Role of Cisplatin in Inducing Acute Kidney Injury and Pyroptosis in Mice via the Exosome miR-122/ELAVL1 Regulatory Axis

Although cisplatin is an effective chemotherapy drug for the treatment of various cancers, its clinical use is limited due to its side effects, especially nephrotoxicity. Unfortunately, acute kidney injury (AKI) caused by cisplatin remains one of the main challenges in effective cancer treatment. Evidence increasingly suggests that renal inflammation and pyroptotic inflammatory cell death of renal tubular epithelial cells (RTECs) mainly determine the progression and outcome of cisplatin-induced AKI. However, it is not clear how cisplatin regulates the pyroptosis of RTECs cells in AKI. The current study aimed to determine the regulation mechanism of AKI induced by cisplatin. We used cisplatin to induce AKI in vivo. We performed H&E staining of mouse kidney tissue sections and evaluated serological indicators of kidney injury (including blood urea nitrogen (BUN), serum creatinine, and tumor necrosis factor-alpha (TNF-alpha)). We used immunohistochemistry and western blot to detect the important substrate protein gasdermin D (GSDMD) and key target caspase-1 of pyroptosis, respectively. Cisplatin induced mouse AKI and RTECs pyroptosis. HK2 cell-derived exosomes treated with cisplatin influenced pyroptosis of the surrounding HK2 cells. Cisplatin-treated HK2 cells exosome-derived miR-122 regulated pyroptosis in the surrounding cells. Exosome-derived miR-122 affected cisplatin-induced AKI and HK2 cells pyroptosis by regulating the expression of embryonic lethal abnormal vision (ELAVL1). These results suggest that exosome miR-122 inhibited pyroptosis and AKI by targeting ELAVL1 under cisplatin treatment, and this offers a potential target for the treatment of AKI.

The Role of HIF1-related Genes and Non-coding RNAs Expression in Clear Cell Renal Cell Carcinoma

BACKGROUND/AIM

Renal cell carcinoma is one of the three most common malignant urologic tumors, with clear cell renal cell carcinoma (ccRCC) representing its most common subtype. Although nephrectomy can radically cure the disease, a large percentage of patients is diagnosed when metastatic sites are present and thus alternative, pharmaceutical approaches need to be sought. Since HIF1 up-regulates the transcription of genes that range from metabolic enzymes to non-coding RNAs, and is a key molecule of ccRCC pathogenesis, this study aimed to investigate the expression ALDOA, SOX-6, and non-coding RNAs (mir-122, mir-1271, and MALAT-1) in samples from ccRCC patients.

PATIENTS AND METHODS

Tumor and adjacent normal tissue samples from 14 patients with ccRCC were harvested. Expression of ALDOA, mir-122, mir-1271, and MALAT-1 mRNA was estimated using real time PCR, whereas the expression of SOX-6 protein was investigated using immunohistochemistry.

RESULTS

Up-regulation of HIF1 was observed, accompanied with up-regulation of ALDOA, MALAT-1, and mir-122. On the contrary, the expression of mir-1271 was found to be reduced, a finding that can be attributed to a potential MALAT-1 sponge function. Furthermore, SOX-6 protein levels (a transcription factor with tumor suppressing properties) were also reduced.

CONCLUSION

The observed dysregulated expression levels highlight the importance of ALDOA, MALAT-1, mir-122, mir-1271, and SOX-6, which remain less studied than the known and well-studied HIF1 pathways of VEGF, TGF-α, and EPO. Furthermore, inhibition of the up-regulated ALDOA, mir-122, and MALAT-1 could be of therapeutic interest for selected ccRCC patients.

High-intensity interval training (HIIT) alleviated NAFLD feature via miR-122 induction in liver of high-fat high-fructose diet induced diabetic rats

Background: Exercise intervention is strongly recommended to manage metabolic diseases. In this study, we investigate, whether HIIT and CET can induce hepatic miR-122 expression, NAFLD rats with diabetes.Methods: 40 Wistar rats divided into 2 groups, non-diabetic (NDC) and diabetic .Type 2 diabetes was induced by high-fat high-fructose diet (HFHFD). Then diabetic rats were subdivided into three groups: diabetic control (HFHFD + DC), CET (HFHFD + CET), and HIIT (HFHFD + HIIT). After eight weeks of exercise on a rodent treadmill, we measured miR-122 and its target genes expression in the liver of rats.Results: HIIT decreased the expression of FAS, ACC, SREBP-1c compared with HFHFD + DC (p = .004, p = .032, p = .043, respectively), and could partially increase miR-122 expression as compared with HFHFD + DC (26.8%, p = .68).Conclusions: Exercise training could be a non-pharmacological intervention for improvement of NAFLD of diabetic rats by induction of miR-122. HIIT had a greater effect on NAFLD amelioration than CET.

miR-122 Inhibits Hepatocarcinoma Cell Progression by Targeting LMNB2

In the present study, we investigated the role of miR-122 in hepatocarcinoma progression and explored the mechanism. In hepatocarcinoma tissues and cells, we used qRT-PCR to validate the miR-122 expression level. Next, we used colony formation by crystal violet staining assay to compare cell proliferation ability, and we used scratch test or Transwell assay to compare cell migration or invasion ability. We then conducted bioinformatics or luciferase reporter gene assay to prove the regulation effect of miR-122 on lamin B2 (LMNB2), and the biological function of LMNB2 was analyzed. We used nude mouse tumorigenicity assay to test the inhibition effect of miR-122 ASO therapy against hepatocarcinoma. miR-122 was reduced in hepatocarcinoma tissues compared to the paracarcinoma tissues, which was relatively low or high in hepatocarcinoma cell line SMMC7721 or Hep3B, and overexpressed miR-122 inhibited proliferation, migration, and invasion in hepatocarcinoma cells. Additionally, some reports showed that LMNB2 was regulated by miR-122, which inhibited the expression of LMNB2. Moreover, LMNB2 functioned to promote cell proliferation, migration, and invasion. We could achieve the inhibition of hepatocarcinoma using miR-122 therapy through decreasing LMNB2 expression in vivo. Our data indicated that miR-122 could inhibit hepatocellular carcinoma cell progression by targeting LMNB2 and as a therapeutic target for hepatocarcinoma treatment.

The diagnostic role of miR-122 in drug-induced liver injury: A systematic review and meta-analysis

BACKGROUND

Drug-induced liver injury (DILI) is a potentially severe adverse drug reaction especially in susceptible patients. But there are no sensitive or specific parameters to detecting DILI. The specific expression of miR-122 in the liver has been a hotspot in the evaluation of hepatic toxicity due to its high stability and sensitivity.

METHODS

We performed a systematic literature review through July 31, 2017 to identify studies which evolved DILI patients testing miR-122 without limiting a certain drug. According to the PRISMA statement, a meta-analysis: the diagnostic role of miR-122 in DILI was made. QUADAS-2 quality evaluation table was used to evaluate the quality of the documentary evidence, PRISMA flowchart and quality evaluation table were drawn with RevMan, use Stata to calculate the sensitivity and specificity of miR-122 in diagnosing DILI, ROC curve and Deeks funnel plot were also drawn by STATA.

RESULTS

Eleven studies involved 194 DILI patients and 251 controls, all were tested miR-122 (fold change). Sensitivity of miR-122 in diagnosing DILI was [0.85 (95% CI, 0.75-0.91), I = 53.46%] and specificity was [0.93 (95% CI, 0.86-0.97), I = 65.10%], the area under ROC curve was 0.95 (95% CI, 0.93-0.97). While in acetaminophen (APAP)-induced liver injury, the sensitivity was [0.82 (95%CI, 0.67-0.91), I = 65.77%] specificity was [0.96 (95%CI, 0.88-0.99), I = 31.46%], AUROC was 0.97 (95% CI, 0.95-0.98).

CONCLUSIONS

In this systematic review and meta-analysis, we found miR-122 have a high specificity in DILI, and a modest positive diagnostic effects. On the basis of the limited evidence, further research is needed to evaluate the long-term observation and more clinical data to testify miR-122 in diagnosing DILI.

Long Noncoding RNA UCA1 Targets miR-122 to Promote Proliferation, Migration, and Invasion of Glioma Cells

Glioma is the most common and lethal malignant intracranial tumor. Long noncoding RNAs (lncRNAs) have been identified as pivotal regulators in the tumorigenesis of glioma. However, the role of lncRNA urothelial carcinoma-associated 1 (UCA1) in glioma genesis is still unknown. The purpose of this study was to investigate the underlying function of UCA1 on glioma genesis. The results demonstrated that UCA1 was upregulated in glioma tissue and indicated a poor prognosis. UCA1 knockdown induced by si-UCA1 significantly suppressed the proliferative, migrative, and invasive activities of glioma cell lines (U87 and U251). Bioinformatics analysis and luciferase reporter assay verified the complementary binding within UCA1 and miR-122 at the 3'-UTR. Functional experiments revealed that UCA1 acted as an miR-122 "sponge" to modulate glioma cell proliferation, migration, and invasion via downregulation of miR-122. Overall, the present study demonstrated that lncRNA UCA1 acts as an endogenous sponge of miR-122 to promote glioma cell proliferation, migration, and invasion, which provides a novel insight and therapeutic target in the tumorigenesis of glioma.

G6PC3, ALDOA and CS induction accompanies mir-122 down-regulation in the mechanical asphyxia and can serve as hypoxia biomarkers

Hypoxia influences different cellular biological processes. To reveal the dynamics of hypoxia's effects on miRNA regulation in vivo, we examined the expression levels of all miRNAs in human brain and heart specimens from cases of mechanical asphyxia compared with those from cases of craniocerebral injury and hemorrhagic shock. We further validated differently expressed miRNAs in another 84 human specimens and rat models. We found that mir-122 was significantly down-regulated and that its putative targets G6PC3, ALDOA and CS were increased in the brain and cardiac tissues in cases of mechanical asphyxia compared with craniocerebral injury and hemorrhagic shock. Our data indicate that mir-122 and its targets G6PC3, ALDOA and CS play roles in the hypoxia responses that regulate glucose and energy metabolism and can serve as hypoxia biomarkers.

Immune phenotype and function of natural killer and T cells in chronic hepatitis C patients who received a single dose of anti-MicroRNA-122, RG-101

MicroRNA-122 is an important host factor for the hepatitis C virus (HCV). Treatment with RG-101, an N-acetylgalactosamine-conjugated anti-microRNA-122 oligonucleotide, resulted in a significant viral load reduction in patients with chronic HCV infection. Here, we analyzed the effects of RG-101 therapy on antiviral immunity. Thirty-two chronic HCV patients infected with HCV genotypes 1, 3, and 4 received a single subcutaneous administration of RG-101 at 2 mg/kg (n = 14) or 4 mg/kg (n = 14) or received a placebo (n = 2/dosing group). Plasma and peripheral blood mononuclear cells were collected at multiple time points, and comprehensive immunological analyses were performed. Following RG-101 administration, HCV RNA declined in all patients (mean decline at week 2, 3.27 log10 IU/mL). At week 8 HCV RNA was undetectable in 15/28 patients. Plasma interferon-γ-induced protein 10 (IP-10) levels declined significantly upon dosing with RG-101. Furthermore, the frequency of natural killer (NK) cells increased, the proportion of NK cells expressing activating receptors normalized, and NK cell interferon-γ production decreased after RG-101 dosing. Functional HCV-specific interferon-γ T-cell responses did not significantly change in patients who had undetectable HCV RNA levels by week 8 post-RG-101 injection. No increase in the magnitude of HCV-specific T-cell responses was observed at later time points, including 3 patients who were HCV RNA-negative 76 weeks postdosing.

CONCLUSION

Dosing with RG-101 is associated with a restoration of NK-cell proportions and a decrease of NK cells expressing activation receptors; however, the magnitude and functionality of ex vivo HCV-specific T-cell responses did not increase following RG-101 injection, suggesting that NK cells, but not HCV adaptive immunity, may contribute to HCV viral control following RG-101 therapy. (Hepatology 2017;66:57-68).

Truths and controversies concerning the role of miRNAs in atherosclerosis and lipid metabolism

PURPOSE OF REVIEW

Better tools are sorely needed for both the prevention and treatment of cardiovascular diseases, which account for more than one-third of the deaths in Western countries. MicroRNAs typically regulate the expression of several mRNAs involved in the same biological process. Therapeutic manipulation of miRNAs could restore the expression of multiple players within the same physiologic pathway, and ideally offer better curative outcomes than conventional approaches that target only one single player within the pathway. This review summarizes available studies on the prospective value of targeting miRNAs to prevent dyslipidemia and atherogenesis.

RECENT FINDINGS

Silencing the expression of miRNAs that target key genes involved in lipoprotein metabolism in vivo with antisense oligonucleotides results in the expected de-repression of target mRNAs in liver and atherosclerotic plaques. However, the consequences of long-term antimiRNA treatment on both circulating lipoproteins and athero-protection are yet to be established.

SUMMARY

A number of studies have demonstrated the efficacy of miRNA mimics and inhibitors as novel therapeutic tools for treating dyslipidemia and cardiovascular diseases. Nevertheless, concerns over unanticipated side-effects related to de-repression of additional targets should not be overlooked for miRNA-based therapies.

Circulating let-7 levels in plasma and extracellular vesicles correlate with hepatic fibrosis progression in chronic hepatitis C

The goal of this study was to determine whether an association exists between circulating microRNA (miRNA) levels and disease progression in chronic hepatitis C (CHC), whether plasma or extracellular vesicles (EVs) were optimal for miRNA measurement and their correlation with hepatic miRNA expression, and the mechanistic plausibility of this association. We studied 130 CHC patients prospectively followed over several decades. A comprehensive miRNA profile in plasma using microarray with 2578 probe sets showed 323 miRNAs differentially expressed between healthy individuals and CHC patients, but only six that distinguished patients with mild versus severe chronic hepatitis. Eventually, let-7a/7c/7d-5p and miR-122-5p were identified as candidate predictors of disease progression. Cross-sectional analyses at the time of initial liver biopsy showed that reduced levels of let-7a/7c/7d-5p (let-7s) in plasma were correlated with advanced histological hepatic fibrosis stage and other fibrotic markers, whereas miR-122-5p levels in plasma were positively correlated with inflammatory activity, but not fibrosis. Measuring let-7s levels in EVs was not superior to intact plasma for discriminating significant hepatic fibrosis. Longitudinal analyses in 60 patients with paired liver biopsies showed that let-7s levels in plasma markedly declined over time in parallel with fibrosis progression. However, circulating let-7s levels did not parallel those in the liver.

CONCLUSION

Of all miRNAs screened, the let-7 family showed the best correlation with hepatic fibrosis in CHC. A single determination of let-7s levels in plasma did not have superior predictive value for significant hepatic fibrosis compared with that of fibrosis-4 index, but the rate of let-7s decline in paired longitudinal samples correlated well with fibrosis progression. Pathway analysis suggested that low levels of let-7 may influence hepatic fibrogenesis through activation of transforming growth factor β signaling in hepatic stellate cells. (Hepatology 2016;64:732-745).

Micro RNAs mir-106a, mir-122 and mir-197 are increased in severe acute viral hepatitis with coagulopathy

BACKGROUND & AIMS

The severity of acute viral hepatitis, which may be caused by several distinct viruses, varies among individual patients. In rare cases, severe hepatic injury with sudden loss of liver function may occur, which is clinically indicated by the occurrence of coagulopathy or encephalopathy. As the molecular mechanisms of this liver injury are largely unknown, we investigated extracellular micro RNA (miRNA) profiles in 54 patients acutely infected with one of four different hepatotropic viruses, in order to identify those miRNAs which indicate severe viral hepatitis associated with coagulopathy.

METHODS

First, the profile of miRNAs was extensively analysed using a microarray-based approach in highly characterized 24 patients, matched in terms of sex, age and level of liver enzymes, as well as in three healthy controls. The cohort included samples from 18 patients with moderate and six individuals with severe hepatitis, indicated by abnormal prothrombin time and higher alanine aminotransferase and bilirubin levels. miRNAs found to be upregulated in severe hepatitis were then quantified by real-time PCR in the expanded cohort of 54 patients.

RESULTS

Comprehensive microarray-based miRNA profiling identified upregulation of mir-106a, mir-122 and mir-197 in patients with severe acute viral hepatitis with coagulopathy, as compared to patients who did not develop coagulopathy. mir-106a, mir-122 and mir-197 were then proven to be significantly upregulated in patients with severe acute viral hepatitis by quantitative real-time PCR (P < 0.01, Mann-Whitney U-test).

CONCLUSIONS

mir-106a, mir-122 and mir-197 could be potential markers for severe acute viral hepatitis associated with coagulopathy.

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.

Biomarkers distinguish apoptotic and necrotic cell death during hepatic ischemia/reperfusion injury in mice

Hepatic ischemia/reperfusion (IRP) injury is a significant clinical problem during tumor-resection surgery (Pringle maneuver) and liver transplantation. However, the relative contribution of necrotic and apoptotic cell death to the overall liver injury is still controversial. To address this important issue with a standard murine model of hepatic IRP injury, plasma biomarkers of necrotic cell death such as micro-RNA 122, full-length cytokeratin 18 (FK18), and high-mobility group box 1 (HMGB1) protein and plasma biomarkers of apoptosis such as plasma caspase-3 activity and caspase-cleaved fragment of cytokeratin 18 (CK18) coupled with markers of inflammation (hyperacetylated HMGB1) were compared by histological features in hematoxylin and eosin-stained and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL)-stained liver sections. After 45 minutes of hepatic ischemia and 1 to 24 hours of reperfusion, all necrosis markers increased dramatically in plasma by 40- to >10,000-fold over the baseline with a time course similar to that of alanine aminotransferase. These data correlated well with histological characteristics of necrosis. Within the area of necrosis, most cells were TUNEL positive; initially (≤3 hours of reperfusion), the staining was restricted to nuclei, but it later spread to the cytosol, and this is characteristic of karyorrhexis during necrotic cell death. In contrast, the lack of morphological evidence of apoptotic cell death and relevant caspase-3 activity in the postischemic liver correlated well with the absence of caspase-3 activity and CK18 (except for a minor increase at 3 hours of reperfusion) in plasma. A quantitative comparison of FK18 (necrosis) and CK18 (apoptosis) release indicated dominant cell death by necrosis during IRP and only a temporary and very minor degree of apoptosis. These data suggest that the focus of future research should be the elucidation of necrotic signaling mechanisms to identify relevant targets, which may be used to attenuate hepatic IRP injury.

Reciprocal regulation of microRNA-122 and c-Myc in hepatocellular cancer: role of E2F1 and transcription factor dimerization partner 2

c-Myc is a well-known oncogene frequently up-regulated in different malignancies, whereas liver-specific microRNA (miR)-122, a bona fide tumor suppressor, is down-regulated in hepatocellular cancer (HCC). Here we explored the underlying mechanism of reciprocal regulation of these two genes. Real-time reverse-transcription polymerase chain reaction (RT-PCR) and northern blot analysis demonstrated reduced expression of the primary, precursor, and mature miR-122 in c-MYC-induced HCCs compared to the benign livers, indicating transcriptional suppression of miR-122 upon MYC overexpression. Indeed, chromatin immunoprecipitation (ChIP) assay showed significantly reduced association of RNA polymerase II and histone H3K9Ac, markers of active chromatin, with the miR-122 promoter in tumors relative to the c-MYC-uninduced livers, indicating transcriptional repression of miR-122 in c-MYC-overexpressing tumors. The ChIP assay also demonstrated a significant increase in c-Myc association with the miR-122 promoter region that harbors a conserved noncanonical c-Myc binding site in tumors compared to the livers. Ectopic expression and knockdown studies showed that c-Myc indeed suppresses expression of primary and mature miR-122 in hepatic cells. Additionally, Hnf-3β, a liver enriched transcription factor that activates miR-122 gene, was suppressed in c-MYC-induced tumors. Notably, miR-122 also repressed c-Myc transcription by targeting transcriptional activator E2f1 and coactivator Tfdp2, as evident from ectopic expression and knockdown studies and luciferase reporter assays in mouse and human hepatic cells.

CONCLUSION

c-Myc represses miR-122 gene expression by associating with its promoter and by down-regulating Hnf-3β expression, whereas miR-122 indirectly inhibits c-Myc transcription by targeting Tfdp2 and E2f1. In essence, these results suggest a double-negative feedback loop between a tumor suppressor (miR-122) and an oncogene (c-Myc).

Epigenetic regulation of MicroRNA-122 by peroxisome proliferator activated receptor-gamma and hepatitis b virus X protein in hepatocellular carcinoma cells

MicroRNA-122 (miR-122), a pivotal liver-specific miRNA, has been implicated in several liver diseases including hepatocellular carcinoma (HCC) and hepatitis C and B viral infection. This study aimed to explore epigenetic regulation of miR-122 in human HCC cells and to examine the effect of hepatitis C virus (HCV) and hepatitis B virus (HBV). We performed microRNA microarray analysis and identified miR-122 as the most up-regulated miRNA (6-fold) in human HCC cells treated with 5'aza-2'deoxycytidine (5-Aza-CdR, DNA methylation inhibitor) and 4-phenylbutyric acid (PBA, histone deacetylation inhibitor). Real-time polymerase chain reaction (PCR) analysis verified significant up-regulation of miR-122 by 5'aza and PBA in HCC cells, and to a lesser extent in primary hepatocytes. Peroxisome proliferator activated receptor-gamma (PPARγ) and retinoid X receptor alpha (RXRα) complex was found to be associated with the DR1 and DR2 consensus site in the miR-122 gene promoter which enhanced miR-122 gene transcription. 5-Aza-CdR and PBA treatment increased the association of PPARγ/RXRα, but decreased the association of its corepressors (N-CoR and SMRT), with the miR-122 DR1 and DR2 motifs. The aforementioned DNA-protein complex also contains SUV39H1, an H3K9 histone methyl transferase, which down-regulates miR-122 expression.

CONCLUSIONS

These findings establish a novel role of the PPARγ binding complex for epigenetic regulation of miR-122 in human HCC cells. Moreover, we show that hepatitis B virus X protein binds PPARγ and inhibits the transcription of miR-122, whereas hepatitis C viral particles exhibited no significant effect; these findings provide mechanistic insight into reduction of miR-122 in patients with HBV but not with HCV infection.

miR-122 regulates collagen production via targeting hepatic stellate cells and suppressing P4HA1 expression

BACKGROUND & AIMS

MicroRNAs (miRNAs) have been shown to be involved in many biological processes by affecting their target gene expression. miR-122 has been extensively studied in hepatocarcinogenesis. However, the role of miR-122 in liver fibrosis remains unknown.

METHODS

The mRNA expression levels of miR-122, prolyl 4-hydroxylase subunit alpha-1 (P4HA1), and CCAAT/enhancer binding protein alpha (C/EBPα) were assessed by real-time PCR. The protein expression levels of P4HA1, C/EBPα and collagen, type I, alpha 1 (COL1A1) were analyzed by Western blot and immunofluorescence. MTT assay was used to assess cell proliferation. Chromatin immunoprecipitation (ChIP) assay was used to examine the binding activity of C/EBPα to miR-122 promoter.

RESULTS

miR-122 expression was significantly reduced in transactivated HSCs and in the livers of mice treated with CCl(4). Overexpression of miR-122 inhibited the proliferation of LX2 cells. We also demonstrated that P4HA1 was a target gene of miR-122. The mRNA expression level of PAHA1 inversely correlated with that of miR-122 in HSCs and in the mouse liver. Overexpression of miR-122 markedly attenuated the expression of P4HA1 via targeting a binding site located at 3'-UTR of P4HA1 mRNA. We further showed that miR-122 overexpression led to decreased collagen maturation and ECM production. Finally, the binding activity of C/EBPα to miR-122 promoter was significantly decreased in activated HSCs.

CONCLUSIONS

Our study suggests that miR-122 may play an important role in negatively regulating collagen production in HSCs and that targeted expression of miR-122 in HSCs may represent a new strategy for the treatment of liver fibrosis.

Role of miR-122 and lipid metabolism in HCV infection

Hepatitis C virus (HCV) exhibits a narrow host range and a specific tissue tropism. Mice expressing major entry receptors for HCV permit viral entry, and therefore the species tropism of HCV infection is considered to be reliant on the expression of the entry receptors. However, HCV receptor candidates are expressed and replication of HCV-RNA can be detected in several nonhepatic cell lines, suggesting that nonhepatic cells are also susceptible to HCV infection. Recently it was shown that the exogenous expression of a liver-specific microRNA, miR-122, facilitated the efficient replication of HCV not only in hepatic cell lines, including Hep3B and HepG2 cells, but also in nonhepatic cell lines, including Hec1B and HEK-293T cells, suggesting that miR-122 is required for the efficient replication of HCV in cultured cells. However, no infectious particle was detected in the nonhepatic cell lines, in spite of the efficient replication of HCV-RNA. In the nonhepatic cells, only small numbers of lipid droplets and low levels of very-low-density lipoprotein-associated proteins were observed compared with findings in the hepatic cell lines, suggesting that functional lipid metabolism participates in the assembly of HCV. Taken together, these findings indicate that miR-122 and functional lipid metabolism are involved in the tissue tropism of HCV infection. In this review, we would like to focus on the role of miR-122 and lipid metabolism in the cell tropism of HCV.

Circulating microRNAs in exosomes indicate hepatocyte injury and inflammation in alcoholic, drug-induced, and inflammatory liver diseases

MicroRNAs are fine tuners of diverse biological responses and are expressed in various cell types of the liver. Here we hypothesized that circulating microRNAs (miRNAs) may serve as biomarkers of liver damage and inflammation. We studied miRNA-122, which is abundant in hepatocytes, and miR-155, -146a, and -125b, which regulate inflammation in immune cells in mouse models of alcoholic liver disease (ALD), drug (acetaminophen, APAP)-induced liver injury (DILI), and Toll-like receptor (TLR) 9+4 ligand-induced inflammatory cell-mediated liver damage. We found that serum/plasma miR-122 correlated with alanine aminotransferase (ALT) increases in the liver damage caused by alcohol, APAP, and TLR9 (CpG)+4 (LPS) ligands. MiR-155, a regulator of inflammation, was increased in serum/plasma in alcoholic and inflammatory liver injury. Alcohol failed to increase serum miR-122 in TLR4-deficient and p47phox-deficient mice that were protected from ALD. We found the most robust increase in plasma miR-122 in DILI and it correlated with the highest ALT levels. Consistent with the massive inflammatory cell infiltration in the liver, plasma miR-155 and miR-146a were significantly elevated after CpG+LPS administration. We show for the first time that, depending on the type of liver injury, circulating miRNAs are associated either with the exosome-rich or protein-rich compartments. In ALD and in inflammatory liver injury, serum/plasma miR-122 and miR-155 were predominantly associated with the exosome-rich fraction, whereas in DILI/APAP injury these miRNAs were present in the protein-rich fraction.

CONCLUSION

Our results suggest that circulating miRNAs may serve as biomarkers to differentiate between hepatocyte injury and inflammation and the exosome versus protein association of miRNAs may provide further specificity to mechanisms of liver pathology.

Single-stranded microRNA mimics

miRNAs are ∼22-nt RNAs that bind to the Argonaute family of proteins and have important regulatory roles in plants and animals. Here, we show that miRNAs exhibit targeting activity in cells when delivered as single strands that are 5'-phosphorylated and that contain 2'-fluoro ribose modifications. Length preferences, chemical modification sensitivity, and genome-wide seed-based targeting all suggest that this activity is Ago-based. Activity could be enhanced by annealing of segmented passenger strands containing non-nucleic acid spacers. Furthermore, screening of randomly generated sequences identified pyrimidine rich 3' cassette sequences that increased single strand activity. These results provide an initial step in the development of single-stranded miRNA mimics for therapeutic use.

MicroRNA fate upon targeting with anti-miRNA oligonucleotides as revealed by an improved Northern-blot-based method for miRNA detection

MicroRNAs (miRNAs) are small non-coding RNAs involved in fine-tuning of gene regulation. Antisense oligonucleotides (ONs) are promising tools as anti-miRNA (anti-miR) agents toward therapeutic applications and to uncover miRNA function. Such anti-miR ONs include 2'-O-methyl (OMe), cationic peptide nucleic acids like K-PNA-K3, and locked nucleic acid (LNA)-based anti-miRs such as LNA/DNA or LNA/OMe. Northern blotting is a widely used and robust technique to detect miRNAs. However, miRNA quantification in the presence of anti-miR ONs has proved to be challenging, due to detection artifacts, which has led to poor understanding of miRNA fate upon anti-miR binding. Here we show that anti-miR ON bound to miR-122 can prevent the miRNA from being properly precipitated into the purified RNA fraction using the standard RNA extraction protocol (TRI-Reagent), yielding an RNA extract that does not reflect the real cellular levels of the miRNA. An increase in the numbers of equivalents of isopropanol during the precipitation step leads to full recovery of the targeted miRNA back into the purified RNA extract. Following our improved protocol, we demonstrate by Northern blotting, in conjunction with a PNA decoy strategy and use of high denaturing PAGE, that high-affinity anti-miRs (K-PNA-K3, LNA/DNA, and LNA/OMe) sequester miR-122 without causing miRNA degradation, while miR-122 targeting with a lower-affinity anti-miR (OMe) seems to promote degradation of the miRNA. The technical issues explored in this work will have relevance for other hybridization-based techniques for miRNA quantification in the presence of anti-miR ONs.

miR-122 targeting with LNA/2'-O-methyl oligonucleotide mixmers, peptide nucleic acids (PNA), and PNA-peptide conjugates

MicroRNAs are small noncoding RNAs that regulate many cellular processes in a post-transcriptional mode. MicroRNA knockdown by antisense oligonucleotides is a useful strategy to explore microRNA functionality and as potential therapeutics. MicroRNA-122 (miR-122) is a liver-specific microRNA, the main function of which has been linked with lipid metabolism and liver homeostasis. Here, we show that lipofection of an antisense oligonucleotide based on a Locked Nucleic Acids (LNA)/2'-O-methyl mixmer or electroporation of a Peptide Nucleic Acid (PNA) oligomer is effective at blocking miR-122 activity in human and rat liver cells. These oligonucleotide analogs, evaluated for the first time in microRNA inhibition, are more effective than standard 2'-O-methyl oligonucleotides in binding and inhibiting microRNA action. We also show that microRNA inhibition can be achieved without the need for transfection or electroporation of the human or rat cell lines, by conjugation of an antisense PNA to the cell-penetrating peptide R6-Penetratin, or merely by linkage to just four Lys residues, highlighting the potential of PNA for future therapeutic applications as well as for studying microRNA function.

Reciprocal effects of micro-RNA-122 on expression of heme oxygenase-1 and hepatitis C virus genes in human hepatocytes

BACKGROUND & AIMS

Heme oxygenase-1 (HO-1) is an antioxidant defense and key cytoprotective enzyme, which is repressed by Bach1. Micro-RNA-122 (miR-122) is specifically expressed and highly abundant in human liver and required for replication of hepatitis C virus (HCV) RNA. This study was to assess whether a specific miR-122 antagomir down-regulates HCV protein replication and up-regulates HO-1.

METHODS

We transfected antagomir of miR-122, 2'-O-methyl-mimic miR-122, or nonspecific control antagomir, into wild-type (WT) Huh-7 cells or Huh-7 stably replicating HCV subgenomic protein core through nonstructural protein 3 of HCV (NS3) (CNS3 replicon cells) or NS3-5B (9-13 replicon cells).

RESULTS

Antagomir of miR-122 reduced the abundance of HCV RNA by 64% in CNS3 and by 84% in 9-13 cells. Transfection with 2'-O-methlyl-mimic miR-122 increased HCV levels up to 2.5-fold. Antagomir of miR-122 also decreased Bach1 and increased HO-1 mRNA levels in CNS3, 9-13, and WT Huh-7 cells. Increasing HO-1 by silencing Bach1 with 50 nmol/L Bach1-short interfering RNA or by treatment with 5 mumol/L cobalt protoporphyrin or heme (known inducers of HO-1) decreased HCV RNA and protein by 50% in HCV replicon cells.

CONCLUSIONS

Down-regulation of HCV replication using an antagomir targeted to miR-122 is effective, specific, and selective. Increasing HO-1, by silencing the Bach1 gene or by treatment with cobalt protoporphyrin or heme, decreases HCV replication. Thus, miR-122 plays an important role in the regulation of HCV replication and HO-1/Bach1 expression in hepatocytes. Down-regulation of miR-122 and up-regulation of HO-1 may be new strategies for anti-HCV intervention and cytoprotection.

Cellular cofactors affecting hepatitis C virus infection and replication

Recently identified hepatitis C virus (HCV) isolates that are infectious in cell culture provide a genetic system to evaluate the significance of virus-host interactions for HCV replication. We have completed a systematic RNAi screen wherein siRNAs were designed that target 62 host genes encoding proteins that physically interact with HCV RNA or proteins or belong to cellular pathways thought to modulate HCV infection. This includes 10 host proteins that we identify in this study to bind HCV NS5A. siRNAs that target 26 of these host genes alter infectious HCV production >3-fold. Included in this set of 26 were siRNAs that target Dicer, a principal component of the RNAi silencing pathway. Contrary to the hypothesis that RNAi is an antiviral pathway in mammals, as has been reported for subgenomic HCV replicons, siRNAs that target Dicer inhibited HCV replication. Furthermore, siRNAs that target several other components of the RNAi pathway also inhibit HCV replication. MicroRNA profiling of human liver, human hepatoma Huh-7.5 cells, and Huh-7.5 cells that harbor replicating HCV demonstrated that miR-122 is the predominant microRNA in each environment. miR-122 has been previously implicated in positively regulating the replication of HCV genotype 1 replicons. We find that 2'-O-methyl antisense oligonucleotide depletion of miR-122 also inhibits HCV genotype 2a replication and infectious virus production. Our data define 26 host genes that modulate HCV infection and indicate that the requirement for functional RNAi for HCV replication is dominant over any antiviral activity this pathway may exert against HCV.