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PubMedDate not supplied

Detection of benzene, toluene, ethyl benzene, and xylenes (BTEX) using toluene dioxygenase-peroxidase coupling reactions.

We have developed a simple, whole-cell bioassay for the detection of bioavailable benzene, toluene, ethyl benzene, and xylenes (BTEX) and similar compounds. A genetically engineered E. coli strain expressing toluene dioxygenase (TDO) and toluene dihydrodiol dehydrogenase (TodD) was constructed, enabling the conversion of BTEX into their respective catechols, which were quickly converted into colored products by a horseradish peroxidase (HRP)-coupled reaction. The intensity of the color formation was correlated to concentrations of the BTEX compounds. Under the optimized conditions, a detection limit (defined as three times the standard deviation of the response obtained from the blank) of 10, 10, 20, and 50 microM was observed for benzene, toluene, ethyl benzene, and xylene, respectively. The bioassay was selective toward BTEX-related compounds with no interference observed with commonly used pesticides, herbicides, and organic solvent. The bioassay was very stable with little change in response over a 10-week period. The excellent stability suggests that the reported bioassay may be suitable for field monitoring of BTEX to identify and track contaminated water and follow the bioremediation progress.

Benzene↗
PubMed2006

High pressure pyrolysis of toluene. 1. Experiments and modeling of toluene decomposition.

The pyrolysis of toluene, the simplest methyl-substituted aromatic molecule, has been studied behind reflected shock waves using a single pulse shock tube. Experiments were performed at nominal high pressures of 27 and 45 bar and spanning a wide temperature range from 1200 to 1900 K. A variety of stable species, ranging from small hydrocarbons to single ring aromatics (principal soot precursors such as phenylacetylene and indene) were sampled from the shock tube and analyzed using standard gas chromatographic techniques. A detailed chemical kinetic model with 262 reactions and 87 species was assembled to simulate the stable species profiles (specifically toluene, benzene and methane) from the current high-pressure pyrolysis data sets and shock tube-atomic resonance absorption spectrometry (ARAS) H atom profiles obtained from prior toluene pyrolysis experiments performed under similar high-temperature conditions and lower pressures from 1.5 to 8 bar. The primary steps in toluene pyrolysis represent the most sensitive and dominant reactions in the model. Consequently, in the absence of unambiguous direct experimental measurements, we have utilized recent high level theoretical estimates of the barrierless association rate coefficients for these primary reactions, C6H5 + CH3 --> C6H5CH3 (1a) and C6H5CH2 + H --> C6H5CH3 (1b) in the detailed chemical kinetic model. The available data sets can be successfully reconciled with revised values for deltaH0f(298K)(C6H5CH2) = 51.5 +/- 1.0 kcal/mol and deltaH0f(298K)(C6H5) = 78.6 +/- 1.0 kcal/mol that translate to primary dissociation rate constants, reverse of 1a and 1b, represented by k(-1a,infinity) = (4.62 x 10(25))T(-2.53)exp[-104.5 x 10(3)/RT] s(-1) and k(-1b,infinity) = (1.524 x 10(16))T(-0.04)exp[-93.5 x 10(3)/RT] s(-1) (R in units of cal/(mol K)). These high-pressure limiting rate constants suggest high-temperature branching ratios for the primary steps that vary from 0.39 to 0.52 over the temperature range 1200-1800 K.

Journal Article↗
PubMed1997

Metabolism of Chlorotoluenes by Burkholderia sp. Strain PS12 and Toluene Dioxygenase of Pseudomonas putida F1: Evidence for Monooxygenation by Toluene and Chlorobenzene Dioxygenases.

The degradation of toluene by Pseudomonas putida F1 and of chlorobenzenes by Burkholderia sp. strain PS12 is initiated by incorporation of dioxygen into the aromatic nucleus to form cis-dihydrodihydroxybenzenes. Toluene-grown cells of P. putida F1 and 3-chlorobenzoate-grown cells of Burkholderia sp. strain PS12 were found to monooxygenate the side chain of 2- and 3-chlorotoluene to the corresponding chlorobenzyl alcohols. Further metabolism of these products was slow, and the corresponding chlorobenzoates were usually observed as end products, whereas the 3-chlorobenzoate produced from 3-chlorotoluene in Burkholderia sp. strain PS12 was metabolized further. Escherichia coli cells containing the toluene dioxygenase genes from P. putida F1 oxidized 2- and 3-chlorotoluene to the corresponding chlorobenzyl alcohols as major products, demonstrating that this enzyme is responsible for the observed side chain monooxygenation. Two methyl- and chloro-substituted 1,2-dihydroxycyclohexadienes were formed as minor products from 2- and 3-chlorotoluene, whereas a chloro- and methyl-substituted cyclohexadiene was the only product formed from 4-chlorotoluene. The toluene dioxygenase of P. putida F1 and chlorobenzene dioxygenase from Burkholderia sp. strain PS12 are the first enzymes described that efficiently catalyze the oxidation of 2-chlorotoluene.

Journal Article↗
PubMed1984

Toluene blood level following subcutaneous injection of toluene in the rat.

A model of toluene level in blood following subcutaneous injection of toluene mixed with polyoxyethylated-vegetable-oil vehicle was developed. The purpose was to provide a means of predicting dose received for subsequent toxicologic studies for any time and dose combination. The pharmacokinetics were of secondary interest. Using data from 111 rats, a four-parameter equation was devised to predict the time course of toluene blood level from 20-480 min post dosing, for dose levels of 50-1000 mg/kg. Blood concentrations rose at a rate which was independent of dose level. Maximum blood levels were uniquely determined by dose level. Blood levels fell at different rates depending upon dose level. Injection exposure, when compared to inhalation, has the advantages of (a) low expense, (b) low equipment requirements, and (c) simplicity. The disadvantage is, for some experiments, poor temporal stimulation of the normal route of administration, inhalation.

Animals↗
PubMed1982

Toluene and telencephalic dopamine: selective reduction of amine turnover in discrete DA nerve terminal systems of the anterior caudate nucleus by low concentrations of toluene.

The present study demonstrates reductions of dopamine (DA) turnover in various areas of the anterior nucleus caudate of rat by toluene at concentrations lower than the current OSHA threshold limit value (100 ppm). Thus, toluene at low concentrations may produce disturbances in dopaminergic mechanisms of the basal ganglia probably leading to functional changes in sensory-motor integration. The increases in DA turnover in the cholecystokinin (CCK)-DA terminals of the subcortical limbic system induced by high concentrations of toluene may be part of the neurochemical basis for its abuse as a euphoric agent in man.

Animals↗
PubMed1999

Outer membrane changes in a toluene-sensitive mutant of toluene-tolerant Pseudomonas putida IH-2000.

We isolated a toluene-sensitive mutant, named mutant No. 32, which showed unchanged antibiotic resistance levels, from toluene-tolerant Pseudomonas putida IH-2000 by transposon mutagenesis with Tn5. The gene disrupted by insertion of Tn5 was identified as cyoC, which is one of the subunits of cytochrome o. The membrane protein, phospholipid, and lipopolysaccharide (LPS) of IH-2000 and that of mutant No. 32 were examined and compared. Some of the outer membrane proteins showed a decrease in mutant No. 32. The fatty acid components of LPS were found to be dodecanoic acid, 2-hydroxydodecanoic acid, 3-hydroxydodecanoic acid, and 3-hydroxydecanoic acid in both IH-2000 and No. 32; however, the relative proportions of these components differed in the two strains. Furthermore, cell surface hydrophobicity was increased in No. 32. These data suggest that mutation of cyoC caused the decrease in outer membrane proteins and the changing fatty acid composition of LPS. These changes in the outer membrane would cause an increase in cell surface hydrophobicity, and mutant No. 32 is considered to be sensitive to toluene.

Cell Membrane↗
PubMed1991

The toxic effects of combined exposure to toluene and m-xylene in animals. II. Blood toluene and m-xylene during single and combined exposure in rats.

The influence of combined exposure to m-xylene and toluene vapours at a concentration of 100 + 100 ppm on blood m-xylene concentration in rats was investigated. Within 6-7 hours of coexposure to m-xylene and toluene a significant increase in blood m-xylene concentration, in comparison to single exposure to m-xylene at concentration of 100 ppm, was observed. Study results may suggest that, reported earlier, the more than additive toxic effects of combined exposure to m-xylene and toluene in animals may result from its metabolic interaction.

Animals↗
PubMed1994

Route-dependent comparative metabolism of [14C]toluene 2,4-diisocyanate and [14C]toluene 2,4-diamine in Fischer 344 rats.

This study was initiated to evaluate the pharmacokinetics/metabolism of 14C-labeled toluene 2,4-diisocyanate (2,4-[14C]-TDI) following oral and inhalation exposure in the rat. For comparison, the pharmacokinetics/metabolism of toluene 2,4-diamine (2,4-[14C]TDA) was also evaluated. Groups of 3 or 4 male rats were given either a single 60 mg/kg oral dose of 2,4-[14C]-TDI or were exposed to 2,4-[14C]TDI vapors at a target concentration of 2 ppm for a 4-hr period. Additional groups of male rats were given single 3 or 60 mg/kg oral doses or a single 3 mg/kg intravenous (iv) dose of 2,4-[14C]TDA. All rats were euthanized by 48 hr postexposure. Following oral administration of 2,4-[14C]TDI, > 93% of the administered radioactivity was recovered in the urine, feces, cage wash, and tissues. Approximately 8% of the oral dose was excreted in the urine while 81% was eliminated in the feces. It is estimated that during inhalation exposure, essentially all of the inhaled 2,4-[14C]TDI was retained by the animal. At 48 hr post-inhalation exposure approximately 15 and 47% of the recovered radioactivity was in the urine and feces, respectively. Following oral or inhalation exposure to 2,4-[14C]TDI, no radioactivity was eliminated as either expired 14C organics or 14CO2. Comparison of the 2,4-[14C]TDI inhalation group with the oral 2,4-[14C]TDI and 2,4-[14C]TDA treatment groups indicated that a larger percentage of the inhaled radioactivity was in the tissues/carcass (34% vs 2-4%) and the excretion of radioactivity into the urine was slower (t1/2 = 20 hr vs 5-8 hr) following TDI inhalation. The total amount of free+acetylated TDA metabolites detected in the urine specimens (0-12 hr) following oral and inhalation exposure to 2,4-[14C]TDI was 15 and 0.26 microgram eq 2,4-TDA, respectively. No free 2,4-TDA was detected in the urine specimen from the inhalation group. In comparison, 638 and 20 micrograms eq 2,4-TDA was detected in the urine specimen after oral administration of 60 and 3 mg/kg 2,4-[14C]TDA, respectively. Following 2,4-[14C]TDI inhalation and oral exposure approximately 90 and 65% of the quantitated urinary metabolites existed as acid-labile conjugates, respectively. In contrast, only 16-39% of the quantitated urinary metabolites existed as acid-labile conjugates following oral administration of 2,4-[14C]TDA. Inhalation exposure to 2,4-TDI primarily results in the formation of acid-labile conjugates with little or no 2,4-TDA being formed.(ABSTRACT TRUNCATED AT 400 WORDS)

Administration, Inhalation↗
PubMed2005

Improvement in the GC-MS method for determining urinary toluene-diamine and its application to the biological monitoring of workers exposed to toluene-diisocyanate.

OBJECTIVES: To develop a simple and sensitive GC-MS method for determining toluene-diamine (TDA) in urine and to apply the method for biological monitoring of workers exposed to toluene-diisocyanate (TDI). METHODS: After acid hydrolysis of 0.1 ml of urine, diluted tenfold with water, for 1.5 h, the free TDA formed was extracted with dichloromethane, and the heptafluorobutyric anhydride derivative was determined by GC-MS. We applied the method to the biological monitoring of 18 workers who were using an 80:20 mixture of 2,4-TDI and 2,6-TDI. RESULTS: 2,6-TDA and 2,4-TDA were simply determined in 7 min by GC-MS. TDA levels in post-shift urine were well correlated with personal exposure levels of TDI. The correlation was improved by correction with creatinine or specific gravity in the 2,6-isomer, but not in the 2,4-isomer because of low exposure levels. From the correlation equation, the 2,6-TDA level (corrected with creatinine), corresponding to the TDI level of 5 ppb, was calculated to be 31.6 mug/g Cre. TDAs in pre-shift urine also correlated significantly with the personal exposure levels of TDIs, although the slope of the correlations for pre-shift samples was 60%-70% of those for post-shift samples. The correlation between 2,4-TDA and 2,6-TDA levels was significant, although the levels of the 2,4-isomer were less than one-tenth of the 2,6-isomers in both air (personal exposure) and urine. CONCLUSION: The present method is simple and practicable and can be useful for biological monitoring of TDI workers.

Air Pollutants, Occupational↗
PubMed2003

Formation of DNA adducts in HL-60 cells treated with the toluene metabolite p-cresol: a potential biomarker for toluene exposure.

We have examined DNA adduct formation in myeloperoxidase containing HL-60 cells treated with the toluene metabolite p-cresol. Treatment of HL-60 cells with the combination of p-cresol and H(2)O(2) produced four DNA adducts 1: (75.0%), 2: (9.1%), 3: (7.0%) and 4: (8.8%) and adduct levels ranging from 0.3 to 33.6 x 10(-7). The levels of DNA adducts formed by p-cresol were dependent on concentrations of p-cresol, H(2)O(2) and treatment time. In vitro incubation of p-cresol with myeloperoxidase and H(2)O(2) produced three DNA adducts 1: (40.5%), 2: (28.4%) and 3: (29.7%) with a relative adduct level of 0.7x10(-7). The quinone methide derivative of p-cresol (PCQM) was prepared by Ag(I)O oxidation. Reaction of calf thymus DNA with PCQM produced four adducts 1: (18.5%), 2: (36.4%), 3: (29.0%) and 5: (16.0%) with a relative adduct level 1.6x10(-7). Rechromatography analyses indicates that DNA adducts 1-3 formed in HL-60 cells treated with p-cresol and after myeloperoxidase activation of p-cresol were similar to those formed by reaction of DNA with PCQM. This observation suggests that p-cresol is activated to a quinone methide intermediate in each of these activation systems. Taken together, these results suggest PCQM is the reactive intermediate leading to the formation of DNA adducts in HL-60 cells treated with p-cresol. Furthermore, the DNA adducts formed by PCQM may provide a biomarker to assess occupational exposure to toluene.

Animals↗
PubMed2004

Quantitative determination of hexamethylene diisocyanate (HDI), 2,4-toluene diisocyanate (2,4-TDI) and 2,6-toluene diisocyanate (2,6-TDI) monomers at ppt levels in air by alkaline adduct coordination ionspray tandem mass spectrometry.

Occupational exposures to isocyanates can lead to occupational asthma. Once sensitized, some workers could react to isocyanate monomers at concentrations below 1% of the Permissible Exposure Limit of 5 ppb in air. Currently available methods are not sufficiently sensitive to adequately evaluate isocyanates present at these levels in workplace air. This article describes a novel method for isocyanate determination allowing the ultratrace quantification in workplace air of hexamethylene diisocyanate, 2,4-toluene diisocyanate and 2,6-toluene diisocyanate monomers. Sampling is performed during a complete workshift at a flow rate of 1 L min(-1) with a cassette containing a 1-(2-methoxyphenyl)piperazine-impregnated 25 mm filter. Analysis is performed using liquid chromatography hyphenated with coordination ionspray tandem mass spectrometry. The analytical method's linearity was measured for a concentration range varying from the limit of detection of 0.04-0.13 ng mL(-1), depending on the monomer, up to approximately 32 ng mL(-1) for every isocyanate monomer, all with correlation coefficients (R(2)) greater than 0.999. The analytical method's lower limit of quantification combined with an adapted sampling strategy allow the quantification of isocyanate monomers down to 0.04 ppt for an 8 h work shift when a lithium adduct is used, which is more than 300 times lower than the most sensitive method currently available. This novel method can be used to confirm the very low level of isocyanate monomers for the safe reassignment of sensitized workers and it is also useful for charting the isocyanate dispersion tail in workplace environments.

Air Pollutants, Occupational↗
PubMed2000

Aerobic degradation of mixtures of chlorinated aliphatics by cloned toluene-o-xylene monooxygenase and toluene o-monooxygenase in resting cells.

Recombinant strains of Escherichia coli constitutively expressing toluene-o-xylene monooxygenase (ToMO) of Pseudomonas stutzeri OX1 and toluene o-monooxygenase (TOM) of Burkholderia cepacia G4 were investigated for their ability to oxidize trichloroethylene (TCE), 1,1-dichloroethylene (1,1-DCE), cis-1,2-dichloroethylene (cis-DCE), trans-1,2-dichloroethylene (trans-DCE), vinyl chloride (VC), and chloroform (CF), individually as well as in various mixtures. ToMO oxidized all of these individual compounds well, whereas TOM did not degrade VC significantly (16-fold less) and degraded cis-DCE and trans-DCE less well (3.7- and 2.4-fold, respectively). For mixtures of these chlorinated aliphatics, ToMO was again more robust than TOM. For example, in binary mixtures including TCE, ToMO degraded all three DCE isomers and CF, but the presence of TCE inhibited VC degradation; TOM degraded both TCE/1,1-DCE and TCE/trans-DCE, but not cis-DCE for TCE/cis-DCE, and the addition of CF or VC to TCE completely inhibited degradation of both compounds and TCE. The addition of CF or trans-DCE stimulated VC degradation in the presence of TCE for ToMO, and the addition of any of the three DCE isomers stimulated VC degradation for TOM. Significant degradation of all ternary mixtures of TCE and less chlorinated ethenes, as well as a mixture of TCE, three DCEs, and VC, was achieved with ToMO (but not TOM). In mixtures of these chlorinated compounds, degradation was found to occur simultaneously rather than sequentially, and the mineralization of many of these compounds could be confirmed through detection of chloride ions.

Burkholderia cepacia↗
PubMed2005

Photoelectron spectroscopy of S1 toluene: I. Photoionization propensities of selected vibrational levels in S1 toluene.

Laser photoelectron spectra have been obtained following the preparation of eight vibrational states in S(1) toluene. For four of the vibrational states (up to approximately 550 cm(-1) excess energy) excitation and ionization with nanosecond laser pulses give rise to photoelectron spectra with well-resolved vibrational peaks. For the other states (>750 cm(-1) excess energy) the photoelectron spectra show a loss of structure when nanosecond pulses are used, as a result of intramolecular dynamics [see Whiteside et al., J. Chem. Phys. 123, 204317 (2005), following paper]. A number of vibrational peaks in the photoelectron spectra are assigned, and we find that the common series of ion vibrational peaks observed following the ionization of p-fluorotoluene in various S(1) vibrational states is not reproduced in toluene.

Journal Article↗
PubMed1989

Possible Involvement of Toluene-2,3-Dioxygenase in Defluorination of 3-Fluoro-Substituted Benzenes by Toluene-Degrading Pseudomonas sp. Strain T-12.

Pseudomonas sp. strain T-12 cells in which the toluene-degradative pathway enzymes have been induced can transform many 3-fluoro-substituted benzenes to the corresponding 2,3-catechols with simultaneous elimination of the fluorine substituent as inorganic fluoride. Substrates for this transformation included 3-fluorotoluene, 3-fluorotrifluorotoluene, 3-fluorohalobenzenes, 3-fluoroanisole, and 3-fluorobenzonitrile. While 3-fluorotoluene and 3-fluoroanisole produced only defluorinated catechols, other substrates generated catechol products with and without the fluorine substituent. The steric size of the C-1 substituent affected the ratio of defluorinated to fluorinated catechols formed from a substrate. A mechanism for the defluorination reaction involving toluene-2,3-dioxygenase is proposed.

Journal Article↗
PubMed2003

A ring walk of methylene groups in toluene radical cations. An extension of the toluene-cycloheptatriene rearrangement of aromatic radical cations. Theory and experiment.

The minimum energy reaction pathway (MERP) of the toluene-cycloheptatriene radical cation rearrangement (TOL/CHT-rearrangement) has been calculated by the UHF and DFT model at the level UHF/6-311+G(3df,2p)//UHF/6-31G(d) and B3LYP/6-311+G(3df,2p)//B3LYp/6-31G(d), respectively, including the ring walk of the substituent by a 1,2-shift around the aromatic ring. This ring walk corresponds to interconversion of distonic ions and norcaradiene radical cations (the two intermediates of the TOL/CHT-rearrangement) by making and breaking of the external C-C bonds of the cyclopropane moiety of the intermediate norcaradiene structure. For toluene radical cation 1, UHF calculations adequately reproduce earlier results(4) and show, that the ring walk of the CH(3)-substituents requires slightly more energy than formation of the cycloheptatriene radical cation. By the DFT model, the distonic ion, which is formed initially by a 1,2-H shift from CH(3) to the benzene ring, is not stable but the transition state of an interconversion of norcaradiene radical cations along a ring walk of the CH(3) substituent. The activation energy for this ring walk exceeds that for formation of the cycloheptatriene radical cation by c. 30 kJ mol(-1). Thus, isomerization of 1 by a ring walk of the CH(3)-substituent competes with the TOL/CHT-rearrangement likely only for excited 1. The calculation was repeated for the MERPs of a TOL/CHT-rearrangement of para-xylene radical cation 5 and ethylbenzene radical cation 2, yielding basically the same results as for 1. According to the calculation, polar substituents alter significantly the relative energies of the competing routes of isomerization. For benzylcyanide 3 (X = CN), the activation energy for a ring walk of the NC-CH(2)-substituent is distinctly below that of a ring enlargement. For benzyl methyl ether 4 (X = OCH(3)), the distonic intermediate along the UHF-MERP is unusually stable. Further, the 7-methoxy-norcaradiene radical ion is unstable and corresponds to a transition state between isomeric distonic intermediates differing by a 1,2-shift of the side chain. In contrast, the 7-methoxy-norcaradiene radical ion is the only intermediate of the DFT-MERP, and the distonic ion is the transition state for a 1,2-shift of the cyclopropane ring. A ring walk of the CH(3)OCH(2)-substituent is much more favorable than formation of a 7-methoxy-cycloheptatriene radical cation in both MERPs. The findings of the theoretical calculation are substantiated by the mass spectrometric fragmentations of meta- and para-methoxymethylated 1-phenylethanols 8 and 9 and of para-methoxymethyl substituted benzyl ethyl ether 10 and benzyl n-propyl ether 11. Important fragmentation routes of metastable molecular ions of these compounds correspond to elimination of alcohols. Use of deuterated derivatives shows that the elimination occurs by a "false" ortho-effect which requires migration of a ROCH(2)-substituent around the benzene ring. Results of particular interest are obtained for the asymmetric bis-ethers 10 and 11. Here, the MIKE spectra of the molecular ions of deuterated analogs reveal a selective ring walk of the C(2)H(5)OCH(2)- and n-C(3)H(7)OCH(2)-side chain, respectively.

Journal Article↗
PubMed1999

Specific IgG, but not specific IgE, antibodies to toluene diisocyanate-human serum albumin conjugate are associated with toluene diisocyanate bronchoprovocation test results.

BACKGROUND: The role of specific IgG to toluene diisocyanate (TDI) in the pathogenesis of TDI-induced asthma still remains unclear. OBJECTIVE: We sought to evaluate the clinical significance of serum-specific IgG to TDI-human serum albumin (HSA) conjugate in subjects with TDI-induced asthma compared with specific IgE antibody. METHODS: One hundred three subjects were enrolled and divided into 4 groups according to specific bronchoprovocation test (BPT) results: 50 subjects with TDI-induced asthma with positive results on TDI BPT were defined as group 1, 13 symptomatic workers exposed to TDI with negative results on TDI BPT were defined as group 2, 20 unexposed patients with allergic asthma were defined as group 3, and 20 unexposed healthy control subjects were defined as group 4. Serum-specific IgG and IgE antibodies to TDI-HSA conjugate were detected by means of ELISA. RESULTS: The prevalence of specific IgG antibody to TDI-HSA conjugate was significantly higher in group 1 than in group 2 (46% vs 7.7%, P =.01) or group 3 (0%, P <.01). No significant difference was noted between group 2 and group 3 (P >. 05). However, the prevalence of specific IgE antibody to TDI-HSA conjugate was not significantly different between group 1 and group 2 (14% vs 7.7%, P >.05) or group 2 and group 3 (7.7% vs 0%, P >.05). There was no significant difference in prevalence of specific IgE or specific IgG according to the type of asthmatic response during the TDI BPT (P >.05). Overall, statistically significant association was noted between the prevalence of specific IgE and IgG antibodies in 103 subjects (P <.05), but no difference was noted within group 1 subjects only (P >.05). CONCLUSION: These findings demonstrate that the presence of serum-specific IgG is closely related to TDI BPT results, and it may contribute to the development of TDI-induced asthma.

Adult↗
PubMed2002

Specific immunoglobulin E and immunoglobulin G antibodies to toluene diisocyanate-human serum albumin conjugate: useful markers for predicting long-term prognosis in toluene diisocyanate-induced asthma.

BACKGROUND: Our previous study reported that more than 50% of toluene diisocyanate (TDI)-induced asthma patients had persistent asthmatic symptoms even after complete avoidance. Although specific IgE (sIgE) has been detected in a portion of patients with TDI-asthma, a recent investigation suggests that the presence of serum specific IgG (sIgG), not sIgE, is more closely associated with positive bronchoprovocation test (BPT) results. OBJECTIVE: To evaluate the possible role of sIgE and sIgG in predicting long-term prognosis of TDI-asthma. MATERIALS AND METHODS: Forty-one TDI-asthma patients whose diagnosis was confirmed by TDI-BPT, and 20 unexposed healthy controls were enrolled. Both sIgE and sIgG to TDI-human serum albumin (HSA) conjugate were detected by ELISA. All patients with persistent asthmatic symptoms took anti-asthmatic medications during the follow-up period (mean: 67.5 months) and were instructed to avoid exposure to TDI. Airway hyper-responsiveness to methacholine (AHM) was monitored every year during the study period. The patients were classified into three groups according to changing patterns of AHM and asthmatic symptoms as follows: group I, no improvement with persistent asthmatic symptoms (n = 12); group II, partial improvement with persistent asthmatic symptoms (n = 13); group III, in remission (n = 16). RESULTS: Favourable prognosis was associated with a mild degree of AHM at initial diagnosis (P < 0.05). Although there were no significant differences in the prevalence of sIgE antibody to TDI-HSA conjugate among the three groups (P > 0.05), prevalence of sIgG in group I tended to be higher than in group II (0.05 < P < 0.1). However, the levels of sIgG were significantly higher in group I than in group II (P = 0.05), whereas levels of sIgE were significantly higher in group II than in group I (P = 0.014). No significant differences were noted in exposure duration, sex, age, atopic status, and total IgE level among the three groups (P > 0.05). CONCLUSION: This study confirmed that a favourable outcome is related to a mild degree of AHM and to low levels of sIgG to predict persistent asthmatic symptoms, it also suggested that the presence of high serum-specific IgE at initial diagnosis may represent a better prognosis.

Asthma↗
PubMed2003

Metalloproteinase-9 is increased after toluene diisocyanate exposure in the induced sputum from patients with toluene diisocyanate-induced asthma.

BACKGROUND AND OBJECTIVE: Persistent asthma symptoms are associated with airway inflammation and remodeling, which may be mediated through metalloproteinase (MMP) and tissue inhibitor of metalloproteinase (TIMP). The aim of this study was to evaluate MMPs and TIMP involvement in toluene diisocyanate (TDI)-induced asthma. MATERIALS AND METHOD: Induced sputum was collected in eight newly diagnosed TDI-induced asthma subjects (group I) before and 7 h after the TDI and placebo challenges and in 12 subjects with TDI-induced occupational asthma diagnosed 5 years previously with persistent asthma symptoms (group II). Sera was collected in group I at diagnosis, and in group II, they were collected at the time of the study. 12 nonasthmatic healthy subjects were enrolled as controls. MMP-9, MMP-2 and TIMP-1 levels in both sputum and serum were measured by enzyme-linked immunosorbent assay (ELISA). Gelatinase activity in the sputum was confirmed by zymographic analysis. RESULTS: The serum TIMP-1 level was significantly higher in asthma patients than in healthy controls (P = 0.01), while MMP-9 level was significantly lower in asthmatic patients (P = 0.03). There was no significant difference in MMP-2 level (P = 0.27). MMP-9 level in the sputum was significantly increased after the TDI challenges (P = 0.01). TIMP-1 level in sputum tended to increase after TDI challenges, but no statistical significance was noted (P = 0.09). MMP-9 and MMP-9/TIMP-1 levels in the sputum were significantly higher in group II than in group I (P = 0.04, P = 0.02) with no significant difference in TIMP-1 level. Minimal amount of MMP-2 was found in sputum. Zymography demonstrated that MMP-9 level increased and active form of MMP-9 was generated after the TDI bronchoprovocation test. CONCLUSION: TDI exposure leads to overproduction of MMP-9, which may induce airway inflammation and remodeling, and then contribute to persistent asthmatic symptoms in TDI-induced asthma.

Adult↗