MicroRNAs are involved in the toxicity of microcystins

Acute microcystin exposure induces reversible histopathological changes in Chinook Salmon (Oncorhynchus tshawytscha) and Atlantic Salmon (Salmo salar)

Atlantic Salmon (Salmo salar) and Chinook Salmon (Oncorhynchus tshawytscha) develop a severe liver disease called net-pen liver disease (NPLD), which is characterized by hepatic lesions that include megalocytosis and loss of gross liver structure. Based on studies where salmonids have been exposed to microcystin (MC) via intraperitoneal injection, NPLD is believed to be caused by MC exposure, a hepatotoxin produced by cyanobacteria. Despite the link between MC and NPLD, it remains uncertain if environmentally relevant MC exposure is responsible for NPLD. To determine if we could produce histopathology consistent with NPLD, we compared the response of Atlantic and Chinook Salmon sub-lethal MC exposure. Salmon were orally gavaged with saline or MC containing algal paste and sampled over 2 weeks post-exposure. Liver lesions appeared by 6 h but were resolved 2-weeks post-exposure; histopathological changes observed in other tissues were not as widespread, nor was their severity as great as those in the liver. There was no evidence for NPLD due to the absence of hepatic megalocytosis. These results indicate that the development of NPLD is not due to acute MC exposure but may be associated with higher MC concentration occurring in food, long-term exposure through drinking of contaminated seawater and/or interactions with other marine toxins.

Negative impacts of microcystin-LR and glyphosate on zebrafish intestine: Linked with gut microbiota and microRNAs?

Microcystin-LR (MC-LR) and glyphosate (GLY) have been classified as a Group 2B and Group 2A carcinogens for humans, respectively, and frequently found in aquatic ecosystems. However, data on the potential hazard of MC-LR and GLY exposure to the fish gut are relatively scarce. In the current study, a subacute toxicity test of zebrafish exposed to MC-LR (35 μg L-1) and GLY (3.5 mg L-1), either alone or in combination was performed for 21 d. The results showed that MC-LR or/and GLY treatment reduced the mRNA levels of tight junction genes (claudin-5, occludin, and zonula occludens-1) and altered the levels of diamine oxidase and D-lactic, indicating increased intestinal permeability in zebrafish. Furthermore, MC-LR and/or GLY treatment remarkably increased the levels of intestinal IL-1β and IL-8 but decreased the levels of IL-10 and TGF-β, indicating that MC-LR and/or GLY exposure induced an inflammatory response in the fish gut. MC-LR and/or GLY exposure also activated superoxide dismutase and catalase, generally upregulated the levels of p53, bax, bcl-2, caspase-3, and caspase-9, downregulated the levels of caspase-8 and caused notable histological injury in the fish gut. Moreover, MC-LR and/or GLY exposure also significantly altered the microbial community in the zebrafish gut and the expression of miRNAs (miR-146a, miR-155, miR-16, miR-21, and miR-223). Chronic exposure to MC-LR and/or GLY can induce intestinal damage in zebrafish, and this study is the first to demonstrate an altered gut microbiome and miRNAs in the zebrafish gut after MC-LR and GLY exposure.

MicroRNA-16 participates in the cell cycle alteration of HepG2 cells induced by MC-LR

Microcystin-LR (MC-LR) is a cyclic hepatotoxin produced by cyanobacteria in freshwater, and chronic MC-LR exposure could induce human hepatitis if consumed in drinking water. In recent years, many studies have indicated that microRNAs participate in the hepatotoxicity of MC-LR. The purpose of this study was to investigate the potential function of miR-16 in the hepatocellular toxicity and cell cycle alteration induced by MC-LR in human hepatocellular carcinoma (HepG2) cells after treatment with 10 μM MC-LR. The result of flow cytometry detection showed that a low concentration of MC-LR (10 μM) failed to induce apoptosis but promoted cell cycle G1/S transition in HepG2 cells. In addition, the expression of apoptosis-related genes was suppressed after MC-LR exposure. These results confirm that MC-LR exposure at a low dose can promote the proliferation of HepG2 cells. Furthermore, we also found that microRNA-16 (miR-16) expression was suppressed in HepG2 cells following MC-LR exposure. Hence, we overexpressed miR-16 in HepG2 cells and treated them with MC-LR, and the results showed that miR-16 overexpression induced an increase in the G0/G1 phase and a decrease in the S phase cell cycle populations in HepG2 cells, suggesting that miR-16 can inhibit the cell proliferation of HepG2 cells. In conclusion, our results suggest that miR-16 may play a vital role in the cell cycle alteration of HepG2 cells after MC-LR exposure.

CYP3A4 and microRNA-122 are involved in the apoptosis of HepG2 cells induced by ILs 1-decyl-3-methylimidazolium bromide

Ionic liquids (ILs) as green alternatives for volatile organic solvents are increasingly used in commercial applications. It is necessary to explore the cytotoxic mechanism of ILs to reduce the risk to human health. For this purpose, cell viability, apoptosis, cytochrome P450 3A4 (CYP3A4), glucose transporter type 2 (GLUT2), and microRNA-122 (miR-122) gene expression in HepG2 cells was evaluated after IL exposure. The results showed that ILs reduced the viability of HepG2 cells through apoptotic cell death. Moreover, ILs markedly upregulated the transcription and protein levels of CYP3A4, but did not affect the expression of GLUT2 in either messenger RNA level or protein level. Finally, ILs increased the expression of miR-122 and inhibition of miR-122 with miR-122 inhibitor blocked ILs-induced apoptosis in HepG2 cells. This finding may contribute to an increased understanding of the in vitro molecular toxicity mechanism of ILs to further understand IL-related human health risks.

Role of miR-731 and miR-2188-3p in mediating chlorpyrifos induced head kidney injury in common carp via targeting TLR and apoptosis pathways

Chlorpyrifos (CPF) is an environmental pollutant with increasing importance due to its high toxicity to fish and aquatic animals. In the present study, we divided 120 common carp (Cyprinus carpio L.) into two groups including control group and CPF group, CPF group was exposed to 14.5 μg/L CPF for 30 d. 17 miRNAs were differentially expressed in CPF group head kidney tissues according to the results of miRNAome analysis. In addition, histopathological examination and electron microscopy proved that CPF exposure could lead to damage of head kidney and obvious apoptosis characteristics. The possible target genes of miRNA were predicted using online target gene prediction websites, miRNAome sequencing, GO and KEGG enrichment. miRNAome results showed that expression of miR-731 and miR-2188-3p in CPF group was 0.48 time and 0.45 time as control group, respectively. qRT-PCR results proved the reality of miRNAome. During CPF exposure, mRNA expression of TLR pathway genes and its downstream genes involved in autophagy and apoptosis pathway including TLR1, TLR2, TLR7, TLR9, MyD88, IRAK1, IRAK4, IRF7, PI3K, AKT, mTOR, Caspase3, Caspase8 and Bax were differentially increased under CPF exposure, along with ATG13 and Bcl2 decreased at the same time. Western blot results indicated that apoptosis related protein Caspase3 and Caspase8 were differentially up-regulated in the CPF group. In summary, CPF exposure could induce apoptosis while inhibited autophagy in head kidney of common carp via the regulation of miR-2188-3p and miR-731 by targeting TLR pathway. These results provide new insights for unveiling the biological effects of CPF and miRNAs in common carp.

Cisplatin decreases cyclin D2 expression via upregulating miR‑93 to inhibit lung adenocarcinoma cell growth

MicroRNAs (miRNAs/miRs) serve important roles in the chemotherapeutic effect of anticancer drugs. To investigate the roles of miRNAs in cisplatin‑induced suppression of lung adenocarcinoma cell proliferation, A549 cells were treated with different concentrations of cisplatin. An MTT assay demonstrated that cisplatin inhibited A549 cell proliferation in a dose‑dependent manner. Cisplatin induced cell apoptosis and inhibited cell migration by increasing the levels of miR‑93, miR‑26a and miR‑26b. Furthermore, as an upstream factor, miR‑93 was proposed to regulate cyclin D2 expression in miR‑93‑transfected A549 cells. Cisplatin also induced Bcl‑2‑associated X protein expression, and decreased that of Bcl‑2 and c‑Myc in lung adenocarcinoma cells. In vivo analysis further supported that cisplatin inhibited lung adenocarcinoma cell growth by regulating cyclin D2 and miR‑93 expression. In conclusion, our findings demonstrated that cisplatin could effectively inhibit lung adenocarcinoma cell proliferation by decreasing cyclin D2 expression via miR‑93.

Identification of serum microRNAs as potential toxicological biomarkers for toosendanin-induced liver injury in mice

BACKGROUND

Toosendan Fructus is traditionally used as an insecticide or digestive tract parasiticide for treating digestive parasites in China. It is recorded to have little toxicity in Chinese Pharmacopoeia and has been found to cause severe liver injury during clinical practice.

PURPOSE

This study aims to identify candidate serum microRNAs (miRNAs) as potential toxicological biomarkers for reflecting the hepatotoxicity induced by toosendanin (TSN), which is the main toxic compound isolated from Toosendan Fructus METHODS: Alanine/aspartate aminotransferase (ALT/AST) activities detection and liver histological observation were performed to evaluate the liver injury induced by TSN or other hepatotoxicants in mice. miRNAs chip analysis and Real-time PCR assay were conducted to identify the altered miRNAs in serum from TSN-treated mice RESULTS: The results of serum ALT/AST and liver histological evaluation showed that TSN (10 mg/kg) induced hepatotoxicity in mice. The results of miRNAs chip showed that the expression of 81 serum miRNAs was obviously altered in mice treated with TSN for 12 h, and 22 of them have passed the further validation in serum from mice treated with TSN for both 6 h and 12 h. These 22 miRNAs were supposed to be the candidate toxicological biomarkers for TSN-induced hepatotoxicity with more sensitivity as compared to the alteration of AST or ALT activity. Moreover, the expression of miRNA-122-3p and mcmv-miRNA-m01-4-3p was not only increased in TSN-treated mice, but also increased in mice treated with other hepatotoxicants including acetaminophen (APAP), monocrotaline (MCT) and diosbuibin B (DB). Only the expression of serum miRNA-367-3p was increased in TSN-treated mice but not changed in the liver injury induced by APAP, MCT or DB CONCLUSION: miR-122-3p and mcmv-miRNA-m01-4-3p may be two commonly sensitive biomarkers for reflecting the hepatotoxicity induced by exogenous hepatotoxicants, and miR-367-3p may be a specific biomarker for reflecting the liver injury induced by TSN.

Molecular characterization of the cyclin-dependent protein kinase 6 in whitefish (Coregonus lavaretus) and its potential interplay with miR-34a

Cyclin-dependent protein kinase 6 (CDK6) plays a pivotal role in the regulation of the cell cycle and cell proliferation in mammals, and disruption of its expression by various microRNAs has been implicated in the pathogenesis of multiple human cancers. In mammals, miR-34a acts as a downstream effector of p53, and thus indirectly targets Cdk6, abrogating its effects. However, no studies have been done so far to examine the mechanistic involvement of miR-34a in the silencing of cdk6 in fish. In the present study, we found that the cDNA sequence of whitefish cdk6 has a 3'UTR region that contains a binding site for miR-34a. Using a luciferase reporter assay, we demonstrated that whitefish cdk6 is a direct target of miR-34a in vitro. In order to confirm this relationship in vivo, we measured the miR-34a and cdk6 mRNA expression patterns in the liver of whitefish after short-term (8, 24, and 48 h) and long-term (14 and 28 days) exposure to microcystin-LR (MC-LR), a known hepatotoxin and tumor promoter. In contrast to the in vitro findings, we noticed an up-regulation of miR-34a and cdk6 expression after long-term MC-LR treatment. While these results indicate that both, miR-34a and cdk6 are responsive to MC-LR treatment, they do not support the presence of a miR-34a:cdk6 mRNA regulatory pair in the MC-LR-challanged whitefish liver in vivo. On the other hand, our findings suggests that cell regulatory elements, partnering with either miR-34a or cdk6, are worthy of further screening to better understand the molecular mechanisms that underlie the physiological response of fish challenged with hepatotoxic environmental pollutants like microcystins.

Extracellular vesicle‑delivered miR‑505‑5p, as a diagnostic biomarker of early lung adenocarcinoma, inhibits cell apoptosis by targeting TP53AIP1

Lung adenocarcinoma (LA) is the most commonly occurring histological type of non‑small cell lung cancer. Diagnosis and treatment of LA remain a major clinical challenge. In the present study, to identify early LA biomarkers, extracellular vesicles (EVs) were separated from the plasma samples from 153 patients with LA and 75 healthy controls. microRNA (miRNA) expression profiling was performed at the screening stage (5 patients with LA vs. 5 controls), followed by verification at the validation stage (40 patients with LA vs. 20 controls) using reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR). The four disordered miRNAs (miR‑505‑5p, miR‑486‑3p, miR‑486‑3p and miR‑382‑3p) identified in the plasma EVs were further evaluated at the testing stage (108 patients with LA vs. 50 controls) by RT‑qPCR. It was revealed that miR‑505‑5p was upregulated, whereas miR‑382‑3p was downregulated, in the EVs from patients with LA. Furthermore, miR‑505‑5p was also upregulated in tumor tissues, compared with adjacent non‑tumor control tissues. Subsequently, the direct targets of miR‑505‑5p were predicted using bioinformatics analyses, and verified by luciferase assay and immunoblotting. The present study determined that miR‑505‑5p functions as an oncogene, promoting lung cancer cell proliferation and inhibiting cancer cell apoptosis via the targeting of tumor protein P53‑regulated apoptosis‑inducing protein 1 (TP53AIP1). Finally, it was confirmed that miR‑505‑5p in plasma EVs could be delivered to lung cancer cells, inhibiting cell apoptosis and promoting cell proliferation by targeting TP53AIP1. In conclusion, the present study indicated that miRNA‑505‑5p functions as an oncogene that may be used as a novel biomarker for the diagnosis and treatment of LA.

Chronic exposure to the ionic liquid [C8mim]Br induces inflammation in silver carp spleen: Involvement of oxidative stress-mediated p38MAPK/NF-κB signalling and microRNAs

The present study aimed to determine the chronic toxicity of 1-methyl-3-octylimidazolium bromide ([C₈mim]Br) on the silver carp to further reveal the toxicological mechanisms of ionic liquids. Chronic exposure of silver carp to [C₈mim]Br at concentrations of 1.095 and 4.380 mg/L for 60 d was conducted under laboratory conditions. The results revealed that chronic exposure to [C₈mim]Br inhibited the activity of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) and reduced glutathione (GSH) levels while markedly increasing malondialdehyde (MDA) and protein carbonyl (PC) levels in fish spleen, indicating that [C₈mim]Br treatment induced oxidative stress. Additionally, long-term exposure to [C₈mim]Br markedly upregulated the expressions of nuclear factor-κB (NF-κB), inducible nitric oxide synthase (iNOS), interleukin-1β (IL-1β), IL-6, tumour necrosis factor-α (TNF-α), and interferon-γ (IFN-γ); altered the levels of transforming growth factor-β (TGF-β); and increased the mRNA levels of p38MAPK, c-fos, c-jun, and c-myc, suggesting that long-term exposure to [C₈mim]Br might promote the inflammatory response in fish spleen and that p38MAPK/NF-κB signalling may potentially be involved in this process. Moreover, [C₈mim]Br-exposure altered lysozyme activity and complement 3 (C3) and immunoglobulin M (IgM) content, indicating that chronic [C₈mim]Br exposure also has immunotoxic effects on silver carp. Furthermore, we also found that [C₈mim]Br exposure reduced miR-125b levels, altered miR-143 levels, and upregulated miR-155 and miR-21 levels, suggesting that these miRNAs may be involved in the [C₈mim]Br-induced inflammatory response in fish spleen. In summary, the present study indicates that chronic exposure to [C₈mim]Br induces inflammation in fish spleen and that oxidative stress-mediated p38MAPK/NF-κB signalling and miRNAs may play a key role in this process.

MicroRNA‑363‑3p inhibits hepatocarcinogenesis by targeting HMGA2 and is associated with liver cancer stage

The importance of microRNAs (miRNAs) in cancer development has been widely recognized in recent decades. In the present study, the function and mechanism of miRNA-363-3p (miR-363-3p), formerly characterized as a tumor suppressor, in the hepatocarcinogenesis of liver cancer cells was investigated. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was applied to detect the expression of miR-363-3p in liver cancer tissues. Cell proliferation, survival and migration capacities were determined by MTT, colony formation and wound-healing assays, respectively. The targeting of high mobility group AT-hook 2 (HMGA2) mRNA by miR-363-3p was confirmed by bioinformatics analysis, and RT-qPCR, luciferase reporter and western blot assays. The correlation between the expression levels of HMGA2 and miR-363-3p was analyzed. The RT-qPCR results revealed that the levels of miR-363-3p were downregulated in liver cancer tissues. Cellular assays validated that miR-363-3p exerted tumor suppressing functions, including the inhibition of cell proliferation, survival and migration abilities in two liver cancer cell lines. Bioinformatics prediction and subsequent experiments demonstrated that HMGA2 was a direct target of miR-363-3p. Restoration of the expression of HMGA2 in miR-363-3p mimic-transfected cells reversed the tumor suppressing effects caused by miR-363-3p. Finally, there was a significant negative correlation between the expression levels of HMGA2 and miR-363-3p in liver cancer tissues. miR-363-3p was identified as an important tumor suppressor in liver cancer via targeting HMGA2, which may have potential benefits in liver cancer therapy.

Serum immune responses in common carp (Cyprinus carpio L.) to paraquat exposure: The traditional parameters and circulating microRNAs

Paraquat (PQ) is a herbicide used worldwide, and it was shown to be a high-risk compound to aquatic organisms. This study was conducted to investigate the effects of PQ on traditional serum parameters and circulating microRNAs (miRNAs) in common carp to further elucidate the mechanism of PQ toxicity in fish. In the current study, a subacute toxicity test of common carp exposed to PQ at 1.596 and 3.192 mg/L for 7 d was conducted under laboratory conditions. The results showed that PQ exposure generally reduced the levels of T-AOC, SOD, CAT, and GST, but significantly increased MDA levels in the serum, indicating that PQ exposure induces oxidative stress and lipid peroxidation in the fish. The results of biochemical assays showed that PQ exposure not only significantly altered the activities of LDH, AST, ALT, ACP, AKP, and lysozyme and the contents of IgM and complement 3 but also promoted the expression of pro-inflammatory cytokines, including IFN-γ, IL-1β, IL-6, IL-8, and TNF-α. Additionally, PQ inhibited the levels of the anti-inflammatory cytokines IL-10 and TGF-β, suggesting that PQ exposure may cause fish tissue injury and promote immune inflammatory responses. Furthermore, we found that serum circulating miRNAs, such as ccr-mir-122, ccr-mir-125b, ccr-mir-146a, and ccr-mir-155, were generally promoted in fish following PQ exposure. Based on our results and reports on miRNA-based diagnosis of tissue damage and inflammatory responses in mammals, we suggest that serum ccr-mir-122, ccr-mir-125b, ccr-mir-146a, and ccr-mir-155 could be new biomarkers of PQ toxicity in fish.

Epigenetic alterations of the Igf2 promoter and the effect of miR‑483‑5p on its target gene expression in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is one of the most widespread malignancies in China. MicroRNAs (miRNAs/miRs) are endogenous evolutionarily-conserved small non-coding RNAs that are able to regulate ESCC formation and deterioration by negatively regulating specific target genes. In the present study, the expression levels of miR-483-5p and its associated mRNAs were measured by quantitative polymerase chain reaction (PCR) analysis, and the methylation levels of the insulin-like growth factor 2 (Igf2) promoter were detected via the methylation-specific PCR method in serum and tissues from patients with ESCC. The results demonstrated that the expression level of miR-483-5p was significantly upregulated in preoperative serum and cancer tissues from patients with ESCC (P<0.01), and the miR-483-5p expression levels were correlated with the tumor, node, metastasis stage (P<0.05) and lymph node metastasis (P<0.05). In addition, the mRNA levels of miR-483-5p target genes (Rho GDP dissociation inhibitor α, activated leukocyte cell adhesion molecule, and suppressor of cytokine signaling 3) in cancer tissues were significantly decreased compared with adjacent non-cancerous tissues. These results indicated that miR-483-5p and its target genes may be involved in the developmental process of ESCC. The Igf2 levels in cancer tissues were significantly increased compared with adjacent non-cancerous tissues (P<0.01). Additionally, the methylation levels of the Igf2 promoter region were 31.82 and 54.55% in cancer tissues and adjacent non-cancerous tissues, respectively, suggesting that low methylation of the Igf2 gene promoter region may promote the expression of Igf2 and miR-483-5p; this, in turn, induces the degradation of miR-483-5p target genes, and leads to the upregulation of oncogenes and the downregulation of tumor suppressors, which promotes the development of ESCC.

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.