Deficiency of programmed cell death 4 results in increased IL-10 expression by macrophages and thereby attenuates atherosclerosis in hyperlipidemic mice

PDCD4 triggers α-synuclein accumulation and motor deficits via co-suppressing TFE3 and TFEB translation in a model of Parkinson's disease

TFE3 and TFEB, as the master regulators of lysosome biogenesis and autophagy, are well characterized to enhance the synaptic protein α-synuclein degradation in protecting against Parkinson's disease (PD) and their levels are significantly decreased in the brain of PD patients. However, how TFE3 and TFEB are regulated during PD pathogenesis remains largely vague. Herein, we identified that programmed cell death 4 (PDCD4) promoted pathologic α-synuclein accumulation to facilitate PD development via suppressing both TFE3 and TFEB translation. Conversely, PDCD4 deficiency significantly augmented global and nuclear TFE3 and TFEB distributions to alleviate neurodegeneration in a mouse model of PD with overexpressing α-synuclein in the striatum. Mechanistically, like TFEB as we reported before, PDCD4 also suppressed TFE3 translation, rather than influencing its transcription and protein stability, to restrain its nuclear translocation and lysosomal functions, eventually leading to α-synuclein aggregation. We proved that the two MA3 domains of PDCD4 mediated the translational suppression of TFE3 through binding to its 5'-UTR of mRNA in an eIF-4A dependent manner. Based on this, we developed a blood-brain barrier penetrating RVG polypeptide modified small RNA drug against pdcd4 to efficiently prevent α-synuclein neurodegeneration in improving PD symptoms by intraperitoneal injections. Together, we suggest PDCD4 as a PD-risk protein to facilitate α-synuclein neurodegeneration via suppressing TFE3 and TFEB translation and further provide a potential small RNA drug against pdcd4 to treat PD by intraperitoneal injections.

Macrophages in cardiovascular diseases: molecular mechanisms and therapeutic targets

The immune response holds a pivotal role in cardiovascular disease development. As multifunctional cells of the innate immune system, macrophages play an essential role in initial inflammatory response that occurs following cardiovascular injury, thereby inducing subsequent damage while also facilitating recovery. Meanwhile, the diverse phenotypes and phenotypic alterations of macrophages strongly associate with distinct types and severity of cardiovascular diseases, including coronary heart disease, valvular disease, myocarditis, cardiomyopathy, heart failure, atherosclerosis and aneurysm, which underscores the importance of investigating macrophage regulatory mechanisms within the context of specific diseases. Besides, recent strides in single-cell sequencing technologies have revealed macrophage heterogeneity, cell-cell interactions, and downstream mechanisms of therapeutic targets at a higher resolution, which brings new perspectives into macrophage-mediated mechanisms and potential therapeutic targets in cardiovascular diseases. Remarkably, myocardial fibrosis, a prevalent characteristic in most cardiac diseases, remains a formidable clinical challenge, necessitating a profound investigation into the impact of macrophages on myocardial fibrosis within the context of cardiac diseases. In this review, we systematically summarize the diverse phenotypic and functional plasticity of macrophages in regulatory mechanisms of cardiovascular diseases and unprecedented insights introduced by single-cell sequencing technologies, with a focus on different causes and characteristics of diseases, especially the relationship between inflammation and fibrosis in cardiac diseases (myocardial infarction, pressure overload, myocarditis, dilated cardiomyopathy, diabetic cardiomyopathy and cardiac aging) and the relationship between inflammation and vascular injury in vascular diseases (atherosclerosis and aneurysm). Finally, we also highlight the preclinical/clinical macrophage targeting strategies and translational implications.

MicroRNA-155 and exosomal microRNA-155: Small pieces in the cardiovascular diseases puzzle

MicroRNAs (miRs, miRNAs) are known to have a part in various human illnesses, such as those related to the heart. One particular miRNA, miR-155, has been extensively studied and has been found to be involved in hematopoietic lineage differentiation, immunity, viral infections, inflammation, as well as vascular remodeling. These processes have all been connected to cardiovascular diseases, including heart failure, diabetic heart disease, coronary artery disease, and abdominal aortic aneurysm. The impacts of miR-155 depend on the type of cell it is acting on and the specific target genes involved, resulting in different mechanisms of disease. Although, the exact part of miR-155 in cardiovascular illnesses is yet not fully comprehended, as some studies have shown it to promote the development of atherosclerosis while others have shown it to prevent it. As a result, to comprehend the underlying processes of miR-155 in cardiovascular disorders, further thorough study is required. It has been discovered that exosomes that could be absorbed by adjacent or distant cells, control post-transcriptional regulation of gene expression by focusing on mRNA. Exosomal miRNAs have been found to have a range of functions, including participating in inflammatory reactions, cell movement, growth, death, autophagy, as well as epithelial-mesenchymal transition. An increasing amount of research indicates that exosomal miRNAs are important for cardiovascular health and have a major role in the development of a number of cardiovascular disorders, including pulmonary hypertension, atherosclerosis, acute coronary syndrome, heart failure, and myocardial ischemia-reperfusion injury. Herein the role of miR-155 and its exosomal form in heart diseases are summarized.

Inhibition of circ_0000231 suppresses oxidized low density lipoprotein-induced apoptosis, autophagy and inflammation in human umbilical vein endothelial cells by regulating miR-590-5p/PDCD4 axis

BACKGROUND

Circular RNAs (circRNAs) are the emerging informative RNAs, involved in cardiovascular diseases including atherosclerosis (AS). Endothelial injury is the initial qualitative change of AS. Thus, the objective of this study was to confirm the dysregulation and mechanism of circ_0000231 in cell model of AS at early stage in human umbilical vein endothelial cells (HUVECs) induced by oxidized low-density lipoprotein (ox-LDL).

METHODS

The expression of circ_0000231, miR-590-5p and programmed cell death 4 (PDCD4) was detected using real-time quantitative PCR and western blot. Cell injury was measured with MTT, flow cytometry, caspase-3 activity assay and enzyme-linked immunosorbent assay (ELISA). The interaction among circ_0000231, miR-590-5p and PDCD4 was validated by dual-luciferase reporter assay, RNA immunoprecipitation (RIP) and pull-down assays.

RESULTS

Stress ox-LDL decreased cell viability, and increased apoptosis rate and caspase-3 activity in HUVECs in a dose- and time-dependent manner in concomitant with promotions of interleukin-6, interleukin-1β, tumor necrosis factor-α, LC3-II/I and Beclin-1 levels. Besides, circ_0000231 and PDCD4 expressions were upregulated, and miR-590-5p was downregulated in ox-LDL-stimulated HUVECs. Functionally, knockdown of circ_0000231 and overexpression of miR-590-5p could suppress ox-LDL-elicited above effects on apoptosis, autophagy and inflammatory response, accompanied with PDCD4 downregulation. Physically, miR-590-5p could directly interact with circ_0000231 and PDCD4.

CONCLUSION

Downregulation of circ_0000231 suppresses HUVECs from ox-LDL-induced injury partially through regulating miR-590-5p/PDCD4 axis via competing endogenous RNA mechanism, showing a novel potential target for the pathology and treatment of endothelial injury in AS.

PRMT5 knockdown enhances cell viability and suppresses cell apoptosis, oxidative stress, inflammation and endothelial dysfunction in ox-LDL-induced vascular endothelial cells via interacting with PDCD4

Atherosclerosis (AS) is an important pathological basis of cardiovascular disease (CVD). The development of AS commences with endothelial dysfunction due to vascular endothelial cell injury. It is well documented that protein arginine methyltransferase 5 (PRMT5) is highly related to cardiovascular events. BioGRID database analysis indicates that PRMT5 may interact with programmed cell death 4 (PDCD4), which is reported to be involved in AS progression. This present research was formulated to elucidate the biological roles of PRMT5/PDCD4 in vascular endothelial cell injury during AS. In this current work, HUVECs were stimulated with 100 mg/L ox-LDL for 48 h to construct an in vitro AS model. Expression levels of PRMT5 and PDCD4 were analyzed by performing RT-qPCR and western blot. The viability and apoptosis of HUVECs were determined using CCK-8, flow cytometry and western blot assays. The status of oxidative stress and inflammation was assessed via commercial detection kits and ELISA assay, respectively. Besides, biomarkers of endothelial dysfunction were detected via commercial detection kit and western blot assay. In addition, the interacting relationship between PRMT5 and PDCD4 was verified by Co-IP assay. Highly expressed PRMT5 was observed in ox-LDL-stimulated HUVECs. Knockdown of PRMT5 enhanced the viability and inhibited the apoptosis of ox-LDL-induced HUVECs as well as alleviated ox-LDL-triggered oxidative stress, inflammation and endothelial dysfunction in HUVECs. PRMT5 interacted and bound with PDCD4. Furthermore, the enhancing effect on cell viability as well as the suppressing effects on cell apoptosis, oxidative stress, inflammation and endothelial dysfunction of PRMT5 knockdown in ox-LDL-induced HUVECs were partially abolished upon up-regulation of PDCD4. To conclude, down-regulation of PRMT5 might exert protective effects against vascular endothelial cell injury during AS by suppressing PDCD4 expression.

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 β-glycerophosphate (β-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.

The Role of Macrophages in the Pathogenesis of Atherosclerosis

A wide variety of cell populations, including both immune and endothelial cells, participate in the pathogenesis of atherosclerosis. Among these groups, macrophages deserve special attention because different populations of them can have completely different effects on atherogenesis and inflammation in atherosclerosis. In the current review, the significance of different phenotypes of macrophages in the progression or regression of atherosclerosis will be considered, including their ability to become the foam cells and the consequences of this event, as well as their ability to create a pro-inflammatory or anti-inflammatory medium at the site of atherosclerotic lesions as a result of cytokine production. In addition, several therapeutic strategies directed to the modulation of macrophage activity, which can serve as useful ideas for future drug developments, will be considered.

The mir-21 Inhibition Enhanced HUVEC Cellular Viability during Hypoxia-Reoxygenation Injury by Regulating PDCD4

The purpose of this study was to explore the clinical value of altered plasma mir-21 expression level as a biomarker for the severity of coronary artery disease (CAD) and its molecular impact on HUVEC cellular injuries. Angiographically validated 56 patients with single-vessel CAD disease, 92 patients with double-vessel CAD, 139 complex coronary artery stenosis patients, and 56 healthy individuals ( $n=343$ ) were enrolled in this study. The expressions of plasma mir-21 were evidently and progressively higher while PDCD4 levels were significantly and steadily lower in single-, dual-, and multivessel occluded CAD patients than in healthy participants ( $P<0.001$ ). The relative expressions of mir-21 in hypoxia-reoxygenation- (HR-) exposed HUVECs were markedly upregulated, but PDCD4 concentrations were obviously downregulated as compared with normal control cells ( $P<0.001$ ). Moreover, altered circulatory mir-21 expression levels were able to significantly differentiate single- (AUC 0.893), double- (AUC 0.914), and multivessel stenosis CAD (AUC 0.933) patients from healthy subjects. Besides, the plasma mir-21 expressions in elderly (66-85 years) groups were remarkably higher than those in younger aged (25-45 years) subjects. Caspase-3 and ROS expression levels were remarkably elevated, but cellular viability noticeably declined in HR-induced HUVECs than in normoxic cells ( $P<0.001$ ). In contrast, mir-21 inhibition markedly reduced caspase-3 activity and ROS concentrations while significantly ameliorating HUVEC cellular viability in HR conditions. PDCD4 expressions in HR-exposed HUVECs were prominently decreased whereas mir-21 inhibition significantly enhanced PDCD4 levels ( $P<0.001$ ). Upregulated plasma mir-21 can be a valuable clinical biomarker for the detection of the severity of coronary artery stenosis patients. Elevated circulatory mir-21 concentrations have a positive correlation with aging. Inhibitory mir-21 evidently increased HUVEC cellular viability through upregulation of targeting PDCD4 and recommended a newer possible therapeutic molecule for the management of CAD patients.

The Role and Interactions of Programmed Cell Death 4 and its Regulation by microRNA in Transformed Cells of the Gastrointestinal Tract

Data from GLOBOCAN 2020 estimates that there were 19.3 million new cases of cancer and 10.0 million cancer-related deaths in 2020 and that this is predicted to increase by 47% in 2040. The combined burden of cancers of the gastrointestinal (GI) tract, including oesophageal-, gastric- and colorectal cancers, resulted in 22.6% of the cancer-related deaths in 2020 and 18.7% of new diagnosed cases. Understanding the aetiology of GI tract cancers should have a major impact on future therapies and lessen this substantial burden of disease. Many cancers of the GI tract have suppression of the tumour suppressor Programmed Cell Death 4 (PDCD4) and this has been linked to the expression of microRNAs which bind to the untranslated region of PDCD4 mRNA and either inhibit translation or target the mRNA for degradation. This review highlights the properties of PDCD4 and documents the evidence for the regulation of PDCD4 expression by microRNAs in cancers of the GI tract.

C1q/tumour necrosis factor-related protein-9 aggravates lipopolysaccharide-induced inflammation via promoting NLRP3 inflammasome activation

The NLRP3 inflammasome plays a vital role in inflammation by increasing the maturation of interleukin-1β (IL-1β) and promoting pyroptosis. Given that C1q/tumour necrosis factor-related protein-9 (CTRP9) has been shown to be involved in diverse inflammatory diseases, we sought to assess the underlying impact of CTRP9 on NLRP3 inflammasome activation. In vitro, macrophages isolated from murine peritonea were stimulated with exogenous CTRP9, followed by lipopolysaccharide (LPS) and adenosine 5'-triphosphate (ATP). We demonstrated that CTRP9 markedly augmented the activation of the NLRP3 inflammasome, as shown by increased mature IL-1β secretion, triggering ASC speck formation and promoting pyroptosis. Mechanistically, CTRP9 increased the levels of NADPH oxidase 2 (NOX2)-derived reactive oxygen species (ROS). Suppressing ROS with N-acetylcysteine (NAC) or interfering with NOX2 by small interfering RNA weakened the promoting effect of CTRP9 on the NLRP3 inflammasome. Furthermore, NLRP3 inflammasome activation, pyroptosis and secretion of mature IL-1β were significantly decreased in macrophages from CTRP9-KO mice compared to those from WT mice with the same treatment. In vivo, we established a sepsis model by intraperitoneal injection of LPS into WT and CTRP9-KO mice. CTRP9 knockout improved the survival rates of the septic mice and attenuated NLRP3 inflammasome-mediated inflammation. In conclusion, our study indicates that CTRP9 aggravates LPS-induced inflammation by promoting NLRP3 inflammasome activation via the NOX2/ROS pathway. CTRP9 could be a promising target for NLRP3 inflammasome-driven inflammatory diseases.

MicroRNAs and Diabetes Mellitus Type 1

Type 1 diabetes mellitus is a multifactorial, progressive, autoimmune disease with a strong genetic feature that can affect multiple organs, including the kidney, eyes, and nerves. Early detection of type 1 diabetes can help critically to avoid serious damages to these organs. MicroRNAs are small RNA molecules that act in post-transcriptional gene regulation by attaching to the complementary sequence in the 3'-untranslated region of their target genes. Alterations in the expression of microRNA coding genes are extensively reported in several diseases, such as type 1 diabetes. Presenting non-invasive biomarkers for early detection of type 1 diabetes by quantifying microRNAs gene expression level can be a significant step in biotechnology and medicine. This review discusses the area of microRNAs dysregulation in type 1 diabetes and affected molecular mechanisms involved in pancreatic islet cell formation and dysregulation in the expression of inflammatory elements as well as pro-inflammatory cytokines.

p38 regulates the tumor suppressor PDCD4 via the TSC-mTORC1 pathway

Programmed cell death protein 4 (PDCD4) exerts critical functions as tumor suppressor and in immune cells to regulate inflammatory processes. The phosphoinositide 3-kinase (PI3K) promotes degradation of PDCD4 via mammalian target of rapamycin complex 1 (mTORC1). However, additional pathways that may regulate PDCD4 expression are largely ill-defined. In this study, we have found that activation of the mitogen-activated protein kinase p38 promoted degradation of PDCD4 in macrophages and fibroblasts. Mechanistically, we identified a pathway from p38 and its substrate MAP kinase-activated protein kinase 2 (MK2) to the tuberous sclerosis complex (TSC) to regulate mTORC1-dependent degradation of PDCD4. Moreover, we provide evidence that TSC1 and TSC2 regulate PDCD4 expression via an additional mechanism independent of mTORC1. These novel data extend our knowledge of how PDCD4 expression is regulated by stress- and nutrient-sensing pathways.

Roles of Macrophages in Atherogenesis

Atherosclerosis is a chronic inflammatory disease that may ultimately lead to local proteolysis, plaque rupture, and thrombotic vascular disease, resulting in myocardial infarction, stroke, and sudden cardiac death. Circulating monocytes are recruited to the arterial wall in response to inflammatory insults and differentiate into macrophages which make a critical contribution to tissue damage, wound healing, and also regression of atherosclerotic lesions. Within plaques, macrophages take up aggregated lipoproteins which have entered the vessel wall to give rise to cholesterol-engorged foam cells. Also, the macrophage phenotype is influenced by various stimuli which affect their polarization, efferocytosis, proliferation, and apoptosis. The heterogeneity of macrophages in lesions has recently been addressed by single-cell sequencing techniques. This article reviews recent advances regarding the roles of macrophages in different stages of disease pathogenesis from initiation to advanced atherosclerosis. Macrophage-based therapies for atherosclerosis management are also described.

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.

Quorum Sensing by Gelsolin Regulates Programmed Cell Death 4 Expression and a Density-Dependent Phenotype in Macrophages

Quorum-sensing mechanisms that sense the density of immune cells at the site of inflammation to initiate inflammation resolution have recently been demonstrated as a major determinant of the inflammatory response. We observed a density-dependent increase in expression of the inflammatory tumor suppressor protein programmed cell death 4 (PDCD4) in mouse macrophage cells. Conditioned medium from high-density cells upregulated PDCD4 expression, revealing the presence of a secreted factor(s) acting as a macrophage quorum sensor. Secreted gelsolin (GSN) was identified as the quorum-sensing autoinducer. Alteration of GSN levels changed PDCD4 expression and the density-dependent phenotype of cells. LPS induced the expression of microRNA miR-21, which downregulated both GSN and PDCD4 expression, and reversed the high-density phenotype. The high-density phenotype was correlated with an anti-inflammatory gene expression program, which was counteracted by inflammatory stimulus. Together, our observations establish the miR-21-GSN-PDCD4 regulatory network as a crucial mediator of a macrophage quorum-sensing mechanism for the control of inflammatory responses.

PDCD4 Negatively Regulated Osteogenic Differentiation and Bone Defect Repair of Mesenchymal Stem Cells Through GSK-3β/β-Catenin Pathway

Mesenchymal stem cells (MSCs) have been shown to be involved in bone injury repair. Programmed cell death 4 (PDCD4) is not only a tumor suppressor gene but also plays roles in the regulation of MSC function. The aim of the study was to uncover PDCD4 potential regulatory roles and mechanisms in the osteogenic differentiation and bone defect repair of MSCs. shRNA technique was used to knock down PDCD4 expression in umbilical cord-derived mesenchymal stem cells (shPDCD4-UCMSCs). Their phenotype was characterized by flow cytometry and the differentiation potential was verified. We found that PDCD4 knockdown did not affect the surface molecule expression of UCMSCs, but significantly enhanced their osteogenic differentiation and osteogenesis-related molecule expression. Mechanistically, glycogen synthase kinase-3β (GSK-3β) phosphorylation and β-catenin expression were significantly increased in shPDCD4-UCMSCs during the osteogenic differentiation process. The β-catenin inhibitor PNU-74654 reversed shPDCD4-increased osteogenesis and osteogenesis-related molecule expression. The results of animal experiments showed that shPDCD4-UCMSCs markedly improved the defect healing in rabbits. Our findings suggest that PDCD4 acts as a negative regulator of MSC osteogenic differentiation through GSK-3β/β-catenin pathway. Targeting PDCD4 may be a way to improve MSC-mediated therapeutic effects on bone injury.

Elevated microRNA-21 Is a Brake of Inflammation Involved in the Development of Nasal Polyps

Background

CRSwNP is an inflammatory disease but the mechanism is not yet fully understood. MiR-21, a member of miRNAs, has been reported to play roles in mediating inflammation. However, the expression of miR-21 and its role in patients with CRSwNP remain elusive.

Methods

Turbinates from control subjects, uncinate processes from CRSsNP, polyp tissues from CRSwNP, and nasal epithelial cells brushed from nasal mucosa were collected. The expression of miR-21 and cytokines in nasal tissues and epithelial cells were detected by qPCR. The localization of miR-21 was detected by ISH, and its target was identified by bioinformation analysis, qPCR, IHC, WB, and luciferase reporter system. The protein and mRNA of PDCD4 and NF-κB P65 were determined by WB and qPCR after miR-21 transfection in HNEpC. The role of miR-21 on cytokines was analyzed in HNEpC and nasal polyp explants.

Results

MiR-21 was upregulated in CRSwNP relative to control subjects by qPCR, which was determined mainly in nasal epithelial cells of CRSwNP by ISH. Both pro-inflammation cytokines (IL-1β, IL-6, IL-8, IL-25, and TSLP) and a suppressive cytokine (IL-10) were overexpressed in the epithelial cells of CRSwNP. The expression of miR-21 was positively correlated with IL-10 and negatively correlated with IL-6, IL-8, IL-33, and TSLP in the epithelial cells of CRSwNP. As a potential target of miR-21, the expression of PDCD4 was negatively correlated with miR-21 in CRSwNP. In HNEpC, miR-21 could reduce the expression of PDCD4 at both mRNA and protein levels, and bioinformation analysis and luciferase reporter system confirmed PDCD4 as one target of miR-21. Furthermore, miR-21 could decrease the activation of NF-κB and increase IL-10 mRNA. Both SEB and LPS could elevate miR-21, with IL-25, IL-33, TSLP induced by SEB and IL-1β, IL-6, IL-8 induced by LPS, while the miR-21 could regulate the expression of IL-33, TSLP, IL-1β, IL- 6 and IL-8 in vitro and ex vivo. Clinically, miR-21 expression was inversely correlated with the Lund-Mackay CT scores and the Lund-Kennedy scores in CRSwNP.

Conclusion

MiR-21 could be a prominent negative feedback factor in the inflammation process to attenuate the expression of pro-inflammatory cytokines, thereby playing an anti-inflammation role in CRSwNP.

Communications via the Small Leucine-rich Proteoglycans: Molecular Specificity in Inflammation and Autoimmune Diseases

Inflammation is a highly regulated biological response of the immune system that is triggered by assaulting pathogens or endogenous alarmins. It is now well established that some soluble extracellular matrix constituents, such as small leucine-rich proteoglycans (SLRPs), can act as danger signals and trigger aseptic inflammation by interacting with innate immune receptors. SLRP inflammatory signaling cascade goes far beyond its canonical function. By choosing specific innate immune receptors, coreceptors, and adaptor molecules, SLRPs promote a switch between pro- and anti-inflammatory signaling, thereby determining disease resolution or chronification. Moreover, by orchestrating signaling through various receptors, SLRPs fine-tune inflammation and, despite their structural homology, regulate inflammatory processes in a molecule-specific manner. Hence, the overarching theme of this review is to highlight the molecular and functional specificity of biglycan-, decorin-, lumican-, and fibromodulin-mediated signaling in inflammatory and autoimmune diseases.

Programmed cell death factor 4 (PDCD4), a novel therapy target for metabolic diseases besides cancer

Programmed cell death factor 4 (PDCD4) is originally described as a tumor suppressor gene that exerts antineoplastic effects by promoting apoptosis and inhibiting tumor cell proliferation, invasion, and metastasis. Several investigations have probed the aberrant expression of PDCD4 with the progression of metabolic diseases, such as polycystic ovary syndrome (PCOS), obesity, diabetes, and atherosclerosis. It has been ascertained that PDCD4 causes glucose and lipid metabolism disorders, insulin resistance, oxidative stress, chronic inflammatory response, and gut flora disorders to regulate the progression of metabolic diseases. This review aims to summarize the latest researches to uncover the structure, expression regulation, and biological functions of PDCD4 and to elucidate the regulatory mechanism of the development of tumors and metabolic diseases. This review has emphasized the understanding of the PDCD4 role and to provide new ideas for the research, diagnosis, and treatment of tumors and metabolic diseases.

Overexpression of MicroRNA-16 Alleviates Atherosclerosis by Inhibition of Inflammatory Pathways

Background

Our previous study demonstrated that the expression of miR-16 was downregulated in the cell and animal models of atherosclerosis (AS), a main contributor to coronary artery disease (CAD). Overexpression of miR-16 inhibited the formation of foam cells by exerting anti-inflammatory roles. These findings indicated miR-16 may be an anti-atherogenic and CAD miRNA. The goal of this study was to further validate the expression of miR-16 in CAD patients and explore its therapeutic roles in an AS animal model.

Methods

A total of 40 CAD patients and 40 non-CAD people were prospectively registered in our study. The AS model was established in ApoE-/- mice fed a high-fat diet. The model mice were randomly treated with miR-16 agomiR (n = 10) or miR-negative control (n = 10). Hematoxylin-eosin staining was conducted for histopathological examination in thoracic aorta samples. ELISA and immunohistochemistry were performed to determine the expression levels of inflammatory factors (IL-6, TNF-α, MCP-1, IL-1β, IL-10, and TGF-β). qRT-PCR and western blotting were carried out to detect the mRNA and protein expression levels of PDCD4, miR-16, and mitogen-activated protein kinase pathway-related genes.

Results

Compared with the normal control, miR-16 was downregulated in the plasma and peripheral blood mononuclear cell of CAD patients, and its expression level was negatively associated with IL-6 and the severity of CAD evaluated by the Gensini score, but positively related with IL-10. Injection of miR-16 agomiR in ApoE-/- mice reduced the formation of atherosclerotic plaque and suppressed the accumulation of proinflammatory factors (IL-6, TNF-α, MCP-1, and IL-1β) in the plasma and tissues but promoted the secretion of anti-inflammatory factors (IL-10 and TGF-β). Mechanism analysis showed overexpression of miR-16 might downregulate target mRNA PDCD4 and then activate p38 and ERK1/2, but inactivate the JNK pathway.

Conclusions

Our findings suggest miR-16 may be a potential diagnostic biomarker and therapeutic target for atherosclerotic CAD.

Control Mechanisms of the Tumor Suppressor PDCD4: Expression and Functions

PDCD4 is a novel tumor suppressor to show multi-functions inhibiting cell growth, tumor invasion, metastasis, and inducing apoptosis. PDCD4 protein binds to the translation initiation factor eIF4A, some transcription factors, and many other factors and modulates the function of the binding partners. PDCD4 downregulation stimulates and PDCD4 upregulation inhibits the TPA-induced transformation of cells. However, PDCD4 gene mutations have not been found in tumor cells but gene expression was post transcriptionally downregulated by micro environmental factors such as growth factors and interleukins. In this review, we focus on the suppression mechanisms of PDCD4 protein that is induced by the tumor promotors EGF and TPA, and in the inflammatory conditions. PDCD4-protein is phosphorylated at 2 serines in the SCF^βTRCP ubiquitin ligase binding sequences via EGF and/or TPA induced signaling pathway, ubiquitinated, by the ubiquitin ligase and degraded in the proteasome system. The PDCD4 protein synthesis is inhibited by microRNAs including miR21.

Effects of Tumor Necrosis Factor α (TNF-α) and Interleukina 10 (IL-10) on Intercellular Cell Adhesion Molecule-1 (ICAM-1) and Cluster of Differentiation 31 (CD31) in Human Coronary Artery Endothelial Cells

BACKGROUND The aim of this study was to investigate the effects of TNF-α and IL-10 on the expression of ICAM-1 and CD31 in human coronary artery endothelial cells (HCAEC). MATERIAL AND METHODS HCAEC was treated with 0, 2.5 μg/l, 5 μg/l, and 10 μg/l of TNF-α for 2 h, 6 h, and 10 h, and with 0 μg/l, 10 μg/l, 100 μg/l, and 200 μg/l of IL-10 for 5 h, 10 h and 15 h, respectively. RNA inference of TNF-αR was performed with siRNA. Real-time PCR, Western blot analysis, and ELSA were used to detect the mRNA level and protein level of ICAM-1 and CD31. RESULTS TNF-α significantly increased the mRNA and protein expression of ICAM-1 (P<0.05), and 2.5 μg/l TNF-α had the most obvious effect. RNAi of TNF-aR reduced the induction of TNF-α on the mRNA and protein expression of ICAM-1 (P<0.05). TNF-α significantly decreased the CD31 in the supernatant (P<0.05), and 2.5 μg/l TNF-a had the most obvious effect. IL-10 significantly decreased the ICAM-1 protein level. IL-10 decreased the mRNA expression and the protein expression of CD31. The effect on mRNA was not significant (P>0.05), while the effect on the protein expression was significant (P<0.05). CONCLUSIONS TNF-α and IL-10 treatment can affect the expression of ICAM-1 and CD31 in HCAEC.

BRD7 plays an anti-inflammatory role during early acute inflammation by inhibiting activation of the NF-кB signaling pathway

Increasing evidence has shown a strong association between tumor-suppressor genes and inflammation. However, the role of BRD7 as a novel tumor suppressor in inflammation remains unknown. In this study, by observing BRD7 knockout mice for 6-12 months, we discovered that compared with BRD7+/+ mice, BRD7-/- mice were more prone to inflammation, such as external inflammation and abdominal abscess. By using mouse embryo fibroblast (MEF) cells from the BRD7 knockout mouse, an in vitro lipopolysaccharide (LPS)-stimulated MEF cell line was established. The mRNA levels of interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), chemokine (C-X-C motif) ligand 1 (CXCL-1) and inducible nitric oxide synthase (iNOS) were significantly increased in BRD7-/- MEF cells compared with BRD7+/+ MEF cells after LPS stimulation for 1 or 6 h. In addition, the cytoplasm-to-nucleus translocation of nuclear factor kappa-B (NF-κB; p65) and an increased NF-κB reporter activity were observed in BRD7-/- MEF cells at the 1 h time point but not at the 6 h time point. Furthermore, an in vivo dextran sodium sulfate (DSS)-induced acute colitis model was created. As expected, the disease activity index (DAI) value was significantly increased in the BRD7-/- mice after DSS treatment for 1-5 days, which was demonstrated by the presence of a significantly shorter colon, splenomegaly and tissue damage. Moreover, higher expression levels of IL-6, TNF-α, p65, CXCL-1 and iNOS, and an increased level of NF-κB (p65) nuclear translocation were also found in the DSS-treated BRD7-/- mice. These findings suggest that BRD7 has an anti-inflammatory role during early acute inflammation by inhibiting activation of the NF-кB signaling pathway, which provides evidence to aid in understanding the therapeutic effects of BRD7 on inflammatory diseases.

Histamine promotes the differentiation of macrophages from CD11b+ myeloid cells and formation of foam cells through a Stat6-dependent pathway

BACKGROUND AND AIMS

The enzyme histidine decarboxylase (Hdc), which generates histamine, is highly expressed in CD11b⁺Gr-1⁺ myeloid cells that play a critical role in infection, inflammation and tumorigenesis. The aim of this study was to explore the role of Hdc-expressing CD11b⁺ myeloid cells or histamine in atherogenesis.

METHODS

Hdc-EGFP bacterial artificial chromosome (BAC) transgenic reporter mice (Hdc-EGFP) were used to track Hdc expression during the development of atherosclerosis. The expression of EGFP fluorescence was examined by immunofluorescence staining in a variety of adult tissues. Wild-type (WT), Apoe knockout (Apoe^-/-), Hdc knockout (Hdc^-/-), and Stat6 knockout (Stat6^-/-) mice were used. Serum concentration of histamine was determined with ELISA. Changes in subsets of immune cells were evaluated by flow cytometry (FACS). Non-invasive tracking of the expression of CD11b⁺ myeloid cells was tested using ¹²⁵I-anti-CD11b SPECT/CT imaging in the early stages of atherogenesis. Microarray analysis and RT-PCR were applied to detect gene expressions while Western blot was used to assess protein levels.

RESULTS

Using Hdc-EGFP transgenic mice, we demonstrated that Hdc⁺CD11b⁺ myeloid cells increase in the circulation in response to hypercholesterolemia and contribute to foam cell formation in atherosclerosis. Histamine deficiency in Hdc knockout (Hdc^-/-) mice repressed the differentiation of CD11b⁺Ly6C^high classically activated M1-type macrophages and CD11b⁺CD11c⁺ dendritic cells (DCs), which was associated with downregulation of signal transducer and activator of transcription 6 (Stat6) expression. Furthermore, the results of in vivo and in vitro studies demonstrated that histamine could promote macrophage differentiation and foam cell formation via the Stat6 signal.

CONCLUSIONS

Modulation of histamine and Stat6-signaling may represent an attractive therapeutic strategy for the prevention or treatment of atherosclerosis.

miR-155 Regulated Inflammation Response by the SOCS1-STAT3-PDCD4 Axis in Atherogenesis

Inflammation response plays a critical role in all phases of atherosclerosis (AS). Increased evidence has demonstrated that miR-155 mediates inflammatory mediators in macrophages to promote plaque formation and rupture. However, the precise mechanism of miR-155 remains unclear in AS. Here, we also found that miR-155 and PDCD4 were elevated in the aortic tissue of atherosclerotic mice and ox-LDL treated RAW264.7 cells. Further studies showed that miR-155 not only directly inhibited SOCS1 expression, but also increased the expression of p-STAT and PDCD4, as well as the production of proinflammation mediators IL-6 and TNF-α. Downregulation of miR-155 and PDCD4 and upregulation of SOCS1 obviously decreased the IL-6 and TNF-α expression. In addition, inhibition of miR-155 levels in atherosclerotic mice could notably reduce the IL-6 and TNF-α level in plasma and aortic tissue, accompanied with increased p-STAT3 and PDCD4 and decreased SOCS1. Thus, miR-155 might mediate the inflammation in AS via the SOCS1-STAT3-PDCD4 axis. These results provide a rationale for intervention of intracellular miR-155 as possible antiatherosclerotic targets.

Pdcd4 Is Involved in the Formation of Stress Granule in Response to Oxidized Low-Density Lipoprotein or High-Fat Diet

Stress granules (SGs) in response to various stresses have been reported in many diseases. We previously reported the implication of programmed cell death 4 (Pdcd4) in obesity-induced stress responses, but the possible link between Pdcd4 and SGs remains lacking. In this study we showed that oxidized low-density lipoprotein (ox-LDL) or high-fat diet (HFD) induced SG formation in mouse macrophages and liver tissues, and Pdcd4 deficiency in mice remarkably reduced its formation. In response to ox-LDL, either endogenous or ectopic Pdcd4 displayed granule-like expression and co-localized with SG markers including T-cell-restricted intracellular antigen-1, fragile X mental retardation-related protein 1, and eukaryotic initiation factor 4A. Ectopic expression of truncated Pdcd4 that depleted specific RNA-binding motif significantly disrupted the SG formation, suggesting the direct involvement of Pdcd4 in ox-LDL-induced SGs through its RNA-binding activity. Additionally, Pdcd4 deficiency drove AKT activation and suppression of eIF2α phosphorylation, thereby contributing to the resistance to ox-LDL or HFD-induced SG formation. Collectively, our data suggest that Pdcd4 as a crucial regulator in SGs induced by ox-LDL or HFD maybe a potential target for mitigating SG-associated stress responses in obesity and related diseases.

Pdcd4 restrains the self-renewal and white-to-beige transdifferentiation of adipose-derived stem cells

The stemness maintenance of adipose-derived stem cells (ADSCs) is important for adipose homeostasis and energy balance. Programmed cell death 4 (Pdcd4) has been demonstrated to be involved in the development of obesity, but its possible roles in ADSC function and adipogenic capacity remain unclear. In this study, we demonstrate that Pdcd4 is a key controller that limits the self-renewal and white-to-beige transdifferentiation of ADSCs. Pdcd4 deficiency in mice caused stemness enhancement of ADSCs as evidenced by increased expression of CD105, CD90, Nanog and Oct4 on ADSCs, together with enhanced in situ proliferation in adipose tissues. Pdcd4 deficiency promoted proliferation, colony formation of ADSCs and drove more ADSCs entering the S phase accompanied by AKT activation and cyclinD1 upregulation. Blockade of AKT signaling in Pdcd4-deficient ADSCs led to a marked decline in cyclinD1, S-phase entry and cell proliferation, revealing AKT as a target for repressing ADSC self-renewal by Pdcd4. Intriguingly, depletion of Pdcd4 promoted the transdifferentiation of ADSCs into beige adipocytes. A reduction in lipid contents and expression levels of white adipocyte markers including C/EBPα, PPAR-γ, adiponectin and αP2 was detected in Pdcd4-deficient ADSCs during white adipogenic differentiation, substituted by typical beige adipocyte characteristics including small, multilocular lipid droplets and UCP1 expression. More lactate produced by Pdcd4-deficient ADSCs might be an important contributor to the expression of UCP1 and white-to-beige transdifferentiation. In addition, an elevation of UCP1 expression was confirmed in white adipose tissues from Pdcd4-deficient mice upon high-fat diet, which displayed increased energy expenditure and resistance to obesity as compared with wild-type obese mice. These findings provide evidences that Pdcd4 produces unfavorable influences on ADSC stemness, which contribute to adipose dysfunction, obesity and metabolic syndromes, thereby proposing Pdcd4 as a potential intervening target for regulating ADSC function.

MicroRNA-16 suppresses the activation of inflammatory macrophages in atherosclerosis by targeting PDCD4

Programmed cell death 4 (PDCD4) is involved in a number of bioprocesses, such as apoptosis and inflammation. However, its regulatory mechanisms in atherosclerosis remain unclear. In this study, we investigated the role and mechanisms of action of PDCD4 in high-fat diet-induced atherosclerosis in mice and in foam cells (characteristic pathological cells in atherosclerotic lesions) derived from ox-LDL-stimulated macrophages. MicroRNA (miR)-16 was predicted to bind PDCD4 by bioinformatics analysis. In the mice with atherosclerosis and in the foam cells, PDCD4 protein expression (but not the mRNA expression) was enhanced, while that of miR-16 was reduced. Transfection with miR-16 mimic decreased the activity of a luciferase reporter containing the 3′ untranslated region (3′UTR) of PDCD4 in the macrophage-derived foam cells. Conversely, treatment with miR-16 inhibitor enhanced the luciferase activity. However, by introducing mutations in the predicted binding site located in the 3′UTR of PDCD4, the miR-16 mimic and inhibitor were unable to alter the level of PDCD4, suggesting that miR-16 is a direct negative regulator of PDCD4 in atherosclerosis. Furthermore, transfection wtih miR-16 mimic and siRNA targeting PDCD4 suppressed the secretion and mRNA expression of pro-inflammatory factors, such as interleukin (IL)-6 and tumor necrosis factor-α (TNF-α), whereas it enhanced the secretion and mRNA expression of the anti-inflammatory factor, IL-10. Treatment with miR-16 inhibitor exerted the opposite effects. In addition, the phosphorylation of p38 and extracellular signal-regulated kinase (ERK), and nuclear factor-κB (NF-κB) expression were altered by miR-16. In conclusion, our data demonstrate that the targeting of PDCD4 by miR-16 may suppress the activation of inflammatory macrophages though mitogen-activated protein kinase (MAPK) and NF-κB signaling in atherosclerosis; thus, PDCD4 may prove to be a potential therapeutic target in the treatment of atherosclerosis.

Pdcd4 deficiency enhances macrophage lipoautophagy and attenuates foam cell formation and atherosclerosis in mice

Macrophage foam cells, a major component of the atherosclerotic lesion, have vital roles in the development of atherosclerosis. Lipoautophagy, a type of autophagy characterized by selective delivery of lipid droplet for lysosomal degradation, may impact atherosclerosis by regulating macrophage foam cell formation. Previously, we reported that programmed cell death 4 (PDCD4), a tumor suppressor, negatively regulated autophagy in tumor cells. However, its roles in macrophage lipoautophagy, foam cell formation and atherosclerosis remain to be established. Here we found that Pdcd4 deficiency clearly improved oxidized low-density lipoproteins-impaired autophagy efflux, promoted autophagy-mediated lipid breakdown in murine macrophages and thus prevented macrophage conversion into foam cells. Importantly, Pdcd4 deficiency in mice significantly upregulated macrophage autophagy in local plaques along with attenuated lipid accumulation and atherosclerotic lesions in high-fat-fed Apolipoprotein E knockout mice. Bone marrow transplantation experiment demonstrated that PDCD4-mediated autophagy in hematopoietic cells contributed to the development of atherosclerosis. These results indicate that endogenous PDCD4 promotes for macrophage foam cell formation and atherosclerosis development via inhibiting autophagy and provides new insights into atherogenesis, suggesting that promoting macrophage autophagy through downregulating PDCD4 expression may be beneficial for treating atherosclerosis.