Docosahexaenoic acid inhibits hepatic stellate cell activation to attenuate liver fibrosis in a PPARγ-dependent manner

Application of PPAR Ligands and Nanoparticle Technology in Metabolic Steatohepatitis Treatment

Metabolic dysfunction-associated steatotic liver disease/steatohepatitis (MASLD/MASH) is a major disease worldwide whose effective treatment is challenging. Peroxisome proliferator-activated receptors (PPARs) belong to the nuclear receptor superfamily and function as ligand-activated transcription factors. To date, three distinct subtypes of PPARs have been characterized: PPARα, PPARβ/δ, and PPARγ. PPARα and PPARγ are crucial regulators of lipid metabolism that modulate the transcription of genes involved in fatty acid (FA), bile acid, and cholesterol metabolism. Many PPAR agonists, including natural (FAs, eicosanoids, and phospholipids) and synthetic (fibrate, thiazolidinedione, glitazar, and elafibranor) agonists, have been developed. Furthermore, recent advancements in nanoparticles (NPs) have led to the development of new strategies for MASLD/MASH therapy. This review discusses the applications of specific cell-targeted NPs and highlights the potential of PPARα- and PPARγ-targeted NP drug delivery systems for MASLD/MASH treatment.

Lipidomics Investigation Reveals the Reversibility of Hepatic Injury by Silica Nanoparticles in Rats After a 6-Week Recovery Duration

Given the inevitable human exposure owing to its increasing production and utilization, the comprehensive safety evaluation of silica nanoparticles (SiNPs) has sparked concerns. Substantial evidence indicated liver damage by inhaled SiNPs. Notwithstanding, few reports focused on the persistence or reversibility of hepatic injuries, and the intricate molecular mechanisms involved remain limited. Here, rats are intratracheally instilled with SiNPs in two regimens (a 3-month exposure and a subsequent 6-week recovery after terminating SiNPs administration) to assess the hepatic effects. Nontargeted lipidomics revealed alterations in lipid metabolites as a contributor to the hepatic response and recovery effects of SiNPs. In line with the functional analysis of differential lipid metabolites, SiNPs activated oxidative stress, and induced lipid peroxidation and lipid deposition in the liver, as evidenced by the elevated hepatic levels of ROS, MDA, TC, and TG. Of note, these indicators showed great improvements after a 6-week recovery, even returning to the control levels. According to the correlation, ROC curve, and SEM analysis, 11 lipids identified as potential regulatory molecules for ameliorating liver injury by SiNPs. Collectively, the work first revealed the reversibility of SiNP-elicited hepatotoxicity from the perspective of lipidomics and offered valuable laboratory evidence and therapeutic strategy to facilitate nanosafety.

Serum metabolomics characteristics and fatty-acid-related mechanism of cirrhosis with histological response in chronic hepatitis B

Background and aims: The serum metabolites changes in patients with hepatitis B virus (HBV)-related cirrhosis as progression. Peroxisome proliferator-activated receptor gamma (PPARγ) is closely related to lipid metabolism in cirrhotic liver. However, the relationship between fatty acids and the expression of hepatic PPARγ during cirrhosis regression remains unknown. In this study, we explored the serum metabolic characteristics and expression of PPARγ in patients with histological response to treatment with entecavir. Methods: Sixty patients with HBV-related cirrhosis were selected as the training cohort with thirty patients each in the regression (R) group and non-regression (NR) group based on their pathological changes after 48-week treatment with entecavir. Another 72 patients with HBV-related cirrhosis and treated with entecavir were collected as the validation cohort. All of the serum samples were tested using ultra-performance liquid chromatography coupled to tandem mass spectrometry. Data were processed through principal component analysis and orthogonal partial least square discriminant analysis. Hepatic PPARγ expression was observed using immunohistochemistry. The relationship between serum fatty acids and PPARγ was calculated using Pearson's or Spearman's correlation analysis. Results: A total of 189 metabolites were identified and 13 differential metabolites were screened. Compared to the non-regression group, the serum level of fatty acids was higher in the R group. At baseline, the expression of PPARγ in hepatic stellate cells was positively correlated with adrenic acid (r 2 = 0.451, p = 0.046). The expression of PPARγ in both groups increased after treatment, and the expression of PPARγ in the R group was restored in HSCs much more than that in the NR group (p = 0.042). The adrenic acid and arachidonic acid (AA) in the R group also upgraded more than the NR group after treatment (p = 0.037 and 0.014). Conclusion: Baseline serum differential metabolites, especially fatty acids, were identified in patients with HBV-related cirrhosis patients who achieved cirrhosis regression. Upregulation of adrenic acid and arachidonic acid in serum and re-expression of PPARγ in HSCs may play a crucial role in liver fibrosis improvement.

Novel Therapeutic Approaches to Liver Fibrosis Based on Targeting Oxidative Stress

Chronic liver disease (CLD) constitutes a growing global health issue, with no effective treatments currently available. Oxidative stress closely interacts with other cellular and molecular processes to trigger stress pathways in different hepatic cells and fuel the development of liver fibrosis. Therefore, inhibition of reactive oxygen species (ROS)-mediated effects and modulation of major antioxidant responses to counteract oxidative stress-induced damage have emerged as interesting targets to prevent or ameliorate liver injury. Although many preclinical studies have shown that dietary supplements with antioxidant properties can significantly prevent CLD progression in animal models, this strategy has not proved effective to significantly reduce fibrosis when translated into clinical trials. Novel and more specific therapeutic approaches are thus required to alleviate oxidative stress and reduce liver fibrosis. We have reviewed the relevant literature concerning the crucial role of alterations in redox homeostasis in different hepatic cell types during the progression of CLD and discussed current pharmacological approaches to ameliorate fibrosis by reducing oxidative stress focusing on selective modulation of enzymatic oxidant sources, antioxidant systems and ROS-mediated pathogenic processes.

Immune microenvironment changes of liver cirrhosis: emerging role of mesenchymal stromal cells

Cirrhosis is a progressive and diffuse liver disease characterized by liver tissue fibrosis and impaired liver function. This condition is brought about by several factors, including chronic hepatitis, hepatic steatosis, alcohol abuse, and other immunological injuries. The pathogenesis of liver cirrhosis is a complex process that involves the interaction of various immune cells and cytokines, which work together to create the hepatic homeostasis imbalance in the liver. Some studies have indicated that alterations in the immune microenvironment of liver cirrhosis are closely linked to the development and prognosis of the disease. The noteworthy function of mesenchymal stem cells and their paracrine secretion lies in their ability to promote the production of cytokines, which in turn enhance the self-repairing capabilities of tissues. The objective of this review is to provide a summary of the alterations in liver homeostasis and to discuss intercellular communication within the organ. Recent research on MSCs is yielding a blueprint for cell typing and biomarker immunoregulation. Hopefully, as MSCs researches continue to progress, novel therapeutic approaches will emerge to address cirrhosis.

Dietary docosahexaenoic acid reduces fat deposition and alleviates liver damage induced by D-galactosamine and lipopolysaccharides in Nile tilapia (Oreochromis niloticus)

Liver health is important to maintain survival and growth of fish. Currently, the role of dietary docosahexaenoic acid (DHA) in improving fish liver health is largely unknown. This study investigated the role of DHA supplementation in fat deposition and liver damage caused by D-galactosamine (D-GalN) and lipopolysaccharides (LPS) in Nile tilapia (Oreochromis niloticus). Four diets were formulated as control diet (Con), Con supplemented with 1 % DHA, 2 % DHA and 4 % DHA diets, respectively. The diets were fed to 25 Nile tilapia (2.0 ± 0.1 g, average initial weight) in triplicates for four weeks. After the four weeks, 20 fish in each treatment were randomly selected and injected with a mixture of 500 mg D-GalN and 10 μL LPS per mL to induce acute liver injury. The results showed that the Nile tilapia fed on DHA diets decreased visceral somatic index, liver lipid content and serum and liver triglyceride concentrations than those fed on the Con diet. Moreover, after D-GalN/LPS injection, the fish fed on DHA diets decreased alanine aminotransferase and aspartate transaminase activities in the serum. The results of liver qPCR and transcriptomics assays together showed that the DHA diets feeding improved liver health by downregulating the expression of the genes related to toll-like receptor 4 (TLR4) signaling pathway, inflammation and apoptosis. This study indicates that DHA supplementation in Nile tilapia alleviates the liver damage caused by D-GalN/LPS through increasing lipid catabolism, decreasing lipogenesis, TLR4 signaling pathway, inflammation, and apoptosis. Our study provides novel knowledge on the role of DHA in improving liver health in cultured aquatic animals for sustainable aquaculture.

PPAR-γ signaling in nonalcoholic fatty liver disease: Pathogenesis and therapeutic targets

Non-alcoholic fatty liver disease (NAFLD), currently the leading cause of global chronic liver disease, has emerged as a major public health problem, more efficient therapeutics of which are thus urgently needed. Peroxisome proliferator-activated receptor γ (PPAR-γ), ligand-activated transcription factors of the nuclear hormone receptor superfamily, is considered a crucial metabolic regulator of hepatic lipid metabolism and inflammation. The role of PPAR-γ in the pathogenesis of NAFLD is gradually being recognized. Here, we outline the involvement of PPAR-γ in the pathogenesis of NAFLD through adipogenesis, insulin resistance, inflammation, oxidative stress, endoplasmic reticulum stress, and fibrosis. In addition, the evidence for PPAR-γ- targeted therapy for NAFLD are summarized. Altogether, PPAR-γ is a promising therapeutic target for NAFLD, and the development of drugs that can balance the beneficial and undesirable effects of PPAR-γ will bring new light to NAFLD patients.

An integrated approach for identifying the efficacy and potential mechanisms of TCM against atherosclerosis-Wu-Zhu-Yu decoction as a case study

ETHNOPHARMACOLOGICAL RELEVANCE

Atherosclerosis (AS) is a chronic disease that is associated with high morbidity. However, therapeutic approaches are limited. Wu-Zhu-Yu decoction (WZYD) is a well-known traditional Chinese medicine prescription that is traditionally used to treat headaches and vomiting. Modern studies have demonstrated the cardiotonic effects of WZYD. However, whether WZYD can alleviate AS and its underlying mechanisms remain unclear.

AIM OF THE STUDY

This study aims to investigate the antiatherosclerotic efficacy of WZYD and illustrate its potential mechanisms using an integrated approach combining in vivo and in vitro assessments, including metabolomics, network pharmacology, cell experiments, and molecular docking analyses.

MATERIALS AND METHODS

In this work, an atherosclerotic mouse model was established by administering a high-fat diet to apolipoprotein-E deficient (ApoE^-/-) mice for twelve weeks. Meanwhile, the mice were intragastrically administered WZYD at different dosages. Efficacy evaluation was performed through biochemical and histopathological assessments. The potential active constituents, metabolites, and targets of WZYD in atherosclerosis were predicted by metabolomics combined with network pharmacology analysis, the constituents and targets were further assessed through cell experiments and molecular docking analysis.

RESULTS

WZYD decreased the lipid levels in serum, reduced the areas of aortic lesions, and attenuated intimal thickening, which had antiatherosclerotic effects in ApoE^-/- mice. Metabolomics and network pharmacology approach revealed that the ten constituents (6-shogaol, evodiamine, isorhamnetin, quercetin, beta-carotene, 8-gingerol, kaempferol, 6-paradol, 10-gingerol, and 6-gingerol) of WZYD affected 24 metabolites by acting on the candidate targets, thus resulting in changes in five metabolic pathways (sphingolipid metabolism; glycine, serine and threonine metabolism; arachidonic acid metabolism; tryptophan metabolism; and fatty acid biosynthesis pathway). Cell experiments indicated that the ten key compounds showed antiproliferative effects on the vascular smooth muscle cell. Moreover, the key compounds exhibited direct interactions with the key targets, as assessed by molecular docking analysis.

CONCLUSION

This study revealed that WZYD exerted therapeutic effects on atherosclerosis, and the potential mechanisms were elucidated. Furthermore, it offered a powerful integrated strategy for studying the efficacy of traditional Chinese medicine and exploring its active components and possible mechanisms.

Lycorine Ameliorates Thioacetamide-Induced Hepatic Fibrosis in Rats: Emphasis on Antioxidant, Anti-Inflammatory, and STAT3 Inhibition Effects

Liver fibrosis is a foremost medical concern worldwide. In Saudi Arabia, numerous risk factors contribute to its high rates. Lycorine—a natural alkaloid—has antioxidant, anti-inflammatory, and antitumor activates. It has been reported to inhibit STAT3 in cancer. Therefore, this study aimed at investigating the possible antifibrotic effect of lycorine against thioacetamide (TAA)-induced liver fibrosis in rats and at elucidating the possible mechanisms. Liver fibrosis was induced by TAA (200 mg/kg i.p.), three per week for four weeks. Treatment with lycorine (0.5 and 1 mg/kg/d) amended TAA-induced rise of serum transaminases that was confirmed histopathologically. Moreover, it ameliorated liver fibrosis in a dose-dependent manner, as indicated by hindering the TAA-induced increase of hepatic hydroxyproline content, α-smooth muscle actin (α-SMA) and transforming growth factor (TGF-β1) expressions. TAA-induced oxidative stress was amended by lycorine treatment via restoring reduced glutathione and diminishing lipid peroxidation. Moreover, lycorine ameliorated hepatic inflammation by preventing the rise of inflammatory cytokines. Notably, lycorine inhibited STAT3 activity, as evidenced by the decreased phospho-STAT3 expression, accompanied by the elevation of the hepatic Bax/Bcl-2 ratio. In conclusion, lycorine hinders TAA-induced liver fibrosis in rats, due to—at least partly—its antioxidative and anti-inflammatory properties, along with its ability to inhibit STAT3 signaling.

Methoxyeugenol deactivates hepatic stellate cells and attenuates liver fibrosis and inflammation through a PPAR-ɣ and NF-kB mechanism

ETHNOPHARMACOLOGICAL RELEVANCE

Studies have shown interest in nutraceuticals for the prevention of liver diseases. Methoxyeugenol, is a molecule found in foods, such as nutmeg (Myristica fragrans Houtt.) and Brazilian red propolis. These two sources of methoxyeugenol, propolis and nutmeg, are used in folk medicine for the treatment of hepatic and gastrointestinal disorders, although little is known about their effects on the prevention of liver fibrosis. Natural PPAR (Peroxisome proliferator-activated receptor) agonists would represent unique molecules for therapy, considering the lack of therapeutics to treat liver fibrosis in chronic liver disease. Thus, investigation on new alternatives are necessary, including the search for natural compounds from renewable and sustainable sources. Liver fibrosis is a pathological process characterized by an exacerbated cicatricial response in the hepatic tissue, which compromises liver function. Therefore, inhibition of HSC (hepatic stellate cell) activation and hepatocyte damage are considered major strategies for the development of new anti-fibrotic treatments.

AIM OF THE STUDY

This study aimed to investigate the effects of methoxyeugenol treatment on HSC phenotype modulation in human and murine cells, hepatocyte damage prevention, and protective effects in vivo, in order to evaluate its therapeutic potential for liver fibrosis prevention.

METHODS

We investigated the effects of methoxyeugenol in (i) in vitro models using human and murine HSC and hepatocytes, and (ii) in vivo models of CCl₄ (carbon tetrachloride) -induced liver fibrosis in mice.

RESULTS

We herein report that methoxyeugenol decreases HSC activation through the activation of PPAR-ɣ, ultimately inducing a quiescent phenotype highlighted by an increase in lipid droplets, loss of contraction ability, and a decrease in the proliferative rate and mRNA expression of fibroblast markers. In addition, methoxyeugenol prevented hepatocytes from oxidative stress damage. Moreover, in mice submitted to chronic liver disease through CCl₄ administration, methoxyeugenol decreased the inflammatory profile, liver fibrosis, mRNA expression of fibrotic genes, and the inflammatory pathway signaled by NF-kB (Nuclear factor kappa B).

CONCLUSION

We propose methoxyeugenol as a novel and potential therapeutic approach to treat chronic liver disease and fibrosis.

Liver Fibrosis and MAFLD: From Molecular Aspects to Novel Pharmacological Strategies

Metabolic-associated fatty liver disease (MAFLD) is a new disease definition, and this nomenclature MAFLD was proposed to renovate its former name, non-alcoholic fatty liver disease (NAFLD). MAFLD/NAFLD have shared and predominate causes from nutrition overload to persistent liver damage and eventually lead to the development of liver fibrosis and cirrhosis. Unfortunately, there is an absence of effective treatments to reverse MAFLD/NAFLD-associated fibrosis. Due to the significant burden of MAFLD/NAFLD and its complications, there are active investigations on the development of novel targets and pharmacotherapeutics for treating this disease. In this review, we cover recent discoveries in new targets and molecules for antifibrotic treatment, which target pathways intertwined with the fibrogenesis process, including lipid metabolism, inflammation, cell apoptosis, oxidative stress, and extracellular matrix formation. Although marked advances have been made in the development of antifibrotic therapeutics, none of the treatments have achieved the endpoints evaluated by liver biopsy or without significant side effects in a large-scale trial. In addition to the discovery of new druggable targets and pharmacotherapeutics, personalized medication, and combinatorial therapies targeting multiple profibrotic pathways could be promising in achieving successful antifibrotic interventions in patients with MAFLD/NAFLD.

The Immunometabolic Roles of Various Fatty Acids in Macrophages and Lymphocytes

Macrophages and lymphocytes demonstrate metabolic plasticity, which is dependent partly on their state of activation and partly on the availability of various energy yielding and biosynthetic substrates (fatty acids, glucose, and amino acids). These substrates are essential to fuel-based metabolic reprogramming that supports optimal immune function, including the inflammatory response. In this review, we will focus on metabolism in macrophages and lymphocytes and discuss the role of fatty acids in governing the phenotype, activation, and functional status of these important cells. We summarize the current understanding of the pathways of fatty acid metabolism and related mechanisms of action and also explore possible new perspectives in this exciting area of research.

PPARs as Metabolic Sensors and Therapeutic Targets in Liver Diseases

Carbohydrates and lipids are two components of the diet that provide the necessary energy to carry out various physiological processes to help maintain homeostasis in the body. However, when the metabolism of both biomolecules is altered, development of various liver diseases takes place; such as metabolic-associated fatty liver diseases (MAFLD), hepatitis B and C virus infections, alcoholic liver disease (ALD), and in more severe cases, hepatocelular carcinoma (HCC). On the other hand, PPARs are a family of ligand-dependent transcription factors with an important role in the regulation of metabolic processes to hepatic level as well as in other organs. After interaction with specific ligands, PPARs are translocated to the nucleus, undergoing structural changes to regulate gene transcription involved in lipid metabolism, adipogenesis, inflammation and metabolic homeostasis. This review aims to provide updated data about PPARs’ critical role in liver metabolic regulation, and their involvement triggering the genesis of several liver diseases. Information is provided about their molecular characteristics, cell signal pathways, and the main pharmacological therapies that modulate their function, currently engaged in the clinic scenario, or in pharmacological development.

The Agonists of Peroxisome Proliferator-Activated Receptor-γ for Liver Fibrosis

Liver fibrosis is a common link in the transformation of acute and chronic liver diseases to cirrhosis. It is of great clinical significance to study the factors associated with the induction of liver fibrosis and elucidate the method of reversal. Peroxisome proliferator-activated receptors (PPARs) are a class of nuclear transcription factors that can be activated by peroxisome proliferators. PPARs play an important role in fibrosis of various organs, especially the liver, by regulating downstream targeted pathways, such as TGF-β, MAPKs, and NF-κB p65. In recent years, the development and screening of PPAR-γ ligands have become a focus of research. The PPAR-γ ligands include synthetic hypolipidemic and antidiabetic drugs. In addition, microRNAs, lncRNAs, circRNAs and nano new drugs have attracted research interest. In this paper, the research progress of PPAR-γ in the pathogenesis and treatment of liver fibrosis was discussed based on the relevant literature in recent years.

Peroxisome proliferator-activated receptors in the pathogenesis and therapies of liver fibrosis

Liver fibrosis is a dynamic wound-healing process associated with the deposition of extracellular matrix produced by myofibroblasts. HSCs activation, inflammation, oxidative stress, steatosis and aging play critical roles in the progression of liver fibrosis, which is correlated with the regulation of the peroxisome proliferator-activated receptor (PPAR) pathway. As nuclear receptors, PPARs reduce inflammatory response, regulate lipid metabolism, and inhibit fibrogenesis in the liver associated with aging. Thus, PPAR ligands have been investigated as possible therapeutic agents. Mounting evidence indicated that some PPAR agonists could reverse steatohepatitis and liver fibrosis. Consequently, targeting PPARs might be a promising and novel therapeutic option against liver fibrosis. This review summarizes recent studies on the role of PPARs on the pathogenesis and treatment of liver fibrosis.

Peroxisome proliferator-activated receptor γ inhibits hepatic stellate cell activation regulated by miR-942 in chronic hepatitis B liver fibrosis

AIMS

Liver fibrosis is a chronic liver disease characterized by hepatic stellate cell (HSC) activation. Peroxisome proliferator-activated receptor gamma (PPARγ) play an important role in HSC activation. This study aimed to investigate the role of PPARγ in the progression of human hepatic fibrosis and the mechanism by which microRNA-942 regulates HSC activation.

METHODS

70 chronic hepatitis B (CHB) patients liver tissues were used to assess PPARγ, α-SMA and miR-942 levels by immunoblot and real-time PCR. Human primary HSCs or LX2 cells were used to perform multiple molecular experiments based on the transfection of small interfering RNA (siRNA) or co-transfection of microRNA inhibitor. Site-directed mutagenesis and luciferase reporter assays were used to identify miR-942 targets. miR-942 expression and localization in hepatic fibrosis and co-localization between α-SMA were determined by fluorescence in situ hybridization (FISH).

KEY FINDINGS

The mRNA expression of PPARγ was decreased in activated HSCs and CHB patients with liver fibrosis, which was negatively correlated with F stage and α-SMA. miR-942 negatively regulates PPARγ expression via targeting the PPARγ 3'UTR. Inhibiting PPARγ promoted TGFβ1 induced HSC activation, and this effect was blocked after inhibiting the miR-942. Moreover, miR-942 was mainly expressed in fibrous septa and negatively correlated with PPARγ in liver fibrosis.

SIGNIFICANCE

PPARγ targeting by miR-942 and decreasing HSC activation in human hepatic fibrosis. Hence, regulating PPARγ may be a promising therapeutic strategy for hepatic fibrosis.