Biological monitoring of isocyanates and related amines

Summary Five male subjects were exposed to 1,6-hexamethylene diisocyanate (HDI) atmospheres for 7.5 h. The exposures were performed in an 8 m3 stainless steel test chamber, and the HDI atmospheres were generated by a gas-phase permeation method. HDI in air was determined by an HPLC method utilizing the 9-(N-methylaminomethyl)-anthracene reagent, and by a continuous monitoring device (MDA 7100). The average air concentration was ca 25 g/m³, and the inhaled dose of HDI for the different subjects was estimated at ca 100 g. The related amine 1,6-hexamethylene diamine (HDA) was, after acid hydrolysis of urine and plasma, determined as a heptafluorobutyric derivative, by glass capillary gas-chromatography and selected ion monitoring (SIM), in a chemical ionization mode using ammonia as reagent gas. The cumulated urinary excretion of HDA during 28 h was 8.0 to 14 g, which corresponds to ca 11 to 21% of the inhaled dose of HDI. The urinary level of HDA, in samples collected immediately after the end of the exposures, was on average 0.02 mmol/mol creatinine (range 0.01–0.03 mmol/mol creatinine). The urinary elimination was rapid, and half-time (t_1/2), for the concentration of HDA in urine, showed an average of 1.2 h (range 1.1–1.4 h). No specific IgE and IgG antibodies to HDI were detected before and after provocation; nor were spirometry or bronchial reactivity changed immediately and 15 h after provocation. Analysis of HDA in hydrolysed urine, as a marker of short-time exposure to HDI, is proposed.     

Increased nasal epithelial ciliary beat frequency associated with lifestyle tobacco smoke exposure

The ciliated epithelium of the respiratory airways is one of the first vital systemic surfaces in contact with the ambient air. Ex vivo nasal epithelial ciliary beat frequency (CBF) at room temperature is on the order of 7–8 Hz but may be stimulated by irritant exposure. The upregulation of CBF in response to acute irritant exposure is generally considered to be a transient event with eventual return to baseline. However, studies of CBF dynamics in response to typical lifestyle exposures are limited. This study assessed nasal epithelial CBF among human subjects as a function of quantifiable lifestyle tobacco smoke exposure. Nasal epithelial biopsies were obtained from human subjects with well documented histories of tobacco smoke exposure. CBF was determined using a digital photometric technique and concurrent assays of nasal nitric oxide and urine cotinine and creatinine were performed. Mean CBF among active smokers and non-smokers exposed to environmental tobacco smoke (ETS) was elevated over non-smokers. Although there were dramatic differences in relative levels of tobacco smoke exposure, CBF values among tobacco smoke-exposed groups were comparable. Parallel in vitro studies of cultured nasal epithelium exposed to cigarette smoke condensate further supported these observations. These studies suggest that persistent elevation in nasal epithelial CBF is an early, subtle, physiologic effect associated with lifestyle tobacco smoke exposure. The molecular mechanisms that upregulate CBF may also create a cell molecular milieu capable of provoking the eventual emergence of more overt adverse health effects and the pathogenesis of chronic airway disease.     

Acute and subchronic toxicity of inhaled toluene in male Long–Evans rats: Oxidative stress markers in brain

The effects of exposure to volatile organic compounds (VOCs), which are of concern to the EPA, are poorly understood, in part because of insufficient characterization of how human exposure duration impacts VOC effects. Two inhalation studies with multiple endpoints, one acute and one subchronic, were conducted to seek effects of the VOC, toluene, in rats and to compare the effects between acute and subchronic exposures. Adult male Long–Evans rats were exposed to toluene vapor (n = 6 per group) at a concentration of 0 or 1019 ± 14 ppm for 6 h in the acute study and at 0 ± 0, 10 ± 1.4, 97 ± 7, or 995 ± 43 ppm for 6 h/d, 5 d/week for 13 weeks in the subchronic study. For the acute study, brains were dissected on ice within 30 min of the end of exposure, while for the subchronic study, brains were dissected 18 h after the last exposure. Frontal cortex, hippocampus, cerebellum, and striatum were assayed for a variety of oxidative stress (OS) parameters including total aconitase (TA), protein carbonyls, glutathione peroxidase (GPX), glutathione reductase (GRD), glutathione transferase (GST), γ-glutamylcysteine synthetase (GCS), superoxide dismutase (SOD), total antioxidants (TAS), NADPH quinone oxidoreductase-1 (NQO1), and NADH ubiquinone reductase (UBIQ-RD) activities using commercially available kits. Following acute exposure, UBIQ-RD, GCS and GRD were increased significantly only in the cerebellum, while TAS was increased in frontal cortex. On the other hand, subchronic exposure affected several OS markers including increases in NQO1 and UBIQ-RD. The effect of subchronic toluene exposure on SOD and TAS was greater in the striatum than in the other brain regions. TA activity (involved in maintaining iron homeostasis and an indicator of DNA damage) was inhibited in striatum and cerebellum, increased in hippocampus, and unchanged in frontal cortex. Protein carbonyls increased significantly in both the frontal cortex and cerebellum. In general, the results showed that acute exposure to toluene affected OS parameters to a lesser extent than did subchronic exposure. These results suggest that toluene exposure induces OS in the brain and this may be a component of an adverse outcome pathway for some of the neurotoxic effects reported following toluene exposure.     

A Murine Monoclonal Antibody with Broad Specificity for Occupationally Relevant Diisocyanates

Diisocyanates (dNCOs) used in industrial applications are well known low molecular weight allergens. Occupational exposure is associated with adverse health outcomes including allergic sensitization and occupational asthma. In this study, we report the production and initial characterization of a dNCO-hapten specific murine IgM monoclonal antibody (mAb). Female BALB/c mice were immunized intraperitoneally with 25 μg of 4,4′-methylene diphenyl diisocyanate (MDI)-keyhole limpet hemocyanin. Following six biweekly booster immunizations, splenocytes were recovered and fused to Sp2/0-Ag14 murine myeloma cell line for hybridoma production. Hybridomas were then screened in a solid-phase indirect enzyme-linked immunosorbent assay (ELISA) against 40:1 4,4′-MDI– human serum albumin (HSA). mAb reactivity to dNCO-HSA conjugates and dNCO-HSA spiked human serum were characterized using a sandwich ELISA. One hybridoma produced a multimeric IgM mAb (15D4) that reacted with 4,4′-MDI-HSA. Sandwich ELISA analysis demonstrated comparable reactivity with other occupationally relevant dNCO-HSA adducts, including 2,4-toluene diisocyanate (TDI)-HSA, 2,6-TDI-HSA, and 1,6-hexamethylene diisocyanate (HDI)-HSA, but not other electrophilic chemical HSA conjugates. The limit of quantification (LOQ) of 4,4′-MDI-HSA, 2,4-TDI-HSA, 2,6-TDI-HSA, and 1,6-HDI-HSA sandwich ELISAs were 567.2, 172.7, 184.2, and 403.5 ng/mL (8.67, 2.60, 2.77, and 6.07 pmol/mL), respectively. In contrast, experiments using dNCO-supplemented human sera showed an increase in the detectable limit of the assay. A mAb has been produced that has potential utility for detecting mixed diisocyanate exposures in occupational environments. The mAb may have additional utility in the standardization of specific IgE detection immunoassays as well as chromatographic-mass spectrometric methods to enrich dNCO adducted HSA in the plasma of occupationally exposed workers.     

Utility of aripiprazole in co-occurring problem gambling and toluene dependence: A case report

Inhalant use is a global problem but in spite of its large prevalence and significant physical and psychological complications, there is inadequate literature on the management of inhalant dependence. Inhalants are also considered a substance of adolescence with most users giving up use in adulthood. There is also limited literature on co-occurring behavioral and substance addictions and the linkage between them. We describe the case of 28-year-old man who had been using toluene in a dependent pattern for 14 years. He also had problem gambling in the past, abstaining from which led to an increase in the daily quantity of use of toluene. The patient was tried on Carbabmazepine but following an adverse event he was prescribed Aripiprazole. He improved over the course of 6 weeks and has been abstaining from inhalants since 3 months.     

Clinical presentation and management in acute toluene intoxication: a case series

Context: Toluene inhalation is a common form of drug abuse throughout the world. Acute toluene toxicity causes neurological changes as well as various metabolic alterations. Hypokalemic paralysis and renal failure are life-threatening complications.

Objective: To identify the clinical and metabolic alterations associated with toluene intoxication.

Materials and methods: We retrospectively analyzed the records of 22 patients that were admitted to a single center’s emergency department from 2006 to 2012 with clinical and metabolic alterations due to toluene inhalation.

Results: Of the 22 patients, 77% were male and mean age was 23.5 years (range: 17–30). The main clinical presentation was weakness associated to severe hypokalemia. Severe metabolic acidosis was found in 20 patients. Renal tubular acidosis was diagnosed in five patients. The patients responded to supportive measures and aggressive potassium repletion. Prognosis was generally good.

Conclusion: Toluene inhalation is associated with various severe metabolic alterations. Treatment guidelines are needed considering the frequency of toluene inhalation in the population.     

昆明鼠腹腔注射甲苯急性中毒的行为学实验研究

目的研究昆明鼠腹腔注射甲苯急性中毒的行为学表现,探讨甲苯急性毒性神经损伤。方法昆明鼠随机分成6组,8 000mg/kg,4 000mg/kg,2 000mg/kg,1 000mg/kg,500 mg/kg等不同剂量甲苯小鼠腹腔注射制作急性中毒模型,生理盐水对照组,染毒后观察24h一般行为学改变和4d、6d、8d、10d、12d、14d运用程控自主活动箱检测神经兴奋性变化,运用寇氏法公式计算药物半数致死剂量LD50。结果甲苯染毒各组都有急性中毒的表现,主要表现为抑制;甲苯急性毒性对小鼠有严重损伤,其自主活动表现为短暂的兴奋后迅速转为抑制。LD50=1782.38?/?,S lg LD50=0.0602(LD50的标准误),LD5095%C I(可信区间)=(1358.31 2338.84)?/?。自主活动明显降低(P<0.05),2 000 mg/kg与1 000 mg/kg、500 mg/kg比较有差异(P<0.05)。结论小鼠腹腔注射甲苯发现具有急性毒性,LD50=1782.38?/?;中毒小鼠自主活动性降低(P<0.05)。     

A fatal case of acute hepatitis B developed in a toluene abuser

Liver dysfunction involving toluene intoxicity includes elevation of transaminase level and delayed complications of liver failure, but its effect on hepatitis B virus (HBV) infection is as yet unknown. Here, we report a case of fulminant hepatitis B developed in a toluene abuser. A 23-year-old female toluene abuser was admitted to a local clinic because of nausea, vomiting, and dizziness, and a mild elevation of serum transaminase level was identified. She was treated as an outpatient, but continued toluene inhalation during follow-up. Five days later, she was found in a drowsy state of consciousness and taken to the emergency unit of our institution. Laboratory findings showed an alanine aminotransferase level of 4,659 IU, a remarkably prolonged prothrombin time, and she was diagnosed with fulminant hepatitis B. Intensive care was carried out, but she died the next day. Molecular analysis revealed that the HBV isolate was classified as genotype C, and nucleotide positions that are prone to fulminant hepatitis were A at 1,762 and G at 1,764 in the core promoter region, and G at 1,896 in codon 28 in the precore region. The long-term toluene inhalation could have contributed to drastic clinical course of acute hepatitis B in this patient.     

Developmental and reproductive toxicity evaluation of toluene vapor in the rat II. Developmental toxicity

The developmental toxicity of toluene was evaluated via whole body inhalation exposure, in pregnant Sprague Dawley rats exposed to toluene (99.9% pure) from gestation day (GD) 6–15 inclusive, 6 h/day, at concentrations of 0, 250, 750, 1500 and 3000 ppm (0, 938, 2812, 5625 and 11250 mg/m³). Doses were selected from a preliminary study performed over a range of concentrations from 0 to 5000 ppm, in which maternal and fetal toxicity were observed at 2000 ppm and above. This study has been cited in various regulatory documents and is presented here to allow greater accessibility to results and conclusions.

Toluene induced clinical signs in pregnant dams (ataxia, hyper-responsivity, increased water intake, decreased food consumption) at 3000 ppm, ataxia and hyper-responsivity at 1500 ppm, and reduced maternal body weight gain at 1500 during the exposure period only and at 3000 ppm from initiation of exposure to GD20. At Caesarean section on GD20, no adverse effects on implantation, number and viability of fetuses, or fetal sex distribution were observed. Litter weight and mean fetal weight was reduced at 3000 ppm and mean fetal weight was reduced at 1500 ppm. Instances of reduced or unossified skeletal elements occurred at the same dose levels. Mean fetal weight was also reduced at 250 ppm but not at 750 ppm. Extensive statistical analysis of fetal body weight data support the conclusion that there is no toxicologically significant dose-related effect on fetal body weight at or below 750 ppm. Low incidences (≤2.5%) of various malformations occurred in the 250, 1500, and 3000 ppm groups; there was no increase in the incidence of specific or total malformations with increased exposure and thus these were not attributed to toluene.

In this Toluene study, the maternal toxicity NOAEL was 750 ppm with a defined maternal and developmental toxicity LOAEL of 1500 ppm.