Expression Of Angiopoietin-like Protein Research Articles

PM2.5 induces lung inflammation through ANGPTL4

Fine particulate matter (PM2.5) is a common major air pollutant and is associated with decreased lung function, induced allergic airway inflammation and is closely correlated with chronic lung diseases. Angiopoietin-like protein 4 (ANGPTL4) is a cytokine with multiple functions, participating in processes such as inflammation, angiogenesis, and metastasis. Curcumin is an active compound found in turmeric plants and possesses various pharmacological effects, including antioxidant, anti-inflammatory, anticancer, and immunomodulatory properties. The aim of this study was twofold: firstly, to investigate the involvement of ANGPTL4 in lung inflammation and carcinogenesis under PM2.5 exposure, and secondly, to explore the impact of curcumin on ANGPTL4 expression and its potential in lung cancer chemoprevention. We used protein array to detect severe proinflammatory cytokines and then used qPCR to confirm by increasing the concentration of PM2.5 to enhance the expressions of CXCL1, CXCL5; IL-1α, IL-1β, MIP-3α and inflammatory or fibrosis associated proteins. Curcumin inhibits PM2.5 induced ANGPTL4 and the IκB-α (inhibitor of NFκB) dependent inflammatory pathway. Silencing of ANGPTL4 by shRNA will restore IκB-α and MIP-3α expression. In conclusion, the increased expression of ANGPTL4 after treatment with PM2.5 in lung cells may be one of the mechanisms by which PM2.5 exposure contributes to lung inflammation progression and our results provide evidence that curcumin in anti-inflammation therapeutics could be a beneficial chemopreventive agent.

Activation of Peroxisome Proliferator-Activated Receptor-β/δ (PPARβ/δ) in Keratinocytes by Endogenous Fatty Acids.

Nuclear hormone receptors exist in dynamic equilibrium between transcriptionally active and inactive complexes dependent on interactions with ligands, proteins, and chromatin. The present studies examined the hypothesis that endogenous ligands activate peroxisome proliferator-activated receptor-β/δ (PPARβ/δ) in keratinocytes. The phorbol ester treatment or HRAS infection of primary keratinocytes increased fatty acids that were associated with enhanced PPARβ/δ activity. Fatty acids caused PPARβ/δ-dependent increases in chromatin occupancy and the expression of angiopoietin-like protein 4 (Angptl4) mRNA. Analyses demonstrated that stearoyl Co-A desaturase 1 (Scd1) mediates an increase in intracellular monounsaturated fatty acids in keratinocytes that act as PPARβ/δ ligands. The activation of PPARβ/δ with palmitoleic or oleic acid causes arrest at the G2/M phase of the cell cycle of HRAS-expressing keratinocytes that is not found in similarly treated HRAS-expressing Pparb/d-null keratinocytes. HRAS-expressing Scd1-null mouse keratinocytes exhibit enhanced cell proliferation, an effect that is mitigated by treatment with palmitoleic or oleic acid. Consistent with these findings, the ligand activation of PPARβ/δ with GW0742 or oleic acid prevented UVB-induced non-melanoma skin carcinogenesis, an effect that required PPARβ/δ. The results from these studies demonstrate that PPARβ/δ has endogenous roles in keratinocytes and can be activated by lipids found in diet and cellular components.

HIF-1α regulates osteoclastogenesis and alveolar bone resorption in periodontitis via ANGPTL4

ObjectiveThe mechanism of alveolar bone resorption caused by periodontitis is not fully understood. We sought to investigate whether microenvironmental changes of local hypoxia are involved in these processes. MethodsIn this study, periodontitis models of control mice and knockout of Hypoxia Induced Factor 1α (HIF-1α) harboring Cathepsin K (CTSK) Cre mice were constructed to study the effect of osteoclasts affected by hypoxic environment on alveolar bone resorption. RAW264.7 cells were subsequently induced by CoCl2 to observe the effects of HIF-1α and Angiopoietin-like Protein 4 (ANGPTL4) on osteoblast differentiation and fusion. ResultsThe degree of alveolar bone resorption in the periodontitis tissues was lesser in mice with conditional knockout of HIF-1α in osteoclasts than in wild-type mice. We also observed that HIF-1α conditional knockout mice had fewer osteoclasts on the alveolar bone surface than control mice. HIF-1α increases the expression of ANGPTL4 and promotes the differentiation of RAW264.7 cells into osteoblasts and cell fusion under chemically simulated hypoxic conditions. ConclusionHIF-1α regulates osteoclastogenesis and participates in bone resorption in periodontitis through ANGPTL4.

Effects of Peroxisome Proliferator-Activated Receptor γ on Modulating Angiopoietin-Like Protein 4 Synthesis in Caco-2 Cells Exposed to <i>Clostridium butyricum</i>

Angiopoietin-like protein 4 (ANGPTL4) is considered to be one of the important circulating mediators linking intestinal microorganisms and host lipid metabolism. The objective of this study was to assess the effects of peroxisome proliferator-activated receptor γ (PPARγ) on modulating ANGPTL4 synthesis in Caco-2 cells exposed to Clostridium butyricum. The viability of Caco-2 cells and the expression of PPARγ and ANGPTL4 in Caco-2 cells were detected after the Caco-2 cells were co-cultured with C. butyricum at the concentration of 1 × 106, 1 × 107 and 1 × 108 CFU/mL. The results showed that cell viability was enhanced by C. butyricum. Besides, PPARγ and ANGPTL4 expression and secretion in Caco-2 cells was significantly increased by 1 × 107 and 1 × 108 CFU/mL of C. butyricum. Furthermore, the effects of PPARγ on modulating ANGPTL4 synthesis in Caco-2 cells regulated by 1 × 108 CFU/mL of C. butyricum was also be expounded in PPARγ activation/inhibition model based on Caco-2 cells and via ChIP technique. It was found that C. butyricum promoted the binding of PPARγ to the PPAR binding site (chr19: 8362157-8362357, located upstream of the transcriptional start site of angptl4) of the angptl4 gene in Caco-2 cells. However, the PPARγ was not the only way for C. butyricum to stimulate ANGPTL4 production. Taken together, PPARγ played a role in the regulation of ANGPTL4 synthesis by C. butyricum in Caco-2 cells.

Effects of Peroxisome Proliferator-Activated Receptor γ on Modulating Angiopoietin-Like Protein 4 Synthesis in Caco-2 Cells Exposed to Clostridium butyricum

Angiopoietin-like protein 4 (ANGPTL4) is considered to be one of the important circulating mediators linking intestinal microorganisms and host lipid metabolism. The objective of this study was to assess the effects of peroxisome proliferator-activated receptor у (PPARγ) on modulating ANGPTL4 synthesis in Caco-2 cells exposed to Clostridium butyricum. The viability of Caco-2 cells and the expression of PPARγ and ANGPTL4 in Caco-2 cells were detected after the Caco-2 cells were co-cultured with C. butyricum at the concentration of 1 x 10^(6), 1 x 10^(7) and 1 x 10^(8) CFU/mL. The results showed that cell viability was enhanced by C. butyricum. Besides, PPARγ and ANGPTL4 expression and secretion in Caco-2 cells was significantly increased by 1 x 10^(7) and 1 x 10^(8) CFU/mL of C. butyricum. Furthermore, the effects of PPARγ on modulating ANGPTL4 synthesis in Caco-2 cells regulated by 1 x 10^(8) CFU/mL of C. butyricum was also be expounded in PPARγ activation/inhibition model based on Caco-2 cells and via ChIP technique. It was found that C. butyricum promoted the binding of PPARγ to the PPAR binding site (chr19: 8362157-8362357, located upstream of the transcriptional start site of angptl4) of the angptl4 gene in Caco-2 cells. However, the PPARγ was not the only way for C. butyricum to stimulate ANGPTL4 production. Taken together, PPARγ played a role in the regulation of ANGPTL4 synthesis by C. butyricum in Caco-2 cells.

Increased expression of angiopoietin-like protein 4 regulates matrix metalloproteinase-13 expression in Porphyromonas gingivalis lipopolysaccharides-stimulated gingival fibroblasts and ligature-induced experimental periodontitis.

Angiopoietin-like protein 4 (ANGPTL4) is produced in chronic or acute inflammation. Although ANGPTL4 increases in the periodontal ligament fibroblasts during hypoxia, the involvement and role of ANGPTL4 in periodontitis have not been elucidated. In this study, we investigated whether ligature-induced experimental periodontitis and/or Porphyromonas gingivalis lipopolysaccharides (Pg-LPS) would upregulate ANGPTL4 expression and whether ANGPTL4 would somehow involve in the expression of matrix metalloproteinases (MMPs) which are key molecules in the process of periodontal tissue destruction. Experimental periodontitis was induced in 6-week-old male Sprague-Dawley rats by placing a nylon suture around the neck of the maxillary second molar. Two weeks after the induction of periodontitis, the periodontal tissue was excised and analyzed by histological/immunohistochemical staining and gene expression analyses. Human gingival fibroblasts (hGFs) were stimulated with Pg-LPS. The gene expression of ANGPTLs and receptors involved in ANGPTL4 recognition were observed. We also confirmed the changes in gene expression of MMPs upon stimulation with human ANGPTL4. Furthermore, we downregulated ANGPTL4 expression by short interfering RNA in hGFs and investigated the effect of Pg-LPS on MMP production. Induction of periodontitis significantly increased the expression of ANGPTL4 in the gingiva. Pg-LPS significantly increased the gene and protein expression of ANGPTL4 in hGFs but not the gene expression of other ANGPTLs or ANGPTL receptors. Recombinant human ANGPTL4 significantly increased MMP13 gene expression in hGFs. We also confirmed that MMP13 expression was increased in the gingiva during experimental periodontitis. Pg-LPS induced MMP13 gene expression in hGFs. These results suggest the pivotal role of ANGPTL4 in periodontitis. Periodontitis increases ANGPTL4 expression in the gingiva, further suggesting that increased ANGPTL4 may be a factor involved in enhancing MMP13 expression.

Molecular characterisation, temporal expression and involvement of ANGPTL4 in fat deposition in Muscovy ducks

ABSTRACT 1. Angiopoietin-like protein 4 (ANGPTL4) plays a key role in promoting fat metabolism and reducing blood lipid. This study characterised the ANGPTL4 gene in Muscovy ducks (Cairina moschata) and investigated its potential functions in fat metabolism in Muscovy ducks. 2. The Muscovy duck ANGPTL4 cDNA was successfully cloned for the first time, showing a length of 2591 bp. After phylogenetic analysis by RT-qPCR analysis, it was found that the ANGPTL4 gene of Anas platyrhynchos shared the highest sequence similarity with that of Muscovy ducks. 3. The ANGPTL4 gene was commonly expressed in 23 different tissues with the highest expression in the abdominal fat in Muscovy ducks. A significant association was observed between abdominal fat percentage (AFP) and the mRNA expression of the ANGPTL4 gene. Moreover, Muscovy ducks showed a peak of ANGPTL4 expression in the liver and abdominal fat at 1–2 weeks old. 4. These findings suggest that the ANGPTL4 gene is related to fat deposition and regulation in Muscovy ducks.

Dual roles of ANGPTL4 in multiple inflammatory responses in stomatitis mice.

Stomatitis is inflammation of the oral mucosa. Angiopoietin-like protein 4 (ANGPTL4) has pleiotropic functions both anti-inflammatory and pro-inflammatory properties. In the present study, we tested whether there is a correlation between increased ANGPTL4 expression and inflammation in stomatitis mice and the mechanisms involved. In this study, the oral mucosa of mice was burned with 90% phenol and intraperitoneal injection of 5-fluorouracil to establish the model of stomatitis mice. The pathological changes of stomatitis mice were observed by H&E staining of paraffin section. The expressions of cytokines and ANGPTL4 were detected by fluorescence quantitative PCR, and the protein levels of ANGPTL4 were detected by western blot. Compared with control group, the oral mucosal structure of model mice was damaged. The expression of ANGPTL4 were significantly increased concomitantly with elevated production of anti-inflammatory cytokine (peroxisome proliferator-activated receptoralpha) and pro-inflammatory cytokines [nuclear transcription factor-kappaB, interleukin-6 (IL-6), IL-1β, and tumor necrosis factor-α] in mice with stomatitis. This study suggests that ANGPTL4 may be a double-edged sword in multiple inflammatory responses in stomatitis mice.

Angiopoietin-Like Protein 4 Is Involved in Manganese Superoxide Dismutase-Mediated Suppression of Breast Cancer Cell Growth.

This study aims to understand the molecular basis of manganese superoxide dismutase (MnSOD) impacts on breast cancer cell growth. Modulation of the level of MnSOD by genetic engineering led significant changes in the expression of angiopoietin-like protein 4 (ANGPTL4) and activity of peroxisome proliferator-activated receptor α (PPARα) in MCF7 cells. PPARα agonist increased ANGPTL4 expression inhibited by MnSOD. Proliferation of MCF7 cells was inhibited by MnSOD, however, ANGPTL4 transduction into MCF7 cells with MnSOD overexpression significantly stimulated cell proliferation. MnSOD induced G0/G1 cell cycle arrest, nevertheless, ANGPTL4 transduction significantly reduced the percentage of cells in G0/G1 phase overexpressing MnSOD. In conclusion, MnSOD suppressed the expression of ANGPTL4 in breast cancer cells via the PPARα signaling pathway, and ANGPTL4 was involved in MnSOD-mediated proliferation inhibition and cell cycle arrest.

Serum Angiopoietin-Like Protein 4: A Potential Prognostic Biomarker for Prediction of Vascular Invasion and Lymph Node Metastasis in Cholangiocarcinoma Patients.

Cholangiocarcinoma (CCA) is a tumor arising from cholangiocytes lining the bile ducts. Vascular invasion and lymph node metastasis are important prognostic factors for disease staging as well as clinical therapeutic decisions for CCA patients. In the present study, we applied CCA sera proteomic analysis to identify a potential biomarker for prognosis of CCA patients. Then, using bioinformatics tools, we identified angiopoietin-like protein 4 (ANGPTL4) which expressed highest signal intensity among candidate proteins in proteomic analysis of CCA sera. Expression of ANGPTL4 in CCA tissues was determined using immunohistochemistry. The results showed that ANGPTL4 was stained at higher level in CCA cells when compared with normal cholangiocytes. The high expression of ANGPTL4 was associated with lymph node metastasis and advanced tumor stage (p = 0.013 and p = 0.031, respectively). Furthermore, serum ANGPTL4 levels in CCA and healthy control (HC) were analyzed using a dot blot assay. And it was found that ANGPTL4 level was significantly higher in CCA than HC group (p < 0.0001). ROC curve analysis revealed that serum ANGPTL4 level was effectively distinguished CCA from healthy patients (cutoff = 0.2697 arbitrary unit (AU), 80.0% sensitivity, 72.7% specificity, AUC = 0.825, p < 0.0001). Serum ANGPTL4 level was associated with vascular invasion and lymph node metastasis (p = 0.0004 and p = 0.006), so that it differentiated CCA with vascular invasion from CCA without vascular invasion (cutoff = 0.5526 AU, 64.9% sensitivity, 92.9% specificity, AUC = 0.751, p = 0.006) and it corresponded to CCA with/without lymph node metastasis (cutoff = 0.5399 AU, 71.4% sensitivity, 70.8% specificity, AUC = 0.691, p = 0.01) by ROC analysis. Serum ANGPTL4 levels showed superior predictive efficiency compared with CA 19-9 and CEA for vascular invasion and lymph node metastasis. In addition, serum ANGPTL4 level was an independent predictive indicator by multivariate regression analysis. In conclusion, serum ANGPTL4 could be a novel prognostic biomarker for prediction of vascular invasion and lymph node metastasis of CCA patients.

Expression of ANGPTL4 in Nucleus Pulposus Tissues Is Associated with Intervertebral Disc Degeneration.

Objective Angiopoietin-like protein 4 (ANGPTL4), encoding a glycosylated secreted protein, has been reported to be closely related to many kinds of diseases, including diabetes, tumor, and some musculoskeletal pathologies, such as rheumatoid arthritis, osteoarthritis, and osteoporosis. The aim of the current study is to investigate the role of ANGPTL4 in intervertebral disc degeneration and analyze the association of ANGPTL4 expression with Pfirrmann grades. Methods A total of 162 nucleus pulposus tissues were collected from lumbar intervertebral disc herniation patients undergoing interforaminal endoscopic surgery. Real-time quantitative PCR and western blot were performed to determine the mRNA and protein expression of ANGPTL4 in nucleus pulposus samples. Statistical analysis was performed to analyze the association of ANGPTL4 expression with Pfirrmann grades. Results Based on the clinical data of 162 patients, results showed that Pfirrmann grades were significantly associated with patients' age (r = 0.162, P = 0.047) and were not significantly associated with patients' gender (P > 0.05). RT-qPCR and western blot results showed that the mRNA (r = 0.287, P < 0.05) and protein (r = 0.356, P < 0.05) expressions of ANGPTL4 were both closely associated with Pfirrmann grades. The expression of ANGPTL4 was remarkably increased in the groups of high IVDD Pfirrmann grades. Conclusion The results demonstrated that ANGPTL4 expression was positively associated with the Pfirrmann grades and the severity of intervertebral disc degeneration. ANGPTL4 may be served as a candidate biomarker for intervertebral disc degeneration.

Expression of angiopoietin-like protein 2 in ovarian tissue of rat polycystic ovarian syndrome model and its correlation study

BackgroundThis study investigated the expression of angiopoietin-like protein 2 (ANGPTL2) in the tissues of rat models of polycystic ovary syndrome (PCOS) and its correlation with PCOS.MethodsSix-weeks-old female specific pathogen-free rats (n = 60) were divided into blank control, PCOS model, and metformin groups (n = 20/group). After 21 days of metformin intervention, the serum sex hormones, fasting blood glucose, fasting insulin, and insulin resistance (IR) of rats in each group were measured. The mRNA levels of ANGPTL2, Foxol, and Akt in the ovarian tissues were monitored by real-time fluorescence quantitative PCR.ResultsCompared with the control group, the levels of serum sex hormones, fasting blood glucose, fasting insulin, and IR in the model group showed significant increases, and the levels of ANGPTL2, Foxol, and Akt in the ovarian tissue also showed significant increases. Compared with the PCOS group, the serum sex hormones, fasting blood glucose, fasting insulin, and IR of rats in the metformin group were significantly decreased, and the levels of ANGPTL2, Foxol, and Akt in ovarian tissues also showed significant decreases.ConclusionsThese findings suggest that ANGPTL2 might participate in the development of PCOS through the PI3K/Akt signaling pathway. Metformin improves IR by reducing the expression of ANGPTL2, thus improving the endocrine environment of PCOS and might change the disease outcome.

Decreased ANGPTL4 impairs endometrial angiogenesis during peri-implantation period in patients with recurrent implantation failure.

Insufficient endometrial angiogenesis during peri‐implantation impairs endometrial receptivity (ER), which contributes to recurrent implantation failure (RIF) during in vitro fertilization and embryo transfer (IVF‐ET). Angiopoietin‐like protein 4 (ANGPTL4) acts as a multifunctional secretory protein and is involved in the regulation of lipid metabolism and angiogenesis in various tissues including the endometrium. Herein, we found decreased ANGPTL4 expression in endometrial tissue and serum during peri‐implantation period in 18 RIF‐affected women with elevated uterine arterial impedance (UAI) compared with the pregnancy controls. ANGPTL4 and peroxisome proliferator‐activated receptor gamma (PPARγ) expression were up‐regulated upon decidualization on human endometrial stromal cells (HESCs). Rosiglitazone promoted the expression of ANGPTL4 in HESCs and human umbilical vein endothelial cells (HUVECs) via PPARγ. ANGPTL4 promoted the proliferation, migration and angiogenesis of HUVECs in vitro. Our results suggest that decreased abundance of ANGPTL4 in endometrial tissues impairs the endometrial receptivity via restraining endometrial angiogenesis during decidualization; while rosiglitazone‐induced ANGPTL4 up‐regulation in hESCs and HUVECs through PPARγ. Therefore, ANGPTL4 could be a potential therapeutic approach for some RIF‐affected women with elevated UAI.

Knockdown of Angiopoietin-like protein 4 suppresses the development of colorectal cancer

Colorectal cancer, is the growth of cancer cells in the part of the colon. Angiopeptin is one of the growth factors in the human body that is particularly effective in the regulatory process. In this research, the regulatory role and its mechanism of Angiopoietin-like protein 4 (ANGPTL4) in colorectal cancer (CRC) metastasis, has been studied. Protein expression of ANGPLT4 was analyzed by immunohistochemistry in tumor samples and adjacent normal specimens of 40 patients with CRC cancer of various phases. A gene knockout test was conducted, two effective siRNA of ANGPTL4, named siRNA1 and siRNA2, were constructed and transfected into two CRC cell lines SW480 and HT-29 to block the expression of ANGPTL4. QRT-PCR and western blotting were used to validate the knockdown efficiency of the mRNA and proteins. Based on the results, the protein expression of ANGPTL4 was increased in human CRC tissues with the development of CRC. Knockdown of ANGPTL4 by siRNA in SW480 and HT-29 cells in vitro inhibited cell proliferation, promoted cell apoptosis, and suppressed the ability of cell migration and invasion. Besides, the sensitivity of CRC cells to Cisplatin was increased in the low ANGPTL4 expression group. ANGPTL4 might be a new potential therapeutic target for patients with CRC.

Circulating and tissue specific transcription of angiopoietin-like protein 4 in human Type 2 diabetes

AimsObesity is associated with adipose tissue (AT) dysfunction marked by cellular hypertrophy, inflammation, hypoxia and fibrosis. Angiopoietin-like protein 4 (ANGPTL4) inhibits lipoprotein lipase which regulates triglyceride storage. Recently, inhibition of ANGPTL4 has been suggested as potential treatment for type 2 diabetes. Here we evaluate ANGPTL4's role in diabetes and examine ANGPTL4 in relation to markers of AT dysfunction and fatty liver disease. Materials & methodsWe obtained a unique set of paired samples from subjects undergoing weight loss surgery including subcutaneous AT (SCAT), omental AT (OMAT), liver, thigh muscle biopsies and serum including a post-surgical SCAT biopsy after 9 months. ResultsSCAT ANGPTL4 expression and circulating protein levels were higher in people with diabetes and correlated with glucose levels and HOMA-IR but not BMI. At post-surgical follow up, SCAT ANGPTL4 declined in subjects with diabetes to levels of those without diabetes. ANGPTL4 expression correlated with HIF1A and inflammation (MCP-1, IL-6). ConclusionsWe found that SCAT ANGPTL4 was closely linked with the expression of ANGPTL4 in the liver and represented a good proxy for liver steatosis. We suggest the elevation of ANGPTL4 levels in diabetes and the association with inflammation and hypoxia is due to a compensatory mechanism to limit further AT dysfunction. A reduction of ANGPTL4 for the treatment of T2DM as previously suggested is thus unlikely to be of further benefit.

Growth hormone upregulates ANGPTL4 mRNA and suppresses lipoprotein lipase via fatty acids: Randomized experiments in human individuals

ObjectivesLipoprotein lipase (LPL) catalyzes the hydrolysis of circulating triglycerides into free fatty acids (FFA) and thereby promotes FFA uptake in peripheral tissues. LPL is negatively regulated by angiopoietin-like protein 4 (ANGPTL4) presumably by an FFA-dependent mechanism. Growth hormone (GH) suppresses LPL activity, but it is unknown whether this is mediated by FFA and ANGPTL4. Therefore, we investigated the concerted effect of GH on ANGPTL4 and LPL in the presence and absence of lipolysis in two in vivo studies in human subjects. MethodsIn a randomized, placebo-controlled, cross-over study, nine obese men were examined after injection of 1) a GH bolus, and 2) a GH-receptor antagonist followed by four adipose tissue biopsies obtained over a 5-h period. In a second study, nine hypopituitary men were examined in a 2 × 2 factorial design including GH and acipimox (an anti-lipolytic agent), with biopsies from adipose tissue and skeletal muscle obtained during a basal period and a subsequent hyperinsulinemic-euglycemic clamp. The mRNA expression of ANGPTL4 and LPL as well as LPL activity were analyzed in the biopsies. ResultsIn both studies, GH increased serum FFA levels, upregulated ANGPTL4 mRNA expression and suppressed LPL activity. In study 2, acipimox completely suppressed FFA levels and antagonized the effects of GH on ANGPTL4 and LPL. ConclusionsThese human in vivo studies demonstrate that GH upregulates ANGPTL4 mRNA and suppresses LPL activity via an FFA-dependent mechanism.

Metformin Mitigates Nickel-Elicited Angiopoietin-Like Protein 4 Expression via HIF-1α for Lung Tumorigenesis

Nickel (Ni), which is a carcinogenic workplace hazard, increases the risk of lung cancer. Angiopoietin-like protein 4 (ANGPTL4) is a multifunctional cytokine that is involved in both angiogenesis and metastasis, but its role in lung cancer is still not clear. In this study, we assessed the role of ANGPTL4 in lung carcinogenesis under nickel exposure and investigated the effects of the antidiabetic drug metformin on ANGPTL4 expression and lung cancer chemoprevention. Our results showed that ANGPTL4 is increased in NiCl2-treated lung cells in a dose- and time-course manner. The expression of ANGPTL4 and HIF-1α induced by NiCl2 were significantly repressed after metformin treatment. The downregulation of HIF-1α expression by ROS savenger and HIF-1α inhibitor or knockdown by lentiviral shRNA infection diminished NiCl2-activated ANGPTL4 expression. Chromatin immunoprecipitation and the luciferase assay revealed that NiCl2-induced HIF-1α hypoxia response element interactions activate ANGPTL4 expression, which is then inhibited by metformin. In conclusion, the increased presence of ANGPTL4 due to HIF-1α accumulation that is caused by nickel in lung cells may be one mechanism by which nickel exposure contributes to lung cancer progression. Additionally, metformin has the ability to prevent NiCl2-induced ANGPTL4 through inhibiting HIF-1α expression and its binding activity. These results provide evidence that metformin in oncology therapeutics could be a beneficial chemopreventive agent.

Angiopoietin-Like Protein 4 (ANGPTL4) Induces Retinal Pigment Epithelial Barrier Breakdown by Activating Signal Transducer and Activator of Transcription 3 (STAT3): Evidence from ARPE-19 Cells Under Hypoxic Condition and Diabetic Rats.

BackgroundDiabetic retinopathy is a primary contributor of visual impairment in adult diabetes mellitus patients. Diabetic retinopathy causes breakdown of blood retinal barrier (BRB), and leads to diabetic macular edema. Previous studies have demonstrated angiopoietin-like protein 4 (ANGPTL4) as an effective diabetic retinopathy therapeutic target, however, its role in maintaining the outer BRB in diabetic retinopathy has yet not elucidated.Material/MethodsWe established an in vivo diabetic rat model with the use of streptozotocin injections and cultured ARPE-19 cells under (hypoxia, 1%) condition. We first investigated the expression of hypoxia induced factor-1α (HIF-1α) and ANGPTL4 in vivo and subsequently studied the transcriptional regulation and underlying molecular mechanisms in ARPE-19 cells under oxygen-deprived situations.ResultsThe expression of HIF-1α and ANGPTL4 was increased with diabetic retinopathy progression both in vivo and in vitro. Depletion of HIF-1α by siRNA inhibited hypoxia-induced ANGPTL4 expression. Repressing the HIF-1α/ANGPTL4 signaling effectively alleviated the migration and cellular permeability induced by hypoxia in ARPE-19 cells. Depletion of ANGPTL4 by siRNA significantly alleviated signal transducer and activator of transcription 3 (STAT3) activity in vitro, thereby attenuating the decrease of tight junction proteins occludin and zona occludens-1 (ZO-1) under hypoxia in ARPE-19 cells.ConclusionsOur results suggest that ANGPTL4 partially modulates STAT3 and could serve as an effective diabetic retinopathy treatment strategy.

Effects of non‐esterified fatty acids on the expression and secretion of angiopoietin‐like protein 4 and fibroblast growth factor 21 in calf hepatocytes cultured in vitro

IntroductionNegative energy balance (NEB) is considered as the pathological basis of energy metabolic disorders, such as fatty liver and ketosis, in periparturient dairy cows. An elevated serum non‐esterified fatty acids (NEFA) concentration is one of the most important indicators of NEB. Angiopoietin‐like protein 4 (ANGPTL4) and fibroblast growth factor 21 (FGF21) have been identified as hepatokines, which involved in regulation of metabolic adaptations. In dairy cows, most circulating ANGPTL4 and FGF21 originate from the liver. However, the direct effects of NEFA on the expression and secretion of ANGPTL4 and FGF21 in bovine hepatocytes are not entirely clear. The purpose of the present study was to investigate the effects of different NEFA concentrations on the expression and secretion of these two hepatokines in calf hepatocytes cultured in vitro.MethodsBovine hepatocytes were cultured using the collagenase perfusion method. After culture for 72 h, the hepatocytes were treated with NEFA at final concentrations of 0 (control), 0.6, 1.2, 1.8 and 2.4 mmol/L. After 24 h of continuous culture, the mRNA and protein expression levels of ANGPTL4 and FGF21 in the hepatocytes were determined by real‐time PCR and Western blot, respectively. ANGPTL4 and FGF21 secretions in the supernatant were determined by enzyme‐linked immunosorbent assay (ELISA).ResultsThe results showed similar levels of ANGPTL4 expression and secretion following treatment with 0.6 and 1.2 mmol/L NEFA, which were higher than those observed for the controls (P&lt;0.05). ANGPTL4 expression and secretion were also similar at 1.8 and 2.4 mmol/L NEFA and significantly higher than those observed for controls (P&lt;0.01). The expression and secretion of FGF21 at 0.6 mmol/L NEFA‐treated hepatocytes was higher than that of the control group (P&lt;0.05). The FGF21 expression and secretion were similar at 1.2, 1.8 and 2.4 mmol/L NEFA‐treated hepatocytes and significantly higher than those observed for controls (P&lt;0.01).ConclusionThe results of this study indicate that high concentrations of NEFA significantly increase the expression and secretion of ANGPTL4 and FGF21 in bovine hepatocytes cultured in vitro in a dose‐dependent manner. Specifically, NEFA promotes the expression and secretion of ANGPTL4 and FGF21, which may worsen fat mobilization under NEB conditions and thereby lead to the pathological processes of energy metabolism disorders in dairy cows in the peripartum period. However, further studies are needed to elucidate the underlying mechanisms.Support or Funding InformationThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

ANGPTL4 mediates the protective role of PPAR\u03b3 activators in the pathogenesis of preeclampsia

Peroxisome proliferator-activated receptor γ (PPARγ) has been shown to be a therapeutic target for preeclampsia (PE). Angiopoietin-like protein 4 (ANGPTL4) is a multifunctional secretory protein involved in regulating lipid metabolism and angiogenesis in various tissues. However, the expression of PPARγ and ANGPTL4 and their interaction in PE remain elusive. Here we showed that PPARγ agonist rosiglitazone upregulated the expression and secretion of ANGPTL4 in a dose-dependent manner in HTR8/SVneo cells, human umbilical vein endothelial cells (HUVECs) and placental explants. More importantly, we confirmed that the PPARγ/retinoid X receptor α heterodimer specifically binds to the ANGPTL4 promoter region and enhances its transcriptional activity. In addition, the levels of ANGPTL4 and PPARγ activators in the serum and their expression in placental tissues were significantly reduced in preeclamptic patients compared with normal pregnant subjects. Furthermore, functional studies demonstrated that ANGPTL4 mediates the facilitative effects of the PPARγ agonist on the survival, proliferation, migration and invasion of HTR8/SVneo cells, placental explants outgrowth and angiogenesis in HUVECs. Taken together, our results suggest that ANGPTL4 is a potential target gene for PPARγ and mediates the protective role of PPARγ activators in the pathogenesis of PE.