Roles of miRNAs in microcystin-LR-induced Sertoli cell toxicity

Bta-miR-149-3p suppresses inflammatory response in bovine Sertoli cells exposed to microcystin-leucine arginine (MC-LR) through TLR4/NF-kB signaling pathway

This study explored the regulatory role of bta-miR-149-3p in the inflammatory response induced by microcystin-leucine arginine (MC-LR) exposure in bovine Sertoli cells. The research endeavored to enhance the comprehension of the epigenetic mechanisms underlying MC-LR-induced cytotoxicity in Sertoli cells and establish a foundation for mitigating these effects in vitro. In this study, we elucidated the regulatory mechanism of bta-miR-149-3p in the MC-LR-induced inflammatory response by verifying the target gene of bta-miR-149-3p through luciferase assays and treating the cells with a bta-miR-149-3p inhibitor for 24 h. The results demonstrate that nuclear factor κB (NF-κB) acts as a downstream target gene of bta-miR-149-3p, which inhibits the MC-LR-induced inflammatory response in bovine Sertoli cells. This inhibition occurs by regulating the downregulation of tight junction constitutive proteins of the blood-testis barrier (BTB) through the suppression of the TLR-4/NF-κB signaling pathway (p < 0.05) and the up-regulation of the adhesion junction protein β-catenin (p < 0.05). Notably, MC-LR exposure resulted in the up-regulation (p < 0.05) of inflammatory cytokines (IL-6, IL-1β, and NLRP3) and the down-regulation (p < 0.05) of BTB tight junction constitutive proteins (ZO-1, Occludin) in Sertoli cells. Furthermore, the BTB constitutive protein ZO-1 exhibited significant down-regulation in Sertoli cells pretreated with the bta-miR-149-3p inhibitor compared to controls (p < 0.05), while Occludin showed no significant difference from CTNNB1 (p > 0.05). In summary, our findings suggest that bta-miR-149-3p suppresses the MC-LR-induced inflammatory response and alterations in the expression of BTB proteins in bovine Sertoli cells by inhibiting the TLR-4/NF-κB signaling pathway.

Organic anion transporting polypeptide 3a1 is a novel influx pump for Perfluorooctane sulfonate in Sertoli cells and contributes to its reproductive toxicity

Persistent organic pollutant perfluorooctane sulfonate (PFOS) is strongly associated with male reproductive disorders, but the related mechanisms are still not fully understood. In this study, we used in vivo and in vitro models to explore the role of organic anion transporting polypeptide 3a1 (Oatp3a1) on PFOS-induced male reproductive injury. Thirty male C57BL/6 (B6) mice were orally given PFOS (0-10 mg/kg/bw) for 28 days. Body weight, organ index, sperm count, histology, and blood-testis barrier (BTB) integrity were evaluated. Primary Sertoli cells were used to describe the related molecular mechanisms of male reproductive injury caused by PFOS. Our results showed that PFOS induced a decrease in sperm count, morphological damage to testicular Sertoli cells, and disruption of BTB. In the in vitro model, exposure to PFOS significantly increased Oatp3a1 mRNA and protein levels and decreased miR-23a-3p expression in Sertoli cells, accompanied by reduced trans-epithelial electrical resistance (TEER) value. By performing the 14C-PFOS uptake experiment, we showed that 14C-PFOS uptake in HEK293-Oatp3a1 cells was apparently higher than in HEK293-MOCK cells. Meanwhile, treating Sertoli cells with Oatp3a1 siRNA significantly decreased Oatp3a1 expression and rescued PFOS-induced decreases in TEER value. As such, the present study highlights that Oatp3a1 may play an important role in the toxic effect of PFOS on Sertoli cells, advancing our understanding of molecular mechanisms for PFOS-induced male reproductive disorders.

T-2 mycotoxin Induces male germ cell apoptosis by ROS-mediated JNK/p38 MAPK pathway

T-2 mycotoxin, a type A trichothecene toxin that, specifically, causes male and female reproductive toxicity. We evaluated T-2 toxin toxicity in testes from neonatal testes after in vitro tissue cultured. Additionally, current study focuses on the molecular mechanism of toxicity and germ cell damage in GC-1 spermatogonial cells. Mouse testicular fragments were subjected to T-2 toxin (0-20 nM) during days 5 of in vitro culture. Testicular germ cell number were reduced and downregulated the expression of corresponding markers depending on the exposure concentration of T-2 toxin; however, Sertoli cell markers and steroidogenic enzyme expression increased when treated with 20 nM T-2 toxin. The cell viability decreased, apoptosis increased, and pro-apoptotic protein expression increased in 5-20 nM T-2 toxin-exposed spermatogonia. Moreover, T-2 toxin generated reactive oxygen species (ROS) and induced mitochondrial dysfunction, indicating that activation of p38 MAPK signaling triggered by ROS is involved in the apoptotic molecular mechanism of T-2 toxin. T-2 toxin induced the phosphorylation of ERK1/2, c-Jun, JNK/SAPK, p38, and p53, and the subsequent inhibition of AKT phosphorylation. The upregulation of genes related to apoptosis and MAPK/JNK signaling was consistently observed in cells exposed to T-2 toxin. These results indicate that T-2 toxin triggers apoptotic cell death in germ cells through the triggering of ROS-mediated JNK/p38-MAPK signaling pathways.

MicroRNA‑30a‑5p regulates cypermethrin-induced apoptosis of Sertoli cells by targeting KLF9 in vitro

Cypermethrin (CYP) has been identified as one kind of endocrine-disrupting chemicals (EDCs) to induce male reproduction damage. This study aimed to investigate the effects and mechanisms of miR-30a-5p on CYP induced apoptosis of TM4 mouse Sertoli cells in vitro. In the present study, 0 μM, 10 μM, 20 μM, 40 μM and 80 μM CYP were used to treat TM4 cells for 24 h. The apoptosis of TM4 cells, the expression level of miR-30a-5p, the protein expressions and the interaction between miR-30a-5p and KLF9 were detected by flow cytometry, quantitative Real-Time PCR, Western blot and luciferase reporter assays. CYP induced apoptosis of TM4 cells, inhibited expression of miR-30a-5p in TM4 cells, and overexpression of miR-30a-5p partially recovered CYP induced cells apoptosis. Furthermore, KLF9 was a potential downstream target of miR-30a-5p predicted by publicly available databases. KLF9 expression level in TM4 cells was significantly elevated after treatment with CYP, and the induction was inhibited by miR-30a-5p mimics transfection. Meanwhile, dual-luciferase reporter assay demonstrated that miR-30a-5p directly targeted KLF9-3'UTR. Moreover, in the presence of CYP, the apoptosis regulator p53 expression was also increased in TM4 cells. Overexpression miR-30a-5p or down-regulation of KLF9 both attenuated the induction of CYP on p53 expression. Overall, the present study demonstrated that miR-30a-5p regulated CYP induced TM4 cells apoptosis by targeting KLF9/p53 axis.

miR-146a-5p Promotes the Inflammatory Response in PBMCs Induced by Microcystin-Leucine-Arginine

Background

Microcystin-leucine-arginine (MC-LR) is the most abundant and most toxic variant of microcystin isomers. Various experiments have clearly shown that MC-LR has hepatotoxicity and carcinogenicity, but there are relatively few studies on its immune damage effect. In addition, numerous studies have shown that microRNAs (miRNAs) are involved in a wide range of biological processes. Do miRNAs also play a role in inflammatory response caused by microcystin exposure? This is the question to be answered in this study. Moreover, this study can also provides experimental evidence for the significance of miRNA applications.

Objective

To investigate the effect of MC-LR on the expressions of miR-146a and pro/anti-inflammatory cytokines in human peripheral blood mononuclear cells (PBMCs) and to further explore the role of miR-146a in the inflammatory responses caused by MC-LR.

Methods

Serum samples from 1789 medical examiners were collected and detect the concentrations of MCs, and 30 serum samples with concentrations of MCs around P₂₅, P₅₀, and p₇₅ were randomly selected for the detection of inflammatory factors. PBMCs from fresh peripheral blood extracted from these 90 medical examiners were subsequently tested for relative miR-146a expression. In vitro, the MC-LR were exposed to the PBMCs to detect the levels of inflammatory factors as well as the relative expression of miR-146a-5p. Then, a miRNA transfection assay was performed to verify the regulation of inflammatory factors by miR-146a-5p.

Results

In population samples, the expression of inflammatory factors and miR-146a-5p increased with increasing MCs concentration. In vitro experiments showed that the expression of inflammatory factors and miR-146a-5p in PBMCs increased with MC-LR exposure time or exposure dose too. In addition, inhibiting the expression of miR-146a-5p in PBMCs reduced inflammatory factor levels.

Conclusion

miR-146a-5p exerts a promoting effect on the MC-LR-induced inflammatory response by positively regulating inflammatory factor levels.

An identified PfHMGB1 promotes microcystin-LR-induced liver injury of yellow catfish (Pelteobagrus fulvidraco)

Microcystin-LR (MC-LR) is a potent hepatotoxin that can cause liver inflammation and injury. However, the mode of action of related inflammatory factors is not fully understood. PfHMGB1 is an inflammatory factor induced at the mRNA level in the liver of juvenile yellow catfish (Pelteobagrus fulvidraco) that were intraperitoneally injected with 50 μg/kg MC-LR. The PfHMGB1 mRNA level was highest in the liver and muscle among 11 tissues examined. The full-length cDNA sequence of PfHMGB1 was cloned and overexpressed in E. coli, and the purified protein rPfHMGB1 demonstrated DNA binding affinity. Endotoxin-free rPfHMGB1 (6-150 μg/mL) also showed dose-dependent hepatotoxicity and induced inflammatory gene expression of primary hepatocytes. PfHMGB1 antibody (anti-PfHMGB1) in vitro reduced MC-LR (30 and 50 μmol/L)-induced hepatotoxicity, suggesting PfHMGB1 is important in the toxic effects of MC-LR. In vivo study showed that MC-LR upregulated PfHMGB1 protein in the liver. The anti-PfHMGB1 blocked its counterpart and reduced ALT/AST activities after MC-LR exposure. Anti-PfHMGB1 partly neutralized MC-LR-induced hepatocyte disorganization, nucleus shrinkage, mitochondria, and rough endoplasmic reticula destruction. These findings suggest that PfHMGB1 promotes MC-LR-induced liver damage in the yellow catfish. HMGB1 may help protect catfish against widespread microcystin pollution.

The mechanisms in the altered ontogenetic development and lung-related pathology in microcystin-leucine arginine (MC-LR)-paternal-exposed offspring mice

A father's lifetime experience is a major risk factor for a range of diseases in an individual, and the consequences of the exposure can also be transmitted to his offspring. Our previous work has demonstrated that damage to testicular structures and decline in sperm quality in male mice can be caused by microcystin-leucine arginine (MC-LR), but the overall effects of the scope and extent of paternal exposure on health and disease in the offspring remain underexplored. Here, we report that MC-LR-paternal-exposed offspring mice showed reduced litter size and body weight accompanied by increased abnormalities in the lung. Analyses of the small noncoding RNAs (sncRNAs) in the sperm from MC-LR-exposed males demonstrated the downregulation of a wide range of piRNAs enriched for those target genes involved in the regulation of the embryo implantation pathways. Gene and protein expression analyses, as well as biochemical and functional studies, revealed suppressed expression of Hsp90α in testicular tissues from MC-LR-exposed males. Decreased Hsp90α in testicular tissues impaired the development of the offspring. In this study, we revealed that MC-LR alters the expression of Hsp90α in testicular tissues to cause changes in the expression profiles of sperm piRNAs produced by paternal mice. These changes lead to aberrant activation of the Wnt/β-catenin signaling pathway in pulmonary tissues of offspring mice, causing lung tissue damage and abnormal development. We hereby confirmed that MC-LR-induced alterations in epigenetic inheritance are capable of contributing to intergenerational developmental defects in paternal-exposed offspring mice.

Maternal Exposure to T-2 Toxin Induces Changes in Antioxidant System and Testosterone Synthesis in the Testes of Mice Offspring

Simple Summary

This study investigated the effects of maternal T-2 toxin exposure on the development of testis in the mice offspring. The detrimental effects were assessed by testicular weight, antioxidant capacity, and testosterone synthesis and secretion. Studies have shown that the toxin carried by the mother has bad effects on the testicular development of offspring at puberty, affecting the antioxidant system and testosterone synthesis in the testis, but the maternal exposure of T-2 toxin had no significant impact on the testes of offspring after sexual maturity, suggesting the recovery of reproductive function.

Abstract

T-2 toxin, the most toxic member of trichothecene mycotoxin, is widely distributed in cereals, and has been extensively studied, but few studies focus on the toxicity of maternal exposure to offspring. This study focused on the effects of maternal exposure to T-2 toxin (during gestation and lactation) on the testicular development of mice offspring. Dams were orally administered with T-2 toxin at 0, 0.005, or 0.05 mg/kg body weight from the late stage of gestation to the end of lactation. Testicular samples of the mice offspring were collected on the postnatal day 21, 28, and 56. The results showed significant decreases in body weight and testicular weight on the postnatal day 28. Moreover, significant inhibition of antioxidant system and testosterone synthesis was detected on the postnatal day 28. Furthermore, there were significant decreases in the gene expression levels of StAR and 3β-HSD, which are involved in testosterone synthesis. In general, present results demonstrated that maternal exposure to T-2 toxin during gestation and lactation led to bad effects on the capacity of antioxidant system and inhibited testosterone synthesis in testes during pre-puberty with no significant effects on post-puberty.

Icariin attenuate microcystin-LR-induced gap junction injury in Sertoli cells through suppression of Akt pathways

Microcystin-leucine-arginine (MC-LR) can cause male reproductive disorder. However, the underlying mechanism are not yet entirely elucidated. In this study, we aimed to investigated the effects of MC-LR on the integrity of blood-testis barrier (BTB) and the related molecular mechanisms. Both in vivo and in vitro experiments revealed that MC-LR caused disruption of BTB and gap junctions between Sertoli cells respectively, which was paralleled by the alteration of connexin43 (Cx43). Our data demonstrated that MC-LR decreased gap junction intercellular communication (GJIC) and impaired Cx43 expression by activating the phosphatidylinositol 3-kinase/Akt cascades. In addition, a possible protective effect of Icariin (ICA), a flavonoid isolated from Chinese medicinal herb, against MC-LR toxicity was investigated. The ICA prevented the degradation of GJIC and impairment of Cx43 induced by MC-LR via suppressing the Akt pathway. Together, our results confirmed that the expression of Cx43 induced by MC-LR was regulated in vivo and in vitro, which was involved in the destruction of BTB. Additionally, ICA seems to be able to mitigate the MC-LR toxic effects.

A transcriptomic regulatory network among miRNAs, piRNAs, circRNAs, lncRNAs and mRNAs regulates microcystin-leucine arginine (MC-LR)-induced male reproductive toxicity

Microcystin-leucine arginine (MC-LR) which is produced by cyanobacteria is a potent toxin for the reproductive system. Our previous work has demonstrated that both acute and chronic reproductive toxicity engendered by MC-LR can result in the decline of sperm quality and damage of testicular structures in male mice. The present study was designed to investigate the impact of chronic low-dose exposure to MC-LR on the regulation of RNA networks including mRNA, microRNA (miRNA), piwi-associated RNA (piRNA), covalently closed circular RNA (circRNA) and long non-coding RNA (lncRNA) in testicular tissues. By high-throughput sequencing analysis, 1091 mRNAs, 21 miRNAs, 644 piRNAs, 278 circRNAs and 324 lncRNAs were identified to be significantly altered in testicular tissues treated with MC-LR. We performed gene ontology (GO) analysis to ascertain the biological functions of differentially expressed genes. Among the altered 21 miRNAs and 644 piRNAs, the miRNA chr13_8977, which is a newly discovered species, and the piRNA mmu_piR_027558 were dramatically down-regulated after exposure to MC-LR. Consistently, both mRNA levels and protein expression levels of their predicted targets were increased significantly when chr13_8977 and mmu_piR_027558 were each down-regulated. Testicular structures, germ cell apoptosis and sperm quality were also affected by the altered expression of chr13_8977 and mmu_piR_027558 severally. We further investigated the differential expression of circRNAs and lncRNAs and their biological functions in testicular tissues following treatment with chronic low-dose exposure to MC-LR. We also constructed a competing endogenous RNA (ceRNA) network to predict the functions of the altered expressed RNAs using MiRanda. Our study suggested a crucial role for the potential network regulation of miRNAs, piRNAs, circRNAs, lncRNAs and mRNAs impacting the cytotoxicity of MC-LR in testicular tissues, which provides new perspectives in the development of diagnosis and treatment strategies for MC-LR-induced male reproductive toxicity.

piRNA-DQ722010 contributes to prostate hyperplasia of the male offspring mice after the maternal exposed to microcystin-leucine arginine

BACKGROUND

Microcystin-leucine arginine (MC-LR) could disrupt prostate development and cause prostate hyperplasia. But whether and how maternal and before-weaning MC-LR exposure causes prostate hyperplasia in male offspring by changing expression profile of P-element-induced wimpy (PIWI)-interacting RNAs (piRNAs) have not yet been reported.

METHODS

From the 12th day in the embryonic period to the 21st day after offspring birth, three groups of pregnant mice that were randomly assigned were exposed to 0, 10, and 50 μg/L of MC-LR through drinking water followed by the analyses of their male offspring. Abortion rate and litter size of maternal mice were recorded. The prostate histopathology was observed. Differential expressed piRNAs of prostate were screened by piRNA microarray analysis. Murine prostate cancer cell line (RM-1) was used for further mechanism study. Luciferase report assay was used to determine the relationship between piRNA-DQ722010 and polypeptide 3 (Pik3r3).

RESULTS

The downregulated expression of piRNA-DQ722010 was the most significant in piRNA microarray analysis in 10 μg/L MC-LR treated group, while Pik3r3 was significantly upregulated, consistent with the results that a distinct prostatic epithelial hyperplasia was observed and phosphoinositide-3-kinase (PI3K)/protien kinase B (AKT) signaling pathway was activated. Pik3r3 was verified as the target gene of piRNA-DQ722010. In addition, we found MC-LR decreased the expression of PIWI-like RNA-mediated gene silencing 2 (Piwil2) and 4 (Piwil4) both in vivo and in vitro, and both Piwil4 and Piwil2 could regulate the expression of DQ722010.

CONCLUSION

MC-LR caused downregulation of piRNA-DQ722010 and PIWI proteins, while piRNA-DQ722010 downregulation promoted activation of PI3K/AKT signaling pathway inducing prostate hyperplasia by upregulating the expression of Pik3r3. In contrast, piRNA-DQ722010 downregulation may be attributed to PIWI proteins downregulation.

Sodium Selenite inhibits mitophagy, downregulation and mislocalization of blood-testis barrier proteins of bovine Sertoli cell exposed to microcystin-leucine arginine (MC-LR) via TLR4/NF-kB and mitochondrial signaling pathways blockage

This study was conducted to investigate the ameliorative effect of selenium on microcystin-LR induced toxicity in bovine Sertoli cells. Bovine Sertoli cells were pretreated with selenium (Na₂SeO₃) for 24 h after which selenium pretreated and non-pretreated Sertoli cells were cultured in medium containing 10% heat activated fetal bovine serum FBS+ 80 µg/L MC-LR to assess its ameliorative effect on MC-LR toxicity. The results show that selenium pretreatment inhibited the MC-LR induced mitophagy, downregulation and mislocalization of blood-testis barrier constituent proteins in bovine Sertoli cells via NF-kB and cytochrome c release blockage. The observed downregulation of electron transport chain (ETC) related genes (mt-ND2, COX-1, COX-2) and upregulation of inflammatory cytokines (IL-6, TNF-α, IL-1β, IFN-γ, IL-4, IL-10, 1 L-13, TGFβ1) in non-pretreated cells exposed to MC-LR were ameliorated in selenium pretreated cells. There was no significant difference (P > 0.05) in the protein levels of blood-testis barrier constituent proteins (ZO-1, occludin, connexin-43, CTNNB1, N-cadherin) and mitochondria related genes (mt-ND2, COX-1, COX-2, ACAT1, mtTFA) of selenium pretreated Sertoli cell compared to the control. Taken together, we conclude that selenium inhibits MC-LR caused Mitophagy, downregulation and mislocalization of blood-testis barrier proteins of bovine Sertoli cell via mitochondrial and TLR4/NF-kB signaling pathways blockage.

Microcystin-leucine arginine (MC-LR) induced inflammatory response in bovine sertoli cell via TLR4/NF-kB signaling pathway

Sertoli cells were treated with 0, 20, 40, 60 and 80 μg/L of MC-LR to investigate its toxic effects, mechanism of action and immune response of the cells. Our results revealed that treatment containing 20 μg/L of MC-LR was non-toxic to the cells. Treatments containing 40, 60 and 80 μg/L of MC-LR reduced the cell viability, induced nuclear morphological changes and downregulated the blood-testis barrier constituent proteins within 48 h after treatment. The toll-like receptor 4 (TLR4) and nuclear factor-kappaB (NF-kB) were activated and significantly (P < 0.05) upregulated in cells treated with 40, 60 and 80 μg/L of MC-LR compared to the control. The pro-inflammatory cytokines were upregulated within 48 h after treatment. However commencing from 72 h, upregulation of anti-inflammatory cytokines and expression of blood-testis barrier constituent proteins was observed. This study indicates that MC-LR induced inflammatory response in bovine Sertoli cell via activation of TLR4/NF-kB signaling pathway.

MicroRNA-7450 regulates non-thermal plasma-induced chicken Sertoli cell apoptosis via adenosine monophosphate-activated protein kinase activation

Non-thermal plasma treatment is an emerging innovative technique with a wide range of biological applications. This study was conducted to investigate the effect of a non-thermal dielectric barrier discharge plasma technique on immature chicken Sertoli cell (SC) viability and the regulatory role of microRNA (miR)-7450. Results showed that plasma treatment increased SC apoptosis in a time- and dose-dependent manner. Plasma-induced SC apoptosis possibly resulted from the excess production of reactive oxygen species via the suppression of antioxidant defense systems and decreased cellular energy metabolism through the inhibition of adenosine triphosphate (ATP) release and respiratory enzyme activity in the mitochondria. In addition, plasma treatment downregulated miR-7450 expression and activated adenosine monophosphate-activated protein kinase α (AMPKα), which further inhibited mammalian target of rapamycin (mTOR) phosphorylation in SCs. A single-stranded synthetic miR-7450 antagomir disrupted mitochondrial membrane potential and decreased ATP level and mTOR phosphorylation by targeting the activation of AMPKα, which resulted in significant increases in SC lethality. A double-stranded synthetic miR-7450 agomir produced opposite effects on these parameters and ameliorated plasma-mediated apoptotic effects on SCs. Our findings suggest that miR-7450 is involved in the regulation of plasma-induced SC apoptosis through the activation of AMPKα and the further inhibition of mTOR signaling pathway.

Essential roles of Akt/Snail pathway in microcystin-LR-induced tight junction toxicity in Sertoli cell

Microcystin (MC)-LR is a cyclic heptapeptide that acts as a potent reproductive system toxin. However, the underlying pathways of MCLR-induced reproductive system toxicity have not been well elucidated. The blood-testis barrier is mainly constituted by tight junctions (TJs) between adjacent Sertoli cells in the seminiferous epithelium near the basement membrane. The present study was designed to investigate changes in TJs and the underlying pathway in MC-LR-induced TJs toxicity in Sertoli cell. In our study, the transepithelial electrical resistance (TER) value was decreased in a dose dependent manner due to the markers of TJs occludin, claudin and zonula occludens-1 (ZO-1) expression decline. MC-LR is shown to induce cytotoxicity by inhibiting protein phosphatase 2A (PP2A) activity. Our results also showed that the PP2A activity presented a dose-dependent decline. Moreover, MC-LR stimulated protein expression of snail by Akt/GSK-3β activation. The activated Akt/GSK-3β and snail signaling pathway largely accounted for MC-LRinduced TJs toxicity, which could be partially reversed by snail siRNA interference or AKT chemical inhibitor in TM4 cells. These findings indicated that MC-LR inhibit the protein expression of TJs, and the activation of Akt/Snail signaling pathways due to PP2A inhibition is proposed to participate in this process.

T-2 toxin induces cytotoxicity and disrupts tight junction barrier in SerW3 cells

T-2 toxin, which is produced in grain and grain products as a secondary metabolite by Fusarium species, is also potentially dangerous for human health. Up to date, no study was reported the cytotoxicity of T-2 toxin on SerW3 cells in the perspective of junctional barriers. This study focused on revealing the cytotoxic effects of T-2 on Sertoli cells associated with cell junctional barriers. In the present study, SerW3 cells were exposed to T-2 toxin at 12, 120 and 1200ng/ml doses for 24 and 48h. Cytotoxicity tests including cell viability (MTT), lactate dehydrogenase (LDH) cytotoxicity test and trypan blue exclusion assay were performed. Occludin, ZO-1, N-cadherin and β-catenin were immunolabelled, expressions of occludin and N-cadherin were determined by western blotting. SerW3 cell barrier integrity was measured by transepithelial electrical resistance (TEER). Cytotoxicity caused by T-2 toxin increased in a dose dependent manner, expressions of proteins and TEER measurement decreased. This study may underlie the early targets of T-2 toxin on SerW3 cells mimicking blood-testis barrier in vitro.

MiR-301b-3p/3584-5p enhances low-dose mono-n-butyl phthalate (MBP)-induced proliferation by targeting Rasd1 in Sertoli cells

To investigate the possible molecular mechanism of low concentration plasticizer mono-n-butyl phthalate (MBP) -induced juvenile Sertoli cells (SCs) proliferation, we evaluated global alterations of miRNA and mRNA expression in rat SCs treated with 0.1mM MBP. Microarray analysis revealed that miR-3584-5p and miR-301b-3p were up-regulated and their common target gene Dexamethasone-induced Ras-related protein 1 (Rasd1) was down-regulated. Further work suggested that SCs proliferation induced by low concentration MBP in vitro might be mediated by Rasd1 regulating ERK1/2 signaling pathway. The present study is first to investigate the effect of low-dose MBP on SCs proliferation and may enhance our understanding on the modes of action of low concentration MBP on male reproductive system. We hope the results will contribute to explain the causes of precocious puberty and testicular tumors induced by exogenous chemicals.

Characterization of in vitro effects of microcystin-LR on intestinal epithelial cells

The intestinal epithelium is a single-cell layer that provides an important barrier against natural toxins. Microcystin-LR (MC-LR), a cyclic heptapeptide, is one of the best known toxins able to alter the functions of intestine. This study evaluated the toxic effects and the possible mechanisms of MC-LR on barrier function of the intestinal epithelial cells. Intestinal epithelial cells (IEC-6) were exposed to 0, 6.25, 12.5, 25 and 50 μM MC-LR. Cell viability significantly decreased, while the ratio of apoptotic cells increased after exposure to 12.5μM and higer concentration of MC-LR. As expected, the integrity of a polarized IEC-6 monolayer was affected by MC-LR exposure, as demonstrated by a decrease in the transepithelial electrical resistance (TEER) values, becoming most pronounced at 50μM, 24 h. No effects were detected on the protein expression levels of the tight junction protein claudin at 50μM. However, the expression of occludin and zonula occludens-1 (ZO-1) declined. Furthermore, MC-LR can immigrate into IEC-6 cells. The activity of protein phosphatases 2A (PP2A) decreased from the concentration of 12.5 μM, showing a dose-dependent decline. These results provide new information that strengthens the concept that the intestinal epithelium is important targets for toxic effects of water contaminants like MC-LR. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1539-1547, 2017.

Alterations in microRNA expression in the tissues of silver carp (Hypophthalmichthys molitrix) following microcystin-LR exposure

In the field of toxicology, the relationship between microRNAs (miRNAs) and microcystin-LR (MC-LR) toxicity in fish is still poorly understood. In the present study, we used quantitative real-time PCR (qPCR) to examine the expression of 7 miRNAs (let-7b, miR-21, miR-122, miR-27b, miR-148, miR-125a, and miR-143) that play regulatory roles in biological processes such as signal transduction, apoptosis, cell cycle, and fatty acid metabolism. Expression patterns were assessed in the liver, spleen, and kidney of silver carp following 8, 24, and 48 h of exposure to MC-LR via intraperitoneal injection (50 or 200 μg/kg of body weight). The results of qPCR analysis showed that the expression of the 7 miRNAs was either upregulated or downregulated in response to MC-LR exposure. These results indicate that acute MC-LR exposure altered miRNAs expression profiles in the liver, spleen, and kidney of silver carp, suggesting that miRNAs may be involved in MC-LR toxicity.

Analysis of MicroRNA Expression Profiling Involved in MC-LR-Induced Cytotoxicity by High-Throughput Sequencing

In recent years, microRNAs (miRNAs) in toxicology have attracted great attention. However, the underlying mechanism of miRNAs in the cytotoxicity of microcystin-LR (MC-LR) is lacking. The objective of this study is to analyze miRNA profiling in HepG2 cells after 24 h of MC-LR-exposure to affirm whether and how miRNAs were involved in the cytotoxicity of MC-LR. The results showed that totally 21 and 37 miRNAs were found to be significantly altered in the MC-LR treated cells at concentrations of 10 and 50 μM, respectively, when compared to the control cells. In these two groups, 37,566 and 39,174 target genes were predicted, respectively. The further analysis showed that MC-LR-exposure promoted the expressions of has-miR-149-3p, has-miR-449c-5p, and has-miR-454-3p while suppressed the expressions of has-miR-4286, has-miR-500a-3p, has-miR-500a-5p, and has-miR-500b-5p in MC-LR-treated groups when compared to the control group. Moreover, the result of qPCR confirmed the above result, suggesting that these miRNAs may be involved in MC-LR-hepatotoxicity and they may play an important role in the hepatitis and liver cancer caused by MC-LR. The target genes for differentially expressed miRNAs in MC-LR treatment groups were significantly enriched to totally 23 classes of GO, in which three were significantly enriched in both 10 and 50 μM MC-LR groups. Moreover, the results of KEGG pathway analysis showed that MC-LR-exposure altered some important signaling pathways such as MAPK, biosynthesis of secondary metabolites, and pyrimidine and purine metabolism, which were possibly negatively regulated by the corresponding miRNAs and might play important role in MC-LR-mediated cytotoxicity in HepG2 cells.

Microcystin-Leucine Arginine Causes Cytotoxic Effects in Sertoli Cells Resulting in Reproductive Dysfunction in Male Mice

Microcystin-leucine arginine (MC-LR) is a potent toxin for Sertoli cells. However, the specific molecular mechanisms of MC-induced cytotoxicity still remain unclear. In this study, we performed a comprehensive analyses of changes of miRNAs and mRNAs in Sertoli cells treated with MC-LR. Through computational approaches, we showed the pivotal roles of differentially expressed miRNAs that were associated with cell metabolism, cellular growth and proliferation, cell-to-cell signaling and interaction and cellular movement. Ingenuity Pathway Analyses (IPA) revealed some differentially expressed miRNAs and mRNAs that may cause reproductive system diseases. Target gene analyses suggested that destruction in tight junctions (TJ) and adherens junctions (AJ) in testes may be mediated by miRNAs. Consistent with a significant enrichment of chemokine signaling pathways, we observed numerous macrophages in the testes of mice following treatment with MC-LR, which may cause testicular inflammation. Moreover, miR-98-5p and miR-758 were predicted to bind the 3′-UTR region of the mitogen-activated protein kinase 11 (MAPK11, p38 β isoform) gene which stimulates tumor necrosis factor-α (TNF-α) expression in Sertoli cells. TNF-α could interact with the tumor necrosis factor receptor 1 (TNFR1) on germ cells leading to induction of germ cell apoptosis. Collectively, our integrated miRNA/mRNA analyses provided a molecular paradigm, which was experimentally validated, for understanding MC-LR-induced cytotoxicity.

A review of reproductive toxicity of microcystins

Animal studies provide strong evidence of positive associations between microcystins (MCs) exposure and reproductive toxicity, representing a threat to human reproductive health and the biodiversity of wild life. This paper reviews current knowledge of the reproductive toxicity of MCs, with regard to mammals, fishes, amphibians, and birds, mostly in males. Toxicity of MCs is primarily governed by the inhibition of protein phosphatases 1 and 2A (PP1 and PP2A) and disturbance of cellular phosphorylation balance. MCs exposure is related to excessive production of reactive oxygen species (ROS) and oxidative stress, leading to cytoskeleton disruption, mitochondria dysfunction, endoplasmic reticulum (ER) stress, and DNA damage. MCs induce cell apoptosis mediated by the mitochondrial and ROS and ER pathways. Through PP1/2A inhibition and oxidative stress, MCs lead to differential expression/activity of transcriptional factors and proteins involved in the pathways of cellular differentiation, proliferation, and tumor promotion. MC-induced DNA damage is also involved in carcinogenicity. Apart from a direct effect on testes and ovaries, MCs indirectly affect sex hormones by damaging the hypothalamic-pituitary-gonad (HPG) axis and liver. Parental exposure to MCs may result in hepatotoxicity and neurotoxicity of offspring. We also summarize the current research gaps which should be addressed by further studies.