Toluene inhalation induced 8-hydroxy-2'-deoxyguanosine formation as the peroxidative degeneration in rat organs

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.

Airborne toluene exposure causes germline apoptosis and neuronal damage that promotes neurobehavioural changes in Caenorhabditis elegans

Toluene is a highly volatile organic solvent present in gasoline. Exposure mainly occurs by absorption via the pulmonary tract and easily reaches the central nervous system, which causes toxic effects. Toluene toxicity has been described but not well established. The present work aimed to evaluate the effects of airborne exposure to toluene, the in vivo model Caenorhabditis elegans was assessed to determine whether nematode could be used to evaluate the effects of exposure to toluene and the possible mechanisms of toxicity of the solvent. Worms at the first or fourth larval stages were exposed to toluene for 48 or 24 h, respectively, in a laboratory-developed vapor chamber at concentrations of 450, 850, 1250 and 1800 ppm. We observed increases in worm mortality and significant developmental delays that occurred in a concentration-dependent manner. An increased incidence of apoptotic events in treated germline cells was shown, which was consistent with observed reductions in reproductive capacity. In addition, toluene promoted significant behavioural changes affecting swimming movements and radial locomotion, which were associated with changes in the fluorescence intensity and morphology of GABAergic and cholinergic neurons. We conclude that toluene exposure was toxic to C. elegans, with effects produced by the induction of apoptosis and neuronal damage.

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.

Acute toluene intoxication--clinical presentation, management and prognosis: a prospective observational study

Background

Toluene is one of the most widely abused inhaled drugs due to its acute neurologic effects including euphoria and subsequent depression. However, dangerous metabolic abnormalities are associated to acute toluene intoxication. It has been previously reported that rhabdomyolysis and acute hepatorenal injury could be hallmarks of the condition, and could constitute risk factors for poor outcomes. The objective was to describe the clinical presentation, to characterize the renal and liver abnormalities, the management and prognosis associated to acute toluene intoxication.

Methods

We prospectively assessed 20 patients that were admitted to a single center’s emergency department from September 2012 to June 2014 with clinical and metabolic alterations due to acute toluene intoxication.

Results

The main clinical presentation consisted of weakness associated to severe hypokalemia and acidosis. Renal glomerular injury (proteinuria) is ubiquitous. Biliary tract injury (alkaline phosphatase and gamma-glutamyl transpeptidase elevations) disproportional to hepatocellular injury is common. Rhabdomyolysis occurred in 80 % of patients, probably due to hypokalemia and hypophosphatemia. There were three deaths, all female, and all associated with altered mental status, severe acidosis, hypokalemia and acute oliguric renal failure. The cause of death was in all cases due to cardiac rhythm abnormalities.

Conclusion

The hallmarks of acute toluene intoxication are hypokalemic paralysis and metabolic acidosis. Liver injury and rhabdomyolysis are common. On admission, altered mental status, renal failure, severe acidemia and female gender (not significant in our study, but present in all three deaths) could be associated with a poor outcome, and patients with these characteristics should be considered to be treated in an intensive care unit.

Oxidative stress effects of thinner inhalation

Thinners are chemical mixtures used as industrial solvents. Humans can come into contact with thinner by occupational exposure or by intentional inhalation abuse. Thinner sniffing causes damage to the brain, kidney, liver, lung, and reproductive system. We discuss some proposed mechanism by which thinner induces damage. Recently, the induction of oxidative stress has been suggested as a possible mechanism of damage. This paper reviews the current evidence for oxidative stress effects induced by thinner inhalation. Early ideas about the effects of thinner on lipids are discussed in one section. We discuss several studies that have shown the oxidative effects of thinner inhalation on: lipid peroxidation, levels of antioxidant enzymes, glutathione depletion, and oxidation of proteins and DNA. We have also included studies about oxidative stress effects induced by toluene, the principal component (60-70%) of thinner. Finally, work describing the effects of oxidative stress induced by thinner inhalation on different organs is discussed.

Immunochemical detection of oxidatively damaged DNA

Oxidatively damaged DNA is implicated in various diseases, including neurodegenerative disorders, cancer, diabetes, cardiovascular and inflammatory diseases as well as aging. Several methods have been developed to detect oxidatively damaged DNA. They include chromatographic techniques, the Comet assay, (32)P-postlabelling and immunochemical methods that use antibodies to detect oxidized lesions. In this review, we discuss the detection of 8-oxo-7,8-dihydro-29-deoxyguanosine (8-oxodG), the most abundant oxidized nucleoside. This lesion is frequently used as a marker of exposure to oxidants, including environmental pollutants, as well as a potential marker of disease progression. We concentrate on studies published between the years 2000 and 2011 that used enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry to detect 8-oxodG in humans, laboratory animals and in cell lines. Oxidative damage observed in these organisms resulted from disease, exposure to environmental pollutants or from in vitro treatment with various chemical and physical factors.

Pulmonary toxicity and environmental contamination: radicals, electron transfer, and protection by antioxidants

The atmosphere is replete with a mixture of toxic substances, both natural and man-made. Inhalation of toxic substances produces a variety of insults to the pulmonary system. Lung poisons include industrial materials, particulates from mining and combustion, agricultural chemicals, cigarette smoke, ozone, and nitrogen oxides, among a large number of other chemicals and environmental contaminants. Many proposals have been advanced to explain the mode of action of pulmonary toxicants. In this review we focus on mechanisms of pulmonary toxicity that involve ET, ROS, and OS. The vast majority of toxicants or their metabolites possess chemical ET functionalities that can undergo redox cycling. Such recycling may generate ROS that can injure various cellular constituents in the lung and in other tissues. ET agents include quinones, metal complexes, aromatic nitro compounds, and conjugated iminium ions. Often, these agents are formed metabolically from parent toxicants. Such metabolic reactions are often catalytic and require only small amounts of the offending material. Oxidative attack is commonly associated with lipid peroxidation and oxidation of DNA, and it may result in strand cleavage and 8-OH-DG production. Toxicity is often accompanied by depletion of natural AOs, which further exacerbates the toxic effect. It is not surprising that the use of AOs, both natural in fruits and vegetables, as well as synthetic, may provide protection from the adverse effects of toxicant exposure. The mechanistic framework described earlier is also applicable to some of the more prominent pulmonary illnesses, such as asthma, COPD, and cancer.

Correlation between formamidopyrimidine DNA glycosylase (Fpg)-sensitive sites determined by a comet assay, increased MDA, and decreased glutathione during long exposure to thinner inhalation

Thinner inhalation causes toxic effects in a variety of organs, principally in the central nervous system. Some studies have shown oxidative stress effects of thinner inhalation, such as: activation of free radical processes, decrease of antioxidants, and oxidation products of proteins and lipids but not of DNA. The aim of this study is to investigate the effect of thinner inhalation on DNA. We used the comet assay in conjunction with the enzyme formamidopyrimidine glycoslyase (Fpg). Our results show a significant increase in Fpg-sensitive sites in DNA of lymphocytes from rats exposed to thinner fumes compared to lymphocytes from control rats (p < 0.05). Moreover, DNA damage detected with Fpg shows a high correlation with increased malondialdehyde (MDA) and decreased glutathione (GSH), two widely used biomarkers of oxidative stress. The most abundant base oxidation product found in DNA is 8-oxoguanine; it is the main substrate of Fpg and the most commonly used biomarker for oxidative DNA damage. This suggests that oxidative DNA damage is at least partly responsible for the DNA damage detected by Fpg. We propose the comet assay in combination with Fpg as a sensitive biomarker to monitor exposure to thinner inhalation. Limitations of this method are discussed.

In vitro evaluation of oxidative damage from organic solvent vapours on human skin

Aim of this study is to focus on the cutaneous effects of occupational exposure to the vapours of common organic solvents. Higher incidence of cancer is suspected in subjects exposed to organic solvents characterized by reactive metabolic intermediates, which are assumed to induce oxidative damage on liver, kidney and haematopoietic system. To our knowledge there are no relevant data about the oxidative effect of the organic solvents on skin after exposure to their vapours. An in vitro model was optimized to evaluate the viability and integrity of the barrier function of human skin following occupational exposure to solvent vapours. To evaluate the role of oxidative stress, the antioxidant status of skin and some biomarkers of oxidative damage as lipid and protein peroxidation products and DNA fragmentation were also studied. It was investigated if decreasing concentrations of styrene, toluene, acetone, xylene and perchloroethylene vapours, up to be comparable to the TLV-TWA, were able to damage skin integrity. Solvent vapours reduced tissue viability and impaired skin barrier function, as indicated by the increase of transepidermal water loss. Reduced glutathione depletion, decreased activity of antioxidant enzymes and oxidative damage of biological macromolecules were also observed. The overall trend of these results indicates that the tested compounds damage human skin even at concentrations comparable to their TLV, and that oxidative stress is involved in these effects.

Urinary 8-hydoxydeoxyguanosine (8-OHdG) and plasma malondialdehyde (MDA) levels in Aldh2 knock-out mice under acetaldehyde exposure

To clarify the carcinogenicity of acetaldehyde when associated with ALDH (aldehyde dehydrogenase) 2 polymorphism, Aldh2 knock-out (Aldh2-/-) mice and their wild type (Aldh2+/+) mice were exposed to two different concentrations of acetaldehyde (125 ppm and 500 ppm) for two weeks. Aldh2-/- mice, which have the same genetic background as C57BL/6J (wild mice) except for the Aldh2 gene, were used as models of humans who lack ALDH2 activity. Urinary 8-hydroxydeoxyguanosine (8-OHdG) and plasma malondialdehyde (MDA) levels were measured as indicators of oxidative DNA damage and lipid peroxidation, respectively. At 125 ppm acetaldehyde exposure for 12 d, urinary 8-OHdG levels in Aldh2+/+ mice did not increase. However, urinary 8-OHdG levels in Aldh2-/- mice were slightly increased by the end of the exposure. On the other hand, plasma MDA levels did not increase in either Aldh2-/- orAldh2+/+ mice. At 500 ppm, urinary 8-OHdG levels in both Aldh2-/- and Aldh2+/+ mice significantly increased after 6 and 12 d, but there was no genetic difference. On the other hand, plasma MDA levels in Aldh2+/+ and Aldh2-/- mice did not increase at either 125 ppm or 500 ppm after two weeks of exposure. In conclusion, it is suspected that DNA was damaged by acetaldehyde inhalation, and that susceptibility to acetaldehyde varies according to Aldh2 genotype.

Changes in renal function and oxidative damage in methamphetamine-treated rat

In this study, we observed renal damage and peroxidative injury as the acute or sub-acute effect of methamphetamine (MA) to determine whether MA intoxication can be diagnosed from immunohistochemical changes in the kidney. In addition, renal function was investigated in relation to the immunohistochemical changes. A single administration of MA (group I) (50mg/kg/ (i.p.)) and repeated administration (group II) (10mg/kg/day (i.p.) for 5 days) were designed as an acute model and a sub-acute or chronic model. Immunohistochemically, cell damage markers were observed. Then, renal function markers and minerals in blood were measured. Myoglobin and creatinine phosphokinase (CPK) in blood were also analyzed. In group I, ubiquitin immunoreactivity was enhanced only in the renal tubules. Creatinine increased, while K, Ca, and P decreased (P<0.01). CPK increased significantly (P<0.01). Therefore, it was suspected that MA might induce renal dysfunction with renal tubule damage. This damage might be related to leakage of CPK from muscle. In group II, 8-hydroxy-2'-deoxyguanosine (8-OH-dG) increased immunohistochemically and quantitatively (P<0.01). It was considered that oxidative DNA damage might be induced by repeated administration. It was considered that this study offers basic information for the evaluation of pathological changes in the kidney in MA-related autopsy cases.

Immunohistochemical study of rat spermatogenesis after toluene-inhalation

After prolonged toluene-inhalation (for 20 days) at the common abuse density (1500 ppm for 4 h per day), the effect of toluene on spermatogenesis in rats was investigated. Body weight was significantly decreased in the toluene group (P < 0.05). However, the weights of the testis and epididymis were maintained. To confirm whether the toluene-inhalation influences testis and epididymis as a stress factor; anti-70kD heat-shock protein (HSP70) and c-fos gene product (c-Fos) were observed. To observe the change of the cell division and the proliferation in spermatogenesis, proliferating cell nuclear antigen (PCNA) were stained immunohistochemically, and apoptosis was also detected. There was no positive immunoreactivity for HSP70 or c-Fos. There was no significant difference in the PCNA-expression in both groups. It was considered that toluene-inhalation did not have a clear influence in the division of spermatogonium and spermatocytes. On in situ apoptosis detection, slightly enhanced signals were observed in the toluene-inhalation groups. This might have some influence on meiosis from spermatocyte to spermatid. However, in toluene-inhalation rats exposed to a common abuse density, it was considered that spermatogenesis was well maintained and not apparently damaged.