Formation Pathways and Trade-Offs between Haloacetamides and Haloacetaldehydes during Combined Chlorination and Chloramination of Lignin Phenols and Natural Waters.

In vitro bioassays have indicated that haloacetamides and haloacetaldehydes exhibit the highest cytotoxicity among DBP classes. Previous research has focused on their potential formation from the chlorination or chloramination of aliphatic compounds, particularly nonaromatic amino acids, and acetaldehyde. The present work found that acetaldehyde served as a relatively poor precursor for trichloroacetaldehyde and dichloroacetamide, generally the most prevalent of the haloacetaldehydes and haloacetamides, during chlorination or chlorination/chloramination. Using phenolic model compounds, particularly 4-hydroxybenzoic acid, as models for structures in humic substances, we found significantly higher formation of trichloroacetaldehyde and dichloroacetamide from prechlorination followed by chloramination. Evaluation of the stoichiometry of chlorine reactions with 4-hydroxybenzoic acid and several intermediates indicated that seven successive Cl[+1] transfers, faster with chlorination than chloramination, can form 2,3,5,5,6-pentachloro-6-hydroxy-cyclohexa-2-ene-1,4-dione via chlorophenol and chlorobenzoquinone intermediates. Formation of 2,3,5,5,6-pentachloro-6-hydroxy-cyclohexa-2-ene-1,4-dione may serve as a key branching point, with chloramines promoting the formation of dichloroacetamide and chlorination promoting the formation of trichloroacetaldehyde. The behavior of 4-hydroxybenzoic acid with respect to yields of dichloroacetamide and trichloroacetaldehyde during chlorination followed by chloramination was similar to the behavior observed for model humic acids and several surface waters, suggesting that phenolic structures in natural waters may serve as the predominant, and common pool of precursors for haloacetamides and haloacetaldehydes. Experiments with natural waters indicated that the branching point is reached over prechlorine exposures (100-500 mg-min/L) relevant to drinking water utilities using chlorine as a primary disinfectant and chloramines for maintenance of a distribution system residual.

Formation and control of disinfection by-products during the trichloroisocyanuric acid disinfection in swimming pool water.

The increasing demand for trichloroisocyanuric acid (TCCA) in swimming pool disinfection highlights the need to evaluate its applicability in terms of disinfection by-product (DBP) formation. Nevertheless, there is limited understanding of DBP formation and control during TCCA disinfection, particularly concerning the effects of various management parameters. This study aimed to fill this knowledge gap by comprehensively investigating DBP formation during TCCA chlorination, with a particular focus on assessing the contribution and interaction of influencing factors using Box-Behnken Design and response surface methodology. Results indicated that the concentrations of trichloroacetaldehyde, chloroform, dichloroacetic acid, trichloroacetic acid, and dichloroacetonitrile produced by TCCA disinfectant were 42.5%, 74.0%, 48.1%, 94.7% and 42.6% of those by the conventional sodium hypochlorite disinfectant, respectively. Temperature exhibited the most significant impact on chloroform formation (49%), while pH played a major role in trichloroacetaldehyde formation (44%). pH2 emerged as the primary contributor to dichloroacetic acid (90%) and trichloroacetic acid (93%) formation. The optimum water quality conditions were determined based on the minimum total DBPs (pH = 7.32, Temperature = 23.7 °C, [Cl-] = 437 mg/L). Chlorine dosage and contact time exhibited greater influence than precursor concentration on chloroform, dichloroacetonitrile, trichloroacetaldehyde, trichloroacetic acid, and total DBPs. Although the interaction between water quality parameters was weak, the interaction between disinfection operating parameters demonstrated substantial effects on DBP formation (8.56-19.06%). Furthermore, the DBP predictive models during TCCA disinfection were provided for the first time, which provides valuable insights for DBP control and early warning programs.

Adsorption and hydrolysis of alcohols and carbonyls on ice at temperatures of the upper troposphere.

The uptake of gaseous ethanol, 1,1,1-trifluoroethanol, acetone, chloral (CCl(3)CHO), and fluoral (CF(3)CHO) on ice films has been investigated using a coated-wall flow tube at temperatures 208-228 K corresponding to the upper troposphere (UT), with a mass spectrometric measurement of gas concentration. The uptake was largely reversible and followed Langmuir-type kinetic behavior, i.e., surface coverage increased with the trace gas concentration approaching a maximum surface coverage at a gas phase concentration of N(max) ∼ (2-4) × 10(14) molecules cm(-3), corresponding to a surface coverage of ∼30% of a monolayer (ML). The equilibrium partition coefficients, K(LinC), were obtained from the experimental data by analysis using the simple Langmuir model for specific conditions of temperature and concentration. The analysis showed that the K(LinC) depend only weakly on surface coverages. The following expressions described the temperature dependence of the partition coefficients (K(LinC)) in centimeters, at low coverage for ethanol, trifluoroethanol, acetone, chloral, and fluoral: K(LinC) = 1.36 × 10(-11) exp(5573.5/T), K(LinC) = 3.74 × 10(-12) exp(6427/T), K(LinC) = 3.04 × 10(-9) exp(4625/T), K(LinC) = 7.52 × 10(-4) exp(2069/T), and K(LinC) = 1.06 × 10(-2) exp(904/T). For acetone and ethanol the enthalpies and entropies of adsorption derived from all available data showed systematic temperature dependence, which is attributed to temperature dependent surface modifications, e.g., QLL formation. For chloral and fluoral, there was an irreversible component of uptake, which was attributed to hydrate formation on the surface. Rate constants for these surface reactions derived using a Langmuir-Hinshelwood mechanism are reported.

Visual signal sensor coupling to nitrification for sustainable monitoring of trichloroacetaldehyde and the response mechanisms.

In this work, a toxicity monitoring microbial system (TMMS) with a nitrifying biofilm as a sensing element and cathode oxygen reduction as an electrical signal was successfully constructed for trichloroacetaldehyde (TCAL) detection. The current and nitrification rate showed a linear relationship with TCAL concentration from 0 to 100 µg/L (R2current = 0.9892, R2nitrification = 0.9858), indicating that the target substrate concentration can be directly obtained from an electrical signal without further sample concentration. High-throughput sequencing revealed that the TMMS was composed of autotrophic/heterotrophic nitrifying and denitrifying microorganisms. Further analysis via a symbiotic relationship network demonstrated that unclassified_Comamonadaceae and unclassified_Xanthobacteraceae were the core nodes for maintaining the interaction between autotropic and heterotrophic nitrifying bacteria. Kyoto Encyclopedia of Genes and Genomes analysis showed that the electron transfer process primarily relied on ferredoxin and cytochromes under TCAL stress, and the abundance of functional enzymes involved in the process of nitrification was decreased, resulting in changes in electrical signal output. This work explored a visual signal sensor combined with electrochemistry and autotrophic/heterotrophic nitrification, which provided new insights into recognition and response mechanisms for microbial monitoring of toxic substances.

Iron foam coupled hydrolysis acidification for trichloroacetaldehyde treatment: Strengthening characteristics and mechanism.

This research studied transformative characteristics and enhanced mechanism of trichloroacetaldehyde (TCAL), one of chlorinated acetaldehydes (CAAs), by coupled-type iron foam enhanced hydrolysis acidification (HA) reactor. Main results were given that better dechlorination and aldehyde removal were achieved at this process than coupled-type iron foam enhanced HA, alone iron foam and HA reactor. The reasons were due to better strengthening effects of iron foam and HA, iron foam reduced TCAL toxicity to microbes caused an improvement of microbial activity, therefore, volatile fatty acids (VFAs) content and acetate acid (Ac) ratio were increased compared with HA. Moreover, it promoted the enrichment of Actinobacteriota and Firmicutes, and more extracellular polymeric substance (EPS) and enzymes enhanced dechlorination and aldehyde removal. Certainly, microbes reduced iron foam passivation and facilitated its oxidation further improved the strengthening effect.

Occurrence and fate of ozonation disinfection by-products in two Canadian drinking water systems.

The occurrence and the fate of 18 ozonation by-products (OBPs) (17 different aldehydes and bromate) were studied over one year in two Canadian drinking water systems. This is the first and only study reporting the occurrence of all these non-halogenated aldehydes (NON-HALs) and haloacetaldehydes (HALs) simultaneously, based on the multi-point monitoring of water in full-scale conditions from source to distribution network. In general, the application of both post-ozonation and liquid chlorine contributed to the formation of OBPs (aldehydes and bromate). NON-HALs were present in higher concentrations than HALs. Formaldehyde, acetaldehyde, glyoxal and methylglyoxal were the most common forms of NON-HALs in the two water systems that were studied. Chloral hydrate (CH), the hydrated form of trichloroacetaldehyde, was the most dominant HAL observed. The nature of the organic matter and the water temperature proved to be important parameters for explaining the variability of aldehydes. Summer and autumn (warm seasons) were more favorable for the formation of chloral hydrate and bromate. The highest concentrations of NON-HALs were observed in spring.

Inhibition and removal of trichloroacetaldehyde by biological acidification with glucose co-metabolism.

Biological acidification plays a crucial role in biological removal of organic compounds during petrochemical wastewater treatment. Trichloroacetaldehyde is a typical organic pollutant in petrochemical wastewater, however, no studies have been conducted on its effect on biological acidification. In this study, batch bioassays of volatile fatty acids were conducted to explore the inhibitory effect of trichloroacetaldehyde on biological acidification, the variations of key enzymes and extracellular polymeric substances under trichloroacetaldehyde shock, and the mechanism of trichloroacetaldehyde removal. The results of these bioassays indicated that trichloroacetaldehyde inhibited the acid yield at higher concentrations (EC50 112.20 mg/L), and butyric fermentation was predominant. Moreover, the contents of extracellular polymeric substances and several key acidifying enzymes greatly decreased when the trichloroacetaldehyde concentration exceeded 100 mg/L, which was due to the toxicity that trichloroacetaldehyde poses to the microbes involved in biological acidification. The trichloroacetaldehyde mechanism was as follows: first, trichloroacetaldehyde was adsorbed by extracellular polymeric substances and anaerobic granular sludge, and then transformed into trichloroethanol, trichloroethane, dichloroacetaldehyde, and dichloroethanol under the combined action of the aldehyde reductase and reductive dehalogenases secreted from the microbial consortium. The ability of biological acidification to remove trichloroacetaldehyde was limited; therefore, trichloroacetaldehyde should be pretreated before it enters biological treatment systems.

500 days of swimmers: the chemical water quality of swimming pool waters from the beginning.

Many studies of disinfection by-products (DBPs) in pools have focused on haloacetic acids, trihalomethanes, and chloramines, with less studies investigating the occurrence of other DBPs, such as haloketones, haloacetaldehydes, haloacetonitriles, halonitromethanes, and haloacetamides. Furthermore, while many studies have achieved a broadscreen analysis across several pools, fewer studies have followed the water quality of pools over time, with information regarding the production and fate of DBPs in pools over extended periods (e.g. > 1 year) being limited. This study reports the occurrence of 39 DBPs and several general water quality parameters in two newly built and filled swimming pools over 15 months, where investigations began prior to opening. DBP concentrations measured in this study were generally similar to or higher than those previously reported in chlorinated pools, with concentrations of chloroacetic acid, dichloroacetic acid, trichloroacetic acid, and chloral hydrate (trichloroacetaldehyde) in some samples being higher than previously reported maximum concentrations. Considering both pools, lower concentrations of DBPs were measured in the pool where a steady state non-purgeable organic carbon concentration was achieved, highlighting the importance of the establishment of a steady state balance of mineralisation versus addition of organic carbon to reduce precursors for DBP formation in pools. Pools were found to exhibit significantly higher estimated cytotoxicity than their filling water, which reflects the significantly higher concentrations of DBPs measured in the pools in comparison to the filling water. Chloral hydrate accounted for up to 99% the total estimated cytotoxicity and was found to be correlated to the number of pool entries, suggesting that swimmers may be a potential source of chloral hydrate precursors in pools. The presence and subsequent peak of non-purgeable organic carbon and DBPs prior to, and soon after, opening suggest that the building process and/or new pool infrastructure may have had a significant impact on the chemical water quality, particularly on DBP formation. This study includes the first quantification of bromochloroacetaldehyde, bromodichloroacetaldehyde, bromochloronitromethane, and dichloronitromethane in chlorinated swimming pools, and provides important new knowledge on the long-term trends of DBPs in pools.

Yield of trihalomethane, haloacetic acid and chloral upon chlorinating algae after coagulation-filtration: Is pre-oxidation necessarily negative for disinfection by-product control?

Effect of pre-chlorination and pre-ozonation on Microcystis aeruginosa (MA) and Coccomyxa subellipsoidea (CS) as disinfection by-products (DBPs) precursors was investigated after coagulation-filtration. Pre-chlorination considerably decreased the autofluorescence of algae cells but barely influenced cell granularity. In comparison, after pre-ozonation more algae cells were associated with decreased cell size; yet less reduction in the autofluorescence was observed. In MA case, pre-chlorination increased the residual algae density after coagulation-filtration by 132%-146% while pre-ozonation enhanced the algae removal by 26%-28%. In CS case, algae removal was improved by pre-chlorination (32%-45%) and pre-ozonation (7%-45%). Pre-chlorination enhanced the removal of algogenic organic matters (AOM) by coagulation-filtration, especially for tryptophan-like and soluble microbial products. Effect of pre-ozonation on the fluorescence intensity of AOM after coauglation-filtration depended on AOM species and the ratio of [ozone dose]:[algae density]. In both MA and CS cases, chlorine increased the yields of trihalomethane (THM, 25%-78% and 51%-103%), haloacetic acid (HAA, 140%-360% and 167%-233%) and chloral (50%-161% and 68%-108%), respectively. Pre-ozonation decreased the total DBPs yields. For MA-added suspensions, ozone decreased the production of THM, HAA and chloral by 15%-37%, 28%-39% and 60%, respectively. In CS case, chloral yield was decreased by 12%-31% while THM formation was largely unchanged. HAA production varied by ± 1.5 µg/L.

Effect of trichloroacetaldehyde on the activation of CD4+T cells in occupational medicamentosa-like dermatitis: An in vivo and in vitro study.

Occupational medicamentosa-like dermatitis induced by trichloroethylene (OMLDT) is a hypersensitivity disease with autoimmune liver injury, which has increasingly become a serious occupational health problem in China. However, the pathogenesis of OMLDT remained undefined. In this study, 30 TCE-induced OMLDT patients, 58 exposure controls, and 40 non-exposure controls were recruited. We showed that the ratio of activated CD4+ T cells (downregulation of CD62 L) was dramatically increased in OMLDT patients compared to exposure and non-exposure control, suggesting that CD4+ T cells activation was a key cellular event in the development of OMLDT. In parallel, the expression of cytokine including IL-2, IFN-γ, TNF-α and IL-17A were increased obviously and IL-4 decreased in CD4+ T cells from OMLDT patients. in vitro assay, we found that trichloroethylene metabolites trichloroacetaldehyde (TCAH), not trichloroacetic acid (TCA) or Trichloroethanol (TCOH) could activate the naïve CD4+ T cells characterized by a rise in intracellular calcium, down-regulated CD62 L and subsequently trigger the secretion of IL-2, IFN-γ and TNF-α. Notably, the phosphorylation status of NF-κB and p38MAPK were elevated in OMLDT patients. Moreover, TCAH also could activate the p38MAPK and NF-κB, suggesting the role of p38MAPK and NF-κB pathways in the activation of CD4+ T cells. In addition, we found that the inhibition of Schiff base formation decreased the ability of TCAH to induce the activation of naïve CD4+ T cells and p38MAPK and NF-κB pathway. In conclusion, we revealed that the CD4+ T activation and increased the cytokines including IL-2, IFN-γ and TNF-α but decreased IL-4 in CD4+ T cells were associated with OMLDT. TCAH could activate naïve CD4+ T cells through NF-κB and p38MAPK activation induced by Schiff base formation, which might contribute to the development of OMLDT. These findings provide a new insight into the pathogenesis of OMLDT.

Chronic exposure to a trichloroethylene metabolite in autoimmune-prone MRL+/+ mice promotes immune modulation and alopecia.

The industrial solvent trichloroethylene (TCE) is a widespread environmental contaminant known to impact the immune system. In the present study, female MRL+/+ mice were treated for 40 weeks with trichloroacetaldehyde hydrate (TCAH), a metabolite of TCE, in the drinking water. The results were compared with the data from an earlier study in which MRL+/+ mice were exposed to TCAH for 4 weeks. Following a 40-week exposure, the mice developed skin inflammation and dose-dependent alopecia. In addition, TCAH appeared to modulate the CD4(+) T-cell subset by promoting the expression of an activated/effector (i.e., CD62L(lo)) phenotype with an increased capacity to secrete the proinflammatory cytokine interferon-gamma. However, unlike what was observed after only 4 weeks of exposure, TCAH did not significantly attenuate activation-induced cell death (AICD) or the expression of the death receptor FasL in CD4(+) T cells. Some metalloproteinases (MMPs) are thought to play a role in susceptibility to AICD by inducing FasL shedding. Thus, both the 4- and 40-week sera were tested for MMP-7 levels in an attempt to explain the disparate results of TCAH on AICD and FasL expression. Serum MMP-7 levels were significantly higher in mice exposed to TCAH for 4 weeks. In contrast, the serum MMP-7 levels were increased in all the mice by 40 weeks when compared with a nonautoimmune strain. Taken together, a chronic exposure to TCAH promotes alopecia and skin inflammation. The early effects of TCAH on MMP-7 levels may provide a mechanism by which TCAH promotes skin pathology.

Oxidative Stress Challenge Uncovers Trichloroacetaldehyde Hydrate-Induced Mitoplasticity in Autistic and Control Lymphoblastoid Cell Lines.

Mitoplasticity occurs when mitochondria adapt to tolerate stressors. Previously we hypothesized that a subset of lymphoblastoid cell lines (LCLs) from children with autistic disorder (AD) show mitoplasticity (AD-A), presumably due to previous environmental exposures; another subset of AD LCLs demonstrated normal mitochondrial activity (AD-N). To better understand mitoplasticity in the AD-A LCLs we examined changes in mitochondrial function using the Seahorse XF96 analyzer in AD and Control LCLs after exposure to trichloroacetaldehyde hydrate (TCAH), an in vivo metabolite of the environmental toxicant and common environmental pollutant trichloroethylene. To better understand the role of reactive oxygen species (ROS) in mitoplasticity, TCAH exposure was followed by acute exposure to 2,3-dimethoxy-1,4-napthoquinone (DMNQ), an agent that increases ROS. TCAH exposure by itself resulted in a decline in mitochondrial respiration in all LCL groups. This effect was mitigated when TCAH was followed by acute DMNQ exposure but this varied across LCL groups. DMNQ did not affect AD-N LCLs, while it neutralized the detrimental effect of TCAH in Control LCLs and resulted in a increase in mitochondrial respiration in AD-A LCLs. These data suggest that acute increases in ROS can activate mitochondrial protective pathways and that AD-A LCLs are better able to activate these protective pathways.

Chemical modification of human aldehyde dehydrogenase by physiological substrate.

Employing 3,4-dihydroxyphenylacetaldehyde (dopal) as a substrate for human aldehyde dehydrogenase (aldehyde:NAD+ oxidoreductase, EC 1.2.1.3) in anaerobic conditions, inactivation of both cytoplasmic E1 and mitochondrial E2 isozymes during catalysis has been observed. Incorporation of 14C-labelled dopal has been demonstrated by retention of label following denaturation and exhaustive dialysis and by peptide mapping following tryptic digestion. Incorporation of label gave linear plots vs. activity remaining with up to two molecules incorporated per molecule of enzyme and 30% activity remaining. Further incorporation (up to 16 molecules) occurred, but was non-linear when plotted vs. activity remaining. Protection against activity loss during incorporation of the first two molecules was afforded by NAD, NADH, chloral, and by chloral and NAD together, the last being the most effective. Saturation kinetics gave y-axis intercepts, suggesting interaction at a specific point on the enzyme surface. The Ki value from saturation kinetics was the same as that from the slope replot in catalytic reaction. Peptide mapping of tryptic digests showed that a single peptide was labelled, confirming specificity of interaction. Even in the absence of complete inactivation, the results suggest that reaction with the first two molecules occurs at some point on the enzyme surface important for enzyme activity. The possibility of such a reaction occurring in vivo is discussed.

Cardiac teratogenicity of trichloroethylene metabolites.

OBJECTIVES: The hypothesis of this study was that metabolites of trichloroethylene (TCE), dichloroethylene (DCE) and related compounds were responsible for fetal cardiac teratogenic effects seen when TCE or DCE is consumed by pregnant rats during organogenesis. Identification of teratogenic metabolites would allow more accurate assessment of environmental contaminants and public health risks from contaminated water or possibly municipal water supplies which, when chlorinated, may produce these potentially dangerous chemicals. BACKGROUND: Human epidemiologic studies and previous teratogenic studies using chick embryos and fetal rats have shown an increased incidence of congenital cardiac lesions in animals exposed to TCE and DCE. METHODS: Metabolites and compounds studied in drinking water exposure included: trichloroacetic acid (TCAA), monochloroacetic acid (MCAA), trichloroethanol (TCEth), carboxy methylcystine (CMC), trichloroacetaldehyde (TCAld), dichloroacetaldehyde (DCAld), and dichlorovinyl cystine (DCVC). Compounds were administered to pregnant rats during fetal heart development. RESULTS: Fetuses of rats receiving 2,730 ppm TCAA in drinking water were the only group that demonstrated a significant increase in cardiac defects (10.53%) compared with controls (2.15%) on a per fetus basis (p = 0.0001, Fischer's exact test), and a per litter basis (p = 0.0004, Wilcoxon and p = 0.0015, exact permutation tests). Trichloroacetic acid also demonstrated an increased number of implantation and resorption sites (p < 0.05) over controls. Other maternal and fetal variables showed no statistically significant differences between treated and untreated groups. CONCLUSIONS: Of the metabolites tested, only TCAA appeared to be a specific cardiac teratogen in the fetus when imbibed by the maternal rat.

Reversible segmental cerebral arterial vasospasm and cerebral infarction: possible association with excessive use of sumatriptan and Midrin.

OBJECTIVE: To describe a patient who developed reversible segmental cerebral arterial vasospasm and cerebral infarction while taking excessive amounts of sumatriptan succinate and a combination drug (Midrin) consisting of isometheptene mucate, 65 mg, dichloralphenazone, 100 mg, and acetaminophen, 325 mg. DESIGN: Case report. SETTING: Tertiary care center. PATIENT: A 43-year-old man who developed a left occipital infarct after taking a total of 23 sumatriptan succinate tablets (25 mg per tablet) and 32 Midrin tablets during a 7-day period and who on digital subtraction angiography was shown to have segmental cerebral arterial narrowing in multiple vessels. An extensive evaluation for other possible risk factors for cerebral infarction was unrevealing. MAIN OUTCOME AND RESULTS: Discontinuation of sumatriptan and Midrin regimens and administration of nicardipine hydrochloride led to nearly total resolution of the angiographic findings, and the patient had no recurrent strokes. CONCLUSIONS: One should consider the diagnosis of drug-induced vasospasm in patients with cerebral infarction and a history of excessive use of sumatriptan and Midrin. The initial angiographic abnormalities may resemble those found in patients with primary angiitis of the central nervous system.

Histamine-induced rise in core temperature of chloral-anaesthetized rats: mediation by H2-receptors located in the preopticus area of hypothalamus.

Intracerebroventricular (i.c.v.) administration of histamine in chloral anaesthetized rats exposed to an ambient temperature of 22 C elicited a rise in their colonic temperature associated with a shivering. This effect was shared by the H2 receptor agonists dimaprit and impromidine. Impromidine is, in this respect, a partial agonist with an ED50 much lower than histamine. The histamine-induced rise in core temperature was antagonized by cimetidine administered either centrally (in doses of 25-40 micrograms, i.c.v.) or peripherally (large doses greater than or equal to 50 mg/kg i.p.) This constitutes an indication for the crossing of the blood-brain barrier by cimetidine. The H2 histamine receptors involved in this effect seem to be located mainly in the preopticus medialis nucleus (p.o.m.n.) of the hypothalamus since bilateral microinjections of histamine (5 ng) into this nucleus induced the effect, whereas cimetidine injected into the p.o.m.n., antagonised the relative hyperthermia elicited by an intracerebroventricular administration of histamine.

Practical asymmetric synthesis of beta-trichloromethyl-beta-hydroxy ketones by the reaction of chloral or chloral hydrate with chiral imines.

[reaction: see text] Chloral or its hydrate undergoes the carbon-carbon bond-formation reaction with various optically active imines in the absence of any additive, followed by hydrolysis, to produce the corresponding beta-trichloromethyl-beta-hydroxy ketones in good yields with high enantioselectivities. In addition, the products with higher ee values were obtained by a simple recrystallization process.

Environmental contaminant and disinfection by-product trichloroacetaldehyde stimulates T cells in vitro.

It had been shown previously that MRL+/+ mice exposed to occupationally relevant doses of the environmental contaminant trichloroethylene in their drinking water developed lupus-like symptoms and autoimmune hepatitis in association with activation of Interferon-gamma (IFN-gamma)-producing CD4+ T cells. Since trichloroethylene must be metabolized in order to promote the T-cell activation associated with autoimmunity, the present study was initiated to determine whether the immunoregulatory effects of trichloroethylene could be mimicked by one of its major metabolites, trichloroacetaldehyde (TCAA). At concentrations ranging from 0.04 to 1 mM TCAA co-stimulated proliferation of murine T-helper type 1 (Th1) cells treated with anti-CD3 antibody or antigen in vitro. TCAA at similar concentrations also induced phenotypic alterations commensurate with activation (upregulation of CD28 and downregulation of CD62L) in both cloned memory Th1 cells, as well as naïve CD4+ T cells from MRL+/+ mice. TCAA-induced Th1 cell activation was accompanied by phoshorylation of activating transcription factor 2 (ATF-2) and c-Jun, two components of the activator protein-1 (AP-1) transcription factor. TCAA at higher concentrations was also shown to form a Schiff base on T cells, and inhibition of Schiff base formation suppressed the ability of TCAA to phosphorylate ATF-2. Taken together, these results suggest that TCAA promotes T-cell activation via stimulation of the mitogen-activated protein (MAP) kinase pathway in association with Schiff base formation on T-cell surface proteins. By demonstrating that TCAA can stimulate T-cell function directly, these results may explain how the environmental toxicant trichloroethylene promotes T-cell activation and related autoimmunity in vivo.

Catalysis of dehydrogenation of 4-trans-(N,N-dimethylamino)cinnamaldehyde by aldehyde dehydrogenase.

4-trans-(N,N-dimethylamino)cinnamaldehyde (DACA) is a chromophoric and fluorogenic substrate of aldehyde dehydrogenase. Fluorescence of DACA is enhanced by binding to aldehyde dehydrogenase in the absence of catalysis both in the presence and absence of the coenzyme analogue 5'AMP. DACA binds to aldehyde dehydrogenase with a dissociation constant of 1-3 microM and stoichiometry of 2 mol mol(-1) enzyme. Incorporation of DACA during catalysis was also investigated and found to be 2 mol DACA mol(-1) enzyme. Effect of pH on the stoichiometry of DACA incorporation during catalysis has shown that DACA incorporation remained constant at 2 mol DACA mol(-1) enzyme, despite a 74-fold velocity enhancement between pH 5.0 and 9.0. Increase of pH increased decomposition of enzyme-acyl intermediate without affecting the rate-limiting step of the reaction. At pH 7.0 the pH stimulated velocity enhancement was 10-fold over that at pH 5.0; further velocity enhancement (11.5-fold that of pH 7.0) was achieved by 150 microM Mg(2+) ions. The velocity at pH 7.0 with Mg(2+) exceeded that of pH 9.0, and that at maximal pH stimulation at pH 9.5. It was observed that level of intermediate decreased to about 1 mol mol(-1) enzyme, indicating that Mg(2+) ions increased the rate of decomposition of the enzyme-acyl intermediate and shifted the rate-limiting step of the reaction to another step in the reaction sequence.