Abnormal innervation patterns in the anorectum of ETU-induced fetal rats with anorectal malformations

Study of the enteric and motor inervation, pelvic musculature, and alterations in the sacral region of rat fetuses with ethylenethiourea-induced anorectal anomaly

PURPOSE

The aims of this work were to induce anorectal anomaly in rat fetuses via the planned administration of ethylenethiourea (ETU), and to study fetuses exhibiting anorectal malformation, as well as apparently normal fetuses submitted to the effect of ETU.

METHODS

Time-mated pregnant Wistar rats were randomly divided into control and experimental groups. On gestational day 10, the experimental group received 10% ETU (130 mg/kg) by gavage, whereas the control rats received vehicle only. The embryos were harvested by cesarean section on gestational day 21. The fetuses exposed to ETU were divided into two groups: affected (without any clear anorectal alterations); and the malformed (with anorectal anomaly). The neuromotor plates were identified by immunohistochemistry with acetylcholinesterase, and alterations in the sacral region were evaluated by histological and morphometric studies.

RESULTS

We used 43 control fetuses, 82 affected fetuses, and 118 malformed fetuses in this study. The most frequent associated macroscopic anomalies were spina bifida (55 fetuses), encephalocele (20), and alterations in the lower limbs (5). The sacroiliac was malformed in 45% of the affected fetuses and in 53.2 % of the malformed fetuses.

CONCLUSION

ETU leads to a reduced number of motor neurons in the pelvic musculature of both the malformed and the affected rats. The enteric neurons are altered in the malformed fetuses, but not in the affected ones. Both the affected and malformed rats exhibit sacral alterations that do not interfere with neurons.

Ethylene thiourea exposure induces neurobehavioral toxicity in zebrafish by disrupting axon growth and neuromuscular junctions

Ethylene thiourea (ETU) converted from ethylene bisdithiocarbamate (EBDC) fungicides has aroused great concern because of its prevalence and harmful effects. Although ETU-induced neurotoxicity has been reported, the potential mechanisms remain unclear. This study provided insights into its neurotoxic effects at environmentally relevant concentrations in zebrafish. Our findings showed that embryonic exposure to ETU decreased the hatch rate and delayed somite development. Furthermore, ETU treatment significantly reduced the dark velocity in the locomotion assay. The upregulated tendency of the mitogen-activated protein kinases (MAPK) pathway (mknk1, atf4, mapkapk3) screened by transcriptome analysis implied motor neuron degeneration, which was validated by subsequent morphological observation, as axon length and branches were truncated in the 62.5 µg/L ETU group. However, although the rescue experiment with a p38 MAPK inhibitor (SB203580) successfully ameliorated axon degeneration, it failed to reverse the locomotion behaviors. Further exploration of transcriptome data revealed the varied expression of presynaptic scaffold protein-related genes (pcloa, pclob, bsna), whose downregulation might impair the neuromuscular junction (NMJ). Therefore, we reasonably suspected that ETU-induced neurobehavioral deficits might result from the combined effects of the MAPK pathway and presynaptic proteins. Considering this, we highlighted the necessity to take precautions and early interventions for susceptible ETU-exposed populations.

Endocrine disruptors also function as nervous disruptors and can be renamed endocrine and nervous disruptors (ENDs)

Endocrine disruption (ED) and endocrine disruptors (EDs) emerged as scientific concepts in 1995, after numerous chemical pollutants were found to be responsible for reproductive dysfunction. The World Health Organization established in the United Nations Environment Programme a list of materials, plasticizers, pesticides, and various pollutants synthesized from petrochemistry that impact not only reproduction, but also hormonal functions, directly or indirectly. Cells communicate via either chemical or electrical signals transmitted within the endocrine or nervous systems. To investigate whether hormone disruptors may also interfere directly or indirectly with the development or functioning of the nervous system through either a neuroendocrine or a more general mechanism, we examined the scientific literature to ascertain the effects of EDs on the nervous system, specifically in the categories of neurotoxicity, cognition, and behaviour. To date, we demonstrated that all of the 177 EDs identified internationally by WHO are known to have an impact on the nervous system. Furthermore, the precise mechanisms underlying this neurodisruption have also been established. It was previously believed that EDs primarily function via the thyroid. However, this study presents substantial evidence that approximately 80 % of EDs operate via other mechanisms. It thus outlines a novel concept: EDs are also neurodisruptors (NDs) and can be collectively termed endocrine and nervous disruptors (ENDs). Most of ENDs are derived from petroleum residues, and their various mechanisms of action are similar to those of "spam" in electronic communications technologies. Therefore, ENDs can be considered as an instance of spam in a biological context.

Abnormal serum vitamin A levels and retinoic acid receptor α expression patterns in children with anorectal malformation

BACKGROUND

Anorectal malformation (ARM) is known to be associated with maldevelopment of the enteric nervous system (ENS), and vitamin A (VA) and its metabolite retinoic acid (RA) play important roles in ENS development. Thus, our aim was to investigate serum VA levels in ARM newborns and RA receptor (RAR) expression in the rectum of ARM patients and animal models.

METHODS

Serum VA concentrations were detected in newly diagnosed ARM neonates (n = 32) and neonates with non-alimentary tract malformations (n = 30). Intestinal specimens were divided into three groups: rectum from ARM patients (n = 30), colon from a stoma (n = 30) and rectum from controls (n = 4). RAR mRNA expression was evaluated by RT-qPCR. Rectum specimens from ARM patients were divided into two groups by postoperative pathology: the normal and lesion ganglion cell groups. Immunohistochemistry and Western blot were employed to detect RARα protein expression in rectum specimens. In addition, the ARM mouse model was induced by all-trans retinoid acid (ATRA), and the expression levels of RARα and the neuronal marker NeuN in the rectum of mice on embryonic day 16.5-18.5 (E16.5-18.5) were investigated.

RESULTS

The serum concentration of VA in ARM neonates was lower than that in control neonates (P < 0.0001), and RARα mRNA expression was lower in the rectum specimens from ARM patients than in the colon specimens from a stoma and the rectum specimens from controls (P < 0.05); there was no significant difference between the colon from a stoma and the rectum from controls. RARα protein was expressed in the nucleus of ganglion cells and nerve fibers, and RARα protein expression in the lesion ganglion cell group was significantly lower than that in the normal ganglion cell group (P < 0.01). Compared with the control mice, ARM mice at E16.5-18.5 showed decreased fluorescence intensity of RARα and NeuN in the rectum. RARα and NeuN mRNA expression in the rectum on E16.5-18.5 was lower in ARM mice than in control mice (P < 0.05).

CONCLUSION

Serum VA concentration and the RARα expression pattern are abnormal in the rectum in ARM and may contribute to the ENS maldevelopment in ARM.

Microarray analysis of miRNAs during hindgut development in rat embryos with ethylenethiourea‑induced anorectal malformations

Anorectal malformations (ARMs) are one of the most common congenital malformations of the digestive tract; however, the pathogenesis of this disease remains to be fully elucidated. MicroRNAs (miRNAs) are important in gastrointestinal development and may be involved in the pathogenesis of ARMs. The present study aimed to profile miRNAs and examine their potential functions in rats with ethylenethiourea (ETU)-induced ARMs. Pregnant Wistar rats (n=36) were divided randomly into ETU-treated and control groups. The rats in the ETU-treated group were gavage-fed 1% ETU (125 mg/kg) on gestational day 10 (GD10), whereas the control group rats received a corresponding dose of saline. Embryos were harvested by cesarean section on GD14, GD15 and GD16. Hindgut tissue was isolated from the fetuses for RNA extraction and microarray analysis, followed by bioinformatics analysis and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) validation. Overall, 38 miRNAs were differentially expressed (all upregulated) on GD14, 49 (32 upregulated and 17 downregulated) on GD15, and 42 (all upregulated) on GD16 in the ARM group compared with the normal group. The top 18 miRNAs with |log₂(fold change)| >4.25 were selected for further bioinformatics analysis. Among these miRNAs, five were differentially expressed at two time-points and were involved in ARM-associated signaling pathways. The RT-qPCR analysis revealed that three miRNA (miR), miR-125b-2-3p, miR-92a-2-5p and miR-99a-5p, were significantly differentially expressed in rats with ARMs compared with the normal group. In conclusion, the results suggested that the differential expression of miR-125b-2-3p, miR-92a-2-5p and miR-99a-5p during key time-points of anorectal formation in rats may have functions in the pathogenesis of ARM.

Abnormal neural crest innervation in Sox10-Venus mice with all-trans retinoic acid-induced anorectal malformations

BACKGROUND/PURPOSE

Despite technical advances in the surgical/medical care of anorectal malformation (ARM), persistent unsatisfactory postoperative bowel habit has been attributed to histopathologic abnormalities of the distal rectum/pouch (DRP) and hypoplasia of anal sphincter muscles (ASM). We used Sox10-Venus mice with ARM induced by all-trans retinoic acid (ATRA) to investigate neural crest cell (NCC) innervation in the DRP and ASM.

METHOD

Pregnant Sox10-Venus mice were administered single doses of 50, 70, or 100 mg/kg of ATRA on embryonic day 8.5 (E8.5) then sacrificed on either E16.5 or E19.5. Bowel specimens comprising the anorectum were examined using fluorescence microscopy without immunohistochemical staining (FMIS). Anti-PGP9.5 was used to delineate ganglion cells and anti-SMA for smooth muscles.

RESULTS

The appropriate dose of ATRA for inducing ARM was 50 mg/kg. Under FMIS, all ARM embryos (n = 5; all high type; 3 male:2 female) had less NCC innervation with thick Venus-positive nerve fibers in the DRP compared with normal embryos (n = 8); there was abnormal NCC innervation in the DRP and absent ASM in ARM mice.

CONCLUSION

We are the first to delineate abnormal enteric nervous system innervation in the DRP of ARM mice without using immunohistochemical staining techniques thus allowing specimens to be examined without any distortion.