Rapamycin effects transcriptional programs in smooth muscle cells controlling proliferative and inflammatory properties

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.

IRF-1 mediates the suppressive effects of mTOR inhibition on arterial endothelium

AIMS

Mammalian target of rapamycin (mTOR) inhibitors used in drug-eluting stents (DES) to control restenosis have been found to delay endothelialization and increase incidence of late-stent thrombosis through mechanisms not completely understood. We revealed that mTOR inhibition (mTORi) upregulated the expression of cell growth suppressor IRF-1 in primary human arterial endothelial cells (HAEC). This study aimed to examine how mTOR-regulated IRF-1 expression contributes to the suppressive effect of mTORi on arterial endothelial proliferation.

METHODS AND RESULTS

Western blotting, quantitative PCR, and a dual-luciferase reporter assay indicated that mTOR inhibitors rapamycin and torin 1 upregulated IRF-1 expression and increased its transcriptional activity. IRF-1 in turn contributed to the suppressive effect of mTORi by mediating HAEC apoptosis and cell cycle arrest in part through upregulation of caspase 1 and downregulation of cyclin D3, as revealed by CCK-8 assay, Annexin V binding assay, measurement of activated caspase 3, BrdU incorporation assay, and matrigel tube formation assay. In a mouse model of femoral artery wire injury, administration of rapamycin inhibited EC recovery, an effect alleviated by EC deficiency of IRF-1. Chromatin immunoprecipitation assay with HAEC and rescue expression of wild type or dominant-negative IRF-1 in EC isolated from Irf1^-/- mice confirmed transcriptional regulation of IRF-1 on the expression of CASP1 and CCND3. Furthermore, mTORi activated multiple PKC members, among which PKCζ was responsible for the growth-inhibitory effect on HAEC. Activated PKCζ increased IRF1 transcription through JAK/STAT-1 and NF-κB signaling. Finally, overexpression of wild type or mutant raptor incapable of binding mTOR indicated that mTOR-free raptor contributed to PKCζ activation in mTOR-inhibited HAEC.

CONCLUSIONS

The study reveals an IRF-1-mediated mechanism that contributes to the suppressive effects of mTORi on HAEC proliferation. Further study may facilitate the development of effective strategies to reduce the side effects of DES used in coronary interventions.

Activation of mammalian target of rapamycin induces lipid accumulation in the diaphragm of ventilated rats and hypoxia-treated C2C12 cells

BACKGROUND

Our previous study demonstrated that ventilators increase diaphragmatic lipid accumulation in rabbits, but their cellular mechanism is poorly understood. Mammalian target of rapamycin (mTOR) plays an important role in atherosclerosis in rat vascular smooth muscle cells. The present study investigated the role of mTOR pathway activation in the diaphragmatic muscle of ventilated rats and hypoxia-induced C2C12 cells.

MATERIALS AND METHODS

Male Sprague-Dawly rats were randomized into a control group (n = 8), controlled mechanical ventilation (CMV) group (n = 8), and CMV + Rapa group (n = 8). We evaluated the diaphragmatic contractility, lipid accumulation, and protein expression of the mTOR pathways. To explore the mechanism underlying ventilator-induced lipid accumulation, we observed protein expression of the mTOR and low-density lipoprotein receptor (LDLr) pathways in C2C12 cells under hypoxic and mTOR pathway inhibitor treatments.

RESULTS

Compared with the control group, there was a significant decrease in the peak twitch and peak tetanic forces in the CMV group (384.24 ± 70.39 versus 496.33 ± 78.64 g/cm², P < 0.05, and 869.24 ± 76.67 versus 1090.72 ± 118.91 g/cm², P < 0.05, respectively). There was a significant increase in peak twitch and peak tetanic forces in the CMV + Rapa group compared with that in the CMV group (501.81 ± 23.15 versus 384.24 ± 70.39 g/cm², P < 0.05, and 992.91 ± 88.99 versus 869.24 ± 76.67 g/cm², P < 0.05, respectively). In the CMV group, there were significant increases in lipid accumulation (0.086 ± 0.009 versus 0.005 ± 0.002, P < 0.05) and expression of mTOR in diaphragmatic fibers compared with those in the control group (P < 0.05). Rapamycin prevented lipid accumulation in rats of the CMV + Rapa group compared with that in the CMV group rats (0.024 ± 0.004 versus 0.086 ± 0.009, P < 0.05). Compared with the CMV group, there was a significant decrease in the phosphorylated protein expression levels of mTOR in rats of the CMV + Rapa group (P < 0.05). Hypoxic conditions activated the mTOR and LDLr pathways in C2C12 cells, which were correlated with an increase in expression of the mTOR and LDLr pathways compared with the control group (P < 0.05). In C2C12 cells treated with hypoxia + rapamycin, activation of the mTOR and LDLr pathways was blocked compared with C2C12 cells treated with hypoxia (P < 0.05).

CONCLUSIONS

These data suggest that CMV and hypoxia-induced activation of the mTOR pathway, resulting in lipid accumulation, and impaired the diaphragmatic contractile function. Therefore, pharmacologic agents that inhibit the mTOR pathway could potentially be useful for mitigating the diaphragmatic contractile dysfunction induced by mechanical ventilation.

Improving data quality and preserving HCD-generated reporter ions with EThcD for isobaric tag-based quantitative proteomics and proteome-wide PTM studies

Mass spectrometry (MS)-based isobaric labeling has undergone rapid development in recent years due to its capability for high throughput quantitation. Apart from its originally designed use with collision-induced dissociation (CID) and higher-energy collisional dissociation (HCD), isobaric tagging technique could also work with electron-transfer dissociation (ETD), which provides complementarity to CID and is preferred in sequencing peptides with post-translational modifications (PTMs). However, ETD suffers from long reaction time, reduced duty cycle and bias against peptides with lower charge states. In addition, common fragmentation mechanism in ETD results in altered reporter ion production, decreased multiplexing capability, and even loss of quantitation capability for some of the isobaric tags, including custom-designed dimethyl leucine (DiLeu) tags. Here, we demonstrate a novel electron-transfer/higher-energy collision dissociation (EThcD) approach that preserves original reporter ion channels, mitigates bias against lower charge states, improves sensitivity, and significantly improves data quality for quantitative proteomics and proteome-wide PTM studies. Systematic optimization was performed to achieve a balance between data quality and sensitivity. We provide direct comparison of EThcD with ETD and HCD for DiLeu- and TMT-labeled HEK cell lysate and IMAC enriched phosphopeptides. Results demonstrate improved data quality and phosphorylation localization accuracy while preserving sufficient reporter ion production. Biological studies were performed to investigate phosphorylation changes in a mouse vascular smooth muscle cell line treated with four different conditions. Overall, EThcD exhibits superior performance compared to conventional ETD and offers distinct advantages compared to HCD in isobaric labeling based quantitative proteomics and quantitative PTM studies.

Erythropoietin Induces Excessive Neointima Formation: A Study in a Rat Carotid Artery Model of Vascular Injury

A therapeutic strategy that would mitigate the events leading to hyperplasia and facilitate re-endothelialization of an injured artery after balloon angioplasty could be effective for a long-term patency of the artery. It is hypothesized that erythropoietin (EPO), which has both anti-inflammatory and antiapoptotic properties, will prevent hyperplasia, and its ability to proliferate and mobilize endothelial progenitor cells will re-endothelialize the injured artery. To test this hypothesis, EPO (5000 IU/kg) in solution was injected intraperitoneally 6 hours before vascular injury and then on every alternate day for a week or as a single dose (5000 IU/kg) in a sustained release gel formulation 1 week before the vascular injury. Morphometric analysis revealed nearly continuous re-endothelialization of the injured artery in EPO solution-treated animals (90% vs less than 20% in saline control); however, the treatment also caused excessive neointima formation (intima/media ratio, 2.10 ± 0.09 vs 1.60 ± 0.02 saline control, n = 5, P < .001). The EPO gel also induced similar excessive neointima formation. Immunohistochemical analysis of the injured arteries from the animals treated with EPO solution demonstrated a significant angiogenic response in adventitia and media, thus explaining the formation of excessive neointima. Although the results are in contrast to expectation, they explain a greater degree of stenosis seen in hemodialysis access fistulas in patients who are on EPO therapy for anemic condition. The results also caution the use of EPO, particularly in patients who are at a risk of vascular injury or are suffering from an atherosclerotic condition.

Vascular mTOR-dependent mechanisms linking the control of aging to Alzheimer's disease

Aging is the strongest known risk factor for Alzheimer's disease (AD). With the discovery of the mechanistic target of rapamycin (mTOR) as a critical pathway controlling the rate of aging in mice, molecules at the interface between the regulation of aging and the mechanisms of specific age-associated diseases can be identified. We will review emerging evidence that mTOR-dependent brain vascular dysfunction, a universal feature of aging, may be one of the mechanisms linking the regulation of the rate of aging to the pathogenesis of Alzheimer's disease. This article is part of a Special Issue entitled: Vascular Contributions to Cognitive Impairment and Dementia edited by M. Paul Murphy, Roderick A. Corriveau and Donna M. Wilcock.

A novel CX3CR1 antagonist eluting stent reduces stenosis by targeting inflammation

We evaluated the therapeutic efficacy of a novel drug eluting stent (DES) inhibiting inflammation and smooth muscle cell (SMC) proliferation. We identified CX3CR1 as a targetable receptor for prevention of monocyte adhesion and inflammation and in-stent neointimal hyperplasia without interfering with stent re-endothelization. Efficacy of AZ12201182 (AZ1220), a CX3CR1 antagonist was evaluated in inhibition of monocyte attachment in vitro. A prototype AZ1220 eluting PLGA-based polymer coated stent developed with an optimal elution profile and dose of 1 μM/stent was tested over 4 weeks in a porcine model of coronary artery stenting. Polymer coated stents without AZ1220 and bare metal stents were used as controls. AZ1220 inhibited monocyte attachment to CX3CL1 in a dose dependent manner. AZ1220 eluted from polymer coated stents in an ex vivo flow system retained bioactivity in inhibiting monocyte attachment to CX3CL1. At 4 weeks following deployment, AZ1220 eluting stents significantly reduced (∼60%) in-stent stenosis compared to both bare metal and polymer only coated stents and markedly reduced peri-stent inflammation and monocyte/macrophage accumulation without affecting re-endothelization. Anti-CX3CR1 drug eluting stents potently inhibited in-stent stenosis and may offer an alternative to mTOR targeting by current DES, specifically inhibiting polymer-induced inflammatory response and SMC proliferation, while retaining an equivalent re-endothelization response to bare metal stents.

Periadventitial application of rapamycin-loaded nanoparticles produces sustained inhibition of vascular restenosis

Open vascular reconstructions frequently fail due to the development of recurrent disease or intimal hyperplasia (IH). This paper reports a novel drug delivery method using a rapamycin-loaded poly(lactide-co-glycolide) (PLGA) nanoparticles (NPs)/pluronic gel system that can be applied periadventitially around the carotid artery immediately following the open surgery. In vitro studies revealed that rapamycin dispersed in pluronic gel was rapidly released over 3 days whereas release of rapamycin from rapamycin-loaded PLGA NPs embedded in pluronic gel was more gradual over 4 weeks. In cultured rat vascular smooth muscle cells (SMCs), rapamycin-loaded NPs produced durable (14 days versus 3 days for free rapamycin) inhibition of phosphorylation of S6 kinase (S6K1), a downstream target in the mTOR pathway. In a rat balloon injury model, periadventitial delivery of rapamycin-loaded NPs produced inhibition of phospho-S6K1 14 days after balloon injury. Immunostaining revealed that rapamycin-loaded NPs reduced SMC proliferation at both 14 and 28 days whereas rapamycin alone suppressed proliferation at day 14 only. Moreover, rapamycin-loaded NPs sustainably suppressed IH for at least 28 days following treatment, whereas rapamycin alone produced suppression on day 14 with rebound of IH by day 28. Since rapamycin, PLGA, and pluronic gel have all been approved by the FDA for other human therapies, this drug delivery method could potentially be translated into human use quickly to prevent failure of open vascular reconstructions.

Early changes of gene expression profiles in the rat model of arterial injury

PURPOSE

Restenosis caused by intimal hyperplasia (IH) remains a significant drawback for vascular interventions. It is crucial to understand the molecular mechanisms that control activation of smooth muscle cells (SMCs) after the injury in order to develop strategies to prevent IH. The purpose of the present study was to investigate the early alterations in arterial-wall gene expression after balloon injury in the rat carotid artery with focus on the induction of an inflammatory response.

MATERIALS AND METHODS

Twenty-four male Sprague-Dawley rats were subjected to injury of the left common carotid artery by using a 2-F Fogarty catheter. The arteries were harvested 5, 10, and 20 hours after injury. Uninjured arteries from an additional eight rats were used as controls. RNA was isolated and used for genome-wide microarray expression analysis, followed by validation of selected genes with quantitative real-time polymerase chain reaction (qRT-PCR). Immunohistochemistry was performed on the cross-sectioned vessels.

RESULTS

Analysis of gene expression by microarrays showed that the most differentially expressed genes were primarily associated with inflammation, cell proliferation, migration, and adhesion. As confirmed by qRT-PCR, microarray data showed a significant (P < .005) upregulation of cytokines and chemokines (IL-6, CCL2, CXCL1, AIMP1, and CD44) just 5 hours after injury. Immunohistochemistry demonstrated that CCL2 and the adhesion receptor CD44 were expressed by SMCs in the early response to injury and in the absence of leukocyte infiltration.

CONCLUSIONS

Arterial injury is followed by an early induction of inflammatory genes in the vessel wall that appears to be confined to SMCs.

Activation of mTOR modulates SREBP-2 to induce foam cell formation through increased retinoblastoma protein phosphorylation

AIMS

Our previous studies demonstrated that inflammation contributes to atherosclerosis through disruption of the low density lipoprotein receptor (LDLr) pathway. However, this effect is overridden by rapamycin, which is an inhibitor of mammalian target of rapamycin (mTOR). This study investigated the role of the mTOR pathway in atherosclerosis in vivo and in vitro.

METHODS AND RESULTS

To induce inflammation, we used subcutaneous injection of 10% casein in apolipoprotein E knockout (ApoE KO) mice and lipopolysaccharide stimulation in rat vascular smooth muscle cells (VSMCs). Results showed that inflammation increased lipid accumulation in aortas of ApoE KO mice and in VSMCs, which were correlated with increased expressions of LDLr, sterol regulatory element-binding protein (SREBP) cleavage-activating protein (SCAP), and SREBP-2 as well as with enhanced translocation of SCAP/SREBP-2 complex from the endoplasmic reticulum (ER) to the Golgi. Furthermore, inflammation increased both the percentage of cells in the S phase of cell cycle and protein expressions of the phosphorylated forms of retinoblastoma tumour suppressor protein (Rb), mTOR, eukaryotic initiation factor 4E-binding protein 1 (4EBP1), and P70 S6 kinase. After treatment with rapamycin or mTOR siRNA, the activity of the mTOR pathway was blocked. Interestingly, the expression levels of LDLr, SCAP, and SREBP-2 and the translocation of SCAP/SREBP-2 complex from the ER to the Golgi in treated VSMCs were decreased even in the presence of inflammatory stress.

CONCLUSION

Our findings demonstrate for the first time that inflammation disrupts LDLr feedback regulation through the activation of the mTOR pathway. Increased mTORC1 activity was found to up-regulate SREBP-2-mediated cholesterol uptake through Rb phosphorylation.

Anticipated classes of new medications and molecular targets for pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) remains a life-limiting condition with a major impact on the ability to lead a normal life. Although existing therapies may improve the outlook in some patients there remains a major unmet need to develop more effective therapies in this condition. There have been significant advances in our understanding of the genetic, cell and molecular basis of PAH over the last few years. This research has identified important new targets that could be explored as potential therapies for PAH. In this review we discuss whether further exploitation of vasoactive agents could bring additional benefits over existing approaches. Approaches to enhance smooth muscle cell apotosis and the potential of receptor tyrosine kinase inhibition are summarised. We evaluate the role of inflammation, epigenetic changes and altered glycolytic metabolism as potential targets for therapy, and whether inherited genetic mutations in PAH have revealed druggable targets. The potential of cell based therapies and gene therapy are also discussed. Potential candidate pathways that could be explored in the context of experimental medicine are identified.

Krüppel-like factor 4 is induced by rapamycin and mediates the anti-proliferative effect of rapamycin in rat carotid arteries after balloon injury

BACKGROUND AND PURPOSE

The transcription factor, Krüppel-like factor 4 (KLF4), plays an important role in regulating the proliferation of vascular smooth muscle cells. This study aimed to examine the effect of rapamycin on the expression of KLF4 and the role of KLF4 in arterial neointimal formation.

EXPERIMENTAL APPROACH

Expression of KLF4 was monitored using real-time PCR and immunoblotting in cultured vascular smooth muscle cells. and in rat carotid arteries in vivo after balloon injury. Adenovirus-mediated overexpression and siRNA-mediated knockdown of KLF4 were used to examine the role of KLF4 in mediating the anti-proliferative role of rapamycin . KLF4-regulated genes were identified using cDNA microarray.

KEY RESULTS

Rapamycin induced the expression of KLF4 in vitro and in vivo. Overexpression of KLF4 inhibited cell proliferation and the activity of mammalian target of rapamycin (mTOR) and its downstream pathways, including 4EBP-1 and p70S6K in vascular smooth muscle cells and prevented the neointimal formation in the balloon-injured arteries. KLF4 up-regulated the expression of GADD45β, p57(kip2) and p27(kip1) . Furthermore, knockdown of KLF4 attenuated the anti-proliferative effect of rapamycin both in vitro and in vivo.

CONCLUSIONS AND IMPLICATIONS

KLF4 plays an important role in mediating the anti-proliferative effect of rapamycin in VSMCs and balloon-injured arteries. Thus, it is a potential target for the treatment of proliferative vascular disorders such as restenosis after angioplasty.

The role of anti-inflammatory agents in age-related macular degeneration (AMD) treatment

Although age-related macular degeneration (AMD) is not a classic inflammatory disease like uveitis, inflammation has been found to have an important role in disease pathogenesis and progression. Innate immunity and autoimmune components, such as complement factors, chemokines, cytokines, macrophages, and ocular microglia, are believed to be heavily involved in AMD development. Targeting these specific inflammatory molecules has recently been explored in an attempt to better understand and treat AMD. Although antivascular endothelial growth factor therapy is the first line of defence against neovascular AMD, anti-inflammatory agents such as corticosteroids, nonsteroidal anti-inflammatory drugs (NSAIDs), immunosuppressive agents (eg, methotrexate and rapamycin), and biologics (eg, infliximab, daclizumab, and complement inhibitors) may provide an adjunct or alternative mechanism to suppress the inflammatory processes driving AMD progression. Further investigation is required to evaluate the long-term safety and efficacy of these drugs for both neovascular and non-neovascular AMD.

The TRAF-interacting protein (TRIP) is a regulator of keratinocyte proliferation

The TRAF-interacting protein (TRIP/TRAIP) is a RING-type E3 ubiquitin ligase inhibiting tumor necrosis factor-α (TNF-α)-mediated NF-κB activation. TRIP ablation results in early embryonic lethality in mice. To investigate TRIP function in epidermis, we examined its expression and the effect of TRIP knockdown (KD) in keratinocytes. TRIP mRNA expression was strongly downregulated in primary human keratinocytes undergoing differentiation triggered by high cell density or high calcium. Short-term phorbol-12-myristate-13-acetate (TPA) treatment or inhibition of phosphatidylinositol-3 kinase signaling in proliferative keratinocytes suppressed TRIP transcription. Inhibition by TPA was protein kinase C dependent. Keratinocytes undergoing KD of TRIP expression by lentiviral short-hairpin RNA (shRNA; T4 and T5) had strongly reduced proliferation rates compared with control shRNA. Cell cycle analysis demonstrated that TRIP-KD caused growth arrest in the G1/S phase. Keratinocytes with TRIP-KD resembled differentiated cells consistent with the augmented expression of differentiation markers keratin 1 and filaggrin. Luciferase-based reporter assays showed no increase in NF-κB activity in TRIP-KD keratinocytes, indicating that NF-κB activity in keratinocytes is not regulated by TRIP. TRIP expression was increased by ∼2-fold in basal cell carcinomas compared with normal skin. These results underline the important role of TRIP in the regulation of cell cycle progression and the tight linkage of its expression to keratinocyte proliferation.

Activation of the AMP-activated protein kinase-p38 MAP kinase pathway mediates apoptosis induced by conjugated linoleic acid in p53-mutant mouse mammary tumor cells

Conjugated linoleic acid (CLA) inhibits tumorigenesis and tumor growth in most model systems, an effect mediated in part by its pro-apoptotic activity. We previously showed that trans-10,cis-12 CLA induced apoptosis of p53-mutant TM4t mouse mammary tumor cells through both mitochondrial and endoplasmic reticulum stress pathways. In the current study, we investigated the role of AMP-activated protein kinase (AMPK), a key player in fatty acid metabolism, in CLA-induced apoptosis in TM4t cells. We found that t10,c12-CLA increased phosphorylation of AMPK, and that CLA-induced apoptosis was enhanced by the AMPK agonist 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR) and inhibited by the AMPK inhibitor compound C. The increased AMPK activity was not due to nutrient/energy depletion since ATP levels did not change in CLA-treated cells, and knockdown of the upstream kinase LKB1 did not affect its activity. Furthermore, our data do not demonstrate a role for the AMPK-modulated mTOR pathway in CLA-induced apoptosis. Although CLA decreased mTOR levels, activity was only modestly decreased. Moreover, rapamycin, which completely blocked the activity of mTORC1 and mTORC2, did not induce apoptosis, and attenuated rather than enhanced CLA-induced apoptosis. Instead, the data suggest that CLA-induced apoptosis is mediated by the AMPK-p38 MAPK-Bim pathway: CLA-induced phosphorylation of AMPK and p38 MAPK, and increased expression of Bim, occurred with a similar time course as apoptosis; phosphorylation of p38 MAPK was blocked by compound C; the increased Bim expression was blocked by p38 MAPK siRNA; CLA-induced apoptosis was attenuated by the p38 inhibitor SB-203580 and by siRNAs directed against p38 MAPK or Bim.

Emerging therapies for the treatment of pulmonary hypertension

Current treatment of pulmonary arterial hypertension, which includes the use of prostacyclins, endothelin receptor antagonists, and phosphodiesterase type 5 inhibitors, either alone or in combination, often leads to improvements in functional capacity and modest decreases in pulmonary artery pressure. Disappointingly, however, two recent meta-analysis reviewing the controlled trials in pulmonary arterial hypertension, using these three agents, demonstrated little or no increase in survival. Importantly, however, increasing knowledge of the cellular and molecular basis of pulmonary arterial hypertension has led to the development of new agents aimed at either reversing sustained vasoconstriction or stopping/reversing the abnormal cell and extracellular matrix accumulation that, in combination, obstruct pulmonary blood flow and ultimately cause right heart failure. Rho kinase inhibitors, vasodilator peptides (such as vasoactive intestinal peptide and adrenomedullin), and endothelial nitric oxide synthase coupling agents (cicletanine) have been shown sometimes to exert potent pulmonary vasodilatory effects in animal models and in pilot studies in humans. Tyrosine kinase inhibitors (platelet-derived growth factor and epidermal growth factor receptor inhibitors), multikinase inhibitors (tyrosine kinase and serine/threonine kinase), elastase inhibitors, metabolic modulators (e.g., dichloroacetate), survivin inhibitors, and HMG-COA reductase inhibitors have been shown to reverse pulmonary hypertension in rodent models of pulmonary hypertension through inhibition of cell proliferation and induction of apoptosis. Early success in human pulmonary arterial hypertension with tyrosine kinase inhibitors has appeared in case reports. Furthermore, anti-inflammatory/immunomodulatory agents (thiazolidinedinones, rapamycin, cyclosporine, and STAT3 inhibitors) have been demonstrated to be effective at reducing vascular remodeling in animal models. Collectively, these studies are exciting and open potential new avenues for treatment. Caution should be exercised, however, as many agents, which are successful at preventing or reversing pulmonary arterial hypertension in currently used animal models, do not result in similar long-term success in the treatment of human pulmonary arterial hypertension.

Novel role of the CXC chemokine receptor 3 in inflammatory response to arterial injury: involvement of mTORC1

Atherosclerosis, restenosis, and posttransplant graft atherosclerosis are characterized by endothelial damage, infiltration of inflammatory cells, and proliferation of smooth muscle cells. The CXCR3-activating chemokines interferon-gamma inducible protein 10 (IP10) and MIG (monokine induced by interferon-gamma) have been implicated in vascular repair and remodeling. The underlying molecular mechanisms, however, remain elusive. Here, we show that wire-mediated arterial injury induced local and systemic expression of IP10 and MIG, resulting in enhanced recruitment of CXCR3(+) leukocytes and hematopoietic progenitor cells. This was accompanied by profound activation of mammalian target of rapamycin complex (mTORC)1, increased reactive oxygen species production, apoptosis, and intimal hyperplasia. Genetic and pharmacological inactivation of CXCR3 signaling not only suppressed recruitment of inflammatory cells but also abolished mTORC1 activation, reduced reactive oxygen species generation, and blocked apoptosis of vascular cells, resulting in significant reduction of intimal hyperplasia in vivo. In vitro, stimulation of T cells with IP10 directly activated mTORC1 and induced generation of reactive oxygen species and apoptosis in an mTORC1-dependent manner. These results strongly indicate that CXCR3-dependent activation of mTORC1 directly links stimulation of the Th1 immune system with the proliferative response of intimal cells in vascular remodeling.

Inhibition of Apoptosis Through Localized Delivery of Rapamycin-Loaded Nanoparticles Prevented Neointimal Hyperplasia and Reendothelialized Injured Artery

Background— A significant fraction of vascular smooth muscle cells (VSMCs) undergo rapid apoptosis after balloon angioplasty. In this study, we tested the hypothesis that protecting VSMCs from undergoing apoptosis prevents the cascade of events that lead to intimal hyperplasia.

Methods and Results— Rapamycin-loaded gel-like nanoparticles (mean diameter, 54�5 nm) were infused locally in a rat carotid artery model of vascular injury. The drug has both antiapoptotic and antiproliferative effects on VSMCs and hence was selected for the current study. Localized delivery of nanoparticles sustained the drug level in the target artery for >2 weeks; demonstrated significant inhibition of hyperplasia (intima/media ratio, 1.5�0.02 versus 2.7�0.6; P <0.01); and most importantly, reendothelialized the injured artery (endothelium coverage: treated 82% versus control 28%). We also demonstrated inhibition of activation of caspase-3/7 enzymes in the treated artery, preventing VSMCs from undergoing apoptosis and subsequent infiltration of macrophages.

Conclusions— It may be postulated that the localized delivery of rapamycin inhibited apoptosis of VSMCs, minimizing the inflammatory response to the injury and, thus, creating conditions conducive to vascular repair (reendothelialization). Unlike stenting, which can lead to thrombosis and increased risk for in-stent restenosis, our approach could eliminate or minimize long-term complications because the injured artery undergoes a natural process of reendothelialization.

Hsf1 activation inhibits rapamycin resistance and TOR signaling in yeast revealed by combined proteomic and genetic analysis

TOR kinases integrate environmental and nutritional signals to regulate cell growth in eukaryotic organisms. Here, we describe results from a study combining quantitative proteomics and comparative expression analysis in the budding yeast, S. cerevisiae, to gain insights into TOR function and regulation. We profiled protein abundance changes under conditions of TOR inhibition by rapamycin treatment, and compared this data to existing expression information for corresponding gene products measured under a variety of conditions in yeast. Among proteins showing abundance changes upon rapamycin treatment, almost 90% of them demonstrated homodirectional (i.e., in similar direction) transcriptomic changes under conditions of heat/oxidative stress. Because the known downstream responses regulated by Tor1/2 did not fully explain the extent of overlap between these two conditions, we tested for novel connections between the major regulators of heat/oxidative stress response and the TOR pathway. Specifically, we hypothesized that activation of regulator(s) of heat/oxidative stress responses phenocopied TOR inhibition and sought to identify these putative TOR inhibitor(s). Among the stress regulators tested, we found that cells (hsf1-R206S, F256S and ssa1-3 ssa2-2) constitutively activated for heat shock transcription factor 1, Hsf1, inhibited rapamycin resistance. Further analysis of the hsf1-R206S, F256S allele revealed that these cells also displayed multiple phenotypes consistent with reduced TOR signaling. Among the multiple Hsf1 targets elevated in hsf1-R206S, F256S cells, deletion of PIR3 and YRO2 suppressed the TOR-regulated phenotypes. In contrast to our observations in cells activated for Hsf1, constitutive activation of other regulators of heat/oxidative stress responses, such as Msn2/4 and Hyr1, did not inhibit TOR signaling. Thus, we propose that activated Hsf1 inhibits rapamycin resistance and TOR signaling via elevated expression of specific target genes in S. cerevisiae. Additionally, these results highlight the value of comparative expression analyses between large-scale proteomic and transcriptomic datasets to reveal new regulatory connections.

The cell cycle: a critical therapeutic target to prevent vascular proliferative disease

Percutaneous coronary intervention is the preferred revascularization approach for most patients with coronary artery disease. However, this strategy is limited by renarrowing of the vessel by neointimal hyperplasia within the stent lumen (in-stent restenosis). Vascular smooth muscle cell proliferation is a major component in this healing process. This process is mediated by multiple cytokines and growth factors, which share a common pathway in inducing cell proliferation: the cell cycle. The cell cycle is highly regulated by numerous mechanisms ensuring orderly and coordinated cell division. The present review discusses current concepts related to regulation of the cell cycle and new therapeutic options that target aspects of the cell cycle.

Interferon-gamma induces human vascular smooth muscle cell proliferation and intimal expansion by phosphatidylinositol 3-kinase dependent mammalian target of rapamycin raptor complex 1 activation

Interferon (IFN)-gamma, a cytokine characteristically expressed in arteriosclerotic diseases, acts directly on vascular smooth muscle cells to induce cellular proliferation and intimal expansion. Signaling by the mammalian target of rapamycin raptor complex, known as mTORC1, is associated with cell growth and is active within arteriosclerotic lesions but is not known to be triggered by proinflammatory factors in vascular smooth muscle cells. We investigated the mechanisms for the proarteriosclerotic effects of IFN-gamma in the absence of leukocytes by exploiting the species specificity of this cytokine in a chimeric model of immunodeficient mouse recipients bearing human coronary artery grafts and intravenously inoculated with adenovirus encoding a human IFN-gamma transgene. We found that IFN-gamma-mediated vascular smooth muscle cell proliferation and intimal expansion were associated with phosphorylation of the mTORC1 effector ribosomal protein S6 kinase 1, that the graft morphological changes and S6 kinase 1 activation were inhibited by the mTORC1 inhibitor rapamycin in vivo, and that IFN-gamma-induced mTORC1 signaling was dependent on phosphatidylinositol 3-kinase activity under serum-free conditions in vitro. Our work establishes an immunologic stimulus for mTORC1 signaling in vascular smooth muscle cells, emphasizes that mTORC1 activation is critical in immune-mediated vascular remodeling, and provides further mechanistic insight into the successful clinical application of rapamycin therapy for atherosclerosis and graft arteriosclerosis.

mTOR-inhibitors simultaneously inhibit proliferation and basal IL-6 synthesis of human coronary artery endothelial cells

Divergent results regarding the immunosuppressive effects of mammalian-target-of-rapamycin-(mTOR)-inhibitors on venous endothelial cells (ECs) have highlighted the importance of an accurate EC-model. The purpose of this study was to determine mTOR-inhibitor effects at a specific site of action -- the human coronary-artery-ECs (HCAECs) -- and to compare these data with results gained from cultures of human saphenous vein ECs (HSVECs). This EC-model could enable us to gain insight into site-specific pharmacodynamics and the immunosuppressive management of transplant vasculopathy. ECs were cultivated with rising concentrations of mTOR-inhibitors in the presence/absence of tumor necrosis factor (TNF). Cell counts, DNA-synthesis, cytotoxicity and concentrations of the cytokine IL-6 as well as the chemokines IL-8 and MCP-1 were measured. Half-maximal inhibitory effects on cell growth were reached after about 30 h incubation and both cell types showed equal responses regarding cell growth and DNA-synthesis after 48 h incubation time. mTOR-inhibitors failed to suppress basal/TNF-induced secretion of IL-8 and MCP-1, but IL-6 synthesis after TNF-induction was reduced to 35%. In contrast to human saphenous vein ECs (HSVECs), mTOR-inhibitors also reduced basal IL-6-secretion of HCAECs (to 55%) and cell proliferation was simultaneously inhibited within the same concentration range. Taking everything into account, we conclude that EC-proliferation is inhibited at concentrations needed to suppress TNF-stimulated IL-6 synthesis. Furthermore, the specific suppression of basal arterial IL-6-secretion and the delayed onset of the mTOR-inhibitor effect on HCAEC-proliferation (maximum reached after about 36 h) might be of relevance for the prevention of transplant vasculopathy at its initial stage, e.g. as a component of cardioplegic solutions.

The impact of the mTOR inhibitor sirolimus on the proliferation and function of pancreatic islets and ductal cells

AIMS/HYPOTHESIS

The Edmonton Protocol for islet transplantation has provided hope for type 1 diabetic patients. However, this protocol requires lifelong immunosuppression, specifically sirolimus, a cellular antiproliferate. The effect of sirolimus on human pancreatic ductal cells (HDCs) is not known. This may be important since HDCs are believed to be islet precursors. Since neonatal porcine islets (NPIs), which contain many ductal precursor cells, could be a potential clinical source of islets, we also tested the effects of sirolimus on this tissue.

METHODS

HDCs (n=4), NPIs (n=9) and human islets (n=5) were cultured with and without sirolimus (20 ng/ml) for 6 days.

RESULTS

HDCs and NPIs cultured with sirolimus showed a 50 and 28% decrease, respectively, in cell number relative to control (p<0.05). Control cultures expanded 1.65- and 2.44-fold relative to time 0. Decreases in cell number of sirolimus-treated HDCs were not due to apoptosis as measured by TUNEL staining. No functional effects on human islets or NPIs were observed following static incubation with high glucose. Treatment of syngeneically transplanted and naïve BALC/c mice with sirolimus resulted in altered OGTT profiles with prolonged elevation of hyperglycaemia and weight gain. There was no difference in graft and organ insulin content between treatment groups.

CONCLUSIONS/INTERPRETATION

Our results indicate that sirolimus decreases ductal cell numbers in culture and alters glucose-stimulated insulin secretion in vivo. The administration of sirolimus to islet transplant recipients is likely to impair graft function as a result of decreasing ductal neogenesis and induction of insulin resistance.

Endothelial monocyte-activating polypeptide-II and its functions in (patho)physiological processes

Endothelial monocyte-activating polypeptide-II (EMAP-II) is a pro-inflammatory cytokine with anti-angiogenic properties. Its precursor, proEMAP, is identical to the p43 auxiliary component of the tRNA multisynthetase complex and therefore involved in protein translation. Although most of the activities have been ascribed to the active form EMAP-II, also p43 has reported cytokine properties. ProEMAP/p43 and EMAP-II act on many levels and on many cell types including endothelial cells, immune cells and fibroblasts. In this review we summarize all available data on isolation, expression and functions of EMAP-II both in physiological processes as well as in pathological settings, like cancer. We also discuss the different reported mechanisms for processing of proEMAP/p43 into EMAP-II. Finally, we speculate on the possible applications of this cytokine for (cancer) therapy.

Molecular activity of sirolimus and its possible application in tuberous sclerosis treatment

Sirolimus is one of the intensively investigated drugs with pluripotent activities. It binds to its intracellular receptor FKBP12 (FK506-binding protein 12), a member of the family of FK506-binding proteins, and inhibits the activity of mTOR, a serine/threonine kinase involved in numerous cell processes linked to cell growth control. The drug is currently registered for the prophylaxis of organ rejection and for use in coronary stents. However, unique characteristics of sirolimus make it a good candidate for anti-cancer therapy. Indeed, phase II and III clinical studies in humans with several types of neoplasms are already under way. The review describes molecular activity of sirolimus and its analogs, characteristic for specific applications, in view of very recent advances involving tuberous sclerosis complex (TSC)-mediated signaling pathways. Current studies with sirolimus performed in tuberous sclerosis animal models are presented. Possible application of sirolimus for treating tuberous sclerosis, disease caused by mutations of TSC proteins, is discussed.

Countervailing effects of rapamycin (sirolimus) on nuclear factor-κB activities in neointimal and medial smooth muscle cells

OBJECTIVE

Local application of rapamycin (sirolimus) by drug-eluting stents prevents lumen obliteration after angioplasty by inhibition of neointimal hyperplasia. The effects of rapamycin on neointimal smooth muscle cells (niSMC) which are responsible for the occurrence of restenosis have not been investigated so far.

METHODS AND RESULTS

Rat niSMC and medial SMC (mSMC) were obtained from balloon catheter-injured arteries. The niSMC exhibited higher basal NF-kappaB activity and TNF-alpha mRNA levels. Nuclear protein binding to NF-kappaB-DNA was attenuated in niSMC by incubation with rapamycin (0.1 and 1 microg/ml) for 24 and 48 h. In contrast in mSMC, 0.1 microg/ml rapamycin had no effect and at 1 microg/ml even increased nuclear protein binding to NF-kappaB-DNA. After 12 h incubation, rapamycin (0.001-10 microg/ml) induced IkappaB-alpha protein in niSMC, whereas in mSMC it stimulated IkappaB-alpha at much lower levels. Prolonged rapamycin treatment (1 microg/ml for 72 h) had no effect on TNF-alpha mRNA level and NF-kappaB activity in niSMC, whereas it led to their increase in mSMC. Vascular endothelial growth factor (VEGF) secretion was higher in mSMC than in niSMC; rapamycin decreased VEGF levels in both cell types. Ultrastructural analysis suggested that rapamycin caused early signs of degeneration in niSMC, but enhanced protein synthesis in mSMC.

CONCLUSIONS

This study shows that rapamycin influences the inflammatory phenotypes of SMC in opposite directions: it reduces the high basal NF-kappaB activity in niSMC and enhances NF-kappaB activity and TNF-alpha expression in mSMC. In addition, rapamycin inhibits VEGF production regardless of the phenotype of SMC. These findings shed light on molecular mechanisms and structural changes underlying therapeutic applications of rapamycin in prevention of restenosis, inhibition of chronic transplant arteriosclerosis and reduction of secondary malignoma formation due to immunosuppression.

Inhibition of fibroblast growth factor receptor signaling attenuates atherosclerosis in apolipoprotein E-deficient mice

OBJECTIVE

To determine the significance of fibroblast growth factor receptor (FGFR) expression for the development of atherosclerotic lesions in apoE-deficient (apoE-/-) mice.

METHODS AND RESULTS

ApoE-/- mice fed a high-fat diet were administered the FGFR tyrosine kinase inhibitor SU5402 (25 mg/kg/d sc), which inhibited neointima growth by 85%. We measured its effects on lesion size at the aortic sinus, macrophage and smooth muscle cell (SMC) accumulation, the expression of monocyte chemotactic and retention factors, as well as its effects on FGFR expression/phosphorylation. FGFR tyrosine kinase inhibition reduced phosphorylated FGFRs in lesions by 90%, associated with a 65% reduction in lesion size measured using Oil Red O. Macrophages and SMCs within lesions were reduced by 58% and 78%, respectively. Monocyte chemotactic protein-1 (MCP-1) expression was also reduced, as was the expression of hyaluronan synthase, cyclooxygenase-2, CD36, and endothelial monocyte-activating polypeptide-II. Although 3 FGFR types were expressed in lesions, the effects of SU5402 could be attributed largely to inhibition of FGFR-1 phosphorylation.

CONCLUSIONS

Atherosclerotic lesions in apoE-/- mice express multiple FGFRs and an active FGF:FGFR-1 signaling system that promotes atherosclerosis development via increased SMC proliferation, and by augmenting macrophage accumulation via increased expression of MCP-1 and factors promoting macrophage retention in lesions.

Sirolimus-eluting coronary stents in small vessels

BACKGROUND

This prospective multicenter study compared angiographic in-lesion late lumen loss in de novo native coronary artery lesions (vessel diameter range 2.25-2.75 mm, length range > or = 15 to < or = 30 mm) 8 months after the implantation of a sirolimus-eluting stent with that of similar vessels with the same drug-eluting stent or a bare stent of the SIRIUS study (historical controls).

METHODS AND RESULTS

One hundred one patients (study group) were matched and compared with 323 patients receiving the bare stent (bare control group) and with 350 receiving the Cypher stent (Cypher control group) in the SIRIUS trial. Mean in-lesion late loss in the study group was lower than that in the bare control group (0.20 versus 0.76 mm, P < .0001) and not inferior to that in the Cypher control group (0.27 mm, P = .3). Adverse event rates (death and myocardial infarction) were similar between groups. At 8 months, target lesion revascularization rates were 0% in the study group, 13.2% in the bare control group (P < .001), and 4.6% in the Cypher control group (P = .03).

CONCLUSIONS

The Cypher Bx Velocity stent was confirmed to be superior to the bare Bx Velocity stent in small coronary vessels in terms of in-lesion late loss 8 months after implantation.

Heme oxygenase-1 mediates the protective effects of rapamycin in monocrotaline-induced pulmonary hypertension

Rapamycin inhibits the development and progression of vascular disease. We previously showed that rapamycin induces the cytoprotective protein, heme oxygenase-1 (HO-1), and more importantly, chemically inhibiting HO-1 blocked the antiproliferative actions of rapamycin. In this study, we evaluated whether HO-1 is required for the vascular protective effects of rapamycin in vivo using a rat monocrotaline-induced pulmonary hypertension model. Rats were exposed to monocrotaline with or without rapamycin and HO activity was altered using the chemical inhibitor, tin protoporphyrin or the inducer, cobalt protoporphyrin. We also evaluated possible mechanisms of rapamycin-dependent induction of HO-1, and how HO-1 mediates growth factor-dependent antiproliferative actions of rapamycin. Proliferation and cell cycle progression were examined in smooth muscle cells derived from both wild-type and HO-1 knockout (HO-1-/-) mice in response to growth factors and rapamycin. Similar to our previous findings in vitro, rapamycin induced HO-1 in rat lung. Rapamycin also inhibited the development of monocrotaline-induced pulmonary hypertension, and this protective effect was blocked with the addition of tin protoporphyrin. In addition, treatment with cobalt protoporphyrin resulted in a substantial protection in this model of pulmonary hypertension. Rapamycin induction of HO-1 was dependent upon a transcriptional event; however, it was not mediated through an altered redox state or mammalian targets of rapamycin inhibition. Unlike wild-type cells, the growth of HO-1-/- mouse aortic smooth muscle cells was not inhibited or cell cycle arrested in G1 in response to rapamycin. This study demonstrates that HO-1 is critical for the antiproliferative and vascular protective effects of rapamycin in vitro and in vivo in monocrotaline-induced pulmonary hypertension.

Stent-based delivery of ABT-578 via a phosphorylcholine surface coating reduces neointimal formation in the porcine coronary model

Stent-based delivery of the antiproliferative and immunosuppressive macrocyclic lactone sirolimus reduces neointimal formation and restenosis by cytostatic inhibition of vascular smooth muscle cell proliferation. The objective of this study was to determine the feasibility and efficacy of stent-based delivery of ABT-578, a structurally unique macrocyclic lactone. Stainless steel balloon-expandable stents were coated with thin layer of phosphorylcholine (PC) or PC with ABT-578 (10 microg/mm). Fifteen juvenile domestic pigs underwent placement of oversized bare metal (n = 15), PC (n = 8), and PC with ABT-578 (n = 9) stents in the coronary arteries. At 28 days, histology demonstrated similar mean injury scores for the control, PC-, and ABT-578-coated stents. The mean neointimal area (mm2) was significantly reduced for ABT-578 (1.70 +/- 0.47) as compared with PC (2.82 +/- 1.24) and control (2.89 +/- 1.91) stents (P < or = 0.05). The 40% reduction in neointimal area resulted in significantly less mean percent diameter stenosis for ABT-578 (19.4% +/- 4.0%) as compared with PC (30.3 +/- 12.1 %) and control (29.4% +/- 15.5%) stents (P < or = 0.03). Twelve of the 45 bare metal stent cross-sections (26.7%) exhibited a giant cell reaction, while none of the sections from the ABT-578-eluting stents had a giant cell reaction (P = 0.004). Stent-based delivery of ABT-578 via a PC surface coating inhibits neointimal formation at 28 days in the porcine coronary model. Further study is necessary to determine the dose-response and long-term effects ABT-578-eluting stents in the porcine coronary model.

Sirolimus-Eluting Stents to Abolish Intimal Hyperplasia and Improve Flow in Porcine Arteriovenous Grafts

Background— The patency of arteriovenous (AV) expanded polytetrafluoroethylene (ePTFE) hemodialysis grafts is severely compromised by intimal hyperplasia (IH) at the venous anastomosis and in the venous outflow tract. We addressed the potential of primary placement of a sirolimus-eluting stent (SES) in a validated porcine model.

Methods and Results— In 25 pigs, ePTFE AV grafts were created bilaterally between the carotid artery and the jugular vein, whereupon a self-expandable nitinol stent (14 SESs and 11 bare-metal stents) was implanted over the venous anastomosis in 1 of the 2 grafts. After exclusion of technical failures and 1 unilateral occlusion, 16 pigs (9 SESs and 7 bare-metal stents) were included for further analysis. After 28 days, we measured graft flow and performed quantitative angiography. The pigs were then euthanized, and grafts with adjacent vessels were excised for histological analysis. Minimal luminal diameter was substantially larger in the SES group compared with unstented controls (5.9±0.2 versus 3.8±0.4 mm, respectively, P =0.01), which was accompanied by more prominent graft flow (SES, 1360±89 mL/min versus unstented, 861±83 mL/min, P =0.05). IH at the venous anastomosis was 77% less in the SES group compared with unstented controls (0.44±0.05 versus 1.92±0.5 mm 2 , respectively, P =0.01), whereas IH increased markedly when bare-metal stents were used (5.7±1.4 mm 2 , P =0.05).

Conclusions— SESs in the venous outflow of AV grafts significantly reduce IH and increase vessel diameter and graft flow compared with unstented grafts. These findings suggest that SESs have the potential to improve primary patency of AV grafts in hemodialysis patients.

Predominant inhibition of interleukin-6 synthesis in patient-specific endothelial cells by mTOR inhibitors below a concentration range where cell proliferation is affected and mitotic arrest takes place

Organ rejection and inflammation are accompanied by endothelial cell activation. An in vitro model with patient-specific endothelial cells was used to study the impact of mTOR inhibitors on cell growth and release of proinflammatory cytokines.

MATERIAL AND METHODS

Confluent monolayers of human saphenous vein endothelial cells were pretreated with everolimus or sirolimus followed by induction with tumour necrosis factor-alpha (TNF-alpha).

RESULTS

Incubation with sirolimus or everolimus resulted in a dose-dependent deceleration of cell growth. Compared to control, cell count at high concentrations ceased to increase and remained at 60%. This mitotic arrest was accompanied by a dose-dependent inhibition of the TNF-alpha-induced in situ synthesis and release of interleukin-6 per cell by 60%.

CONCLUSIONS

Under conditions mimicking cytokine-induced cell activation a predominant inhibitory effect of everolimus compared to sirolimus on endothelial cell proliferation was observed paralleled by an inhibition of proinflammatory cytokines. This might attenuate the acute proinflammatory status after transplantation.

Rapamycin attenuates vascular wall inflammation and progenitor cell promoters after angioplasty

Rapamycin combines antiproliferative and antiinflammatory properties and reduces neointima formation after angioplasty in patients. Its effect on transcriptional programs governing neointima formation has not yet been investigated. Here, we systematically analyzed the effect of rapamycin on gene expression during neointima formation in a human organ culture model. After angioplasty, renal artery segments were cultured for 21 or 56 days in absence or presence of 100 ng/ml rapamycin. Gene expression analysis of 2312 genes revealed 264 regulated genes with a peak alteration after 21 days. Many of those were associated with recruitment of blood cells and inflammatory reactions of the vessel wall. Likewise, chemokines and cytokines such as M-CSF, IL-1beta, IL-8, beta-thromboglobulin, and EMAP-II were found up-regulated in response to vessel injury. Markers indicative for a facilitated recruitment and stimulation of hematopoetic progenitor cells (HPC), including BST-1 and SDF-1, were also induced. In this setting, rapamycin suppressed the coordinated proadhesive and proinflammatory gene expression pattern next to down-regulation of genes related to metabolism, proliferation, and apoptosis. Our study shows that mechanical injury leads to induction of a proinflammatory, proadhesive gene expression pattern in the vessel wall even in absence of leukocytes. These molecular events could provide a basis for the recruitment of leukocytes and HPC. By inhibiting the expression of such genes, rapamycin may lead to a reduced recruitment of leukocytes and HPC after vascular injury, an effect that may play a decisive role for its effectiveness in reducing restenosis.