1,3,5-Trinitrobenzene-induced alpha-2u-globulin nephropathy

In Vivo Evaluation of the Oral Toxicity of the Chlorobutanol

Chlorobutanol (CB) is used as a preservative in cosmetics and has antibacterial activity. This study investigated the single- and repeated-dose 28-day oral toxicity of a CB solvent in Sprague Dawley (SD) rats. For the single-dose oral toxicity study, a dose of 62.5, 125, or 250 mg per kg of body weight (mg/kg b.w.) of CB was given once orally via gavage. For the repeated-dose 28-day toxicity study, the high dose was set as 100 mg/kg b.w./day, and the middle, middle-low, and low doses were set to 50, 25, and 12.5 mg/kg b.w./day, respectively. Body weight was not significantly changed in the repeated-dose toxicity study. Relative liver and kidney weights were significantly increased in both sexes of the 100 mg/kg b.w./day treatment group. However, there were histopathological changes in liver and kidney for females and males, respectively. These data suggested that the approximate lethal dose (ALD) of CB was over 250 mg/kg b.w./day in the single-dose study, and the no adverse effect level (NOAEL) for CB was over 50 and 12.5 mg/kg b.w./day for female and male rats in the repeated-dose toxicity study.

The para isomer of dinitrobenzene disrupts redox homeostasis in liver and kidney of male wistar rats

Background

Para-Dinitrobenzene (p-DNB) is one of the isomers of dinitrobenzene which have been detected as environmental toxicants. Skin irritation and organ toxicities are likely for industrial workers exposed to p-DNB. This study evaluated the effect of sub-chronic exposure of rats to p-DNB on cellular redox balance, hepatic and renal integrity.

Methods

Forty eight male Wistar rats weighing 160–180 g were administered 50, 75, 1000 and 2000 mg/kg b.wt (body weight) of p-DNB or an equivalent volume of vehicle (control) orally and topically for 14 days. After the period of treatment, the activities of kidney and liver catalase (CAT), alkaline phosphatase (ALP) and superoxide dismutase (SOD) as well as extent of renal and hepatic lipid peroxidation (LPO) were determined. Serum ALP activity and plasma urea concentration were also evaluated.

Results

Compared with control animals, p-DNB -administered rats showed decrease in the body and relative kidney and liver weights as well as increased renal and hepatic hydrogen peroxide and lipid peroxidation levels accompanied by decreased superoxide dismutase and catalase activities. However, p-DNB caused a significant increase in plasma urea concentration and serum, liver and kidney ALP activities relative to control. In addition, p-DNB caused periportal infiltration, severe macro vesicular steatosis and hepatic necrosis in the liver.

Conclusions

Our findings show that sub-chronic oral and sub-dermal administration of p-DNB may produce hepato-nephrotoxicity through oxidative stress.

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Activities of kidney and liver catalase and superoxide dismutase were decreased by p-DNB.

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p-DNB increased serum, liver and kidney activity of alkaline phosphatase.

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Plasma urea concentration was increased by p-DNB.

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Lipid peroxidation and H₂O₂ level were increased by p-DNB.

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p-DNB caused histopathological changes in liver and kidney tissues.

Subchronic Toxicity of 1,3,5-Trinitrobenzene in Fischer 344 Rats

The subchronic toxicity of 1,3,5-trinitrobenzene (TNB) in male and female Fischer 344 rats was evaluated by feeding a powdered certified laboratory diet containing 0, 66.7, 400 and 800 mg TNBl kg diet for 90 days. The calculated average TNB intake was 4.29, 24.70, and 49.28 mg/kg body weight (BW)day for females and 3.91, 22.73, and 44.16 mg/ kg BWI day for males. Food intake in the 400 and 800 mg/kg diet dose groups of both sexes was decreased throughout the study and resulted in a significant decrease in absolute body weights. A significant decrease in relative testicular weights and a significant increase in the relative liver weight were observed in male rats receiving 400 or 800 mg TNB/kg diet. A significant increase in the relative spleen weights of both sexes receiving 400 or 800 mg TNB diet was noted. The relative liver weight was also increased only in female rats maintained on the 800 mg TNB diet. Histopathological examinations revealed that the susceptible organs for TNB toxicity were kidney (hyaline droplets) in all male dose groups and testes (seminiferous tubular degeneration) in rats receiving 400 and 800 mg TNB diet groups. The spleen was also affected (extramedullary hematopoiesis) in both sexes in the 400 and 800 mg dose groups. Hematological studies at both 45 (data not given) and 90 days in the 400 and 800 mg dose groups indicated decreased values for red blood cell counts and hemoglobin content, while reticulocytes and methemoglobin levels were increased. Clinical chemistry parameters were unaffected. Based on kidney toxicity and hematological effects, a Low Observed Adverse Effect Level (LOAEL) of 3.91 mg/kg BWI day was suggested for subchronic toxicity studies on TNB.

Toxicity of Tetryl (N-Methyl-N,2,4,6–Tetranitroaniline) in F344 Rats

The toxicity of tetryl (N-methyl-N,2,4,6–tetranitroaniline) in male and female F344 rats was evaluated after adminstration in the diet for 14 or 90 days. The 14–day study diet concentrations used were 0, 500, 1250, 2000, 2500, and 5000 ppm; the 90–day study diet concentrations were 0, 200, 1000, and 3000 ppm tetryl in the diet. The calculated average daily tetryl intake was 32.1, 82.5, 130.3, 178.9, and 374.4 mg/kg body weight (BW) for females and 31.8, 80.0, 121.0, 170.5, and 349.7 mg/kg BW for males in the 14–day study. For the 90–day studies, the daily tetryl intake was 14.2, 68.8, and 199.0 mg/kg BW for females and 13.0, 62.4, and 179.6 mg/kg BW for males. In the 14–day study, there was a significant decrease in body weights (males), whereas relative(organ/body weight) liver and spleen (females), and kidney (males) weights were significantly increased in the 5000–ppm dose group. Hematological effects observed were decreased hemoglobin and hematocrit and an increased number of reticulocyts in females (2000 to 5000 ppm). Methemoglobin levels in males (2000 to 5000 ppm) and females (5000 ppm) and total blood protein and albumin levels in all groups of males and females (except 500 ppm) were significantly increased. Histopathological changes were observed in kidneys (deposition of cytoplasmic droplets) of all dose groups of male rats. In the sub–chronic (90–day) study, feed intake was reduced in all dose groups, but a significant decrease in terminal body weights was observed in females (1000 and 3000 ppm) and males (3000 ppm). An increase in the relative liver, kidney (1000–3000 ppm), and spleen (3000 ppm) weights were noted in both sexes. The hemoglobin content and red blood cell count were decreased whereas the reticulocyte count was elevated (3000 ppm) in both sexes at 45 and 90 days. Methemoglobin levels were increased in both sexes (1000 and 3000 ppm). Histopathologicalchanges were noted in the spleen (pigment deposition and erythroid cell hyperplasia) of both sexes (3000 ppm) and kidneys (tubular degeneration and cytoplasmic droplets containing alpha-2-micro globulin) of male rats (1000 to 3000 ppm). A no observed adverse effect level (NOAEL) for both sexes was 13 mg/kg BW/day was determined.

In Vitro Inhibition of Mammalian Glutathione Transferases by Selected Nitrobenzenes

Five structurally related nitrobenzenes (1,2-dinitrobenzene, 1,3-dinitrobenzene, 1,4-dinitrobenzene, 1,3,5-trinitrobenzene, and picric acid) and Meisenheimer complex [1-(S-glutathionyl)-2,4,6-trinitrocyclohexadienate] were evaluated as possible inhibitors of affinity purified mammalian glutathione transferases (GSTs) isolated from human liver or human term placenta and rat fiver. The results suggest that the degree of GST inhibition depends upon both the chemical in question and the enzyme source. Among the nitrobenzenes tested, 1,3,5-trinitrobenzene (TNB) was found to be the most potent inhibitor of GST activity toward 1-chloro-2,4-dinitrobenzene (CDNB) from all the sources, whereas 1,3-dinitrobenzene (1,3-DNB) was the least effective. TNB-caused inhibition of GST activity toward CDNB appeared to be isozyme specific in that compared to the enzyme from human term placenta (GSTP1–1), the degree of inhibition of the mixture of GST isozymes present in the fivers of adult rats and humans was low. The enzyme assays conducted with 3,4-dichloro-1-nitrobenzene (DCNB), ethacrynic acid (EA), and 4-nitropyridinei N-oxide also suggested the isozymespecific inhibition of rat fiver GST activity by TNB. The nature of TNB-caused inhibition of GSTP1–1 was competitive with respect to CDNB and yielded a Ki value of 12.5 θ M. With EA, a specific substrate for GSTP1–1, an IC50 value of ∼ 16 θ M was estimated for the GSTP1–1 inhibition by TNB. The Meisenheimer complex, the product of nonenzymatic GSH conjugation with TNB by different GSTs, was found to be the most potent inhibitor of mammalian GSTs, and IC50 values ranged between 1 and 4 θ M when the enzyme activity was assayedusing CDNB. The nature of GSTP1–1 inhibition was noncompetitive with respect to CDNB, with a Ki value of 1 θ M for Meisenheimer complex. Although a precise mechanism was not identified, it is postulated that GSH depletion and/or GST inhibition may contribute, at least partly, to the target organ toxicity caused by exposures of animals to different nitrobenzenes reported in the literature.

Framework analysis for the carcinogenic mode of action of nitrobenzene

Nitrobenzene (CASRN: 98-95-3) has been shown to induce cancers in many tissues including kidney, liver, and thyroid, following chronic inhalation in animals. However, with a few exceptions, genotoxicity assays using nitrobenzene have given negative results. Some DNA binding/adduct studies have brought forth questionable results and, considering the available weight of evidence, it does not appear that nitrobenzene causes cancer via a genotoxic mode of action. Nitrobenzene produces a number of free radicals during its reductive metabolism, in the gut as well as at the cellular level, and generates superoxide anion as a by-product during oxidative melabolism. The reactive species generated during nitrobenzene metabolism are considered candidates for carcinogenicity. Furthermore, several lines of evidence suggest that nitrobenzene exerts its carcinogenicity through a non-DNA reactive (epigenetic) fashion, such as a strong temporal relationship between non-, pre-, and neoplastic lesions leading to carcinogenesis. In this report, we first describe the absorption, distribution, metabolism, and excretion of nitrobenzene followed by a summary of the available genotoxicity studies and the only available cancer bioassay. We subsequently refer to the mode of action framework of the U.S. Environmental Protection Agency's 2005 Guidelines for Carcinogen Risk Assessment as a basis for presenting possible modes of action for nitrobenzene-induced cancers of the liver, thyroid, and kidney, as supported by the available experimental data. The rationale(s) regarding human relevance of each mode of action is also presented. Finally, we hypothesize that the carcinogenic mode of action for nitrobenzene is multifactorial in nature and reflective of free radicals, inflammation, and/or altered methylation.

Chronic Toxicity of 1,3,5-Trinitrobenzene in Fischer 344 Rats

The chronic toxicity of 1,3,5-trinitrobenzene (TNB) in male and female Fischer 344 (F344) rats was evaluated by feeding a diet containing 0, 5, 60, and 300 ppm of TNB for 2 years. The calculated average TNB intake over 2 years for males and females was 0.22, 2.64,13.44 and 0.23, 2.68, 13.31 mg/kg body weight (BW)/day respectively. Terminal body weights were decreased and water intake was increased in both sexes (300 ppm), whereas food consumption was decreased in males (60 and 300 ppm groups) only. The relative spleen weights were significantly decreased in both sexes (300 ppm), whereas the relative brain weights were increased in females only (300 ppm). Hematological effects were not observed in animals killed at the 2-year time point, except significant decrease in the mean corpuscular hemoglobin (MCH) in males (300 ppm) and in females (60 and 300 ppm). Methemoglobin levels were increased in both sexes in the high dose group. Histopathological examination showed treatment-related changes in the kidney (hyaline droplets; 60 and 300 ppm) and the spleen (erythroid cell hyperplasia and pigment deposition; 300 ppm) of both sexes. Cytoplasmic hyaline droplets in the kidneys were characterized by immunohistochemistry as alpha-2μ-globulin. We propose a chronic, oral no-observable-adverse-effect level (NOAEL) of 2.68 mg/kg BW/day for TNB in the rat, based on the hematological and renal changes.

Lysozyme-containing renal tubular hyaline droplets in F344 rats bearing a rat fibrosarcoma-derived transplantable tumor

Renal tubular hyaline droplets developed in male and female F344 rats bearing a rat fibrosarcoma-derived transplantable tumor (SS). The droplets accumulated exclusively in the proximal renal tubular epithelia as eosinophilic granules of various sizes in hematoxylin and eosin-stained sections. The granules stained bright red with azan-Mallory stain. Immunohistochemically, the droplets were positive for lysozyme to various degrees but were negative for alpha 2u-globulin, albumin, and alpha 1-antitrypsin. These findings indicated the involvement of lysozyme, a low-molecular-weight protein, in the droplet formation. The morphological and immunohistochemical findings of the hyaline droplets bore a close resemblance to those reported in rats as a secondary lesion to spontaneous histiocytic sarcomas. Others have speculated that renal tubular hyaline droplets in histiocytic sarcoma-bearing rats are formed in lysosomes through cellular overload of lysozyme secreted excessively by the tumor cells. However, neoplastic cells of SS tumors were negative to lysozyme. The pathogenesis of renal hyaline droplets appearing in SS tumor-bearing rats remains to be investigated.