LncRNA MEG3 Reduces the Ratio of M2/M1 Macrophages Through the HuR/CCL5 Axis in Hepatocellular Carcinoma

Objective

Tumor-associated macrophages play a crucial role in the development of hepatocellular carcinoma (HCC). Our study aimed to investigate the relationship between long coding RNA (lncRNA) maternally expressed gene 3 (MEG3), RNA-binding protein human antigen R (HuR), and messenger RNA C-C motif chemokine 5 (CCL5) in the modulation of M1 and M2 macrophage polarization in HCC.

Methods

To induce M1 or M2 polarization, LPS/IFNγ- or IL4/IL13 were used to treat bone marrow derived macrophages (BMDMs). The localization of MEG3 in M1 and M2 macrophages was assessed using fluorescence in situ hybridization assay. Expression levels of MEG3, HuR, CCL5, M1, and M2 markers were measured by RT-qPCR or immunofluorescence staining. Flow cytometry was performed to determine the proportion of F4/80+CD206+ and F4/80+CD68+ cells. RNA pulldown assay was performed to detect the binding of lncRNA MEG3 and HuR. The impacts of HuR on CCL5 stability and activity of CCL5 promoter were evaluated using actinomycin D treatment and luciferase reporter assay. Cell migration, invasiveness, and angiogenesis were assessed using transwell migration and invasion assays and a tube formation assay. A mixture of Huh-7 cells and macrophages were injected into nude mice to explore the effect of MEG3 on tumorigenesis.

Results

MEG3 promoted M1-like polarization while dampening M2-like polarization of BMDMs. MEG3 bound to HuR in M1 and M2 macrophages. HuR downregulated CCL5 by inhibiting CCL5 transcription in macrophages. In addition, overexpression of MEG3 suppressed cell metastasis, invasion, and angiogenesis by obstructing macrophage M2 polarization. MEG3 inhibited tumorigenesis in HCC via promotion of M1-like polarization and inhibition of M2-like polarization. Rescue experiments showed that depletion of CCL5 in M2 macrophages reversed MEG3-induced suppressive effect on cell migration, invasion, and tube formation.

Conclusion

MEG3 suppresses HCC progression by promoting M1-like while inhibiting M2-like macrophage polarization via binding to HuR and thus upregulating CCL5.

Multifaceted Nature of HuR in Atherosclerosis Development

HuR (Human antigen R) is an RNA binding protein (RBP) that specifically binds to certain RNA sequences, influencing post-transcriptional regulation. HuR is primarily involved in tumor regulation, as well as cell growth, proliferation, inflammation, and angiogenesis. HuR is implicated in endothelial activation, smooth muscle proliferation, inflammatory response, macrophage apoptosis, lipid regulation, and autophagy, playing a crucial regulatory role in atherosclerosis. Accumulating evidence suggests that HuR has dual roles in AS. On the one hand, HuR expedites the development of AS by facilitating endothelial activation, smooth muscle proliferation, and inflammation. On the contrary, it exerts beneficial effects by reducing macrophage apoptosis, regulating lipid efflux, and increasing autophagy. In this review, we aim to provide a comprehensive summary of the role of HuR in the development of AS by examining its involvement in cellular mechanisms, inflammation, autophagy, and apoptosis. Additionally, we discuss the mechanisms of drugs that target HuR, with the goal of offering new perspectives for the treatment of AS.

NKRF in Cardiac Fibroblasts Protects against Cardiac Remodeling Post-Myocardial Infarction via Human Antigen R

Myocardial infarction (MI) remains the leading cause of death worldwide. Cardiac fibroblasts (CFs) are abundant in the heart and are responsible for cardiac repair post-MI. NF-κB-repressing factor (NKRF) plays a significant role in the transcriptional inhibition of various specific genes. However, the NKRF action mechanism in CFs remains unclear in cardiac repair post-MI. This study investigates the NKRF mechanism in cardiac remodeling and dysfunction post-MI by establishing a CF-specific NKRF-knockout (NKRF-CKO) mouse model. NKRF expression is downregulated in CFs in response to pathological cardiac remodeling in vivo and TNF-α in vitro. NKRF-CKO mice demonstrate worse cardiac function and survival and increased infarct size, heart weight, and MMP2 and MMP9 expression post-MI compared with littermates. NKRF inhibits CF migration and invasion in vitro by downregulating MMP2 and MMP9 expression. Mechanistically, NKRF inhibits human antigen R (HuR) transcription by binding to the classical negative regulatory element within the HuR promoter via an NF-κB-dependent mechanism. This decreases HuR-targeted Mmp2 and Mmp9 mRNA stability. This study suggests that NKRF is a therapeutic target for pathological cardiac remodeling.

The Prognostic Role of HuR Varies Between Different Subtypes of Breast Cancer Patients: Data Mining and Retrospective Analysis

Objective

Human-antigen R (HuR) is an RNA-binding protein, which regulates the expression of several oncogenes and tumor suppressor genes through post-transcriptional mechanisms. But the role of HuR in breast cancer remains controversial. The aim of this study was to verify the association between cytoplasmic HuR level and prognosis of breast cancer patients.

Methods

Data mining from the Human Protein Atlas (HPA) and Kaplan-Meier Plotter (KMP) databases was performed. Then, 394 patients with stage I-III primary breast cancer were enrolled between January 2005 and December 2016. We investigated the association between cytoplasmic HuR level and clinicopathological characteristics or survival of these patients. Immunohistochemical analysis was performed to determine HuR expression level. SPSS 21.0 statistical software was used for analysis.

Results

In the HPA and KMP datasets, HuR protein and mRNA expression level were not significantly associated with overall survival of all breast cancer patients enrolled. Results from our 394 patients indicated that higher expression level of cytoplasmic HuR was associated with larger tumor size, lymph node positive, ER negative and triple-negative subtype. For all patients enrolled, the results indicated that compared with HuR negative patients, the DFS (disease-free survival) of HuR 1+ was longer (60.5% vs 78.8, P=0.053, HR=0.616, 95% CI: 0.378-1.005), the P value was borderline. In the triple-negative breast cancer (TNBC) subgroup, HuR positive patients had significantly longer DFS than HuR negative patients (65.5% vs 30.8%, P=0.001, HR=0.345, 95% CI: 0.180-0.658). In the HR+HER2- subgroup, HuR low (0~1+) patients had significantly longer OS than HuR high (2+~3+) patients (97.0% vs 89.5%, P=0.033, HR=2.482, 95% CI: 1.074-5.736).

Conclusion

In conclusion, our results revealed that higher expression level of HuR was related to aggressive biological characteristics which supported the findings from previous researches. In the HR+HER2- subgroup, lower HuR expression level patients had better survival time, while in the TNBC subgroup we got the opposite results. Our work indicated that HuR might play different roles in different breast cancer subtypes.

RNA-Binding Proteins in Bladder Cancer

RNA-binding proteins (RBPs) are key regulators of transcription and translation, with highly dynamic spatio-temporal regulation. They are usually involved in the regulation of RNA splicing, polyadenylation, and mRNA stability and mediate processes such as mRNA localization and translation, thereby affecting the RNA life cycle and causing the production of abnormal protein phenotypes that lead to tumorigenesis and development. Accumulating evidence supports that RBPs play critical roles in vital life processes, such as bladder cancer initiation, progression, metastasis, and drug resistance. Uncovering the regulatory mechanisms of RBPs in bladder cancer is aimed at addressing the occurrence and progression of bladder cancer and finding new therapies for cancer treatment. This article reviews the effects and mechanisms of several RBPs on bladder cancer and summarizes the different types of RBPs involved in the progression of bladder cancer and the potential molecular mechanisms by which they are regulated, with a view to providing information for basic and clinical researchers.

CRC-derived exosomes containing the RNA binding protein HuR promote lung cell proliferation by stabilizing c-Myc mRNA

HuR overexpression is related to poor survival in patients with colon cancer. HuR overexpression leads to stabilization of tumor-promoting mRNAs by binding to 3′UTR-resident AREs. Exosomes, nanosized lipid bilayer vesicles, mediate many steps in cancer progression. The potential role of exosomal HuR in colon cancer lung metastasis is unclear. HuR expression was assessed immunohistochemically in tumor tissue samples from 20 patients with metastatic or nonmetastatic colon cancer and colon cancer lung metastasis and benign lung disease samples from ten patients. Exosomes were isolated from HCT116 WT and HuR KO colon cancer cells, and uptake of PKH67- and PKH26-labeled exosomes by BEAS-2B cells was evaluated using fluorescence and confocal microscopy. C-Myc and p21protein and mRNA levels were measured by western blotting and RT-qPCR, respectively. In clinical patients, HuR overexpression was significantly enhanced in colon tissues of patients with lung metastasis. HuR expression was higher in lung tissue with metastasis of colonic origin than with benign lung disease. The effect of HuR-containing CRC exosomes compared to HuR-deficient exosomes on wound closure was observed as enhanced proliferation. BEAS-2B cell migration and invasion were enhanced after HuR-containing exosomes treatment. BEAS-2B cells showed similar uptake of PKH67 (HCT116 WT)- and PKH26 (HCT116 HuR KO)-labeled exosomes. Exosomal HuR stabilized c-Myc mRNA and downregulated p21 expression, leading to G1/S transition, in human bronchial epithelial cells. HuR overexpression is associated with lung metastasis in colon cancer patients. Exosomal HuR derived from colon cancer cells alter the biological effect on normal lung epithelial cells.

Long non-coding RNA DEPDC1-AS1 promotes proliferation and migration of human gastric cancer cells HGC-27 via the human antigen R-F11R pathway

Objective

Long non-coding (lnc) RNAs are critical regulators in carcinogenesis. The novel lncRNA DEPDC1 antisense RNA 1 (DEPDC1-AS1) was recently associated with poor prognosis in triple-negative breast cancer and lung adenocarcinoma. However, its role in regulating the malignant progression of gastric cancer (GC) and its molecular mechanism are unclear. We herein explored the functions of DEPDC1-AS1 in GC progression.

Methods

DEPDC1-AS1 expression and prognosis in GC tissues were examined by bioinformatics analysis and quantitative reverse transcription polymerase chain reaction. The DEPDC1-AS1 function in GC cells was explored by the cell counting kit-8 assay, colony formation assay, Transwell assay, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling, 5-ethynyl-2′-deoxyuridine-incorporation, and the xenograft tumor model. The DEPDC1-AS1 and human antigen (Hu)R interaction was determined by RNA pull-down and RNA immunoprecipitation.

Results

DEPDC1-AS1 was overexpressed in GC tissues and cell lines, and associated with a worse prognosis in GC patients. In vitro and in vivo assays showed that DEPDC1-AS1 promoted HGC-27 cell proliferation and migration. Mechanistically, DEPDC1-AS1 served as a scaffold by combining with HuR to target the specific mRNA F11R.

Conclusion

DEPDC1-AS1 plays a crucial role in GC development and progression and is a potential biomarker for the early detection or prognosis of GC.

The Role of RNA-Binding Protein HuR in Lung Cancer by RNA Sequencing Analysis

Background: The overexpression of human antigen R (HuR) has been proven in various types of cancer and is associated with the poor survival lung cancer patients. HuR overexpression stabilizes the mRNA of tumor-promoting genes by binding with 3′-UTR AU-rich elements. However, the role of HuR in the proliferation of lung cancer is unclear.

Methods: HuR expression was assessed using immunohistochemistry of tumor tissue samples from ten patients with lung cancer and ten patients with benign lung disease. Gene, protein, mRNA, and lncRNA changes in A549 HuR knockdown (KD) cells were assessed by single-cell RNA sequencing analysis. Furthermore, cell proliferation, migration, and invasion were determined by Cell Counting Kit-8 (CCK-8) assays and Transwell assays with or without Matrigel. The cell cycle was assessed by propidium iodide staining. The protein level, mRNA level and half-life of PLK1 were detected by western blotting and RT-qPCR.

Results: In clinical patients, the expression of HuR was significantly higher in lung cancer patients than in patients with benign lung disease. RNA sequencing analysis of A549 HuR knockdown cells revealed that the main function of HuR was related to ribonucleoprotein complex biogenesis. HuR was found to regulate signaling pathways mainly related to the spliceosome, RNA transport and the cell cycle. HuR KD suppressed the proliferation, migration and invasion of A549 cells, indicating its promotive role in these processes.

Conclusion: These results demonstrate that HuR plays an important role in the progression of lung cancer.

Human antigen R promotes angiogenesis of endothelial cells cultured with adipose stem cells derived exosomes via overexpression of vascular endothelial growth factor in vitro

Recent studies showed that exosomes obtained from adipose-derived stem cells (ADSCs) could improve the angiogenesis of fat grafts via overexpression of vascular endothelial growth factor (VEGF). Human antigen R (HuR) promotes the expression of VEGF in many cancers, but the effect of HuR in normal endothelial cells in the presence of ADSC-derived exosomes remains unclear. We aimed to investigate the effect of HuR on the expression of VEGF and angiogenesis of human umbilical vein endothelial cells (HUVECs) cultured with ADSCs-derived exosomes. The HuR-overexpressed HUVECs (HuR-HUVECs) were cocultured with ADSCs-derived exosomes. qRT-PCR and Western blotting were performed to examine the stability and expression of VEGF-A mRNA and protein. The proliferation, migration, and proangiogenic capacity of HuR-HUVECs were evaluated using cell counting kit-8 (CCK-8), scratch wound healing, and Matrigel tube formation assay. qRT-PCR showed that HuR-HUVECs had higher expression and slower attenuation of VEGF-A mRNA. Western blotting confirmed higher expression of VEGF-A in HuR-HUVECs. CCK-8, scratch wound healing, and Matrigel tube formation assay demonstrated an increased proangiogenic effect in HuR-HUVECs. HuR promotes angiogenesis of HUVECs cocultured with ADSCs-derived exosomes via stabilization and overexpression of VEGF in vitro. The HuR/VEGF pathway is an important regulatory mechanism of angiogenesis in endothelial cells.

Cellular Protein HuR Regulates the Switching of Genomic RNA Templates for Differential Functions during the Coxsackievirus B3 Life Cycle

Coxsackievirus B3 (CVB3) is an enterovirus belonging to the family Picornaviridae. Its 5' untranslated region (UTR) contains a cloverleaf structure followed by an internal ribosome entry site (IRES). The cloverleaf forms an RNA-protein complex known to regulate virus replication, translation, and stability of the genome, and the IRES regulates virus RNA translation. For positive-strand RNA-containing viruses, such as members of the flaviviruses or enteroviruses, the genomic RNA is used for translation, replication, and encapsidation. Only a few regulatory mechanisms which govern the accessibility of genomic RNA templates for translation or replication have been reported. Here, we report the role of human antigen R (HuR) in regulating the fate of CVB3 positive-strand RNA into the replication cycle or translation cycle. We have observed that synthesis of HuR is induced during CVB3 infection, and it suppresses viral replication by displacing PCBP-2 (a positive regulator of virus replication) at the cloverleaf RNA. Silencing of HuR increases viral RNA replication and consequently reduces viral RNA translation in a replication-dependent manner. Furthermore, we have shown that HuR level is upregulated upon CVB3 infection. Moreover, HuR limits virus replication and can coordinate the availability of genomic RNA templates for translation, replication, or encapsidation. Our study highlights the fact that the relative abundance of translation factors and replication factors in the cell decides the outcome of viral infection. IMPORTANCE A positive-strand RNA virus must balance the availability of its genomic template for different viral processes at different stages of its life cycle. A few host proteins are shown to be important to help the virus in switching the usage of a template between these processes. These proteins inhibit translation either by displacing a stimulator of translation or by binding to an alternative site. Both mechanisms lead to ribosome clearance and availability of the genomic strand for replication. We have shown that HuR also helps in maintaining this balance by inhibiting replication and subsequently promoting translation and packaging.

Butyric acid alleviated chronic intermittent hypoxia-induced lipid formation and inflammation through up-regulating HuR expression and inactivating AMPK pathways

To investigate whether butyric acid could alleviate chronic intermittent hypoxia (CIH)-induced lipid formation in human preadipocytes-subcutaneous (HPA-s) through accumulation of human antigen R (HuR) and inactivation of AMP-activated protein kinase (AMPK) pathway, HPA-s were obtained and divided into three groups: Control group: cells were cultured under normal conditions; CIH group: cells were cultured in a three-gas incubator (10% O₂); Butyric acid group: 10 mmol/l butyric acid added into cell culture medium. HuR-siRNA was futher transfected into CIH group for verification the function of HuR. Oil Red O was implemented for observation of lipid droplets within cells. Cell Counting Kit-8 (CCK8) assay was used for detecting cell viability. Terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-nick end labeling (TUNEL) assay as well as flow cytometry analysis was employed for determining cell apoptosis. Western blotting was used for measurement of protein expression levels. RT-qPCR analysis was used for detecting mRNA expression. CIH treatment increased adipocytes proliferation, while butyric acid inhibited cell proliferation and promoted cell apoptosis. The treatment of butyric acid in CIH group down-regulated expression of inflammatory factors and increased cell apoptotic rate. Butyric acid treatment increased HuR expression in both cytoplasm and nucleus and decreased the level of p-AMPK and p-ACC, while transfection of AMPK activator or HuR-siRNA would down-regulate HuR expression. Moreover, butyric acid alleviated CIH-induced cell proliferation, lipid formation and inflammatory status and promoted cell apoptosis through regulating related genes including p21, PPARγ, C/EBPa, IL-1β, IL-6, TLR4, caspase-8 and caspase-3. In conclusion, butyric acid could alleviate CIH-induced inflammation, cell proliferation and lipid formation through accumulation of HuR and inactivation of AMPK pathway.

Human antigen R promotes lung fibroblast differentiation to myofibroblasts and increases extracellular matrix production

Idiopathic pulmonary fibrosis (IPF) is a disease of progressive scarring caused by excessive extracellular matrix (ECM) deposition and activation of α-SMA-expressing myofibroblasts. Human antigen R (HuR) is an RNA binding protein that promotes protein translation. Upon translocation from the nucleus to the cytoplasm, HuR functions to stabilize messenger RNA (mRNA) to increase protein levels. However, the role of HuR in promoting ECM production, myofibroblast differentiation, and lung fibrosis is unknown. Human lung fibroblasts (HLFs) treated with transforming growth factor β1 (TGF-β1) showed a significant increase in translocation of HuR from the nucleus to the cytoplasm. TGF-β-treated HLFs that were transfected with HuR small interfering RNA had a significant reduction in α-SMA protein as well as the ECM proteins COL1A1, COL3A, and FN1. HuR was also bound to mRNA for ACTA2, COL1A1, COL3A1, and FN. HuR knockdown affected the mRNA stability of ACTA2 but not that of the ECM genes COL1A1, COL3A1, or FN. In mouse models of pulmonary fibrosis, there was higher cytoplasmic HuR in lung structural cells compared to control mice. In human IPF lungs, there was also more cytoplasmic HuR. This study is the first to show that HuR in lung fibroblasts controls their differentiation to myofibroblasts and consequent ECM production. Further research on HuR could assist in establishing the basis for the development of new target therapy for fibrotic diseases, such as IPF.

Cisplatin Relocalizes RNA Binding Protein HuR and Enhances the Oncolytic Activity of E4orf6 Deleted Adenovirus

The combination of adenoviruses and chemotherapy agents is a novel approach for human cancer therapeutics. A meticulous analysis between adenovirus and chemotherapeutic agents can help to design an effective anticancer therapy. Human antigen R (HuR) is an RNA binding protein that binds to the AU-rich element (ARE) of specific mRNA and is involved in the export and stabilization of ARE-mRNA. Our recent report unveiled that the E4orf6 gene deleted oncolytic adenovirus (dl355) replicated for certain types of cancers where ARE-mRNA is stabilized. This study aimed to investigate whether a combined treatment of dl355 and Cis-diamminedichloroplatinum (CDDP) can have a synergistic cell-killing effect on cancer cells. We confirmed the effect of CDDP in nucleocytoplasmic HuR shuttling. In vitro and in vivo experiments showed the enhancement of cancer cell death by apoptosis induction and a significant reduction in tumor growth following combination treatment. These results suggested that combination therapy exerted a synergistic antitumor activity by upregulation of CDDP induced cytoplasmic HuR, which led to ARE mRNA stabilization and increased virus proliferation. Besides, the enhanced cell-killing effect was due to the activation of the intrinsic apoptotic pathway. Therefore, the combined treatment of CDDP and dl355 could represent a rational approach for cancer therapy.

miR-519 regulates the proliferation of breast cancer cells via targeting human antigen R

Breast cancer is one of the most prevalent types of cancer among women that leads to millions of deaths worldwide every year. The mechanisms of breast cancer pathogenesis remain unclear. It has been reported that aberrant expression of miR-519, is associated with breast cancer development; however, the effects of miR-519 on breast cancer cell proliferation remain unknown. Therefore, the present study aimed to determine whether miR-519 could regulate breast cancer cell proliferation. A total of 20 pairs of primary breast cancer and adjacent normal tissues were collected from patients with breast cancer. miR-519 expression level was determined by reverse transcription-quantitative polymerase chain reaction. Furthermore, miR-519 mimics or inhibitors were transfected into breast cancer MCF-7 cells in order to up- or downregulate miR-519 expression. Subsequently, human antigen R (HUR), BCL-2 and BAX protein levels were analyzed by western blotting. MCF-7 cell proliferation was assessed using MTT and colony formation assays. A luciferase assay was performed to verify whether miR-519 could directly bind to HUR mRNA. The results demonstrated that miR-519 expression level was lower in primary breast cancer tissues compared with adjacent normal tissues. Furthermore, miR-519 overexpression and downregulation inhibited and stimulated MCF-7 cell proliferation, respectively. In addition, the results from luciferase assay demonstrated that HUR was a target of miR-519. HUR overexpression could reverse the effect of miR-519 mimics on MCF-7 cell proliferation, whereas HUR silencing could rescue the effect of miR-519 inhibitors on MCF-7 cell proliferation. These findings suggested that miR-519 may regulate MCF-7 cell proliferation by targeting HUR.

Rosiglitazone-dependent dissociation of HuR from PPAR-γ regulates adiponectin expression at the posttranscriptional level

Peroxisome proliferator-activated receptor (PPAR)-γ has been implicated as a key player in the regulation of adiponectin levels via both transcriptional and posttranscriptional mechanisms. Herein, we show that PPAR-γ interacts with human antigen R (HuR) and that the PPAR-γ-HuR complex dissociates following activation of PPAR-γ by rosiglitazone, a specific ligand of PPAR-γ. This rosiglitazone-dependent dissociation of HuR from PPAR-γ leads to nucleocytoplasmic shuttling of HuR and its binding to the 3'-UTR of adiponectin mRNA. PPAR-γ with H321A and H447A double mutation (PPAR-γ^H321/447A), a mutant lacking ligand-binding activity, impaired HuR dissociation from the PPAR-γ-HuR complex, resulting in reduced nucleocytoplasmic shuttling, even in the presence of rosiglitazone. Consequently, rosiglitazone up-regulated adiponectin levels by modulating the stability of adiponectin mRNA, whereas these effects were abolished by HuR ablation or blocked in cells expressing the PPAR-γ^H321/447A mutant, indicating that the interaction of PPAR-γ and HuR is a critical event during adiponectin expression. Taken together, the findings demonstrate a novel mechanism for regulating adiponectin expression at the posttranscriptional level and suggest that ligand-mediated activation of PPAR-γ to interfere with interaction of HuR could offer a therapeutic strategy for inflammation-associated diseases that involve decreased adiponectin mRNA stability.-Hwang, J. S., Lee, W. J., Hur, J., Lee, H. G., Kim, E., Lee, G. H., Choi, M.-J., Lim, D.-S., Paek, K. S., Seo, H. G. Rosiglitazone-dependent dissociation of HuR from PPAR-γ regulates adiponectin expression at the posttranscriptional level.

Human antigen R as a predictive marker for response to gemcitabine-based chemotherapy in advanced cisplatin-resistant urothelial cancer

In patients with advanced urothelial cancer (UC), a combination of cisplatin (CDDP) and gemcitabine (GEM) is the most commonly used first-line systematic chemotherapy regimen. Although no standard regime for the treatment of CDDP-resistant UC has been established, GEM-based regimens are frequently used in these patients. In other types of cancer, human antigen R (HuR) status in cancer cells is closely associated with patient response to GEM. The aim of the present study was to establish the predictive potential of HuR expression for disease progression and survival in patients with UC who were treated with GEM-based regimens as a first or second-line chemotherapy. A total of 50 patients with advanced UC were enrolled in the current study. As first-line chemotherapy, methotrexate, vinblastine, epirubicin and CDDP (MVEC) combination therapy and GEM and CDDP combination therapy were administered in 34 (68.0%) and 16 patients (32.0%), respectively. Following progression, 45 patients (90.0%) were treated with combined GEM and paclitaxel therapy, and 5 patients (10.0%) were treated with GEM monotherapy. Cytoplasmic and nuclear HuR expression was evaluated using immunohistochemical techniques. The associations between HuR expression levels and local tumor response and treatment outcomes were analyzed. In first-line chemotherapy, no anticancer effects were observed to be significantly associated with nuclear or cytoplasmic HuR expression. In second-line chemotherapy nuclear HuR expression also exhibited no significant association with anticancer effects; however, the local tumor response was significantly improved if positive cytoplasmic HuR expression was present (P=0.002). Multivariate analyses revealed that cytoplasmic HuR expression levels were a significant predictive marker for longer OS (hazard ratio, 0.22; 95% confidence interval, 0.09-0.56; P=0.001). No significant association was observed between nuclear HuR expression levels and the overall survival. Therefore, cytoplasmic HuR expression is a significant predictive marker of response to GEM-based chemotherapy in patients with CDDP-resistant UC. Despite the limitations of a small and retrospective study, the results of the present study may facilitate the development of novel treatment strategies and provide a focus for additional basic and clinical studies.

Modulation of TNF-α mRNA stability by human antigen R and miR181s in sepsis-induced immunoparalysis

Immunoparalysis is an important pathological mechanism in sepsis. However, an effective small molecule therapy is lacking. Here, we show that ouabain, a Na⁺,K⁺-ATPase ligand, can reverse immunoparalysis in vitro, in vivo, and in clinical samples. Notably, the effect of ouabain was critically dependent on TNF-α expression. However, ouabain had opposing effects on the stability of TNF-α mRNA: Ouabain triggered miR-181 transcription, which promoted TNF-α mRNA degradation and induced immunoparalysis, and ouabain triggered the nuclear export of human antigen R (HuR), which stabilized TNF-α mRNA and suppressed immuno-paralysis. Interestingly, because the miR-181 binding site is located within the HuR binding site in the 3′-untranslated region of TNF-α, in ouabain-treated cells, HuR competed with miR-181 for binding to TNF-α mRNA and recruited TNF-α mRNA to stress granules, thereby stabilizing TNF-α mRNA and reversing immunoparalysis. Ouabain also induced GM-CSF and interferon-γ expression in a HuR-dependent manner. Hence, the fine-tuning of TNF-α mRNA stability by HuR and miR181 plays a crucial role in immunoparalysis, and Na⁺,K⁺-ATPase ligands are promising agents for immunoparalysis therapy.

Human antigen R mediated post-transcriptional regulation of epithelial-mesenchymal transition related genes in diabetic nephropathy

BACKGROUND

Human antigen R (HuR) is a ubiquitously expressed RNA-binding protein that modulates gene expression at the post-transcriptional level. While cytoplasmic HuR expression was identified as a marker in epithelial-mesenchymal transition (EMT) process of several types of cancer, its role in diabetic nephropathy (DN) remains unclear.

METHODS

Renal biopsies from Type 2 diabetic patients and STZ-induced DN rats were stained for HuR and EMT markers. Redistribution of HuR was detected by immunostaining and western blot in high glucose stimulated cells. RNAi was used to supress HuR expression. The binding affinity for EMT-related genes was evaluated by immunoprecipitation.

RESULTS

Cytoplasmic HuR expression was elevated in human and rat DN specimens along with EMT changes compared to normal controls. HuR shuttling between nucleus and cytoplasm facilitated epithelial to mesenchymal transition in renal epithelial cells. The suppression of HuR partially inhibited EMT of high glucose stimulated HK-2 cells. Furthermore, HuR bound to 3'-UTRs of critical cytokines or transcription factors mRNA involved in EMT process.

CONCLUSION

Acquired phenotypic traits of EMT were partially through the enhanced HuR-binding proteins and its post-transcriptional regulation role in DN.

MicroRNA-146a and microRNA-146b expression and anti-inflammatory function in human airway smooth muscle

MicroRNA (miR)-146a and miR-146b are negative regulators of inflammatory gene expression in lung fibroblasts, epithelial cells, monocytes, and endothelial cells. The abundance of cyclooxygenase-2 (COX-2) and IL-1β is negatively regulated by the miR-146 family, suggesting miR-146a and/or miR-146b might modulate inflammatory mediator expression in airway smooth muscle thereby contributing to pathogenesis of asthma. To test this idea we compared miR-146a and miR-146b expression in human airway smooth muscle cells (hASMCs) from nonasthmatic and asthmatic subjects treated with cytomix (IL-1β, TNF-α, and IFNγ) and examined the miRNAs' effects on COX-2 and IL-1β expression. We found that cytomix treatment elevated miR-146a and miR-146b abundance. Induction with cytomix was greater than induction with individual cytokines, and asthmatic cells exhibited higher levels of miR-146a expression following cytomix treatment than nonasthmatic cells. Transfection of miR-146a or miR-146b mimics reduced COX-2 and IL-1β expression. A miR-146a inhibitor increased COX-2 and IL-1β expression, but a miR-146b inhibitor was ineffective. Repression of COX-2 and IL-1β expression by miR-146a correlated with reduced abundance of the RNA-binding protein human antigen R. These results demonstrate that miR-146a and miR-146b expression is inducible in hASMCs by proinflammatory cytokines and that miR-146a expression is greater in asthmatic cells. Both miR-146a and miR-146b can negatively regulate COX-2 and IL-1β expression at pharmacological levels, but loss-of-function studies showed that only miR-146a is an endogenous negative regulator in hASMCs. The results suggest miR-146 mimics may be an attractive candidate for further preclinical studies as an anti-inflammatory treatment of asthma.

RNA binding protein HuR regulates the expression of ABCA1

ABCA1 is a major regulator of cellular cholesterol efflux and plasma HDL biogenesis. Even though the transcriptional activation of ABCA1 is well established, the posttranscriptional regulation of ABCA1 expression is poorly understood. Here, we investigate the potential contribution of the RNA binding protein (RBP) human antigen R (HuR) on the posttranscriptional regulation of ABCA1 expression. RNA immunoprecipitation assays demonstrate a direct interaction between HuR and ABCA1 mRNA. We found that HuR binds to the 3' untranslated region of ABCA1 and increases ABCA1 translation, while HuR silencing reduces ABCA1 expression and cholesterol efflux to ApoA1 in human hepatic (Huh-7) and monocytic (THP-1) cells. Interestingly, cellular cholesterol levels regulate the expression, intracellular localization, and interaction between HuR and ABCA1 mRNA. Finally, we found that HuR expression was significantly increased in macrophages from human atherosclerotic plaques, suggesting an important role for this RBP in controlling macrophage cholesterol metabolism in vivo. In summary, we have identified HuR as a novel posttranscriptional regulator of ABCA1 expression and cellular cholesterol homeostasis, thereby opening new avenues for increasing cholesterol efflux from atherosclerotic foam macrophages and raising circulat-ing HDL cholesterol levels.

Nox2/ROS-dependent human antigen R translocation contributes to TNF-α-induced SOCS-3 expression in human tracheal smooth muscle cells

Elevated levels of TNF-α have been detected in the airway fluids, which may induce upregulation of inflammatory proteins. Suppressors of cytokine signaling (SOCS)-3 proteins can be induced by various cytokines and negatively regulated inflammatory responses. Although TNF-α has been shown to induce SOCS-3 expression, the mechanisms underlying TNF-α-induced SOCS-3 expression in human tracheal smooth muscle cells (HTSMCs) remain unclear. Here, we showed that TNF-α induced SOCS-3 expression, which was inhibited by pretreatment with the inhibitor of transcription level (actinomycin D), translation level (cycloheximide), JNK1/2 (SP600125), MEK1/2 (U0126), NADPH oxidase (Nox; apocynin and diphenyleneiodonium chloride), or reactive oxygen species (ROS; N-acetyl-l-cysteine) and transfection with siRNA of JNK1, p47(phox), p42, Nox2, or human antigen R (HuR). In addition, TNF-α-stimulated JNK1/2 and p42/p44 MAPK phosphorylation, Nox activation, and ROS generation were inhibited by pretreatment with U0126 or SP600125 and transfection with siRNA of JNK1 or p42. We further showed that TNF-α markedly induced HuR protein expression and translocation from the nucleus to the cytosol, which could stabilize SOCS-3 mRNA. Moreover, TNF-α-enhanced HuR translocation was reduced by transfection with siRNA of p42, JNK1, or p47(phox). These results suggested that TNF-α induces SOCS-3 protein expression and mRNA stabilization via a TNFR1/JNK1/2, p42/p44 MAPK/Nox2/ROS-dependent HuR signaling in HTSMCs. Lipopolysaccharide (LPS) has been shown to play a key role in inflammation via induction of adhesion molecules and then causes airway and lung injury. Moreover, we also demonstrated that overexpression of SOCS-3 protects against LPS-induced adhesion molecules expression and airway inflammation.

Sphingosine 1-phosphate (S1P) induces COX-2 expression and PGE2 formation via S1P receptor 2 in renal mesangial cells

Understanding the mechanisms of sphingosine 1-phosphate (S1P)-induced cyclooxygenase (COX)-2 expression and prostaglandin E2 (PGE2) formation in renal mesangial cells may provide potential therapeutic targets to treat inflammatory glomerular diseases. Thus, we evaluated the S1P-dependent signaling mechanisms which are responsible for enhanced COX-2 expression and PGE2 formation in rat mesangial cells under basal conditions. Furthermore, we investigated whether these mechanisms are operative in the presence of angiotensin II (Ang II) and of the pro-inflammatory cytokine interleukin-1β (IL-1β). Treatment of rat and human mesangial cells with S1P led to concentration-dependent enhanced expression of COX-2. Pharmacological and molecular biology approaches revealed that the S1P-dependent increase of COX-2 mRNA and protein expression was mediated via activation of S1P receptor 2 (S1P2). Further, inhibition of Gi and p42/p44 MAPK signaling, both downstream of S1P2, abolished the S1P-induced COX-2 expression. In addition, S1P/S1P2-dependent upregulation of COX-2 led to significantly elevated PGE2 levels, which were further potentiated in the presence of Ang II and IL-1β. A functional consequence downstream of S1P/S1P2 signaling is mesangial cell migration that is stimulated by S1P. Interestingly, inhibition of COX-2 by celecoxib and SC-236 completely abolished the migratory response. Overall, our results demonstrate that extracellular S1P induces COX-2 expression via activation of S1P2 and subsequent Gi and p42/p44 MAPK-dependent signaling in renal mesangial cells leading to enhanced PGE2 formation and cell migration that essentially requires COX-2. Thus, targeting S1P/S1P2 signaling pathways might be a novel strategy to treat renal inflammatory diseases.

Domain-specific phosphomimetic mutation allows dissection of different protein kinase C (PKC) isotype-triggered activities of the RNA binding protein HuR

The ubiquitous mRNA binding protein human antigen R (HuR) participates in the post-transcriptional regulation of many AU-rich element (ARE)-bearing mRNAs. Previously, by using in vitro kinase assay, we have identified serines (Ser) 158, 221 and 318 as targets of protein kinase C (PKC)-triggered phosphorylation. In this study, we tested whether GFP- or GST-tagged HuR constructs bearing a phosphomimetic Ser (S)-to-Asp (D) substitution at the different PKC target sites, would affect different HuR functions including HuR nucleo-cytoplasmic redistribution and binding to different types of ARE-containing mRNAs. The phosphomimetic GFP-tagged HuR protein bearing a phosphomimetic substitution in the hinge region of HuR (HuR-S221D) showed an increased cytoplasmic abundance when compared to wild-type HuR. Conversely, data from in vitro kinase assay and electrophoretic mobility shift assay (EMSA), implicates that phosphorylation at Ser 221 is not relevant for mRNA binding of HuR. Quantification of in vitro binding affinities of GST-tagged wild-type HuR and corresponding HuR proteins bearing a phosphomimetic substitution in either RRM2 (HuR-S158D) or in RRM3 (HuR-S318D) by microscale thermophoresis (MST) indicates a specific binding of wild-type HuR to type I, II or type III-ARE-oligonucleotides in the high nanomolar range. Interestingly, phosphomimetic mutation at position 158 or 318 had a negative influence on HuR binding to type I- and type II-ARE-mRNAs whereas it significantly enhanced HuR affinity to a type III-ARE substrate. Our data suggest that differential phosphorylation of HuR by PKCs at different HuR domains coordinates subcellular HuR distribution and leads to a preferential binding to U-rich bearing target mRNA.