Alcohol facilitates HCV RNA replication via up-regulation of miR-122 expression and inhibition of cyclin G1 in human hepatoma cells

MicroRNAs in metabolic dysfunction-associated diseases: Pathogenesis and therapeutic opportunities

Metabolic dysfunction-associated diseases often refer to various diseases caused by metabolic problems such as glucose and lipid metabolism disorders. With the improvement of living standards, the increasing prevalence of metabolic diseases has become a severe public health problem, including metabolic dysfunction-associated steatotic liver disease (MASLD), alcohol-related liver disease (ALD), diabetes and obesity. These diseases are both independent and interdependent, with complex and diverse molecular mechanisms. Therefore, it is urgent to explore the molecular mechanisms and find effective therapeutic targets of these diseases. MicroRNAs (miRNAs) have emerged as key regulators of metabolic homoeostasis due to their multitargets and network regulatory properties within the past few decades. In this review, we discussed the latest progress in the roles of miRNA-mediated regulatory networks in the development and progression of MASLD, ALD, diabetes and obesity.

Molecular Targets and Signaling Pathways of microRNA-122 in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the leading global causes of cancer mortality. MicroRNAs (miRNAs) are small interfering RNAs that alleviate the levels of protein expression by suppressing translation, inducing mRNA cleavage, and promoting mRNA degradation. miR-122 is the most abundant miRNA in the liver and is responsible for several liver-specific functions, including metabolism, cellular growth and differentiation, and hepatitis virus replication. Recent studies have shown that aberrant regulation of miR-122 is a key factor contributing to the development of HCC. In this review, the signaling pathways and the molecular targets of miR-122 involved in the progression of HCC have been summarized, and the importance of miR-122 in therapy has been discussed.

Prenatal and adolescent alcohol exposure programs immunity across the lifespan: CNS-mediated regulation

For many individuals, first exposure to alcohol occurs either prenatally due to maternal drinking, or during adolescence, when alcohol consumption is most likely to be initiated. Prenatal Alcohol Exposure (PAE) and its associated Fetal Alcohol Spectrum Disorders (FASD) in humans is associated with earlier initiation of alcohol use and increased rates of Alcohol Use Disorders (AUD). Initiation of alcohol use and misuse in early adolescence correlates highly with later AUD diagnosis as well. Thus, PAE and adolescent binge drinking set the stage for long-term health consequences due to adverse effects of alcohol on subsequent immune function, effects that may persist across the lifespan. The overarching goal of this review, therefore, is to determine the extent to which early developmental exposure to alcohol produces long-lasting, and potentially life-long, changes in immunological function. Alcohol affects the whole body, yet most studies are narrowly focused on individual features of immune function, largely ignoring the systems-level interactions required for effective host defense. We therefore emphasize the crucial role of the Central Nervous System (CNS) in orchestrating host defense processes. We argue that alcohol-mediated disruption of host immunity can occur through both (a) direct action of ethanol on neuroimmune processes, that subsequently disrupt peripheral immune function (top down); and (b) indirect action of ethanol on peripheral immune organs/cells, which in turn elicit consequent changes in CNS neuroimmune function (bottom up). Recognizing that alcohol consumption across the entire body, we argue in favor of integrative, whole-organism approaches toward understanding alcohol effects on immune function, and highlight the need for more work specifically examining long-lasting effects of early developmental exposure to alcohol (prenatal and adolescent periods) on host immunity.

Drugs of Abuse and Their Impact on Viral Pathogenesis

Commonly misused substances such as alcohol, cocaine, heroin, methamphetamine, and opioids suppress immune responses and may impact viral pathogenesis. In recent years, illicit use of opioids has fueled outbreaks of several viral pathogens, including the human immunodeficiency virus (HIV), hepatitis B virus (HBV), and hepatitis C virus (HCV). This review focuses on the myriad of mechanisms by which drugs of abuse impact viral replication and disease progression. Virus–drug interactions can accelerate viral disease progression and lead to increased risk of virus transmission.

Silencing the Expression of Cyclin G1 Enhances the Radiosensitivity of Hepatocellular Carcinoma In Vitro and In Vivo by Inducing Apoptosis

Radiotherapy plays an important role in the treatment of hepatocellular carcinoma (HCC). Cyclin G1 is a novel member of the cyclin family, and it is abnormally expressed in HCC. In this study we investigated the role of cyclin G1 in the radiotherapy of HCC cells. The expression of cyclin G1 was silenced by transfection of cyclin G1-siRNA into HepG2 cells and Huh7 cells, and the expression of cyclin G1 mRNA and protein was measured by qRT-PCR and Western blot analysis. The proliferation was analyzed using MTT assay, and the radiosensitivity of HCC cells was detected using colony formation assay and a xenograft tumor model. The expression of apoptosis-related proteins (Bcl-2 and Bax) was detected by Western blot analysis, and caspase-3 was detected using fluorimetry. The expression of cyclin G1 mRNA and protein in HepG2/Huh7-cyclin G1-siRNA cells was found to be significantly decreased compared to that in HepG2/Huh7 cells. Silencing the expression of cyclin G1 inhibited the proliferation of HCC cells and enhanced radiosensitivity in HCC cells in vitro and in vivo. Knockdown of cyclin G1 expression significantly decreased Bcl-2 expression, and increased Bax expression and caspase-3 activity in HCC cells. Silencing of cyclin G1 expression enhances the radiosensitivity of HCC cells in vitro and in vivo. The mechanism for this may be related to the regulation of apoptosis-related proteins.

Impact of hepatitis C virus and alcohol, alone and combined, on the unfolded protein response in primary human hepatocytes

Hepatitis C virus (HCV) infection and alcohol abuse are leading causes of chronic liver disease and frequently coexist in patients. The unfolded protein response (UPR), a cellular stress response ranging along a spectrum from cytoprotection to apoptosis commitment, has emerged as a major contributor to human diseases including liver injuries. However, the literature contains conflicting reports as to whether HCV and ethanol activate the UPR and which UPR genes are involved. Here we have used primary human hepatocytes (PHH) to reassess this issue and address combined impacts. In this physiologically relevant model, either stressor activated a chronic complete UPR. However, the levels of UPR gene induction were only modest in the case of HCV infection. Moreover, when combined to the strong stressor thapsigargin, ethanol exacerbated the activation of pro-apoptotic genes whereas HCV tended to limit the induction of key UPR genes. The UPR resulting from HCV plus ethanol was comparable to that induced by ethanol alone with the notable exception of three pro-survival genes the expressions of which were selectively enhanced by HCV. Interestingly, HCV genome replication was maintained at similar levels in PHH exposed to ethanol. In conclusion, while both HCV and alcohol activate the hepatocellular UPR, only HCV manipulates UPR signalling in the direction of a cytoprotective response, which appears as a viral strategy to spare its own replication.

miR-122, small RNA annealing and sequence mutations alter the predicted structure of the Hepatitis C virus 5' UTR RNA to stabilize and promote viral RNA accumulation

Annealing of the liver-specific microRNA, miR-122, to the Hepatitis C virus (HCV) 5′ UTR is required for efficient virus replication. By using siRNAs to pressure escape mutations, 30 replication-competent HCV genomes having nucleotide changes in the conserved 5′ untranslated region (UTR) were identified. In silico analysis predicted that miR-122 annealing induces canonical HCV genomic 5′ UTR RNA folding, and mutant 5′ UTR sequences that promoted miR-122-independent HCV replication favored the formation of the canonical RNA structure, even in the absence of miR-122. Additionally, some mutant viruses adapted to use the siRNA as a miR-122-mimic. We further demonstrate that small RNAs that anneal with perfect complementarity to the 5′ UTR stabilize and promote HCV genome accumulation. Thus, HCV genome stabilization and life-cycle promotion does not require the specific annealing pattern demonstrated for miR-122 nor 5′ end annealing or 3′ overhanging nucleotides. Replication promotion by perfect-match siRNAs was observed in Ago2 knockout cells revealing that other Ago isoforms can support HCV replication. At last, we present a model for miR-122 promotion of the HCV life cycle in which miRNA annealing to the 5′ UTR, in conjunction with any Ago isoform, modifies the 5′ UTR structure to stabilize the viral genome and promote HCV RNA accumulation.

miRNA Signature in NAFLD: A Turning Point for a Non-Invasive Diagnosis

Nonalcoholic fatty liver disease (NAFLD) defines a wide pathological spectrum ranging from simple steatosis to nonalcoholic steatohepatitis (NASH) which may predispose to liver cirrhosis and hepatocellular carcinoma. It represents the leading cause of hepatic damage worldwide. Diagnosis of NASH still requires liver biopsy but due to the high prevalence of NAFLD, this procedure, which is invasive, is not practicable for mass screening. Thus, it is crucial to non-invasively identify NAFLD patients at higher risk of progression to NASH and fibrosis. It has been demonstrated that hepatic fat content and progressive liver damage have a strong heritable component. Therefore, genetic variants associated with NAFLD have been proposed as non-invasive markers to be used in clinical practice. However, genetic variability is not completely explained by these common variants and it is possible that many of the phenotypic differences result from gene-environment interactions. Indeed, NAFLD development and progression is also modulated by epigenetic factors, in particular microRNAs (miRNAs), which control at post-transcriptional level many complementary target mRNAs and whose dysregulation has been shown to have high prognostic and predictive value in NAFLD. The premise of the current review is to discuss the role of miRNAs as pathogenic factors, risk predictors and therapeutic targets in NAFLD.

Alcoholic liver fibrosis: detection and treatment

Alcohol consumption is one of the main risks to public health. Alcohol use disorders (AUDs) cause 80% of hepatotoxic deaths, and approximately 50% of cirrhosis is alcohol-related. The acceptable daily intake (ADI) for ethanol is 2.6 g/day, deduced from morbidity and mortality rates due to liver fibrosis. The relative risk of cirrhosis increases significantly for doses above 60 g/day for men and 20 g/day for women over a period of around 10 years. Twenty to 40% of steatosis cases will evolve into steatohepatitis/steatofibrosis, and 8 to 20% will evolve directly into liver cirrhosis. About 20 to 40% of steatohepatitis cases will evolve into cirrhosis, and 4 to 5% into hepatocellular carcinoma. This cascade of events evolves in 5 to 40 years, with the temporal variability caused by the subjects' genetic patterns and associated risk/comorbidity factors. Steatohepatitis should be considered "the rate limiting step:" usually, it can be resolved through abstinence, although for some patients, once this situation develops, it is not substantially modified by abstention and there is a risk of fibrotic evolution. Early detection of fibrosis, obtained by hepatic elastography, is a crucial step in patients with AUDs. Such strategy allows patients to be included in a detoxification program in order to achieve abstention. Drugs such as silybin, metadoxine, and adenosylmethionine can be used. Other drugs, with promising antifibrotic effects, are currently under study. In this review, we discuss clinical and pathogenetic aspects of alcohol-related liver fibrosis and present and future strategies to prevent cirrhosis.

A General Overview on Non-coding RNA-Based Diagnostic and Therapeutic Approaches for Liver Diseases

Liver diseases contribute to the global mortality and morbidity and still represent a major health problem leading to the death of people worldwide. Although there are several treatment options available for Hepatitis C infections, for most liver disease the pharmacological options are still limited. Therefore, the development of new targets against liver diseases is of high interest. Non-coding RNA (ncRNA) such as microRNA (miRNA) or long ncRNA (lncRNA) have been shown to be deeply involved in the pathophysiology of almost all acute and chronic liver diseases. The emerging evidence showed the potential therapeutic use of miRNA associated with different steps of hepatic pathophysiology. In the present review, we summarize emerging insights of ncRNA in liver diseases. We also highlight example of ncRNAs participating in the pathogenesis of different forms of liver disease and how they can be used as potential therapeutic targets for novel treatment paradigms. Furthermore, we describe an overview of up-to-date clinical trials and discuss about its future in clinical applications. Finally, we highlight the role of circulating ncRNAs in diagnosis of liver diseases and discuss the challenges and drawbacks of the usage of ncRNAs in clinical setting.

Regulation of insulin resistance and type II diabetes by hepatitis C virus infection: A driver function of circulating miRNAs

Hepatitis C virus (HCV) infection is a serious worldwide healthcare issue. Its association with various liver diseases including hepatocellular carcinoma (HCC) is well studied. However, the study on the relationship between HCV infection and the development of insulin resistance and diabetes is very limited. Current research has already elucidated some underlying mechanisms, especially on the regulation of metabolism and insulin signalling by viral proteins. More studies have emerged recently on the correlation between HCV infection‐derived miRNAs and diabetes and insulin resistance. However, no studies have been carried out to directly address if these miRNAs, especially circulating miRNAs, have causal effects on the development of insulin resistance and diabetes. Here, we proposed a new perspective that circulating miRNAs can perform regulatory functions to modulate gene expression in peripheral tissues leading to insulin resistance and diabetes, rather than just a passive factor associated with these pathological processes. The detailed rationales were elaborated through comprehensive literature review and bioinformatic analyses. miR‐122 was identified to be one of the most potential circulating miRNAs to cause insulin resistance. This result along with the idea about the driver function of circulating miRNAs will promote further investigations that eventually lead to the development of novel strategies to treat HCV infection‐associated extrahepatic comorbidities.

MicroRNA 122, Regulated by GRLH2, Protects Livers of Mice and Patients From Ethanol-Induced Liver Disease

BACKGROUND & AIMS

Chronic, excessive alcohol consumption leads to alcoholic liver disease (ALD) characterized by steatosis, inflammation, and eventually cirrhosis. The hepatocyte specific microRNA 122 (MIR122) regulates hepatocyte differentiation and metabolism. We investigated whether an alcohol-induced decrease in level of MIR122 contributes to development of ALD.

METHODS

We obtained liver samples from 12 patients with ALD and cirrhosis and 9 healthy individuals (controls) and analyzed them by histology and immunohistochemistry. C57Bl/6 mice were placed on a Lieber-DeCarli liquid diet, in which they were fed ethanol for 8 weeks, as a model of ALD, or a control diet. These mice were also given injections of CCl4, to increase liver fibrosis, for 8 weeks. On day 28, mice with ethanol-induced liver disease and advanced fibrosis, and controls, were given injections of recombinant adeno-associated virus 8 vector that expressed the primary miR-122 transcript (pri-MIR122, to overexpress MIR122 in hepatocytes) or vector (control). Two weeks before ethanol feeding, some mice were given injections of a vector that expressed an anti-MIR122, to knock down its expression. Serum and liver tissues were collected; hepatocytes and liver mononuclear cells were analyzed by histology, immunoblots, and confocal microscopy. We performed in silico analyses to identify targets of MIR122 and chromatin immunoprecipitation quantitative polymerase chain reaction analyses in Huh-7 cells.

RESULTS

Levels of MIR122 were decreased in liver samples from patients with ALD and mice on the Lieber-DeCarli diet, compared with controls. Transgenic expression of MIR122 in hepatocytes of mice with ethanol-induced liver disease and advanced fibrosis significantly reduced serum levels of alanine aminotransferase (ALT) and liver steatosis and fibrosis, compared with mice given injections of the control vector. Ethanol feeding reduced expression of pri-MIR122 by increasing expression of the spliced form of the transcription factor grainyhead like transcription factor 2 (GRHL2) in liver tissues from mice. Levels of GRHL2 also were increased in liver tissues from patients with ALD, compared with controls; increases correlated with decreases in levels of MIR122 in human liver. Mice given injections of the anti-MIR122 before ethanol feeding had increased steatosis, inflammation, and serum levels of alanine aminotransferase compared with mice given a control vector. Levels of hypoxia-inducible factor 1 alpha (HIF1α) mRNA, a target of MIR122, were increased in liver tissues from patients and mice with ALD, compared with controls. Mice with hepatocyte-specific disruption of Hif1α developed less-severe liver injury following administration of ethanol, injection of anti-MIR122, or both.

CONCLUSIONS

Levels of MIR122 decrease in livers from patients with ALD and mice with ethanol-induced liver disease, compared with controls. Transcription of MIR122 is inhibited by GRHL2, which is increased in livers of mice and patients with ALD. Expression of an anti-MIR122 worsened the severity of liver damage following ethanol feeding in mice. MIR122 appears to protect the liver from ethanol-induced damage by reducing levels of HIF1α. These processes might be manipulated to reduce the severity of ALD in patients.

Noncoding RNA Profiles in Tobacco- and Alcohol-Associated Diseases

Tobacco and alcohol are the leading environmental risk factors in the development of human diseases, such as cancer, cardiovascular disease, and liver injury. Despite the copious amount of research on this topic, by 2030, 8.3 million deaths are projected to occur worldwide due to tobacco use. The expression of noncoding RNAs, primarily microRNAs (miRNAs) and long noncoding RNAs (lncRNAs), is modulated by tobacco and alcohol consumption. Drinking alcohol and smoking cigarettes can modulate the expression of miRNAs and lncRNAs through various signaling pathways, such as apoptosis, angiogenesis, and inflammatory pathways—primarily interleukin 6 (IL-6)/signal transducer and activator of transcription 3 (STAT3), which seems to play a major role in the development of diseases associated with these risk factors. Since they may be predictive and prognostic biomarkers, they can be used both as predictors of the response to therapy and as a targeted therapy. Further, circulating miRNAs might be valuable noninvasive tools that can be used to examine diseases that are related to the use of tobacco and alcohol. This review discusses the function of noncoding RNAs in cancer and other human tobacco- and alcohol-associated diseases.

Comprehensive phenotypic analysis of knockout mice deficient in cyclin G1 and cyclin G2

Cyclin G1 (CycG1) and Cyclin G2 (CycG2) play similar roles during the DNA damage response (DDR), but their detailed roles remain elusive. To investigate their distinct roles, we generated knockout mice deficient in CycG1 (G1KO) or CycG2 (G2KO), as well as double knockout mice (DKO) deficient in both proteins. All knockouts developed normally and were fertile. Generation of mouse embryonic fibroblasts (MEFs) from these mice revealed that G2KO MEFs, but not G1KO or DKO MEFs, were resistant to DNA damage insults caused by camptothecin and ionizing radiation (IR) and underwent cell cycle arrest. CycG2, but not CycG1, co-localized with γH2AX foci in the nucleus after γ-IR, and γH2AX-mediated DNA repair and dephosphorylation of CHK2 were delayed in G2KO MEFs. H2AX associated with CycG1, CycG2, and protein phosphatase 2A (PP2A), suggesting that γH2AX affects the function of PP2A via direct interaction with its B'γ subunit. Furthermore, expression of CycG2, but not CycG1, was abnormal in various cancer cell lines. Kaplan-Meier curves based on TCGA data disclosed that head and neck cancer patients with reduced CycG2 expression have poorer clinical prognoses. Taken together, our data suggest that reduced CycG2 expression could be useful as a novel prognostic marker of cancer.

The Effects of Alcohol on Other Chronic Liver Diseases

Alcohol consumption is often a comorbid condition in other chronic liver diseases. It has been shown to act in synergy to increase liver injury in viral hepatitis, hereditary hemochromatosis, and nonalcoholic fatty liver disease (NAFLD), leading to an increased risk of cirrhosis, hepatocellular carcinoma, and liver-related mortality. Data suggest that modest alcohol consumption may be inversely related to the risk of developing NAFLD and lower rates of progression of NAFLD to nonalcoholic steatohepatitis (NASH). This article reviews data on the relationship between alcohol consumption and other chronic liver diseases.

Role of apoptotic hepatocytes in HCV dissemination: regulation by acetaldehyde

Alcohol consumption exacerbates hepatitis C virus (HCV) pathogenesis and promotes disease progression, although the mechanisms are not quite clear. We have previously observed that acetaldehyde (Ach) continuously produced by the acetaldehyde-generating system (AGS), temporarily enhanced HCV RNA levels, followed by a decrease to normal or lower levels, which corresponded to apoptosis induction. Here, we studied whether Ach-induced apoptosis caused depletion of HCV-infected cells and what role apoptotic bodies (AB) play in HCV-alcohol crosstalk. In liver cells exposed to AGS, we observed the induction of miR-122 and miR-34a. As miR-34a has been associated with apoptotic signaling and miR-122 with HCV replication, these findings may suggest that cells with intensive viral replication undergo apoptosis. Furthermore, when AGS-induced apoptosis was blocked by a pan-caspase inhibitor, the expression of HCV RNA was not changed. AB from HCV-infected cells contained HCV core protein and the assembled HCV particle that infect intact hepatocytes, thereby promoting the spread of infection. In addition, AB are captured by macrophages to switch their cytokine profile to the proinflammatory one. Macrophages exposed to HCV(+) AB expressed more IL-1β, IL-18, IL-6, and IL-10 mRNAs compared with those exposed to HCV(-) AB. The generation of AB from AGS-treated HCV-infected cells even enhanced the induction of aforementioned cytokines. We conclude that HCV and alcohol metabolites trigger the formation of AB containing HCV particles. The consequent spread of HCV to neighboring hepatocytes via infected AB, as well as the induction of liver inflammation by AB-mediated macrophage activation potentially exacerbate the HCV infection course by alcohol and worsen disease progression.

Direct Peritoneal Resuscitation Alters Hepatic miRNA Expression after Hemorrhagic Shock

BACKGROUND

MicroRNAs (miRNAs) are small segments of noncoding RNA that regulate gene expression and protein function, and therefore are key regulators of cellular processes including those of the inflammatory cascade after hemorrhagic shock (HS). We have previously shown that direct peritoneal resuscitation (DPR), as an adjunct to traditional IV fluid resuscitation, improves visceral blood flow and reduces pro-inflammatory cytokines released during HS. The effects of DPR on hepatic miRNA (miR) expression patterns after resuscitated HS are not known.

STUDY DESIGN

Male Sprague-Dawley rats were divided into 3 groups: sham (no HS); conventional resuscitation (CR; HS, then resuscitated with shed blood and 2 volumes of saline); and DPR (CR plus 30 mL peritoneal dialysis solution). Animals were sacrificed at 4 hours, and miRNAs were measured using reverse transcription polymerase chain reaction.

RESULTS

Use of DPR downregulated 68 of 92 hepatic miRNAs compared with only 2 of 92 upregulated when compared with CR alone, p < 0.01). Specifically, miR-9-5p, miR-122-5p, and miR-146, which regulate NFκB, were downregulated 4.1-, 3.4-, and 0.86-fold, respectively; miR-29a and miR-126 were upregulated 0.88- and 3.7-fold when DPR was compared with CR.

CONCLUSIONS

Adding DPR downregulated most hepatic miRNAs compared with CR alone. Some miRNAs were affected more significantly, suggesting that although this clinical intervention causes a near-global downregulation of hepatic miRNA, it still targets specific inflammatory pathways. Use of DPR for resuscitation of patients in HS may reduce hepatic inflammation to improve patient outcomes after hemorrhage.

Alcoholic liver disease and hepatitis C virus infection

Alcohol consumption and hepatitis C virus (HCV) infection have a synergic hepatotoxic effect, and the coexistence of these factors increases the risk of advanced liver disease. The main mechanisms of this effect are increased viral replication and altered immune response, although genetic predisposition may also play an important role. Traditionally, HCV prevalence has been considered to be higher (up to 50%) in alcoholic patients than in the general population. However, the presence of advanced alcoholic liver disease (ALD) or intravenous drug use (IDU) may have confounded the results of previous studies, and the real prevalence of HCV infection in alcoholic patients without ALD or prior IDU has been shown to be lower. Due to the toxic combined effect of HCV and alcohol, patients with HCV infection should be screened for excessive ethanol intake. Patients starting treatment for HCV infection should be specifically advised to stop or reduce alcohol consumption because of its potential impact on treatment efficacy and adherence and may benefit from additional support during antiviral therapy. This recommendation might be extended to all currently recommended drugs for HCV treatment. Patients with alcohol dependence and HCV infection, can be treated with acamprosate, nalmefene, topiramate, and disulfiram, although baclofen is the only drug specifically tested for this purpose in patients with ALD and/or HCV infection.

Alcoholic liver disease and hepatitis C virus infection

Alcohol consumption and hepatitis C virus (HCV) infection have a synergic hepatotoxic effect, and the coexistence of these factors increases the risk of advanced liver disease. The main mechanisms of this effect are increased viral replication and altered immune response, although genetic predisposition may also play an important role. Traditionally, HCV prevalence has been considered to be higher (up to 50%) in alcoholic patients than in the general population. However, the presence of advanced alcoholic liver disease (ALD) or intravenous drug use (IDU) may have confounded the results of previous studies, and the real prevalence of HCV infection in alcoholic patients without ALD or prior IDU has been shown to be lower. Due to the toxic combined effect of HCV and alcohol, patients with HCV infection should be screened for excessive ethanol intake. Patients starting treatment for HCV infection should be specifically advised to stop or reduce alcohol consumption because of its potential impact on treatment efficacy and adherence and may benefit from additional support during antiviral therapy. This recommendation might be extended to all currently recommended drugs for HCV treatment. Patients with alcohol dependence and HCV infection, can be treated with acamprosate, nalmefene, topiramate, and disulfiram, although baclofen is the only drug specifically tested for this purpose in patients with ALD and/or HCV infection.

MicroRNAs Expressed during Viral Infection: Biomarker Potential and Therapeutic Considerations

MicroRNAs (miRNAs) are short sequences of noncoding single-stranded RNAs that exhibit inhibitory effects on complementary target mRNAs. Recently, it has been discovered that certain viruses express their own miRNAs, while other viruses activate the transcription of cellular miRNAs for their own benefit. This review summarizes the viral and/or cellular miRNAs that are transcribed during infection, with a focus on the biomarker and therapeutic potential of miRNAs (or their antagomirs). Several human viruses of clinical importance are discussed, namely, herpesviruses, polyomaviruses, hepatitis B virus, hepatitis C virus, human papillomavirus, and human immunodeficiency virus.

Hepatitis C Virus-Induced Monocyte Differentiation Into Polarized M2 Macrophages Promotes Stellate Cell Activation via TGF-β

BACKGROUND & AIMS

Monocyte and macrophage (MΦ) activation contributes to the pathogenesis of chronic hepatitis C virus (HCV) infection. Disease pathogenesis is regulated by both liver-resident MΦs and monocytes recruited as precursors of MΦs into the damaged liver. Monocytes differentiate into M1 (classic/proinflammatory) or M2 (alternative/anti-inflammatory) polarized MΦs in response to tissue microenvironment. We hypothesized that HCV-infected hepatoma cells (infected with Japanese fulminant hepatitis-1 [Huh7.5/JFH-1]) induce monocyte differentiation into polarized MΦs.

METHODS

Healthy human monocytes were co-cultured with Huh7.5/JFH-1 cells or cell-free virus for 7 days and analyzed for MΦ markers and cytokine levels. A similar analysis was performed on circulating monocytes and liver MΦs from HCV-infected patients and controls.

RESULTS

Huh7.5/JFH-1 cells induced monocytes to differentiate into MΦs with increased expression of CD14 and CD68. HCV-MΦs showed M2 surface markers (CD206, CD163, and Dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin (DC-SIGN)) and produced both proinflammatory and anti-inflammatory cytokines. HCV-induced early interleukin 1β production promoted transforming growth factor (TGF)β production and MΦ polarization to an M2 phenotype. TGF-β secreted by M2-MΦ led to hepatic stellate cell activation indicated by increased expression of collagen, tissue inhibitor of metalloproteinase 1, and α-smooth muscle actin. In vivo, we observed a significant increase in M2 marker (CD206) expression on circulating monocytes and in the liver of chronic HCV-infected patients. Furthermore, we observed the presence of a unique collagen-expressing CD14⁺CD206⁺ monocyte population in HCV patients that correlated with liver fibrosis.

CONCLUSIONS

We show an important role for HCV in induction of monocyte differentiation into MΦs with a mixed M1/M2 cytokine profile and M2 surface phenotype that promote stellate cell activation via TGF-β. We also identified circulating monocytes expressing M2 marker and collagen in chronic HCV infection that can be explored as a biomarker.

miR-122 plays an important role in ochratoxin A-induced hepatocyte apoptosis in vitro and in vivo

OTA can induce hepatotoxicity. Our previous research has shown that miRNAs play important roles in the OTA-induced hepatotoxicity. And miR-122 is the most abundant miRNA in the liver and is involved in diverse biological processes. This study was performed to clarify the role of miR-122 in OTA-induced hepatotoxicity. The expression levels of miR-122 and the target genes were quantified by real-time PCR. The OTA-induced apoptosis of hepatocyte and HepG2 cells was evaluated using a TUNEL kit, a CCK-8 kit, a flow cytometer and Hoechst 33342. miR-122 was inhibited in HepG2 cells. The results revealed that OTA affected rat hepatocyte apoptosis. miR-122 decreased at 4 weeks but increased at 13 weeks in the OTA-treated livers, and increased in the OTA-treated HepG2 cells; and the mRNA levels of CCNG1 and Bcl-w increased at 4 weeks and decreased at 13 weeks in the high-dose OTA-treatment groups and decreased in HepG2 cells. The apoptosis of HepG2 cells displayed a dose-related increase with OTA. However, the inhibition of miR-122 greatly reduced OTA-induced apoptosis. p53 decreased in vivo and in vitro. miR-122 is a primary effector of OTA-induced hepatocyte apoptosis through the CCNG1/p53 pathway and Bcl-w/caspase-3 pathway in vivo and in vitro. And miR-122 plays an important role in OTA-induced hepatotoxicity.

In vivo inhibition of liver miR-122 expression by CRISPRi

AIM: To investigate whether CRISPRi can repress miR-122 expression in the mouse liver in vivo.

METHODS: sgRNAs (sgT1 and sgT2) were designed, targeting the region of mmu-miR-122 promoter. sgRNAs (sgT1 or sgT2) and catalytically inactive dCas9-KRAB were delivered into 8-10-week-old mice by hydrodynamic tail-vein injection. The expression of mmu-miR-122 was detected at 1, 2 and 4 weeks after injection by quantitative real-time PCR (qRT-PCR) to determine the more effective sgRNA. Different concentrations of sgRNA were tested in order to address whether CRISPRi was concentration dependent in vivo. The expression of miR-122 downstream target genes HOMX1 and CyclinG1 was assessed by qRT-PCR and Western blot.

RESULTS: Compared to the control group, CRISPRi mediated by sgT1 could repress miR-122 expression by 23% (P < 0.05) and 16% (P < 0.05) in the mouse liver at 1 and 2 weeks after injection, respectively. The effect of CRISPRi was enhanced with increased concentrations of sgRNA. After mmu-miR-122 expression in the mouse liver was inhibited by CRISPRi in vivo, the expression of miR-122 downstream target genes HMOX1 and CyclinG1 was upregulated.

CONCLUSION: CRISPRi can specially repress miR-122 expression in the liver in vivo, which provides a novel therapeutic strategy against hepatitis C virus (HCV) infections.

Alcoholic hepatitis and HCV interactions in the modulation of liver disease

Most HCV-infected patients regularly consume alcohol. Alcoholic liver disease (ALD) and chronic hepatitis C virus (HCV) infection together are the most common causes of liver disease worldwide. Although both factors independently cause liver disease, they synergistically promote rapid liver disease progression with devastating outcomes for patients. This review focuses on the prevalence, clinical characteristics and molecular pathophysiologic mechanisms of HCV infection associated with alcohol abuse. Recent findings have centred on the synergistic effect of alcohol and HCV on viral replication, hepatocyte apoptosis, oxidative stress, alcohol-induced 'leaky gut', miR-122 and immune dysregulation. Clinical and basic research findings presented here summarize key scientific findings with the aim of highlighting potential areas for new therapies and identifying ways of optimizing current treatments for alcoholics with HCV infection.

Regulation of expression of HCV replication associated miR-122 by CRISPR interference

AIM: To investigate whether clustered regularly interspaced short palindromic repeat (CRISPR) interference (CRISPRi) specifically represses endogenous miR-122 expression in HepG2 cells.

METHODS: Single-guide RNAs (sgRNAs; sgT1 and sgT2) targeting transcription start site (TSS) and TATA box in the region of miR-122 promoter were designed. After co-transfecting HepG2 cells with sgRNA and catalytically inactive dCas9-KRAB, the expression of miR-122 was determined by quantitative Real-time PCR (qRT-PCR) to determine the more effective sgRNA. Different concentrations of sgRNA were tested in order to address whether CRISPRi was concentration dependent. The expression of miR-122 downstream target genes HOMX1 and CyclinG1 was assessed by qRT-PCR and Western blot.

RESULTS: Compared to the control group, CRISPRi mediated by sgT1 and sgT2 could repress endogenous miR-122 expression by 5.5-fold (P < 0.01) and 3.7-fold (P < 0.01) in HepG2 cells, respectively. The effect of CRISPRi was enhanced with increased concentration of sgRNA, and the miR-122 expression was inhibited by 10.0-fold (P < 0.01) when the amount of lentiGuide-Puro-sgT1 was 500 ng. After endogenous miR-122 expression was inhibited by CRISPRi, the expression of miR-122 downstream target genes HMOX1 and CyclinG1 was upregulated.

CONCLUSION: CRISPRi can specifically repress endogenous miR-122 expression, which provides a novel therapeutic strategy against hepatitis C virus infection.

Revisiting Chaos Theorem to Understand the Nature of miRNAs in Response to Drugs of Abuse

Just like Matryoshka dolls, biological systems follow a hierarchical order that is based on dynamic bidirectional communication among its components. In addition to the convoluted inter-relationships, the complexity of each component spans several folds. Therefore, it becomes rather challenging to investigate phenotypes resulting from these networks as it requires the integration of reductionistic and holistic approaches. One dynamic system is the transcriptome which comprises a variety of RNA species. Some, like microRNAs, have recently received a lot of attention. miRNAs are very pleiotropic and have been considered as therapeutic and diagnostic candidates in the biomedical fields. In this review, we survey miRNA profiles in response to drugs of abuse (DA) using 118 studies. After providing a summary of miRNAs related to substance use disorders (SUD), general patterns of miRNA signatures are compared among studies for single or multiple drugs of abuse. Then, current challenges and drawbacks in the field are discussed. Finally, we provide support for considering miRNAs as a chaotic system in normal versus disrupted states particularly in SUD and propose an integrative approach for studying and analyzing miRNA data.

MicroRNAs: Role in Hepatitis C Virus pathogenesis

Hepatitis C virus (HCV) is a global health burden with an estimated 170-200 million peoples chronically infected worldwide. HCV infection remains as an independent risk factor for chronic hepatitis, liver cirrhosis, hepatocellular carcinoma, and a major reason for liver transplantation. Discovery of direct acting antiviral (DAA) drugs have shown promising results with more than 90% success rate in clearing the HCV RNA in patients, although long-term consequences remain to be evaluated. microRNAs (miRNAs) are important players in establishment of HCV infection and target crucial host cellular factors needed for productive HCV replication and augmented cell growth. Altered expression of miRNAs is involved in the pathogenesis associated with HCV infection by controlling signaling pathways such as immune response, proliferation and apoptosis. miRNA is emerging as a means of communication between various cell types inside the liver. There is likely possibility of developing circulating miRNAs as biomarkers of disease progression and can also serve as diagnostic tool with potential of early therapeutic intervention in HCV associated end stage liver disease. This review focuses on recent studies highlighting the contribution of miRNAs in HCV life cycle and their coordinated regulation in HCV mediated liver disease progression.

The effects of multifunctional MiR-122-loaded graphene-gold composites on drug-resistant liver cancer

Background

Nano drugs have attracted increased attention due to their unique mode of action that offers tumor-inhibiting effects. Therefore, we have previously explored functionalized and drug-loaded graphene-gold nanocomposites that induced cancer cell apoptosis.

Results

In the present study, we developed a combination of monoclonal P-glycoprotein (P-gp) antibodies, folic acid (FA) and miR-122-loaded gold nanoparticles on graphene nanocomposites (GGMPN), which promoted drug-resistant HepG2 cell apoptosis with drug targeting and controlled release properties. We also investigated related apoptosis proteins and apoptosis signal pathways by GGMPN treatment in vitro and in vivo. Moreover, we further demonstrated the inhibition of tumor growth and the apoptosis-inducing effect by means of GGMPN with a semiconductor laser in a xenograft tumor model.

Conclusion

In conclusion, our results collectively suggested that GGMPN could serve as a novel therapeutic approach to control tumor cell apoptosis and growth.

Hepatitis C, innate immunity and alcohol: friends or foes?

Hepatitis C and alcohol are the most widespread causes of liver disease worldwide. Approximately 80% of patients with a history of hepatitis C and alcohol abuse develop chronic liver injury. Alcohol consumption in hepatitis C virus (HCV)-infected patients exacerbates liver disease leading to rapid progression of fibrosis, cirrhosis and even hepatocellular carcinoma. Hepatocytes are the main sites of HCV-infection and ethanol metabolism, both of which generate oxidative stress. Oxidative stress levels affect HCV replication and innate immunity, resulting in a greater susceptibility for HCV-infection and virus spread in the alcoholic patients. In this review paper, we analyze the effects of ethanol metabolism and other factors on HCV replication. In addition, we illustrate the mechanisms of how HCV hijacks innate immunity and how ethanol exposure regulates this process. We also clarify the effects of HCV and ethanol metabolism on interferon signaling-a crucial point for activation of anti-viral genes to protect cells from virus-and the role that HCV- and ethanol-induced impairments play in adaptive immunity which is necessary for recognition of virally-infected hepatocytes. In conclusion, ethanol exposure potentiates the suppressive effects of HCV on innate immunity, which activates viral spread in the liver and finally, leads to impairments in adaptive immunity. The dysregulation of immune response results in impaired elimination of HCV-infected cells, viral persistence, progressive liver damage and establishment of chronic infection that worsens the outcomes of chronic hepatitis C in alcoholic patients.

MicroRNAs in alcoholic liver disease

Alcoholic liver disease (ALD) is characterized by hepatocyte damage, inflammatory cell activation and increased intestinal permeability leading to the clinical manifestations of alcoholic hepatitis. Selected members of the family of microRNAs are affected by alcohol, resulting in an abnormal miRNA profile in the liver and circulation in ALD. Increasing evidence suggests that mRNAs that regulate inflammation, lipid metabolism and promote cancer are affected by excessive alcohol administration in mouse models of ALD. This communication highlights recent findings in miRNA expression and functions as they relate to the pathogenesis of ALD. The cell-specific distribution of miRNAs, as well as the significance of circulating extracellular miRNAs, is discussed as potential biomarkers. Finally, the prospects of miRNA-based therapies are evaluated in ALD.

miR-122--a key factor and therapeutic target in liver disease

Being the largest internal organ of the human body with the unique ability of self-regeneration, the liver is involved in a wide variety of vital functions that require highly orchestrated and controlled biochemical processes. Increasing evidence suggests that microRNAs (miRNAs) are essential for the regulation of liver development, regeneration and metabolic functions. Hence, alterations in intrahepatic miRNA networks have been associated with liver disease including hepatitis, steatosis, cirrhosis and hepatocellular carcinoma (HCC). miR-122 is the most frequent miRNA in the adult liver, and a central player in liver biology and disease. Furthermore, miR-122 has been shown to be an essential host factor for hepatitis C virus (HCV) infection and an antiviral target, complementary to the standard of care using direct-acting antivirals or interferon-based treatment. This review summarizes our current understanding of the key role of miR-122 in liver physiology and disease, highlighting its role in HCC and viral hepatitis. We also discuss the perspectives of miRNA-based therapeutic approaches for viral hepatitis and liver disease.

MicroRNAs in alcoholic liver disease

Alcoholic liver disease (ALD) is characterized by hepatocyte damage, inflammatory cell activation and increased intestinal permeability leading to the clinical manifestations of alcoholic hepatitis. Selected members of the family of microRNAs are affected by alcohol, resulting in an abnormal miRNA profile in the liver and circulation in ALD. Increasing evidence suggests that mRNAs that regulate inflammation, lipid metabolism and promote cancer are affected by excessive alcohol administration in mouse models of ALD. This communication highlights recent findings in miRNA expression and functions as they relate to the pathogenesis of ALD. The cell-specific distribution of miRNAs, as well as the significance of circulating extracellular miRNAs, is discussed as potential biomarkers. Finally, the prospects of miRNA-based therapies are evaluated in ALD.

Alcohol and HCV: implications for liver cancer

Liver cancers are one of the deadliest known malignancies which are increasingly becoming a major public health problem in both developed and developing countries. Overwhelming evidence suggests a strong role of infection with hepatitis B and C virus (HBV and HCV), alcohol abuse, as well as metabolic diseases such as obesity and diabetes either individually or synergistically to cause or exacerbate the development of liver cancers. Although numerous etiologic mechanisms for liver cancer development have been advanced and well characterized, the lack of definite curative treatments means that gaps in knowledge still exist in identifying key molecular mechanisms and pathways in the pathophysiology of liver cancers. Given the limited success with current therapies and preventive strategies against liver cancer, there is an urgent need to identify new therapeutic options for patients. Targeting HCV and or alcohol-induced signal transduction, or virus-host protein interactions may offer novel therapies for liver cancer. This review summarizes current knowledge on the mechanistic development of liver cancer associated with HCV infection and alcohol abuse as well as highlights potential novel therapeutic strategies.

Alcohol's Effect on Host Defense

Alcohol affects many organs, including the immune system, with even moderate amounts of alcohol influencing immune responses. Although alcohol can alter the actions of all cell populations involved in the innate and adaptive immune responses, the effect in many cases is a subclinical immunosuppression that becomes clinically relevant only after a secondary insult (e.g., bacterial or viral infection or other tissue damage). Alcohol's specific effects on the innate immune system depend on the pattern of alcohol exposure, with acute alcohol inhibiting and chronic alcohol accelerating inflammatory responses. The proinflammatory effects of chronic alcohol play a major role in the pathogenesis of alcoholic liver disease and pancreatitis, but also affect numerous other organs and tissues. In addition to promoting proinflammatory immune responses, alcohol also impairs anti-inflammatory cytokines. Chronic alcohol exposure also interferes with the normal functioning of all aspects of the adaptive immune response, including both cell-mediated and humoral responses. All of these effects enhance the susceptibility of chronic alcoholics to viral and bacterial infections and to sterile inflammation.

Regulation of gene expression by microRNA in HCV infection and HCV-mediated hepatocellular carcinoma

MicroRNA (miRNA) exert a profound effect on Hepatitis C virus (HCV) replication and on the manifestation of HCV-associated hepatocellular carcinoma (HCC). miR-122 in particular, is highly enriched in liver and has been shown to interact with HCV, suggesting this virus has evolved to subvert and manipulate the host gene silencing machinery in order to support its life cycle. It is therefore likely that miR-122 and other miRNAs play an important role in the pathophysiology of HCV infection. The changes in post-transcriptional gene regulation by the miRNAs may play a key role in the manifestation of chronic liver disease and hepatocellular carcinoma. Understanding of HCV-host miRNA interactions will ultimately lead to the design of therapeutic modalities against HCV infection and HCV-mediated HCC and may also provide important biomarkers that direct treatment options. Here, we review the current knowledge on the role of miRNA and gene expression on HCV infection and hepatocellular carcinoma, in addition to the possible role of miRNA as future therapeutic targets.

Roadmap of miR-122-related clinical application from bench to bedside

INTRODUCTION

microRNA (miRNA) regulates target gene expression to influence many physiological and pathophysiological processes. The liver-specific miRNA, miR-122, contributes to liver function and plays a very important role in hepatic diseases including the viral hepatitis C (HCV). For this reason, developing an miR-122-related clinical application could be very useful in managing or treating many hepatic disorders.

AREAS COVERED

This review introduces the basic concepts of miRNA and miR-122. It also discusses the possibility of miR-122 as a biomarker and summarizes the results of anti-miR-122 treatment from basic research to a Phase IIa clinical trial. Furthermore, the authors discuss the potential opportunities and challenges found in clinical trials with miravirsen.

EXPERT OPINION

miR-122 may be a useful biomarker as both a diagnostic and prognostic tool. Furthermore, miravirsen is a novel treatment with great potential for hepatic disease treatment, especially in HCV. However, there is certainly the need for future investigations to better determine whether miR-122 is really specific for liver. It is also important to elucidate whether miR-122 is actually specific for HCV genome and further investigate the therapeutic potential of miravirsen. Only once these studies have been completed can anti-miR-122 treatment potentially enter the clinical practice.

Hepatitis C virus infection, microRNA and liver disease progression

Hepatitis C virus (HCV) is a global health problem with an estimated 170-200 million peoples (approximately 3% of world population) are chronically infected worldwide and new infections are predicted to be on rise in coming years. HCV infection remains categorized as a major risk factor for chronic hepatitis, liver cirrhosis and hepatocellular carcinoma worldwide. There has been considerable improvement in our understanding of virus life cycle since, the discovery of HCV two-decades ago. MicroRNAs (miRNAs) are important players in establishment of HCV infection and their propagation in infected hepatocytes. They target crucial host cellular factors needed for productive HCV replication and augmented cell growth. Very first anti-miRNA oligonucleotides, miravirsen has been tested in clinical trial and shown promising results as therapeutic agent in treatment against chronic HCV infection. Deregulated expression of miRNAs has been linked to the pathogenesis associated with HCV infection by controlling signaling pathways such as, proliferation, apoptosis and migration. Circulating miRNAs emerging as growing field in identification of biomarkers in disease progression and their potential as a means of communication between cells inside the liver is an exciting area of research in future. This review focuses on recent studies enforcing the contribution of miRNAs in HCV life cycle and coordinated regulation in HCV mediated liver disease progression.

MicroRNAs in liver disease

Small, noncoding microRNAs (miRNAs) regulate diverse biological functions in the liver and increasing evidence suggests that they have a role in liver pathology. This Review summarizes advances in the field of miRNAs in liver diseases, inflammation and cirrhosis. MicroRNA-122, the most abundant miRNA in hepatocytes, has well-defined roles in HCV replication, and data indicate that it also serves as a viable therapeutic target. The role of miR-122 is also emerging in other liver diseases. Ample evidence exists for the important regulatory potential of other miRNAs in conditions associated with liver inflammation related to alcohol use, the metabolic syndrome or autoimmune processes. In addition, a broad array of miRNAs have been associated with the development of liver fibrosis both in animal models and human studies. The significance of the function and cellular distribution of miRNAs in the liver and the potential of miRNAs as a means of communication between cells and organs is discussed as well as the emerging utility of circulating miRNAs as biomarkers of different forms of liver damage and as early markers of disease and progression in hepatocellular carcinoma. Importantly, miRNA modulation in the liver represents a new therapeutic approach in the treatment armamentarium of hepatologists in the future.