DLPC and SAMe prevent alpha1(I) collagen mRNA up-regulation in human hepatic stellate cells, whether caused by leptin or menadione

Raman imaging investigation of hepatic LX-2 cell reversion under different lipidic treatments

Liver fibrosis resulting from chronic liver injury is characterized by increased extracellular matrix deposition and inflammation, which leads to excessive scar tissue formation. Targeting activated hepatic stellate cells (HSCs), which are the primary drivers of fibrogenesis, stands out as one of the most compelling therapeutic approaches in this regard. In a healthy liver, HSCs remain quiescent and store vitamin A in cytoplasmic lipid droplets. As a consequence of HSC activation and transdifferentiation to a proliferative myofibroblast-like state upon fibrotic stimuli, the distinctive phenotypic feature of the lipid droplets gets lost. While the reversal of activated HSCs is feasible, understanding the quiescent-like state following injury resolution is crucial for effective fibrosis treatment. This study explores the induced quiescent-like state of naïve immortalized human hepatic stellate (LX-2) cells when treated with soybean phospholipid that contains 75% phosphatidylcholine (S80). The lipid profile of the newly formed lipid droplets was analyzed using Raman imaging, which is a label-free technique well-suited for lipidomics. Results indicate the presence of distinct lipid profiles despite maintaining a quiescent-like state, suggesting that diverse mechanisms govern the active-to-inactive state transition. Additionally, our findings support the fact that each hepatic cell state is composed of heterogeneous subpopulations. This emphasizes the complexity of liver fibrosis and highlights the need for a comprehensive understanding of cellular states to develop targeted therapies.

Soybean polyenylphosphatidylcholine (PPC) is beneficial in liver and extrahepatic tissue injury: An update in experimental research

Polyenylphosphatidylcholine (PPC) is a purified polyunsaturated phosphatidylcholine extract of soybeans. This article updates PPC's beneficial effects on various forms of liver cell injury and other tissues in experimental research. PPC downregulates hepatocyte CYP2E1 expression and associated hepatotoxicity, as well as attenuates oxidative stress, apoptosis, lipoprotein oxidation and steatosis in alcoholic and nonalcoholic liver injury. PPC inhibits pro-inflammatory cytokine production, while stimulating anti-inflammatory cytokine secretion in ethanol or lipopolysaccharide-stimulated Kupffer cells/macrophages. It promotes M2-type macrophage polarization and metabolic reprogramming of glucose and lipid metabolism. PPC mitigates steatosis in NAFLD through inhibiting polarization of pro-inflammatory M1-type Kupffer cells, alleviating metabolic inflammation, remodeling hepatic lipid metabolism, correcting imbalances between lipogenesis and lipolysis and enhancing lipoprotein secretion from hepatocytes. PPC is antifibrotic by preventing progression of alcoholic hepatic fibrosis in baboons and also prevents CCl4-induced fibrosis in rats. PPC supplementation replenishes the phosphatidylcholine content of damaged cell membranes, resulting in increased membrane fluidity and functioning. Phosphatidylcholine repletion prevents increased membrane curvature of the endoplasmic reticulum and Golgi and decreases sterol regulatory element binding protein-1-mediated lipogenesis, reducing steatosis. PPC remodels gut microbiota and affects hepatic lipid metabolism via the gut-hepatic-axis and also alleviates brain inflammatory responses and cognitive impairment via the gut-brain-axis. Additionally, PPC protects extrahepatic tissues from injury caused by various toxic compounds by reducing oxidative stress, inflammation, and membrane damage. It also stimulates liver regeneration, enhances sensitivity of cancer cells to radiotherapy/chemotherapy, and inhibits experimental hepatocarcinogenesis. PPC's beneficial effects justify it as a supportive treatment of liver disease.

Synergy of Phospholipid-Drug Formulations Significantly Deactivates Profibrogenic Human Hepatic Stellate Cells

The pivotal role of hepatic stellate cells (HSCs) in orchestrating the bidirectional process of progression and regression of liver fibrosis makes them an ideal target for exploring new antifibrotic therapies. Essential phospholipids (EPLs), with their polyenylphosphatidylcholine (PPC) fraction, either alone or combined with other hepatoprotective substances such as silymarin, are recommended in hepatic impairment, but a scientific rationale for their use is still lacking. Herein, we compared the ability of EPLs to restore quiescent-like features in HSCs with that of dilinoleoylphosphatidylcholine (DLPC), PPC fraction’s main component. Specifically, we screened at the cellular level the antifibrotic effects of PPC formulations in the presence and absence of silymarin, by using LX-2 cells (pro-fibrogenic HSCs) and by assessing the main biochemical hallmarks of the activated and deactivated states of this cell line. We also proved the formulations’ direct effect on the motional order of cell membranes of adherent cells. LX-2 cells, examined for lipid droplets as a quiescence marker, showed that PPCs led to a more prominent deactivation than DLPC. This result was confirmed by a reduction of collagen and α-SMA expression, and by a profound alteration in the cell membrane fluidity. PPC–silymarin formulations deactivated HSCs with a significant synergistic effect. The remarkable bioactivity of PPCs in deactivating fibrogenic HSCs paves the way for the rational design of new therapeutics aimed at managing hepatic fibrosis.

Klotho acts as a tumor suppressor in cancers

The klotho gene is a classical "aging suppressor" gene. Its roles in the pathology of chronic kidney diseases have been well documented. However, the role of Klotho in tumorigenesis, cancer progression, and prognosis is attracting more and more attention. Recent studies have shown that Klotho participates in the progression of several types of human cancers. Klotho functions as a tumor suppressor by inhibiting insulin/IGF1, p53/p21, and Wnt signaling. Silencing klotho gene expression is mainly mediated through promoter hypermethylation and histone deacetylation in cancer. Klotho has been proposed to take part in cell proliferation, survival, autophagy, and resistance to anti-cancer therapies.

A systems biology approach for understanding the collagen regulatory network in alcoholic liver disease

Among the pathogenesis and risk factors of alcoholic liver disease (ALD) are the source of dietary fat, obesity, insulin resistance, adipokines and acetaldehyde. Translocation of Gram-negative bacteria from the gut, the subsequent effects mediated by endotoxin, and the increased production of matricellular proteins, cytokines, chemokines and growth factors, actively participate in the progression of liver injury. In addition, generation of reactive oxygen and nitrogen species and the activation of non-parenchymal cells also contribute to the pathophysiology of ALD. A key event leading to liver damage is the transition of quiescent hepatic stellate cells into activated myofibroblasts, with the consequent deposition of fibrillar collagen I resulting in significant scarring. Thus, it is becoming clearer that matricellular proteins are critical players in the pathophysiology of liver disease; however, additional mechanistic insight is needed to understand the signalling pathways involved in the up-regulation of collagen I protein. At present, systems biology approaches are helping to answer the many unresolved questions in this field and are allowing to more comprehensively identify protein networks regulating pathological collagen I deposition in hopes of determining how to prevent the onset of liver fibrosis and/or to slow disease progression. Thus, this review article provides a snapshot on current efforts for identifying pathological protein regulatory networks in the liver using systems biology tools. These approaches hold great promise for future research in liver disease.

Targeting collagen expression in alcoholic liver disease

Alcoholic liver disease (ALD) is a leading cause of liver disease and liver-related deaths globally, particularly in developed nations. Liver fibrosis is a consequence of ALD and other chronic liver insults, which can progress to cirrhosis and hepatocellular carcinoma if left untreated. Liver fibrosis is characterized by accumulation of excess extracellular matrix components, including type I collagen, which disrupts liver microcirculation and leads to injury. To date, there is no therapy for the treatment of liver fibrosis; thus treatments that either prevent the accumulation of type I collagen or hasten its degradation are desirable. The focus of this review is to examine the regulation of type I collagen in fibrogenic cells of the liver and to discuss current advances in therapeutics to eliminate excessive collagen deposition.

Activity of essential phospholipids (EPL) from soybean in liver diseases

Essential phospholipids (EPL) contain a highly purified extract of polyenylphosphatidylcholine (PPC) molecules from soybean. The main active ingredient is 1,2-dilinoleoylphosphatidylcholine (DLPC), which differentiates it from other phospholipids, lecithins, or extracts from other sources. Although EPLis widely used in liver diseases of various origins, its mode of action and pharmacological and clinical evidence of its efficacy have not yet been concisely reviewed. This paper critically summarizes experimental and clinical results. With regard to in-vitro and animal tests, EPL influenced membrane-dependent cellular functions and showed anti-oxidant, anti-inflammatory, anti-fibrotic, apoptosis-modulating, regenerative, membrane-repairing and -protective, cell-signaling and receptor-influencing, as well as lipid-regulating effects in intoxication models with chemicals or drugs. Clinical studies, primarily from European and Asian countries, have shown improvement in subjective symptoms; clinical, biochemical and imaging findings; and histology in liver indications such as fatty liver of different origin, drug hepatotoxicity, and adjuvant in chronic viral hepatitis and hepatic coma. The available studies characterize EPL as evidence-based medicine, although further long-term controlled clinical trials are required to precisely determine its benefit for alleviating symptoms, improving well-being, inducing histological changes and slowing the progression of liver disease. EPL-related relevant side effects were not observed.

P38 mitogen-activated protein kinase signal pathway and hepatic stellate cells

Mitogen-activated protein kinases (MAPKs) play a pivotal role in the transduction of extracellular signals to the nucleus, which results in numerous cellular responses, including proliferation, differentiation, and regulation of specific metabilic pathways. P38 MAPK is one of the MAPK-family groups. Hepatic stellate cells (HSCs) are the main effector cells in the occurrence of liver fibrosis, so this review describes P38 MAPK signal pathway and its role in HSCs.

Participation of reactive oxygen species generated by NADPH oxidase in regulating signal transduction in hepatic stellate cells

Reactive oxygen species (ROS) are established molecules that are injurious to such biomolecules as DNA and protein, and that can induce lipid peroxidation. However, it is now held that Nox/Duox family of NADPH oxidases generate ROS in a carefully regulated manner, which can act as second messengers influencing signal transduction in various cells including hepatic stellate cells (HSCs). This paper focused on mechanism of ROS generated by NOX/Duox regulating signal transduction, and then reviewed signal transduction of ROS-mediated liver profibrogenic factors, e.g., transforming growth factor-β (TGF-β), platelet-derived growth factor (PDGF), Angiotensin II (Ang II) and leptin, et al in HSCs.

Hepatic stellate cells: protean, multifunctional, and enigmatic cells of the liver

The hepatic stellate cell has surprised and engaged physiologists, pathologists, and hepatologists for over 130 years, yet clear evidence of its role in hepatic injury and fibrosis only emerged following the refinement of methods for its isolation and characterization. The paradigm in liver injury of activation of quiescent vitamin A-rich stellate cells into proliferative, contractile, and fibrogenic myofibroblasts has launched an era of astonishing progress in understanding the mechanistic basis of hepatic fibrosis progression and regression. But this simple paradigm has now yielded to a remarkably broad appreciation of the cell's functions not only in liver injury, but also in hepatic development, regeneration, xenobiotic responses, intermediary metabolism, and immunoregulation. Among the most exciting prospects is that stellate cells are essential for hepatic progenitor cell amplification and differentiation. Equally intriguing is the remarkable plasticity of stellate cells, not only in their variable intermediate filament phenotype, but also in their functions. Stellate cells can be viewed as the nexus in a complex sinusoidal milieu that requires tightly regulated autocrine and paracrine cross-talk, rapid responses to evolving extracellular matrix content, and exquisite responsiveness to the metabolic needs imposed by liver growth and repair. Moreover, roles vital to systemic homeostasis include their storage and mobilization of retinoids, their emerging capacity for antigen presentation and induction of tolerance, as well as their emerging relationship to bone marrow-derived cells. As interest in this cell type intensifies, more surprises and mysteries are sure to unfold that will ultimately benefit our understanding of liver physiology and the diagnosis and treatment of liver disease.

Leptin stimulates alpha1(I) collagen expression in human hepatic stellate cells via the phosphatidylinositol 3-kinase/Akt signalling pathway

BACKGROUND/AIMS

Leptin has been recognized as a profibrogenic hormone in the liver and is involved in collagen type I formation by activated hepatic stellate cells (HSCs) in response to fibrogenic substances, but the molecular signal mechanisms by which leptin promotes liver fibrogenesis through upregulation of collagen type I expression is not clear. We investigated whether leptin-induced collagen type I is mediated by the Janus kinase-phosphatidylinositol 3-kinase-Akt (JAKs-PI3K-Akt) pathway in a human HSC cell line, LX-2.

METHODS

LX-2 cells were treated with or without various inhibitors in the presence of leptin.

RESULTS

Leptin increased alpha1(I) collagen mRNA and protein. JAK1, PI3K and Akt were activated after leptin stimulation. AG490, a JAK inhibitor, blocked JAK1 phosphorylation accompanied by inhibition of PI3K and Akt activation as well as alpha1(I) collagen mRNA expression, indicating a JAK1-dependent mechanism. Wortmannin, a PI3K inhibitor, prevented PI3K and Akt activation and resulted in suppression of alpha1(I) collagen mRNA expression, suggesting a PI3K-mediated process. These changes were reproduced by overexpression of the dominant-negative p85alpha mutant. A443654.3, an Akt inhibitor, opposed Akt activation, leading to downregulation of alpha1(I) collagen mRNA. Overexpression of the dominant-negative Akt mutant led to similar alterations.

CONCLUSION

Leptin has a direct action on liver fibrogenesis by stimulating alpha1(I) collagen production in activated HSC. The process appears to be mediated by the PI3K/Akt pathway through activated JAK1.

The Combination of S-adenosylmethionine and Dilinoleoylphosphatidylcholine Attenuates Non-alcoholic Steatohepatitis Produced in Rats by a High-Fat Diet

In the pathogenesis of non-alcoholic steatohepatitis (NASH), oxidative stress resulting from free radicals generated by cytochrome P4502E1 (CYP2E1) plays a major role suggesting the importance of antioxidants. The objective of this study was to assess in a high-fat diet (HF) rat model the effects of the combination of s-adenosylmethionine (SAMe) plus dilinoleoylphosphatidylcholine (DLPC) in the treatment of NASH. To test the hypothesis that these two antioxidants are beneficial in NASH, male Sprague-Dawley rats were fed five different diets for six weeks: control, HF diet and HF plus SAMe and DLPC or their combination. As expected, the HF diet significantly increased hepatic triacylglycerols and CYP2E1 levels. However, only the combination diet opposed this effect, consistent with different actions of the two antioxidants. Next, 24 additional rats divided in two groups were fed the HF or the HF+SAMe+DLPC diets for 3 weeks. Dietary intake was similar, but liver triacylglycerols dropped from 76.1+/-6.8 to 49.4+/-3.5 mg/g (p=0.002) and hepatic CYP2E1 mRNA decreased after treatment (p=0.01) with a trend for less CYP2E1 protein. This was accompanied by a 41% reduction of hepatic 4-hydroxynonenal (4-HNE) (p=0.008), reflecting control of oxidative stress. Furthermore, the hepatic inflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) mRNA and TNF-alpha protein decreased (p=0.05 and p=0.01 respectively) with attenuation of alpha1(I) procollagen mRNA and type I collagen levels (p=0.01 and p=0.02, respectively). We concluded that the combination SAMe+DLPC might be beneficial in NASH by reducing oxidative stress and associated liver injury.