Conversion of taurine into N-chlorotaurine (taurine chloramine) and sulphoacetaldehyde in response to oxidative stress

Changes in Neutrophil Metabolism upon Activation and Aging

Neutrophil activation is an important mechanism of host defense against pathogens. Chronic inflammation and autoimmunity are often associated with abnormalities in phenotype and functions of neutrophils. Since effector functions of immune cells during inflammation are tightly linked to their metabolic state, changes in neutrophil metabolome upon activation have been investigated in this study. Human neutrophils from healthy blood donors (n = 6) were treated either with tumor necrosis factor α (TNF-α) or lipopolysaccharide (LPS), whereas untreated neutrophils were used as control. Since apoptotic cells are abundant at sites of inflammation, the metabolome of aged, mainly apoptotic neutrophils was analyzed too. NMR spectroscopy of water-soluble metabolites revealed a clear distinction between aged neutrophils and neutrophils in control and activated samples. Higher levels of NAD⁺ (4- to 9-fold) and lower levels of ATP (0.3-fold), glutathione (0.8-fold), hypotaurine (0.8-fold), and phosphocholine (0.6-fold) were detected in aged neutrophils than in the other samples. Differences in metabolic profiles between LPS and TNF-α-stimulated cells as well as between stimulated and control neutrophils were statistically not significant. Replication with additional six blood donors confirmed increased NAD⁺ levels in aged cells compared to activated and control neutrophils.

Gut microbiota and serum metabolite differences in African Americans and White Americans with high blood pressure

BACKGROUND

Black Americans have greater rates, severity and resistance to treatment of hypertension than White Americans. The gut microbiota and its metabolites may contribute to this. This concept was tested in a pilot study.

METHODS

Subjects with high (HBP, >140/80 mm Hg) and normal (NBP, <120/80 mm Hg) blood pressure (BP) provided stool and blood samples for whole genome sequencing (WGS) of gut microbiota and global untargeted metabolomics of serum. Patients were either black (B) with NBP (n = 10 for WGS, 5 for metabolomics) and HBP (n = 10 and 9, BHBP) or white (W) with NBP (n = 20 and 13, WNBP) and HBP (n = 12 and 8, WHBP).

RESULTS

All four subject groups had distinct gut microbiota taxonomy by partial least squares discriminant analysis (PLS-DA). More importantly, linear discriminant analysis effect size showed marked differences in function of the microbiota of BHBP and WHBP (PLS-DA) with LDA scores <1. This included pathways for synthesis and interconversion of amino acids and inflammatory antigens. Similarly, metabolites differed (PLS-DA) with BHBP having significantly higher sulfacetaldehyde, quinolinic acid, 5-aminolevulinic acid, leucine and phenylalanine and lower 4-oxoproline and l-anserine.

DISCUSSION

Combination analyses of functional gut metabolic pathways and metabolomics data in this small pilot study suggest that BHBP may have greater oxidative stress markers in plasma, greater inflammatory potential of the gut microbiome and altered metabolites with gut microbial functions implying insulin resistance. A fuller understanding of these potential differences could lead to race-based treatments for hypertension.

Chemistry and Redox Biology of Mycothiol

SIGNIFICANCE

Mycothiol (MSH, AcCys-GlcN-Ins) is the main low-molecular weight (LMW) thiol of most Actinomycetes, including the human pathogen Mycobacterium tuberculosis that affects millions of people worldwide. Strains with decreased MSH content show increased susceptibilities to hydroperoxides and electrophilic compounds. In M. tuberculosis, MSH modulates the response to several antituberculosis drugs. Enzymatic routes involving MSH could provide clues for specific drug design. Recent Advances: Physicochemical data argue against a rapid, nonenzymatic reaction of MSH with oxidants, disulfides, or electrophiles. Moreover, exposure of the bacteria to high concentrations of two-electron oxidants resulted in protein mycothiolation. The recently described glutaredoxin-like protein mycoredoxin-1 (Mrx-1) provides a route for catalytic reduction of mycothiolated proteins, protecting critical cysteines from irreversible oxidation. The description of MSH/Mrx-1-dependent activities of peroxidases helped to explain the higher susceptibility to oxidants observed in Actinomycetes lacking MSH. Moreover, the first mycothiol-S-transferase, member of the DinB superfamily of proteins, was described. In Corynebacterium, both the MSH/Mrx-1 and the thioredoxin pathways reduce methionine sulfoxide reductase A. A novel tool for in vivo imaging of the MSH/mycothiol disulfide (MSSM) status allows following changes in the mycothiol redox state during macrophage infection and its relationship with antibiotic sensitivity.

CRITICAL ISSUES

Redundancy of MSH with other LMW thiols is starting to be unraveled and could help to rationalize the differences in the reported importance of MSH synthesis observed in vitro versus in animal infection models.

FUTURE DIRECTIONS

Future work should be directed to establish the structural bases of the specificity of MSH-dependent enzymes, thus facilitating drug developments. Antioxid. Redox Signal. 28, 487-504.

Myocardial Metabolism and Improved OutcomesAfter High Risk Heart Surgery

The healthy heart relies primarily upon the oxidation of fatty acids for energy, with the remaining coming from the oxidation of glucose and lactate. Changes in energy requirements are met by altering the balance of fuels depending upon the hormonal milieu as well as upon the availability of oxygen and substrates. The use of carbohydrates for fuel is metabolically more efficient and may improve the coupling between glycolysis and pyruvate oxidation. Therefore, promoting a shift in metabolic fuel substrate use during times of reduced oxygen availability may represent a cardioprotective strategy. Subsequently, there has been interest in pharmacologic strategies such insulin or drugs like ranolazine and dichloroacetate that stimulate carbohydrate oxidation either by enhancing oxidation at the pyruvate dehydrogenase complex or by limiting fatty acid oxidation. There is evidence that nutrients may also be able to stimulate carbohydrate oxidation. Previous studies by our group suggest that a combination of nutrients (carnitine, coenzyme Q10, and taurine) may work together, resulting in pleiotropic cardioprotective effects. Our current studies are investigating the potential of nutrients as both a preventative and adjunctive treatment before and after an ischemic event. These investigations will determine the role of nutritional supplementation in the care of patients with ischemic injury.

Health effects from swimming training in chlorinated pools and the corresponding metabolic stress pathways

Chlorination is the most popular method for disinfecting swimming pool water; however, although pathogens are being killed, many toxic compounds, called disinfection by-products (DBPs), are formed. Numerous epidemiological publications have associated the chlorination of pools with dysfunctions of the respiratory system and with some other diseases. However, the findings concerning these associations are not always consistent and have not been confirmed by toxicological studies. Therefore, the health effects from swimming in chlorinated pools and the corresponding stress reactions in organisms are unclear. In this study, we show that although the growth and behaviors of experimental rats were not affected, their health, training effects and metabolic profiles were significantly affected by a 12-week swimming training program in chlorinated water identical to that of public pools. Interestingly, the eyes and skin are the organs that are more directly affected than the lungs by the irritants in chlorinated water; instead of chlorination, training intensity, training frequency and choking on water may be the primary factors for lung damage induced by swimming. Among the five major organs (the heart, liver, spleen, lungs and kidneys), the liver is the most likely target of DBPs. Through metabolomics analysis, the corresponding metabolic stress pathways and a defensive system focusing on taurine were presented, based on which the corresponding countermeasures can be developed for swimming athletes and for others who spend a lot of time in chlorinated swimming pools.

Activation of glycine and extrasynaptic GABA(A) receptors by taurine on the substantia gelatinosa neurons of the trigeminal subnucleus caudalis

The substantia gelatinosa (SG) of the trigeminal subnucleus caudalis (Vc) has been known for the processing and transmission of orofacial nociceptive information. Taurine, one of the most plentiful free amino-acids in humans, has proved to be involved in pain modulation. In this study, using whole-cell patch clamp technique, we investigated the direct membrane effects of taurine and the action mechanism behind taurine-mediated responses on the SG neurons of the Vc. Taurine showed non-desensitizing and repeatable membrane depolarizations and inward currents which remained in the presence of amino-acid receptors blocking cocktail (AARBC) with tetrodotoxin, indicating that taurine acts directly on the postsynaptic SG neurons. Further, application of taurine at different doses (10 μM to 3 mM) showed a concentration dependent depolarizations and inward currents with the EC₅₀ of 84.3 μM and 723 μM, respectively. Taurine-mediated responses were partially blocked by picrotoxin (50 μM) and almost completely blocked by strychnine (2 μM), suggesting that taurine-mediated responses are via glycine receptor (GlyR) activation. In addition, taurine (1 mM) activated extrasynaptic GABA_A receptor (GABA_AR)-mediated currents. Taken together, our results indicate that taurine can be a target molecule for orofacial pain modulation through the activation of GlyRs and/or extrasynaptic GABA_ARs on the SG neurons.

Paracoccus denitrificans PD1222 utilizes hypotaurine via transamination followed by spontaneous desulfination to yield acetaldehyde and, finally, acetate for growth

Hypotaurine (HT; 2-aminoethane-sulfinate) is known to be utilized by bacteria as a sole source of carbon, nitrogen, and energy for growth, as is taurine (2-aminoethane-sulfonate); however, the corresponding HT degradation pathway has remained undefined. Genome-sequenced Paracoccus denitrificans PD1222 utilized HT (and taurine) quantitatively for heterotrophic growth and released the HT sulfur as sulfite (and sulfate) and HT nitrogen as ammonium. Enzyme assays with cell extracts suggested that an HT-inducible HT:pyruvate aminotransferase (Hpa) catalyzes the deamination of HT in an initial reaction step. Partial purification of the Hpa activity and peptide fingerprinting-mass spectrometry (PF-MS) identified the Hpa candidate gene; it encoded an archetypal taurine:pyruvate aminotransferase (Tpa). The same gene product was identified via differential PAGE and PF-MS, as was the gene of a strongly HT-inducible aldehyde dehydrogenase (Adh). Both genes were overexpressed in Escherichia coli. The overexpressed, purified Hpa/Tpa showed HT:pyruvate-aminotransferase activity. Alanine, acetaldehyde, and sulfite were identified as the reaction products but not sulfinoacetaldehyde; the reaction of Hpa/Tpa with taurine yielded sulfoacetaldehyde, which is stable. The overexpressed, purified Adh oxidized the acetaldehyde generated during the Hpa reaction to acetate in an NAD(+)-dependent reaction. Based on these results, the following degradation pathway for HT in strain PD1222 can be depicted. The identified aminotransferase converts HT to sulfinoacetaldehyde, which desulfinates spontaneously to acetaldehyde and sulfite; the inducible aldehyde dehydrogenase oxidizes acetaldehyde to yield acetate, which is metabolized, and sulfite, which is excreted.

Taurine plays an important role in the protection of spermatogonia from oxidative stress

It has been demonstrated that taurine has various physiological functions in the body. We demonstrated that taurine is abundant in the serum, liver, muscle and testis of the Japanese eel (Anguilla japonica). In the eel testis, taurine is found mainly in spermatogonia and is weakly expressed also in the Sertoli cells. We have further found in the eel testis that taurine is actively accumulated via the sodium/chloride-dependent taurine transporter (TauT; SLC6A6), which is expressed in germ cells. In our current study, the effects of taurine on the anti-oxidant response were examined. Taurine was found to promote the total superoxide dismutase (SOD) activity in the testis. Moreover, our results indicate that taurine does not affect the mRNA levels of copper-zinc (Cu/Zn) SOD or manganese SOD, but promotes the translation of Cu/Zn SOD. Overall, our present data suggest that taurine may modulate Cu/Zn SOD at the translational level and thereby may play an important role in the protection of germ cells from oxidative stress.

Chemical characterization and biological properties of NVC-422, a novel, stable N-chlorotaurine analog

During oxidative burst, neutrophils selectively generate HOCl to destroy invading microbial pathogens. Excess HOCl reacts with taurine, a semi-essential amino acid, resulting in the formation of the longer-lived biogenerated broad-spectrum antimicrobial agent, N-chlorotaurine (NCT). In the presence of an excess of HOCl or under moderately acidic conditions, NCT can be further chlorinated, or it can disproportionate to produce N,N-dichlorotaurine (NNDCT). In the present study, 2,2-dimethyltaurine was used to prepare a more stable N-chlorotaurine, namely, N,N-dichloro-2,2-dimethyltaurine (NVC-422). In addition, we report on the chemical characterization, in vitro antimicrobial properties, and cytotoxicity of this compound. NVC-422 was shown effectively to kill all 17 microbial strains tested, including antibiotic-resistant Staphylococcus aureus and Enterococcus faecium. The minimum bactericidal concentration of NVC-422 against Gram-negative and Gram-positive bacteria ranged from 0.12 to 4 μg/ml. The minimum fungicidal concentrations against Candida albicans and Candida glabrata were 32 and 16 μg/ml, respectively. NVC-422 has an in vitro cytotoxicity (50% cytotoxicity = 1,440 μg/ml) similar to that of NNDCT. Moreover, our data showed that this agent possesses rapid, pH-dependent antimicrobial activity. At pH 4, NVC-422 completely killed both Escherichia coli and S. aureus within 5 min at a concentration of 32 μg/ml. Finally, the effect of NVC-422 in the treatment of an E. coli-infected granulating wound rat model was evaluated. Treatment of the infected granulating wound with NVC-422 resulted in significant reduction of the bacterial tissue burden and faster wound healing compared to a saline-treated control. These findings suggest that NVC-422 could have potential application as a topical antimicrobial.

N-chlorotaurine, a natural antiseptic with outstanding tolerability

N-chlorotaurine, the N-chloro derivative of the amino acid taurine, is a long-lived oxidant produced by activated human granulocytes and monocytes. Supported by a high number of in vitro studies, it has mainly anti-inflammatory properties and seems to be involved in the termination of inflammation. The successful synthesis of the crystalline sodium salt (Cl-HN-CH(2)-CH(2)-SO(3)Na, NCT) facilitated its development as an endogenous antiseptic. NCT can be stored long-term at low temperatures, and it has killing activity against bacteria, fungi, viruses and parasites. Transfer of the active chlorine to amino groups of molecules of both the pathogens and the human body (transhalogenation) enhances rather than decreases its activity, mainly because of the formation of monochloramine. Furthermore, surface chlorination after sublethal incubation times in NCT leads to a post-antibiotic effect and loss of virulence of pathogens, as demonstrated for bacteria and yeasts. Being a mild oxidant, NCT proved to be very well tolerated by human tissue in Phase I and II clinical studies. A 1% aqueous solution can be applied to the eye, skin ulcerations, outer ear canal, nasal and paranasal sinuses, oral cavity and urinary bladder, and can probably be used for inhalation. Therapeutic efficacy in Phase II studies has been shown in external otitis, purulently coated crural ulcerations and keratoconjunctivitis, so far. Based upon all presently available data, NCT seems to be an antiseptic with a very good relation between tolerability and activity. Recently, C-methylated derivatives of NCT have been invented, which are of interest because of improved stability at room temperature.

Bifurcated degradative pathway of 3-sulfolactate in Roseovarius nubinhibens ISM via sulfoacetaldehyde acetyltransferase and (S)-cysteate sulfolyase

Data from the genome sequence of the aerobic, marine bacterium Roseovarius nubinhibens ISM were interpreted such that 3-sulfolactate would be degraded as a sole source of carbon and energy for growth via a novel bifurcated pathway including two known desulfonative enzymes, sulfoacetaldehyde acetyltransferase (EC 2.3.3.15) (Xsc) and cysteate sulfo-lyase (EC 4.4.1.25) (CuyA). Strain ISM utilized sulfolactate quantitatively with stoichiometric excretion of the sulfonate sulfur as sulfate. A combination of enzyme assays, analytical chemistry, enzyme purification, peptide mass fingerprinting, and reverse transcription-PCR data supported the presence of an inducible, tripartite sulfolactate uptake system (SlcHFG), and a membrane-bound sulfolactate dehydrogenase (SlcD) which generated 3-sulfopyruvate, the point of bifurcation. 3-Sulfopyruvate was in part decarboxylated by 3-sulfopyruvate decarboxylase (EC 4.1.1.79) (ComDE), which was purified. The sulfoacetaldehyde that was formed was desulfonated by Xsc, which was identified, and the acetyl phosphate was converted to acetyl-coenzyme A by phosphate acetyltransferase (Pta). The other portion of the 3-sulfopyruvate was transaminated to (S)-cysteate, which was desulfonated by CuyA, which was identified. The sulfite that was formed was presumably exported by CuyZ (TC 9.B.7.1.1 in the transport classification system), and a periplasmic sulfite dehydrogenase is presumed. Bioinformatic analyses indicated that transporter SlcHFG is rare but that SlcD is involved in three different combinations of pathways, the bifurcated pathway shown here, via CuyA alone, and via Xsc alone. This novel pathway involves ComDE in biodegradation, whereas it was discovered in the biosynthesis of coenzyme M. The different pathways of desulfonation of sulfolactate presumably represent final steps in the biodegradation of sulfoquinovose (and exudates derived from it) in marine and aquatic environments.

Apoptosis-inducing high (.)NO concentrations are not sustained either in nascent or in developed cancers

Nitric oxide ((.)NO) induces apoptosis at high concentrations by S-nitrosating proteins such as glyceraldehyde-3-phosphate dehydrogenase. This literature analysis revealed that failure to sustain high (.)NO concentrations is common to all cancers. In cervical, gastric, colorectal, breast, and lung cancer, the cause of this failure is the inadequate expression of inducible nitric oxide synthase (iNOS), resulting from the inhibition of iNOS expression by TGF-beta1 at the mRNA level. In bladder, renal, and prostate cancer, the reason for the insufficient (.)NO levels is the depletion of arginine, resulting from arginase overexpression. Arginase competes with iNOS for arginine, catalyzing its hydrolysis to ornithine and urea. In gliomas and ovarian sarcomas, low (.)NO levels are caused by inhibition of iNOS by N-chlorotaurine, produced by infiltrating neutrophils. Stimulated neutrophils express myeloperoxidase, catalyzing H2O2 oxidation of Cl- to HOCl, which N-chlorinates taurine at its concentration of 19 mM in neutrophils. In squamous cell carcinomas of the skin, ovarian cancers, lymphomas, Hodgkin's disease, and breast cancers, low (.)NO concentrations arise from the inhibition of iNOS by N-bromotaurine, produced by eosinophil-peroxidase-expressing infiltrating eosinophils. Eosinophil peroxidase catalyzes the H2O2 oxidation of Br- to HOBr, which N-brominates taurine to N-bromotaurine at its concentration of 15 mM in eosinophils. In microvascularized tumors, the (.)NO concentration is further depleted; (.)NO is rapidly consumed by red blood cells (RBCs) through S-nitrosation of RBC glutathione and hemoglobin, and by oxidation to nitrate by RBC oxyhemoglobin. Angiogenesis-inhibiting antibodies are currently used to treat cancers; their mode of action is not, as previously thought, reduction of the tumor O2 or nutrient supply. They actually decrease the loss of (.)NO to RBCs.

Beneficial effect of taurine treatment against doxorubicin-induced cardiotoxicity in mice

Though the administration of taurine is clinically efficacious against heart failure, the mechanism underlying its cardioprotection remains to be established. To provide information on the mechanism, we examined the effects of taurine on doxorubicin (DOX)-induced cardiotoxicity, with an emphasis on ROS generation and cardiac gene inhibition. Oral administration of taurine (3% w/v in tap water) dramatically reduced the mortality rate in both the acute or sub-acute toxic models of DOX toxicity. It was shown that taurine prevented DOX-induced oxidative stress as determined from cardiac glutathione content. Interestingly, Northern blot analysis revealed that DOX altered cardiac gene expression, including that of alpha-myosin heavy chain, ventricular myosin light chain-2 isoform and brain natriuretic peptide, an effect partially ameliorated by taurine treatment. In conclusion, taurine suppresses ROS generation and regulates gene expression in the DOX treated heart.

Sulfoacetate released during the assimilation of taurine-nitrogen by Neptuniibacter caesariensis: purification of sulfoacetaldehyde dehydrogenase

Taurine (2-aminoethanesulfonate) is a widespread natural product whose nitrogen moiety was recently shown to be assimilated by bacteria, usually with excretion of an organosulfonate via undefined novel pathways; other data involve transcriptional regulator TauR in taurine metabolism. A screen of genome sequences for TauR with the BLAST algorithm allowed the hypothesis that the marine gammaproteobacterium Neptuniibacter caesariensis MED92 would inducibly assimilate taurine-nitrogen and excrete sulfoacetate. The pathway involved an ABC transporter (TauABC), taurine:pyruvate aminotransferase (Tpa), a novel sulfoacetaldehyde dehydrogenase (SafD) and exporter(s) of sulfoacetate (SafE) (DUF81). Ten candidate genes in two clusters involved three sets of paralogues (for TauR, Tpa and SafE). Inducible Tpa and SafD were detected in cell extracts. SafD was purified 600-fold to homogeneity in two steps. The monomer had a molecular mass of 50 kDa (SDS-PAGE); data from gel filtration chromatography indicated a tetrameric native protein. SafD was specific for sulfoacetaldehyde with a K (m)-value of 0.12 mM. The N-terminal amino acid sequence of SafD confirmed the identity of the safD gene. The eight pathway genes were transcribed inducibly, which indicated expression of the whole hypothetical pathway. We presume that this pathway is one source of sulfoacetate in nature, where this compound is dissimilated by many bacteria.

Assimilation of homotaurine-nitrogen by Burkholderia sp. and excretion of sulfopropanoate

Homotaurine (3-aminopropanesulfonate), free or derivatized, is in widespread pharmaceutical and laboratory use. Studies with enrichment cultures indicated that the compound is degradable as a sole source of carbon or as a sole source of nitrogen for bacterial growth. A pure culture of Burkholderia sp. was isolated which assimilated the amino group from homotaurine in a glucose-salts medium, and which released an organosulfonate, 3-sulfopropanoate, into the medium stoichiometrically. The deamination involved an inducible 2-oxoglutarate-dependent aminotransferase to yield glutamate, and 3-sulfopropanal. Release of the amino group was attributed to the measured NADP-coupled glutamate dehydrogenase.

Comparative global transcription analysis of sodium hypochlorite, peracetic acid, and hydrogen peroxide on Pseudomonas aeruginosa

Disinfectants are routinely used in hospitals and health care facilities for surface sterilization. However, the mechanisms by which these disinfectants kill and the extent to which bacteria, including Pseudomonas aeruginosa, are resistant remains unclear. Consequently, P. aeruginosa nosocomial infections result in considerable casualties and economic hardship. Previously, DNA microarrays were utilized to analyze the genome-wide transcription changes in P. aeruginosa after oxidative antimicrobial (sodium hypochlorite, peracetic acid, and hydrogen peroxide) exposure. Simultaneous analysis of these transcriptome datasets provided a comprehensive understanding of the differential responses to these disinfectants. An analysis of variance, functional classification analysis, metabolic pathway analysis, Venn diagram analysis, and principal component analysis revealed that sodium hypochlorite exposure resulted in more genome-wide changes than either peracetic acid or hydrogen peroxide exposures.

Which mechanisms are involved in taurine-dependent granulocytic immune response or amino- and α-keto acid homeostasis?

We examined the effects of beta-alanine (taurine analogue and taurine transport antagonist), taurine (regarding its role in neutrophil (PMN) immunonutrition) and taurine combined either with L-NAME (inhibitor of *NO-synthase), SNAP (*NO donor), DON (glutamine-analogue and inhibitor of glutamine-requiring enzymes), DFMO (inhibitor of ornithine-decarboxylase) and beta-alanine on neutrophil amino- and alpha-keto acid profiles or important PMN immune functions in order to establish whether taurine transport-, nitric oxide-, glutamine- or ornithine-dependent mechanisms are involved in any of the taurine-induced effects. According to the present findings, the taurine-mediated effect appears to be based primarily on a modulation of important transmembraneous transport mechanisms and only secondarily on directly or indirectly induced modifications in intragranulocytic amino- and alpha-keto acid homoeostasis or metabolism. Although a direct relation to the parallel observed immunological modifications can only be presumed, these results show very clearly that compositional modifications in the free intragranulocytic amino- and alpha keto-acid pools coinciding with changes in intragranulocytic taurine levels are relevant metabolic determinants that can significantly influence the magnitude and quality of the granulocytic immune response.

Toxicogenomic analysis of sodium hypochlorite antimicrobial mechanisms in Pseudomonas aeruginosa

Sodium hypochlorite (bleach) is routinely used in hospitals and health care facilities for surface sterilization; however, the mechanism of action by which this disinfectant kills and the extent to which Pseudomonas aeruginosa is resistant to sodium hypochlorite have not been elucidated. Consequently, nosocomial infections from P. aeruginosa result in considerable casualties and economic hardship. We report the genome-wide transcriptome response of P. aeruginosa to sodium hypochlorite-induced oxidative stress via the use of DNA microarrays. In addition to a general oxidative stress response, our data revealed a downregulation of virtually all genes related to oxidative phosphorylation and electron transport and an upregulation of many organic sulfur transport and metabolism genes.

Cytotoxicity of taurine metabolites depends on the cell type

We report that the effect of Tau-Cl on the cell fate strongly depends on the cellular context. In leukemic Jurkat cells Tau-Cl (> 200 microM) triggers mitochondrial, p53-independent apoptosis and amplifies PCD induced by anti-Fas treatment. In contrast, Tau-Cl affects RA FLS in a dose-dependent manner. At the noncytotoxic (200-400 microM) concentrations it induces: (i) p53-dependent growth arrest (Kontny et al., 2005), and (ii) Bax translocation and caspase 9 activity. Although the last events are characteristic for apoptotic state, there is not execution of RA FLS apoptosis, probably due to simultaneous inhibition of caspase 3 activity and prevention of PARP degradation. The last two events suggest an excessive ATP deprivation in Tau-Cl-treated RA FLS. At sufficiently high concentrations (> or = 500 microM) Tau-Cl causes therefore necrosis of these cells. Altogether our results suggest that Tau-Cl is able to eliminate the cells with both functional (RA FLS) and mutated (Jurkat) p53 tumor suppressor. This observation is clinically relevant because Tau-Cl is used in many animal inflammatory models and its sodium salt (used in this study) has been introduced to human therapy (Gottardi and Nagl, 2002; Teuchner et al., 2005).

Changes in composition of spider orb web sticky droplets with starvation and web removal, and synthesis of sticky droplet compounds

The sticky spiral of araneoid spider orb webs consists of silk fibers coated with adhesive droplets. The droplets contain a variety of low-molecular-mass compounds (LMM). Within a species, a fairly consistent ratio of LMM is often observed, but substantial variability can exist. To gain insight into factors influencing LMM composition, spiders of three araneid species were starved and LMM from their webs were analyzed for changes in composition. To determine if these changes were consistent with the spider's ability to synthesize the different organic LMM, synthetic capacities were estimated following the feeding of radiolabeled metabolites. Some changes in droplet composition were broadly consistent with differing synthetic capacities: molar percentages of less readily synthesized compounds (e.g. choline, isethionate, N-acetyltaurine) typically declined with starvation, at least during a portion of the imposed fast, while more readily synthesized compounds (e.g. GABamide, glycine) tended to increase. Most striking was the apparent partial substitution of N-acetylputrescine by the more readily synthesized GABamide in fasting Argiope trifasciata. However, departures from expected compositional shifts demonstrated that synthetic capacity alone does not adequately predict sticky droplet compositional shifts with starvation. Moreover, feeding controls exhibited some changes in composition similar to starving spiders. As the webs of both feeding and starving spiders were removed for chemical analysis and could not be recycled, the loss of LMM contained in these webs likely contributed to similarities between treatments. In addition, feeding spiders molted, oviposited and/or built heavier webs. The added metabolic demands of these activities may have contributed to changes in composition similar to those resulting from starvation.

N-acetyltaurine dissimilated via taurine by Delftia acidovorans NAT

The naturally occurring sulfonate N-acetyltaurine was synthesized chemically and its identity was confirmed. Aerobic enrichment cultures for bacteria able to utilize N-acetyltaurine as sole source of fixed nitrogen or as sole source of carbon were successful. One representative isolate, strain NAT, which was identified as a strain of Delftia acidovorans, grew with N-acetyltaurine as carbon source and excreted stoichiometric amounts of sulfate and ammonium. Inducible enzyme activities were measured in crude extracts of this organism to elucidate the degradative pathway. Cleavage of N-acetyltaurine by a highly active amidase yielded acetate and taurine. The latter was oxidatively deaminated by taurine dehydrogenase to ammonium and sulfoacetaldehyde. This key intermediate of sulfonate catabolism was desulfonated by the known reaction of sulfoacetaldehyde acetyltransferase to sulfite and acetyl phosphate, which was further degraded to enter central metabolism. A degradative pathway including transport functions is proposed.

Is Taurine A Biomarker?

Taurine, a sulfur-containing amino acid present in high concentrations in mammals, plays an important role in several essential biological processes. Taurine is not incorporated into protein and is the most abundant free amino acid in the heart, retina, skeletal muscle, brain, and leukocytes. The ideal biomarker or biological measure should be reliable, reproducible, noninvasive, simple to perform, and inexpensive. Samples for biological measures should be easily obtained from physiological fluids such as blood or urine. Taurine levels in physiologic fluids have been useful for both diagnosing pathology and establishing a disease modifying therapy. In the specific case of taurine, it is important that patient information include nutritional supplementation as well as information on disease status and medications. Taurine has been measured in biological fluids due to the importance of this simple amino acid and its relative ease of determination. Taurine has been measured in animal models of disease as well as a variety of human conditions. However, it remains unclear how taurine should be used as a biomarker and in which situations this measurement would be a good prognostic or diagnostic indicator.

The sulfonated osmolyte N-methyltaurine is dissimilated by Alcaligenes faecalis and by Paracoccus versutus with release of methylamine

Selective enrichments yielded bacterial cultures able to utilize the osmolyte N-methyltaurine as sole source of carbon and energy or as sole source of fixed nitrogen for aerobic growth. Strain MT1, which degraded N-methyltaurine as a sole source of carbon concomitantly with growth, was identified as a strain of Alcaligenes faecalis. Stoichiometric amounts of methylamine, whose identity was confirmed by matrix-assisted, laser-desorption ionization time-of-flight mass spectrometry, and of sulfate were released during growth. Inducible N-methyltaurine dehydrogenase, sulfoacetaldehyde acetyltransferase (Xsc) and a sulfite dehydrogenase could be detected. Taurine dehydrogenase was also present and it was hypothesized that taurine dehydrogenase has a substrate range that includes N-methyltaurine. Partial sequences of a tauY-like gene (encoding the putative large component of taurine dehydrogenase) and an xsc gene were obtained by PCR with degenerate primers. Strain N-MT utilized N-methyltaurine as a sole source of fixed nitrogen for growth and could also utilize the compound as sole source of carbon. This bacterium was identified as a strain of Paracoccus versutus. This organism also expressed inducible (N-methyl)taurine dehydrogenase, Xsc and a sulfite dehydrogenase. The presence of a gene cluster with high identity to a larger cluster from Paracoccus pantotrophus NKNCYSA, which is now known to dissimilate N-methyltaurine via Xsc, allowed most of the overall pathway, including transport and excretion, to be defined. N-Methyltaurine is thus another compound whose catabolism is channelled directly through sulfoacetaldehyde.

N,N-Dichlorotaurine: Chemical and Bactericidal Properties

The biogenous antimicrobial agent N-chlorotaurine (NCT) converts by disproportionation to N,N-dichlorotaurine (NDCT) at a rate proportional to acidity. This occurs at appreciable amounts already in weakly acidic biological systems. To understand the consequences of NDCT formation, a thorough investigation of this undescribed compound was mandatory, which needed its synthesis. Differently from NCT, this was possible in the aqueous system using trichloroisocyanuric acid. While the free acid, Cl(2)HNCH(2)CH(2)SO(3)H, was not available in pure form, its sodium and potassium salts were analytically pure and showed melting points (decomposition) of 125-128 degrees C (potassium) and 162-164 degrees C (sodium). The sodium salt demonstrated unexpected long-term stability even at room temperature (8.4 % loss of activity within 4 months). The aqueous solutions of both salts exhibited a weak acid reaction, and they were less stable than NCT. With regard to chlorination of amines (transhalogenation), NDCT was, surprisingly, less efficacious than NCT, which manifested itself by a lack of reactivity at pH < 7, for which a mechanistic explanation is given. Compared on a molar scale, NDCT was more bactericidal than NCT against the gram-negative bacteria E. coli, P. aeruginosa and P. mirabilis, while there was no difference concerning the gram-positive ones, S. aureus and S. epidermidis. The increase of bactericidal activity at acidic pH was the same as observed with NCT and is attributed to a higher susceptibility of bacteria in this environment. Taken together, NDCT seems not to be suited to substitute NCT as a preparation fit for medical practice.

Sulfoacetaldehyde is excreted quantitatively by Acinetobacter calcoaceticus SW1 during growth with taurine as sole source of nitrogen

Eighteen enrichment cultures with taurine (2-aminoethanesulfonate) as the sole source of combined nitrogen under aerobic conditions were all successful, and 24 pure cultures were obtained. Only three of the cultures yielded an inorganic product, sulfate, from the sulfonate moiety of taurine, and the others were presumed to yield organosulfonates. Sulfoacetate, known from Rhodopseudomonas palustris CGA009 under these conditions, was not detected in any culture, but sulfoacetaldehyde (as a hydrazone derivative) was tentatively detected in the outgrown medium of nine isolates. The compound was stable under these conditions and the identification was confirmed by MALDI-TOF-MS. Most sulfoacetaldehyde-releasing isolates were determined to be strains of Acinetobacter calcoaceticus, and a representative organism, strain SW1, was chosen for further work. A quantitative enzymic determination of sulfoacetaldehyde and its bisulfite addition complex was developed: it involved the NAD-coupled sulfoacetaldehyde dehydrogenase from R. palustris. A. calcoaceticus SW1 utilized taurine quantitatively and concomitantly with growth in, for example, an adipate-salts medium, and the release of sulfoacetaldehyde was stoichiometric. The deamination reaction involved a taurine dehydrogenase. Enrichment cultures to explore the possible release of organophosphonates from the analogous substrate, 2-aminoethanephosphonate, led to 33 isolates, all of which released inorganic phosphate quantitatively.

Dissimilation of cysteate via 3-sulfolactate sulfo-lyase and a sulfate exporter in Paracoccus pantotrophus NKNCYSA

Paracoccus pantotrophusNKNCYSA utilizes (R)-cysteate (2-amino-3-sulfopropionate) as a sole source of carbon and energy for growth, with either nitrate or molecular oxygen as terminal electron acceptor, and the specific utilization rate of cysteate is about 2 mkat (kg protein)−1. The initial degradative reaction is catalysed by an (R)-cysteate : 2-oxoglutarate aminotransferase, which yields 3-sulfopyruvate. The latter was reduced to 3-sulfolactate by an NAD-linked sulfolactate dehydrogenase [3·3 mkat (kg protein)−1]. The inducible desulfonation reaction was not detected initially in cell extracts. However, a strongly induced protein with subunits of 8 kDa (α) and 42 kDa (β) was found and purified. The corresponding genes had similarities to those encoding altronate dehydratases, which often require iron for activity. The purified enzyme could then be shown to convert 3-sulfolactate to sulfite and pyruvate and it was termed sulfolactate sulfo-lyase (Suy). A high level of sulfite dehydrogenase was also induced during growth with cysteate, and the organism excreted sulfate. A putative regulator, OrfR, was encoded upstream ofsuyABon the reverse strand. Downstream ofsuyABwassuyZ, which was cotranscribed withsuyB. The gene, an allele oftauZ, encoded a putative membrane protein with transmembrane helices (COG2855), and is a candidate to encode the sulfate exporter needed to maintain homeostasis during desulfonation.suyAB-like genes are widespread in sequenced genomes and environmental samples where, in contrast to the current annotation, several presumably encode the desulfonation of 3-sulfolactate, a component of bacterial spores.

Differential effects on innate versus adaptive immune responses by WF10

Oxidative compounds that are physiologically generated in vivo can induce natural defense mechanisms to enhance the elimination of pathogens and to limit inflammatory tissue damage in the course of inflammation. Here, we have investigated WF10, a chlorite-based non-toxic compound for its functional activities on human PBMC in vitro. WF10 exerts potent immune-modulatory effects through generating endogenous oxidative compounds such as taurine chloramine. Proliferation and IL-2 production of anti-CD3 stimulated PBMC were inhibited by WF10, as was the nuclear translocation of the transcription factor NFATc. In PBMC and monocytes, however, WF10 induced pro-inflammatory cytokines like IL-1beta, IL-8, and TNF-alpha. In the monocytic cell line THP-1, the activation of the transcription factors AP-1 and NFkappaB by WF10 was demonstrated. Inhibition of NFAT regulated genes in activated lymphocytes in concert with the induction of several myeloid cell associated pro-inflammatory genes in monocytes represents a novel mechanism of immune modulation.

Rhodococcus opacus expresses the xsc gene to utilize taurine as a carbon source or as a nitrogen source but not as a sulfur source

The Gram-positive bacteria Rhodococcus opacus ISO-5 and Rhodococcus sp. RHA1 utilized taurine (2-aminoethanesulfonate) as the sole source of carbon or of nitrogen or of sulfur for growth. Different gene clusters and enzymes were active under these different metabolic situations. Under carbon- or nitrogen-limited conditions three enzymes were induced, though to different levels: taurine-pyruvate aminotransferase (Tpa), alanine dehydrogenase (Ald) and sulfoacetaldehyde acetyltransferase (Xsc). The specific activities of these enzymes in R. opacus ISO-5 were sufficient to explain the growth rates under the different conditions. These three enzymes were purified and characterized, and the nature of each reaction was confirmed. Analyses of the genome of Rhodococcus sp. RHA1 revealed a gene cluster, tauR-ald-tpa, putatively encoding regulation and oxidation of taurine, located 20 kbp from the xsc gene and separate from two candidate phosphotransacetylase (pta) genes, as well as many candidate ABC transporters (tauBC). PCR primers allowed the amplification and sequencing of the tauR-ald-tpa gene cluster and the xsc gene in R. opacus ISO-5. The N-terminal sequences of the three tested proteins matched the derived amino acid sequences of the corresponding genes. The sequences of the four genes found in each Rhodococcus strain shared high degrees of identity (>95 % identical positions). RT-PCR studies proved transcription of the xsc gene when taurine was the source of carbon or of nitrogen. Under sulfur-limited conditions no xsc mRNA was generated and no Xsc was detected. Taurine dioxygenase (TauD), the enzyme catalysing the anticipated desulfonative reaction when taurine sulfur is assimilated, was presumed to be present because oxygen-dependent taurine disappearance was demonstrated with taurine-grown cells only. A putative tauD gene (with three other candidates) was detected in strain ISO-5. Regulation of the different forms of metabolism of taurine remains to be elucidated.

Is taurine beneficial in reducing risk factors for diabetes mellitus?

Taurine is a semiessential amino acid, and its deficiency is involved in retinal and cardiac degenerations. In recent years, it was found that diabetes mellitus (DM) is associated with taurine, and many in vivo experimental studies showed that taurine administration is able to reduce the alterations induced by DM in the retina, lens, and peripheral nerve, although its effects on diabetic kidney are dubious. Interestingly, long-term taurine supplementation reduces the mortality rate in diabetic rats. The mechanisms by which taurine exerts beneficial effects in DM are discussed below. Recently, it has been suggested that taurine deficiency may alter the endocrine pancreas "fetal programming," increasing the risk of insulin resistance in adult life. The bulk of experimental data suggests that taurine administration could be useful in the treatment of type 1 DM and in the prevention of insulin resistance.

Enzymes and genes of taurine and isethionate dissimilation in Paracoccus denitrificans

Growth of the alpha-proteobacterium Paracoccus denitrificans NKNIS with taurine or isethionate as sole source of carbon involves sulfoacetaldehyde acetyltransferase (Xsc), which is presumably encoded by an xsc gene in subgroup 3, none of whose gene products has been characterized. The genome of the alpha-proteobacterium Rhodobacter sphaeroides 2.4.1 was interpreted to contain a nine-gene cluster encoding the inducible dissimilation of taurine, and this deduced pathway included a regulator, a tripartite ATP-independent transporter, taurine dehydrogenase (TDH; presumably TauXY) as well as Xsc (subgroup 3), a hypothetical protein and phosphate acetyltransferase (Pta). A similar cluster was found in P. denitrificans NKNIS, in contrast to an analogous cluster encoding an ATP-binding cassette transporter in Paracoccus pantotrophus. Inducible TDH, Xsc and Pta were found in extracts of taurine-grown cells of strain NKNIS. TDH oxidized taurine to sulfoacetaldehyde and ammonium ion with cytochrome c as electron acceptor. Whereas Xsc and Pta were soluble enzymes, TDH was located in the particulate fraction, where inducible proteins with the expected masses of TauXY (14 and 50 kDa, respectively) were detected by SDS-PAGE. Xsc and Pta were separated by anion-exchange chromatography. Xsc was effectively pure; the molecular mass of the subunit (64 kDa) and the N-terminal amino acid sequence confirmed the identification of the xsc gene. Inducible isethionate dehydrogenase (IDH), Xsc and Pta were assayed in extracts of isethionate-grown cells of strain NKNIS. IDH was located in the particulate fraction, oxidized isethionate to sulfoacetaldehyde with cytochrome c as electron acceptor and correlated with the expression of a 62 kDa protein. Strain NKNIS excreted sulfite and sulfate during growth with a sulfonate and no sulfite dehydrogenase was detected. There is considerable biochemical, genetic and regulatory complexity in the degradation of these simple molecules.

Taurine prevents streptozotocin impairment of hormone-stimulated glucose uptake in rat adipocytes

Streptozotocin-treated rats were used as models of type 1 diabetes to study the effects of dietary taurine on insulin- and adrenergic-stimulated 2-deoxyglucose uptake by isolated adipocytes. In addition to the well-established impairment of basal and insulin-stimulated 2-deoxyglucose uptakes in adipocytes prepared from streptozotocin-diabetic rats, the alpha-(phenylephrine) and beta-(isoproterenol) adrenergic stimulations of glucose uptake were also abolished. The insulin stimulation of glucose uptake in adipocytes was selectively abolished by the phosphatidylinositol 3-kinase inhibitor wortmannin, whereas that by the adrenergic agonists, phenylephrine and isoproterenol, was inhibited by prazosin and propranolol, respectively. Dietary taurine, 4 weeks before and 4 weeks after streptozotocin administration, prevented the loss of both insulin and adrenergic agonist stimulations of 2-deoxyglucose uptake, without affecting hyperglycaemia. Because insulin and adrenergic activations of glucose transport by adipocytes are coupled to different signalling pathways, it is unlikely that these effects of taurine are related to these disparate postreceptor mechanisms.

Biological and dietary antioxidants protect against DNA nitration induced by reaction of hypochlorous acid with nitrite

Nitryl chloride, formed by reaction of hypochlorous acid with nitrite, might contribute to nitrative damage of biomolecules in addition to peroxynitrite. Damage of DNA by these reactive nitrogen oxide species is implicated in carcinogenesis associated with chronic infections and inflammation. Nitrated DNA adducts, such as 8-nitroguanine and 8-nitroxanthine, are not stable in DNA since they undergo spontaneous depurination, leading to apurinic site formation. In this report, we investigate the protective effect of biological and dietary antioxidants in inhibiting DNA nitration induced by nitryl chloride. The effect of inhibition was evaluated by decrease of 8-nitroxanthine and 8-nitroguanine formation. Among the 21 compounds examined, dihydrolipoic acid is the most effective in preventing DNA nitration, followed by N-acetyl-L-cysteine and folic acid. For sulfur-containing compounds, the more highly reduced compounds are stronger inhibitors of DNA nitration. The major product of N-acetyl-L-cysteine reaction with nitryl chloride is characterized as the (R)-2-acetylamino-3-sulfopropionic acid, a physiologically irreversible product, suggesting that nitryl chloride is a strong oxidizing agent.

Sulphoacetaldehyde acetyltransferase yields acetyl phosphate: purification from Alcaligenes defragrans and gene clusters in taurine degradation

The facultatively anaerobic bacterium Alcaligenes defragrans NKNTAU was found to oxidize taurine (2-aminoethanesulphonate) with nitrate as the terminal electron acceptor. Taurine was transaminated to 2-sulphoacetaldehyde. This was not converted into sulphite and acetate by a "sulphoacetaldehyde sulpho-lyase" (EC 4.4.1.12), but into sulphite and acetyl phosphate, which was identified by three methods. The enzyme, which required the addition of phosphate, thiamin diphosphate and Mg(2+) ions for activity, was renamed sulphoacetaldehyde acetyltransferase (Xsc; EC 2.3.1.-). Inducible Xsc was expressed at high levels, and a three-step 11-fold purification yielded an essentially homogeneous soluble protein, which was a homotetramer in its native form; the molecular mass of the subunit was found to be between about 63 kDa (SDS/PAGE) and 65.3 kDa (matrix-assisted laser-desorption ionization-time-of-flight MS). The N-terminal and two internal amino acid sequences were determined, and PCR primers were generated. The xsc gene was amplified and sequenced; the derived molecular mass of the processed protein was 65.0 kDa. The downstream gene presumably encoded the inducible phosphate acetyltransferase (Pta) found in crude extracts. The desulphonative enzymes ("EC 4.4.1.12") from Achromobacter xylosoxidans NCIMB 10751 and Desulfonispora thiosulfatigenes GKNTAU were shown to be Xscs. We detected at least three subclasses of xsc in Proteobacteria and in Gram-positive bacteria, and they comprised a distinct group within the acetohydroxyacid synthase supergene family. Genome sequencing data revealed xsc genes in Burkholderia fungorum (80% sequence identity) and Sinorhizobium meliloti (61%) with closely linked pta genes. Different patterns of regulation for the transport and dissimilation of taurine were hypothesized for S. meliloti and B. fungorum.

Cytoprotective effect of taurine against hypochlorous acid toxicity to PC12 cells

Taurine has been shown to be an effective scavenger of hypochlorous acid (HOCl). The role of HOCl is well established in tissue damage associated with reperfusion injury mediated by neutrophils. The role of HOCl in CNS injury and inflammatory reactions has not been well established. Myeloperoxidase activity is present in the CNS and it has been associated with ischemic injury. The aim of the present study was to determine the cytotoxicity of HOCl in a neuronal cell line (PC12) and the ability of taurine to prevent or reverse neurotoxicity. PC12 cells were grown in 96 well plates at a plating density of approximately 100,000 cells per well. HOCl was made up fresh from NaOCl for each experiment and the concentration verified spectrophotometrically. PC12 cells were exposed to HOCl for 1 hour in phosphate-buffered saline. Taurine was added at the time of HOCl treatment and in some experiments a post-treatment with taurine was performed by adding 1 or 10 mM taurine to the culture media (RPMI 1640). The cells were allowed 24 hours to recover and viability was determined using a tetrazolium-based (MTT) assay. The first series of experiments evaluated the toxicity of HOCl and the efficacy of taurine to protect PC12 cells. HOCl at 50 microM reduced PC12 cell viability by 50% and 150 microM reduced viability to <25% of control levels. Taurine (0.5-20 mM) was tested for cytoprotection against 150 microM HOCl and PC12 cells treated with 0.5 mM taurine exhibited only a 20% reduction in viability compared to untreated controls. Taurine concentrations of 1 mM or higher provided nearly 100% protection against HOCl. A second study was performed comparing taurine to beta-alanine, glutathione and isethionic acid. HOCl (100 microM) reduced viability to 25 +/- 1% of controls and taurine, beta-alanine and glutathione at 1 mM provided nearly complete protection. In contrast, isethionic acid, which lacks an amino group, failed to provide protection. Taurine (1 or 10 mM) added after 50 microM HOCl treatment did not provide any protection and PC12 cell viability was reduced to <39% of controls. In contrast, if taurine (50 microM) was present during the HOCl treatment and 1 mM taurine was added after the treatment, PC12 cell viability was 80 +/- 5% of controls. A combination of 250 microM taurine during the HOCl treatment and 1 mM taurine post-treatment produced 100% protection. These results clearly show that taurine is an efficient scavenger of HOCl and can prevent neuronal damage caused by HOCl. Since myeloperoxidase expression in the CNS is increased by ischemia, one function of taurine released during an ischemic event may be to scavenge HOCl and provide neuroprotection.