Protective Role of Ethanol Extract of Cibotium barometz (Cibotium Rhizome) against Dexamethasone-Induced Muscle Atrophy in C2C12 Myotubes.

Sarcopenia is a progressive muscle disease characterized by the loss of skeletal muscle mass, strength, function, and physical performance. Since the disease code was assigned, attention has been focused on natural products that can protect against muscle atrophy. Cibotium barometz (Cibotium Rhizome) has been used as an herbal medicine for the treatment of bone or joint diseases in Asian countries. However, no studies have identified the mechanism of action of Cibotium Rhizome on muscle atrophy related to sarcopenia at the site of myotubes. The aim of this study was to investigate the improvement effect of the ethanol extract of Cibotium Rhizome (ECR) on dexamethasone-induced muscle atrophy in an in vitro cell model, i.e., the C2C12 myotubes. High-performance liquid chromatography was performed to examine the phytochemicals in ECR. Seven peaks in the ECR were identified, corresponding to the following compounds: protocatechuic acid, (+)-catechin hydrate, p-coumaric acid, ellagic acid, chlorogenic acid, caffeic acid, and ferulic acid. In atrophy-like conditions induced by 100 µM dexamethasone for 24 h in C2C12, ECR increased the expression of the myosin heavy chain, p-Akt, the p-mammalian target of rapamycin (mTOR), p-p70S6K, and repressed the expression of regulated in development and DNA damage responses 1 (REDD1), kruppel-like factor 15 (KLF 15), muscle atrophy F-box, and muscle-specific RING finger protein-1 in C2C12. In addition, ECR alleviated dexamethasone-induced muscle atrophy by repressing REDD1 and KLF15 transcription in C2C12 myotubes, indicating the need for further studies to provide a scientific basis for the development of useful therapeutic agents using ECR to alleviate the effects of skeletal muscle atrophy or sarcopenia.

The Krüppel-like factor 15-NFATc1 axis ameliorates podocyte injury: a novel rationale for using glucocorticoids in proteinuria diseases.

Podocyte injury and loss contribute to proteinuria, glomerulosclerosis and eventually kidney failure. Recent studies have demonstrated that the loss of Kruppel-like factor 15 (KLF15) in podocytes increases the susceptibility to injury; however, the mechanism underlying the protective effects on podocyte injury remains incompletely understood. Herein, we showed that KLF15 ameliorates podocyte injury through suppressing NFAT signaling and the salutary effects of the synthetic glucocorticoid dexamethasone in podocyte were partially mediated by the KLF15-NFATc1 axis. We found that KLF15 was significantly reduced in glomerular cells of proteinuric patients and in ADR-, LPS- or HG-treated podocyets in vitro. Overexpression of KLF15 attenuated podocyte apoptosis induced by ADR, LPS or HG and resulted in decreased expression of pro-apoptotic Bax and increased expression of anti-apoptotic Bcl-2. Conversely, the flow cytometry analysis and TUNEl assay demonstrated that loss of KLF15 accelerated podocyte apoptosis and we further found that 11R-VIVIT, a specific NFAT inhibitor, and NFATc1-siRNA rescued KLF15-deficient induced podocyte apoptosis. Meanwhile, Western blot and RT-qPCR showed that the expression of NFATc1 was up-regulated in KLF15 silenced podocytes and reduced in KLF15 overexpressed podocytes. Mechanistically, ChIP analysis showed that KLF15 bound to the NFATc1 promoter region -1984 to -1861base pairs upstream of the transcription start site and the binding amount was decreased after treatment with LPS. The dual-luciferase reporter assay indicated that NFATc1 was a direct target of KLF15. In addition, we found that in vitro treatment with dexamethasone induced a decrease of NFATc1 expression in podocytes and was abrogated by knockdown of KLF15. Hence, our results identify the critical role of the KLF15-NFATc1 axis in podocyte injury and loss, which may be involved in mediating the salutary effects of dexamethasone in podocytes.

Left ventricular hypertrophy in experimental chronic kidney disease is associated with reduced expression of cardiac Kruppel-like factor 15.

BACKGROUND: Left ventricular hypertrophy (LVH) increases the risk of death in chronic kidney disease (CKD). The transcription factor Kruppel-like factor 15 (KLF15) is expressed in the heart and regulates cardiac remodelling through inhibition of hypertrophy and fibrosis. It is unknown if KLF15 expression is changed in CKD induced LVH, or whether expression is modulated by blood pressure reduction using angiotensin converting enzyme (ACE) inhibition. METHODS: CKD was induced in Sprague-Dawley rats by subtotal nephrectomy (STNx), and rats received vehicle (n = 10) or ACE inhibition (ramipril, 1 mg/kg/day, n = 10) for 4 weeks. Control, sham-operated rats (n = 9) received vehicle. Cardiac structure and function and expression of KLF15 were assessed. RESULTS: STNx caused impaired kidney function (P < 0.001), hypertension (P < 0.01), LVH (P < 0.001) and fibrosis (P < 0.05). LVH was associated with increased gene expression of hypertrophic markers, atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP, P < 0.01) and connective tissue growth factor (CTGF) (P < 0.05). Cardiac KLF15 mRNA and protein expression were reduced (P < 0.05) in STNx and levels of the transcription regulator, GATA binding protein 4 were increased (P < 0.05). Ramipril reduced blood pressure (P < 0.001), LVH (P < 0.001) and fibrosis (P < 0.05), and increased cardiac KLF15 gene (P < 0.05) and protein levels (P < 0.01). This was associated with reduced ANP, BNP and CTGF mRNA (all P < 0.05). CONCLUSION: This is the first evidence that loss of cardiac KLF15 in CKD induced LVH is associated with unchecked trophic and fibrotic signalling, and that ACE inhibition ameliorates loss of cardiac KLF15.

Kruppel-Like Factor 15 Is Critical for the Development of Left Ventricular Hypertrophy.

Left ventricular hypertrophy (LVH) is an independent risk factor for adverse cardiovascular events and is often present in patients with hypertension. Treatment to reduce blood pressure and regress LVH is key to improving health outcomes, but currently available drugs have only modest cardioprotective effects. Improved understanding of the molecular mechanisms involved in the development of LVH may lead to new therapeutic targets in the future. There is now compelling evidence that the transcription factor Kruppel-like factor 15 (KLF15) is an important negative regulator of cardiac hypertrophy in both experimental models and in man. Studies have reported that loss or suppression of KLF15 contributes to LVH, through lack of inhibition of pro-hypertrophic transcription factors and stimulation of trophic and fibrotic signaling pathways. This review provides a summary of the experimental and human studies that have investigated the role of KLF15 in the development of cardiac hypertrophy. It also discusses our recent paper that described the contribution of genetic variants in KLF15 to the development of LVH and heart failure in high-risk patients.

Glucocorticoid Receptor ChIP-Seq Identifies PLCD1 as a KLF15 Target that Represses Airway Smooth Muscle Hypertrophy.

Glucocorticoids exert important therapeutic effects on airway smooth muscle (ASM), yet few direct targets of glucocorticoid signaling in ASM have been definitively identified. Here, we show that the transcription factor, Krüppel-like factor 15 (KLF15), is directly induced by glucocorticoids in primary human ASM, and that KLF15 represses ASM hypertrophy. We integrated transcriptome data from KLF15 overexpression with genome-wide analysis of RNA polymerase (RNAP) II and glucocorticoid receptor (GR) occupancy to identify phospholipase C delta 1 as both a KLF15-regulated gene and a novel repressor of ASM hypertrophy. Our chromatin immunoprecipitation sequencing data also allowed us to establish numerous direct transcriptional targets of GR in ASM. Genes with inducible GR occupancy and putative antiinflammatory properties included IRS2, APPL2, RAMP1, and MFGE8. Surprisingly, we also observed GR occupancy in the absence of supplemental ligand, including robust GR binding peaks within the IL11 and LIF loci. Detection of antibody-GR complexes at these areas was abrogated by dexamethasone treatment in association with reduced RNA polymerase II occupancy, suggesting that noncanonical pathways contribute to cytokine repression by glucocorticoids in ASM. Through defining GR interactions with chromatin on a genome-wide basis in ASM, our data also provide an important resource for future studies of GR in this therapeutically relevant cell type.

Resveratrol-Mediated Expression of KLF15 in the Ischemic Myocardium is Associated with an Improved Cardiac Phenotype.

PURPOSE: Myocardial infarction results in physiological derangements that lead to structural and functional alterations to the myocardium. In addition, oxidative stress potentiates cardiac remodeling and drives disease progression. Unfortunately, treatment with antioxidants in clinical trials have failed to show any therapeutic benefits despite the positive results reported in animal studies, which warrants further investigation into their mechanism(s) of action. Accordingly, the aim of this study was to elucidate a previously unknown mechanism of action for the antioxidant, resveratrol, in the treatment of the ischemic heart. METHODS: Male Sprague-Dawley rats underwent four weeks of chronic myocardial ischemia with or without daily resveratrol treatment (10 mg/kg/day). The expression and signaling of Krüppel-like factor 15 (KLF15) were determined by immunoblot and qPCR analyses, respectively. RESULTS: Chronic myocardial ischemia reduced the protein expression of KLF15. In parallel, mRNA transcripts of KLF15 gene targets actively involved in cardiac remodeling were robustly increased in untreated hearts. Importantly, daily treatment with resveratrol stimulated KLF15 expression, which was associated with attenuated gene expression and an improved cardiac phenotype. Additionally, we describe a novel role for KLF15 in the regulation of redox homeostasis. CONCLUSION: Based on our current findings, it appears that resveratrol treatment induces KLF15 expression, which may, in part, explain its therapeutic efficacy to improve the cardiac phenotype following ischemic injury.

KLF 15 Works as an Early Anti-Fibrotic Transcriptional Regulator in Ang II-Induced Renal Fibrosis via Down-Regulation of CTGF Expression.

BACKGROUND/AIMS: Angiotensin II (Ang II) has been regarded as an important profibrogenic cytokine in renal fibrosis. Krüppel-like factor 15 (KLF15) has been identified as an important negative transcription factor in renal fibrosis. However, little is known about the role of KLF15 in Ang II-induced renal fibrosis. METHODS: In this study, we randomized mice into a control group, Ang II group or Ang II plus losartan group. KLF15 expression was examined with real-time PCR and immunofluorescence in these groups. In vitro, KLF15 expression was examined by Western blot in rat renal fibroblasts (NRK-49F) stimulated with Ang II, and the effect of altered KLF15 expression on the regulation of the profibrotic factor connective tissue growth factor (CTGF) was further explored with co-immunoprecipitation (CoIP) and chromatin immunoprecipitation (ChIP) analyses. RESULTS: Compared with the control group, the murine model of Ang II-induced renal fibrosis demonstrated a significant decrease in renal KLF15 expression at 4 weeks and presented with progressive renal fibrosis at 6 weeks. Meanwhile, losartan, an angiotensin type 1 (AT1) receptor antagonist, effectively prevented the down-regulation of KLF15 expression induced by Ang II infusion. In vitro, NRK-49F cells stimulated with Ang II exhibited a significant decrease in KLF15 expression, accompanied by a marked increase in the expression of profibrotic factors and in the production of extracellular matrix. The up-regulation of CTGF expression induced by Ang II stimulation was inhibited by KLF15 overexpression in NRK-49F cells, and losartan treatment prevented the down-regulation of KLF15 expression and the up-regulation of CTGF expression induced by Ang II stimulation. Furthermore, CoIP and ChIP assays revealed that the transcription regulator KLF15 directly bound to the co-activator P/CAF and repressed its recruitment to the CTGF promoter. CONCLUSIONS: Ang II down-regulates KLF15 expression via the AT1 receptor, and KLF15 is likely to inhibit Ang II-induced CTGF expression by repressing the recruitment of the co-activator P/CAF to the CTGF promoter.

KLF15 Inhibits Cell Proliferation in Gastric Cancer Cells via Up-Regulating CDKN1A/p21 and CDKN1C/p57 Expression.

BACKGROUND: Krüppel-like factors (KLFs) have been identified in multi-cancers and act as oncogenes or tumor suppressors. The function of KLF15, one member of KLFs, has not been well elucidated, especially in gastric cancer (GC). AIMS: This study was designed to investigate the prognostic value and biological functions of KLF15 in GC. METHODS: KLF15 protein expression in GC patients was evaluated by immunohistochemistry assays in 50 paired GC tissues and adjacent normal tissues, and correlations between KLF15 expression and clinicopathological characteristics and prognosis were analyzed. Then, we investigated the over-expression of KLF15 on cell proliferation and its mechanism in GC cells. RESULTS: KLF15 expression levels were significantly down-regulated in GC tissues compared to adjacent normal tissues. And KLF15 expression was negatively correlated with clinical stage, lymphatic metastasis, and distant metastasis. Furthermore, KLF15 expression could predict prognosis in patients with GC. Moreover, over-expression of KLF15 could inhibit cell proliferation partly via regulating CDKN1A/p21 and CDKN1C/p57. CONCLUSION: These findings demonstrate that KLF15 plays a significant role in GC progression and could be a therapeutic target for GC.

KLF15 alleviates oxidative stress and apoptosis of H/R-induced trophoblast cells to improve invasion and migration capacity via the activation of IGF1R.

BACKGROUND: Krüppel-like factor 15 (KLF15) has been reported to be involved in ischemia injury of multiple types of diseases. Nevertheless, the roles and underlying mechanisms of KLF15 in preeclampsia (PE) are still unclear. METHODS: In this study, the expression of KLF15 in placenta tissues and hypoxia/reoxygenation (H/R)-induced HTR8/SVneo cells was evaluated by GSE66273 database, qRT-PCR and western blot assay. CCK-8 assay was employed to detect cell proliferation. Wound healing assay and transwell assay were used to detect cell migration and invasion. Cell oxidative stress was measured by DCFH-DA staining and kits. Cell apoptosis was evaluated by TUNEL assay and western blot assay. The JASPAR database was used to analyze the binding site of KLF15 and insulin-like growth factor-1 receptor (IGF1R) promoter region. The luciferase reporter assay was used to detect IGF1R promoter activity and ChIP assay was used to verify the combination of KLF15 and IGF1R promoter. Moreover, western blot was employed to measure the expressions of PI3K/Akt-related proteins. RESULTS: The data showed that the expression of KLF15 was significantly downregulated in GSE66273 database, tissues and HTR8/SVneo cells. KLF15 overexpression increased H/R-induced HTR8/SVneo cell proliferation, invasion and migration, and inhibited oxidative stress and cell apoptosis. In addition, IGF1R was highly expressed in H/R-induced HTR8/SVneo cells after KLF15 overexpression, and the binding of KLF15 and IGF1R promoter was verified. Silencing of IGF1R reversed the effects of KLF15 overexpression on H/R-induced HTR8/SVneo cell proliferation, migration, invasion, oxidative stress and cell apoptosis. Moreover, KLF15 overexpression and IGF1R silencing regulated the expressions of PI3K/Akt-related proteins in H/R-induced HTR8/SVneo cells. CONCLUSION: In conclusion, KLF15 overexpression promoted the proliferation and metastasis, and suppressed oxidative stress and cell apoptosis of H/R-induced HTR8/SVneo cells through mediating the PI3K/Akt pathway, which may provide a promising target for the treatment of preeclampsia.

Krüppel-like factor 15 in liver diseases: Insights into metabolic reprogramming.

Liver diseases, characterized by metabolic disorder, have become a global public health problem with high morbidity and mortality. Krüppel-like factor 15 (KLF15) is a zinc-finger transcription factor mainly enriched in liver. Increasing evidence suggests that hepatic KLF15 is activated rapidly during fasting, and contributes to the regulation of gluconeogenesis, lipid, amino acid catabolism, bile acids, endobiotic and xenobiotic metabolism. This review summarizes the latest advances of KLF15 in metabolic reprogramming, and explore the function of KLF15 in acute liver injury, hepatitis B virus, and autoimmune hepatitis. which aims to evaluate the potential of KLF15 as a therapeutic target and prognostic biomarker for liver diseases.

Activation of PKG-CREB-KLF15 by melatonin attenuates Angiotensin II-induced vulnerability to atrial fibrillation via enhancing branched-chain amino acids catabolism.

Mitochondrial reactive oxygen species (ROS) damage and atrial remodeling serve as the crucial substrates for the genesis of atrial fibrillation (AF). Branched-chain amino acids (BCAAs) catabolic defect plays critical roles in multiple cardiovascular diseases. However, the alteration of atrial BCAA catabolism and its role in AF remain largely unknown. This study aimed to explore the role of BCAA catabolism in the pathogenesis of AF and to further evaluate the therapeutic effect of melatonin with a focus on protein kinase G (PKG)-cAMP response element binding protein (CREB)-Krüppel-like factor 15 (KLF15) signaling. We found that angiotensin II-treated atria exhibited significantly elevated BCAA level, reduced BCAA catabolic enzyme activity, increased AF vulnerability, aggravated atrial electrical and structural remodeling, and enhanced mitochondrial ROS damage. These deleterious effects were attenuated by melatonin co-administration while exacerbated by BCAA oral supplementation. Melatonin treatment ameliorated BCAA-induced atrial damage and reversed BCAA-induced down-regulation of atrial PKGIα expression, CREB phosphorylation as well as KLF15 expression. However, inhibition of PKG partly abolished melatonin-induced beneficial actions. In summary, these data demonstrated that atrial BCAA catabolic defect contributed to the pathogenesis of AF by aggravating tissue fibrosis and mitochondrial ROS damage. Melatonin treatment ameliorated Ang II-induced atrial structural as well as electrical remodeling by activating PKG-CREB-KLF15. The present study reveals additional mechanisms contributing to AF genesis and highlights the opportunity of a novel therapy for AF by targeting BCAA catabolism. Melatonin may serve as a potential therapeutic agent for AF intervention.

Independent Cis-Regulatory Modules within the Herpes Simplex Virus 1 Infected Cell Protein 0 (ICP0) Promoter Are Transactivated by Krüppel-like Factor 15 and Glucocorticoid Receptor.

A corticosteroid antagonist impairs Herpes Simplex Virus 1 (HSV-1) productive infection and explant-induced reactivation from latency, suggesting corticosteroids and the glucocorticoid receptor (GR) mediate certain aspects of these complex virus-host interactions. GR-hormone complexes regulate transcription positively and negatively, in part, by binding GR response elements (GREs). Recent studies revealed infected cell protein 0 (ICP0), ICP4, and ICP27 promoter/cis-regulatory modules (CRMs) are cooperatively transactivated by GR and Krüppel-like factor 15 (KLF15), which forms a feed-forward transcription loop. We hypothesized the ICP0 promoter contains independent CRMs that are transactivated by GR, KLF15, and the synthetic corticosteroid dexamethasone (DEX). This hypothesis is based on the finding that the ICP0 promoter contains multiple transcription factor binding sites, and GR and KLF15 cooperatively transactivate the full-length ICP0 promoter. ICP0 promoter sequences spanning -800 to -635 (fragment A) were efficiently transactivated by GR, KLF15, and DEX in monkey kidney cells (Vero), whereas GR and DEX significantly enhanced promoter activity in mouse neuroblastoma cells (Neuro-2A). Furthermore, ICP0 fragment B (-458 to -635) was efficiently transactivated by GR, KLF15, and DEX in Vero cells, but not Neuro-2A cells. Finally, fragment D (-232 to -24) was transactivated significantly in Vero cells by GR, KLF15, and DEX, whereas KLF15 and DEX were sufficient for transactivation in Neuro-2A cells. Collectively, these studies revealed efficient transactivation of three independent CRMs within the ICP0 promoter by GR, KLF15, and/or DEX. Finally, GC-rich sequences containing specificity protein 1 (Sp1) binding sites were essential for transactivation.

Kruppel-like factor 15 regulates fuel switching between glucose and fatty acids in brown adipocytes.

AIMS/INTRODUCTION: Brown adipose tissue (BAT) utilizes large amounts of fuel for thermogenesis, but the mechanism by which fuel substrates are switched in response to changes in energy status is poorly understood. We have now investigated the role of Kruppel-like factor 15 (KLF15), a transcription factor expressed at a high level in adipose tissue, in the regulation of fuel utilization in BAT. MATERIALS AND METHODS: Depletion or overexpression of KLF15 in HB2 differentiated brown adipocytes was achieved by adenoviral infection. Glucose and fatty acid oxidation were measured with radioactive substrates, pyruvate dehydrogenase complex activity was determined with a colorimetric assay, and gene expression was examined by reverse transcription and real-time polymerase chain reaction analysis. RESULTS: Knockdown of KLF15 in HB2 cells attenuated fatty acid oxidation in association with downregulation of the expression of genes related to this process including Acox1 and Fatp1, whereas it increased glucose oxidation. Expression of the gene for pyruvate dehydrogenase kinase 4 (PDK4), a negative regulator of pyruvate dehydrogenase complex, was increased or decreased by KLF15 overexpression or knockdown, respectively, in HB2 cells, with these changes being accompanied by a respective decrease or increase in pyruvate dehydrogenase complex activity. Chromatin immunoprecipitation showed that Pdk4 is a direct target of KLF15 in HB2 cells. Finally, fasting increased expression of KLf15, Pdk4 and genes involved in fatty acid utilization in BAT of mice, whereas refeeding suppressed Klf15 and Pdk4 expression. CONCLUSIONS: Our results implicate KLF15 in the regulation of fuel switching between glucose and fatty acids in response to changes in energy status in BAT.

Inhibition of miR-431-5p attenuated liver apoptosis through KLF15/p53 signal pathway in S100 induced autoimmune hepatitis mice.

AIMS: The purpose of this study was to investigate the effects of miR-431-5p on hepatocyte apoptosis in AIH. MATERIALS AND METHODS: We used intraperitoneal injection of S100 to establish AIH mouse model and injected AAV into tail vein on day 14 of modeling to regulate miR-431-5p expression. The expression of ALT, AST, IgG and apoptosis-related proteins Bax, Bcl-2 and cleaved caspase 3 were measured in each group. Cellular experiments were performed using miR-431-5p mimics or inhibitors to transfect LPS-stimulated AML12 cells, and apoptosis was verified using Western blot and Hoechst 33342/PI Double Staining. The target of miR-431-5p, KLF15, was screened using databases and verified by the luciferase reporter assay. The relationship between KLF15 and p53 was verified by si-KLF15 and PFTß (a p53-specific inhibitor). KEY FINDINGS: Here, we observed that the increase in the level of miR-431-5p was accompanied by a decrease in the expression of Krüppel-like zinc finger transcription factor 15 (KLF15). In addition, the deletion of miR-431-5p significantly reduced hepatocyte apoptosis in AIH mice induced by liver S100 and apoptosis of AML12 cells induced by LPS stimulation, accompanied by decreased expression of Bax and cleaved caspase-3 as well as increased expression of Bcl-2. Moreover, KLF15 was the direct and functional target of miR-431-5p. Furthermore, miR-431-5p negatively regulated the expression of KLF15, and KLF15 deletion partially abolished the inhibitory effect of miR-431-5p deletion on apoptosis by activating p53 signaling. SIGNIFICANCE: In summary, miR-431-5p may be a potential therapeutic target for AIH.

Stress Induced Transcription Factors Transactivate the Herpes Simplex Virus 1 Infected Cell Protein 27 (ICP27) Transcriptional Enhancer.

Following acute infection, herpes simplex virus 1 (HSV-1) establishes lifelong latency in neurons, including sensory neurons within trigeminal ganglia. During latency, lytic cycle viral gene expression is silenced. However, stressful stimuli can trigger reactivation from latency. The viral tegument protein, VP-16, transactivates all immediate early (IE) promoters during productive infection. Conversely, cellular factors are expected to trigger viral gene expression during early stages of reactivation from latency and in non-neuronal cells that do not support high levels of productive infection. The glucocorticoid receptor (GR), synthetic corticosteroid dexamethasone, and certain stress-induced transcription factors cooperatively transactivate infected cell protein 0 (ICP0) and ICP4 promoters. Since ICP27 protein expression is required for productive infection, we hypothesized that the ICP27 promoter is transactivated by stress-induced transcription factors. New studies have demonstrated that ICP27 enhancer sequences were transactivated by GR and Krüppel-like factor 15 (KLF15). Mutation of a consensus Sp1 binding site within ICP27 enhancer sequences impaired transactivation by GR and KLF15. Chromatin immunoprecipitation studies have demonstrated that GR and KLF15 occupy ICP27 promoter sequences during productive infection. Cells transfected with an ICP27 enhancer fragment revealed the GR and KLF15 occupancy of ICP27 enhancer sequences required the intact Sp1 binding site. Notably, GR and KLF15 form a feed-forward transcription loop in response to stress, suggesting these cellular factors promote viral replication following stressful stimuli.

Regulation of Krüppel-Like Factor 15 Expression by Herpes Simplex Virus Type 1 or Bovine Herpesvirus 1 Productive Infection.

Expression of Krüppel-like factor 15 (KLF15), a stress-induced transcription factor, is induced during bovine herpesvirus 1 (BoHV-1) reactivation from latency, and KLF15 stimulates BoHV-1 replication. Transient transfection studies revealed that KLF15 and glucocorticoid receptor (GR) cooperatively transactivate the BoHV-1-immediate-early transcription unit 1 (IEtu1), herpes simplex virus type 1 (HSV-1) infected cell protein 0 (ICP0), and ICP4 promoters. The IEtu1 promoter drives expression of bICP0 and bICP4, two key BoHV-1 transcriptional regulatory proteins. Based on these studies, we hypothesized infection is a stressful stimulus that increases KLF15 expression and enhances productive infection. New studies demonstrated that silencing KLF15 impaired HSV-1 productive infection, and KLF15 steady-state protein levels were increased at late stages of productive infection. KLF15 was primarily localized to the nucleus following infection of cultured cells with HSV-1, but not BoHV-1. When cells were transfected with a KLF15 promoter construct and then infected with HSV-1, promoter activity was significantly increased. The ICP0 gene, and to a lesser extent, bICP0 transactivated the KLF15 promoter in the absence of other viral proteins. In contrast, BoHV-1 or HSV-1 encoded VP16 had no effect on KLF15 promoter activity. Collectively, these studies revealed that HSV-1 and BoHV-1 productive infection increased KLF15 steady-state protein levels, which correlated with increased virus production.

KLF15 is a protective regulatory factor of heart failure induced by pressure overload.

The aim of the present study was to investigate the protective effect of Kruppel­like factor 15 (KLF15) overexpression on heart failure (HF) induced by left ventricular (LV) pressure overload in mice. Wild­type (WT) mice and cardiac­specific KLF15­overexpressed transgenic (TG) mice were selected as research subjects, and an LV pressure overload model was constructed by ascending aortic constriction surgery. Changes in cardiac morphology and function, and ultrastructure and molecular expression were observed via M­mode echocardiography, histological and immunohistochemical staining, ELISA and western blotting at 2 and 6 weeks of LV overload. WT and TG mice subjected to 2 weeks of overload displayed adaptive LV hypertrophy characterized by ventricular thickness, cardiomyocyte size, ejection fraction and fractional shortening of heart­lung weight ratio and KLF15, and increases in vascular endothelial growth factor (VEGF) expression without other pathological changes. WT mice subjected to 6 weeks of overload displayed enlargement of the LV chamber, severe interstitial remodeling, and HW/LW, cardiac capillary and heart function decline, accompanied by downregulated expression of KLF15 and VEGF, and upregulated expression of connective tissue growth factor, phosphorylated p38 (p­p38) and phosphorylated Smad3 (p­Smad3). In contrast, TG mice exhibited improved resistance to 6 weeks of overload and a slighter molecular expression response compared with WT mice. KLF15 was revealed to be a critical factor regulating the expression of CTGF, VEGF, p­p38 and p­Smad3, and could alleviate the progression from adaptive LV hypertrophy to decompensatory cardiac insufficiency.

A Special Amino-Acid Formula Tailored to Boosting Cell Respiration Prevents Mitochondrial Dysfunction and Oxidative Stress Caused by Doxorubicin in Mouse Cardiomyocytes.

Anthracycline anticancer drugs, such as doxorubicin (DOX), can induce cardiotoxicity supposed to be related to mitochondrial damage. We have recently demonstrated that a branched-chain amino acid (BCAA)-enriched mixture (BCAAem), supplemented with drinking water to middle-aged mice, was able to promote mitochondrial biogenesis in cardiac and skeletal muscle. To maximally favor and increase oxidative metabolism and mitochondrial function, here we tested a new original formula, composed of essential amino acids, tricarboxylic acid cycle precursors and co-factors (named 5), in HL-1 cardiomyocytes and mice treated with DOX. We measured mitochondrial biogenesis, oxidative stress, and BCAA catabolic pathway. Moreover, the molecular relevance of endothelial nitric oxide synthase (eNOS) and mechanistic/mammalian target of rapamycin complex 1 (mTORC1) was studied in both cardiac tissue and HL-1 cardiomyocytes. Finally, the role of Krüppel-like factor 15 (KLF15), a critical transcriptional regulator of BCAA oxidation and eNOS-mTORC1 signal, was investigated. Our results demonstrate that the 5 mixture prevents the DOX-dependent mitochondrial damage and oxidative stress better than the previous BCAAem, implying a KLF15/eNOS/mTORC1 signaling axis. These results could be relevant for the prevention of cardiotoxicity in the DOX-treated patients.

Krüppel-like Factor 15: A Potential Therapeutic Target For Kidney Disease.

Krüppel-like factor 15 (KLF15) is a zinc-finger transcription factor highly expressed in the glomeruli and interstitial cells of kidneys. An increasing number of studies have demonstrated a critical role for KLF15 in the kidney, involving tubular physiology, podocyte injury, renal fibrosis, and mesangial pathology. In this review, we discuss recent advances and update our overview of the functions of KLF15 in kidney biology, hoping to provide new perspectives on the progression and therapy of Chronic Kidney Disease (CKD). A better understanding of KLF15 with respect to its diverse roles in specific cells or diseases will be beneficial in pursuing novel therapeutic targets and moving forward to precision medicine.

Advances in the relationship between Kruppel-like factor 15 and cardiovascular disease research.

Kruppel-like factor 15 (KLF15) is a subtype of the Kruppel-like family of transcription factors (KLFs). KLFs have three high-fidelity zinc fingers at the carboxyl terminus that enable them to regulate the biological processes of proliferation, differentiation, cellular development, and apoptosis. KLF15 is highly expressed in the kidney, pancreas, and cardiac and skeletal muscle, and plays an essential role in the development and occurrence of multiple system diseases. In this paper, we underscored the important relationship between KLF15 and cardiovascular diseases such as atherosclerosis, heart failure, arrhythmia, aortic lesions, etc. On this basis, we identified KLF15 as a potential therapeutic target for the treatment of cardiovascular disease.