Potential therapeutic effects of mTOR inhibition in atherosclerosis

From defense to dysfunction: Autophagy's dual role in disease pathophysiology

Autophagy is a fundamental pillar of cellular resilience, indispensable for maintaining cellular health and vitality. It coordinates the meticulous breakdown of cytoplasmic macromolecules as a guardian of cell metabolism, genomic integrity, and survival. In the complex play of biological warfare, autophagy emerges as a firm defender, bravely confronting various pathogenic, infectious, and cancerous adversaries. Nevertheless, its role transcends mere defense, wielding both protective and harmful effects in the complex landscape of disease pathogenesis. From the onslaught of infectious outbreaks to the devious progression of chronic lifestyle disorders, autophagy emerges as a central protagonist, convolutedly shaping the trajectory of cellular health and disease progression. In this article, we embark on a journey into the complicated web of molecular and immunological mechanisms that govern autophagy's profound influence over disease. Our focus sharpens on dissecting the impact of various autophagy-associated proteins on the kaleidoscope of immune responses, spanning the spectrum from infectious outbreaks to chronic lifestyle ailments. Through this voyage of discovery, we unveil the vast potential of autophagy as a therapeutic linchpin, offering tantalizing prospects for targeted interventions and innovative treatment modalities that promise to transform the landscape of disease management.

Elucidating the crosstalk between endothelial-to-mesenchymal transition (EndoMT) and endothelial autophagy in the pathogenesis of atherosclerosis

Atherosclerosis, a chronic systemic inflammatory condition, is implicated in most cardiovascular ischemic events. The pathophysiology of atherosclerosis involves various cell types and associated processes, including endothelial cell activation, monocyte recruitment, smooth muscle cell migration, involvement of macrophages and foam cells, and instability of the extracellular matrix. The process of endothelial-to-mesenchymal transition (EndoMT) has recently emerged as a pivotal process in mediating vascular inflammation associated with atherosclerosis. This transition occurs gradually, with a significant portion of endothelial cells adopting an intermediate state, characterized by a partial loss of endothelial-specific gene expression and the acquisition of "mesenchymal" traits. Consequently, this shift disrupts endothelial cell junctions, increases vascular permeability, and exacerbates inflammation, creating a self-perpetuating cycle that drives atherosclerotic progression. While endothelial cell dysfunction initiates the development of atherosclerosis, autophagy, a cellular catabolic process designed to safeguard cells by recycling intracellular molecules, is believed to exert a significant role in plaque development. Identifying the pathological mechanisms and molecular mediators of EndoMT underpinning endothelial autophagy, may be of clinical relevance. Here, we offer new insights into the underlying biology of atherosclerosis and present potential molecular mechanisms of atherosclerotic resistance and highlight potential therapeutic targets.

Therapeutic Potential of Targeting p27kip1 in Plaque Vulnerability

Atherosclerosis, a critical contributor to coronary artery diseases, involves the accumulation of cholesterol, fibrin, and lipids within arterial walls, inciting inflammatory reactions culminating in plaque formation. This multifaceted interplay encompasses excessive fibrosis, fatty plaque development, vascular smooth muscle cell (VSMC) proliferation, and leukocyte migration in response to inflammatory pathways. While stable plaques demonstrate resilience against complications, vulnerable ones, with lipid-rich cores, necrosis, and thin fibrous caps, lead to thrombosis, myocardial infarction, stroke, and acute cerebrovascular accidents. The nuanced phenotypes of VSMCs, modulated by gene regulation and environmental cues, remain pivotal. Essential markers like alpha-SMA, myosin heavy chain, and calponin regulate VSMC migration and contraction, exhibiting diminished expression during VSMC de-differentiation and proliferation. p27kip, a CDK inhibitor, shows promise in regulating VSMC proliferation and appears associated with TNF-α-induced pathways impacting unstable plaques. Oncostatin M (OSM), an IL-6 family cytokine, correlates with MMP upregulation and foam cell formation, influencing plaque development. Efforts targeting mammalian target of rapamycin (mTOR) inhibition, notably using rapamycin and its analogs, demonstrate potential but pose challenges due to associated adverse effects. Exploration of the impact of p27kip impact on plaque macrophages presents promising avenues, yet its complete therapeutic potential remains untapped. Similarly, while OSM has exhibited potential in inducing cell cycle arrest via p27kip, direct links necessitate further investigation. This critical review discusses the role of mTOR, p27kip, and OSM in VSMC proliferation and differentiation followed by the therapeutic potential of targeting these mediators in atherosclerosis to attenuate plaque vulnerability.

Understanding the intricacies of cellular senescence in atherosclerosis: Mechanisms and therapeutic implications

Cardiovascular disease is currently the largest cause of mortality and disability globally, surpassing communicable diseases, and atherosclerosis is the main contributor to this epidemic. Aging is intimately linked to atherosclerosis development and progression, however, the mechanism of aging in atherosclerosis is not well known. To emphasize the significant research on the involvement of senescent cells in atherosclerosis, we begin by outlining compelling evidence that indicates various types of senescent cells and SASP factors linked to atherosclerotic phenotypes. We subsequently provide a comprehensive summary of the existing knowledge, shedding light on the intricate mechanisms through which cellular senescence contributes to the pathogenesis of atherosclerosis. Further, we cover that senescence can be identified by both structural changes and several senescence-associated biomarkers. Finally, we discuss that preventing accelerated cellular senescence represents an important therapeutic potential, as permanent changes may occur in advanced atherosclerosis. Together, the review summarizes the relationship between cellular senescence and atherosclerosis, and inspects the molecular knowledge, and potential clinical significance of senescent cells in developing senescent-based therapy, thus providing crucial insights into their biology and potential therapeutic exploration.

MTMR7 suppresses the phenotypic switching of vascular smooth muscle cell and vascular intimal hyperplasia after injury via regulating p62/mTORC1-mediated glucose metabolism

BACKGROUND AND AIMS

Myotubularin-related protein 7 (MTMR7) suppresses proliferation in various cell types and is associated with cardiovascular and cerebrovascular diseases. However, whether MTMR7 regulates vascular smooth muscle cell (VSMC) and vascular intimal hyperplasia remains unclear. We explored the role of MTMR7 in phenotypic switching of VSMC and vascular intimal hyperplasia after injury.

METHODS AND RESULTS

MTMR7 expression was significantly downregulated in injured arteries. Compared to wild type (WT) mice, Mtmr7-transgenic (Mtmr7-Tg) mice showed reduced intima/media ratio, decreased percentage of Ki-67-positive cells within neointima, and increased Calponin expression in injured artery. In vitro, upregulating MTMR7 by Len-Mtmr7 transfection inhibited platelet derived growth factor (PDGF)-BB-induced proliferation, migration of VSMC and reversed PDGF-BB-induced decrease in expression of Calponin and SM-MHC. Microarray, single cell sequence, and other bioinformatics analysis revealed that MTMR7 is highly related to glucose metabolism and mammalian target of rapamycin complex 1 (mTORC1). Further experiments confirmed that MTMR7 markedly repressed glycolysis and mTORC1 activity in PDGF-BB-challenged VSMC in vitro. Restoring mTORC1 activity abolished MTMR7-mediated suppression of glycolysis, phenotypic shift in VSMC in vitro and protection against vascular intimal hyperplasia in vivo. Furthermore, upregulating MTMR7 in vitro led to dephosphorylation and dissociation of p62 from mTORC1 in VSMC. External expression of p62 in vitro also abrogated the inhibitory effects of MTMR7 on glycolysis and phenotypic switching in PDGF-BB-stimulated VSMC.

CONCLUSIONS

Our study demonstrates that MTMR7 inhibits injury-induced vascular intimal hyperplasia and phenotypic switching of VSMC. Mechanistically, the beneficial effects of MTMR7 are conducted via suppressing p62/mTORC1-mediated glycolysis.

Contractile and Genetic Characterization of Cardiac Constructs Engineered from Human Induced Pluripotent Stem Cells: Modeling of Tuberous Sclerosis Complex and the Effects of Rapamycin

The implementation of three-dimensional tissue engineering concurrently with stem cell technology holds great promise for in vitro research in pharmacology and toxicology and modeling cardiac diseases, particularly for rare genetic and pediatric diseases for which animal models, immortal cell lines, and biopsy samples are unavailable. It also allows for a rapid assessment of phenotype-genotype relationships and tissue response to pharmacological manipulation. Mutations in the TSC1 and TSC2 genes lead to dysfunctional mTOR signaling and cause tuberous sclerosis complex (TSC), a genetic disorder that affects multiple organ systems, principally the brain, heart, skin, and kidneys. Here we differentiated healthy (CC3) and tuberous sclerosis (TSP8-15) human induced pluripotent stem cells (hiPSCs) into cardiomyocytes to create engineered cardiac tissue constructs (ECTCs). We investigated and compared their mechano-elastic properties and gene expression and assessed the effects of rapamycin, a potent inhibitor of the mechanistic target of rapamycin (mTOR). The TSP8-15 ECTCs had increased chronotropy compared to healthy ECTCs. Rapamycin induced positive inotropic and chronotropic effects (i.e., increased contractility and beating frequency, respectively) in the CC3 ECTCs but did not cause significant changes in the TSP8-15 ECTCs. A differential gene expression analysis revealed 926 up- and 439 down-regulated genes in the TSP8-15 ECTCs compared to their healthy counterparts. The application of rapamycin initiated the differential expression of 101 and 31 genes in the CC3 and TSP8-15 ECTCs, respectively. A gene ontology analysis showed that in the CC3 ECTCs, the positive inotropic and chronotropic effects of rapamycin correlated with positively regulated biological processes, which were primarily related to the metabolism of lipids and fatty and amino acids, and with negatively regulated processes, which were predominantly associated with cell proliferation and muscle and tissue development. In conclusion, this study describes for the first time an in vitro TSC cardiac tissue model, illustrates the response of normal and TSC ECTCs to rapamycin, and provides new insights into the mechanisms of TSC.

Trehalose promotes atherosclerosis regression in female mice

Introduction

Atherosclerosis is a chronic inflammatory disease caused by the deposition of lipids within the artery wall. During atherogenesis, efficient autophagy is needed to facilitate efferocytosis and cholesterol efflux, limit inflammation and lipid droplet buildup, and eliminate defective mitochondria and protein aggregates. Central to the regulation of autophagy is the transcription factor EB (TFEB), which coordinates the expression of lysosomal biogenesis and autophagy genes. In recent years, trehalose has been shown to promote TFEB activation and protect against atherogenesis. Here, we sought to investigate the role of autophagy activation during atherosclerosis regression.

Methods and results

Atherosclerosis was established in C57BL/6N mice by injecting AAV-PCSK9 and 16 weeks of Western diet feeding, followed by switching to a chow diet to induce atherosclerosis regression. During the regression period, mice were either injected with trehalose concomitant with trehalose supplementation in their drinking water or injected with saline for 6 weeks. Female mice receiving trehalose had reduced atherosclerosis burden, as evidenced by reduced plaque lipid content, macrophage numbers and IL-1β content in parallel with increased plaque collagen deposition, which was not observed in their male counterparts. In addition, trehalose-treated female mice had lower levels of circulating leukocytes, including inflammatory monocytes and CD4+ T cells. Lastly, we found that autophagy flux in male mice was basally higher than in female mice during atherosclerosis progression.

Conclusions

Our data demonstrate a sex-specific effect of trehalose in atherosclerosis regression, whereby trehalose reduced lipid content, inflammation, and increased collagen content in female mice but not in male mice. Furthermore, we discovered inherent differences in the autophagy flux capacities between the sexes: female mice exhibited lower plaque autophagy than males, which rendered the female mice more responsive to atherosclerosis regression. Our work highlights the importance of understanding sex differences in atherosclerosis to personalize the development of future therapies to treat cardiovascular diseases.

Immune Homeostasis Maintenance Through Advanced Immune Therapeutics to Target Atherosclerosis

Atherosclerosis remains the leading cause of coronary heart disease (CHD) with enormous health and societal tolls. Traditional drug development approaches have been focused on small molecule-based compounds that aim to lower plasma lipids and reduce systemic inflammation, two primary causes of atherosclerosis. However, despite the widely available lipid-lowering and anti-inflammatory small compounds and biologic agents, CHD prevalence still remains high. Based on recent advances revealing disrupted immune homeostasis during atherosclerosis pathogenesis, novel strategies aimed at rejuvenating immune homeostasis with engineered immune leukocytes are being developed. This chapter aims to assess basic and translational efforts on these emerging strategies for the effective development of atherosclerosis treatment, as well as key challenges in this important translational field.

A New Hypothesis Describing the Pathogenesis of Oral Mucosal Injury Associated with the Mammalian Target of Rapamycin (mTOR) Inhibitors

It has been 24 years since rapamycin (sirolimus) was approved to mitigate solid organ transplant rejection and 16 years since mTOR (mammalian/mechanistic target of rapamycin) inhibitors reached patients as a cancer therapy. While the clinical benefits of mTOR inhibitors (mTORi) are robust, so too are their toxicities. Among the most common issues is the development of ulcers of the oral mucosa (mTOR-inhibitor associated stomatitis; mIAS). These lesions are distinct from those of other anti-cancer agents, occur with regularity, and impact patient outcomes. mIAS' pathogenesis has been the subject of speculation, and its similar presentation to recurrent aphthous stomatitis (RAS) has led to the hypothesis that it might serve as a surrogate to better understand RAS. Based on a review of the literature, the current manuscript provides a hypothesis regarding the mechanisms by which mTORis uniquely initiate mucosal injury and an explanation for the observation that steroids (also an immunosuppressive) are effective in its treatment through a non-immunologic mechanism. Unexplained unique features of mIAS are discussed in this review in the context of future investigation.

Nanogels with covalently bound and releasable trehalose for autophagy stimulation in atherosclerosis

Atherosclerosis, cholesterol-driven plaque formation in arteries, is a complex multicellular disease which is a leading cause of vascular diseases. During the progression of atherosclerosis, the autophagic function is impaired, resulting in lipid accumulation-mediated foam cell formation. The stimulation of autophagy is crucial for the recovery of cellular recycling process. One of the potential autophagy inducers is trehalose, a naturally occurring non-reducing disaccharide. However, trehalose has poor bioavailability due to its hydrophilic nature which results in poor penetration through cell membranes. To enhance its bioavailability, we developed trehalose-releasing nanogels (TNG) for the treatment of atherosclerosis. The nanogels were fabricated through copolymerization of 6-O-acryloyl-trehalose with the selected acrylamide-type monomers affording a high trehalose conjugation (~ 58%, w/w). TNG showed a relatively small hydrodynamic diameter (dH, 67 nm) and a uniform spherical shape and were characterized by negative ζ potential (-18 mV). Thanks to the trehalose-rich content, TNG demonstrated excellent colloidal stability in biological media containing serum and were non-hemolytic to red blood cells. In vitro study confirmed that TNG could stimulate autophagy in foam cells and enhance lipid efflux and in vivo study in ApoE-/- mice indicated a significant reduction in atherosclerotic plaques, while increasing autophagic markers. In conclusion, TNG hold great promise as a trehalose delivery system to restore impaired autophagy-mediated lipid efflux in atherosclerosis and subsequently reduce atherosclerotic plaques.

Cells in Atherosclerosis: Focus on Cellular Senescence from Basic Science to Clinical Practice

Aging is a major risk factor of atherosclerosis through different complex pathways including replicative cellular senescence and age-related clonal hematopoiesis. In addition to aging, extracellular stress factors, such as mechanical and oxidative stress, can induce cellular senescence, defined as premature cellular senescence. Senescent cells can accumulate within atherosclerotic plaques over time and contribute to plaque instability. This review summarizes the role of cellular senescence in the complex pathophysiology of atherosclerosis and highlights the most important senotherapeutics tested in cardiovascular studies targeting senescence. Continued bench-to-bedside research in cellular senescence might allow the future implementation of new effective anti-atherosclerotic preventive and treatment strategies in clinical practice.

AMPK activators suppress cholesterol accumulation in macrophages via suppression of the mTOR pathway

Atherosclerosis is a persistent inflammatory state that contributes significantly to cardiovascular disease, a primary cause of mortality worldwide. Enhanced lipid uptake by macrophages and their transformation into foam cells play a key role in the development of atherosclerosis. Recent studies using in vivo mouse models indicated that activation of AMPK has anti-atherosclerotic effects by upregulating the expression of cholesterol efflux transporters in foam cells and promoting cholesterol efflux. However, the pathway downstream of AMPK that contributes to elevated expression of cholesterol efflux transporters remains unclear. In this study, we found that activation of AMPK by AICAR and metformin inhibits foam cell formation via suppression of mTOR in macrophages. Specifically, activation of AMPK indirectly reduced the phosphorylation level of mTOR at Ser2448 and promoted the expression of cholesterol efflux transporters and cholesterol efflux. These inhibitory effects on foam cell formation were counteracted by mTOR activators. Metformin, a more nonspecific AMPK activator than AICAR, appears to inhibit foam cell formation via anti-inflammatory effects in addition to suppression of the mTOR pathway. The results of this study suggest that the development of new drugs targeting AMPK activation and mTOR inhibition may lead to beneficial results in the prevention and treatment of atherosclerosis.

Monocytes reprogrammed by 4-PBA potently contribute to the resolution of inflammation and atherosclerosis

Background

Chronic inflammation initiated by inflammatory monocytes underlies the pathogenesis of atherosclerosis. However, approaches that can effectively resolve chronic low-grade inflammation targeting monocytes are not readily available. The small chemical compound 4-phenylbutyric acid (4-PBA) exhibits broad anti-inflammatory effects in reducing atherosclerosis. Selective delivery of 4-PBA reprogrammed monocytes may hold novel potential in providing targeted and precision therapeutics for the treatment of atherosclerosis.

Methods

Systems analyses integrating single-cell RNA-sequencing and complementary immunological approaches characterized key resolving characteristics as well as defining markers of reprogrammed monocytes trained by 4-PBA. Molecular mechanisms responsible for monocyte reprogramming was assessed by integrated biochemical and genetic approaches. The inter-cellular propagation of homeostasis resolution was evaluated by co-culture assays with donor monocytes trained by 4-PBA and recipient naïve monocytes. The in vivo effects of monocyte resolution and atherosclerosis prevention by 4-PBA were assessed with the high fat diet-fed ApoE -/- mouse model with i.p. 4-PBA administration. Furthermore, the selective efficacy of 4-PBA trained monocytes were examined by i.v. transfusion of ex vivo trained monocytes by 4-PBA into recipient high fat diet-fed ApoE -/- mice.

Results

In this study, we found that monocytes can be potently reprogrammed by 4-PBA into an immune-resolving state characterized by reduced adhesion and enhanced expression of anti-inflammatory mediator CD24. Mechanistically, 4-PBA reduced the expression of ICAM-1 via reducing peroxisome stress and attenuating SYK-mTOR signaling. Concurrently, 4-PBA enhanced the expression of resolving mediator CD24 through promoting PPARγ neddylation mediated by TOLLIP. 4-PBA trained monocytes can effectively propagate anti-inflammation activity to neighboring monocytes through CD24. Our data further demonstrated that 4-PBA trained monocytes effectively reduce atherosclerosis pathogenesis when administered in vivo .

Conclusion

Our study describes a robust and effective approach to generate resolving monocytes, characterizes novel mechanisms for targeted monocyte reprogramming, and offers a precision-therapeutics for atherosclerosis based on delivering reprogrammed resolving monocytes.

Etiology of lipid-laden macrophages in the lung

Uniquely positioned as sentinel cells constantly exposed to the environment, pulmonary macrophages are vital for the maintenance of the lung lining. These cells are responsible for the clearance of xenobiotics, pathogen detection and clearance, and homeostatic functions such as surfactant recycling. Among the spectrum of phenotypes that may be expressed by macrophages in the lung, the pulmonary lipid-laden phenotype is less commonly studied in comparison to its circulatory counterpart, the atherosclerotic lesion-associated foam cell, or the acutely activated inflammatory macrophage. Herein, we propose that lipid-laden macrophage formation in the lung is governed by lipid acquisition, storage, metabolism, and export processes. The cellular balance of these four processes is critical to the maintenance of homeostasis and the prevention of aberrant signaling that may contribute to lung pathologies. This review aims to examine mechanisms and signaling pathways that are involved in lipid-laden macrophage formation and the potential consequences of this phenotype in the lung.

Genetic inhibition of CARD9 accelerates the development of atherosclerosis in mice through CD36 dependent-defective autophagy

Caspase recruitment-domain containing protein 9 (CARD9) is a key signaling pathway in macrophages but its role in atherosclerosis is still poorly understood. Global deletion of Card9 in Apoe-/- mice as well as hematopoietic deletion in Ldlr-/- mice increases atherosclerosis. The acceleration of atherosclerosis is also observed in Apoe-/-Rag2-/-Card9-/- mice, ruling out a role for the adaptive immune system in the vascular phenotype of Card9 deficient mice. Card9 deficiency alters macrophage phenotype through CD36 overexpression with increased IL-1β production, increased lipid uptake, higher cell death susceptibility and defective autophagy. Rapamycin or metformin, two autophagy inducers, abolish intracellular lipid overload, restore macrophage survival and autophagy flux in vitro and finally abolish the pro-atherogenic effects of Card9 deficiency in vivo. Transcriptomic analysis of human CARD9-deficient monocytes confirms the pathogenic signature identified in murine models. In summary, CARD9 is a key protective pathway in atherosclerosis, modulating macrophage CD36-dependent inflammatory responses, lipid uptake and autophagy.

Role of miR-15a-5p and miR-199a-3p in the inflammatory pathway regulated by NF-κB in experimental and human atherosclerosis

BACKGROUND

Cardiovascular diseases (CVDs) prevalence has significantly increased in the last decade and atherosclerosis development is the main trigger. MicroRNAs (miRNAs) are non-coding RNAs that negatively regulate gene expression of their target and their levels are frequently altered in CVDs.

METHODS

By RT-qPCR, we analysed miR-9-5p, miR-15a-5p, miR-16-5p and miR-199a-3p levels in aorta from apolipoprotein knockout (ApoE-/- ) mice, an experimental model of hyperlipidemia-induced atherosclerosis, and in human aortic and carotid atherosclerotic samples. By in silico studies, Western blot analysis and immunofluorescence studies, we detected the targets of the altered miRNAs.

RESULTS

Our results show that miR-15a-5p and miR-199a-3p are significantly decreased in carotid and aortic samples from patients and mice with atherosclerosis. In addition, we found an increased expression in targets of both miRNAs that participate in the inflammatory pathway of nuclear factor kappa B (NF-κB), such as IKKα, IKKβ and p65. In human vein endothelial cells (HUVECs) and vascular smooth muscle cells (VSMCs), the overexpression of miR-15a-5p or miR-199a-3p decreased IKKα, IKKβ and p65 protein levels as well as NF-κB activation. On the other hand, miR-15a-5p and miR-199a-3p overexpression reduced ox-LDL uptake and the inflammation regulated by NF-κB in VSMCs. Moreover, although miR-15a-5p and miR-199a-3p were significantly increased in exosomes from patients with advanced carotid atherosclerosis, only in the ROC analyses for miR-15a-5p, the area under the curve was 0.8951 with a p value of .0028.

CONCLUSIONS

Our results suggest that the decrease of miR-199a-3p and miR-15a-5p in vascular samples from human and experimental atherosclerosis could be involved in the NF-κB activation pathway, as well as in ox-LDL uptake by VSMCs, contributing to inflammation and progression atherosclerosis. Finally, miR-15a-5p could be used as a novel diagnostic biomarker for advanced atherosclerosis.

Loss of Macrophage mTORC2 Drives Atherosclerosis via FoxO1 and IL-1β Signaling

BACKGROUND

The mTOR (mechanistic target of rapamycin) pathway is a complex signaling cascade that regulates cellular growth, proliferation, metabolism, and survival. Although activation of mTOR signaling has been linked to atherosclerosis, its direct role in lesion progression and in plaque macrophages remains poorly understood. We previously demonstrated that mTORC1 (mTOR complex 1) activation promotes atherogenesis through inhibition of autophagy and increased apoptosis in macrophages.

METHODS

Using macrophage-specific Rictor- and mTOR-deficient mice, we now dissect the distinct functions of mTORC2 pathways in atherogenesis.

RESULTS

In contrast to the atheroprotective effect seen with blockade of macrophage mTORC1, macrophage-specific mTORC2-deficient mice exhibit an atherogenic phenotype, with larger, more complex lesions and increased cell death. In cultured macrophages, we show that mTORC2 signaling inhibits the FoxO1 (forkhead box protein O1) transcription factor, leading to suppression of proinflammatory pathways, especially the inflammasome/IL (interleukin)-1β response, a key mediator of vascular inflammation and atherosclerosis. In addition, administration of FoxO1 inhibitors efficiently rescued the proinflammatory response caused by mTORC2 deficiency both in vitro and in vivo. Interestingly, collective deletion of macrophage mTOR, which ablates mTORC1- and mTORC2-dependent pathways, leads to minimal change in plaque size or complexity, reflecting the balanced yet opposing roles of these signaling arms.

CONCLUSIONS

Our data provide the first mechanistic details of macrophage mTOR signaling in atherosclerosis and suggest that therapeutic measures aimed at modulating mTOR need to account for its dichotomous functions.

A review of the signaling pathways of aerobic and anaerobic exercise on atherosclerosis

Atherosclerosis (AS), a chronic inflammatory vascular disease with lipid metabolism abnormalities, is one of the major pathological bases of coronary heart disease. As people's lifestyles and diets change, the incidence of AS increases yearly. Physical activity and exercise training have recently been identified as effective strategies for lowering cardiovascular disease (CVD) risk. However, the best exercise mode to ameliorate the risk factors related to AS is not clear. The effect of exercise on AS is affected by the type of exercise, intensity, and duration. In particular, aerobic and anaerobic exercise are the two most widely discussed types of exercise. During exercise, the cardiovascular system undergoes physiological changes via various signaling pathways. The review aims to summarize signaling pathways related to AS in two different exercise types and provide new ideas for the prevention and treatment of AS in clinical practice.

Sulfamethizole attenuates poloxamer 407-induced atherosclerotic neointima formation via inhibition of mTOR in C57BL/6 mice

Mammalian target of Rapamycin C1 (mTORC1) inhibition limits plaque progression in atherosclerosis. The present study evaluated the protective effect of sulfamethizole on poloxamer 407-induced atherosclerotic neointima formation in C57BL/6 mice via mTOR inhibition. Poloxamer 407 (P-407) (0.5 g/kg body weight) was administered intraperitoneally to male C57BL/6 mice every third day for 148 days to induce chronic hyperlipidemia. From Day 121 to 148, animals were additionally administered Sulfamethizole (5, 10, and 50 mg/kg, p.o.), Rapamycin (0.5 mg/kg, positive control), or vehicle (1 ml/kg). Plasma lipid levels were measured on Days 120 and 148. Upon sacrifice, histological studies were performed, and aortic tissue interleukin (IL)-6, tumor necrosis factor-α (TNF-α), and mTOR levels were evaluated. A molecular docking study was carried out to mimic the interaction of sulfamethizole with mTOR protein. Chronic P-407 administration significantly (p < 0.001) elevated plasma lipid levels, compared with those of the normal control group. Chronic hyperlipidemia resulted in increased tunica intima thickness, collagen deposition, and IL-6, TNF-α, and mTOR levels. Treatment with Sulfamethizole attenuated these parameters significantly in a dose-dependent manner. Molecular docking studies showed a significant interaction of Sulfamethizole with mTOR. In conclusion, this study suggests that sulfamethizole significantly limits poloxamer 407-induced atherosclerotic neointima formation in C57BL/6 mice via mTOR inhibition.

Celecoxib activates autophagy by inhibiting the mTOR signaling pathway and prevents apoptosis in nucleus pulposus cells

BACKGROUND

Intervertebral disc degeneration results from a variety of etiologies, including inflammation and aging. Degenerated intervertebral discs feature down-regulated extracellular matrix synthesis, resulting in losing their ability to retain water and absorb compression. Celecoxib is a well-known selective cyclooxygenase-2 inhibitor for treating arthritis and relieving pain. Nevertheless, the mechanism of Celecoxib for treating inflammation-related intervertebral disc degeneration has not yet been clarified.

METHOD

Protein synthesis was analyzed by western blot. Fluorescent probes DCFH-DA and MitoSox Red detected reactive oxygen species and were measured by flow cytometry. The activity of the kinase pathway was evaluated by protein phosphorylation. Autophagy was monitored by mRFP-GFP-LC3 transfection and LC3 analysis. Mitochondrial apoptotic proteins were analyzed by western blot and cell membrane integrity was measured by flow cytometry. The autophagic gene was silenced by siRNA.

RESULTS

In this study, interleukin-1β stimulation reduced the synthesis of aggrecan, type I and II collagen and caused excessive production of reactive oxygen species. We looked for a therapeutic window of Celecoxib for nucleus pulposus cells to regain extracellular matrix synthesis and reduce oxidative stress. To look into nucleus pulposus cells in response to stimuli, enhancement of autophagy was achieved by Celecoxib, confirmed by mRFP-GFP-LC3 transfection and LC3 analysis. The mammalian target of rapamycin and a panel of downstream proteins responded to Celecoxib and propelled autophagy machinery to stabilize homeostasis. Ultimately, inhibition of autophagy by silencing autophagy protein 5 disrupted the protective effects of Celecoxib, culminating in apoptosis.

CONCLUSION

In summary, we have demonstrated a new use for the old drug Celecoxib that treats intervertebral disc degeneration by enhancing autophagy in nucleus pulposus cells and opening a door for treating other degenerative diseases.

Celecoxib activates autophagy by inhibiting the mTOR signaling pathway and prevents apoptosis in nucleus pulposus cells

BACKGROUND

Intervertebral disc degeneration results from a variety of etiologies, including inflammation and aging. Degenerated intervertebral discs feature down-regulated extracellular matrix synthesis, resulting in losing their ability to retain water and absorb compression. Celecoxib is a well-known selective cyclooxygenase-2 inhibitor for treating arthritis and relieving pain. Nevertheless, the mechanism of Celecoxib for treating inflammation-related intervertebral disc degeneration has not yet been clarified.

METHOD

Protein synthesis was analyzed by western blot. Fluorescent probes DCFH-DA and MitoSox Red detected reactive oxygen species and were measured by flow cytometry. The activity of the kinase pathway was evaluated by protein phosphorylation. Autophagy was monitored by mRFP-GFP-LC3 transfection and LC3 analysis. Mitochondrial apoptotic proteins were analyzed by western blot and cell membrane integrity was measured by flow cytometry. The autophagic gene was silenced by siRNA.

RESULTS

In this study, interleukin-1β stimulation reduced the synthesis of aggrecan, type I and II collagen and caused excessive production of reactive oxygen species. We looked for a therapeutic window of Celecoxib for nucleus pulposus cells to regain extracellular matrix synthesis and reduce oxidative stress. To look into nucleus pulposus cells in response to stimuli, enhancement of autophagy was achieved by Celecoxib, confirmed by mRFP-GFP-LC3 transfection and LC3 analysis. The mammalian target of rapamycin and a panel of downstream proteins responded to Celecoxib and propelled autophagy machinery to stabilize homeostasis. Ultimately, inhibition of autophagy by silencing autophagy protein 5 disrupted the protective effects of Celecoxib, culminating in apoptosis.

CONCLUSION

In summary, we have demonstrated a new use for the old drug Celecoxib that treats intervertebral disc degeneration by enhancing autophagy in nucleus pulposus cells and opening a door for treating other degenerative diseases.

Everolimus-Loaded Reconstituted High-Density Lipoprotein Prepared by a Novel Dual Centrifugation Approach for Anti-Atherosclerotic Therapy

PURPOSE

The conventional techniques for the preparation of reconstituted high-density lipoprotein (rHDL) are hampered by long process times, the need for large amounts of starting material, and harsh preparation conditions. Here, we present a novel rHDL preparation method to overcome these challenges. Furthermore, we propose a dual mode of action for rHDL loaded with the immunosuppressant drug everolimus (Eve-rHDL) in the context of atherosclerosis and cardiovascular disease.

METHODS

We use dual centrifugation for rHDL nanoparticle preparation and characterize the physicochemical properties by NS-TEM, N-PAGE, DLS, AF4, and HPLC. In addition, we determine the biological efficacy in human and murine cell culture with regard to cellular uptake, cholesterol efflux, and proliferation.

RESULTS

We confirm the characteristic particle size of 10 nm, discoidal morphology, and chemical composition of the rHDL preparations and identify dual centrifugation as an ideal method for cost-effective aseptic rHDL manufacturing. rHDL can be prepared in approx. 1.5 h with batch sizes as little as 89 µL. Moreover, we demonstrate the cholesterol efflux capacity and anti-proliferative activity of Eve-rHDL in vitro. The anti-proliferative effects were comparable to free Eve, thus confirming the suitability of rHDL as a capable drug delivery vehicle.

CONCLUSION

Eve-rHDL shows great efficacy in vitro and may further be employed to target atherosclerotic plaques in vivo. Highly effective anti-atherosclerotic therapy might be feasible by reducing both inflammatory- and lipid burden of the plaques. Dual centrifugation is an ideal technique for the efficient application of the rHDL platform in cardiovascular disease and beyond.

Shear Stress and Metabolic Disorders-Two Sides of the Same Plaque

Significance: Shear stress and metabolic disorder are the two sides of the same atherosclerotic coin. Atherosclerotic lesions are prone to develop at branches and curvatures of arteries, which are exposed to oscillatory and low shear stress exerted by blood flow. Meanwhile, metabolic disorders are pivotal contributors to the formation and advancement of atherosclerotic plaques. Recent Advances: Accumulated evidence has provided insight into the impact and mechanisms of biomechanical forces and metabolic disorder on atherogenesis, in association with mechanotransduction, epigenetic regulation, and so on. Moreover, recent studies have shed light on the cross talk between the two drivers of atherosclerosis. Critical Issues: There are extensive cross talk and interactions between shear stress and metabolic disorder during the pathogenesis of atherosclerosis. The communications may amplify the proatherogenic effects through increasing oxidative stress and inflammation. Nonetheless, the precise mechanisms underlying such interactions remain to be fully elucidated as the cross talk network is considerably complex. Future Directions: A better understanding of the cross talk network may confer benefits for a more comprehensive clinical management of atherosclerosis. Critical mediators of the cross talk may serve as promising therapeutic targets for atherosclerotic vascular diseases, as they can inhibit effects from both sides of the plaque. Hence, further in-depth investigations with advanced omics approaches are required to develop novel and effective therapeutic strategies against atherosclerosis. Antioxid. Redox Signal. 37, 820-841.

Retinoic acid increases the cellular cholesterol predominantly in a mTOR-independent manner

Retinoic acid (RA) plays a role in the mounting immune response and controls several functions of the human body, including cholesterol homeostasis. The synthesis, uptake, and efflux of cellular cholesterol are significantly linked to the mammalian target of rapamycin complex-1 (mTORC1). Activation of mTORC1 promotes the synthesis and uptake of the cholesterol and suppresses its efflux, thus causing accumulation of cellular cholesterol. It is intriguing to know the effect of a high dose of RA on cholesterol accumulation in macrophages (mφ) and whether it is via mTOR activation. It is important to note that the long-term treatment of RA in humans is safe. Therefore, we chose a high dose of RA to observe its effect, which may be implicated in diseases like visceral leishmaniasis, where cholesterol deficiency is established. In the present study, we found the increased expression of RAPTOR, a regulatory component of the mTORC1 complex, in mφ upon treatment with RA. We observed the increased expression of SREBP2, LDLR, and PCSK9 in RA-treated mφ under sufficient cholesterol conditions, which further increased cellular cholesterol levels. Notably, their expressions were decreased when the mTOR pathway was inhibited by rapamycin. However, treatment with rapamycin did not result in the loss of cellular cholesterol in RA-treated mφ. Comparison with rapamycin-treated mφ suggests that RA induces cellular cholesterol levels in a mTORC1-independent manner.

Rapamycin in Cerebral Cavernous Malformations: What Doses to Test in Mice and Humans

Cerebral cavernous malformations (CCMs) are hemorrhagic neurovascular lesions that affect more than 1 million people in the United States. Rapamycin inhibits CCM development and bleeding in murine models. The appropriate dosage to modify disease phenotype remains unknown. Current approved indications by the U.S. Food and Drug Administration and clinicaltrials.gov were queried for rapamycin human dosing for various indications. A systematic literature search was conducted on PubMed to investigate mouse dosimetry of rapamycin. In humans, low daily doses of <2 mg/day or trough level targets <15 ng/mL were typically used for benign indications akin to CCM disease, with relatively low complication rates. Higher oral doses in humans, used for organ rejection, result in higher complication rates. Oral dosing in mice, between 2 and 4 mg/kg/day, achieved blood trough levels in the 5-15 ng/mL range, a concentration likely to be targeted in human studies to treat CCM. Preclinical studies are needed utilizing dosing strategies which achieve blood levels corresponding to likely human dosimetry.

Autophagy Is Differentially Regulated in Leukocyte and Nonleukocyte Foam Cells During Atherosclerosis

RATIONALE

Atherosclerosis is characterized by an accumulation of foam cells within the arterial wall, resulting from excess cholesterol uptake and buildup of cytosolic lipid droplets (LDs). Autophagy promotes LD clearance by freeing stored cholesterol for efflux, a process that has been shown to be atheroprotective. While the role of autophagy in LD catabolism has been studied in macrophage-derived foam cells, this has remained unexplored in vascular smooth muscle cell (VSMC)-derived foam cells that constitute a large fraction of foam cells within atherosclerotic lesions.

OBJECTIVE

We performed a comparative analysis of autophagy flux in lipid-rich aortic intimal populations to determine whether VSMC-derived foam cells metabolize LDs similarly to their macrophage counterparts.

METHODS AND RESULTS

Atherosclerosis was induced in GFP-LC3 transgenic mice by PCSK9 (proprotein convertase subtilisin/kexin type 9)-adeno-associated viral injection and Western diet feeding. Using flow cytometry of aortic digests, we observed a significant increase in dysfunctional autophagy of VSMC-derived foam cells during atherogenesis relative to macrophage-derived foam cells. Using cell culture models of lipid-loaded VSMC and macrophage, we show that autophagy-mediated cholesterol efflux from VSMC foam cells was poor relative to macrophage foam cells, and largely occurs when HDL (high-density lipoprotein) is used as a cholesterol acceptor, as opposed to apoA-1 (apolipoproteinA-1). This was associated with the predominant expression of ABCG1 in VSMC foam cells. Using metformin, an autophagy activator, cholesterol efflux to HDL was significantly increased in VSMC, but not in macrophage, foam cells.

CONCLUSIONS

These data demonstrate that VSMC and macrophage foam cells perform cholesterol efflux by distinct mechanisms, and that autophagy flux is highly impaired in VSMC foam cells, but can be induced by pharmacological means. Further investigation is warranted into targeting autophagy specifically in VSMC foam cells, the predominant foam cell subtype of advanced atherosclerotic plaques, to promote reverse cholesterol transport and resolution of the atherosclerotic plaque.

Modulating mTOR Signaling as a Promising Therapeutic Strategy for Atherosclerosis

For more than a decade, atherosclerosis has been one of the leading causes of death in developed countries. The issue of treatment and prevention of the disease is especially acute. Despite the huge amount of basic and clinical research, a significant number of gaps remain in our understanding of the pathogenesis of atherosclerosis, and only their closure will bring us closer to understanding the causes of the disease at the cellular and molecular levels and, accordingly, to the development of an effective treatment. One of the seemingly well-studied elements of atherogenesis is the mTOR signaling pathway. However, more and more new details are still being clarified. Therapeutic strategies associated with rapamycin have worked well in a number of different diseases, and there is every reason to believe that targeting components of the mTOR pathway may pay off in atherosclerosis as well.

IL-1 family cytokines as drivers and inhibitors of trained immunity

Trained immunity is the long-term memory of innate immune cells, characterised by increased pro-inflammatory responses towards homo- and heterologous secondary stimuli. Interleukin (IL)-1 signalling plays an essential role in the induction of trained immunity, also called innate immune memory. As such, certain anti-inflammatory members of the IL-1 family of cytokines (IL-1F) which interfere with the inflammatory process have the potential to regulate the induction of a trained phenotype. The aim of this review is to provide an update on the role of IL-1F members in the context of trained immunity, emphasising the role of anti-inflammatory cytokines from the IL-1F to inhibit the induction of trained immunity, and touching upon their potential as therapeutics in IL-1-driven inflammatory disorders.

Pim-2 kinase inhibits inflammation by suppressing the mTORC1 pathway in atherosclerosis

Background: Inflammatory immunity theory has raised considerable concern in the pathogenesis of atherosclerosis. Proviral integration site of murine 2 (Pim-2) kinases functions in apoptosis pathways and the anti-inflammatory response. Here, we investigated whether Pim-2 kinase inhibits atherosclerotic inflammation by suppressing the mTORC1 pathway.

Methods: An atherosclerosis animal model was established by feeding ApoE ^-/- mice a high-fat diet. THP-1-derived macrophages were subjected to ox-LDL (50 μg/ml, 24h) conditions in vitro to mimic the in vivo conditions.

Result: The protein expression of Pim-2 was upregulated in ox-LDL-treated THP-1-derived macrophages and an atherosclerotic mouse model. Additionally, ox-LDL upregulated the protein expression of p-mTOR, p-S6K1 and p-4EBP1, intracellular lipid droplets, free cholesterol and cholesterylester and the mRNA expression of inflammatory cytokines, including IL-6, MCP-1, TLR-4 and TNF-α, in THP-1-derived macrophages. Functionally, overexpressed Pim-2 (Pim-2 OE) attenuated atherosclerotic inflammation associated with the mTORC1 signaling pathway in vitro and in vivo, whereas knocked down Pim-2 (Pim-2 KD) markedly promoted atherosclerotic inflammation associated with upregulation of the mTORC1 signaling pathway. The plaque areas and lesions in the whole aorta and aortic root sections were alleviated in ApoE ^-/- mice with Pim-2 OE, but aggravated by Pim-2 KD. Additionally, an mTOR agonist (MHY1485) counteracted the anti-inflammatory effect of Pim-2 in ox-LDL-treated THP-1-derived macrophages after Pim-2 OE, whereas rapamycin rescued atherosclerotic inflammation in ox-LDL-treated THP-1-derived macrophages after Pim-2 KD. Furthermore, si-mTOR and si-Raptor alleviated the atherosclerotic proinflammatory effect in ox-LDL-treated THP-1-derived macrophages in a the background of Pim-2 KD.

Conclusions:These results indicated that Pim-2 kinase inhibits atherosclerotic inflammation by suppressing the mTORC1 pathway.

Regulatory role of mammalian target of rapamycin signaling in exosome secretion and osteogenic changes in smooth muscle cells lacking acid ceramidase gene

Acid ceramidase (murine gene code: Asah1) (50 kDa) belongs to N-terminal nucleophile hydrolase family. This enzyme is located in the lysosome, which mediates conversion of ceramide (CER) into sphingosine and free fatty acids at acidic pH. CER plays an important role in intracellular sphingolipid metabolism and its increase causes inflammation. The mammalian target of rapamycin complex 1 (mTORC1) signaling on late endosomes (LEs)/lysosomes may control cargo selection, membrane biogenesis, and exosome secretion, which may be fine controlled by lysosomal sphingolipids such as CER. This lysosomal-CER-mTOR signaling may be a crucial molecular mechanism responsible for development of arterial medial calcification (AMC). Torin-1 (5 mg/kg/day), an mTOR inhibitor, significantly decreased aortic medial calcification accompanied with decreased expression of osteogenic markers like osteopontin (OSP) and runt-related transcription factor 2 (RUNX2) and upregulation of smooth muscle 22α (SM22-α) in mice receiving high dose of Vitamin D (500 000 IU/kg/day). Asah1^fl/fl /SM^Cre mice had markedly increased co-localization of mTORC1 with lysosome-associated membrane protein-1 (Lamp-1) (lysosome marker) and decreased co-localization of vacuolar protein sorting-associated protein 16 (VPS16) (a multivesicular bodies [MVBs] marker) with Lamp-1, suggesting mTOR activation caused reduced MVBs interaction with lysosomes. Torin-1 significantly reduced the co-localization of mTOR vs Lamp-1, increased lysosome-MVB interaction which was associated with reduced accumulation of CD63 and annexin 2 (exosome markers) in the coronary arterial wall of mice. Using coronary artery smooth muscle cells (CASMCs), P_i -stimulation significantly increased p-mTOR expression in Asah1^fl/fl /SM^Cre CASMCs as compared to WT/WT cells associated with increased calcium deposition and mineralization. Torin-1 blocked P_i -induced calcium deposition and mineralization. siRNA mTOR and Torin-1 significantly reduce co-localization of mTORC1 with Lamp-1, increased VPS16 vs Lamp-1 co-localization in P_i -stimulated CASMCs, associated with decreased exosome release. Functionally, Torin-1 significantly reduces arterial stiffening as shown by restoration from increased pulse wave velocity and decreased elastin breaks. These results suggest that lysosomal CER-mTOR signaling may play a critical role for the control of lysosome-MVB interaction, exosome secretion and arterial stiffening during AMC.

The Mechanisms of L-Arginine Metabolism Disorder in Endothelial Cells

L-arginine is a key metabolite for nitric oxide production by endothelial cells, as well as signaling molecule of the mTOR signaling pathway. mTOR supports endothelial cells homeostasis and regulates activity of L-arginine-metabolizing enzymes, endothelial nitric oxide synthase, and arginase II. Disruption of the L-arginine metabolism in endothelial cells leads to the development of endothelial dysfunction. Conflicting results of the use of L-arginine supplement to improve endothelial function reveals a controversial role of the amino acid in the endothelial cell biology. The review is aimed at analysis of the current data on the role of L-arginine metabolism in the development of endothelial dysfunction.

Role of intracellular signaling pathways and their inhibitors in the treatment of inflammation

Inflammation is not only a defense mechanism of the innate immune system against invaders, but it is also involved in the pathogenesis of many diseases such as atherosclerosis, thrombosis, diabetes, epilepsy, and many neurodegenerative disorders. The World Health Organization (WHO) reports worldwide estimates of people (9.6% in males and 18.0% in females) aged over 60 years, suffering from symptomatic osteoarthritis, and around 339 million suffering from asthma. Other chronic inflammatory diseases, such as ulcerative colitis and Crohn's disease are also highly prevalent. The existing anti-inflammatory agents, both non-steroidal and steroidal, are highly effective; however, their prolonged use is marred by the severity of associated side effects. A holistic approach to ensure patient compliance requires understanding the pathophysiology of inflammation and exploring new targets for drug development. In this regard, various intracellular cell signaling pathways and their signaling molecules have been identified to be associated with inflammation. Therefore, chemical inhibitors of these pathways may be potential candidates for novel anti-inflammatory drug approaches. This review focuses on the anti-inflammatory effect of these inhibitors (for JAK/STAT, MAPK, and mTOR pathways) describing their mechanism of action through literature search, current patents, and molecules under clinical trials.

Activation of GPR30 with G1 inhibits oscillatory shear stress-induced adhesion of THP-1 monocytes to HAECs by increasing KLF2

Atherosclerosis is a chronic inflammatory disease known to be mediated by numerous factors, among which endothelial dysfunction plays a critical role. Oscillatory shear stress induces endothelial cells to lose their anti-atherosclerotic properties and downregulates the expression of the innate protective transcription factor, Krüppel-like factor 2 (KLF2), which is typically upregulated in vascular endothelial cells in response to harmful stimuli. Oxidative stress and inflammation impair endothelial function and damage their survival. Oscillatory shear stress also promotes generation of reactive oxygen species and production of pro-inflammatory cytokines such as tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), thereby further promoting endothelial dysfunction and formation of atherosclerotic plaque. A major event in the development of atherosclerotic plaque is rolling and adhesion of monocytes to endothelial cells, which is mediated by adhesion molecules including vascular cellular adhesion molecule 1 and endothelial-selectin. Expression of these molecules is also upregulated by oscillatory shear stress. Estrogen has long been recognized as a protective agent against atherosclerosis, but the mechanisms through which estrogen receptors prevent atherogenesis remain unclear. In the present study, we investigated the role of the G-coupled protein estrogen receptor (GPR30) in oscillatory shear stress- induced endothelial dysfunction. We show that agonism of GPR30 by its specific agonist G1 prevented oscillatory shear stress -induced oxidative stress markers and production of inflammatory cytokines and adhesion molecules. As a result, GPR30 activation suppresses monocytes adhesion to endothelial cells. Furthermore, we demonstrate that GPR30 prevents oscillatory shear stress- induced downregulation of KLF2 via ERK5 pathway. These findings suggest that endothelial GPR30 is potential target to suppress oscillatory shear stress mediated atherogenesis.

Combined application of rapamycin and atorvastatin improves lipid metabolism in apolipoprotein E-deficient mice with chronic kidney disease

Atherosclerosis arising from the pro-inflammatory conditions associated with chronic kidney disease (CKD) increases major cardiovascular morbidity and mortality. Rapamycin (RAPA) is known to inhibit atherosclerosis under CKD and non-CKD conditions, but it can cause dyslipidemia; thus, the co-application of lipid-lowering agents is recommended. Atorvastatin (ATV) has been widely used to reduce serum lipids levels, but its synergistic effect with RAPA in CKD remains unclear. Here, we analyzed the effect of their combined treatment on atherosclerosis stimulated by CKD in apolipoprotein E-deficient (ApoE^−/−) mice. Oil Red O staining revealed that treatment with RAPA and RAPA＋ ATV, but not ATV alone, significantly decreased the atherosclerotic lesions in the aorta and aortic sinus, compared to those seen in the control (CKD) group. The co-administration of RAPA and ATV improved the serum lipid profile and raised the expression levels of proteins involved in reverse cholesterol transport (LXRα, CYP7A1, ABCG1, PPARγ, ApoA1) in the liver. The CKD group showed increased levels of various genes encoding atherosclerosis-promoting cytokines in the spleen (Tnf-α, Il-6 and Il-1β) and aorta (Tnf-α and Il-4), and these increases were attenuated by RAPA treatment. ATV and RAPA＋ATV decreased the levels of Tnf-α and Il-1β in the spleen, but not in the aorta. Together, these results indicate that, in CKD-induced ApoE^−/− mice, RAPA significantly reduces the development of atherosclerosis by regulating the expression of inflammatory cytokines and the co-application of ATV improves lipid metabolism.

Adropin inhibits the phenotypic modulation and proliferation of vascular smooth muscle cells during neointimal hyperplasia by activating the AMPK/ACC signaling pathway

In-stent restenosis (ISR) remains an inevitable problem for some patients receiving drug-eluting stent (DES) implantation. Intimal hyperplasia is an important biological cause of ISR. It has been previously reported that adropin is a potentially protective factor in cardiovascular disease. Therefore, the present study investigated the function of adropin in inhibiting smooth muscle cell (SMC) phenotype modulation and proliferation, causing intimal hyperplasia. A total of 56 patients who visited the hospital consecutively (25 with ISR and 31 without ISR), who were followed up between April 2016 and March 2019, 1 year following DES, were analyzed to evaluate the association between in-stent neointimal volume and adropin serum levels. Rat aorta smooth muscle cells (RASMCs) were used to determine the effects of adropin on their phenotypic modulation and proliferation using western blot, MTT, PCR and immunofluorescence analyses. Adropin serum levels in the ISR group were significantly lower than those in the non-ISR group. Furthermore, linear regression analysis revealed that only adropin levels were negatively associated with neointimal volume in both groups. The overall adropin levels of the 56 patients and the percentages of neointimal volume revealed a strong negative association. In vitro, adropin suppressed angiotensin II (Ang II)-induced phenotypic modulation in RASMCs by restoring variations of osteopontin and α-smooth muscle actin. Furthermore, compared with the Ang II group, adropin markedly decreased the percentage of G₂/M-phase cells. Finally, adropin negatively regulated the phenotypic modulation and proliferation of RASMCs via the AMP-activated protein kinase/acetyl-CoA carboxylase (AMPK/ACC) signaling pathway. In conclusion, an independent, negative association was revealed between adropin and intimal hyperplasia; specifically, adropin inhibited the phenotypic modulation and proliferation of RASMCs by activating the AMPK/ACC signaling pathway. Therefore, adropin may be used as a potential predictor and therapeutic target for intimal hyperplasia and ISR.

The Protective Role of Sestrin2 in Atherosclerotic and Cardiac Diseases

Atherosclerotic disease, such as coronary artery disease (CAD), is known to be a chronic inflammatory disease, as well as an age-related disease. Excessive oxidative stress produced by reactive oxygen species (ROS) contributes to the pathogenesis of atherosclerosis. Sestrin2 is an anti-oxidant protein that is induced by various stresses such as hypoxia, DNA damage, and oxidative stress. Sestrin2 is also suggested to be associated with aging. Sestrin2 is expressed and secreted mainly by macrophages, endothelial cells, and cardiomyocytes. Sestrin2 plays an important role in suppressing the production and accumulation of ROS, thus protecting cells from oxidative damage. Since sestrin2 is reported to have anti-oxidant and anti-inflammatory properties, it may play a protective role against the progression of atherosclerosis and may be a potential therapeutic target for the amelioration of atherosclerosis. Regarding the association between blood sestrin2 levels and atherosclerotic disease, the blood sestrin2 levels in patients with CAD or carotid atherosclerosis were reported to be high. High blood sestrin2 levels in patients with such atherosclerotic disease may reflect a compensatory response to increased oxidative stress and may help protect against the progression of atherosclerosis. This review describes the protective role of sestrin2 against the progression of atherosclerotic and cardiac diseases.

An observational study on the effect of hypercholesterolemia developed after living donor liver transplantation on cardiac event and graft failure

This study sought to evaluate the association between newly-developed significant hypercholesterolemia within one year following living donor liver transplantation (LDLT) and long term outcomes in light of cardiovascular events and graft failure. From October 2003 to July 2017, 877 LDLT recipients were stratified according to development of significant hypercholesterolemia within one year following LDLT. The primary outcome was occurrence of a major adverse cardiac event (MACE), defined as a composite of cardiac death, myocardial infarction, and coronary revascularization after LDLT. The incidence of graft failure, defined as all-cause death or retransplantation, was also compared. A total of 113 (12.9%) recipients developed significant hypercholesterolemia within one year. The differences in incidences of cardiac related events and graft related events began emerging significantly higher in the hypercholesterolemia group after 24 months and 60 months since the LDLT, respectively. After adjustment using the inverse probability of weighting, the hazard ratio (HR) for MACE was 2.77 (95% confidence interval (CI) 1.16–6.61; p = 0.02), while that for graft failure was 3.76 (95% CI 1.97–7.17, p < 0.001). A significant hypercholesterolemia after LDLT may be associated with cardiac and graft-related outcome; therefore, a further study and close monitoring of cholesterol level after LDLT is needed.

Biological Versus Chronological Aging: JACC Focus Seminar

Aging is the main risk factor for vascular disease and ensuing cardiovascular and cerebrovascular events, the leading causes of death worldwide. In a progressively aging population, it is essential to develop early-life biomarkers that efficiently identify individuals who are at high risk of developing accelerated vascular damage, with the ultimate goal of improving primary prevention and reducing the health care and socioeconomic impact of age-related cardiovascular disease. Studies in experimental models and humans have identified 9 highly interconnected hallmark processes driving mammalian aging. However, strategies to extend health span and life span require understanding of interindividual differences in age-dependent functional decline, known as biological aging. This review summarizes the current knowledge on biological age biomarkers, factors influencing biological aging, and antiaging interventions, with a focus on vascular aspects of the aging process and its cardiovascular disease related manifestations.

Dysregulation of leukocyte trafficking in ageing: Causal factors and possible corrective therapies

Ageing is a universal biological phenomenon that is accompanied by the development of chronic, low-grade inflammation and remodelling of the immune system resulting in compromised immune function. In this review, we explore how the trafficking of innate and adaptive immune cells under homeostatic and inflammatory conditions is dysregulated in ageing. We particularly highlight the age-related changes in the expression of adhesion molecules and chemokine receptor/ligands, and the accumulation of senescent cells that drive modulated leukocyte trafficking. These age-related changes to leukocyte trafficking are multifactorial and specific to leukocyte subset, tissue, type of vascular bed, and inflammatory status. However, dysregulated leukocyte trafficking ultimately affects immune responses in older adults. We therefore go on to discuss approved drugs, including anti-integrins, anti-chemokines and statins, as well as novel therapeutics that may be used to target dysregulated leukocyte trafficking in ageing, improve immune responses and delay the onset of age-related diseases.

VAMP3 and SNAP23 as Potential Targets for Preventing the Disturbed Flow-Accelerated Thrombus Formation

Disturbed blood flow has been recognized to promote platelet aggregation and thrombosis via increasing accumulation of von Willebrand factor (VWF) at the arterial post-stenotic sites. The mechanism underlying the disturbed-flow regulated endothelial VWF production remains elusive. Here we described a mouse model, in which the left external carotid artery (LECA) is ligated to generate disturbed flow in the common carotid artery. Ligation of LECA increased VWF accumulation in the plasma. Carotid arterial thrombosis was induced by ferric chloride (FeCl₃) application and the time to occlusion in the ligated vessels was reduced in comparison with the unligated vessels. In vitro, endothelial cells were subjected to oscillatory shear (OS, 0.5 ± 4 dynes/cm²) or pulsatile shear (PS, 12 ± 4 dynes/cm²). OS promoted VWF secretion as well as the cell conditioned media-induced platelet aggregation by regulating the intracellular localization of vesicle-associated membrane protein 3 (VAMP3) and synaptosomal-associated protein 23 (SNAP23). Disruption of vimentin intermediate filaments abolished the OS-induced translocation of SNAP23 to the cell membrane. Knockdown of VAMP3 and SNAP23 reduced the endothelial secretion of VWF. Systemic inhibition of VAMP3 and SNAP23 by treatment of mice with rapamycin significantly ameliorated the FeCl₃-induced thrombogenesis, whereas intraluminal overexpression of VAMP3 and SNAP23 aggravated it. Our findings demonstrate VAMP3 and SNAP23 as potential targets for preventing the disturbed flow-accelerated thrombus formation.

Juglanin suppresses oscillatory shear stress-induced endothelial dysfunction: An implication in atherosclerosis

INTRODUCTION

Atherosclerosis is characterized by endothelial cell dysfunction followed by lesion formation, arterial stenosis, potentially arterial occlusion, and severe outcomes. Novel treatments to slow or prevent the progression of the disease are of considerable clinical value. In the present study, we investigated the potential anti-atherosclerotic effects of the natural product juglanin in oscillatory shear stress (OSS) exposed endothelial cells.

METHODS

Human aortic endothelial cells (HAECs) were exposed to OSS generated by a micro fluidal Teflon cone at 1 Hz frequency cycles (±5 dyn/cm²) in the presence or absence of 2.5 and 5 μM juglanin for 24 h. The expression levels of inflammatory factors and vascular adhesion molecules were evaluated using qRT-PCR, Western Blot, and ELISA. DHE assay was used to detect the production of ROS. The monocytic THP-1 cells were labeled with calcein-AM and incubated with HAECs for adhesion assay.

RESULTS

Juglanin reduces OSS-induced oxidative stress by reducing the production of ROS through downregulation of NOX-2 and rescuing OSS-induced reduced expression of eNOS. Juglanin also inhibits the inflammatory response by suppressing OSS-induced expressions of IL-1β, MCP-1, and HMGB1. Using THP-1 monocytes, we show that juglanin reduces the attachment of monocytes to endothelial cells by inhibiting the expression of VCAM-1 and E-selectin. Moreover, Juglanin rescues OSS-reduced expression of atheroprotective transcriptional factor KLF2.

CONCLUSIONS

Our findings indicate that juglanin protects against various atheroprone OSS-induced endothelial dysfunction. Juglanin has potential implication as a candidate for vascular intervention of atherosclerosis.

Loss of the nutrient receptor Tas1R3 reduces atherosclerotic plaque accumulation and hepatic steatosis in ApoE-/- mice

The taste receptor type I (Tas1R) family consists of three G protein-coupled receptors (T1R1, T1R2, and T1R3) that form heterodimers recognizing sweet compounds (T1R2/T1R3) or amino acids (T1R1/T1R3). These receptors are nutrient sensors that facilitate appropriate physiological responses with nutrient availability. However, their contribution to the development of pathologies associated with overnutrition (e.g., atherosclerosis) is unclear. The aim of the present study was to determine if T1R3 deletion would reduce atherosclerotic plaque development in mice. We generated atherosclerotic mice with whole-body deletion of T1R3 by crossing T1R3^-/- mice with ApoE^-/- mice. T1R3^+/+ ApoE^-/- and T1R3^-/- ApoE^-/- mice were maintained on an atherogenic high-fat diet for 8 weeks. Weight gain and food consumption were measured during the 8-week diet. Atherosclerotic lesion development and size were assessed by en face analysis of intact aortas and microscopic analysis of aortic roots. Our results indicate that T1R3 deletion in male and female ApoE^-/- mice reduces aortic atherosclerotic plaque accumulation. Hepatic triglyceride accumulation, which was measured by quantification of oil red O staining, was also reduced in T1R3^-/- mice. While the ablation of T1R3 reduced the final body weight of both males and females by approximately 12%, serum lipids, insulin, and glucose were either unchanged or slightly reduced. Immunoblot analysis of the phosphorylation of p70S6K, an effector of mTORC1, suggests T1R3 ablation reduces mTORC1 activity by approximately 50% in the male livers. Collectively, these findings suggest that the whole-body deletion of T1R3 reduces atherosclerosis and hepatic steatosis in a manner largely independent of the measured effects on whole-body glucose and lipid homeostasis.

Vascular autophagy in health and disease

Homeostasis is maintained within organisms through the physiological recycling process of autophagy, a catabolic process that is intricately involved in the mobilization of nutrients during starvation, recycling of cellular cargo, as well as initiation of cellular death pathways. Specific to the cardiovascular system, autophagy responds to both chemical (e.g. free radicals) and mechanical stressors (e.g. shear stress). It is imperative to note that autophagy is not a static process, and measurement of autophagic flux provides a more comprehensive investigation into the role of autophagy. The overarching themes emerging from decades of autophagy research are that basal levels of autophagic flux are critical, physiological stressors may increase or decrease autophagic flux, and more importantly, aberrant deviations from basal autophagy may elicit detrimental effects. Autophagy has predominantly been examined within cardiac or vascular smooth muscle tissue within the context of disease development and progression. Autophagic flux within the endothelium holds an important role in maintaining vascular function, demonstrated by the necessary role for intact autophagic flux for shear-induced release of nitric oxide however the underlying mechanisms have yet to be elucidated. Within this review, we theorize that autophagy itself does not solely control vascular homeostasis, rather, it works in concert with mitochondria, telomerase, and lipids to maintain physiological function. The primary emphasis of this review is on the role of autophagy within the human vasculature, and the integrative effects with physiological processes and diseases as they relate to the vascular structure and function.

Sestrin2 as a potential therapeutic target for cardiovascular diseases

Sestrin2 is a cysteine sulfinyl reductase that plays crucial roles in regulation of antioxidant actions. Sestrin2 provides cytoprotection against multiple stress conditions, including hypoxia, endoplasmic reticulum (ER) stress and oxidative stress. Recent research reveals that upregulation of Sestrin2 is induced by various transcription factors such as p53 and activator protein 1 (AP-1), which further promotes AMP-activated protein kinase (AMPK) activation and inhibits mammalian target of rapamycin protein kinase (mTOR) signaling. Sestrin2 triggers autophagy activity to reduce cellular reactive oxygen species (ROS) levels by promoting nuclear factor erythroid 2 (NF-E2)-related factor 2 (Nrf2) activation and Kelch-like ECH-associated protein 1 (Keap1) degradation, which plays a pivotal role in homeostasis of metabolic regulation. Under hypoxia and ER stress conditions, elevated Sestrin2 expression maintains cellular homeostasis through regulation of antioxidant genes. Sestrin2 is responsible for diminishing cellular ROS accumulation through autophagy via AMPK activation, which displays cardioprotection effect in cardiovascular diseases. In this review, we summarize the recent understanding of molecular structure, biological roles and biochemical functions of Sestrin2, and discuss the roles and mechanisms of Sestrin2 in autophagy, hypoxia and ER stress. Understanding the precise functions and exact mechanism of Sestrin2 in cellular homeostasis will provide the evidence for future experimental research and aid in the development of novel therapeutic strategies for cardiovascular diseases.

Progression of vascular remodeling in pulmonary vein obstruction

OBJECTIVES

Pulmonary vein obstruction (PVO) frequently occurs after repair of total anomalous pulmonary vein connection with progression of intimal hyperplasia from the anastomotic site toward upstream pulmonary veins (PVs). However, the understanding of mechanism in PVO progression is constrained by lack of data derived from a physiological model of the disease, and no prophylaxis has been established. We developed a new PVO animal model, investigated the mechanisms of PVO progression, and examined a new prophylactic strategy.

METHODS

We developed a chronic PVO model using infant domestic pigs by cutting and resuturing the left lower PV followed by weekly hemodynamic parameter measurement and angiographic assessment of the anastomosed PV. Subsequently, we tested a novel therapeutic strategy with external application of rapamycin-eluting film to the anastomotic site.

RESULTS

We found the pig PVO model mimicked human PVO hemodynamically and histopathologically. This model exhibited increased expression levels of Ki-67 and phospho-mammalian target of rapamycin in smooth muscle-like cells at the anastomotic neointima. In addition, contractile to synthetic phenotypic transition; that is, dedifferentiation of smooth muscle cells and mammalian target of rapamycin pathway activation in the neointima of upstream PVs were observed. Rapamycin-eluting films externally applied around the anastomotic site inhibited the activation of mammalian target of rapamycin in the smooth muscle-like cells of neointima, and delayed PV anastomotic stenosis.

CONCLUSIONS

We demonstrate the evidence on dedifferentiation of smooth muscle-like cells and mammalian target of rapamycin pathway activation in the pathogenesis of PVO progression. Delivery of rapamycin to the anastomotic site from the external side delayed PV anastomotic stenosis, implicating a new therapeutic strategy to prevent PVO progression.

Autophagy as an emerging therapeutic target for age-related vascular pathologies

Introduction: The incidence of age-related vascular diseases such as arterial stiffness, hypertension and atherosclerosis, is rising dramatically and is substantially impacting healthcare systems. Mounting evidence suggests that there is an important role for autophagy in maintaining (cardio)vascular health. Impaired vascular autophagy has been linked to arterial aging and the initiation of vascular disease.Areas covered: The function and implications of autophagy in vascular smooth muscle cells and endothelial cells are discussed in healthy blood vessels and arterial disease. Furthermore, we discuss current treatment options for vascular disease and their links with autophagy. A literature search was conducted in PubMed up to October 2019.Expert opinion: Although the therapeutic potential of inducing autophagy in age-related vascular pathologies is considerable, several issues should be addressed before autophagy induction can be clinically used to treat vascular disease. These issues include uncertainty regarding the most effective drug target as well as the lack of potency and selectivity of autophagy inducing drugs. Moreover, drug tolerance or autophagy mediated cell death have been reported as possible adverse effects. Special attention is required for determining the cause of autophagy deficiency to optimize the treatment strategy.