Expression of wild-type and noncleavable Fas ligand by tetracycline-regulated adenoviral vectors to limit intimal hyperplasia in vascular lesions

tRNA-derived fragments tRFGlnCTG induced by arterial injury promote vascular smooth muscle cell proliferation

tRNA-derived fragments (tRFs) and tRNA halves (tiRNAs) are originated from the specific cleavage of endogenous tRNAs or their precursors and regulate gene expression when the cells are in stressful circumstances. Here, we replicated the rat common carotid artery (CCA) intimal hyperplasia model and investigated the expression of tRFs/tiRNAs in the artery. The normal and the balloon-injured rat CCAs were subjected to small RNA sequencing, and then the differentially expressed tRFs/tiRNAs were identified and analyzed. The expression profiles of tRFs/tiRNAs in the healthy and injured CCAs were remarkably different. tRNA^GlnCTG-derived fragments (tRF^GlnCTG) were found to be overexpressed with a high abundance in the injured CCA. In in vitro experiments, the synthetic tRF^GlnCTG mimetics elevated the proliferation and migration of rat vascular smooth muscle cells (VSMCs). Through bioinformatics analysis and an overexpression experiment, tRF^GlnCTG was found to negatively regulate the expression of FAS cell surface death receptor (FAS). This study revealed that tRF^GlnCTG is a crucial regulator in promoting VSMC proliferation. The investigation of the roles of tRFs/tiRNAs is of significance for understanding the mechanism, diagnosis, and treatment of intimal hyperplasia.

Nanoparticle drug- and gene-eluting stents for the prevention and treatment of coronary restenosis

Percutaneous coronary intervention (PCI) has become the most common revascularization procedure for coronary artery disease. The use of stents has reduced the rate of restenosis by preventing elastic recoil and negative remodeling. However, in-stent restenosis remains one of the major drawbacks of this procedure. Drug-eluting stents (DESs) have proven to be effective in reducing the risk of late restenosis, but the use of currently marketed DESs presents safety concerns, including the non-specificity of therapeutics, incomplete endothelialization leading to late thrombosis, the need for long-term anti-platelet agents, and local hypersensitivity to polymer delivery matrices. In addition, the current DESs lack the capacity for adjustment of the drug dose and release kinetics appropriate to the disease status of the treated vessel. The development of efficacious therapeutic strategies to prevent and inhibit restenosis after PCI is critical for the treatment of coronary artery disease. The administration of drugs using biodegradable polymer nanoparticles as carriers has generated immense interest due to their excellent biocompatibility and ability to facilitate prolonged drug release. Despite the potential benefits of nanoparticles as smart drug delivery and diagnostic systems, much research is still required to evaluate potential toxicity issues related to the chemical properties of nanoparticle materials, as well as to their size and shape. This review describes the molecular mechanism of coronary restenosis, the use of DESs, and progress in nanoparticle drug- or gene-eluting stents for the prevention and treatment of coronary restenosis.

High soluble Fas and soluble Fas Ligand serum levels before stent implantation are protective against restenosis

Percutaneous coronary intervention (PCI) represents the most important treatment of coronary artery stenosis today. But instent restenosis (ISR) is a limitation for the outcome. Fas and Fas Ligand have been implicated in apoptosis and vessel wall inflammation. Their role in ISR is not known so far. In this prospective study we studied 137 patients with stable coronary artery disease who underwent elective PCI. Blood samples were taken directly before and 24 hours after PCI. Soluble (s)Fas and sFas Ligand serum levels were measured by ELISA. Restenosis was evaluated six to eight months later either by coronary angiography or by exercise testing. During the follow-up period, 18 patients (13%) developed ISR. At baseline, patients with ISR had significantly lower median sFas, as well as sFas Ligand levels compared to patients without ISR (sFAS: ISR 492 pg/ml, no ISR 967 pg/ml, p=0.014; sFAS Ligand: ISR: 26 pg/ml, no ISR: 42 pg/ml, p=0.001). After PCI median sFas levels significantly decreased in patients with ISR compared to patients without ISR [ISR: -152 pg/ml (IQR -36 to -227), no ISR: -38 pg/ml (IQR -173 to +150 pg/ml), p=0.03]. sFas Ligand levels after PCI significantly increased in ISR patients compared to patients without ISR [ISR: 14 pg/ml (IQR -3 to +26 pg/ml), no ISR -6 pg/ml (IQR -22 to +21 pg/ml), p=0.014]. In conclusion, sFas and sFas Ligand seem to be associated with the development of ISR. Determination of serum levels before and after PCI might help identifying patients at higher risk of ISR.

Delivery of large biopharmaceuticals from cardiovascular stents: a review

This review focuses on new and emerging large-molecule bioactive agents delivered from stent surfaces in drug-eluting stents (DESs) to inhibit vascular restenosis in the context of interventional cardiology. New therapeutic agents representing proteins, nucleic acids (small interfering RNAs and large DNA plasmids), viral delivery vectors, and even engineered cell therapies require specific delivery designs distinct from traditional smaller-molecule approaches on DESs. While small molecules are currently the clinical standard for coronary stenting, extension of the DESs to other lesion types, peripheral vasculature, and nonvasculature therapies will seek to deliver an increasingly sophisticated armada of drug types. This review describes many of the larger-molecule and biopharmaceutical approaches reported recently for stent-based delivery with the challenges associated with formulating and delivering these drug classes compared to the current small-molecule drugs. It also includes perspectives on possible future applications that may improve safety and efficacy and facilitate diversification of the DESs to other clinical applications.

Fas Ligand Delivery by a Prostate-Restricted Replicative Adenovirus Enhances Safety and Antitumor Efficacy

PURPOSE

Recent studies showed that Fas ligand (FasL) induced apoptosis in tumor cells and suppressed the immune response in several types of tumors. However, the toxicity of FasL limited further administration. This study delivered FasL in prostate cancer cells using an improved prostate-restricted replicative adenovirus (PRRA), thereby improving the antitumor effect while decreasing systemic toxicity.

EXPERIMENTAL DESIGN

We designed a FasL-armed PRRA, called AdIU3, by placing adenoviral E1a and E4 genes, FasL cDNA, and E1b gene under the control of two individual PSES enhancers. Tissue-specific viral replication and FasL expression were analyzed, and the tumor killing effect of AdIU3 was investigated both in vitro and in vivo using androgen-independent CWR22rv s.c. models via local administration and bone models via systemic administration. The safety of systemic administration of AdIU3 was evaluated. AdCMVFasL, in which FasL was controlled by a universal cytomegalovirus (CMV) promoter, was used as a control.

RESULTS

AdIU3 enhanced FasL expression in prostate-specific antigen (PSA)/prostate-specific membrane antigen (PSMA)-positive cells but not in PSA/PMSA-negative cells. It induced apoptosis and killed PSA/PMSA-positive prostate cancer cells but spared normal human fibroblasts, hepatocytes, and negative cells. The increase in killing activity was confirmed to result in part from a bystander killing effect. Furthermore, AdIU3 was more effective than a plain PRRA in inhibiting the growth of androgen-independent prostate cancer xenografts and bone tumor formation. Importantly, systemic administration of AdIU3 resulted in undetectable toxicity, whereas the same doses of AdCMVFasL killed all mice due to multiviscera failure in 16 h.

CONCLUSIONS

AdIU3 decreased the toxicity of FasL by controlling its expression with PSES, with greatly enhanced prostate cancer antitumor efficacy. The results suggested that toxic antitumor factors can be delivered safely by a PRRA.

The dual role of Fas-ligand as an injury effector and defense strategy in diabetes and islet transplantation

The exact process that leads to the eruption of autoimmune reactions against beta cells and the evolution of diabetes is not fully understood. Macrophages and T cells may launch an initial immune reaction against the pancreatic islets of Langerhans, provoking inflammation and destructive insulitis. The information on the molecular mechanisms of the emergence of beta cell injury is controversial and points to possibly important roles for the perforin-granzyme, Fas-Fas-ligand (FasL) and tumor-necrosis-factor-mediated apoptotic pathways. FasL has several unique features that make it a potentially ideal immunomodulatory tool. Most important, FasL is selectively toxic to cytotoxic T cells and less harmful to regulatory T cells. This review discusses the intrinsic sensitivity of beta cells to FasL-mediated apoptosis, the conditions that underlie this beta cell sensitivity, and the feasibility of using FasL to arrest autoimmunity and prevent islet allograft rejection. In both the autoimmune and transplant settings, it is imperative to progress from the administration of nonspecific immunosuppressive therapy to the concept of beta-cell-specific immunomodulation. FasL evolves as a prime candidate for antigen-specific immunomodulation.

Inhibition of intimal hyperplasia in transgenic mice conditionally expressing the chemokine-binding protein M3

Chemokines have been implicated in the pathogenesis of a wide variety of diseases. This report describes the generation of transgenic mice that conditionally express M3, a herpesvirus protein that binds and inhibits chemokines. In response to doxycycline, M3 expression was induced in a variety of tissues and M3 was detectable in the blood by Western blotting. No gross or histological abnormalities were seen in mice expressing M3. To determine whether M3 expression could modify a significant pathophysiological response, we examined its effect on the development of intimal hyperplasia in response to femoral arterial injury. Intimal hyperplasia is thought to play a critical role in the development of restenosis after percutaneous transluminal coronary angioplasty and in the progression of atherosclerosis. Induction of M3 expression resulted in a 67% reduction in intimal area and a 68% reduction in intimal/medial ratio after femoral artery injury. These data support a role for chemokines in regulating intimal hyperplasia and suggest that M3 may be effective in attenuating this process. This transgenic mouse model should be a valuable tool for investigating the role of chemokines in a variety of pathological states.

Endothelial overexpression of Fas ligand decreases atherosclerosis in apolipoprotein E-deficient mice

OBJECTIVE

Fas ligand (FasL) can induce apoptosis in cells bearing the Fas receptor. The role of FasL in the vasculature with regard to atherosclerosis is controversial. This study examined the function of endothelial FasL during atherosclerosis.

METHODS AND RESULTS

Transgenic (Tg) mice that specifically overexpress different levels of FasL on vascular endothelial cells were crossed into the apolipoprotein E-knockout background (ApoE-KO) to generate ApoE-KO/FasL-Tg mice. Although plasma cholesterol and triglyceride levels were not different between ApoE-KO/FasL-Tg mice and ApoE-KO mice after 12 weeks of a high-fat diet, overexpression of the FasL transgene significantly reduced atherosclerotic lesion area in aortae by 49%. The reduction of atherosclerotic lesion area was more pronounced in thoracic and abdominal aortae than in the aortic arch, and a 34% reduction in lesion area was observed in aortic root sections from the ApoE-KO/FasL-Tg group compared with the ApoE-KO group. Immunostaining revealed significant decreases in both macrophage and CD8 T-cell accumulation in lesions of ApoE-KO/FasL-Tg mice. ApoE-KO/FasL-Tg mice that express lower levels of endothelial FasL also displayed reduced lesion size, but this reduction was statistically significant at the aortic arch only.

CONCLUSIONS

Overexpression of endothelial FasL is antiinflammatory and inhibits atherosclerosis under hypercholesterolemic conditions.

Heat shock protein 70 participates in the neuroprotective response to intracellularly expressed beta-amyloid in neurons

Intracellular beta-amyloid 42 (Abeta42) accumulation is increasingly recognized as an early event in the pathogenesis of Alzheimer's disease (AD). We have developed a doxycycline-inducible adenoviral-based system that directs intracellular Abeta42 expression and accumulation into the endoplasmic reticulum of primary neuronal cultures in a regulated manner. Abeta42 exhibited a perinuclear distribution in cell bodies and an association with vesicular compartments. Virally expressed intracellular Abeta42 was toxic to neuronal cultures 24 hr after induction in a dose-dependent manner. Abeta42 expression prompted the rapid induction of stress-inducible Hsp70 protein in neurons, and virally mediated Hsp70 overexpression rescued neurons from the toxic effects of intracellular Abeta accumulation. Together, these results implicate the cellular stress response as a possible modulator of Abeta-induced toxicity in neuronal cultures.

Rheumatoid arthritis synovial fluid macrophages express decreased tumor necrosis factor-related apoptosis-inducing ligand R2 and increased decoy receptor tumor necrosis factor-related apoptosis-inducing ligand R3

OBJECTIVE

To characterize the expression pattern of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and its cognate receptors (TRAIL R1, R2, R3, and R4) on rheumatoid arthritis (RA) synovial fluid (SF) lymphocytes and monocyte/macrophages and on cultured RA synovial fibroblasts.

METHODS

The expression of TRAIL and TRAIL receptors on RA SF lymphocytes and monocyte/macrophages, normal macrophages, and RA synovial fibroblasts was examined by flow cytometry with previously characterized monoclonal antibodies. The ability of adenoviral-mediated delivery of TRAIL to induce macrophage or RA synovial fibroblast apoptosis was examined by flow cytometry.

RESULTS

By flow cytometry, neither TRAIL nor its cognate receptors was detectable on RA SF lymphocytes or RA synovial fibroblasts. In contrast, RA SF macrophages expressed TRAIL R3, a decoy receptor (P < 0.01 versus isotype control), but not TRAIL, or TRAIL R1, R2, or R4. Normal peripheral blood-derived monocyte-differentiated macrophages expressed TRAIL R2 (P < 0.01), but not TRAIL or the other TRAIL receptors. Adenoviral-mediated delivery of TRAIL had no effect on the survival of normal macrophages or RA synovial fibroblasts but readily induced apoptosis in the prostate cancer cell line (PC-3) that expressed TRAIL R1 and R2.

CONCLUSION

TRAIL R1 and R2, which are required for signal transmission by TRAIL, were not detected on RA SF lymphocytes, macrophages, or synovial fibroblasts. These observations do not support a potential therapeutic role for TRAIL in RA.

The Akt-regulated forkhead transcription factor FOXO3a controls endothelial cell viability through modulation of the caspase-8 inhibitor FLIP

FLICE-inhibitory protein (FLIP) is a homolog of caspase-8 that lacks catalytic activity and has been shown to be important in protecting endothelial cells from apoptosis. The serine/threonine kinase Akt/PKB was recently reported to promote FLIP expression in endothelial and tumor cells. Here we examined the role of the forkhead transcription factor FOXO3a, a downstream target of Akt, in controlling FLIP regulation in endothelial cells. FOXO3a nuclear translocation was regulated by Akt in human umbilical vein endothelial cells. Transduction of a nonphosphorylatable, constitutively active mutant of FOXO3a (TM-FOXO3a) led to the down-regulation of FLIP levels. Transduction with TM-FOXO3a also increased caspase-8 activity and promoted apoptosis in endothelial cells. Conversely, transduction of a dominant-negative mutant of FOXO3a up-regulated FLIP levels and protected endothelial cells from apoptosis under serum deprivation conditions. Restoration of intracellular FLIP blocked caspase-8 activation and inhibited apoptosis in TM-FOXO3a-transduced cells. These data suggest that FOXO3a is a downstream target of Akt in endothelial cells that can promote apoptosis via FLIP down-regulation and activation of the extrinsic apoptotic pathway.

A tetracycline-regulated adenoviral expression system for in vivo delivery of transgenes to lung and liver

BACKGROUND

Recombinant adenoviruses are an established tool for somatic gene transfer to multiple cell types in animals as well as in tissue culture. However, generation of adenoviruses expressing transgenes that are potentially toxic to the host cell line represents a practical problem. The aim of this study was to construct an adenoviral expression system that prevents transgene expression during the generation and propagation of the virus, and allows efficient gene transfer to lung and liver, major target organs of gene therapy.

METHODS

Using the tet-off system we constructed tetracycline (tet) regulatable recombinant adenoviruses expressing the marker gene LacZ (Adtet-off.LacZ) as well as a secretory protein, human group IIA secretory phospholipase A(2) (Adtet-off.hsPLA(2)). Expression (Western blot, activity assay) was tested in vitro (HeLa cells), and in vivo by gene transfer to lung and liver.

RESULTS

Without addition of tetracycline we demonstrated expression of LacZ (Adtet-off.LacZ) and sPLA(2) (Adtet-off.hsPLA(2)) in HeLa cells. Providing additional tet-transactivator (tTA) protein either by stable transfection or coinfection with a tTA-expressing adenovirus resulted in a further increase of LacZ and sPLA(2) expression. Transgene expression in vitro was eliminated by the addition of tetracycline to the culture medium. Adtet-off.LacZ and Adtet-off.hsPLA(2) allowed successful gene transfer in vivo to lung and liver. While the expression was highly efficient within the lungs, however, additional tTA was necessary to achieve high-level expression within liver.

CONCLUSIONS

Tet-regulatable adenoviral expression systems may facilitate the construction of recombinant adenoviruses encoding potentially toxic transgenes and permit regulated transgene expression.

Display of Fas ligand protein on cardiac vasculature as a novel means of regulating allograft rejection

BACKGROUND

Fas ligand (FasL) is a potent death-inducing molecule with important functions in immune homeostasis and tolerance to self-antigens. The complex biological activities of FasL and its inefficient expression using conventional gene transfer approaches limit its use for immunomodulation to prevent allograft rejection. We have recently generated a chimeric FasL with core streptavidin (SA-FasL) with potent apoptotic activity and designed a novel approach to display it on the surface of several cell types via biotinylation. We herein tested whether SA-FasL can also be displayed on vascular endothelial cells in the heart and examined its effect on graft survival after transplantation into syngeneic and allogeneic hosts.

METHODS AND RESULTS

SA-FasL was efficiently displayed on the vasculature of BALB/c hearts with a half-life of 9 days in vivo. Transplantation of hearts displaying SA-FasL into syngeneic hosts resulted in indefinite graft survival without detectable toxicity to the grafts and hosts. In contrast, transplantation of allogeneic C57BL/10 hearts displaying SA-FasL into BALB/c recipients resulted in graft rejection, but in a delayed fashion as compared with control hearts (mean survival time=17.4+/-5 versus 9.6+/-1 days). Allograft survival was further extended to 21+/-2.6 and 24+/-3 days (P<0.05) by intravenous treatment of graft recipients with 1 dose of SA-FasL-decorated donor splenocytes on days 2 and 6 after transplantation, respectively.

CONCLUSIONS

This study shows for the first time that exogenous proteins can be displayed on the endothelium of solid organs for therapeutic purposes. This approach provides a convenient and rapid means of displaying exogenous proteins on the surface of cells, tissues, and solid organs, with broad research and therapeutic implications.

Restoration of a functional open reading frame by homologous recombination between two adenoviral vectors

In this study, we examined the ability of adenoviral (Ad) vectors to undergo homologous recombination. The lacZ gene was divided between two parental, first-generation vectors such that neither encoded a functional product but both shared 494 bp in common. The open reading frame could only be restored by homologous recombination. We observed beta-galactosidase activity only upon co-infection of both parental vectors and after the onset of viral DNA replication, creating a delay in expression of 24-36 hours in HeLa cells. At peak efficiency, this recombination vector system resulted in beta-galactosidase activity levels 100x above background and just 18x less than a conventional, first-generation vector in HeLa cells. After recombination, the resultant progeny vector genomes containing reconstituted expression cassettes were devoid of all viral genes and contained two packaging signals. These progeny genomes were efficiently packaged, could be separated from their parental vectors based on their lighter buoyant densities in CsCl gradients, and were subsequently used as functional gene transfer vectors. This novel recombination vector system should be useful for transferring large transgenes (because the carrying capacity of two Ad vectors can be exploited) or expressing any cytotoxic or Ad replication inhibitory protein (because the parental vectors exhibit no background expression).

Spatial and temporal control of transgene expression through ultrasound-mediated induction of the heat shock protein 70B promoter in vivo

Adenoviral vectors have been constructed that express the transgenes luciferase (Adeno-HSP-Luc) or Fas ligand (Adeno-HSP-FasL) under the control of the heat shock protein 70B (hsp70B) promoter. Cultures infected with Adeno-HSP-Luc transiently expressed high levels of luciferase after heat shock. When cultures infected with Adeno-HSP-FasL were maintained at 37 degrees C, no transgene expression was observed, but when cultures were exposed to heat stress, transgene expression resulted in apoptotic cell death. In vivo, transgene expression was induced by ultrasound-mediated heating of adenovirus-infected tissue. In mice or rats injected with the Adeno-HSP-Luc construct, high levels of localized expression of luciferase activity were observed in regions subjected to ultrasound-mediated irradiation. Adeno-HSP-FasL was administered systemically to mice via the tail vein to evaluate safety. Animals receiving Adeno-HSP-FasL in the absence of ultrasound treatment did not display liver toxicity, whereas animals receiving ultrasound treatment to induce the expression of Fas ligand from the hsp70B promoter had significant increases in serum levels of liver enzymes. These data demonstrate that combining the inducible hsp70B promoter with ultrasound induction allows safe local expression of cytotoxic genes with possible therapeutic utility.

Suppression of Akt signaling induces Fas ligand expression: involvement of caspase and Jun kinase activation in Akt-mediated Fas ligand regulation

Fas and Fas ligand (FasL) expression has been detected in chronic vascular lesions, and Fas-mediated apoptosis of vascular smooth muscle cells (VSMC) may influence the integrity of the atherosclerotic plaque. Here we report that FasL is not expressed by normal VSMC, but its expression is upregulated by stresses that induce apoptosis, including serum deprivation, exposure to the phosphatidylinositol 3-kinase (PI 3-kinase) inhibitor wortmannin, and ablation of Akt signaling. Conversely, constitutive activation of Akt signaling diminished FasL expression in VSMC cultures exposed to low-mitogen media or wortmannin. Under conditions of suppressed PI 3-kinase/Akt signaling, VSMC apoptosis was partially inhibited by treatment with neutralizing antibody against FasL. Suppression of Akt signaling increased the activity of c-Jun N-terminal kinase, and transduction of dominant-negative c-Jun inhibited FasL induction under these conditions. Diminished Akt signaling promoted the cleavage of caspase 3, and both caspase 3 cleavage and FasL induction were inhibited by transduction of dominant-negative caspase 9 or the caspase 8 inhibitor CrmA. Similarly, induction of FasL by the Akt-regulated forkhead transcription factor FKHRL1 was dependent upon caspase and c-Jun activation. Taken together, these results indicate that the sequential activation of caspase 3 and c-Jun participates in the induction of FasL under conditions of suppressed Akt signaling or FKHRL1 activation and that FasL participates in a positive-feedback loop to promote cell death under conditions of cellular stress.

Phosphatidylinositol 3-kinase/Akt signaling controls endothelial cell sensitivity to Fas-mediated apoptosis via regulation of FLICE-inhibitory protein (FLIP)

Fas is constitutively expressed on endothelial cells, but in contrast to smooth muscle and other cell types, endothelial cells are highly resistant to Fas-mediated apoptosis. In this study, we examined the role of the serine/threonine kinase Akt/PKB in controlling the sensitivity of endothelial cells to Fas-mediated apoptosis. Serum deprivation inhibited expression of the caspase-8 inhibitor FLICE-inhibitory protein (FLIP), which functions downstream from Fas. FLIP expression levels were restored when serum-depleted cells were treated with vascular endothelial growth factor. Treatment with the phosphatidylinositol 3-kinase (PI 3-kinase) inhibitors wortmannin or LY294002 or infection of the adenoviral construct expressing dominant-negative Akt (Adeno-dnAkt) also inhibited the expression of FLIP in endothelial cells, whereas the MEK inhibitor PD98059 had no effect. Conversely, adenovirus-mediated transfection of a constitutively-active Akt gene abolished the wortmannin- and LY294002-mediated downregulation of FLIP. Suppression of PI 3-kinase signaling sensitized endothelial cells to Fas-mediated apoptosis. Under conditions of suppressed PI 3-kinase signaling, restoration of FLIP expression reversed the induced sensitivity of endothelial cells to Fas-mediated apoptosis. These data suggest that inhibition of Fas-mediated apoptosis, via promotion of FLIP expression, is a mechanism through which Akt signaling can promote endothelial cell survival.