PDCD4 restricts PRRSV replication in an eIF4A-dependent manner and is antagonized by the viral nonstructural protein 9.

As obligate parasites, viruses have evolved multiple strategies to evade the host immune defense. Manipulation of the host proteasome system to degrade specific detrimental factors is a common viral countermeasure. To identify host proteins targeted for proteasomal degradation by porcine reproductive and respiratory syndrome virus (PRRSV), we conducted a quantitative proteomics screen of PRRSV-infected Marc-145 cells under the treatment with proteasome inhibitor MG132. The data revealed that the expression levels of programmed cell death 4 (PDCD4) were strongly downregulated by PRRSV and significantly rescued by MG132. Further investigation confirmed that PRRSV infection induced the translocation of PDCD4 from the nucleus to the cytoplasm, and the viral nonstructural protein 9 (Nsp9) promoted PDCD4 proteasomal degradation in the cytoplasm by activating the Akt-mTOR-S6K1 pathway. The C-terminal domain of Nsp9 was responsible for PDCD4 degradation. As for the role of PDCD4 during PRRSV infection, we demonstrated that PDCD4 knockdown favored viral replication, while its overexpression significantly attenuated replication, suggesting that PDCD4 acts as a restriction factor for PRRSV. Mechanistically, we discovered eukaryotic translation initiation factor 4A (eIF4A) was required for PRRSV. PDCD4 interacted with eIF4A through four sites (E249, D253, D414, and D418) within its two MA3 domains, disrupting eIF4A-mediated translation initiation in the 5'-untranslated region of PRRSV, thereby inhibiting PRRSV infection. Together, our study reveals the antiviral function of PDCD4 and the viral strategy to antagonize PDCD4. These results will contribute to our understanding of the immune evasion strategies employed by PRRSV and offer valuable insights for developing new antiviral targets.IMPORTANCEPorcine reproductive and respiratory syndrome virus (PRRSV) infection results in major economic losses in the global swine industry and is difficult to control effectively. Here, using a quantitative proteomics screen, we identified programmed cell death 4 (PDCD4) as a host protein targeted for proteasomal degradation by PRRSV. We demonstrated that PDCD4 restricts PRRSV replication by interacting with eukaryotic translation initiation factor 4A, which is required for translation initiation in the viral 5'-untranslated region. Additionally, four sites within two MA3 domains of PDCD4 are identified to be responsible for its antiviral function. Conversely, PRRSV nonstructural protein 9 promotes PDCD4 proteasomal degradation in the cytoplasm by activating the Akt-mTOR-S6K1 pathway, thus weakening the anti-PRRSV function. Our work unveils PDCD4 as a previously unrecognized host restriction factor for PRRSV and reveals that PRRSV develops countermeasures to overcome PDCD4. This will provide new insights into virus-host interactions and the development of new antiviral targets.

Bone Marrow Mesenchymal Stem Cells-Derived miR-21-5p Protects Grafted Islets Against Apoptosis by Targeting PDCD4.

The apoptosis of grafted islets is an urgent problem due to the high rate of islet loss soon after transplantation. MicroRNA-21-5p (miR-21-5p) is an essential mediator of bone marrow mesenchymal stem cells-derived exosomes (BMSCs-Exo) during anti-apoptosis, but its effect and the underlying molecular mechanism in islet transplantation remain partially understood. Here, we found that miR-21-5p could be delivered to islet cells via BMSCs-Exo. Subsequently, we demonstrated that miR-21-5p overexpression reduced apoptosis in islets and INS-1 cells, whereas miR-21-5p inhibition enhanced apoptosis. A mechanistic analysis involving RNA sequencing and bioinformatic analysis was performed to determine the interaction between miR-21-5p and its target gene programmed cell death 4 (PDCD4), which was further verified by a dual luciferase assay. In vivo, the grafted islets overexpressing miR-21-5p showed a higher survival rate, better insulin secretion function, and a lower apoptosis rate. In conclusion, these results demonstrated that miR­21­5p from BMSCs-Exo protects against the apoptosis of grafted islets by inhibiting PDCD4 expression. Hence, miR-21-5p can be used as a cell-free therapeutic agent to minimize ß-cell apoptosis at the early stage of islet transplantation.

PDCD4 deficiency improved 4-vinylcyclohexene dioxide-induced mouse premature ovarian insufficiency.

RESEARCH QUESTION: What role does programmed cell death 4 (PDCD4) play in premature ovarian insufficiency (POI)? DESIGN: A PDCD4 gene knockout (PDCD4-/-) mouse model was constructed, a POI mouse model was established similar to human POI with 4-vinylcyclohexene dioxide (VCD), a PDCD4-overexpressed adenovirus was designed and the regulatory role in POI in vitro and in vivo was investigated. RESULTS: PDCD4 expression was significantly increased in the ovarian granulosa cells of patients with POI (P ≤ 0.002 protein and mRNA) and mice with VCD-induced POI (P < 0.001 protein expression in both mouse ovaries and granulosa cells). In POI-induced mice model, PDCD4 knockouts significantly increased anti-Müllerian hormone, oestrodiol and numbers of developing follicles, and the PI3K-AKT-Bcl2/Bax signalling pathway is involved in it. CONCLUSION: The expression and regulation of PDCD4 significantly affects the POI pathology in a mouse model. This effect is closely related to the regulation of Bcl2/Bax and the activation of the PI3K-AKT signalling pathway.

Programmed cell death 4 governs NLRP3-mediated pyroptosis in septic lung disorders.

INTRODUCTION: Sepsis is a pathogenic syndrome of prolonged excessive inflammation and immunosuppression produced by invading pathogens. Programmed cell death 4 (PDCD4) may be implicated in a range of inflammatory lesions, and this study aimed to confirm the involvement of PDCD4 in septic lung injury. MATERIALS AND METHODS: Mice and bronchial epithelial 16HBE cells were separately subjected to CLP and LPS to generate in vivo and in vitro models. Following the level of PDCD4 was determined, the impacts of PDCD4 knockdown on mouse lung injury degree, inflammation, apoptosis, and pyroptosis levels were evaluated. Afterward, cells were treated with the NLRP3 agonist, and the influences of NLRP3 activation on the regulations of PDCD4 knockdown were determined. RESULTS: PDCD4 was elevated following mice developed septic lung injury, PDCD4 knockdown ameliorated septic lung injury and reduced lung inflammation and apoptosis. Moreover, PDCD4 knockdown suppressed NLRP3-mediated pyroptosis, indicating that PDCD4 also mediated pyroptosis. According to cellular models, NLRP3 activation broke the effects of PDCD4 knockdown on cells. CONCLUSIONS: The current study reveals that PDCD4 governs NLRP3-mediated pyroptosis in septic lung injury. PDCD4 is not only related to apoptosis and expands the knowledge of PDCD4 regulation of different cell death modes.

Progress on the relationship between tumor suppressor PDCD4 and diseases based on the analysis of structural characteristics.

The tumor suppressor programmed cell death 4 (PDCD4) is downregulated in various tumor tissues indicating poor prognosis. PDCD4 is the first protein found to resist tumor transformation, invasion, and metastasis by inhibiting translation. The functions of PDCD4 dependent on its structures are affected by extracellular signals. It regulates tumor-related proteins through a variety of mechanisms, especially involved in two major signaling pathways, PI3K-Akt-mTOR and MAPK. By analyzing the relationship between the structures, functions and diseases of PDCD4, this review summarizes the roles of PDCD4 in several physiological processes and diseases such as apoptosis, autophagy, tumor, and inflammation in recent years, thereby providing insights for the study of the signaling pathways of PDCD4 and related proteins and the treatment of diseases targeting them.

Knockdown of miR-150-5p reduces hypoxia-induced autophagy and epithelial-mesenchymal transition of endometriotic cells via regulating the PDCD4/NF-κB signaling pathway.

BACKGROUND: Hypoxia is an important microenvironmental factor that induces Endometriosis (EMs), but its mechanism remains unclear. Our study aims to investigate the mechanisms of miR-150-5p on hypoxia-induced EMs. METHODS: Ovarian endometriosis cyst wall stromal cell lines CRL-7566 cells were treated with hypoxia. Cell migration ability was measured by Transwell assay. qRT-PCR was performed to detect miR-150-5p and PDCD4 expression. The autophagy-related proteins (LC3-I, LC3-II, Beclin-1, and p62), epithelial-mesenchymal transition (EMT) related proteins (E-cadherin, N-cadherin, and Vimentin) and NF-κB signaling pathway related proteins p65 expression were measured by western blot. Dual-luciferase reporter gene assay verified the binding relationship between miR-150-5p and PDCD4. RESULTS: After hypoxia treatment, the miR-150-5p expression was up-regulated in CRL-7566 cells, while the expression of PDCD4 was down-regulated. In CRL-7566 cells, autophagy, migration and EMT were increased after hypoxia treatment. The autophagy inhibitor 3-MA inhibited hypoxia-induced the autophagy, migration and EMT of CRL-7566 cells. Hypoxia-induced autophagy and EMT of CRL-7566 cells were inhibited after knocking down miR-150-5p. Then miR-150-5p negatively regulated PDCD4 expression. PDCD4 knockdown reversed the inhibitory effect of miR-150-5p silencing on hypoxia-induced autophagy and EMT of CRL-7566 cells. Inhibiting the NF-κB signaling pathway weakened the effect of PDCD4 knockdown on hypoxia-induced autophagy and EMT of CRL-7566 cells. CONCLUSION: MiR-150-5p silencing inhibited hypoxia-induced autophagy and EMT of endometriotic cells by regulating the PDCD4/NF-κB signaling pathway.

Higher expression of programmed cell death 4 (PDCD4) in acute myeloid leukemia is associated with better prognosis after chemotherapy.

Acute myeloid leukemia (AML) is a common heterogeneous malignancy. Novel molecular markers aid diagnosis, patient sub-categorization, and optimal clinical decisions. Here, we explored the prognostic implications associated with the expression of the programmed cell death (PDCD) family of molecules in AML patients. Based on the findings from the TCGA and OHSU cohorts, we observed that the mRNA abundance of PDCD4 is significantly higher compared to other molecules within the PDCD family. Furthermore, high expression of PDCD4 was associated with predicted long-term patient survival in diagnosed AML patients. In the chemotherapy group, patients with high PDCD4 expression showed a tendency toward longer overall survival (OS) (P = 0.0266) and event-free survival (EFS) (P = 0.0008). High PDCD4 levels served as a favorable independent predictor for both OS and EFS in AML patients. However, subgroup analyses in the hematopoietic stem cell transplantation (HSCT) group revealed no significant difference in OS or EFS between individuals with high and low PDCD4 expression. Furthermore, in the low PDCD4 expression group, AML patients who underwent HSCT experienced improved survival outcomes (P = 0.0015), helping to mitigate the unfavorable prognosis associated with PDCD4 downregulation. Conversely, in the high PDCD4 expression group, HSCT offered a notable short-term survival advantage, while patients with high PDCD4 expression responded favorably to long-term survival through chemotherapy. Biological function enrichment showed that the expression of PDCD4 was correlated with complement and coagulation cascades, cell receptor signaling pathways, and cholesterol metabolism. The findings from this study will aid in better categorizing heterogeneous AML patients and guiding more appropriate clinical decision-making.

Arctigenin impairs UBC12 enzyme activity and cullin neddylation to attenuate cancer cells.

Neddylation is a type of posttranslational protein modification that has been observed to be overactivated in various cancers. UBC12 is one of two key E2 enzymes in the neddylation pathway. Reports indicate that UBC12 deficiency may suppress lung cancer cells, such that UBC12 could play an important role in tumor progression. However, systematic studies regarding the expression profile of UBC12 in cancers and its relationship to cancer prognosis are lacking. In this study, we comprehensively analyzed UBC12 expression in diverse cancer types and found that UBC12 is markedly overexpressed in most cancers (17/21), a symptom that negatively correlates with the survival rates of cancer patients, including gastric cancer. These results demonstrate the suitability of UBC12 as a potential target for cancer treatment. Currently, no effective inhibitor targeting UBC12 has been discovered. We screened a natural product library and found, for the first time, that arctigenin has been shown to significantly inhibit UBC12 enzyme activity and cullin neddylation. The inhibition of UBC12 enzyme activity was newly found to contribute to the effects of arctigenin on suppressing the malignant phenotypes of cancer cells. Furthermore, we performed proteomics analysis and found that arctigenin intervened with cullin downstream signaling pathways and substrates, such as the tumor suppressor PDCD4. In summary, these results demonstrate the importance of UBC12 as a potential therapeutic target for cancer treatment, and, for the first time, the suitability of arctigenin as a potential compound targeting UBC12 enzyme activity. Thus, these findings provide a new strategy for inhibiting neddylation-overactivated cancers.

Cold exposure protects against medial arterial calcification development via autophagy.

Medial arterial calcification (MAC), a systemic vascular disease different from atherosclerosis, is associated with an increased incidence of cardiovascular events. Several studies have demonstrated that ambient temperature is one of the most important factors affecting cardiovascular events. However, there has been limited research on the effect of different ambient temperatures on MAC. In the present study, we showed that cold temperature exposure (CT) in mice slowed down the formation of vitamin D (VD)-induced vascular calcification compared with room temperature exposure (RT). To investigate the mechanism involved, we isolated plasma-derived exosomes from mice subjected to CT or RT for 30 days (CT-Exo or RT-Exo, respectively). Compared with RT-Exo, CT-Exo remarkably alleviated the calcification/senescence formation of vascular smooth muscle cells (VSMCs) and promoted autophagy by activating the phosphorylation of AMP-activated protein kinase (p-AMPK) and inhibiting phosphorylation of mammalian target of rapamycin (p-mTOR). At the same time, CT-Exo promoted autophagy in ß-glycerophosphate (ß-GP)-induced VSMCs. The number of autophagosomes and the expression of autophagy-related proteins ATG5 and LC3B increased, while the expression of p62 decreased. Based on a microRNA chip microarray assay and real-time polymerase chain reaction, miR-320a-3p was highly enriched in CT-Exo as well as thoracic aortic vessels in CT mice. miR-320a-3p downregulation in CT-Exo using AntagomiR-320a-3p inhibited autophagy and blunted its anti-calcification protective effect on VSMCs. Moreover, we identified that programmed cell death 4 (PDCD4) is a target of miR-320a-3p, and silencing PDCD4 increased autophagy and decreased calcification in VSMCs. Treatment with CT-Exo alleviated the formation of MAC in VD-treated mice, while these effects were partially reversed by GW4869. Furthermore, the anti-arterial calcification protective effects of CT-Exo were largely abolished by AntagomiR-320a-3p in VD-induced mice. In summary, we have highlighted that prolonged cold may be a good way to reduce the incidence of MAC. Specifically, miR-320a-3p from CT-Exo could protect against the initiation and progression of MAC via the AMPK/mTOR autophagy pathway.

LncRNA H19 Contributes to Smoke-Related Chronic Obstructive Pulmonary Disease by Targeting miR-181/PDCD4 Axis.

Chronic obstructive pulmonary disease (COPD) kills more than 3 million people worldwide every year. Despite progress in the treatment of symptoms and prevention of acute exacerbations, few advances have been made to ameliorate disease progression or affect mortality. Exercise plays a positive role in the prevention and treatment of diaphragm dysfunction in COPD, and the changes in diaphragm structure and function induced by exercise are closely related to the regulation of oxidative stress. But the mechanism remains unclear. So the aim of this study was to reveal the therapeutic mechanism of exercise to COPD using both in vivo and in vitro experiments. In this study, cigarette smoke (CS) induced COPD mice model, treadmill aerobic training for COPD mice were constructed and cigarette smoke extract (CSE) induced bronchial epithelial cells (BECs) model were used for COPD study. Bioinformatics analysis, luciferase reporting analysis, and RT-qPCR detection were used to clarify the interacted relationship among lncRNA, miRNA, and mRNA. ROS, inflammatory cytokines expression, and EMT relative protein α-SMA were detected using immunofluorescence and ELISA detection. The result shows that exercise ameliorates COPD induced lung injury by inhibit ROS, inflammation, and epithelial-mesenchymal transition (EMT) relative protein α-SMA expression. RT-qPCR detection shows that lnc-H19 expression was increased in lung tissues of COPD mice. Exercise decreased COPD induced lnc-H19 expression. Downregulation lnc-H19 inhibits COPD mediated lung injury. Bioinformatics analysis and luciferase reporting analysis confirmed that miR-181 and PDCD4 were downstream targets of lnc-H19. Upregulation of PDCD4 or downregulation of miR-181 reversed the protective effect of si-lnc-H19 to BECs after exposure to CSE. In conclusion, lncRNA H19 contributes to smoke-related chronic obstructive pulmonary disease by targeting miR-181/PDCD4 Axis.

Discovery of a novel role of tumor suppressor PDCD4 in stimulation of translation termination.

Programmed cell death 4 protein (PDCD4) regulates many vital cell processes, although is classified as a tumor suppressor because it inhibits neoplastic transformation and tumor growth. For example, PCDC4 has been implicated in the regulation of transcription and mRNA translation. PDCD4 is known to inhibit translation initiation by binding to eukaryotic initiation factor 4A and elongation of oncogenic c- and A-myb mRNAs. Additionally, PDCD4 has been shown to interact with poly(A)-binding protein (PABP), which affects translation termination, although the significance of this interaction is not fully understood. Considering the interaction between PABP and PDCD4, we hypothesized that PDCD4 may also be involved in translation termination. Using in vitro translation systems, we revealed that PDCD4 directly activates translation termination. PDCD4 stimulates peptidyl-tRNA hydrolysis induced by a complex of eukaryotic release factors, eRF1-eRF3. Moreover, in combination with the PABP, which also stimulates peptide release, PDCD4 activity in translation termination increases. PDCD4 regulates translation termination by facilitating the binding of release factors to the ribosome, increasing the GTPase activity of eRF3, and dissociating eRF3 from the posttermination complex. Using a toe-printing assay, we determined the first stage at which PDCD4 functions-binding of release factors to the A-site of the ribosome. However, preventing binding of eRF3 with PABP, PDCD4 suppresses subsequent rounds of translation termination. Based on these data, we assumed that human PDCD4 controls protein synthesis during translation termination. The described mechanism of the activity of PDCD4 in translation termination provides a new insight into its functioning during suppression of protein biosynthesis.

RNA-binding proteins La and HuR cooperatively modulate translation repression of PDCD4 mRNA.

Posttranscriptional regulation of gene expression plays a critical role in controlling the inflammatory response. An uncontrolled inflammatory response results in chronic inflammation, often leading to tumorigenesis. Programmed cell death 4 (PDCD4) is a proinflammatory tumor-suppressor gene which helps to prevent the transition from chronic inflammation to cancer. PDCD4 mRNA translation is regulated by an interplay between the oncogenic microRNA miR-21 and the RNA-binding protein (RBP) human antigen R (HuR) in response to lipopolysaccharide stimulation, but the role of other regulatory factors remains unknown. Here, we report that the RBP lupus antigen (La) interacts with the 3'-untranslated region of PDCD4 mRNA and prevents miR-21-mediated translation repression. While lipopolysaccharide causes nuclear-cytoplasmic translocation of HuR, it enhances cellular La expression. Remarkably, La and HuR were found to bind cooperatively to the PDCD4 mRNA and mitigate miR-21-mediated translation repression. The cooperative action of La and HuR reduced cell proliferation and enhanced apoptosis, reversing the pro-oncogenic function of miR-21. Together, these observations demonstrate a cooperative interplay between two RBPs, triggered differentially by the same stimulus, which exerts a synergistic effect on PDCD4 expression and thereby helps maintain a balance between inflammation and tumorigenesis.

Differential regulation of miR-21-5p delays wound healing of melanocyte-deprived vitiligo skin by modulating the expression of tumor-suppressors PDCD4 and Maspin.

The loss of melanocytes in vitiligo is associated with architectural, transcriptional, and cellular perturbations of keratinocytes and manifests as a reduced proliferation potential in vitro and delayed re-epithelialization in vivo. To understand the molecular mechanisms underlying this delay, microRNA (miRNA) profiling was performed on split skin biopsies collected on Day 1 (basal level) and Day 14 (wound re-epithelialization) from nonlesional (NL) and lesional (L) skin of five subjects with stable nonsegmental vitiligo and 129 miRNAs were found to be differentially regulated between the NL and L healed epidermis. miR-21-5p, expressed at comparable levels on NL and L Day 1 samples, demonstrated significant upregulation during re-epithelialization. However, the extent of its upregulation was relatively lower in L (10 times compared to Day 1) as compared to NL skin (17 times compared to Day 1). The overexpression of miR-21 in keratinocytes led to a significant increase in the expression of proliferation markers (Ki67 and MCM6 messenger RNA, Ki67 positivity), along with an increase in keratinocyte migration. Using a small interfering RNA mediated knockdown approach, we further demonstrated that miR-21-5p mediates its effects by suppressing the expression of programmed cell death 4 (PDCD4) and mammary serine protease inhibitor (Maspin), both tumor-suppressor genes. Investigation of clinical samples corroborated the lower miR-21 levels and a higher expression of PDCD4 and Maspin in L Day 14 compared to the NL Day 14 epidermis. In conclusion, this study revealed that a relatively lower upregulation of miR-21-5p in L skin leads to significantly higher levels of PDCD4 and Maspin, delaying wound re-epithelialization by reducing the proliferation and migration of keratinocytes.

Ssc-miR-21-5p regulates endometrial epithelial cell proliferation, apoptosis and migration via the PDCD4/AKT pathway.

Endometrial receptivity plays a vital role in successful embryo implantation in pigs. MicroRNAs (miRNAs), known as regulators of gene expression, have been implicated in the regulation of embryo implantation. However, the role of miRNAs in endometrial receptivity during the pre-implantation period remains elusive. In this study, we report that the expression level of Sus scrofa (ssc)-miR-21-5p in porcine endometrium tissues was significantly increased from day 9 to day 12 of pregnancy. Knockdown of ssc-miR-21-5p inhibited proliferation and migration of endometrial epithelial cells (EECs), and induced their apoptosis. We verified that programmed cell death 4 (PDCD4) was a target gene of ssc-miR-21-5p. Inhibition of PDCD4 rescued the effect of ssc-miR-21-5p repression on EECs. Our results also revealed that knockdown of ssc-miR-21-5p impeded the phosphorylation of AKT (herein referring to AKT1) by targeting PDCD4, which further upregulated the expression of Bax, and downregulated the levels of Bcl2 and Mmp9. Furthermore, loss of function of Mus musculus (mmu)-miR-21-5p in vivo resulted in a decreased number of implanted mouse embryos. Taken together, knockdown of ssc-miR-21-5p hampers endometrial receptivity by modulating the PDCD4/AKT pathway.

PDCD4 regulates axonal growth by translational repression of neurite growth-related genes and is modulated during nerve injury responses.

Programmed cell death 4 (PDCD4) protein is a tumor suppressor that inhibits translation through the mTOR-dependent initiation factor EIF4A, but its functional role and mRNA targets in neurons remain largely unknown. Our work identified that PDCD4 is highly expressed in axons and dendrites of CNS and PNS neurons. Using loss- and gain-of-function experiments in cortical and dorsal root ganglia primary neurons, we demonstrated the capacity of PDCD4 to negatively control axonal growth. To explore PDCD4 transcriptome and translatome targets, we used Ribo-seq and uncovered a list of potential targets with known functions as axon/neurite outgrowth regulators. In addition, we observed that PDCD4 can be locally synthesized in adult axons in vivo, and its levels decrease at the site of peripheral nerve injury and before nerve regeneration. Overall, our findings demonstrate that PDCD4 can act as a new regulator of axonal growth via the selective control of translation, providing a target mechanism for axon regeneration and neuronal plasticity processes in neurons.

Arsenic activates STAT3 signaling during the transformation of the human bronchial epithelial cells.

Arsenic (As3+), a metalloid abundant in environment, is classified as a group I carcinogen associated with several common human cancers, including cancers in lung, skin, bladder, liver, and prostate (Wei et al., 2019). The mechanisms of As3+-induced carcinogenesis had been extensively studied, and different mechanisms might be involved in different types of cancer (Wei et al., 2019). Recent studies showed that exposure to a high dose of arsenic is able to induce lung cancer. Meanwhile, prolonged exposure to a low concentration of arsenic can increase the risk of lung cancer also (Liao et al., 2009; Fernández et al., 2012). Emerging evidence indicated that prolonged exposure to arsenic promotes malignant transformation and some of the transformed cells have cancer-stem-like properties (Ngalame et al., 2014). In the present report, we revealed that exposure to As3+ for short time period inhibited tyrosine-705 phosphorylation of signal transducer and activator of transcription 3 (pSTAT3Y705) and induced Src homology region 2 domain-containing phosphatase-1 (SHP-1) in bronchial epithelial cell line, BEAS-2B. In addition, we found that long term exposure of the cells to As3+ activates phosphorylation of STAT3 at serine 727 (pSTAT3S727) as well as pSTAT3Y705. Moreover, As3+ is able to induce the expression of miRNA-21 (miR-21) and decrease the expression of PDCD4. Taken together, our data suggest that activation of STAT3 and induction of miR-21 are important contributing factors to the reduced expression of PDCD4, which may play significant role in As3+-induced transformation of BEAS-2B cells.

Upregulation of miR-499a-5p Decreases Cerebral Ischemia/Reperfusion Injury by Targeting PDCD4.

MiR-499a-5p was significantly downregulated in degenerative tissues and correlated with apoptosis. Nonetheless, the biological function of miR-499a-5p in acute ischemic stroke has been still unclear. In this study, we found that the plasma levels of miR-499a-5p were significantly downregulated in 64 ischemic stroke patients and negatively correlated with the National Institutes of Health Stroke Scale score. Then, we constructed cerebral ischemia/reperfusion (I/R) injury in rats after middle cerebral artery occlusion and subsequent reperfusion and oxygen-glucose deprivation and reoxygenation (OGD/R)-treated SH-SY5Y cell model. Transfection with miR-499a-5p mimic was accomplished by intracerebroventricular injection in the in vivo I/R injury model. We further found that miR-499a-5p overexpression decreased infarct volumes and cell apoptosis in the in vivo I/R stroke model using TTC and TUNEL staining. PDCD4 was a direct target of miR-499a-5p by luciferase report assay and Western blotting. Knockdown of PDCD4 reduced the infarct damage and cortical neuron apoptosis caused by I/R injury. MiR-499a-5p exerted neuroprotective roles mainly through inhibiting PDCD4-mediated apoptosis by CCK-8 assay, LDH release assay, and flow cytometry analysis. These findings suggest that miR-499a-5p might represent a novel target that regulates brain injury by inhibiting PDCD4-mediating apoptosis.

miR-208 inhibits myocardial tissues apoptosis in mice with acute myocardial infarction by targeting inhibition of PDCD4.

This article aimed to investigate the role of miR-208 in the apoptosis of myocardial tissues in acute myocardial infarction (AMI) mice. The AMI mouse model was constructed. Then, miR-208 expression in AMI mice was regulated by transfection. The mouse myocardial tissues were subject to hematoxylin-eosin (HE) staining, TUNEL assay, and immunofluorescence analysis. H9c2 cell transfection and hypoxia induction were then completed, and cell apoptosis and cytokine levels were tested. Additionally, RNA pull-down and dual luciferase reporter gene assays were conducted for exploring the relation of miR-208 with programmed cell death 4 (PDCD4). Additionally, fluorescence in situ hybridization (FISH) was conducted for investigating miR-208 and PDCD4 colocalization within H9c2 cells. AMI mice had severe damage, apoptosis, decreased miR-208 expression, increased IL-1ß, IL-6, IL-8 levels, whereas reduced IL-10 level within myocardial tissues. H9c2 cells under hypoxia induction exhibited decreased miR-208 expression, promoted apoptosis, increased protein expression of Bax and cleaved-caspase-3, decreased protein expression of Bcl-2 and caspase-3, elevated IL-1ß, IL-6, IL-8 levels and decreased IL-10 level. miR-208 upregulation alleviated the damage and apoptosis of myocardial tissues in AMI mice. AMI mice with miR-208 upregulation showed decreased expression of Bax and cleaved-caspase-3, increased expression of Bcl-2 and caspase-3, reduced levels of IL-1ß, IL-6, IL-8, whereas an increased level of IL-10. miR-208 showed direct inhibition of PDCD4. PDCD4 and miR-208 were mainly co-expressed in the cytoplasm. The upregulated PDCD4 expression abolished miR-208's suppression of H9c2 cell apoptosis induced by hypoxia. Besides this, miR-208 inhibited myocardial tissue apoptosis in AMI mice by inhibiting PDCD4 expression.

Exosomal miR-208b related with oxaliplatin resistance promotes Treg expansion in colorectal cancer.

Oxaliplatin resistance is a challenge in the treatment of colorectal cancer (CRC) patients. Regulatory T cells (Tregs) are well known for their immunosuppressive roles, and targeting Tregs is an effective way to improve chemosensitivity. Exosome-delivered microRNA (miRNA) might be used as a potential biomarker for predicting chemosensitivity. However, the relationship between Tregs and exosomal miRNAs remains largely unknown. TaqMan low-density array was performed to screen the differentially expressed serum miRNAs from pooled serum of patients who had FOLFOX treatment. Differential expression was validated using qRT-PCR in individual samples. Exosomes were isolated by sequential differential centrifugation, and they were verified by transmission electron microscopy. The RNA and protein levels were determined by quantitative real-time PCR and western blotting. A mouse xenograft model was adopted to evaluate the correlation between exosome-derived miR-208b and Tregs in vivo. We demonstrated that circulating miR-208b is a non-invasive marker for predicting FOLFOX sensitivity in CRC. miR-208b in colon cancer was secreted by tumor cells in the pattern of exosomes, and oxaliplatin-resistant cells showed the most obvious phenomenon of miR-208b increase. Colon cancer cell-secreted miR-208b was sufficiently delivered into recipient T cells to promote Treg expansion by targeting programmed cell death factor 4 (PDCD4). Furthermore, in vivo studies indicated that Treg expansion mediated by cancer cell-secreted miR-208b resulted in tumor growth and oxaliplatin resistance. Our results demonstrate that tumor-secreted miR-208b promotes Treg expansion by targeting PDCD4, and it may be related to a decrease of oxaliplatin-based chemosensitivity in CRC. These findings highlight a potential role of exosomal miR-208b as a predictive biomarker for oxaliplatin-based therapy response, and they provide a novel target for immunotherapy.

Tumor-derived exosomal microRNA-106b-5p activates EMT-cancer cell and M2-subtype TAM interaction to facilitate CRC metastasis.

Epithelial-mesenchymal transition (EMT) is reported to involve in the crosstalk between tumor cells and tumor-associated macrophages (TAMs). Exosomes are considered as important mediators of orchestrating intercellular communication. However, the underlying mechanisms by which EMT-colorectal cancer (CRC) cells promote the M2 polarization of TAMs remain less understood. In this study, we found that EMT-CRC cells promoted the M2-like polarization of macrophages by directly transferring exosomes to macrophages, leading to a significant increase of the microRNA-106b-5p (miR-106b) level in macrophages. Mechanically, an increased level of miR-106b activated the phosphatidylinositol 3-kinase (PI3K)γ/AKT/mammalian target of rapamycin (mTOR) signaling cascade by directly suppressing programmed cell death 4 (PDCD4) in a post-transcription level, contributing to the M2 polarization of macrophages. Activated M2 macrophages, in a positive-feedback manner, promote EMT-mediated migration, invasion, and metastasis of CRC cells. Clinically, miR-106b was significantly elevated in CRC tissues and negatively correlated with the levels of PDCD4 in CRC specimens, and high expression of exosomal miR-106b in plasma was significantly associated with the malignant progression of CRC. Taken together, our results indicate that exosomal miR-106b derived from EMT-CRC cells has an important role in intercellular communication for inducing M2 macrophage polarization, illuminating a novel mechanism underlying CRC progression and offering potential targets for prevention of CRC metastasis.