Alcohol Promotes Exosome Biogenesis and Release via Modulating Rabs and miR-192 Expression in Human Hepatocytes

Exosomes are membrane vesicles released by various cell types into the extracellular space under different conditions including alcohol exposure. Exosomes are involved in intercellular communication and as mediators of various diseases. Alcohol use causes oxidative stress that promotes exosome secretion. Here, we elucidated the effects of alcohol on exosome biogenesis and secretion using human hepatocytes. We found that alcohol treatment induces the expression of genes involved in various steps of exosome formation. Expression of Rab proteins such as Rab1a, Rab5c, Rab6, Rab10, Rab11, Rab27a and Rab35 were increased at the mRNA level in primary human hepatocytes after alcohol treatment. Rab5, Rab6 and Rab11 showed significant induction in the livers of patients with alcohol-associated liver disease. Further, alcohol treatment also led to the induction of syntenin, vesicle-associated membrane proteins (VAMPs), and syntaxin that all play various roles in exosome biogenesis and secretion. VAMP3, VAMP5, VAPb, and syntaxin16 mRNA transcripts were increased in alcohol treated cells and in the livers of alcohol-associated liver disease (ALD) patients. Induction in these genes was associated with increases in exosome secretion in alcohol treated hepatocytes. We found that hepatocyte enriched miR-192 and miR-122 levels were significantly decreased in alcohol treated hepatocytes whereas their levels were increased in the cell-free supernatant. The primary transcripts of miR-192 and miR-122 were reduced in alcohol treated hepatocytes, suggesting alcohol partially affects these miRNAs at the transcriptional level. We found that miR-192 has putative binding sites for genes involved in exosome secretion. Inhibition of miR-192 in human hepatoma cells caused a significant increase in Rab27a, Rab35, syntaxin7 and syntaxin16 and a concurrent increase in exosome secretion, suggesting miR-192 regulates exosomes release in hepatocytes. Collectively, our results reveal that alcohol modulates Rabs, VAMPs and syntaxins directly and partly via miR-192 to induce exosome machinery and release.

Investigation of Reactive Oxygen Species production in Human Hepatocytes

1. Aim/Background: Reactive oxygen species (ROS) have been identified as compounds responsible for producing cellular damage. The purpose of this research is to examine if there is production of reactive oxygen species through free radical intermediates within human hepatocytes treated with morphine, bilirubin, or furosemide. The investigation examines the early stages of biotransformation by measuring the levels of reactive oxygen species produced inside of the treated hepatocytes within the first and second hours of treatment. The experiment was designed upon a case of a jaundiced (elevated bilirubin) infant who received morphine and furosemide and later died through unknown mechanisms. The experiment looks to examine if these drug compounds could contribute to cellular damage. This can help to further understand the potential interactions and complications of free radical intermediates produced during the phases of biotransformation. 2. Method: Previously cultured human hepatocytes were washed by centrifugation and re-suspended in 1x supplemental buffer to a concentration of 1x106 cells/mL and seeded in a dark clear bottom 96-well microplate at 100,000 stained cells/well. The cells were treated with either furosemide, morphine, bilirubin, a Tert-Butyl hydro peroxide (TBHP) positive control, or left as a background. Reactive oxygen generated in the presence of these agents were quantified by fluorescence excitation/emission measurement at 495nm/529nm. Fluorescence was measured at one and two hours. ROS generated convert 2',7'-dichlorodihydrofluorescein diacetate to 2',7'-dichlorodihydrofluorescein within the cells, which fluoresces. The fluorescence intensity detected is equivalent to the level of ROS generated. Wells that were untreated were used as blanks and subtracted from background and TBPH. 3. Results: Furosemide and Morphine did not produce statistically significant levels of ROS (p >0.05) above the background in both hours 1 and 2 of biotransformation and ROS measurement (Figure 1). Although Bilirubin did not produce statistically significant (p >0.05) levels of ROS above the background (Figure 2) during the first hour, it did produce statistically significant levels in the second hour of biotransformation. Each compound’s level of ROS was reduced during the second hour, signaling the removal of intermediate ROS metabolites (Figure 2). The production of ROS in each compound signifies that there is biotransformation to an intermediate that produces ROS. 4. Conclusion: The production of ROS above the background by each of the compounds shows there is an intermediate free radical compound that is produced during the biotransformation of each compound [21]. In this study, although furosemide and morphine did not produce statistically significant levels of ROS in both hours of biotransformation, bilirubin did produce significant levels of ROS in the second hour of biotransformation. This finding is in line with previous studies that shows morphine to offer protective effects against ROS production [16, 17]; and bilirubin demonstrating deleterious production of ROS at high doses [18]. Further work must be done to examine the correlation between the levels of ROS and extent of hepatocellular damage.

In Vitro Ballooned Hepatocytes Can Be Produced By Primary Human Hepatocytes and Hepatic Stellate Cell Sheets

Background Despite the increasing prevalence of Nonalcoholic steatohepatitis (NASH) worldwide, there is no effective treatment available for this disease. “Ballooned hepatocyte” is a characteristic finding in NASH and is correlated with disease prognosis, but their mechanisms of action are poorly understood; furthermore, neither animal nor in vitro models of NASH have been able to adequately represent ballooned hepatocytes. Herein, we engineered cell sheets to develop a new in vitro model of ballooned hepatocytes. Methods Primary human hepatocytes (PHH) and Hepatic stellate cells (HSC) were co-cultured to produce cell sheets, which were cultured in glucose and lipid containing medium, following which histological and functional analyses were performed. Results Histological findings showed hepatocyte ballooning, accumulation of fat droplets, abnormal cytokeratin arrangement, and the presence of Mallory-Denk bodies and abnormal organelles. These findings are similar to those of ballooned hepatocytes in human NASH. Functional analysis showed elevated levels of TGFβ-1, SHH, and p62, but not TNF-α, IL-8. Conclusions Exposure of PHH/HSC sheets to a glucolipotoxicity environment induces ballooned hepatocyte without inflammation. Moreover, fibrosis is an important mechanism underlying ballooned hepatocytes and could be the basis for the development of a new in vitro NASH model with ballooned hepatocytes.

RNR-R2 Upregulation by a Short Non-Coding Viral Transcript

DNA viruses require dNTPs for replication and have developed different strategies to increase intracellular dNTP pools. Hepatitis B virus (HBV) infects non-dividing cells in which dNTPs are scarce and the question is how viral replication takes place. Previously we reported that the virus induces the DNA damage response (DDR) pathway culminating in RNR-R2 expression and the generation of an active RNR holoenzyme, the key regulator of dNTP levels, leading to an increase in dNTPs. How the virus induces DDR and RNR-R2 upregulation is not completely known. The viral HBx open reading frame (ORF) was believed to trigger this pathway. Unexpectedly, however, we report here that the production of HBx protein is dispensable. We found that a small conserved region of 125 bases within the HBx ORF is sufficient to upregulate RNR-R2 expression in growth-arrested HepG2 cells and primary human hepatocytes. The observed HBV mRNA embedded regulatory element is named ERE. ERE in isolation is sufficient to activate the ATR-Chk1-E2F1-RNR-R2 DDR pathway. These findings demonstrate a non-coding function of HBV transcripts to support its propagation in non-cycling cells.

Single cell Raman spectroscopy to identify different stages of proliferating human hepatocytes for cell therapy

Background Cell therapy provides hope for treatment of advanced liver failure. Proliferating human hepatocytes (ProliHHs) were derived from primary human hepatocytes (PHH) and as potential alternative for cell therapy in liver diseases. Due to the continuous decline of mature hepatic genes and increase of progenitor like genes during ProliHHs expanding, it is challenge to monitor the critical changes of the whole process. Raman microspectroscopy is a noninvasive, label free analytical technique with high sensitivity capacity. In this study, we evaluated the potential and feasibility to identify ProliHHs from PHH with Raman spectroscopy. Methods Raman spectra were collected at least 600 single spectrum for PHH and ProliHHs at different stages (Passage 1 to Passage 4). Linear discriminant analysis and a two-layer machine learning model were used to analyze the Raman spectroscopy data. Significant differences in Raman bands were validated by the associated conventional kits. Results Linear discriminant analysis successfully classified ProliHHs at different stages and PHH. A two-layer machine learning model was established and the overall accuracy was at 84.6%. Significant differences in Raman bands have been found within different ProliHHs cell groups, especially changes at 1003 cm−1, 1206 cm−1 and 1440 cm−1. These changes were linked with reactive oxygen species, hydroxyproline and triglyceride levels in ProliHHs, and the hypothesis were consistent with the corresponding assay results. Conclusions In brief, Raman spectroscopy was successfully employed to identify different stages of ProliHHs during dedifferentiation process. The approach can simultaneously trace multiple changes of cellular components from somatic cells to progenitor cells.

Human hepatocyte-derived extracellular vesicles attenuate the carbon tetrachloride-induced acute liver injury in mice

Acute liver injury (ALI) induced by chemicals or viruses can progress rapidly to acute liver failure (ALF), often resulting in death of patients without liver transplantation. Since liver transplantation is limited due to a paucity of donors, expensive surgical costs, and severe immune rejection, novel therapies are required to treat liver injury. Extracellular vesicles (EVs) are used for cellular communication, carrying RNAs, proteins, and lipids and delivering them intercellularly after being endocytosed by target cells. Recently, it was reported that EVs secreted from human hepatocytes have an ability to modulate the immune responses; however, these roles of EVs secreted from human hepatocytes were studied only with in vitro experiments. In the present study, we evidenced that EVs secreted from human hepatocytes attenuated the CCL4-induced ALI by inhibiting the recruitment of monocytes through downregulation of chemokine receptor in the bone marrow and recruitment of neutrophils through the reduction of C-X-C motif chemokine ligand 1 (CXCL1) and CXCL2 expression levels in the liver.