Na/K-ATPase signaling regulates collagen synthesis through microRNA-29b-3p in cardiac fibroblasts

Promising Therapeutic Treatments for Cardiac Fibrosis: Herbal Plants and Their Extracts

Cardiac fibrosis is closely associated with multiple heart diseases, which are a prominent health issue in the global world. Neurohormones and cytokines play indispensable roles in cardiac fibrosis. Many signaling pathways participate in cardiac fibrosis as well. Cardiac fibrosis is due to impaired degradation of collagen and impaired fibroblast activation, and collagen accumulation results in increasing heart stiffness and inharmonious activity, leading to structure alterations and finally cardiac function decline. Herbal plants have been applied in traditional medicines for thousands of years. Because of their naturality, they have attracted much attention for use in resisting cardiac fibrosis in recent years. This review sheds light on several extracts from herbal plants, which are promising therapeutics for reversing cardiac fibrosis.

New Insights on the Role of Marinobufagenin from Bench to Bedside in Cardiovascular and Kidney Diseases

Marinobufagenin (MBG) is a member of the bufadienolide family of compounds, which are natural cardiac glycosides found in a variety of animal species, including man, which have different physiological and biochemical functions but have a common action on the inhibition of the adenosine triphosphatase sodium-potassium pump (Na+/K+-ATPase). MBG acts as an endogenous cardiotonic steroid, and in the last decade, its role as a pathogenic factor in various human diseases has emerged. In this paper, we have collated major evidence regarding the biological characteristics and functions of MBG and its implications in human pathology. This review focused on MBG involvement in chronic kidney disease, including end-stage renal disease, cardiovascular diseases, sex and gender medicine, and its actions on the nervous and immune systems. The role of MBG in pathogenesis and the development of a wide range of pathological conditions indicate that this endogenous peptide could be used in the future as a diagnostic biomarker and/or therapeutic target, opening important avenues of scientific research.

Microneedle Patch Loaded with Exosomes Containing MicroRNA-29b Prevents Cardiac Fibrosis after Myocardial Infarction

Myocardial infarction (MI) is a cardiovascular disease that poses a serious threat to human health. Uncontrolled and excessive cardiac fibrosis after MI has been recognized as a primary contributor to mortality by heart failure. Thus, prevention of fibrosis or alleviation of fibrosis progression is important for cardiac repair. To this end, a biocompatible microneedle (MN) patch based on gelatin is fabricated to load exosomes containing microRNA-29b (miR-29b) mimics with antifibrotic activity to prevent excessive cardiac fibrosis after MI. Exosomes are isolated from human umbilical cord mesenchymal stem cells and loaded with miR-29b mimics via electroporation, which can be internalized effectively in cardiac fibroblasts to upregulate the expression of miR-29b and downregulate the expression of fibrosis-related proteins. After being implanted in the infarcted heart of a mouse MI model, the MN patch can increase the retention of loaded exosomes in the infarcted myocardium, leading to alleviation of inflammation, reduction of the infarct size, inhibition of fibrosis, and improvement of cardiac function. This design explored the MN patch as a suitable platform to deliver exosomes containing antifibrotic biomolecules locally for the prevention of cardiac fibrosis, showing the potential for MI treatment in clinical applications.

Hypoxic Stress-Dependent Regulation of Na,K-ATPase in Ischemic Heart Disease

In cardiomyocytes, regular activity of the Na,K-ATPase (NKA) and its Na/K pump activity is essential for maintaining ion gradients, excitability, propagation of action potentials, electro-mechanical coupling, trans-membrane Na⁺ and Ca²⁺ gradients and, thus, contractility. The activity of NKA is impaired in ischemic heart disease and heart failure, which has been attributed to decreased expression of the NKA subunits. Decreased NKA activity leads to intracellular Na⁺ and Ca²⁺ overload, diastolic dysfunction and arrhythmias. One signal likely related to these events is hypoxia, where hypoxia-inducible factors (HIF) play a critical role in the adaptation of cells to low oxygen tension. HIF activity increases in ischemic heart, hypertension, heart failure and cardiac fibrosis; thus, it might contribute to the impaired function of NKA. This review will mainly focus on the regulation of NKA in ischemic heart disease in the context of stressed myocardium and the hypoxia-HIF axis and argue on possible consequences of treatment.

miRNAs in Uremic Cardiomyopathy: A Comprehensive Review

Uremic Cardiomyopathy (UCM) is an irreversible cardiovascular complication that is highly pervasive among chronic kidney disease (CKD) patients, particularly in End-Stage Kidney Disease (ESKD) individuals undergoing chronic dialysis. Features of UCM are an abnormal myocardial fibrosis, an asymmetric ventricular hypertrophy with subsequent diastolic dysfunction and a complex and multifactorial pathogenesis where underlying biological mechanisms remain partly undefined. In this paper, we reviewed the key evidence available on the biological and clinical significance of micro-RNAs (miRNAs) in UCM. miRNAs are short, noncoding RNA molecules with regulatory functions that play a pivotal role in myriad basic cellular processes, such as cell growth and differentiation. Deranged miRNAs expression has already been observed in various diseases, and their capacity to modulate cardiac remodeling and fibrosis under either physiological or pathological conditions is well acknowledged. In the context of UCM, robust experimental evidence confirms a close involvement of some miRNAs in the key pathways that are known to trigger or worsen ventricular hypertrophy or fibrosis. Moreover, very preliminary findings may set the stage for therapeutic interventions targeting specific miRNAs for ameliorating heart damage. Finally, scant but promising clinical evidence may suggest a potential future application of circulating miRNAs as diagnostic or prognostic biomarkers for improving risk stratification in UCM as well.

Gene module regulation in dilated cardiomyopathy and the role of Na/K-ATPase

Dilated cardiomyopathy (DCM) is a major cause of cardiac death and heart transplantation. It has been known that black people have a higher incidence of heart failure and related diseases compared to white people. To identify the relationship between gene expression and cardiac function in DCM patients, we performed pathway analysis and weighted gene co-expression network analysis (WGCNA) using RNA-sequencing data (GSE141910) from the NCBI Gene Expression Omnibus (GEO) database and identified several gene modules that were significantly associated with the left ventricle ejection fraction (LVEF) and DCM phenotype. Genes included in these modules are enriched in three major categories of signaling pathways: fibrosis-related, small molecule transporting-related, and immune response-related. Through consensus analysis, we found that gene modules associated with LVEF in African Americans are almost identical as in Caucasians, suggesting that the two groups may have more common rather than disparate genetic regulations in the etiology of DCM. In addition to the identified modules, we found that the gene expression level of Na/K-ATPase, an important membrane ion transporter, has a strong correlation with the LVEF. These clinical results are consistent with our previous findings and suggest the clinical significance of Na/K-ATPase regulation in DCM.

MicroRNA-325-3p Targets Human Epididymis Protein 4 to Relieve Right Ventricular Fibrosis in Rats with Pulmonary Arterial Hypertension

Background

Pulmonary arterial hypertension (PAH) usually causes right ventricular dysfunction, which is closely related to cardiac fibrosis. But cardiac fibrosis mechanism remains unclear. Our purpose was to explore microRNA-325-3p (miR-325-3p)/human epididymis protein 4's (HE4) role in the occurrence and development of right ventricular fibrosis in PAH.

Methods

The right ventricular fibrosis model of rats with PAH was constructed, and miR-325-3p was overexpressed to explore miR-325-3p's effect on myocardial fibrosis in rats with PAH. Pearson correlation coefficient examined the correlation between HE4 and miR-325-3p. We separated and identified the primary rat myocardial fibroblasts from the heart tissue. Then, the Ang II-treated myocardial fibroblast fibrosis model was constructed. miR-325-3p mimics and si-HE4 and oe-HE4 cell lines were constructed to investigate miR-325-3p and HE4 effects on myocardial cell fibrosis. Then, we added PI3K inhibitor LY294002 to study the effects of HE4 in cell fibrosis by the PI3K/AKT pathway. Starbase was used to predict miR-325-3p and HE4 binding sites. Dual-luciferase reporter assay verified whether miR-325-3p and HE4 were targeted.

Results

Overexpression of miR-325-3p alleviated myocardial fibrosis in rats with PAH. Pearson correlation coefficient showed that HE4 was negatively correlated with miR-325-3p expression. Starbase predicted that miR-325-3p had binding sites with HE4. Dual-luciferase reporter assay demonstrated that miR-325-3p targeted HE4. Overexpression of miR-325-3p downregulated HE4 and inhibited myocardial fibroblast fibrosis. HE4 knockdown inhibited myocardial fibroblast fibrosis. HE4 promoted myocardial fibroblast fibrosis and activated the PI3K/AKT pathway. In addition, HE4 affected myocardial fibroblast fibrosis through the PI3K/AKT pathway.

Conclusions

miR-325-3p could target HE4 to relieve right ventricular fibrosis in rats with PAH. This study could provide new targets and strategies for right ventricular fibrosis in PAH.

Six Decades of History of Hypertension Research at the University of Toledo: Highlighting Pioneering Contributions in Biochemistry, Genetics, and Host-Microbiota Interactions

PURPOSE OF REVIEW

The study aims to capture the history and lineage of hypertension researchers from the University of Toledo in Ohio and showcase their collective scientific contributions dating from their initial discoveries of the physiology of adrenal and renal systems and genetics regulating blood pressure (BP) to its more contemporary contributions including microbiota and metabolomic links to BP regulation.

RECENT FINDINGS

The University of Toledo College of Medicine and Life Sciences (UTCOMLS), previously known as the Medical College of Ohio, has contributed significantly to our understanding of the etiology of hypertension. Two of the scientists, Patrick Mulrow and John Rapp from UTCOMLS, have been recognized with the highest honor, the Excellence in Hypertension award from the American Heart Association for their pioneering work on the physiology and genetics of hypertension, respectively. More recently, Bina Joe has continued their legacy in the basic sciences by uncovering previously unknown novel links between microbiota and metabolites to the etiology of hypertension, work that has been recognized by the American Heart Association with multiple awards. On the clinical research front, Christopher Cooper and colleagues lead the CORAL trials and contributed importantly to the investigations on renal artery stenosis treatment paradigms. Hypertension research at this institution has not only provided these pioneering insights, but also grown careers of scientists as leaders in academia as University Presidents and Deans of Medical Schools. Through the last decade, the university has expanded its commitment to Hypertension research as evident through the development of the Center for Hypertension and Precision Medicine led by Bina Joe as its founding Director. Hypertension being the top risk factor for cardiovascular diseases, which is the leading cause of human mortality, is an important area of research in multiple international universities. The UTCOMLS is one such university which, for the last 6 decades, has made significant contributions to our current understanding of hypertension. This review is a synthesis of this rich history. Additionally, it also serves as a collection of audio archives by more recent faculty who are also prominent leaders in the field of hypertension research, including John Rapp, Bina Joe, and Christopher Cooper, which are cataloged at Interviews .

Role of the microRNA-29 family in myocardial fibrosis

Myocardial fibrosis (MF) is an inevitable pathological process in the terminal stage of many cardiovascular diseases, often leading to serious cardiac dysfunction and even death. Currently, microRNA-29 (miR-29) is thought to be a novel diagnostic and therapeutic target of MF. Understanding the underlying mechanisms of miR-29 that regulate MF will provide a new direction for MF therapy. In the present review, we concentrate on the underlying signaling pathway of miR-29 affecting MF and the crosstalk regulatory relationship among these pathways to illustrate the complex regulatory network of miR-29 in MF. Additionally, based on our mechanistic understanding, we summarize opportunities and challenges of miR-29-based MF diagnosis and therapy.

The Na/K-ATPase Signaling and SGLT2 Inhibitor-Mediated Cardiorenal Protection: A Crossed Road?

In different large-scale clinic outcome trials, sodium (Na⁺)/glucose co-transporter 2 (SGLT2) inhibitors showed profound cardiac- and renal-protective effects, making them revolutionary treatments for heart failure and kidney disease. Different theories are proposed according to the emerging protective effects other than the original purpose of glucose-lowering in diabetic patients. As the ATP-dependent primary ion transporter providing the Na⁺ gradient to drive other Na⁺-dependent transporters, the possible role of the sodium–potassium adenosine triphosphatase (Na/K-ATPase) as the primary ion transporter and its signaling function is not explored.

Non-Coding RNAs in the Cardiac Action Potential and Their Impact on Arrhythmogenic Cardiac Diseases

Cardiac arrhythmias are prevalent among humans across all age ranges, affecting millions of people worldwide. While cardiac arrhythmias vary widely in their clinical presentation, they possess shared complex electrophysiologic properties at cellular level that have not been fully studied. Over the last decade, our current understanding of the functional roles of non-coding RNAs have progressively increased. microRNAs represent the most studied type of small ncRNAs and it has been demonstrated that miRNAs play essential roles in multiple biological contexts, including normal development and diseases. In this review, we provide a comprehensive analysis of the functional contribution of non-coding RNAs, primarily microRNAs, to the normal configuration of the cardiac action potential, as well as their association to distinct types of arrhythmogenic cardiac diseases.

Cardiac Oxidative Signaling and Physiological Hypertrophy in the Na/K-ATPase α1s/sα2s/s Mouse Model of High Affinity for Cardiotonic Steroids

The Na/K-ATPase is the specific receptor for cardiotonic steroids (CTS) such as ouabain and digoxin. At pharmacological concentrations used in the treatment of cardiac conditions, CTS inhibit the ion-pumping function of Na/K-ATPase. At much lower concentrations, in the range of those reported for endogenous CTS in the blood, they stimulate hypertrophic growth of cultured cardiac myocytes through initiation of a Na/K-ATPase-mediated and reactive oxygen species (ROS)-dependent signaling. To examine a possible effect of endogenous concentrations of CTS on cardiac structure and function in vivo, we compared mice expressing the naturally resistant Na/K-ATPase α1 and age-matched mice genetically engineered to express a mutated Na/K-ATPase α1 with high affinity for CTS. In this model, total cardiac Na/K-ATPase activity, α1, α2, and β1 protein content remained unchanged, and the cardiac Na/K-ATPase dose–response curve to ouabain shifted to the left as expected. In males aged 3–6 months, increased α1 sensitivity to CTS resulted in a significant increase in cardiac carbonylated protein content, suggesting that ROS production was elevated. A moderate but significant increase of about 15% of the heart-weight-to-tibia-length ratio accompanied by an increase in the myocyte cross-sectional area was detected. Echocardiographic analyses did not reveal any change in cardiac function, and there was no fibrosis or re-expression of the fetal gene program. RNA sequencing analysis indicated that pathways related to energy metabolism were upregulated, while those related to extracellular matrix organization were downregulated. Consistent with a functional role of the latter, an angiotensin-II challenge that triggered fibrosis in the α1^r/rα2^s/s mouse failed to do so in the α1^s/sα2^s/s. Taken together, these results are indicative of a link between circulating CTS, Na/K-ATPase α1, ROS, and physiological cardiac hypertrophy in mice under baseline laboratory conditions.

Nutraceutical, Dietary, and Lifestyle Options for Prevention and Treatment of Ventricular Hypertrophy and Heart Failure

Although well documented drug therapies are available for the management of ventricular hypertrophy (VH) and heart failure (HF), most patients nonetheless experience a downhill course, and further therapeutic measures are needed. Nutraceutical, dietary, and lifestyle measures may have particular merit in this regard, as they are currently available, relatively safe and inexpensive, and can lend themselves to primary prevention as well. A consideration of the pathogenic mechanisms underlying the VH/HF syndrome suggests that measures which control oxidative and endoplasmic reticulum (ER) stress, that support effective nitric oxide and hydrogen sulfide bioactivity, that prevent a reduction in cardiomyocyte pH, and that boost the production of protective hormones, such as fibroblast growth factor 21 (FGF21), while suppressing fibroblast growth factor 23 (FGF23) and marinobufagenin, may have utility for preventing and controlling this syndrome. Agents considered in this essay include phycocyanobilin, N-acetylcysteine, lipoic acid, ferulic acid, zinc, selenium, ubiquinol, astaxanthin, melatonin, tauroursodeoxycholic acid, berberine, citrulline, high-dose folate, cocoa flavanols, hawthorn extract, dietary nitrate, high-dose biotin, soy isoflavones, taurine, carnitine, magnesium orotate, EPA-rich fish oil, glycine, and copper. The potential advantages of whole-food plant-based diets, moderation in salt intake, avoidance of phosphate additives, and regular exercise training and sauna sessions are also discussed. There should be considerable scope for the development of functional foods and supplements which make it more convenient and affordable for patients to consume complementary combinations of the agents discussed here. Research Strategy: Key word searching of PubMed was employed to locate the research papers whose findings are cited in this essay.

The role of miR-29 family in disease

MicroRNAs are small noncoding RNAs that can bind to the target sites in the 3’‐untranslated region of messenger RNA to regulate posttranscriptional gene expression. Increasing evidence has identified the miR‐29 family, consisting of miR‐29a, miR‐29b‐1, miR‐29b‐2, and miR‐29c, as key regulators of a number of biological processes. Moreover, their abnormal expression contributes to the etiology of numerous diseases. In the current review, we aimed to summarize the differential expression patterns and functional roles of the miR‐29 family in the etiology of diseases including osteoarthritis, osteoporosis, cardiorenal, and immune disease. Furthermore, we highlight the therapeutic potential of targeting members of miR‐29 family in these diseases. We present miR‐29s as promoters of osteoblast differentiation and apoptosis but suppressors of chondrogenic and osteoclast differentiation, fibrosis, and T cell differentiation, with clear avenues for therapeutic manipulation. Further research will be crucial to identify the precise mechanism of miR‐29 family in these diseases and their full potential in therapeutics.

Biased Effect of Cardiotonic Steroids on Na/K-ATPase-Mediated Signal Transduction

Recent studies have revealed that Na/K-ATPase (NKA) can transmit signals through ion-pumping-independent activation of pathways relayed by distinct intracellular protein/lipid kinases, and endocytosis challenges the traditional definition that cardiotonic steroids (CTS) are NKA inhibitors. Although additional effects of CTS have long been suspected, revealing its agonist impact through the NKA receptor could be a novel mechanism in understanding the basic biology of NKA. In this study, we tested whether different structural CTS could trigger different sets of NKA/effector interactions, resulting in biased signaling responses without compromising ion-pumping capacity. Using purified NKA, we found that ouabain, digitoxigenin, and somalin cause comparable levels of NKA inhibition. However, although endogenous ouabain stimulates both protein kinases and NKA endocytosis, digitoxigenin and somalin bias to protein kinases and endocytosis, respectively, in LLC-PK1 cells. The positive inotropic effects of CTS are traditionally regarded as NKA inhibitors. However, CTS-induced signaling occurs at concentrations at least one order of magnitude lower than that of inotropy, which eliminates their well known toxic actions on the heart. The current study adds a novel mechanism that CTS could exert its biased signaling properties through the NKA signal transducer. SIGNIFICANCE STATEMENT: Although it is now well accepted that NKA has an ion-pumping-independent signaling function, it is still debated whether direct and conformation-dependent NKA/effector interaction is a key to this function. Therefore, this investigation is significant in advancing our understanding of the basic biology of NKA-mediated signal transduction and gaining molecular insight into the structural elements that are important for cardiotonic steroid's biased action.

Overexpression of MiR-29b-3p Inhibits Atrial Remodeling in Rats by Targeting PDGF-B Signaling Pathway

Purpose

Studies have found that microRNAs (miRNAs) are closely associated with atrial fibrillation, but their specific mechanism remains unclear. The purpose of this experiment is to explore the function of miR-29b-3p in regulating atrial remodeling by targeting PDGF-B signaling pathway and thereby also explore the potential mechanisms.

Methods

We randomly divided twenty-four rats into four groups. Caudal intravenous injections of angiotensin-II (Ang-II) were administered to establish atrial fibrosis models. Expressions of miR-29b-3p and PDGF-B were then tested via RT-PCR, western blot, and immunohistochemistry. Binding sites were then analyzed via the bioinformatics online software TargetScan and verified by Luciferase Reporter. We used Masson staining to detect the degree of atrial fibrosis, while immunofluorescence and western blot were used to detect the expressions of Collagen-I and a-SMA. We used immunohistochemistry and western blot to detect the expression of connexin 43 (Cx43).

Results

In comparison with the Ang-II group, miR-29b-3p was seen to lower the degree of atrial fibrosis, decrease the expression of fibrosis markers such as Collagen-I and a-SMA, and increase the protein expression of Cx43. MiR-29b-3p can lower the expression of PDGF-B, while the Luciferase Reporter showed that PDGF-B is the verified target gene of miR-29b-3p.

Conclusions

MiR-29b-3p was able to reduce atrial structural and electrical remodeling in the study's rat fibrosis model. This biological function may be expressed through the targeted regulation of the PDGF-B signaling pathway.

A previously undescribed phenylethanoid glycoside from Callicarpa kwangtungensis Chun acts as an agonist of the Na/K-ATPase signal transduction pathway

The new concept that Na/K-ATPase acts as a receptor prompted us to look for new ligands from Callicarpa kwangtungensis Chun. Using column chromatography, an undescribed phenethyl alcohol glycoside, callicarpanoside A, and an undescribed benzyl alcohol glycoside, callicarpanoside B, along with twelve known polyphenols were isolated from Callicarpa kwangtungensis Chun. All the isolated compounds were evaluated for their Na/K-ATPase (NKA) inhibitory activities. Using our NKA technology platform-based screening assay protocols, callicarpanoside B was identified as an undescribed Na/K-ATPase agonist. In particular, the newly identified benzyl alcohol glycoside was found to bind NKA and activate the receptor NKA/Src complex, resulting in the activation of protein kinase cascades. These cascades included extracellular signal-regulated kinases and protein kinase C epsilon, as well as NKA α1 endocytosis at nanomolar concentrations. Unlike the class of cardiotonic steroids, callicarpanoside B showed less inhibition of NKA activity and caused less cellular toxicity. Moreover, callicarpanoside B was found to bind NKA at a different site other than the cardiotonic steroids binding site. Thus, we have identified an undescribed NKA α1 agonist that may be used to enhance the physiological processes of NKA α1 signaling.

A strategic expression method of miR-29b and its anti-fibrotic effect based on RNA-sequencing analysis

Tissue fibrosis is a significant health issue associated with organ dysfunction and failure. Increased deposition of collagen and other extracellular matrix (ECM) proteins in the interstitial area is a major process in tissue fibrosis. The microRNA-29 (miR-29) family has been demonstrated as anti-fibrotic microRNAs. Our recent work showed that dysregulation of miR-29 contributes to the formation of cardiac fibrosis in animal models of uremic cardiomyopathy, whereas replenishing miR-29 attenuated cardiac fibrosis in these animals. However, excessive overexpression of miR-29 is a concern because microRNAs usually have multiple targets, which could result in unknown and unexpected side effect. In the current study, we constructed a novel Col1a1-miR-29b vector using collagen 1a1 (Col1a1) promoter, which can strategically express miR-29b-3p (miR-29b) in response to increased collagen synthesis and reach a dynamic balance between collagen and miR-29b. Our experimental results showed that in mouse embryonic fibroblasts (MEF cells) transfected with Col1a1-miR-29b vector, the miR-29b expression is about 1000 times less than that in cells transfected with CMV-miR-29b vector, which uses cytomegalovirus (CMV) as a promoter for miR-29b expression. Moreover, TGF-β treatment increased the miR-29b expression by about 20 times in cells transfected with Col1a1-miR-29b, suggesting a dynamic response to fibrotic stimulation. Western blot using cell lysates and culture media demonstrated that transfection of Col1a1-miR-29b vector significantly reduced TGF-β induced collagen synthesis and secretion, and the effect was as effective as the CMV-miR-29b vector. Using RNA-sequencing analysis, we found that 249 genes were significantly altered (180 upregulated and 69 downregulated, at least 2-fold change and adjusted p-value <0.05) after TGF-β treatment in MEF cells transfected with empty vector. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis using GAGE R-package showed that the top 5 upregulated pathways after TGF-β treatment were mostly fibrosis-related, including focal adhesion, ECM reaction, and TGF-β signaling pathways. As expected, transfection of Col1a1-miR-29b or CMV-miR-29b vector partially reversed the activation of these pathways. We also analyzed the expression pattern of the top 100 miR-29b targeting genes in these cells using the RNA-sequencing data. We identified that miR-29b targeted a broad spectrum of ECM genes, but the inhibition effect is mostly moderate. In summary, our work demonstrated that the Col1a1-miR-29b vector can be used as a dynamic regulator of collagen and other ECM protein expression in response to fibrotic stimulation, which could potentially reduce unnecessary side effect due to excessive miR-29b levels while remaining an effective potential therapeutic approach for fibrosis.

Heart failure in chronic kidney disease: the emerging role of myocardial fibrosis

Heart failure (HF) is one of the main causes of morbidity and mortality in patients with chronic kidney disease (CKD). Decreased glomerular filtration rate is associated with diffuse deposition of fibrotic tissue in the myocardial interstitium [i.e. myocardial interstitial fibrosis (MIF)] and loss of cardiac function. MIF results from cardiac fibroblast-mediated alterations in the turnover of fibrillary collagen that lead to the excessive synthesis and deposition of collagen fibres. The accumulation of stiff fibrotic tissue alters the mechanical properties of the myocardium, thus contributing to the development of HF. Accumulating evidence suggests that several mechanisms are operative along the different stages of CKD that may converge to alter fibroblasts and collagen turnover in the heart. Therefore, focusing on MIF might enable the identification of fibrosis-related biomarkers and targets that could potentially lead to a new strategy for the prevention and treatment of HF in patients with CKD. This article summarizes current knowledge on the mechanisms and detrimental consequences of MIF in CKD and discusses the validity and usefulness of available biomarkers to recognize the clinical-pathological variability of MIF and track its clinical evolution in CKD patients. Finally, the currently available and potential future therapeutic strategies aimed at personalizing prevention and reversal of MIF in CKD patients, especially those with HF, will be also discussed.

Cardiac Remodeling in Chronic Kidney Disease

Cardiac remodeling occurs frequently in chronic kidney disease patients and affects quality of life and survival. Current treatment options are highly inadequate. As kidney function declines, numerous metabolic pathways are disturbed. Kidney and heart functions are highly connected by organ crosstalk. Among others, altered volume and pressure status, ischemia, accelerated atherosclerosis and arteriosclerosis, disturbed mineral metabolism, renal anemia, activation of the renin-angiotensin system, uremic toxins, oxidative stress and upregulation of cytokines stress the sensitive interplay between different cardiac cell types. The fatal consequences are left-ventricular hypertrophy, fibrosis and capillary rarefaction, which lead to systolic and/or diastolic left-ventricular failure. Furthermore, fibrosis triggers electric instability and sudden cardiac death. This review focuses on established and potential pathophysiological cardiorenal crosstalk mechanisms that drive uremia-induced senescence and disease progression, including potential known targets and animal models that might help us to better understand the disease and to identify novel therapeutics.

The Redox-Sensitive Na/K-ATPase Signaling in Uremic Cardiomyopathy

In recent years, Na/K-ATPase signaling has been implicated in different physiological and pathophysiological conditions, including cardiac hypertrophy and uremic cardiomyopathy. Cardiotonic steroids (CTS), specific ligands of Na/K-ATPase, regulate its enzymatic activity (at higher concentrations) and signaling function (at lower concentrations without significantly affecting its enzymatic activity) and increase reactive oxygen species (ROS) generation. On the other hand, an increase in ROS alone also regulates the Na/K-ATPase enzymatic activity and signaling function. We termed this phenomenon the Na/K-ATPase-mediated oxidant-amplification loop, in which oxidative stress regulates both the Na/K-ATPase activity and signaling. Most recently, we also demonstrated that this amplification loop is involved in the development of uremic cardiomyopathy. This review aims to evaluate the redox-sensitive Na/K-ATPase-mediated oxidant amplification loop and uremic cardiomyopathy.

miRNA-mediated macrophage behaviors responding to matrix stiffness and ox-LDL

Atherosclerosis is one of the leading causes of morbidity and mortality, mainly due to the immune response triggered by the recruitment of monocytes/macrophages in the artery wall. Accumulating evidence have shown that matrix stiffness and oxidized low-density lipoproteins (ox-LDL) play important roles in atherosclerosis through modulating cellular behaviors. However, whether there is a synergistic effect for ox-LDL and matrix stiffness on macrophages behavior has not been explored yet. In this study, we developed a model system to investigate the synergistic role of ox-LDL and matrix stiffness on macrophage behaviors, such as migration, inflammatory and apoptosis. We found that there was a matrix stiffness-dependent behavior of monocyte-derived macrophages stimulated with ox-LDL. What's more, macrophages were more sensitive to ox-LDL on the stiff matrices compared to cells cultured on the soft matrices. Through next-generation sequencing, we identified miRNAs in response to matrix stiffness and ox-LDL and predicted pathways that showed the capability of miRNAs in directing macrophages fates. Our study provides a novel understanding of the important synergistic role of ox-LDL and matrix stiffness in modulating macrophages behaviors, especially through miRNAs signaling pathways, which could be potential key regulators in atherosclerosis and immune-targeted therapies.

LncRNA XIST promotes extracellular matrix synthesis, proliferation and migration by targeting miR-29b-3p/COL1A1 in human skin fibroblasts after thermal injury

Background

Long noncoding RNAs (lncRNAs) have been reported to be associated with dermis process during burn wound healing. This study aimed to investigate the role of lncRNA X-inactive specific transcript (XIST) in human skin fibroblasts (HSF) and extracellular matrix (ECM) as well as the regulatory network of XIST/microRNA-29b-3p (miR-29b-3p)/collagen 1 alpha 1 (COL1A1).

Methods

The wound samples were collected from 25 patients with deep partial thickness burn at day 5 after burn. The thermal injured model was established using HSF cells. The expressions of XIST, miR-29b-3p and COL1A1 were measured by quantitative real-time polymerase chain reaction and western blot. ECM synthesis, cell proliferation and migration were detected by western blot, cell counting kit-8 and trans-well assays, respectively. The interaction between miR-29b-3p and XIST or COL1A1 was explored by bioinformatics analysis and luciferase reporter assay.

Results

The expressions of XIST and COL1A1 were enhanced but miR-29b-3p expression was decreased after thermal injury. XIST overexpression promoted ECM synthesis, cell proliferation and migration in thermal injured HSF cells. However, XIST knockdown played an opposite effect. miR-29b-3p overexpression inhibited ECM synthesis, cell proliferation and migration, which was reversed by XIST. COL1A1 silence suppressed ECM synthesis, cell proliferation and migration by miR-29b-3p targeting. Moreover, COL1A1 up-regulation weakened the effect of XIST silence on ECM synthesis and HSF cell function.

Conclusion

XIST promoted ECM synthesis, cell proliferation and migration by sponging miR-29b-3p and targeting COL1A1 in HSF cells after thermal injury, indicating the promoting role of XIST in wound healing.

LncRNA TUG1 contributes to cardiac hypertrophy via regulating miR-29b-3p

Cardiac hypertrophy with maladjusted cardiac remodeling is the leading cause of heart failure. In the past decades, long non-coding RNAs (lncRNAs) and microRNAs (miRNAs) have been proved to exert multiple functions in cellular biological behaviors; however, their role in cardiac hypertrophy remains largely unclear. Presently, we first obtained hypertrophic H9c2 cells by treating with angiotensin II (Ang II) and uncovered upregulation of lncRNA taurine upregulated gene 1 (TUG1) in such H9c2 cells. Then, we demonstrated that silencing TUG1 attenuated Ang II-induced cardiac hypertrophy. Besides, a strong interactivity of TUG1 with miR-29b-3p at the putative sites was validated, suggesting that TUG1 was an endogenous sponge of miR-29b-3p in H9c2 cells. Additionally, the expression of miR-29b-3p was strikingly reduced by TUG1 upregulation and also inhibited under Ang II treatment, whereas it was restored after silencing TUG1 in hypertrophic cells. Also, we proved miR-29b-3p as a negative regulator in cardiac hypertrophy. Finally, miR-29b-3p inhibition abolished the anti-hypertrophy effect of TUG1 depletion in Ang II-treated H9c2 cells. Collectively, our findings confirmed that TUG1 functioned as a positive modulator of cardiac hypertrophy via sponging miR-29b-3p, indicating that TUG1 might serve as a potential target for the treatment of cardiac hypertrophy and even heart failure.

Proinflammatory Effects of Cardiotonic Steroids Mediated by NKA α-1 (Na+/K+-ATPase α-1)/Src Complex in Renal Epithelial Cells and Immune Cells

Cardiotonic steroids (CTSs) are NKA α-1 (Na⁺/K⁺-ATPase α-1) ligands that are increased in volume expanded states and associated with cardiac and renal diseases. Although initiation and resolution of inflammation is an important component of cellular injury and repair in renal disease, it is unknown whether CTS activation of NKA α-1 signaling in this setting regulates this inflammatory response. On this background, we hypothesized that CTS signaling through the NKA α-1-Src kinase complex promotes a proinflammatory response in renal epithelial and immune cells. First, we observed that the CTS telocinobufagin activated multiple proinflammatory cytokines/chemokines in renal epithelial cells, and these effects were attenuated after either NKA α-1 knockdown or with a specific inhibitor of the NKA α-1-Src kinase complex (pNaKtide). Similar findings were observed in immune cells, where we demonstrated that while telocinobufagin induced both oxidative burst and enhanced Nuclear factor kappa-light-chain-enhancer of activated B cells activation in macrophages ( P<0.05), the effects were abolished in NKA α-1^+/- macrophages or by pretreatment with pNaKtide or the Src inhibitor PP2 ( P<0.01). In a series of in vivo studies, we found that 5/6th partial nephrectomy induced significantly less oxidative stress in the remnant kidney of NKA α-1^+/- versus wild-type mice. Similarly, 5/6th partial nephrectomy yielded decreased levels of the urinary oxidative stress marker 8-Oxo-2'-deoxyguanosine in NKA α-1^+/- versus wild-type mice. Finally, we found that in vivo inhibition of the NKA α-1-Src kinase complex with pNaKtide significantly inhibited renal proinflammatory gene expression after 5/6th partial nephrectomy. These findings suggest that the NKA α-1-Src kinase complex plays a central role in regulating the renal inflammatory response induced by elevated CTS both in vitro and in vivo.

The Na,K-ATPase in vascular smooth muscle cells

The Na,K-ATPase is an enzyme essential for ion homeostasis in all cells. Over the last decades, it has been well-established that in addition to the transport of Na⁺/K⁺ over the cell membrane, the Na,K-ATPase acts as a receptor transducing humoral signals intracellularly. It has been suggested that ouabain-like compounds serve as endogenous modulators of this Na,K-ATPase signal transduction. The molecular mechanisms underlying Na,K-ATPase signaling are complicated and suggest the confluence of divergent biological pathways. This review discusses recent updates on the Na,K-ATPase signaling pathways characterized or suggested in vascular smooth muscle cells. The conventional view on this signaling is based on a microdomain structure where the Na,K-ATPase controls the Na,Ca-exchanger activity via modulation of intracellular Na⁺ in the spatially restricted submembrane space. This, in turn, affects intracellular Ca²⁺ and Ca²⁺ load in the sarcoplasmic reticulum leading to modulation of contractility as well as gene expression. An ion-transport-independent signal transduction from the Na,K-ATPase is based on molecular interactions. This was primarily characterized in other cell types but recently also demonstrated in vascular smooth muscles. The downstream signaling from the Na,K-ATPase includes Src and phosphatidylinositol-4,5-bisphosphate 3 kinase signaling pathways and generation of reactive oxygen species. Moreover, in vascular smooth muscle cells the interaction between the Na,K-ATPase and proteins responsible for Ca²⁺ homeostasis, e.g., phospholipase C and inositol triphosphate receptors, contributes to an integration of the signaling pathways. Recent update on the Na,K-ATPase dependent intracellular signaling and the significance for physiological functions and pathophysiological changes are discussed in this review.

Chronic kidney disease induces left ventricular overexpression of the pro-hypertrophic microRNA-212

Chronic kidney disease (CKD) is a public health problem that increases the risk of cardiovascular morbidity and mortality. Heart failure with preserved ejection fraction (HFpEF) characterized by left ventricular hypertrophy (LVH) and diastolic dysfunction is a common cardiovascular complication of CKD. MicroRNA-212 (miR-212) has been demonstrated previously to be a crucial regulator of pathologic LVH in pressure-overload-induced heart failure via regulating the forkhead box O3 (FOXO3)/calcineurin/nuclear factor of activated T-cells (NFAT) pathway. Here we aimed to investigate whether miR-212 and its hypertrophy-associated targets including FOXO3, extracellular signal-regulated kinase 2 (ERK2), and AMP-activated protein kinase (AMPK) play a role in the development of HFpEF in CKD. CKD was induced by 5/6 nephrectomy in male Wistar rats. Echocardiography and histology revealed LVH, fibrosis, preserved systolic function, and diastolic dysfunction in the CKD group as compared to sham-operated animals eight and/or nine weeks later. Left ventricular miR-212 was significantly overexpressed in CKD. However, expressions of FOXO3, AMPK, and ERK2 failed to change significantly at the mRNA or protein level. The protein kinase B (AKT)/FOXO3 and AKT/mammalian target of rapamycin (mTOR) pathways are also proposed regulators of LVH induced by pressure-overload. Interestingly, phospho-AKT/total-AKT ratio was increased in CKD without significantly affecting phosphorylation of FOXO3 or mTOR. In summary, cardiac overexpression of miR-212 in CKD failed to affect its previously implicated hypertrophy-associated downstream targets. Thus, the molecular mechanism of the development of LVH in CKD seems to be independent of the FOXO3, ERK1/2, AMPK, and AKT/mTOR-mediated pathways indicating unique features in this form of LVH.

Garlic (Allium sativum) exhibits a cardioprotective effect in experimental chronic renal failure rat model by reducing oxidative stress and controlling cardiac Na+/K+-ATPase activity and Ca2+ levels

Gentamicin (GNT)-induced nephrotoxicity culminates into renal failure with a possible cardiovascular impact. Garlic extract (GE) is a cardiovascular protectant with limited mechanistic data. Therefore, we assessed the disturbance in specific cardiac parameters and the potential protective effect of GE supplementation against them in a rat model of GNT-induced chronic renal failure (CRF). Adult male rats (n = 24) were randomly assigned into four groups (n = 6 each): normal controls (CON), garlic extract controls (GE; 250 mg kg-1, orally), GNT-induced CRF (GNT; 100 mg kg-1, i.p.), and GNT + GE (GNT and GE in the same previous doses) groups. GNT and GE were given daily for 3 weeks. Animals co-treated with GNT and GE exhibited improved renal functions, body weight (BW), and heart weight (HW)/BW ratio; declined blood pressure; lowered plasma levels of lactate dehydrogenase (LDH), creatine kinase-MB (CK-MB), and total peroxides (TP); and elevated total antioxidant capacity (TAC) levels. Moreover, the heart tissue contained raised levels of TAC and Na+/K+-ATPase activity and lowered levels of TP and Ca2+. Findings provide evidence that administration of GE in experimental CRF model helped protect the heart through reducing oxidative stress and controlling cardiac Na+/K+-ATPase activity and Ca2+ levels.

Cardiotonic Steroids and the Sodium Trade Balance: New Insights into Trade-Off Mechanisms Mediated by the Na⁺/K⁺-ATPase

In 1972 Neal Bricker presented the "trade-off" hypothesis in which he detailed the role of physiological adaptation processes in mediating some of the pathophysiology associated with declines in renal function. In the late 1990's Xie and Askari published seminal studies indicating that the Na⁺/K⁺-ATPase (NKA) was not only an ion pump, but also a signal transducer that interacts with several signaling partners. Since this discovery, numerous studies from multiple laboratories have shown that the NKA is a central player in mediating some of these long-term "trade-offs" of the physiological adaptation processes which Bricker originally proposed in the 1970's. In fact, NKA ligands such as cardiotonic steroids (CTS), have been shown to signal through NKA, and consequently been implicated in mediating both adaptive and maladaptive responses to volume overload such as fibrosis and oxidative stress. In this review we will emphasize the role the NKA plays in this "trade-off" with respect to CTS signaling and its implication in inflammation and fibrosis in target organs including the heart, kidney, and vasculature. As inflammation and fibrosis exhibit key roles in the pathogenesis of a number of clinical disorders such as chronic kidney disease, heart failure, atherosclerosis, obesity, preeclampsia, and aging, this review will also highlight the role of newly discovered NKA signaling partners in mediating some of these conditions.

Telocinobufagin, a Novel Cardiotonic Steroid, Promotes Renal Fibrosis via Na⁺/K⁺-ATPase Profibrotic Signaling Pathways

Cardiotonic steroids (CTS) are Na⁺/K⁺-ATPase (NKA) ligands that are elevated in volume-expanded states and associated with cardiac and renal dysfunction in both clinical and experimental settings. We test the hypothesis that the CTS telocinobufagin (TCB) promotes renal dysfunction in a process involving signaling through the NKA α-1 in the following studies. First, we infuse TCB (4 weeks at 0.1 µg/g/day) or a vehicle into mice expressing wild-type (WT) NKA α-1, as well as mice with a genetic reduction (~40%) of NKA α-1 (NKA α-1^+/−). Continuous TCB infusion results in increased proteinuria and cystatin C in WT mice which are significantly attenuated in NKA α-1^+/− mice (all p < 0.05), despite similar increases in blood pressure. In a series of in vitro experiments, 24-h treatment of HK2 renal proximal tubular cells with TCB results in significant dose-dependent increases in both Collagens 1 and 3 mRNA (2-fold increases at 10 nM, 5-fold increases at 100 nM, p < 0.05). Similar effects are seen in primary human renal mesangial cells. TCB treatment (100 nM) of SYF fibroblasts reconstituted with cSrc results in a 1.5-fold increase in Collagens 1 and 3 mRNA (p < 0.05), as well as increases in both Transforming Growth factor beta (TGFb, 1.5 fold, p < 0.05) and Connective Tissue Growth Factor (CTGF, 2 fold, p < 0.05), while these effects are absent in SYF cells without Src kinase. In a patient study of subjects with chronic kidney disease, TCB is elevated compared to healthy volunteers. These studies suggest that the pro-fibrotic effects of TCB in the kidney are mediated though the NKA-Src kinase signaling pathway and may have relevance to volume-overloaded conditions, such as chronic kidney disease where TCB is elevated.

Bone marrow mesenchymal stem cells reduce ureteral stricture formation in a rat model via the paracrine effect of extracellular vesicles

With no effective therapy to prevent or treat ureteral stricture (US), a multifactorial fibrotic disease after iatrogenic injury of the ureter, the need for new therapies is urgent. Mesenchymal stem cells (MSCs) have been widely studied for treating tissue defects and excessive fibrosis, and recent studies established that one of the main therapeutic vectors of MSCs is comprised in their secretome and represented by extracellular vesicles (EVs). Thus, we have determined to explore the specific role of MSCs‐derived EVs (MSC‐EVs) treatment in a pre‐clinical model of US. The results firstly showed that either a bolus dose of MSCs or a bolus dose of MSC‐EVs (administration via renal‐arterial) significantly ameliorated ureteral fibrosis and recuperated ureter morphological development in a US rat model. We confirmed our observations through MSCs or MSC‐EVs treatment alleviated hydronephrosis, less renal dysfunction and blunted transforming growth factor‐β1 induced fibration. Due to MSC‐EVs are the equivalent dose of MSCs, and similar curative effects of transplantation of MSCs and MSC‐EVs were observed, we speculated the curative effect of MSCs in treating US might on account of the release of EVs through paracrine mechanisms. Our study demonstrated an innovative strategy to counteract ureteral stricture formation in a rat model of US.

Na/K-ATPase signaling mediates miR-29b-3p regulation and cardiac fibrosis formation in mice with chronic kidney disease

The Na/K-ATPase is an important membrane ion transporter and a signaling receptor that is essential for maintaining normal cell function. The current study examined the role of Na/K-ATPase signaling in regulating miR-29b-3p, an anti-fibrotic microRNA, in a mouse chronic kidney disease (CKD) model (5/6th partial nephrectomy or PNx). The results showed that CKD induced significant reduction of miR-29b-3p expression in the heart tissue by activation of Src and NFκB signaling in these animals. To demonstrate the role of Na/K-ATPase signaling, we also performed the PNx surgery on Na/K-ATPase α1 heterozygous (α1+/-) mice, which expresses ~40% less Na/K-ATPase α1 compared to their wild type littermates (WT) and exhibits deficiency in Na/K-ATPase signaling. We found that CKD did not significantly change the miR-29b-3p expression in heart tissue from the α1+/- animals. We also found that CKD failed to activate Src and NFκB signaling in these animals. Using isolated cardiac fibroblasts from α1+/- mice and their WT littermates, we showed that ouabain, a specific Na/K-ATPase ligand, induces decreased miR-29b-3p expression in fibroblasts isolated from WT mice, but had no effect in cells from α1+/- mice. Inhibition of NFκB by Bay11-7082 prevented ouabain-induced miR-29b-3p reduction in WT fibroblasts. To further confirm the in vivo effect of Na/K-ATPase signaling in regulation of miR-29b-3p and cardiac fibrosis in CKD animals, we used pNaKtide, a Src inhibiting peptide derived from the sequence of Na/K-ATPase, to block the activation of Na/K-ATPase signaling. The result showed that pNaKtide injection significantly increased miR-29b-3p expression and mitigated the CKD-induced cardiac fibrosis in these animals. These results clearly demonstrated that Na/K-ATPase signaling is an important mediator in CKD that regulates miR-29b-3p expression and cardiac fibrosis, which provides a novel target for regulation of miR-29b-3p in CKD. We also demonstrate that antagonizing Na/K-ATPase signaling by pNaKtide can reduce organ fibrosis through the stimulation of tissue miR-29b-3p expression.

Chronic inhalation of e-cigarette vapor containing nicotine disrupts airway barrier function and induces systemic inflammation and multiorgan fibrosis in mice

Electronic (e)-cigarettes theoretically may be safer than conventional tobacco. However, our prior studies demonstrated direct adverse effects of e-cigarette vapor (EV) on airway cells, including decreased viability and function. We hypothesize that repetitive, chronic inhalation of EV will diminish airway barrier function, leading to inflammatory protein release into circulation, creating a systemic inflammatory state, ultimately leading to distant organ injury and dysfunction. C57BL/6 and CD-1 mice underwent nose only EV exposure daily for 3-6 mo, followed by cardiorenal physiological testing. Primary human bronchial epithelial cells were grown at an air-liquid interface and exposed to EV for 15 min daily for 3-5 days before functional testing. Daily inhalation of EV increased circulating proinflammatory and profibrotic proteins in both C57BL/6 and CD-1 mice: the greatest increases observed were in angiopoietin-1 (31-fold) and EGF (25-fold). Proinflammatory responses were recapitulated by daily EV exposures in vitro of human airway epithelium, with EV epithelium secreting higher IL-8 in response to infection (227 vs. 37 pg/ml, respectively; P < 0.05). Chronic EV inhalation in vivo reduced renal filtration by 20% ( P = 0.017). Fibrosis, assessed by Masson's trichrome and Picrosirius red staining, was increased in EV kidneys (1.86-fold, C57BL/6; 3.2-fold, CD-1; P < 0.05), heart (2.75-fold, C57BL/6 mice; P < 0.05), and liver (1.77-fold in CD-1; P < 0.0001). Gene expression changes demonstrated profibrotic pathway activation. EV inhalation altered cardiovascular function, with decreased heart rate ( P < 0.01), and elevated blood pressure ( P = 0.016). These data demonstrate that chronic inhalation of EV may lead to increased inflammation, organ damage, and cardiorenal and hepatic disease.

Comprehensive transcriptional landscape of porcine cardiac and skeletal muscles reveals differences of aging

Aging significantly affects the cardiac muscle (CM) and skeletal muscles (SM). Since the aging process of CM and SM may be different, high throughput RNA sequencing was performed using CM and SM in different age conditions to evaluate the expression profiles of messenger RNA (mRNA), long non-coding RNA (lncRNA), micro RNA (miRNA), and circular (circRNA). Several mRNAs, lncRNAs, and miRNAs were highly expressed and consistently appeared in both ages in one of the two muscle tissues. Gene ontology (GO) annotation described that these genes were required for maintaining normal biological functions of CM and SM tissues. Furthermore, 26 mRNAs, 4 lncRNAs, 22 miRNAs, and 26 circRNAs were differentially expressed during cardiac muscle aging. Moreover, 81 mRNAs, 5 lncRNAs, 79 miRNAs, and 62 circRNAs were differentially expressed during aging of skeletal muscle. When comparing the expression profiles of CM and SM during aging, the senescence process in CM and SM was found to be fundamentally different. In addition, we assessed multi-group cooperative control relationships and constructed circRNA-miRNA-mRNA co-expression networks in muscular aging. In conclusion, our findings will contribute to the understanding of muscular aging and provide a foundation for future studies on the molecular mechanisms underlying muscular aging.

MicroRNA-29c Prevents Pulmonary Fibrosis by Regulating Epithelial Cell Renewal and Apoptosis

Successful repair and renewal of alveolar epithelial cells (AECs) are critical in prohibiting the accumulation of myofibroblasts in pulmonary fibrogenesis. MicroRNAs (miRNAs) are multifocal regulators involved in lung injury and repair. However, the contribution of miRNAs to AEC2 renewal and apoptosis is incompletely understood. We report that miRNA-29c (miR-29c) expression is lower in AEC2s of individuals with idiopathic pulmonary fibrosis than in healthy lungs. Epithelial cells overexpressing miR-29c show higher proliferative rates and viability. miR-29c protects epithelial cells from apoptosis by targeting forkhead box O3a (Foxo3a). Both overexpression of miR-29c conventionally and AEC2s specifically lead to less fibrosis and better recovery in vivo. Furthermore, deficiency of miR-29c in AEC2s results in higher apoptosis and reduced epithelial renewal. Interestingly, a gene network including a subset of apoptotic genes was coregulated by both Toll-like receptor 4 and miR-29c. Taken together, miR-29c maintains epithelial integrity and promotes recovery from lung injury, thereby attenuating lung fibrosis in mice.

Puerarin Suppresses Na+-K+-ATPase-Mediated Systemic Inflammation and CD36 Expression, and Alleviates Cardiac Lipotoxicity In Vitro and In Vivo

Puerarin, a type of isoflavone, was shown to have multiple protective effects on myocardial injury. The objective of this study was to investigate the role of puerarin in the progression of lipotoxic cardiomyopathy. Primary cardiomyocytes were isolated from FATP1 transgenic (Tg) mice with lipotoxic cardiomyopathy, and various concentrations of puerarin were used to incubate with the cardiomyocytes. Our results showed low-dose puerarin (≤20 μM) treatment increased the cell viability and decreased the accumulation of free fatty acid (FFA). The data on enzyme-linked immunosorbent assay indicated that 15 μM puerarin treatment greatly increased Na-K-ATPase activity and decreased C-reactive protein secretion, thus suppressing the expression of CD36, a key contributor to the FFA accumulation. Additionally, low-dose puerarin (≤100 mg/kg body weight) administration improved Na-K-ATPase activity. Our data on serum analysis and histological detection in vivo indicated that systemic inflammation, CD36-induced lipid infiltration, and cardiomyocyte apoptosis were markedly alleviated in Tg mice injected with 90 mg/kg dose of puerarin. Finally, the uptake rates of H-palmitate and C-glucose were monitored on ex vivo working hearts that were obtained from wild-type (WT), Tg-control, and Tg-puerarin mice. Compared with WT hearts, Tg hearts displayed a significant decrease in Na/K-ATPase activity and glucose consumption rate and an increase in palmitate uptake rate and FFA accumulation. In Tg-puerarin hearts, Na/K-ATPase activity and glucose consumption rate were significantly rescued, and palmitate uptake and FFA accumulation were sharply suppressed. In conclusion, low-dose puerarin suppressed Na-K-ATPase-mediated CD36 expression and systemic inflammation and alleviated cardiac lipotoxicity in vitro and in vivo.

Biomarkers in patients with myocardial fibrosis

Myocardial fibrosis is observed in many cardiovascular diseases including hypertension, heart failure and cardiomyopathy. Myocardial fibrosis has been proved to be reversible and treatable only under timely intervention, which makes early detection and assessment of fibrosis crucial. Aside from tissue biopsy as the gold standard for the diagnosis of myocardial fibrosis, circulating biomarkers have been adopted as noninvasive assessment of this lesion. Dysregulated collagen deposition is thought to be the major cause of myocardial fibrosis. Collagens, procollagens, TGF-β, TIMP, galectin-3, and microRNAs are thought to be indicators of myocardial fibrosis. In this review, we summarize the molecules that are frequently used as biomarkers in diagnosis of cardiac fibrosis. Mechanisms of fibrosis that they take part in are also introduced.

MicroRNA profiling in kidney disease: Plasma versus plasma-derived exosomes

Liquid biopsies have advanced rapidly in recent years for use in diagnostic and prognostic applications. One important aspect of this advancement is the growth in our understanding of microRNA (miRNA) biology. The measurement of miRNAs packaged within exosomes, which are constantly released into the blood stream, may reflect pathological changes within the body. The current study performed miRNA profiling using plasma and plasma-derived exosome samples from two animal models of kidney disease, the 5/6th partial nephrectomy (PNx) and two-kidney-one-clip (2K1C) models. The RT-qPCR-based profiling results revealed that the overall miRNA expression level was much higher in plasma than in plasma-derived exosomes. With 200μl of either plasma or exosomes derived from the same volume of plasma, 629 out of 665 total miRNAs analyzed were detectable in plasma samples from sham-operated rats, while only 403 were detectable in exosomes with a cutoff value set at 35cycles. Moreover, the average miRNA expression level in plasma was about 16-fold higher than that in exosomes. We also found a select subset of miRNAs that were enriched within exosomes. The number of detectable miRNAs from plasma-derived exosomes was increased in rats subjected to PNx or 2K1C surgery compared to sham-operated animals. Importantly, we found that the changes of individual miRNAs measured in plasma had very poor concordance with that measured in plasma-derived exosomes in both animal models, suggesting that miRNAs in plasma and plasma-derived exosomes are differentially regulated in these disease conditions. Interestingly, PNx and 2K1C surgeries induced similar changes in miRNA expression, implying that common pathways were activated in these two disease models. Pathway analyses using DIANA-miRPath v3.0 showed that significantly changed exosomal miRNAs were associated with extracellular matrix (ECM) receptor interaction and mucin type-O-glycan synthesis pathways, which are related with tissue fibrosis and kidney injury, respectively. In conclusion, our results demonstrated that due to the differential changes in miRNAs, the measurement of exosomal miRNAs cannot be replaced by the measurement of miRNAs in plasma, or vice versa. We also showed that a set of miRNAs related with kidney injury and organ fibrosis were dysregulated in plasma-derived exosomes from animal models of kidney disease.

miR-29b promotes skin wound healing and reduces excessive scar formation by inhibition of the TGF-β1/Smad/CTGF signaling pathway

The hypertrophic scar is a medical difficulty of humans, which has caused great pain to patients. Here, we investigated the inhibitory effect of miR-29b on scar formation. The scalded model was established in mice and miR-29b mimics or a negative control was subcutaneously injected into the injury skin. Then various molecular biological experiments were performed to assess the effect of miR-29b on scar formation. According to our present study, first, the results demonstrated that miR-29b was down-regulated in thermal injury tissue and miR-29b treatment could promote wound healing, inhibit scar formation, and alleviate histopathological morphologic alteration in scald tissues. Additionally, miR-29b treatment suppressed collagen deposition and fibrotic gene expression in scar tissues. Finally, we found that miR-29b treatment inhibited the TGF-β1/Smad/CTGF signaling pathway. Taken together, our data suggest that miR-29b treatment has an inhibitory effect against scar formation via inhibition of the TGF-β1/Smad/CTGF signaling pathway and may provide a potential molecular basis for future treatments for hypertrophic scars.

Na-K-ATPase regulates intercellular communication in the vascular wall via cSrc kinase-dependent connexin43 phosphorylation

Communication between vascular smooth muscle cells (VSMCs) is dependent on gap junctions and is regulated by the Na-K-ATPase. The Na-K-ATPase is therefore important for synchronized VSMC oscillatory activity, i.e., vasomotion. The signaling between the Na-K-ATPase and gap junctions is unknown. We tested here the hypothesis that this signaling involves cSrc kinase. Intercellular communication was assessed by membrane capacitance measurements of electrically coupled VSMCs. Vasomotion in isometric myograph, input resistance, and synchronized [Ca2+]i transients were used as readout for intercellular coupling in rat mesenteric small arteries in vitro. Phosphorylation of cSrc kinase and connexin43 (Cx43) were semiquantified by Western blotting. Micromole concentration of ouabain reduced the amplitude of norepinephrine-induced vasomotion and desynchronized Ca2+ transients in VSMC in the arterial wall. Ouabain also increased input resistance in the arterial wall. These effects of ouabain were antagonized by inhibition of tyrosine phosphorylation with genistein, PP2, and by an inhibitor of the Na-K-ATPase-dependent cSrc activation, pNaKtide. Moreover, inhibition of cSrc phosphorylation increased vasomotion amplitude and decreased the resistance between cells in the vascular wall. Ouabain inhibited the electrical coupling between A7r5 cells, but pNaKtide restored the electrical coupling. Ouabain increased cSrc autophosphorylation of tyrosine 418 (Y418) required for full catalytic activity whereas pNaKtide antagonized it. This cSrc activation was associated with Cx43 phosphorylation of tyrosine 265 (Y265). Our findings demonstrate that Na-K-ATPase regulates intercellular communication in the vascular wall via cSrc-dependent Cx43 tyrosine phosphorylation.

Src-independent ERK signaling through the rat α3 isoform of Na/K-ATPase

The Na/K-ATPase α1 polypeptide supports both ion-pumping and signaling functions. The Na/K-ATPase α3 polypeptide differs from α1 in both its primary structure and its tissue distribution. The expression of α3 seems particularly important in neurons, and recent clinical evidence supports a unique role of this isoform in normal brain function. The nature of this specific role of α3 has remained elusive, because the ubiquitous presence of α1 has hindered efforts to characterize α3-specific functions in mammalian cell systems. Using Na/K-ATPase α1 knockdown pig kidney cells (PY-17), we generated the first stable mammalian cell line expressing a ouabain-resistant form of rat Na/K-ATPase α3 in the absence of endogenous pig α1 detectable by Western blotting. In these cells, Na/K-ATPase α3 formed a functional ion-pumping enzyme and rescued the expression of Na/K-ATPase β1 and caveolin-1 to levels comparable with those observed in PY-17 cells rescued with a rat Na/K-ATPase α1 (AAC-19). The α3-containing enzymes had lower Na+ affinity and lower ouabain-sensitive transport activity than their α1-containing counterparts under basal conditions, but showed a greater capacity to be activated when intracellular Na+ was increased. In contrast to Na/K-ATPase α1, α3 could not regulate Src. Upon exposure to ouabain, Src activation did not occur, yet ERK was activated through Src-independent pathways involving PI3K and PKC. Hence, α3 expression confers signaling and pumping properties that are clearly distinct from that of cells expressing Na/K-ATPase α1.

Reducing Cardiac Fibrosis: Na/K-ATPase Signaling Complex as a Novel Target

Cardiac fibrosis is a common pathological process in cardiac disease and may lead to heart failure. It can also cause sudden death even in those without cardiac symptoms. Tissue fibrosis can be categorized into two categories: replacement fibrosis (also called reparative fibrosis) and reactive fibrosis. In replacement fibrosis, infiltration of inflammatory cells and accumulation of Extracellular Matrix (ECM) proteins are the initial steps in forming scarlike fibrotic tissue after acute cardiac injury and cardiac cell necrosis. Reactive fibrosis can be formed in response to hormonal change and pressure or volume overload. Experimental studies in animals have identified important pathways such as the Renin-Angiotensin-Aldosterone System (RAAS) and the endothelin pathway that contribute to fibrosis formation. Despite the fact that clinical trials using RAAS inhibitors as therapies for reducing cardiac fibrosis and improving cardiac function have been promising, heart failure is still the leading cause of deaths in the United States. Intensive efforts have been made to find novel targets and to develop new treatments for cardiac fibrosis and heart failure in the past few decades. The Na/K-ATPase, a canonical ion transporter, has been shown to also function as a signal transducer and prolonged activation of Na/K-ATPase signaling has been found to promote the formation of cardiac fibrosis. Novel tools that block the activation of Na/K-ATPase signaling have been developed and have shown promise in reducing cardiac fibrosis. This review will discuss the recent development of novel molecular targets, focusing on the Na/K-ATPase signaling complex as a therapeutic target in treatment of cardiac fibrosis.

Cigarette smoking causes epigenetic changes associated with cardiorenal fibrosis

Clinical studies indicate that smoking combustible cigarettes promotes progression of renal and cardiac injury, leading to functional decline in the setting of chronic kidney disease (CKD). However, basic studies using in vivo small animal models that mimic clinical pathology of CKD are lacking. To address this issue, we evaluated renal and cardiac injury progression and functional changes induced by 4 wk of daily combustible cigarette smoke exposure in the 5/6th partial nephrectomy (PNx) CKD model. Molecular evaluations revealed that cigarette smoke significantly (P < 0.05) decreased renal and cardiac expression of the antifibrotic microRNA miR-29b-3 and increased expression of molecular fibrosis markers. In terms of cardiac and renal organ structure and function, exposure to cigarette smoke led to significantly increased systolic blood pressure, cardiac hypertrophy, cardiac and renal fibrosis, and decreased renal function. These data indicate that decreased expression of miR-29b-3p is a novel mechanism wherein cigarette smoke promotes accelerated cardiac and renal tissue injury in CKD. (155 words).

Regulation of Cardiac Remodeling by Cardiac Na(+)/K(+)-ATPase Isoforms

Cardiac remodeling occurs after cardiac pressure/volume overload or myocardial injury during the development of heart failure and is a determinant of heart failure. Preventing or reversing remodeling is a goal of heart failure therapy. Human cardiomyocyte Na⁺/K⁺-ATPase has multiple α isoforms (1–3). The expression of the α subunit of the Na⁺/K⁺-ATPase is often altered in hypertrophic and failing hearts. The mechanisms are unclear. There are limited data from human cardiomyocytes. Abundant evidences from rodents show that Na⁺/K⁺-ATPase regulates cardiac contractility, cell signaling, hypertrophy and fibrosis. The α1 isoform of the Na⁺/K⁺-ATPase is the ubiquitous isoform and possesses both pumping and signaling functions. The α2 isoform of the Na⁺/K⁺-ATPase regulates intracellular Ca²⁺ signaling, contractility and pathological hypertrophy. The α3 isoform of the Na⁺/K⁺-ATPase may also be a target for cardiac hypertrophy. Restoration of cardiac Na⁺/K⁺-ATPase expression may be an effective approach for prevention of cardiac remodeling. In this article, we will overview: (1) the distribution and function of isoform specific Na⁺/K⁺-ATPase in the cardiomyocytes. (2) the role of cardiac Na⁺/K⁺-ATPase in the regulation of cell signaling, contractility, cardiac hypertrophy and fibrosis in vitro and in vivo. Selective targeting of cardiac Na⁺/K⁺-ATPase isoform may offer a new target for the prevention of cardiac remodeling.