Paternal exposure to di-n-butyl-phthalate induced developmental toxicity in zebrafish (Danio rerio)

Micro-injection as a tool to detect the effects of bisphenol A, diethyl phthalate, and 17ß-estradiol on ontogenesis of zebrafish (Danio rerio)

Diethyl phthalate (DEP), bisphenol A (BPA), and external estradiol 17β-estradiol (E2) all are endocrine disrupting chemicals (EDCs). Our previous study has found that the development of ceratohyal cartilage (CH) in embryos could be disrupted when the maternal generation was exposed with 8.06 μM DEP, 2.86 μM BPA, and 1.11 μM E2. However, it is still unknown how doses of the residual EDCs in eggs cause abnormal CH development in their offspring. Microinjection is used at the 2-cell stage of embryos to mimic the maternal effect and to observe the toxicities of EDCs in embryos. Results shown that the amounts of DEP, BPA, and E2 were 1.3 × 10-6 ng, 4.7 × 10-7 ng, and 1.4 × 10-7 ng, respectively, inducing the CH angles to become bigger than the control. However, related genes to the migratory pathways of neural crest cells (NCCs) were not influenced upon BPA and E2 treatments. Both sox10 and smad3 gene expressions were up-regulated upon DEP treatment. On the other hand, the CH angles were smaller than the control upon 1.3 × 10-5, 9.4 × 10-6, and 1.4 × 10-6 ng of DEP, BPA, and E2 microinjection, respectively. Furthermore, genes related to migratory NCCs were significantly influenced upon 10-5 ng of BPA, and 10-4 ng of DEP treatments on embryos. According to the data, we suggested that 10-5-10-7 ng of EDCs in eggs could disrupt CH development as well as significantly increase the mortality on their embryos. The present study raises concern that the responses were highly sensitive in embryos through maternal effects.

Di-n-butyl phthalate induces toxicity in male fetal mouse testicular development by regulating the MAPK signaling pathway

"White pollution" has a significant impact on male reproduction. Di-n-butyl phthalate (DBP) is one of the most important factors in this type of pollution. Currently, research from international sources has demonstrated the significant reproductive toxicity of DBP. However, most of these studies have focused mainly on hormones expression at the protein and mRNA levels and the specific molecular targets of DBP and its mechanisms of action remain unclear. In this study, we established a Sprague Dawley pregnant mouse model exposed to DBP, and all male offspring were immediately euthanized at birth and bilateral testes were collected. We found through transcriptome sequencing that cell apoptosis and MAPK signaling pathway are the main potential pathways for DBP induced reproductive toxicity. Molecular biology analyses revealed a significant increase in the protein levels of JNK1(MAPK8) and BAX, as well as a significant increase in the BAX/BCL2 ratio after DBP exposure. Therefore, we propose that DBP induces reproductive toxicity by regulating JNK1 expression to activate the MAPK signaling pathway and induce reproductive cell apoptosis. In conclusion, our study provides the first evidence that the MAPK signaling pathway is involved in DBP-induced reproductive toxicity and highlights the importance of JNK1 as a potential target of DBP in inducing reproductive toxicity.

Paternal exposures to endocrine-disrupting chemicals induce intergenerational epigenetic influences on offspring: A review

Endocrine-disrupting chemicals (EDCs) are ubiquitous in ecological environments and have become a great issue of public health concern since the 1990 s. There is a deep scientific understanding of the toxicity of EDCs. However, recent studies have found that the abnormal physiological functions of the parents caused by EDCs could be transmitted to their unexposed offspring, leading to intergenerational toxicity. We questioned whether sustained epigenetic changes occur through the male germline. In this review, we (1) systematically searched the available research on the intergenerational impacts of EDCs in aquatic and mammal organisms, including 42 articles, (2) summarized the intergenerational genetic effects, such as decreased offspring survival, abnormal reproductive dysfunction, metabolic disorders, and behavioral abnormalities, (3) summarized the mechanisms of intergenerational toxicity through paternal interactions, and (4) propose suggestions on future research directions to develop a deeper understanding of the ecological risk of EDCs.

Are New Phthalate Ester Substitutes Safer than Traditional DBP and DiBP? Comparative Endocrine-Disrupting Analyses on Zebrafish Using In Vivo, Transcriptome, and In Silico Approaches

Although previous studies have confirmed the association between phthalate esters (PAEs) exposure and endocrine disorders in humans, few studies to date have systematically assessed the threats of new PAE alternatives to endocrine disruptions. Herein, zebrafish embryos were continuously exposed to two PAEs [di-n-butyl phthalate (DBP) and diisobutyl phthalate (DiBP)], two structurally related alternatives [diiononyl phthalate (DINP) and diisononyl hexahydrophthalate (DINCH)], and two non-PAE substitutes [dipropylene glycol dibenzoate (DGD) and glyceryl triacetate (GTA)], and the endocrine-disrupting effects were investigated during the early stages (8-48 hpf). For five endogenous hormones, including progesterone, testosterone, 17β-estradiol, triiodothyronine (T3), and cortisol, the tested chemicals disturbed the contents of at least one hormone at environmentally relevant concentrations (≤3.9 μM), except DINCH and GTA. Then, the concentration-dependent reduced zebrafish transcriptome analysis was performed. Thyroid hormone (TH)- and androgen/estrogen-regulated adverse outcome pathways (AOPs) were the two types of biological pathways most sensitive to PAE exposure. Notably, six compounds disrupted four TH-mediated AOPs, from the inhibition of deiodinases (molecular initiating event, MIE), a decrease in T3 levels (key event, KE), to mortality (adverse outcome, AO) with the quantitatively linear relationships between MIE-KE (|r| = 0.96, p = 0.002), KE-AO (|r| = 0.88, p = 0.02), and MIE-AO (|r| = 0.89, p = 0.02). Multiple structural analyses showed that benzoic acid is the critical toxicogenic fragment. Our data will facilitate the screening and development of green alternatives.

Endocrine-Disrupting Chemicals Exposure Alter Neuroendocrine Factors, Disrupt Cardiac Functions and Provokes Hypoxia Conditions in Zebrafish Model

Zebrafish (Danio rerio) is an increasingly popular vertebrate model used for assessing the toxicity of endocrine-disrupting chemicals (EDCs) on living beings. The zebrafish features high genetic homology to mammals, because of its rapid embryonic development, optical transparency of phenotypic screening embryos, high throughput genetic and chemical screening which make them a powerful toxicological model. This systematic review aimed to assess the recent literature on the use of zebrafish model in EDCs toxicity studies. We capture the data on the types of EDCs used, zebrafish life stages associated with the toxicity, and its effects on the alterations in neuroendocrine factors and cardiac hypoxia in zebrafish. A total of 17 articles published between 2010 and 2020 were curated. The information gathered highlighted the association of EDCs with cardiological outcomes and neurobehavioral effects and distorted expression of genes. The genes that were highlighted in the paper include bdnf, ntrk2a, grin2cb, VTG-1, HIF-1α, tnnt2, ntrk1, and pax6b. The effect of EDCs on cardiac hypoxia and neurodevelopmental and behavioral factors of zebrafish were described in all the papers chosen for this review. The involvement of EDCs in altered regulation of gene expression can be studied further to identify the potential EDC compounds on its toxicological and endocrine disruption function at the molecular level.

Long-term co-exposure DBP and BaP causes imbalance in liver macrophages polarization via activation of Notch signaling regulated by miR-34a-5p in rats

Humans are often exposed to complex mixtures of environmental pollutants over long periods of time. It is reported that Dibutyl phthalate (DBP) and benzo[a]pyrene (BaP) are typical environmental pollutants, which are associated with liver injury. Nevertheless, little is known about the effects of DBP and BaP combined exposure on liver. In the current study, rats were exposed to DBP alone (50, or 250 mg/kg), BaP alone (1, or 5 mg/kg), or DBP and BaP (50 + 1, or 250 + 5 mg/kg) for ninety days. More serious liver damage, including abnormal liver function, infiltration of inflammatory cells and disturbed secretion of inflammatory factors, were observed in long-term co-exposure to DBP and BaP group relative to those in single exposure group. Our data showed that long-term co-exposure to DBP and BaP induces macrophages to polarize toward M1 and inhibits polarization of M2 macrophages. Long-term co-exposure to DBP and BaP downregulated miR-34a-5p level and upregulated Notch signaling. These results indicated that imbalance in macrophages M1/M2 polarization mediated by activation of Notch signaling due to reduced miR-34a-5p level may contribute to additive effects on disorder of inflammatory factors secretion and subsequent liver injury following long-term DBP and BaP co-exposure.

Ecotoxicological evaluation of zebrafish liver (Danio rerio) induced by dibutyl phthalate

Dibutyl phthalate (DBP), one of the most commonly applied plasticizers, has been frequently detected in the aquatic environment, posing potential risks to aquatic organisms. Currently, reports about the toxicity of zebrafish liver with DBP exposure are rare, and the toxic mechanism is still not clear. In this study, zebrafish (Danio rerio) were used to explore the ecotoxicological effects of DBP from the physiological, biochemical, genetic, and molecular levels. The results showed oxidative stress, lipid peroxidation, and DNA damage occurred in zebrafish liver according to changes in antioxidant enzymes, MDA and 8-OHdG content. AchE activity was always active, and negatively correlated with the DBP concentration. The expression of Cu/Zn-sod and gpx genes were similar to that of antioxidant enzymes from 7 to 21 days, while in the end, the inconsistent result appeared due to the time lag effect in protein modification, gene transcription and translation. Besides, the mRNA abundance of Caspase-3 and p53 were upregulated, showing a "dose-response" relationship. The integrated biomarker reaction indicated that the effects of exposure time on zebrafish liver was 14th day> 28th day> 7th day> 21th day. These results are of great significance to evaluate the toxicological effects and explore the toxic mechanism of DBP on aquatic organisms.