Synthetic high-density lipoproteins delivering liver X receptor agonist prevent atherogenesis by enhancing reverse cholesterol transport

Liver X nuclear receptor (LXR) agonists are promising anti-atherosclerotic agents that increase the expression of cholesterol transporters on atheroma macrophages leading to increased efflux of cholesterol to endogenous high-density lipoprotein (HDL) acceptors. HDL subsequently delivers effluxed cholesterol to the liver by the process of reverse cholesterol transport, resulting in reduction of atherosclerotic plaques. However, LXR agonists administration triggers undesirable liver steatosis and hypertriglyceridemia due to increased fatty acid and sterol synthesis. LXR-induced liver toxicity, poor drug aqueous solubility and low levels of endogenous HDL acceptors in target patient populations limit the clinical translation of LXR agonists. Here, we propose a dual-antiatherogenic strategy for administration of the LXR agonist, T0901317 (T1317), by encapsulating in synthetic HDL (sHDL) nanoparticles. sHDL had been clinically proven to serve as cholesterol acceptors, resulting in plaque reduction in atherosclerosis patients. In addition, the hydrophobic core and endogenous atheroma-targeting ability of sHDL allow for encapsulation of water-insoluble drugs and their subsequent delivery to atheroma. Several compositions of sHDL were tested to optimize both T1317 encapsulation efficiency and ability of T1317-sHDL to efflux cholesterol. Optimized T1317-sHDL exhibited more efficient cholesterol efflux from macrophages and enhanced atheroma-targeting relative to free drug. Most importantly, in an apolipoprotein E deficient (ApoE-/-) atherosclerosis progression murine model, T1317-sHDL showed superior inhibition of atherogenesis and reduced hypertriglyceridemia side effects in comparison to the free drug and blank sHDL. The T1317-sHDL pharmacological efficacy was observed at doses lower than those previously described for LXR agents, which may have additional safety benefits. In addition, the established clinical manufacturing, safety and efficacy of blank sHDL nanoparticles used in this study could facilitate future clinical translation of LXR-loaded sHDLs.

Transcription factor EB regulates cardiovascular homeostasis

Cardiovascular diseases (CVDs) are the leading cause of death and a major cause of disability globally. Transcription factor EB (TFEB), as a member of the microphthalmia transcription factor (MITF) family, has been demonstrated to be a master regulator of autophagy and lysosomal biogenesis. Emerging studies suggest that TFEB regulates homeostasis in the cardiovascular system and shows beneficial effects on CVDs, including atherosclerosis, aortic aneurysm, postischemic angiogenesis, and cardiotoxicity, constituting a promising molecular target for the prevention and treatment of these diseases. Post-translational modifications regulate TFEB nuclear translocation and its transcriptional activity. Therapeutic strategies have been pursued to enhance TFEB activity and facilitate TFEB beneficial effects on CVDs. The elucidation of TFEB function and the precise underlying mechanisms will accelerate drug development and potential applications of TFEB drugs in the treatment of human diseases.

Genome engineering technologies in rabbits

The rabbit has been recognized as a valuable model in various biomedical and biological research fields because of its intermediate size and phylogenetic proximity to primates. However, the technology for precise genome manipulations in rabbit has been stalled for decades, severely limiting its applications in biomedical research. Novel genome editing technologies, especially CRISPR/Cas9, have remarkably enhanced precise genome manipulation in rabbits, and shown their superiority and promise for generating rabbit models of human genetic diseases. In this review, we summarize the brief history of transgenic rabbit technology and the development of novel genome editing technologies in rabbits.

Human apolipoprotein A-II reduces atherosclerosis in knock-in rabbits

BACKGROUND AND AIMS

Apolipoprotein A-II (apoAII) is the second major apolipoprotein of the high-density lipoprotein (HDL) particle, after apoAI. Unlike apoAI, the biological and physiological functions of apoAII are unclear. We aimed to gain insight into the specific roles of apoAII in lipoprotein metabolism and atherosclerosis using a novel rabbit model.

METHODS

Wild-type (WT) rabbits are naturally deficient in apoAII, thus their HDL contains only apoAI. Using TALEN technology, we replaced the endogenous apoAI in rabbits through knock-in (KI) of human apoAII. The newly generated apoAII KI rabbits were used to study the specific function of apoAII, independent of apoAI.

RESULTS

ApoAII KI rabbits expressed exclusively apoAII without apoAI, as confirmed by RT-PCR and Western blotting. On a standard diet, the KI rabbits exhibited lower plasma triglycerides (TG, 52%, p < 0.01) due to accelerated clearance of TG-rich particles and higher lipoprotein lipase activity than the WT littermates. ApoAII KI rabbits also had higher plasma HDL-C (28%, p < 0.05) and their HDL was rich in apoE, apoAIV, and apoAV. When fed a cholesterol-rich diet for 16 weeks, apoAII KI rabbits were resistant to diet-induced hypertriglyceridemia and developed significantly less aortic atherosclerosis compared to WT rabbits. HDL isolated from rabbits with apoAII KI had similar cholesterol efflux capacity and anti-inflammatory effects as HDL isolated from the WT rabbits.

CONCLUSIONS

ApoAII KI rabbits developed less atherosclerosis than WT rabbits, possibly through increased plasma HDL-C, reduced TG and atherogenic lipoproteins. These results suggest that apoAII may serve as a potential target for the treatment of atherosclerosis.

Loss-of-function genomic variants highlight potential therapeutic targets for cardiovascular disease

Pharmaceutical drugs targeting dyslipidemia and cardiovascular disease (CVD) may increase the risk of fatty liver disease and other metabolic disorders. To identify potential novel CVD drug targets without these adverse effects, we perform genome-wide analyses of participants in the HUNT Study in Norway (n = 69,479) to search for protein-altering variants with beneficial impact on quantitative blood traits related to cardiovascular disease, but without detrimental impact on liver function. We identify 76 (11 previously unreported) presumed causal protein-altering variants associated with one or more CVD- or liver-related blood traits. Nine of the variants are predicted to result in loss-of-function of the protein. This includes ZNF529:p.K405X, which is associated with decreased low-density-lipoprotein (LDL) cholesterol (P = 1.3 × 10-8) without being associated with liver enzymes or non-fasting blood glucose. Silencing of ZNF529 in human hepatoma cells results in upregulation of LDL receptor and increased LDL uptake in the cells. This suggests that inhibition of ZNF529 or its gene product should be prioritized as a novel candidate drug target for treating dyslipidemia and associated CVD.

Glycine-based treatment ameliorates NAFLD by modulating fatty acid oxidation, glutathione synthesis, and the gut microbiome

Nonalcoholic fatty liver disease (NAFLD) including nonalcoholic steatohepatitis (NASH) has reached epidemic proportions with no pharmacological therapy approved. Lower circulating glycine is consistently reported in patients with NAFLD, but the causes for reduced glycine, its role as a causative factor, and its therapeutic potential remain unclear. We performed transcriptomics in livers from humans and mice with NAFLD and found suppression of glycine biosynthetic genes, primarily alanine-glyoxylate aminotransferase 1 (AGXT1). Genetic (Agxt1 -/- mice) and dietary approaches to limit glycine availability resulted in exacerbated diet-induced hyperlipidemia and steatohepatitis, with suppressed mitochondrial/peroxisomal fatty acid β-oxidation (FAO) and enhanced inflammation as the underlying pathways. We explored glycine-based compounds with dual lipid/glucose-lowering properties as potential therapies for NAFLD and identified a tripeptide (Gly-Gly-L-Leu, DT-109) that improved body composition and lowered circulating glucose, lipids, transaminases, proinflammatory cytokines, and steatohepatitis in mice with established NASH induced by a high-fat, cholesterol, and fructose diet. We applied metagenomics, transcriptomics, and metabolomics to explore the underlying mechanisms. The bacterial genus Clostridium sensu stricto was markedly increased in mice with NASH and decreased after DT-109 treatment. DT-109 induced hepatic FAO pathways, lowered lipotoxicity, and stimulated de novo glutathione synthesis. In turn, inflammatory infiltration and hepatic fibrosis were attenuated via suppression of NF-κB target genes and TGFβ/SMAD signaling. Unlike its effects on the gut microbiome, DT-109 stimulated FAO and glutathione synthesis independent of NASH. In conclusion, impaired glycine metabolism may play a causative role in NAFLD. Glycine-based treatment attenuates experimental NAFLD by stimulating hepatic FAO and glutathione synthesis, thus warranting clinical evaluation.

MiCas9 increases large size gene knock-in rates and reduces undesirable on-target and off-target indel edits

Gene editing nuclease represented by Cas9 efficiently generates DNA double strand breaks at the target locus, followed by repair through either the error-prone non-homologous end joining or the homology directed repair pathways. To improve Cas9's homology directed repair capacity, here we report the development of miCas9 by fusing a minimal motif consisting of thirty-six amino acids to spCas9. MiCas9 binds RAD51 through this fusion motif and enriches RAD51 at the target locus. In comparison to spCas9, miCas9 enhances double-stranded DNA mediated large size gene knock-in rates, systematically reduces off-target insertion and deletion events, maintains or increases single-stranded oligodeoxynucleotides mediated precise gene editing rates, and effectively reduces on-target insertion and deletion rates in knock-in applications. Furthermore, we demonstrate that this fusion motif can work as a "plug and play" module, compatible and synergistic with other Cas9 variants. MiCas9 and the minimal fusion motif may find broad applications in gene editing research and therapeutics.

MEPE loss-of-function variant associates with decreased bone mineral density and increased fracture risk

A major challenge in genetic association studies is that most associated variants fall in the non-coding part of the human genome. We searched for variants associated with bone mineral density (BMD) after enriching the discovery cohort for loss-of-function (LoF) mutations by sequencing a subset of the Nord-Trøndelag Health Study, followed by imputation in the remaining sample (N = 19,705), and identified ten known BMD loci. However, one previously unreported variant, LoF mutation in MEPE, p.(Lys70IlefsTer26, minor allele frequency [MAF] = 0.8%), was associated with decreased ultradistal forearm BMD (P-value = 2.1 × 10⁻¹⁸), and increased osteoporosis (P-value = 4.2 × 10⁻⁵) and fracture risk (P-value = 1.6 × 10⁻⁵). The MEPE LoF association with BMD and fractures was further evaluated in 279,435 UK (MAF = 0.05%, heel bone estimated BMD P-value = 1.2 × 10⁻¹⁶, any fracture P-value = 0.05) and 375,984 Icelandic samples (MAF = 0.03%, arm BMD P-value = 0.12, forearm fracture P-value = 0.005). Screening for the MEPE LoF mutations before adulthood could potentially prevent osteoporosis and fractures due to the lifelong effect on BMD observed in the study. A key implication for precision medicine is that high-impact functional variants missing from the publicly available cosmopolitan panels could be clinically more relevant than polygenic risk scores.

Bone mineral density (BMD) is associated with fracture risk and many genetic loci with small effect sizes have been discovered by genome-wide association studies (GWAS). Here, the authors discover a large-effect rare loss-of-function genetic variant for BMD in the MEPE gene in the Norwegian HUNT study which replicates in the UK Biobank.

BAF60a Deficiency in Vascular Smooth Muscle Cells Prevents Abdominal Aortic Aneurysm by Reducing Inflammation and Extracellular Matrix Degradation

OBJECTIVE

Currently, there are no approved drugs for abdominal aortic aneurysm (AAA) treatment, likely due to limited understanding of the primary molecular mechanisms underlying AAA development and progression. BAF60a-a unique subunit of the SWI/SNF (switch/sucrose nonfermentable) chromatin remodeling complex-is a novel regulator of metabolic homeostasis, yet little is known about its function in the vasculature and pathogenesis of AAA. In this study, we sought to investigate the role and underlying mechanisms of vascular smooth muscle cell (VSMC)-specific BAF60a in AAA formation. Approach and Results: BAF60a is upregulated in human and experimental murine AAA lesions. In vivo studies revealed that VSMC-specific knockout of BAF60a protected mice from both Ang II (angiotensin II)-induced and elastase-induced AAA formation with significant suppression of vascular inflammation, monocyte infiltration, and elastin fragmentation. Through RNA sequencing and pathway analysis, we found that the expression of inflammatory response genes in cultured human aortic smooth muscle cells was significantly downregulated by small interfering RNA-mediated BAF60a knockdown while upregulated upon adenovirus-mediated BAF60a overexpression. BAF60a regulates VSMC inflammation by recruiting BRG1 (Brahma-related gene-1)-a catalytic subunit of the SWI/SNF complex-to the promoter region of NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells) target genes. Furthermore, loss of BAF60a in VSMCs prevented the upregulation of the proteolytic enzyme cysteine protease CTSS (cathepsin S), thus ameliorating ECM (extracellular matrix) degradation within the vascular wall in AAA.

CONCLUSIONS

Our study demonstrated that BAF60a is required to recruit the SWI/SNF complex to facilitate the epigenetic regulation of VSMC inflammation, which may serve as a potential therapeutic target in preventing and treating AAA.

Apolipoprotein CIII Deficiency Protects Against Atherosclerosis in Knockout Rabbits

OBJECTIVE

Apo (apolipoprotein) CIII mediates the metabolism of triglyceride (TG)-rich lipoproteins. High levels of plasma apoCIII are positively correlated with the plasma TG levels and increase the cardiovascular risk. However, whether apoCIII is directly involved in the development of atherosclerosis has not been fully elucidated. Approach and Results: To examine the possible roles of apoCIII in lipoprotein metabolism and atherosclerosis, we generated apoCIII KO (knockout) rabbits using ZFN (zinc finger nuclease) technique. On a normal standard diet, apoCIII KO rabbits exhibited significantly lower plasma levels of TG than those of WT (wild type) rabbits while total cholesterol and HDL (high-density lipoprotein) cholesterol levels were unchanged. Analysis of lipoproteins isolated by sequential ultracentrifugation revealed that reduced plasma TG levels in KO rabbits were accompanied by prominent reduction of VLDLs (very-low-density lipoproteins) and IDLs (intermediate-density lipoproteins). In addition, KO rabbits showed faster TG clearance rate after intravenous fat load than WT rabbits. On a cholesterol-rich diet, KO rabbits exhibited constantly and significantly lower levels of plasma total cholesterol and TG than WT rabbits, which was caused by a remarkable reduction of β-VLDLs-the major atherogenic lipoproteins. β-VLDLs of KO rabbits showed higher uptake by cultured hepatocytes and were cleared faster from the circulation than β-VLDLs isolated from WT rabbits. Both aortic and coronary atherosclerosis was significantly reduced in KO rabbits compared with WT rabbits.

CONCLUSIONS

These results indicate that apoCIII deficiency facilitates TG-rich lipoprotein catabolism, and therapeutic inhibition of apoCIII expression may become a novel means not only for the treatment of hyperlipidemia but also for atherosclerosis.

Causal relationships between NAFLD, T2D and obesity have implications for disease subphenotyping

BACKGROUND & AIMS

Non-alcoholic fatty liver disease (NAFLD), type 2 diabetes (T2D) and obesity are epidemiologically correlated with each other but the causal inter-relationships between them remain incompletely understood. We aimed to explore the causal relationships between the 3 diseases.

METHODS

Using both UK Biobank and publicly available genome-wide association study data, we performed a 2-sample bidirectional Mendelian randomization analysis to test the causal inter-relationships between NAFLD, T2D, and obesity. Transgenic mice expressing the human PNPLA3-I148M isoforms (TghPNPLA3-I148M) were used as an example to validate causal effects and explore underlying mechanisms.

RESULTS

Genetically driven NAFLD significantly increased the risk of T2D and central obesity but not insulin resistance or generalized obesity, while genetically driven T2D, body mass index and WHRadjBMI causally increased NAFLD risk. The animal study focusing on PNPLA3 corroborated these causal effects: compared to the TghPNPLA3-I148I controls, the TghPNPLA3-I148M mice developed glucose intolerance and increased visceral fat, but maintained normal insulin sensitivity, reduced body weight, and decreased circulating total cholesterol. Mechanistically, the TghPNPLA3-I148M mice demonstrated decreased pancreatic insulin but increased glucagon secretion, which was associated with increased pancreatic inflammation. In addition, transcription of hepatic cholesterol biosynthesis pathway genes was significantly suppressed, while transcription of thermogenic pathway genes was activated in subcutaneous and brown adipose tissues but not in visceral fat in TghPNPLA3-I148M mice.

CONCLUSIONS

Our study suggests that lifelong, genetically driven NAFLD causally promotes T2D with a late-onset type 1-like diabetic subphenotype and central obesity; while genetically driven T2D, obesity, and central obesity all causally increase the risk of NAFLD. This causal relationship revealed new insights into how nature and nurture drive these diseases, providing novel hypotheses for disease subphenotyping.

LAY SUMMARY

Non-alcoholic fatty liver disease, type 2 diabetes and obesity are epidemiologically correlated with each other, but their causal relationships were incompletely understood. Herein, we identified causal relationships between these conditions, which suggest that each of these closely related diseases should be further stratified into subtypes. This is important for accurate diagnosis, prevention and treatment of these diseases.

TMAVA, a Metabolite of Intestinal Microbes, Is Increased in Plasma From Patients With Liver Steatosis, Inhibits γ-Butyrobetaine Hydroxylase, and Exacerbates Fatty Liver in Mice

BACKGROUND & AIMS

Nonalcoholic fatty liver disease is characterized by excessive hepatic accumulation of triglycerides. We aimed to identify metabolites that differ in plasma of patients with liver steatosis vs healthy individuals (controls) and investigate the mechanisms by which these might contribute to fatty liver in mice.

METHODS

We obtained blood samples from 15 patients with liver steatosis and 15 controls from a single center in China (discovery cohort). We performed untargeted liquid chromatography with mass spectrometry analysis of plasma to identify analytes associated with liver steatosis. We then performed targeted metabolomic analysis of blood samples from 2 independent cohorts of individuals who underwent annual health examinations in China (1157 subjects with or without diabetes and 767 subjects with or without liver steatosis; replication cohorts). We performed mass spectrometry analysis of plasma from C57BL/6J mice, germ-free, and mice given antibiotics. C57BL/6J mice were given 0.325% (m/v) N,N,N-trimethyl-5-aminovaleric acid (TMAVA) in their drinking water and placed on a 45% high-fat diet (HFD) for 2 months. Plasma, liver tissues, and fecal samples were collected; fecal samples were analyzed by 16S ribosomal RNA gene sequencing. C57BL/6J mice with CRISPR-mediated disruption of the gene encoding γ-butyrobetaine hydroxylase (BBOX-knockout mice) were also placed on a 45% HFD for 2 months. Hepatic fatty acid oxidation (FAO) in liver tissues was determined by measuring liberation of ³H₂O from [³H] palmitic acid. Liver tissues were analyzed by electron microscopy, to view mitochondria, and proteomic analyses. We used surface plasmon resonance analysis to quantify the affinity of TMAVA for BBOX.

RESULTS

Levels of TMAVA, believed to be a metabolite of intestinal microbes, were increased in plasma from subjects with liver steatosis compared with controls, in the discovery and replication cohorts. In 1 replication cohort, the odds ratio for fatty liver in subjects with increased liver plasma levels of TMAVA was 1.82 (95% confidence interval [CI], 1.14-2.90; P = .012). Plasma from mice given antibiotics or germ-free mice had significant reductions in TMAVA compared with control mice. We found the intestinal bacteria Enterococcus faecalis and Pseudomonas aeruginosa to metabolize trimethyllysine to TMAVA; levels of trimethyllysine were significantly higher in plasma from patients with steatosis than controls. We found TMAVA to bind and inhibit BBOX, reducing synthesis of carnitine. Mice given TMAVA had alterations in their fecal microbiomes and reduced cold tolerance; their plasma and liver tissue had significant reductions in levels of carnitine and acyl-carnitine and their hepatocytes had reduced mitochondrial FAO compared with mice given only an HFD. Mice given TMAVA on an HFD developed liver steatosis, which was reduced by carnitine supplementation. BBOX-knockout mice had carnitine deficiency and decreased FAO, increasing uptake and liver accumulation of free fatty acids and exacerbating HFD-induced fatty liver.

CONCLUSIONS

Levels of TMAVA are increased in plasma from subjects with liver steatosis. In mice, intestinal microbes metabolize trimethyllysine to TMAVA, which reduces carnitine synthesis and FAO to promote steatosis.

Endothelial Lipase Exerts its Anti-Atherogenic Effect through Increased Catabolism of β-VLDLs

Aim: Endothelial lipase (EL) plays an important role in lipoprotein metabolism. Our recent study showed that increased hepatic expression of EL attenuates diet-induced hypercholesterolemia, thus subsequently reducing atherosclerosis in transgenic (Tg) rabbits. However, it is yet to be determined whether increased EL activity itself per se is anti-atherogenic or whether the anti-atherogenic effect of EL is exclusively dependent on its lipid-lowering effect.

Methods: To determine the mechanisms underlying EL-mediated anti-atherogenic effect, we fed Tg and non-Tg rabbits diets containing different amounts of cholesterol to make their plasma cholesterol levels similarly high. Sixteen weeks later, we examined their lipoprotein profiles and compared their susceptibility to atherosclerosis.

Results: With Tg and non-Tg rabbits having hypercholesterolemia, the plasma lipids and lipoprotein profiles were observed to be similar, while pathological examinations revealed that lesion areas of both aortic and coronary atherosclerosis of Tg rabbits were not significantly different from non-Tg rabbits. Moreover, Tg rabbits exhibited faster clearance of DiI-labeled β-VLDLs than non-Tg rabbits.

Conclusion: The results of our study suggest that the enhancement of β-VLDL catabolism is the major mechanism for atheroprotective effects of EL in Tg rabbits.

In Vitro Lineage-Specific Differentiation of Vascular Smooth Muscle Cells in Response to SMAD3 Deficiency: Implications for SMAD3-Related Thoracic Aortic Aneurysm

OBJECTIVE

SMAD3 pathogenic variants are associated with the development of thoracic aortic aneurysms. We sought to determine the role of SMAD3 in lineage-specific vascular smooth muscle cells (VSMCs) differentiation and function. Approach and Results: SMAD3 c.652delA, a frameshift mutation and nonsense-mediated decay, was introduced in human-induced pluripotent stem cells using CRISPR-Cas9. The wild-type and SMAD3^-/- (c.652delA) human-induced pluripotent stem cells were differentiated into cardiovascular progenitor cells or neural crest stem cells and then to lineage-specific VSMCs. Differentiation, contractility, extracellular matrix synthesis, and TGF-β (transforming growth factor-β) signaling of the differentiated VSMCs were analyzed. The homozygous frameshift mutation resulted in SMAD3 deficiency and was confirmed in human-induced pluripotent stem cells by Sanger sequencing and immunoblot analysis. In cardiovascular progenitor cell-VSMCs, SMAD3 deletion significantly disrupted canonical TGF-β signaling and decreased gene expression of VSMC markers, including SM α-actin, myosin heavy chain 11, calponin-1, SM22α, and key controlling factors, SRF and myocardin, but increased collagen expression. The loss of SMAD3 significantly decreased VSMC contractility. In neural crest stem cells-VSMCs, SMAD3 deficiency did not significantly affect the VSMC differentiation but decreased ELN (elastin) expression and increased phosphorylated SMAD2. Expression of mir-29 was increased in SMAD3^-/- VSMCs, and inhibition of mir-29 partially rescued ELN expression.

CONCLUSIONS

SMAD3-dependent TGF-β signaling was essential for the differentiation of cardiovascular progenitor cell-VSMCs but not for the differentiation of neural crest stem cell-VSMCs. The lineage-specific TGF-β responses in human VSMCs may potentially contribute to the development of aortic root aneurysms in patients with SMAD3 mutations.

Cyclodextrin Prevents Abdominal Aortic Aneurysm via Activation of Vascular Smooth Muscle Cell Transcription Factor EB

BACKGROUND

Abdominal aortic aneurysm (AAA) is a severe aortic disease with a high mortality rate in the event of rupture. Pharmacological therapy is needed to inhibit AAA expansion and prevent aneurysm rupture. Transcription factor EB (TFEB), a master regulator of autophagy and lysosome biogenesis, is critical to maintain cell homeostasis. In this study, we aim to investigate the role of vascular smooth muscle cell (VSMC) TFEB in the development of AAA and establish TFEB as a novel target to treat AAA.

METHODS

The expression of TFEB was measured in human and mouse aortic aneurysm samples. We used loss/gain-of-function approaches to understand the role of TFEB in VSMC survival and explored the underlying mechanisms through transcriptome and functional studies. Using VSMC-selective Tfeb knockout mice and different mouse AAA models, we determined the role of VSMC TFEB and a TFEB activator in AAA in vivo.

RESULTS

We found that TFEB is downregulated in both human and mouse aortic aneurysm lesions. TFEB potently inhibits apoptosis in VSMCs, and transcriptome analysis revealed that TFEB regulates apoptotic signaling pathways, especially apoptosis inhibitor B-cell lymphoma 2. B-cell lymphoma 2 is significantly upregulated by TFEB and is required for TFEB to inhibit VSMC apoptosis. We consistently observed that TFEB deficiency increases VSMC apoptosis and promotes AAA formation in different mouse AAA models. Furthermore, we demonstrated that 2-hydroxypropyl-β-cyclodextrin, a clinical agent used to enhance the solubility of drugs, activates TFEB and inhibits AAA formation and progression in mice. Last, we found that 2-hydroxypropyl-β-cyclodextrin inhibits AAA in a VSMC TFEB-dependent manner in mouse models.

CONCLUSIONS

Our study demonstrated that TFEB protects against VSMC apoptosis and AAA. TFEB activation by 2-hydroxypropyl-β-cyclodextrin may be a promising therapeutic strategy for the prevention and treatment of AAA.

Macrophage M2 polarization induced by exosomes from adipose-derived stem cells contributes to the exosomal proangiogenic effect on mouse ischemic hindlimb

BACKGROUND

M2 macrophages and exosomes from adipose-derived stem cells (ASCs) are both reported to promote angiogenesis. However, the possible synergistic effects between exogenous exosomes and endogenous M2 macrophages are poorly understood.

METHODS

Exosomes were isolated from conditioned medium of normoxic and hypoxic ASCs using the combined techniques of ultrafiltration and size-exclusion chromatography and were identified with nanoparticle tracking analysis and immunoblotting for exosomal markers. Macrophages were collected from the mouse peritoneal cavity. M1 and M2 macrophages were detected by immunoblotting for the intracellular markers inducible nitric oxide synthase (iNOS) and arginase-1 (Arg-1) and by flow cytometry for the surface markers F4/80, CD86, and CD206. Murine models of Matrigel plug and hindlimb ischemia were employed as in vivo angiogenic assays.

RESULTS

When M1 macrophages were treated with exosomes from normoxic ASCs (Nor/Exo), and particularly from hypoxic ASCs (Hyp/Exo), the expression of the M1 marker iNOS decreased, and the M2 marker Arg-1 increased in a time- and dose-dependent manner. Additionally, a decrease in the M1 surface marker CD86 and an increase in the M2 surface marker CD206 were observed, which suggested that M1 macrophages were polarized to an M2-like phenotype. Conditioned medium from these M2-like macrophages presented lower levels of proinflammatory cytokines and higher levels of proangiogenic factors and promoted endothelial cell proliferation, migration, and tube formation. Furthermore, M2 polarization and angiogenesis were induced upon the administration of exosomes in mouse Matrigel plug and hindlimb ischemia (HLI) models. Interestingly, these exosomal effects were attenuated by using a colony stimulating factor 1 receptor (CSF-1R) inhibitor, BLZ945, in vitro and in vivo. Downregulation of microRNA-21 (miR-21) in hypoxic ASCs reduced the exosomal effects on M2 polarization, Akt phosphorylation, and CSF-1 secretion. A similar reduction in exosomal activity was also observed when exosomes were administered along with BLZ945.

CONCLUSION

Our findings provide evidence that exosomes from ASCs polarize macrophages toward an M2-like phenotype, which further enhances the exosomal proangiogenic effects. Exosomal delivery of miR-21 and positive feedback of secreted CSF-1 may be involved in macrophage polarization.

Endothelium-targeted overexpression of Krüppel-like factor 11 protects the blood-brain barrier function after ischemic brain injury

Microvascular endothelial cell (EC) injury and the subsequent blood-brain barrier (BBB) breakdown are frequently seen in many neurological disorders, including stroke. We have previously documented that peroxisome proliferator-activated receptor gamma (PPARγ)-mediated cerebral protection during ischemic insults needs Krüppel-like factor 11 (KLF11) as a critical coactivator. However, the role of endothelial KLF11 in cerebrovascular function and stroke outcome is unclear. This study is aimed at investigating the regulatory role of endothelial KLF11 in BBB preservation and neurovascular protection after ischemic stroke. EC-targeted overexpression of KLF11 significantly mitigated BBB leakage in ischemic brains, evidenced by significantly reduced extravasation of BBB tracers and infiltration of peripheral immune cells, and less brain water content. Endothelial cell-selective KLF11 transgenic (EC-KLF11 Tg) mice also exhibited smaller brain infarct and improved neurological function in response to ischemic insults. Furthermore, EC-targeted transgenic overexpression of KLF11 preserved cerebral tight junction (TJ) levels and attenuated the expression of pro-inflammatory factors in mice after ischemic stroke. Mechanistically, we demonstrated that KLF11 directly binds to the promoter of major endothelial TJ proteins including occludin and ZO-1 to promote their activities. Our data indicate that KLF11 functions at the EC level to preserve BBB structural and functional integrity, and therefore, confers brain protection in ischemic stroke. KLF11 may be a novel therapeutic target for the treatment of ischemic stroke and other neurological conditions involving BBB breakdown and neuroinflammation.

Clopidogrel Resistance in a Murine Model of Diet-Induced Obesity Is Mediated by the Interleukin-1 Receptor and Overcome With DT-678

OBJECTIVE

Clopidogrel is a commonly used P2Y₁₂ inhibitor to treat and prevent arterial thrombotic events. Clopidogrel is a prodrug that requires bioactivation by CYP (cytochrome P450) enzymes to exert antiplatelet activity. Diabetes mellitus is associated with an increased risk of ischemic events, and impaired ability to generate the active metabolite (AM) from clopidogrel. The objective of this study is to identify the mechanism of clopidogrel resistance in a murine model of diet-induced obesity (DIO). Approach and Results: C57BL/6J mice and IL-1R^-/- mice were given high-fat diet for 10 weeks to generate a murine model of diet-induced obesity. Platelet aggregation and carotid arterial thrombosis were assessed in response to clopidogrel treatment. Wild-type DIO mice exhibited resistance to antiplatelet and antithrombotic effects of clopidogrel that was associated with reduced hepatic expression of CYP genes and reduced generation of the AM. IL (Interleukin)-1 receptor-deficient DIO (IL1R^-/- DIO) mice showed no resistance to clopidogrel. Lack of resistance was accompanied by increased exposure of the clopidogrel AM. This resistance was also absent when wild-type DIO mice were treated with the conjugate of the clopidogrel AM, DT-678.

CONCLUSIONS

These findings indicate that antiplatelet effects of clopidogrel may be impaired in the setting of diabetes mellitus due to reduced prodrug bioactivation related to IL-1 receptor signaling. Therapeutic targeting of P2Y₁₂ in patients with diabetes mellitus using the conjugate of clopidogrel AM may lead to improved outcomes.

"The Secret Life of Human Donor Hearts": An Examination of Transcriptomic Events During Cold Storage

BACKGROUND

Ischemic tolerance of donor hearts has a major impact on the efficiency in utilization and clinical outcomes. Molecular events during storage may influence the severity of ischemic injury.

METHODS

RNA sequencing was used to study the transcriptional profile of the human left ventricle (LV, n=4) and right ventricle (RV, n=4) after 0, 4, and 8 hours of cold storage in histidine-tryptophan-ketoglutarate preservation solution. Gene set enrichment analysis and gene ontology analysis was used to examine transcriptomic changes with cold storage. Terminal deoxynucleotidyl transferase 2´-Deoxyuridine, 5´-Triphosphate nick end labeling and p65 staining was used to examine for cell death and NFκB activation, respectively.

RESULTS

The LV showed activation of genes related to inflammation and allograft rejection but downregulation of oxidative phosphorylation and fatty acid metabolism pathway genes. In contrast, inflammation-related genes were down-regulated in the RV and while oxidative phosphorylation genes were activated. These transcriptomic changes were most significant at the 8 hours with much lower differences observed between 0 and 4 hours. RNA velocity estimates corroborated the finding that immune-related genes were activated in the LV but not in the RV during storage. With increasing preservation duration, the LV showed an increase in nuclear translocation of NFκB (p65), whereas the RV showed increased cell death close to the endocardium especially at 8 hours.

CONCLUSIONS

Our results demonstrated that the LV and RV of human donor hearts have distinct responses to cold ischemic storage. Transcriptomic changes related to inflammation, oxidative phosphorylation, and fatty acid metabolism pathways as well as cell death and NFκB activation were most pronounced after 8 hours of storage.

Perivascular Adipose Tissue Regulates Vascular Function by Targeting Vascular Smooth Muscle Cells

Adipose tissues are present at multiple locations in the body. Most blood vessels are surrounded with adipose tissue which is referred to as perivascular adipose tissue (PVAT). Similarly to adipose tissues at other locations, PVAT harbors many types of cells which produce and secrete adipokines and other undetermined factors which locally modulate PVAT metabolism and vascular function. Uncoupling protein-1, which is considered as a brown fat marker, is also expressed in PVAT of rodents and humans. Thus, compared with other adipose tissues in the visceral area, PVAT displays brown-like characteristics. PVAT shows a distinct function in the cardiovascular system compared with adipose tissues in other depots which are not adjacent to the vascular tree. Growing and extensive studies have demonstrated that presence of normal PVAT is required to maintain the vasculature in a functional status. However, excessive accumulation of dysfunctional PVAT leads to vascular disorders, partially through alteration of its secretome which, in turn, affects vascular smooth muscle cells and endothelial cells. In this review, we highlight the cross talk between PVAT and vascular smooth muscle cells and its roles in vascular remodeling and blood pressure regulation.

Histidine-Tryptophan-Ketoglutarate Solution for Donor Heart Preservation Is Safe for Transplantation

BACKGROUND

Various solutions are used for donor heart preservation. We examined the outcomes in our heart transplant population where histidine-tryptophan-ketoglutarate (HTK) solution has been used for heart preservation since 2004.

METHODS

This was a retrospective review of the United Network for Organ Sharing (UNOS) database (2004-2016) comparing our heart transplant outcomes with other national centers. Propensity matching in a 1:3 ratio was performed to adjust for preoperative recipient variables.

RESULTS

After propensity matching comparing UNOS outcomes (n = 1080) with our institutional data (n = 360), there was no difference in matched preoperative variables. Donor hearts were similar for donor age, sex, donor-to-recipient size ratio, LVEF, and ischemic time. Our HTK cohort had a larger proportion with donor cardiac arrest (26.3% vs 6.1%, P < .001) and longer cardiac arrest duration (22.1 ± 16.0 vs 17.2 ± 14.0 minutes, P = .052). Our primary graft dysfunction (PGD) rate requiring mechanical support was 4.2% (n = 1). Postoperative mechanical support use for PGD included extracorporeal membrane oxygenation in 9 (60.0%), intraaortic balloon pump in 4 (26.7%), right ventricular assist device in 3 (20%), and biventricular assist device in 3 (20%). Overall survival at our institution was similar to the national average (P = .649). Survival at 1, 5, and 10 years with HTK was 92.2%, 81.3%, and 70.8%, and for the UNOS population was 91.6%, 80.3%, and 62.0%, respectively.

CONCLUSIONS

Use of HTK solution for donor hearts was associated with a low rate of severe PGD. Overall survival was not significantly different from other institutions using a variety of preservation solutions in the UNOS database during the same period. HTK solution is efficacious for preservation of donor hearts.

KLF11 (Krüppel-Like Factor 11) Inhibits Arterial Thrombosis via Suppression of Tissue Factor in the Vascular Wall

Objective- Mutations in Krüppel like factor-11 ( KLF11), a gene also known as maturity-onset diabetes mellitus of the young type 7, contribute to the development of diabetes mellitus. KLF11 has anti-inflammatory effects in endothelial cells and beneficial effects on stroke. However, the function of KLF11 in the cardiovascular system is not fully unraveled. In this study, we investigated the role of KLF11 in vascular smooth muscle cell biology and arterial thrombosis. Approach and Results- Using a ferric chloride-induced thrombosis model, we found that the occlusion time was significantly reduced in conventional Klf11 knockout mice, whereas bone marrow transplantation could not rescue this phenotype, suggesting that vascular KLF11 is critical for inhibition of arterial thrombosis. We further demonstrated that vascular smooth muscle cell-specific Klf11 knockout mice also exhibited significantly reduced occlusion time. The expression of tissue factor (encoded by the F3 gene), a main initiator of the coagulation cascade, was increased in the artery of Klf11 knockout mice, as determined by real-time quantitative polymerase chain reaction and immunofluorescence. Furthermore, vascular smooth muscle cells isolated from Klf11 knockout mouse aortas showed increased tissue factor expression, which was rescued by KLF11 overexpression. In human aortic smooth muscle cells, small interfering RNA-mediated knockdown of KLF11 increased tissue factor expression. Consistent results were observed on adenovirus-mediated overexpression of KLF11. Mechanistically, KLF11 downregulates F3 at the transcriptional level as determined by reporter and chromatin immunoprecipitation assays. Conclusions- Our data demonstrate that KLF11 is a novel transcriptional suppressor of F3 in vascular smooth muscle cells, constituting a potential molecular target for inhibition of arterial thrombosis.

Superoxide dismutase 3 as an inflammatory suppressor in A549 cells infected with Mycoplasma pneumoniae

Herein, we found that serum concentration of superoxide dismutase 3 (SOD3) was significantly reduced in children with mycoplasma pneumonia (MP) infection. To study the roles of SOD3 in inflammatory regulation of MP infection, human A549 type II alveolar epithelial cells were stimulated with 10⁷ CCU/ml of MP to build MP infection in vitro. Secretion of pro-inflammatory cytokine interleukin (IL)-8 and tumor necrosis factor (TNF)-α were measured via enzyme-linked immunosorbent assay (ELISA) to assess the inflammatory response of A549 cells. Levofloxacin (LVFX) was used as an anti-inflammatory drug while recombinant TNF-α was used as an inflammatory promotor in MP-infected cells. Transcriptional activity of nuclear factor (NF)-κB was assessed by detecting protein levels of nuclear NF-κB and cytoplasm NF-κB using Western blot analysis. Our data suggested that the expression of SOD3 mRNA and protein, as well as content of SOD3 in cultured supernatant, were time-dependently inhibited in MP-infected A549 cells. However, lentiviruses-mediated SOD3 overexpression alleviated inflammatory response of MP-infected A549 cells, and prevented the unclear translocation of NF-κB, as evidenced by obviously reducing the production of IL-8 and TNF-α in cell cultured supernatant, as well as decreasing nuclear NF-κB while increasing cytoplasm NF-κB. Inspiringly, SOD3 overexpression induced anti-inflammatory effect and the inactivation of NF-κB was similar to that of 2 lg/ml of LVFX, but reversed by additional TNF-α treatment. Therefore, we can conclude that transcriptional activity of NF-jB was the underlying mechanism, by which SOD3 regulated inflammatory response in MP infection in vitro.