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Freshwater prokaryotic cyanobacteria within harmful algal blooms produce cyanotoxins which are considered major pollutants in the aquatic system. Direct exposure to cyanotoxins through inhalation, skin contact, or ingestion of contaminated drinking water can target the liver and may cause hepatotoxicity. In the current study, we investigated the effect of low concentrations of cyanotoxins on cytotoxicity, inflammation, modulation of unfolded protein response (UPR), steatosis, and fibrosis signaling in human hepatocytes and liver cell models. Exposure to low concentrations of microcystin-LR (MC-LR), microcystin-RR (MC-RR), nodularin (NOD), and cylindrospermopsin (CYN) in human bipotent progenitor cell line HepaRG and hepatocellular carcinoma (HCC) cell lines HepG2 and SK-Hep1 resulted in increased cell toxicity. MC-LR, NOD, and CYN differentially regulated inflammatory signaling, activated UPR signaling and lipogenic gene expression, and induced cellular steatosis and fibrotic signaling in HCC cells. MC-LR, NOD, and CYN also regulated AKT/mTOR signaling and inhibited autophagy. Chronic exposure to MC-LR, NOD, and CYN upregulated the expression of lipogenic and fibrosis biomarkers. Moreover, RNA sequencing (RNA seq) data suggested that exposure of human hepatocytes, HepaRG, and HCC HepG2 cells to MC-LR and CYN modulated expression levels of several genes that regulate non-alcoholic fatty liver disease (NAFLD). Our data suggest that low concentrations of cyanotoxins can cause hepatotoxicity and cell steatosis and promote NAFLD progression.

Crude oil naphtha fraction C9 alkylbenzenes consist of trimethylbenzenes, ethyltoluenes, cumene, and n-propylbenzene. The major fraction of C9 alkylbenzenes is ethyltoluenes (ETs) consisting of three isomers: 2-ethyltoluene (2-ET), 3-ethyltoluene (3-ET), and 4-ethyltoluene (4-ET). Occupational and environmental exposure to ETs can occur via inhalation and ingestion and cause several health problems. Exposure to ETs causes eye and upper respiratory tract irritation, coughing, gagging, vomiting, griping, diarrhea, distress, and depressed respiration. Previous studies suggest that ETs target the respiratory tract and liver and produce several lesions in the nose, lungs, and liver areas. In the current study, we investigated the impact of low concentrations of ETs on cell metabolism, cell inflammation, steatosis, and fibrosis signaling in liver cell models in vitro. Dose-dependent exposure of 2-ET, 3-ET, and 4-ET to HepaRG and hepatocellular carcinoma (HCC) HepG2 and SK-Hep1 cells affects cell survival/real-time proliferation and increases ROS production. ETs induce inflammatory CAT, SOD1, CXCL8, IL1B, HMOX1, NAT1 (3), and STAT3 gene expression. Exposure of 2-ET, 3-ET, and 4-ET to HepaRG and HCC HepG2 and SK-Hep1 cells affects mitochondrial respiration/cellular energetics and upregulates metabolic CYP1-A1, CYP1-A2, CYP2-D6, CYP2-E1, CYP3-A4, CYP3-B4, and VEGFA gene expression. However, no significant change in lipogenesis-related gene expression and modulation of cell steatosis was observed after ET exposure. Acute exposure to induvial ETs and in combination or chronic 2-ET exposure alone modulates cell fibrosis markers such as AST, FGF-23, Cyt-7 p21, TGFβ, TIMP2, and MMP2 in liver cell models, suggesting that ETs target liver cells and may dysregulate liver function.

MicroRNAs (miRNAs) are small non-coding RNA molecules that bind with the 3′ untranslated regions (UTRs) of genes to regulate expression. Downregulation of miR-483-5p (miR-483) is associated with the progression of hepatocellular carcinoma (HCC). However, the significant roles of miR-483 in nonalcoholic fatty liver disease (NAFLD), alcoholic fatty liver diseases (AFLD), and HCC remain elusive. In the current study, we investigated the biological significance of miR-483 in NAFLD, AFLD, and HCC in vitro and in vivo. The downregulation of miR-483 expression in HCC patients’ tumor samples was associated with Notch 3 upregulation. Overexpression of miR-483 in a human bipotent progenitor liver cell line HepaRG and HCC cells dysregulated Notch signaling, inhibited cell proliferation/migration, induced apoptosis, and increased sensitivity towards antineoplastic agents sorafenib/regorafenib. Interestingly, the inactivation of miR-483 upregulated cell steatosis and fibrosis signaling by modulation of lipogenic and fibrosis gene expression. Mechanistically, miR-483 targets PPARα and TIMP2 gene expression, which leads to the suppression of cell steatosis and fibrosis. The downregulation of miR-483 was observed in mice liver fed with a high-fat diet (HFD) or a standard Lieber-Decarli liquid diet containing 5% alcohol, leading to increased hepatic steatosis/fibrosis. Our data suggest that miR-483 inhibits cell steatosis and fibrogenic signaling and functions as a tumor suppressor in HCC. Therefore, miR-483 may be a novel therapeutic target for NAFLD/AFLD/HCC management in patients with fatty liver diseases and HCC.

Lemurs are highly endangered mammals inhabiting the forests of Madagascar. In this study, we performed virus discovery on serum samples collected from 84 wild lemurs and identified viral sequence fragments from 4 novel viruses within the family Flaviviridae, including members of the genera Hepacivirus and Pegivirus. The sifaka hepacivirus (SifHV, two genotypes) and pegivirus (SifPgV, two genotypes) were discovered in the diademed sifaka (Propithecus diadema), while other pegiviral fragments were detected in samples from the indri (Indri indri, IndPgV) and the weasel sportive lemur (Lepilemur mustelinus, LepPgV). Although data are preliminary, each viral species appeared host species-specific and frequent infection was detected (18 of 84 individuals were positive for at least one virus). The complete coding sequence and partial 5’ and 3’ untranslated regions (UTRs) were obtained for SifHV and its genomic organization was consistent with that of other hepaciviruses, with one unique polyprotein and highly structured UTRs. Phylogenetic analyses showed the SifHV belonged to a clade that includes several viral species identified in rodents from Asia and North America, while SifPgV and IndPgV were more closely related to pegiviral species A and C, that include viruses found in humans as well as New- and Old-World monkeys. Our results support the current proposed model of virus-host co-divergence with frequent occurrence of cross-species transmission for these genera and highlight how the discovery of more members of the Flaviviridae can help clarify the ecology and evolutionary history of these viruses. Furthermore, this knowledge is important for conservation and captive management of lemurs.