Krüppel-like factor 10 upregulates the expression of cyclooxygenase 1 and further modulates angiogenesis in endothelial cell and platelet aggregation in gene-deficient mice

The kruppel-like factor (KLF) family, diseases, and physiological events

The Kruppel-Like Factor family of regulatory proteins, which has 18 members, is transcription factors. This family contains zinc finger proteins, regulates the activation and suppression of transcription, and binds to DNA, RNA, and proteins. Klfs related to the immune system are Klf1, Klf2, Klf3, Klf4, Klf6, and Klf14. Klfs related to adipose tissue development and/or glucose metabolism are Klf3, Klf7, Klf9, Klf10, Klf11, Klf14, Klf15, and Klf16. Klfs related to cancer are Klf3, Klf4, Klf5, Klf6, Klf7, Klf8, Klf9, Klf10, Klf11, Klf12, Klf13, Klf14, Klf16, and Klf17. Klfs related to the cardiovascular system are Klf4, Klf5, Klf10, Klf13, Klf14, and Klf15. Klfs related to the nervous system are Klf4, Klf7, Klf8, and Klf9. Klfs are associated with diseases such as carcinogenesis, oxidative stress, diabetes, liver fibrosis, thalassemia, and the metabolic syndrome. The aim of this review is to provide information about the relationship of Klfs with some diseases and physiological events and to guide future studies.

MicroRNAs in Tumor Endothelial Cells: Regulation, Function and Therapeutic Applications

Tumor endothelial cells (TECs) are key stromal components of the tumor microenvironment, and are essential for tumor angiogenesis, growth and metastasis. Accumulating evidence has shown that small single-stranded non-coding microRNAs (miRNAs) act as powerful endogenous regulators of TEC function and blood vessel formation. This systematic review provides an up-to-date overview of these endothelial miRNAs. Their expression is mainly regulated by hypoxia, pro-angiogenic factors, gap junctions and extracellular vesicles, as well as long non-coding RNAs and circular RNAs. In preclinical studies, they have been shown to modulate diverse fundamental angiogenesis-related signaling pathways and proteins, including the vascular endothelial growth factor (VEGF)/VEGF receptor (VEGFR) pathway; the rat sarcoma virus (Ras)/rapidly accelerated fibrosarcoma (Raf)/mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) pathway; the phosphoinositide 3-kinase (PI3K)/AKT pathway; and the transforming growth factor (TGF)-β/TGF-β receptor (TGFBR) pathway, as well as krüppel-like factors (KLFs), suppressor of cytokine signaling (SOCS) and metalloproteinases (MMPs). Accordingly, endothelial miRNAs represent promising targets for future anti-angiogenic cancer therapy. To achieve this, it will be necessary to further unravel the regulatory and functional networks of endothelial miRNAs and to develop safe and efficient TEC-specific miRNA delivery technologies.

Krüppel-like factor 10 modulates stem cell phenotypes of pancreatic adenocarcinoma by transcriptionally regulating notch receptors

BACKGROUND

Pancreatic adenocarcinoma (PDAC) is well known for its rapid distant metastasis and local destructive behavior. Loss of Krüppel-like factor 10 (KLF10) contributes to distant migration of PDAC. The role of KLF10 in modulating tumorigenesis and stem cell phenotypes of PDAC is unclear.

METHODS

Additional depletion of KLF10 in KC (LSL: Kras^G12D; Pdx1-Cre) mice, a spontaneous murine PDAC model, was established to evaluate tumorigenesis. Tumor specimens of PDAC patients were immune-stained of KLF10 to correlate with local recurrence after curative resection. Conditional overexpressing KLF10 in MiaPaCa and stably depleting KLF10 in Panc-1 (Panc-1-pLKO-shKLF10) cells were established for evaluating sphere formation, stem cell markers expression and tumor growth. The signal pathways modulated by KLF10 for PDAC stem cell phenotypes were disclosed by microarray analysis and validated by western blot, qRT-PCR, luciferase reporter assay. Candidate targets to reverse PDAC tumor growth were demonstrated in murine model.

RESULTS

KLF10, deficient in two-thirds of 105 patients with resected pancreatic PDAC, was associated with rapid local recurrence and large tumor size. Additional KLF10 depletion in KC mice accelerated progression from pancreatic intraepithelial neoplasia to PDAC. Increased sphere formation, expression of stem cell markers, and tumor growth were observed in Panc-1-pLKO-shKLF10 compared with vector control. Genetically or pharmacologically overexpression of KLF10 reversed the stem cell phenotypes induced by KLF10 depletion. Ingenuity pathway analysis and gene set enrichment analysis showed that Notch signaling molecules, including Notch receptors 3 and 4, were over-expressed in Panc-1-pLKO-shKLF10. KLF10 transcriptionally suppressed Notch-3 and -4 by competing with E74-like ETS transcription factor 3, a positive regulator, for promoter binding. Downregulation of Notch signaling, either genetically or pharmacologically, ameliorated the stem cell phenotypes of Panc-1-pLKO-shKLF10. The combination of metformin, which upregulated KLF10 expression via phosphorylating AMPK, and evodiamine, a non-toxic Notch-3 methylation stimulator, delayed tumor growth of PDAC with KLF10 deficiency in mice without prominent toxicity.

CONCLUSIONS

These results demonstrated a novel signaling pathway by which KLF10 modulates stem cell phenotypes in PDAC through transcriptionally regulating Notch signaling pathway. The elevation of KLF10 and suppression of Notch signaling may jointly reduce PDAC tumorigenesis and malignant progression.

Transcription factor AP-2 gamma/Krüppel-like factor 10 axis is involved in miR-3656-related dysfunction of endothelial cells in hypertension

BACKGROUND

Dysfunction of endothelial cells links to microvascular rarefaction, reflecting the pathogenesis of hypertension. Our previous studies found that miR-3656 reduces nitric oxide generation and von Willebrand factor (vWF) cleavage, thereby retarding blood flow and potentially increasing blood pressure. In this paper, we investigated mechanism of transcription regulation contributing to miR-3656-damaged endothelial cells in hypertension.

METHODS

The effects of miR-3656 on function of endothelial cells were analyzed on the basis of proliferation, migration, tube formation, and apoptosis. The mRNA level and protein level of genes were examined using quantitative real-time polymerase chain reaction (qRT-PCR) and western blot. Dual-luciferase reporter assay was performed to confirm the binding between miR-3656 and 3' untranslated region (UTR) of transcription factor AP-2 gamma ( TFAP2C ). The binding between TFAP2C and the promoter region of Krüppel-like factor 10 ( KLF10 ) was confirmed by chromatin immunoprecipitation-qPCR assay.

RESULTS

miR-3656 impaired the cell proliferation, migration, tube formation, and apoptosis of endothelial cells. miR-3656 inhibited the expression of TFAP2C by directly targeting 3'UTR of TFAP2C ; moreover, miR-3656-induced injury of endothelial cells was rescued by TFAP2C overexpression. Furthermore, downregulated TFAP2C decreased KLF10 expression by binding to KLF10 promoter region, and upregulated KLF10 reversed the effects of silencing TFAP2C on endothelial cells. These inhibitory processes led to interference of miR-3656 to KLF10-promoted function of endothelial cells.

CONCLUSION

TFAP2C/KLF10 axis is involved in miR-3656-related dysfunction of endothelial cells in hypertension. The 3'UTR of TFAP2C and KLF10 promoter region are the hubs of the TFAP2C/KLF10 axis.

Langerhans cells are essential components of the angiogenic niche during murine skin repair

Angiogenesis, the growth of new blood vessels from pre-existing vessels, occurs during development, injury repair, and tumorigenesis to deliver oxygen, immune cells, and nutrients to tissues. Defects in angiogenesis occur in cardiovascular and inflammatory diseases, and chronic, non-healing wounds, yet treatment options are limited. Here, we provide a map of the early angiogenic niche by analyzing single-cell RNA sequencing of mouse skin wound healing. Our data implicate Langerhans cells (LCs), phagocytic, skin-resident immune cells, in driving angiogenesis during skin repair. Using lineage-driven reportersw, three-dimensional (3D) microscopy, and mouse genetics, we show that LCs are situated at the endothelial cell leading edge in mouse skin wounds and are necessary for angiogenesis during repair. These data provide additional future avenues for the control of angiogenesis to treat disease and chronic wounds and extend the function of LCs beyond their canonical role in antigen presentation and T cell immunity.

Knockout of KLF10 Ameliorated Diabetic Renal Fibrosis via Downregulation of DKK-1

Diabetes-induced chronic kidney disease leads to mortality and morbidity and thus poses a great health burden worldwide. Krüppel-like factor 10 (KLF10), a zinc finger-containing transcription factor, regulates numerous cellular functions, such as proliferation, differentiation, and apoptosis. In this study, we explored the effects of KLF10 on diabetes-induced renal disease by using a KLF10 knockout mice model. Knockout of KLF10 obviously diminished diabetes-induced tumor growth factor-β (TGF-β), fibronectin, and type IV collagen expression, as evidenced by immunohistochemical staining. KLF10 knockout also repressed the expression of Dickkopf-1 (DKK-1) and phosphorylated β-catenin in diabetic mice, as evidenced by immunohistochemical staining and Western blot analysis. Quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) revealed that significantly decreased type IV collagen, fibronectin, and DKK-1 existed in KLF10 knockout diabetic mice compared with control diabetic mice. Moreover, knockout of KLF10 reduced the renal fibrosis, as shown by Masson's Trichrome analysis. Overall, the results indicate that depletion of KLF10 ameliorated diabetic renal fibrosis via the downregulation of DKK-1 expression and inhibited TGF-β1 and phosphorylated β-catenin expression. Our findings suggest that KLF10 may be a promising therapeutic choice for the treatment of diabetes-induced renal fibrosis.

Upregulating sirtuin 6 ameliorates glycolysis, EMT and distant metastasis of pancreatic adenocarcinoma with krüppel-like factor 10 deficiency

Krüppel-like factor 10 (KLF10) is a tumor suppressor in multiple cancers. In a murine model of spontaneous pancreatic adenocarcinoma (PDAC), additional KLF10 depletion accelerated distant metastasis. However, Klf10 knockout mice, which suffer from metabolic disorders, do not develop malignancy. The mechanisms of KLF10 in PDAC progression deserve further exploration. KLF10-depleted and KLF10-overexpressing PDAC cells were established to measure epithelial-mesenchymal transition (EMT), glycolysis, and migration ability. A murine model was established to evaluate the benefit of genetic or pharmacological manipulation in KLF10-depleted PDAC cells (PDACshKLF10). Correlations of KLF10 deficiency with rapid metastasis, elevated EMT, and glycolysis were demonstrated in resected PDAC tissues, in vitro assays, and murine models. We identified sirtuin 6 (SIRT6) as an essential mediator of KLF10 that modulates EMT and glucose homeostasis. Overexpressing SIRT6 reversed the migratory and glycolytic phenotypes of PDACshKLF10 cells. Linoleic acid, a polyunsaturated essential fatty acid, upregulated SIRT6 and prolonged the survival of mice injected with PDACshKLF10. Modulating HIF1α and NFκB revealed that EMT and glycolysis in PDAC cells were coordinately regulated upstream by KLF10/SIRT6 signaling. Our study demonstrated a novel KLF10/SIRT6 pathway that modulated EMT and glycolysis coordinately via NFκB and HIF1α. Activation of KLF10/SIRT6 signaling ameliorated the distant progression of PDAC.Clinical Trial Registration: ClinicalTrials.gov. identifier: NCT01666184.

Salvia miltiorrhiza bunge exerts anti-oxidative effects through inhibiting KLF10 expression in vascular smooth muscle cells exposed to high glucose

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional Chinese medicinal herb Salvia miltiorrhiza Bunge(Danshen) and its components have been widely used to treat cardiovascular diseases for hundreds of years in China, including hypertension, diabetes, atherosclerosis, and chronic heart failure. Salvia miltiorrhiza injection (SMI), an aqueous extracts of Salvia miltiorrhiza Bunge, is one of most widely used traditional Chinese medicine injections. SMI is widely used in the treatment of diabetic vascular complications, However, the mechanisms remain to be defined.

AIM OF THE STUDY

To investigate protective mechanism of Salvia miltiorrhiza Bunge against ROS generation in VSMCs of diabetic mice and patients.

MATERIALS AND METHODS

Salvia miltiorrhiza injection (hereinafter referred to as SMI, 1.5 g mL^-1), which was approved by the State Food and Drug Administration (approval number: Z32020161), was obtained from Shenlong Pharmaceutical Co., Ltd. (batch number: 11040314). SMI or vehicle were intraperitoneally administrated to the HFD-fed db/db mice, artery was harvested after 24weeks later. qRT-PCR and Western blot analysis were used to detect the expression of KLF6, KLF5, KLF4, KLF10, KLF12, and HO-1. DCFH-DA staining detected intracellular ROS production. Loss- and gain-of-function experiments of KLF10 were used to investigate the effect of KLF10 on the expression of HO-1. Dual-luciferase reporter assay evaluated the effect of KLF10 on the activity of the HO-1 promoter.

RESULTS

KLF10 expression and ROS generation are significantly increased in the arteries of HFD-fed db/db mice, VSMCs of diabetic patients, as well as in high glucose-treated VSMCs. KLF10 overexpression suppresses, while its knockdown facilitates the expression of heme oxygenase (HO-1) mRNA and protein. Further, Salvia miltiorrhiza injection (SMI) abrogates KLF10 upregulation and reduces ROS generation induced by high glucose in VSMCs. Mechanistically, KLF10 negatively regulates the HO-1 gene transcription via directly binding to its promoter. Accordingly, SMI treatment of VSMCs reduces ROS generation through inhibiting KLF10 expression and thus relieving KLF10 repression of the expression of HO-1 gene, subsequently contributing to upregulation of HO-1.

CONCLUSION

SMI exerts anti-oxidative effects on VSMCs exposed to high glucose through inhibiting KLF10 expression and thus upregulating HO-1.

A KDM6A-KLF10 reinforcing feedback mechanism aggravates diabetic podocyte dysfunction

Diabetic nephropathy is the leading cause of end‐stage renal disease. Although dysfunction of podocytes, also termed glomerular visceral epithelial cells, is critically associated with diabetic nephropathy, the mechanism underlying podocyte dysfunction still remains obscure. Here, we identify that KDM6A, a histone lysine demethylase, reinforces diabetic podocyte dysfunction by creating a positive feedback loop through up‐regulation of its downstream target KLF10. Overexpression of KLF10 in podocytes not only represses multiple podocyte‐specific markers including nephrin, but also conversely increases KDM6A expression. We further show that KLF10 inhibits nephrin expression by directly binding to the gene promoter together with the recruitment of methyltransferase Dnmt1. Importantly, inactivation or knockout of either KDM6A or KLF10 in mice significantly suppresses diabetes‐induced proteinuria and kidney injury. Consistent with the notion, we also show that levels of both KDM6A and KLF10 proteins or mRNAs are substantially elevated in kidney tissues or in urinary exosomes of human diabetic nephropathy patients as compared with control subjects. Our findings therefore suggest that targeting the KDM6A–KLF10 feedback loop may be beneficial to attenuate diabetes‐induced kidney injury.

Deciphering the Active Compounds and Mechanisms of Qixuehe Capsule on Qi Stagnation and Blood Stasis Syndrome: A Network Pharmacology Study

BACKGROUND

Qixuehe capsule (QXH), a Chinese patent medicine, has been demonstrated to be effective in the treatment of menstrual disorders. In traditional Chinese medicine (TCM) theory, qi stagnation and blood stasis syndrome (QS-BSS) is the main syndrome type of menstrual disorders. However, the pharmacodynamic effect of QXH in treating QS-BSS is not clear, and the main active compounds and underlying mechanisms remain unknown.

METHODS

A rat model of QS-BSS was established to evaluate the pharmacodynamic effect of QXH. Thereafter, a network pharmacology approach was performed to decipher the active compounds and underlying mechanisms of QXH.

RESULTS

QXH could significantly reduce the rising whole blood viscosity (WBV) and plasma viscosity (PV) but also normalize prothrombin time (PT), activated partial thromboplastin time (APTT), thrombin time (TT), and fibrinogen (FIB) content in QS-BSS rats. Based on partial least-squares-discriminant analysis (PLS-DA), the low-dose QXH-intervened (QXH-L) and the high-dose QXH-intervened (QXH-H) groups seemed the most effective by calculating the relative distance to normality. Through network pharmacology, QXH may improve hemorheological abnormality mainly via 185 compounds-51 targets-28 pathways, whereas 184 compounds-68 targets-28 pathways were associated with QXH in improving coagulopathy. Subsequently, 25 active compounds of QXH were verified by UPLC-Q/TOF-MS. Furthermore, 174 active compounds of QXH were shared in improving hemorheological abnormality and coagulopathy in QS-BSS, each of which can act on multiple targets to be mainly involved in complement and coagulation cascades, leukocyte transendothelial migration, PPAR signaling pathway, VEGF signaling pathway, and arachidonic acid metabolism. The attribution of active compounds indicated that Angelicae Sinensis Radix (DG), Paeoniae Radix Rubra (CS), Carthami Flos (HH), Persicae Semen (TR), and Corydalis Rhizoma (YHS) were the vital herbs of QXH in treating QS-BSS.

CONCLUSION

QXH can improve the hemorheology abnormality and coagulopathy of QS-BSS, which may result from the synergy of multiple compounds, targets, and pathways.

CDK8 regulates the angiogenesis of pancreatic cancer cells in part via the CDK8-β-catenin-KLF2 signal axis

BACKGROUND

CDK8 is associated with the transcriptional Mediator complex and has been shown to regulate several transcription factors implicated in cancer. As a pancreatic cancer oncogene, the role of CDK8 in cancer angiogenesis remains unclear. Here, we investigated the contribution of CDK8 in pancreatic cancer angiogenesis and examined the underlying molecular mechanisms.

METHODS

CDK8 expression was evaluated via immunohistochemistry, western blotting, and qRT-PCR in relation to the clinicopathological characteristics of pancreatic cancer patients. The effects of silencing or overexpressing CDK8 on cancer angiogenesis were assessed in vitro by western blotting assays in pancreatic cancer cell lines and in vivo with nude mice xenograft models.

RESULTS

Compared with adjacent normal tissues, pancreatic cancer tissues showed upregulation of CDK8 expression, which was inversely correlated with T grade, liver metastasis, size, lymph node metastasis and poor survival. CDK8 overexpression promoted angiogenesis in pancreatic cancer via activation of the CDK8-β-catenin-KLF2 signaling axis, as demonstrated by the upregulation and downregulation of signals representing the rate-limiting steps in angiogenesis. Silencing CDK8 inhibited angiogenesis in pancreatic cancer in vitro. Additionally, these results were confirmed in nude mice xenograft models in vivo.

CONCLUSIONS

CDK8 promotes angiogenesis in pancreatic cancer via activation of the CDK8-β-catenin-KLF2 signaling axis, thus providing valid targets for the treatment of pancreatic cancer.

Effect of ximenynic acid on cell cycle arrest and apoptosis and COX-1 in HepG2 cells

Ximenynic acid is a conjugated enyne fatty acid, which is currently of interest due to its anti-inflammatory activity. Due to the association between inflammation and cancer, the present study was designed to investigate the anti‑cancer activity of ximenynic acid in the HepG2 human hepatoma cell line and the underlying mechanisms. The current study demonstrated the anti‑proliferation and pro‑apoptosis activities of ximenynic acid by cell viability assay and flow cytometry analysis. The expression of anti‑apoptosis protein silent information regulator T1 (SIRT1) was significantly suppressed by ximenynic acid. Furthermore, ximenynic acid blocked G1/S phase transition by inhibiting the protein expression of the cell cycle‑associated protein general control of amino acid synthesis yeast homolog like 2 (GCN5L2), and the mRNA expression of cyclin D3 and cyclin E1. Furthermore, ximenynic acid suppressed the expression of angiogenesis‑associated genes, including vascular endothelial growth factor (VEGF)‑B and VEGF‑C. Finally, ximenynic acid significantly inhibited the expression of cyclooxygenase‑1 (COX‑1) mRNA and protein, however COX‑2 expression was not reduced. The results of the present study suggested that ximenynic acid may inhibit growth of HepG2 cells by selective inhibition of COX‑1 expression, which leads to cell cycle arrest, and alters the apoptosis pathway and expression of angiogenic factors. The current study aimed to investigate whether ximenynic acid might be developed as novel anticancer agent.

Klf10 deficiency in mice exacerbates pulmonary inflammation by increasing expression of the proinflammatory molecule NPRA

KLF10 is a transforming growth factor (TGF)-β/Smad downstream regulated gene. KLF10 binds to the promoter of target genes and mimics the effects of TGF-β as a transcriptional factor. In our laboratory, we noted that Klf10 deficiency in mice is associated with significant inflammation of the lungs. However, the precise mechanism of this association remains unknown. We previously identified NPRA as a target gene potentially regulated by KLF10 through direct binding; NPRA knockout have known that prevented lung inflammation in a mouse model of allergic asthma. Here, we further explored the regulatory association between KLF10 and NPRA on the basis of the aforementioned findings. Our results demonstrated that KLF10 acts as a transcriptional repressor of NPRA and that KLF10 binding reduces NPRA expression in vitro. Compared with wild-type mice, Klf10-deficient mice were more sensitive to lipopolysaccharide or ovalbumin challenge and showed more severe inflammatory histological changes in the lungs. Moreover, Klf10-deficient mice showed pulmonary neutrophil accumulation. These findings collectively reveal the precise site where KLF10 signaling affects pulmonary inflammation by attenuating NPRA expression. They also verify the importance of KLF10 and atrial natriuretic peptide/NPRA in exerting influences on chronic pulmonary disease pathogenesis.

Expression of pro-angiogenic genes in mesenchymal stem cells derived from dermis of patients with psoriasis

BACKGROUND

Recent experimental studies revealed that angiogenesis and lymphangiogenesis are closely related to psoriasis. Our microarray analysis suggested that the pro-angiogenic genes platelet endothelial cell adhesion molecule-1 (PECAM1), facio-genital dysplasia-5 (FGD5), prostaglandin-endoperoxide synthase-1 (PTGS1), melanoma cell adhesion molecule (MCAM), vasohibin-2 (VASH2), and stabilin-1 (STAB1) are differentially expressed in dermal mesenchymal stem cells in psoriasis.

OBJECTIVES

The aim of this study was to investigate the mRNA and protein expression of PECAM1, FGD5, PTGS1, MCAM, VASH2, and STAB1 for angiogenesis and the possible mechanisms in psoriasis.

METHODS

We studied 12 patients with plaque psoriasis and 14 healthy controls matched for age and sex. Dermal mesenchymal stem cells were expanded, passaged, and identified by cellular morphology, immunophenotyping, and multipotential differentiation. The mRNA and protein expression of the above-mentioned six genes were confirmed by quantitative real-time reverse transcription-polymerase chain reaction and Western blotting.

RESULTS

The significantly decreased expression of PECAM1, PTGS1, FGD5, and MCAM at both mRNA and protein level (except VASH2 and STAB1) were demonstrated in mesenchymal stem cells from psoriatic skin lesions compared with non-lesional from healthy controls.

CONCLUSIONS

We provide the first report that pro-angiogenic genes PECAM1, PTGS1, FGD5, and MCAM rather than VASH2 and STAB1 may be play a vital role in pathological dermal angiogenesis disorders of psoriasis. Therefore, anti-angiogenesis is attractive and offers future potential for application in patients with psoriasis.

Klf10 regulates odontoblast differentiation and mineralization via promoting expression of dentin matrix protein 1 and dentin sialophosphoprotein genes

Klf10, a member of the Krüppel-like family of transcription factors, is critical for osteoblast differentiation, bone formation and mineralization. However, whether Klf10 is involved in odontoblastic differentiation and tooth development has not been determined. In this study, we investigate the expression patterns of Klf10 during murine tooth development in vivo and its role in odontoblastic differentiation in vitro. Klf10 protein was expressed in the enamel organ and the underlying mesenchyme, ameloblasts and odontoblasts at early and later stages of murine molar formation. Furthermore, the expression of Klf10, Dmp1, Dspp and Runx2 was significantly elevated during the process of mouse dental papilla mesenchymal differentiation and mineralization. The overexpression of Klf10 induced dental papilla mesenchymal cell differentiation and mineralization as detected by alkaline phosphatase staining and alizarin red S assay. Klf10 additionally up-regulated the expression of odontoblastic differentiation marker genes Dmp1, Dspp and Runx2 in mouse dental papilla mesenchymal cells. The molecular mechanism of Klf10 in controlling Dmp1 and Dspp expression is thus to activate their regulatory regions in a dosage-dependent manner. Our results suggest that Klf10 is involved in tooth development and promotes odontoblastic differentiation via the up-regulation of Dmp1 and Dspp transcription.

KLF4 Promotes Angiogenesis by Activating VEGF Signaling in Human Retinal Microvascular Endothelial Cells

The transcription factor Krüppel-like factor 4 (KLF4) has been implicated in regulating cell proliferation, migration and differentiation in a variety of human cells and is one of four factors required for the induction of pluripotent stem cell reprogramming. However, its role has not been addressed in ocular neovascular diseases. This study investigated the role of KLF4 in angiogenesis and underlying molecular mechanisms in human retinal microvascular endothelial cells (HRMECs). The functional role of KLF4 in HRMECs was determined following lentiviral vector mediated inducible expression and shRNA knockdown of KLF4. Inducible expression of KLF4 promotes cell proliferation, migration and tube formation. In contrast, silencing KLF4 inhibits cell proliferation, migration, tube formation and induces apoptosis in HRMECs. KLF4 promotes angiogenesis by transcriptionally activating VEGF expression, thus activating the VEGF signaling pathway in HRMECs.

Transcriptomic changes triggered by hypoxia: evidence for HIF-1α-independent, [Na+]i/[K+]i-mediated, excitation-transcription coupling

This study examines the relative impact of canonical hypoxia-inducible factor-1alpha- (HIF-1α and Na⁺_i/K⁺_i-mediated signaling on transcriptomic changes evoked by hypoxia and glucose deprivation. Incubation of RASMC in ischemic conditions resulted in ∼3-fold elevation of [Na⁺]_i and 2-fold reduction of [K⁺]_i. Using global gene expression profiling we found that Na⁺,K⁺-ATPase inhibition by ouabain or K⁺-free medium in rat aortic vascular smooth muscle cells (RASMC) led to the differential expression of dozens of genes whose altered expression was previously detected in cells subjected to hypoxia and ischemia/reperfusion. For further investigations, we selected Cyp1a1, Fos, Atf3, Klf10, Ptgs2, Nr4a1, Per2 and Hes1, i.e. genes possessing the highest increments of expression under sustained Na⁺,K⁺-ATPase inhibition and whose implication in the pathogenesis of hypoxia was proved in previous studies. In ouabain-treated RASMC, low-Na⁺, high-K⁺ medium abolished amplification of the [Na⁺]_i/[K⁺]_i ratio as well as the increased expression of all tested genes. In cells subjected to hypoxia and glucose deprivation, dissipation of the transmembrane gradient of Na⁺ and K⁺ completely eliminated increment of Fos, Atf3, Ptgs2 and Per2 mRNAs and sharply diminished augmentation expression of Klf10, Edn1, Nr4a1 and Hes1. In contrast to low-Na⁺, high-K⁺ medium, RASMC transfection with Hif-1a siRNA attenuated increments of Vegfa, Edn1, Klf10 and Nr4a1 mRNAs triggered by hypoxia but did not impact Fos, Atf3, Ptgs2 and Per2 expression. Thus, our investigation demonstrates, for the first time, that Na⁺_i/K⁺_i-mediated, Hif-1α- -independent excitation-transcription coupling contributes to transcriptomic changes evoked in RASMC by hypoxia and glucose deprivation.

Vitamin D manipulates miR-181c, miR-20b and miR-15a in human umbilical vein endothelial cells exposed to a diabetic-like environment

BACKGROUND

High blood and tissue concentrations of glucose and advanced glycation end-products are believed to play an important role in the development of vascular complications in patients with diabetes mellitus (DM) and chronic kidney disease. MicroRNAs (miRNA) are non-coding RNAs that regulate gene expression in a sequence specific manner. MiRNA are involved in various biological processes and become novel biomarkers, modulators and therapeutic targets for diseases such as cancer, atherosclerosis, and DM. Calcitriol (the active form of vitamin D) may inhibit endothelial proliferation, blunt angiogenesis, and be a cardioprotective agent. Calcitriol deficiency is a risk factor for DM and hypertension. The aim of this project was to study the miRNA microarray expression changes in human umbilical vein endothelial cells (HUVEC) treated in a diabetic-like environment with the addition of calcitriol.

METHODS

HUVEC were treated for 24 h with 200 μg/ml human serum albumin (HSA) and 100 mg/dl glucose (control group) or 200 μg/ml AGE-HSA, and 250 mg/dl glucose (diabetic-like environment), and physiological concentrations (10-10 mol/l) of calcitriol. miRNA microarray analysis and real time PCR to validate the miRNA expression profile and mRNA target gene expression were carried out.

RESULTS

Compared to control, 31 mature human miRNA were differentially expressed in the presence of a diabetic-like environment. Addition of physiological concentrations of calcitriol revealed 39 differentially expressed mature human miRNA. MiR-181c, miR-15a, miR-20b, miR-411, miR-659, miR-126 and miR-510 were selected for further analysis because they are known to be modified in DM and in other biological disorders. The predicted targets of these miRNA (such as KLF6, KLF9, KLF10, TXNIP and IL8) correspond to molecular and biological processes such as immune and defense responses, signal transduction and regulation of RNA.

CONCLUSION

This study identified novel miRNA in the field of diabetic vasculopathy and might provide new information about the effect of vitamin D on gene regulation induced by a diabetic-like environment. New gene targets that are part of the molecular mechanism and the therapeutic treatment in diabetic vasculopathy are highlighted.

Effect of platelet lysate on human cells involved in different phases of wound healing

Background

Platelets are rich in mediators able to positively affect cell activity in wound healing. Aim of this study was to characterize the effect of different concentrations of human pooled allogeneic platelet lysate on human cells involved in the different phases of wound healing (inflammatory phase, angiogenesis, extracellular matrix secretion and epithelialization).

Methodology/Principal Findings

Platelet lysate effect was studied on endothelial cells, monocytes, fibroblasts and keratinocytes, in terms of viability and proliferation, migration, angiogenesis, tissue repair pathway activation (ERK1/2) and inflammatory response evaluation (NFκB). Results were compared both with basal medium and with a positive control containing serum and growth factors. Platelet lysate induced viability and proliferation at the highest concentrations tested (10% and 20% v/v). Whereas both platelet lysate concentrations increased cell migration, only 20% platelet lysate was able to significantly promote angiogenic activity (p<0.05 vs. control), comparably to the positive control. Both platelet lysate concentrations activated important inflammatory pathways such as ERK1/2 and NFκB with the same early kinetics, whereas the effect was different for later time-points.

Conclusion/Significance

These data suggest the possibility of using allogeneic platelet lysate as both an alternative to growth factors commonly used for cell culture and as a tool for clinical regenerative application for wound healing.

FBW7 regulates endothelial functions by targeting KLF2 for ubiquitination and degradation

F-box and WD repeat domain-containing 7 (FBW7), the substrate-binding subunit of E3 ubiquitin ligase SCF(FBW7) (a complex of SKP1, cullin-1 and FBW7), plays important roles in various physiological and pathological processes. Although FBW7 is required for vascular development, its function in the endothelium remains to be investigated. In this study, we show that FBW7 is an important regulator of endothelial functions, including angiogenesis, leukocyte adhesion and the endothelial barrier integrity. Using RNA interference, we found that the depletion of FBW7 markedly impairs angiogenesis in vitro and in vivo. We identified the zinc finger transcription factor Krüppel-like factor 2 (KLF2) as a physiological target of FBW7 in endothelial cells. Knockdown of FBW7 expression resulted in the accumulation of endogenous KLF2 protein in endothelial cells. FBW7-mediated KLF2 destruction was shown to depend on the phosphorylation of KLF2 via glycogen synthase kinase-3 (GSK3) at two conserved phosphodegrons. Mutating these phosphodegron motifs abolished the FBW7-mediated degradation and ubiquitination of KLF2. The siRNA-mediated knockdown of FBW7 showed that KLF2 is an essential target of FBW7 in the regulation of endothelial functions. Moreover, FBW7-mediated KLF2 degradation was shown to be critical for angiogenesis in teratomas and in zebrafish development. Taken together, our study suggests a role for FBW7 in the processes of endothelial cell migration, angiogenesis, inflammation and barrier integrity, and provides novel insights into the regulation of KLF2 stability in vivo.