Oxygen Generation in the Reaction of Biological Haloamines of Amino Acids and Polyamines with Hydrogen Peroxide

Leucocytes generate hypohalous acids (HOCl and HOBr) to defend against pathogens. In cells, hypohalous acids react with amine-containing molecules, such as amino acids and polyamines, producing chloramines and bromamines, reservoirs of oxidizing power that can potentially damage host tissues at sites of inflammation. Hypohalous acids also react with H₂ O₂ to produce stoichiometric amounts of singlet molecular oxygen (¹ O₂ ), but its generation in leucocytes is still under debate. Additionally, it is unclear if haloamines generate ¹ O₂ following a reaction with H₂ O₂ . Herein, we provide evidence of the generation of ¹ O₂ in the reactions between amino acid-derived (taurine, N-α-acetyl-Lysine, and glycine) and polyamine-derived (spermine and spermidine) haloamines and H₂ O₂ in an aqueous solution. The unequivocal formation of ¹ O₂ was detected by monitoring its characteristic monomol light emission at 1270 nm in the near-infrared region. For amino acid-derived haloamines, the presence of ¹ O₂ was further confirmed by chemical trapping with anthracene-9,10-divinylsulfonate and HPLC-MS/MS detection. Altogether, photoemission and chemical trapping studies demonstrated that chloramines were less effective at producing ¹ O₂ than bromamines of amino acids and polyamines. Thus, ¹ O₂ formation via bromamines and H₂ O₂ may be a potential source of ¹ O₂ in non-illuminated biological systems.

The role of chronic muscle (in)activity on carnosine homeostasis: a study with spinal cord-injured athletes

To examine the role of chronic (in)activity on muscle carnosine (MCarn) and how chronic (in)activity affects MCarn responses to β-alanine supplementation in spinal cord-injured athletes, 16 male athletes with paraplegia were randomized (2:1 ratio) to receive β-alanine (n = 11) or placebo (PL, n = 5). They consumed 6.4 g/day of β-alanine or PL for 28 days. Muscle biopsies of the active deltoid and the inactive vastus lateralis (VL) were taken before and after supplementation. MCarn in the VL was also compared with the VL of a group of individuals without paraplegia (n = 15). MCarn was quantified in whole muscle and in pools of individual fibers by high-performance liquid chromatography. MCarn was higher in chronically inactive VL vs. well-trained deltoid (32.0 ± 12.0 vs. 20.5 ± 6.1 mmol/kg DM; P = 0.018). MCarn was higher in inactive vs. active VL (32.0 ± 12.0 vs. 21.2 ± 7.5 mmol/kg DM; P = 0.011). In type-I fibers, MCarn was significantly higher in the inactive VL than in the active deltoid (38.3 ± 4.7 vs. 27.3 ± 11.8 mmol/kg DM, P = 0.014). MCarn increased similarly between inactive VL and active deltoid in the β-alanine group (VL: 68.9 ± 55.1%, P = 0.0002; deltoid: 90.5 ± 51.4%, P < 0.0001), with no changes in the PL group. MCarn content was higher in the inactive VL than in the active deltoid and the active VL, but this is probably a consequence of fiber type shift (type I to type II) that occurs with chronic inactivity. Chronically inactive muscle showed an increase in MCarn after BA supplementation equally to the active muscle, suggesting that carnosine accretion following β-alanine supplementation is not influenced by muscle inactivity.

Insulin does not stimulate β-alanine transport into human skeletal muscle

To test whether high circulating insulin concentrations influence the transport of β-alanine into skeletal muscle at either saturating or subsaturating β-alanine concentrations, we conducted two experiments whereby β-alanine and insulin concentrations were controlled. In experiment 1, 12 men received supraphysiological amounts of β-alanine intravenously (0.11 g·kg−1·min−1for 150 min), with or without insulin infusion. β-Alanine and carnosine were measured in muscle before and 30 min after infusion. Blood samples were taken throughout the infusion protocol for plasma insulin and β-alanine analyses. β-Alanine content in 24-h urine was assessed. In experiment 2, six men ingested typical doses of β-alanine (10 mg/kg) before insulin infusion or no infusion. β-Alanine was assessed in muscle before and 120 min following ingestion. In experiment 1, no differences between conditions were shown for plasma β-alanine, muscle β-alanine, muscle carnosine and urinary β-alanine concentrations (all P > 0.05). In experiment 2, no differences between conditions were shown for plasma β-alanine or muscle β-alanine concentrations (all P > 0.05). Hyperinsulinemia did not increase β-alanine uptake by skeletal muscle cells, neither when substrate concentrations exceed the Vmaxof β-alanine transporter TauT nor when it was below saturation. These results suggest that increasing insulin concentration is not necessary to maximize β-alanine transport into muscle following β-alanine intake.

Cardioprotection induced by a brief exposure to acetaldehyde: role of aldehyde dehydrogenase 2

Aims

We previously demonstrated that acute ethanol administration protects the heart from ischaemia/reperfusion (I/R) injury thorough activation of aldehyde dehydrogenase 2 (ALDH2). Here, we characterized the role of acetaldehyde, an intermediate product from ethanol metabolism, and its metabolizing enzyme, ALDH2, in an ex vivo model of cardiac I/R injury.

Methods and results

We used a combination of homozygous knock-in mice (ALDH2*2), carrying the human inactivating point mutation ALDH2 (E487K), and a direct activator of ALDH2, Alda-1, to investigate the cardiac effect of acetaldehyde. The ALDH2*2 mice have impaired acetaldehyde clearance, recapitulating the human phenotype. Yet, we found a similar infarct size in wild type (WT) and ALDH2*2 mice. Similar to ethanol-induced preconditioning, pre-treatment with 50 μM acetaldehyde increased ALDH2 activity and reduced cardiac injury in hearts of WT mice without affecting cardiac acetaldehyde levels. However, acetaldehyde pre-treatment of hearts of ALDH2*2 mice resulted in a three-fold increase in cardiac acetaldehyde levels and exacerbated I/R injury. Therefore, exogenous acetaldehyde appears to have a bimodal effect in I/R, depending on the ALDH2 genotype. Further supporting an ALDH2 role in cardiac preconditioning, pharmacological ALDH2 inhibition abolished ethanol-induced cardioprotection in hearts of WT mice, whereas a selective activator, Alda-1, protected ALDH2*2 against ethanol-induced cardiotoxicity. Finally, either genetic or pharmacological inhibition of ALDH2 mitigated ischaemic preconditioning.

Conclusion

Taken together, our findings suggest that low levels of acetaldehyde are cardioprotective whereas high levels are damaging in an ex vivo model of I/R injury and that ALDH2 is a major, but not the only, regulator of cardiac acetaldehyde levels and protection from I/R.

Quantification of three DNA Lesions by Mass Spectrometry and Assessment of Their Levels in Tissues of Mice Exposed to Ambient Fine Particulate Matter

DNA adducts and oxidized DNA bases are examples of DNA lesions that are useful biomarkers for the toxicity assessment of substances that are electrophilic, generate reactive electrophiles upon biotransformation, or induce oxidative stress. Among the oxidized nucleobases, the most studied one is 8-oxo-7,8-dihydroguanine (8-oxoGua) or 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo), a biomarker of oxidatively induced base damage in DNA. Aldehydes and epoxyaldehydes resulting from the lipid peroxidation process are electrophilic molecules able to form mutagenic exocyclic DNA adducts, such as the etheno adducts 1,N²-etheno-2'-deoxyguanosine (1,N²-εdGuo) and 1,N⁶-etheno-2'-deoxyadenosine (1,N⁶-εdAdo), which have been suggested as potential biomarkers in the pathophysiology of inflammation. Selective and sensitive methods for their quantification in DNA are necessary for the development of preventive strategies to slow down cell mutation rates and chronic disease development (e.g., cancer, neurodegenerative diseases). Among the sensitive methods available for their detection (high performance liquid chromatography coupled to electrochemical or tandem mass spectrometry detectors, comet assay, immunoassays, ³²P-postlabeling), the most selective are those based on high performance liquid chromatography coupled to tandem mass spectrometry (HPLC-ESI-MS/MS). Selectivity is an essential advantage when analyzing complex biological samples and HPLC-ESI-MS/MS evolved as the gold standard for quantification of modified nucleosides in biological matrices, such as DNA, urine, plasma and saliva. The use of isotopically labeled internal standards adds the advantage of corrections for molecule losses during the DNA hydrolysis and analyte enrichment steps, as well as for differences of the analyte ionization between samples. It also aids in the identification of the correct chromatographic peak when more than one peak is present. We present here validated sensitive, accurate and precise HPLC-ESI-MS/MS methods that were successfully applied for the quantification of 8-oxodGuo, 1,N⁶-dAdo and 1,N²-dGuo in lung, liver and kidney DNA of A/J mice for the assessment of the effects of ambient PM2.5 exposure.

Oxidation of 1-N2-etheno-2'-deoxyguanosine by singlet molecular oxygen results in 2'-deoxyguanosine: a pathway to remove exocyclic DNA damage?

Exocyclic DNA adducts are considered as potential tools for the study of oxidative stress-related diseases, but an important aspect is their chemical reactivity towards oxidant species. We report here the oxidation of 1-N2-etheno-2'-deoxyguanosine (1,N2-εdGuo) by singlet molecular oxygen (1O2) generated by a non-ionic water-soluble endoperoxide [N,N'-di(2,3-dihydroxypropyl)-1,4-naphthalenedipropanamide endoperoxide (DHPNO2)] and its corresponding oxygen isotopically labeled [18O]-[N,N'-di(2,3-dihydroxypropyl)-1,4- naphthalenedipropanamide endoperoxide (DHPN18O2)], and by photosensitization with two different photosensitizers [methylene blue (MB) and Rose Bengal (RB)]. Products detection and characterization were achieved using high performance liquid chromatography (HPLC) coupled to ultraviolet and electrospray ionization (ESI) tandem mass spectrometry, and nuclear magnetic resonance (NMR) analyses. We found that dGuo is regenerated via reaction of 1O2 with the ε-linkage, and we propose a dioxetane as an intermediate, which cleaves and loses the aldehyde groups as formate residues, or alternatively, it generates a 1,2-ethanediol adduct. We also report herein the quenching rate constants of 1O2 by 1,N2-εdGuo and other etheno modified nucleosides. The rate constant (kt) values obtained for etheno nucleosides are comparable to the kt of dGuo. From these results, we suggest a possible role of 1O2 in the cleanup of etheno adducts by regenerating the normal base.

Direct participation of DNA in the formation of singlet oxygen and base damage under UVA irradiation

UVA light is hardly absorbed by the DNA molecule, but recent works point to a direct mechanism of DNA lesion by these wavelengths. UVA light also excite endogenous chromophores, which causes DNA damage through ROS. In this study, DNA samples were irradiated with UVA light in different conditions to investigate possible mechanisms involved in the induction of DNA damage. The different types of DNA lesions formed after irradiation were determined through the use of endonucleases, which recognize and cleave sites containing oxidized bases and cyclobutane pyrimidine dimers (CPDs), as well as through antibody recognition. The formation of 8-oxo-7,8-dihydro-2'-deoxyguanine (8-oxodG) was also studied in more detail using electrochemical detection. The results show that high NaCl concentration and concentrated DNA are capable of reducing the induction of CPDs. Moreover, concerning damage caused by oxidative stress, the presence of sodium azide and metal chelators reduce their induction, while deuterated water increases the amounts of oxidized bases, confirming the involvement of singlet oxygen in the generation of these lesions. Curiously, however, high concentrations of DNA also enhanced the formation of oxidized bases, in a reaction that paralleled the increase in the formation of singlet oxygen in the solution. This was interpreted as being due to an intrinsic photosensitization mechanism, depending directly on the DNA molecule to absorb UVA and generate singlet oxygen. Therefore, the DNA molecule itself may act as a chromophore for UVA light, locally producing a damaging agent, which may lead to even greater concerns about the deleterious impact of sunlight.

Luminescent threat: toxicity of light stick attractors used in pelagic fishery

Light sticks (LS) are sources of chemiluminescence commonly used in pelagic fishery, where hundreds are discarded and reach the shores. Residents from fishing villages report an improper use of LS contents on the skin. Given the scarce information regarding LS toxicity, the effects of LS solutions in cell cultures were evaluated herein. Loss of viability, cell cycle changes and DNA fragmentation were observed in HepG2 cell line and skin fibroblasts. A non-cytotoxic LS concentration increased the occurrence of the mutagenic lesion 1,N(6)-εdAdo in HepG2 DNA by three-fold. Additionally, in vitro incubations of spent LS contents with DNA generated dGuo-LS adducts, whose structure elucidation revealed the presence of a reactive chlorinated product. In conclusion, the LS contents were found to be highly cyto- and genotoxic. Our data indicate an urgent need for LS waste management guidelines and for adequate information regarding toxic outcomes that may arise from human exposure.

Unveiling benznidazole's mechanism of action through overexpression of DNA repair proteins in Trypanosoma cruzi

Benznidazole (BZ) is the most commonly used drug for the treatment of Chagas disease. Although BZ is known to induce the formation of free radicals and electrophilic metabolites within the parasite Trypanosoma cruzi, its precise mechanisms of action are still elusive. Here, we analyzed the survival of T. cruzi exposed to BZ using genetically modified parasites overexpressing different DNA repair proteins. Our results indicate that BZ induces oxidation mainly in the nucleotide pool, as heterologous expression of the nucleotide pyrophosphohydrolase MutT (but not overexpression of the glycosylase TcOgg1) increased drug resistance in the parasite. In addition, electron microscopy indicated that BZ catalyzes the formation of double-stranded breaks in the parasite, as its genomic DNA undergoes extensive heterochromatin unpacking following exposure to the drug. Furthermore, the overexpression of proteins involved in the recombination-mediated DNA repair increased resistance to BZ, reinforcing the idea that the drug causes double-stranded breaks. Our results also show that the overexpression of mitochondrial DNA repair proteins increase parasite survival upon BZ exposure, indicating that the drug induces lesions in the mitochondrial DNA as well. These findings suggest that BZ preferentially oxidizes the nucleotide pool, and the extensive incorporation of oxidized nucleotides during DNA replication leads to potentially lethal double-stranded DNA breaks in T. cruzi DNA.

Characterization of O(2) ((1)delta(g))-derived oxidation products of tryptophan: a combination of tandem mass spectrometry analyses and isotopic labeling studies

The fragmentation mechanisms of singlet oxygen [O(2) ((1)Delta(g))]-derived oxidation products of tryptophan (W) were analyzed using collision-induced dissociation coupled with (18)O-isotopic labeling experiments and accurate mass measurements. The five identified oxidized products, namely two isomeric alcohols (trans and cis WOH), two isomeric hydroperoxides (trans and cis WOOH), and N-formylkynurenine (FMK), were shown to share some common fragment ions and losses of small neutral molecules. Conversely, each oxidation product has its own fragmentation mechanism and intermediates, which were confirmed by (18)O-labeling studies. Isomeric WOH lost mainly H(2)O + CO, while WOOH showed preferential elimination of C(2)H(5)NO(3) by two distinct mechanisms. Differences in the spatial arrangement of the two isomeric WOHs led to differences in the intensities of the fragment ions. The same behavior was also found for trans and cis WOOH. FMK was shown to dissociate by a diverse range of mechanisms, with the loss of ammonia the most favored route. MS/MS analyses, (18)O-labeling, and H(2)(18)O experiments demonstrated the ability of FMK to exchange its oxygen atoms with water. Moreover, this approach also revealed that the carbonyl group has more pronounced oxygen exchange ability compared with the formyl group. The understanding of fragmentation mechanisms involved in O(2) ((1)Delta(g))-mediated oxidation of W provides a useful step toward the structural characterization of oxidized peptides and proteins.

Spiroiminodihydantoin nucleoside formation from 2'-deoxyguanosine oxidation by [(18)O-labeled] singlet molecular oxygen in aqueous solution

The main singlet molecular oxygen ((1)O(2)) oxidation products of free 2'-deoxyguanosine (dGuo) in aqueous solution were identified as a pair of diastereomeric spiroiminodihydantoin 2'-deoxyribonucleosides (dSp) together with 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo). In the present work, evidence is provided from (18)[(1)O(2)] and H(2) (18)O labeling experiments, using HPLC-ESI-MS/MS, that the formation of dSp is explained by the addition of water to a reactive quinonoid intermediate, and a second reaction pathway leading to dSp involves (1)O(2) oxidation of initially generated 8-oxodGuo.

Oxidative stress in Perna perna and other bivalves as indicators of environmental stress in the Brazilian marine environment: Antioxidants, lipid peroxidation and DNA damage

Oxidative stress can take place in marine bivalves under a series of environmental adverse conditions. The study of different systems related to oxidative stress in these organisms can give important information about their physiological status and also about environmental health. Bivalves have been proposed as good sentinel organisms in pollution monitoring studies through the analysis of biochemical biomarkers, and most of the biomarkers analyzed are those related to oxidative stress. However, it is very important to know how other environmental factors not associated to the presence of pollutants might affect these parameters. We have studied a series of mechanisms related to oxidative stress in mussels which inhabit the Brazilian coast, especially in Perna perna species, subjected to different stress conditions, such as the exposure to different contaminants in the laboratory and in the field, the exposure of mussels to air and re-submersion, simulating the tidal oscillations, and in mussels collected at different seasons. Both oxidative damage levels and antioxidant defense systems were strongly affected by the different environmental stress. This review summarizes the data obtained in some studies carried out in bivalves from the Brazilian coast.

Protective effect of phospholipid hydroperoxide glutathione peroxidase (PHGPx) against lipid peroxidation in mussels Perna perna exposed to different metals

Levels of antioxidant defenses and lipid peroxidation were evaluated in mussels exposed to lead (200 mg/l), iron (500 microg/l), cadmium (200 microg/l) and copper (40 microg/l), for 12, 24, 72 and 120 h. Glutathione S-transferase (GST) activity was unchanged with all treatments. Catalase (CAT) increased after 120 h of exposure to all metals. Mussels exposed to Cd for 12 h, and to Cu and Fe for 120 h had increased lipid peroxidation, which might be associated to decreased levels of reduced glutathione (GSH) and glutathione peroxidase (GPx) activity. Pb exposure caused GSH depletion after 12 h and increased GPx activity after 120 h. Negative correlations were observed between the enzyme phospholipid hydroperoxide glutathione peroxidase (PHGPx) and malonaldehyde (MDA) levels after Fe and Cu exposure, indicating a protective role of PHGPx against lipid peroxidation, and suggesting the use of this enzyme as a new potential biomarker of toxicity associated with contaminant exposure in mussels.

DNA damage in digestive gland and mantle tissue of the mussel Perna perna

Data concerning the susceptibility of DNA to damage by reactive oxygen and nitrogen species and other endogenous compounds produced by physiological stress in marine organisms is lacking, especially in bivalve mollusks. In this article, we analyzed the background levels of lipid peroxidation (malondialdehyde, MDA), 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) and 1,N2-etheno-2'-deoxyguanosine (1,N2-epsilon dGuo) in digestive gland and mantle tissue of mussels Perna perna collected at a cultivation zone in Florianópolis (Santa Catarina, Brazil). The present data point to the possibility of the use of both 8-oxodGuo and 1,N2-epsilon dGuo as complementary indicators of oxidative stress processes in mussels. A sensitive method coupling high performance liquid chromatography to mass spectrometry was applied for the detection of 1,N2-epsilon dGuo in mussel tissues.