Kruppel-like factor 4 is critical for transcriptional control of cardiac mitochondrial homeostasis

Hypertriglyceridemia: Molecular and Genetic Landscapes

Lipid disorders represent one of the most worrisome cardiovascular risk factors. The focus on the impact of lipids on cardiac and vascular health usually concerns low-density lipoprotein cholesterol, while the role of triglycerides (TGs) is given poor attention. The literature provides data on the impact of higher plasma concentrations in TGs on the cardiovascular system and, therefore, on the outcomes and comorbidities of patients. The risk for coronary heart diseases varies from 57 to 76% in patients with hypertriglyceridemia. Specifically, the higher the plasma concentrations in TGs, the higher the incidence and prevalence of death, myocardial infarction, and stroke. Nevertheless, the metabolism of TGs and the exact physiopathologic mechanisms which try to explain the relationship between TGs and cardiovascular outcomes are not completely understood. The aims of this narrative review were as follows: to provide a comprehensive evaluation of the metabolism of triglycerides and a possible suggestion for understanding the targets for counteracting hypertriglyceridemia; to describe the inner physiopathological background for the relationship between vascular and cardiac damages derived from higher plasma concentrations in TGs; and to outline the need for promoting further insights in therapies for reducing TGs plasma levels.

Transcriptional control of cardiac energy metabolism in health and disease: Lessons from animal models

Cardiac ATP production is tightly regulated in order to satisfy the evolving energetic requirements imposed by different cues during health and pathological conditions. In order to sustain high ATP production rates, cardiac cells are endowed with a vast mitochondrial network that is essentially acquired during the perinatal period. Nevertheless, adult cardiac cells also adapt their mitochondrial mass and oxidative function to changes in energy demand and substrate availability by fine-tuning the pathways and mitochondrial machinery involved in energy production. The reliance of cardiac cells on mitochondrial metabolism makes them particularly sensitive to alterations in proper mitochondrial function, so that deficiency in energy production underlies or precipitates the development of heart diseases. Mitochondrial biogenesis is a complex process fundamentally controlled at the transcriptional level by a network of transcription factors and co-regulators, sometimes with partially redundant functions, that ensure adequate energy supply to the working heart. Novel uncovered regulators, such as RIP140, PERM1, MED1 or BRD4 have been recently shown to modulate or facilitate the transcriptional activity of the PGC-1s/ERRs/PPARs regulatory axis, allowing cardiomyocytes to adapt to a variety of physiological or pathological situations requiring different energy provision. In this review, we summarize the current knowledge on the mechanisms that regulate cardiac mitochondrial biogenesis, highlighting the recent discoveries of new transcriptional regulators and describing the experimental models that have provided solid evidence of the relevant contribution of these factors to cardiac function in health and disease.

The therapeutic perspective of NAD+ precursors in age-related diseases

Nicotinamide adenine dinucleotide (NAD+) is the fundamental molecule that performs numerous biological reactions and is crucial for maintaining cellular homeostasis. Studies have found that NAD+ decreases with age in certain tissues, and age-related NAD+ depletion affects physiological functions and contributes to various aging-related diseases. Supplementation of NAD+ precursor significantly elevates NAD+ levels in murine tissues, effectively mitigates metabolic syndrome, enhances cardiovascular health, protects against neurodegeneration, and boosts muscular strength. Despite the versatile therapeutic functions of NAD+ in animal studies, the efficacy of NAD+ precursors in clinical studies have been limited compared with that in the pre-clinical study. Clinical studies have demonstrated that NAD+ precursor treatment efficiently increases NAD+ levels in various tissues, though their clinical proficiency is insufficient to ameliorate the diseases. However, the latest studies regarding NAD+ precursors and their metabolism highlight the significant role of gut microbiota. The studies found that orally administered NAD+ intermediates interact with the gut microbiome. These findings provide compelling evidence for future trials to further explore the involvement of gut microbiota in NAD+ metabolism. Also, the reduced form of NAD+ precursor shows their potential to raise NAD+, though preclinical studies have yet to discover their efficacy. This review sheds light on NAD+ therapeutic efficiency in preclinical and clinical studies and the effect of the gut microbiota on NAD+ metabolism.

Krüpple-like factors in cardiomyopathy: emerging player and therapeutic opportunities

Cardiomyopathy, a heterogeneous pathological condition characterized by changes in cardiac structure or function, represents a significant risk factor for the prevalence and mortality of cardiovascular disease (CVD). Research conducted over the years has led to the modification of definition and classification of cardiomyopathy. Herein, we reviewed seven of the most common types of cardiomyopathies, including Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC), diabetic cardiomyopathy, Dilated Cardiomyopathy (DCM), desmin-associated cardiomyopathy, Hypertrophic Cardiomyopathy (HCM), Ischemic Cardiomyopathy (ICM), and obesity cardiomyopathy, focusing on their definitions, epidemiology, and influencing factors. Cardiomyopathies manifest in various ways ranging from microscopic alterations in cardiomyocytes, to tissue hypoperfusion, cardiac failure, and arrhythmias caused by electrical conduction abnormalities. As pleiotropic Transcription Factors (TFs), the Krüppel-Like Factors (KLFs), a family of zinc finger proteins, are involved in regulating the setting and development of cardiomyopathies, and play critical roles in associated biological processes, including Oxidative Stress (OS), inflammatory reactions, myocardial hypertrophy and fibrosis, and cellular autophagy and apoptosis, particularly in diabetic cardiomyopathy. However, research into KLFs in cardiomyopathy is still in its early stages, and the pathophysiologic mechanisms of some KLF members in various types of cardiomyopathies remain unclear. This article reviews the roles and recent research advances in KLFs, specifically those targeting and regulating several cardiomyopathy-associated processes.

Doxycycline induces mitochondrial dysfunction in aortic smooth muscle cells

The antibiotic doxycycline is known to inhibit inflammation and was therefore considered as a therapeutic to prevent abdominal aortic aneurysm (AAA) growth. Yet mitochondrial dysfunction is a key-characteristic of clinical AAA disease. We hypothesize that doxycycline impairs mitochondrial function in the aorta and aortic smooth muscle cells (SMCs). Doxycycline induced mitonuclear imbalance, reduced proliferation and diminished expression of typical contractile smooth muscle cell (SMC) proteins. To understand the underlying mechanism, we studied krüppel-like factor 4 (KLF4). The expression of this transcription factor was enhanced in SMCs after doxycycline treatment. Knockdown of KLF4, however, did not affect the doxycycline-induced SMC phenotypic changes. Then we used the bioenergetics drug elamipretide (SS-31). Doxycycline-induced loss of SMC contractility markers was not rescued, but mitochondrial genes and mitochondrial connectivity improved upon elamipretide. Thus while doxycycline is anti-inflammatory, it also induces mitochondrial dysfunction in aortic SMCs and causes SMC phenotypic switching, potentially contributing to aortic aneurysm pathology. The drug elamipretide helps mitigate the harmful effects of doxycycline on mitochondrial function in aortic SMC, and may be of interest for treatment of aneurysm diseases with pre-existing mitochondrial dysfunction.

KLF4 and CD55 expression and function depend on each other

The transcription factor Kruppel-like factor 4 (KLF4) regulates the expression of immunosuppressive and anti-thrombotic proteins. Despite its importance in maintaining homeostasis, the signals that control its expression and the mechanism of its transactivation remain unclarified. CD55 [aka decay accelerating factor (DAF)], now known to be a regulator of T and B cell responses, biases between pro- and anti-inflammatory processes by controlling autocrine C3a and C5a receptor (C3ar1/C5ar1) signaling in cells. The similarity in CD55's and KLF4's regulatory effects prompted analyses of their functional relationship. In vascular endothelial cells (ECs), CD55 upregulation accompanied KLF4 expression via a p-CREB and CREB Binding Protein (CBP) mechanism. In both ECs and macrophages, CD55 expression was essential for KLF4's downregulation of pro-inflammatory/pro-coagulant proteins and upregulation of homeostatic proteins. Mechanistic studies showed that upregulation of KLF4 upregulated CD55. The upregulated CD55 in turn enabled the recruitment of p-CREB and CBP to KLF4 needed for its transcription. Activation of adenylyl cyclase resulting from repression of autocrine C3ar1/C5ar1 signaling by upregulated CD55 concurrently led to p-CREB and CBP recruitment to KLF4-regulated genes, thereby conferring KLF4's transactivation. Accordingly, silencing CD55 in statin-treated HUVEC disabled CBP transfer from the E-selectin to the eNOS promoter. Importantly, silencing CD55 downregulated KLF4's expression. It did the same in untreated HUVEC transitioning from KLF4low growth to KLF4hi contact inhibition. KLF4's and CD55's function in ECs and macrophages thus are linked via a novel mechanism of gene transactivation. Because the two proteins are co-expressed in many cell types, CD55's activity may be broadly tied to KLF4's immunosuppressive and antithrombotic activities.

Cardiac maturation

The heart undergoes a dynamic maturation process following birth, in response to a wide range of stimuli, including both physiological and pathological cues. This process entails substantial re-programming of mitochondrial energy metabolism coincident with the emergence of specialized structural and contractile machinery to meet the demands of the adult heart. Many components of this program revert to a more "fetal" format during development of pathological cardiac hypertrophy and heart failure. In this review, emphasis is placed on recent progress in our understanding of the transcriptional control of cardiac maturation, encompassing the results of studies spanning from in vivo models to cardiomyocytes derived from human stem cells. The potential applications of this current state of knowledge to new translational avenues aimed at the treatment of heart failure is also addressed.

Novel Pan-ERR Agonists Ameliorate Heart Failure Through Enhancing Cardiac Fatty Acid Metabolism and Mitochondrial Function

BACKGROUND

Cardiac metabolic dysfunction is a hallmark of heart failure (HF). Estrogen-related receptors ERRα and ERRγ are essential regulators of cardiac metabolism. Therefore, activation of ERR could be a potential therapeutic intervention for HF. However, in vivo studies demonstrating the potential usefulness of ERR agonist for HF treatment are lacking, because compounds with pharmacokinetics appropriate for in vivo use have not been available.

METHODS

Using a structure-based design approach, we designed and synthesized 2 structurally distinct pan-ERR agonists, SLU-PP-332 and SLU-PP-915. We investigated the effect of ERR agonist on cardiac function in a pressure overload-induced HF model in vivo. We conducted comprehensive functional, multi-omics (RNA sequencing and metabolomics studies), and genetic dependency studies both in vivo and in vitro to dissect the molecular mechanism, ERR isoform dependency, and target specificity.

RESULTS

Both SLU-PP-332 and SLU-PP-915 significantly improved ejection fraction, ameliorated fibrosis, and increased survival associated with pressure overload-induced HF without affecting cardiac hypertrophy. A broad spectrum of metabolic genes was transcriptionally activated by ERR agonists, particularly genes involved in fatty acid metabolism and mitochondrial function. Metabolomics analysis showed substantial normalization of metabolic profiles in fatty acid/lipid and tricarboxylic acid/oxidative phosphorylation metabolites in the mouse heart with 6-week pressure overload. ERR agonists increase mitochondria oxidative capacity and fatty acid use in vitro and in vivo. Using both in vitro and in vivo genetic dependency experiments, we show that ERRγ is the main mediator of ERR agonism-induced transcriptional regulation and cardioprotection and definitively demonstrated target specificity. ERR agonism also led to downregulation of cell cycle and development pathways, which was partially mediated by E2F1 in cardiomyocytes.

CONCLUSIONS

ERR agonists maintain oxidative metabolism, which confers cardiac protection against pressure overload-induced HF in vivo. Our results provide direct pharmacologic evidence supporting the further development of ERR agonists as novel HF therapeutics.

KLF4 facilitates chromatin accessibility remodeling in porcine early embryos

Chromatin accessibility remodeling driven by pioneer factors is critical for the development of early embryos. Current studies have illustrated several pioneer factors as being important for agricultural animals, but what are the pioneer factors and how the pioneer factors remodel the chromatin accessibility in porcine early embryos is not clear. By employing low-input DNase-seq (liDNase-seq), we profiled the landscapes of chromatin accessibility in porcine early embryos and uncovered a unique chromatin accessibility reprogramming pattern during porcine preimplantation development. Our data revealed that KLF4 played critical roles in remodeling chromatin accessibility in porcine early embryos. Knocking down of KLF4 led to the reduction of chromatin accessibility in early embryos, whereas KLF4 overexpression promoted the chromatin openness in porcine blastocysts. Furthermore, KLF4 deficiency resulted in mitochondrial dysfunction and developmental failure of porcine embryos. In addition, we found that overexpression of KLF4 in blastocysts promoted lipid droplet accumulation, whereas knockdown of KLF4 disrupted this process. Taken together, our study revealed the chromatin accessibility dynamics and identified KLF4 as a key regulator in chromatin accessibility and cellular metabolism during porcine preimplantation embryo development.

The SIRT3-ATAD3A axis regulates MAM dynamics and mitochondrial calcium homeostasis in cardiac hypertrophy

Mitochondria are energy-producing organelles that are mobile and harbor dynamic network structures. Although mitochondria and endoplasmic reticulum (ER) play distinct cellular roles, they are physically connected to maintain functional homeostasis. Abnormal changes in this interaction have been linked to pathological states, including cardiac hypertrophy. However, the exact regulatory molecules and mechanisms are yet to be elucidated. Here, we report that ATPase family AAA-domain containing protein 3A (ATAD3A) is an essential regulator of ER-mitochondria interplay within the mitochondria-associated membrane (MAM). ATAD3A prevents isoproterenol (ISO)-induced mitochondrial calcium accumulation, improving mitochondrial dysfunction and ER stress, which preserves cardiac function and attenuates cardiac hypertrophy. We also find that ATAD3A is a new substrate of NAD+-dependent deacetylase Sirtuin 3 (SIRT3). Notably, the heart mitochondria of SIRT3 knockout mice exhibited excessive formation of MAMs. Mechanistically, ATAD3A specifically undergoes acetylation, which reduces self-oligomerization and promotes cardiac hypertrophy. ATAD3A oligomerization is disrupted by acetylation at K134 site, and ATAD3A monomer closely interacts with the IP3R1-GRP75-VDAC1 complex, which leads to mitochondrial calcium overload and dysfunction. In summary, ATAD3A localizes to the MAMs, where it protects the homeostasis of ER-mitochondria contacts, quenching mitochondrial calcium overload and keeping mitochondrial bioenergetics unresponsive to ER stress. The SIRT3-ATAD3A axis represents a potential therapeutic target for cardiac hypertrophy.

Early-life exposure to lead changes cardiac development and compromises long-term cardiac function

Lead (Pb) is widely used in industrial and daily-use consumer products. Early-life exposure may increase the risk of lead-related heart problems in childhood. However, the effects of early-life lead exposure on fetal heart development and long-term cardiac outcomes are unknown. In this study, pregnant ICR mice were exposed to lead acetate trihydrate (50 mg/kg/d) via oral gavage from gestation day 1.5 until offspring weaning. Thereafter, the second hit model was established, two groups of offspring (4 weeks old) were either administered sterile saline or Angiotensin II (Ang II) for 4 weeks until euthanasia. We investigated lead-induced offspring heart damage from embryonic period to adulthood by echocardiographic analysis, pathological H&E staining, and ultrastructural examination, as well as mitochondrial function detection. The results showed early-life lead exposure predisposed offspring mice to decreased ejection fraction, increased left ventricular volume, accompanied by hypertrophy and dilation, cardiomyocyte sarcomere dysplasia, abnormal mitochondrial structure, mitochondrial dysfunction, and decreased expression of key sarcomeric and mitochondrial genes, rendering them more susceptible to cardiac hypertrophy, vascular wall thickening, cardiac fibrosis, apoptosis, and heart failure induced by Ang II infusion. This study elucidates early-life low dose lead exposure compromises cardiac development and exacerbates second hit-induced cardiac pathological responses in adulthood, which furnishes crucial scientific evidence pertaining to the cardiac toxicity and risk evaluation associated with early-life exposure to lead.

Fatty acid metabolism disorders and potential therapeutic traditional Chinese medicines in cardiovascular diseases

Cardiovascular diseases are currently the primary cause of mortality in the whole world. Growing evidence indicated that the disturbances in cardiac fatty acid metabolism are crucial contributors in the development of cardiovascular diseases. The abnormal cardiac fatty acid metabolism usually leads to energy deficit, oxidative stress, excessive apoptosis, and inflammation. Targeting fatty acid metabolism has been regarded as a novel approach to the treatment of cardiovascular diseases. However, there are currently no specific drugs that regulate fatty acid metabolism to treat cardiovascular diseases. Many traditional Chinese medicines have been widely used to treat cardiovascular diseases in clinics. And modern studies have shown that they exert a cardioprotective effect by regulating the expression of key proteins involved in fatty acid metabolism, such as peroxisome proliferator-activated receptor α and carnitine palmitoyl transferase 1. Hence, we systematically reviewed the relationship between fatty acid metabolism disorders and four types of cardiovascular diseases including heart failure, coronary artery disease, cardiac hypertrophy, and diabetic cardiomyopathy. In addition, 18 extracts and eight monomer components from traditional Chinese medicines showed cardioprotective effects by restoring cardiac fatty acid metabolism. This work aims to provide a reference for the finding of novel cardioprotective agents targeting fatty acid metabolism.

Mitophagy for cardioprotection

Mitochondrial function is maintained by several strictly coordinated mechanisms, collectively termed mitochondrial quality control mechanisms, including fusion and fission, degradation, and biogenesis. As the primary source of energy in cardiomyocytes, mitochondria are the central organelle for maintaining cardiac function. Since adult cardiomyocytes in humans rarely divide, the number of dysfunctional mitochondria cannot easily be diluted through cell division. Thus, efficient degradation of dysfunctional mitochondria is crucial to maintaining cellular function. Mitophagy, a mitochondria specific form of autophagy, is a major mechanism by which damaged or unnecessary mitochondria are targeted and eliminated. Mitophagy is active in cardiomyocytes at baseline and in response to stress, and plays an essential role in maintaining the quality of mitochondria in cardiomyocytes. Mitophagy is mediated through multiple mechanisms in the heart, and each of these mechanisms can partially compensate for the loss of another mechanism. However, insufficient levels of mitophagy eventually lead to mitochondrial dysfunction and the development of heart failure. In this review, we discuss the molecular mechanisms of mitophagy in the heart and the role of mitophagy in cardiac pathophysiology, with the focus on recent findings in the field.

Premature senescence and cardiovascular disease following cancer treatments: mechanistic insights

Cardiovascular disease (CVD) is a leading cause of morbidity and mortality, especially among the aging population. The "response-to-injury" model proposed by Dr. Russell Ross in 1999 emphasizes inflammation as a critical factor in atherosclerosis development, with atherosclerotic plaques forming due to endothelial cell (EC) injury, followed by myeloid cell adhesion and invasion into the blood vessel walls. Recent evidence indicates that cancer and its treatments can lead to long-term complications, including CVD. Cellular senescence, a hallmark of aging, is implicated in CVD pathogenesis, particularly in cancer survivors. However, the precise mechanisms linking premature senescence to CVD in cancer survivors remain poorly understood. This article aims to provide mechanistic insights into this association and propose future directions to better comprehend this complex interplay.

Krüppel-like factor 12 regulates aging ovarian granulosa cell apoptosis by repressing SPHK1 transcription and sphingosine-1-phosphate (S1P) production

Oxidative stress triggered by aging, radiation, or inflammation impairs ovarian function by inducing granulosa cell (GC) apoptosis. However, the mechanism inducing GC apoptosis has not been characterized. Here, we found that ovarian GCs from aging patients showed increased oxidative stress, enhanced reactive oxygen species activity, and significantly decreased expression of the known antiapoptotic factor sphingosine-1-phosphate/sphingosine kinase 1 (SPHK1) in GCs. Interestingly, the expression of Krüppel-like factor 12 (KLF12) was significantly increased in the ovarian GCs of aging patients. Furthermore, we determined that KLF12 was significantly upregulated in hydrogen peroxide-treated GCs and a 3-nitropropionic acid-induced in vivo model of ovarian oxidative stress. This phenotype was further confirmed to result from inhibition of SPHK1 by KLF12. Interestingly, when endogenous KLF12 was knocked down, it rescued oxidative stress-induced apoptosis. Meanwhile, supplementation with SPHK1 partially reversed oxidative stress-induced apoptosis. However, this function was lost in SPHK1 with deletion of the binding region to the KLF12 promoter. SPHK1 reversed apoptosis caused by hydrogen peroxide-KLF12 overexpression, a result further confirmed in an in vitro ovarian culture model and an in vivo 3-nitropropionic acid-induced ovarian oxidative stress model. Overall, our study reveals that KLF12 is involved in regulating apoptosis induced by oxidative stress in aging ovarian GCs and that sphingosine-1-phosphate/SPHK1 can rescue GC apoptosis by interacting with KLF12 in negative feedback.

The translational landscape of human vascular smooth muscle cells identifies novel short open reading frame-encoded peptide regulators for phenotype alteration

AIMS

The plasticity of vascular smooth muscle cells (VSMCs) enables them to alter phenotypes under various physiological and pathological stimuli. The alteration of VSMC phenotype is a key step in vascular diseases, including atherosclerosis. Although the transcriptome shift during VSMC phenotype alteration has been intensively investigated, uncovering multiple key regulatory signalling pathways, the translatome dynamics in this cellular process, remain largely unknown. Here, we explored the genome-wide regulation at the translational level of human VSMCs during phenotype alteration.

METHODS AND RESULTS

We generated nucleotide-resolution translatome and transcriptome data from human VSMCs undergoing phenotype alteration. Deep sequencing of ribosome-protected fragments (Ribo-seq) revealed alterations in protein synthesis independent of changes in messenger ribonucleicacid levels. Increased translational efficiency of many translational machinery components, including ribosomal proteins, eukaryotic translation elongation factors and initiation factors were observed during the phenotype alteration of VSMCs. In addition, hundreds of candidates for short open reading frame-encoded polypeptides (SEPs), a class of peptides containing 200 amino acids or less, were identified in a combined analysis of translatome and transcriptome data with a high positive rate in validating their coding capability. Three evolutionarily conserved SEPs were further detected endogenously by customized antibodies and suggested to participate in the pathogenesis of atherosclerosis by analysing the transcriptome and single cell RNA-seq data from patient atherosclerotic artery samples. Gain- and loss-of-function studies in human VSMCs and genetically engineered mice showed that these SEPs modulate the alteration of VSMC phenotype through different signalling pathways, including the mitogen-activated protein kinase pathway and p53 pathway.

CONCLUSION

Our study indicates that an increase in the capacity of translation, which is attributable to an increased quantity of translational machinery components, mainly controls alterations of VSMC phenotype at the level of translational regulation. In addition, SEPs could function as important regulators in the phenotype alteration of human VSMCs.

Paeoniflorin suppresses kidney inflammation by regulating macrophage polarization via KLF4-mediated mitophagy

BACKGROUND

Macrophages M1 polarization involved in the process of renal inflammatory injury, is a well-established hallmark of chronic kidney disease (CKD). Paeoniflorin (PF), a water-soluble monoterpene glycoside extracted from Paeonia lactiflora, revealed renal anti-inflammatory activities in our previous study. However, the potential molecular mechanism of PF on CKD remains unknown.

PURPOSE

The present study aims to investigate the regulation of PF on macrophage polarization in CKD.

METHODS

A CKD model was established by cationic bovine serum albumin and a murine macrophage cell line RAW264.7 induced with lipopolysaccharide (LPS) were used to clarify the underlying mechanisms of PF in CKD.

RESULTS

Results showed that PF exhibited favorable protective effects on CKD model mice by promoting renal function, ameliorating renal pathological injury and podocyte damage. Furthermore, PF inhibited the infiltration of M1 macrophage marker CD68 and iNOS in kidney tissue, but increased the proportion of M2 macrophage marker CD206. In RAW264.7 cells stimulated with LPS, the levels of cytokines including IL-6, IL-1β, TNF-α, MCP-1 were lessened under PF treatment, while the levels of Arg1, Fizz1, IL-10 and Ym-1 were augmented. These results indicated that PF promoted macrophage polarization from M1 to M2 in vivo and in vitro. More importantly, PF repaired the damaged mitochondria through increasing mitochondrial membrane potential and reducing ROS accumulation. The mitophagy-related proteins PINK1, Parkin, Bnip3, P62 and LC3 were up-regulated by PF, accompanied by the incremental expressions of Krüppel-like transcription factor 4 (KLF4). Moreover, the promotion of mitophagy and inhibition of M1 macrophage polarization owing to PF were reversed by mitophagy inhibitor Mdivi-1 or silencing KLF4.

CONCLUSION

Overall, PF suppressed renal inflammation by promoting macrophage polarization from M1 to M2 and inducing mitophagy via regulating KLF4. It is expected to provide a new strategy for exploring the effects of PF in treating CKD.

Kinases in cerebral cavernous malformations: Pathogenesis and therapeutic targets

Cerebral cavernous malformations (CCMs) are low-flow, hemorrhagic vascular lesions of the central nervous system of genetic origin, which can cause stroke-like symptoms and seizures. From the identification of CCM1, CCM2 and CCM3 as genes related to disease progression, molecular and cellular mechanisms for CCM pathogenesis have been established and the search for potential drugs to target CCM has begun. Broadly speaking, kinases are the major group signaling in CCM pathogenesis. These include the MEKK3/MEK5/ERK5 cascade, Rho/Rock signaling, CCM3/GCKIII signaling, PI3K/mTOR signaling, and others. Since the discovery of Rho/Rock in CCM pathogenesis, inhibitors for Rho signaling and subsequently other components in CCM signaling were discovered and applied in preclinical and clinical trials to ameliorate CCM progression. This review discusses the general aspects of CCM disease, kinase-mediated signaling in CCM pathogenesis and the current state of potential treatment options for CCM. It is suggested that kinase target drug development in the context of CCM might facilitate and meet the unmet requirement - a non-surgical option for CCM disease.

Adriamycin downregulates the expression of KLF4 in cardiomyocytes in vitro and contributes to impaired cardiac energy metabolism in Adriamycin-induced cardiomyopathy

Adriamycin is a well-known anthracycline chemotherapeutic agent widely used in treating a variety of malignancies. However, Adriamycin's clinical use is limited due to its adverse side-effects, most importantly cardiomyopathy. Adriamycin-induced cardiotoxicity reportedly includes mitochondrial dysfunction. We hypothesize that modulation of KLF4, a key regulator of cardiac mitochondrial homeostasis might play a role in the development of Adriamycin-induced cardiomyopathy. Therefore, in the current work, we evaluated the interaction of Adriamycin with KLF4 and its subsequent downstream targets. Molecular docking revealed that Adriamycin interacts strongly with KLF4 at residues Thr 448, Arg 452, Ser 444 falls within C2H2 motif which is the active site. Quantitative real-time PCR also revealed that KLF4 is downregulated by Adriamycin in cardiomyocytes in vitro. The expression of KLF4 is downregulated in a dose-dependent manner, with a 0.12 ± 0.09-fold (p ≤ 0.05, n = 3) downregulation at a low dosage and 0.21 ± 0.02-fold (p ≤ 0.05, n = 3) downregulation at high dosage. Deficiency of KLF4 leads to an impairment of PPARγ that consequently supresses the proteins/enzymes involved in the fatty acid metabolism. Adriamycin-mediated suppression of KLF4 also affected the expression of PPARα in vitro. PPARα dysfunction is likely to cause defects in β-oxidation which ultimately results in impaired ATP synthesis. Cardiac cells are thus forced to switch over the substrate from free fatty acid to glucose. Moreover, Adriamycin elevates the expression of PPARβ due to downregulation of KLF4 leads to increased myocardial glucose utilization. Thus, a change in substrate preference affects the flexibility of metabolic network culminating in diminished energy production and other regulatory activities, altogether contributing to the development of cardiomyopathy. Thus, we conclude that the effect of Adriamycin on KLF4 disrupts mitochondrial homeostasis and lipid/glucose homeostasis resulting in a reduction of ATP synthesis which ultimately results in dilated cardiomyopathy.

The KLF7/PFKL/ACADL axis modulates cardiac metabolic remodelling during cardiac hypertrophy in male mice

The main hallmark of myocardial substrate metabolism in cardiac hypertrophy or heart failure is a shift from fatty acid oxidation to greater reliance on glycolysis. However, the close correlation between glycolysis and fatty acid oxidation and underlying mechanism by which causes cardiac pathological remodelling remain unclear. We confirm that KLF7 simultaneously targets the rate-limiting enzyme of glycolysis, phosphofructokinase-1, liver, and long-chain acyl-CoA dehydrogenase, a key enzyme for fatty acid oxidation. Cardiac-specific knockout and overexpression KLF7 induce adult concentric hypertrophy and infant eccentric hypertrophy by regulating glycolysis and fatty acid oxidation fluxes in male mice, respectively. Furthermore, cardiac-specific knockdown phosphofructokinase-1, liver or overexpression long-chain acyl-CoA dehydrogenase partially rescues the cardiac hypertrophy in adult male KLF7 deficient mice. Here we show that the KLF7/PFKL/ACADL axis is a critical regulatory mechanism and may provide insight into viable therapeutic concepts aimed at the modulation of cardiac metabolic balance in hypertrophied and failing heart.

Klf4-Sirt3/Pparα-Lcad pathway contributes to high phosphate-induced lipid degradation

BACKGROUND

Phosphorus commonly reduces lipid deposition in the vertebrates. However, the underlying mechanisms involved in the process remain unclear.

METHODS

Yellow catfish were given three experimental diets with dietary phosphate levels of 3.22, 6.47 and 7.99 g Pi kg^- 1, respectively, for 8 weeks. The contents of triglyceride, non-esterified free fatty acids, adenosine triphosphate, nicotinamide adenine dinucleotide, nicotinamide adenine dinucleotide, enzymatic activities, mRNA and protein expression were determined in the intestinal tissues. Hematoxylin and eosin, Oil Red O staining, and transmission electron microscope were performed for intestinal tissues. Primary intestinal epithelial cells were isolated from yellow catfish intestine. Western blot analysis, Immunoprecipitation assays, Immunofluorescence staining, and RNA extraction and quantitative real-time PCR were decided. Luciferase reporter assays and electrophoretic mobility shift assay were used to evaluate the function of Sirt3, PPARα and Lcad promoters.

RESULTS

High dietary phosphate intake activated intestinal phosphate absorption and excretion, and reduced lipid deposition through increasing lipolysis in the intestine. Moreover, phosphate incubation increased the mRNA and protein expression of krüppel like factor 4 (klf4), silent mating-type information regulation 2 homolog 3 (sirt3), peroxisome proliferator activated receptor alpha (pparα) and long chain acyl-CoA dehydrogenase (lcad) in the intestinal epithelial cells (IECs), and klf4 knockdown attenuated the phosphate-induced increase of protein levels of Sirt3, Pparα and Lcad. Further investigation found that Klf4 overexpression increased the activity of sirt3 and pparα promoters, which in turn reduced the acetylation and protein level of Lcad.

CONCLUSION

Dietary Pi excess induced lipid degradation by the activation of the Klf4-Sirt3/Pparα-Lcad pathway in the intestine and primary IECs. Video Abstract.

Klf4 deficiency exacerbates myocardial ischemia/reperfusion injury in mice via enhancing ROCK1/DRP1 pathway-dependent mitochondrial fission

RATIONAL

Excessive mitochondrial fission is considered key process involved in myocardial ischemia/reperfusion (I/R) injury. However, the upstream mechanism remains largely unclear. Decreased level of Kruppel Like Factor 4 (KLF4) has been implicated in the pathogenesis of mitochondrial dysfunction and heart's adaption to stress. However, the role of Klf4 in I/R process is not fully elucidated. This study aims to investigate how Klf4 regulates mitochondrial dynamics and further clarify its underlying mechanism during cardiac I/R injury.

METHODS

Loss-of-function and gain-of-function strategies were applied to investigate the role of Klf4 in cardiac I/R injury via genetic ablation or intra-myocardial adenovirus injection. Mitochondrial dynamics was analyzed by confocal microscopy in vitro and transmission electron microscopy in vivo. Chromatin immunoprecipitation and luciferase reporter assay were performed to explore the underlying mechanisms.

RESULTS

KLF4 was downregulated in I/R heart. Cardiac-specific Klf4 knockout significantly exacerbated cardiac dysfunction in I/R mice. Mechanistically, Klf4 deficiency aggravated mitochondrial apoptosis, reduced ATP generation and boosted ROS overproduction via enhancing DRP1-dependent mitochondrial fission. ROCK1 was identified as a kinase regulating DRP1 activity at Ser616. Klf4 deficiency upregulated the expression of ROCK1 at transcriptional level, thus increasing S616-DRP1-mediated mitochondrial fission during I/R. Finally, reconstitution of Klf4 inhibited mitochondrial fission, restored mitochondrial function and alleviated I/R injury.

CONCLUSION

Our study provides the first evidence that Klf4 deficiency exacerbates myocardial I/R injury through regulating ROCK1 expression at transcriptional level to induce DRP1-mediated mitochondrial fission. Targeting mitochondrial dynamics by restoring Klf4 might be potentially cardio-protective strategies attenuating I/R injury.

PGC-1α participates in tumor chemoresistance by regulating glucose metabolism and mitochondrial function

Chemotherapy resistance is the main reason for the failure of cancer treatment. The mechanism of drug resistance is complex and diverse. In recent years, the role of glucose metabolism and mitochondrial function in cancer resistance has gathered considerable interest. The increase in metabolic plasticity of cancer cells' mitochondria and adaptive changes to the mitochondrial function are some of the mechanisms through which cancer cells resist chemotherapy. As a key molecule regulating the mitochondrial function and glucose metabolism, PGC-1α plays an indispensable role in cancer progression. However, the role of PGC-1α in chemotherapy resistance remains controversial. Here, we discuss the role of PGC-1α in glucose metabolism and mitochondrial function and present a comprehensive overview of PGC-1α in chemotherapy resistance.

Mitochondrial Fission Process 1 controls inner membrane integrity and protects against heart failure

Mitochondria are paramount to the metabolism and survival of cardiomyocytes. Here we show that Mitochondrial Fission Process 1 (MTFP1) is an inner mitochondrial membrane (IMM) protein that is dispensable for mitochondrial division yet essential for cardiac structure and function. Constitutive knockout of cardiomyocyte MTFP1 in mice resulted in a fatal, adult-onset dilated cardiomyopathy accompanied by extensive mitochondrial and cardiac remodeling during the transition to heart failure. Prior to the onset of disease, knockout cardiac mitochondria displayed specific IMM defects: futile proton leak dependent upon the adenine nucleotide translocase and an increased sensitivity to the opening of the mitochondrial permeability transition pore, with which MTFP1 physically and genetically interacts. Collectively, our data reveal new functions of MTFP1 in the control of bioenergetic efficiency and cell death sensitivity and define its importance in preventing pathogenic cardiac remodeling.

Metabolic regulation of type 2 immune response during tissue repair and regeneration

Type 2 immune responses are mediated by the cytokines interleukin (IL)-4, IL-5, IL-10, and IL-13 and associated cell types, including T helper (Th)2 cells, group 2 innate lymphoid cells (ILC2s), basophils, mast cells, eosinophils, and IL-4- and IL-13-activated macrophages. It can suppress type 1-driven autoimmune diseases, promote antihelminth immunity, maintain cellular metabolic homeostasis, and modulate tissue repair pathways following injury. However, when type 2 immune responses become dysregulated, they can be a significant pathogenesis of many allergic and fibrotic diseases. As such, there is an intense interest in studying the pathways that modulate type 2 immune response so as to identify strategies of targeting and controlling these responses for tissue healing. Herein, we review recent literature on the metabolic regulation of immune cells initiating type 2 immunity and immune cells involved in the effector phase, and talk about how metabolic regulation of immune cell subsets contribute to tissue repair. At last, we discuss whether these findings can provide a novel prospect for regenerative medicine.

PGC1α Cooperates with FOXA1 to Regulate Epithelial Mesenchymal Transition through the TCF4-TWIST1

The peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α) is a critical transcriptional coactivator that maintains metabolic homeostasis and energy expenditure by cooperating with various transcription factors. Recent studies have shown that PGC1α deficiency promotes lung cancer metastasis to the bone through activation of TCF4 and TWIST1-mediated epithelial–mesenchymal transition (EMT), which is suppressed by the inhibitor of DNA binding 1 (ID1); however, it is not clear which transcription factor participates in PGC1α-mediated EMT and lung cancer metastasis. Here, we identified forkhead box A1 (FOXA1) as a potential transcription factor that coordinates with PGC1α and ID1 for EMT gene expression using transcriptome analysis. Cooperation between FOXA1 and PGC1α inhibits promoter occupancy of TCF4 and TWIST1 on CDH1 and CDH2 proximal promoter regions due to increased ID1, consequently regulating the expression of EMT-related genes such as CDH1, CDH2, VIM, and PTHLH. Transforming growth factor beta 1 (TGFβ1), a major EMT-promoting factor, was found to decrease ID1 due to the suppression of FOXA1 and PGC1α. In addition, ectopic expression of ID1, FOXA1, and PGC1α reversed TGFβ1-induced EMT gene expression. Our findings suggest that FOXA1- and PGC1α-mediated ID1 expression involves EMT by suppressing TCF4 and TWIST1 in response to TGFβ1. Taken together, this transcriptional framework is a promising molecular target for the development of therapeutic strategies for lung cancer metastasis.

Identification of potential dilated cardiomyopathy-related targets by meta-analysis and co-expression analysis of human RNA-sequencing datasets

AIMS

Dilated cardiomyopathy (DCM) remains among the most refractory heart diseases because of its complicated pathogenesis, and the key molecules that cause it remain unclear.

MAIN METHODS

To elucidate the molecules and upstream pathways critical for DCM pathogenesis, we performed meta-analysis and co-expression analysis of RNA-sequencing (RNA-seq) datasets from publicly available databases. We analyzed three RNA-seq datasets containing comparisons of RNA expression in left ventricles between healthy controls and DCM patients. We extracted differentially expressed genes (DEGs) and clarified upstream regulators of cardiovascular disease-related DEGs by Ingenuity Pathway Analysis (IPA). Weighted Gene Co-expression Network Analysis (WGCNA) and Protein-Protein Interaction (PPI) analysis were also used to identify the hub gene candidates strongly associated with DCM.

KEY FINDINGS

In total, 406 samples (184 healthy, 222 DCM) were used in this study. Overall, 391 DEGs [absolute fold change (FC) ≥ 1.5; P < 0.01], including 221 upregulated and 170 downregulated ones in DCM, were extracted. Seven common hub genes (LUM, COL1A2, CXCL10, FMOD, COL3A1, ADAMTS4, MRC1) were finally screened. IPA showed several upstream transcriptional regulators, including activating (NFKBIA, TP73, CALR, NFKB1, KLF4) and inhibiting (CEBPA, PPARGC1A) ones. We further validated increased expression of several common hub genes in the transverse aortic constriction-induced heart failure model.

SIGNIFICANCE

In conclusion, meta-analysis and WGCNA using RNA-seq databases of DCM patients identified seven hub genes and seven upstream transcriptional regulators.

AP-1 activation mediates postnatal cardiomyocyte maturation

AIMS

Postnatal maturation of mammalian cardiomyocytes proceeds rapidly after birth, with most of the myocytes exiting cell cycle, becoming binucleated, and adopting oxidative phosphorylation as the primary metabolic route. The triggers and transcriptional programs regulating cardiomyocyte maturation have not been fully understood yet. We performed single cell RNA-Seq in postnatal rat hearts in order to identify the important factors for this process.

METHODS AND RESULTS

Single cell RNA-Seq profiling was performed of postnatal day 1 and day 7 rat hearts, and we found that members of the AP-1 transcription factors showed a transient upregulation in the maturing cardiomyocytes, suggesting their functional involvement in the process. Activating members of the AP-1 family by palmitate or adrenergic stimulation inhibited cardiomyocyte cytokinesis and promoted cardiomyocyte maturation. In contrast, knocking down AP-1 members Atf3 and Jun promoted cardiomyocyte cytokinesis, reduced polyploidy and inhibited maturation. Mechanistically, RNA-Seq results and rescue experiments indicated that AP-1 members activate the expression of fatty acid metabolic genes to promote cardiomyocyte maturation. Finally, intraperitoneal injection of AP-1 inhibitor T-5224 in neonatal mice inhibits cardiomyocyte maturation in vivo.

CONCLUSION

Our results are the first evidence implicating AP-1 transcription factors in postnatal cardiomyocyte maturation both in vitro and in vivo, which expand our understanding of the molecular mechanism of cardiomyocyte maturation, and may lead to novel therapies to treat congenital heart diseases.

TRANSLATIONAL PERSPECTIVE

Postnatal cardiomyocyte maturation is a crucial process of cardiac development that determines fitness of the adult heart, and can be affected by multiple congenital heart diseases which lead to adult heart conditions. Our finding that AP-1 transcription factors transiently activated by multiple cues such as fatty acid and adrenergic signal promote cardiomyocyte maturation provided novel targets for therapeutic intervention, which may be applied during the narrow time window of postnatal cardiomyocyte maturation to treat congenital heart diseases and limit their impact on the adult heart.

ALG-bFGF Hydrogel Inhibiting Autophagy Contributes to Protection of Blood-Spinal Cord Barrier Integrity via PI3K/Akt/FOXO1/KLF4 Pathway After SCI

Promoting blood–spinal cord barrier (BSCB) repair at the early stage plays a crucial role in treatment of spinal cord injury (SCI). Excessive activation of autophagy can prevent recovery of BSCB after SCI. Basic fibroblast growth factor (bFGF) has been shown to promote BSCB repair and locomotor function recovery in SCI. However, the therapeutic effect of bFGF via direct administration on SCI is limited because of its rapid degradation and dilution at injury site. Based on these considerations, controlled release of bFGF in the lesion area is becoming an attractive strategy for SCI repair. At present, we have designed a sustained-release system of bFGF (called ALG-bFGF) using sodium alginate hydrogel, which is able to load large amounts of bFGF and suitable for in situ administration of bFGF in vivo. Here, traumatic SCI mice models and oxygen glucose deprivation (OGD)–stimulated human brain microvascular endothelial cells were performed to explore the effects and the underlying mechanisms of ALG-bFGF in promoting SCI repair. After a single in situ injection of ALG-bFGF hydrogel into the injured spinal cord, sustained release of bFGF from ALG hydrogel distinctly prevented BSCB destruction and improved motor functional recovery in mice after SCI, which showed better therapeutic effect than those in mice treated with bFGF solution or ALG. Evidences have demonstrated that autophagy is involved in maintaining BSCB integrity and functional restoration in animals after SCI. In this study, SCI/OGD exposure–induced significant upregulations of autophagy activation-related proteins (Beclin1, ATG5, LC3II/I) were distinctly decreased by ALG-bFGF hydrogel near the baseline and not less than it both in vivo and in vitro, and this inhibitory effect contributed to prevent BSCB destruction. Finally, PI3K inhibitor LY294002 and KLF4 inhibitor NSC-664704 were applied to further explore the underlying mechanism by which ALG-bFGF attenuated autophagy activation to alleviate BSCB destruction after SCI. The results further indicated that ALG-bFGF hydrogel maintaining BSCB integrity by inhibiting autophagy activation was regulated by PI3K/Akt/FOXO1/KLF4 pathway. In summary, our current study revealed a novel mechanism by which ALG-bFGF hydrogel improves BSCB and motor function recovery after SCI, providing an effective therapeutic strategy for SCI repair.

Sirt6 regulates autophagy in AGE-treated endothelial cells via KLF4

BACKGROUND AND AIMS

High glucose and its byproducts are important factors causing dysfunction of endothelial cells. Autophagy is critical for endothelial cellular homeostasis. However, the specific molecular mechanism of how autophagy is regulated in endothelial cells under high-glucose condition remains unknown. We aim to explore the role Sirt6 plays in regulating autophagy in AGE-treated endothelial cells and how this function is exerted via KLF4.

METHODS AND RESULTS

Our results indicate that autophagy level increased in AGE-treated endothelial cells alongside with higher Sirt6 and KLF4 expression level. What's more, knock-in of Sirt6 by adenovirus led to augmented autophagy level while knockdown of Sirt6 led to the opposite. We also verified that Sirt6 affected KLF4 expression positively but KLF4 didn't influence Sirt6 expression level while knocking out of KLF4 impaired Sirt6-enhanced autophagy. Finally we found that STZ-induced diabetic mice showed more autophagosomes in endothelium and Sirt6 knockdown by adeno-associated virus reduced the number of autophagosomes. Knockdown of Sirt6 also caused impaired endothelium integrity but echocardiography indicated there were no significant functional differences.

CONCLUSION

Our research reveals more about how Sirt6 regulates autophagy in endothelial cells under high-glucose simulated condition and provides further insight into the relationships between Sirt6 and KLF4.

Cardiac macrophages regulate isoproterenol-induced Takotsubo-like cardiomyopathy

Takotsubo syndrome (TTS) is an acute, stress-induced cardiomyopathy that occurs predominantly in women after extreme physical and/or emotional stress. To date, our understanding of the molecular basis for TTS remains unknown and, consequently, specific therapies are lacking. Myocardial infiltration of monocytes and macrophages in TTS has been documented in clinical studies. However, the functional importance of these findings remains poorly understood. Here, we show that a single high dose of isoproterenol (ISO) in mice induced a TTS-like cardiomyopathy phenotype characterized by female predominance, severe cardiac dysfunction, and robust myocardial infiltration of macrophages. Single-cell RNA-Seq studies of myocardial immune cells revealed that TTS-like cardiomyopathy is associated with complex activation of innate and adaptive immune cells in the heart, and macrophages were identified as the dominant immune cells. Global macrophage depletion (via clodronate liposome administration) or blockade of macrophage infiltration (via a CCR2 antagonist or in CCR2-KO mice) resulted in recovery of cardiac dysfunction in ISO-challenged mice. In addition, damping myeloid cell activation by HIF1α deficiency or exposure to the immunomodulatory agent bortezomib ameliorated ISO-induced cardiac dysfunction. Collectively, our findings identify macrophages as a critical regulator of TTS pathogenesis that can be targeted for therapeutic gain.

Krüppel-like factor (KLF)5: An emerging foe of cardiovascular health

Krüppel-like factors (KLFs) are DNA-binding transcriptional factors, which regulate various pathways that pertain to development, metabolism and other cellular mechanisms. KLF5 was first cloned in 1993 and by 1999, it was reported as the intestinal-enriched KLF. Beyond findings that have associated KLF5 with normal development and cancer, it has been associated with various types of cardiovascular (CV) complications and regulation of metabolic pathways in the liver, heart, adipose tissue and skeletal muscle. Specifically, increased KLF5 expression has been linked with cardiomyopathy in diabetes, end-stage heart failure, and as well as in vascular atherosclerotic lesions. In this review article, we summarize research findings about transcriptional, post-transcriptional and post-translational regulation of KLF5, as well as the role of KLF5 in the biology of cells and organs that affect cardiovascular health either directly or indirectly. Finally, we propose KLF5 inhibition as an emerging approach for cardiovascular therapeutics.

Deranged Myocardial Fatty Acid Metabolism in Heart Failure

The heart requires fatty acids to maintain its activity. Various mechanisms regulate myocardial fatty acid metabolism, such as energy production using fatty acids as fuel, for which it is known that coordinated control of fatty acid uptake, β-oxidation, and mitochondrial oxidative phosphorylation steps are important for efficient adenosine triphosphate (ATP) production without unwanted side effects. The fatty acids taken up by cardiomyocytes are not only used as substrates for energy production but also for the synthesis of triglycerides and the replacement reaction of fatty acid chains in cell membrane phospholipids. Alterations in fatty acid metabolism affect the structure and function of the heart. Recently, breakthrough studies have focused on the key transcription factors that regulate fatty acid metabolism in cardiomyocytes and the signaling systems that modify their functions. In this article, we reviewed the latest research on the role of fatty acid metabolism in the pathogenesis of heart failure and provide an outlook on future challenges.

Therapeutic Potential of Emerging NAD+-Increasing Strategies for Cardiovascular Diseases

Cardiovascular diseases are the leading cause of death worldwide. Aging and/or metabolic stress directly impact the cardiovascular system. Over the last few years, the contributions of altered nicotinamide adenine dinucleotide (NAD+) metabolism to aging and other pathological conditions closely related to cardiovascular diseases have been intensively investigated. NAD+ bioavailability decreases with age and cardiometabolic conditions in several mammalian tissues. Compelling data suggest that declining tissue NAD+ is commonly related to mitochondrial dysfunction and might be considered as a therapeutic target. Thus, NAD+ replenishment by either genetic or natural dietary NAD+-increasing strategies has been recently demonstrated to be effective for improving the pathophysiology of cardiac and vascular health in different experimental models, as well as human health, to a lesser extent. Here, we review and discuss recent experimental evidence illustrating that increasing NAD+ bioavailability, particularly by the use of natural NAD+ precursors, may offer hope for new therapeutic strategies to prevent and treat cardiovascular diseases.

1α,25-Dihydroxyvitamin D3 promotes angiogenesis by alleviating AGEs-induced autophagy

Diabetes mellitus (DM) induces abnormal angiogenesis and results in multiple chronic vascular complications. Previous studies showed that advanced glycation end products (AGEs) up-regulated in diabetic patients and induced a series of cellular effects such as oxidative stress, inflammation, and autophagy. 1α,25-Dihydroxyvitamin D3 (1,25D), a hormonal form of vitamin D, proved to be beneficial for vascular diseases. However, the underlying mechanism of 1,25D in angiogenesis in DM remains unclear. Using CCK8 assay and transwell assay, we found that 1,25D could partly ameliorate impaired proliferation and migration ability of endothelial cells (ECs) induced by AGEs (200 μg/mL). Furthermore, tube formation assay, Western blot, and real-time qPCR assay were conducted to demonstrate that AGEs impaired angiogenetic ability, and that angiogenesis-related gene expression (i.e., VEGFA, VEGFB, VEGFR1, VEGFR2, TGFβ1, MMP2, MMP9) in ECs and 1,25D could promote angiogenesis and angiogenetic markers expression. By using DCFH-DA, ELISA, and Western blot assay, we also found that AGEs-induced oxidative stress impaired angiogenic ability of ECs, and 1,25D alleviated angiogenesis dysfunction by inhibiting oxidative stress. Of note, AGEs-induced excessive autophagy was found to impair angiogenesis. We elucidated that the detrimental autophagy is modulated by 1,25D and AGEs via PI3K/Akt pathway. Observed together, our findings illustrated that AGEs-induced oxidative stress and autophagy resulted in angiogenic disorder and 1,25D improved angiogenesis by restraining excessive autophagy and oxidative stress, providing a novel insight for the treatment of vascular complications in DM.

Mechanical forces and metabolic changes cooperate to drive cellular memory and endothelial phenotypes

Endothelial cells line the innermost layer of arterial, venous, and lymphatic vascular tree and accordingly are subject to hemodynamic, stretch, and stiffness mechanical forces. Normally quiescent, endothelial cells have a hemodynamic set point and become "activated" in response to disturbed hemodynamics, which may signal impending nutrient or gas depletion. Endothelial cells in the majority of tissue beds are normally inactivated and maintain vessel barrier functions, are anti-inflammatory, anti-coagulant, and anti-thrombotic. However, under aberrant mechanical forces, endothelial signaling transforms in response, resulting cellular changes that herald pathological diseases. Endothelial cell metabolism is now recognized as the primary intermediate pathway that undergirds cellular transformation. In this review, we discuss the various mechanical forces endothelial cells sense in the large vessels, microvasculature, and lymphatics, and how changes in environmental mechanical forces result in changes in metabolism, which ultimately influence cell physiology, cellular memory, and ultimately disease initiation and progression.

A Genome-Wide Association Study Identifies Novel Susceptibility loci in Chronic Chagas Cardiomyopathy

BACKGROUND

Chagas disease is an infectious disease caused by the parasite Trypanosoma cruzi and is endemic from Latin American countries. The goal of our study was to identify novel genetic loci associated with chronic Chagas cardiomyopathy development in Chagas disease patients from different Latin American populations.

METHODS

We performed a cross-sectional, nested case-control study including 3 sample collections from Colombia, Argentina, and Bolivia. Samples were genotyped to conduct a genome-wide association study (GWAS). These results were meta-analyzed with summary statistic data from Brazil, gathering a total of 3413 Chagas disease patients. To identify the functional impact of the associated variant and its proxies, we performed an in silico analysis of this region.

RESULTS

The meta-analysis revealed a novel genome-wide statistically significant association with chronic Chagas cardiomyopathy development in rs2458298 (OR = 0.90, 95%CI = 0.87-0.94, P-value = 3.27 × 10-08), nearby the SAC3D1 gene. In addition, further in silico analyses displayed functional relationships between the associated variant and the SNX15, BAFT2, and FERMT3 genes, related to cardiovascular traits.

CONCLUSIONS

Our findings support the role of the host genetic factors in the susceptibility to the development of the chronic cardiac form of this neglected disease.

Berberine improves dietary-induced cardiac remodeling by upregulating Kruppel-like factor 4-dependent mitochondrial function

Multiple studies have showed that berberine protects against heart diseases, including obesity-associated cardiomyopathy. However, it is not fully disclosed the potential molecular mechanisms of berberine on controlling cardiac remodeling. Kruppel-like factor (KLF) 4, identified as a critical transcriptional factor, participates in multiple cardiac injuries. The present study was to explore whether KLF4 determined the cardioprotective benefits of berberine in dietary-induced obese mice. High fat diet-induced obese mice were treated with berberine with or without lentivirus encoding Klf4 siRNA, and cardiac parameters were analyzed by multiple biological approaches. In dietary-induced obese mouse model, administration of berberine obviously increased cardiac level of KLF4, which closely correlated with improvement of cardiac functional parameters. Co-treatment of lentivirus encoding Klf4 siRNA abolished cardioprotective benefits of berberine, including induction of cardiac hypertrophy, fibrosis, functional disorders, inflammatory response and oxidative stress. Mechanistically, we found berberine improved cardiac mitochondrial biogenesis and activities, whereas silencing Klf4 decreased berberine-upregulated mitochondrial quality, ATP production and oxygen consumption. Our present study demonstrated that berberine protected against dietary-induced cardiac structural disorders and mitochondrial dysfunction dependent on cardiac KLF4 signaling. Cardiac KLF4 was one of potential therapeutic targets for obesity-induced cardiac injuries.

Trans-omic analysis reveals obesity-associated dysregulation of inter-organ metabolic cycles between the liver and skeletal muscle

Systemic metabolic homeostasis is regulated by inter-organ metabolic cycles involving multiple organs. Obesity impairs inter-organ metabolic cycles, resulting in metabolic diseases. The systemic landscape of dysregulated inter-organ metabolic cycles in obesity has yet to be explored. Here, we measured the transcriptome, proteome, and metabolome in the liver and skeletal muscle and the metabolome in blood of fasted wild-type and leptin-deficient obese (ob/ob) mice, identifying components with differential abundance and differential regulation in ob/ob mice. By constructing and evaluating the trans-omic network controlling the differences in metabolic reactions between fasted wild-type and ob/ob mice, we provided potential mechanisms of the obesity-associated dysfunctions of metabolic cycles between liver and skeletal muscle involving glucose-alanine, glucose-lactate, and ketone bodies. Our study revealed obesity-associated systemic pathological mechanisms of dysfunction of inter-organ metabolic cycles.

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Multi-omic data in liver and skeletal muscle of WT and ob/ob mice were measured

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We developed the trans-omic network of differentially regulated metabolic reactions

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Dysregulation of inter-organ metabolic cycles associated with obesity was revealed

The novel STING antagonist H151 ameliorates cisplatin-induced acute kidney injury and mitochondrial dysfunction

Stimulator of interferon genes (STING) is an important adaptor in cytosolic DNA-sensing pathways. A recent study found that the deletion of STING ameliorated cisplatin-induced acute kidney injury (AKI), suggesting that STING could serve as a potential target for AKI therapy. Up to now, a series of small-molecule STING inhibitors/antagonists have been identified. However, none of the research was performed to explore the role of human STING inhibitors in AKI. Here, we investigated the effect of a newly generated covalent antagonist, H151, which targets both human and murine STING, in cisplatin-induced AKI. We found that H151 treatment significantly ameliorated cisplatin-induced kidney injury as shown by the improvement of renal function, kidney morphology, and renal inflammation. In addition, tubular cell apoptosis and increased renal tubular injury marker neutrophil gelatinase-associated lipocalin induced by cisplatin were also effectively attenuated in H151-treated mice. Moreover, the mitochondrial injury caused by cisplatin was also reversed as evidenced by improved mitochondrial morphology, restored mitochondrial DNA content, and reversed mitochondrial gene expression. Finally, we observed enhanced mitochondrial DNA levels in the plasma of patients receiving platinum-based chemotherapy compared with healthy controls, which could potentially activate STING signaling. Taken together, these findings suggested that H151 could be a potential therapeutic agent for treating AKI possibly through inhibiting STING-mediated inflammation and mitochondrial injury.NEW & NOTEWORTHY Although various stimulator of interferon genes (STING) inhibitors have been identified, no research was performed to investigate the role of human STING inhibitors in AKI. Here, we evaluated the effect of H151 targeting both human and murine STING on cisplatin-induced AKI and observed a protection against renal injury possibly through ameliorating inflammation and mitochondrial dysfunction.

Mitochondrial Homeostasis Mediates Lipotoxicity in the Failing Myocardium

Heart failure remains the most common cause of death in the industrialized world. In spite of new therapeutic interventions that are constantly being developed, it is still not possible to completely protect against heart failure development and progression. This shows how much more research is necessary to understand the underlying mechanisms of this process. In this review, we give a detailed overview of the contribution of impaired mitochondrial dynamics and energy homeostasis during heart failure progression. In particular, we focus on the regulation of fatty acid metabolism and the effects of fatty acid accumulation on mitochondrial structural and functional homeostasis.

ATPIF1 maintains normal mitochondrial structure which is impaired by CCM3 deficiency in endothelial cells

Background

Numerous signaling pathways have been demonstrated experimentally to affect the pathogenesis of cerebral cavernous malformations (CCM), a disease that can be caused by CCM3 deficiency. However, the understanding of the CCM progression is still limited. The objective of the present work was to elucidate the role of CCM3 by RNA-seq screening of CCM3 knockout mice.

Results

We found that ATPIF1 was decreased in siCCM3-treated Human Umbilical Vein Endothelial Cells (HUVECs), and the overexpression of ATPIF1 attenuated the changes in cell proliferation, adhesion and migration caused by siCCM3. The probable mechanism involved the conserved ATP concentration in mitochondria and the elongated morphology of the organelles. By using the CRISPR-cas9 system, we generated CCM3-KO Endothelial Progenitor Cells (EPCs) and found that the knockout of CCM3 destroyed the morphology of mitochondria, impaired the mitochondrial membrane potential and increased mitophagy. Overexpression of ATPIF1 contributed to the maintenance of normal structure of mitochondria, inhibiting activation of mitophagy and other signaling proteins (e.g., KLF4 and Tie2). The expression of KLF4 returned to normal in CCM3-KO EPCs after 2 days of re-overexpression of CCM3, but not other signaling proteins.

Conclusion

ATPIF1 maintains the normal structure of mitochondria, inhibiting the activation of mitophagy and other signaling pathway in endothelial cells. Loss of CCM3 leads to the destruction of mitochondria and activation of signaling pathways, which can be regulated by KLF4.

KLF4 (Kruppel-Like Factor 4)-Dependent Perivascular Plasticity Contributes to Adipose Tissue inflammation

OBJECTIVE

Smooth muscle cells and pericytes display remarkable plasticity during injury and disease progression. Here, we tested the hypothesis that perivascular cells give rise to Klf4-dependent macrophage-like cells that augment adipose tissue (AT) inflammation and metabolic dysfunction associated with diet-induced obesity (DIO). Approach and Results: Using Myh11-CreERT2 eYFP (enhanced yellow fluorescent protein) mice and flow cytometry of the stromovascular fraction of epididymal AT, we observed a large fraction of smooth muscle cells and pericytes lineage traced eYFP+ cells expressing macrophage markers. Subsequent single-cell RNA sequencing, however, showed that the majority of these cells had no detectable eYFP transcript. Further exploration revealed that intraperitoneal injection of tamoxifen in peanut oil, used for generating conditional knockout or reporter mice in thousands of previous studies, resulted in large increase in the autofluorescence and false identification of macrophages within epididymal AT as being eYFP+; and unintended proinflammatory consequences. Using newly generated Myh11-DreERT2tdTomato mice given oral tamoxifen, we virtually eliminated the problem with autofluorescence and identified 8 perivascular cell dominated clusters, half of which were altered upon DIO. Given that perivascular cell KLF4 (kruppel-like factor 4) can have beneficial or detrimental effects, we tested its role in obesity-associated AT inflammation. While smooth muscle cells and pericytes-specific Klf4 knockout (smooth muscle cells and pericytes Klf4Δ/Δ) mice were not protected from DIO, they displayed improved glucose tolerance upon DIO, and showed marked decreases in proinflammatory macrophages and increases in LYVE1+ lymphatic endothelial cells in the epididymal AT.

CONCLUSIONS

Perivascular cells within the AT microvasculature dynamically respond to DIO and modulate tissue inflammation and metabolism in a KLF4-dependent manner.

Recent Discoveries on the Involvement of Krüppel-Like Factor 4 in the Most Common Cancer Types

Krüppel-like factor 4 (KLF4) is a transcription factor highly conserved in evolution. It is particularly well known for its role in inducing pluripotent stem cells. In addition, KLF4 plays many roles in cancer. The results of most studies suggest that KLF4 is a tumor suppressor. However, the functioning of KLF4 is regulated at many levels. These include regulation of transcription, alternative splicing, miRNA, post-translational modifications, subcellular localization, protein stability and interactions with other molecules. Simple experiments aimed at assaying transcript levels or protein levels fail to address this complexity and thus may deliver misleading results. Tumor subtypes are also important; for example, in prostate cancer KLF4 is highly expressed in indolent tumors where it impedes tumor progression, while it is absent from aggressive prostate tumors. KLF4 is important in regulating response to many known drugs, and it also plays a role in tumor microenvironment. More and more information is available about upstream regulators, downstream targets and signaling pathways associated with the involvement of KLF4 in cancer. Furthermore, KLF4 performs critical function in the overall regulation of tissue homeostasis, cellular integrity, and progression towards malignancy. Here we summarize and analyze the latest findings concerning this fascinating transcription factor.

Eosinophil function in adipose tissue is regulated by Krüppel-like factor 3 (KLF3)

The conversion of white adipocytes to thermogenic beige adipocytes represents a potential mechanism to treat obesity and related metabolic disorders. However, the mechanisms involved in converting white to beige adipose tissue remain incompletely understood. Here we show profound beiging in a genetic mouse model lacking the transcriptional repressor Krüppel-like factor 3 (KLF3). Bone marrow transplants from these animals confer the beige phenotype on wild type recipients. Analysis of the cellular and molecular changes reveal an accumulation of eosinophils in adipose tissue. We examine the transcriptomic profile of adipose-resident eosinophils and posit that KLF3 regulates adipose tissue function via transcriptional control of secreted molecules linked to beiging. Furthermore, we provide evidence that eosinophils may directly act on adipocytes to drive beiging and highlight the critical role of these little-understood immune cells in thermogenesis.

Immune cells are important regulators of adipose tissue function, including adaptive thermogenesis. Here the authors show that mice with Krüppel-like factor 3 (KLF3) deficiency in bone marrow-derived cells have increased adipose tissue beiging which may at least in part be due to altered eosinophil paracrine signaling.

The long and winding road of cardiomyocyte maturation

Knowledge about the molecular mechanisms regulating cardiomyocyte (CM) proliferation and differentiation has increased exponentially in recent years. Such insights together with the availability of more efficient protocols for generation of CMs from induced pluripotent stem cells (iPSCs) have raised expectations for new therapeutic strategies to treat congenital and non-congenital heart diseases. However, the poor regenerative potential of the postnatal heart and the incomplete maturation of iPSC-derived CMs represent important bottlenecks for such therapies in future years. CMs undergo dramatic changes at the doorstep between prenatal and postnatal life, including terminal cell cycle withdrawal, change in metabolism, and further specialization of the cellular machinery required for high-performance contraction. Here, we review recent insights into pre- and early postnatal developmental processes that regulate CM maturation, laying specific focus on genetic and metabolic pathways that control transition of CMs from the embryonic and perinatal to the fully mature adult CM state. We recapitulate the intrinsic features of CM maturation and highlight the importance of external factors, such as energy substrate availability and endocrine regulation in shaping postnatal CM development. We also address recent approaches to enhance maturation of iPSC-derived CMs in vitro, and summarize new discoveries that might provide useful tools for translational research on repair of the injured human heart.

Inhibition of Wnt signaling by Frizzled7 antibody-coated nanoshells sensitizes triple-negative breast cancer cells to the autophagy regulator chloroquine

Despite improvements in our understanding of the biology behind triple-negative breast cancer (TNBC), it remains a devastating disease due to lack of an effective targeted therapy. Inhibiting Wnt signaling is a promising strategy to combat TNBC because Wnt signaling drives TNBC progression, chemoresistance, and stemness. However, Wnt inhibition can lead to upregulation of autophagy, which confers therapeutic resistance. This provides an opportunity for combination therapy, as autophagy inhibitors applied concurrently with Wnt inhibitors could increase treatment efficacy. Here, we applied the autophagy inhibitor chloroquine (CQ) to TNBC cells in combination with Frizzled7 antibody-coated nanoshells (FZD7-NS) that suppress Wnt signaling by blocking Wnt ligand/FZD7 receptor interactions, and evaluated this dual treatment in vitro. We found that FZD7-NS can inhibit Axin2 and CyclinD1, two targets of canonical Wnt signaling, and increase the expression of LC3, an autophagy marker. When FZD7-NS and CQ are applied together, they reduce the expression of several stemness genes in TNBC cells, leading to inhibition of TNBC cell migration and self-renewal. Notably, co-delivery of FZD7-NS and CQ is more effective than either therapy alone or the combination of CQ with free FZD7 antibodies. This demonstrates that the nanocarrier design is important to its therapeutic utility. Overall, these findings indicate that combined regulation of Wnt signaling and autophagy by FZD7-NS and CQ is a promising strategy to combat TNBC.

Nicotinamide Mononucleotide: A Promising Molecule for Therapy of Diverse Diseases by Targeting NAD+ Metabolism

NAD+, a co-enzyme involved in a great deal of biochemical reactions, has been found to be a network node of diverse biological processes. In mammalian cells, NAD+ is synthetized, predominantly through NMN, to replenish the consumption by NADase participating in physiologic processes including DNA repair, metabolism, and cell death. Correspondingly, aberrant NAD+ metabolism is observed in many diseases. In this review, we discuss how the homeostasis of NAD+ is maintained in healthy condition and provide several age-related pathological examples related with NAD+ unbalance. The sirtuins family, whose functions are NAD-dependent, is also reviewed. Administration of NMN surprisingly demonstrated amelioration of the pathological conditions in some age-related disease mouse models. Further clinical trials have been launched to investigate the safety and benefits of NMN. The NAD+ production and consumption pathways including NMN are essential for more precise understanding and therapy of age-related pathological processes such as diabetes, ischemia–reperfusion injury, heart failure, Alzheimer’s disease, and retinal degeneration.