Inhibition of collar-induced carotid atherosclerosis by recombinant apoA-I cysteine mutants in apoE-deficient mice

Targeted Suppression of miRNA-33 Using pHLIP Improves Atherosclerosis Regression

BACKGROUND

miRNA therapeutics have gained attention during the past decade. These oligonucleotide treatments can modulate the expression of miRNAs in vivo and could be used to correct the imbalance of gene expression found in human diseases such as obesity, metabolic syndrome, and atherosclerosis. The in vivo efficacy of current anti-miRNA technologies hindered by physiological and cellular barriers to delivery into targeted cells and the nature of miRNAs that allows one to target an entire pathway that may lead to deleterious off-target effects. For these reasons, novel targeted delivery systems to inhibit miRNAs in specific tissues will be important for developing effective therapeutic strategies for numerous diseases including atherosclerosis.

METHODS

We used pH low-insertion peptide (pHLIP) constructs as vehicles to deliver microRNA-33-5p (miR-33) antisense oligonucleotides to atherosclerotic plaques. Immunohistochemistry and histology analysis was performed to assess the efficacy of miR-33 silencing in atherosclerotic lesions. We also assessed how miR-33 inhibition affects gene expression in monocytes/macrophages by single-cell RNA transcriptomics.

RESULTS

The anti-miR-33 conjugated pHLIP constructs are preferentially delivered to atherosclerotic plaque macrophages. The inhibition of miR-33 using pHLIP-directed macrophage targeting improves atherosclerosis regression by increasing collagen content and decreased lipid accumulation within vascular lesions. Single-cell RNA sequencing analysis revealed higher expression of fibrotic genes (Col2a1, Col3a1, Col1a2, Fn1, etc) and tissue inhibitor of metalloproteinase 3 (Timp3) and downregulation of Mmp12 in macrophages from atherosclerotic lesions targeted by pHLIP-anti-miR-33.

CONCLUSIONS

This study provides proof of principle for the application of pHLIP for treating advanced atherosclerosis via pharmacological inhibition of miR-33 in macrophages that avoid the deleterious effects in other metabolic tissues. This may open new therapeutic opportunities for atherosclerosis-associated cardiovascular diseases via selective delivery of other protective miRNAs.

ABCA1, ABCG1, and Cholesterol Homeostasis

Cholesterol is a major component of mammalian cell membranes and plays important structural and functional roles. However, excessive cholesterol accumulation is toxic to cells and constitutes the molecular basis for many diseases, especially atherosclerotic cardiovascular disease. Thus, cellular cholesterol is tightly regulated to maintain a homeostasis. Reverse cholesterol transport (RCT) is thought to be one primary pathway to eliminate excessive cholesterol from the body. The first and rate-limiting step of RCT is ATP-binding cassette (ABC) transports A1 (ABCA1)- and ABCG1-dependent cholesterol efflux. In the process, ABCA1 mediates initial transport of cellular cholesterol to apolipoprotein A-I (apoA-I) for forming nascent high-density lipoprotein (HDL) particles, and ABCG1 facilitates subsequent continued cholesterol efflux to HDL for further maturation. In this chapter, we summarize the roles of ABCA1 and ABCG1 in maintaining cellular cholesterol homoeostasis and discuss the underlying mechanisms by which they mediate cholesterol export.

Efficacy and Safety of High-Density Lipoprotein/Apolipoprotein A1 Replacement Therapy in Humans and Mice With Atherosclerosis: A Systematic Review and Meta-Analysis

Background: Although elevation of HDL-C levels by pharmaceutical drugs have no benefit of cardiovascular endpoint, the effect of high-density lipoprotein/apolipoprotein A1 (HDL/apoA-1) replacement therapy on atherosclerosis is controversial. The current meta-analysis analyzed the effects of HDL/apoA-1 replacement therapies on atherosclerotic lesions both in humans and mice.

Methods: The PubMed, Cochrane Library, Web of Science, and EMBASE databases were searched through June 6, 2020. The methodological quality of the human studies was assessed using Review Manager (RevMan, version 5.3.). The methodological quality of the mouse studies was assessed using a stair list. STATA (version 14.0) was used to perform all statistical analyses.

Results: Fifteen randomized controlled human trials and 17 animal studies were included. The pooled results showed that HDL/apoA-1 replacement therapy use did not significantly decrease the percent atheroma volume (p = 0.766) or total atheroma volume (p = 0.510) in acute coronary syndrome (ACS) patients (N = 754). However, HDL/apoA-1 replacement therapies were significantly associated with the final percent lesion area, final lesion area, and changes in lesion area (SMD, −1.75; 95% CI: −2.21~-1.29, p = 0.000; SMD, −0.78; 95% CI: −1.18~-0.38, p = 0.000; SMD: −2.06; 95% CI, −3.92~-0.2, p = 0.03, respectively) in mice.

Conclusions: HDL/apoA-1 replacement therapies are safe but do not significantly improve arterial atheroma volume in humans. The results in animals suggest that HDL/apoA-1 replacement therapies decrease the lesion area. Additional studies are needed to investigate and explain the differences in HDL/apoA-1 replacement therapy efficacies between humans and animals.

Trial registration number: Human pooled analysis: PROSPERO, CRD42020210772. prospectively registered.

Urate-lowering therapy alleviates atherosclerosis inflammatory response factors and neointimal lesions in a mouse model of induced carotid atherosclerosis

Hyperuricemia (HU) is a cause of gout. Clinical studies show a link between HU and cardiovascular disease. However, the role of soluble serum urate (SU) on atherosclerosis development remains elusive. We aimed to use a new HU mouse model [Uricase/Uox knockout (KO)] to further investigate the relationship between HU and atherosclerosis. A mouse model by perivascular collar placement of induced carotid atherosclerosis was established in male Uox-KO mice. The Uox-KO mice had elevated SU levels and enhanced levels of atherosclerosis inflammatory response proteins. In contrast, Uox-KO mice with carotid atherosclerosis showed severe neointimal changes in histology staining consistent with increases in intimal area and increases in proliferating cell nuclear antigen (PCNA)- and F4/80-positive cells. Allopurinol reduced neointimal areas induced by the perivascular collar in hyperuricemic mice, accompanied by decreased expression of PCNA- and F4/80-positive cells. Urate-lowering treatment alleviated atherosclerosis inflammatory response factors and reactive oxygen species (ROS) intensities in both collar placement Uox-KO mice and urate-stimulated human umbilical vein endothelial cells (HUVECs). In vitro results using HUVECs showed ROS was induced by urate and ROS induction was abrogated using antioxidants. These data demonstrate that urate per se does not trigger atherosclerosis intima lesions in male mice. Urate worsens carotid neointimal lesions induced by the perivascular collar and urate-lowering therapy partially abrogates the effects. The current study warrants clinical studies on the possible benefits of urate-lowering therapy in atherosclerosis patients with HU.

Cholesterol transport system: An integrated cholesterol transport model involved in atherosclerosis

Atherosclerosis, the pathological basis of most cardiovascular disease (CVD), is closely associated with cholesterol accumulation in the arterial intima. Excessive cholesterol is removed by the reverse cholesterol transport (RCT) pathway, representing a major antiatherogenic mechanism. In addition to the RCT, other pathways are required for maintaining the whole-body cholesterol homeostasis. Thus, we propose a working model of integrated cholesterol transport, termed the cholesterol transport system (CTS), to describe body cholesterol metabolism. The novel model not only involves the classical view of RCT but also contains other steps, such as cholesterol absorption in the small intestine, low-density lipoprotein uptake by the liver, and transintestinal cholesterol excretion. Extensive studies have shown that dysfunctional CTS is one of the major causes for hypercholesterolemia and atherosclerosis. Currently, several drugs are available to improve the CTS efficiently. There are also several therapeutic approaches that have entered into clinical trials and shown considerable promise for decreasing the risk of CVD. In recent years, a variety of novel findings reveal the molecular mechanisms for the CTS and its role in the development of atherosclerosis, thereby providing novel insights into the understanding of whole-body cholesterol transport and metabolism. In this review, we summarize the latest advances in this area with an emphasis on the therapeutic potential of targeting the CTS in CVD patients.

Endoplasmic reticulum stress in perivascular adipose tissue promotes destabilization of atherosclerotic plaque by regulating GM-CSF paracrine

Background

Perivascular adipose tissue (PVAT) accelerates plaque progression and increases cardiovascular risk. We tested the hypothesis that PVAT contributed to plaque vulnerability and investigated whether endoplasmic reticulum stress (ER stress) in PVAT played an important role in vulnerable plaque.

Methods

We transplanted thoracic aortic PVAT or subcutaneous adipose tissue as a control, from donor mice to carotid arteries of recipient apolipoprotein E deficient (apoE^−/−) mice after removing carotid artery collar placed for 6 weeks. Two weeks after transplantation, ER stress inhibitor 4-phenyl butyric acid (4-PBA) was locally administrated to the transplanted PVAT and then animals were euthanized after 4 weeks. Immunohistochemistry was performed to quantify plaque composition and neovascularization. Mouse angiogenesis antibody array kit was used to test the angiogenic factors produced by transplanted adipose tissue. In vitro tube formation assay, scratch wound migration assay and mouse aortic ring assay were used to assess the angiogenic capacity of supernatant of transplanted PVAT.

Results

Ultrastructural detection by transmission electron microscopy showed transplanted PVAT was a mixed population of white and brown adipocytes with abundant mitochondria. Transplanted PVAT increased the intraplaque macrophage infiltration, lipid core, intimal and vasa vasorum neovascularization and MMP2/9 expression in plaque while decreased smooth muscle cells and collagen in atherosclerotic plaque, which were restored by local 4-PBA-treatment. Antibody array analysis showed that 4-PBA reduced several angiogenic factors [Granulocyte Macrophage Colony Stimulating Factor (GM-CSF), MCP-1, IL-6] secreted by PVAT. Besides, conditioned medium from 4-PBA treated-PVAT inhibited tube formation and migration capacity of endothelial cells and ex vivo mouse aortic ring angiogenesis compared to conditioned medium from transplanted PVAT. mRNA expression and protein levels of GM-CSF were markedly elevated in adipocytes under ER stress which would be suppressed by 4-PBA. In addition, ER stress enhanced NF-κB binding to the promoter of the mouse GM-CSF gene in adipocytes confirmed by Chromatin immunoprecipitation analyses.

Conclusions

Our findings demonstrate that ER stress in PVAT destabilizes atherosclerotic plaque, in part through increasing GM-CSF paracrine via transcription factor NF-κB.

Electronic supplementary material

The online version of this article (10.1186/s12967-018-1481-z) contains supplementary material, which is available to authorized users.

Effect of lipid-bound apolipoprotein A-I cysteine mutant on ATF3 in RAW264.7 cells

Activating transcription factor 3 (ATF3) is a TLR-induced repressor that plays an important role in the inhibition of specific inflammatory signals. We previously constructed recombinant high density lipoproteins (rHDL) (including rHDL_WT, rHDL_M, rHDL₂₂₈ and rHDL₇₄) and found that rHDL₇₄ had a strong anti-inflammatory ability. In the present study, we investigate the roles of recombinant apolipoprotein A-I (ApoA-I) (rHDL_WT) and its cysteine mutant HDLs (rHDL_M, rHDL₂₂₈ and rHDL₇₄) on ATF3 function in RAW264.7 cells stimulated by lipopolysaccharide. Our results showed that compared with the LPS group, rHDL₇₄ can decrease the level of TNF-α and IL-6, whereas rHDL₂₂₈ increases their expression levels. RT-PCR and Western blotting results showed that compared with the LPS group, rHDL₇₄, rHDL_WT and rHDL_M can markedly increase the expression level of ATF3, whereas the level of ATF3 decreases in the rHDL₂₂₈ group. In summary, the different anti-inflammatory mechanisms of the ApoA-I cysteine mutants might be associated with the regulation of ATF3 level.

Myeloperoxidase-oxidized high density lipoprotein impairs atherosclerotic plaque stability by inhibiting smooth muscle cell migration

Background

High density lipoprotein (HDL) has been proved to be a protective factor for coronary heart disease. Notably, HDL in atherosclerotic plaques can be nitrated (NO₂-oxHDL) and chlorinated (Cl-oxHDL) by myeloperoxidase (MPO), likely compromising its cardiovascular protective effects.

Method

Here we determined the effects of NO₂-oxHDL and Cl-oxHDL on SMC migration using wound healing and transwell assays, proliferation using MTT and BrdU assays, and apoptosis using Annexin-V assay in vitro, as well as on atherosclerotic plaque stability in vivo using a coratid artery collar implantation mice model.

Results

Our results showed that native HDL promoted SMC proliferation and migration, whereas NO₂-oxHDL and Cl-oxHDL inhibited SMC migration and reduced capacity of stimulating SMC proliferation as well as migration, respectively. OxHDL had no significant influence on SMC apoptosis. In addition, we found that ERK1/2-phosphorylation was significantly lower when SMCs were incubated with NO₂-oxHDL and Cl-oxHDL. Furthermore, transwell experiments showed that differences between native HDL, NO₂-oxHDL and Cl-oxHDL was abolished after PD98059 (MAPK kinase inhibitor) treatment. In aortic SMCs from scavenger receptor BI (SR-BI) deficient mice, differences between migration of native HDL, NO₂-oxHDL and Cl-oxHDL treated SMCs vanished, indicating SR-BI’s possible role in HDL-associated SMC migration. Importantly, NO₂-oxHDL and Cl-oxHDL induced neointima formation and reduced SMC positive staining cells in atherosclerotic plaque, resulting in elevated vulnerable index of atherosclerotic plaque.

Conclusion

These findings implicate MPO-catalyzed oxidization of HDL may contribute to atherosclerotic plaque instability by inhibiting SMC proliferation and migration through MAPK-ERK pathway which was dependent on SR-BI.

Electronic supplementary material

The online version of this article (doi:10.1186/s12944-016-0388-z) contains supplementary material, which is available to authorized users.

Recombinant HDL (Milano) protects endotoxin-challenged rats from multiple organ injury and dysfunction

Endotoxemia, the systemic inflammatory host response to infection, leads to severe septic shock and multiple organ injury and dysfunction syndrome (MOPS), which cause mortality. Apolipoprotein A-IMilano (apoAIM), a naturally occurring cysteine mutant of apoAI with dimers as its effective form, showed an enhanced cardiovascular protective activity compared with wild-type apoAI (apoAIwt). To investigate the role of recombinant high-density lipoprotein (rHDL) reconstituted with apoAIM (rHDLM) on endotoxemia and MOPS, we examined the anti-inflammatory, anti-oxidant, and protective effects of this cysteine mutant against organ injury in endotoxin-challenged rat models compared with rHDLwt. In the present study, we demonstrated for the first time that pretreatment with rHDLM significantly attenuated liver and renal dysfunction and histopathological features of lung injury in endotoxin-challenged endotoxemia rats. Administration of rHDLM to endotoxemia rats dramatically suppressed proinflammatory cytokines and adhesion molecule increase in tumor necrosis factor α, interleukin 1β, interleukin 6, and intercellular adhesion molecule 1. In addition, rHDLM pretreatment inhibited lipid peroxidation and enhanced total antioxidant capacity in vivo. In comparison with rHDLwt, rHDLM showed enhanced capacity on anti-inflammatory and anti-oxidant functions. In summary, administration of rHDLM protected endotoxin-challenged endotoxemia and MOPS through enhanced anti-inflammatory and anti-oxidant properties.

Animal models of surgically manipulated flow velocities to study shear stress-induced atherosclerosis

Atherosclerosis is a chronic inflammatory disease of the arterial tree that develops at predisposed sites, coinciding with locations that are exposed to low or oscillating shear stress. Manipulating flow velocity, and concomitantly shear stress, has proven adequate to promote endothelial activation and subsequent plaque formation in animals. In this article, we will give an overview of the animal models that have been designed to study the causal relationship between shear stress and atherosclerosis by surgically manipulating blood flow velocity profiles. These surgically manipulated models include arteriovenous fistulas, vascular grafts, arterial ligation, and perivascular devices. We review these models of manipulated blood flow velocity from an engineering and biological perspective, focusing on the shear stress profiles they induce and the vascular pathology that is observed.

Functionality of HDL: antioxidation and detoxifying effects

High-density lipoproteins (HDL) are complexes of multiple talents, some of which have only recently been recognised but all of which are under active investigation. Clinical interest initially arose from their amply demonstrated role in atherosclerotic disease with their consequent designation as a major cardiovascular disease (CVD) risk factor. However, interest is no longer confined to vascular tissues, with the reports of impacts of the lipoprotein on pancreatic, renal and nervous tissues, amongst other possible targets. The ever-widening scope of HDL talents also encompasses environmental hazards, including infectious agents and environmental toxins. In almost all cases, HDL would appear to have a beneficial impact on health. It raises the intriguing question of whether these various talents emanate from a basic ancestral function to protect the cell.The following chapter will illustrate and review our current understanding of some of the functions attributed to HDL. The first section will look at the antioxidative functions of HDL and possible mechanisms that are involved. The second section will focus specifically on paraoxonase-1 (PON1), which appears to bridge the divide between the two HDL functions discussed herein. This will lead into the final section dealing with HDL as a detoxifying agent protecting against exposure to environmental pathogens and other toxins.

Mononuclear cell therapy reverts cuff-induced thrombosis in apolipoprotein E-deficient mice

Background

Stem/progenitor cell-based therapy has successfully been used as a novel therapeutic strategy for vascular diseases triggered by endothelial dysfunction. The aim of this study was to investigate the effects of mononuclear cell (MNC) therapy in situ on carotid cuff-induced occlusive thrombus in the apolipoprotein E knockout (apoE^-/-) mouse.

Methods

Spleen-derived MNCs were isolated from green fluorescent protein (GFP)-transgenic mice for cell treatment. A cuff-induced thrombus model was produced by placing a nonconstrictive silastic collar around the left common carotid artery in 20-week-old female apoE^-/- mice. After 10 days, the cuff was removed, and the animals received in situ MNCs (Cuff-MNC) or vehicle (Cuff-Vehicle) and were compared with sham-operated animals (Sham).

Results

The histological analysis showed that the MNC treatment reverted occlusive thrombus formation compared to the vehicle and the vessel lumen area to that observed in the Sham group (MNC, 50 ± 4; Vehicle, 20 ± 4; Sham, 55 ± 2 x10³ μm²; p < 0.01). The animals that underwent the carotid cuff placement developed compensatory vessel enlargement, which was reduced by the MNC therapy. In addition, the treatment was able to reduce superoxide anion production, which likely contributed to the reduced apoptosis that was observed. Lastly, the immunofluorescence analysis revealed the presence of endothelial progenitor cells (EPCs) in the carotid endothelia of the apoE^-/- mice.

Conclusion

In situ short-term MNC therapy was able to revert cuff-induced occlusive thrombi in the carotid arteries of apoE^-/- mice, possibly through the homing of EPCs, reduction of oxidative stress and decreased apoptosis.