New DNA enzyme targeting Egr-1 mRNA inhibits vascular smooth muscle proliferation and regrowth after injury

G-Quadruplex-Programmed Versatile Nanorobot Combined with Chemotherapy and Gene Therapy for Synergistic Targeted Therapy

Developing synergistic targeted therapeutics to improve treatment efficacy while reducing side effects has proven promising for anticancer therapies, but how to conveniently modulate multidrug cooperation remains a challenge. Here, a novel synergistic strategy using a G-quadruplex-programmed versatile nanorobot (G4VN) containing two subunits of DNAzyme (DzG4) and ligand-drug conjugates (LDCs) is proposed to precisely target tumors and then execute both gene silencing and chemotherapy. As the core module of this nanorobot, a well-designed G4 responding to a high level of K+ in tumor microenvironment smartly kills three birds with one stone, which makes two TfR aptamers proximate to improve their efficiency of targeting tumor cells, and in situ activates a split 10-23 DNAzyme to downregulate target mRNA expression, meanwhile promotes the cell uptake of a GSH-responsive LDCs to enhance drug efficacy. Such a design enables a potently synergistic anticancer therapy with low side effects in vivo, showing great promise for broad applications in precision disease treatment.

Cleaving Folded RNA with DNAzyme Agents

Cleavage of biological mRNA by DNAzymes (Dz) has been proposed as a variation of oligonucleotide gene therapy (OGT). The design of Dz-based OGT agents includes computational prediction of two RNA-binding arms with low affinity (melting temperatures (Tm ) close to the reaction temperature of 37 °C) to avoid product inhibition and maintain high specificity. However, RNA cleavage might be limited by the RNA binding step especially if the RNA is folded in secondary structures. This calls for the need for two high-affinity RNA-binding arms. In this study, we optimized 10-23 Dz-based OGT agents for cleavage of three RNA targets with different folding energies under multiple turnover conditions in 2 mM Mg2+ at 37 °C. Unexpectedly, one optimized Dz had each RNA-binding arm with a Tm ≥60 °C, without suffering from product inhibition or low selectivity. This phenomenon was explained by the folding of the RNA cleavage products into stable secondary structures. This result suggests that Dz with long (high affinity) RNA-binding arms should not be excluded from the candidate pool for OGT agents. Rather, analysis of the cleavage products' folding should be included in Dz selection algorithms. The Dz optimization workflow should include testing with folded rather than linear RNA substrates.

The MEK-ERK-Egr-1 axis and its regulation in cardiovascular disease

Cardiovascular disease (CVD) is the primary cause of morbidity and mortality in the Western world. Multiple molecular and cellular processes underpinning the pathogenesis of CVD are regulated by the zinc finger transcription factor and product of an immediate-early gene, early growth response-1 (Egr-1). Egr-1 regulates multiple pro-inflammatory processes that underpin the manifestation of CVD. The activity of Egr-1 itself is influenced by a range of post-translational modifications including sumoylation, ubiquitination and acetylation. Egr-1 also undergoes phosphorylation by protein kinases, such as extracellular-signal regulated kinase (ERK) which is itself phosphorylated by MEK. This article reviews recent progress on the MEK-ERK-Egr-1 cascade, notably regulation in conjunction with factors and agents such as TET2, TRIB2, MIAT, SphK1, cAMP, teneligliptin, cholinergic drugs, red wine and flavonoids, wogonin, febuxostat, docosahexaenoic acid and AT1R blockade. Such insights should provide new opportunity for therapeutic intervention in CVD.

Biomimetic Construction of Degradable DNAzyme-Loaded Nanocapsules for Self-Sufficient Gene Therapy of Pulmonary Metastatic Breast Cancer

Pulmonary metastasis of breast cancer is the major cause of deaths of breast cancer patients, but the effective treatment of pulmonary metastases is still lacking at present. Herein, a degradable biomimetic DNAzyme biocapsule is developed with the poly(ethylenimine) (PEI)-DNAzyme complex encapsulated in a Mn2+/Zn2+-coordinated inositol hexaphosphate (IP6) capsule modified with the cRGD targeting peptide for high-efficiency gene therapy of both primary and pulmonary metastatic breast tumors. This DNAzyme biocapsule is degradable inside acidic lysosomes, leading to the release of DNAzyme and abundant Mn2+/Zn2+ for catalytic cleavage of EGR-1 mRNA. We find that PEI promotes the lysosomal escape of the released DNAzyme. Both in vitro and in vivo experiments demonstrate the apparent downregulation of EGR-1 and Bcl-2 protein expression after treatment with the DNAzyme biocapsule, thereby inducing apoptotic death of tumor cells. We further verify that the DNAzyme biocapsule exhibits potent therapeutic efficacy against both primary and pulmonary metastatic breast tumors with significant inhibition of peri-pulmonary metastasis. This study provides a promising effective strategy for constructing degradable DNAzyme-based platforms with self-supply of abundant metal ion cofactors for high-efficiency gene therapy of metastatic breast cancer.

Metal-Organic Frameworks Facilitate Nucleic Acids for Multimode Synergistic Therapy of Breast Cancer

Compared with traditional medical methods, gene therapy and photodynamic therapy are the new fields of cancer treatment, and they more accurately and effectively obtain preferable therapeutic effects. In this study, a chemotherapy drug-free nanotherapeutic system based on ZIF-90 encapsulated with Ce6-G3139 and Ce6-DNAzyme for gene and photodynamic therapies was constructed. Once entering the cancer cell, the therapy system will decompose and release Zn²⁺, Ce6-G3139, and Ce6-DNAzyme in the acidic environment. On the one hand, G3139 binds to the antiapoptotic gene BCL-2 in tumor cells and downregulates related proteins to inhibit tumor proliferation. On the other hand, Zn²⁺ produced by the decomposition of ZIF-90 can be used as a cofactor to activate the cleavage activity of DNAzyme to initiate gene therapy. Proliferation and metastasis of tumors were further inhibited by DNAzyme, targeting and cutting the gene of human early growth factor-1 (EGR-1). In addition, the photosensitizer Ce6 carried by the nucleic acid will produce cytotoxic ROS to kill cancer cells after irradiation. The results of this study demonstrated that the designed nanoplatform, which synergistically combines gene and photodynamic therapies, has shown great potential for cancer treatment.

DNAzymes: Expanding the Potential of Nucleic Acid Therapeutics

Nucleic acids drugs have been proven in the clinic as a powerful modality to treat inherited and acquired diseases. However, key challenges including drug stability, renal clearance, cellular uptake, and movement across biological barriers (foremost the blood-brain barrier) limit the translation and clinical efficacy of nucleic acid-based therapies, both systemically and in the central nervous system. In this study we provide an overview of an emerging class of nucleic acid therapeutic, called DNAzymes. In particular, we review the use of chemical modifications and carrier molecules for the stabilization and/or delivery of DNAzymes in cell and animal models. Although this review focuses on DNAzymes, the strategies described are broadly applicable to most nucleic acid technologies. This review should serve as a general guide for selecting chemical modifications to improve the therapeutic performance of DNAzymes.

Early Growth Response-1: Friend or Foe in the Heart?

Cardiovascular disease is a major cause of mortality and morbidity worldwide. Early growth response-1 (Egr-1) plays a critical regulatory role in a range of experimental models of cardiovascular diseases. Egr-1 is an immediate-early gene and is upregulated by various stimuli including shear stress, oxygen deprivation, oxidative stress and nutrient deprivation. However, recent research suggests a new, underexplored cardioprotective side of Egr-1. The main purpose of this review is to explore and summarise the dual nature of Egr-1 in cardiovascular pathobiology.

Hedgehog signaling reprograms hair follicle niche fibroblasts to a hyper-activated state

Hair follicle stem cells are regulated by dermal papilla fibroblasts, their principal signaling niche. Overactivation of Hedgehog signaling in the niche dramatically accelerates hair growth and induces follicle multiplication in mice. On single-cell RNA sequencing, dermal papilla fibroblasts increase heterogeneity to include new Wnt5a^high states. Transcriptionally, mutant fibroblasts activate regulatory networks for Gli1, Alx3, Ebf1, Hoxc8, Sox18, and Zfp239. These networks jointly upregulate secreted factors for multiple hair morphogenesis and hair-growth-related pathways. Among these is non-conventional TGF-β ligand Scube3. We show that in normal mouse skin, Scube3 is expressed only in dermal papillae of growing, but not in resting follicles. SCUBE3 protein microinjection is sufficient to induce new hair growth, and pharmacological TGF-β inhibition rescues mutant hair hyper-activation phenotype. Moreover, dermal-papilla-enriched expression of SCUBE3 and its growth-activating effect are partially conserved in human scalp hair follicles. Thus, Hedgehog regulates mesenchymal niche function in the hair follicle via SCUBE3/TGF-β mechanism.

Transcriptional regulation of vascular smooth muscle cell proliferation, differentiation and senescence: Novel targets for therapy

Vascular smooth muscle cells (SMC) possess a unique cytoplasticity, regulated by transcriptional, translational and phenotypic transformation in response to a diverse range of extrinsic and intrinsic pathogenic factors. The mature, differentiated SMC phenotype is physiologically typified transcriptionally by expression of genes encoding "contractile" proteins, such as SMα-actin (ACTA2), SM-MHC (myosin-11) and SM22α (transgelin). When exposed to various pathological conditions (e.g., pro-atherogenic risk factors, hypertension), SMC undergo phenotypic modulation, a bioprocess enabling SMC to de-differentiate in immature stages or trans-differentiate into other cell phenotypes. As recent studies suggest, the process of SMC phenotypic transformation involves five distinct states characterized by different patterns of cell growth, differentiation, migration, matrix protein expression and declined contractility. These changes are mediated via the action of several transcriptional regulators, including myocardin and serum response factor. Conversely, other factors, including Kruppel-like factor 4 and nuclear factor-κB, can inhibit SMC differentiation and growth arrest, while factors such as yin yang-1, can promote SMC differentiation whilst inhibiting proliferation. This article reviews recent advances in our understanding of regulatory mechanisms governing SMC phenotypic modulation. We propose the concept that transcription factors mediating this switching are important biomarkers and potential pharmacological targets for therapeutic intervention in cardiovascular disease.

EGR1 Is Implicated in Right Ventricular Cardiac Remodeling Associated with Pulmonary Hypertension

Background: Pulmonary hypertension (PH) is a vasoconstrictive disease characterized by elevated mean pulmonary arterial pressure (mPAP) at rest. Idiopathic pulmonary arterial hypertension (iPAH) and chronic thromboembolic pulmonary hypertension (CTEPH) represent two distinct subtypes of PH. Persisting PH leads to right ventricular (RV) hypertrophy, heart failure, and death. RV performance predicts survival and surgical interventions re-establishing physiological mPAP reverse cardiac remodeling. Nonetheless, a considerable number of PH patients are deemed inoperable. The underlying mechanism(s) governing cardiac regeneration, however, remain largely elusive. Methods: In a longitudinal approach, we profiled the transcriptional landscapes of hypertrophic RVs and recovered hearts 3 months after surgery of iPAH and CTEPH patients. Results: Genes associated with cellular responses to inflammatory stimuli and metal ions were downregulated, and cardiac muscle tissue development was induced in iPAH after recovery. In CTEPH patients, genes related to muscle cell development were decreased, and genes governing cardiac conduction were upregulated in RVs following regeneration. Intriguingly, early growth response 1 (EGR1), a profibrotic regulator, was identified as a major transcription factor of hypertrophic RVs in iPAH and CTEPH. A histological assessment confirmed our biocomputational results, and suggested a pivotal role for EGR1 in RV vasculopathy. Conclusion: Our findings improved our understanding of the molecular events driving reverse cardiac remodeling following surgery. EGR1 might represent a promising candidate for targeted therapy of PH patients not eligible for surgical treatment.

A Proton-Activatable DNA-Based Nanosystem Enables Co-Delivery of CRISPR/Cas9 and DNAzyme for Combined Gene Therapy

CRISPR/Cas9 is emerging as a platform for gene therapeutics, and the treatment efficiency is expected to be enhanced by combination with other therapeutic agents. Herein, we report a proton-activatable DNA-based nanosystem that enables co-delivery of Cas9/sgRNA and DNAzyme for the combined gene therapy of cancer. Ultra-long ssDNA chains, which contained the recognition sequences of sgRNA in Cas9/sgRNA, DNAzyme sequence and HhaI enzyme cleavage site, were synthesized as the scaffold of the nanosystem. The DNAzyme cofactor Mn²⁺ was used to compress DNA chains to form nanoparticles and acid-degradable polymer-coated HhaI enzymes were assembled on the surface of nanoparticles. In response to protons in lysosome, the polymer coating was decomposed and HhaI enzyme was consequently exposed to recognize and cut off the cleavage sites, thus triggering the release of Cas9/sgRNA and DNAzyme to regulate gene expressions to achieve a high therapeutic efficacy of breast cancer.

Selection of M2+-independent RNA-cleaving DNAzymes with Sidechains Mimicking Arginine and Lysine

Sequence-specific cleavage of RNA by nucleic acid catalysts in the absence of a divalent metal cation (M 2+ ) has remained an important goal in biomimicry with potential therapeutic applications. Given the lack of functional group diversity in canonical nucleotides, modified nucleotides with amino acid-like side chains were used to enhance self-cleavage rates at a single embedded ribonucleoside site. Previous works relied on three functional groups: an amine, a guanidine and an imidazole ensconced on three different nucleosides. However, to date, few studies have systematically addressed the necessity of all three modifications, as the value of any single modified nucleoside is contextualized at the outset of selection. Herein, we report on the use of only two modified dNTPs, excluding an imidazole, i.e. 5-(3-guanidinoallyl)-2'-dUTP (dU ga TP) and 5-aminoallyl-2'-dCTP (dC aa TP), to select in-vitro self-cleaving DNAzymes that cleave in the absence of M 2+ in a pH-independent fashion. Cleavage shows biphasic kinetics with rate constants that are significantly higher than in unmodified DNAzymes and compare favorably to certain DNAzymes involving an imidazole. This work is the first report of a M2+-independent DNAzyme with two cationic modifications; as such it shows appreciable self-cleaving activity in the absence of an imidazole modification.

Early Growth Response-1, an Integrative Sensor in Cardiovascular and Inflammatory Disease

Early growth response‐1 (Egr‐1) is a master regulator and transcriptional sensor in vascular dysfunction and disease. This article reviews recent developments in our understanding of the regulatory roles this zinc finger protein and product of an immediate‐early gene plays in a range of cardiovascular and inflammatory disorders. Egr‐1 can amplify pathologic signals from the extracellular environment by serving as a molecular conduit in the inducible expression of proliferative, migratory and proinflammatory genes driving disease progression. Strategies targeting Egr‐1 may provide therapeutic benefit in cardiovascular and inflammatory disorders.

Serine 26 in Early Growth Response-1 Is Critical for Endothelial Proliferation, Migration, and Network Formation

Background

Vascular endothelial cell proliferation, migration, and network formation are key proangiogenic processes involving the prototypic immediate early gene product, Egr‐1 (early growth response‐1). Egr‐1 undergoes phosphorylation at a conserved Ser26 but its function is completely unknown in endothelial cells or any other cell type.

Methods and Results

A CRISPR/Cas9 strategy was used to introduce a homozygous Ser26>Ala mutation into endogenous Egr‐1 in human microvascular endothelial cells. In the course of generating mutant cells, we produced cells with homozygous deletion in Egr‐1 caused by frameshift and premature termination. We found that Ser26 mutation in Egr‐1, or Egr‐1 deletion, perturbed endothelial cell proliferation in models of cell counting or real‐time growth using the xCELLigence System. We found that Ser26 mutation or Egr‐1 deletion ameliorated endothelial cell migration toward VEGF‐A₁₆₅ (vascular endothelial growth factor‐A) in a dual‐chamber model. On solubilized basement membrane preparations, Ser26 mutation or Egr‐1 deletion prevented endothelial network (or tubule) formation, an in vitro model of angiogenesis. Flow cytometry further revealed that Ser26 mutation or Egr‐1 deletion elevated early and late apoptosis. Finally, we demonstrated that Ser26 mutation or Egr‐1 deletion increased VE‐cadherin (vascular endothelial cadherin) expression, a regulator of endothelial adhesion and signaling, permeability, and angiogenesis.

Conclusions

These findings not only indicate that Egr‐1 is essential for endothelial cell proliferation, migration, and network formation, but also show that point mutation in Ser26 is sufficient to impair each of these processes and trigger apoptosis as effectively as the absence of Egr‐1. This highlights the importance of Ser26 in Egr‐1 for a range of proangiogenic processes.

Ultrathin 2D Copper(I) 1,2,4-Triazolate Coordination Polymer Nanosheets for Efficient and Selective Gene Silencing and Photodynamic Therapy

Gene silencing holds promise for cancer therapeutics because of its potential to inhibit genes involved in tumor development. However, gene silencing is still restricted by its limited efficacy and safety. Nanoscale coordination polymers (CPs) emerge as promising nanocarriers for gene delivery, but their responsiveness and potential therapeutic properties have rarely been explored simultaneously. Here, multifunctional ultrathin 2D nanosheets of Cu(I) 1,2,4-triazolate CP with a thickness of 4.5 ± 0.8 nm are synthesized using a bottom-up method. These CP nanosheets can act as both an effective DNAzyme nanocarrier for gene therapy and an intrinsic photosensitizer for hypoxia-tolerant type I photodynamic therapy (PDT), which is ascribed to the Fenton-like reaction. Because of the glutathione (GSH)-responsiveness of the CP nanosheets, DNAzyme-loaded CP nanosheets exhibit excellent cancer-cell-targeting gene silencing of the early growth response factor-1 (EGR-1), with messenger RNA inhibited by 84% in MCF-7 (human breast cancer cells) and only 6% in MCF-10A (normal human mammary epithelial cells). After tail intravenous injection into MCF-7-tumor-bearing mice, the CP nanosheets loaded with chlorin-e6-modified DNAzyme under photoirradiation show a high antitumor efficacy (88.0% tumor regression), demonstrating a promising therapeutic platform with efficient and selective gene silencing and PDT of cancer.

Angiotensin II-induced histone deacetylase 5 phosphorylation, nuclear export, and Egr-1 expression are mediated by Akt pathway in A10 vascular smooth muscle cells

Angiotensin II (ANG II) regulates an array of physiological and pathological responses in vascular smooth muscle cells (VSMCs) by activating ERK1/2 and phosphoinositide 3-kinase (PI3K)/Akt signaling pathways. We have demonstrated that ANG II and insulin-like growth factor-1 (IGF-1) induce the expression of early growth response protein-1 (Egr-1), a zinc finger transcription factor, which regulates the transcription of cell cycle regulatory genes network in VSMCs. We have reported that IGF-1 induces the phosphorylation of histone deacetylase 5 (HDAC5), which has been implicated in the expression of genes linked to VSMC growth and hypertrophy, via a PI3K/Akt-dependent pathway in VSMCs. However, the involvement of PI3K/Akt pathways in ANG II-induced HDAC5 phosphorylation and the contribution of HDAC5 in Egr-1 expression and hypertrophy in VSMCs remain unexplored. Here, we show that pharmacological blockade of the PI3K/Akt pathway either by wortmannin/SC66 or siRNA-induced silencing of Akt attenuated ANG II-induced HDAC5 phosphorylation and its nuclear export. Moreover, SC66 or Akt knockdown also suppressed ANG II-induced Egr-1 expression. Furthermore, pharmacological inhibition of HDAC5 by MC1568 or TMP-195 or knockdown of HDAC5 and the blockade of the nuclear export of HDAC5 by leptomycin B or KPT-330 significantly reduced ANG II-induced Egr-1 expression. In addition, depletion of either HDAC5 or Egr-1 by siRNA attenuated VSMC hypertrophy in response to ANG II. In summary, our results demonstrate that ANG II-induced HDAC5 phosphorylation and its nuclear exclusion are mediated by PI3K/Akt pathway and HDAC5 is an upstream regulator of Egr-1 expression and hypertrophy in VSMCs.NEW & NOTEWORTHY ANG II-induced histone deacetylase 5 (HDAC5) phosphorylation and nuclear export occurs via the phosphoinositide 3-kinase/Akt pathway. Akt, through HDAC5, regulates ANG II-induced expression of early growth response protein-1 (Egr-1), which is a transcription factor linked with vascular dysfunction. Inhibition of HDAC5 exclusion by nuclear export inhibitors suppresses ANG II-induced Egr-1 expression. HDAC5 is an upstream mediator of Egr-1 expression and cell hypertrophy in response to ANG II in vascular smooth muscle cells.

Development of orally administered insulin-loaded polymeric-oligonucleotide nanoparticles: statistical optimization and physicochemical characterization

INTRODUCTION

Therapeutic peptides are administered via parenteral route due to poor absorption in the gastrointestinal (GI) tract, instability in gastric acid, and GI enzymes. Polymeric drug delivery systems have achieved significant interest in pharmaceutical research due to its feasibility in protecting proteins, tissue targeting, and controlled drug release pattern.

MATERIALS AND METHODS

In this study, the size, polydispersity index, and zeta potential of insulin-loaded nanoparticles were characterized by dynamic light scattering and laser Doppler micro-electrophoresis. The main and interaction effects of chitosan concentration and Dz13Scr concentration on the physicochemical properties of the prepared insulin-loaded nanoparticles (size, polydispersity index, and zeta potential) were evaluated statistically using analysis of variance. A robust procedure of reversed-phase high-performance liquid chromatography was developed to quantify insulin release in simulated GI buffer. Results and discussion: We reported on the effect of two independent parameters, including polymer concentration and oligonucleotide concentration, on the physical characteristics of particles. Chitosan concentration was significant in predicting the size of insulin-loaded CS-Dz13Scr particles. In terms of zeta potential, both chitosan concentration and squared term of chitosan were significant factors that affect the surface charge of particles, which was attributed to the availability of positively-charged amino groups during interaction with negatively-charged Dz13Scr. The excipients used in this study could fabricate nanoparticles with negligible toxicity in GI cells and skeletal muscle cells. The developed formulation could conserve the physicochemical properties after being stored for 1 month at 4 °C.

CONCLUSION

The obtained results revealed satisfactory results for insulin-loaded CS-Dz13Scr nanoparticles (159.3 nm, pdi 0.331, -1.08 mV). No such similar study has been reported to date to identify the main and interactive significance of the above parameters for the characterization of insulin-loaded polymeric-oligonucleotide nanoparticles. This research is of importance for the understanding and development of protein-loaded nanoparticles for oral delivery.

Molecular Features and Metal Ions That Influence 10-23 DNAzyme Activity

Deoxyribozymes (DNAzymes) with RNA hydrolysis activity have a tremendous potential as gene suppression agents for therapeutic applications. The most extensively studied representative is the 10-23 DNAzyme consisting of a catalytic loop and two substrate binding arms that can be designed to bind and cleave the RNA sequence of interest. The RNA substrate is cleaved between central purine and pyrimidine nucleotides. The activity of this DNAzyme in vitro is considerably higher than in vivo, which was suggested to be related to its divalent cation dependency. Understanding the mechanism of DNAzyme catalysis is hindered by the absence of structural information. Numerous biological studies, however, provide comprehensive insights into the role of particular deoxynucleotides and functional groups in DNAzymes. Here we provide an overview of the thermodynamic properties, the impact of nucleobase modifications within the catalytic loop, and the role of different metal ions in catalysis. We point out features that will be helpful in developing novel strategies for structure determination and to understand the mechanism of the 10-23 DNAzyme. Consideration of these features will enable to develop improved strategies for structure determination and to understand the mechanism of the 10-23 DNAzyme. These insights provide the basis for improving activity in cells and pave the way for developing DNAzyme applications.

DNAzyme-Mediated Genetically Encoded Sensors for Ratiometric Imaging of Metal Ions in Living Cells

Genetically encoded fluorescent proteins (FPs) have been used for metal ion detection. However, their applications are restricted to a limited number of metal ions owing to the lack of available metal-binding proteins or peptides that can be fused to FPs and the difficulty in transforming the binding of metal ions into a change of fluorescent signal. We report herein the use of Mg²⁺ -specific 10-23 or Zn²⁺ -specific 8-17 RNA-cleaving DNAzymes to regulate the expression of FPs as a new class of ratiometric fluorescent sensors for metal ions. Specifically, we demonstrate the use of DNAzymes to suppress the expression of Clover2, a variant of the green FP (GFP), by cleaving the mRNA of Clover2, while the expression of Ruby2, a mutant of the red FP (RFP), is not affected. The Mg²⁺ or Zn²⁺ in HeLa cells can be detected using both confocal imaging and flow cytometry. Since a wide variety of metal-specific DNAzymes can be obtained, this method can likely be applied to imaging many other metal ions, expanding the range of the current genetically encoded fluorescent protein-based sensors.

Transcription Factors Targeted by miRNAs Regulating Smooth Muscle Cell Growth and Intimal Thickening after Vascular Injury

Neointima formation after percutaneous coronary intervention (PCI) is a manifestation of “phenotype switching” by vascular smooth muscle cells (SMC), a process that involves de-differentiation from a contractile quiescent phenotype to one that is richly synthetic. In response to injury, SMCs migrate, proliferate, down-regulate SMC-specific differentiation genes, and later, can revert to the contractile phenotype. The vascular response to injury is regulated by microRNAs (or miRNAs), small non-coding RNAs that control gene expression. Interactions between miRNAs and transcription factors impact gene regulatory networks. This article briefly reviews the roles of a range of miRNAs in molecular and cellular processes that control intimal thickening, focusing mainly on transcription factors, some of which are encoded by immediate-early genes. Examples include Egr-1, junB, KLF4, KLF5, Elk-1, Ets-1, HMGB1, Smad1, Smad3, FoxO4, SRF, Rb, Sp1 and c-Myb. Such mechanistic information could inform the development of strategies that block SMC growth, neointima formation, and potentially overcome limitations of lasting efficacy following PCI.

Cationic copolymer-chaperoned short-armed 10-23 DNAzymes

The cationic copolymer poly(L-lysine)-graft-dextran (PLL-g-Dex) has nucleic acid chaperone-like activity. The copolymer facilitates both DNA hybridization and strand exchange reactions. For these reasons, DNA-based enzyme (DNAzyme) activity is enhanced in the presence of copolymer. In this study, we evaluated activities of DNAzymes with substrate-binding arms (S-arms) of various lengths. The copolymer promoted DNAzyme reactivity and turnover efficacy, and, depending on S-arm length, maximally accelerated the reaction rate by 250-fold compared to the rate in the absence of copolymer. The copolymer permitted up to six nucleotides truncation of the S-arms having initial length of 10 and 11 nucleotides without loss of catalytic efficiency, enable tuning of the optimal temperature ranging from 30 to 55 °C. The approach might be useful for the development of DNAzyme systems targeting short or highly structured RNAs as well for improvement of DNAzyme-based nanomachines and biosensors.

DNAzyme-Loaded Metal-Organic Frameworks (MOFs) for Self-Sufficient Gene Therapy

DNAzymes have been recognized as potent therapeutic agents for gene therapy, while their inefficient intracellular delivery and insufficient cofactor supply precludes their practical biological applications. Metal-organic frameworks (MOFs) have emerged as promising drug carriers without in-depth consideration of their disassembled ingredients. Herein, we report a self-sufficient MOF-based chlorin e6-modified DNAzyme (Ce6-DNAzyme) therapeutic nanosystem for combined gene therapy and photodynamic therapy (PDT). The ZIF-8 nanoparticles (NPs) could efficiently deliver the therapeutic DNAzyme without degradation into cancer cells. The pH-responsive ZIF-8 NPs disassemble with the concomitant release of the guest DNAzyme payloads and the host Zn²⁺ ions that serve, respectively, as messenger RNA-targeting agent and required DNAzyme cofactors for activating gene therapy. The auxiliary photosensitizer Ce6 could produce reactive oxygen species (ROS) and provide a fluorescence signal for the imaging-guided gene therapy/PDT.

Extracellular signal-regulated kinase-1 phosphorylates early growth response-1 at serine 26

Egr-1, an immediate-early gene product and master regulator was originally described as a phosphoprotein following its discovery in the 1980s. However specific residue(s) phosphorylated in Egr-1 remain elusive. Here we phosphorylated recombinant Egr-1 in vitro with ERK1 prior to mass spectrometry, which identified phosphorylation of Ser¹² and Ser²⁶ with the latter ∼12 times more abundant than Ser¹². Phosphorylation of wild-type recombinant Egr-1 (as compared with Ser²⁶>Ala²⁶ mutant Egr-1) revealed that Ser²⁶ accounts for the majority of phosphorylation of Egr-1 by ERK1. N-FGSFPH(pS)PTMDNYC-C was used as an antigen to generate mouse monoclonal antibodies (pS26 MAb). pS26 MAb recognised ERK1-phosphorylated Egr-1 but not Egr-1 bearing a point mutation at Ser²⁶. pS26 MAb recognised inducible ∼75 kDa and 100 kDa species in nuclear extracts of cells exposed to FGF-2. Peptide blocking revealed both inducible species were phosphosite-specific. Immunoprecipitation of nuclear extracts of cells exposed to FGF-2 with pS26 MAb followed by SDS-PAGE and mass spectrometry identified Egr-1 sequences corresponding to the ∼75 kDa species but not ∼100 kDa species. This study identifies a specific amino acid phosphorylated in endogenous Egr-1.

Promoter Usage and Dynamics in Vascular Smooth Muscle Cells Exposed to Fibroblast Growth Factor-2 or Interleukin-1β

Smooth muscle cells (SMC) in blood vessels are normally growth quiescent and transcriptionally inactive. Our objective was to understand promoter usage and dynamics in SMC acutely exposed to a prototypic growth factor or pro-inflammatory cytokine. Using cap analysis gene expression (FANTOM5 project) we report differences in promoter dynamics for immediate-early genes (IEG) and other genes when SMC are exposed to fibroblast growth factor-2 or interleukin-1β. Of the 1871 promoters responding to FGF2 or IL-1β considerably more responded to FGF2 (68.4%) than IL-1β (18.5%) and 13.2% responded to both. Expression clustering reveals sets of genes induced, repressed or unchanged. Among IEG responding rapidly to FGF2 or IL-1β were FOS, FOSB and EGR-1, which mediates human SMC migration. Motif activity response analysis (MARA) indicates most transcription factor binding motifs in response to FGF2 were associated with a sharp induction at 1 h, whereas in response to IL-1β, most motifs were associated with a biphasic change peaking generally later. MARA revealed motifs for FOS_FOS{B,L1}_JUN{B,D} and EGR-1..3 in the cluster peaking 1 h after FGF2 exposure whereas these motifs were in clusters peaking 1 h or later in response to IL-1β. Our findings interrogating CAGE data demonstrate important differences in promoter usage and dynamics in SMC exposed to FGF2 or IL-1β.

Target induced reconstruction of DNAzymatic amplifier nanomachines in living cells for concurrent imaging and gene silencing

A novel DNAzymatic amplifier nanomachine that enables the functions of concurrent mRNA imaging and gene silencing in living cells has been reported.

Crystal structure of an RNA-cleaving DNAzyme

In addition to storage of genetic information, DNA can also catalyze various reactions. RNA-cleaving DNAzymes are the catalytic DNAs discovered the earliest, and they can cleave RNAs in a sequence-specific manner. Owing to their great potential in medical therapeutics, virus control, and gene silencing for disease treatments, RNA-cleaving DNAzymes have been extensively studied; however, the mechanistic understandings of their substrate recognition and catalysis remain elusive. Here, we report three catalytic form 8-17 DNAzyme crystal structures. 8-17 DNAzyme adopts a V-shape fold, and the Pb²⁺ cofactor is bound at the pre-organized pocket. The structures with Pb²⁺ and the modification at the cleavage site captured the pre-catalytic state of the RNA cleavage reaction, illustrating the unexpected Pb²⁺-accelerated catalysis, intrinsic tertiary interactions, and molecular kink at the active site. Our studies reveal that DNA is capable of forming a compacted structure and that the functionality-limited bio-polymer can have a novel solution for a functional need in catalysis.

Inhibition of intimal thickening after vascular injury with a cocktail of vascular endothelial growth factor and cyclic Arg-Gly-Asp peptide

BACKGROUND

Percutaneous coronary intervention is widely used for the treatment of coronary artery disease; however, significant challenges such as restenosis remain. Key to solving these problems is to inhibit smooth muscle cell activation while enhancing re-endothelialization. Early growth response-1 (Egr-1) is a transcription factor that regulates vascular smooth muscle cell (SMC) proliferation and migration through its control of an array of downstream genes.

METHODS

A "cocktail" of vascular endothelial growth factor (VEGF)-A, VEGF-D and cyclic RGD was tested for its ability to inhibit neointima formation and accelerate re-endothelialization following balloon injury to carotid arteries of rats.

RESULTS

In vitro, the cocktail stimulated endothelial cell growth yet inhibited smooth muscle cell growth. In vivo, cocktail-treated injured arteries exhibited reduced intimal thickening by >50% (P<0.05). It increased both re-endothelialization and endothelial nitric oxide synthase (NOS) expression. Cocktail reduced Egr-1 expression, an effect blocked by the NOS inhibitor L-N(G)-nitroarginine methyl ester (L-NAME) that also prevented cocktail inhibition of neointima inhibition.

CONCLUSIONS

This combination may potentially be useful for the treatment of restenosis with concomitant stimulation of revascularization.

Early growth response-1 in the pathogenesis of cardiovascular disease

This article reviews the regulatory roles of the immediate-early gene product and prototypic zinc finger transcription factor, early growth response-1 in models of cardiovascular pathobiology, focusing on insights using microRNA, DNAzymes, small hairpin RNA, small interfering RNA, oligonucleotide decoy strategies and mice deficient in early growth response-1.

Biostable L-DNAzyme for Sensing of Metal Ions in Biological Systems

DNAzymes, an important type of metal ion-dependent functional nucleic acid, are widely applied in bioanalysis and biomedicine. However, the use of DNAzymes in practical applications has been impeded by the intrinsic drawbacks of natural nucleic acids, such as interferences from nuclease digestion and protein binding, as well as undesired intermolecular interactions with other nucleic acids. On the basis of reciprocal chiral substrate specificity, the enantiomer of D-DNAzyme, L-DNAzyme, could initiate catalytic cleavage activity with the same achiral metal ion as a cofactor. Meanwhile, by using the advantage of nonbiological L-DNAzyme, which is not subject to the interferences of biological matrixes, as recognition units, a facile and stable L-DNAzyme sensor was proposed for sensing metal ions in complex biological samples and live cells.

DNA Catalysis: The Chemical Repertoire of DNAzymes

Deoxyribozymes or DNAzymes are single-stranded catalytic DNA molecules that are obtained by combinatorial in vitro selection methods. Initially conceived to function as gene silencing agents, the scope of DNAzymes has rapidly expanded into diverse fields, including biosensing, diagnostics, logic gate operations, and the development of novel synthetic and biological tools. In this review, an overview of all the different chemical reactions catalyzed by DNAzymes is given with an emphasis on RNA cleavage and the use of non-nucleosidic substrates. The use of modified nucleoside triphosphates (dN*TPs) to expand the chemical space to be explored in selection experiments and ultimately to generate DNAzymes with an expanded chemical repertoire is also highlighted.

DNA enzymes as potential therapeutics: towards clinical application of 10-23 DNAzymes

INTRODUCTION

Ongoing studies on the inhibition of gene expression at the mRNA level have identified several types of specific inhibitors such as antisense oligonucleotides, small interfering RNA, ribozymes and DNAzymes (Dz). After its discovery in 1997, the 10-23 Dz (which can cleave RNA efficiently and site-specifically, has flexible design, is independent from cell mechanisms, does not require expensive chemical modifications for effective use in vivo) has been employed to downregulate a range of therapeutically important genes. Recently, 10-23 Dzs have taken their first steps into clinical trials.

AREAS COVERED

This review focuses predominantly on Dz applications as potential antiviral, antibacterial, anti-cancer and anti-inflammatory agents as well as for the treatment of cardiovascular disease and diseases of CNS, summarizing results of their clinical trials up to the present day.

EXPERT OPINION

In comparison with antisense oligonucleotides and small interfering RNAs, Dzs do not usually show off-target effects due to their high specificity and lack of immunogenicity in vivo. As more results of clinical trials carried out so far are gradually becoming available, Dzs may turn out to be safe and well-tolerated therapeutics in humans. Therefore, there is a good chance that we may witness a deoxyribozyme drug reaching the clinic in the near future.

Enhancement of deoxyribozyme activity by cationic copolymers

A cationic copolymer enhanced DNAzyme activity.

A critical role for Egr-1 during vascular remodelling in pulmonary arterial hypertension

AIMS

Pulmonary arterial hypertension (PAH) is characterized by the development of unique neointimal lesions in the small pulmonary arteries, leading to increased right ventricular (RV) afterload and failure. Novel therapeutic strategies are needed that target these neointimal lesions. Recently, the transcription factor Egr-1 (early growth response protein 1) was demonstrated to be up-regulated early in experimental neointimal PAH. Its effect on disease development, however, is unknown. We aimed to uncover a novel role for Egr-1 as a molecular inductor for disease development in PAH.

METHODS AND RESULTS

In experimental flow-associated PAH in rats, we investigated the effects of Egr-1 down-regulation on pulmonary vascular remodelling, including neointimal development, and disease progression. Intravenous administration of catalytic oligodeoxynucleotides (DNA enzymes, DNAzymes) resulted in down-regulation of pulmonary vascular Egr-1 expression. Compared with vehicle or scrambled DNAzymes, DNAzymes attenuated pulmonary vascular remodelling, including the development of occlusive neointimal lesions. Selective down-regulation of Egr-1 in vivo led to reduced expression of vascular PDGF-B, TGF-β, IL-6, and p53, resulting in a reduction of vascular proliferation and increased apoptosis. DNAzyme treatment further attenuated pulmonary vascular resistance, RV systolic pressure, and RV hypertrophy. In contrast, in non-neointimal PH rodents, DNAzyme treatment had no effect on pulmonary vascular and RV remodelling. Finally, pharmacological inhibition of Egr-1 with pioglitazone, a peroxisome proliferator activated receptor-γ ligand, attenuated vascular remodelling including the development of neointimal lesions.

CONCLUSIONS

These results indicate that Egr-1 governs pulmonary vascular remodelling and the development of characteristic vascular neointimal lesions in flow-associated PAH. Egr-1 is therefore a potential target for future PAH treatment.

Antiangiogenic and antitumoral effects mediated by a vascular endothelial growth factor receptor 1 (VEGFR-1)-targeted DNAzyme

Antiangiogenesis is a promising antitumor strategy that inhibits tumor vascular formation to suppress tumor growth. DNAzymes are synthetic single-strand deoxyribonucleic acid (DNA) molecules that can cleave ribonucleic acids (RNAs). Here, we conducted a comprehensive in vitro selection of active DNAzymes for their activity to cleave the vascular endothelial growth factor receptor (VEGFR-1) mRNA and screened for their biological activity in a matrigel tube-formation assay. Among the selected DNAzymes, DT18 was defined as a lead molecule that was further investigated in several model systems. In a rat corneal vascularization model, DT18 demonstrated significant and specific antiangiogenic activity, as evidenced by the reduced area and vessel number in VEGF-induced corneal angiogenesis. In a mouse melanoma model, DT18 was shown to inhibit B16 tumor growth, whereas it did not affect B16 cell proliferation. We further assessed the DT18 effect in mice with established human nasopharyngeal carcinoma (NPC). A significant inhibition of tumor growth was observed, which accompanied downregulation of VEGFR-1 expression in NPC tumor tissues. To evaluate DT18 effect on vasculature, we performed dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) on the human NPC xenograft mice treated with DT18 and showed a reduction of the parameter of K(trans) (volume constant for transfer of contrast agent), which reflects the condition of tumor microvascular permeability. When examining the safety and tolerability of DT18, intravenous administration of Dz18 to healthy mice caused no substantial toxicities, as shown by parameters such as body weight, liver/kidney function, and histological and biochemical analyses. Taken together, our data suggest that the anti-VEGFR-1 DNAzyme may be used as a therapeutic agent for the treatment of cancer, such as NPC.

Sustained delivery of siRNA from dopamine-coated stainless steel surfaces

Dopamine, an adhesive protein can be covalently deposited onto biomaterials. In this study, we evaluated the ability of dopamine-coated surfaces for small interfering RNA (siRNA) immobilization and release. Dopamine was deposited onto 316L stainless steel discs either as a monolayer at acidic pH or as polydopamine at alkaline pH, following which siRNA was immobilized onto these discs. To investigate the RNA interference ability of immobilized siRNA, reduction of luciferase expression in HeLa, and reduction of Egr-1 expression and cell proliferation in human aortic smooth muscle cells (HAoSMCs) were determined. Dopamine treatment of 316L stainless steel discs under both the acidic and alkaline conditions resulted in the deposition of amino (NH2) groups, which enabled electrostatic immobilization of siRNA. The immobilized siRNA was released from both types of coatings, and enhanced the percent suppression of firefly luciferase activity of HeLa significantly up to ~96.5% compared to HeLa on non-dopamine controls (18%). Both the release of siRNA and the percent suppression of firefly luciferase activity were sustained for at least 7 days. In another set of experiments, siRNA sequences targeting to inhibit the activity of the transcription factor Egr-1 were eluted from dopamine-coated surfaces to HAoSMCs. Egr-1 siRNA eluted from dopamine-coated surfaces, significantly reduced the proliferation of HAoSMCs and their protein expression of Egr-1. Therefore, this method of surface immobilization of siRNA onto dopamine-coated surfaces might be effective for nucleic acid delivery from stents.

Role of the phosphatase PTEN in early vascular remodeling

Background

The phosphatase PTEN represents an important physiological inhibitor of phosphatidylinositol-3 kinase (PI3-K)/protein kinase B (Akt) signalling, however, the functional role of PTEN in the initial phase of angioplasty-induced vascular injury remains elusive. In the present study we sought to determine PTEN's effect on vascular smooth muscle cell (VSMC) apoptosis following acute injury in vivo and in vitro.

Methods and Results

Immunohistochemistry indicated a faint basal expression and equal distribution of PTEN in uninjured rat carotid arteries. 12 h following balloon-injury, PTEN expression was strongly increased in apoptotic (TUNEL+) VSMC. In vitro, stimulation with serum or different growth factors or subjecting VSMC to cyclic stretch had no effect on PTEN expression, whereas stimulation with H₂O₂ robustly increased PTEN expression in a time- and dose-dependent manner. To evaluate the functional role of PTEN expression, human VSMC were transduced with WT-PTEN. Overexpression of PTEN increased the number of apoptotic VSMC (19.8%±4.4 vs. 5.6%±2.3; P<0.001) as determined by TUNEL assay. In contrast, siRNA-mediated knock-down of PTEN attenuated the basal as well as H₂O₂-induced apoptosis of VSMC. Mechanistically, overexpression of PTEN prevented serum-induced Akt-phosphorylation, whereas siRNA-mediated knock down of PTEN augmented Akt-activation. Moreover, co-transfection of PTEN and a constitutive active Akt mutant prevented PTEN-dependent augmentation of VSMC apoptosis, indicating, that PTEN regulates VSMC apoptosis by inhibition of Akt phosphorylation/activation.

Conclusion

By interfering with the PI3-K/Akt-dependent survival signalling, the oxidative stress-induced up regulation of PTEN in VSMC of injured arteries augments the sensitivity of VSMC to apoptotic stimuli in the early phase following vascular injury, augmenting the initial injury and cell loss of the injured vessel wall. Thus, these data add to our understanding of PTEN's role during vascular remodelling.

IL-1beta signals through the EGF receptor and activates Egr-1 through MMP-ADAM

The immediate-early gene Egr-1 controls the inducible expression of many genes implicated in the pathogenesis of a range of vascular disorders, yet our understanding of the mechanisms controlling the rapid expression of this prototypic zinc finger transcription factor is poor. Here we show that Egr-1 expression induced by IL-1beta is dependent on metalloproteinases (MMP) and a disintegrin and a metalloproteinase (ADAM). Pharmacologic MMP/ADAM inhibitors and siRNA knockdown prevent IL-1beta induction of Egr-1. Further, IL-1beta activates Egr-1 via the epidermal growth factor receptor (EGFR). This is blocked by EGFR tyrosine kinase inhibition and EGFR knockdown. IL-1beta induction of Egr-1 expression is reduced in murine embryonic fibroblasts (mEFs) deficient in ADAM17 despite unbiased expression of EGFR and IL-1RI in ADAM17-deficient and wild-type mEFs. Finally, we show that IL-1beta-inducible wound repair after mechanical injury requires both EGFR and MMP/ADAM. This study reports for the first time that Egr-1 induction by IL-1beta involves EGFR and MMP/ADAM-dependent EGFR phosphorylation.