ERK Pathway in Activated, Myofibroblast-Like, Hepatic Stellate Cells: A Critical Signaling Crossroad Sustaining Liver Fibrosis. Int J Mol Sci. 2019;20. [PMID: 31159366 PMCID: PMC6600376 DOI: 10.3390/ijms20112700]

Production and activity of matrix metalloproteinases during liver fibrosis progression of chronic hepatitis C patients

BACKGROUND

Matrix metalloproteinases (MMPs) participate in the degradation of extracellular matrix compounds, maintaining the homeostasis between fibrogenesis and fibrolytic processes in the liver. However, there are few studies on the regulation of liver MMPs in fibrosis progression in humans.

AIM

To assess the production activity and regulation of matrix metalloproteinases in liver fibrosis stages in chronic hepatitis C (CHC).

METHODS

A prospective, cross-sectional, multicenter study was conducted. CHC patients were categorized in fibrosis grades through FibroTest^®and/or FibroScan^®. Serum MMP-2, -7, and -9 were determined by western blot and multiplex suspension array assays. Differences were validated by the Kruskal-Wallis and Mann-Whitney U tests. The Spearman correlation coefficient and area under the receiver operating characteristic curve were calculated. Collagenolytic and gelatinase activity was determined through the Azocoll substrate and zymogram test, whereas tissue inhibitor of metalloproteinase-1 production was determined by dot blot assays.

RESULTS

Serum concentrations of the MMPs evaluated were higher in CHC patients than in healthy subjects. MMP-7 distinguished early and advanced stages, with a correlation of 0.32 (P < 0.001), and the area under the receiver operating characteristic displayed moderate sensitivity and specificity for MMP-7 in F4 (area under the receiver operating characteristic, 0.705; 95% confidence interval: 0.605-0.805; P < 0.001). Collagenolytic activity was detected at F0 and F1, whereas gelatinase activity was not detected at any fibrosis stage. Tissue inhibitor of metalloproteinase-1 determination showed upregulation in F0 and F1 but downregulation in F2 (P < 0.001).

CONCLUSION

High concentrations of inactive MMPs were present in the serum of CHC patients, reflecting the impossibility to restrain liver fibrosis progression. MMPs could be good diagnostic candidates and therapeutic targets for improving novel strategies to reverse liver fibrosis in CHC.

Propolis in Metabolic Syndrome and Its Associated Chronic Diseases: A Narrative Review

Propolis is a resinous product collected by bees from plants to protect and maintain the homeostasis of their hives. Propolis has been used therapeutically by humans for centuries. This review article attempts to analyze the potential use of propolis in metabolic syndrome (MetS) and its associated chronic diseases. MetS and its chronic diseases were shown to be involved in at least seven out of the top 10 causes of death in 2019. Patients with MetS are also at a heightened risk of severe morbidity and mortality in the present COVID-19 pandemic. Propolis with its antioxidant and anti-inflammatory properties is potentially useful in ameliorating the symptoms of MetS and its associated chronic diseases. The aim of this article is to provide a comprehensive review on propolis and its therapeutic benefit in MetS and its chronic diseases, with an emphasis on in vitro and in vivo studies, as well as human clinical trials. Moreover, the molecular and biochemical mechanisms of action of propolis are also discussed. Propolis inhibits the development and manifestation of MetS and its chronic diseases by inhibiting of the expression and interaction of advanced glycation end products (AGEs) and their receptors (RAGEs), inhibiting pro-inflammatory signaling cascades, and promoting the cellular antioxidant systems.

Function of Mitogen-Activated Protein Kinases in Hepatic Inflammation

The western diet and overuse of anti-inflammatory medication have caused a great deal of stress on the liver. Obesity and the associated inflammatory state in insulin-responsive tissues result in the release of pro-inflammatory cytokine that activates the stress-responsive MAPKs, p38 MAPK, and JNK. These MAPKs have figured prominently as critical effectors in physiological and pathophysiological hepatic inflammation. In contrast, evidence for a role for ERK1/2 in hepatic inflammation has been less well developed. In this review article, we describe recent insights into the physiology and pathophysiology of the role of stress-responsive MAPKs in hepatic inflammation during obesity and liver injury with a focus on macrophages, hepatocytes and hepatic stellate cells. In response to metabolic stress and liver injury, JNK activation in macrophages and hepatocytes promotes the secretion of inflammatory cytokines and macrophage and neutrophil infiltration. p38 MAPK plays an important role in contributing to the progression of hepatic inflammation in response to various hepatic cellular stresses, although the precise substrates mediating these effects in hepatocytes and hepatic stellate cells remain to be identified. Both JNK and p38 MAPK promotes profibrotic behavior in hepatic stellate cells.

Deletion of KLF10 Leads to Stress-Induced Liver Fibrosis upon High Sucrose Feeding

Liver fibrosis is a consequence of chronic liver injury associated with chronic viral infection, alcohol abuse, and nonalcoholic fatty liver. The evidence from clinical and animal studies indicates that transforming growth factor-β (TGF-β) signaling is associated with the development of liver fibrosis. Krüppel-like factor 10 (KLF10) is a transcription factor that plays a significant role in TGF-β-mediated cell growth, apoptosis, and differentiation. In recent studies, it has been reported to be associated with glucose homeostasis and insulin resistance. In the present study, we investigated the role of KLF10 in the progression of liver disease upon a high-sucrose diet (HSD) in mice. Wild type (WT) and Klf10 knockout (KO) mice were fed either a control chow diet or HSD (50% sucrose) for eight weeks. Klf10 KO mice exhibited significant hepatic steatosis, inflammation, and liver injury upon HSD feeding, whereas the WT mice exhibited mild hepatic steatosis with no apparent liver injury. The livers of HSD-fed Klf10 KO mice demonstrated significantly increased endoplasmic reticulum stress, oxidative stress, and proinflammatory cytokines. Klf10 deletion led to the development of sucrose-induced hepatocyte cell death both in vivo and in vitro. Moreover, it significantly increased fibrogenic gene expression and collagen accumulation in the liver. Increased liver fibrosis was accompanied by increased phosphorylation and nuclear localization of Smad3. Here, we demonstrate that HSD-fed mice develop a severe liver injury in the absence of KLF10 due to the hyperactivation of the endoplasmic reticulum stress response and CCAAT/enhance-binding protein homologous protein (CHOP)-mediated apoptosis of hepatocytes. The current study suggests that KLF10 plays a protective role against the progression of hepatic steatosis into liver fibrosis in a lipogenic state.

Paeoniflorin modulates oxidative stress, inflammation and hepatic stellate cells activation to alleviate CCl4-induced hepatic fibrosis by upregulation of heme oxygenase-1 in mice

OBJECTIVES

The role of Paeoniflorin on hepatic fibrosis and the specific mechanisms has not yet been elucidated. Therefore, we explored whether Paeoniflorin exerted protective effects on carbon tetrachloride (CCl4)-induced hepatic fibrosis and the underlying mechanisms.

METHODS

A model of hepatic fibrosis was induced by intraperitoneally injecting with CCl4 (10% 5 μl/g) twice a week for 7 weeks. To explore the effects of Paeoniflorin, mice were treated with Paeoniflorin (100 mg/kg) by gavage once a day at 1 week after modeling until they were sacrificed.

KEY FINDINGS

Paeoniflorin remarkably improved liver function and histopathological changes of hepatic tissues in CCl4-induced liver injury. Besides, the serum MAO enzyme activity and hydroxyproline contents were notably decreased following the intervention of Paeoniflorin. The decreased expression of Vimentin, α-SMA, Col1a and Desmin manifested the inhibition of the hepatic stellate cells (HSCs) activation. Interestingly, Paeoniflorin intervention significantly upregulated the expression of heme oxygenase-1, and attenuated the inflammatory cytokines production as well as the CCl4-induced oxidative stress imbalance.

CONCLUSIONS

Paeoniflorin could effectively alleviate CCl4-induced hepatic fibrosis by upregulation of heme oxygenase-1, and it might be a new effective option for the comprehensive treatment of hepatic fibrosis.

The role of neutrophil extracellular traps and TLR signaling in skeletal muscle ischemia reperfusion injury

Ischemia reperfusion (IR) injury results in devastating skeletal muscle fibrosis. Here, we recapitulate this injury with a mouse model of hindlimb IR injury which leads to skeletal muscle fibrosis. Injury resulted in extensive immune infiltration with robust neutrophil extracellular trap (NET) formation in the skeletal muscle, however, direct targeting of NETs via the peptidylarginine deiminase 4 (PAD4) mechanism was insufficient to reduce muscle fibrosis. Circulating levels of IL-10 and TNFα were significantly elevated post injury, indicating toll-like receptor (TLR) signaling may be involved in muscle injury. Administration of hydroxychloroquine (HCQ), a small molecule inhibitor of TLR7/8/9, following injury reduced NET formation, IL-10, and TNFα levels and ultimately mitigated muscle fibrosis and improved myofiber regeneration following IR injury. HCQ treatment decreased fibroadipogenic progenitor cell proliferation and partially inhibited ERK1/2 phosphorylation in the injured tissue, suggesting it may act through a combination of TLR7/8/9 and ERK signaling mechanisms. We demonstrate that treatment with FDA-approved HCQ leads to decreased muscle fibrosis and increased myofiber regeneration following IR injury, suggesting short-term HCQ treatment may be a viable treatment to prevent muscle fibrosis in ischemia reperfusion and traumatic extremity injury.

Chemical Components and Hepatoprotective Mechanism of Xwak Granule in Mice Treated with Acute Alcohol

Objective

To evaluate the hepatoprotective mechanism of Xwak granule (Xwak) in treatment of mice with alcoholic liver injury via activating ERK/NF-κB and Nrf/HO-1 signaling pathways.

Methods

The chemical composition of Xwak was tested by liquid chromatography coupled with mass spectrometry (LC-MS). Herein, 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging assay and 2,2-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid (ABTS) radical tests were performed in vitro. The hepatoprotective effect of Xwak was assessed at different concentrations (1.5, 3, and 6 g/kg) in a mouse model of alcoholic liver injury.

Results

Totally, 48 compounds, including 16 flavonoids, 8 tannins, 9 chlorogenic acids, and 15 other compounds, were identified from Xwak. Xwak showed to have a satisfactory antioxidant activity in vitro. In a group of Xwak-treated mice, the serum levels of alanine transaminase (ALT), aspartate transaminase (AST), and alkaline phosphatase (ALP) were decreased compared with a group of the mouse model of alcoholic liver injury. In addition, the levels of antioxidant enzymes, such as glutathione peroxidase (GSH-PX), total superoxide dismutase (T-SOD), and catalase (CAT), were noticeably increased and the levels of malondialdehyde (MDA), tumor necrosis factor-α (TNF-α), transforming growth factor-β (TGF-β), and interleukin-6 (IL-6) were markedly reduced in the liver of mice. The state of oxidative stress in the mouse model of alcoholic liver injury was improved after treatment with Xwak. The improvement of inflammation-mediated disruption may conducive to the Xwak activity in the control of liver injury. The signals of p-ERK1/2, p-NF-κB, COX-2, iNOS, CYP2E1, Nrf, and HO-1 were significantly induced in the liver of mice after treatment with Xwak.

Conclusions

The abovementioned findings indicated that the hepatoprotective mechanism of Xwak could be achieved by activating ERK/NF-κB and Nrf/HO-1 signaling pathways to alleviate oxidative stress and inflammatory.

The HSP90 Inhibitor, AUY-922, Ameliorates the Development of Nitrogen Mustard-Induced Pulmonary Fibrosis and Lung Dysfunction in Mice

Increased levels of heat shock protein 90 (HSP90) have been recently implicated in the pathogenesis of pulmonary fibrosis and the use of HSP90 inhibitors constitutes a potential therapeutic approach. Similarly, acute exposure to nitrogen mustard (NM) is related to the development of chronic lung injury driven by TNF-α, TGF-β, ERK and HSP90. Thus, we developed a murine model of NM-induced pulmonary fibrosis by instilling C57BI/6J mice with 0.625 mg/kg mechlorethamine hydrochloride. After 24 h, mice began receiving AUY-922, a second generation HSP90 inhibitor, at 1 mg/kg 2 times per week or 2 mg/kg 3 times per week, for either 10 or 30 days. AUY-922 suppressed the NM-induced sustained inflammation, as reflected in the reduction of leukocyte and protein concentrations in bronchoalveolar lavage fluid (BALF), and inhibited the activation of pro-fibrotic biomarkers, ERK and HSP90. Furthermore, AUY-922 maintained normal lung function, decreased the overexpression and accumulation of extracellular matrix proteins, and dramatically reduced histologic evidence of fibrosis in the lungs of mice exposed to NM. The HSP90 inhibitor, AUY-922, successfully blocked the adverse effects associated with acute exposures to NM, representing a promising approach against NM-induced pulmonary fibrosis.

The Potentiality of Herbal Remedies in Primary Sclerosing Cholangitis: From In Vitro to Clinical Studies

Primary sclerosing cholangitis is a complex pathological condition, characterized by chronic inflammation and fibrosis of the biliary epithelium. Without proper clinical management, progressive bile ducts and liver damage lead to cirrhosis and, ultimately, to liver failure. The known limited role of current drugs for treating this cholangiopathy has driven researchers to assess alternative therapeutic options. Some herbal remedies and their phytochemicals have shown anti-fibrotic properties in different experimental models of hepatic diseases and, occasionally, in clinical trials in primary sclerosing cholangitis patients; however their mechanism of action is not completely understood. This review briefly examines relevant studies focusing on the potential anti-fibrotic properties of Silybum marianum, Curcuma longa, Salvia miltiorrhiza, and quercetin. Each natural product is individually reviewed and the possible mechanisms of action discussed.

Gan Shen Fu Fang ameliorates liver fibrosis in vitro and in vivo by inhibiting the inflammatory response and extracellular signal-regulated kinase phosphorylation

BACKGROUND

Liver fibrosis is a common health problem worldwide and there is still a lack of effective medicines. The Chinese herbal medicine, Gan Shen Fu Fang (GSFF) is composed of salvianolic acid B and diammonium glycyrrhizinate. In this study, we observed the effects of GSFF on liver fibrosis in vivo and in vitro in an attempt to provide some hope for the treatment.

AIM

To observe the effects of GSFF on liver fibrosis in vivo and in vitro and investigate the mechanism from the perspective of the inflammatory response and extracellular signal-regulated kinase (ERK) phosphorylation.

METHODS

Common bile duct-ligated rats were used for in vivo experiments. Hepatic stellate cells-T6 (HSC-T6) cells were used for in vitro experiments. Hematoxylin and eosin staining and Masson staining, biochemical assays, hydroxyproline (Hyp) assays, enzyme-linked immunoasorbent assay and western blotting were performed to evaluate the degree of liver fibrosis, liver function, the inflammatory response and ERK phosphorylation. The CCK8 assay, immunofluorescence and western blotting were applied to test the effect of GSFF on HSC-T6 cell activation and determine whether GSFF had an effect on ERK phosphorylation in HSC-T6 cells.

RESULTS

GSFF improved liver function and inhibited liver fibrosis in common bile duct-ligated rats after 3 wk of treatment, as demonstrated by histological changes, hydroxyproline assays and collagen I concentrations. GSFF alleviated inflammatory cell infiltration and reduced the synthesis of pro-inflammatory cytokines [tumor necrosis factor-α (TNF-α) and interlukin-1β] and NF-κB. In addition, GSFF decreased ERK phosphorylation. In vitro, GSFF inhibited the viability of HSC-T6 cells with and without transforming growth factor β1 (TGF-β1) stimulation and decreased the synthesis of collagen I. GSFF had the greatest effect at a concentration of 0.5 μmol/L. GSFF inhibited the expression of α-smooth muscle actin (α-SMA), a marker of HSC activation, in HSC-T6 cells. Consistent with the in vivo results, GSFF also inhibited the phosphorylation of ERK and downregulated the expression of NF-κB.

CONCLUSION

GSFF inhibited liver fibrosis progression in vivo and HSC-T6 cell activation in vitro. These effects may be related to an alleviated inflammatory response and downregulated ERK phosphorylation.

Liver Fibrosis and Inflammation under the Control of ERK2

Chronic liver injury could lead the formation of liver fibrosis, eventually some would develop to hepatocellular carcinoma (HCC), one of the leading malignancies worldwide. The aim of the study is to dissect the role of extracellular signal-regulated kinase 2 (ERK2) signaling in liver fibrosis and inflammation. The choline-deficient, ethionine-supplemented (CDE) diet could lead to fatty livers and generate oval cells, activate hepatocyte stellate cell (HSC) and recruit immune cells as the liver fibrosis model mice. WT and ERK2 deficient (ERK2^−/−) mice were compared in terms of liver weight/body weight, liver function, liver fibrosis markers and the differential gene expression in hepatotoxicity. ERK2^−/− mice display the less degree of liver fibrosis when compared to WT mice. The protein level of alpha smooth muscle (α-SMA) was reduced and several hepatocellular carcinoma-related genes such as MMP9, FoxM1 were down-regulated. In addition, the cell proliferation and the percentages of activated T cells were reduced in ERK2^−/− mice upon liver injury. Therefore, ERK2 plays an important role in regulating liver cirrhosis and inflammation.

Blocking CTGF/CCN2 reduces established skeletal muscle fibrosis in a rat model of overuse injury

Tissue fibrosis is a hallmark of overuse musculoskeletal injuries and contributes to functional declines. We tested whether inhibition of CCN2 (cellular communication network factor 2, previously known as connective tissue growth factor, CTGF) using a specific antibody (termed FG‐3019 or pamrevlumab) reduces established overuse‐induced muscle fibrosis in a clinically relevant rodent model of upper extremity overuse injury. Young adult rats performed a high repetition high force (HRHF) reaching and lever‐pulling task for 18 weeks, after first being shaped for 6 weeks to learn this operant task. Rats were then euthanized (HRHF‐Untreated), or rested and treated for 6 weeks with FG‐3019 (HRHF‐Rest/FG‐3019) or a human IgG as a vehicle control (HRHF‐Rest/IgG). HRHF‐Untreated and HRHF‐Rest/IgG rats had higher muscle levels of several fibrosis‐related proteins (TGFβ1, CCN2, collagen types I and III, and FGF2), and higher muscle numbers of alpha SMA and pERK immunopositive cells, compared to control rats. Each of these fibrogenic changes was restored to control levels by the blocking of CCN2 signaling in HRHF‐Rest/FG‐3019 rats, as were HRHF task‐induced increases in serum CCN2 and pro‐collagen I intact N‐terminal protein. Levels of cleaved CCN3, an antifibrotic protein, were lowered in HRHF‐Untreated and HRHF‐Rest/IgG rats, compared to control rats, yet elevated back to control levels in HRHF‐Rest/FG‐3019 rats. Significant grip strength declines observed in HRHF‐Untreated and HRHF‐Rest/IgG rats, were restored to control levels in HRHF‐Rest/FG‐3019 rats. These results are highly encouraging for use of FG‐3019 for therapeutic treatment of persistent skeletal muscle fibrosis, such as those induced with chronic overuse.

Integrative Analysis of Proteomics and DNA Methylation in Orbital Fibroblasts From Graves' Ophthalmopathy

BACKGROUND

Graves' ophthalmopathy (GO) is a frequent extrathyroidal complication of Graves' hyperthyroidism. Orbital fibroblasts contribute to both orbital tissue inflammation and remodeling in GO, and as such are crucial cellular elements in active GO and inactive GO. However, so far it is largely unknown whether GO disease progression is associated with functional reprogramming of the orbital fibroblast effector function. Therefore, the aim of this study was to compare both the proteome and global DNA methylation patterns between orbital fibroblasts isolated from active GO, inactive GO and healthy controls.

METHODS

Orbital fibroblasts from inactive GO (n=5), active GO (n=4) and controls (n=5) were cultured and total protein and DNA was isolated. Labelled and fractionated proteins were analyzed with a liquid chromatography tandem-mass spectrometer (LC-MS/MS). Data are available via ProteomeXchange with identifier PXD022257. Furthermore, bisulphite-treated DNA was analyzed for methylation pattern with the Illumina Infinium Human Methylation 450K beadchip. In addition, RNA was isolated from the orbital fibroblasts for real-time quantitative (RQ)-PCR. Network and pathway analyses were performed.

RESULTS

Orbital fibroblasts from active GO displayed overexpression of proteins that are typically involved in inflammation, cellular proliferation, hyaluronan synthesis and adipogenesis, while various proteins associated with extracellular matrix (ECM) biology and fibrotic disease, were typically overexpressed in orbital fibroblasts from inactive GO. Moreover, orbital fibroblasts from active GO displayed hypermethylation of genes that linked to inflammation and hypomethylated genes that linked to adipogenesis and autoimmunity. Further analysis revealed networks that contained molecules to which both hypermethylated and hypomethylated genes were linked, including NF-κB, ERK1/2, Alp, RNA polymerase II, Akt and IFNα. In addition, NF-κB, Akt and IFNα were also identified in networks that were derived from the differentially expressed proteins. Generally, poor correlation between protein expression, DNA methylation and mRNA expression was observed.

CONCLUSIONS

Both the proteomics and DNA methylation data support that orbital fibroblasts from active GO are involved in inflammation, adipogenesis, and glycosaminoglycan production, while orbital fibroblasts from inactive disease are more skewed towards an active role in extracellular matrix remodeling. This switch in orbital fibroblast effector function may have therapeutic implications and further studies into the underlying mechanism are thus warranted.