Targeted therapy of liver fibrosis/cirrhosis and its complications

Separation Methods of Phenolic Compounds from Plant Extract as Antioxidant Agents Candidate

In recent years, discovering new drug candidates has become a top priority in research. Natural products have proven to be a promising source for such discoveries as many researchers have successfully isolated bioactive compounds with various activities that show potential as drug candidates. Among these compounds, phenolic compounds have been frequently isolated due to their many biological activities, including their role as antioxidants, making them candidates for treating diseases related to oxidative stress. The isolation method is essential, and researchers have sought to find effective procedures that maximize the purity and yield of bioactive compounds. This review aims to provide information on the isolation or separation methods for phenolic compounds with antioxidant activities using column chromatography, medium-pressure liquid chromatography, high-performance liquid chromatography, counter-current chromatography, hydrophilic interaction chromatography, supercritical fluid chromatography, molecularly imprinted technologies, and high-performance thin layer chromatography. For isolation or purification, the molecularly imprinted technologies represent a more accessible and more efficient procedure because they can be applied directly to the extract to reduce the complicated isolation process. However, it still requires further development and refinement.

Berberine prevents NAFLD and HCC by modulating metabolic disorders

Non-alcoholic fatty liver disease (NAFLD) is a global metabolic disease with high prevalence in both adults and children. Importantly, NAFLD is becoming the main cause of hepatocellular carcinoma (HCC). Berberine (BBR), a naturally occurring plant component, has been demonstrated to have advantageous effects on a number of metabolic pathways as well as the ability to kill liver tumor cells by causing cell death and other routes. This permits us to speculate and make assumptions about the value of BBR in the prevention and defense against NAFLD and HCC by a global modulation of metabolic disorders. Herein, we briefly describe the etiology of NAFLD and NAFLD-related HCC, with a particular emphasis on analyzing the potential mechanisms of BBR in the treatment of NAFLD from aspects including increasing insulin sensitivity, controlling the intestinal milieu, and controlling lipid metabolism. We also elucidate the mechanism of BBR in the treatment of HCC. More significantly, we provided a list of clinical studies for BBR in NAFLD. Taking into account our conclusions and perspectives, we can make further progress in the treatment of BBR in NAFLD and NAFLD-related HCC.

Chinese herbal medicines: The modulator of nonalcoholic fatty liver disease targeting oxidative stress

ETHNOPHARMACOLOGICAL RELEVANCE

Plants are a natural treasure trove; their secondary metabolites participate in several pharmacological processes, making them a crucial component in the synthesis of novel pharmaceuticals and serving as a reserve resource foundation in this process. Nonalcoholic fatty liver disease (NAFLD) is associated with the risk of progression to hepatitis and liver cancer. The "Treatise on Febrile Diseases," "Compendium of Materia Medica," and "Thousand Golden Prescriptions" have listed herbal remedies to treat liver diseases.

AIM OF THE REVIEW

Chinese herbal medicines have been widely used for the prevention and treatment of NAFLD owing to their efficacy and low side effects. The production of reactive oxygen species (ROS) during NAFLD, and the impact and potential mechanism of ROS on the pathogenesis of NAFLD are discussed in this review. Furthermore, common foods and herbs that can be used to prevent NAFLD, as well as the structure-activity relationships and potential mechanisms, are discussed.

METHODS

Web of Science, PubMed, CNKI database, Google Scholar, and WanFang database were searched for natural products that have been used to treat or prevent NAFLD in the past five years. The primary search was performed using the following keywords in different combinations in full articles: NAFLD, herb, natural products, medicine, and ROS. More than 400 research papers and review articles were found and analyzed in this review.

RESULTS

By classifying and discussing the literature, we obtained 86 herbaceous plants, 28 of which were derived from food and 58 from Chinese herbal medicines. The mechanism of NAFLD was proposed through experimental studies on thirteen natural compounds (quercetin, hesperidin, rutin, curcumin, resveratrol, epigallocatechin-3-gallate, salvianolic acid B, paeoniflorin, ginsenoside Rg1, ursolic acid, berberine, honokiol, emodin). The occurrence and progression of NAFLD could be prevented by natural antioxidants through several pathways to prevent ROS accumulation and reduce hepatic cell injuries caused by excessive ROS.

CONCLUSION

This review summarizes the natural products and routinely used herbs (prescription) in the prevention and treatment of NAFLD. Firstly, the mechanisms by which natural products improve NAFLD through antioxidant pathways are elucidated. Secondly, the potential of traditional Chinese medicine theory in improving NAFLD is discussed, highlighting the safety of food-medicine homology and the broader clinical potential of multi-component formulations in improving NAFLD. Aiming to provide theoretical basis for the prevention and treatment of NAFLD.

Galectin-3 and Severity of Liver Fibrosis in Metabolic Dysfunction-Associated Fatty Liver Disease

Metabolic dysfunction-associated Fatty Liver Disease (MAFLD) is a chronic liver disease characterized by the accumulation of fat in the liver and hepatic steatosis, which can progress to critical conditions, including Metabolic dysfunction-associated Steatohepatitis (MASH), liver fibrosis, hepatic cirrhosis, and hepatocellular carcinoma. Galectin-3, a member of the galectin family of proteins, has been involved in cascades that are responsible for the pathogenesis and progression of liver fibrosis in MAFLD. This review summarizes the present understanding of the role of galectin-3 in the severity of MAFLD and its associated liver fibrosis. The article assesses the underlying role of galectin-3-mediated fibrogenesis, including the triggering of hepatic stellate cells, the regulation of extracellular degradation, and the modulation of immune reactions and responses. It also highlights the assessments of the potential diagnostic and therapeutic implications of galectin-3 in liver fibrosis during MAFLD. Overall, this review provides insights into the multifaceted interaction between galectin-3 and liver fibrosis in MAFLD, which could lead to the development of novel strategies for diagnosis and treatment of this prevalent liver disease.

Serum vitamin D is associated with ultrasound-defined hepatic fibrosis

BACKGROUND

Evidences from population-based investigations on the exact relationship between vitamin D and the severity of liver fibrosis remain debated and conflicting. Here, we aim to explore the relationship between serum vitamin D and ultrasound-defined advanced hepatic fibrosis in the US participants with nonalcoholic fatty liver disease (NAFLD).

METHODS

In the retrospective study, individuals with intact information on interesting variables from the 2017-2018 National Health and Nutrition Examination Survey (NHANES) were included. NAFLD was diagnosed on the basis of controlling attenuation parameter (CAP) value≥ 274 dB/m without causes of other chronic hepatic diseases. We identified advanced fibrosis grades (F2) by liver stiffness measurement (LSM) score of ≥ 8.2 kPa in NAFLD patients. The impact of elevated serum vitamin D on the prevalence of hepatic fibrosis was assessed by multivariate logistic regression models on the basis of the NHANES recommended weights.

RESULTS

The study involved 1624 subjects with NAFLD in total, and 305 (18.28 %, weighted%) of whom were diagnosed with advanced hepatic fibrosis according to the definition based on parameters obtained from vibration controlled transient elastography (VCTE). In the multivariate logistic regression analysis, serum vitamin D presented a negative relationship to hepatic fibrosis with lower odds in patients with hepatic steatosis after being adjusted for potential confounding factors (fully adjusted: OR=0.47, 95 % CI: 0.24-0.90, p = 0.034). Our subgroup analysis revealed that the inverse relationship was still existed in males (fully adjusted: OR = 0.34, 95 % CI: 0.17-0.70, p = 0.014), non-obese subjects (fully adjusted: OR = 0.20, 95 % CI: 0.04-0.89, p = 0.042) and participants below 60 years (fully adjusted: OR = 0.43, 95 % CI: 0.21-0.90, p = 0.033), whereas in models adjusted for the potential confounding factors, no statistically significant correlation was noted in females, obese subjects or subjects with age≥ 60 years.

CONCLUSIONS

This large population-based investigation indicated that elevated serum vitamin D reduced the onset of advanced fibrosis diagnosed by ultrasound in males, non-obese subjects and younger participants with NAFLD.

Isolation and Biological Evaluation of Alfa-Mangostin as Potential Therapeutic Agents against Liver Fibrosis

The increased proliferation and activation of hepatic stellate cells (HSCs) are associated with liver fibrosis development. To date, there are no FDA-approved drugs for the treatment of liver cirrhosis. Augmentation of HSCs apoptosis is one of the resolutions for liver fibrosis. In this study, we extracted α-mangostin (1,3,6-trihydroxy-7-methoxy-2,8-bis(3-methyl-2-butenyl)-9H-xanthen-9-one) from the fruit waste components of mangosteen pericarp. The isolated α-mangostin structure was determined and characterized with nuclear magnetic resonance (NMR) and high-resolution mass spectrometry (HRMS) and compared with those known compounds. The intracellular signaling pathway activities of α-mangostin on Transforming growth factors-beta 1 (TGF-β1) or Platelet-derived growth factor subunit B (PDGF-BB) induced HSCs activation and were analyzed via Western blot and Real-time Quantitative Polymerase Chain Reaction (Q-PCR). α-Mangostin-induced mitochondrial dysfunction and apoptosis in HSCs were measured by seahorse assay and caspase-dependent cleavage. The in vivo anti-fibrotic effect of α-mangostin was assessed by carbon tetrachloride (CCl4) treatment mouse model. The data showed that α-mangostin treatment inhibited TGF-β1-induced Smad2/3 phosphorylation and alpha-smooth muscle actin (α-SMA) expression in HSCs in a dose-dependent manner. Regarding the PDGF-BB-induced HSCs proliferation signaling pathways, α-mangostin pretreatment suppressed the phosphorylation of extracellular-signal-regulated kinase (ERK) and p38. The activation of caspase-dependent apoptosis and dysfunction of mitochondrial respiration (such as oxygen consumption rate, ATP production, and maximal respiratory capacity) were observed in α-mangostin-treated HSCs. The CCl4-induced liver fibrosis mouse model showed that the administration of α-mangostin significantly decreased the expression of the fibrosis markers (α-SMA, collagen-a2 (col1a2), desmin and matrix metalloproteinase-2 (MMP-2)) as well as attenuated hepatic collagen deposition and liver damage. In conclusion, this study demonstrates that α-mangostin attenuates the progression of liver fibrosis through inhibiting the proliferation of HSCs and triggering apoptosis signals. Thus, α-mangostin may be used as a potential novel therapeutic agent against liver fibrosis.

Pharmacological modulation of ferroptosis as a therapeutic target for liver fibrosis

Liver fibrosis, which is characterized by the excessive deposition of extracellular matrix (ECM) materials (primarily fibrillar collagen-I), is an abnormal repair reaction and pathological outcome of chronic liver diseases caused by alcohol abuse, non-alcoholic fatty liver disease, and chronic hepatitis B and C virus infections. Liver fibrosis often progresses to liver cirrhosis and hepatocellular carcinoma. Ferroptosis, characterized by lipid peroxidation, is a form of iron-dependent non-apoptotic cell death, and recent studies have reported that ferroptosis contribute to the development of liver fibrosis. Moreover, several agents have demonstrated therapeutic effects in experimental liver fibrosis models by inducing hepatic stellate cell (HSCs) ferroptosis. This review delineates the specific mechanism by which ferroptosis contributes to the development of liver fibrosis. Specifically, we focused on the different types of therapeutic agents that can induce HSCs ferroptosis and summarize their pharmacological effectiveness for liver fibrosis treatment. We suggest that HSCs ferroptosis may be a potential useful target of novel therapies for preventing and treating liver fibrosis.

Hepatic Stellate Cell Targeting Using Peptide-Modified Biologicals

Liver diseases are a leading cause of death worldwide and are rising exponentially due to increasing prevalence of metabolic disorders. Hepatic stellate cells (HSCs) are recognized as a key therapeutic target in liver diseases as these cells, upon activation during liver damage and ongoing liver inflammation, secrete excessive amounts of extracellular matrix that leads to liver tissue scarring (fibrosis) responsible for liver dysfunction (end-stage liver disease) and desmoplasia in hepatocellular carcinoma. Targeting of HSCs to reverse fibrosis progression has been realized by several experts in the field, including us. We have developed strategies to target activated HSCs by utilizing the receptors overexpressed on the surface of activated HSCs. One well-known receptor is platelet derived growth factor receptor-beta (PDGFR-β). Using PDGFR-β recognizing peptides (cyclic PPB or bicyclic PPB), we can deliver biologicals, e.g., interferon gamma (IFNγ) or IFNγ activity domain (mimetic IFNγ), to the activated HSCs that can inhibit their activation and reverse liver fibrosis. In this chapter, we provide the detailed methods and the principles involved in the synthesis of these targeted (mimetic) IFNγ constructs. These methods can be adapted for synthesizing constructs for targeted/cell-specific delivery of peptides/proteins, drugs, and imaging agents useful for various applications including diagnosis and treatment of inflammatory and fibrotic diseases and cancer.

Clodronate-nintedanib-loaded exosome-liposome hybridization enhances the liver fibrosis therapy by inhibiting Kupffer cell activity

Liver fibrosis therapy remains limited due to the inefficiency of drug delivery and inflammation induced by Kupffer cells. In this study, an exosome-liposome hybrid drug delivery system (LIEV) was developed to increase the efficacy of clodronate (CLD)-inhibition of Kupffer cells and to effectively deliver nintedanib (NIN) to liver fibroblasts to ensure enhanced anti-fibrosis therapy. CLD and NIN co-loaded LIEV (CLD/NIN@LIEV) exerted non-specific inhibition of phagocytosis by Kupffer cells, reduced inflammatory cytokines, and showed homologous homing properties mediated by fibroblast-derived exosomes, thereby achieving superior antifibrotic effects in a CCl4-induced fibrosis mouse model by inhibiting the proliferation of fibroblasts. Furthermore, the inhibited Kupffer cells regenerated within 10 days after dosage withdrawal. Unlike carrier-free NIN treatment, CLD/NIN@LIEV induced a marked decrease in liver enzymes, indicating improved safety and anti-fibrosis efficacy. These results indicate its great potential for treatment with the combined anti-fibrosis agent and Kupffer cell inhibition strategies to enhance the liver fibrosis therapy.

Drug Targeting and Nanomedicine: Lessons Learned from Liver Targeting and Opportunities for Drug Innovation

Drug targeting and nanomedicine are different strategies for improving the delivery of drugs to their target. Several antibodies, immuno-drug conjugates and nanomedicines are already approved and used in clinics, demonstrating the potential of such approaches, including the recent examples of the DNA- and RNA-based vaccines against COVID-19 infections. Nevertheless, targeting remains a major challenge in drug delivery and different aspects of how these objects are processed at organism and cell level still remain unclear, hampering the further development of efficient targeted drugs. In this review, we compare properties and advantages of smaller targeted drug constructs on the one hand, and larger nanomedicines carrying higher drug payload on the other hand. With examples from ongoing research in our Department and experiences from drug delivery to liver fibrosis, we illustrate opportunities in drug targeting and nanomedicine and current challenges that the field needs to address in order to further improve their success.

Oxidative Stress Is a Key Modulator in the Development of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease worldwide, and scientific studies consistently report that NAFLD development can be accelerated by oxidative stress. Oxidative stress can induce the progression of NAFLD to NASH by stimulating Kupffer cells, hepatic stellate cells, and hepatocytes. Therefore, studies are underway to identify the role of antioxidants in the treatment of NAFLD. In this review, we have summarized the origins of reactive oxygen species (ROS) in cells, the relationship between ROS and NAFLD, and have discussed the use of antioxidants as therapeutic agents for NAFLD.

SIRT3 protects bovine mammary epithelial cells from heat stress damage by activating the AMPK signaling pathway

With global warming, heat stress has become an important challenge for the global dairy industry. Sirtuin 3 (SIRT3), an important mitochondrial NAD+dependent decarboxylase and a major regulator of cellular energy metabolism and antioxidant defense, is integral to maintaining normal mitochondrial function. The aim of this study was to assess the protective effect of SIRT3 on damage to bovine mammary epithelial cells (BMECs) induced by heat stress and to explore its potential mechanism. Our results indicate that SIRT3 is significantly downregulated in heat-stressed mammary tissue and high-temperature-treated BMECs. SIRT3 knockdown significantly increased the expression of HSP70, Bax, and cleaved-caspase 3 and inhibited the production of antioxidases, thus promoting ROS production and cell apoptosis in BMECs. In addition, SIRT3 knockdown can aggravate mitochondrial damage by mediating the expression of genes related to mitochondrial fission and fusion, including dynamin-related protein 1, mitochondrial fission 1 protein, and mitochondrial fusion proteins 1and 2. In addition, SIRT3 knockdown substantially decreased AMPK phosphorylation in BMECs. In contrast, SIRT3 overexpression in high-temperature treatment had the opposite effect to SIRT3 knockdown in BMECs. SIRT3 overexpression reduced mitochondrial damage and weakened the oxidative stress response of BMECs induced by heat stress and promoted the phosphorylation of AMPK. Taken together, our results indicate that SIRT3 can protect BMECs from heat stress damage through the AMPK signaling pathway. Therefore, the reduction of oxidative stress by SIRT3 may be the primary molecular mechanism underlying resistance to heat stress in summer cows.

Targeting cell-intrinsic metabolism for antifibrotic therapy

In recent years, there have been major advances in our understanding of the mechanisms underlying fibrosis progression and regression, and how coordinated interactions between parenchymal and non-parenchymal cells impact on the fibrogenic process. Recent studies have highlighted that metabolic reprogramming of parenchymal cells, immune cells (immunometabolism) and hepatic stellate cells is required to support the energetic and anabolic demands of phenotypic changes and effector functions. In this review, we summarise how targeting cell-intrinsic metabolic modifications of the main fibrogenic cell actors may impact on fibrosis progression and we discuss the antifibrogenic potential of metabolically targeted interventions.

Drug delivery nanosystems targeted to hepatic ischemia and reperfusion injury

Hepatic ischemia and reperfusion injury (IRI) is an acute inflammatory process that results from surgical interventions, such as liver resection surgery or transplantation, or hemorrhagic shock. This pathology has become a severe clinical issue, due to the increasing incidence of hepatic cancer and the high number of liver transplants. So far, an effective treatment has not been implemented in the clinic. Despite its importance, hepatic IRI has not attracted much interest as an inflammatory disease, and only a few reviews addressed it from a therapeutic perspective with drug delivery nanosystems. In the last decades, drug delivery nanosystems have proved to be a major asset in therapy because of their ability to optimize drug delivery, either by passive or active targeting. Passive targeting is achieved through the enhanced permeability and retention (EPR) effect, a main feature in inflammation that allows the accumulation of the nanocarriers in inflammation sites, enabling a higher efficacy of treatment than conventional therapies. These systems also can be actively targeted to specific compounds, such as inflammatory markers and overexpressed receptors in immune system intermediaries, allowing an even more specialized therapy that have already showed encouraging results. In this manuscript, we review drug delivery nanosystems designed for hepatic IRI treatment, addressing their current state in clinical trials, discussing the main hurdles that hinder their successful translation to the market and providing some suggestions that could potentially advance their clinical translation.

Progress in drug delivery system for fibrosis therapy

Fibrosis is a necessary process in the progression of chronic disease to cirrhosis or even cancer, which is a serious disease threatening human health. Recent studies have shown that the early treatment of fibrosis is turning point and particularly important. Therefore, how to reverse fibrosis has become the focus and research hotspot in recent years. So far, the considerable progress has been made in the development of effective anti-fibrosis drugs and targeted drug delivery. Moreover, the existing research results will lay the foundation for more breakthrough delivery systems to achieve better anti-fibrosis effects. Herein, this review summaries anti-fibrosis delivery systems focused on three major organ fibrotic diseases such as liver, pulmonary, and renal fibrosis accompanied by the elaboration of relevant pathological mechanisms, which will provide inspiration and guidance for the design of fibrosis drugs and therapeutic systems in the future.

Serine Protease HtrA2/Omi Deficiency Impairs Mitochondrial Homeostasis and Promotes Hepatic Fibrogenesis via Activation of Hepatic Stellate Cells

The loss of mitochondrial function impairs intracellular energy production and potentially results in chronic liver disease. Increasing evidence suggests that mitochondrial dysfunction in hepatocytes contributes to the activation of hepatic stellate cells (HSCs), thereby resulting in hepatic fibrogenesis. High-temperature requirement protein A2 (HtrA2/Omi), a mitochondrial serine protease with various functions, is responsible for quality control in mitochondrial homeostasis. However, little information is available regarding its role in mitochondrial damage during the development of liver fibrosis. This study examined whether HtrA2/Omi regulates mitochondrial homeostasis in hepatocyte during the development of hepatic fibrogenesis. In this study, we demonstrated that HtrA2/Omi expression considerably decreased in liver tissues from the CCl₄-induced liver fibrotic mice model and from patients with liver cirrhosis. Knockdown of HtrA2/Omi in hepatocytes induced the accumulation of damaged mitochondria and provoked mitochondrial reactive oxygen species (mtROS) stress. We further show that the damaged mtDNA isolated from HtrA2/Omi-deficient hepatocytes as a form of damage-associated molecular patterns can induce HSCs activation. Moreover, we found that motor neuron degeneration 2-mutant mice harboring the missense mutation Ser276Cys in the protease domain of HtrA2/Omi displayed altered mitochondrial morphology and function, which increased oxidative stress and promoted liver fibrosis. Conversely, the overexpression of HtrA2/Omi via hydrodynamics-based gene transfer led to the antifibrotic effects in CCl₄-induced liver fibrosis mice model through decreasing collagen accumulation and enhancing anti-oxidative activity by modulating mitochondrial homeostasis in the liver. These results suggest that suppressing HtrA2/Omi expression promotes hepatic fibrogenesis via modulating mtROS generation, and these novel mechanistic insights involving the regulation of mitochondrial homeostasis by HtrA2/Omi may be of importance for developing new therapeutic strategies for hepatic fibrosis.

Dahuang Zhechong Pill suppresses colorectal cancer liver metastasis via ameliorating exosomal CCL2 primed pre-metastatic niche

ETHNOPHARMACOLOGICAL RELEVANCE

Dahuang Zhechong Pill (DZP) is a classical formula from "Synopsis of Prescriptions of the Golden Chamber". It has been used for treatment of abdominal masses (including tumorous diseases) for thousands of years.

AIM OF THE STUDY

Our previous work showed that DZP suppresses CCl-4 induced hepatic fibrosis by downregulating the expression of interleukin-13. We aimed to test if DZP suppresses the metastasis of colorectal cancer (CRC) by ameliorating the fibrosis status of the future metastatic organ.

MATERIALS AND METHODS

Liver metastasis was observed by injection of MC38-EGFP cells with stably expressing enhanced green fuorescence protein beneath the splenic capsule of C57BL/6J mice. MC38-EGFP-derived exosomes were analyzed by Label-free comparative proteomics. mRNA expression was determined by Quantitative PCR. Protein expression was determined by immunohistochemistry, immunofuorescence and Western blot. Collagen deposition was determined by Masson staining. All data were statistically analyzed using SPSS.

RESULTS

DZP drastically reduced the metastatic tumor number and fluorescence intensity in a splenic liver metastasis model. It also lowered the expression of mature TGF-β1 and decreased the fibronectin contents & collagen deposition. Exosome proteomics showed that the upregualted CC chemokine ligand-2 (CCL2) was repressed by DZP treatment. Importantly, DZP markedly lowered the expression of CCL2 and its receptor CCR2 in the liver. Exosomal CCL2 activated macrophage recruitment and shifted the M1/M2 paradigm to a M2 phenotype. DZP reduced the macrophage infiltration and attenuated the M2 polarizaion in tumor-bearing mice liver. It decreased the F4/80 positive areas and specifically reduced the ratio of CCR2⁺ positive macrophage. Anti-fibrosis and inhibition of CCR2 suppress the growth and metastasis of CRC.

CONCLUSIONS

DZP inhibits the liver metastasis of CRC by suppressing CCL2 mediated M2-skewing paradigm and ameliorating the pro-fibrotic microenvironment.

Liver Macrophages: Old Dogmas and New Insights

Inflammation is a hallmark of virtually all liver diseases, such as liver cancer, fibrosis, nonalcoholic steatohepatitis, alcoholic liver disease, and cholangiopathies. Liver macrophages have been thoroughly studied in human disease and mouse models, unravelling that the hepatic mononuclear phagocyte system is more versatile and complex than previously believed. Liver macrophages mainly consist of liver‐resident phagocytes, or Kupffer cells (KCs), and bone marrow‐derived recruited monocytes. Although both cell populations in the liver demonstrate principal functions of macrophages, such as phagocytosis, danger signal recognition, cytokine release, antigen processing, and the ability to orchestrate immune responses, KCs and recruited monocytes retain characteristic ontogeny markers and remain remarkably distinct on several functional aspects. While KCs dominate the hepatic macrophage pool in homeostasis (“sentinel function”), monocyte‐derived macrophages prevail in acute or chronic injury (“emergency response team”), making them an interesting target for novel therapeutic approaches in liver disease. In addition, recent data acquired by unbiased large‐scale techniques, such as single‐cell RNA sequencing, unraveled a previously unrecognized complexity of human and murine macrophage polarization abilities, far beyond the old dogma of inflammatory (M1) and anti‐inflammatory (M2) macrophages. Despite tremendous progress, numerous challenges remain in deciphering the full spectrum of macrophage activation and its implication in either promoting liver disease progression or repairing injured liver tissue. Being aware of such heterogeneity in cell origin and function is of crucial importance when studying liver diseases, developing novel therapeutic interventions, defining macrophage‐based prognostic biomarkers, or designing clinical trials. Growing knowledge in gene expression modulation and emerging technologies in drug delivery may soon allow shaping macrophage populations toward orchestrating beneficial rather than detrimental inflammatory responses.

Liver fibrosis: Direct antifibrotic agents and targeted therapies

Liver fibrosis and in particular cirrhosis are the major causes of morbidity and mortality of patients with chronic liver disease. Their prevention or reversal have become major endpoints in clinical trials with novel liver specific drugs. Remarkable progress has been made with therapies that efficiently address the cause of the underlying liver disease, as in chronic hepatitis B and C. Highly effective antiviral therapy can prevent progression or even induce reversal in the majority of patients, but such treatment remains elusive for the majority of liver patients with advanced alcoholic or nonalcoholic steatohepatitis, genetic or autoimmune liver diseases. Moreover, drugs that would speed up fibrosis reversal are needed for patients with cirrhosis, since even with effective causal therapy reversal is slow or the disease may further progress. Therefore, highly efficient and specific antifibrotic agents are needed that can address advanced fibrosis, i.e., the detrimental downstream result of all chronic liver diseases. This review discusses targeted antifibrotic therapies that address molecules and mechanisms that are central to fibrogenesis or fibrolysis, including strategies that allow targeting of activated hepatic stellate cells and myofibroblasts and other fibrogenic effector cells. Focus is on collagen synthesis, integrins and cells and mechanisms specific including specific downregulation of TGFbeta signaling, major extracellular matrix (ECM) components, ECM-crosslinking, and ECM-receptors such as integrins and discoidin domain receptors, ECM-crosslinking and methods for targeted delivery of small interfering RNA, antisense oligonucleotides and small molecules to increase potency and reduce side effects. With an increased understanding of the biology of the ECM and liver fibrosis and an improved preclinical validation, the translation of these approaches to the clinic is currently ongoing. Application to patients with liver fibrosis and a personalized treatment is tightly linked to the development of noninvasive biomarkers of fibrosis, fibrogenesis and fibrolysis.

The good and the bad collagens of fibrosis - Their role in signaling and organ function

Usually the dense extracellular structure in fibrotic tissues is described as extracellular matrix (ECM) or simply as collagen. However, fibrosis is not just fibrosis, which is already exemplified by the variant morphological characteristics of fibrosis due to viral versus cholestatic, autoimmune or toxic liver injury, with reticular, chicken wire and bridging fibrosis. Importantly, the overall composition of the ECM, especially the relative amounts of the many types of collagens, which represent the most abundant ECM molecules and which centrally modulate cellular functions and physiological processes, changes dramatically during fibrosis progression. We hypothesize that there are good and bad collagens in fibrosis and that a change of location alone may change the function from good to bad. Whereas basement membrane collagen type IV anchors epithelial and other cells in a polarized manner, the interstitial fibroblast collagens type I and III do not provide directional information. In addition, feedback loops from biologically active degradation products of some collagens are examples of the importance of having the right collagen at the right place and at the right time controlling cell function, proliferation, matrix production and fate. Examples are the interstitial collagen type VI and basement membrane collagen type XVIII. Their carboxyterminal propeptides serve as an adipose tissue hormone, endotrophin, and as a regulator of angiogenesis, endostatin, respectively. We provide an overview of the 28 known collagen types and propose that the molecular composition of the ECM in fibrosis needs careful attention to assess its impact on organ function and its potential to progress or reverse. Consequently, to adequately assess fibrosis and to design optimal antifibrotic therapies, we need to dissect the molecular entity of fibrosis for the molecular composition and spatial distribution of collagens and the associated ECM.

SIRT3 protects hepatocytes from oxidative injury by enhancing ROS scavenging and mitochondrial integrity

Evidences of oxidative stress and mitochondrial dysfunction have been recognized in most of clinical and experimental liver diseases. SIRT3, a member of NAD⁺-dependent deacetylases, is mainly localized in mitochondria. So far, the role of SIRT3 in protecting hepatocytes against oxidative stress remains elusive. Herein, we found SIRT3 protein expression is decreased in tert-butyl hydroperoxide (t-BHP)-treated AML12 cells in vitro and primary hepatocytes from CCl₄-injured mice in vivo. To further verify the role of SIRT3 in protecting hepatocytes from t-BHP-induced injury, SIRT3 overexpressed AML12 cell line and primary hepatocytes were generated. SIRT3 overexpressed hepatocytes showed improved cell viability upon t-BHP challenge, with less intracellular reactive oxygen species (ROS) accumulation. SIRT3 overexpression reduced superoxide dismutase 2 acetylation level and stimulated nuclear factor erythroid 2-related factor 2 nuclear translocation to enhance anti-oxidative capacity. Moreover, SIRT3 deacetylated peroxisome proliferator-activated receptor γ coactivator 1α to promote mitochondrial biogenesis, and 8-oxoguanine DNA glycosylase 1 to orchestrate DNA repair, resulting in improved mitochondrial function. Through deacetylating Ku70, SIRT3 also abated mitochondrial translocation of dynamin-related protein 1, to attenuate mitochondrial fragmentation in t-BHP-injured hepatocytes. These results suggested that SIRT3 protected hepatocytes against oxidative stress by enhancing ROS scavenging and maintaining mitochondrial integrity.

Highly Selective Targeting of Hepatic Stellate Cells for Liver Fibrosis Treatment Using a d-Enantiomeric Peptide Ligand of Fn14 Identified by Mirror-Image mRNA Display

Although liver fibrosis is a major public health issue, there is still no effective drug therapy in the clinic. Fibroblast growth factor-inducible 14 (Fn14), a membrane receptor highly specifically expressed in activated hepatic stellate cells (HSCs), is the key driver of liver fibrosis, and thus, it has a great potential as a novel target for the development of effective treatment. Here, we identified a d-enantiomeric peptide ligand of Fn14 through mirror-image mRNA display. This included the chemical synthesis of a d-enantiomer of the target protein (extracellular domain of Fn14), identification of an l-peptide ligand of d-Fn14 using a constructed mRNA peptide library, and identification of a d-enantiomer of the l-peptide, which is a ligand of the natural Fn14 for reasons of symmetry. The obtained d-peptide ligand showed strong binding to Fn14 while maintaining high proteolytic resistance. As a targeting moiety, this d-peptide successfully mediated high selectivity of activated HSCs for liposomal vehicles compared to that of other major cell types in the liver and significantly enhanced the accumulation of liposomes in the liver fibrosis region of a carbon tetrachloride-induced mouse model. Moreover, in combination with curcumin as an encapsulated load, a liposomal formulation conjugated with this d-peptide showed powerful inhibition of the proliferation of activated HSCs and reduced the liver fibrosis to a significant extent in vivo. This Fn14-targeting strategy may represent a promising approach to targeted drug delivery for liver fibrosis treatment. Meanwhile, the mirror-image mRNA display can provide a new arsenal for the development of d-peptide-based therapeutics against a variety of human diseases.

Macrophage Phenotype in Liver Injury and Repair

Macrophages hold a critical position in the pathogenesis of liver injury and repair, in which their infiltrations is regarded as a main feature for both acute and chronic liver diseases. It is noted that, based on the distinct phenotypes and origins, hepatic macrophages are capable of clearing pathogens, promoting/or inhibiting liver inflammation, while regulating liver fibrosis and fibrolysis through interplaying with hepatocytes and hepatic stellate cells (HSC) via releasing different types of pro- or anti-inflammatory cytokines and growth factors. Macrophages are typically categorized into M1 or M2 phenotypes by adapting to local microenvironment during the progression of liver injury. In most occasions, M1 macrophages play a pro-inflammatory role in liver injury, while M2 macrophages exert an anti-inflammatory or pro-fibrotic role during liver repair and fibrosis. In this review, we focused on the up-to-date information about the phenotypic and functional plasticity of the macrophages and discussed the detailed mechanisms through which the phenotypes and functions of macrophages are regulated in different stages of liver injury and repair. Moreover, their roles in determining the fate of liver diseases were also summarized. Finally, the macrophage-targeted therapies against liver diseases were also be evaluated.

Tyrosine kinase inhibitor BIBF1120 ameliorates inflammation, angiogenesis and fibrosis in CCl4-induced liver fibrogenesis mouse model

Hepatic fibrosis, a progressive chronic disease mainly caused by hepatitis viral infections, alcohol abuse or metabolic syndrome leading to liver dysfunction and is the growing cause of mortality worldwide. Tyrosine kinase inhibitor BIBF1120 (Nintedanib) has been evaluated in clinical trials for idiopathic pulmonary fibrosis and advanced Hepatocellular carcinoma, but has not been explored for liver fibrosis yet. In this study, we aimed to investigate the therapeutic effects and mechanism of BIBF1120 in liver fibrogenesis. The effects of BIBF1120 were evaluated in TGFβ-activated mouse 3T3 fibroblasts, LX2 cells, primary human hepatic stellate cells (HSCs) and CCl₄-induced liver fibrogenesis mouse model. Fibroblasts-conditioned medium studies were performed to assess the paracrine effects on macrophages and endothelial cells. In-vitro in TGFβ-activated fibroblasts, BIBF1120 significantly inhibited expression of major fibrotic parameters, wound-healing and contractility. In vivo in CCl₄-induced acute liver injury model, post-disease BIBF1120 administration significantly attenuated collagen accumulation and HSC activation. Interestingly, BIBF1120 drastically inhibited intrahepatic inflammation and angiogenesis. To further elucidate the mechanism of action, 3T3-conditioned medium studies demonstrated increased 3T3-mediated macrophage chemotaxis and endothelial cells tube formation and activation, which was significantly decreased by BIBF1120. These results suggests that BIBF1120 can be a potential therapeutic approach for the treatment of liver fibrosis.

The progenitor cell dilemma: Cellular and functional heterogeneity in assistance or escalation of liver injury

Liver progenitor cells (LPCs) are quiescent cells that are activated during liver injury and thought to give rise to hepatocytes and cholangiocytes in order to support liver regeneration and tissue restitution. While hepatocytes are capable of self-renewal, during most chronic injuries the proliferative capacity of hepatocytes is inhibited, thus LPCs provide main source for regeneration. Despite extensive lineage tracing studies, their role and involvement in these processes are often controversial. Additionally, increasing evidence suggests that the LPC compartment consists of heterogeneous cell populations that are actively involved in cellular interactions with myeloid and lymphoid cells during regeneration. On the other hand, LPC expansion has been associated with an increased fibrogenic response, raising concerns about the therapeutic use of these cells. This review aims to summarize the current understanding of the identity, the cellular interactions and the key pathways affecting the biology of LPCs. Understanding the regulatory circuits and the specific role of LPCs is especially important as it could provide novel therapeutic platforms for the treatment of liver inflammation, fibrosis and regeneration.

Epigenetic regulation of hepatic stellate cell activation and liver fibrosis

Chronic liver injury to hepatocytes or cholangiocytes, when left unmanaged, leads to the development of liver fibrosis, a condition characterized by the excessive intrahepatic deposition of extracellular matrix proteins. Activated hepatic stellate cells constitute the predominant source of extracellular matrix in fibrotic livers and their transition from a quiescent state during fibrogenesis is associated with important alterations in their transcriptional and epigenetic landscape. Areas covered: We briefly describe the processes involved in hepatic stellate cell activation and discuss our current understanding of alterations in the epigenetic landscape, i.e DNA methylation, histone modifications and the functional role of non-coding RNAs that accompany this key event in the development of chronic liver disease. Expert commentary: Although great progress has been made, our understanding of the epigenetic regulation of hepatic stellate cell activation is limited and, thus far, insufficient to allow the development of epigenetic drugs that can selectively interrupt liver fibrosis.

A positive feedback loop between RIP3 and JNK controls non-alcoholic steatohepatitis

Non-alcoholic fatty liver disease (NAFLD) represents the most common liver disease in Western countries and often progresses to non-alcoholic steatohepatitis (NASH) leading ultimately to liver fibrosis and liver cancer. The occurrence of hepatocyte cell death—so far characterized as hepatocyte apoptosis—represents a fundamental step from benign steatosis toward progressive steatohepatitis. In contrast, the function of RIP3-dependent “necroptosis” in NASH and NASH-induced fibrosis is currently unknown. We show that RIP3 is upregulated in human NASH and in a dietary mouse model of steatohepatitis. RIP3 mediates liver injury, inflammation, induction of hepatic progenitor cells/activated cholangiocytes, and liver fibrosis through a pathway suppressed by Caspase-8. This function of RIP3 is mediated by a positive feedback loop involving activation of Jun-(N)-terminal Kinase (JNK). Furthermore, RIP3-dependent JNK activation promotes the release of pro-inflammatory mediators like MCP-1, thereby attracting macrophages to the injured liver and further augmenting RIP3-dependent signaling, cell death, and liver fibrosis. Thus, RIP3-dependent necroptosis controls NASH-induced liver fibrosis. This pathway might represent a novel and specific target for pharmacological strategies in patients with NASH.

Subject Categories Digestive System; Metabolism

Targeted recombinant fusion proteins of IFNγ and mimetic IFNγ with PDGFβR bicyclic peptide inhibits liver fibrogenesis in vivo

Hepatic stellate cells (HSCs), following transdifferentiation to myofibroblasts plays a key role in liver fibrosis. Therefore, attempts to attenuate this myofibroblastic phenotype would be a promising therapeutic approach. Interferon gamma (IFNγ) is a potent anti-fibrotic cytokine, but its pleiotropic receptor expression leading to severe adverse effects has limited its clinical application. Since, activated HSC express high-level of platelet derived growth factor beta receptor (PDGFβR), we investigated the potential of PDGFβR-specific targeting of IFNγ and its signaling peptide that lacks IFNγR binding site (mimetic IFNγ or mimIFNγ) in liver fibrosis. We prepared DNA constructs expressing IFNγ, mimIFNγ or BiPPB (PDGFβR-specific bicyclic peptide)-IFNγ, BiPPB-mimIFNγ fusion proteins. Both chimeric proteins alongwith IFNγ and mimIFNγ were produced in E.coli. The expressed proteins were purified and analyzed for PDGFβR-specific binding and in vitro effects. Subsequently, these recombinant proteins were investigated for the liver uptake (pSTAT1α signaling pathway), for anti-fibrotic effects and adverse effects (platelet counts) in CCl₄-induced liver fibrogenesis in mice. The purified HSC-targeted IFNγ and mimIFNγ fusion proteins showed PDGFβR-specific binding and significantly reduced TGFβ-induced collagen-I expression in human HSC (LX2 cells), while mouse IFNγ and mimIFNγ did not show any effect. Conversely, mouse IFNγ and BiPPB-IFNγ induced activation and dose-dependent nitric oxide release in mouse macrophages (express IFNγR while lack PDGFβR), which was not observed with mimIFNγ and BiPPB-mimIFNγ, due to the lack of IFNγR binding sites. In vivo, targeted BiPPB-IFNγ and BiPPB-mimIFNγ significantly activated intrahepatic IFNγ-signaling pathway compared to IFNγ and mimIFNγ suggesting increased liver accumulation. Furthermore, the targeted fusion proteins ameliorated liver fibrogenesis in mice by significantly reducing collagen and α-SMA expression and potentiating collagen degradation. IFNγ also induced reduction in fibrogenesis but showed significant decrease in platelet counts, which was restored with targeted proteins. These results suggest that these rationally designed proteins can be further developed as novel anti-fibrotic therapeutics.

Interferon gamma peptidomimetic targeted to hepatic stellate cells ameliorates acute and chronic liver fibrosis in vivo

Hepatic stellate cells play a crucial role in the pathogenesis of hepatic fibrosis. Thus, pharmacological inhibition of pro-fibrotic activities of these cells might lead to an effective therapy for this disease. Among the potent anti-fibrotics, interferon gamma (IFNγ), a proinflammatory cytokine, is highly efficacious but it failed in clinical trials due to the poor efficacy and multiple adverse effects attributed to the ubiquitous IFNγ receptor (IFNγR) expression. To resolve these drawbacks, we chemically synthesized a chimeric molecule containing (a) IFNγ signaling peptide (IFNγ peptidomimetic, mimγ) that retains the agonistic activities of IFNγ but lacks an extracellular receptor recognition sequence for IFNγR; coupled via heterobifunctional PEG linker to (b) bicyclic platelet derived growth factor beta receptor (PDGFβR)-binding peptide (BiPPB) to induce internalization into the stellate cells that express PDGFβR. The synthesized targeted IFNγ peptidomimetic (mimγ-BiPPB) was extensively investigated for its anti-fibrotic and adverse effects in acute and chronic CCl4-induced liver fibrosis models in mice. Treatment with mimγ-BiPPB, after the onset of disease, markedly inhibited both early and established hepatic fibrosis as reflected by a reduced intrahepatic α-SMA, desmin and collagen-I mRNA expression and protein levels. While untargeted mimγ and BiPPB had no effect, and native IFNγ only induced a moderate reduction. Additionally, no off-target effects, e.g. systemic inflammation, were found with mimγ-BiPPB, which were substantially observed in mice treated with native IFNγ. The present study highlights the beneficial effects of a novel BiPPB mediated cell-specific targeting of IFNγ peptidomimetic to the disease-inducing cells and therefore represents a highly potential therapeutic approach to treat fibrotic diseases.

Hepatic stellate cell-targeted delivery of hepatocyte growth factor transgene via bile duct infusion enhances its expression at fibrotic foci to regress dimethylnitrosamine-induced liver fibrosis

Liver fibrosis generates fibrotic foci with abundant activated hepatic stellate cells and excessive collagen deposition juxtaposed with healthy regions. Targeted delivery of antifibrotic therapeutics to hepatic stellate cells (HSCs) might improve treatment outcomes and reduce adverse effects on healthy tissue. We delivered the hepatocyte growth factor (HGF) gene specifically to activated hepatic stellate cells in fibrotic liver using vitamin A-coupled liposomes by retrograde intrabiliary infusion to bypass capillarized hepatic sinusoids. The antifibrotic effects of DsRed2-HGF vector encapsulated within vitamin A-coupled liposomes were validated by decreases in fibrotic markers in vitro. Fibrotic cultures transfected with the targeted transgene showed a significant decrease in fibrotic markers such as transforming growth factor-β1. In rats, dimethylnitrosamine-induced liver fibrosis is manifested by an increase in collagen deposition and severe defenestration of sinusoidal endothelial cells. The HSC-targeted transgene, administered via retrograde intrabiliary infusion in fibrotic rats, successfully reduced liver fibrosis markers alpha-smooth muscle actin and collagen, accompanied by an increase in the expression of DsRed2-HGF near the fibrotic foci. Thus, targeted delivery of HGF gene to hepatic stellate cells increased the transgene expression at the fibrotic foci and strongly enhanced its antifibrotic effects.

Experimental liver fibrosis research: update on animal models, legal issues and translational aspects

Liver fibrosis is defined as excessive extracellular matrix deposition and is based on complex interactions between matrix-producing hepatic stellate cells and an abundance of liver-resident and infiltrating cells. Investigation of these processes requires in vitro and in vivo experimental work in animals. However, the use of animals in translational research will be increasingly challenged, at least in countries of the European Union, because of the adoption of new animal welfare rules in 2013. These rules will create an urgent need for optimized standard operating procedures regarding animal experimentation and improved international communication in the liver fibrosis community. This review gives an update on current animal models, techniques and underlying pathomechanisms with the aim of fostering a critical discussion of the limitations and potential of up-to-date animal experimentation. We discuss potential complications in experimental liver fibrosis and provide examples of how the findings of studies in which these models are used can be translated to human disease and therapy. In this review, we want to motivate the international community to design more standardized animal models which might help to address the legally requested replacement, refinement and reduction of animals in fibrosis research.

Cellular mechanisms of tissue fibrosis. 5. Novel insights into liver fibrosis

Liver fibrosis is the common scarring reaction associated with chronic liver injury that results from prolonged parenchymal cell injury and/or inflammation. The fibrogenic response is characterized by progressive accumulation of extracellular matrix components enriched in fibrillar collagens and a failure of matrix turnover. This process is driven by a heterogeneous population of hepatic myofibroblasts, which mainly derive from hepatic stellate cells and portal fibroblasts. Regression of fibrosis can be achieved by the successful control of chronic liver injury, owing to termination of the fibrogenic reaction following clearance of hepatic myofibroblasts and restoration of fibrolytic pathways. Understanding of the complex network underlying liver fibrogenesis has allowed the identification of a large number of antifibrotic targets, but no antifibrotic drug has as yet been approved. This review will highlight recent advances regarding the mechanisms that regulate liver fibrogenesis and fibrosis regression, with special focus on novel signaling pathways and the role of inflammatory cells. Translation of these findings to therapies will require continued efforts to develop multitarget therapeutic approaches that will improve the grim prognosis of liver cirrhosis.

Progression of liver fibrosis in post-transplant hepatitis C: mechanisms, assessment and treatment

Liver fibrosis results from an excessive wound healing response in most chronic liver diseases, such as hepatitis C. Despite great advances in antiviral therapy in recent years, progressive liver fibrosis remains a major problem for patients with recurrent hepatitis C after liver transplantation. Liver biopsy remains a central tool in the management of HCV-positive liver transplant recipients, but reliable non-invasive methods for the assessment of liver fibrosis, such as ultrasound elastography, are increasingly being incorporated in the management of post-transplant patients, helping predict prognosis, guide treatment decisions, and stratify patients for emerging antifibrotic therapies. In this manuscript, we will review the natural history as well as tools to monitor fibrosis progression in the HCV-positive liver transplant recipient, the mechanisms underlying rapid fibrosis progression in up to 30% of these patients, the effect of antiviral therapies and highlight promising antifibrotic approaches.

Evolving therapies for liver fibrosis

Fibrosis is an intrinsic response to chronic injury, maintaining organ integrity when extensive necrosis or apoptosis occurs. With protracted damage, fibrosis can progress toward excessive scarring and organ failure, as in liver cirrhosis. To date, antifibrotic treatment of fibrosis represents an unconquered area for drug development, with enormous potential but also high risks. Preclinical research has yielded numerous targets for antifibrotic agents, some of which have entered early-phase clinical studies, but progress has been hampered due to the relative lack of sensitive and specific biomarkers to measure fibrosis progression or reversal. Here we focus on antifibrotic approaches for liver that address specific cell types and functional units that orchestrate fibrotic wound healing responses and have a sound preclinical database or antifibrotic activity in early clinical trials. We also touch upon relevant clinical study endpoints, optimal study design, and developments in fibrosis imaging and biomarkers.

Translating an understanding of the pathogenesis of hepatic fibrosis to novel therapies

The response to injury is one of wound healing and fibrogenesis, which ultimately leads to fibrosis. The fibrogenic response to injury is a generalized one across virtually all organ systems. In the liver, the injury response, typically occurring over a prolonged period of time, leads to cirrhosis (although it should be pointed out that not all patients with liver injury develop cirrhosis). The fact that many different diseases result in cirrhosis suggests a common pathogenesis. The study of hepatic fibrogenesis over the past 2 decades has been remarkably active, leading to a considerable understanding of this process. It clearly has been shown that the hepatic stellate cell is a central component in the fibrogenic process. It also has been recognized that other effector cells are important in the fibrogenic process, including resident fibroblasts, bone marrow-derived cells, fibrocytes, and even perhaps cells derived from epithelial cells (ie, through epithelial to mesenchymal transition). A key aspect of the biology of fibrogenesis is that the fibrogenic process is dynamic; thus, even advanced fibrosis (or cirrhosis) is reversible. Together, an understanding of the cellular basis for liver fibrogenesis, along with multiple aspects of the basic pathogenesis of fibrosis, have highlighted many exciting potential therapeutic opportunities. Thus, although the most effective antifibrotic therapy is simply treatment of the underlying disease, in situations in which this is not possible, specific antifibrotic therapy is likely not only to become feasible, but will soon become a reality. This review highlights the mechanisms underlying fibrogenesis that may be translated into future antifibrotic therapies and to review the current state of clinical development.

Class II HDAC inhibition hampers hepatic stellate cell activation by induction of microRNA-29

Background

The conversion of a quiescent vitamin A storing hepatic stellate cell (HSC) to a matrix producing, contractile myofibroblast-like activated HSC is a key event in the onset of liver disease following injury of any aetiology. Previous studies have shown that class I histone deacetylases (HDACs) are involved in the phenotypical changes occurring during stellate cell activation in liver and pancreas.

Aims

In the current study we investigate the role of class II HDACs during HSC activation.

Methods

We characterized the expression of the class II HDACs freshly isolated mouse HSCs. We inhibited HDAC activity by selective pharmacological inhibition with MC1568, and by repressing class II HDAC gene expression using specific siRNAs.

Results

Inhibition of HDAC activity leads to a strong reduction of HSC activation markers α-SMA, lysyl oxidase and collagens as well as an inhibition of cell proliferation. Knock down experiments showed that HDAC4 contributes to HSC activation by regulating lysyl oxidase expression. In addition, we observed a strong up regulation of miR-29, a well-known anti-fibrotic miR, upon treatment with MC1568. Our in vivo work suggests that a successful inhibition of class II HDACs could be promising for development of future anti-fibrotic compounds.

Conclusions

In conclusion, the use of MC1568 has enabled us to identify a role for class II HDACs regulating miR-29 during HSC activation.

Retinol binding protein-albumin domain III fusion protein deactivates hepatic stellate cells

Liver fibrosis is characterized by accumulation of extracellular matrix, and activated hepatic stellate cells (HSCs) are the primary source of the fibrotic neomatrix and considered as therapeutic target cells. We previously showed that albumin in pancreatic stellate cells (PSCs), the key cell type for pancreatic fibrogenesis, is directly involved in the formation of vitamin A-containing lipid droplets, inhibiting PSC activation. In this study, we evaluated the anti-fibrotic activity of both albumin and retinol binding protein-albumin domain III fusion protein (R-III), designed for stellate cell-targeted delivery of albumin III, in rat primary HSCs and investigated the underlying mechanism. Forced expression of albumin or R-III in HSCs after passage 2 (activated HSCs) induced lipid droplet formation and deactivated HSCs, whereas point mutations in high-affinity fatty acid binding sites of albumin domain III abolished their activities. Exogenous R-III, but not albumin, was successfully internalized into and deactivated HSC-P2. When HSCs at day 3 after plating (pre-activated HSCs) were cultured in the presence of purified R-III, spontaneous activation of HSCs was inhibited even after passage 2, suggestive of a potential for preventive effect. Furthermore, treatment of HSCs-P2 with R-III led to a significant reduction in both cytoplasmic levels of all-trans retinoic acid and the subsequent retinoic acid signaling. Therefore, our data suggest that albumin deactivates HSCs with reduced retinoic acid levels and that R-III may have therapeutic and preventive potentials on liver fibrosis.

Anti-fibrotic therapy: lost in translation?

While preclinical development of potential anti-fibrotics is far advanced, with numerous pharmacological targets and promising agents, almost none has entered clinical validation. Reasons are manifold, including the usually slow progression of liver fibrosis, requiring high numbers of well-stratified patients undergoing long-term treatment when conventional liver biopsy based parameters or hard liver-related endpoints are used. Importantly, there is a notorious lack of sensitive and specific surrogate markers or imaging technologies for liver fibrosis progression or regression that would permit a rapid clinical screening for potential anti-fibrotics. Nonetheless, in view of an urgent need for anti-fibrotics that positively impact morbidity and mortality from chronic liver diseases, the field is now moving more quickly towards clinical translation. This development is driven by thoughtful preclinical validation, a better study design and improved surrogate readouts using currently available methodologies. Moreover, upcoming novel biomarkers and imaging technologies will soon permit a more exact and efficient assessment of fibrosis progression and regression.

Nonalcoholic steatohepatitis: the therapeutic challenge of a global epidemic

PURPOSE OF REVIEW

Nonalcoholic fatty liver (NAFL) and especially its inflammatory variant nonalcoholic steatohepatitis (NASH) have become a major challenge to healthcare systems worldwide because of the increasing prevalence of its major risk factors obesity and type 2 diabetes, which are closely linked to overeating, physical inactivity, and the metabolic syndrome.

RECENT FINDINGS

Between 10 and 20% of patients with NAFL develop NASH, which can progress to cirrhosis, end-stage liver disease, and hepatocellular carcinoma. The overall mortality in these patients is significantly increased because of both cardiovascular and liver-related complications. Sustained weight loss by diet and exercise, which is the most effective therapeutic measure, is only achieved by a minority of patients, having led to a great yet unmet need for medical therapies of NASH.

SUMMARY

Pharmacological therapies should target the underlying pathophysiology that involves insulin resistance, enhanced peripheral lipolysis and release of free fatty acids, oxidative stress, accumulation of toxic lipids, adipose tissue inflammation, sensitization of hepatocytes toward apoptotic cell death, and fibrogenesis. However, pharmacological therapy that is well tolerated, cost-effective, and poses an acceptable risk-to-benefit ratio has still to be identified. This review summarizes the current and promising treatment options and their implications for future research and clinical practice.