GDF11 contributes to hepatic hepcidin (HAMP) inhibition through SMURF1-mediated BMP-SMAD signalling suppression

Serum Iron Overload Activates the SMAD Pathway and Hepcidin Expression of Hepatocytes via SMURF1

Background and Aims

Liver iron overload can induce hepatic expression of bone morphogenic protein (BMP) 6 and activate the BMP/SMAD pathway. However, serum iron overload can also activate SMAD but does not induce BMP6 expression. Therefore, the mechanisms through which serum iron overload activates the BMP/SMAD pathway remain unclear. This study aimed to clarify the role of SMURF1 in serum iron overload and the BMP/SMAD pathway.

Methods

A cell model of serum iron overload was established by treating hepatocytes with 2 mg/mL of holo-transferrin (Holo-Tf). A serum iron overload mouse model and a liver iron overload mouse model were established by intraperitoneally injecting 10 mg of Holo-Tf into C57BL/6 mice and administering a high-iron diet for 1 week followed by a low-iron diet for 2 days. Western blotting and real-time PCR were performed to evaluate the activation of the BMP/SMAD pathway and the expression of hepcidin.

Results

Holo-Tf augmented the sensitivity and responsiveness of hepatocytes to BMP6. The E3 ubiquitin-protein ligase SMURF1 mediated Holo-Tf-induced SMAD1/5 activation and hepcidin expression; specifically, SMURF1 expression dramatically decreased when the serum iron concentration was increased. Additionally, the expression of SMURF1 substrates, which are important molecules involved in the transduction of BMP/SMAD signaling, was significantly upregulated. Furthermore, in vivo analyses confirmed that SMURF1 specifically regulated the BMP/SMAD pathway during serum iron overload.

Conclusions

SMURF1 can specifically regulate the BMP/SMAD pathway by augmenting the responsiveness of hepatocytes to BMPs during serum iron overload.

A deep dive into future therapies for microcytic anemias and clinical considerations

INTRODUCTION

Microcytic anemias (MA) have frequent or rare etiologies. New discoveries in understanding and treatment of microcytic anemias need to be reviewed.

AREAS COVERED

Microcytic anemias with a focus on most frequent causes and on monogenic diseases that are relevant for understanding biocellular mechanisms of MA. All treatments excepting gene therapy, with a focus on recent advances. Pubmed search with references selected by expert opinion.

EXPERT OPINION

As the genetic and cellular background of dyserythropoiesis will continue to be clarified, collaboration with bioengineering of treatments acting specifically at the protein domain level will continue to provide new therapies in haematology as well as oncology and neurology.

Assessment of Diagnosis, Prognosis and Immune Infiltration Response to the Expression of the Ferroptosis-Related Molecule HAMP in Clear Cell Renal Cell Carcinoma

BACKGROUND

Hepcidin antimicrobial peptide (HAMP) is a key factor in maintaining iron metabolism, which may induce ferroptosis when upregulated. However, its prognostic value and relation to immune infiltrating cells remains unclear.

METHODS

This study analyzed the expression levels of HAMP in the Oncomine, Timer and Ualcan databases, and examined its prognostic potential in KIRC with R programming. The Timer and GEPIA databases were used to estimate the correlations between HAMP and immune infiltration and the markers of immune cells. The intersection genes and the co-expression PPI network were constructed via STRING, R programming and GeneMANIA, and the hub genes were selected with Cytoscape. In addition, we analyzed the gene set enrichment and GO/KEGG pathways by GSEA.

RESULTS

Our study revealed higher HAMP expression levels in tumor tissues including KIRC, which were related to poor prognosis in terms of OS, DSS and PFI. The expression of HAMP was positively related to the immune infiltration level of macrophages, Tregs, etc., corresponding with the immune biomarkers. Based on the intersection genes, we constructed the PPI network and used the 10 top hub genes. Further, we performed a pathway enrichment analysis of the gene sets, including Huntington's disease, the JAK-STAT signaling pathway, ammonium ion metabolic process, and so on.

CONCLUSION

In summary, our study gave an insight into the potential prognosis of HAMP, which may act as a diagnostic biomarker and therapeutic target related to immune infiltration in KIRC.

The hepatic effects of GDF11 on health and disease

The growth differentiation factor 11 (GDF11), a member of the superfamily of the transforming growth factor β, has gained relevance in the last few years due to its remarkable effects in cellular biology, particularly in the nervous system, skeletal muscle, the heart, and many epithelial tissues. Some controversies have been raised about this growth factor. Many of them have been related to technical factors but also the nature of the cellular target. In liver biology and pathobiology, the GDF11 has shown to be related in many molecular aspects, with a significant impact on the physiology and the initiation and progression of the natural history of liver diseases. GDF11 has been involved as a critical regulator in lipid homeostasis, which, as it is well known, is the first step in the progression of liver disease. However, also it has been reported that the GDF11 is involved in fibrosis, senescence, and cancer. Although there are some controversies, much of the literature indicates that GDF11 displays effects tending to solve or mitigate pathological states of the liver, with reasonable evidence of correlation with other organs or systems. To a large extent, the controversy, as mentioned, is due to technical problems, such as the specificity of GDF11 antibodies, confusion with its closer family member, myostatin, and the state of differentiation in the tissues. In the present work, we reviewed the specific effects of GDF11 in the biology and pathobiology of the liver as a potential and promising factor for therapeutic intervention shortly.

The addition of oral iron improves chemotherapy-induced anemia in patients receiving erythropoiesis-stimulating agents

Although many studies have shown that supplementation with iron and erythropoiesis-stimulating agents (ESA) is frequently used for managing chemotherapy-induced anemia (CIA), optimal combination therapy using these agents together to ameliorate anemia is not well characterized. To assess the effects of ESA combined with oral or intravenous (IV) iron on relieving CIA, PubMed, Cochrane Library, Embase, China National Knowledge Infrastructure (CNKI) were searched for articles. Data collected in the articles were meta-analyzed using RevMan 5.3 software with a random-effects model. Our comprehensive search yielded 1666 potentially relevant trials. A total of 41 trials randomizing 4200 patients with CIA fulfilled inclusion criteria, including 34 Chinese articles and 7 English articles. Meta-analysis showed that treatment with both ESA and iron more effectively improved CIA relative to iron supplementation alone, with increased hemoglobin, hematocrit, red blood cell count and haematopoietic response rate. Subgroup analyses revealed iron administration, both oral and IV iron, improved anemia in ESA-treated cancer patients with CIA. Our analysis demonstrates that iron supplementation combined with ESA more effectively ameliorates CIA relative to iron supplementation alone, without regard to whether IV or oral iron was used. Together, our findings may contribute to the clinical treatment of CIA using iron therapy with or without ESA. This article is protected by copyright. All rights reserved.

Identifying In Vitro Cultured Human Hepatocytes Markers with Machine Learning Methods Based on Single-Cell RNA-Seq Data

Cell transplantation is an effective method for compensating for the loss of liver function and improve patient survival. However, given that hepatocytes cultivated in vitro have diverse developmental processes and physiological features, obtaining hepatocytes that can properly function in vivo is difficult. In the present study, we present an advanced computational analysis on single-cell transcriptional profiling to resolve the heterogeneity of the hepatocyte differentiation process in vitro and to mine biomarkers at different periods of differentiation. We obtained a batch of compressed and effective classification features with the Boruta method and ranked them using the Max-Relevance and Min-Redundancy method. Some key genes were identified during the in vitro culture of hepatocytes, including CD147, which not only regulates terminally differentiated cells in the liver but also affects cell differentiation. PPIA, which encodes a CD147 ligand, also appeared in the identified gene list, and the combination of the two proteins mediated multiple biological pathways. Other genes, such as TMSB10, TMEM176B, and CD63, which are involved in the maturation and differentiation of hepatocytes and assist different hepatic cell types in performing their roles were also identified. Then, several classifiers were trained and evaluated to obtain optimal classifiers and optimal feature subsets, using three classification algorithms (random forest, k-nearest neighbor, and decision tree) and the incremental feature selection method. The best random forest classifier with a 0.940 Matthews correlation coefficient was constructed to distinguish different hepatic cell types. Finally, classification rules were created for quantitatively describing hepatic cell types. In summary, This study provided potential targets for cell transplantation associated liver disease treatment strategies by elucidating the process and mechanism of hepatocyte development at both qualitative and quantitative levels.

Ineffective Erythropoiesis in β-Thalassaemia: Key Steps and Therapeutic Options by Drugs

β-thalassaemia is a rare genetic condition caused by mutations in the β-globin gene that result in severe iron-loading anaemia, maintained by a detrimental state of ineffective erythropoiesis (IE). The role of multiple mechanisms involved in the pathophysiology of the disease has been recently unravelled. The unbalanced production of α-globin is a major source of oxidative stress and membrane damage in red blood cells (RBC). In addition, IE is tightly linked to iron metabolism dysregulation, and the relevance of new players of this pathway, i.e., hepcidin, erythroferrone, matriptase-2, among others, has emerged. Advances have been made in understanding the balance between proliferation and maturation of erythroid precursors and the role of specific factors in this process, such as members of the TGF-β superfamily, and their downstream effectors, or the transcription factor GATA1. The increasing understanding of IE allowed for the development of a broad set of potential therapeutic options beyond the current standard of care. Many candidates of disease-modifying drugs are currently under clinical investigation, targeting the regulation of iron metabolism, the production of foetal haemoglobin, the maturation process, or the energetic balance and membrane stability of RBC. Overall, they provide tools and evidence for multiple and synergistic approaches that are effectively moving clinical research in β-thalassaemia from bench to bedside.

Physiological and pathophysiological mechanisms of hepcidin regulation: clinical implications for iron disorders

The discovery of hepcidin has provided a solid foundation for understanding the mechanisms of systemic iron homeostasis and the aetiologies of iron disorders. Hepcidin assures the balance of circulating and stored iron levels for multiple physiological processes including oxygen transport and erythropoiesis, while limiting the toxicity of excess iron. The liver is the major site where regulatory signals from iron, erythropoietic drive and inflammation are integrated to control hepcidin production. Pathologically, hepcidin dysregulation by genetic inactivation, ineffective erythropoiesis, or inflammation leads to diseases of iron deficiency or overload such as iron-refractory iron-deficiency anaemia, anaemia of inflammation, iron-loading anaemias and hereditary haemochromatosis. In the present review, we discuss recent insights into the molecular mechanisms governing hepcidin regulation, how these pathways are disrupted in iron disorders, and how this knowledge is being used to develop novel diagnostic and therapeutic strategies.

Growth differentiation factor 11: a "rejuvenation factor" involved in regulation of age-related diseases?

Growth differentiation factor 11 (GDF11), a member of the transforming growth factor β superfamily of cytokines, is a critical rejuvenation factor in aging cells. GDF11 improves neurodegenerative and neurovascular disease outcomes, increases skeletal muscle volume, and enhances muscle strength. Its wide-ranging biological effects may include the reversal of senescence in clinical applications, as well as the ability to reverse age-related pathological changes and regulate organ regeneration after injury. Nevertheless, recent data have led to controversy regarding the functional roles of GDF11, because the underlying mechanisms were not clearly established in previous studies. In this review, we examine the literature regarding GDF11 in age-related diseases and discuss potential mechanisms underlying the effects of GDF11 in regulation of age-related diseases.

[Expression of iron-regulating erythroid factors in different types of erythropoiesis disorders]

目的

研究Erythroferrone（ERFE）等铁代谢红系调节因子（iron-regulatory erythroid factor）在不同类型红系造血异常疾病中的表达情况。

方法

采用ELISA方法检测2016年1月至2019年11月共47例真性红细胞增多症（PV）、纯红细胞再生障碍（PRCA）、自身免疫性溶血性贫血（AIHA）和骨髓增生异常综合征（MDS）患者血浆ERFE、生长分化因子15（GDF15）、生长分化因子11（GDF11）和扭转原肠胚形成同系物（TWSG1）的表达，分析铁代谢调节因子与红系造血异常类型及旺盛程度（以骨髓有核红细胞比例反映）的适配性。

结果

血浆GDF15表达水平在PV、PRCA、AIHA、MDS各组依次为266.01（112.40,452.37）、110.63（81.41,220.42）、52.11（32.61,171.66）、276.53（132.16,525.70）ng/L，均显著高于正常对照组的37.45（19.65,57.72）ng/L（P值均<0.01）。不同类型红系造血异常患者血浆TWSG1表达水平与正常对照组比较差异均无统计学意义（P值均>0.05）。血浆GDF11表达水平仅在PV组患者中明显高于正常对照组[74.75（10.95,121.32）ng/L对36.90（3.38,98.34）ng/L，P<0.01]，而PRCA、AIHA、MDS 3组患者与正常对照组比较差异无统计学意义（P>0.05）。PV组血浆ERFE水平为129.63（47.02, 170.03）ng/L，AIHA组血浆ERFE水平最高为121.76（68.12,343.11）ng/L，二者均明显高于正常对照组的43.23（35.18,65.41）ng/L（P值均<0.01）；PRCA组、MDS组血浆ERFE水平分别为48.92（44.59，84.83）、40.47（26.97,72.87）ng/L，与正常对照组比较差异无统计学意义（P值均>0.05）。骨髓有核红细胞比例与ERFE（r＝0.458，P＝0.001）呈正相关，而与GDF15（r＝−0.163，P＝0.274）、GDF11（r＝0.120，P＝0.421）、TWSG1（r＝−0.166，P＝0.269）无明显相关性。

结论

铁代谢红系调节因子在不同红系造血异常疾病的表达谱不尽一致，ERFE与红系造血旺盛程度相关度最高。

The Interplay between Drivers of Erythropoiesis and Iron Homeostasis in Rare Hereditary Anemias: Tipping the Balance

Rare hereditary anemias (RHA) represent a group of disorders characterized by either impaired production of erythrocytes or decreased survival (i.e., hemolysis). In RHA, the regulation of iron metabolism and erythropoiesis is often disturbed, leading to iron overload or worsening of chronic anemia due to unavailability of iron for erythropoiesis. Whereas iron overload generally is a well-recognized complication in patients requiring regular blood transfusions, it is also a significant problem in a large proportion of patients with RHA that are not transfusion dependent. This indicates that RHA share disease-specific defects in erythroid development that are linked to intrinsic defects in iron metabolism. In this review, we discuss the key regulators involved in the interplay between iron and erythropoiesis and their importance in the spectrum of RHA.

The Clinical Significance of Iron Overload and Iron Metabolism in Myelodysplastic Syndrome and Acute Myeloid Leukemia

Myelodysplasticsyndrome (MDS) and acute myeloid leukemia (AML) are clonal hematopoietic stem cell diseases leading to an insufficient formation of functional blood cells. Disease-immanent factors as insufficient erythropoiesis and treatment-related factors as recurrent treatment with red blood cell transfusions frequently lead to systemic iron overload in MDS and AML patients. In addition, alterations of function and expression of proteins associated with iron metabolism are increasingly recognized to be pathogenetic factors and potential vulnerabilities of these diseases. Iron is known to be involved in multiple intracellular and extracellular processes. It is essential for cell metabolism as well as for cell proliferation and closely linked to the formation of reactive oxygen species. Therefore, iron can influence the course of clonal myeloid disorders, the leukemic environment and the occurrence as well as the defense of infections. Imbalances of iron homeostasis may induce cell death of normal but also of malignant cells. New potential treatment strategies utilizing the importance of the iron homeostasis include iron chelation, modulation of proteins involved in iron metabolism, induction of leukemic cell death via ferroptosis and exploitation of iron proteins for the delivery of antileukemic drugs. Here, we provide an overview of some of the latest findings about the function, the prognostic impact and potential treatment strategies of iron in patients with MDS and AML.

Iron overload and its impact on outcome of patients with hematological diseases

Systemic iron overload (SIO) is a common challenge in patients with hematological diseases and develops as a result of ineffective erythropoiesis, multiple red blood cell (RBC) transfusions and disease-specific therapies. Iron homeostasis is tightly regulated as there is no physiological pathway to excrete iron from the body. Excess iron is, therefore, stored in tissues like liver, heart and bone marrow and can lead to progressive organ damage. The presence of free iron in the form of non-transferrin bound iron (NTBI) is especially detrimental. Reactive oxygen species can also cause stromal damage in the bone marrow and promote leukemic cell growth in vitro. In acute leukemias and myelodysplastic syndromes outcome is worse in patients with SIO compared to patients without. Especially in patients undergoing allogeneic HSCT presence of NTBI before or during transplant has been shown to negatively affect non-relapse mortality and overall survival. Although the mechanisms, of how these effects are mediated by SIO are not very well understood monitoring of iron status by serum markers and imaging techniques is, therefore, mandatory especially in these patients. Whether peri-interventional iron chelation may improve outcome of these patients is part of current clinical research.

Controversies on the Consequences of Iron Overload and Chelation in MDS

Many patients with MDS are prone to develop systemic and tissue iron overload in part as a consequence of disease-immanent ineffective erythropoiesis. However, chronic red blood cell transfusions, which are part of the supportive care regimen to correct anemia, are the major source of iron overload in MDS. Increased systemic iron levels eventually lead to the saturation of the physiological systemic iron carrier transferrin and the occurrence of non-transferrin-bound iron (NTBI) together with its reactive fraction, the labile plasma iron (LPI). NTBI/LPI-mediated toxicity and tissue iron overload may exert multiple detrimental effects that contribute to the pathogenesis, complications and eventually evolution of MDS. Until recently, the evidence supporting the use of iron chelation in MDS was based on anecdotal reports, uncontrolled clinical trials or prospective registries. Despite not fully conclusive, these and more recent studies, including the TELESTO trial, unravel an overall adverse action of iron overload and therapeutic benefit of chelation, ranging from improved hematological outcome, reduced transfusion dependence and superior survival of iron-loaded MDS patients. The still limited and somehow controversial experimental and clinical data available from preclinical studies and randomized trials highlight the need for further investigation to fully elucidate the mechanisms underlying the pathological impact of iron overload-mediated toxicity as well as the effect of classic and novel iron restriction approaches in MDS. This review aims at providing an overview of the current clinical and translational debated landscape about the consequences of iron overload and chelation in the setting of MDS.