Effect of D-cycloserine on spatial learning performance and memory function-related gene expression in mice following toluene exposure

D-cycloserine (DCS), a partial N-methyl-D-aspartate (NMDA) receptor agonist, is a well-known cognitive enhancer. To investigate the effect of DCS in cognitive function following toluene exposure, eight-week-old male C3H/HeN mice were exposed to filtered air (0 ppm) or 50 ppm toluene for 6 h a day on 5 consecutive days a week for 6 weeks. The day after the day of final exposure, a spatial learning task was performed using a Morris water maze apparatus. During the learning task, some mice were treated with DCS intraperitoneally (20 mg/kg) 30 min before the first trial of the acquisition phase and probe trial. After completion of the spatial learning task, the hippocampus was collected from each mouse to examine memory function-related gene expression using the real-time RT-PCR method. During the acquisition phase, on day 3 and 4, toluene-exposed mice with DCS treatment showed significantly better learning performance than corresponding saline treated groups. Moreover, the toluene-exposed mice with DCS treatment also showed significantly improved memory retention during the probe trial and up-regulation of hippocampal NMDA receptor subunit 2B mRNA expression compared with the saline treated groups. Our findings indicate that a subunit-specific modulation of hippocampal NMDA receptor mRNA expression by DCS contributes to improvement of spatial learning performance in mice following toluene exposure.

Influence of toluene co-exposure on the metabolism and genotoxicity of benzene in mice using continuous and intermittent exposures

Benzene exposure in occupational settings often occurs with concurrent exposure to toluene, the methyl-substituted derivative of benzene. Toluene is also readily metabolized by CYP450 isozymes although oxidation primarily occurs in the methyl group. While earlier mouse studies addressing co-exposure to benzene and toluene at high concentrations demonstrated a reduction in benzene-induced genotoxicity, we have previously found, using an intermittent exposure regimen with lower concentrations of benzene (50 ppm) and toluene (100 ppm), that toluene enhances benzene-induced clastogenic or aneugenic bone marrow injury in male CD-1 mice with significantly increased CYP2E1, and depleted GSH and GSSG levels. The follow-up study reported here also used the same daily and total co-exposures but over consecutive days and compared the effects of co-exposure on genotoxicity and metabolism in CD-1 mice both with and without buthionine sulfoximine (BSO) treatment to deplete GSH. In this study the toluene co-exposure doubled the genotoxic response (as determined by the erythrocyte micronucleus test) to benzene alone. Further, GSH depletion caused a reduction in this genotoxicity in both benzene exposed and benzene/toluene co-exposed mice. The results are discussed in terms of the analyses of urinary metabolites from this consecutive day study and the intermittent exposure study as well as levels of CYP2E1, epoxide hydrolase, quinone reductase, alcohol dehydrogenase, and aldehyde dehydrogenase activities. The results suggest that the presence of glutathione is necessary for benzene genotoxicity either as a metabolite conjugate or through an indirect mechanism such as TNF-induced apoptosis.

Cytogenetic methods for assessing human exposure to toluene in Coimbatore, South India

The aim of the present study was to identify genetic alterations occurring in rotograving workers chronically exposed to toluene. A total of 60 samples from 30 exposed subjects and 30 age-matched controls, selected based on the toluene level present in their urine, were recruited. Exposed subjects were categorized based on their duration of exposure and smoking habitats. Controls were normal and healthy and categorized based on their smoking habits. Cell cultures were established from blood samples collected from the control and experimental subjects after obtaining informed consent. G-banding and comet assays were used to identify genetic alterations. A higher degree of total chromosome aberration was identified in exposed subjects compared to controls. As expected, controls exhibited minimal number of alterations. The overall CA frequency due to toluene exposure was significantly different from that of the controls for both chromatid and chromosome type aberrations (P\0.05 by ANOVA). . The habit of cigarette smoking among the workers had a synergistic effect on inducing DNA damage. In conclusion, this work shows a clear genotoxic effect associated with toluene exposure, our results also reinforcing the conclusion of higher sensitivity of cytogenetic assays for the biomonitoring of occupationally exposed populations. There is a strong need to educate those who work with potentially hazardous materials about adverse effects and highlight the importance of using protective measures.

Organic solvents and hearing loss: The challenge for audiology

Organic solvents have been reported to adversely affect human health, including hearing health. Animal models have demonstrated that solvents may induce auditory damage, especially to the outer hair cells. Research on workers exposed to solvents has suggested that these chemicals may also induce auditory damage through effects on the central auditory pathways. Studies conducted with both animals and humans demonstrate that the hearing frequencies affected by solvent exposure are different to those affected by noise, and that solvents may interact synergistically with noise. The present article aims to review the contemporary literature of solvent-induced hearing loss, and consider the implications of solvent-induced auditory damage for clinical audiologists. Possible audiological tests that may be used when auditory damage due to solvent exposure is suspected are discussed.

Studies on kidney function in subjects exposed to organic solvents. I. Excretion of albumin and beta-2-microglobulin in the urine

The urine of 134 subjects, exposed to different organic solvents, and 48 unexposed subjects has been analysed with reference to albumin and beta-2-microglobulin excretion. The exposed subjects excreted significantly larger quantities of albumin than the unexposed. Those exposed to styrene excreted the largest amounts. No significant difference in beta-microglobulin excretion could be demonstrated between the groups.

Indoor contaminants from newspapers: VOCs emissions in newspaper stands

Mean volatile organic compound (VOC) concentrations in 16 newspaper stands and in two printing shops were monitored for the purpose of quantifying the various VOCs in these areas and to relate the results. In each site halogenated, oxygenated, aliphatic, and aromatic compounds were monitored during one workweek. They were sampled with diffusive samplers for thermal desorption and analysed by GC-MS. The results showed that in all newspaper stands the indoor levels of toluene were much higher than the outdoor levels; some sites had toluene indoor concentrations 100 times higher than their correspondent outdoor levels. The investigations in two printing shops confirmed that newspapers, in particular the inks, are the main sources of toluene in the newspaper stands.

Risk of leukemia and multiple myeloma associated with exposure to benzene and other organic solvents: evidence from the Italian Multicenter Case-control study

BACKGROUND

While there is a general consensus about the ability of benzene to induce acute myeloid leukemia (AML), its effects on chronic lymphoid leukemia and multiple myeloma (MM) are still under debate. We conducted a population-based case-control study to evaluate the association between exposure to organic solvents and risk of myeloid and lymphoid leukemia and MM.

METHODS

Five hundred eighty-six cases of leukemia (and 1,278 population controls), 263 cases of MM (and 1,100 population controls) were collected. Experts assessed exposure at individual level to a range of chemicals.

RESULTS

We found no association between exposure to any solvent and AML. There were elevated point estimates for the associations between medium/high benzene exposure and chronic lymphatic leukemia (OR = 1.8, 95% CI = 0.9-3.9) and MM (OR = 1.9, 95% CI = 0.9-3.9). Risks of chronic lymphatic leukemia were somewhat elevated, albeit with wide confidence intervals, from medium/high exposure to xylene and toluene as well.

CONCLUSIONS

We did not confirm the known association between benzene and AML, though this is likely explained by the strict regulation of benzene in Italy nearly three decades prior to study initiation. Our results support the association between benzene, xylene, and toluene and chronic lymphatic leukemia and between benzene and MM with longer latencies than have been observed for AML in other studies.

[Neurochemical mechanisms for development of psychological dependence on volatile organic solvents]

Abuse of volatile organic solvents among youth remains a major social problem. Organic solvents are cheap and relatively easy to obtain, so they carry the risk of becoming a "gateway drug" for users. The effect of repeated inhalation of toluene on subsequent responses to other drugs of abuse is unclear. In the present study, we investigated the effect of toluene inhalation on methamphetamine-induced behavioral change using a newly developed sealed inhalation shuttlebox. The influence of the cyclic AMP response element binding (CREB) protein expression following toluene inhalation was also examined. Mice were exposed to toluene or air once daily for five days. Methamphetamine produced significant hyperlocomotion in air-exposed mice. This stimulatory effect of methamphetamine was significantly enhanced following repeated inhalation of toluene. Furthermore, repeated toluene inhalation increased the levels of CREB proteins in the limbic forebrain. The present study demonstrated that adaptation of the adenylate cyclase system following repeated toluene inhalation might be involved in the expression of behavioral sensitization to subsequent methamphetamine administration. Inhalant abuse could thus be associated with the risk of other substances of abuse.

A clinical assessment of a patch test kit marketed to U.K. hairdressers for detecting hair dye allergy

BACKGROUND

In 2004 a U.K.-based company developed and marketed a patch test kit (Colourstart); Trichocare, Ridgmont, Beds, U.K.) for use by hairdressers. It is intended to assess whether clients have a 'problem with hair dye' and promotes itself as the 'only practical solution to sensitivity testing'. However, a patient presented with a hair dye reaction that had not been detected while using this patch test system.

OBJECTIVES

To assess the Colourstart system in the next seven consecutive patients presenting with a history of adverse reactions to hair dyes.

METHODS

The Colourstart system was tested in parallel with commercially available hair dye patch test reagents, where applicable.

RESULTS

Only three of seven patients allergic to p-phenylenediamine were detected using this system and one patient allergic to toluene-2,5-diamine sulphate was not detected using this system.

CONCLUSIONS

The results raise concerns about the sensitivity of this kit for consumer protection, but also wider questions about the regulation, use and interpretation of 'home diagnostic patch test kits' in general.

[Review of sick house syndrome]

'Sick house syndrome' (SHS) is a health issue that closely resembles sick building syndrome (SBS) that had occurred in European countries. The aim of this review is to clarify the characteristics of SHS by reviewing previous reports rigorously. We propose the definition of SHS as "health impairments caused by indoor air pollution, regardless of the place, causative substance, or pathogenesis". Cases of SBS are reported to occur predominantly in offices and sometimes schools, whereas those of SHS are usually found in general dwellings. In many cases, SHS is caused by biologically and/or chemically polluted indoor air. Physical factors might affect the impairments of SHS in some cases. It is considered that symptoms of SHS develop through toxic, allergic and/or some unknown mechanisms. Psychological mechanisms might also affect the development of SHS. It is still unclear whether SBS and SHS are very close or identical clinical entities, mostly because a general agreement on a diagnostic standard for SHS has not been established. Previous research gradually clarified the etiology of SHS. Further advances in research, diagnosis, and treatment of SHS are warranted with the following measures. Firstly, a clinical diagnostic standard including both subjective and objective findings must be established. Secondly, a standard procedure for assessing indoor air contamination should be established. Lastly, as previous research indicated multiple causative factors for SHS, an interdisciplinary approach is needed to obtain the grand picture of the syndrome.

Toluene inhalation induced neuronal damage in the spinal cord and changes of neurotrophic factors in rat

We investigated the effects of toluene inhalation on neurons and neurotrophic factors in the spinal cord and the relationship between them. Male Wistar rats were exposed to toluene (1500ppm for 4h per day) for 7 days. To observe damage of the neurons in spinal cord with the toluene, expression of microtubule associated protein 2 (MAP2) and 70kDa heat shock protein (HSP70) in spinal cord were performed by immunohistochemistry. MAP2 was degraded and HSP70-immunoreactivity was enhanced in nerve cell bodies of the gray matter in toluene inhalation group. Immunoreactivity of glial fibrillary acidic protein (GFAP), a marker of astrocytes, was enhanced in the toluene-treated group. Furthermore, glial cell line-derived neurotrophic factor (GDNF)- and brain-derived neurotrophic factor (BDNF)-immunoreactivity in spinal cord were slightly decreased in the treated group. In addition, the concentrations of GDNF and BDNF in the spinal cord were determined using enzyme linked immunosorbent assay (ELISA). Concentration of GDNF was reduced significantly by toluene exposure. BDNF also reduced, but not significantly. The toluene inhalation caused the damage of the neuron in the spinal cord, which was accompanied by the decrease in the neurotrophic factors, such as BDNF and GDNF.

Benzyl alcohol as a marker of occupational exposure to toluene

Benzyl alcohol (BeOH) is a urinary metabolite of toluene, which has been seldom evaluated for biological monitoring of exposure to this popular solvent. The present study was initiated to develop a practical method for determination of BeOH in urine and to examine if this metabolite can be applied as a marker of occupational exposure to toluene. A practical gas-liquid chromatographic method was successfully developed in the present study with sensitivity low enough for the application (the limit of detection; 5 microg BeOH /l urine with CV=2.7%). Linearity was confirmed up to 10 mg BeOH/l, the highest concentration tested, and the reproducibility was also satisfactory with a coefficient of variation of 2.7% (n=10). A tentative application of the method in a small scale study with 45 male workers [exposed to toluene up to 130 ppm as an 8-h time-weighted average (8-h TWA)] showed that BeOH in the end-of-shift urine samples was proportional to the intensity of exposure to toluene. The calculated regression equation was Y=50+1.7X (r=0.80, p<0.01), where X was toluene in air (in ppm as 8-h TWA) and Y was BeOH in urine (in microg/l of end-of-shift urine). The levels of BeOH in the urine of the non-exposed was about 50 microg/l, and ingestion of benzoate as a preservative in soft drinks did not affect the BeOH level in urine. The findings as a whole suggest that BeOH is a promising candidate for biological monitoring of occupational exposure to toluene.

Hearing loss in workers exposed to toluene and noise

In this study we investigated the risk of hearing loss among workers exposed to both toluene and noise. We recruited 58 workers at an adhesive materials manufacturing plant who were exposured to both toluene and noise [78.6-87.1 A-weighted decibels; dB(A)], 58 workers exposed to noise only [83.5-90.1 dB(A)], and 58 administrative clerks [67.9-72.6 dB(A)] at the same company. We interviewed participants to obtain sociodemographic and employment information and performed physical examinations, including pure-tone audiometry tests between 0.5 and 6 kHz. A contracted laboratory certified by the Council of Labor in Taiwan conducted on-site toluene and noise exposure measurements. The prevalence of hearing loss of >or=25 dB in the toluene plus noise group (86.2%) was much greater than that in the noise-only group (44.8%) and the administrative clerks (5.0%) (p<0.001). The prevalence rates were 67.2, 32.8, and 8.3% (p<0.001), respectively, when 0.5 kHz was excluded from the estimation. Multivariate logistic regression analysis showed that the toluene plus noise group had an estimated risk for hearing loss>or=25 dB, 10.9 times higher than that of the noise-only group. The risk ratio dropped to 5.8 when 0.5 kHz was excluded from the risk estimation. Hearing impairment was greater for the pure-tone frequency of 1 kHz than for that of 2 kHz. However, the mean hearing threshold was the poorest for 6 kHz, and the least effect was observed for 2 kHz. Our results suggest that toluene exacerbates hearing loss in a noisy environment, with the main impact on the lower frequencies.

Mortality of workers employed in shoe manufacturing: an update

BACKGROUND

In the late 1970s, the National Institute for Occupational Safety and Health identified two shoe manufacturing facilities where workers experienced relatively "pure" exposures to toluene. A mortality study was conducted through December 31, 1982. An original study did not detect elevated leukemia mortality but did detect increased lung cancer mortality. The present study is an update of the mortality of the original cohort.

METHODS

The study cohort consisted of workers employed 1 month or more between 1940 and 1979 at two Ohio shoe manufacturing plants. Vital status was ascertained through December 31, 1999.

RESULTS

Seven thousand eight hundred twenty eight workers, contributing 300,777 person years, were available for analysis. An excess of lung cancer deaths persisted with additional years of follow-up (SMR = 1.36, 95% confidence interval (CI) = 1.19-1.54). Trend tests did not indicate a positive trend between lung cancer risk and duration of employment. Mortality from leukemia was not significantly elevated in the updated analysis.

CONCLUSIONS

Results indicate a possible association between lung cancer mortality and exposure to chronic, low-levels of organic solvents. Although the strength of this conclusion was weakened by the lack of increasing lung cancer risk in relation to duration of employment, other studies have supported this association.

Dilated Cardiomyopathy Associated with Toluene Abuse

The use of paint thinner and glue to achieve an euphoric state has been associated with serious social and health problems in children and young adults. We present the case of a 21-year-old man with dilated cardiomyopathy occurring following abuse of paint thinner and glue containing toluene as main compound. After cessation of toluene abuse, the patient recovered rapidly and completely. Because of the increasing prevalence of toluene abuse, harmful effects of this volatile agent on the heart are also discussed.

[Combined and isolated effects of toluene and general vibration on the body]

The paper presents the results of an investigation of the isolated and combined effect of toluene (at the level of the maximum pennissible concentration (MPC), general vibration, and its concomitant noise on experimental animals (rats). The changes detected in the morphofunctional status of the cardiovascular system are indicative of the isolated and combined effect of toluene, general vibration, and noise at the level of MPC on the morphology of the myocardium and aorta of experimental animals.

[Role of the monoamine system in the brain on the development of psychological dependence on toluene]

Abuse of volatile organic solvents among youth remains a major social problem in Japan. Organic solvents are cheap and relatively easy to obtain, so they carry the risk of becoming a so-called "gate-way drug" for users. Psychological dependence assessment systems have been established for drug inhalation using the conditioned place preference (CPP) procedure. We found toluene produced the rewarding effect in this new CPP system. The mesolimbic dopamine pathway, which includes dopaminergic neurons in the ventral tegmental area (VTA) of the midbrain and their targets in the limbic forebrain, especially the nucleus accumbens (NAC), is one of the most important substrates for the development of psychological dependence on drugs such as stimulants, cocaine, and heroin. Recently, it has indicated that the VTA-NAC pathway (monoamine system) may play an important role of the expression of psychological dependence on the volatile organic solvent toluene. Clarification of organic solvent's mechanism for the development of psychological dependence focusing on the monoamine system can be exploited for the new medicine and useful treatments for dependence on toluene.

[Interactions between solvents and noise: state of the art]

There are several environmental and occupational scenes where a co-exposure of noise and solvents occurs, therefore between a neurotoxic and a ototoxic agent. Epidemiological and experimental studies with simultaneous exposure to noise and solvents like toluene, styrene and carbon disulfide have been analysed. These studies investigate possible ototoxic effects through audiometry, auditory brainstem response, potential recall and reflex decay test. The current available data show that with high exposure levels, that are responsible for tissue damage by themselves, the interaction between noise and solvents could occur. The present knowledge can not permit a conclusion for low exposure levels.

Occupational exposure to toluene and its possible causative role in renal damage development in shoe workers

OBJECTIVES

An important, although, unprecise number of shoe workers in Leon, Mexico, are in continuous contact with toluene-based glues. The induction of renal glomerular and/or tubular lesions as a result of toluene exposure is still being discussed controversially. Our objective was to evaluate the extent of occupational exposure, assessing urinary o-Cresol excretion as a measure for toluene exposure in a population at risk as compared to a control population. Urinary albumin excretion (UAE) and N-acetyl-beta-D-glucosaminidase (NAG) enzymatic activity were tested to assess renal dysfunction.

METHODS

A cross-sectional study was performed comparing 50 toluene-exposed shoe workers and 25 control subjects. Urinary o-cresol was assessed on first and last day of labor week from exposed subjects. A single urine sample was obtained from control subjects. Urinary Albumin excretion (UAE) and (NAG) activity were examined in 12 h urine samples in all subjects. Urine and serum creatinine were measured to asses renal function.

RESULTS

At the end of the labor week, urinary o-cresol levels were higher in samples obtained from exposed subjects. Albumin excretion was similar in the exposed and control groups. NAG activity was greater in the exposed group compared to control group (median 3.5 U/g creatinine vs 1.9 U/g creatinine, z=2.6, P=0.009). An inverse relationship was found between schooling years and the NAG enzymatic activity for the two studied groups (r= -0.27, P=0.02),

CONCLUSIONS

Our findings support the hypothesis that toluene may be a factor associated with the presence of renal damage in exposed shoe workers. As NAG activity is increased, we believe the lesion initiates in the renal tubular cells.

Toward cost-benefit analysis of acute behavioral effects of toluene in humans

There is increasing interest in being able to express the consequences of exposure to potentially toxic compounds in monetary terms in order to evaluate potential cost-benefit relationships of controlling exposure. Behavioral effects of acute toluene exposure could be subjected to cost-benefit analysis if the effects of toluene were quantitatively compared to those of ethanol ingestion, which has been monetized for applied contexts. Behavioral effects of toluene and ethanol were quantified by meta-analysis of studies from the peer-reviewed literature describing their effects on choice reaction time (reaction time in a test requiring a subject to choose among two or more alternatives before responding). The internal doses of these compounds were estimated by a general physiological and toxicokinetic (GPAT) simulation from exposure parameters provided in the reports. The reported effects were converted to a common metric (proportion of baseline) and related to the estimated internal doses of toluene and ethanol, from which dose-effect equations were fitted. The estimated effect of toluene was compared to the estimated effect of ethanol on the same dependent variable by deriving a dose-equivalence equation (DEE) to express the dose of toluene as an equivalent dose of ethanol on the basis of equal effect magnitude. A nomogram was constructed by GPAT simulation to relate the environmental exposure concentration of toluene to the equivalent effect magnitude of a range of ethanol internal doses. Behavioral effects and their evaluation are determined by internal doses, which in turn are determined by a variety of variables. In addition to concentration and duration of exposure, which determine internal dose by pharmacokinetic processes, the activity level of exposed persons is a major factor. This analysis provides a continuous function of the consequences of toluene exposure expressed as ethanol-equivalent doses within confidence limits. The resulting function has the potential to estimate the monetary values of behavioral deficits caused by a range of exposures to toluene from existing monetized information on ethanol.

Renal tubular acidosis and severe hypophosphataemia due to toluene inhalation

A 21-year-old woman developed severe muscle paralysis after sniffing toluene-containing thinner solution for 2 weeks. Her serum chemistries revealed severe hypokalaemia and a normal anion gap hyperchloraemic metabolic acidosis secondary to renal tubular acidosis. Her initial presentation mimicked hypokalaemic periodic paralysis, but toxicology screening of her blood and urine revealed the correct diagnosis of toluene poisoning. Her electrolyte and acid-base status returned to normal 4 days after cessation of toluene sniffing. On another occasion, apart from renal tubular acidosis, the patient also developed severe hypophosphataemia with the phosphate level decreasing to 0.15 mmol/L. Hypophosphataemia with such a low phosphate level after toluene poisoning has been rarely reported in the literature. Toluene inhalation can result in multiple electrolyte and acid-base abnormalities, and should be considered in the diagnosis of any young patient who presents with unexplained hypokalaemia and normal anion gap metabolic acidosis.