MicroRNA-130a is up-regulated in mouse liver by iron deficiency and targets the bone morphogenetic protein (BMP) receptor ALK2 to attenuate BMP signaling and hepcidin transcription

RNA regulatory mechanisms controlling TGF-β signaling and EMT in cancer

Epithelial-mesenchymal transition (EMT) is a major contributor to metastatic progression and is prominently regulated by TGF-β signalling. Both EMT and TGF-β pathway components are tightly controlled by non-coding RNAs - including microRNAs (miRNAs), long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs) - that collectively have major impacts on gene expression and resulting cellular states. While miRNAs are the best characterised regulators of EMT and TGF-β signaling and the miR-200-ZEB1/2 feedback loop plays a central role, important functions for lncRNAs and circRNAs are also now emerging. This review will summarise our current understanding of the roles of non-coding RNAs in EMT and TGF-β signaling with a focus on their functions in cancer progression.

miR-761-hepcidin/Gpx4 pathway contribute to unexplained liver dysfunction in polycystic ovary syndrome by regulating liver iron overload and ferroptosis

Aims: To investigate the underling mechanisms of liver dysfunction in patients with polycystic ovary syndrome (PCOS).Materials and methods: PCOS patients were enrolled according to the Amsterdam criteria while PCOS animal model was established by dihydrotestosterone (DHEA) sustained release tablet implantation on its neck. Further liver damage and iron overload were detected by HE and Prussian blue staining. The liver related enzymes, mRNA and protein levels of hepcidin and GPX4 were tested by ELISA, qRT-PCR and Western blot. RNA interference and miR-761 transfection were routinely performed while the regulation of miR-761 on hepcidin and GPX4 was confirmed by luciferase reporter gene analysis.Results: We found that a part of PCOS patients and animal model had unexplained liver damage, which is independent of nonalcoholic fatty liver disease (NAFLD) and accompanied by increased ferrum (Fe) deposition. Besides, the expression of hepcidin and GPX4 that is important effector proteins for ferroptosis was down regulated in liver, showing the importance of iron metabolism in this unexplained liver damage. Based on the miR-761-hepcidin/GPX4 axis, we systematically studied the effects of miR-761 on ferroptosis and Fe deposition, which further influence the phenotype and liver function of PCOS model. From both in vivo and in vitro levels, changes in PCOS disease phenotype and ferroptosis were observed through hierarchical antagonism or overexpression of miR-761, hepcidin and GPX4.Conclusions: our results provide a novel explanation for unexplained liver damage in PCOS and a potential therapeutic target.

LncXIST Facilitates Iron Overload and Iron Overload-Induced Islet Beta Cell Injury in Type 2 Diabetes through miR-130a-3p/ALK2 Axis

Iron overload is directly associated with diabetes mellitus, loss of islet beta cell, and insulin resistance. Likewise, long noncoding RNA (lncRNA) is associated with type 2 diabetes (T2D). Moreover, lncRNAs could be induced by iron overload. Therefore, we are going to explore the molecular mechanism of lncRNA XIST in iron overload-related T2D. Real-time quantitative PCR and Western blot were used to detect gene and protein levels, respectively. TUNEL and MTT assay were performed to examine cell survival. The glucose test strip, colorimetric analysis kit, ferritin ELISA kit, and insulin ELISA kit were performed to examine the levels of glycolic, iron, and total iron-binding capacity, ferritin, and insulin in serum. Fluorospectrophotometry assay was used to examine labile iron pool level. XIST was higher expressed in T2D and iron overload-related T2D rat tissues and cells, and iron overload-induced promoted XIST expression in T2D. Higher XIST expression was associated with iron overload in patients with T2D. Knockdown of XIST alleviated iron overload and iron overload-induced INS-1 cells injury. Further, we found that XIST can sponge miR-130a-3p to trigger receptor-like kinase 2 (ALK2) expression. Moreover, knockdown of ALK2 alleviated iron overload and iron overload-induced INS-1 cells injury by inhibiting bone morphogenetic protein 6 (BMP6)/ALK2/SMAD1/5/8 axis but reversed with XIST upregulation, which was terminally boosted by overexpression of miR-130a-3p. XIST has the capacity to promote iron overload and iron overload-related T2D initiation and development through inhibition of ALK2 expression by sponging miR-130a-3p, and that targeting this axis may be an effective strategy for treating patients with T2D.

Iron-Deficiency in Atopic Diseases: Innate Immune Priming by Allergens and Siderophores

Although iron is one of the most abundant elements on earth, about a third of the world's population are affected by iron deficiency. Main drivers of iron deficiency are beside the chronic lack of dietary iron, a hampered uptake machinery as a result of immune activation. Macrophages are the principal cells distributing iron in the human body with their iron restriction skewing these cells to a more pro-inflammatory state. Consequently, iron deficiency has a pronounced impact on immune cells, favoring Th2-cell survival, immunoglobulin class switching and primes mast cells for degranulation. Iron deficiency during pregnancy increases the risk of atopic diseases in children, while both children and adults with allergy are more likely to have anemia. In contrast, an improved iron status seems to protect against allergy development. Here, the most important interconnections between iron metabolism and allergies, the effect of iron deprivation on distinct immune cell types, as well as the pathophysiology in atopic diseases are summarized. Although the main focus will be humans, we also compare them with innate defense and iron sequestration strategies of microbes, given, particularly, attention to catechol-siderophores. Similarly, the defense and nutritional strategies in plants with their inducible systemic acquired resistance by salicylic acid, which further leads to synthesis of flavonoids as well as pathogenesis-related proteins, will be elaborated as both are very important for understanding the etiology of allergic diseases. Many allergens, such as lipocalins and the pathogenesis-related proteins, are able to bind iron and either deprive or supply iron to immune cells. Thus, a locally induced iron deficiency will result in immune activation and allergic sensitization. However, the same proteins such as the whey protein beta-lactoglobulin can also transport this precious micronutrient to the host immune cells (holoBLG) and hinder their activation, promoting tolerance and protecting against allergy. Since 2019, several clinical trials have also been conducted in allergic subjects using holoBLG as a food for special medical purposes, leading to a reduction in the allergic symptom burden. Supplementation with nutrient-carrying lipocalin proteins can circumvent the mucosal block and nourish selectively immune cells, therefore representing a new dietary and causative approach to compensate for functional iron deficiency in allergy sufferers.

Calcium Supplement by Tetracycline guided amorphous Calcium Carbonate potentiates Osteoblast promotion for Synergetic Osteoporosis Therapy

Background: The calcium supplement is a clinically approved approach for osteoporosis therapy but usually requires a large dosage without targetability and with poor outcome. This modality is not fully explored in current osteoporosis therapy due to the lack of proper calcium supplement carrier.

Methods: In this study, we constructed a tetracycline (Tc) modified and simvastatin (Sim) loaded phospholipid-amorphous calcium carbonate (ACC) hybrid nanoparticle (Tc/ACC/Sim).

Results: The resulted Tc/ACC/Sim was able to enhance its accumulation at the osteoporosis site. Most importantly, the combination of calcium supplement and Sim offered synergetic osteoblast promotion therapy of osteoporosis with advanced performance than non-targeted system or mono therapy.

Conclusion: This platform provides an alternative approach to stimulate bone formation by synergetic promotion of osteoblast differentiation using calcium supplement and Sim.

Regulation of Iron Homeostasis and Related Diseases

The liver is the organ for iron storage and regulation; it senses circulating iron concentrations in the body through the BMP-SMAD pathway and regulates the iron intake from food and erythrocyte recovery into the bloodstream by secreting hepcidin. Under iron deficiency, hypoxia, and hemorrhage, the liver reduces the expression of hepcidin to ensure the erythropoiesis but increases the excretion of hepcidin during infection and inflammation to reduce the usage of iron by pathogens. Excessive iron causes system iron overload; it accumulates in never system and damages neurocyte leading to neurodegenerative diseases such as Parkinson's syndrome. When some gene mutations affect the perception of iron and iron regulation ability in the liver, then they decrease the expression of hepcidin, causing hereditary diseases such as hereditary hemochromatosis. This review summarizes the source and utilization of iron in the body, the liver regulates systemic iron homeostasis by sensing the circulating iron concentration, and the expression of hepcidin regulated by various signaling pathways, thereby understanding the pathogenesis of iron-related diseases.

Bone marrow niche crosses paths with BMPs: a road to protection and persistence in CML

Chronic myeloid leukaemia (CML) is a paradigm of precision medicine, being one of the first cancers to be treated with targeted therapy. This has revolutionised CML therapy and patient outcome, with high survival rates. However, this now means an ever-increasing number of patients are living with the disease on life-long tyrosine kinase inhibitor (TKI) therapy, with most patients anticipated to have near normal life expectancy. Unfortunately, in a significant number of patients, TKIs are not curative. This low-level disease persistence suggests that despite a molecularly targeted therapeutic approach, there are BCR-ABL1-independent mechanisms exploited to sustain the survival of a small cell population of leukaemic stem cells (LSCs). In CML, LSCs display many features akin to haemopoietic stem cells, namely quiescence, self-renewal and the ability to produce mature progeny, this all occurs through intrinsic and extrinsic signals within the specialised microenvironment of the bone marrow (BM) niche. One important avenue of investigation in CML is how the disease highjacks the BM, thereby remodelling this microenvironment to create a niche, which enables LSC persistence and resistance to TKI treatment. In this review, we explore how changes in growth factor levels, in particular, the bone morphogenetic proteins (BMPs) and pro-inflammatory cytokines, impact on cell behaviour, extracellular matrix deposition and bone remodelling in CML. We also discuss the challenges in targeting LSCs and the potential of dual targeting using combination therapies against BMP receptors and BCR-ABL1.

[Progress on epigenetic regulation of iron homeostasis]

Iron homeostasis plays an important role for the maintenance of human health. It is known that iron metabolism is tightly regulated by several key genes, including divalent metal transport-1(DMT1), transferrin receptor 1(TFR1), transferrin receptor 2(TFR2), ferroportin(FPN), hepcidin(HAMP), hemojuvelin(HJV) and Ferritin H. Recently, it is reported that DNA methylation, histone acetylation, and microRNA (miRNA) epigenetically regulated iron homeostasis. Among these epigenetic regulators, DNA hypermethylation of the promoter region of FPN, TFR2, HAMP, HJV and bone morphogenetic protein 6 (BMP6) genes result in inhibitory effect on the expression of these iron-related gene. In addition, histone deacetylase (HADC) suppresses HAMP gene expression. On the contrary, HADC inhibitor upregulates HAMP gene expression. Additional reports showed that miRNA can also modulate iron absorption, transport, storage and utilization via downregulation of DMT1, FPN, TFR1, TFR2, Ferritin H and other genes. It is noteworthy that some key epigenetic regulatory enzymes, such as DNA demethylase TET2 and histone lysine demethylase JmjC KDMs, require iron for the enzymatic activities. In this review, we summarize the recent progress of DNA methylation, histone acetylation and miRNA in regulating iron metabolism and also discuss the future research directions.

miR-130a-3p inhibition protects against renal fibrosis in vitro via the TGF-β1/Smad pathway by targeting SnoN

BACKGROUND

Renal fibrosis, a common pathological outcome of chronic kidney disease (CKD), is characterized by extracellular matrix (ECM) accumulation, damage to the tubular epithelium, and the proliferation and activation of fibroblasts. SnoN, a TGF-β1/Smad transcriptional co-suppressor, is downregulated in obstructive nephropathy. However, the relationship between miR-130a-3p and SnoN expression in the regulation of renal fibrosis is still unknown.

METHODS

We used human renal proximal tubular epithelial cells (HRPTEpiCs, HK-2 and primary HRPTEpiCs) treated with TGF-β1 to establish an in vitro renal fibrosis model. The expression of miR-130a-3p, SnoN and other proteins related to epithelial mesenchymal transition (EMT) and TGF-β1/Smad signalling was investigated by western blotting or qRT-PCR. A luciferase reporter assay was conducted to confirm the interaction of SnoN mRNA and miR-130a-3p. The translocation of p-Smad 2/3 and Smad 7 was determined using immunofluorescence staining.

RESULTS

After TGF-β1 treatment, miR-130a-3p was highly expressed in renal tubular epithelial cells, while SnoN was poorly expressed. The cell morphology changed to fibroblast-like, indicating evidence of EMT. The levels of EMT and fibrosis-related proteins were decreased through miR-130a-3p inhibition. Additionally, miR-130a-3p acted upon the 3'-UTR of SnoN directly to suppress SnoN expression. Furthermore, miR-130a-3p/SnoN promoted the activation of TGF-β1/Smad signalling, as revealed by p-Smad 2/3 and Smad 7 expression levels and distribution patterns.

CONCLUSION

Our study verified that miR-130a-3p facilitates the TGF-β1/Smad pathway in renal tubular epithelial cells and may participate in renal fibrosis by targeting SnoN, which could be a possible strategy for renal fibrosis treatment.

Expression and Functional Analysis of Hepcidin from Mandarin Fish (Siniperca chuatsi)

Hepcidin is a liver-derived peptide hormone that is related to iron balance and immunity in humans. However, its function in Siniperca chuatsi has not been well elucidated. In this study, we analyzed the expression and function of the S. chuatsi hepcidin (Sc-hep) gene. Sc-hep was specifically expressed in the liver and appeared to be one of the most highly expressed genes in the liver. After spleen and kidney necrosis virus (ISKNV) infection and lipopolysaccharide (LPS) and polyinosinic—polycytidylic acid (Poly I:C) stimulation, the expression of Sc-hep in the liver increased by approximately 110, 6500, and 225 times, respectively. After ferrous sulfate (FS) injection, the expression of Sc-hep in the liver increased approximately 520-fold. We found that miR-19c-5p could inhibit Sc-hep expression. Five CpG dinucleotides distributed in the promoter region showed no differential methylation between the liver and the stomach, both presenting high methylation rates. After FS or LPS injection, the expression of three iron balance-related genes (FPN1, TFR1, and FTN) and five immune-related cytokine genes (IL-1β, IL8, TNF-α, TLR22, and SOCS3) significantly changed. These results indicate that Sc-hep participates in the regulation of iron balance and plays an important role in the immune system. Sc-hep increased approximately 52-fold when mandarin fish were domesticated with artificial diets. Sc-hep might be used as a real-time biomarker of mandarin fish liver because its expression markedly varies under different physiological conditions.

Targeting heterotopic ossification by inhibiting activin receptor‑like kinase 2 function (Review)

Heterotopic ossification (HO) refers to the appearance of osteoblasts in soft tissues under pathological conditions, such as trauma or infection. HO arises in an unpredictable way without any recognizable initiation. Activin receptor-like kinase-2 (ALK2) is a type I cell surface receptor for bone morphogenetic proteins (BMPs). The dysregulation of ALK2 signaling is associated with a variety of diseases, including cancer and HO. At present, the prevention and treatment of HO in the clinic predominantly includes nonsteroidal anti-inflammatory drugs (NSAIDs), bisphosphonates and other drug treatments, low-dose local radiation therapy and surgical resection, rehabilitation treatment and physical therapy. However, most of these therapies have adverse effects. These methods do not prevent the occurrence of HO. The pathogenesis of HO is not being specifically targeted; the current treatment strategies target the symptoms, not the disease. These treatments also cannot solve the fundamental problem of the occurrence of HO. Therefore, scholars have been working to develop targeted therapies based on the pathogenesis of HO. The present review focuses on advances in the understanding of the underlying mechanisms of HO, and possible options for the prevention and treatment of HO. In addition, the role of ALK2 in the process of HO is introduced and the progress made towards the targeted inhibition of ALK2 is discussed. The present study aims to offer a platform for further research on possible targets for the prevention and treatment of HO.

Molecular perspective of iron uptake, related diseases, and treatments

Iron deficiency anemia and anemia of chronic disorders are the most common types of anemia. Disorders of iron metabolism lead to different clinical scenarios such as iron deficiency anemia, iron overload, iron overload with cataract and neurocognitive disorders. Regulation of iron in the body is a complex process and different regulatory proteins are involved in iron absorption and release from macrophages into hematopoietic tissues. Mutation in these regulatory genes is the most important cause of iron refractory iron deficiency anemia (IRIDA). This review provides a glance into the iron regulation process, diseases related to iron metabolism, and appropriate treatments at the molecular level.

Hepcidin and the BMP-SMAD pathway: An unexpected liaison

Hepcidin, the main regulator of iron metabolism, is synthesized and released by hepatocytes in response to increased body iron concentration and inflammation. Deregulation of hepcidin expression is a common feature of genetic and acquired iron disorders: in Hereditary Hemochromatosis (HH) and iron-loading anemias low hepcidin causes iron overload, while in Iron Refractory Iron Deficiency Anemia (IRIDA) and anemia of inflammation (AI), high hepcidin levels induce iron-restricted erythropoiesis. Hepcidin expression in the liver is mainly controlled by the BMP-SMAD pathway, activated in a paracrine manner by BMP2 and BMP6 produced by liver sinusoidal endothelial cells. The BMP type I receptors ALK2 and ALK3 are responsible for iron-dependent hepcidin upregulation and basal hepcidin expression, respectively. Characterization of animal models with genetic inactivation of the key components of the pathway has suggested the existence of two BMP/SMAD pathway branches: the first ALK3 and HH proteins dependent, responsive to BMP2 for basal hepcidin activation, and the second ALK2 dependent, activated by BMP6 in response to increased tissue iron. The erythroid inhibitor of hepcidin Erythroferrone also impacts on the liver BMP-SMAD pathway although its effect is blunted by pathway hyper-activation. The liver BMP-SMAD pathway is required also in inflammation to cooperate with JAK2/STAT3 signaling for full hepcidin activation. Pharmacologic targeting of BMP-SMAD pathway components or regulators may improve the outcome of both genetic and acquired disorders of iron overload and deficiency by increasing or inhibiting hepcidin expression.

Circulating plasma microRNAs as biomarkers for iron status in blood donors

OBJECTIVES

To investigate whether microRNAs can serve as biomarkers for iron status in blood donors.

BACKGROUND

Serum ferritin is a widely used biochemical test for detecting iron deficiency, but it has its limitations. Certain microRNAs (miRNAs) reportedly have a role in regulating iron homeostasis. Circulating miRNAs have been reported as potential biomarkers for various conditions but have not yet been studied in iron deficiency.

METHODS

Participating blood donors were divided into two groups: high ferritin (HF) (>150 µg L^-1 ) and low ferritin (LF) (<15 µg L^-1 ). MiRNA analysis was performed by an miRNA profiling service (Exiqon) using commercial qPCR assays. The study had two phases: (i) a pilot study (20 participants) where 179 miRNAs were analysed and (ii) a confirmation study (50 participants) of 13 selected miRNAs.

RESULTS

Mean serum ferritin was 13·8 µg L^-1 in the LF arm compared to 231 µg L^-1 in the HF group (P < 0·001). Hepcidin plasma levels were higher in the HF arm (P < 0·001), whereas soluble transferrin receptor 1 was higher in the LF group (P < 0·001). In the pilot study, samples did not separate according to study group on unsupervised analysis. When directly comparing HF vs LF groups, 17 miRNAs were differentially expressed (P < 0·05, t-test) but did not pass correction for multiple testing. The confirmation study of 13 selected miRNAs verified these findings as no miRNA was significantly different between the study groups.

CONCLUSION

In this study, circulating plasma miRNAs did not emerge as promising biomarkers for iron status in healthy individuals. However, in the future, alternative detection methods such as next-generation sequencing might indicate miRNAs that correlate with iron stores.

The Horizon of a Therapy for Rare Genetic Diseases: A "Druggable" Future for Fibrodysplasia Ossificans Progressiva

Fibrodysplasia ossificans progressiva (FOP) is a rare genetic condition characterized by progressive extra-skeletal ossification leading to cumulative and severe disability. FOP has an extremely variable and episodic course and can be induced by trauma, infections, iatrogenic harms, immunization or can occur in an unpredictable way, without any recognizable trigger. The causative gene is ACVR1, encoding the Alk-2 type I receptor for bone morphogenetic proteins (BMPs). The signaling is initiated by BMP binding to a receptor complex consisting of type I and II molecules and can proceed into the cell through two main pathways, a canonical, SMAD-dependent signaling and a p38-mediated cascade. Most FOP patients carry the recurrent R206H substitution in the receptor Glycine-Serine rich (GS) domain, whereas a few other mutations are responsible for a limited number of cases. Mutations cause a dysregulation of the downstream BMP-dependent pathway and make mutated ACVR1 responsive to a non-canonical ligand, Activin A. There is no etiologic treatment for FOP. However, many efforts are currently ongoing to find specific therapies targeting the receptor activity and the downstream aberrant pathway at different levels or targeting cellular components and/or processes that are important in modifying the local environment leading to bone neo-formation.

MicroRNA-130a regulates chondrocyte proliferation and alleviates osteoarthritis through PTEN/PI3K/Akt signaling pathway

The function of microRNA‑130a in development and progression of osteoarthritis was determined. In osteoarthritis patients, the serum levels of microRNA‑130a were decreased, compared with normal group. Overexpression of microRNA‑130a increased cell proliferation and decreased apoptosis of chondrocytes, and downregulation of microRNA‑130a also decreased cell proliferation and induced apoptosis in chondrocytes. Downregulation of microRNA‑130a promoted Bax and caspase‑3/9 protein expression, increased inflammation divisors and suppressed the PTEN/PI3K/Akt signaling pathway. PTEN inhibitor, VO‑Ohpic trihydrate increased the destructive effect of microRNA‑130a on cell proliferation of chondrocytes. PI3K inhibitor, wortmannin also increased the destructive effect of microRNA‑130a on osteoarthritis. In conclusion, microRNA‑130a is an important regulator of osteoarthritis in chondrocytes through PTEN/PI3K/Akt signaling pathway.

miR-208a-3p Suppresses Osteoblast Differentiation and Inhibits Bone Formation by Targeting ACVR1

Emerging evidence indicates that many microRNAs (miRNAs) are indispensable regulators of osteoblast differentiation and bone formation. However, the role of miRNAs in mechanotransduction of osteoblasts remains to be elucidated. This study aimed to identify a mechanosensitive miRNA that regulates Activin A receptor type I (ACVR1)-induced osteogenic differentiation. After 4 weeks of hindlimb unloading (HLU) suspension of 6-month-old male C57BL/6J mice, femurs and tibias were harvested to extract total bone RNAs. Elevated levels of miR-208a-3p correlated with a lower degree of bone formation in whole-bone samples of HLU mice. However, in vitro overexpression of miR-208a-3p inhibited osteoblast differentiation, whereas silencing of miR-208a-3p by antagomiR-208a-3p promoted expression of osteoblast activity, bone formation marker genes, and matrix mineralization under mechanical unloading condition. Bioinformatics analysis and a luciferase assay revealed that ACVR1 is a target gene of miR-208a-3p that negatively regulates osteoblast differentiation under mechanical unloading environment. Further, this study also demonstrates that in vivo pre-treatment with antagomiR-208a-3p led to an increase in bone formation and trabecular microarchitecture and partly rescued the bone loss caused by mechanical unloading. Collectively, these results suggest that in vivo, inhibition of miRNA-208a-3p by antagomiR-208a-3p may be a potential therapeutic strategy for ameliorating bone loss.

Bone morphogenetic protein 2 controls iron homeostasis in mice independent of Bmp6

Hepcidin is a key iron regulatory hormone that controls expression of the iron exporter ferroportin to increase the iron supply when needed to support erythropoiesis and other essential functions, but to prevent the toxicity of iron excess. The bone morphogenetic protein (BMP)-SMAD signaling pathway, through the ligand BMP6 and the co-receptor hemojuvelin, is a central regulator of hepcidin transcription in the liver in response to iron. Here, we show that dietary iron loading has a residual ability to induce Smad signaling and hepcidin expression in Bmp6-/- mice, effects that are blocked by a neutralizing BMP2/4 antibody. Moreover, BMP2/4 antibody inhibits hepcidin expression and induces iron loading in wildtype mice, whereas a BMP4 antibody has no effect. Bmp2 mRNA is predominantly expressed in endothelial cells of the liver, where its baseline expression is higher, but its induction by iron is less robust than Bmp6. Mice with a conditional ablation of Bmp2 in endothelial cells exhibit hepcidin deficiency, serum iron overload, and tissue iron loading in liver, pancreas and heart, with reduced spleen iron. Together, these data demonstrate that in addition to BMP6, endothelial cell BMP2 has a non-redundant role in hepcidin regulation by iron.

Large G protein α-subunit XLαs limits clathrin-mediated endocytosis and regulates tissue iron levels in vivo

Alterations in the activity/levels of the extralarge G protein α-subunit (XLαs) are implicated in various human disorders, such as perinatal growth retardation. Encoded by GNAS, XLαs is partly identical to the α-subunit of the stimulatory G protein (Gsα), but the cellular actions of XLαs remain poorly defined. Following an initial proteomic screen, we identified sorting nexin-9 (SNX9) and dynamins, key components of clathrin-mediated endocytosis, as binding partners of XLαs. Overexpression of XLαs in HEK293 cells inhibited internalization of transferrin, a process that depends on clathrin-mediated endocytosis, while its ablation by CRISPR/Cas9 in an osteocyte-like cell line (Ocy454) enhanced it. Similarly, primary cardiomyocytes derived from XLαs knockout (XLKO) pups showed enhanced transferrin internalization. Early postnatal XLKO mice showed a significantly higher degree of cardiac iron uptake than wild-type littermates following iron dextran injection. In XLKO neonates, iron and ferritin levels were elevated in heart and skeletal muscle, where XLαs is normally expressed abundantly. XLKO heart and skeletal muscle, as well as XLKO Ocy454 cells, showed elevated SNX9 protein levels, and siRNA-mediated knockdown of SNX9 in XLKO Ocy454 cells prevented enhanced transferrin internalization. In transfected cells, XLαs also inhibited internalization of the parathyroid hormone and type 2 vasopressin receptors. Internalization of transferrin and these G protein-coupled receptors was also inhibited in cells expressing an XLαs mutant missing the Gα portion, but not Gsα or an N-terminally truncated XLαs mutant unable to interact with SNX9 or dynamin. Thus, XLαs restricts clathrin-mediated endocytosis and plays a critical role in iron/transferrin uptake in vivo.

Identification and Characterization of MicroRNAs in the Liver of Blunt Snout Bream (Megalobrama amblycephala) Infected by Aeromonas hydrophila

MicroRNAs (miRNAs) are small RNA molecules that play key roles in regulation of various biological processes. In order to better understand the biological significance of miRNAs in the context of Aeromonas hydrophila infection in Megalobrama amblycephala, small RNA libraries obtained from fish liver at 0 (non-infection), 4, and 24 h post infection (poi) were sequenced using Illumina deep sequencing technology. A total of 11,244,207, 9,212,958, and 7,939,157 clean reads were obtained from these three RNA libraries, respectively. Bioinformatics analysis identified 171 conserved miRNAs and 62 putative novel miRNAs. The existence of ten randomly selected novel miRNAs was validated by RT-PCR. Pairwise comparison suggested that 61 and 44 miRNAs were differentially expressed at 4 and 24 h poi, respectively. Furthermore, the expression profiles of nine randomly selected miRNAs were validated by qRT-PCR. MicroRNA target prediction, gene ontology (GO) annotation, and Kyoto Encylopedia of Genes and Genomes (KEGG) analysis indicated that a variety of biological pathways could be affected by A. hydrophila infection. Additionally, transferrin (TF) and transferrin receptor (TFR) genes were confirmed to be direct targets of miR-375. These results will expand our knowledge of the role of miRNAs in the immune response of M. amblycephala to A. hydrophila infection, and facilitate the development of effective strategies against A. hydrophila infection in M. amblycephala.

Endothelial cells produce bone morphogenetic protein 6 required for iron homeostasis in mice

Bone morphogenetic protein 6 (BMP6) signaling in hepatocytes is a central transcriptional regulator of the iron hormone hepcidin that controls systemic iron balance. How iron levels are sensed to regulate hepcidin production is not known, but local induction of liver BMP6 expression by iron is proposed to have a critical role. To identify the cellular source of BMP6 responsible for hepcidin and iron homeostasis regulation, we generated mice with tissue-specific ablation of Bmp6 in different liver cell populations and evaluated their iron phenotype. Efficiency and specificity of Cre-mediated recombination was assessed by using Cre-reporter mice, polymerase chain reaction of genomic DNA, and quantitation of Bmp6 messenger RNA expression from isolated liver cell populations. Localization of the BMP co-receptor hemojuvelin was visualized by immunofluorescence microscopy. Analysis of the Bmp6 conditional knockout mice revealed that liver endothelial cells (ECs) expressed Bmp6, whereas resident liver macrophages (Kupffer cells) and hepatocytes did not. Loss of Bmp6 in ECs recapitulated the hemochromatosis phenotype of global Bmp6 knockout mice, whereas hepatocyte and macrophage Bmp6 conditional knockout mice exhibited no iron phenotype. Hemojuvelin was localized on the hepatocyte sinusoidal membrane immediately adjacent to Bmp6-producing sinusoidal ECs. Together, these data demonstrate that ECs are the predominant source of BMP6 in the liver and support a model in which EC BMP6 has paracrine actions on hepatocyte hemojuvelin to regulate hepcidin transcription and maintain systemic iron homeostasis.

TGF-β Signaling from Receptors to Smads

Transforming growth factor β (TGF-β) and related growth factors are secreted pleiotropic factors that play critical roles in embryogenesis and adult tissue homeostasis by regulating cell proliferation, differentiation, death, and migration. The TGF-β family members signal via heteromeric complexes of type I and type II receptors, which activate members of the Smad family of signal transducers. The main attribute of the TGF-β signaling pathway is context-dependence. Depending on the concentration and type of ligand, target tissue, and developmental stage, TGF-β family members transmit distinct signals. Deregulation of TGF-β signaling contributes to developmental defects and human diseases. More than a decade of studies have revealed the framework by which TGF-βs encode a context-dependent signal, which includes various positive and negative modifiers of the principal elements of the signaling pathway, the receptors, and the Smad proteins. In this review, we first introduce some basic components of the TGF-β signaling pathways and their actions, and then discuss posttranslational modifications and modulatory partners that modify the outcome of the signaling and contribute to its context-dependence, including small noncoding RNAs.

Signaling Receptors for TGF-β Family Members

Transforming growth factor β (TGF-β) family members signal via heterotetrameric complexes of type I and type II dual specificity kinase receptors. The activation and stability of the receptors are controlled by posttranslational modifications, such as phosphorylation, ubiquitylation, sumoylation, and neddylation, as well as by interaction with other proteins at the cell surface and in the cytoplasm. Activation of TGF-β receptors induces signaling via formation of Smad complexes that are translocated to the nucleus where they act as transcription factors, as well as via non-Smad pathways, including the Erk1/2, JNK and p38 MAP kinase pathways, and the Src tyrosine kinase, phosphatidylinositol 3'-kinase, and Rho GTPases.

The Repair of Skeletal Muscle Requires Iron Recycling through Macrophage Ferroportin

Macrophages recruited at the site of sterile muscle damage play an essential role in the regeneration of the tissue. In this article, we report that the selective disruption of macrophage ferroportin (Fpn) results in iron accumulation within muscle-infiltrating macrophages and jeopardizes muscle healing, prompting fat accumulation. Macrophages isolated from the tissue at early time points after injury express ferritin H, CD163, and hemeoxygenase-1, indicating that they can uptake heme and store iron. At later time points they upregulate Fpn expression, thus acquiring the ability to release the metal. Transferrin-mediated iron uptake by regenerating myofibers occurs independently of systemic iron homeostasis. The inhibition of macrophage iron export via the silencing of Fpn results in regenerating muscles with smaller myofibers and fat accumulation. These results highlight the existence of a local pathway of iron recycling that plays a nonredundant role in the myogenic differentiation of muscle precursors, limiting the adipose degeneration of the tissue.

A Survey of Strategies to Modulate the Bone Morphogenetic Protein Signaling Pathway: Current and Future Perspectives

Bone morphogenetic proteins (BMPs) constitute the largest subdivision of the TGF-β family of ligands and are unequivocally involved in regulating stem cell behavior. Appropriate regulation of canonical BMP signaling is critical for the development and homeostasis of numerous human organ systems, as aberrations in the BMP pathway or its regulation are increasingly associated with diverse human pathologies. In this review, we provide a wide-perspective on strategies that increase or decrease BMP signaling. We briefly outline the current FDA-approved approaches, highlight emerging next-generation technologies, and postulate prospective avenues for future investigation. We also detail how activating other pathways may indirectly modulate BMP signaling, with a particular emphasis on the relationship between the BMP and Activin/TGF-β pathways.

Activin B Induces Noncanonical SMAD1/5/8 Signaling via BMP Type I Receptors in Hepatocytes: Evidence for a Role in Hepcidin Induction by Inflammation in Male Mice

Induction of the iron regulatory hormone hepcidin contributes to the anemia of inflammation. Bone morphogenetic protein 6 (BMP6) signaling is a central regulator of hepcidin expression in the liver. Recently, the TGF-β/BMP superfamily member activin B was implicated in hepcidin induction by inflammation via noncanonical SMAD1/5/8 signaling, but its mechanism of action and functional significance in vivo remain uncertain. Here, we show that low concentrations of activin B, but not activin A, stimulate prolonged SMAD1/5/8 signaling and hepcidin expression in liver cells to a similar degree as canonical SMAD2/3 signaling, and with similar or modestly reduced potency compared with BMP6. Activin B stimulates hepcidin via classical activin type II receptors ACVR2A and ACVR2B, noncanonical BMP type I receptors activin receptor-like kinase 2 and activin receptor-like kinase 3, and SMAD5. The coreceptor hemojuvelin binds to activin B and facilitates activin B-SMAD1/5/8 signaling. Activin B-SMAD1/5/8 signaling has some selectivity for hepatocyte-derived cells and is not enabled by hemojuvelin in other cell types. Liver activin B mRNA expression is up-regulated in multiple mouse models of inflammation associated with increased hepcidin and hypoferremia, including lipopolysaccharide, turpentine, and heat-killed Brucella abortus models. Finally, the activin inhibitor follistatin-315 blunts hepcidin induction by lipopolysaccharide or B. abortus in mice. Our data elucidate a novel mechanism for noncanonical SMAD activation and support a likely functional role for activin B in hepcidin stimulation during inflammation in vivo.

MiR-130a-3p regulates cell migration and invasion via inhibition of Smad4 in gemcitabine resistant hepatoma cells

Background

Emerging evidence demonstrates that microRNAs (miRNAs) play an important role in regulation of cell growth, invasion and metastasis through inhibiting the expression of their targets. It has been reported that miR-130a-3p controls cell growth, migration and invasion in a variety of cancer cells. However, it is unclear whether miR-130a-3p regulates epithelial-mesenchymal transition (EMT) in drug resistant cancer cells. Therefore, in the current study, we explore the role and molecular mechanisms of miR-130a-3p in gemcitabine resistant (GR) hepatocellular carcinoma (HCC) cells.

Methods

The real-time RT-PCR was used to measure the miR-130a-3p expression in GR HCC cells compared with their parental cells. The wound healing assay was conducted to determine the cell migratory activity in GR HCC cells treated with miR-130a-3p mimics. The migration and invasion assays were also performed to explore the role of miR-130a-3p in GR HCC cells. Western blotting analysis was used to measure the expression of Smad4, E-cadherin, Vimentin, and MMP-2 in GR HCC cells after depletion of Smad4. The luciferase assay was conducted to validate whether Smad4 is a target of miR-130a-3p. The student t-test was used to analyze our data.

Results

We found the down-regulation of miR-130a-3p in GR HCC cells. Moreover, we validate the Smad4 as a potential target of miR-130a-3p. Furthermore, overexpression of miR-130a-3p suppressed Smad4 expression, whereas inhibition of miR-130a-3p increased Smad4 expression. Consistently, overexpression of miR-130a-3p or down-regulation of Smad4 suppressed the cell detachment, attachment, migration, and invasion in GR HCC cells.

Conclusions

Our findings provide a molecular insight on understanding drug resistance in HCC cells. Therefore, activation of miR-130a-3p or inactivation of Smad4 could be a novel approach for the treatment of HCC.

Iron and the liver

Humans have evolved to retain iron in the body and are exposed to a high risk of iron overload and iron-related toxicity. Excess iron in the blood, in the absence of increased erythropoietic needs, can saturate the buffering capacity of serum transferrin and result in non-transferrin-bound highly reactive forms of iron that can cause damage, as well as promote fibrogenesis and carcinogenesis in the parenchymatous organs. A number of hereditary or acquired diseases are associated with systemic or local iron deposition or iron misdistribution in organs or cells. Two of these, the HFE- and non-HFE hemochromatosis syndromes represent the paradigms of genetic iron overload. They share common clinical features and the same pathogenic basis, in particular, a lack of synthesis or activity of hepcidin, the iron hormone. Before hepcidin was discovered, the liver was simply regarded as the main site of iron storage and, as such, the main target of iron toxicity. Now, as the main source of hepcidin, it appears that the loss of the hepcidin-producing liver mass or genetic and acquired factors that repress hepcidin synthesis in the liver may also lead to iron overload. Usually, there is low-grade excess iron which, through oxidative stress, is sufficient to worsen the course of the underlying liver disease or other chronic diseases that are apparently unrelated to iron, such as chronic metabolic and cardiovascular diseases. In the future, modulation of hepcidin synthesis and activity or hepcidin hormone-replacing strategies may become therapeutic options to cure iron-related disorders.

Saturated fatty acids induce post-transcriptional regulation of HAMP mRNA via AU-rich element-binding protein, human antigen R (HuR)

Iron is implicated in fatty liver disease pathogenesis. The human hepcidin gene, HAMP, is the master switch of iron metabolism. The aim of this study is to investigate the regulation of HAMP expression by fatty acids in HepG2 cells. For these studies, both saturated fatty acids (palmitic acid (PA) and stearic acid (SA)) and unsaturated fatty acid (oleic acid (OA)) were used. PA and, to a lesser extent, SA, but not OA, up-regulated HAMP mRNA levels, as determined by real-time PCR. To understand whether PA regulates HAMP mRNA at the transcriptional or post-transcriptional level, the transcription inhibitor actinomycin D was employed. PA-mediated induction of HAMP mRNA expression was not blocked by actinomycin D. Furthermore, PA activated HAMP 3'-UTR, but not promoter, activity, as shown by reporter assays. HAMP 3'-UTR harbors a single AU-rich element (ARE). Mutation of this ARE abolished the effect of PA, suggesting the involvement of ARE-binding proteins. The ARE-binding protein human antigen R (HuR) stabilizes mRNA through direct interaction with AREs on 3'-UTR. HuR is regulated by phosphorylation-mediated nucleo-cytoplasmic shuttling. PA activated this process. The binding of HuR to HAMP mRNA was also induced by PA in HepG2 cells. Silencing of HuR by siRNA abolished PA-mediated up-regulation of HAMP mRNA levels. PKC is known to phosphorylate HuR. Staurosporine, a broad-spectrum PKC inhibitor, inhibited both PA-mediated translocation of HuR and induction of HAMP expression. Similarly, rottlerin, a novel class PKC inhibitor, abrogated PA-mediated up-regulation of HAMP expression. In conclusion, lipids mediate post-transcriptional regulation of HAMP throughPKC- and HuR-dependent mechanisms.

An overview of molecular basis of iron metabolism regulation and the associated pathologies

Iron is essential for several vital biological processes. Its deficiency or overload drives to the development of several pathologies. To maintain iron homeostasis, the organism controls the dietary iron absorption by enterocytes, its recycling by macrophages and storage in hepatocytes. These processes are mainly controlled by hepcidin, a liver-derived hormone which synthesis is regulated by iron levels, inflammation, infection, anemia and erythropoiesis. Besides the systemic regulation of iron metabolism mediated by hepcidin, cellular regulatory processes also occur. Cells are able to regulate themselves the expression of the iron metabolism-related genes through different post-transcriptional mechanisms, such as the alternative splicing, microRNAs, the IRP/IRE system and the proteolytic cleavage. Whenever those mechanisms are disturbed, due to genetic or environmental factors, iron homeostasis is disrupted and iron related pathologies may arise.

Identification of reference microRNAs for quantitative expression analysis in porcine peripheral blood mononuclear cells treated with polyinosinic-polycytidylic acid

Peripheral blood mononuclear cells (PBMCs) are clinically important cells. Detection of microRNAs (miRNAs) expression in PBMCs can be useful for miRNA biomarker discovery for various diseases. Quantitative real-time PCR (qRT-PCR) has become an important method used for measuring miRNAs expression. However, the reliability of qRT-PCR data critically depends on proper selection of reference genes. Here, we performed qRT-PCR to quantify the expression levels of nine miRNAs (Ssc-miR-16, Hsa-miR-25, Ssc-miR-34a, Hsa-miR-93, Bta-miR-92b, Ssc-miR-103, Ssc-miR-106a, Ssc-miR-128 and Ssc-miR-107) and one small nuclear RNA (U6) in PBMCs treated with polyinosinic-polycytidylic acid [poly (I:C)] that widely used for simulating viral infection. We used the four statistical algorithms (GeNorm 3.5, NormFinder, BestKeeper and comparative ∆ Ct method) to evaluate gene expression stability and observed that Ssc-miR-34a was the best single reference gene and the pair of Ssc-miR-107 and Ssc-miR-103 was the best combination of reference miRNAs for porcine PBMCs treated with poly (I:C). Our study shows the first evidence of careful selection of reference miRNAs in porcine PBMCs and maybe helpful for discovering miRNA biomarkers for double-stranded RNA-induced disease.