Experimental Steatohepatitis Research Articles

Dual-Emissive Detection of ATP and Hypochlorite Ions for Monitoring Inflammation-Driven Liver Injury In Vitro and In Vivo.

Reactive oxygen species play a pivotal role in liver disease, contributing to severe liver damage and chronic inflammation. In liver injury driven by inflammation, adenosine-5'-triphosphate (ATP) and hypochlorite ion (ClO-) emerge as novel biomarkers, reflecting mitochondrial dysfunction and amplified oxidative stress, respectively. However, the dynamic fluctuations of ATP and ClO- in hepatocytes and mouse livers remain unclear, and multidetection techniques for these biomarkers are yet to be developed. This study presents RATP-NClO, a dual-channel fluorescent bioprobe capable of synchronously detecting ATP and ClO- ions. RATP-NClO exhibits excellent selectivity and sensitivity for ATP and ClO- ions, demonstrating a dual-channel fluorescence response in a murine hepatocyte cell line. Upon intravenous administration, RATP-NClO reveals synchronized ATP depletion and ClO- amplification in the livers of mice with experimental metabolic dysfunction-associated steatohepatitis (MASH). Through a comprehensive analysis of the principal mechanism of the developed bioprobe and the verification of its reliable detection ability in both in vitro and in vivo settings, we propose it as a unique tool for monitoring changes in intracellular ATP and ClO- level. These findings underscore its potential for practical image-based monitoring and functional phenotyping of MASH pathogenesis.

Glycyrrhizinic Acid and Phosphatidylcholine Combination as a Preventive Therapy for Experimental Murine Non-Alcoholic Steatohepatitis

Non-alcoholic metabolic-associated steatohepatitis (MASH) is a condition characterized by increasingly high prevalence and incidence, and also represents an important unmet medical need when it comes to effective pharmacotherapy. In this work, we aimed to explore the therapeutic possibilities of the synergistic combined use of glycyrrhizinic acid (GA) and phosphatidylcholine (PC) to prevent experimental MASH. Adult C57Bl/6 mice were used to model dietary/toxic MASH and treated orally by either GA (34.3 mg/kg/d) or a GA + PC combination (34.3 + 158.1 mg/kg/d) for 3 months. Animal locomotion, behaviour, short-term memory, physical performance, neuromuscular joint function, blood biochemistry, and oxidative stress marker levels were evaluated, followed by histological examination of the liver, skeletal muscle and sciatic nerve with tissue ammonia and lipid content determination. Real-time polymerase chain reaction was used to measure the relative expression of several pathogenetic transcript markers. GA and PC showed moderate additive synergism in their anti-inflammatory, antioxidant, hypoammonaemic, hypoglycaemic, and pro-cognitive activities. Differential effects of the agents were seen in regard to anxiety- and depression-like behaviour as well as gene expression. Our results indicate partial pharmacological synergism between GA and PC and validate further research of its potential clinical applications.

Sestrin2 maintains hepatic immune homeostasis and redox balance partially via inhibiting RIPK3-mediated necroptosis in metabolic dysfunction-associated steatohepatitis

Background & aimsNecroptosis, a novel type of programmed cell death, is intricately associated with inflammatory response. Currently, most studies focus on the activation of necroptosis, while the mechanisms underlying the negative regulation of necroptosis remain poorly understood. MethodsThe effects of sestrin2 (SESN2) overexpression or knockdown on the regulation of necroptosis were assessed in the TNFα/Smac-mimetic/Z-VAD-FMK (T/S/Z)-induced necroptosis model and palmitic acid (PA)-induced lipotoxicity model. Western-blot, co-Immunoprecipitation, Glutathione S-transferase pull-down, and confocal assays were employed to explore the regulatory mechanisms including protein–protein interactions and post-translational modification. Furthermore, we used GSK'872, a specific inhibitor of receptor-interacting serine/threonine-protein kinase (RIPK) 3, to evaluate the relationship between SESN2-related alterations and RIPK3-mediated necroptosis in T/S/Z-induced necroptosis model, PA-induced lipotoxicity model, and high-fat high-cholesterol diet (HFHCD)-induced non-alcoholic steatohepatitis model. ResultsOur findings revealed that SESN2 was upregulated under conditions that induce necroptosis and functioned as a negative regulator of necroptosis. High levels of SESN2 could equipped hepatocytes with the ability to defend against necroptotic inflammation and oxidative stress. Mechanistically, SESN2 interacted with RIPK3 and tuned down necroptosis by inhibiting the phosphorylation of RIPK3, promoting the ubiquitination of RIPK3, and preventing the formation of the RIPK1/RIPK3 necrosome. The depletion of SESN2 resulted in excessive necroptosis, accompanied by increased fat accumulation, inflammation, and oxidative stress in the experimental steatohepatitis model. Blocking necroptosis by GSK’872 reduced the liberation of pro-inflammatory cytokines and reactive oxygen species generation, but not hepatocyte fat deposition, in both PA-treated SESN2 knockout cells and HFHCD-fed SESN2 knockout mice, suggesting that the activation of RIPK3-mediated necroptosis may partially account for the hyperinflammation and excessive oxidative stress induced by SESN2 deficiency. ConclusionOur results suggested that SESN2 inhibited RIPK3-mediated necroptosis; this regulation is an important for the immune homeostasis and the redox balance in the liver.

Role of the co-stimulatory molecule inducible T-cell co-stimulator ligand (ICOSL) in the progression of experimental metabolic dysfunction-associated steatohepatitis.

Inducible T-cell Co-Stimulator (ICOS) present on T-lymphocytes and its ligand ICOSL expressed by myeloid cells play multiple roles in regulating T-cell functions. However, recent evidence indicates that reverse signalling involving ICOSL is also important in directing the differentiation of monocyte-derived cells. In this study, we investigated the involvement of ICOS/ICOSL dyad in modulating macrophage functions during the evolution of metabolic dysfunction-associated steatohepatitis (MASH). In animal models of MASH, ICOS was selectively up-regulated on CD8+ T-cells in parallel with an expansion of ICOSL-expressing macrophages. An increase in circulating soluble ICOSL was also evident in patients with MASH as compared to healthy individuals. ICOSL knockout (ICOSL-/-) mice receiving choline/methionine deficient (MCD) diet for 6 weeks had milder steatohepatitis than wild type mice. MASH improvement was confirmed in mice fed with cholesterol-enriched Western diet for 24 weeks in which ICOSL deficiency greatly reduced liver fibrosis along with the formation of crown-like macrophage aggregates producing the pro-fibrogenic mediators osteopontin (OPN) and galectin-3 (Gal-3). These effects associated with a selective shewing of F4-80+/CD11bhigh monocyte-derived macrophages (MoMFs) expressing the Triggering Receptor Expressed on Myeloid cells 2 (TREM2) to CD11blow/F4-80+ cells positive for the Kupffer cell marker C-type lectin-like type 2 receptor (CLEC-2), thus indicating an increased MoMF maturation toward monocyte-derived Kupffer cells. These results suggest that CD8+ T-cells interaction with monocyte-derived macrophages through ICOS/ICOSL critically supports a specific subset of TREM2+-expressing cells contributing to the evolution of steatohepatitis. The data also point ICOS/ICOSL dyad as a possible target for therapeutic interventions in MASH.

Sex-based differences in natural killer T cell-mediated protection against diet-induced steatohepatitis in Balb/c mice

BackgroundMetabolic dysfunction-associated steatotic liver disease (MASLD) is prevalent in Western countries, evolving into metabolic dysfunction-associated steatohepatitis (MASH) with a sexual dimorphism. Fertile women exhibit lower MASLD risk than men, which diminishes post-menopause. While NKT-cell involvement in steatohepatitis is debated, discrepancies may stem from varied mouse strains used, predominantly C57BL6/J with Th1-dominant responses. Exploration of steatohepatitis, encompassing both genders, using Balb/c background, with Th2-dominant immune response, and CD1d-deficient mice in the Balb/c background (lacking Type I and Type II NKT cells) can clarify gender disparities and NKT-cell influence on MASH progression.MethodsA high fat and choline-deficient (HFCD) diet was used in male and female mice, Balb/c mice or CD1d−/− mice in the Balb/c background that exhibit a Th2-dominant immune response. Liver fibrosis and inflammatory gene expression were measured by qPCR, and histology assessment. NKT cells, T cells, macrophages and neutrophils were assessed by flow cytometry.ResultsFemale mice displayed milder steatohepatitis after 6 weeks of HFCD, showing reduced liver damage, inflammation, and fibrosis compared to males. Male Balb/c mice exhibited NKT-cell protection against steatohepatitis whereas CD1d−/− males on HFCD presented decreased hepatoprotection, increased liver fibrosis, inflammation, neutrophilic infiltration, and inflammatory macrophages. In contrast, the NKT-cell role was negligible in early steatohepatitis development in both female mice, as fibrosis and inflammation were similar despite augmented liver damage in CD1d−/− females. Relevant, hepatic type I NKT levels in female Balb/c mice were significantly lower than in male.ConclusionsNKT cells exert a protective role against experimental steatohepatitis as HFCD-treated CD1d−/− males had more severe fibrosis and inflammation than male Balb/c mice. In females, the HFCD-induced hepatocellular damage and the immune response are less affected by NKT cells on early steatohepatitis progression, underscoring sex-specific NKT-cell influence in MASH development.

Genetic deletion or pharmacologic inhibition of the Nlrp3 inflammasome did not ameliorate experimental NASH

It has been postulated that inflammasomes, in particular the NLRP3 (NLR family pyrin domain containing 3) inflammasome, mediate the necroinflammation and fibrosis that characterize nonalcoholic steatohepatitis (NASH) by engaging innate immune responses. We aimed to investigate the impact of genetic deletion or pharmacologic inhibition of the NLRP3 inflammasome on experimental steatohepatitis. Global Nlrp3 KO (expected to inhibit the NLRP3 inflammasome) or Casp1 KO (expected to inhibit all inflammasomes) mice were compared to wild type controls after 6 months on a high-fat, high-cholesterol (HFHC, 1% cholesterol) diet known to induce fibrosing steatohepatitis. Additionally, wildtype mice on a HFHC diet (0.75% or 0.5% cholesterol) for 6 months were either treated or not treated with an oral, pharmacologic inhibitor of Nlrp3 (MCC950) that was delivered in the drinking water (0.3 mg/ml). We found that genetic deletion or pharmacologic inhibition of the NLRP3 inflammasome did not ameliorate any of the histological components of fibrosing NASH in HFHC-fed mice. Collectively, these results do not support NLRP3 inhibition as a potential target for human NASH.

Myeloid-specific blockade of Notch signaling ameliorates nonalcoholic fatty liver disease in mice.

Rationale: Macrophages play a central role in the development and progression of nonalcoholic fatty liver disease (NAFLD). Studies have shown that Notch signaling mediated by transcription factor recombination signal binding protein for immunoglobulin kappa J region (RBP-J), is implicated in macrophage activation and plasticity. Naturally, we asked whether Notch signaling in macrophages plays a role in NAFLD, whether regulating Notch signaling in macrophages could serve as a therapeutic strategy to treat NAFLD. Methods: Immunofluorescence staining was used to detect the changes of macrophage Notch signaling in the livers of human patients with NAFLD and choline deficient amino acid-defined (CDAA) diet-fed mice. Lyz2-Cre RBP-Jflox or wild-type C57BL/6 male mice were fed with CDAA or high fat diet (HFD) to induce experimental steatohepatitis or steatosis, respectively. Liver histology examinations were performed using hematoxylin-eosin (H&E), Oil Red O staining, Sirius red staining and immunohistochemistry staining for F4/80, Col1α1 and αSMA. The expression of inflammatory factors, fibrosis or lipid metabolism associated genes were evaluated by quantitative reverse transcription (qRT)-PCR, Western blot or enzyme-linked immunosorbent assay (ELISA). The mRNA expression of liver samples was profiled by using RNA-seq. A hairpin-type decoy oligodeoxynucleotides (ODNs) for transcription factor RBP-J was loaded into bEnd.3-derived exosomes by electroporating. Mice with experimental NAFLD were treated with exosomes loading RBP-J decoy ODNs via tail vein injection. In vivo distribution of exosomes was analyzed by fluorescence labeling and imaging. Results: The results showed that Notch signaling was activated in hepatic macrophages in human with NAFLD or in CDAA-fed mice. Myeloid-specific RBP-J deficiency decreased the expression of inflammatory factors interleukin-1 beta (IL1β) and tumor necrosis factor alpha (TNFα), attenuated experimental steatohepatitis in mice. Furthermore, we found that Notch blockade attenuated lipid accumulation in hepatocytes by inhibiting the expression of IL1β and TNFα in macrophages in vitro. Meanwhile, we observed that tail vein-injected exosomes were mainly taken up by hepatic macrophages in mice with steatohepatitis. RBP-J decoy ODNs delivered by exosomes could efficiently inhibit Notch signaling in hepatic macrophages in vivo and ameliorate steatohepatitis or steatosis in CDAA or HFD mice, respectively. Conclusions: Combined, macrophage RBP-J promotes the progression of NAFLD at least partially through regulating the expression of pro-inflammatory cytokines IL1β and TNFα. Infusion of exosomes loaded with RBP-J decoy ODNs might be a promising therapy to treat NAFLD.

Cis-4-[18F]fluoro-L-proline PET/CT molecular imaging quantifying liver collagenogenesis: No existing fibrotic deposition in experimental advanced-stage alcoholic liver fibrosis.

Heavy alcohol drinking-induced alcoholic fatty liver, steatohepatitis, and early-stage alcoholic liver fibrosis may progress to advanced-stage alcoholic liver fibrosis (AALF)/cirrhosis. The lack of non-invasive imaging techniques for the diagnosising collagenogenesis in activated hepatic stellate cells (HSCs) can lead to incurable liver fibrosis at the early reversible stage. Proline has been known as the most abundant amino acid of collagen type 1 synthesized by activated HSC with the transportation of proline transporter. cis-4-[18F]fluoro-L-proline ([18F]proline) was reported as a useful tool to quantify collagenogenesis in experimental alcoholic steatohepatitis. This study aims to use [18F]proline micro PET as non-invasive imaging to quantify liver collagenogenesis in HSC of experimental AALF. AALF model was set up by a modified Lieber-DeCarli liquid ethanol diet for 12 weeks along with intraperitoneal injection (IP) of CCl 4 (0.5 ml/kg) between the 5th and 12th weeks. Controls were fed an isocaloric liquid diet and IP. PBS. In vitro [3H]proline uptake by HSCs isolated from livers was quantified using a liquid scintillation counter. Collagen type 1 production in HSCs culture medium was assayed by ELISA. Ex vivo liver collagen type 1 and proline transporter protein were compared between AALF rats (n = 8) and mice (n = 8). [3H]Proline uptake specificity in ex vivo liver tissues was tested using unlabeled proline and transporter inhibitor benztropine at different doses. Liver H&E, trichrome stain, and blood biochemistry were tested in rats and mice. In vivo, at varying times after instillation, dynamic and static [18F]proline micro PET/CT were done to quantify tracer uptake in AALF mice (n = 3). Correlation among liver collagen, liver SUVmax, normalized liver-to-brain ratio, normalized liver-to-thigh ratio, and fluoro-proline-induced collagen levels in ex vivo liver tissues were analyzed. In vitro HSCs study showed significant higher [3H]proline uptake (23007.9 ± 5089.2 vs. 1075.4 ± 119.3 CPM/mg, p < 0.001) in HSCs isolated from AALF rats than controls and so was collagen type 1 production (24.3 ± 5.8 vs. 3.0 ± 0.62 mg/ml, p < 0.001) in HSCs culture medium. Highly positive correlation between [3H]proline uptake and collagen type 1 by HSCs of AALF rats was found (r value = 0.92, p < 0.01). Ex vivo liver tissue study showed no significant difference in collagen type 1 levels between AALF rats (14.83 ± 5.35 mg/g) and AALF mice (12.91 ± 3.62 mg/g, p > 0.05), so was proline transporter expression between AALF rats (7.76 ± 1.92-fold) and AALF mice (6.80 ± 0.97-fold). Unlabeled fluoro-proline induced generation of liver tissue collagen type 1 and [3H]proline uptake were specifically blocked by transporter inhibitor. In vivo [18F]proline micro PET/CT imaging showed higher SUVmax in liver (4.90 ± 0.91 vs. 1.63 ± 0.38, p < 0.01), higher normalized liver/brain ratio (12.54 ± 0.72 vs. 2.33 ± 0.41, p < 0.01), and higher normalized liver/thigh ratio (6.03 ± 0.78 vs. 1.09 ± 0.09, p < 0.01) in AALF mice than controls, which are all positively correlated with fluoro-proline-induced levels of collagen in liver tissue (r value ≥ 0.93, p < 0.01) in AALF mice, but not correlated with existing liver collagen. Liver histology showed increased collagen in the liver of AALF mice. Blood serum ALT and AST levels were remarkably higher in AALF mice than in controls, but there is no significant difference in blood fibrotic parameters HA, A2M, TGFβ1, and MMP1. [18F]proline micro PET/CT might be useful to visualize collagenogenesis in activated HSC of experimental AALF but fails to quantify existing liver collagen in AALF mice. [18F]proline has the potential sensitivity to assess the activity and severity of liver fibrosis.

Glucagon-like Peptide-1 Receptor-based Therapeutics for Metabolic Liver Disease.

Glucagon-like peptide-1 (GLP-1) controls islet hormone secretion, gut motility, and body weight, supporting development of GLP-1 receptor agonists (GLP-1RA) for the treatment of type 2 diabetes (T2D) and obesity. GLP-1RA exhibit a favorable safety profile and reduce the incidence of major adverse cardiovascular events in people with T2D. Considerable preclinical data, supported by the results of clinical trials, link therapy with GLP-RA to reduction of hepatic inflammation, steatosis, and fibrosis. Mechanistically, the actions of GLP-1 on the liver are primarily indirect, as hepatocytes, Kupffer cells, and stellate cells do not express the canonical GLP-1R. GLP-1RA reduce appetite and body weight, decrease postprandial lipoprotein secretion, and attenuate systemic and tissue inflammation, actions that may contribute to attenuation of metabolic-associated fatty liver disease (MAFLD). Here we discuss evolving concepts of GLP-1 action that improve liver health and highlight evidence that links sustained GLP-1R activation in distinct cell types to control of hepatic glucose and lipid metabolism, and reduction of experimental and clinical nonalcoholic steatohepatitis (NASH). The therapeutic potential of GLP-1RA alone, or in combination with peptide agonists, or new small molecule therapeutics is discussed in the context of potential efficacy and safety. Ongoing trials in people with obesity will further clarify the safety of GLP-1RA, and pivotal studies underway in people with NASH will define whether GLP-1-based medicines represent effective and safe therapies for people with MAFLD.

Effects of aqueous extract of Amorphophallus paeoniifolius tuber in treatment of experimental steatohepatitis

Effects of aqueous extract of Amorphophallus paeoniifolius tuber in treatment of experimental steatohepatitis

Myriocin Treatment Reverses Alcohol-Induced Alterations in Polyunsaturated Fatty Acid-Containing Phospholipid Expression in the Liver.

Chronic heavy alcohol exposure causes steatohepatitis manifested by abnormal intra-hepatocyte accumulation of lipid and parenchymal inflammation. Attendant alterations in polyunsaturated fatty acid (PUFA)-containing phospholipids could cause alcoholic liver disease (ALD) to progress by promoting oxidative stress, inflammation, and fibrogenesis. Previously we showed that myriocin, a serine palmitoyltransferase inhibitor, ameliorates experimental alcohol-induced steatohepatitis. However, the surprising overall therapeutic responses suggested that myriocin’s targets may go beyond sphingolipids. To this end, the present study examines the effects of myriocin on hepatic composition of docosahexaenoic acid (DHA)- and arachidonic acid (AA)-containing phospholipids in an experimental model of ALD. A chronic+binge ethanol exposure model was generated by feeding Long Evans rats with ethanol-containing diets (24% caloric content) for 8 weeks and simultaneously binge gavage administering 2 g/kg ethanol on Tuesdays, Thursdays and Saturdays during Weeks 6-8. Myriocin was administered by i.p. injection on Mondays, Wednesdays, and Fridays of Weeks 3-8. Control rats were studied in parallel. Upon euthanasia, the livers were harvested to examine ethanol- and/or myriocin-modulation of hepatic lipids using matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI-IMS). Results were analyzed statistically by two-way analysis of variance and depicted with data bar plots and heatmaps. Chronic+binge ethanol exposures significantly increased hepatic expression of AA-containing phospholipids including PE(36:4) (P = .005), PE(38:4) (P = .03), and PI(38:4) (P = .04) and reduced DHA-containing phospholipids including PS(40:6) (P = .03) and PE(40:6) (P = .04) relative to control. Myriocin partially reversed ethanol’s effects on hepatic PUFA expression by decreasing PE(36:4) (P = .004) and increasing PS(40:6) (P = .04) and PI(40:6) (P = .0003) relative to ethanol-exposed rats. Ethanol-mediated alterations in hepatic PUFA-containing phospholipids may contribute to hepatic oxidative and inflammatory injury by increasing AA and fibrogenesis by inhibiting DHA. The results suggest that Myriocin may help reduce or prevent long-term and progressive liver injury stemming from excessive chronic+binge ethanol consumption.

Oltipraz ameliorates the progression of steatohepatitis in Nrf2-null mice fed a high-fat diet.

Oltipraz, a synthetic dithiolethione, has chemopreventive effect through nuclear factor erythroid 2-related factor 2 (Nrf2) activation. Nrf2 is known to be involved in the development of experimental steatohepatitis in rodents. In this study, to evaluate the effect of oltipraz on lipid and bile acid metabolism, wild-type and Nrf2-null mice were fed the standard diet (containing 4% soybean oil) with or without oltipraz. Based on these results, we examined the effect of oltipraz on the experimental steatohepatitis in high-fat diet (containing 4% soybean oil and 20% lard) fed Nrf2-null mice. Oltipraz induced hepatic mRNA expression of peroxisome proliferator-activated receptor α, carnitine palmityl transferase 1, and bile salt export pump by Nrf2 independent mechanisms. In Nrf2-null mice fed a high-fat diet for 12 weeks, moderate to severe inflammation and fibrosis were observed. Oral administration of oltipraz suppressed the degree of inflammation and fibrosis in Nrf2-null mouse liver fed a high-fat diet. These histopathological findings approximately corresponded to the data of mRNA expression of tumor necrosis factor α, monocyte chemoattractant protein-1, Timp-1, and collagen type 1α1. These results indicated that oltipraz administration ameliorated liver injury by Nrf2 independent manner in a model of steatohepatitis generated by Nrf2-null mice with high-fat diet.

Inhibition of NOX4 by Cissus quadrangularis extract protects from Type 2 diabetes induced-steatohepatitis

BackgroundCissus quadrangularis L. is commonly known as hadjod and traditionally used as a medicinal plant for the treatment of osteoporosis, dyspepsia, tumors, chronic ulcers, and hepatic diseases. Existing studies have proclaimed the proinflammatory property of NOX4 through instigating ROS and oxidative stress, which is considered to be one of the instrumental causes of steatohepatitis. PurposeTo investigate the protective effect of ethanolic extract of C. quadrangularis (EECQ) on the steatohepatitis associated with type 2 diabetes (DM) through inhibition of NOX4. MethodsAn experimental DM-induced steatohepatitis was developed by feeding a high-fat diet for 12 weeks in Sprague Dawley rats. Treatment of EECQ was given at a dose of 200 mg/kg (po), for six weeks. Glucose and insulin tolerance test was conducted. Hematoxylin and eosin and picrosirius red staining of liver sections was done. Steatosis and lobular inflammation were scored, and hepatocyte ballooning was assessed to confirm the NASH. qPCR, Immunofluorescence, and Immunoblotting determined the mRNA and protein expression of NOX4. ResultsNASH group rats manifested features of DM, marked by aggravated glucose and insulin tolerance tests. Moreover, the DM rats exhibited the presence of steatohepatitis, characterized by elevated serum lipid content, aminotransferases, and presence of steatosis, lobular inflammation, and ballooning in the liver section. Nevertheless, EECQ treatment prevented all of these abnormalities. Besides, the level of AGEs and the expression of its receptor, RAGE was found to be increased in DM rats. Parallelly, the expression of NOX4 and the accompanying level of ROS, oxidative stress markers, and inflammatory cytokines were determined to be surged in palmitic acid exposed HepG2 cells and DM rats. However, EECQ treatment exemplified safeguards from the soared level of the aforementioned markers. ConclusionCollectively, the above findings propounded the protective effect of EECQ against steatohepatitis. Nonetheless, further studies on humans necessitate to scrutinize and reinforce its therapeutic potential so that it may be employed as a remedy for DM-induced steatohepatitis.

Oscillating lncRNA Platr4 regulates NLRP3 inflammasome to ameliorate nonalcoholic steatohepatitis in mice

Background: Understanding the molecular events and mechanisms underlying development and progression of nonalcoholic steatohepatitis is essential in an attempt to formulating a specific treatment. Here, we uncover Platr4 as an oscillating and NF-κB driven lncRNA that is critical to the pathological conditions in experimental steatohepatitisMethods: RNA-sequencing of liver samples was used to identify differentially expressed lncRNAs. RNA levels were analyzed by qPCR and FISH assays. Proteins were detected by immunoblotting and ELISA. Luciferase reporter, ChIP-sequencing and ChIP assays were used to investigate transcriptional gene regulation. Protein interactions were evaluated by Co-IP experiments. The protein-RNA interactions were studied using FISH, RNA pull-down and RNA immunoprecipitation analysesResults: Cyclic expression of Platr4 is generated by the core clock component Rev-erbα via two RevRE elements (i.e., -1354/-1345 and -462/-453 bp). NF-κB transcriptionally drives Platr4 through direct binding to two κB sites (i.e., -1066/-1056 and -526/-516 bp), potentially accounting for up-regulation of Platr4 in experimental steatohepatitis. Intriguingly, Platr4 serves as a circadian repressor of Nlrp3 inflammasome pathway by inhibiting NF-κB-dependent transcription of the inflammasome components Nlrp3 and Asc. Loss of Platr4 down-regulates Nlrp3 inflammasome activity in the liver, blunts its diurnal rhythm, and sensitizes mice to experimental steatohepatitis, whereas overexpression of Platr4 ameliorates the pathological conditions in an Nlrp3-dependent manner. Mechanistically, Platr4 prevents binding of the NF-κB/Rxrα complex to the κB sites via a physical interaction, thereby inhibiting the transactivation of Nlrp3 and Asc by NF-κB.Conclusions: Platr4 functions to inactivate Nlrp3 inflammasome via intercepting NF-κB signaling. This lncRNA might be an attractive target that can be modulated to ameliorate the pathological conditions of steatohepatitis.

Astaxanthin Attenuates Hepatic Damages and Mitochondrial Dysfunction in Nonalcoholic Fatty Liver Disease by Regulating the FGF21/PGC-1α Pathway

Introduction: Non-alcoholic fatty liver disease(NAFLD) is considered to be one of the most common chronic liver diseases across worldwide. Inflammation, cell apoptosis and fibrogenesis are all typical lipotoxicity-associated changes during NAFLD. Beneficial effects of astaxanthin(Ax) have been identified,including anti-oxidative, anti-inflammatory, and anti-tumor activity. The present study aimed to elucidate the protective effect of Ax against NAFLD and its underlying mechanism. Method: Mice were fed either a high fat or control diet, with or without AX, for up to 12 weeks. L02 cells were treated with free fatty acids combined with different doses of Ax for 48 h. Histopathology, expression of lipid metabolism, inflammation, apoptosis, and fibrosis-related genes were assessed. Results: The results indicated that Ax attenuated HFD- and FFA-induced lipid accumulation and its associated oxidative stress, cell apoptosis, inflammation, and fibrosis both in vivo and in vitro. Ax upregulated FGF21 and PGC-1α expression in damaged hepatocytes, which suggested an unrecognized mechanism of Ax on ameliorating NAFLD. Conclusions: Ax prevented hepatic triglyceride accumulation,and attenuated hepatocyte damage and mitochondrial dysfunction.And Ax decreased the severity of experimental steatohepatitis via mechanisms likely to involve the up-regulation of FGF21/PGC-1α.

TXNIP/VDUP1 attenuates steatohepatitis via autophagy and fatty acid oxidation

ABSTRACT Impaired macroautophagy/autophagy has been implicated in experimental and human nonalcoholic steatohepatitis (NASH). However, the mechanism underlying autophagy dysregulation in NASH is largely unknown. Here, we investigated the role and mechanism of TXNIP/VDUP1 (thioredoxin interacting protein), a key mediator of cellular stress responses, in the pathogenesis of NASH. Hepatic TXNIP expression was upregulated in nonalcoholic fatty liver disease (NAFLD) patients and in methionine choline-deficient (MCD) diet-fed mice, as well as in palmitic acid (PA)-treated hepatocytes. Upregulation of hepatic TXNIP was positively correlated with impaired autophagy, as evidenced by a decreased number of MAP1LC3B/LC3B (microtubule-associated protein 1 light chain 3 beta) puncta and increased SQSTM1/p62 (sequestosome 1) expression. Deletion of the Txnip gene enhanced hepatic steatosis, inflammation, and fibrosis, accompanied by impaired autophagy and fatty acid oxidation (FAO) in MCD diet-fed mice. Mechanistically, TXNIP directly interacted with and positively regulated p-PRKAA, leading to inactivation of MTOR (mechanistic target of rapamycin kinase) complex 1 (MTORC1) and nuclear translocation of TFEB (transcription factor EB), which in turn promoted autophagy. Inhibition of MTORC1 by rapamycin induced autophagy and increased the expression levels of FAO-related genes and concomitantly attenuated lipid accumulation in PA-treated txnip-knockout (KO) hepatocytes, which was further abolished by silencing of Atg7. Rapamycin treatment also attenuated MCD diet-induced steatosis, inflammation, and fibrosis with increased TFEB nuclear translocation and restored FAO in txnip-KO mice. Our findings suggest that elevated TXNIP ameliorates steatohepatitis by interacting with PRKAA and thereby inducing autophagy and FAO. Targeting TXNIP may be a potential therapeutic approach for NASH. Abbreviations: ACOX1: acyl-Coenzyme A oxidase 1, palmitoyl; ACSL1: acyl-CoA synthetase long-chain family member 1; ACTA2/α-SMA: actin, alpha 2, smooth muscle, aorta; ACTB: actin beta; ADGRE1/F4/80: adhesion G protein-coupled receptor E1; AMPK: AMP-activated protein kinase; ATG: autophagy-related; BafA1: bafilomycin A1; COL1A1/Col1α1: collagen, type I, alpha 1; CPT1A: carnitine palmitoyltransferase 1a, liver; CQ: chloroquine; DGAT1: diacylglycerol O-acyltransferase 1; DGAT2: diacylglycerol O-acyltransferase 2; ECI2/Peci: enoyl-Coenzyme A isomerase 2; EHHADH: enoyl-Coenzyme A, hydratase/3-hydroxyacyl Coenzyme A dehydrogenase; FAO: fatty acid oxidation; FASN: fatty acid synthase; FFA: free fatty acids; GFP: green fluorescent protein; GK/GYK: glycerol kinase; GOT1/AST: glutamic-oxaloacetic transaminase 1, soluble; GPAM: glycerol-3-phosphate acyltransferase, mitochondrial; GPT/ALT: glutamic pyruvic transaminase, soluble; H&E: hematoxylin and eosin; IL1B/IL-1β: interleukin 1 beta; IL6: interleukin 6; IOD: integral optical density; KO: knockout; Leu: leupeptin; LPIN1: lipin 1; MAP1LC3B/LC3B: microtubule-associated protein 1 light chain 3 beta; MCD: methionine choline-deficient; MMP9: matrix metallopeptidase 9; mRNA: messenger RNA; MTORC1: mechanistic target of rapamycin kinase complex 1; NAFLD: nonalcoholic fatty liver diseases; NASH: nonalcoholic steatohepatitis; PA: palmitic acid; PPARA/PPARα: peroxisome proliferator activated receptor alpha; PPARG/PPARγ: peroxisome proliferator activated receptor gamma; qRT-PCR: quantitative real-time PCR; RPS6KB1/p70S6K1: ribosomal protein S6 kinase, polypeptide 1; RPTOR: regulatory associated protein of MTOR complex 1; SCD1: stearoyl-Coenzyme A desaturase 1; SEM: standard error of the mean; siRNA: small interfering RNA; SQSTM1/p62: sequestosome 1; TFEB: transcription factor EB; TG: triglyceride; TGFB/TGF-β: transforming growth factor, beta; TIMP1: tissue inhibitor of metalloproteinase 1; TNF/TNF-α: tumor necrosis factor; TXNIP/VDUP1: thioredoxin interacting protein; WT: wild-type

Naringin ameliorates type 2 diabetes mellitus-induced steatohepatitis by inhibiting RAGE/NF-κB mediated mitochondrial apoptosis

AimsRecent findings have instituted the role of hyperglycemia-related AGE/RAGE and NF-κB in instigating reactive oxygen species (ROS) mediated mitochondrial dysfunction and apoptosis of hepatocyte, which leads to steatohepatitis. Naringin, a flavanone glycoside found to possess myriads of pharmacological benefits along with its antioxidant and anti-inflammatory properties. Consequently, we aimed to decipher the effect of naringin on RAGE/NF-κB mediated mitochondrial apoptosis in type 2 diabetes mellitus (T2DM)-induced steatohepatitis. Main methodsHepatic HepG2 cells were cultured in palmitic acid medium with and without naringin. Lipid content was examined by Oil Red O and Nile Red staining. Cellular apoptosis was determined by Annexin V-FITC/PI staining. An experimental T2DM-induced steatohepatitis was developed in Sprague Dawley rats by high-fat diet (HFD) for 12 weeks. The naringin was administrated orally at a dose of 100 mg/kg, daily for eight weeks. Glucose and insulin tolerance test was performed. Liver sections were stained by hematoxylin-eosin and picrosirius red. The mRNA and protein expression of RAGE and NF-κB were determined by qPCR, Immunofluorescence, and Immunoblotting. Mitochondrial membrane potential (MMP), cellular and mitochondrial ROS were measured by FACS. Key findingsPalmitic acid encountered HepG2 cells and HFD fed rats exhibited hyperlipidemia, insulin resistance, abnormal aminotransferases, steatosis, and fibrosis. Besides, the level of AGEs, RAGE, NF-κB, and oxidative stress were exacerbated. Moreover, MMP, cellular and mitochondrial ROS were altered in diabetic rats. Nevertheless, the naringin treatment ameliorated the steatohepatitis by improving the levels of aforementioned parameters. SignificanceCollectively, these findings suggested anti-steatohepatitis potential of naringin in diabetics.

Differential effects of selective- and pan-PPAR agonists on experimental steatohepatitis and hepatic macrophages☆

Peroxisome proliferator-activated receptors (PPARs) are essential regulators of whole-body metabolism, but also modulate inflammation in immune cells, notably macrophages. We compared the effects of selective PPAR agonists to those of the pan-PPAR agonist lanifibranor in non-alcoholic fatty liver disease (NAFLD), and studied isoform-specific effects on hepatic macrophage biology. Lanifibranor or selective PPARα (fenofibrate), PPARγ (pioglitazone) and PPARδ (GW501516) agonists were therapeutically administered in choline-deficient, amino acid-defined high-fat diet (CDAA-HFD)- and Western diet (WD)-fed mouse models of NAFLD. Acute liver injury was induced by carbon tetrachloride (CCl4). The role of PPARs on macrophage functionality was studied in isolated hepatic macrophages, bone marrow-derived macrophages stimulated with palmitic acid, and circulating monocytes from patients with NAFLD. Lanifibranor improved all histological features of steatohepatitis in CDAA-HFD-fed mice, including liver fibrosis, thereby combining and exceeding specific effects of the single PPAR agonists. Its potent anti-steatotic efficacy was confirmed in a 3D liver biochip model with primary cells. Infiltrating hepatic monocyte-derived macrophages were reduced following PPAR agonist administration, especially with lanifibranor, even after short-term treatment, paralleling improved steatosis and hepatitis. Lanifibranor similarly decreased steatosis, liver injury and monocyte infiltration in the WD model. In the acute CCl4 model, neither single nor pan-PPAR agonists directly affected monocyte recruitment. Hepatic macrophages isolated from WD-fed mice displayed a metabolically activated phenotype. Lanifibranor attenuated the accompanying inflammatory activation in both murine palmitic acid-stimulated bone marrow-derived macrophages, as well as patient-derived circulating monocytes, in a PPARδ-dependent fashion. Pan-PPAR agonists combine the beneficial effects of selective PPAR agonists and may counteract inflammation and disease progression more potently. PPARδ agonism and lanifibranor directly modulate macrophage activation, but not infiltration, thereby synergizing with beneficial metabolic effects of PPARα/γ agonists. Peroxisome proliferated-activated receptors (PPARs) are essential regulators of metabolism and inflammation. We demonstrated that the pan-PPAR agonist lanifibranor ameliorated all aspects of non-alcoholic fatty liver disease in independent experimental mouse models. Non-alcoholic fatty liver disease and fatty acids induce a specific polarization status in macrophages, which was altered by lanifibranor to increase expression of lipid handling genes, thereby decreasing inflammation. PPAR isoforms have differential therapeutic effects on fat-laden hepatocytes, activated hepatic stellate cells and inflammatory macrophages, supporting the clinical development of pan-PPAR agonists.

The SGLT2 inhibitor dapagliflozin attenuates the activity of ROS-NLRP3 inflammasome axis in steatohepatitis with diabetes mellitus.

Diabetes mellitus (DM) is considered as a risk factor for the progress of liver diseases. After tissue damage, there is the highest amplitude of ubiquitously sterile inflammatory response in the liver, resulting in a major clinical consequence concerning a high prevalence of steatohepatitis in DM patients. This study aimed to investigate the inhibitory efficacy of dapagliflozin (DAPA), a sodium glucose cotransporter-2 (SGLT2) inhibitor, on experimental steatohepatitis with DM. DM-steatohepatitis model was established by dual intraperitoneal injection of streptozotocin (STZ) and feeding with the high-fat diet (HFD) in apolipoprotein E-deficient (ApoE-/-) mice (n=40). The mice were concurrently treated with DAPA (1 mg/kg/d) by gavage for 12 weeks. In ApoE-/- mice, dual HFD/STZ dramatically induced hepatic damage and inflammation as compared with HFD alone. DAPA treatment was effective to protect from hepatic damage and inflammation in dual HFD/STZ treated ApoE-/- mice. DAPA also significantly the probability decreased the blood glucose, hepatic lipid accumulation, liver steatosis, and fibrotic response in dual HFD/STZ treated ApoE-/- mice. Further mechanistic investigations indicated that the protection of DAPA on diabetic liver injury was associated with the suppressed production of hepatic reactive oxygen species (ROS) and malondialdehyde (MDA) and the inhibited activation of NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome. These data demonstrate the efficacy of DAPA for protecting liver damage, inflammation and steatosis from experimental steatohepatitis with DM, and indicate a possible involvement of the inhibited activity of ROS-NLRP3 inflammasome.

Effect of angiolin on the functional state of the liver in experimental steatohepatitis

For a real impact on the functional state of the liver in steatohepatitis, the appointment of metabolic correctors is suggested. The aim of the study is to evaluate the effect of the biologically active compound angiolin on markers of cytolysis and liver function in experimental nonalcoholic steatohepatitis. Experimental studies were performed on 110 white, non-linear, mature male rats weighing 180–200 g at the start of the experiment. A model of non-alcoholic steatohepatitis was created, rats were maintained for 8 weeks on a high-calorie, high-cholesterol diet. After creating the model some of the animals were transferred to a standard semi-synthetic starch-casein diet and administered for 4 weeks the biologically active compound Angiolin. The activity of enzyme markers of cytolysis — alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma-glutamyltranspeptidase (GGT) in serum was determined by standard methods. Liver biosynthetic function was assessed by the level of total protein and albumin. Statistical analysis of the obtained results was carried out with the use of the license program “STATISTICA 8” by Statsoft. After creating a model of non-alcoholic fatty liver disease in rats, an increase in body mass index occurred, high activity of ALT, AST, GGT was manifested and the concentration of total protein and albumin in the blood serum decreased compared to intact animals. An inverse correlation of mean strength was found between body mass index and total protein concentration as well as serum albumin. A strong inverse correlation between the value of ALT activity and the concentration of total protein and albumin in blood serum was established. The use of angiolin contributed to an increase in the concentration of total protein and albumin in the blood serum, an increase in the albumin / globulin coefficient, and a decrease in cytolysis. It was concluded that the biologically active compound angiolin positively affects the parameters of cytolysis and protein synthesis of the liver.