Cholesterol metabolism disorder in hepatocytes predicts a higher risk of metabolic syndrome (MetS). Long noncoding RNAs (lncRNAs) have emerged as critical players in cellular cholesterol metabolism, but their functions are not systematically clarified. Here, we have identified a novel lncRNA named lnc‐HC negatively regulating cholesterol metabolism within hepatocytes through physical interaction with hnRNPA2B1. By further binding to the target messenger RNA of Cyp7a1 or Abca1, the lnc‐HC‐hnRNPA2B1 complex decreases expressions of the two genes that are implicated in cellular cholesterol excretion. lnc‐HC knockdown can strongly recover the cholesterol disorder in vivo. In the upstream pathway, lnc‐HC is up‐regulated by high cholesterol by the transcription activator, CCAAT/enhancer‐binding protein beta. Conclusion: These findings suggest a subtle feed‐forward regulation of lnc‐HC in cholesterol metabolism and define a novel line of evidence by which lncRNAs modulate the metabolic system at the post‐transcriptional level. (Hepatology 2016;64:58‐72)

Coronavirus disease 2019 is a kind of viral pneumonia caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, the mechanism whereby SARS-CoV-2 invades host cells remains poorly understood. Here we used SARS-CoV-2 pseudoviruses to infect human angiotensin-converting enzyme 2 (ACE2) expressing HEK293T cells and evaluated virus infection. We confirmed that SARS-CoV-2 entry was dependent on ACE2 and sensitive to pH of endosome/lysosome in HEK293T cells. The infection of SARS-CoV-2 pseudoviruses is independent of dynamin, clathrin, caveolin and endophilin A2, as well as macropinocytosis. Instead, we found that the infection of SARS-CoV-2 pseudoviruses was cholesterol-rich lipid raft dependent. Cholesterol depletion of cell membranes with methyl-β-cyclodextrin resulted in reduction of pseudovirus infection. The infection of SARS-CoV-2 pseudoviruses resumed with cholesterol supplementation. Together, cholesterol-rich lipid rafts, and endosomal acidification, are key steps of SARS-CoV-2 required for infection of host cells. Therefore, our finding expands the understanding of SARS-CoV-2 entry mechanism and provides a new anti-SARS-CoV-2 strategy.

Introduction: Abnormal toll-like receptor (TLR)3 signaling plays an indispensable role in pathogenesis of both experimental and human rheumatoid arthritis, and microRNAs (miRNAs) might orchestrate this signaling pathway. This study was performed to determine the relationship between miR-26a and TLR3 in rat macrophages and to observe effects of miR-26a mimic on pristane induced arthritis (PIA) in rats. Methods: Dual luciferase reporter assay was used to validate the direct interaction between miR-26a (a candidate miRNA to target tlr3 mRNA) and tlr3 3′UTR. MiR-26a regulation on TLR3 gene expression was determined using RT-qPCR and Western blotting after miR-26a mimics and inhibitors were transfected into rat macrophage line NR8383 cells. Poly I:C (TLR3 ligand) was used to trigger TLR3 activation, and mRNA expression of its downstream cytokines interferon (ifn)-β and tumor necrosis factor (tnf)-α was accordingly detected to determine the regulation of TLR3 signaling. Expressions of TLR3 and miR-26a were detected during rat bone marrow derived macrophage (BMDM) induction, in pristane stimulated NR8383 cells and spleens from methotrexate (MTX) treated PIA rats. A miR-26a mimic was administrated intraperitoneally to PIA rats, and arthritis severity was evaluated by macroscopic or microscopic observations. Results: Direct target relationship between miR-26a and tlr3 mRNA in rats was confirmed. Modifications of miR-26a function by transfection of miR-26a mimics and inhibitors exhibited corresponding repression and augmentation of TLR3 and its signaling downstream cytokine expressions in NR8383 cells. The alteration of miR-26a expression was negatively related with TLR3 expression during BMDM induction, in pristane-primed NR8383 cells and PIA rat spleens. Moreover, both abnormal expressions were rescued in MTX treated arthritis rat spleens. The miR-26a mimic treatment displayed the depression of TLR3 expression and ameliorated the disease severity in the rats with pristane induced arthritis. Conclusions: MiR-26a negatively regulates TLR3 signaling via targeting of TLR3 itself in rat macrophages, and this finding provides a novel insight into abnormal TLR3 overexpression during experimental arthritis.

Ym1 is a rodent-specific chitinase-like protein (CLP) lacking catalytic activity, whose cellular origins are mainly macrophages, neutrophils and other cells. Although the detailed function of Ym1 remains poorly understood, Ym1 has been generally recognized as a fundamental feature of alternative activation of macrophages in mice and hence one of the prevalent detecting targets in macrophage phenotype distinguishment. Studies have pointed out that Ym1 may have regulatory effects, which are multifaceted and even contradictory, far more than just a mere marker. Allergic lung inflammation, parasite infection, autoimmune diseases, and central nervous system diseases have been found associations with Ym1 to varying degrees. Thus, insights into Ym1’s role in diseases would help us understand the pathogenesis of different diseases and clarify the genuine roles of CLPs in mammals. This review summarizes the information on Ym1 from the gene to its expression and regulation and focuses on the association between Ym1 and diseases.

Introduction: Toll-like receptors (TLRs) are involved in both innate and adaptive immune responses and are likely to play a complex role in the pathogenesis of human rheumatoid arthritis (RA) and experimental arthritis. The objective of this study was to identify the key TLR in pristane-induced arthritis (PIA), a rat model for RA, and to clarify its roles in the initiation and maintenance of arthritis. Methods: Arthritis in DA rats was induced by pristane and the severity was evaluated by macroscopic and microscopic score systems. Spleen TLR and cytokine expression was detected at different time points by real-time polymerase chain reaction (PCR) and flow cytometry. Polyinosine-polycytidylic acid (polyI:C, a ligand of TLR3) or TLR3 specific short-hairpin RNA plasmid for RNA interference was administrated to PIA rats in vivo. Serum nitrogen oxide concentration was determined by Griess method, and tumor necrosis factor alpha (TNF-α) was determined by L929 biotest. In splenic macrophages, TLR3 expression was measured by flow cytometry. A rat macrophage cell line (NR8383) was stimulated by pristane, and anti-TLR3 antibody were used to block TLR3 pathway. TLR3 and cytokine expression in NR8383 were detected by real-time PCR. Results: By screening the TLR expression profile in spleen of DA rats after pristane injection, we found that TLR3 was the most early and prominently upregulated TLR. Both TLR3 mRNA and protein expression of spleen were upregulated at 6 and 26 days after pristane injection. Furthermore, administration of polyI:C exacerbated, whereas RNA interference targeting TLR3 ameliorated, the arthritis. Particularly, TLR3 expression was induced in splenic macrophages of PIA rats, and also in the NR8383 cell line after pristane stimulation in a dose- and time- dependent manner. Upregulation of interferon beta (IFN-β) and TNF-α by pristane stimulation was blocked by anti-TLR3 antibody in NR8383. Conclusions: TLR3 plays a pivotal role in the initiation and development of PIA which may dependent on macrophage. These findings are useful to understand the pathogenesis of RA and may provide an intriguing therapeutic opportunity for RA.