Toluene abuse and white matter: a model of toxic leukoencephalopathy

Emissions of Semi-Volatile Organic Compounds from Architectural Coatings and Polyvinyl Chloride Floorings: Microchamber Method

Semi-volatile organic compounds (SVOCs) are modern chemical substances that are present in large quantities in indoor environments. Understanding the emission of SVOCs from building materials is essential to identify the main sources of indoor SVOCs and to improve indoor air quality. In this study, a reference method employing custom-designed microchambers (630 mL) was optimized by improving the structure of the gas path and adding polytetrafluoroethylene inner coating to the chamber. After optimization, the recoveries of the microchamber method were significantly improved (75.4-96.7%), and the background in the microchamber was greatly reduced (<0.02 μg/h). By using the microchamber method, 33 SVOCs (including two alkanes, one aromatic, one nitrogen compound, and twenty-nine oxygenated compounds) and 32 SVOCs (including seven alkanes, eight aromatics, and seventeen oxygenated compounds) were detected in the emissions of the architectural coating and the PVC flooring samples, respectively. The area-specific emission rates (SERa) of total SVOCs emitted from architectural coatings and PVC floorings were in the range of 4.09-1309 μg/m2/h) (median: 10.3 μg/m2/h) and 0.508-345 μg/m2/h (median: 11.9 μg/m2/h), respectively. Propanoic acid had the highest SERa (3143 μg/m2/h) in architectural coatings, while methylbenzene (345 μg/m2/h), 2-methylnaphthalene (65.2 μg/m2/h), and naphthalene (60.3 μg/m2/h) were main SVOCs emitted from PVC floorings. Meanwhile, the average second-stage (adsorbed phase) emission mass of the total SVOCs accounts for 66.3% and 47.3% in architectural coatings and PVC floorings, respectively, suggesting that the SVOCs emitted from building materials have a strong tendency to be absorbed on the surface of the room, e.g., the interior wall, the desk or even the skin.

The Experience of Using Urinary Liver-Type Fatty Acid-Binding Protein for Follow-Up of Toluene Poisoning: A Case Report

Toluene poisoning is diagnosed based on toluene exposure history and the level of hippuric acid in the urine. Regular blood and urine tests are performed for follow-up. A 54-year-old man collided with a utility pole while driving a car and was rushed to our hospital with a complaint of loss of consciousness. Although the trauma was minor, toluene poisoning was suspected based on the presence of impaired consciousness, occupation is a painting job that involves toluene, and the presence of metabolic acidosis of the normal anion gap. Urinary hippuric acid and urinary liver-type fatty acid-binding protein (L-FABP) were measured, and a diagnosis of renal tubular acidosis (RTA) due to toluene toxicity was made. Urinary L-FABP levels decreased as the condition improved. Urinary L-FABP is a practical and rapid diagnostic and follow-up tool for toluene-induced RTA, and it is helpful to measure it in addition to conventional methods.

Exposure to volatile hydrocarbons and neurologic function among oil spill workers up to 6 years after the Deepwater Horizon disaster

BACKGROUND

During the 2010 Deepwater Horizon (DWH) disaster, oil spill response and cleanup (OSRC) workers were exposed to toxic volatile components of crude oil. Few studies have examined exposure to individual volatile hydrocarbon chemicals below occupational exposure limits in relation to neurologic function among OSRC workers.

OBJECTIVES

To investigate the association of several spill-related chemicals (benzene, toluene, ethylbenzene, xylene, n-hexane, i.e., BTEX-H) and total petroleum hydrocarbons (THC) with neurologic function among DWH spill workers enrolled in the Gulf Long-term Follow-up Study.

METHODS

Cumulative exposure to THC and BTEX-H across the oil spill cleanup period were estimated using a job-exposure matrix that linked air measurement data to detailed self-reported DWH OSRC work histories. We ascertained quantitative neurologic function data via a comprehensive test battery at a clinical examination that occurred 4-6 years after the DWH disaster. We used multivariable linear regression and modified Poisson regression to evaluate relationships of exposures (quartiles (Q)) with 4 neurologic function measures. We examined modification of the associations by age at enrollment (<50 vs. ≥50 years).

RESULTS

We did not find evidence of adverse neurologic effects from crude oil exposures among the overall study population. However, among workers ≥50 years of age, several individual chemical exposures were associated with poorer vibrotactile acuity of the great toe, with statistically significant effects observed in Q3 or Q4 of exposures (range of log mean difference in Q4 across exposures: 0.13-0.26 μm). We also observed suggestive adverse associations among those ≥ age 50 years for tests of postural stability and single-leg stance, although most effect estimates did not reach thresholds of statistical significance (p < 0.05).

CONCLUSIONS

Higher exposures to volatile components of crude oil were associated with modest deficits in neurologic function among OSRC workers who were age 50 years or older at study enrollment.

The Effects of the Inhalant Toluene on Cognitive Function and Behavioral Flexibility: A Review of Recent Findings

Substance use disorder (SUD) is characterized, in part, by lack of control over drug seeking and taking. The prefrontal cortex (PFC) is highly involved in control of behavior and deficits in PFC structure and function have been demonstrated in clinical and preclinical studies of SUD. Of the various classes of drugs associated with the development of SUD, inhalants are among the least studied despite their widespread use among adolescents and children. In this work, we review what is currently known regarding the sites and mechanisms of action of inhalants with a focus on the volatile solvent toluene that is contained in a wide variety of legal and easily obtained products. We then describe how inhalants including toluene affect various behaviors with an emphasis on those associated with PFC function and how chronic use of inhalants alters brain structure and neuronal signaling. Findings from these studies highlight advances made in recent years that have expanded our understanding of the effects of inhalants on brain structure and reinforce the need for continued work in this field.

Molecular evidence of the amelioration of toluene induced encephalopathy by human breast milk mesenchymal stem cells

Toluene was widely used volatile organic compound that accumulates in tissues with high lipid content. Stem cells have been proposed as an increasingly attractive approach for repair of damaged nervous system, we aimed to evaluate the ability of breast milk mesenchymal stem cells (MSc) to ameliorate toluene-induced encephalopathy. Sixty adult male albino rats were assigned to 3 groups, control, toluene, and toluene/breast milk-MSc. Neurological assessment was evaluated as well as serum levels of glial fibrillary acidic protein (GFAP), tumor necrosis factor-alpha (TNF-α), nerve growth factor (NGF), vascular endothelial growth factor (VEGF), tissue dopamine and oxidative markers. Gene expression of peroxisome Proliferator-Activated Receptor-Gamma (PPAR-ɣ), nuclear factor-kappaB (NF-kB), and interleukin-6 (IL-6) were evaluated. Moreover, histological and immunohistochemical investigation were done. Results revealed that toluene caused cerebral injury, as evidenced by a significant increase in serum GFAP, TNF-α, malondialdehyde (MDA) and nitric oxide (NO), a significant decrease in serum NGF, tissue dopamine and oxidative markers, besides, a non-significant change in VEGF. Toluene also caused changes in normal cerebral structure and cellular degeneration, including a significant decrease in the total number of neurons and thickness of frontal cortex. Meninges showing signs of inflammation with inflammatory cell infiltration and exudation, a significant decrease in MBP immunoreactivity, and increase in the percent of high motility group box protein-1 (HMGB1) positive cells. PPAR- ɣ, NF-kB, and IL-6 gene expression were all considerably elevated by toluene. These changes were greatly improved by breast milk MSc. Therefore, we conclude that breast milk MSc can attenuate toluene-induced encephalopathy.

Involuntary Emotional Expression Disorder in a Patient With Toluene Leukoencephalopathy

OBJECTIVE

Inhalant users may develop toluene leukoencephalopathy, a devastating neuropsychiatric disorder. We present a case of toluene-induced damage to the corticospinal and the corticonuclear tracts, which presented with involuntary emotional expression disorder.

METHODS

Case study of a 20-year-old man with a 3-year history of frequent solvent abuse was admitted to the Neuropsychiatry Unit of the National Institute of Neurology and Neurosurgery because "he could not speak or walk" but would keep "laughing and crying without reason".

RESULTS

Neuropsychiatric examination revealed pathological laughter and crying, facial and speech apraxia, a bilateral pyramidal syndrome, and lack of control of urinary sphincter. Magnetic resonance imaging revealed a highly selective bilateral damage to the pyramidal system and the somatosensory pathway. SPECT imaging showed left fronto-parietal hypoperfusion.

CONCLUSIONS

This document provides support for the understanding of involuntary emotional expression disorders as a differential diagnosis in the clinical practice of psychiatrists, as well as the functional anatomy of these conditions.

Chronic thinner inhalation alters olfactory behaviors in adult mice

Volatile solvents exposure can result in various behavioral impairments that have been partly associated to altered adult hippocampal neurogenesis. Despite recent evidence supporting this association, few studies have been devoted to examine the impact on olfactory functioning and olfactory bulb (OB) neurogenesis, although olfactory system is directly in contact with volatile molecules. Thus, this study was designed to evaluate in adult mice the potential modifications of the olfactory functioning after acute (1 day), subchronic (6 weeks) and chronic (12 weeks) exposure to thinner vapor at both behavioral and cellular levels. Firstly, behavioral evaluations showed that chronic thinner exposure impacts on odor detection ability of treated mice but does not affect mice ability to efficiently discriminate between two different odors. Moreover, chronic thinner exposure produces impairment in the olfactory-mediated associative memory. Secondly, analysis of the effects of thinner exposure in the subventricular zone (SVZ) of the lateral ventricle and in the OB revealed that thinner treatments do not induce apoptosis nor glial activation. Thirdly, immunohistochemical quantification of different markers of adult olfactory neurogenesis showed that inhalant treatments do not change the number of proliferating progenitors in the SVZ and the rostral migratory stream (RMS), as well as the number of newborn cells reaching and integrating in the OB circuitry. Altogether, our data highlight that the impaired olfactory performances in chronically-exposed mice are not associated to an alteration of adult neurogenesis in the SVZ-OB system.

ACUTE EXPOSURE TO ABUSE-LIKE CONCENTRATIONS OF TOLUENE INDUCES INFLAMMATION IN MOUSE LUNGS AND BRAIN

Toluene is an aromatic hydrocarbon commonly abused by young adolescents for its central nervous system depressant effects. While toluene's pharmacological effects at high concentrations are relatively well known, few studies have assessed toluene's effects on lung and brain tissues. The present study characterized the pathological effects of acute inhaled toluene exposure in the lungs and brains of male Swiss-Webster mice (N = 68). Using a static vapor exposure chamber, mice (PND 28) received a single 30-min toluene administration (0, 1000, 2000, or 4000 ppm). Lung and brain tissues were extracted 24 hrs post-exposure. Histology results revealed significant changes in the morphology lung tissue (e.g., irregular cellular architecture) with the 2000 and 4000 ppm exposures expressing greater signs of pathology than control 0-ppm exposure. Markers of immune system activity (F4/80 and Ly-6G) and cellular proliferation (Ki-67) in the lung revealed no significant differences. Additionally, brain tissues were analyzed for changes of astrogliosis (GFAP) and oxidative stress (GPx). GFAP showed increased astrogliosis in the striatum with 2000 ppm toluene showing significantly higher expression than control (p < 0.05), and a marginal effect in the hippocampus. No other markers showed significant changes. The increased signs of inflammation and cellular damage suggest that exposure to a single high concentration of toluene, typical of abuse, are capable of producing pathology in both lung and brain tissue.

Toluene-induced leukodystrophy from glue sniffing

A 33-year-old man with a history of chronic toluene abuse through glue sniffing, developed tremors, cerebellar signs and cognitive decline. MR scan of the brain showed global cerebral and cerebellar atrophy with symmetrical T2-weighted hypointensities in the basal ganglia, thalami and midbrain. After stopping glue sniffing, his tremors, ataxia of gait, speech and cognition partially improved. Early recognition and intervention of toluene-induced leukodystrophy could prevent ongoing morbidity and premature mortality.

Involuntary Emotional Expression Disorder in a Patient With Toluene Leukoencephalopathy

OBJECTIVE

Inhalant users may develop toluene leukoencephalopathy, a devastating neuropsychiatric disorder. We present a case of toluene-induced damage to the corticospinal and the corticonuclear tracts, which presented with involuntary emotional expression disorder.

METHODS

Case study of a 20-year-old man with a 3-year history of frequent solvent abuse was admitted to the Neuropsychiatry Unit of the National Institute of Neurology and Neurosurgery because "he could not speak or walk" but would keep "laughing and crying without reason".

RESULTS

Neuropsychiatric examination revealed pathological laughter and crying, facial and speech apraxia, a bilateral pyramidal syndrome, and lack of control of urinary sphincter. Magnetic resonance imaging revealed a highly selective bilateral damage to the pyramidal system and the somatosensory pathway. SPECT imaging showed left fronto-parietal hypoperfusion.

CONCLUSIONS

This document provides support for the understanding of involuntary emotional expression disorders as a differential diagnosis in the clinical practice of psychiatrists, as well as the functional anatomy of these conditions.

Increased behavioral and neuronal responses to a hallucinogenic drug after adolescent toluene exposure in mice: Effects of antipsychotic treatment

Toluene has been characterized as a non-classical hallucinogen drug through activation of 5-HT_2A receptors and antagonism of NMDA receptors. It remains unclear whether psychotic symptoms after long-term and intense toluene exposure are associated with abnormalities in 5-HT_2A receptor function. The present study examined whether the responses to a hallucinogenic 5-HT_2A receptor agonist 2,5-dimethoxy-4-iodoamphetamine (DOI) were altered in a mouse model of toluene psychosis. Male NMRI mice were subchronically treated with toluene during adolescence. Reciprocal social interaction test and novel object recognition test were conducted to confirm the persistent behavioral deficits in adulthood. Subsequently, DOI-induced head twitch, c-Fos and Egr-2 expression, field potentials in the medial prefrontal cortex (mPFC), and the levels of 5-HT_2A, 5-HT_1A and mGlu2 receptors in the mPFC were monitored. Toluene exposure during adolescence produced social and memory impairments and enhanced DOI-induced behavioral, molecular and electrophysiological responses, but did not change the levels of 5-HT_2A, 5-HT_1A or mGlu2 receptors in the mPFC. Moreover, the effects of haloperidol and risperidone on the behavioral deficits and hyper-responsiveness to DOI after adolescent toluene exposure were compared. When administered after adolescent toluene exposure, risperidone could reverse social withdrawal, cognitive impairment and hypersensitivity to DOI, whereas haloperidol was only beneficial for social withdrawal. These findings suggest that increased functionality of 5-HT_2A receptors may play a critical role in solvent-induced psychosis and recommend the antipsychotics with more selective 5-HT_2A receptor antagonism as the first-line treatment for solvent-induced psychosis.

Default Mode Network Efficiency Is Correlated With Deficits in Inhibition in Adolescents With Inhalant Use Disorder

It is well established that alterations in cognitive function and damage to brain structures are often found in adolescents who have substance use disorder (SUD). However, deficits in executive cognitive functioning in adolescents related to the vulnerability and consumption of such substances are not well known. In this study, we use graph theoretic analysis to compare the network efficiency in the resting state for three networks-default mode network (DMN), salience network (SN) and fronto-parietal network (FPN)-between inhalant-consuming adolescents and a control group (12 to 17 years old). We analyzed whether the efficiency of these functional networks was related to working memory, mental flexibility, inhibition of response, and sequential planning. We found that, when compared to the control group, inhalant-consuming adolescents presented with important deficits in communication among brain regions that comprise the DMN, SN, and FPN networks. DMN is the most affected network by inhalant abuse during adolescence. The mediation analyses suggested that the relationship between inhalant abuse and inhibitory control and sequential planning was partly mediated by DMN efficiency.

Adolescent inhalant use and psychosis risk - a prospective longitudinal study

BACKGROUND

Cross-sectional studies have suggested inhalant use is associated with psychosis. This association was examined in a longitudinal study accounting for other substance use and potential confounders.

METHODS

We used a prospective sample (N = 6542) from the Northern Finland Birth Cohort 1986. Self-report questionnaires on substance use and psychotic experiences were completed when the cohort members were 15-16 years old. Inhalant use was categorized into four groups (never, once, 2-4 times, 5 times or more). Subsequent psychosis diagnoses (ICD-10) until age 30 years were obtained from national registers. Cox regression analysis was used to examine the association between adolescent inhalant use and risk of psychosis.

RESULTS

During the observation period 124 individuals were diagnosed with incident psychosis. Overall, there were 225 (3.4%) subjects with any inhalant use, 18 (8.0%) of whom were diagnosed with psychosis during the follow up. Of non-inhalant users (n = 6317) 106 (1.7%) were diagnosed with psychosis. Compared to non-users, those using inhalants had increased risk of incident psychosis with most frequent inhalant use associated with the greatest risk (unadjusted HR = 9.46; 3.86-23.20). After adjusting for baseline psychotic experiences, other substance use, comorbid mental disorder and parental substance abuse, the increased risk of psychosis persisted (HR = 3.06; 1.05-8.95). Furthermore, a dose-response effect between inhalant use and risk of psychosis was identified (OR = 2.34; 1.83-2.99).

CONCLUSIONS

Inhalant use in adolescence was independently associated with incident psychosis. The adverse health outcomes associated with adolescent inhalant use provide compelling reasons for implementation of policies to reduce the use of volatile substances in adolescents.

White matter and cognition: making the connection

Whereas the cerebral cortex has long been regarded by neuroscientists as the major locus of cognitive function, the white matter of the brain is increasingly recognized as equally critical for cognition. White matter comprises half of the brain, has expanded more than gray matter in evolution, and forms an indispensable component of distributed neural networks that subserve neurobehavioral operations. White matter tracts mediate the essential connectivity by which human behavior is organized, working in concert with gray matter to enable the extraordinary repertoire of human cognitive capacities. In this review, we present evidence from behavioral neurology that white matter lesions regularly disturb cognition, consider the role of white matter in the physiology of distributed neural networks, develop the hypothesis that white matter dysfunction is relevant to neurodegenerative disorders, including Alzheimer's disease and the newly described entity chronic traumatic encephalopathy, and discuss emerging concepts regarding the prevention and treatment of cognitive dysfunction associated with white matter disorders. Investigation of the role of white matter in cognition has yielded many valuable insights and promises to expand understanding of normal brain structure and function, improve the treatment of many neurobehavioral disorders, and disclose new opportunities for research on many challenging problems facing medicine and society.

Acute high-level toluene exposure decreases hippocampal neurogenesis in rats

Toluene is an organic solvent that is used in various industrial applications. Despite its usefulness, toluene has toxic effects on the brain and is a substance that is commonly abused. Toluene causes behavioral and functional abnormalities such as decreased memory capacity, cognitive impairment, and depression-like symptoms. However, the target sites and toxic mechanisms of inhaled toluene in the brain are poorly understood. In this study, we subjected Sprague-Dawley (SD) rats to acute high-level toluene exposure (7000 ppm) to investigate its neuronal toxicity, and in particular, its effect on neurogenesis in the hippocampus. In order to assay the effects of inhaled toluene on hippocampal neurogenesis, we measured the levels of neurogenesis markers Ki-67 and doublecortin (DCX) in the hippocampus 1, 2, 5, and 8 days after cessation of toluene exposure. In addition to assaying clinical signs, body weight, and bronchoalveolar lavage fluid, the liver, lungs, and kidneys were subjected to histopathological examination to investigate the toxic effects of high-level toluene exposure. Although abnormal neurological signs were observed after toluene exposure, these disappeared within 24 h and no toluene-related toxicological effects were observed in the liver, lungs, or kidneys. The animals exposed to toluene showed significantly decreased hippocampal neurogenesis, which persisted until the 8th and final day of measurement. Thus, acute high-level toluene exposure inhibited hippocampal neurogenesis and produced transient abnormal neurological signs, but did not produce toxicity in the other organs studied.

Fragile X tremor ataxia syndrome and white matter dementia

OBJECTIVE

Fragile X tremor ataxia syndrome (FXTAS) is an inherited neurodegenerative disease in which dementia is common and disabling. The pathogenesis of dementia in FXTAS is poorly understood, but the salience of executive dysfunction and slowed processing speed, the frequent presence of the middle cerebellar peduncle sign on magnetic resonance imaging (MRI), and striking neuropathological alterations of white matter all suggest that myelinated tracts are significantly involved. This paper considers the role of white matter disease in FXTAS dementia, particularly with regard to the concept of white matter dementia (WMD).

METHOD

A focused review of FXTAS in relation to known white matter disorders is provided to propose that the concept of WMD may illuminate the basis of dementia in FXTAS. The putative pathogenetic contribution of white matter involvement in other neurodegenerative diseases is also considered.

RESULTS

Considerable evidence supports the importance of white matter disease in the pathogenesis of dementia in FXTAS. Whereas, gray matter regions are also involved, white matter degeneration is prominent, even early in the disease, and correlates with executive dysfunction and slowed processing speed. Evidence for white matter involvement in other neurodegenerative diseases lends additional support to the relevance of white matter in FXTAS.

CONCLUSION

The dementia of FXTAS is closely related to the profile of WMD, and white matter involvement is also supported by MRI and neuropathological observations. White matter pathology is also relevant to the pathogenesis of other neurodegenerative diseases. Further study of white matter promises to clarify the origin of dementia in FXTAS.

Occupation and the risk of chronic toxic leukoencephalopathy

Among the hundreds of environmental insults capable of inducing nervous system injury, a small number can produce clinically significant damage to the brain white matter. The use of magnetic resonance imaging (MRI) in affected individuals has greatly illuminated this previously obscure area of neurotoxicology. Toxic leukoencephalopathy has acute and chronic forms, in both of which cognitive dysfunction is the major clinical manifestation. Chronic toxic leukoencephalopathy (CTL) has been most thoroughly described in individuals with intense and prolonged exposure to leukotoxins, but the consequences of lesser degrees of exposure are not well understood. Rare cases of CTL have been reported in workers exposed to culpable leukotoxins, but study of this syndrome is hindered by many confounds such as uncertain level of toxin exposure, the presence of multiple toxins, vague dose-response relationship, comorbid medical or neurologic disorders, psychiatric illness, and legal issues. The risk of CTL in workers is low, although it is not possible to determine quantitative risk estimates. More knowledge can be expected with the application of advanced MRI techniques to the assessment of workers who may have been exposed to known or potential leukotoxins. Preventive measures for avoiding workplace CTL will be informed by clinical assessment involving the use of advanced neuroimaging and neuropsychologic evaluation in combination with accurate measurement of leukotoxin exposure.

Reversible cerebral periventricular white matter changes with corpus callosum involvement in acute toluene-poisoning

Substance poisoning, such as toluene intoxication, has seldom been reported in the relevant literature. The documented cerebral neuroimaging has mostly described reversible symmetrical white matter changes in both the cerebral and cerebellar hemispheres. This paper presents 2 patients with toluene poisoning, whose brain magnetic resonance imaging studies showed a similar picture that included extra involvement over the corpus callosum; however, such corpus callosum involvement has never been mentioned and is quite rare in the literature. We discussed the underlying neuropathological pathways in this article. Hopefully, these cases will provide first-line clinicians with some valuable information with regard to toluene intoxication and clinical neuroimaging presentations.