MicroRNA-33 Regulates the Innate Immune Response via ATP Binding Cassette Transporter-mediated Remodeling of Membrane Microdomains

Targeting ABCG1 and SREBP-2 mediated cholesterol homeostasis ameliorates Zika virus-induced ocular pathology

Zika virus (ZIKV) infection during pregnancy causes severe neurological and ocular abnormalities in infants, yet no vaccine or antivirals are available. Our transcriptomic analysis of ZIKV-infected retinal pigment epithelial (RPE) cells revealed alterations in the cholesterol pathway. Thus, we investigated the functional roles of ATP binding cassette transporter G1 (ABCG1) and sterol response element binding protein 2 (SREPB-2), two key players in cholesterol metabolism, during ocular ZIKV infection. Our in vitro data showed that increased ABCG1 activity via liver X receptors (LXRs), reduced ZIKV replication, while ABCG1 knockdown increased replication with elevated intracellular cholesterol. Conversely, inhibiting SREBP-2 or its knockdown reduced ZIKV replication by lowering cholesterol levels. In vivo, LXR agonist or SREBP-2 inhibitor treatment mitigated ZIKV-induced chorioretinal lesions in mice, concomitant with decreased expression of inflammatory mediators and increased activation of antiviral response genes. In summary, our study identifies ABCG1's antiviral role and SREBP-2's proviral effects in ocular ZIKV infection, offering cholesterol metabolism as a potential target to develop antiviral therapies.

Inhibition of miR-33a-5p in Macrophage-like Cells In Vitro Promotes apoAI-Mediated Cholesterol Efflux

Atherosclerosis is caused by cholesterol accumulation within arteries. The intima is where atherosclerotic plaque accumulates and where lipid-laden foam cells reside. Intimal foam cells comprise of both monocyte-derived macrophages and macrophage-like cells (MLC) of vascular smooth muscle cell (VSMC) origin. Foam cells can remove cholesterol via apoAI-mediated cholesterol efflux and this process is regulated by the transporter ABCA1. The microRNA miR-33a-5p is thought to be atherogenic via silencing ABCA1 which promotes cholesterol retention and data has shown inhibiting miR-33a-5p in macrophages may be atheroprotective via enhancing apoAI-mediated cholesterol efflux. However, it is not entirely elucidated whether precisely inhibiting miR-33a-5p in MLC also increases ABCA1-dependent cholesterol efflux. Therefore, the purpose of this work is to test the hypothesis that inhibition of miR-33a-5p in cultured MLC enhances apoAI-mediated cholesterol efflux. In our study, we utilized the VSMC line MOVAS cells in our experiments, and cholesterol-loaded MOVAS cells to convert this cell line into MLC. Inhibition of miR-33a-5p was accomplished by transducing cells with a lentivirus that expresses an antagomiR directed at miR-33a-5p. Expression of miR-33a-5p was analyzed by qRT-PCR, ABCA1 protein expression was assessed via immunoblotting, and apoAI-mediated cholesterol efflux was measured using cholesterol efflux assays. In our results, we demonstrated that lentiviral vector-mediated knockdown of miR-33a-5p resulted in decreasing expression of this microRNA in cultured MLC. Moreover, reduction of miR-33a-5p in cultured MLC resulted in de-repression of ABCA1 expression, which caused ABCA1 protein upregulation in cultured MLC. Additionally, this increase in ABCA1 protein expression resulted in enhancing ABCA1-dependent cholesterol efflux through increasing apoAI-mediated cholesterol efflux in cultured MLC. From these findings, we conclude that inhibiting miR-33a-5p in MLC may protect against atherosclerosis by promoting ABCA1-dependent cholesterol efflux.

Identification of Important Genes Associated with the Development of Atherosclerosis

Atherosclerosis is one of the most important medical problems due to its prevalence and significant contribution to the structure of temporary and permanent disability and mortality. Atherosclerosis is a complex chain of events occurring in the vascular wall over many years. Disorders of lipid metabolism, inflammation, and impaired hemodynamics are important mechanisms of atherogenesis. A growing body of evidence strengthens the understanding of the role of genetic and epigenetic factors in individual predisposition and development of atherosclerosis and its clinical outcomes. In addition, hemodynamic changes, lipid metabolism abnormalities, and inflammation are closely related and have many overlapping links in regulation. A better study of these mechanisms may improve the quality of diagnosis and management of such patients.

Molecular mechanisms in the miR-33a/LPPR4 pathway regulating unsaturated fatty acid synthesis in bovine mammary epithelial cells

The regulatory mechanisms governing metabolism of fatty acids in cow mammary gland are crucial for establishing relationships between milk quality and fatty acid content. Both, microRNAs (miRNAs) and protein-coding genes are important factors involved in the regulation of milk fat synthesis. In this study, high-throughput sequencing of miRNAs and mRNAs in bovine mammary gland tissue was performed during peak lactation (3 samples) and late lactation (3 samples) periods to characterize expression profiles. Differential expression (DE) analyses of miRNA and mRNA and miRNA-mRNA regulatory pathway screening were performed. Two-hundred eighty regulatory miRNA-mRNA pairs were identified, including the miR-33a-lipid phosphate phosphatase-related protein type 4 (LPPR4) pathway. Bioinformatics prediction, dual-luciferase reporter system detection, qRT-PCR, and Western blotting revealed that miR-33a can directly target LPPR4 and inhibit its expression. Experiments also revealed that miR-33a promotes the synthesis of triglycerides and increases the content of unsaturated fatty acids (UFAs) in bovine mammary epithelial cells (BMECs). These results indicate that miR-33a via LPPR4 plays an important role in the regulation of milk fat synthesis and UFA levels.

Constructing Lipoparticles Capable of Endothelial Cell-Derived Exosome-Mediated Delivery of Anti-miR-33a-5p to Cultured Macrophages

Atherosclerosis is driven by intimal arterial macrophages accumulating cholesterol. Atherosclerosis also predominantly occurs in areas consisting of proinflammatory arterial endothelial cells. At time of writing, there are no available clinical treatments that precisely remove excess cholesterol from lipid-laden intimal arterial macrophages. Delivery of anti-miR-33a-5p to macrophages has been shown to increase apoAI-mediated cholesterol efflux via ABCA1 upregulation but delivering transgenes to intimal arterial macrophages is challenging due to endothelial cell barrier integrity. In this study, we aimed to test whether lipoparticles targeting proinflammatory endothelial cells can participate in endothelial cell-derived exosome exploitation to facilitate exosome-mediated transgene delivery to macrophages. We constructed lipoparticles that precisely target the proinflammatory endothelium and contain a plasmid that expresses XMOTIF-tagged anti-miR-33a-5p (LP-pXMoAntimiR33a5p), as XMOTIF-tagged small RNA demonstrates the capacity to be selectively shuttled into exosomes. The cultured cells used in our study were immortalized mouse aortic endothelial cells (iMAECs) and RAW 264.7 macrophages. From our results, we observed a significant decrease in miR-33a-5p expression in macrophages treated with exosomes released basolaterally by LPS-challenged iMAECs incubated with LP-pXMoAntimiR33a5p when compared to control macrophages. This decrease in miR-33a-5p expression in the treated macrophages caused ABCA1 upregulation as determined by a significant increase in ABCA1 protein expression in the treated macrophages when compared to the macrophage control group. The increase in ABCA1 protein also simulated ABCA1-dependent cholesterol efflux in treated macrophages-as we observed a significant increase in apoAI-mediated cholesterol efflux-when compared to the control group of macrophages. Based on these findings, strategies that involve combining proinflammatory-targeting lipoparticles and exploitation of endothelial cell-derived exosomes appear to be promising approaches for delivering atheroprotective transgenes to lipid-laden arterial intimal macrophages.

Advancements in understanding the role of microRnas in regulating macrophage polarization during acute lung injury

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) is a critical and life-threatening illness that causes severe dyspnea, and respiratory distress and is often caused by a variety of direct or indirect factors that damage the alveolar epithelium and capillary endothelial cells, leading to inflammation factors and macrophage infiltration. Macrophages play a crucial role in the progression of ALI/ARDS, exhibiting different polarized forms at different stages of the disease that control the disease outcome. MicroRNAs (miRNA) are conserved, endogenous, short non-coding RNAs composed of 18-25 nucleotides that serve as potential markers for many diseases and are involved in various biological processes, including cell proliferation, apoptosis, and differentiation. In this review, we provide a brief overview of miRNA expression in ALI/ARDS and summarize recent research on the mechanism and pathways by which miRNAs respond to macrophage polarization, inflammation, and apoptosis. The characteristics of each pathway are also summarized to provide a comprehensive understanding of the role of miRNAs in regulating macrophage polarization during ALI/ARDS.

Effects of miR-33 Deficiency on Metabolic and Cardiovascular Diseases: Implications for Therapeutic Intervention

MicroRNAs (miRNAs) are small noncoding RNAs that post-transcriptionally inhibit gene expression. These small molecules are involved in several biological conditions such as inflammation, cell growth and proliferation, and regulation of energy metabolism. In the context of metabolic and cardiovascular diseases, miR-33 is of particular interest as it has been implicated in the regulation of lipid and glucose metabolism. This miRNA is located in introns harboured in the genes encoding sterol regulatory element-binding protein (SREBP)-1 and SREBP-2, which are key transcription factors involved in lipid biosynthesis and cholesterol efflux. This review outlines the role of miR-33 in a range of metabolic and cardiovascular pathologies, such as dyslipidaemia, nonalcoholic fatty liver disease (NAFLD), obesity, diabetes, atherosclerosis, and abdominal aortic aneurysm (AAA), and it provides discussion about the effectiveness of miR-33 deficiency as a possible therapeutic strategy to prevent the development of these diseases.

Crosstalk between cholesterol metabolism and psoriatic inflammation

Psoriasis is a chronic autoinflammatory skin disease associated with multiple comorbidities, with a prevalence ranging from 2 to 3% in the general population. Decades of preclinical and clinical studies have revealed that alterations in cholesterol and lipid metabolism are strongly associated with psoriasis. Cytokines (tumor necrosis factor-α (TNF-α), interleukin (IL)-17), which are important in the pathogenesis of psoriasis, have been shown to affect cholesterol and lipid metabolism. Cholesterol metabolites and metabolic enzymes, on the other hand, influence not only the biofunction of keratinocytes (a primary type of cell in the epidermis) in psoriasis, but also the immune response and inflammation. However, the relationship between cholesterol metabolism and psoriasis has not been thoroughly reviewed. This review mainly focuses on cholesterol metabolism disturbances in psoriasis and their crosstalk with psoriatic inflammation.

The prohibitin complex regulates macrophage fatty acid composition, plasma membrane packing, and lipid raft-mediated inflammatory signaling

Prohibitins (PHB1 and PHB2) are ubiquitously expressed proteins which play critical roles in multiple biological processes, and together form the ring-like PHB complex found in phospholipid-rich cellular compartments including lipid rafts. Recent studies have implicated PHB1 as a mediator of fatty acid transport as well as a membrane scaffold mediating B lymphocyte and mast cell signal transduction. However, the specific role of PHBs in the macrophage have not been characterized, including their role in fatty acid uptake and lipid raft-mediated inflammatory signaling. We hypothesized that the PHB complex regulates macrophage inflammatory signaling through the formation of lipid rafts. To evaluate our hypothesis, RAW 264.7 macrophages were transduced with shRNA against PHB1, PHB2, or scrambled control (Scr), and then stimulated with lipopolysaccharide (LPS) or tumor necrosis factor-alpha (TNF-α), which activate lipid raft-dependent receptor signaling (CD14/TLR4 and TNFR1, respectively). PHB1 knockdown was lethal, whereas PHB2 knockdown (PHB2kd), which also resulted in decreased PHB1 expression, led to attenuated nuclear factor-kappa-B (NF-κB) activation and subsequent cytokine and chemokine production. PHB2kd macrophages also had decreased cell surface TNFR1, CD14, TLR4, and lipid raft marker ganglioside GM1 at baseline and post-stimuli. Post-LPS, PHB2kd macrophages did not increase the concentration of cellular saturated, monounsaturated, and polyunsaturated fatty acids. This was accompanied by decreased lipid raft formation and modified plasma membrane molecular packing, further supporting the PHB complex's importance in lipid raft formation. Taken together, these data suggest a critical role for PHBs in regulating macrophage inflammatory signaling via maintenance of fatty acid composition and lipid raft structure. SUMMARY: Prohibitins are proteins found in phospholipid-rich cellular compartments, including lipid rafts, that play important roles in signaling, transcription, and multiple other cell functions. Macrophages are key cells in the innate immune response and the presence of membrane lipid rafts is integral to signal transduction, but the role of prohibitins in macrophage lipid rafts and associated signaling is unknown. To address this question, prohibitin knockdown macrophages were generated and responses to lipopolysaccharide and tumor necrosis factor-alpha, which act through lipid raft-dependent receptors, were analyzed. Prohibitin knockdown macrophages had significantly decreased cytokine and chemokine production, transcription factor activation, receptor expression, lipid raft assembly and membrane packing, and altered fatty acid remodeling. These data indicate a novel role for prohibitins in macrophage inflammatory signaling through regulation of fatty acid composition and lipid raft formation.

Lung microRNAs Expression in Lung Cancer and COPD: A Preliminary Study

Non-small cell lung cancer (NSCLC) is one of the deadliest diseases worldwide and represents an impending burden on the healthcare system. Despite increasing attention, the mechanisms underlying tumorigenesis in cancer-related diseases such as COPD remain unclear, making novel biomarkers necessary to improve lung cancer early diagnosis. MicroRNAs (miRNAs) are short non-coding RNA that interfere with several pathways and can act as oncogenes or tumor suppressors. This study aimed to compare miRNA lung expression between subjects with NSCLC and COPD and healthy controls to obtain the miRNA expression profile by analyzing shared pathways. Lung specimens were collected from a prospective cohort of 21 sex-matched subjects to determine the tissue miRNA expression of hsa-miR-34a-5p, 33a-5p, 149-3p, 197-3p, 199-5p, and 320a-3p by RT-PCR. In addition, an in silico prediction of miRNA target genes linked to cancer was performed. We found a specific trend for has-miR-149-3p, 197-3p, and 34a-5p in NSCLC, suggesting their possible role as an index of the tumor microenvironment. Moreover, we identified novel miRNA targets, such as the Cyclin-Dependent Kinase (CDK) family, linked to carcinogenesis by in silico analysis. In conclusion. this study identified lung miRNA signatures related to the tumorigenic microenvironment, suggesting their possible role in improving the evaluation of lung cancer onset.

miR-33b in human cancer: Mechanistic and clinical perspectives

The microRNAs (miRNAs), an extensive class of small noncoding RNAs (∼22 nucleotides), have been shown to have critical functions in various biological processes during development. miR-33b (or hsa-miR-33b) is down-regulated in cancer of multiple systems. Notably, at least 27 protein-coding genes can be targeted by miR-33b. miR-33b regulates the cell cycle, cell proliferation, various metabolism pathways, epithelial-mesenchymal transition (EMT), cancer cell invasion and migration, etc. In prostate cancer, Cullin 4B (CUL4B) can be recruited to the promoter to inhibit the expression of miR-33b. In gastric cancer, the hypermethylation of the CpG island regulated the expression of miR-33b. Besides, miR-33b could be negatively regulated by 7 competing-endogenous RNAs (ceRNAs), which are all long non-coding RNAs (lncRNAs). There are at least 4 signaling pathways, including NF-κB, MAP8, Notch1, and Wnt/β-catenin signaling pathways, which could be regulated partially by miR-33b. Additionally, low expression of miR-33b was associated with clinicopathology and prognosis in cancer patients. In addition, the aberrant expression of miR-33b was connected with the resistance of cancer cells to 5 anticancer drugs (cisplatin, docetaxel, bortezomib, paclitaxel, and daunorubicin). Importantly, our work systematically summarizes the aberrant expression of miR-33b in various neoplastic diseases and the effect of its downregulation on the biological behavior of cancer cells. Furthermore, this review focuses on recent advances in understanding the molecular regulation mechanisms of miR-33b. Moreso, the relationship between the miR-33b expression levels and the clinicopathological data and prognosis of tumor patients was summarized for the first time. Overall, we suggest that the current studies of miR-33b are insufficient but provide potential hints and direction for future miR-33b-related research.

Is microRNA-33 an Appropriate Target in the Treatment of Atherosclerosis?

The maintenance of cholesterol homeostasis is a complicated process involving regulation of cholesterol synthesis, dietary uptake and bile acid synthesis and excretion. Reverse cholesterol transport, described as the transfer of cholesterol from non-hepatic cells, including foam cells in atherosclerotic plaques, to the liver and then its excretion in the feces is important part of this regulation. High-density lipoproteins are the key mediators of reverse cholesterol transport. On the other hand, microRNA-33 was identified as a key regulator of cholesterol homeostasis. Recent studies indicate the impact of microRNA-33 not only on cellular cholesterol efflux and HDL production but also on bile metabolism in the liver. As proper coordination of cholesterol metabolism is essential to human health, discussion of recent findings in this field may open new perspectives in the microRNA-dependent treatment of a cholesterol imbalance.

Effect of Er Miao San on peritoneal macrophage polarisation through the miRNA-33/NLRP3 signalling pathway in a rat model of adjuvant arthritis

CONTEXT

Er Miao San (EMS) is a formulation that contains Atractylodis Rhizoma and Phellodendri Cortex in 1:1 ratio, and is commonly used to treat rheumatoid arthritis (RA) and other inflammatory diseases.

OBJECTIVE

We investigated the mechanism of action and effects of EMS on peritoneal macrophage differentiation in a rat model of adjuvant arthritis (AA).

MATERIALS AND METHODS

EMS (3, 1.5 and 0.75 g/kg; once daily) and methotrexate (0.5 mg/kg; once every 3 days) were administered orally from days 21 to 35 after immunisation. Paw swelling and arthritis index were measured; pathological changes in the ankle joint were observed using x-ray and haematoxylin eosin staining. The ratio of CD86/CD206 in macrophages was detected by flow cytometry. Examination of the miRNA-33/NLRP3 signalling pathway was examined by RT-qPCR and western blotting. The levels of cytokines in the serum and cell supernatants were tested by ELISA.

RESULTS

EMS significantly reduced the AA index in rats (from 11.0 to 9.3) and pathological changes in the ankle joint (from 3.8 to 1.4). The ratio of CD86/CD206 was reduced, and polarisation to M1 improved (from 0.9 to 0.6) in macrophages of EMS-treated rats. EMS downregulated the miRNA-33/NLRP3 pathway. Furthermore, EMS treatment increased IL-10 and TGF-β levels in the serum and supernatant of macrophages of AA rats and simultaneously decreased the levels of IL-1β and TNF-α.

DISCUSSION AND CONCLUSIONS

Our results suggest that EMS may reduce macrophage polarisation to the M1 inflammatory phenotype by downregulating the miRNA-33/NLRP3 pathway in AA rats. These findings may provide new insights into the treatment of RA.

Identification of a novel prognostic ADME-related signature associated with tumor immunity for aiding therapy in head and neck squamous cell carcinoma

The genes that control drug absorption, distribution, metabolism, and excretion (ADME) are also involved in carcinogenesis, cancer progression, and chemoresistance. However, no studies have systematically investigated the clinical significance and underlying functions of ADME genes in head and neck squamous cell carcinoma. Herein, we comprehensively explored the ADME genes in this disease, constructed and validated as a prognostic ADME gene signature (ADMEGS), using three ADME genes (ABCB1, ALDH1B1, and PON2) utilizing multiple datasets, including the training and test sets of The Cancer Genome Atlas and the Gene Expression Omnibus validation set. Moreover, we analyzed the relationship between the ADMEGS and clinical parameters, tumor immunity, and therapeutic response. We found that the ADMEGS was significantly correlated with the clinical, T, and N stages. Additionally, we were able to effectively differentiate tumor immune scores, immune cell infiltration statuses, and treatment responses based on the ADMEGS. As such, ADMEGS may be promising predictors for clinical outcome, tumor immunity, and treatment response.

The lipid paradox in neuroprogressive disorders: Causes and consequences

Chronic systemic inflammation is associated with an increased risk of cardiovascular disease in an environment of low low-density lipoprotein (LDL) and low total cholesterol and with the pathophysiology of neuroprogressive disorders. The causes and consequences of this lipid paradox are explored. Circulating activated neutrophils can release inflammatory molecules such as myeloperoxidase and the pro-inflammatory cytokines interleukin-1 beta, interleukin-6 and tumour necrosis factor-alpha. Since activated neutrophils are associated with atherosclerosis and cardiovascular disease and with major depressive disorder, bipolar disorder and schizophrenia, it seems reasonable to hypothesise that the inflammatory molecules released by them may act as mediators of the link between systemic inflammation and the development of atherosclerosis in neuroprogressive disorders. This hypothesis is tested by considering the association at a molecular level of systemic inflammation with increased LDL oxidation; increased small dense LDL levels; increased lipoprotein (a) concentration; secretory phospholipase A₂ activation; cytosolic phospholipase A₂ activation; increased platelet activation; decreased apolipoprotein A1 levels and function; decreased paroxonase-1 activity; hyperhomocysteinaemia; and metabolic endotoxaemia. These molecular mechanisms suggest potential therapeutic targets.

Cholesterol metabolism: a new molecular switch to control inflammation

The immune system protects the body against harm by inducing inflammation. During the immune response, cells of the immune system get activated, divided and differentiated in order to eliminate the danger signal. This process relies on the metabolic reprogramming of both catabolic and anabolic pathways not only to produce energy in the form of ATP but also to generate metabolites that exert key functions in controlling the response. Equally important to mounting an appropriate effector response is the process of immune resolution, as uncontrolled inflammation is implicated in the pathogenesis of many human diseases, including allergy, chronic inflammation and cancer. In this review, we aim to introduce the reader to the field of cholesterol immunometabolism and discuss how both metabolites arising from the pathway and cholesterol homeostasis are able to impact innate and adaptive immune cells, staging cholesterol homeostasis at the centre of an adequate immune response. We also review evidence that demonstrates the clear impact that cholesterol metabolism has in both the induction and the resolution of the inflammatory response. Finally, we propose that emerging data in this field not only increase our understanding of immunometabolism but also provide new tools for monitoring and intervening in human diseases, where controlling and/or modifying inflammation is desirable.

MicroRNA-33/33* inhibit the activation of MAVS through AMPK in antiviral innate immunity

Innate immunity plays a prominent role in the host defense against pathogens and must be precisely regulated. As vital orchestrators in cholesterol homeostasis, microRNA-33/33* have been widely investigated in cellular metabolism. However, their role in antiviral innate immunity is largely unknown. Here, we report that VSV stimulation decreased the expression of miR-33/33* through an IFNAR-dependent manner in macrophages. Overexpression of miR-33/33* resulted in impaired RIG-I signaling, enhancing viral load and lethality whereas attenuating type I interferon production both in vitro and in vivo. In addition, miR-33/33* specifically prevented the mitochondrial adaptor mitochondrial antiviral-signaling protein (MAVS) from forming activated aggregates by targeting adenosine monophosphate activated protein kinase (AMPK), subsequently impeding the mitophagy-mediated elimination of damaged mitochondria and disturbing mitochondrial homeostasis which is indispensable for efficient MAVS activation. Our findings establish miR-33/33* as negative modulators of the RNA virus-triggered innate immune response and identify a previously unknown regulatory mechanism linking mitochondrial homeostasis with antiviral signaling pathways.

miR-33 in cardiometabolic diseases: lessons learned from novel animal models and approaches

miRNAs have emerged as critical regulators of nearly all biologic processes and important therapeutic targets for numerous diseases. However, despite the tremendous progress that has been made in this field, many misconceptions remain among much of the broader scientific community about the manner in which miRNAs function. In this review, we focus on miR‐33, one of the most extensively studied miRNAs, as an example, to highlight many of the advances that have been made in the miRNA field and the hurdles that must be cleared to promote the development of miRNA‐based therapies. We discuss how the generation of novel animal models and newly developed experimental techniques helped to elucidate the specialized roles of miR‐33 within different tissues and begin to define the specific mechanisms by which miR‐33 contributes to cardiometabolic diseases including obesity and atherosclerosis. This review will summarize what is known about miR‐33 and highlight common obstacles in the miRNA field and then describe recent advances and approaches that have allowed researchers to provide a more complete picture of the specific functions of this miRNA.

MicroRNA in cardio-metabolic disorders

Hyperlipidemia is correlated with several health problems that contain the combination of hypertension, obesity, and diabetes mellitus, which are grouped as metabolic syndrome. Though the lipid-lowering agents, such as statins, which aims to reduce serum low-density lipoprotein cholesterol (LDL-C) has been considered as one of the most effective therapeutics in treating hyperlipidemia and coronary artery diseases, the persistent high risk of atherosclerosis after intensive lipid-lowering therapy could not be simply explained by hyperlipidemia. Therefore, it is necessary to identify novel factors to manage treatment and to predict risk of cardio-metabolic events. Endeavor over the past several decades has demonstrated the important functions of microRNAs in modulating macrophage activation, lipid metabolism, and hyperlipidemia. In the present review, we summarized the recent findings which highlighted the contributions of microRNAs in regulating serum lipid metabolism. Furthermore, we also provided the potential mechanisms whereby microRNAs controlled lipid metabolism and the risk of cardio-metabolic disorders, which could help us to identify microRNAs as a promising therapeutic target for hyperlipidemia and its related cardiovascular diseases.

Astragalin Retards Atherosclerosis by Promoting Cholesterol Efflux and Inhibiting the Inflammatory Response via Upregulating ABCA1 and ABCG1 Expression in Macrophages

ABSTRACT

Lipid metabolism disorder and inflammatory response are considered to be the major causes of atherosclerogenesis. Astragalin, the most important functional component of flavonoid obtained from persimmon leaves, has the hypolipidemic effects. However, it is unknown, how astragalin protects against atherosclerosis. The aim of this study was to observe the effects of astragalin on cholesterol efflux and inflammatory response and to explore the underlying mechanisms. Our results showed that astragalin upregulated the expression of ATP-binding cassette transporters A1 and G1 (ABCA1 and ABCG1), promoted cholesterol efflux, and suppressed foam cell formation. Inhibition of the PPARγ/LXRα pathway abrogated the promotive effects of astragalin on both transporter expression and cholesterol efflux. In addition, treatment of astragalin markedly decreased the secretion of inflammatory factors, including interleukin 6, monocyte chemotactic protein 1, tumor necrosis factor α, and interleukin 1β. Mechanistically, astragalin upregulated ABCA1 and ABCG1 expression, which in turn reduced TLR4 surface levels and inhibited NF-κB nuclear translocation. Consistently, astragalin reduced atherosclerotic plaque area in apoE-/- mice. Taken together, these findings suggest that astragalin protects against atherosclerosis by promoting ABCA1- and ABCG1-mediated cholesterol efflux and inhibiting proinflammatory mediator release.

MicroRNA regulation of cholesterol metabolism

MicroRNAs are small noncoding RNAs that regulate gene expression at the posttranscriptional level. Since many microRNAs have multiple mRNA targets, they are uniquely positioned to regulate the expression of several molecules and pathways simultaneously. For example, the multiple stages of cholesterol metabolism are heavily influenced by microRNA activity. Understanding the scope of microRNAs that control this pathway is highly relevant to diseases of perturbed cholesterol metabolism, most notably cardiovascular disease (CVD). Atherosclerosis is a common cause of CVD that involves inflammation and the accumulation of cholesterol-laden cells in the arterial wall. However, several different cell types participate in atherosclerosis, and perturbations in cholesterol homeostasis may have unique effects on the specialized functions of these various cell types. Therefore, our review discusses the current knowledge of microRNA-mediated control of cholesterol homeostasis, followed by speculation as to how these microRNA-mRNA target interactions might have distinctive effects on different cell types that participate in atherosclerosis.

Interactions between ABCC4/MRP4 and ABCC7/CFTR in human airway epithelial cells in lung health and disease

ATP binding cassette (ABC) transporters are present in all three domains of life - Archaea, Bacteria, and Eukarya. The conserved nature is a testament to the importance of these transporters in regulating endogenous and exogenous substrates required for life to exist. In humans, 49 ABC transporters have been identified to date with broad expression in different lung cell types with multiple transporter family members contributing to lung health and disease. The ABC transporter most commonly known to be linked to lung pathology is ABCC7, also known as cystic fibrosis transmembrane conductance regulator - CFTR. Closely related to the CFTR genomic sequence is ABCC4/multi-drug resistance protein-4. Genomic proximity is shared with physical proximity, with ABCC4 and CFTR physically coupled in cell membrane microenvironments of epithelial cells to orchestrate functional consequences of cyclic-adenosine monophosphate (cAMP)-dependent second messenger signaling and extracellular transport of endogenous and exogenous substrates. The present concise review summarizes the emerging data defining a role of the (ABCC7/CFTR)-ABCC4 macromolecular complex in human airway epithelial cells as a physiologically important pathway capable of impacting endogenous and exogenous mediator transport and ion transport in both lung health and disease.

Role of the Sterol Regulatory Element Binding Protein Pathway in Tumorigenesis

Metabolic changes are a major feature of tumors, including various metabolic forms, such as energy, lipid, and amino acid metabolism. Sterol regulatory element binding proteins (SREBPs) are important modules in regulating lipid metabolism and play an essential role in metabolic diseases. In the previous decades, the regulatory range of SREBPs has been markedly expanded. It was found that SREBPs also played a critical role in tumor development. SREBPs are involved in energy supply, lipid supply, immune environment and inflammatory environment shaping in tumor cells, and as a protective umbrella to support the malignant proliferation of tumor cells. Natural medicine and traditional Chinese medicine, as an important part of drug therapy, demonstrates the multifaceted effects of SREBPs regulation. This review summarizes the core processes in the involvement of SREBPs in tumors and provides a comprehensive understanding of the pathways through which natural drugs target the SREBP pathway and regulate tumor progression.

Conditional Deoxyribozyme-Nanoparticle Conjugates for miRNA-Triggered Gene Regulation

DNA-nanoparticle (NP) conjugates have been used to knockdown gene expression transiently and effectively, making them desirable tools for gene regulation therapy. Because DNA-NPs are constitutively active and are rapidly taken up by most cell types, they offer limited control in terms of tissue or cell type specificity. To take a step toward solving this issue, we incorporate toehold-mediated strand exchange, a versatile molecular programming modality, to switch the DNA-NPs from an inactive state to an active state in the presence of a specific RNA input. Because many transcripts are unique to cell subtype or disease state, this approach could one day lead to responsive nucleic acid therapeutics with enhanced specificity. As a proof of concept, we designed conditional deoxyribozyme-nanoparticles (conditional DzNPs) that knockdown tumor necrosis factor α (TNFα) mRNA upon miR-33 triggering. We demonstrate toehold-mediated strand exchange and restoration of TNFα DNAzyme activity in the presence of miR-33 trigger, with optimization of the preparation, configuration, and toehold length of conditional DzNPs. Our results indicate specific and strong ON/OFF response of conditional DzNPs to the miR-33 trigger in buffer. Furthermore, we demonstrate endogenous miR-33-triggered knockdown of TNFα mRNA in mouse macrophages, implying the potential of conditional gene regulation applications using these DzNPs.

The impact of ATP-binding cassette transporters on metabolic diseases

Currently, many people worldwide suffer from metabolic diseases caused by heredity and external factors, such as diet. One of the symptoms of metabolic diseases is abnormal lipid metabolism. ATP binding cassette (ABC) transporters are one of the largest transport protein superfamilies that exist in nearly all living organisms and are mainly located on lipid-processing cells. ABC transporters have been confirmed to be closely related to the pathogenesis of diseases such as metabolic diseases, cancer and Alzheimer's disease based on their transport abilities. Notably, the capability to transport lipids makes ABC transporters critical in metabolic diseases. In addition, gene polymorphism in ABC transporters has been reported to be a risk factor for metabolic diseases, and it has been reported that relevant miRNAs have significant roles in regulating ABC transporters. In this review, we integrate recent studies to examine the roles of ABC transporters in metabolic diseases and aim to build a network with ABC transporters as the core, linking their transport abilities with metabolic and other diseases.

Epithelial membrane protein 2 governs transepithelial migration of neutrophils into the airspace

Whether respiratory epithelial cells regulate the final transit of extravasated neutrophils into the inflamed airspace or are a passive barrier is poorly understood. Alveolar epithelial type 1 (AT1) cells, best known for solute transport and gas exchange, have few established immune roles. Epithelial membrane protein 2 (EMP2), a tetraspan protein that promotes recruitment of integrins to lipid rafts, is highly expressed in AT1 cells but has no known function in lung biology. Here, we show that Emp2-/- mice exhibit reduced neutrophil influx into the airspace after a wide range of inhaled exposures. During bacterial pneumonia, Emp2-/- mice had attenuated neutrophilic lung injury and improved survival. Bone marrow chimeras, intravital neutrophil labeling, and in vitro assays suggested that defective transepithelial migration of neutrophils into the alveolar lumen occurs in Emp2-/- lungs. Emp2-/- AT1 cells had dysregulated surface display of multiple adhesion molecules, associated with reduced raft abundance. Epithelial raft abundance was dependent upon putative cholesterol-binding motifs in EMP2, whereas EMP2 supported adhesion molecule display and neutrophil transmigration through suppression of caveolins. Taken together, we propose that EMP2-dependent membrane organization ensures proper display on AT1 cells of a suite of proteins required to instruct paracellular neutrophil traffic into the alveolus.

Cholesterol 25-hydroxylase promotes efferocytosis and resolution of lung inflammation

Alveolar macrophages (AM) play a central role in initiation and resolution of lung inflammation, but the integration of these opposing core functions is poorly understood. AM expression of cholesterol 25-hydroxylase (CH25H), the primary biosynthetic enzyme for 25-hydroxycholesterol (25HC), far exceeds the expression of macrophages in other tissues, but no role for CH25H has been defined in lung biology. As 25HC is an agonist for the antiinflammatory nuclear receptor, liver X receptor (LXR), we speculated that CH25H might regulate inflammatory homeostasis in the lung. Here, we show that, of natural oxysterols or sterols, 25HC is induced in the inflamed lung of mice and humans. Ch25h-/- mice fail to induce 25HC and LXR target genes in the lung after LPS inhalation and exhibit delayed resolution of airway neutrophilia, which can be rescued by systemic treatment with either 25HC or synthetic LXR agonists. LXR-null mice also display delayed resolution, suggesting that native oxysterols promote resolution. During resolution, Ch25h is induced in macrophages upon their encounter with apoptotic cells and is required for LXR-dependent prevention of AM lipid overload, induction of Mertk, efferocytic resolution of airway neutrophilia, and induction of TGF-β. CH25H/25HC/LXR is, thus, an inducible metabolic axis that programs AMs for efferocytic resolution of inflammation.

Lipid rafts as a therapeutic target

Lipid rafts regulate the initiation of cellular metabolic and signaling pathways by organizing the pathway components in ordered microdomains on the cell surface. Cellular responses regulated by lipid rafts range from physiological to pathological, and the success of a therapeutic approach targeting "pathological" lipid rafts depends on the ability of a remedial agent to recognize them and disrupt pathological lipid rafts without affecting normal raft-dependent cellular functions. In this article, concluding the Thematic Review Series on Biology of Lipid Rafts, we review current experimental therapies targeting pathological lipid rafts, including examples of inflammarafts and clusters of apoptotic signaling molecule-enriched rafts. The corrective approaches include regulation of cholesterol and sphingolipid metabolism and membrane trafficking by using HDL and its mimetics, LXR agonists, ABCA1 overexpression, and cyclodextrins, as well as a more targeted intervention with apoA-I binding protein. Among others, we highlight the design of antagonists that target inflammatory receptors only in their activated form of homo- or heterodimers, when receptor dimerization occurs in pathological lipid rafts. Other therapies aim to promote raft-dependent physiological functions, such as augmenting caveolae-dependent tissue repair. The overview of this highly dynamic field will provide readers with a view on the emerging concept of targeting lipid rafts as a therapeutic strategy.jlr;61/5/687/F1F1f1.

Comorbidities of HIV infection: role of Nef-induced impairment of cholesterol metabolism and lipid raft functionality

Combination antiretroviral therapy has dramatically changed the outcome of HIV infection, turning it from a death sentence to a manageable chronic disease. However, comorbidities accompanying HIV infection, such as metabolic and cardio-vascular diseases, as well as cognitive impairment, persist despite successful virus control by combination antiretroviral therapy and pose considerable challenges to clinical management of people living with HIV. These comorbidities involve a number of pathological processes affecting a variety of different tissues and cells, making it challenging to identify a common cause(s) that would link these different diseases to HIV infection. In this article, we will present evidence that impairment of cellular cholesterol metabolism may be a common factor driving pathogenesis of HIV-associated comorbidities. Potential implications for therapeutic approaches are discussed.

Anti-ApoA-1 IgGs in Familial Hypercholesterolemia Display Paradoxical Associations with Lipid Profile and Promote Foam Cell Formation

AIMS

Anti-Apolipoprotein A-1 autoantibodies (anti-ApoA-1 IgG) promote atherogenesis via innate immune receptors, and may impair cellular cholesterol homeostasis (CH). We explored the presence of anti-ApoA-1 IgG in children (5-15 years old) with or without familial hypercholesterolemia (FH), analyzing their association with lipid profiles, and studied their in vitro effects on foam cell formation, gene regulation, and their functional impact on cholesterol passive diffusion (PD).

METHODS

Anti-ApoA-1 IgG and lipid profiles were measured on 29 FH and 25 healthy children. The impact of anti-ApoA-1 IgG on key CH regulators (SREBP2, HMGCR, LDL-R, ABCA1, and miR-33a) and foam cell formation detected by Oil Red O staining were assessed using human monocyte-derived macrophages. PD experiments were performed using a validated THP-1 macrophage model.

RESULTS

Prevalence of high anti-ApoA-1 IgG levels (seropositivity) was about 38% in both study groups. FH children seropositive for anti-ApoA-1 IgG had significant lower total cholesterol LDL and miR-33a levels than those who were seronegative. On macrophages, anti-ApoA-1 IgG induced foam cell formation in a toll-like receptor (TLR) 2/4-dependent manner, accompanied by NF-kB- and AP1-dependent increases of SREBP-2, LDL-R, and HMGCR. Despite increased ABCA1 and decreased mature miR-33a expression, the increased ACAT activity decreased membrane free cholesterol, functionally culminating to PD inhibition.

CONCLUSIONS

Anti-ApoA-1 IgG seropositivity is frequent in children, unrelated to FH, and paradoxically associated with a favorable lipid profile. In vitro, anti-ApoA-1 IgG induced foam cell formation through a complex interplay between innate immune receptors and key cholesterol homeostasis regulators, functionally impairing the PD cholesterol efflux capacity of macrophages.

Tanshinone IIA reduces oxidized low-density lipoprotein-induced inflammatory responses by downregulating microRNA-33 in THP-1 macrophages

Atherosclerosis is a leading cause of cardiovascular diseases. Oxidized low-density lipoprotein (ox-LDL) is commonly used to construct atherosclerosis cell models. Macrophages-secreted pro-inflammatory factors play vital roles in the development of atherosclerosis. Tanshinone IIA (Tan) is an effective therapeutic agent for atherosclerotic cardiovascular diseases. However, the molecular mechanisms by which Tan protects against atherogenesis have not been thoroughly elucidated. In the present study, we aimed to search for microRNA targets of Tan in ox-LDL-stimulated macrophages. Interleukin-1β (IL-1β), IL-6 and tumor necrosis factor-α (TNF-α) levels were determined by matching ELISA commercial kits. RT-qPCR assay was conducted to measure microRNA-33 (miR-33) expression. We found that ox-LDL induced the secretion of pro-inflammatory cytokines (IL-1β, IL-6, TNF-α) and the expression of microRNA-33 (miR-33) in THP-1 macrophages. Tan inhibited pro-inflammatory cytokine secretion and miR-33 expression in ox-LDL-stimulated THP-1 macrophages. Also, the depletion of miR-33 suppressed pro-inflammatory cytokine secretion in ox-LDL-stimulated THP-1 macrophages. Moreover, miR-33 upregulation abrogated the inhibitory effect of Tan on pro-inflammatory cytokine secretion in ox-LDL-stimulated THP-1 macrophages. In conclusion, Tan inhibited ox-LDL-induced pro-inflammatory cytokine secretion by downregulating miR-33 in THP-1 macrophages, hinting that Tan might exert its atheroprotective effects by targeting miR-33 and reducing pro-inflammatory responses.

SREBF1/MicroRNA-33b Axis Exhibits Potent Effect on Unstable Atherosclerotic Plaque Formation In Vivo

Objective- Atherosclerosis is a common disease caused by a variety of metabolic and inflammatory disturbances. MicroRNA (miR)-33a within SREBF2 (sterol regulatory element-binding factor 2) is a potent target for treatment of atherosclerosis through regulating both aspects; however, the involvement of miR-33b within SREBF1 remains largely unknown. Although their host genes difference could lead to functional divergence of miR-33a/b, we cannot dissect the roles of miR-33a/b in vivo because of lack of miR-33b sequences in mice, unlike human. Approach and Results- Here, we analyzed the development of atherosclerosis using miR-33b knock-in humanized mice under apolipoprotein E-deficient background. MiR-33b is prominent both in human and mice on atheroprone condition. MiR-33b reduced serum high-density lipoprotein cholesterol levels and systemic reverse cholesterol transport. MiR-33b knock-in macrophages showed less cholesterol efflux capacity and higher inflammatory state via regulating lipid rafts. Thus, miR-33b promotes vulnerable atherosclerotic plaque formation. Furthermore, bone marrow transplantation experiments strengthen proatherogenic roles of macrophage miR-33b. Conclusions- Our data demonstrated critical roles of SREBF1-miR-33b axis on both lipid profiles and macrophage phenotype remodeling and indicate that miR-33b is a promising target for treating atherosclerosis.

Exosomes containing HIV protein Nef reorganize lipid rafts potentiating inflammatory response in bystander cells

HIV infection has a profound effect on “bystander” cells causing metabolic co-morbidities. This may be mediated by exosomes secreted by HIV-infected cells and containing viral factors. Here we show that exosomes containing HIV-1 protein Nef (exNef) are rapidly taken up by macrophages releasing Nef into the cell interior. This caused down-regulation of ABCA1, reduction of cholesterol efflux and sharp elevation of the abundance of lipid rafts through reduced activation of small GTPase Cdc42 and decreased actin polymerization. Changes in rafts led to re-localization of TLR4 and TREM-1 to rafts, phosphorylation of ERK1/2, activation of NLRP3 inflammasome, and increased secretion of pro-inflammatory cytokines. The effects of exNef on lipid rafts and on inflammation were reversed by overexpression of a constitutively active mutant of Cdc42. Similar effects were observed in macrophages treated with exosomes produced by HIV-infected cells or isolated from plasma of HIV-infected subjects, but not with exosomes from cells and subjects infected with ΔNef-HIV or uninfected subjects. Mice injected with exNef exhibited monocytosis, reduced ABCA1 in macrophages, increased raft abundance in monocytes and augmented inflammation. Thus, Nef-containing exosomes potentiated pro-inflammatory response by inducing changes in cholesterol metabolism and reorganizing lipid rafts. These mechanisms may contribute to HIV-associated metabolic co-morbidities.

HIV infects only a limited repertoire of cells expressing HIV receptors. Nevertheless, co-morbidities of HIV infection, such as atherosclerosis, dementia, renal impairment, myocardial pathology, abnormal haematopoiesis and others, involve dysfunction of cells that can not be infected by HIV. These co-morbidities persist even after successful application of antiretroviral therapy, when no virus is found in the blood. Many co-morbidities of HIV have a common element in their pathogenesis, impairment of cholesterol metabolism. In this study we show that HIV protein Nef released from infected cells in extracellular vesicles is taken up by un-infected (‘bystander’) cells impairing cholesterol metabolism in these cells. This impairment causes formation of excessive lipid rafts, re-localization of the inflammatory receptors into rafts, and triggers inflammation. These mechanisms may contribute to HIV-associated metabolic co-morbidities. Our work demonstrates how a single viral factor released from infected cells into circulation may cause a pleiotropy of pathogenic responses.

Role of cholesterol homeostasis and its efflux pathways in cancer progression

Tumor cells show high avidity for cholesterol in order to support their inherent nature to divide and proliferate. This results in the rewiring of cholesterol homeostatic pathways by influencing not only de novo synthesis but also uptake or efflux pathways of cholesterol. Recent findings have pointed towards the importance of cholesterol efflux in tumor pathogenesis. Cholesterol efflux is the first and foremost step in reverse cholesterol transport and any perturbation in this pathway may lead to the accumulation of intracellular cholesterol, thereby altering the cellular equilibrium. This review addresses the different mechanisms of cholesterol efflux from the cell and highlights their role and regulation in context to tumor development. There are four different routes by which cholesterol can be effluxed from the cell namely, 1) passive diffusion of cholesterol to mature HDL particles, 2) SR-B1 mediated facilitated diffusion, 3) Active efflux to apo A1 via ABCA1 and 4) ABCG1 mediated efflux to mature HDL. These molecular players facilitating cholesterol efflux are engaged in a complex interplay with different signaling pathways. Thus, an understanding of the efflux pathways, their regulation and cross-talk with signaling molecules may provide novel prognostic markers and therapeutic targets to combat the onset of carcinogenesis.

miR-33-5p knockdown attenuates abdominal aortic aneurysm progression via promoting target adenosine triphosphate-binding cassette transporter A1 expression and activating the PI3K/Akt signaling pathway

PURPOSE

The aim of this study was to investigate the role of miR-33-5p in abdominal aortic aneurysm progression, which regulated adenosine triphosphate-binding cassette transporter A1 (ABCA1)-mediated cholesterol efflux and lipid accumulation in THP-1 macrophage-derived foam cells through the PI3K/Akt pathway.

METHODS

Quantitative reverse transcription polymerase chain reaction was used to evaluate the expression level of miR-33-5p and ABCA1 mRNA in abdominal aortic aneurysm patient and normal person tissues. The relationship between miR-33-5p and ABCA1 was examined by dual luciferase report assay. High-performance liquid chromatography was used to evaluate the levels of cholesterol contents. Cholesterol efflux detection was performed by liquid scintillator. The expression of inflammatory cytokines was detected by quantitative reverse transcription polymerase chain reaction. Western blot was applied to determine the expression levels of ABCA1, PI3K (p-PI3K), and Akt (p-Akt).

RESULTS

The quantitative reverse transcription polymerase chain reaction analysis results revealed miR-33-5p overexpression in abdominal aortic aneurysm tissues, but the expression level of ABCA1 was lower in abdominal aortic aneurysm tissues than non-abdominal aortic aneurysm tissues. Subsequently, the dual luciferase report gene assay confirmed that ABCA1 was a target of miR-33-5p, and miR-33-5p-negative regulated ABCA1 expression. Moreover, the expression levels of p-PI3K, p-Akt, and ABCA1 were decreased in THP-1 cell transferred with ABCA1 siRNA, but knockdown of miR-33-5p had an opposite effect. Furthermore, knockdown of miR-33-5p decreased the expression of MMP-2, MMP-9, TNF-α, total cellular cholesterol, and promoted cholesterol efflux in THP-1-derived foam cells. Importantly, LY294002 (PI3K inhibitor) or si-ABCA1 completely inhibited the stimulatory effects of miR-33-5p inhibitor.

CONCLUSION

This study has found that knockdown of miR-33-5p induced ABCA1 expression and promoted inflammatory cytokines and cholesterol efflux likely via activating the PI3K/Akt signaling pathway.

Effects of restrictions on maternal feed intake on the immune indexes of umbilical cord blood and liver Toll-like receptor signaling pathways in fetal goats during pregnancy

Background

Liver has important immune function during fetal development and after birth. However, the effect of maternal malnutrition on immune function of the fetal liver is rarely reported. In this study, twelve pregnant goats (Xiangdong black goat, at d 45 of gestation) were assigned to the control group (fed 100% of nutritional requirements) and the restriction group (fed 60% of the intake of the control group) during gestation from d 55 to 100. Fetal goats were harvested at d 100 of gestation and immune indexes and amino acid profiles of the umbilical cord blood and liver Toll-like receptors (TLRs) signaling pathways were measured.

Results

Maternal body weight in the restriction group was lower than the control group (P < 0.05). Maternal feed intake restriction decreased (P < 0.05) heart weight, heart index, alkaline phosphatase and serum amyloid protein A in the umbilical cord blood (UCB). Moreover, only histidine was decreased in the restricted group (P = 0.084), and there were no differences in other amino acids contents in the UCB between the two groups (P > 0.05). The TLR2 and TLR4 mRNA expression in the fetal liver in the restriction group was greater (P < 0.05) than that in the control group. Furthermore, the mRNA expression levels of myeloid differentiation primary response 88 (MyD88), TNF receptor associated factor 6, nuclear factor kappa B subunit 1, NFKB inhibitor alpha, IFN-β, TGF-β, TNF-α and IL-1β in the restricted group were upregulated (P < 0.05), and the expression of TLR3 (P = 0.099) tended to be higher in the restricted group. However, protein levels of TLR2, TLR4, IκBα, phosphorylated IκBα, phosphorylated IκBα/total IκBα, TRIF and MyD88 were not affected (P > 0.05) by maternal intake restriction.

Conclusions

These results revealed that the restriction of maternal feed intake influenced the development of heart and hepatic protein synthesis at the acute phase of fetal goats and upregulated the mRNA expression of genes involved in MyD88-dependent signaling pathways and of target cytokines.

Circulating microRNAs in patients with immune thrombocytopenia before and after treatment with thrombopoietin-receptor agonists

MicroRNAs (miRNAs) are small non-coding RNAs involved in the regulation of gene expression. Dysregulated expression of several miRNAs has been found in primary immune thrombocytopenia (ITP) suggesting that miRNAs are likely involved in the pathogenesis of ITP. We aimed to explore the differential expression of miRNAs in patients with ITP before and after starting treatment with thrombopoietin-receptor agonists (TPO-RAs) to clarify their roles in the pathophysiology of ITP, and as potential diagnostic and prognostic markers of this disorder.We performed a profiling study where 179 miRNAs were analyzed in eight ITP patients before and during treatment with TPO-RAs and in eight controls using miRNA PCR panel; 81 miRNAs were differentially expressed in ITP patients compared to controls, and 14 miRNAs showed significant changes during TPO-RA-treatment. Ten miRNAs were selected for validation that was performed in 23 patients and 22 controls using droplet digital PCR. Three miRNAs were found to be differentially expressed in ITP patients before TPO-RA-treatment compared to controls: miR-199a-5p was down-regulated (p = 0.0001), miR-33a-5p (p = 0.0002) and miR-195-5p (p = 0.035) were up-regulated. Treatment with TPO-RAs resulted in changes in six miRNAs including miR-199a-5p (p = 0.001), miR-33a-5p (p = 0.003), miR-382-5p (p = 0.004), miR-92b-3p (p = 0.005), miR-26a-5p (p = 0.008) and miR-221-3p (p = 0.023); while miR-195-5p remained unchanged and significantly higher than in controls, despite the increase in the platelet count, which may indicate its possible role in the pathophysiology of ITP. Regression analysis revealed that pre-treatment levels of miR-199a-5p and miR-221-3p could help to predict platelet response to TPO-RA-treatment. ROC curve analysis showed that the combination of miR-199a-5p and miR-33a-5p could distinguish patients with ITP from controls with AUC of 0.93.This study identifies a number of differentially expressed miRNAs in ITP patients before and after initiation of TPO-RAs with potential roles in the pathophysiology, as well as with a possible utility as diagnostic and prognostic biomarkers. These interesting findings deserve further exploration and validation in future studies.

Crohn's disease IRGM risk alleles are associated with altered gene expression in human tissues

Crohn's disease (CD) is a chronic inflammatory gastrointestinal disorder. Genetic association studies have implicated dysregulated autophagy in CD. Among risk loci identified are a promoter single nucleotide polymorphism (SNP)( rs13361189 ) and two intragenic SNPs ( rs9637876 , rs10065172 ) in immunity-related GTPase family M ( IRGM) a gene that encodes a protein of the autophagy initiation complex. All three SNPs have been proposed to modify IRGM expression, but reports have been divergent and largely derived from cell lines. Here, analyzing RNA-Sequencing data of human tissues from the Genotype-Tissue Expression Project, we found that rs13361189 minor allele carriers had reduced IRGM expression in whole blood and terminal ileum, and upregulation in ileum of ZNF300P1, a locus adjacent to IRGM on chromosome 5q33.1 that encodes a long noncoding RNA. Whole blood and ileum from minor allele carriers had altered expression of multiple additional genes that have previously been linked to colitis and/or autophagy. Notable among these was an increase in ileum of LTF (lactoferrin), an established fecal inflammatory biomarker of CD, and in whole blood of TNF, a key cytokine in CD pathogenesis. Last, we confirmed that risk alleles at all three loci associated with increased risk for CD but not ulcerative colitis in a case-control study. Taken together, our findings suggest that genetically encoded IRGM deficiency may predispose to CD through dysregulation of inflammatory gene networks. Gene expression profiling of disease target tissues in genetically susceptible populations is a promising strategy for revealing new leads for the study of molecular pathogenesis and, potentially, for precision medicine. NEW & NOTEWORTHY Single nucleotide polymorphisms in immunity-related GTPase family M ( IRGM), a gene that encodes an autophagy initiation protein, have been linked epidemiologically to increased risk for Crohn's disease (CD). Here, we show for the first time that subjects with risk alleles at two such loci, rs13361189 and rs10065172 , have reduced IRGM expression in whole blood and terminal ileum, as well as dysregulated expression of a wide array of additional genes that regulate inflammation and autophagy.

Assessing the functional association of intronic miRNAs with their host genes

In human, nearly half of the known microRNAs (miRNAs) are encoded within the introns of protein-coding genes. The embedment of these miRNA genes within the sequences of protein-coding genes alludes to a possible functional relationship between intronic miRNAs and their hosting genes. Several studies, using predicted targets, suggested that intronic miRNAs influence their hosts' function either antagonistically or synergistically. New experimental data of miRNA expression patterns and targets enable exploring this putative association by relying on actual data rather than on predictions. Here, our analysis based on currently available experimental data implies that the potential functional association between intronic miRNAs and their hosting genes is limited. For host-miRNA examples where functional associations were detected, it was manifested by either autoregulation, common targets of the miRNA and hosting gene, or through the targeting of transcripts participating in pathways in which the host gene is involved. This low prevalence of functional association is consistent with our observation that many intronic miRNAs have independent transcription start sites and are not coexpressed with the hosting gene. Yet, the intronic miRNAs that do show functional association with their hosts were found to be more evolutionarily conserved compared to other intronic miRNAs. This might suggest a selective pressure to maintain this architecture when it has a functional consequence.

A New Frontier in Immunometabolism. Cholesterol in Lung Health and Disease

The lung has a unique relationship to cholesterol that is shaped by its singular physiology. On the one hand, the lungs receive the full cardiac output and have a predominant dependence on plasma lipoprotein uptake for their cholesterol supply. On the other hand, surfactant lipids, including cholesterol, are continually susceptible to oxidation owing to direct environmental exposure and must be cleared or recycled because of the very narrow biophysical mandates placed upon surfactant lipid composition. Interestingly, increased lipid-laden macrophage "foam cells" have been noted in a wide range of human lung pathologies. This suggests that lipid dysregulation may be a unifying and perhaps contributory event in chronic lung disease pathogenesis. Recent studies have shown that perturbations in intracellular cholesterol trafficking critically modify the immune response of macrophages and other cells. This minireview discusses literature that has begun to demonstrate the importance of regulated cholesterol traffic through the lung to pulmonary immunity, inflammation, and fibrosis. This emerging recognition of coupling between immunity and lipid homeostasis in the lung presents potentially transformative concepts for understanding lung disease and may also offer novel and exciting avenues for therapeutic development.

Emerging roles of microRNAs in the metabolic control of immune cells

Immunometabolism is an emerging field that focuses on the role of cellular metabolism in the regulation of immune cells. Recent studies have revealed an intensive link between the metabolic state and the functions of immune cells. MicroRNAs (miRNAs) are small non-coding, single-stranded RNAs generally consisting of 18-25 nucleotides that exert crucial roles in regulating gene expression at the posttranscriptional level. Although the role of miRNAs in immune regulation has long been recognized, their roles in immunometabolism have not yet been well established. Over the past decade, increasing studies have proven that miRNAs are intensively involved in the metabolic control of immune cells including macrophages, T cells, B cells and dendritic cells. In this review, we highlight recent emerging findings in the miRNA-mediated metabolic control of immune cells.

Genetic Dissection of the Impact of miR-33a and miR-33b during the Progression of Atherosclerosis

As an important regulator of macrophage cholesterol efflux and HDL biogenesis, miR-33 is a promising target for treatment of atherosclerosis, and numerous studies demonstrate that inhibition of miR-33 increases HDL levels and reduces plaque burden. However, important questions remain about how miR-33 impacts atherogenesis, including whether this protection is primarily due to direct effects on plaque macrophages or regulation of lipid metabolism in the liver. We demonstrate that miR-33 deficiency in Ldlr^-/- mice promotes obesity, insulin resistance, and hyperlipidemia but does not impact plaque development. We further assess how loss of miR-33 or addition of miR-33b in macrophages and other hematopoietic cells impact atherogenesis. Macrophage-specific loss of miR-33 decreases lipid accumulation and inflammation under hyperlipidemic conditions, leading to reduced plaque burden. Therefore, the pro-atherogenic effects observed in miR-33-deficient mice are likely counterbalanced by protective effects in macrophages, which may be the primary mechanism through which anti-miR-33 therapies reduce atherosclerosis.

Role of MicroRNAs in Obesity-Induced Metabolic Disorder and Immune Response

In all living organisms, metabolic homeostasis and the immune system are the most fundamental requirements for survival. Recently, obesity has become a global public health issue, which is the cardinal risk factor for metabolic disorder. Many diseases emanating from obesity-induced metabolic dysfunction are responsible for the activated immune system, including innate and adaptive responses. Of note, inflammation is the manifest accountant signal. Deeply studied microRNAs (miRNAs) have participated in many pathways involved in metabolism and immune responses to protect cells from multiple harmful stimulants, and they play an important role in determining the progress through targeting different inflammatory pathways. Thus, immune response and metabolic regulation are highly integrated with miRNAs. Collectively, miRNAs are the new targets for therapy in immune dysfunction.

Immunometabolic Signaling Pathways Contribute to Macrophage and Dendritic Cell Function

Understanding of antigen-presenting cell (APC) participation in tissue inflammation and metabolism has advanced through numerous studies using systems biology approaches. Previously unrecognized connections between these research areas have been elucidated in the context of inflammatory disease involving innate and adaptive immune responses. A new conceptual framework bridges APC biology, metabolism, and cytokines in the generation of effective T-cell responses. Exploring these connections is paramount to addressing the rising tide of multi-organ system diseases, particularly chronic diseases associated with metabolic syndrome, infection, and cancer. Focused research in these areas will aid the development of strategies to harness and manipulate innate immunology to improve vaccine development, anti-viral, anti-inflammatory, and anti-tumor therapies. This review highlights recent advances in APC "immunometabolism" specifically related to chronic viral and metabolic disease in humans. The goal of this review is to develop an abridged and consolidated outlook on recent thematic updates to APC immunometabolism in the areas of regulation and crosstalk between metabolic and inflammatory signaling and the integrated stress response and how these signals dictate APC function in providing T-cell activation Signal 3.

Inhibition of airway inflammation in a cockroach allergen model of asthma by agonists of miRNA-33b

MicroRNAs (miRNAs) play powerful roles in immune function by regulating target genes that mediate cell behavior. It is well known that mast cells have essential effector and immune regulatory functions in IgE-associated allergic disorders and in innate and adaptive immune responses. However, the role of miRNAs in mediating mast cell functions and the relevant mechanisms require further exploration. The roles of miR-33b in airway inflammation and mast cell functions are still unknown. To examine the role of miR-33b in mouse mast cells in cockroach allergen-induced asthma, we developed a lentiviral system for miRNA-33b overexpression to examine whether miRNA-33b mediates airway inflammation by regulating mast cell function and to evaluate the underlying mechanism. The results showed that miR-33b inhibited cockroach allergen-induced asthma in vivo: in particular, it inhibited T_H2 cytokine production. In addition, we found that in cells in which miRNA-33b had been transfected, mast cell degranulation was inhibited through suppression of the calcium release and IgE/FcεRI pathway. Our study provides new insight into the roles of miR-33b in asthma and mast cell biology and identifies novel mechanisms that may contribute to mast cell-related pathological conditions in airway inflammation.

Diabetes-mediated myelopoiesis and the relationship to cardiovascular risk

Diabetes is the greatest risk factor for the development of cardiovascular disease, which, in turn, is the most prevalent cause of mortality and morbidity in diabetics. These patients have elevations in inflammatory monocytes, a factor consistently reported to drive the development of atherosclerosis. In preclinical models of both type 1 and type 2 diabetes, studies have demonstrated that the increased production and activation of monocytes is driven by enhanced myelopoiesis, promoted by factors, including hyperglycemia, impaired cholesterol efflux, and inflammasome activation, that affect the proliferation of bone marrow precursor cells. This suggests that continued mechanistic investigations of the enhanced myelopoiesis and the generation of inflammatory monocytes are timely, from the dual perspectives of understanding more deeply the underlying bases of diabetes pathophysiology and identifying therapeutic targets to reduce cardiovascular risk in these patients.

MicroRNA-125a-5p plays a role as a tumor suppressor in lung carcinoma cells by directly targeting STAT3

Increasing evidence supports that the dysregulation of microRNA expression plays an important role in the process of tumor occurrence and development. Studies have found that mir-125a-5p expression was downregulated in a variety of tumors, but the effects and mechanism of mir-125a-5p in lung cancer are still unclear. The aim of this study is to detect the expression of mir-125a-5p in lung cancer tissues and lung cancer cell lines and to explore the effects of mir-125a-5p on the biological characteristics of lung cancer cells; thus, this study aims to provide new methods and new strategies for the treatment of lung cancer. The result from quantitative reverse transcription polymerase chain reaction showed that the expression of miR-125a-5p was significantly lower in lung cancer tissues and lung cancer cell lines (95-D, A549, HCC827, and NCI-H1299) than that in normal tissue adjacent to lung cancer or normal human bronchial epithelial cells. In order to explore the function and mechanism of mir-125a-5p in lung cancer cells, miR-125a-5p mimic or mir-125a-5p inhibitor was transfected into A549 cells. Mir-125a-5p displayed an obvious upregulation in A549 cells transfected with miR-125a-5p and an obvious downregulation in A549 cells transfected with mir-125a-5p inhibitor compared to that in A549 cells transfected with control miRNA. 3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide, BrdU staining, flow cytometry, and Transwell assay showed that the upregulation of miR-125a-5p could significantly decrease the cell viability, proliferation, and invasion of lung cancer cells and increase apoptosis of lung cancer cells. The downregulation of miR-125a-5p provided very contrasting results. Computational algorithms predicted that the STAT3 is a target of miR-125a-5p. Here, we validated that miR-125a-5p could directly bind to the 3'-untranslated region of STAT3, and miR-125a-5p overexpression could significantly inhibit the protein expression of STAT3. These results suggested that mir-125a-5p can regulate the expression of STAT3 in lung cancer cells. To further verify whether mir-125a-5p can play a biological role through regulating STAT3, 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide, flow cytometry, and Transwell analysis demonstrated that overexpression of STAT3 can reverse the cells' biological effects induced by mir-125a-5p overexpression. Mir-125a-5p downregulated in lung cancer tissue and cell lines can negatively regulate STAT3 protein expression. Taken together, mir-125a-5p inhibited the proliferation and invasion of lung cancer cells and facilitated lung cancer cell apoptosis through suppressing STAT3. Enhancing the expression of miR-125a-5p is expected to benefit the therapy for the patients with lung cancer.

MicroRNAs and lipid metabolism

PURPOSE OF REVIEW

Work over the past decade has identified the important role of microRNAs (miRNAS) in regulating lipoprotein metabolism and associated disorders including metabolic syndrome, obesity, and atherosclerosis. This review summarizes the most recent findings in the field, highlighting the contribution of miRNAs in controlling LDL-cholesterol (LDL-C) and HDL-cholesterol (HDL-C) metabolism.

RECENT FINDINGS

A number of miRNAs have emerged as important regulators of lipid metabolism, including miR-122 and miR-33. Work over the past 2 years has identified additional functions of miR-33 including the regulation of macrophage activation and mitochondrial metabolism. Moreover, it has recently been shown that miR-33 regulates vascular homeostasis and cardiac adaptation in response to pressure overload. In addition to miR-33 and miR-122, recent GWAS have identified single-nucleotide polymorphisms in the proximity of miRNA genes associated with abnormal levels of circulating lipids in humans. Several of these miRNAs, such as miR-148a and miR-128-1, target important proteins that regulate cellular cholesterol metabolism, including the LDL receptor (LDLR) and the ATP-binding cassette A1 (ABCA1).

SUMMARY

MicroRNAs have emerged as critical regulators of cholesterol metabolism and promising therapeutic targets for treating cardiometabolic disorders including atherosclerosis. Here, we discuss the recent findings in the field, highlighting the novel mechanisms by which miR-33 controls lipid metabolism and atherogenesis, and the identification of novel miRNAs that regulate LDL metabolism. Finally, we summarize the recent findings that identified miR-33 as an important noncoding RNA that controls cardiovascular homeostasis independent of its role in regulating lipid metabolism.

Extracellular Vesicles Mediate Radiation-Induced Systemic Bystander Signals in the Bone Marrow and Spleen

Radiation-induced bystander effects refer to the induction of biological changes in cells not directly hit by radiation implying that the number of cells affected by radiation is larger than the actual number of irradiated cells. Recent in vitro studies suggest the role of extracellular vesicles (EVs) in mediating radiation-induced bystander signals, but in vivo investigations are still lacking. Here, we report an in vivo study investigating the role of EVs in mediating radiation effects. C57BL/6 mice were total-body irradiated with X-rays (0.1, 0.25, 2 Gy), and 24 h later, EVs were isolated from the bone marrow (BM) and were intravenously injected into unirradiated (so-called bystander) animals. EV-induced systemic effects were compared to radiation effects in the directly irradiated animals. Similar to direct radiation, EVs from irradiated mice induced complex DNA damage in EV-recipient animals, manifested in an increased level of chromosomal aberrations and the activation of the DNA damage response. However, while DNA damage after direct irradiation increased with the dose, EV-induced effects peaked at lower doses. A significantly reduced hematopoietic stem cell pool in the BM as well as CD4⁺ and CD8⁺ lymphocyte pool in the spleen was detected in mice injected with EVs isolated from animals irradiated with 2 Gy. These EV-induced alterations were comparable to changes present in the directly irradiated mice. The pool of TLR4-expressing dendritic cells was different in the directly irradiated mice, where it increased after 2 Gy and in the EV-recipient animals, where it strongly decreased in a dose-independent manner. A panel of eight differentially expressed microRNAs (miRNA) was identified in the EVs originating from both low- and high-dose-irradiated mice, with a predicted involvement in pathways related to DNA damage repair, hematopoietic, and immune system regulation, suggesting a direct involvement of these pathways in mediating radiation-induced systemic effects. In conclusion, we proved the role of EVs in transmitting certain radiation effects, identified miRNAs carried by EVs potentially responsible for these effects, and showed that the pattern of changes was often different in the directly irradiated and EV-recipient bystander mice, suggesting different mechanisms.