Development of immortalized mouse aortic endothelial cell lines

Bioactivity of cerium dioxide nanoparticles as a function of size and surface features

Nano-dispersed cerium dioxide is promising for use in medicine due to its unique physicochemical properties, including low toxicity, the safety of in vivo usage, active participation in different redox processes occurring in living cells, and its regenerative potential, manifested in the ability of CeO2 to participate repeatedly in redox reactions. In this work, we examined the biological activity of cerium dioxide nanoparticles (CeO2 NPs) synthesized by precipitation in mixed water/alcohol solutions at a constant pH of 9. This synthesis method allowed controlling the size and Ce3+/Ce4+ proportion on the surface of NPs, changing the synthesis conditions and obtaining highly stable suspensions of "naked" CeO2 NPs. Changes in the surface properties upon contact of CeO2 NPs with protein-rich media, e.g., bovine serum albumin and DMEM cell culture medium supplemented with 10% fetal bovine serum, the characteristics of nanoparticle uptake by mouse aortic endothelial cells and the antioxidant activity of the nanoparticles of different sizes were investigated by various state-of-the-art analytical methods.

Gamma protocadherins in vascular endothelial cells inhibit Klf2/4 to promote atherosclerosis

Atherosclerotic cardiovascular disease (ASCVD) is the leading cause of mortality worldwide1. Laminar shear stress (LSS) from blood flow in straight regions of arteries protects against ASCVD by upregulating the Klf2/4 anti-inflammatory program in endothelial cells (ECs)2-8. Conversely, disturbed shear stress (DSS) at curves or branches predisposes these regions to plaque formation9,10. We previously reported a whole genome CRISPR knockout screen11 that identified novel inducers of Klf2/4. Here we report suppressors of Klf2/4 and characterize one candidate, protocadherin gamma A9 (Pcdhga9), a member of the clustered protocadherin gene family12. Pcdhg deletion increases Klf2/4 levels in vitro and in vivo and suppresses inflammatory activation of ECs. Pcdhg suppresses Klf2/4 by inhibiting the Notch pathway via physical interaction of cleaved Notch1 intracellular domain (NICD Val1744) with nuclear Pcdhg C-terminal constant domain (CCD). Pcdhg inhibition by EC knockout (KO) or blocking antibody protects from atherosclerosis. Pcdhg is elevated in the arteries of human atherosclerosis. This study identifies a novel fundamental mechanism of EC resilience and therapeutic target for treating inflammatory vascular disease.

Constructing Lipoparticles Capable of Endothelial Cell-Derived Exosome-Mediated Delivery of Anti-miR-33a-5p to Cultured Macrophages

Atherosclerosis is driven by intimal arterial macrophages accumulating cholesterol. Atherosclerosis also predominantly occurs in areas consisting of proinflammatory arterial endothelial cells. At time of writing, there are no available clinical treatments that precisely remove excess cholesterol from lipid-laden intimal arterial macrophages. Delivery of anti-miR-33a-5p to macrophages has been shown to increase apoAI-mediated cholesterol efflux via ABCA1 upregulation but delivering transgenes to intimal arterial macrophages is challenging due to endothelial cell barrier integrity. In this study, we aimed to test whether lipoparticles targeting proinflammatory endothelial cells can participate in endothelial cell-derived exosome exploitation to facilitate exosome-mediated transgene delivery to macrophages. We constructed lipoparticles that precisely target the proinflammatory endothelium and contain a plasmid that expresses XMOTIF-tagged anti-miR-33a-5p (LP-pXMoAntimiR33a5p), as XMOTIF-tagged small RNA demonstrates the capacity to be selectively shuttled into exosomes. The cultured cells used in our study were immortalized mouse aortic endothelial cells (iMAECs) and RAW 264.7 macrophages. From our results, we observed a significant decrease in miR-33a-5p expression in macrophages treated with exosomes released basolaterally by LPS-challenged iMAECs incubated with LP-pXMoAntimiR33a5p when compared to control macrophages. This decrease in miR-33a-5p expression in the treated macrophages caused ABCA1 upregulation as determined by a significant increase in ABCA1 protein expression in the treated macrophages when compared to the macrophage control group. The increase in ABCA1 protein also simulated ABCA1-dependent cholesterol efflux in treated macrophages-as we observed a significant increase in apoAI-mediated cholesterol efflux-when compared to the control group of macrophages. Based on these findings, strategies that involve combining proinflammatory-targeting lipoparticles and exploitation of endothelial cell-derived exosomes appear to be promising approaches for delivering atheroprotective transgenes to lipid-laden arterial intimal macrophages.

The Impact of MiR-33a-5p Inhibition in Pro-Inflammatory Endothelial Cells

Evidence suggests cholesterol accumulation in pro-inflammatory endothelial cells (EC) contributes to triggering atherogenesis and driving atherosclerosis progression. Therefore, inhibiting miR-33a-5p within inflamed endothelium may prevent and treat atherosclerosis by enhancing apoAI-mediated cholesterol efflux by upregulating ABCA1. However, it is not entirely elucidated whether inhibition of miR-33a-5p in pro-inflammatory EC is capable of increasing ABCA1-dependent cholesterol efflux. In our study, we initially transfected LPS-challenged, immortalized mouse aortic EC (iMAEC) with either pAntimiR33a5p plasmid DNA or the control plasmid, pScr. We detected significant increases in both ABCA1 protein expression and apoAI-mediated cholesterol efflux in iMAEC transfected with pAntimiR33a5p when compared to iMAEC transfected with pScr. We subsequently used polymersomes targeting inflamed endothelium to deliver either pAntimiR33a5p or pScr to cultured iMAEC and showed that the polymersomes were selective in targeting pro-inflammatory iMAEC. Moreover, when we exposed LPS-challenged iMAEC to these polymersomes, we observed a significant decrease in miR-33a-5p expression in iMAEC incubated with polymersomes containing pAntimR33a5p versus control iMAEC. We also detected non-significant increases in both ABCA1 protein and apoAI-mediated cholesterol in iMAEC exposed to polymersomes containing pAntimR33a5p when compared to control iMAEC. Based on our results, inhibiting miR-33a-5p in pro-inflammatory EC exhibits atheroprotective effects, and so precisely delivering anti-miR-33a-5p to these cells is a promising anti-atherogenic strategy.

MasR and pGCA receptor activation protects primary vascular smooth muscle cells and endothelial cells against oxidative stress via inhibition of intracellular calcium

Cardiovascular diseases (CVDs) are associated with vascular smooth muscle cell (VSMC) and endothelial cell (EC) damage. Angiotensin1-7 (Ang1-7) and B-type natriuretic peptide (BNP) are responsible for vasodilation and regulation of blood flow. These protective effects of BNP are primarily mediated by the activation of sGCs/cGMP/cGKI pathway. Conversely, Ang1-7 inhibits Angiotensin II-induced contraction and oxidative stress via Mas receptor activation. Thus, the aim of the study was to determine the effect of co-activation of MasR and particulate guanylate cyclase receptor (pGCA) pathways by synthesized novel peptide (NP) in oxidative stress-induced VSMCs and ECs. MTT and Griess reagent assay kits were used for the standardization of the oxidative stress (H₂ O₂ ) induced model in VSMCs. The expression of targeted receptors in VSMC was done by RT-PCR and Western blot analysis. Protective effect of NP in VSMC and EC was determined by immunocytochemistry, FACS analysis, and Western blot analysis. Underlying mechanisms of EC-dependent VSMC relaxation were done by determining downstream mRNA gene expression and intracellular calcium imaging of cells. Synthesized NP significantly improved oxidative stress-induced injury in VSMCs. Remarkably, the actions of NP were superior to that of the Ang1-7 and BNP alone. Further, a mechanistic study in VSMC and EC suggested the involvement of upstream mediators of calcium inhibition for the therapeutic effect. NP is reported to possess vascular protective activities and is also involved in the improvement of endothelial damage. Moreover, it is highly effective than that of individual peptides BNP and Ang1-7 and therefore it may represent a promising strategy for CVDs.

A mitochondrial contribution to anti-inflammatory shear stress signaling in vascular endothelial cells

Atherosclerosis, the major cause of myocardial infarction and stroke, results from converging inflammatory, metabolic, and biomechanical factors. Arterial lesions form at sites of low and disturbed blood flow but are suppressed by high laminar shear stress (LSS) mainly via transcriptional induction of the anti-inflammatory transcription factor, Kruppel-like factor 2 (Klf2). We therefore performed a whole genome CRISPR-Cas9 screen to identify genes required for LSS induction of Klf2. Subsequent mechanistic investigation revealed that LSS induces Klf2 via activation of both a MEKK2/3-MEK5-ERK5 kinase module and mitochondrial metabolism. Mitochondrial calcium and ROS signaling regulate assembly of a mitophagy- and p62-dependent scaffolding complex that amplifies MEKK-MEK5-ERK5 signaling. Blocking the mitochondrial pathway in vivo reduces expression of KLF2-dependent genes such as eNOS and inhibits vascular remodeling. Failure to activate the mitochondrial pathway limits Klf2 expression in regions of disturbed flow. This work thus defines a connection between metabolism and vascular inflammation that provides a new framework for understanding and developing treatments for vascular disease.

Isolation and culture of murine aortic cells and RNA isolation of aortic intima and media: Rapid and optimized approaches for atherosclerosis research

BACKGROUND AND AIMS

Isolation of cellular constituents from the mouse aorta is commonly used for expression or functional analyses in atherosclerosis research. However, current procedures to isolate primary cells are difficult, inefficient, and require separate mice. RNA extraction from aortic intima and media for transcriptomic analysis is also considered difficult with mixed RNA yields. To address these gaps, we provide: 1) a rapid, efficient protocol to isolate and culture diverse cell types concomitantly from the mouse aorta using immunomagnetic cell isolation; and 2) an optimized aortic intimal peeling technique for efficient RNA isolation from the intima and media.

METHODS AND RESULTS

Aortic cells were obtained using an enzymatic solution and different cell types were isolated by magnetic beads conjugated to antibodies targeting endothelial cells (CD31+), leukocytes (CD45+), and fibroblast cells (CD90.2+), and smooth muscle cells were isolated by negative selection. Our protocol allows the isolation of relatively large numbers of cells (10,000 cells per aorta) in a predictable manner with high purity (>90%) verified by cell-marker gene expression, immunofluorescence, and flow cytometry. These cells are all functionally active when grown in cell culture. We also provide a rapid method to collect aortic intima-enriched RNA from Ldlr-/- mice utilizing an intima peeling approach and assess transcriptomic profiling associated with accelerated lesion formation.

CONCLUSIONS

This protocol provides an effective means for magnetic bead-based isolation of different cell types from the mouse aortic wall, and the isolated cells can be utilized for functional and mechanistic studies for a range of vascular diseases including atherosclerosis.

Isolation and Profiling of Human Primary Mesenteric Arterial Endothelial Cells at the Transcriptome Level

Endothelial cells (ECs) are crucial for vascular and whole-body function through their dynamic response to environmental cues. Elucidating the transcriptome and epigenome of ECs is paramount to understanding their roles in development, health, and disease, but is limited in the availability of isolated primary cells. Recent technologies have enabled the high-throughput profiling of EC transcriptome and epigenome, leading to the identification of previously unknown EC cell subpopulations and developmental trajectories. While EC cultures are a useful tool in the exploration of EC function and dysfunction, the culture conditions and multiple passages can introduce external variables that alter the properties of native EC, including morphology, epigenetic state, and gene expression program. To overcome this limitation, the present paper demonstrates a method of isolating human primary ECs from donor mesenteric arteries aiming to capture their native state. ECs in the intimal layer are dissociated mechanically and biochemically with the use of particular enzymes. The resultant cells can be directly used for bulk RNA or single-cell RNA-sequencing or plated for culture. In addition, a workflow is described for the preparation of human arterial tissue for spatial transcriptomics, specifically for a commercially available platform, although this method is also suitable for other spatial transcriptome profiling techniques. This methodology can be applied to different vessels collected from a variety of donors in health or disease states to gain insights into EC transcriptional and epigenetic regulation, a pivotal aspect of endothelial cell biology.

Using Immortalized Endothelial Cells to Study the Roles of Adhesion Molecules in VEGF-Induced Signaling

The ability to study the role of specific genes in endothelial cell biology is made possible by our ability to modulate their expression through siRNA or knockout technologies. However, many in vitro protocols, particularly those of a biochemical nature, require large numbers of endothelial cells. These types of analyses are encumbered by the need to repeatedly produce and characterize primary endothelial cell cultures and can be greatly facilitated by the use of immortalized microvascular endothelial cells. However, we have found that the manipulation of gene expression in these cells is not always straight forward. Here we describe how we alter gene expression in polyoma middle T antigen immortalized microvascular endothelial cells isolated from wild-type and genetically modified mice to study the role of cell adhesion molecules in downstream assays.

Anti-Aging β-Klotho Gene-Activated Scaffold Promotes Rejuvenative Wound Healing Response in Human Adipose-Derived Stem Cells

Wound healing requires a tight orchestration of complex cellular events. Disruption in the cell-signaling events can severely impair healing. The application of biomaterial scaffolds has shown healing potential; however, the potential is insufficient for optimal wound maturation. This study explored the functional impact of a collagen-chondroitin sulfate scaffold functionalized with nanoparticles carrying an anti-aging gene β-Klotho on human adipose-derived stem cells (ADSCs) for rejuvenative healing applications. We studied the response in the ADSCs in three phases: (1) transcriptional activities of pluripotency factors (Oct-4, Nanog and Sox-2), proliferation marker (Ki-67), wound healing regulators (TGF-β3 and TGF-β1); (2) paracrine bioactivity of the secretome generated by the ADSCs; and (3) regeneration of basement membrane (fibronectin, laminin, and collagen IV proteins) and expression of scar-associated proteins (α-SMA and elastin proteins) towards maturation. Overall, we found that the β-Klotho gene-activated scaffold offers controlled activation of ADSCs' regenerative abilities. On day 3, the ADSCs on the gene-activated scaffold showed enhanced (2.5-fold) activation of transcription factor Oct-4 that was regulated transiently. This response was accompanied by a 3.6-fold increase in the expression of the anti-fibrotic gene TGF-β3. Through paracrine signaling, the ADSCs-laden gene-activated scaffold also controlled human endothelial angiogenesis and pro-fibrotic response in dermal fibroblasts. Towards maturation, the ADSCs-laden gene-activated scaffold further showed an enhanced regeneration of the basement membrane through increases in laminin (2.1-fold) and collagen IV (8.8-fold) deposition. The ADSCs also expressed 2-fold lower amounts of the scar-associated α-SMA protein with improved qualitative elastin matrix deposition. Collectively, we determined that the β-Klotho gene-activated scaffold possesses tremendous potential for wound healing and could advance stem cell-based therapy for rejuvenative healing applications.

Combined LXR and RXR Agonist Therapy Increases ABCA1 Protein Expression and Enhances ApoAI-Mediated Cholesterol Efflux in Cultured Endothelial Cells

Endothelial ABCA1 expression protects against atherosclerosis and this atheroprotective effect is partially attributed to enhancing apoAI-mediated cholesterol efflux. ABCA1 is a target gene for LXR and RXR; therefore, treating endothelial cells with LXR and/or RXR agonists may increase ABCA1 expression. We tested whether treating cultured immortalized mouse aortic endothelial cells (iMAEC) with the endogenous LXR agonist 22(R)-hydroxycholesterol, synthetic LXR agonist GW3965, endogenous RXR agonist 9-cis-retinoic acid, or synthetic RXR agonist SR11237 increases ABCA1 protein expression. We observed a significant increase in ABCA1 protein expression in iMAEC treated with either GW3965 or SR11237 alone, but no significant increase in ABCA1 protein was observed in iMAEC treated with either 22(R)-hydroxycholesterol or 9-cis-retionic acid alone. However, we observed significant increases in both ABCA1 protein expression and apoAI-mediated cholesterol efflux when iMAEC were treated with a combination of either 22(R)-hydroxycholesterol and 9-cis-retinoic acid or GW3965 and SR11237. Furthermore, treating iMAEC with either 22(R)-hydroxycholesterol and 9-cis-retinoic acid or GW3965 and SR11237 did not trigger an inflammatory response, based on VCAM-1, ICAM-1, CCL2, and IL-6 mRNA expression. Based on our findings, delivering LXR and RXR agonists precisely to endothelial cells may be a promising atheroprotective approach.

Effect of low wall shear stress on the morphology of endothelial cells and its evaluation indicators

OBJECTIVE

This study is designed to explore the morphological changes of endothelial cells (ECs) under different levels of shear stress and find the effective evaluation indicators with in vivo and in vitro experiments.

METHODS

Human umbilical vein endothelial cells (HUVECs) and Sprague-Dawley rats were used to study the effect of different shear stress which applied by means of parallel plate-flow chamber and abdominal aorta banding model on the morphology of endothelial cells. Then, fluorescence images were acquired by means of a confocal laser-scanning microscope. Finally, Cell morphological indicators were extracted by SRAD-MCW computer image processing algorithm for quantitative analysis.

RESULTS

1) The morphological changes of HUVECs were observed after exposure to shear stress for 6 h, the HUVECs were elongated and spindle-shaped. And the degree of cell deformability was different while the exposure time was different, then it became stable after 18 h. The HUVECs exposure to high shear stress (HSS) exhibited an ordered cell arrangement, while the HUVECs exposure to low shear stress (LSS) showed a disordered cell arrangement. 2) Traditional cell morphological indicators such as area, perimeter, long axis diameter, short axis diameter and orientation angle were not significantly different between the normal shear stress (NSS) group and the LSS group (P > 0.05), but the intercellular space characteristics such as the junction length per unit area and the triple points per unit area were significantly different (P < 0.05).

CONCLUSION

These results demonstrate that the size and duration of shear stress can affect the morphology and arrangement of endothelial cells. The commonly used evaluation indicators for studying the effect of shear stress on the morphology of endothelial cells, including area, perimeter, long axis diameter, short axis diameter and orientation angle, etc., had no significant statistical significance, while the intercellular space characteristics including the junction length per unit area and the triple points per unit area can be used as effective indicator to study the effect of shear stress on the morphology of endothelial cells.

Delivery of Anti-microRNA-712 to Inflamed Endothelial Cells Using Poly(β-amino ester) Nanoparticles Conjugated with VCAM-1 Targeting Peptide

Endothelial cells (ECs) are an important target for therapy in a wide range of diseases, most notably atherosclerosis. Developing efficient nanoparticle (NP) systems that deliver RNA interference (RNAi) drugs specifically to dysfunctional ECs in vivo to modulate their gene expression remains a challenge. To date, several lipid-based NPs are developed and shown to deliver RNAi to ECs, but few of them are optimized to specifically target dysfunctional endothelium. Here, a novel, targeted poly(β-amino ester) (pBAE) NP is demonstrated. This pBAE NP is conjugated with VHPK peptides that target vascular cell adhesion molecule 1 protein, overexpressed on inflamed EC membranes. To test this approach, the novel NPs are used to deliver anti-microRNA-712 (anti-miR-712) specifically to inflamed ECs both in vitro and in vivo, reducing the high expression of pro-atherogenic miR-712. A single administration of anti-miR-712 using the VHPK-conjugated-pBAE NPs in mice significantly reduce miR-712 expression, while preventing the loss of its target gene, tissue inhibitor of metalloproteinase 3 (TIMP3) in inflamed endothelium. miR-712 and TIMP3 expression are unchanged in non-inflamed endothelium. This novel, targeted-delivery platform may be used to deliver RNA therapeutics specifically to dysfunctional endothelium for the treatment of vascular disease.

The subcellular redistribution of NLRC5 promotes angiogenesis via interacting with STAT3 in endothelial cells

Angiogenesis is a critical step in repair of tissue injury. The pattern recognition receptors (PRRs) recognize pathogen and damage associated molecular patterns (DAMPs) during injury and achieve host defense directly. However, the role of NLR family CARD domain containing 5 (NLRC5), an important member of PPRs, beyond host defense in angiogenesis during tissue repair remains unknown. Methods: In vitro, western blot and real-time PCR (RT-PCR) were used to detect the expression of NLRC5 in endothelial cells (ECs). Immunofluorescence microscopy was used to reveal the subcellular location of NLRC5 in ECs. Cell proliferation, wound healing, tube formation assays of ECs were performed to study the role of NLRC5 in angiogenesis. By using Tie2Cre-NLRC5^flox/flox mice and bone marrow transplantation studies, we defined an EC-specific role for NLRC5 in angiogenesis. Mechanistically, co-immunoprecipitation studies and RNA sequencing indicated that signal transducer and activator of transcription 3 (STAT3) was the target of NLRC5 in the nucleus. And Co-IP was used to verify the specific domain of NLRC5 binding with STAT3. ChIP assay determined the genes regulated by interaction of STAT3 and NLRC5. Results: Knockdown of NLRC5 in vitro or in vivo inhibited pathological angiogenesis, but had no effect on physiological angiogenesis. NLRC5 was also identified to bind to STAT3 in the nucleus required the integrated death-domain and nucleotide-binding domain (DD+NACHT domain) of NLRC5. And the interaction of STAT3 and NLRC5 could enhance the transcription of angiopoietin-2 (Ang2) and cyclin D1 (CCND1) to participate in angiogenesis. Conclusions: In the ischemic microenvironment, NLRC5 protein accumulates in the nucleus of ECs and enhances STAT3 transcriptional activity for angiogenesis. These findings establish NLRC5 as a novel modulator of VEGFA signaling, providing a new target for angiogenic therapy to foster tissue regeneration.

Delivery of siRNA to Endothelial Cells In Vivo Using Lysine/Histidine Oligopeptide-Modified Poly(β-amino ester) Nanoparticles

PURPOSE

Endothelial cell (EC) dysfunction underlies the pathology of multiple disease conditions including cardiovascular and pulmonary diseases. Dysfunctional ECs have a distinctive gene expression profile compared to healthy ECs. RNAi therapy is a powerful therapeutic approach that can be used to silence multiple genes of interests simultaneously. However, the delivery of RNAi to ECs in vivo continues to be a major challenge. Here, we optimized a polymer formulation based on poly(β-amino ester)s (pBAEs) to deliver siRNA to vascular ECs.

METHODS

We developed a library of bioinspired oligopeptide-modified pBAE nanoparticles (NPs) with different physicochemical proprieties and screened them for cellular uptake and efficacy of RNAi delivery in vitro using ECs, vascular smooth muscle cells, and THP-1 monocytes. From the screening, the lysine-/histidine-oligopeptide modified pBAE (C6-KH) NP was selected and further tested ex vivo using mouse aorta and in mice to determine efficiency of siRNA delivery in vivo.

RESULTS

The in vitro screening study showed that C6-KH was most efficient in delivering siRNA to ECs. Ex vivo study showed that C6-KH nanoparticles containing siRNAs accumulated in the endothelial layer of mouse aortas. In vivo study showed that C6-KH nanoparticles carrying siICAM2 injected via tail-vein in mice significantly reduced ICAM2 level in the artery endothelium (55%), lung (52%), and kidney (31%), but not in the liver, heart, and thymus, indicating a tissue-specific delivery pattern.

CONCLUSIONS

We demonstrate that C6-KH pBAE can used for delivery of siRNAs to the artery endothelium and lung, while minimizing potential side or toxic effects in the liver and heart.

Increased PIP3 activity blocks nanoparticle mRNA delivery

The biological pathways that affect drug delivery in vivo remain poorly understood. We hypothesized that altering cell metabolism with phosphatidylinositol (3,4,5)-triphosphate (PIP3), a bioactive lipid upstream of the metabolic pathway PI3K (phosphatidylinositol 3-kinase)/AKT/ mTOR (mammalian target of rapamycin) would transiently increase protein translated by nanoparticle-delivered messenger RNA (mRNA) since these pathways increase growth and proliferation. Instead, we found that PIP3 blocked delivery of clinically-relevant lipid nanoparticles (LNPs) across multiple cell types in vitro and in vivo. PIP3-driven reductions in LNP delivery were not caused by toxicity, cell uptake, or endosomal escape. Interestingly, RNA sequencing and metabolomics analyses suggested an increase in basal metabolic rate. Higher transcriptional activity and mitochondrial expansion led us to formulate two competing hypotheses that explain the reductions in LNP-mediated mRNA delivery. First, PIP3 induced consumption of limited cellular resources, "drowning out" exogenously-delivered mRNA. Second, PIP3 triggers a catabolic response that leads to protein degradation and decreased translation.

A simple protocol for isolating mouse lung endothelial cells

Endothelial dysfunction is the common molecular basis of multiple human diseases, such as atherosclerosis, diabetes, hypertension, and acute lung injury. Therefore, primary isolation of high-purity endothelial cells (ECs) is crucial to study the mechanisms of endothelial function and disease pathogenesis. Mouse lung ECs (MLECs) are widely used in vascular biology and lung cell biology studies such as pulmonary inflammation, angiogenesis, vessel permeability, leukocyte/EC interaction, nitric oxide production, and mechanotransduction. Thus, in this paper, we describe a simple, and reproducible protocol for the isolation and culture of MLECs from adult mice using collagenase I-based enzymatic digestion, followed by sequential sorting with PECAM1 (also known as CD31)- and ICAM2 (also known as CD102)-coated microbeads. The morphology of isolated MLECs were observed with phase contrast microscope. MLECs were authenticated by CD31 immunoblotting, and immunofluorescent staining of established EC markers VE-cadherin and von Willebrand factor (vWF). Cultured MLECs also showed functional characteristics of ECs, evidenced by DiI-oxLDL uptake assay and THP-1 monocyte adhesion assay. Finally, we used MLECs from endothelium-specific enhancer of zeste homolog 2 (EZH2) knockout mice to show the general applicability of our protocol. To conclude, we describe here a simple and reproducible protocol to isolate highly pure and functional ECs from adult mouse lungs. Isolation of ECs from genetically engineered mice is important for downstream phenotypic, genetic, or proteomic studies.

Nanoparticles That Deliver RNA to Bone Marrow Identified by in Vivo Directed Evolution

Bone marrow endothelial cells (BMECs) regulate their microenvironment, which includes hematopoietic stem cells. This makes BMECs an important target cell type for siRNA or gene editing (e.g., CRISPR) therapies. However, siRNA and sgRNA have not been delivered to BMECs using systemically administered nanoparticles. Given that in vitro nanoparticle screens have not identified nanoparticles with BMEC tropism, we developed a system to quantify how >100 different nanoparticles deliver siRNA in a single mouse. This is the first barcoding system capable of quantifying functional cytosolic siRNA delivery (where the siRNA drug is active), distinguishing it from in vivo screens that quantify biodistribution (where the siRNA drug went). Combining this approach with bioinformatics, we performed in vivo directed evolution, and identified BM1, a lipid nanoparticle (LNP) that delivers siRNA and sgRNA to BMECs. Interestingly, chemical analysis revealed BMEC tropism was not related to LNP size; tropism changed with the structure of poly(ethylene glycol), as well as the presence of cholesterol. These results suggest that significant changes to vascular targeting can be imparted to a LNP by making simple changes to its chemical composition, rather than using active targeting ligands. BM1 is the first nanoparticle to efficiently deliver siRNA and sgRNA to BMECs in vivo, demonstrating that this functional in vivo screen can identify nanoparticles with novel tropism in vivo. More generally, in vivo screening may help reveal the complex relationship between nanoparticle structure and tropism, thereby helping scientists understand how simple chemical changes control nanoparticle targeting.

Modifying a Commonly Expressed Endocytic Receptor Retargets Nanoparticles in Vivo

Nanoparticles are often targeted to receptors expressed on specific cells, but few receptors are (i) highly expressed on one cell type and (ii) involved in endocytosis. One unexplored alternative is manipulating an endocytic gene expressed on multiple cell types; an ideal gene would inhibit delivery to cell type A more than cell type B, promoting delivery to cell type B. This would require a commonly expressed endocytic gene to alter nanoparticle delivery in a cell type-dependent manner in vivo; whether this can occur is unknown. Based on its microenvironmental regulation, we hypothesized Caveolin 1 (Cav1) would exert cell type-specific effects on nanoparticle delivery. Fluorescence was not sensitive enough to investigate this question, and as a result, we designed a platform named QUANT to study nanoparticle biodistribution. QUANT is 108× more sensitive than fluorescence and can be multiplexed. By measuring how 226 lipid nanoparticles (LNPs) delivered nucleic acids to multiple cell types in vivo in wild-type and Cav1 knockout mice, we found Cav1 altered delivery in a cell-type specific manner. Cav1 knockout did not alter LNP delivery to lung and kidney macrophages but substantially reduced LNP delivery to Kupffer cells, which are liver-resident macrophages. These data suggest caveolin-mediated endocytosis of nanomedicines by macrophages varies with tissue type. These results suggest manipulating receptors expressed on multiple cell types can tune drug delivery.

Clozapine attenuates mitochondrial burdens and abnormal behaviors elicited by phencyclidine in mice via inhibition of p47 phox; Possible involvements of phosphoinositide 3-kinase/Akt signaling

BACKGROUND

Oxidative stress and mitochondrial dysfunction have been implicated in the pathophysiology of schizophrenia.

AIMS

We investigated whether antipsychotic clozapine modulates nicotinamide adenine dinucleotide phosphate oxidase and mitochondrial burdens induced by phencyclidine in mice.

METHODS

We examined the effect of clozapine on nicotinamide adenine dinucleotide phosphate oxidase activation, mitochondrial burdens (i.e. oxidative stress and mitochondrial dysfunction), and activities of enzymatic antioxidant in the prefrontal cortex, and subsequent abnormal behaviors induced by repeated treatment with phencyclidine. p47 ^phox Knockout mice and LY294002, a phosphoinositide 3-kinase inhibitor, were employed to elucidate the pharmacological mechanism of clozapine.

RESULTS

Phencyclidine treatment resulted in an early increase nicotinamide adenine dinucleotide phosphate oxidase activity, membrane translocation of p47 ^phox, interaction between p-Akt and p47 ^phox, and mitochondrial burdens in wild-type mice. Although these increases returned to near control level four days post-phencyclidine, mitochondrial superoxide dismutase and glutathione peroxidase activities were decreased at that time. Clozapine, LY294002, or p47 ^phox knockout significantly ameliorated social withdrawal and recognition memory deficits produced by phencyclidine. Importantly, LY294002 did not significantly alter the effects of clozapine against abnormal behaviors and the interaction between p-Akt and p47 ^phox induced by phencyclidine. Furthermore, neither LY294002 nor clozapine exhibited any additive effects to the protection afforded by p47 ^phox knockout against phencyclidine insult.

CONCLUSION

Our results suggest that p47 ^phox gene mediates phencyclidine-induced mitochondrial burdens and abnormal behaviors, and that the interactive modulation between p47 ^phox and phosphoinositide 3-kinase/Akt is important for the understanding on the pharmacological mechanism of clozapine.

A Direct Comparison of in Vitro and in Vivo Nucleic Acid Delivery Mediated by Hundreds of Nanoparticles Reveals a Weak Correlation

Endothelial cells and macrophages play active roles in disease and as a result are important targets for nucleic acid therapies. While thousands of chemically distinct lipid nanoparticles (LNPs) can be synthesized to deliver nucleic acids, studying more than a few LNPs in vivo is challenging. As a result, it is difficult to understand how nanoparticles target these cells in vivo. Using high throughput LNP barcoding, we quantified how well LNPs delivered DNA barcodes to endothelial cells and macrophages in vitro, as well as endothelial cells and macrophages isolated from the lung, heart, and bone marrow in vivo. We focused on two fundamental questions in drug delivery. First, does in vitro LNP delivery predict in vivo LNP delivery? By comparing how 281 LNPs delivered barcodes to endothelial cells and macrophages in vitro and in vivo, we found in vitro delivery did not predict in vivo delivery. Second, does LNP delivery change within the microenvironment of a tissue? We quantified how 85 LNPs delivered barcodes to eight splenic cell populations, and found that cell types derived from myeloid progenitors tended to be targeted by similar LNPs, relative to cell types derived from lymphoid progenitors. These data demonstrate that barcoded LNPs can elucidate fundamental questions about in vivo nanoparticle delivery.

PKCδ-dependent p47phox activation mediates methamphetamine-induced dopaminergic neurotoxicity

Protein kinase C (PKC) has been recognized to activate NADPH oxidase (PHOX). However, the interaction between PKC and PHOX in vivo remains elusive. Treatment with methamphetamine (MA) resulted in a selective increase in PKCδ expression out of PKC isoforms. PKCδ co-immunoprecipitated with p47phox, and facilitated phosphorylation and membrane translocation of p47phox. MA-induced increases in PHOX activity and reactive oxygen species were attenuated by knockout of p47phox or PKCδ. In addition, MA-induced impairments in the Nrf-2-related glutathione synthetic system were also mitigated by knockout of p47phox or PKCδ. Glutathione-immunoreactivity was co-localized in Iba-1-labeled microglial cells and in NeuN-labeled neurons, but not in GFAP-labeled astrocytes, reflecting the necessity for self-protection against oxidative stress by mainly microglia. Buthionine-sulfoximine, an inhibitor of glutathione biosynthesis, potentiated microglial activation and pro-apoptotic changes, leading to dopaminergic losses. These neurotoxic processes were attenuated by rottlerin, a pharmacological inhibitor of PKCδ, genetic inhibitions of PKCδ [i.e., PKCδ knockout mice (KO) and PKCδ antisense oligonucleotide (ASO)], or genetic inhibition of p47phox (i.e., p47phox KO or p47phox ASO). Rottlerin did not exhibit any additive effects against the protective activity offered by genetic inhibition of p47phox. Therefore, we suggest that PKCδ is a critical regulator for p47phox activation induced by MA, and that Nrf-2-dependent GSH induction via inhibition of PKCδ or p47phox, is important for dopaminergic protection against MA insult.

Atherosclerosis is exacerbated by chitinase-3-like-1 in amyloid precursor protein transgenic mice

Although the important role of amyloid precursor protein (APP) in vascular diseases associated with Alzheimer's disease (AD) has been demonstrated, the underlying molecular mechanisms and physiological consequences are unclear. We aimed to evaluate vascular inflammation and atherosclerosis in Swedish mutant of human APP transgenic (APPsw-Tg) and ApoE^-/-/APPsw-Tg mice. We also aimed to explore the mechanisms underlying any changes observed in these mice compared with non-Tg controls. Methods: The transgenic and non-Tg mouse strains were subjected to partial ligation of the left carotid artery to induce atherosclerotic changes, which were measured using histological approaches, immunohistochemistry, quantitative polymerase chain reaction, and gene expression microarrays. Results: Our results showed increased vascular inflammation, arterial wall thickness, and atherosclerosis in APPsw-Tg and ApoE^-/-/APPsw-Tg mice. We further found that the expression of chitinase-3-like-1 (Chi3l1) is increased in the APPsw-Tg mouse artery and Chi3l1 mediates endothelial cell (EC) inflammation and vascular smooth muscle cell (VSMC) activation, which in turn exacerbates atherosclerosis. In addition, using two publicly available microarray datasets from the dorsolateral prefrontal cortex of people with AD and unaffected controls as well as inflamed human umbilical vein endothelial cells, we found that Chi3l1 and associated inflammatory gene were significantly associated with AD, evaluated by co-expression network analysis and functional annotation. Knockdown of Chi3l1 in the arterial endothelium in vivo suppressed the development of atherosclerosis. We also show that microRNA 342-3p (miR-342-3p) inhibits EC inflammation and VSMC activation through directly targeting Chi3l1, and that APPsw increased Chi3l1 expression by reducing miR-342-3p expression in the arterial endothelium, promoting atherosclerosis. Conclusion: Our findings suggest that targeting Chi3l1 might provide new diagnostic and therapeutic strategies for vascular diseases in patients with AD.

Detection of frequency-dependent endothelial response to oscillatory shear stress using a microfluidic transcellular monitor

The endothelial microenvironment is critical in maintaining the health and function of the intimal layer in vasculature. In the context of cardiovascular disease (CVD), the vascular endothelium is the layer of initiation for the progression of atherosclerosis. While laminar blood flows are known to maintain endothelial homeostasis, disturbed flow conditions including those the endothelium experiences in the carotid artery are responsible for determining the fate of CVD progression. We present a microfluidic device designed to monitor the endothelium on two fronts: the real-time monitoring of the endothelial permeability using integrated electrodes and the end-point characterization of the endothelium through immunostaining. Our key findings demonstrate endothelial monolayer permeability and adhesion protein expression change in response to oscillatory shear stress frequency. These changes were found to be significant at certain frequencies, suggesting that a frequency threshold is needed to elicit an endothelial response. Our device made possible the real-time monitoring of changes in the endothelial monolayer and its end-point inspection through a design previously absent from the literature. This system may serve as a reliable research platform to investigate the mechanisms of various inflammatory complications of endothelial disorders and screen their possible therapeutics in a mechanistic and high-throughput manner.

Quercetin reduces hydroxyurea induced cytotoxicity in immortalized mouse aortic endothelial cells

Background

Chronic inflammation is a characteristic of sickle cell disease (SCD), and is invariably associated with vascular endothelial injury. Hydroxyurea (HU), a naturally cytotoxic chemotherapeutic agent, is the only FDA drug approved for SCD, and is therefore naturally cytotoxic. Quercetin (QCT) is a dietary flavonoid found ubiquitously in plants and foods that have anti-oxidative and anti-inflammatory characteristics. Our hypothesis is that dietary QCT will decrease cytotoxic effects of lipopolysaccharide (LPS) and HU induced vascular cell damage.

Methods

Lipopolysaccharide (LPS) was used to induce inflammation in immortalized mouse aortic endothelial cells (iMAECs), providing an in vitro model of inflamed endothelial cells. The cells were exposed to LPS throughout the entire experiment. Interventions included treating the LPS exposed cells with QCT, HU, or QCT + HU over 50 hours. The 50-hour period included 24 hours of varying treatments, followed by two hours of hypoxic exposure and then 24 hours under normal aerobic exposure.

Results

LDH level was significantly higher for LPS treated versus untreated cells (P = 0.0004). LPS plus 30 micromole QCT reduced the LDH (p = 0.1, trend), whereas LPS plus 100 micromoles HU, significantly increased LDH (p = 0.0004). However, LPS plus treatment with 30 micromoles QCT/100 micromoles HU, significantly reduced LDH, compared with HU alone (p = 0.0002).

Discussion

These results suggest that quercetin may be effective against vascular endothelial cell damage for iMAECs in vitro. In particular, it shows promise in preventing HU-induced cytotoxicity, surprisingly found from these results. This latter finding is important, and should be given more consideration, since HU is the only FDA-approved drug for treating sickle cell patients, and its use is rapidly increasing.

Functional screening of mammalian mechanosensitive genes using Drosophila RNAi library- Smarcd3/Bap60 is a mechanosensitive pro-inflammatory gene

Disturbed blood flow (d-flow) induces atherosclerosis by altering the expression of mechanosensitive genes in the arterial endothelium. Previously, we identified >580 mechanosensitive genes in the mouse arterial endothelium, but their role in endothelial inflammation is incompletely understood. From this set, we obtained 84 Drosophila RNAi lines that silences the target gene under the control of upstream activation sequence (UAS) promoter. These lines were crossed with C564-GAL4 flies expressing GFP under the control of drosomycin promoter, an NF-κB target gene and a marker of pathogen-induced inflammation. Silencing of psmd12 or ERN1 decreased infection-induced drosomycin expression, while Bap60 silencing significantly increased the drosomycin expression. Interestingly, knockdown of Bap60 in adult flies using temperature-inducible Bap60 RNAi (C564^ts-GAL4-Bap60-RNAi) enhanced drosomycin expression upon Gram-positive bacterial challenge but the basal drosomycin expression remained unchanged compared to the control. In the mammalian system, smarcd3 (mammalian ortholog of Bap60) expression was reduced in the human- and mouse aortic endothelial cells exposed to oscillatory shear in vitro as well as in the d-flow regions of mouse arterial endothelium in vivo. Moreover, siRNA-mediated knockdown of smarcd3 induced endothelial inflammation. In summary, we developed an in vivo Drosophila RNAi screening method to identify flow-sensitive genes that regulate endothelial inflammation.

Discovery of novel peptides targeting pro-atherogenic endothelium in disturbed flow regions -Targeted siRNA delivery to pro-atherogenic endothelium in vivo

Atherosclerosis occurs preferentially in arterial regions exposed to disturbed blood flow. Targeting these pro-atherogenic regions is a potential anti-atherogenic therapeutic approach, but it has been extremely challenging. Here, using in vivo phage display approach and the partial carotid ligation model of flow-induced atherosclerosis in mouse, we identified novel peptides that specifically bind to endothelial cells (ECs) exposed to disturbed flow condition in pro-atherogenic regions. Two peptides, CLIRRTSIC and CPRRSHPIC, selectively bound to arterial ECs exposed to disturbed flow not only in the partially ligated carotids but also in the lesser curvature and branching point of the aortic arch in mice as well as human pulmonary artery branches. Peptides were conjugated to branched polyethylenimine-polyethylene glycol polymer to generate polyplexes carrying siRNA targeting intercellular adhesion molecule-1 (siICAM-1). In mouse model, CLIRRTSIC polyplexes carrying si-ICAM-1 specifically bound to endothelium in disturbed flow regions, reducing endothelial ICAM-1 expression. Mass spectrometry analysis revealed that non-muscle myosin heavy chain II A (NMHC IIA) is a protein targeted by CLIRRTSIC peptide. Further studies showed that shear stress regulates NMHC IIA expression and localization in ECs. The CLIRRTSIC is a novel peptide that could be used for targeted delivery of therapeutics such as siRNAs to pro-atherogenic endothelium.

Apocynin prevents mitochondrial burdens, microglial activation, and pro-apoptosis induced by a toxic dose of methamphetamine in the striatum of mice via inhibition of p47phox activation by ERK

BACKGROUND

Activation of NADPH oxidase (PHOX) plays a critical role in mediating dopaminergic neuroinflammation. In the present study, we investigated the role of PHOX in methamphetamine (MA)-induced neurotoxic and inflammatory changes in mice.

METHODS

We examined changes in mitogen-activated protein kinases (MAPKs), mitochondrial function [i.e., mitochondrial membrane potential, intramitochondrial Ca(2+) accumulation, mitochondrial oxidative burdens, mitochondrial superoxide dismutase expression, and mitochondrial translocation of the cleaved form of protein kinase C delta type (cleaved PKCδ)], microglial activity, and pro-apoptotic changes [i.e., cytosolic cytochrome c release, cleaved caspase 3, and terminal deoxynucleotidyl transferase dUDP nick-end labeling (TUNEL) positive populations] after a neurotoxic dose of MA in the striatum of mice to achieve a better understanding of the effects of apocynin, a non-specific PHOX inhibitor, or genetic inhibition of p47phox (by using p47phox knockout mice or p47phox antisense oligonucleotide) against MA-induced dopaminergic neurotoxicity.

RESULTS

Phosphorylation of extracellular signal-regulated kinases (ERK1/2) was most pronounced out of MAPKs after MA. We observed MA-induced phosphorylation and membrane translocation of p47phox in the striatum of mice. The activation of p47phox promoted mitochondrial stresses followed by microglial activation into the M1 phenotype, and pro-apoptotic changes, and led to dopaminergic impairments. ERK activated these signaling pathways. Apocynin or genetic inhibition of p47phox significantly protected these signaling processes induced by MA. ERK inhibitor U0126 did not exhibit any additional positive effects against protective activity mediated by apocynin or p47phox genetic inhibition, suggesting that ERK regulates p47phox activation, and ERK constitutes the crucial target for apocynin-mediated inhibition of PHOX activation.

CONCLUSIONS

Our results indicate that the neuroprotective mechanism of apocynin against MA insult is via preventing mitochondrial burdens, microglial activation, and pro-apoptotic signaling process by the ERK-dependent activation of p47phox.

Suppression of β3-integrin in mice triggers a neuropilin-1-dependent change in focal adhesion remodelling that can be targeted to block pathological angiogenesis

Anti-angiogenic treatments against αvβ3-integrin fail to block tumour growth in the long term, which suggests that the tumour vasculature escapes from angiogenesis inhibition through αvβ3-integrin-independent mechanisms. Here, we show that suppression of β3-integrin in mice leads to the activation of a neuropilin-1 (NRP1)-dependent cell migration pathway in endothelial cells via a mechanism that depends on NRP1's mobilisation away from mature focal adhesions following VEGF-stimulation. The simultaneous genetic targeting of both molecules significantly impairs paxillin-1 activation and focal adhesion remodelling in endothelial cells, and therefore inhibits tumour angiogenesis and the growth of already established tumours. These findings provide a firm foundation for testing drugs against these molecules in combination to treat patients with advanced cancers.

Summary: Targeting both β3-integrin and neuropilin-1 prevents anti-angiogenic treatment escape.

Isolation and in vitro culture of vascular endothelial cells from mice

In cardiovascular disorders, understanding of endothelial cell (EC) function is essential to elucidate the disease mechanism. Although the mouse model has many advantages for in vivo and in vitro research, efficient procedures for the isolation and propagation of primary mouse EC have been problematic. We describe a high yield process for isolation and in vitro culture of primary EC from mouse arteries (aorta, braches of superior mesenteric artery, and cerebral arteries from the circle of Willis). Mouse arteries were carefully dissected without damage under a light microscope, and small pieces of the vessels were transferred on/in a Matrigel matrix enriched with endothelial growth supplement. Primary cells that proliferated in Matrigel were propagated in advanced DMEM with fetal calf serum or platelet-derived serum, EC growth supplement, and heparin. To improve the purity of the cell culture, we applied shearing stress and anti-fibroblast antibody. EC were characterized by a monolayer cobble stone appearance, positive staining with acetylated low density lipoprotein labeled with 1,1'-dioctadecyl-3,3,3',3'-tetramethyl-indocarbocyanine perchlorate, RT-PCR using primers for von-Willebrand factor, and determination of the protein level endothelial nitric oxide synthase. Our simple, efficient method would facilitate in vitro functional investigations of EC from mouse vessels.

Role of flow-sensitive microRNAs in endothelial dysfunction and atherosclerosis: mechanosensitive athero-miRs

Atherosclerosis preferentially occurs in arterial regions exposed to disturbed flow, in part, due to alterations in gene expression. MicroRNAs (miRNAs) are small, noncoding genes that post-transcriptionally regulate gene expression by targeting messenger RNA transcripts. Emerging evidence indicates that alteration of flow conditions regulate expression of miRNAs in endothelial cells both in vitro and in vivo. These flow-sensitive miRNAs, known as mechano-miRs, regulate endothelial gene expression and can regulate endothelial dysfunction and atherosclerosis. MiRNAs such as, miR-10a, miR-19a, miR-23b, miR-17-92, miR-21, miR-663, miR-92a, miR-143/145, miR-101, miR-126, miR-712, miR-205, and miR-155, have been identified as mechano-miRs. Many of these miRNAs were initially identified as flow sensitive in vitro and were later found to play a critical role in endothelial function and atherosclerosis in vivo through either gain-of-function or loss-of-function approaches. The key signaling pathways that are targeted by these mechano-miRs include the endothelial cell cycle, inflammation, apoptosis, and nitric oxide signaling. Furthermore, we have recently shown that the miR-712/205 family, which is upregulated by disturbed flow, contributes to endothelial inflammation and vascular hyperpermeability by targeting tissue inhibitor of metalloproteinase-3, which regulates metalloproteinases and a disintegrin and metalloproteinases. The mechano-miRs that are implicated in atherosclerosis are termed as mechanosensitive athero-miRs and are potential therapeutic targets to prevent or treat atherosclerosis. This review summarizes the current knowledge of mechanosensitive athero-miRs and their role in vascular biology and atherosclerosis.