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      Remdesivir attenuates high fat diet (HFD)-induced NAFLD by regulating hepatocyte dyslipidemia and inflammation via the suppression of STING

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          Abstract

          High-fat diet (HFD) is a predisposing factor for metabolic syndrome-related systemic inflammation and non-alcoholic fatty liver disease (NAFLD). However, there is still no effective therapeutic treatment for NAFLD. Here, we showed that remdesivir (RDV, GS-5734), as a broad-spectrum antiviral nucleotide prodrug with anti-inflammatory effects, was effective for attenuating HFD-induced metabolic disorder and insulin resistance. Results revealed that the liver weight, hepatic dysfunction and lipid accumulation were markedly increased compared with that of the Control group, while that of the RDV group exhibited significant reduction, accompanied by the improved signaling pathway regulating fatty acid metabolism. In agreement with reduced lipid deposition, RDV supplementation suppressed the systematic and hepatic inflammation, as evidenced by reduction of inflammatory cytokines and the blockage of nuclear factor κB (NF-κB) signaling. In addition, stimulator of interferon genes (STING) and its down-streaming factor interferon regulatory factor 3 (IRF3) were greatly increased in livers of HFD-fed mice, which were considerably restrained by RDV treatment. The in vitro analysis suggested that RDV functioned as an inhibitor of STING, contributing to the suppression of dyslipidemia and inflammation induced by palmitate (PA). However, PA-triggered lipid deposition and inflammatory response was further accelerated in hepatocytes with STING over-expression. Notably, RDV-attenuated lipid disorder and inflammation were significantly abrogated by the over-expression of STING in PA-stimulated hepatocytes. Taken together, these findings indicated that RDV exhibited protective effects against NAFLD development mainly through repressing STING signaling, and thus could be considered as a potential therapeutic strategy.

          Highlights

          • Remdesivir attenuates metabolic syndrome in HFD-fed mice.

          • Remdesivir alleviates hepatic function and lipid accumulation in HFD-induced mice.

          • Remdesivir inhibits inflammatory response in liver of HFD-fed mice.

          • Remdesivir-regulated lipid accumulation and inflammation is dependent on STING in PA-incubated hepatocytes.

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          Most cited references18

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          Mechanism of Inhibition of Ebola Virus RNA-Dependent RNA Polymerase by Remdesivir

          Remdesivir (GS-5734) is a 1′-cyano-substituted adenosine nucleotide analogue prodrug that shows broad-spectrum antiviral activity against several RNA viruses. This compound is currently under clinical development for the treatment of Ebola virus disease (EVD). While antiviral effects have been demonstrated in cell culture and in non-human primates, the mechanism of action of Ebola virus (EBOV) inhibition for remdesivir remains to be fully elucidated. The EBOV RNA-dependent RNA polymerase (RdRp) complex was recently expressed and purified, enabling biochemical studies with the relevant triphosphate (TP) form of remdesivir and its presumptive target. In this study, we confirmed that remdesivir-TP is able to compete for incorporation with adenosine triphosphate (ATP). Enzyme kinetics revealed that EBOV RdRp and respiratory syncytial virus (RSV) RdRp incorporate ATP and remdesivir-TP with similar efficiencies. The selectivity of ATP against remdesivir-TP is ~4 for EBOV RdRp and ~3 for RSV RdRp. In contrast, purified human mitochondrial RNA polymerase (h-mtRNAP) effectively discriminates against remdesivir-TP with a selectivity value of ~500-fold. For EBOV RdRp, the incorporated inhibitor at position i does not affect the ensuing nucleotide incorporation event at position i+1. For RSV RdRp, we measured a ~6-fold inhibition at position i+1 although RNA synthesis was not terminated. Chain termination was in both cases delayed and was seen predominantly at position i+5. This pattern is specific to remdesivir-TP and its 1′-cyano modification. Compounds with modifications at the 2′-position show different patterns of inhibition. While 2′-C-methyl-ATP is not incorporated, ara-ATP acts as a non-obligate chain terminator and prevents nucleotide incorporation at position i+1. Taken together, our biochemical data indicate that the major contribution to EBOV RNA synthesis inhibition by remdesivir can be ascribed to delayed chain termination. The long distance of five residues between the incorporated nucleotide analogue and its inhibitory effect warrant further investigation.
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            The DNA Inflammasome in Human Myeloid Cells Is Initiated by a STING-Cell Death Program Upstream of NLRP3.

            Detection of cytosolic DNA constitutes a central event in the context of numerous infectious and sterile inflammatory conditions. Recent studies have uncovered a bipartite mode of cytosolic DNA recognition, in which the cGAS-STING axis triggers antiviral immunity, whereas AIM2 triggers inflammasome activation. Here, we show that AIM2 is dispensable for DNA-mediated inflammasome activation in human myeloid cells. Instead, detection of cytosolic DNA by the cGAS-STING axis induces a cell death program initiating potassium efflux upstream of NLRP3. Forward genetics identified regulators of lysosomal trafficking to modulate this cell death program, and subsequent studies revealed that activated STING traffics to the lysosome, where it triggers membrane permeabilization and thus lysosomal cell death (LCD). Importantly, the cGAS-STING-NLRP3 pathway constitutes the default inflammasome response during viral and bacterial infections in human myeloid cells. We conclude that targeting the cGAS-STING-LCD-NLRP3 pathway will ameliorate pathology in inflammatory conditions that are associated with cytosolic DNA sensing.
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              Expression of STING Is Increased in Liver Tissues From Patients With NAFLD and Promotes Macrophage-Mediated Hepatic Inflammation and Fibrosis in Mice

              Background & Aims: Transmembrane protein 173 (TMEM173 or STING) signaling by macrophage activates the type I interferon-mediated innate immune response. The innate immune response contributes to hepatic steatosis and non-alcoholic fatty liver disease (NAFLD). We investigated wither STING regulates diet-induced in hepatic steatosis, inflammation, and liver fibrosis in mice. Methods: Mice with disruption of Tmem173 (STING gt ) on a C57BL/6J background, mice without disruption of this gene (controls), and mice with disruption of Tmem173 only in myeloid cells were fed a standard chow diet, a high-fat diet (HFD, 60% fat calories), or a methionine- and choline-deficient diet (MCD). Liver tissues were collected and analyzed by histology and immunohistochemistry. Bone marrow cells were isolated from mice, differentiated into macrophages, and incubated with DMXAA (an activator of STING) or cGAMP. Macrophages or their media were applied to mouse hepatocytes or human hepatic stellate cells (LX2) cells, which were analyzed for cytokine expression, protein phosphorylation, and fat deposition (oil red O staining following incubation with palmitate). We obtained liver tissues from patients with and without NAFLD and analyzed these by immunohistochemistry. Results: Non-parenchymal cells of liver tissues from patients with NAFLD had higher levels of STING than liver tissues from patients without NAFLD. STING gt mice and mice with disruption only in myeloid cells developed less severe hepatic steatosis, inflammation, and/or fibrosis following a HFD or MCD than control mice. Levels of phosphorylated JNK and p65 and the mRNAs encoding TNF, IL1B, and IL6 (markers of inflammation) were significantly lower in liver tissues from STING gt mice vs control mice after a HFD or MCD. Transplantation of bone marrow cells from control mice to STING gt mice restored the severity of steatosis and inflammation following a HFD. Macrophages from control, but not STING gt mice, increased markers of inflammation in response to lipopolysaccharide and cGAMP. Hepatocytes and stellate cells co-cultured with STING gt macrophages in the presence of DMXAA, or incubated with the medium collected from these macrophages, had decreased fat deposition and markers of inflammation compared to hepatocytes incubated with control macrophages. Conclusions: We found levels of STING to be increased in liver tissues from patients with NAFLD mice with HFD-induced steatosis. In mice, loss of STING from liver macrophages reduces the severity of fibrosis and the inflammatory response. STING might be a therapeutic target for NAFLD.
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                Author and article information

                Contributors
                Journal
                Biochem Biophys Res Commun
                Biochem. Biophys. Res. Commun
                Biochemical and Biophysical Research Communications
                Published by Elsevier Inc.
                0006-291X
                1090-2104
                27 March 2020
                28 May 2020
                27 March 2020
                : 526
                : 2
                : 381-388
                Affiliations
                [a ]Department of Endocrinology, Hanzhong Central Hospital Shaanxi Province, Hanzhong, 723000, China
                [b ]Department of Endocrinology, Shaanxi Provincial People’s Hospital, Xi’an, 710068, China
                Author notes
                []Corresponding author. Shaanxi Provincial People’s Hospital, No. 256 Youyi West Road, Xi’an, 710068, China. su200hui@ 123456163.com
                Article
                S0006-291X(20)30513-1
                10.1016/j.bbrc.2020.03.034
                7194706
                32223926
                b28a84be-17e6-45b1-aa25-c24375721ccb
                © 2020 Published by Elsevier Inc.

                Since January 2020 Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on the novel coronavirus COVID-19. The COVID-19 resource centre is hosted on Elsevier Connect, the company's public news and information website. Elsevier hereby grants permission to make all its COVID-19-related research that is available on the COVID-19 resource centre - including this research content - immediately available in PubMed Central and other publicly funded repositories, such as the WHO COVID database with rights for unrestricted research re-use and analyses in any form or by any means with acknowledgement of the original source. These permissions are granted for free by Elsevier for as long as the COVID-19 resource centre remains active.

                History
                : 21 February 2020
                : 5 March 2020
                Categories
                Article

                Biochemistry
                nafld,remdesivir,dyslipidemia,inflammation,sting
                Biochemistry
                nafld, remdesivir, dyslipidemia, inflammation, sting

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