Acute reproductive toxicity of 3,3′-iminodipropionitrile in female rats

High-throughput assessment of metabolism-mediated neurotoxicity by combining 3D-cultured neural stem cells and liver cell spheroids

Despite the fact that biotransformation in the liver plays an important role in the augmented toxicity and detoxification of chemicals, relatively little efforts have been made to incorporate biotransformation into in vitro neurotoxicity testing. Conventional in vitro systems for neurotoxicity tests lack the capability of investigating the qualitative and quantitative differences between parent chemicals and their metabolites in the human body. Therefore, there is a need for an in vitro toxicity screening system that can incorporate hepatic biotransformation of chemicals and predict the susceptibility of their metabolites to induce neurotoxicity. To address this need, we adopted 3D cultures of metabolically competent HepaRG cell line with ReNcell VM and established a high-throughput, metabolism-mediated neurotoxicity testing system. Briefly, spheroids of HepaRG cells were generated in an ultralow attachment (ULA) 384-well plate while 3D-cultured ReNcell VM was established on a 384-pillar plate with sidewalls and slits (384PillarPlate). Metabolically sensitive test compounds were added in the ULA 384-well plate with HepaRG spheroids and coupled with 3D-cultured ReNcell VM on the 384PillarPlate, which allowed us to generate metabolites in situ by HepaRG cells and test them against neural stem cells. We envision that this approach could be potentially adopted in pharmaceutical and chemical industries when high-throughput screening (HTS) is necessary to assess neurotoxicity of compounds and their metabolites.

Risk assessment and environmental consequences of the use of the Allium-derived compound propyl-propane thiosulfonate (PTSO) in agrifood applications

The organosulfur compound propyl-propane thiosulfonate (PTSO), mainly found in Allium cepa, has a promising use in the agrifood industry. To confirm its safety for livestock, consumers, and environment, toxicological assessment is needed. In this regard, endocrine-disrupting chemicals (EDCs) are in the spotlight of research. Therefore, as part of the risk assessment of PTSO, in the present work, an in vivo study was performed in mice exposed to PTSO to investigate its potential reproductive toxicity considering fertility, genetic and endocrine endpoints. Five-weeks-old CD1 mice (80 males, 80 females) were exposed for 11 or 16 weeks (males or females, respectively) to different doses of PTSO (0, 14, 28 and 55 mg PTSO/kg b.w./day; 20 animals per group and sex) through the food pellets. No clinical observations or mortality and no changes in absolute organ weights and relative organ weights/body weight or brain ratios occurred during the study. The estrous cycle did not undergo any significant toxicologically relevant change. Most of the sex hormones displayed normal values. Some alterations in the expression of some genes related to reproduction is only observed in females, but they do not appear to have consequences in the development of sex organs. Docking results showed the impossibility of stable binding to estrogen and androgen receptors. Considering all the results obtained, the safe profile of PTSO can be confirmed for different agrifood applications at the conditions assayed.

Immune function changes of the IDPN-induced Tourette syndrome rat model

There may be immunologic alternations during Tourette syndrome (TS) development. This study aimed to determine the immune function changes in different aspects (spleen or thymus index, plasma cytokines, and T cell) in an 3,3'-iminodipropionitrile (IDPN)-induced rat model of TS. Male Sprague-Dawley rats were assigned to control and TS groups. The control group received intraperitoneal infections of normal saline (5 ml kg^-1  day^-1 ), and the TS rats were injected with IDPN (150 mg kg^-1  day^-1 ). The spleen and thymus indices were calculated. The expression of anti-inflammatory cytokines and inflammatory cytokines TNF-α, in peripheral blood were measured by ELISA and Western blotting. The proportion of CD3+, CD4+, CD8+, Treg, Th1, and Th2 cells were determined by fluorescence-activated cell sorting analysis. After 1 week of IDPN treatment, TS rats had decreased spleen and thymus weights versus control. The plasma levels of IL-4, IL-10, IL-12, IFN-γ, and TNF-α were significantly increased, while no significant difference in TGF-β was found. Flow cytometry analysis demonstrated that TS rats had significantly reduced CD3+ and CD4+ cells in spleen, without any change in the proportion of CD8+ cells. Furthermore, the ratio of Treg cells (CD4+/CD25+/FoxP3+) was decreased in TS rats; simultaneously, Th1 cells (CD4+/IFN-γ+) and Th2 cells (CD4+/IL4+) were dramatically increased. Together, IDPN can trigger immune dysfunction through impairment of matured Th cells, in particular for the Treg subset.

cVEMP correlated with imbalance in a mouse model of vestibular disorder

Background

Cervical vestibular evoked myogenic potential (cVEMP) testing is a strong tool that enables objective determination of balance functions in humans. However, it remains unknown whether cVEMP correctly expresses vestibular disorder in mice.

Objective

In this study, correlations of cVEMP with scores for balance-related behavior tests including rotarod, beam, and air-righting reflex tests were determined in ICR mice with vestibular disorder induced by 3,3′-iminodipropiontrile (IDPN) as a mouse model of vestibular disorder.

Methods

Male ICR mice at 4 weeks of age were orally administered IDPN in saline (28 mmol/kg body weight) once. Rotarod, beam crossing, and air-righting reflex tests were performed before and 3–4 days after oral exposure one time to IDPN to determine balance functions. The saccule and utricles were labeled with fluorescein phalloidin. cVEMP measurements were performed for mice in the control and IDPN groups. Finally, the correlations between the scores of behavior tests and the amplitude or latency of cVEMP were determined with Spearman’s rank correlation coefficient. Two-tailed Student’s t test and Welch’s t test were used to determine a significant difference between the two groups. A difference with p < 0.05 was considered to indicate statistical significance.

Results

After oral administration of IDPN at 28 mmol/kg, scores of the rotarod, beam, and air-righting reflex tests in the IDPN group were significantly lower than those in the control group. The numbers of hair cells in the saccule, utricle, and cupula were decreased in the IDPN group. cVEMP in the IDPN group was significantly decreased in amplitude and increased in latency compared to those in the control group. cVEMP amplitude had significant correlations with the numbers of hair cells as well as scores for all of the behavior tests in mice.

Conclusions

This study demonstrated impaired cVEMP and correlations of cVEMP with imbalance determined by behavior tests in a mouse model of vestibular disorder.

Electronic supplementary material

The online version of this article (10.1186/s12199-019-0794-8) contains supplementary material, which is available to authorized users.

Time-Course Evaluation of Iminodipropionitrile-Induced Liver and Kidney Toxicities in Rats: A Biochemical, Molecular and Histopathological Study

Iminodipropionitrile (IDPN) is known to produce axonopathy and vestibular hair cell degeneration. Recent histopathological studies have shown IDPN-induced liver and kidney toxicities in rodents; however, the associated mechanisms are not clearly understood. We investigated the role of proinflammatory cytokines in IDPN-induced liver and kidney toxicities in rats. Rats were treated with saline (control) and IDPN (100 mg/kg, intraperitoneally) daily for 1, 5, and 10 days, respectively. Animals were killed 24 hours after the last dose and liver and kidneys were collected for histopathology and interleukin-1β (IL-1β), IL-6, and tumor necrosis factor-α messenger RNA expression analysis. Serum aspartate aminotransferase and alanine aminotransferase activities were significantly increased after 10 doses of IDPN. The level of serum creatinine was initially increased after the first dose of IDPN but subsided on days 5 and 10. Blood urea nitrogen levels were significantly increased on days 5 and 10 following IDPN exposure. Histopathology showed dose-dependent hepatotoxicity in IDPN-treated rats. Iminodipropionitrile-induced expression of proinflammatory cytokines peaked after day 1 in liver and after day 5 in kidneys. In conclusion, repeated exposure of IDPN for 10 days produced significant structural and functional damages in rat liver whereas kidneys showed gradual recovery with time. These findings point toward the role of inflammatory mediators in IDPN-induced toxicity in rats.

Ovarian Toxicity in Female Rats after Oral Administration of Melamine or Melamine and Cyanuric Acid

Although the toxicity of melamine to the kidneys and testes is well known, few studies have investigated the effects of melamine on female reproductive organs. Therefore, this study explores the effects of oral administration melamine or melamine and cyanuric acid for 28 days on the ovaries of female rats. Rats that were exposed to the mixture exhibited reduced ovarian and uterine weights, a shorter estrous cycle, and reduced serum estrogen and progesterone levels compared to rats that were exposed to melamine and control rats. Furthermore, morphological analysis revealed pathological changes in the ovaries of rats exposed to melamine or the mixture, such as more atretic follicles and necrosis of oocytes and granulosa cells. TUNEL staining revealed that the exposed groups had a higher proportion of TUNEL-positive granulosa cells than the control group, and the mRNA expressions of SOD1, GPX1, GPX2, P450scc, 17β-HSD I, and 17β-HSD II were reduced in the exposure groups compared with the control group. These results indicated that exposure to melamine alone or to the melamine-cyanuric acid mixture could damage the ovaries in rats.

Pattern of neurobehavioral and organ-specific toxicities of β, β'-iminodipropionitrile in mice

INTRODUCTION

β, β'-iminodipropionitrile (IDPN) is a synthetic nitrile that produces a permanent movement disorder in rodents. Although IDPN-induced vestibular pathology is well documented, the mode of IDPN interaction with other organ systems is poorly understood. We examined the behavioral signs and histopathological changes in the vestibular labyrinth, brain, liver and kidneys of mice exposed to IDPN.

MATERIAL AND METHODS

Adult male SWR/J mice were divided into 2 groups of 6 animals each. One group of mice received normal saline (control group) and the other group was treated with IDPN (400 mg/kg, i.p.) daily for 7 days. Dyskinetic movements including vertical and horizontal head weaving, circling and backward walking were quantified on days 7, 8 and 9.

RESULTS

We observed a direct correlation between the severity of IDPN-induced behavioral deficits and the degeneration of vestibular hair cells in the crista ampullaris of mice. The brain cortex of both groups appeared similar, whereas the kidney histopathology revealed mild nephrotoxicity in some of the IDPN-treated mice. Administration of IDPN caused severe hepatotoxicity, but the intensity of hepatic damage was not correlated with the severity of behavioral deficits.

CONCLUSIONS

Degeneration of vestibular sensory hair cells plays an important role in the development of IDPN-induced behavioral deficits in mice. Exposure to IDPN also caused severe hepatotoxicity which was independent of the behavioral symptoms. These findings could be of potential relevance to human health, particularly after the observation that IDPN not only causes a movement disorder but also produces acute liver injury.

Histological insights in iminodipropionitrile-induced toxicity in rats

Iminodipropionitrile (IDPN) is a prototype nitrile compound that produces excitation, chorea and circling (ECC) syndrome in rodents. Previous studies have implicated vestibular hair cell degeneration in IDPN-induced behavioral abnormalities. Although the pathological changes in vestibular labyrinth of IDPN-treated rats are well documented, the effects of IDPN on other organ systems are not clearly understood. We therefore examined the histopathological alterations in inner ear, brain, liver and kidneys of rats exposed to IDPN. Adult male Wistar rats were divided into two groups of six animals each. Control rats received normal saline whereas the IDPN group was treated with IDPN (100mg/kg, i.p.) daily for 7 days. All the animals were carefully observed for any behavioral abnormality and the dyskinetic movements including the vertical and horizontal head weaving, circling and backward walking were quantified. The animals were sacrificed on day 9 and the samples of cochlea, brain, liver and kidney were collected for histopathology. The results showed a direct correlation between the severity of behavioral deficits and the cellular damage in crista ampullaris in IDPN-treated rats. Histopathology of liver was severely influenced by IDPN treatment, leading to vacuolization of cytoplasm, distorted sinusoids, infiltration of mononuclear cells and necrotic zones. However, the severity of hepatic damage in IDPN-treated rats was independent of the magnitude of vestibular hair cell degeneration as well as the severity of behavioral deficits. Administration of IDPN in the vestibulotoxic doses did not produce any histological changes in the brain cortex and kidneys of rats.