ERp57 is up-regulated in free fatty acids-induced steatotic L-02 cells and human nonalcoholic fatty livers

Decreased Paneth cell α-defensins promote fibrosis in a choline-deficient L-amino acid-defined high-fat diet-induced mouse model of nonalcoholic steatohepatitis via disrupting intestinal microbiota

Nonalcoholic steatohepatitis (NASH) is a chronic liver disease characterized by fibrosis that develops from fatty liver. Disruption of intestinal microbiota homeostasis, dysbiosis, is associated with fibrosis development in NASH. An antimicrobial peptide α-defensin secreted by Paneth cells in the small intestine is known to regulate composition of the intestinal microbiota. However, involvement of α-defensin in NASH remains unknown. Here, we show that in diet-induced NASH model mice, decrease of fecal α-defensin along with dysbiosis occurs before NASH onset. When α-defensin levels in the intestinal lumen are restored by intravenous administration of R-Spondin1 to induce Paneth cell regeneration or by oral administration of α-defensins, liver fibrosis is ameliorated with dissolving dysbiosis. Furthermore, R-Spondin1 and α-defensin improved liver pathologies together with different features in the intestinal microbiota. These results indicate that decreased α-defensin secretion induces liver fibrosis through dysbiosis, further suggesting Paneth cell α-defensin as a potential therapeutic target for NASH.

Bioinformatics-based identification of lipid- and immune-related biomarkers in abdominal aortic aneurysms

Background

Abdominal aortic aneurysm (AAA) manifest as a natural inflammatory process with permanent dilation and terminal rupture. Nevertheless, the pathogenesis of AAA remains a mystery, and treatment is still controversial. Lipid metabolism and immune system are involved in AAA progression, which has been well documented. However, lipid- and immune-related (LIR) biomarkers need to be further elucidated.

Methods

The AAA-related datasets were retrieved from the GEO database, and the datasets were analyzed for differential gene expression by NetworkAnalyst. GO and KEGG pathway enrichment analysis of differentially expressed mRNA (DE-mRNA) was performed using Metscape, and LIR DE-mRNA was further screened. AAA rat model was constructed using porcine pancreatic elastase to verify the differential expression of LIR DE-mRNA.

Results

The GSE47472 and GSE57691 datasets respectively identified 614 (containing 381 down-regulated and 233 up-regulated DE-mRNAs) and 384 (containing 218 down-regulated and 164 up-regulated DE-mRNAs) DE-mRNAs. Intersection and union of DE-mRNAs were 13 and 983, respectively. The main terms involved in the union of DE-mRNAs included "immune system process", "metabolic process", "Chemokine signaling pathway", "hematopoietic cell lineage" and "Cholesterol metabolism". In vivo experiments revealed that LIR DE-mRNAs of PDIA3, TYROBP, and HSPA1A were significantly low expression in AAA abdominal aortic tissues, and HCK and SERPINE1 were significantly high expression, which is consistent with the bioinformatics analysis.

Conclusions

PDIA3, TYROBP, HSPA1A, HCK and SERPINE1 may serve as LIR biomarkers of AAA, which provides new insights and theoretical guidance for the future treatment, early prevention and progression of AAA.

Organometallic Folate Gold Nanoparticles Ameliorate Lipopolysaccharide-Induced Oxidative Damage and Inflammation in Zebrafish Brain

Synthesized organometallic gold-based folate nanoparticles (FAuNPs) were characterized, and its defense against lipopolysaccharide (LPS)-induced brain inflammation in Zebra fish was proven. Vitamin entrapment efficiency of these particles was found to be nearly 70%. The in vitro pH-dependent drug release dialysis study of FAuNPs confirmed a slow, sustained, and gradual release of folate for a period of 24 h. Both AuNPs and FAuNPs did not cause any marked changes in food intake, body weight, color, behavioral pattern, blood parameters, and hepatotoxicity. Histology of liver showed no changes between treated and control groups of fishes. The ex vivo study showed significant uptake of FAuNPs to free folate in folate receptor negative Hek293 cells, confirming a strategy to overcome folate deficiency in the brain. Antioxidant status and activities of few crucial brain enzymes were also measured to assess the brain function and found to be returned to the basal level, following FAuNP treatment. The transcription factor NRF2-Keap 1 expression pattern was also noted, and a prominent modulation was observed in the LPS-treated and FAuNP-administered group. Decisive brain enzymes like AChE and Na⁺K⁺ATPase were decreased significantly after LPS treatment, which is restored with FAuNP treatment. Caspases increased sharply after LPS treatment and diminished following FAuNP treatment. We conclude that FAuNP due to its high physical stability and uptake could be utilized against severe brain inflammation, leading to brain injury and neurodegeneration.

Val-Val-Tyr-Pro protects against non-alcoholic steatohepatitis in mice by modulating the gut microbiota and gut-liver axis activation

Val‐Val‐Tyr‐Pro (VVYP) peptide is one of the main active components of Globin digest (GD). Our previous studies indicated that VVYP could protect against acetaminophen and carbon tetrachloride‐induced acute liver failure in mice and decrease blood lipid level. However, the effects and underlying mechanisms of VVYP in the treatment of non‐alcoholic steatohepatitis (NASH) have not been discovered. Our present study was designed to investigate the preventive effect of VVYP on NASH and its underlying specific mechanisms. We found that VVYP inhibited the cytotoxicity and lipid accumulation in L‐02 cells that were exposed to a mixture of free fatty acid (FFA). VVYP effectively alleviated the liver injury induced by methionine‐choline‐deficient (MCD) diet, demonstrated by reducing the levels of serum alanine aminotransferase (ALT)/aspartate aminotransferase (AST)/triglycerides (TG)/non‐esterified fatty acids (NEFA) and improving liver histology. VVYP decreased expression levels of lipid synthesis‐related genes and reduced levels of the proinflammation cytokines in the liver of mice fed by MCD diet. Moreover, VVYP inhibited the increased level of LPS and reversed the liver mitochondria dysfunction induced by MCD diet. Meanwhile, VVYP significantly increased the abundance of beneficial bacteria such as Eubacteriaceae, coriobacteriacease, Desulfovibrionaceae, S24‐7 and Bacteroidia in high‐fat diet (HFD)‐fed mice, however, VVYP reduced the abundance of Lactobacillus. Moreover, VVYP conferred the protective effect of intestinal barrier via promoting the expression of the mucins and tight junction (TJ)‐associated genes and inhibited subsequent liver inflammatory responses. These results indicated that the protective role of VVYP on NASH is mediated by modulating gut microbiota imbalance and related gut‐liver axis activation. VVYP might be a promising drug candidate for NASH.

SUMOylation of Pdia3 exacerbates proinsulin misfolding and ER stress in pancreatic beta cells

SUMOylation has long been recognized to regulate multiple biological processes in pancreatic beta cells, but its impact on proinsulin disulfide maturation and endoplasmic reticulum (ER) stress remains elusive. Herein, we conducted comparative proteomic analyses of SUMOylated proteins in primary mouse/human islets following proinflammatory cytokine stimulation. Cytokine challenge rendered beta cells to undergo a SUMOylation turnover manifested by the changes of SUMOylation substrates and SUMOylation levels for multiple substrates. Our data support that SUMOylation may play a crucial role to regulate proinsulin misfolding and ER stress at least by targeting Protein Disulfide Isomerase a3 (Pdia3). SUMOylation regulates Pdia3 enzymatic activity, subcellular localization, and protein binding ability. Furthermore, SUMOylation of Pdia3 exacerbated proinsulin misfolding and ER stress, and repressed Stat3 activation. In contrast, disruption of Pdia3 SUMOylation markedly rescued the outcomes. Collectively, our study expands the understanding how SUMOylation regulates ER stress in beta cells, which shed light on developing potential strategies against beta cell dysfunction.

γ-Mangostin Ameliorates Free Fatty Acid-Induced Lipid Accumulation via the SIRT1/LKB1/AMPK Pathway in HepG2 and L02 Cells

Lipid accumulation is a typical characteristic of nonalcoholic fatty liver disease (NAFLD). The inhibition of lipid accumulation is regarded as a potential treatment for NAFLD. In this study, we investigated the effects of γ-mangostin or α-mangostin on lipid accumulation in a cell model. Analysis of the inhibitory effects of γ-mangostin on lipid accumulation revealed that it downregulated NAFLD-related biochemical parameters and stimulated the SIRT1/LKB1/AMPK pathway. Consequently, it suppressed lipid synthesis and enhanced fatty acid oxidation. Moreover, we demonstrated that the blockage of AMP-activated protein kinase (AMPK) by the pharmacological inhibitor Compound C abrogated the promoting effect of AMPK. Similar results were also observed for α-mangostin. The effects of α-mangostin on lipid accumulation were inferior to those of γ-mangostin. The differences in CPT1A activity might be originated from their different chemical structures. Our results suggested that γ-mangostin and α-mangostin can be exploited as potential candidates for NAFLD treatment.

Flavonones from Penthorum chinense Ameliorate Hepatic Steatosis by Activating the SIRT1/AMPK Pathway in HepG2 Cells

Pinocembrin-7-O-β-d-glucoside (PCBG), pinocembrin (PCB), and 5-methoxy-pinocembrin-7-O-β-d-glucoside (MPG) are three flavonones isolated from Penthorum chinense Pursh (P. chinense). The effects of the three flavonones on hepatic steatosis and their molecular mechanisms in HepG2 cells were investigated in this study for the first time. A model of hepatic steatosis in HepG2 cells was induced by free fatty acid (FFA), and co-treated with the three flavonones as mentioned. Intracellular lipid droplets were detected by Oil Red O staining. PCB, PCBG, and MPG suppressed oxidative stress by decreasing malondialdehyde (MDA) levels and increasing superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities. The levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were ameliorated. Moreover, these flavonones enhanced the phosphorylation of AMP-activated protein kinase (AMPK) and the expression of silent mating type information regulation 2 homolog 1 (SIRT1) and peroxisome proliferator-activated receptor α (PPARα), and reduced the expression of sterol regulatory element binding protein-1c (SREBP1c) and the downstream targets fatty acid synthase (FAS), acetyl-CoA carboxylase (ACC), and stearoyl-CoA desaturase 1 (SCD1). Molecular docking was used to predict the interaction and combination patterns between the three flavonones and the enzymes above. The results revealed that the SIRT1/AMPK pathway is involved in the functions of the three flavonones, and the most effective flavonone against hepatic steatosis might be PCBG, followed by MPG and PCB. Therefore, the three flavonones from P. chinense were found to exert preventive effects against hepatic steatosis by regulating the SIRT1/AMPK pathway.

Hepatocyte-specific deletion of LASS2 protects against diet-induced hepatic steatosis and insulin resistance

Homo sapienslongevity assurance homolog 2 of yeast LAG1 (LASS2) is expressed mostly in human liver. Here, we explored roles of LASS2 in pathogenesis of hepatic steatosis. Hepatocyte-specific LASS2 knockout (LASS2^-/-) mice were generated using Cre-LoxP system. LASS2^-/- and wild-type (WT) mice were fed with chow or high-fat diet (HFD). We found LASS2^-/- mice were resistant to HFD-induced hepatic steatosis and insulin resistance. In HFD-fed mice, LASS2 deficiency significantly inhibited p38 MAPK and ERK1/ERK2 signaling in mouse liver. This effect was mediated by a significant increase of V-ATPase activity and a decrease of ROS level. We also observed that elevated expression of LASS2 in mouse hepatocyte cell line AML12 obviously decreased V-ATPase activity and increased ROS level by activation of p38 MAPK and ERK1/ERK2 signaling. Our findings indicate that LASS2 plays an important role in the pathogenesis of diet-induced hepatic steatosis and is a potential novel target for prevention and intervention of liver diseases.

Effects and mechanisms of caffeine to improve immunological and metabolic abnormalities in diet-induced obese rats

In obesity, there are no effective therapies for parallel immune and metabolic abnormalities, including systemic/tissue insulin-resistance/inflammation, adiposity and hepatic steatosis. Caffeine has anti-inflammation, antihepatic steatosis, and anti-insulin resistance effects. In this study, we evaluated the effects and molecular mechanisms of 6 wk of caffeine treatment (HFD-caf) on immunological and metabolic abnormalities of high-fat diet (HFD)-induced obese rats. Compared with HFD vehicle (HFD-V) rats, in HFD-caf rats the suppressed circulating immune cell inflammatory [TNFα, MCP-1, IL-6, intercellular adhesion molecule 1 (ICAM-1), and nitrite] profiles were accompanied by decreased liver, white adipose tissue (WAT), and muscle macrophages and their intracellular cytokine levels. Metabolically, the increase in metabolic rates reduced lipid accumulation in various tissues, resulting in reduced adiposity, lower fat mass, decreased body weight, amelioration of hepatic steatosis, and improved systemic/muscle insulin resistance. Further mechanistic approaches revealed an upregulation of tissue lipogenic [(SREBP1c, fatty acid synthase, acetyl-CoA carboxylase)/insulin-sensitizing (GLUT4 and p-IRS1)] markers in HFD-caf rats. Significantly, ex vivo experiments revealed that the cytokine release by the cocultured peripheral blood mononuclear cell (monocyte) and WAT (adipocyte), which are known to stimulate macrophage migration and hepatocyte lipogenesis, were lower in HFD-V groups than HFD-caf groups. Caffeine treatment simultaneously ameliorates immune and metabolic pathogenic signals present in tissue to normalize immunolgical and metabolic abnormalities found in HFD-induced obese rats.

Myristic acid induces proteomic and secretomic changes associated with steatosis, cytoskeleton remodeling, endoplasmic reticulum stress, protein turnover and exosome release in HepG2 cells

Myristic acid, the 14-carbon saturated fatty acid (C14:0), is associated to an increased cardiovascular disease risk. Since it is found in low concentration in cells, its specific properties have not been fully analyzed. The aim of this study was to explore the cell response to this fatty acid to help explaining clinical findings on the relationship between C14:0 and cardiovascular disease. The human liver HepG2 cell line was used to investigate the hepatic response to C14:0 in a combined proteomic and secretomic approach. A total of 47 intracellular and 32 secreted proteins were deregulated after treatments with different concentrations of C14:0. Data are available via ProteomeXchange (PXD007902). In addition, C14:0 treatment of primary murine hepatocytes confirmed that C14:0 induces lipid droplet accumulation and elevates perilipin-2 levels. Functional enrichment analysis revealed that C14:0 modulates lipid droplet formation and cytoskeleton organization, induce ER stress, changes in exosome and extracellular miRNA sorting in HepG2cells. Our data provide for the first time a proteomic profiling of the effects of C14:0 in human hepatoma cells and contribute to the elucidation of molecular mechanisms through which this fatty acid may cause adverse health effects.

BIOLOGICAL SIGNIFICANCE

Myristic acid is correlated with an increase in plasma cholesterol and mortality due to cardiovascular diseases. This study is the first example of an integration of proteomic and secretomic analysis of HepG2 cells to investigate the specific properties and functional roles of myristic acid on hepatic cells. Our analyses will lead to a better understanding of the myristic acid induced effects and can elicit new diagnostic and treatment strategies based on altered proteins.

Eriodictyol 7‑O‑β‑D glucopyranoside from Coreopsis tinctoria Nutt. ameliorates lipid disorders via protecting mitochondrial function and suppressing lipogenesis

Coreopsis tinctoria (snow chrysanthemum) has been reported to exert antihyperlipidemic effects. The present study aimed to identify the active compounds of Coreopsis tinctoria and to investigate the molecular mechanisms underlying its effects on lipid dysregulation by measuring lipid levels, reactive oxygen species, lipid peroxidation and fatty acid synthesis. The present results demonstrated that snow chrysanthemum aqueous extracts significantly reduced serum lipid levels and oxidative stress in vivo. The main compounds that were isolated were identified as flavanomarein (compound 1) and eriodictyol 7-O-β-D glucopyranoside (compound 2). Compounds 1 and 2 demonstrated potent antioxidative properties, including free radical scavenging activity, inhibition of lipid peroxidation, as well as lipid-lowering effects in human HepG2 hepatocellular carcinoma cells treated with free fatty acids (FFAs). Compound 2 was revealed to suppress the elevation of triglyceride levels and inhibit lipid peroxidation following FFA treatment. In addition, it was demonstrated to significantly reduce intracellular levels of reactive oxygen species and improve the mitochondrial membrane potential and adenosine triphosphate levels, thus protecting mitochondrial function in FFA-treated HepG2 cells. Furthermore, compound 2 markedly suppressed the protein expression levels of disulfide-isomerase A3 precursor and fatty acid synthase, thus suppressing FFA-induced lipogenesis in HepG2 cells. In conclusion, the present study identified compound 2 as one of the main active compounds in Coreopsis tinctoria responsible for its lipid-lowering effects. Compound 2 was revealed to possess antihyperlipidemic properties, exerted via reducing oxidative stress, protecting mitochondrial function and suppressing lipogenesis.

Genomics of human fatty liver disease reveal mechanistically linked lipid droplet-associated gene regulations in bland steatosis and nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) is a common disorder hallmarked by excessive lipid deposits. Based on our recent research on lipid droplet (LD) formation in hepatocytes, we investigated LD-associated gene regulations in NAFLD of different grades, that is, steatosis vs steatohepatitis by comparing liver biopsies from healthy controls (N = 13) and NAFLD patients (N = 102). On average, more than 700 differentially expressed genes (DEGs) were identified of which 146 are mechanistically linked to LD formation. We identified 51 LD-associated DEGs frequently regulated in patient samples (range ≥5 to ≤102) with the liver-receptor homolog-1(NR5A2), that is, a key regulator of cholesterol metabolism being commonly repressed among 100 patients examined. With bland steatosis, notable regulations involved hypoxia-inducible lipid droplet-associated-protein and diacylglycerol-O-acyltransferase-2 renowned for their role in LD-growth. Conversely, nonalcoholic steatohepatitis-associated DEGs coded for epidermal growth factor receptor and TLR4 signaling with decreased expression of the GTPase Rab5 and the lipid phosphohydrolase PPAP2B thus highlighting adaptive responses to inflammation, LDL-mediated endocytosis and lipogenesis, respectively. Studies with steatotic primary human hepatocyte cultures demonstrated induction of LD-associated PLIN2, CIDEC, DNAAF1, whereas repressed expression of CPT1A, ANGPTL4, and PKLR informed on burdened mitochondrial metabolism. Equally, repressed expression of the B-lymphocyte chemoattractant CXCL13 and STAT4 as well as induced FGF21 evidenced amelioration of steatosis-related inflammation. In-vitro/in-vivo patient sample comparisons confirmed C-reactive protein, SOCS3, NR5A2, and SOD2 as commonly regulated. Lastly, STRING network analysis highlighted potential "druggable" targets with PLIN2, CIDEC, and hypoxia-inducible lipid droplet-associated-protein being confirmed by immunofluorescence microscopy. In conclusion, steatosis and steatohepatitis specific gene regulations informed on the pathogenesis of NAFLD to broaden the perspective of targeted therapies.

Protein disulfide isomerase A3-specific Th1 effector cells infiltrate colon cancer tissue of patients with circulating anti-protein disulfide isomerase A3 autoantibodies

To investigate novel colorectal cancer (CRC)-associated antigens that could be targets of humoral or cellular responses, we analyzed the reactivity of serum from a long-surviving CRC patient (for more than 100 months of follow-up) in clinical remission, by serologic proteome analysis. Two-dimensional Western blotting (2D-WB) and mass spectrometry analysis revealed a strong reactivity of this serum against protein disulfide isomerase A3 (PDIA3). Anti-PDIA3 antibodies are not a diagnostic marker of CRC, 2D-WB and Luminex analysis revealed that they were equally present in about 10% of sera from healthy subjects and CRC patients. Kaplan-Meier analysis of survival in CRC patient cohort, after 48 months of follow-up, showed a trend of higher survival in patients with increased levels of autoantibodies to PDIA3. Therefore, the interplay between the presence of these antibodies and T-cell response was investigated. Peripheral blood T cells from CRC patients with high immunoglobulin G (IgG) reactivity to PDIA3 also secreted interferon gamma (IFN-γ) when stimulated in vitro with recombinant PDIA3, whereas those from CRC with low IgG reactivity to PDIA3 did not. PDIA3-pulsed dendritic cells efficiently induced proliferation and IFN-γ production of autologous CD4(+) and CD8(+) T cells. Finally, ex vivo analysis of tumor-infiltrating T lymphocytes from CRC patients with autoantibodies to PDIA3 revealed that PDIA3-specific Th1 effector cells accumulated in tumor tissue. These data indicate that the presence of autoantibodies to PDIA3 favors the development of an efficient and specific T-cell response against PDIA3 in CRC patients. These results may be relevant for the design of novel immunotherapeutic strategies in CRC patients.

Protein disulfide isomerase in redox cell signaling and homeostasis

Thiol proteins may potentially act as redox signaling adaptor proteins, adjusting reactive oxygen species intermediates to specific signals and redox signals to cell homeostasis. In this review, we discuss redox effects of protein disulfide isomerase (PDI), a thioredoxin superfamily oxidoreductase from the endoplasmic reticulum (ER). Abundantly expressed PDI displays ubiquity, interactions with redox and nonredox proteins, versatile effects, and several posttranslational modifications. The PDI family contains >20 members with at least some apparent complementary actions. PDI has oxidoreductase, isomerase, and chaperone effects, the last not directly dependent on its thiols. PDI is a converging hub for pathways of disulfide bond introduction into ER-processed proteins, via hydrogen peroxide-generating mechanisms involving the oxidase Ero1α, as well as hydrogen peroxide-consuming reactions involving peroxiredoxin IV and the novel peroxidases Gpx7/8. PDI is a candidate pathway for coupling ER stress to oxidant generation. Emerging information suggests a convergence between PDI and Nox family NADPH oxidases. PDI silencing prevents Nox responses to angiotensin II and inhibits Akt phosphorylation in vascular cells and parasite phagocytosis in macrophages. PDI overexpression spontaneously enhances Nox activation and expression. In neutrophils, PDI redox-dependently associates with p47phox and supports the respiratory burst. At the cell surface, PDI exerts transnitrosation, thiol reductase, and apparent isomerase activities toward targets including adhesion and matrix proteins and proteases. Such effects mediate redox-dependent adhesion, coagulation/thrombosis, immune functions, and virus internalization. The route of PDI externalization remains elusive. Such multiple redox effects of PDI may contribute to its conspicuous expression and functional role in disease, rendering PDI family members putative redox cell signaling adaptors.