LncRNA-H19 induces hepatic stellate cell activation via upregulating alcohol dehydrogenase III-mediated retinoic acid signals

Conserved long noncoding RNA TILAM promotes liver fibrosis through interaction with PML in hepatic stellate cells

Background & Aims

Fibrosis is the common endpoint for all forms of chronic liver injury, and progression of fibrosis leads to the development of end-stage liver disease. Activation of hepatic stellate cells (HSCs) and their transdifferentiation to myofibroblasts results in the accumulation of extracellular matrix (ECM) proteins that form the fibrotic scar. Long noncoding (lnc) RNAs regulate the activity of HSCs and may provide targets for fibrotic therapies.

Methods

We identified lncRNA TILAM as expressed near COL1A1 in human HSCs and performed loss-of-function studies in human HSCs and liver organoids. Transcriptomic analyses of HSCs isolated from mice defined the murine ortholog of TILAM . We then generated Tilam -deficient GFP reporter mice and quantified fibrotic responses to carbon tetrachloride (CCl 4 ) and choline-deficient L-amino acid defined high fat diet (CDA-HFD). Co-precipitation studies, mass spectrometry, and gene expression analyses identified protein partners of TILAM .

Results

TILAM is conserved between human and mouse HSCs and regulates expression of ECM proteins, including collagen. Tilam is selectively induced in HSCs during the development of fibrosis in vivo . In both male and female mice, loss of Tilam results in reduced fibrosis in the setting of CCl 4 and CDA-HFD injury models. TILAM interacts with promyelocytic leukemia protein (PML) to stabilize PML protein levels and promote the fibrotic activity of HSCs.

Conclusion

TILAM is activated in HSCs and interacts with PML to drive the development of liver fibrosis. Depletion of TILAM may serve as a therapeutic approach to combat the development of end stage liver disease.

Cyp4a12-mediated retinol metabolism in stellate cells is the antihepatic fibrosis mechanism of the Chinese medicine Fuzheng Huayu recipe

BACKGROUND

Hepatic stellate cells (HSCs), which contain multiple retinol-containing lipid droplets, are important profibrotic cells in liver fibrosis. Under Cyp4a12a/b oxidation, HSC activation was accompanied by the downregulation of genes involved in retinol metabolism, inducing RAE-1 production. By eliminating activated HSCs, NK cells expressing the activating receptor NKG2D are recruited to alleviate fibrosis. FZHY was found to significantly reduce the severity of liver fibrosis by inhibiting the activation and proliferation of HSCs. The molecular processes that govern retinol metabolism, on the other hand, are largely unexplored. This study focused on the regulation of Cyp4a12a/b by FZHY to elucidate the antifibrotic molecular mechanisms underlying the effect of FZHY on retinol metabolism.

METHODS

To investigate mechanisms and altered pathways of FZHY against carbon tetrachloride (CCl4)-induced liver fibrosis based on transcriptomics data. Bioinformatics analysis was used to screen its pharmacological targets. The predicted targets were confirmed by a series of in vitro and in vivo experiments, including mass spectrometry, in situ hybridization, immunofluorescence assays and real-time PCR. Then, the results were further characterized by recombinant adenovirus vectors that were constructed and transfected into the cultured primary HSCs.

RESULTS

Transcriptomics revealed that Cyp4a12a/b is nearly completely lost in liver fibrosis, and these effects might be partially reversed by FZHY therapy recovery. In vitro and in vivo studies indicated that Cyp4a12a/b deletion disrupted retinol metabolism and lowered Rae-1 expression. Activated HSCs successfully escape recognition and elimination by natural killer (NK) cells as a result of reduced Rae-1. Notablely, we discovered that FZHY may restore the Cyp4a12a/b capability, allowing the recovery of the cytotoxic function of NK cells against HSCs, and thereby reducing hepatic fibrosis by suppressing HSC activation.

CONCLUSION

Our findings revealed a new role for Cyp4a in retinol metabolism in the development of hepatic fibrosis, and they highlight Cyp4a12/Rae-1 signals as possible therapeutic targets for antifibrotic medicines.

Long Noncoding RNA H19: A Novel Oncogene in Liver Cancer

Liver cancer is the second leading cause of cancer-related death globally, with limited treatment options. Recent studies have demonstrated the critical role of long noncoding RNAs (lncRNAs) in the pathogenesis of liver cancers. Of note, mounting evidence has shown that lncRNA H19, an endogenous noncoding single-stranded RNA, functions as an oncogene in the development and progression of liver cancer, including hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA), the two most prevalent primary liver tumors in adults. H19 can affect many critical biological processes, including the cell proliferation, apoptosis, invasion, and metastasis of liver cancer by its function on epigenetic modification, H19/miR-675 axis, miRNAs sponge, drug resistance, and its regulation of downstream pathways. In this review, we will focus on the most relevant molecular mechanisms of action and regulation of H19 in the development and pathophysiology of HCC and CCA. This review aims to provide valuable perspectives and translational applications of H19 as a potential diagnostic marker and therapeutic target for liver cancer disease.

The Roles and Mechanisms of lncRNAs in Liver Fibrosis

Long non-coding RNAs (lncRNAs) can potentially regulate all aspects of cellular activity including differentiation and development, metabolism, proliferation, apoptosis, and activation, and benefited from advances in transcriptomic and genomic research techniques and database management technologies, its functions and mechanisms in physiological and pathological states have been widely reported. Liver fibrosis is typically characterized by a reversible wound healing response, often accompanied by an excessive accumulation of extracellular matrix. In recent years, a range of lncRNAs have been investigated and found to be involved in several cellular-level regulatory processes as competing endogenous RNAs (ceRNAs) that play an important role in the development of liver fibrosis. A variety of lncRNAs have also been shown to contribute to the altered cell cycle, proliferation profile associated with the accelerated development of liver fibrosis. This review aims to discuss the functions and mechanisms of lncRNAs in the development and regression of liver fibrosis, to explore the major lncRNAs involved in the signaling pathways regulating liver fibrosis, to elucidate the mechanisms mediated by lncRNA dysregulation and to provide new diagnostic and therapeutic strategies for liver fibrosis.

Hepatic Stellate Cell: A Double-Edged Sword in the Liver

Hepatic stellate cells (HSCs) are located in the space of Disse, between liver sinusoidal endothelia cells (LSECs) and hepatocytes. They have surprised and excited hepatologists for their biological characteristics. Under physiological quiescent conditions, HSCs are the major vitamin A-storing cells of the liver, playing crucial roles in the liver development, regeneration, and tissue homeostasis. Upon injury-induced activation, HSCs convert to a pro-fibrotic state, producing the excessive extracellular matrix (ECM) and promoting angiogenesis in the liver fibrogenesis. Activated HSCs significantly contribute to liver fibrosis progression and inactivated HSCs are key to liver fibrosis regression. In this review, we summarize the comprehensive understanding of HSCs features, including their roles in normal liver and liver fibrosis in hopes of advancing the development of emerging diagnosis and treatment for hepatic fibrosis.

Dihydroartemisinin regulates lipid droplet metabolism in hepatic stellate cells by inhibiting lncRNA-H19-induced AMPK signal

Activation of hepatic stellate cells (HSCs) is a central event in the pathogenesis of liver fibrosis and is often accompanied by the disappearance of lipid droplets (LDs). Although interference with LD metabolism can effectively reverse the activation of HSCs, there is currently no effective therapy for liver fibrosis. Our previous evidence indicates that long non-coding RNA (lncRNA)-H19 plays an essential role in LD metabolism of HSC. In this study, we investigated the potential molecular mechanism of dihydroartemisinin (DHA) inhibits LD metabolism and liver fibrosis by regulating H19-AMPK pathway. We found that DHA restores LDs content in activated HSCs via reducing the transcription of H19 driven by hypoxia inducible factor 1 subunit alpha (HIF1α) and inhibiting the lipid oxidation signal mediated by AMP-activated protein kinase (AMPK) phosphorylation. In vivo experiments, we have proved that DHA reduced the deposition of extracellular matrix (ECM) and reduce the level of liver fibrosis in CCl₄-induced liver fibrosis of mice. In summary, our results emphasize the importance of H19 in liver fibrosis and the potential of DHA to regulate H19 to treat liver fibrosis, providing a new direction for the prevention and treatment of liver fibrosis.

The long and the small collide: LncRNAs and small heterodimer partner (SHP) in liver disease

Long non-coding RNAs (lncRNAs) are a large and diverse class of RNA molecules that are transcribed but not translated into proteins, with a length of more than 200 nucleotides. LncRNAs are involved in gene expression and regulation. The abnormal expression of lncRNAs is associated with disease pathogenesis. Small heterodimer partner (SHP, NR0B2) is a unique orphan nuclear receptor that plays a pivotal role in many biological processes by acting as a transcriptional repressor. In this review, we present the critical roles of SHP and summarize recent findings demonstrating the regulation between lncRNAs and SHP in liver disease.

Long noncoding RNA H19 - a new player in the pathogenesis of liver diseases

The liver is a vital organ that controls glucose and lipid metabolism, hormone regulation, and bile secretion. Liver injury can occur from various insults such as viruses, metabolic diseases, and alcohol, which lead to acute and chronic liver diseases. Recent studies have demonstrated the implications of long noncoding RNAs (lncRNAs) in the pathogenesis of liver diseases. These newly discovered lncRNAs have various functions attributing to many cellular biological processes via distinct and diverse mechanisms. LncRNA H19, one of the first lncRNAs being identified, is highly expressed in fetal liver but not in adult normal liver. Its expression, however, is increased in liver diseases with various etiologies. In this review, we focused on the roles of H19 in the pathogenesis of liver diseases. This comprehensive review is aimed to provide useful perspectives and translational applications of H19 as a potential therapeutic target of liver diseases.

Non-Coding RNAs in Retinoic Acid as Differentiation and Disease Drivers

All-trans retinoic acid (RA) is the most active metabolite of vitamin A. Several studies have described a pivotal role for RA signalling in different biological processes such as cell growth and differentiation, embryonic development and organogenesis. Since RA signalling is highly dose-dependent, a fine-tuning regulatory mechanism is required. Thus, RA signalling deregulation has a major impact, both in development and disease, related in many cases to oncogenic processes. In this review, we focus on the impact of ncRNA post-transcriptional regulatory mechanisms, especially those of microRNAs and lncRNAs, in RA signalling pathways during differentiation and disease.