Activator Protein-1 Signaling Pathways Research Articles

PP2 suppresses proliferation and migration of C6 Glioma and MDA-MB-231 cells by targeting both fibroblast growth factor receptor 1 and Src

Fibroblast growth factor (FGF) is involved in the progression of glioma, a most common type of brain tumor, and breast tumors. In this study, we aim to evaluate the effects of the inhibitor PP2 on cell proliferation and migration in glioma and breast tumor cells, and to characterize the molecular mechanisms involved in these processes. The inhibitory effect of PP2 on the tumorigenic potential of C6 glioma and MDA-MB-231 cells was examined by proliferation, migration, and invasion assays, and apoptotic analysis. The molecular mechanism behind the anti-glioma activity of PP2 was investigated by immunoblotting, immunoprecipitation, phosphoprotein assay, cellular thermal shift assay (CETSA), and molecular docking modeling. PP2 suppressed the proliferation and migration of C6 glioma and MDA-MB-231 cells via FGF2. Moreover, PP2 directly blocked the enzyme activity of FGF receptor 1 (FGFR1) and Src, subsequently affecting the nuclear factor-κB and activator protein-1 signaling pathways. CETSA analysis and the docking model indicated that the TK1 domains (Val 492 ad Glu 486) of FGFR2 could be binding sites of PP2. Collectively, therefore, our findings suggest that PP2 mediates antitumor effects by targeting both FGFR1 and Src and may have applications as a therapeutic inhibitor for the treatment of glioma.

Abstract 49: Activator protein 1 (AP-1) Complex in Antigen Presenting Cells contributes to Salt-Sensitive Blood Pressure in Humans

Salt-sensitivity of blood pressure (SSBP) is an independent risk factor for cardiovascular morbidity and mortality. The exact mechanism by which salt intake increases blood pressure is complex and not fully understood. We previously found that sodium entry into antigen-presenting cells (APCs) via the epithelial sodium channel (ENaC) activates proinflammatory cytokines to activate T cells and modulate salt-sensitive hypertension. The activator protein 1 (AP-1) transcriptional factors (FOS/JUN) have been implicated in activating the pro-inflammatory pathway, but its role in SSBP is unknown. We hypothesized that high salt activates the AP-1 signaling pathway and inflammation in APCs and contributes to SSBP. Our bulk RNA-sequencing data in human monocytes, demonstrated that high salt increases the expression of the AP-1 gene family, FOS (2,378.1 ± 480.7 vs 6,494.0 ± 945.5, p= 0.0009), and JUN (7,313.9 ± 984.9 vs11,370.0 ± 1,286.3, p= 0.0015) compared to normal salt-treated monocytes. In additional experiments, we enrolled patients with hypertension and phenotype them for SSBP using an established inpatient protocol of salt-loading/depletion and performed single-cell transcriptomic analyses on peripheral blood mononuclear cells (PBMCs). We observed expression of the e FOS (r= 0.5041, p= 0.0464) and JUN (r= 0.7083, p= 0.0021) genes changes in concert with blood pressure in salt-sensitive (SS) but not in salt-resistant (SR) patients. To confirm whether genes expression translates to protein expression, we cultured total splenocytes from salt-sensitive SV/129 mice for 24 hours in either normal (150 mM) or high salt media (190 mM) and performed flow cytometry. Compared to normal salt, high salt-induced a significant increase in the expression of FOS-JUN genes in monocytes of the spleen. We also adoptively transferred PBMCs from salt-sensitive (SS) and salt-resistant (SR) hypertensive individuals into immunodeficient NSG mice, treated with the high salt diet for three weeks and performed flow cytometry on immune cells of the kidney, aorta, and spleen. We found that immune cells from SS people demonstrated a higher propensity to infiltrate mouse tissues with increased expression of FOS-JUN genes than immune cells from SR people. These preliminary findings disclose the role of the AP-1 gene family in salt-sensitive hypertension and may provide a potential therapeutic target for the treatment and diagnosis of SSBP.

Rotundic acid improves nonalcoholic steatohepatitis in mice by regulating glycolysis and the TLR4/AP1 signaling pathway

BackgroundSteatosis and inflammation are the hallmarks of nonalcoholic steatohepatitis (NASH). Rotundic acid (RA) is among the key triterpenes of Ilicis Rotundae Cortex and has exhibited multipronged effects in terms of lowering the lipid content and alleviating inflammation. The study objective is to systematically evaluate the potential mechanisms through which RA affects the development and progression of NASH.MethodsTranscriptomic and proteomic analyses of primary hepatocytes isolated from the control, high-fat diet-induced NASH, and RA treatment groups were performed through Gene Ontology analysis and pathway enrichment. Hub genes were identified through network analysis. Integrative analysis revealed key RA-regulated pathways, which were verified by gene and protein expression studies and cell assays.ResultsHub genes were identified and enriched in the Toll-like receptor 4 (TLR4)/activator protein-1 (AP1) signaling pathway and glycolysis pathway. RA reversed glycolysis and attenuated the TLR4/AP1 pathway, thereby reducing lipid accumulation and inflammation. Additionally, lactate release in L-02 cells increased with NaAsO2-treated and significantly decreased with RA treatment, thus revealing that RA had a major impact on glycolysis.ConclusionsRA is effective in lowering the lipid content and reducing inflammation in mice with NASH by ameliorating glycolysis and TLR4/AP1 pathways, which contributes to the existing knowledge and potentially sheds light on the development of therapeutic interventions for patients with NASH.

Factors ameliorate pro-inflammatory microglia polarization through inhibition of reactive astrocytes induced by 2-chloroethanol

Our previous studies have demonstrated that the crosstalk between astrocytes and microglia may trigger and amplify the neuroinflammatory response and, in turn, cause brain edema in 1,2-dichloroethane (1,2-DCE)-intoxicated mice. Moreover, findings from our in vitro studies showed that astrocytes are more sensitive to 2-chloroethanol (2-CE), an intermediate metabolite of 1,2-DCE, than microglia, and 2-CE-induced reactive astrocytes (RAs) can promote microglia polarization through releasing the pro-inflammatory mediators. Therefore, it is essential to explore therapeutic agents that may ameliorate microglia polarization through inhibition of 2-CE-induced RAs, which remains unclear till now. Results of this study revealed that exposure to 2-CE could induce RAs with pro-inflammatory effects, and fluorocitrate (FC), GIBH-130 (GI) and diacerein (Dia) pretreatment could all abolish the pro-inflammatory effects of 2-CE-induced RAs. FC and GI pretreatment might suppress 2-CE-induced RAs through inhibition of p38 mitogen-activated protein kinase (p38 MAPK)/activator protein-1 (AP-1) and nuclear factor-kappaB (NF-κB) signaling pathways, but Dia pretreatment might only inhibit p38 MAPK/NF-κB signaling pathway. FC, GI, and Dia pretreatment could all suppress the pro-inflammatory microglia polarization through inhibition of 2-CE-induced RAs. Meanwhile, GI and Dia pretreatment could also restored the anti-inflammatory microglia polarization via inhibition of 2-CE-induced RAs. However, FC pretreatment could not affect the anti-inflammatory polarization of microglia through inhibition of 2-CE-induced RAs. Taken together, findings from the present study demonstrated that FC, GI, and Dia might be the potential candidates with different characteristic for therapeutic use in 1,2-DCE poisoning.

Abstract 3532: Activator protein-1 (AP-1) signaling inhibits the growth of Ewing sarcoma cells in response to DNA replication stress

Abstract Ribonucleotide reductase (RNR) is the rate-limiting enzyme in the synthesis of deoxyribonucleoside triphosphates (dNTPs) and is required for DNA replication and the repair of DNA damage. Multiple types of cancer, including Ewing sarcoma tumors, are sensitive to RNR inhibitors or a reduction in the levels of either the RRM1 or RRM2 subunits of RNR. However, the polypharmacology and off-target effects of RNR inhibitors has complicated the identification of the precise mechanisms that regulate sensitivity and resistance to this class of drugs. Consequently, we used a conditional knockout (CRISPR/Cas9) and rescue approach to target RRM1 in Ewing sarcoma cells and identified that loss of RRM1 results in upregulation of the expression of multiple members of the activator protein-1 (AP-1) transcription factor complex, including c-Jun and c-Fos. This upregulation of AP-1 is mediated, in part, by SLFN11, which is expressed at high levels in Ewing sarcoma tumor and other pediatric sarcomas. Notably, the inducible expression of c-Jun and c-Fos in Ewing sarcoma cells impairs cell growth, downregulates the expression of the stem cell factor Sox2, and upregulates markers of cellular differentiation. In addition, small-molecule inhibitors of RNR, including gemcitabine and hydroxyurea, and HDAC inhibitors, which reduce the level of the RRM1 protein, also activate this AP-1 signaling pathway in Ewing sarcoma cells. Overall, these results provide novel insight into the critical pathways activated by loss of RNR activity and the mechanisms of action of inhibitors of RNR. Citation Format: David Gordon, Emma Croushore, Stacia Koppenhafer, Kelli Goss, Elizabeth Geary. Activator protein-1 (AP-1) signaling inhibits the growth of Ewing sarcoma cells in response to DNA replication stress. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3532.

Antiphotoaging and Skin-Protective Activities of Ardisia silvestris Ethanol Extract in Human Keratinocytes.

Ardisia silvestris is a traditional medicinal herb used in Vietnam and several other countries. However, the skin-protective properties of A. silvestris ethanol extract (As-EE) have not been evaluated. Human keratinocytes form the outermost barrier of the skin and are the main target of ultraviolet (UV) radiation. UV exposure causes skin photoaging via the production of reactive oxygen species. Protection from photoaging is thus a key component of dermatological and cosmetic products. In this research, we found that As-EE can prevent UV-induced skin aging and cell death as well as enhance the barrier effect of the skin. First, the radical-scavenging ability of As-EE was checked using DPPH, ABTS, TPC, CUPRAC, and FRAP assays, and a 3-(4-5-dimethylthiazol-2-yl)-2-5-diphenyltetrazolium bromide assay was used to examine cytotoxicity. Reporter gene assays were used to determine the doses that affect skin-barrier-related genes. A luciferase assay was used to identify possible transcription factors. The anti-photoaging mechanism of As-EE was investigated by determining correlated signaling pathways using immunoblotting analyses. As-EE had no harmful effects on HaCaT cells, according to our findings, and As-EE revealed moderate radical-scavenging ability. With high-performance liquid chromatography (HPLC) analysis, rutin was found to be one of the major components. In addition, As-EE enhanced the expression levels of hyaluronic acid synthase-1 and occludin in HaCaT cells. Moreover, As-EE dose-dependently up-regulated the production of occludin and transglutaminase-1 after suppression caused by UVB blocking the activator protein-1 signaling pathway, in particular, the extracellular response kinase and c-Jun N-terminal kinase. Our findings suggest that As-EE may have anti-photoaging effects by regulating mitogen-activated protein kinase, which is good news for the cosmetics and dermatology sectors.

Anlotinib Benefits the αPDL1 Immunotherapy by Activating ROS/JNK/AP-1 Pathway to Upregulate PDL1 Expression in Colorectal Cancer.

Colorectal cancer (CRC) is one of the prevalent malignant tumors. This study is aimed at evaluating the mechanism of anlotinib (anlo) on tumor microenvironment (TME) in CRC, and its effects in combination with immune checkpoint inhibitors (ICIs) therapy. Firstly, MC38 and CT26 cells were both exposed to different gradient concentrations of anlo for 72 h, to investigate the cell viability and synergetic therapy efficacy with ICIs by CCK8. The results showed that anlo could obviously inhibit cell growth and showed no synergistic efficacy therapy in combination with αPDL1 in vitro. Then, we found the upregulation of programmed cell death ligand 1(PDL1) expression both in vitro and in vivo after anlo treatment. In vivo, anlo could enhance the percentage of natural killer (NK) cells and M1 macrophage cells and decrease the percentage of M2 macrophage cells in TME. Moreover, we explored the mechanism and we proved that anlo could activate reactive oxygen species (ROS)/c-Jun N-terminal kinase (JNK)/activator protein-1 (AP-1) signaling pathway to increase the expression levels of PDL1, IFN-α/β/γ, and CXCL2 in two cell lines in vitro. We also proved that anlo had synergistic effects with ICIs in vivo. Finally, it could also increase the mRNA and protein PDL1 expression levels in human cell lines, which was consistent with mouse CRC cell lines. However, there are still a few limitations. On one hand, the ROS/JNK/AP-1 pathway needs to be proved whether it can be activated in human cell lines. On the other hand, the mechanism behind ROS promoting phosphorylation of JNK needs to be explored.

Induction of Heme Oxygenase-1 by 15d-Prostaglandin J2 Mediated via a ROS-Dependent Sp1 and AP-1 Cascade Suppresses Lipopolysaccharide-Triggered Interleukin-6 Expression in Mouse Brain Microvascular Endothelial Cells.

Heme oxygenase-1 (HO-1) has been shown to exert antioxidant, anti-inflammatory, and anti-apoptotic effects in various types of cells. Therefore, the induction of HO-1 is an excellent rationale for the development of protective drugs. 15-Deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2) can modulate the expression of antioxidant defense proteins and be beneficial for neuroinflammation. Brain endothelial cells play an important role in the pathophysiology of brain disorders. Whether 15d-PGJ2 can induce HO-1 expression and protect against the inflammatory responses in mouse brain microvascular endothelial (bEnd.3) cells remains unclear. Here, we reveal that 15d-PGJ2 stimulated HO-1 protein and mRNA expression in a time- and concentration-dependent manner in bEnd.3 cells, which was attenuated by diphenyleneiodonium chloride (DPI) and MitoTempo. Thus, activation of NADPH oxidase (NOX)- and mitochondria-derived reactive oxygen species (ROS) mediated 15d-PGJ2-induced HO-1 expression. ROS generation could cause phosphorylation of protein kinase C (PKC)δ, leading to HO-1 expression, which was suppressed by Rottlerin (selective inhibitor PKCδ), DPI, and MitoTempo. We further demonstrated that phosphorylation of c-Jun N-terminal kinase (JNK)1/2 participated in 15d-PGJ2-upregulated HO-1 expression, which was blocked by SP600125 or Rottlerin. Moreover, 15d-PGJ2-induced HO-1 expression was mediated through the activation of c-Jun (a subunit of activator protein 1 (AP-1)) and specificity protein 1 (Sp1), leading to their interaction with the HO-1 promoter, revealed by chromatin immunoprecipitation assay, which was attenuated by SP600125, Mithramycin A, or Tanshinone II A. We further verified the anti-inflammatory effect of HO-1 expression. Our results showed that 15d-PGJ2-induced HO-1 could mitigate the lipopolysaccharide-triggered interleukin-6 expression and secretion, as measured by an ELISA assay kit. These results suggest that 15d-PGJ2-induced HO-1 expression is mediated through the activation of NOX- and mitochondria-derived ROS-dependent PKCδ/JNK1/2/Sp1 and the AP-1 signaling pathway and protects against inflammatory responses in bEnd.3 cells.

AP-1 signaling pathway promotes pro-IL-1β transcription to facilitate NLRP3 inflammasome activation upon influenza A virus infection

ABSTRACT NLRP3 inflammasome mainly controls interleukin-1β (IL-1β) secretion, leading to cell death called pyroptosis constituting a major antiviral host defense and inflammatory diseases upon viral infection. The RAF-MEK1/2-ERK1/2 cascade and downstream c-Jun/Fos and Activator protein-1 (AP1) signaling pathway control the degree of inflammatory response. Influenza A virus (IAV) infection is known to stimulate NLRP3 inflammasome activation and inflammatory responses. Nevertheless, the detailed mechanism by which IAV induces NLRP3 inflammasome activation involved in transcription of pro-IL-1β mRNA remains elusive. In our study, we found that IAV infection promotes pro-IL-1β mRNA transcription and activates NLRP3 inflammasome. Detailed studies reveal that type I interferon (IFN-α/IFN-β) as well as U0126 (a selective inhibitor of MEK-1 and MEK-2) typically inhibit IAV-mediated NLRP3 inflammasome activation via downregulating pro-IL-1β mRNA. Moreover, knock-down of c-Jun decreases pro-IL-1β mRNA and inhibits NLRP3 inflammasome activation upon IAV infection. Overall, the findings uncover that AP-1 signaling pathway promotes NLRP3 inflammasome activation upon IAV infection, which provides a new idea for the therapy of NLRP3 inflammasome-associated inflammatory diseases.

ROS generation is involved in titanium dioxide nanoparticle-induced AP-1 activation through p38 MAPK and ERK pathways in JB6 cells.

Titanium dioxide (TiO2 ) is generally regarded as a nontoxic and nongenotoxic white mineral, which is mainly applied in the manufacture of paper, paint, plastic, sunscreen lotion and other products. Recently, TiO2 nanoparticles (TiO2 NPs) have been demonstrated to cause chronic inflammation and lung tumor formation in rats, which may be associated with the particle size of TiO2 . Considering the important role of activator protein-1 (AP-1) in regulating multiple genes involved in the cell proliferation and inflammation and the induction of neoplastic transformation, we aimed to evaluate the potency of TiO2 NPs (≤ 20 nm) on the activation of AP-1 signaling pathway and the generation of reactive oxygen species (ROS) in a mouse epidermal cell line, JB6 cells. MTT, electron spin resonance (ESR), AP-1 luciferase activity assay in vitro and in vivo, and Western blotting assay were used to clarify this problem. Our results indicated that TiO2 NPs dose-dependently caused the hydroxyl radical (·OH) generation and sequentially increased the AP-1 activity in JB6 cells. Using AP-1-luciferase reporter transgenic mice models, an obvious increased AP-1 activity was detected in dermal tissue after exposure to TiO2 NPs for 24 h. Interestingly, TiO2 NPs increased the AP-1 activity via stimulating the expression of mitogen-activated protein kinases (MAPKs) family members, including extracellular signal-regulated protein kinases (ERKs), p38 kinase, and C-Jun N-terminal kinases (JNKs). Of note, the AP-1 activation induced by TiO2 NPs could be blocked by specific inhibitors (SB203580, PD98059, and SP 600125, respectively) that inhibit ERKs and p38 kinase but not JNKs. These findings indicate that ROS generation is involved in TiO2 NPs-induced AP-1 activation mediated by MAPKs signal pathway.

Reactive astrocytes induced by 2-chloroethanol modulate microglia polarization through IL-1β, TNF-α, and iNOS upregulation

The synthetic organic chemical, 1,2-dichloroethane (1,2-DCE), can cause brain edemas under subacute poisoning. Our previous studies indicated that neuroinflammation could be induced due to astrocytes and microglia activation during brain edemas in 1,2-DCE-intoxicated mice. However, the crosstalk between these two glial cells in 1,2-DCE-induced neuroinflammation remained unclear. In this study, primary cultured rat astrocytes and microglia, as well as an immortalized microglia cell line were employed to study the effects of 2-chloroethanol (2-CE, a 1,2-DCE intermediate metabolite in vivo) treated astrocytes on microglia polarization. Our current results revealed that 2-CE treated rat astrocytes were activated through p38 mitogen-activated protein kinase (p38 MAPK)/nuclear factor-κB (NF-κB), and activator protein-1 (AP-1) signaling pathways. Theses pathways were triggered by reactive oxygen species (ROS) produced during 2-CE metabolism. Also, astrocytes were more sensitive to 2-CE effects than microglia. Interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and inducible nitric oxide synthase (iNOS) expressions were upregulated in 2-CE-induced reactive astrocytes, enhancing IL-1β, TNF-α, and nitric oxide (NO) excretions, which stimulated microglia polarization. Therefore, the neuroinflammation induced by 1,2-DCE in mice's brains is probably triggered by reactive astrocytes.

Roles of ERK/JNK in carbon black induced AP-1 cell signaling pathway changes

To investigate the role of ERK/JNK in the alteration of activator protein-1(AP-1) signaling pathway in human embryonic lung fibroblasts(HELFs) induced by carbon black. HELFs were cultured in RPMI 1640 medium containing 0, 15, 30, 60, 120 or 240 μg/mL carbon black for 24 h, and the appropriate dose of carbon black was determined by MTT assay result. HELFs were divided into three groups: HELFs, HELFs transfected with ERK dominant negative mutant plasmid(DN-ERK) and HELFs transfected with JNK dominant negative mutant plasmid(DN-JNK). 100 μg/mL carbon black was used to treat HELFs(CB), DN-ERK HELFs(CB-DN-ERK), DN-JNK HELFs(CB-DN-JNK), and HELFs without any treatment were considered as control group. At 0, 1, 2, 4, 8, 12, 24 and 36 h of CB and control groups HELFs, the western blot was used to detect ERK, p-ERK, JNK, p-JNK, p38, p-p38, c-Jun, p-c-Jun, c-Fos, p-c-Fos protein expression levels, and AP-1 activity was detected by luciferase method. Whereas CB-DN-ERK and CB-DN-JNK HELFs were detected only at 24 h. Compared with the protein expression levels at 0 h, CB group HELFs ERK and p-ERK protein expression increased at each time point, whereas p38 protein expression decreased. AP-1 activity of CB group HELFs was declined to the lowest at 8 h(0.72±0.12), and upregulated to the peak at 36 h(1.38±0.11). CB group HELFs c-Fos, p-c-Fos and c-Jun protein expression levels at each time point from 1 h to 24 h were greater than those of 0 h, and p-c-Jun protein expression levels at 1 h, 2 h, 4 h, 8 h, 36 h were also greater than those of 0 h. CB group HELFs AP-1 activity, ERK, p-ERK, JNK, p-JNK, p38, p-p38, c-Jun, p-c-Jun, c-Fos, p-c-Fos protein expression levels changes followed biphasic patterns. There were no statistically significant differences in AP-1 activity between CB group HELFs(1.03±0.10) and CB-DN-ERK group(1.02±0.04) or CB-DN-JNK group(1.09±0.10) HELFs(t=0.16, P=0.88; t=0.73, P=0.50). However, compared with CB group HELFs, c-Fos(t=5.31, P=0.01), p-c-Fos(t=4.33, P=0.01), p-c-Jun(t=10.95, P& lt; 0.01)in CB-DN-JNK group, and c-Fos protein expression levels in CB-DN-ERK group(t=42.72, P& lt; 0.01)were significantly decreased. While carbon black induces HELFs increased protein expression levels of ERK, p-ERK, c-Jun, p-c-Jun, c-Fos and p-c-Fos, JNK may upregulate c-Fos, p-c-Fos, p-c-Jun protein expression levels, and ERK may upregulate c-Fos protein expression level.

Triptolide inhibits matrix metalloproteinase-9 expression and invasion of breast cancer cells through the inhibition of NF-κB and AP-1 signaling pathways.

Triptolide is a diterpenoid epoxide that is endogenously produced by the thunder god vine, Tripterygium wilfordii Hook F. Triptolide has demonstrated a variety of biological activities, including anticancer activities, in previous studies. Invasion and metastasis are the leading causes of mortality for patients with breast cancer, and the increased expression of matrix metalloproteinase-9 (MMP-9) has been shown to be associated with breast cancer invasion. Therefore, the aim of the present study was to investigate the effect of triptolide on 12-O-tetradecanoyl phorbol-13-acetate (TPA)-induced cell invasion and MMP-9 expression in breast cancer cells. The expression of signal molecules was examined by western blotting, zymography and quantitative polymerase chain reaction; an electrophoretic mobility gel shift assay was also used, and cell invasiveness was measured by an in vitro Matrigel invasion assay. The MCF-7 human breast cancer cell line was treated with triptolide at the highest concentrations at which no marked cytotoxicity was evident. The results demonstrated that triptolide decreased the expression of MMP-9 through inhibition of the TPA-induced phosphorylation of extracellular signal-regulated kinase (ERK) and the downregulation of nuclear factor-κB (NF-κB) and activator protein-1 (AP-1) activity. In addition, a Transwell assay revealed that triptolide reduced the ability of MCF-7 cells to invade Matrigel. These data demonstrate that the anti-invasive effect of triptolide is associated with the inhibition of ERK signaling and NF-κB and AP-1 activation, and suggest that triptolide may be a promising drug for breast cancer.

DNA or Protein Methylation-Dependent Regulation of Activator Protein-1 Function.

Epigenetic regulation and modification govern the transcriptional mechanisms that promote disease initiation and progression, but can also control the oncogenic processes, cell signaling networks, immunogenicity, and immune cells involved in anti-inflammatory and anti-tumor responses. The study of epigenetic mechanisms could have important implications for the development of potential anti-inflammatory treatments and anti-cancer immunotherapies. In this review, we have described the key role of epigenetic progression: DNA methylation, histone methylation or modification, and protein methylation, with an emphasis on the activator protein-1 (AP-1) signaling pathway. Transcription factor AP-1 regulates multiple genes and is involved in diverse cellular processes, including survival, differentiation, apoptosis, and development. Here, the AP-1 regulatory mechanism by DNA, histone, or protein methylation was also reviewed. Various methyltransferases activate or suppress AP-1 activities in diverse ways. We summarize the current studies on epigenetic alterations, which regulate AP-1 signaling during inflammation, cancer, and autoimmune diseases, and discuss the epigenetic mechanisms involved in the regulation of AP-1 signaling.

Euodia pasteuriana Methanol Extract Exerts Anti-Inflammatory Effects by Targeting TAK1 in the AP-1 Signaling Pathway.

Euodia pasteuriana A. Chev. ex Guillaumin, also known as Melicope accedens (Blume) T.G. Hartley, is a herbal medicinal plant native to Vietnam. Although Euodia pasteuriana is used as a traditional medicine to treat a variety of inflammatory diseases, the pharmacological mechanisms related to this plant are unclear. This study aimed to investigate the anti-inflammatory effects of a methanol extract of Euodia pasteuriana leaves (Ep-ME) on the production of inflammatory mediators, the mRNA expression of proinflammatory genes, and inflammatory signaling activities in macrophage cell lines. The results showed that Ep-ME strongly suppressed the release of nitric oxide (NO) in RAW264.7 cells induced with lipopolysaccharide (LPS), pam3CysSerLys4 (Pam3CSK), and polyinosinic-polycytidylic acid (poly I:C) without cytotoxicity. A reverse transcription-polymerase chain reaction further confirmed that Ep-ME suppressed the expression of interleukin 6 (IL-6), matrix metalloproteinase-1 (MMP1), matrix metalloproteinase-2 (MMP2), matrix metalloproteinase-3 (MMP3), tumor necrosis factor-α (TNF-α), and matrix metalloproteinase-9 (MMP9) at the transcriptional level and reduced the luciferase activities of activator protein 1 (AP-1) reporter promoters. In addition, immunoblotting analyses of the whole lysate and nuclear fraction, as well as overexpression assays demonstrated that Ep-ME decreased the translocation of c-Jun and suppressed the activation of transforming growth factor beta-activated kinase 1 (TAK1) in the AP-1 signaling pathways. These results imply that Ep-ME could be developed as an anti-inflammatory agent that targets TAK1 in the AP-1 signaling pathway.

The dipeptidyl peptidase (DPP)-4 inhibitor trelagliptin inhibits IL-1β-induced endothelial inflammation and monocytes attachment

Cardiovascular diseases remain the major cause of death worldwide. Atherosclerosis is recognized as the common ground of cardiovascular diseases. Inflammatory cytokines-induced attachment of monocytes to endothelial cells is a significant event in the progression of atherosclerosis. As a highly selective dipeptidyl peptidase (DPP)-4 inhibitor, trelagliptin is used for the treatment of type 2 diabetes mellitus (T2DM). However, whether trelagliptin possesses an inhibitory effect on endothelial dysfunction and monocyte adhesion is unknown. In the current study, we tested the effect of trelagliptin in endothelial cells. We used human aortic endothelial cells (HAECs) exposed to interleukin (IL)-1β to mimic the microenvironment of atherosclerosis. Our results showed that trelagliptin inhibited the expression of pro-inflammatory chemokines including monocyte chemoattractant protein 1 (MCP-1), CXCL-1, and IL-6. Furthermore, trelagliptin suppressed the expression of adhesion molecules such as vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1). Mechanistically, trelagliptin suppressed the activation of activator protein-1 (AP-1) and NF-κB signaling pathways, which modulate the inflammatory process and monocyte adhesion. Collectively, our results showed that trelagliptin had a powerful inhibitory effect on the attachment of monocytes to endothelial cells, indicating that trelagliptin might have a protective effect on cardiovascular diseases such as atherosclerosis.

Quercetin inhibits TNF-α induced HUVECs apoptosis and inflammation via downregulating NF-kB and AP-1 signaling pathway in vitro.

Background:Quercetin, a major flavonol, wildly exists in plantage, which has been reported to have an anti-apoptosis and anti-inflammation effects on vascular endothelial cells, but its underlying molecular mechanisms remain unclear.Objective:The aim of this study was to investigate the mechanisms of how quercetin inhibits tumor necrosis factor alpha (TNF-α) induced human umbilical vein endothelial cells (HUVECs) apoptosis and inflammation.Methods and Results:HUVECs were preconditioned with quercetin for 18 hours, and subsequently treated with TNF-α for 6 hours to induce apoptosis. The expression of intercellular cell adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1), E-selectin, β-actin mRNA was then detected by RT-PCR. Flow cytometry was used to estimate the apoptosis rates, and the expression of activator protein 1 (AP-1) and nuclear factor kappa B (NF-κB) was measured by Western blot. TNF-α induced elevated apoptosis rates and upregulation of VCAM-1, ICAM-1, and E-selectin were meaningfully reduced in HUVECs by pretreatment with quercetin. In addition, quercetin also inhibited the activation of AP-1and NF-κB.Conclusion:Results indicate that quercetin could suppress TNF-α induced apoptosis and inflammation by blocking NF-κB and AP-1 signaling pathway in HUVECs, which might be one of the underlying mechanisms in treatment of coronary heart disease.

Ghrelin ameliorates chronic obstructive pulmonary disease-associated infllammation and autophagy.

Chronic obstructive pulmonary disease (COPD) is a chronic and devastating condition characterized by poor airflow and breath. Smoking and other environmental factors-caused inflammations triggered excessive autophagy of normal lung epithelial cells, eventually leading to impaired lung functions. Previous studies showed that ghrelin exhibited beneficial effects on patients with COPD. However, the mechanisms underlying this impact remained largely unknown. In this study, in vitro and in vivo models of COPD-associated inflammation were established, and we found that inflammation and autophagy were abonormally activated through nuclear factor kappa b (NF-κB) and activator protein-1 (AP-1) signaling pathways. Interestingly, ghrelin could inhibit the excessive inflammation pathways and autophagy induced by particle matter and/or cigarette extract in bronchial epithelial cells. Furthermore, NF-κB and AP-1 signaling were both inhibited while lung functions were significantly improved. Taken together, identification of downstream signaling of ghrelin in inflammation provided a new avenue in the treatment of COPD.

Fish c-Jun N-Terminal Kinase (JNK) Pathway Is Involved in Bacterial MDP-Induced Intestinal Inflammation.

The c-Jun NH2-terminal kinases (JNKs) are an evolutionarily conserved family of serine/threonine protein kinases that play critical roles in the pathological process in species ranging from insects to mammals. However, the function of JNKs in bacteria-induced intestinal inflammation is still poorly understood. In this study, a fish JNK (CiJNK) pathway was identified, and its potential roles in bacterial muramyl dipeptide (MDP)-induced intestinal inflammation were investigated in Ctenopharyngodon idella. The present CiJNK was found to possess a conserved dual phosphorylation motif (TPY) in a serine/threonine protein kinase (S_TKc) domain and to contain several potential immune-related transcription factor binding sites, including nuclear factor kappa B (NF-κB), activating protein 1 (AP-1), and signal transducer and activator of downstream transcription 3 (STAT3), in its 5′ flanking regions. Quantitative real-time PCR results revealed that the mRNA levels of the JNK pathway genes in the intestine were significantly upregulated after challenge with a bacterial pathogen (Aeromonas hydrophila) and MDP in a time-dependent manner. Additionally, the JNK pathway was found to be involved in regulating the MDP-induced expression levels of inflammatory cytokines (IL-6, IL-8, and TNF-α) in the intestine of grass carp. Moreover, the nutritional dipeptide carnosine and Ala–Gln could effectively alleviate MDP-induced intestinal inflammation by regulating the intestinal expression of JNK pathway genes and inflammatory cytokines in grass carp. Finally, fluorescence microscopy and dual-reporter assays indicated that CiJNK could associate with CiMKK4 and CiMKK7 involved in the regulation of the AP-1 signaling pathway. Overall, these results provide the first experimental demonstration that the JNK signaling pathway is involved in the intestinal immune response to MDP challenge in C. idella, which may provide new insight into the pathogenesis of inflammatory bowel disease.

The association between microRNA-21 and hypertension-induced cardiac remodeling.

Hypertension is a major public health problem among the aging population worldwide. It causes cardiac remodeling, including hypertrophy and interstitial fibrosis, which leads to development of hypertensive heart disease (HHD). Although microRNA-21 (miR-21) is associated with fibrogenesis in multiple organs, its contribution to cardiac remodeling in hypertension is poorly understood. Circulating miR-21 level was higher in patients with HHD than that in the control subjects. It also positively correlated with serum myocardial fibrotic markers. MiR-21 expression levels were significantly upregulated in the mice hearts after angiotensin II (Ang II) infusion or transverse aortic constriction (TAC) compared with control mice. Expression level of programmed cell death 4 (PDCD4), a main target of miR-21, was significantly decreased in Ang II infused mice and TAC mice compared with control mice. Expression levels of transcriptional activator protein 1 (AP-1) and transforming growth factor-β1 (TGF-β1), which were downstream targets of PDCD4, were increased in Ang II infused mice and TAC mice compared with control mice. In vitro, mirVana-miR-21-specific inhibitor attenuated Ang II-induced PDCD4 downregulation and contributed to subsequent deactivation of AP-1/TGF-β1 signaling pathway in neonatal rat cardiomyocytes. Thus, suppression of miR-21 prevents hypertrophic stimulation-induced cardiac remodeling by regulating PDCD4, AP-1, and TGF-β1 signaling pathway.