Effect of everolimus on pre-existing atherosclerosis in LDL-receptor deficient mice

Combination therapy and drug co-delivery systems for atherosclerosis

Atherosclerosis is a chronic inflammatory disease characterized by the accumulation of plaque within the arteries. Despite advances in therapeutic strategies including anti-inflammatory, antioxidant, and lipid metabolism modulation treatments over the past two decades, the treatment of atherosclerosis remains challenging, as arterial damage is the result of interconnected pathological factors. Therefore, current monotherapies often fail to address the complex nature of this disease, leading to insufficient therapeutic outcomes. This review addressed this paucity of effective treatment options by comprehensively exploring the potential for combination therapies and advanced drug co-delivery systems for the treatment of atherosclerosis. We investigated the pathological features of and risk factors for atherosclerosis, underscoring the importance of drug combination therapies for the treatment of atherosclerotic diseases. We discuss herein mathematical models for quantifying the efficacy of the combination therapies and provide a systematic summary of drug combinations for the treatment of atherosclerosis. We also provide a detailed review of the latest advances in nanoparticle-based drug co-delivery systems for the treatment of atherosclerosis, focusing on the design of carriers with high biocompatibility and efficacy. By exploring the possibilities and challenges inherent to this approach, we aim to highlight cutting-edge technologies that can foster the development of innovative strategies, optimize drug co-administration, improve treatment outcomes, and reduce the burden of atherosclerosis-related morbidity and mortality on the healthcare system.

Targeted delivery of rapamycin and inhibition of platelet adhesion with multifunctional peptide nanoparticles for atherosclerosis treatment

There is increasing evidence supporting the unique benefits of targeted therapy in treating atherosclerotic disease. Given the complex nature of atherosclerosis development, we proposed a novel strategy for the efficient delivery of rapamycin (RAPA) by targeting both the exposed subendothelial collagen and oxidized low-density lipoprotein (oxLDL) present in plaques. In response, we developed multifunctional peptide (MP) nanoparticles for targeted drug delivery. The ability of MP nanoparticles to load RAPA and target collagen/oxLDL was investigated through molecular dynamics simulations and in vitro experiments. The efficacy of MP nanoparticles in atherosclerosis treatment was assessed via in vivo experiments on ApoE-/- mice. Results indicate that MP nanoparticles have encapsulation and drug loading efficiencies for RAPA of 78.3 % and 43.9 %, respectively. By targeting collagen, MP nanoparticles create steric hindrance that inhibits 77.2 % of platelet adhesion. These nanoparticles can also target oxLDL, delivering RAPA into plaques and significantly reducing macrophage uptake of oxLDL. In vivo experiments showed that MP nanoparticles effectively targeted and accumulated in plaques. Treating mice with MP@RAPA nanoparticles for 10 weeks led to an 81.3 % reduction in the aortic vascular plaque area and decreased concentrations of MCP-1, hs-CRP, MMP-1, P-selectin, IL-1β, and IL-8 inflammatory factors, as well as the optical density of platelet-associated proteins (CD42, CD61, and PECAM-1). These results highlight the promising potential of MP nanoparticles for atherosclerotic disease treatment.

Delivery of rapamycin by biomimetic peptide nanoparticles targeting oxidized low-density lipoprotein in atherosclerotic plaques

Drug delivery systems based on biomimetic peptide nanoparticles are steadily gaining prominence in the treatment of diverse medical conditions. This study focused on the development of peptides that depend on ligand-receptor interactions to load rapamycin (RAPA). Furthermore, a multifunctional peptide was engineered to target oxidized low-density lipoprotein (oxLDL) within atherosclerotic plaques, facilitating the localized delivery of RAPA. The interactions between peptides and RAPA/oxLDL were analyzed by simulations and experimental approaches. Results show that the main amino acid residues on the mammalian target of rapamycin that bind to RAPA are constructed as peptides (P1 and P2), which have specific interactions with RAPA and can effectively improve the loading efficiency of RAPA. The encapsulation and drug loading efficiencies of P1/P2 were 68.0/47.9% and 48.3/36.5%, respectively. In addition, the interaction force of the multifunctional peptide (P3) and oxLDL surpassed that of their interaction with human umbilical vein endothelial cells by a factor of 3.6, conclusively establishing the specific targeting of oxLDL by these nanoparticles. The encapsulation and drug loading efficiencies of P3 for RAPA were determined to be 60.2% and 41.5%. P3 can effectively load RAPA and target oxLDL within the plaque, suggesting that P3 has potential as a therapeutic agent for atherosclerotic disease.

Long-term intracoronary imaging and physiological measurements of bioresorbable scaffolds and untreated atherosclerotic plaques

BACKGROUND

Bioresorbable scaffolds (BRS) provide the prospect of restoring the anatomic and physiologic characteristics of the vascular wall.

OBJECTIVE

This study sought to examine the long-term outcomes of BRS-based coronary intervention in a young population with diffuse and severe coronary atherosclerotic disease (CAD) and to compare the long-term evolution of treated segments versus the natural progression of untreated non-flow limiting stenoses.

METHODS

Observational, single-center cohort study that prospectively included patients that underwent percutaneous coronary intervention with implantation of ABSORB BRS (Abbott Vascular). The clinical endpoint was the incidence of device-oriented composite endpoint (DoCE) up to 5 years follow-up. A subgroup of patients with baseline intracoronary imaging assessment of long lesions and/or multivessel disease underwent elective angiographic (70 patients, 129 lesions) and intracoronary imaging (55 patients, 102 lesions) follow-up. Paired intravascular ultrasound (IVUS) and quantitative flow reserve (QFR) were analyzed.

RESULTS

Between 2012 and 2017, 159 patients (mean age 54.0 ± 11.1) with native CAD were treated with BRS on 247 lesions. Patients were mainly at their first cardiac event, mostly acute coronary syndromes (86.5%). At the median follow-up time of 56 months [41-65], DoCE occurred in 15/159 (9.4%) patients, while non-target vessel-oriented composite endpoint occurred in 16 patients (10.4%). A significant atherosclerotic progression was detected on residual non-flow limiting plaques as per IVUS and QFR assessment, while no significant change was detected in the treated segment.

CONCLUSIONS

Mild-to-moderate asymptomatic CAD progressed significantly at 5-year despite OMT. BRS-treated segments had a less aggressive progression at 5-year despite more severe and symptomatic CAD at baseline.

Comprehensive view of macrophage autophagy and its application in cardiovascular diseases

Cardiovascular diseases (CVDs) are the primary drivers of the growing public health epidemic and the leading cause of premature mortality and economic burden worldwide. With decades of research, CVDs have been proven to be associated with the dysregulation of the inflammatory response, with macrophages playing imperative roles in influencing the prognosis of CVDs. Autophagy is a conserved pathway that maintains cellular functions. Emerging evidence has revealed an intrinsic connection between autophagy and macrophage functions. This review focuses on the role and underlying mechanisms of autophagy-mediated regulation of macrophage plasticity in polarization, inflammasome activation, cytokine secretion, metabolism, phagocytosis, and the number of macrophages. In addition, autophagy has been shown to connect macrophages and heart cells. It is attributed to specific substrate degradation or signalling pathway activation by autophagy-related proteins. Referring to the latest reports, applications targeting macrophage autophagy have been discussed in CVDs, such as atherosclerosis, myocardial infarction, heart failure, and myocarditis. This review describes a novel approach for future CVD therapies.

Cardiovascular effects of immunosuppression agents

Immunosuppressive medications are widely used to treat patients with neoplasms, autoimmune conditions and solid organ transplants. Key drug classes, namely calcineurin inhibitors, mammalian target of rapamycin (mTOR) inhibitors, and purine synthesis inhibitors, have direct effects on the structure and function of the heart and vascular system. In the heart, immunosuppressive agents modulate cardiac hypertrophy, mitochondrial function, and arrhythmia risk, while in vasculature, they influence vessel remodeling, circulating lipids, and blood pressure. The aim of this review is to present the preclinical and clinical literature examining the cardiovascular effects of immunosuppressive agents, with a specific focus on cyclosporine, tacrolimus, sirolimus, everolimus, mycophenolate, and azathioprine.

Modulation of mTOR Signaling in Cardiovascular Disease to Target Acute and Chronic Inflammation

Inflammation is a key component in the pathogenesis of cardiovascular diseases causing a significant burden of morbidity and mortality worldwide. Recent research shows that mammalian target of rapamycin (mTOR) signaling plays an important role in the general and inflammation-driven mechanisms that underpin cardiovascular disease. mTOR kinase acts prominently in signaling pathways that govern essential cellular activities including growth, proliferation, motility, energy consumption, and survival. Since the development of drugs targeting mTOR, there is proven efficacy in terms of survival benefit in cancer and allograft rejection. This review presents current information and concepts of mTOR activity in myocardial infarction and atherosclerosis, two important instances of cardiovascular illness involving acute and chronic inflammation. In experimental models, inhibition of mTOR signaling reduces myocardial infarct size, enhances functional remodeling, and lowers the overall burden of atheroma. Aside from the well-known effects of mTOR inhibition, which are suppression of growth and general metabolic activity, mTOR also impacts on specific leukocyte subpopulations and inflammatory processes. Inflammatory cell abundance is decreased due to lower migratory capacity, decreased production of chemoattractants and cytokines, and attenuated proliferation. In contrast to the generally suppressed growth signals, anti-inflammatory cell types such as regulatory T cells and reparative macrophages are enriched and activated, promoting resolution of inflammation and tissue regeneration. Nonetheless, given its involvement in the control of major cellular pathways and the maintenance of a functional immune response, modification of this system necessitates a balanced and time-limited approach. Overall, this review will focus on the advancements, prospects, and limits of regulating mTOR signaling in cardiovascular disease.

The role and transformative potential of IL-19 in atherosclerosis

Atherosclerotic cardiovascular disease is the leading cause of death worldwide. Traditionally, IL-19 was thought to be expressed in only immune cells, but studies revealed that IL-19 is also expressed in multiple atherosclerotic plaque cell types, but not normal arteries, in humans and mice. IL-19 reduces the development of atherosclerosis via multiple mechanisms, including balancing cholesterol metabolism; enhancing Th2 immune cell polarization; reducing the inflammatory response; and reducing the proliferation, migration and chemotaxis of vascular smooth muscle cells (VSMCs). Clinical and/or animal studies have primarily aimed to achieve regression and/or stabilization of atherosclerotic plaques, with regression in particular indicating a very good drug response. Most antiatherosclerotic drugs in current clinical use, including atorvastatin and alirocumab, target hyperlipidemia. Several other drugs have also been investigated in clinical trials as anti-inflammatory agents; the development of some of these agents has been terminated (canakinumab, darapladib, varespladib, losmapimod, atreleuton, setileuton, PF-04191834, veliflapon, and methotrexate), but others remain in development (ziltivekimab, tocilizumab, Somalix, IFM-2427, anakinra, mesenchymal stem cells (MSCs), colchicine, everolimus, allopurinol, and montelukast). Most of the tested drugs have shown a limited ability to reverse atherosclerosis in animal studies. Interestingly, recombinant IL-19 (rIL-19) was shown to reduce atherosclerosis development in a time- and dose-dependent manner. A low dose of rIL-19 (1 ng/g/day) reduced aortic arch and root plaque areas by 70.1% and 32.1%, respectively, in LDLR^-/- mice. At 10 ng/g/day, rIL-19 completely eliminated atherosclerotic plaques. There were no sex differences in the effects of rIL-19 on atherosclerotic mice. Thus, low-dose rIL-19 is an effective antiatherosclerotic agent, in addition to its efficacy in intimal hyperplasia, spinal cord injury, stroke, and multiple sclerosis. We propose that IL-19 is a promising biomarker and target for the diagnosis and treatment of atherosclerosis. This review considers the role and mechanism of action of IL-19 in atherosclerosis and discusses whether IL-19 is a potential therapeutic target for this condition.

MicroRNA-761 modulates foam cell formation and inflammation through autophagy in the progression of atherosclerosis

Macrophage-derived foam cells formation is the initial stage of atherosclerosis, and lipid-laden macrophage accumulation is also considered as the symbol of unstable plaque. Autophagy is a subcellular process responsible for the degradation of damaged organelles and aggregated proteins in cells (Grootaert in Oxid Med Cell Longev: 7687083, 2018). Macrophage autophagy plays an important role in atherosclerosis under various stress conditions, and microRNAs are involved in this complicated process. The present study was programmed to explore the effects of microRNA-761 on macrophage-derived foam cell formation, focusing on the role of autophagy in this pathological process. The differentiated human THP-1 macrophages were used in the study. THP-1-derived macrophages were treated with miR-761 mimics or inhibitors and cultured with oxidized low-density lipoprotein to mimic the lipid-rich environment in blood vessel. The expression of miR-761 and mRNA levels of IL-1β and IL-18 were analyzed by quantitative real-time PCR. The effect of miR-761 on autophagy was evaluated by the protein levels of Beclin1, p62/SQSTM1, microtubule-associated protein light chain 3, mammalian target of rapamycin (mTOR), and unc-51-like autophagy activating kinase 1 (ULK1), determined by immunoblot and autophagic flux detected by fluorescent staining. The secretion of IL-1β and IL-18 was tested by enzyme-linked immunosorbent reaction kit. Lipid accumulation in foam cells was detected by oil red "O" staining. We demonstrated that miR-761 was able to repress foam cell formation and reduce the production of atherogenic inflammatory cytokines IL-1β and IL-18 in an autophagy-dependent manner in atherosclerosis, possibly via mTOR-ULK1 signaling pathway. In summary, we described an athero-protective function of miR-761 in macrophages incubated with excess ox-LDL and identified an important novel modulator of mTOR signaling and autophagy in macrophage-derived foam cells. This finding may provide a potential target for the prevention and early treatment in high-risk group of atherosclerosis.

PRAS40 suppresses atherogenesis through inhibition of mTORC1-dependent pro-inflammatory signaling in endothelial cells

Endothelial pro-inflammatory activation plays a pivotal role in atherosclerosis, and many pro-inflammatory and atherogenic signals converge upon mechanistic target of rapamycin (mTOR). Inhibitors of mTOR complex 1 (mTORC1) reduced atherosclerosis in preclinical studies, but side effects including insulin resistance and dyslipidemia limit their clinical use in this context. Therefore, we investigated PRAS40, a cell type-specific endogenous modulator of mTORC1, as alternative target. Indeed, we previously found PRAS40 gene therapy to improve metabolic profile; however, its function in endothelial cells and its role in atherosclerosis remain unknown. Here we show that PRAS40 negatively regulates endothelial mTORC1 and pro-inflammatory signaling. Knockdown of PRAS40 in endothelial cells promoted TNFα-induced mTORC1 signaling, proliferation, upregulation of inflammatory markers and monocyte recruitment. In contrast, PRAS40-overexpression blocked mTORC1 and all measures of pro-inflammatory signaling. These effects were mimicked by pharmacological mTORC1-inhibition with torin1. In an in vivo model of atherogenic remodeling, mice with induced endothelium-specific PRAS40 deficiency showed enhanced endothelial pro-inflammatory activation as well as increased neointimal hyperplasia and atherosclerotic lesion formation. These data indicate that PRAS40 suppresses atherosclerosis via inhibition of endothelial mTORC1-mediated pro-inflammatory signaling. In conjunction with its favourable effects on metabolic homeostasis, this renders PRAS40 a potential target for the treatment of atherosclerosis.

Rapamycin prevents thoracic aortic aneurysm and dissection in mice

OBJECTIVE

The purpose of this study was to investigate whether rapamycin inhibits the development of thoracic aortic aneurysm and dissection (TAAD) in mice.

METHODS

Three-week-old C57BL/6J male mice were fed a normal diet and randomized into a control group (n = 6), β-aminopropionitrile fumarate (BAPN) group (Gp A; n = 15), BAPN plus rapamycin (5 mg) group (Gp B; n = 8), and BAPN plus rapamycin (10 mg) group (Gp C; n = 8). Gp A, Gp B, and Gp C were administered BAPN (1 g/kg/d) for 4 weeks. One week after BAPN administration, Gp B and Gp C were treated with rapamycin (5 mg/kg/d or 10 mg/kg/d) through gavage for 21 days. Thoracic aortas were harvested for Western blot and immunofluorescence staining at day 14 and for morphologic and histologic analyses at day 28.

RESULTS

BAPN treatment induced TAAD formation in mice. The incidence of TAAD in control, Gp A, Gp B, and Gp C mice was 0%, 80%, 25%, and 37.5%, respectively. Smaller thoracic aortic diameters (ascending aorta and arch) were observed in Gp B and Gp C mice than in Gp A mice (Gp B vs Gp A: ascending aorta, ex vivo, 1.07 ± 0.21 mm vs 1.80 ± 0.67 mm [P < .05]; aortic arch, ex vivo, 1.51 ± 0.40 mm vs 2.70 ± 1.06 mm [P < .05]; Gp C vs Gp A: ascending aortas, ex vivo, 1.10 ± 0.33 mm vs 1.80 ± 0.67 mm [P < .05]; aortic arch, ex vivo, 1.55 ± 0.56 mm vs 2.70 ± 1.06 mm [P < .05]). TAAD mice exhibited elastin fragmentation, abundant inflammatory cell infiltration, and significantly increased matrix metalloproteinase production in the aorta, and rapamycin treatment alleviated these changes. The protein levels of p-S6K and p-S6 in TAAD aortic tissues increased significantly, whereas they were suppressed by rapamycin.

CONCLUSIONS

Rapamycin suppressed TAAD formation, probably by inhibition of mechanistic target of rapamycin signaling and reduction of inflammatory cell infiltration and matrix metalloproteinase 9 production. Targeting of the mechanistic target of rapamycin signaling pathway using rapamycin may be a favorable modulation for the clinical treatment of TAAD.

mTOR pathway activation in large vessel vasculitis

BACKGROUND

Mammalian target of rapamycin complex 1 (mTORC 1) drives the proinflammatory expansion of T helper (TH) type 1, TH17 cells and controls fibroblast proliferation, typical features of large vessel vasculitis (LVV) pathogenesis. Molecular pathways involved in arterial lesions of LVV are unknown.

METHODS

We evaluate mTORC pathway activation in vascular aorta lesions and in T cell homeostasis of patients with LVV.

RESULTS

Proliferation of both endothelial cells and vascular smooth-muscle cells was shown in vascular lesions in LVV. The vascular endothelium of proliferating aorta vessels from patients with LVV showed indications of activation of the mTORC1 pathway (S6RP phosphorylation). In cultured vascular endothelial cells, sera from patients with LVV stimulated mTORC1 through the phosphorylation of S6RP. mTORC1 activation was found also in Th1 and Th17 cells both systemically and in inflamed vessels. Patients with LVV exhibited a diminished S6RP phosphorylation in Tregs. Inhibition of mTORC1 pathway with rapamycin, increase Tregs and decrease effector CD4⁺IFNγ⁺, CD4⁺IL17⁺ and CD4⁺IL21⁺ T cells in patients with LVV.

CONCLUSIONS

We provided evidence that mTORC1 pathway has a central role in driving T cell inflammation and vascular lesions in LVV. Targeting mTORC pathway may represent a new therapeutic option in patients with LVV.

Everolimus as cancer therapy: Cardiotoxic or an unexpected antiatherogenic agent? A narrative review

Everolimus (EVE) is now approved by many agencies for the treatment of variable neoplasms. The risk for adverse events with this agent is not adequately defined. The purpose of this review is to summarize the EVE-induced cardiotoxic effect as an antineoplastic factor on patients who received the specific drug and to evaluate any possible antiatherogenic effects due to systemic use of the drug. Articles were searched on PubMed until August 2017. Articles included an expanded-access clinical trial, as well as phase 2 or 3 clinical trials (most of them were randomized). Three experimental studies that provided evidence for the possible antiatherogenic action of EVE were also included. In addition, only studies that evaluated the systemic use of the drug were included. To be eligible for inclusion, trials should have evaluated patients with malignancy, treated by EVE, or assessed the antiatherogenic effect of the systemic use of EVE through clinical or experimental studies. Only articles written in English language were included. No direct cardiotoxic adverse effects (arrhythmia, acute coronary event, heart failure, and echocardiography pathologic findings) were reported. Patients appeared to have a risk of developing adverse events that could be associated with the risk factors of cardiovascular disease. In all clinical studies, patients suffered hyperglycemia, and in most of them, hyperlipidemia was observed. Fewer studies have reported the incidence of hypertension. Finally, there is evidence claiming that EVE has an antiatherogenic action. Three experimental studies have shown that the systemic use of EVE in mice or rabbits with atherosclerotic lesions led to the reduction in atheromatous plaque growth. However, we could not find any clinical study that showed similar results in patients with cancer. To sum up, the only reported cardiac adverse event of EVE treatment in patients with cancer is indirect. They are associated with the risk factors of cardiovascular disease (hyperglycemia, hyperlipidemia, and hypertension), which are mainly mild and easily manageable. Further research and data that support the antiatherogenic action of EVE are needed.

Methods for Measuring Autophagy in Mice

Autophagy is a dynamic intracellular process that mediates the degradation of damaged cytoplasmic components by the lysosome. This process plays important roles in maintaining normal cellular homeostasis and energy balance. Measuring autophagy activity is critical and although the determination of autophagic flux in isolated cells is well documented, there is a need to have reliable and quantitative assays to evaluate autophagy in whole organisms. Because mouse models have been precious in establishing the functional significance of autophagy under physiological or pathological conditions, we present in this chapter a compendium of the current available methods to measure autophagy in mice, and discuss their advantages and limitations.

Sirolimus Therapy Is Associated with Elevation in Circulating PCSK9 Levels in Cardiac Transplant Patients

Sirolimus used in transplantation is often associated with hypercholesterolemia. We measured serum lipid and PCSK9 levels in 51 heart transplant recipients who had their immunosuppressive therapy switched from calcineurin inhibitors to sirolimus. The switch resulted in a 23% increase in LDL cholesterol, and 46% increase in triglycerides and PCSK9 levels increased from 316 ± 105 ng/mL to 343 ± 107 ng/mL (p = 0.04), however the change in PCSK9 levels did not correlate with an increase in lipid levels (p = 0.2). To investigate the mechanism for the variability in the change in PCSK9 levels, lymphoblastoid cell lines were incubated with both sirolimus and everolimus, resulting in a 2-3 fold increase in PCSK9 expression and protein levels in mTOR inhibitor sensitive but not in mTOR inhibitor resistant cell lines. This first in human study demonstrates that sirolimus therapy is associated with elevation in PCSK9 levels which is not associated with sirolimus-induced hypercholesterolemia.

Multiple pathway assessment to predict anti-atherogenic efficacy of drugs targeting macrophages in atherosclerotic plaques

BACKGROUND

Macrophages play a central role in atherosclerosis development and progression, hence, targeting macrophage activity is considered an attractive therapeutic. Recently, we documented nanomedicinal delivery of the anti-inflammatory compound prednisolone to atherosclerotic plaque macrophages in patients, which did however not translate into therapeutic efficacy. This unanticipated finding calls for in-depth screening of drugs intended for targeting plaque macrophages.

METHODS AND RESULTS

We evaluated the effect of several candidate drugs on macrophage activity, rating overall performance with respect to changes in cytokine release, oxidative stress, lipid handling, endoplasmic reticulum (ER) stress, and proliferation of macrophages. Using this in vitro approach, we observed that the anti-inflammatory effect of prednisolone was counterbalanced by multiple adverse effects on other key pathways. Conversely, pterostilbene, T0901317 and simvastatin had an overall anti-atherogenic effect on multiple pathways, suggesting their potential for liposomal delivery.

CONCLUSION

This dedicated assay setup provides a framework for high-throughput assessment. Further in vivo studies are warranted to determine the predictive value of this macrophage-based screening approach and its potential value in nanomedicinal drug development for cardiovascular patients.

Potential therapeutic effects of mTOR inhibition in atherosclerosis

Despite significant improvement in the management of atherosclerosis, this slowly progressing disease continues to affect countless patients around the world. Recently, the mechanistic target of rapamycin (mTOR) has been identified as a pre-eminent factor in the development of atherosclerosis. mTOR is a constitutively active kinase found in two different multiprotein complexes, mTORC1 and mTORC2. Pharmacological interventions with a class of macrolide immunosuppressive drugs, called rapalogs, have shown undeniable evidence of the value of mTORC1 inhibition to prevent the development of atherosclerotic plaques in several animal models. Rapalog-eluting stents have also shown extraordinary results in humans, even though the exact mechanism for this anti-atherosclerotic effect remains elusive. Unfortunately, rapalogs are known to trigger diverse undesirable effects owing to mTORC1 resistance or mTORC2 inhibition. These adverse effects include dyslipidaemia and insulin resistance, both known triggers of atherosclerosis. Several strategies, such as combination therapy with statins and metformin, have been suggested to oppose rapalog-mediated adverse effects. Statins and metformin are known to inhibit mTORC1 indirectly via 5' adenosine monophosphate-activated protein kinase (AMPK) activation and may hold the key to exploit the full potential of mTORC1 inhibition in the treatment of atherosclerosis. Intermittent regimens and dose reduction have also been proposed to improve rapalog's mTORC1 selectivity, thereby reducing mTORC2-related side effects.

The Role of PB1 Domain Proteins in Endothelial Cell Dysfunction and Disease

SIGNIFICANCE

There are a limited number of proteins containing the Phox-Bem1 (PB1) protein interaction domain, and almost all of them play some role in endothelial cell (EC) function, health, and homeostasis.

RECENT ADVANCES

Most of these proteins have been shown to physically interact through PB1-PB1 binding and, as such, are linked together to form complexes that are responsive to hemodynamic force. These complexes range from redox regulation to inflammation to autophagy and back, and they employ multiple feedback mechanisms that are reliant on PB1 domain proteins.

CRITICAL ISSUES

Pathologic roles for PB1 domain-containing proteins have been demonstrated in multiple diseases, including vascular disease, cancer, liver disease, and myriad other concerns. Findings cited in this review show that dimerization of PB1 proteins exerts novel effects on EC function that may be important in multiple cardiovascular diseases, including atherosclerosis, thrombosis, inflammation, and hypertension.

FUTURE DIRECTIONS

As mechanistic understanding of the component pathways (redox regulation, cell polarity, inflammation, atheroprotection, and autophagy) is continually increasing, the larger picture of how these pathways interact with one another is evolving rapidly. We can now evaluate the PB1 domain proteins as a family in the context of multiple phenotypic readouts in EC function as well as evaluate them as drug targets against disease.

Autophagy in Vascular Disease

Autophagy is a reparative, life-sustaining process by which cytoplasmic components are sequestered in double-membrane vesicles and degraded on fusion with lysosomal compartments. Growing evidence reveals that basal autophagy is an essential in vivo process mediating proper vascular function. Moreover, autophagy is stimulated by many stress-related stimuli in the arterial wall to protect endothelial cells and smooth muscle cells against cell death and the initiation of vascular disease, in particular atherosclerosis. Basal autophagy is atheroprotective during early atherosclerosis but becomes dysfunctional in advanced atherosclerotic plaques. Little is known about autophagy in other vascular disorders, such as aneurysm formation, arterial aging, vascular stiffness, and chronic venous disease, even though autophagy is often impaired. This finding highlights the need for pharmacological interventions with compounds that stimulate the prosurvival effects of autophagy in the vasculature. A large number of animal studies and clinical trials have indicated that oral or stent-based delivery of the autophagy inducer rapamycin or derivatives thereof, collectively known as rapalogs, effectively inhibit the basic mechanisms that control growth and destabilization of atherosclerotic plaques. Other autophagy-inducing drugs, such as spermidine or add-on therapy with widely used antiatherogenic compounds, including statins and metformin, are potentially useful to prevent vascular disease with minimal adverse effects.

Neutrophil gelatinase-associated lipocalin (NGAL) in heart transplant recipients after conversion to everolimus therapy

BACKGROUND

Due to the lack of nephrotoxic activity, proliferation signal inhibitors (PSI) such as everolimus are recommended for immunosuppression after heart transplantation, but the assessment of renal function in patients receiving PSI has led to conflicting results. We examined renal integrity and function using neutrophil gelatinase-associated lipocalin (NGAL) and conventional markers [plasma creatinine, cystatin C, urine albumin, α1-microglobulin (α1M)] in heart transplant patients, who underwent conversion to everolimus due to allograft vasculopathy, graft rejection episodes, or renal function deterioration, and in patients maintained on calcineurin inhibitors (CNI).

METHODS

This cross-sectional study included 121 consecutive heart transplant recipients: 44 patients received CNI-free immunosuppressive therapy with everolimus and 77 patients received CNI. Renal parameters were determined in plasma and urine samples using standard enzymatic or immunochemical methods.

RESULTS

Heart transplant recipients receiving everolimus therapy had significantly lower NGAL concentrations in plasma [median (95% CI): 128 (97-176)ng/mL vs. 252 (224-283)ng/mL, p<0.001] and urine [median (95% CI): 6.4 (4.5-7.6)ng/g vs. 15.7 (10.2-25.9)ng/g creatinine, p<0.001]. In contrast, no significant differences were observed between everolimus- and CNI-treated groups with regard to creatinine and cystatin C, as well as urine albumin and α1M levels. Significant correlations were noted between plasma NGAL and creatinine (r=0.42, p<0.001), cystatin C (r=0.44, p<0.001), N-terminal brain natriuretic propeptide (r=0.31, p<0.01) and indicators of chronic inflammation [lipoprotein-associated phospholipase A2 (Lp-PLA2), r=0.31, p<0.01] and soluble CD40 ligand (sCD40L, r=0.22, p<0.05), and between urinary NGAL and α1M (r=0.21, p<0.05). Multiple regression analysis indicated that cystatin C and Lp-PLA2 were the best predictors of plasma NGAL.

CONCLUSION

The present study documents reduced plasma and urinary NGAL levels in the absence of differences in conventional renal parameters in patients on CNI-free immunosuppressive therapy with everolimus. These results support favorable effects of everolimus on renal integrity in heart transplant recipients.

mTOR inhibition: a promising strategy for stabilization of atherosclerotic plaques

Statins are currently able to stabilize atherosclerotic plaques by lowering plasma cholesterol and pleiotropic effects, but a residual risk for atherosclerotic disease remains. Therefore, effective prevention of atherosclerosis and treatment of its complications is still a major clinical challenge. A large body of evidence indicates that mammalian target of rapamycin (mTOR) inhibitors such as rapamycin or everolimus have pleiotropic anti-atherosclerotic effects so that these drugs can be used as add-on therapy to prevent or delay the pathogenesis of atherosclerosis. Moreover, bioresorbable scaffolds eluting everolimus trigger a healing process in the vessel wall, both in pigs and humans, that results in late lumen enlargement and plaque regression. At present, this phenomenon of atheroregression is poorly understood. However, given that mTOR inhibitors suppress cell proliferation and trigger autophagy, a cellular survival pathway and a process linked to cholesterol efflux, we hypothesize that these compounds can inhibit (or reverse) the basic mechanisms that control plaque growth and destabilization. Unfortunately, adverse effects associated with mTOR inhibitors such as dyslipidemia and hyperglycemia have recently been identified. Dyslipidemia is manageable via statin treatment, while the anti-diabetic drug metformin would prevent hyperglycemia. Because metformin has beneficial macrovascular effects, this drug in combination with an mTOR inhibitor might have significant promise to treat patients with unstable plaques. Moreover, both statins and metformin are known to inhibit mTOR via AMPK activation so that they would fully exploit the beneficial effects of mTOR inhibition in atherosclerosis.

Everolimus therapy is associated with reduced lipoprotein-associated phospholipase A2 (Lp-Pla2) activity and oxidative stress in heart transplant recipients

BACKGROUND

Several studies demonstrated decreased severity and incidence of cardiac allograft vasculopathy (CAV) in heart transplant recipients receiving immunosuppressive therapy with everolimus. However, data regarding the influence of everolimus on risk factors predisposing to CAV are hitherto limited. We here systematically evaluated cardiovascular risk factors in heart transplanted patients, who underwent conversion to everolimus or were maintained on conventional therapy with calcineurin inhibitors (CNI).

METHODS

50 Patients receiving everolimus and 91 patients receiving CNI in addition to mycophenolate mofetil and low-dosed steroids were included in the study. CAV risk factors were determined in plasma or urine using standard enzymatic or immunochemical methods.

RESULTS

No significant differences were observed between both groups with regard to lipid (total, LDL- and HDL-cholesterol), metabolic (glucose, insulin), inflammatory (C-reactive protein, IL-6, myeloperoxidase) and cardiac (troponin I, NT-proBNP) risk factors. However, significantly lower activity of lipoprotein-associated phospholipase A2 (Lp-PLA2) and a negative correlation between the Lp-PLA2 activity and the everolimus concentration were observed in plasmas from everolimus-treated patients. Conversion to everolimus significantly lowered Lp-PLA2 activity in heart transplant recipients. Studies in vitro revealed reduced Lp-PLA2 expression in hepatocytes and macrophages pre-exposed to everolimus. In addition, reduced plasma markers of oxidative stress including oxidized LDL, 8-iso-prostaglandin F2α and protein carbonyls were noted in heart transplant recipients receiving everolimus therapy.

CONCLUSION

Our results suggest that everolimus specifically lowers plasma activity and cellular production of Lp-PLA2 and thereby dampens oxidative stress. These effects may additionally contribute to the reduced CAV incidence observed in heart transplant recipients receiving everolimus therapy.