Antirestenotic mechanisms of everolimus on human coronary artery smooth muscle cells: inhibition of human coronary artery smooth muscle cell proliferation, but not migration

Vascular Smooth Muscle Cell Migration and P70S6K: Key Players in Intimal Hyperplasia Development

BACKGROUND

Vascular smooth muscle cell (VSMC) recruitment and activation by vessel injury cause intimal hyperplasia (IH) and restenosis. Drug-eluting stents releasing mTOR (mechanistic target of rapamycin) blockers (sirolimus, everolimus [EV]) improve surgery outcomes but exhibit nonspecific effects and poor efficacy in diseased vessels. Drug combinations targeting the multifactorial processes leading to IH could enhance efficacy and reduce toxicity. Our previous work showed that Kv1.3 channel blockers such as 5-(4-phenoxybutoxy)psoralen (PAP-1) prevented IH. Since Kv1.3 signaling works through the MEK/ERK pathway, we hypothesize that PAP-1 and EV combination could improve antirestenotic therapies.

METHODS AND RESULTS

The effects of PAP-1, EV, and their combination on IH development were studied in vivo using a carotid ligation mouse model and ex vivo in organ culture of human vessels. Individually, both drugs inhibited vessel remodeling, but, surprisingly, their combination canceled these inhibitory effects. In primary human VSMCs cultures, the drug combination abolished the inhibition of cell migration but not cell proliferation, which was even potentiated. We uncovered a crosstalk between mTOR and MEK/ERK pathways in VSMCs, centered on P70S6K activation. P70S6K phosphorylation levels correlated with IH development, even reproducing the differences in EV response between diabetic and nondiabetic samples.

CONCLUSIONS

VSMC migration, rather than proliferation, mirrors PAP-1 and EV effects on IH development in vessels. Critically, we identify VSMC P70S6K phosphorylation as a surrogate marker for IH progression. The nonmonotonic responses of P70S6K activation to pathway blockers suggest the existence of a crosstalk element functioning as an exclusive NOR logic gate providing new insights for IH prevention strategies.

Gelatin microgel-coated balloon catheter with enhanced delivery of everolimus for long-term vascular patency

In-stent restenosis (ISR) after percutaneous coronary intervention is a major reason for limited long-term patency due to complex neointimal proliferation caused by vascular injury. Drug-coated balloon (DCB) has been developed to treat various cardiovascular diseases including ISR by providing anti-proliferative drugs into blood vessel tissues. However, a significant proportion of the drug is lost during balloon tracking, resulting in ineffective drug delivery to the target region. In this study, we report an everolimus-coated balloon (ECB) using everolimus-loaded gelatin-hydroxyphenyl propionic acid microgel (GM) with enhanced everolimus delivery to vascular walls for long-term patency. GM with high drug loading (> 97%) was simply prepared by homogenizing enzyme-mediated crosslinked hydrogels. The optimal condition to prepare GM-coated ECB (GM-ECB) was established by changing homogenization time and ethanol solvent concentration (30 ∼ 80%). In vitro sustained everolimus release for 30 d, and cellular efficacy using smooth muscle cells and vascular endothelial cells were evaluated. Additionally, an in vivo drug transfer levels of GM-ECB using rabbit femoral arteries were assessed with reduced drug loss and efficient drug delivery capability. Finally, using ISR-induced porcine models, effective in vivo vascular patency 4 weeks after treatment of ECBs was also confirmed. Thus, this study strongly demonstrates that GM can be used as a potential drug delivery platform for DCB application. STATEMENT OF SIGNIFICANCE: We report an ECB using everolimus-loaded GM prepared by homogenization of enzymatic cross-linked hydrogel. GM showed efficient drug loading (> 97 %) and controllable size. GM-ECB exhibited potential to deliver everolimus in a sustained manner to target area with drug efficacy and viability against SMC and EC. Although GM-ECB had much lower drug content compared to controls, animal study demonstrated enhanced drug transfer and reduced drug loss of GM-ECB due to the protection of encapsulated drugs by GM, and the possible interaction between GM and endothelium. Finally, vascular patency and safety were assessed using ISR-induced porcine models. We suggest an advanced DCB strategy to alleviate rapid drug clearance by bloodstream while improving drug delivery for a long-term vascular patency.

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.

Do we really understand how drug eluted from stents modulates arterial healing?

The advent of drug-eluting stents (DES) has revolutionised the treatment of coronary artery disease. These devices, coated with anti-proliferative drugs, are deployed into stenosed or occluded vessels, compressing the plaque to restore natural blood flow, whilst simultaneously combating the evolution of restenotic tissue. Since the development of the first stent, extensive research has investigated how further advancements in stent technology can improve patient outcome. Mathematical and computational modelling has featured heavily, with models focussing on structural mechanics, computational fluid dynamics, drug elution kinetics and subsequent binding within the arterial wall; often considered separately. Smooth Muscle Cell (SMC) proliferation and neointimal growth are key features of the healing process following stent deployment. However, models which depict the action of drug on these processes are lacking. In this article, we start by reviewing current models of cell growth, which predominantly emanate from cancer research, and available published data on SMC proliferation, before presenting a series of mathematical models of varying complexity to detail the action of drug on SMC growth in vitro. Our results highlight that, at least for Sodium Salicylate and Paclitaxel, the current state-of-the-art nonlinear saturable binding model is incapable of capturing the proliferative response of SMCs across a range of drug doses and exposure times. Our findings potentially have important implications on the interpretation of current computational models and their future use to optimise and control drug release from DES and drug-coated balloons.

Fas ligand and nitric oxide combination to control smooth muscle growth while sparing endothelium

Metallic stents cause vascular wall damage with subsequent smooth muscle cell (SMC) proliferation, neointimal hyperplasia, and treatment failure. To combat in-stent restenosis, drug-eluting stents (DES) delivering mTOR inhibitors such as sirolimus or everolimus have become standard for coronary stenting. However, the relatively non-specific action of mTOR inhibitors prevents efficient endothelium recovery and mandates dual antiplatelet therapy to prevent thrombosis. Unfortunately, long-term dual antiplatelet therapy leads to increased risk of bleeding/stroke and, paradoxically, myocardial infarction. Here, we took advantage of the fact that nitric oxide (NO) increases Fas receptors on the SMC surface. Fas forms a death-inducing complex upon binding to Fas ligand (FasL), while endothelial cells (ECs) are relatively resistant to this pathway. Selected doses of FasL and NO donor synergistically increased SMC apoptosis and inhibited SMC growth more potently than did everolimus or sirolimus, while having no significant effect on EC viability and proliferation. This differential effect was corroborated in ex vivo pig coronaries, where the neointimal formation was inhibited by the drug combination, but endothelial viability was retained. We also deployed FasL-NO donor-releasing ethylene-vinyl acetate copolymer (EVAc)-coated stents into pig coronary arteries, and cultured them in perfusion bioreactors for one week. FasL and NO donor, released from the stent coating, killed SMCs close to the stent struts, even in the presence of flow rates mimicking those of native arteries. Thus, the FasL-NO donor-combination has a potential to prevent intimal hyperplasia and in-stent restenosis, without harming endothelial restoration, and hence may be a superior drug delivery strategy for DES.

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.

T cell metabolism in metabolic disease-associated autoimmunity

This review discusses the relevant metabolic pathways and their regulators which show potential for T cell metabolism-based immunotherapy in diseases hallmarked by both metabolic disease and autoimmunity. Multiple therapeutic approaches using existing pharmaceuticals are possible from a rationale in which T cell metabolism forms the hub in dampening the T cell component of autoimmunity in metabolic diseases. Future research into the effects of a metabolically aberrant micro-environment on T cell metabolism and its potential as a therapeutic target for immunomodulation could lead to novel treatment strategies for metabolic disease-associated autoimmunity.

Therapeutic Targeting of RNA Polymerase I With the Small-Molecule CX-5461 for Prevention of Arterial Injury-Induced Neointimal Hyperplasia

OBJECTIVE

RNA polymerase I (Pol I)-dependent rRNA synthesis is a determinant factor in ribosome biogenesis and thus cell proliferation. The importance of dysregulated Pol I activity in cardiovascular disease, however, has not been recognized. Here, we tested the hypothesis that specific inhibition of Pol I might prevent arterial injury-induced neointimal hyperplasia.

APPROACH AND RESULTS

CX-5461 is a novel selective Pol I inhibitor. Using this tool, we demonstrated that local inhibition of Pol I blocked balloon injury-induced neointima formation in rat carotid arteries in vivo. Neointimal development was associated with augmented rDNA transcriptional activity as evidenced by the increased phosphorylation of upstream binding factor-1. The beneficial effect of CX-5461 was mainly mediated by inducing G2/M cell cycle arrest of proliferating smooth muscle cells without obvious apoptosis. CX-5461 did not induce p53 stabilization but increased p53 phosphorylation and acetylation and activated the ataxia telangiectasia mutated/ataxia telangiectasia and Rad3-related (ATR) pathway. Inhibition of ATR, but not of ataxia telangiectasia mutated, abolished the cytostatic effect of CX-5461 and p53 phosphorylation. In addition, inhibition of p53 or knockdown of the p53 target GADD45 mimicked the effect of ATR inhibition. In vivo experiments showed that the levels of phospho-p53 and acetyl-p53, and activity of the ataxia telangiectasia mutated/ATR pathway were all augmented in CX-5461-treated vessels.

CONCLUSIONS

Pol I can be therapeutically targeted to inhibit the growth of neointima, supporting that Pol I is a novel biological target for preventing arterial restenosis. Mechanistically, Pol I inhibition elicited G2/M cell cycle arrest in smooth muscle cells via activation of the ATR-p53 axis.

Telomerase Inhibition by Everolimus Suppresses Smooth Muscle Cell Proliferation and Neointima Formation Through Epigenetic Gene Silencing

Proliferation of smooth muscle cells (SMCs) during neointima formation is prevented by drug-eluting stents. The replicative capacity of mammalian cells is enhanced by telomerase expression; however, the contribution of telomerase to the proliferative response underlying neointima formation and its potential role as a pharmacological target are unknown. The present study investigated the mechanisms underlying the mitogenic function of telomerase, and tested the hypothesis that everolimus, which is commonly used on drug-eluting stents, suppresses SMC proliferation by targeting telomerase. Inhibition of neointima formation by everolimus was lost in mice overexpressing telomerase reverse transcriptase (TERT), indicating that repression of telomerase confers the anti-proliferative efficacy of everolimus. Everolimus reduced TERT expression in SMC through an Ets-1-dependent inhibition of promoter activation. The inhibition of TERT-dependent SMC proliferation by everolimus occurred in the absence of telomere shortening but rather as a result of a G1→S-phase arrest. Although everolimus failed to inhibit phosphorylation of the retinoblastoma protein as the gatekeeper of S-phase entry, it potently repressed downstream target genes. Chromatin immunoprecipitation assays demonstrated that TERT induced E2F binding to S-phase gene promoters and supported histone acetylation. These effects were sensitive to inhibition by everolimus. These results characterize telomerase as a previously unrecognized target for the antiproliferative activity of everolimus, and further identify a novel mitogenic pathway in SMC that depends on the epigenetic activation of S-phase gene promoters by TERT.

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The proliferative capacity of smooth muscle cells (SMC) during neointima formation is prevented by everolimus-coated drug-eluting stents.

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Everolimus failed to inhibit neointima formation by in mice overexpressing telomerase reverse transcriptase (TERT).

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Everolimus reduced TERT-dependent SMC proliferation through inhibition of Ets-1–dependent promoter activation.

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The inhibition of TERT-dependent SMC proliferation by everolimus occurred as a result of a G1→S-phase arrest, rather than telomerase shortening.

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Chromatin immunoprecipitation assays demonstrated that TERT induced E2F binding to S-phase gene promoters and supported histone acetylation.

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These studies identify a novel mitogenic pathway in SMC that depends on the epigenetic activation of S-phase gene promoters by TERT.

Chronic Renal Transplant Rejection and Possible Anti-Proliferative Drug Targets

The global prevalence of renal transplants is increasing with time, and renal transplantation is the only definite treatment for end-stage renal disease. We have limited the acute and late acute rejection of kidney allografts, but the long-term survival of renal tissues still remains a difficult and unanswered question as most of the renal transplants undergo failure within a decade of their transplantation. Among various histopathological changes that signify chronic allograft nephropathy (CAN), tubular atrophy, fibrous thickening of the arteries, fibrosis of the kidney interstitium, and glomerulosclerosis are the most important. Moreover, these structural changes are followed by a decline in the kidney function as well. The underlying mechanism that triggers the long-term rejection of renal transplants involves both humoral and cell-mediated immunity. T cells, with their related cytokines, cause tissue damage. In addition, CD 20+ B cells and their antibodies play an important role in the long-term graft rejection. Other risk factors that predispose a recipient to long-term graft rejection include HLA-mismatching, acute episodes of graft rejection, mismatch in donor-recipient age, and smoking. The purpose of this review article is the analyze current literature and find different anti-proliferative agents that can suppress the immune system and can thus contribute to the long-term survival of renal transplants. The findings of this review paper can be helpful in understanding the long-term survival of renal transplants and various ways to improve it.

Expression of OATP2B1 as determinant of drug effects in the microcompartment of the coronary artery

Clinical success of coronary drug-eluting stents (DES) is hampered by simultaneous reduction of smooth muscle cell (HCASMC) and endothelial cell proliferation due to unspecific cytotoxicity of currently used compounds. Previous in vitro data showing SMC-specific inhibition of proliferation suggested that statins may be suitable candidates for DES. It was aim of this study to further investigate statins as DES drug candidates to identify mechanisms contributing to their cell-selectivity. In vitro proliferation assays comparing the influence of various statins on HCASMC and endothelial cells confirmed that atorvastatin exhibits HCASMC-specificity. Due to similar expression levels of the drug target HMG-CoA reductase in both cell types, cellular accumulation of atorvastatin was assessed, revealing enhanced uptake in HCASMC most likely driven by significant expression of OATP2B1, a known uptake transporter for atorvastatin. In accordance with the finding that endogenous OATP2B1 influenced cellular accumulation in HCASMC we used this transporter as a tool to identify teniposide as new DES candidate drug with HCASMC-specific effects. We describe OATP2B1 as a determinant of pharmacokinetics in the coronary artery. Indeed, endogenously expressed OATP2B1 significantly influences the uptake of substrate drugs, thereby governing cell specificity. Screening of candidate drugs for interaction with OATP2B1 may be used to promote SMC-specificity.

Enhanced autophagy by everolimus contributes to the antirestenotic mechanisms in vascular smooth muscle cells

OBJECTIVE

The present study aims to investigate the underlying mechanisms accounting for the activities of everolimus to inhibit the growth of vascular smooth muscle cells (VSMCs), which contributes to restenosis.

METHODS

Primary VSMCs were cultured in media containing smooth muscle growth supplements and incubated with testing agents. Cell proliferation, cell cycle distribution, apoptosis and autophagy, and the key molecules involved, were examined.

RESULTS

Everolimus inhibited the proliferation of VSMCs by inhibiting the activation of ribosomal protein S6 kinase and phosphorylation of eukaryotic translation initiation factor 4E-binding protein 1, and downregulating proliferating cellular nuclear antigen. Everolimus induced cell cycle arrest at the G1 phase by downregulating cyclin D1 and upregulating p27, and increased apoptosis by downregulating Bcl-2, upregulating Bad and activating capsase-3 and poly ADP ribose polymerase. Everolimus enhanced autophagy by increasing the conversion of microtubule-associated protein 1 light chain 3 (LC3)-I to LC3-II, and upregulating Beclin 1. Specific autophagy inhibitors, 3-methyladenine and bafilomycin A1, significantly attenuated the inhibition of cell proliferation, the increased apoptosis and the altered expression of the above key proteins induced by everolimus.

CONCLUSIONS

Enhanced autophagy by everolimus contributes to its antirestenotic activity and its abilities to inhibit cell proliferation and to induce apoptosis of VSMCs.

Effects of everolimus on macrophage-derived foam cell behavior

PURPOSE

The purpose of this study was to investigate the effects of everolimus on foam cell (FC) viability, mRNA levels, and inflammatory cytokine production to better understand its potential inhibitory effects on atheroma progression.

METHODS AND MATERIALS

Human THP1 macrophage-derived FC were formed using acetylated LDL (acLDL, 100 μg/mL) for 72 hours, followed by everolimus treatment (10(-5)-10(-11) M) for 24 hours. FC viability was quantified using fluorescent calcein AM/DAPI staining. FC lysates and media supernatants were analyzed for apoptosis and necrosis using a Cell Death ELISA(PLUS) assay. FC lysates and media supernatants were also analyzed for inflammatory cytokine (IL1β, IL8, MCP1, TNFα) mRNA levels and protein expression using quantitative reverse transcription real-time polymerase chain reaction (QPCR) and a Procarta® immunoassay, respectively. mRNA levels of autophagy (MAP1LC3), apoptosis (survivin, clusterin), and matrix degradation (MMP1, MMP9) markers were evaluated by Quantigene® Plex assay and verified with QPCR. Additionally, hypercholesterolemic rabbits received everolimus-eluting stents (EES) for 28 or 60 days. RAM-11 immunohistochemical staining was performed to compare %RAM-11 positive area between stented sections and unstented proximal sections. Statistical significance was calculated using one-way ANOVA (p≤0.05).

RESULTS

Calcein AM/DAPI staining showed that FC exposed to everolimus (10(-5) M) had significantly decreased viability compared to control. FC apoptosis was significantly increased at a high dose of everolimus (10(-5)M), with no necrotic effects at any dose tested. Everolimus did not affect endothelial (HUVEC) and smooth muscle (HCASMC) cell apoptosis or necrosis. Everolimus (10(-5)M) significantly increased MAP1LC3, caused an increased trend in clusterin (p=0.10), and significantly decreased survivin and MMP1 mRNA levels in FC. MCP1 cytokine mRNA levels and secreted protein expression was significantly decreased by everolimus (10(-5) M) in FC. Percentage of RAM-11 positive area exhibited a reduction trend within sections stented with EES compared to unstented proximal sections at 60 days (p=0.09).

CONCLUSION

Everolimus, a potent anti-proliferative agent used in drug-eluting stents and bioresorbable vascular scaffolds, may inhibit atheroma progression and/or promote atheroma stabilization through diminished viability of FC, decreased matrix degradation, and reduced pro-inflammatory cytokine secretion.

EXECUTIVE SUMMARY

We explored the effects of everolimus on the behavior of human THP1 macrophage-derived foam cells in culture, including cell viability, mRNA levels, and pro-inflammatory cytokine production. We conclude that everolimus, a potent anti-proliferative agent used in drug-eluting stents/bioresorbable vascular scaffolds, may potentially inhibit atheroma progression and/or promote atheroma stabilization through diminished viability of foam cells, decreased matrix degradation, and reduced pro-inflammatory cytokine secretion.

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.

Cardiovascular autophagy: concepts, controversies, and perspectives

Despite recent scientific and technological advances, cardiovascular disease remains the leading cause of morbidity and mortality worldwide. Autophagy, an evolutionarily ancient response to cellular stress, has been implicated in the pathogenesis of a wide range of heart pathologies. However, the precise role of autophagy in these contexts remains obscure owing to its multifarious actions. Here, we review recently derived insights regarding the role of autophagy in multiple manifestations of cardiac plasticity and disease.

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.

New-generation drug-eluting stents: focus on Xience V® everolimus-eluting stent and Resolute® zotarolimus-eluting stent

Compared to bare metal stent angioplasty, first-generation drug-eluting stents (DES) have markedly reduced the incidence of in-stent restenosis. However, given the increased concerns over late and very late stent thrombosis, newer-generation DES were developed. To date, these DES have virtually replaced the use of first-generation DES worldwide. In this review article, we carefully consider the pre-clinical and clinical trials that have been performed with currently available, european conformity-marked and Food and Drug Administration-approved new-generation Resolute(®) and Xience V(®) DES.

Drug-induced macrophage autophagy in atherosclerosis: for better or worse?

Autophagy is a reparative, life-sustaining process by which cytoplasmic components are sequestered in double membrane vesicles and degraded upon fusion with lysosomal compartments. Mice with a macrophage-specific deletion of the essential autophagy gene Atg5 develop plaques with increased apoptosis and oxidative stress as well as enhanced plaque necrosis. This finding indicates that basal autophagy in macrophages is anti-apoptotic and present in atherosclerotic plaques to protect macrophages against various atherogenic stressors. However, autophagy is impaired in advanced stages of atherosclerosis and its deficiency promotes atherosclerosis in part through activation of the inflammasome. Because basal autophagy can be intensified selectively in macrophages by specific drugs such as mammalian target of rapamycin (mTOR) inhibitors or Toll-like receptor 7 (TLR7) ligands, these drugs were recently tested as potential plaque stabilizing compounds. Stent-based delivery of the mTOR inhibitor everolimus promotes a stable plaque phenotype, whereas local administration of the TLR7 ligand imiquimod stimulates inflammation and plaque progression. Therefore, more drugs capable of inducing autophagy should be tested in plaque macrophages to evaluate the feasibility of this approach. Given that drug-induced macrophage autophagy is associated with pro-inflammatory responses due to cytokine release, induction of postautophagic necrosis or activation of phagocytes after clearance of the autophagic corpse, cotreatment with anti-inflammatory compounds may be required. Overall, this review highlights the pros and cons of macrophage autophagy as a drug target for plaque stabilization.