Impact of the gut microbiome on the atorvastatin-dependent modulation of the serum lipidome

Background and aims

The modulation of serum lipids, in particular of the low-density lipoprotein cholesterol (LDL-C), by statins varies between individuals. The mechanisms regulating this interindividual variation are only poorly understood. Here, we investigated the relation between the gut microbiome and the regulatory properties of atorvastatin on the serum lipidome using mice with depleted gut microbiome.

Methods

Over a period of 6 weeks, mice (C57BL/6) with either an intact (conventional mice, CONV, n=24) or antibiotic-based depleted gut microbiome (antibiotic treated mice, ABS, n=16) were put on standard chow diet (SCD) or high fat diet (HFD), respectively. During the last 4 weeks of treatment atorvastatin (Ator, 10mg/kg body weight/day) or control vehicle was administered via daily oral gavage. Blood lipids (total cholesterol, VLDL, LDL-C, HDL-C) and serum sphingolipids were compared among the groups. The expressions of hepatic and intestinal genes involved in cholesterol metabolism were analyzed by qRT-PCR. Alterations in the gut microbiota profile of mice with intact gut microbiome were examined using 16S RNA qRT-PCR.

Results

In CONV mice, HFD led to significantly increased blood LDL-C levels as compared with SCD (HFD: 36.8±1.4 mg/dl vs. SCD: 22.0±1.8 mg/dl; P<0.01). In CONV mice atorvastatin treatment significantly reduced blood LDL-C levels after HFD, whereas in ABS mice the LDL-C lowering effect of atorvastatin was markedly attenuated (CONV+HFD+Ator: 31.0±1.8 mg/dl vs. ABS+HFD+Ator: 46.4±3 mg/dl; P<0.01). A significant reduction in the abundance of several plasma lipids, in particular sphingolipids and glycerophospholipids upon atorvastatin treatment was observed in CONV mice, but not in ABS mice. The expressions of distinct hepatic and intestinal cholesterol-regulating genes (ldlr, srebp2, pcsk9 and npc1l1) upon atorvastatin treatment were significantly altered in gut microbiota depleted mice. In response to HFD a decrease in the relative abundance of the bacterial phyla Bacteroides and an increase in the relative abundance of Firmicutes was observed. The altered ratio between Bacteroides and Firmicutes in HFD fed mice was partly reversed upon atorvastatin treatment.

Conclusions

Our findings indicate a crucial role of the gut microbiome for the regulatory properties of atorvastatin on the serum lipidome and, in turn, support a critical impact of atorvastatin on the gut microbial composition. The results provide novel insights into potential microbiota related mechanisms underlying interindividual variation in modulation of the serum lipidome by statins, given interindividual differences in microbiome composition and function.

Funding Acknowledgement

Type of funding source: Foundation. Main funding source(s): German Heart Research Foundation

P5393Deficiency of the long noncoding RNA NEAT1 disturbs T cell and monocyte-macrophage lineage differentiation and functions and results in systemic inflammation with high circulating interferon levels

Background

Inflammation is a key driver of atherosclerosis and myocardial infarction (MI), and beyond proteins and microRNAs, long noncoding RNAs (lncRNAs) are implicated in inflammation control. To obtain further information on the role of lncRNAs in the context of atherosclerosis, we analyzed transcriptome maps of circulating immune cells (PBMCs) of post-MI patients in whom the lncRNA NEAT1 was suppressed. Here, we report immune disturbances in murine NEAT1 knockout models with wildtype or ApoE−/− genetic background.

Methods and results

RNA-sequencing (RNA-seq) of PBMCs from post-MI patients revealed profound transcriptome disturbances compared to healthy controls. Among these, NEAT1 suppression was notable since it affected the most highly expressed lncRNA as part of a molecular circuit also encompassing chemokines and interleukins.

We used NEAT1−/− mice to evaluate whether NEAT1 depletion per se may cause immune dysfunction. NEAT1−/− splenocytes displayed enhanced baseline ROS production, and RNA-seq identified anomalous expression and regulation of chemokines/ receptors, innate immunity genes, TNF and caspases. FACS revealed displayed anomalous Treg and TH cell differentiation in NEAT1−/− spleens vs. wildtype (WT).

Beyond grossly altered transcriptome, NEAT1−/− bone marrow derived macrophages (BMDMs) responded to LPS with increased (p<0.001) ROS production, enhanced baseline phagocytic activity (p<0.001), and attenuated proliferation (p=0.001). FACS revealed deregulated monocyte-macrophage differentiation in NEAT1−/− bone marrow and blood.

Further, NEAT1−/− mice displayed aortic wall CD68+ cell infiltration and there was evidence of myocardial inflammation which could lead to severe and potentially life-threatening structural damage in some of these animals. This observation suggests that even stochastic activation of the highly unstable NEAT1−/− immune system may trigger uncontrolled pathogenic cascades, explaining the survival disadvantage of NEAT1−/− mice.

In addition to these studies on homozygous NEAT1−/− deficiency in WT background, we obtained data on mice with partial i.e. heterozygous NEAT1−/+ deficiency on ApoE−/− background. Analysis of this new NEAT1−/+ ApoE−/− strain indicates that even partial NEAT1 deficiency leads to systemic inflammation with high IFN-gamma levels, when the animals are exposed to immune stress e.g. high LDL cholesterol.

Conclusions

Regarding the monocyte-enriched NEAT1 suppressed in post-MI PBMCs, the data from NEAT1−/− and NEAT1−/+ ApoE−/− mice document NEAT1 as a key immune system coordinator whose deficiency affects monocyte-macrophage and T cell differentiation and functions and renders the immune system unstable and highly vulnerable to immune stress. Since in patients NEAT1 is part of a molecular circuit persistently deregulated post-MI, too, it appears reasonable to further search for new therapeutic targets within this circuit, taking advantage of the described genetic animal models.

P3688Familial recurrent autoimmune myocarditis associated with a truncating nonsense mutation of the desmoplakin gene

Background

Arrhythmogenic cardiomyopathy (AC) is an important cause of ventricular arrhythmias in children and young adults. AC is associated with mutation of desmosomal proteins, however, cardiac disease penetrance is incomplete and the clinical course varies widely without recognizable exogenous or epi/genetic co-factors. Importantly, DSP mutation carriers may also display entirely non-cardiac e.g. dermatological phenotypes.

Methods and results

In two brothers with recurrent fulminant myocarditis, mutation screening of 218 cardiomyopathy-related genes identified a truncating mutation Arg1458* of desmoplakin (DSP). DSP immunhistology unexpectedly revealed complete loss (“knockout”) of DSP protein in endomyocardial biopsies (EMBs), but none of the histological anomalies of AC. Criteria for histological diagnosis of myocarditis were not either fulfilled, and cardiac MRI revealed no features associated with AC. Screening for infections was negative, there was no substance abuse, medication or vaccination. Possible disease triggers were competitive sport events. Myosin and troponin I autoantibodies were detected at titers up to 1:320.

We used allele-specific RT-PCR to distinguish if the patients' allele classified as “normal” was actually defective due to promotor mutation or epigenetic silencing. RT-PCRs were done on EMBs and peripheral blood mononuclear cells (PBMCs). In a cohort of dilated cardiomyopathy (DCM) patients we were able to detect DSP transcripts in both, PBMC and left-ventricular heart tissue. RNA sequencing of human PBMC subpopulations suggested that DSP transcription may be restricted to certain immune cell subtypes. RT-PCRs revealed that both Arg1458* carriers have a functional second DSP allele, indicating that their “DSP knockout” occurs at the protein level and may be due to protein instability and degradation within desmosomes.

We screened additional existing cohorts for such variants and identified stopgain variant Gln307Ter in a 37-yrs-old woman with ARVC. This patient's sister died from heart failure at the age of 39. In a 59-yrs-old female LVNC patient, stopgain variant Y1391X was identified. Here, family history was unclear, her brother probably died from coronary artery disease. In a 71-yrs-old female DCM patient with no family history, stopgain variant Tyr1512Ter was identified.

Conclusions

The described patients with DSP truncations strongly suggest the existence of additional genetic or exogenous modifiers driving pathogenesis either way. DSP defects may cause recurrent myocarditis, and mutation screening is advisable to enable early detection of high-risk patients with similar phenotypes. Our finding of complete myocardial DSP protein loss emphasizes that DNA sequencing may miss critical molecular disturbances. It is indispensable to also analyze transcriptome and protein level in the tissue actually affected in a patient in order to recognize his/her individual pathogenesis.

54Role of the gut microbiome for the cholesterol lowering effect of atorvastatin

Background and aims

Statins show interindividual differences in the extent of low-density lipoprotein cholesterol (LDL-C) reduction. The mechanisms of this interindividual variation are not fully understood. Here, we examined the potential role of the gut microbiome for the LDL-C lowering property of atorvastatin.

Methods

Mice (C57BL/6) with either intact (conventional mice, CONV, n=24) or with antiobiotic depleted gut microbiome (gnotobiotic, n=16), were put on standard chow diet (SCD) (n=11) or high fat diet (HFD) (n=29) for 6 weeks. During the last 4 weeks atorvastatin (Ator, 10mg/kg body weight/day) or control vehicle was orally applied via gavage. Blood levels of LDL-C and glucose and body weight after 6 weeks of treatment were compared between the groups. Expression of genes involved in hepatic and intestinal cholesterol-metabolism were examined. Faeces of CONV mice were analyzed for alteration of the gut microbiota profile upon atorvastatin treatment using 16S rRNA qPCR.

Results

HFD fed mice with intact gut microbiome showed significantly increased blood LDL-C levels as compared to SCD (HFD: 36.8±1.4 mg/dl vs. SCD: 22.0±1.8 mg/dl; P<0.01). Bodyweight gain or blood glucose levels after HFD were not significantly different between CONV and gnotobiotic mice. While in CONV mice atorvastatin significantly reduced LDL-C levels after HFD, in gnotobiotic mice the LDL-C lowering effect of atorvastatin was attenuated (CONV+HFD+Ator: 31.0±1.8 mg/dl vs. gnotobiotic mice+HFD+Ator: 46.4±3 mg/dl; P<0.01). The expression of genes involved in hepatic cholesterol synthesis was not significantly altered in gnotobiotic mice as compared to CONV mice. In CONV mice HFD decreased the relative abundance of the bacterial phyla Bacteroidetes and increased the abundance of Firmicutes as compared to SCD. The ratio between Firmicutes to Bacteroidetes was shifted towards control conditions upon atorvastatin treatment.

Conclusions

The results of this study suggest a regulatory impact of atorvastatin on the gut-microbial profile and, in turn, a crucial role of the gut-microbiome for the LDL-C lowering effect of atorvastatin independent of its regulation of hepatic cholesterol synthesis. Our findings provide novel insight into potential microbiota-related mechanisms causing interindividual variation in LDL-C lowering effects of statins.

Acknowledgement/Funding

German Heart Research Foundation

Alternatively spliced tissue factor and full-length tissue factor protect cardiomyocytes against TNF-α-induced apoptosis

Tissue Factor (TF) is expressed in various cell types of the heart, such as cardiomyocytes. In addition to its role in the initiation of blood coagulation, the TF:FVIIa complex protects cells from apoptosis. There are two isoforms of Tissue Factor (TF): "full length" (fl)TF--an integral membrane protein, and alternatively spliced (as)TF--a protein that lacks a transmembrane domain and can thus be secreted in a soluble form. Whether asTF or flTF affects apoptosis of cardiomyocytes is unknown. In this study, we examined whether asTF or flTF protects murine cardiomyocytes from TNF-α-induced apoptosis. We used murine cardiomyocytic HL-1 cells and primary murine embryonic cardiomyocytes that overexpressed either murine asTF or murine flTF, and stimulated them with TNF-α to initiate cell death. Apoptosis was assessed by annexin-V assay, propidium iodide assay, as well as activation of caspase-3 and -9. In addition, signaling via integrins, Akt, NFκB and Erk1/2, and gene-expression of Bcl-2 family members were analyzed. We here report that overexpression of asTF reduced phosphatidylserine exposure upon TNF-α-stimulation. asTF overexpression led to an increased expression and phosphorylation of Akt, as well as up-regulation of the anti-apoptotic protein Bcl-x(L). The anti-apoptotic effects of asTF overexpression were mediated via α(V)β(3)/Akt/NFκB signaling and were dependent on Bcl-x(L) expression in HL-1 cells. The anti-apoptotic activity of asTF was also observed using primary cardiomyocytes. Analogous yet less pronounced anti-apoptotic sequelae were observed due to overexpression of flTF. Importantly, cardiomyocytes deficient in TF exhibited increased apoptosis compared to wild type cells. We propose that asTF and flTF protect cardiomyocytes against TNF-α-induced apoptosis via activation of specific signaling pathways, and up-regulation of anti-apoptotic members of the Bcl-2 protein family.

microRNA122-regulated transgene expression increases specificity of cardiac gene transfer upon intravenous delivery of AAV9 vectors

Adeno-associated virus (AAV) vectors with capsids of AAV serotype 9 enable an efficient transduction of the heart upon intravenous injection of adult mice but also transduce the liver. The aim of this study was to improve specificity of AAV9 vector-mediated cardiac gene transfer by microRNA (miR)-dependent control of transgene expression. We constructed plasmids and AAV vectors containing target sites (TSs) of liver-specific miR122, miR192 and miR148a in the 3' untranslated region (3'UTR) of a luciferase expression cassette. Luciferase expression was efficiently suppressed in liver cell lines expressing high levels of the corresponding miRs, whereas luciferase expression was unaffected in cardiac myocytes. Intravenous injections of AAV9 vectors bearing three repeats of miR122 TS in the 3'UTR of an enhanced green fluorescent expression (EGFP) expression cassette resulted in the absence of EGFP expression in the liver of adult mice, whereas the control vectors without miR TS displayed significant hepatic EGFP expression. EGFP expression levels in the heart, however, were comparable between miR122-regulated and control vectors. The liver-specific de-targeting in vivo using miR122 was even more efficient than transcriptional targeting with a cardiac cytomegalovirus (CMV)-enhanced myosin light chain (MLC) promoter. These data indicate that miR-regulated targeting is a powerful new tool to further improve cardiospecificity of AAV9 vectors.

Regulation of cardiomyocyte full-length tissue factor expression and microparticle release under inflammatory conditions in vitro

SUMMARY BACKGROUND

Myocardial inflammation is associated with an increase in circulating microparticles (MPs) and procoagulability.

OBJECTIVES

We determined whether acute inflammation was associated with altered full-length tissue factor (flTF) expression and increased procoagulability in cardiomyocytic cells.

METHODS

This study examined the transcriptional regulation of flTF expression in murine cardiomyocytic (HL-1) cells. Also, the generation of MPs by HL-1 cells and their ability to diffuse through an artificial endothelium was evaluated.

RESULTS

Constitutive and tumor necrosis factor-alpha (TNF-alpha)-induced flTF expression of HL-1 was reduced when c-Jun N-terminal kinase (JNK) was inhibited. Tissue factor (TF)-positive procoagulant MPs were released from HL-1 cells in response to TNF-alpha. JNK inhibition potentiated the release of MPs from HL-1 cells without affecting MP-associated TF activity. MP generation was dependent on RhoA activation and associated with a reorganization of the actin cytoskeleton. Increased diffusion of HL-1-derived MPs through an endothelial monolayer was found after TNF-alpha treatment. The increased diffusion was dependent not only on TNF-alpha but also on HL-1-released mediators.

CONCLUSIONS

Full-length TF expression in HL-1 cells was regulated through JNK. The TNF-alpha-induced increase in procoagulability was mediated through RhoA-dependent release of flTF-bearing MPs. These MPs were able to diffuse through an endothelial barrier adjacent to HL-1 cells and increased the procoagulability of the extracellular endothelial space. Cardiomyocytes seem to be a likely source of flTF-bearing procoagulant MPs.

Prevalence of erythrovirus genotypes in the myocardium of patients with dilated cardiomyopathy

Parvovirus B19 (PVB19) is a member of the human erythrovirus family detected frequently in endomyocardial biopsies from patients with dilated cardiomyopathy. Human erythroviruses cluster into three genotypes 1-3 which share a high degree of homology between major structural proteins and may cause indistinguishable infections clinically and serologically. In human cardiac tissue erythrovirus genotypes other than PVB19 have not yet been reported. Three hundred seventeen consecutive patients with symptomatic dilated cardiomyopathy (median left ventricular ejection fraction: 28.6%, range 5-45%) who underwent endomyocardial biopsy for the elucidation of the etiology, were analyzed using a new consensus PCR assay designed for the detection of the three erythrovirus genotype sequences. Endomyocardial biopsies of 151 (47.6%) patients were erythrovirus-positive. Genotype 1 specific sequences were detected in 43/151 (28.5%) of positive biopsy samples, whereas genotype 2-specific sequences so far considered rare in human disease and not yet been described in human heart tissue was identified in 108/151 (71.5%) of virus-positive endomyocardial biopsies with a preference in patients above 50 years of age. In spite of younger age, systolic left ventricular dysfunction of genotype 1-positive patients was significantly reduced as compared to genotype 2-positive patients (24.4+/-10.4% vs. 31.0+/-9.5%, P=0.0001) at the initial presentation. The data show that two genetically distinct erythrovirus variants with a different age distribution are detectable in endomyocardial biopsies of patients with dilated cardiomyopathy. The erythrovirus genotype 2, not described previously in human heart tissue, is highly prevalent in the heart but the less prevalent genotype 1 is associated with more severe disturbed cardiac function.

RNA Interference and MicroRNA Modulation for the Treatment of Cardiac Disorders

The current status and challenges of RNA interference (RNAi) and microRNA modulation strategies for the treatment of myocardial disorders are discussed and related to the classical gene therapeutic approaches of the past decade. Section 2 summarizes the key issues of current vector technologies which determine if they may be suitable for clinical translation of experimental RNAi or microRNA therapeutic protocols. We then present and discuss examples dealing with the potential of cardiac RNAi therapy. First, an approach to block a key early step in the pathogenesis of a virus-induced cardiomyopathy by RNAi targeting of a cellular receptor for cardiopathogenic viruses (Section 3). Second, an approach to improve cardiac function by RNAi targeting of late pathway of heart failure pathogenesis common to myocardial disorders of multiple etiologies. This strategy is directed at myocardial Ca²⁺ homeostasis which is disturbed in heart failure due to coronary heart disease, heart valve dysfunction, cardiac inflammation, or genetic defects (Section 4). Whereas the first type of strategies (directed at early pathogenesis) need to be tailor-made for each different type of pathomechanism, the second type (targeting late common pathways) has a much broader range of application. This advantage of the second type of approaches is of key importance since enormous efforts need to be undertaken before any regulatory RNA therapy enters the stage of possible clinical translation. If then the number of patients eligible for this protocol is large, the actual transformation of the experimental therapy into a new therapeutic option of clinical importance is far more likely to occur.

Differential internalization and nuclear uncoating of self-complementary adeno-associated virus pseudotype vectors as determinants of cardiac cell transduction

Recently it was shown that several new pseudotyped adeno-associated virus (AAV) vectors support cardioselective expression of transgenes. The molecular mechanisms underlying this propensity for cardiac cell transduction are not well understood. We comparatively analyzed AAV vector attachment, internalization, intracellular trafficking, and nuclear uncoating of recombinant self-complementary (sc) AAV2.2 versus pseudotyped scAAV2.6 vectors expressing green fluorescence protein (GFP) in cells of cardiac origin. In cardiac-derived HL-1 cells and primary neonatal rat cardiomyocytes (PNCMs), expression of GFP increased rapidly after incubation with scAAV2.6-GFP, but remained low after scAAV2.2-GFP. Internalization of scAAV2.6-GFP was more efficient than that of scAAV2.2-GFP. Nuclear translocation was similarly efficient for both, but differential nuclear uncoating rates emerged as a key additional determinant of transduction: 30% of all scAAV2.6-GFP genomes translocated to the nucleus became uncoated within 48 h, but only 16% of scAAV2.2-GFP genomes. In contrast to this situation in cells of cardiac origin, scAAV2.2-GFP displayed more efficient internalization and similar (tumor cell line HeLa) or higher (human microvascular endothelial cell (HMEC)) uncoating rates than scAAV.2.6-GFP in non-cardiac cell types. In summary, both internalization and nuclear uncoating are key determinants of cardiac transduction by scAAV2.6 vectors. Any in vitro screening for the AAV pseudotype most suitable for cardiac gene therapy - which is desirable since it may allow significant reductions in vector load in upcoming clinical trials--needs to quantitate both key steps in transduction.

Coxsackievirus B3 and adenovirus infections of cardiac cells are efficiently inhibited by vector-mediated RNA interference targeting their common receptor

As coxsackievirus B3 (CoxB3) and adenoviruses may cause acute myocarditis and inflammatory cardiomyopathy, isolation of the common coxsackievirus–adenovirus-receptor (CAR) has provided an interesting new target for molecular antiviral therapy. Whereas many viruses show high mutation rates enabling them to develop escape mutants, mutations of their cellular virus receptors are far less likely. We report on antiviral efficacies of CAR gene silencing by short hairpin (sh)RNAs in the cardiac-derived HL-1 cell line and in primary neonatal rat cardiomyocytes (PNCMs). Treatment with shRNA vectors mediating RNA interference against the CAR resulted in almost complete silencing of receptor expression both in HL-1 cells and PNCMs. Whereas CAR was silenced in HL-1 cells as early as 24 h after vector treatment, its downregulation in PNCMs did not become significant before day 6. CAR knockout resulted in inhibition of CoxB3 infections by up to 97% in HL-1 cells and up to 90% in PNCMs. Adenovirus was inhibited by only 75% in HL-1 cells, but up to 92% in PNCMs. We conclude that CAR knockout by shRNA vectors is efficient against CoxB3 and adenovirus in primary cardiac cells, but the efficacy of this approach in vivo may be influenced by cell type-specific silencing kinetics in different tissues.

Genomic expression profiling of human inflammatory cardiomyopathy (DCMi) suggests novel therapeutic targets

The clinical phenotype of human dilated cardiomyopathy (DCM) encompasses a broad spectrum of etiologically distinct disorders. As targeting of etiology-related pathogenic pathways may be more efficient than current standard heart failure treatment, we obtained the genomic expression profile of a DCM subtype characterized by cardiac inflammation to identify possible new therapeutic targets in humans. In this inflammatory cardiomyopathy (DCMi), a distinctive cardiac expression pattern not described in any previous study of cardiac disorders was observed. Two significantly altered gene networks of particular interest and possible interdependence centered around the cysteine-rich angiogenic inducer 61 (CYR61) and adiponectin (APN) gene. CYR61 overexpression, as in human DCMi hearts in situ, was similarly induced by inflammatory cytokines in vascular endothelial cells in vitro. APN was strongly downregulated in DCMi hearts and completely abolished cytokine-dependent CYR61 induction in vitro. Dysbalance between the CYR61 and APN networks may play a pathogenic role in DCMi and contain novel therapeutic targets. Multiple immune cell-associated genes were also deregulated (e.g., chemokine ligand 14, interleukin-17D, nuclear factors of activated T cells). In contrast to previous investigations in patients with advanced or end-stage DCM where etiology-related pathomechanisms are overwhelmed by unspecific processes, the deregulations detected in this study occurred at a far less severe and most probably fully reversible disease stage.

Highly efficient and specific modulation of cardiac calcium homeostasis by adenovector-derived short hairpin RNA targeting phospholamban

Impaired function of the phospholamban (PLB)-regulated sarcoplasmic reticulum Ca(2+) pump (SERCA2a) contributes to cardiac dysfunction in heart failure (HF). PLB downregulation may increase SERCA2a activity and improve cardiac function. Small interfering (si)RNAs mediate efficient gene silencing by RNA interference (RNAi). However, their use for in vivo gene therapy is limited by siRNA instability in plasma and tissues, and by low siRNA transfer rates into target cells. To address these problems, we developed an adenoviral vector (AdV) transcribing short hairpin (sh)RNAs against rat PLB and evaluated its potential to silence the PLB gene and to modulate SERCA2a-mediated Ca(2+) sequestration in primary neonatal rat cardiomyocytes (PNCMs). Over a period of 13 days, vector transduction resulted in stable > 99.9% ablation of PLB-mRNA at a multiplicity of infection of 100. PLB protein gradually decreased until day 7 (7+/-2% left), whereas SERCA, Na(+)/Ca(2+) exchanger (NCX1), calsequestrin and troponin I protein remained unchanged. PLB silencing was associated with a marked increase in ATP-dependent oxalate-supported Ca(2+) uptake at 0.34 microM of free Ca(2+), and rapid loss of responsiveness to protein kinase A-dependent stimulation of Ca(2+) uptake was maintained until day 7. In summary, these results indicate that AdV-derived PLB-shRNA mediates highly efficient, specific and stable PLB gene silencing and modulation of active Ca(2+) sequestration in PNCMs. The availability of the new vector now enables employment of RNAi for the treatment of HF in vivo.

Anti-viral treatment in patients with virus-induced cardiomyopathy

Ongoing viral persistence in the myocardium is associated with an adverse prognosis of cardiomyopathy eventually resulting in a reduced capacity for work and thus it is associated with enormous social costs. Experimental and clinical data highlight that an imbalance of the cytokine network and a defect in the cytokine-induced immune response may constitute major causes leading to the development of virus persistence and progression of myocardial dysfunction. Reversibility of cardiac impairment during the early stages of the disease and the arising chance of specific treatment options demand early diagnosis and treatment of the disease. Our pilot data on anti-viral treatment using INF-beta showed beneficial clinical effects and suggest that some of the ventricular dysfunction and wall motion abnormalities resolved after elimination of the responsible agents. The data also suggest that elimination of cardiotropic viruses and associated clinical effects may occur even in DCM patients presenting with a long history.

[Cardiomyopathies. I: classification of cardiomyopathies--dilated cardiomyopathy]

Cardiomyopathies are common causes of heart failure and sudden cardiac death. According to the WHO classification, "specific" cardiomyopathies are differentiated from "idiopathic" cardiomyopathies. Thus, this classification is primarily based on pathophysiological characteristics. The diagnostic spectrum in cardiomyopathies comprises the entire spectrum of non-invasive and invasive cardiological examination techniques. The exact verification of certain cardiomyopathies necessitates additionally investigations. For example, immunohistological and molecular biological investigations of endomyocardial biopsies may confirm inflammatory cardiomyopathy, which is often induced by viruses. Several studies have shown that specific immunomodulatory treatment options can halt the progressive course of the disease. Several gene mutations have been identified in genetic/familial dilated cardiomyopathy. First-degree relatives should be screened for early stages. Primary prevention of sudden cardiac death shows increasing superiority of the implantable defibrillator compared with pharmacological approaches (i.e. amiodarone).

[Cardiomyopathies II. Hypertrophic cardiomyopathy, restrictive cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy]

This review focuses on hypertrophic (HCM), restrictive (RCM) and arrhythmogenic right ventricular cardiomyopathies (ARVC). The clinical phenotype of HCM depends not only on the gene mutations involved, but also on "modifier genes". It is characterized by an asymmetrical hypertrophy. Investigations of endomyocardial biopsies (EMBs) typically reveal a disarray of the hypertrophied cardiomyocytes. Percutaneous septum ablation has gained relevance as the treatment of choice in hypertrophic obstructive cardiomyopathy. Myocardial and endomyocardial RCM-forms can be differentiated. Enlargement of the atria in concert with normal dimensions of the ventricles and almost normal systolic contractility as well as the dip-plateau phenomenon are characteristic findings in RCM. EMB diagnostics are pivotal to identify the causes underlying secondary RCM types. Treatment is directed at heart failure and specifically at the underlying disease. With ARVC, apoptosis, viral infection/inflammation and genetic dystrophy result in fibrofatty degeneration primarily of the right, and with further progression also of the left ventricle. The primary treatment goal in ARVC is prevention of sudden cardiac death. As for other cardiomyopathies, there is increasing evidence for the superiority of ICD compared with pharmacological approaches.

Tamoxifen-regulated adenoviral E1A chimeras for the control of tumor selective oncolytic adenovirus replication in vitro and in vivo

Pharmacological control is a desirable safety feature of oncolytic adenoviruses (oAdV). It has recently been shown that oAdV replication may be controlled by drug-dependent transcriptional regulation of E1A expression. Here, we present a novel concept that relies on tamoxifen-dependent regulation of E1A activity through functional linkage to the mutated hormone-binding domain of the murine estrogen receptor (Mer). Four different E1A-Mer chimeras (ME, EM, E(DeltaNLS)M, MEM) were constructed and inserted into the adenoviral genome under control of a lung-specific surfactant protein B promoter. The highest degree of regulation in vitro was seen for the corresponding oAdVs Ad.E(DeltaNLS)M and Ad.MEM, which exhibited an up to 100-fold higher oAdV replication in the presence as compared with the absence of 4-OH-tamoxifen. Moreover, destruction of nontarget cells was six- and 13-fold reduced for Ad.E(DeltaNLS)M and Ad.MEM, respectively, as compared with Ad.E. Further investigations supported tamoxifen-dependent regulation of Ad.E(DeltaNLS)M and Ad.MEM in vivo. Induction of Ad.E(DeltaNLS)M inhibited growth of H441 lung tumors as efficient as a control oAdV expressing E1A. E(DeltaNLS)M and the MEM chimeras can be easily inserted into a single vector genome, which extends their application to existing oAdVs and strongly facilitates in vivo application.

Genome-environment interactions in the molecular pathogenesis of dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is a heart muscle disease characterized by impaired contractility and dilation of the ventricles. In a subset of DCM patients, classical inheritance patterns occur (familial DCM), which have led to the identification of specific genomic loci and gene defects causing monogenic DCM subtypes. In the majority of DCM patients, however, there is no evidence for a monogenic etiology of the disorder (sporadic DCM), and in the absence of other recognizable etiological factors, these cases were classified as "idiopathic". Recent research suggests that cardiotropic viruses are important environmental factors in the pathogenesis of "idiopathic" cases and that DCM commonly results from interactions between genetic and environmental factors, whereas "pure" genetic forms are rather rare. Regarding genetics, the clinical cardiomyopathic phenotype associated with single gene defects may be highly variable for unknown reasons. Furthermore, a novel class of genetic defects was identified recently which provide a molecular basis for abnormal reactions of cardiomyocytes to environmental stress. These defects are paradigms of specific molecular links between genome and environment during the pathogenesis of DCM. Regarding environmental factors, a recent molecular virological study based on myocardial biopsies in a large series of sporadic DCM patients has detected cardiac viral infections in the majority of patients, with a broad spectrum of virus species being involved. Apparently, DCM does not only occur as a late sequela of acute viral myocarditis, but also in patients without clinical history of cardiac viral disease. Cardiotropic viruses thus emerge as prevalent environmental factors which may cause or influence the course of DCM in a large fraction of cases. Synopsis of current data suggests that a comprehensive picture of DCM pathogenesis can only be drawn if both genetic and environmental pathogenetic factors are considered. The course of cardiac viral infections depends strongly on genetic host factors and may range from rapid and complete virus elimination or silencing without clinical symptoms, to rapidly progressive or fatal disease. Viruses interact not only with genetically heterogenous host systems of virus uptake, migration, and antiviral immunity, but, due to their prevalence in DCM hearts, are also likely to encounter multiple structural proteins of cardiac cells known to be defective in familial DCM. The combined knowledge on DCM-associated gene defects and viruses therefore suggests in-depth studies on genome-environment interactions in DCM pathogenesis which may underlie the high clinical variability observed both in monogenic and virus-associated DCM and have implications for the clinical management of DCM patients.

Nucleic acid-based modulation of cardiac gene expression for the treatment of cardiac diseases. Approaches and perspectives

During the past few years major conceptual and technical advances have been made towards the therapeutic modulation of cardiac gene expression for the treatment of cardiac diseases. Among these are 1) the identification of new molecular therapy targets in cardiac disorders, often derived from genetic animal models. 2) A better understanding of the molecular and cellular determinants of cardiac gene transfer in vivo, in animal models and in first clinical trials. 3) The development of novel regulatable and long-term stable vector systems. This review is focused on nucleic acid-based modulation of cardiac calcium homeostasis as a paradigm for the new gene therapeutic approaches, since recent landmark papers have suggested this to be a molecular target of key importance in heart failure. In particular, the development of severe heart failure in the genetic MLP(-/-) animal model could be completely abolished by the targeted ablation of phospholamban (PL), a key regulator of cardiac calcium homeostasis. This impressive effect of permanent germline PL ablation provides-in conjunction with former important work on disturbed calcium handling in the failing human heart-a rationale for the gene therapeutic approach of ad hoc suppression of PL by antisense strategies (antisense RNAs, ribozymes, RNA interference) or PL variants. Based on the broad spectrum of methods employed to characterize this general strategy, PL-targeted approaches may be considered as a paradigm of future genetic treatments of cardiac disorders, although the differences between animal models and humans must be kept in mind. High safety of any such therapy will be a prerequisite for any possible clinical application and therefore novel methods to improve control are being devised: 1) The regulation of gene therapy vectors by biochemical abnormalities associated with the target disease itself (" Induction-by-Disease" gene therapy). 2) External control of vector activity by the employment of drug-sensitive promotors. In addition, the important goal of cardiac long-term stability of the therapeutic vectors has recently been achieved in animal models using vectors derived from adeno-associated viruses (AAVs).

A novel tetracycline-controlled transactivator-transrepressor system enables external control of oncolytic adenovirus replication

The use of restricted replication-competent adenoviruses (RRCAs) inducing tumor cell-specific lysis is a promising approach in cancer gene therapy. However, the use of RRCAs in humans carries considerable risk, since after injection into the patient, further regulation or inhibition of virus replication from the outside is impossible. Therefore, we have developed a novel system allowing external pharmacological control of RRCA replication. We show here that a tumor-selective E1B-deleted RRCA can be tightly regulated by use of doxycycline (dox)-controlled adenoviral E1A gene expression, which in turn determines vector replication. RRCA replication is switched on by addition and switched off by withdrawal of dox. The system results in efficient tumor cell killing after induction by dox, whereas cells are unaffected by the uninduced system. It was also employed for efficient external control of transgene expression from cotransfected replication-deficient adenovectors. Furthermore, the use of a liver cell-specific human alpha1-antitrypsin (hAAT)-promoter driving a tetracycline-controlled transcriptional silencer allowed specific protection of cells with hAAT-promoter activity in the absence of dox in vitro and in vivo, delineating a new principle of 'tissue protective' gene therapy. The concept of external control of RRCAs may help to improve the safety of cancer gene therapy.

Highly variable expression of virus receptors in the human cardiovascular system. Implications for cardiotropic viral infections and gene therapy

Coxsackieviruses and adenoviruses are common agents of viral heart disease. In the majority of exposed individuals they do not cause myocardial disease, however, since they are not primarily cardiotropic. Until recently the molecular basis of their anomalous tropism in patients who develop viral heart disease was unknown. An important step towards clarification of the molecular basis of cardiotropic viral infections was achieved in 1997, when a common receptor for the two structurally unrelated viruses was cloned. This coxsackievirus-adenovirus receptor (CAR) is a key determinant for the cellular uptake of both viruses and for the molecular pathogenesis of coxsackievirus and adenovirus diseases. We have mapped the CAR expression in human hearts and observed highly variable expression patterns. Healthy donor hearts had low CAR expression levels, whereas explanted hearts of patients with dilated cardiomyopathy (DCM) displayed high CAR expression in the myocardium. Remarkably, however, heart failure per se was not associated with CAR induction, since in heart failure of non-DCM origin no induction was found. Additional studies on the molecular mechanisms of CAR induction in cardiomyocytes indicated the existence of a cell-cell contact-dependent molecular mechanism regulating CAR expression, whereas cellular virus uptake and low level replication had no effect. Recombinant expression of human CAR in cardiomyocytes strongly increased their virus uptake rate suggesting that CAR induction enhances cardiac vulnerability to viral disease, whereas healthy myocardium is rather resistant to CAR-dependent viruses. Receptor induction may significantly aggravate the clinical course of viral heart disease, so that the blockade of receptor expression or receptor-virus interactions opens new therapeutic perspectives. Elucidation of the molecular mechanism of CAR induction in DCM, but not in heart failure per se, may reveal a particular pathogenetic process in this disease. A broader analysis of the cardiovascular expression patterns of receptors for other potentially cardiotropic viruses (CMV, EBV, HIV, HHV-6, Parvo-B19, etc.) should lead to a better understanding of individual risk factors for viral heart diseases and of their highly variable clinical courses, and offer new therapeutic options.

Adenovirus-mediated overexpression and stimulation of the human angiotensin II type 2 receptor in porcine cardiac fibroblasts does not modulate proliferation, collagen I mRNA expression and ERK1/ERK2 activity, but inhibits protein tyrosine phosphatases

The contribution of the angiotensin (Ang) II type 2 receptor (AT2R) to cardiac hypertrophy is still controversial. Here we examined the effect of overexpressing the human AT2R in cultured porcine cardiac fibroblasts (pFib) on proliferation, procollagen I mRNA expression, and - as putatively underlying signal-transduction pathways - on mitogen-activated protein kinase ERK1/ERK2 and phosphotyrosine phosphatase activities. As quantitated by 125I-(Sar1,Ile8)-Ang II binding, transduction of cardiac fibroblasts with the adenoviral AT2R expression vector led to a six- to tenfold higher AT2 than endogenous Ang II type 1 receptor (AT1R) expression. The overexpressed AT2R had the same apparent molecular mass as the endogenous AT2R in rat PC12W cells. Proliferation was not significantly lower in AT2R expressing pFib than in antisense-transduced controls (TA2) upon stimulation with Ang II (AT2R 110.5+/-4.8% vs. TA2 110.2+/-5.5%), Ang II plus the AT1R blocker Irbesartan (97.1+/-1.4% vs. 108.0+/-5.0; P=0.052) and the partial AT2R antagonist CGP42112 at the agonistic concentration of 50 nM (92.1+/-2.7% vs. 99.8+/-3.1%; P=0.053). Procollagen Ialpha2 (COL1A2) mRNA levels were quantitated by (a) northern blot analysis and (b) reverse transcriptase polymerase chain reaction. COL1A2/GAPDH (a) and COL1A2/beta-actin (b) ratios revealed no differences between AT2R-transduced fibroblasts and antisense controls when stimulated with Ang II (1 microM, 24 h) plus Irbesartan and 10 ng/ml transforming growth factor beta1. Ang II stimulation of the endogenous AT1R increased extracellular signal regulated kinase 1/2 activities. This response was reduced by Irbesartan, but PD123319 had no effect. Time course and magnitude of Ang II stimulated ERK1/ERK2 activation was identical in AT2R-transduced and control cells. Also, neither simultaneous nor Ang II pre-stimulation, suggested to induce gene expression of the MAP kinase phosphatase 1, modulated phorbol myristate acetate-stimulated ERK1/ERK2 activation in AT2R-transduced pFib, in AT2R-transduced human umbilical vein endothelial cells, and in PC12W cells. By the use of a tyrosine phosphatase assay we observed an inhibition of phosphotyrosine phosphatase activity by 30.8% (P=0.009, n=5) after 5 min Ang II stimulation of AT2R-expressing pFib. Immunoprecipitation-tyrosine phosphatase assays revealed that inhibition of phosphotyrosine phosphatase 1B, which regulates insulin signaling, contributed to this effect. In conclusion, stimulation of the overexpressed human AT2R in porcine cardiac fibroblasts inhibited tyrosine phosphatase activity but had no significant effect on fibroblast functions related to cardiac fibrosis. It is conceivable that possible antifibrotic AT2R effects are species specific and/or require the interaction between fibroblasts and cardiomyocytes, probably via paracrine factors, or mechanical load.

Human coxsackie-adenovirus receptor is colocalized with integrins alpha(v)beta(3) and alpha(v)beta(5) on the cardiomyocyte sarcolemma and upregulated in dilated cardiomyopathy: implications for cardiotropic viral infections

BACKGROUND

The coxsackievirus and adenovirus receptor (CAR) was identified as a common cellular receptor for both viruses, but its biological and pathogenic relevance is uncertain. Knowledge of CAR localization in the human cardiovascular system is limited but important with respect to CAR-dependent viral infections and gene transfer using CAR-dependent viral vectors.

METHODS AND RESULTS

Explanted failing hearts from 13 patients (8 with dilated cardiomyopathy [DCM] and 5 with other heart diseases [non-DCM]) and normal donor hearts (n=7) were investigated for the expression levels and subcellular localization of CAR and the adenovirus coreceptors alpha(v)beta(3) and alpha(v)beta(5) integrins. CAR immunoreactivity was very low in normal and non-DCM hearts, whereas strong CAR signals occurred at the intercalated discs and sarcolemma in 5 of the 8 DCM hearts (62.5%); these strong signals colocalized with both integrins. In all hearts, CAR was detectable in subendothelial layers of the vessel wall, but not on the luminal endothelial surface, and on interstitial cells. Human CAR (hCAR) expressed in rat cardiomyocytes was targeted to cell-cell contacts, which resembled CAR localization in DCM hearts and resulted in 15-fold increased adenovirus uptake.

CONCLUSIONS

Low hCAR abundance may render normal human myocardium resistant to CAR-dependent viruses, whereas re-expression of hCAR, such as that observed in DCM, may be a key determinant of cardiac susceptibility to viral infections. Asymmetric expression of hCAR in the vessel wall may be an important determinant of adenovirus tropism in humans. hCAR subcellular localization in human myocardium and hCAR targeting to cell-cell contacts in cardiomyocyte cultures suggest that hCAR may play a role in cell-cell contact formation.

Trans-complementation of vector replication versus Coxsackie-adenovirus-receptor overexpression to improve transgene expression in poorly permissive cancer cells

Gene therapy of cancer requires high-level expression of therapeutic transgenes in the target cells. Poor gene transfer is an important limitation to adenovector-mediated cancer gene therapy. We investigated two fundamentally different approaches to improve transgene expression in poorly permissive cancer cells. First, overexpression of the adenovirus attachment receptor CAR to facilitate receptor-mediated adenovector (AdV) uptake into the target cells; second, co-infection of this vector together with traces of replication competent adenovirus (RCA) accidentally arising by back-recombination during large-scale vector preparation. Among eight gastrointestinal cancer cell lines, the colorectal cancer lines showed particularly poor vector-mediated transgene expression (down to 67-fold lower than in HeLa cells). Expression of the adenovirus receptors CAR, alpha(v)beta5- and alpha(v)beta3-integrin were highly variable between cell lines. AdV uptake was significantly associated with CAR levels on the cell surface, but not with those of the integrins. AdV-mediated CAR overexpression increased CAR density on the surface of all investigated tumor cells and led to enhancement of transgene expression by 1.8- to 6.7-fold. The other principle to enhance transgene expression was 'trans-complementation' of the therapeutic vector, ie induction of its replication within the target cells. Traces of RCA in a vector preparation, as well as purified RCA were found to provide sufficient E1-region transcripts to induce replication of the therapeutic vector genome. The number of adenovector-based transgene expression cassettes was greatly amplified by this principle, notably without any influence on the rate of vector entry. Co-infection of four colorectal cancer cell lines with marker vector plus RCA (at around 240:1 particle ratio) resulted in far stronger enhancement of transgene expression (up to 46-fold) as compared with CAR overexpression, even in cancers almost refractory to standard adenovector-mediated gene transfer. Whereas RCAs need to be strictly avoided in gene therapy of non-malignant diseases for safety reasons, the magnitude of helper virus-induced therapeutic transgene expression could possibly warrant application of this principle to overcome the resistance of highly malignant cancers against gene therapy.

Regulation of human endothelial cell focal adhesion sites and migration by cGMP-dependent protein kinase I

cGMP-dependent protein kinase type I (cGK I), a major constituent of the atrial natriuretic peptide (ANP)/nitric oxide/cGMP signal transduction pathway, phosphorylates the vasodilator-stimulated phosphoprotein (VASP), a member of the Ena/VASP family of proteins involved in regulation of the actin cytoskeleton. Here we demonstrate that stimulation of human umbilical vein endothelial cells (HUVECs) by both ANP and 8-(4-chlorophenylthio)guanosine 3':5'-monophosphate (8-pCPT-cGMP) activates transfected cGK I and causes detachment of VASP and its known binding partner (zyxin) from focal adhesions in >60% of cells after 30 min. The ANP effects, but not the 8-pCPT-cGMP effects, reversed after 3 h of treatment. In contrast, a catalytically inactive cGK Ibeta mutant (cGK Ibeta-K405A) was incapable of mediating these effects. VASP mutated (Ser/Thr to Ala) at all three of its established phosphorylation sites (vesicular stomatitis virus-tagged VASP-AAA mutant) was not phosphorylated by cGK I and was resistant to detaching from HUVEC focal adhesions in response to 8-pCPT-cGMP. Furthermore, activation of cGK I, but not of mutant cGK Ibeta-K405A, caused a 1.5-2-fold inhibition of HUVEC migration, a dynamic process highly dependent on focal adhesion formation and disassembly. These results indicate that cGK I phosphorylation of VASP results in loss of VASP and zyxin from focal adhesions, a response that could contribute to cGK alteration of cytoskeleton-regulated processes such as cell migration.

Biochemical and functional characterization of nitric oxide synthase III gene transfer using a replication-deficient adenoviral vector

Nitric oxide (NO) produced in endothelial cells has been implicated in the regulation of blood pressure, regional blood flow, inhibition of platelet aggregation, and endothelial and vascular smooth muscle cell proliferation. In a variety of cardiovascular disease states, such as atherosclerosis, arterial hypertension, and restenosis, expression of endothelial NO synthase (NOS-III) and endothelial NO production appear to be altered. Thus, NOS-III is an attractive target for cardiovascular gene therapy for which adenoviral vectors are one of the most effective vector systems. Therefore, a recombinant adenoviral vector expressing NOS-III (adenovirus type 5 [Ad5] cytomegalovirus [CMV] NOSIII) was constructed and biochemically and pharmacologically characterized both in vitro and in intact cells. Ad5CMVNOSIII-derived recombinant NOS-III was successfully expressed, as shown by immunoprecipitation and immunocytochemistry, and biologically active, as shown by functional assays in human primary umbilical vein and EA.hy926 endothelial cells, as well as 293 human embryonic kidney and Chinese hamster ovary cells. The Km values for NADPH and L-arginine and the Ka for tetrahydrobiopterin as well as the enzyme's dependency on other cofactors were similar to recombinant reference enzyme and literature values. NOS-III expression levels correlated linearly with the multiplicity of infection with Ad5CMVNOSIII and lasted for at least 8 days. NOS-III transfection inhibited endothelial cell proliferation. In conclusion, adenovirus-mediated gene transfer of Ad5CMVNOSIII to vascular and nonvascular cells resulted in the dose-dependent expression of intact, physiologically regulated, and functionally active NOS-III.

Expression of coxsackie adenovirus receptor and alphav-integrin does not correlate with adenovector targeting in vivo indicating anatomical vector barriers

Recombinant adenoviral vectors are broadly applied in gene therapy protocols. However, adenovector-mediated gene transfer has limitations in vivo. One of these is the low gene transfer rate into organs other than the liver after systemic intravenous vector injection. Local direct injection into the target organ has been used as one possible solution, but increases necessary equipment and methodology and is traumatic to the target. Wild-type adenovirus infection as well as adenovector-mediated gene transfer depends on virus interaction with the Coxsackie adenovirus receptor (CAR) mediating virus attachment to the cell surface, and on interaction with alphavbeta3 and alphavbeta5 integrins mediating virus entry into the cell. In order to assess the receptor-associated potential of different tissues to act as adenovector targets, we have therefore determined CAR and alphav-integrin expression in multiple organs from different species. In addition, we have newly determined several human, rat, pig and dog CAR-mRNA sequences. Sequence comparison and structural analyses of known and of newly determined sequences suggests a potential adenovirus binding site between amino acids 29 and 128 of the CAR. With respect to the virus receptor expression patterns we found that CAR-mRNA expression was extremely variable between different tissues, with the highest levels in the liver, whereas alphav-integrin expression was far more homogenous among different organs. Both CAR and alphav-integrin showed similar expression patterns among different species. There was no correlation, however, between the adenovector expression patterns after intravenous, intracardiac and aortic root injection, respectively, and the virus receptor patterns. In summary, many organs carry both receptors required to make them potential adenovector targets. In sharp contrast, their actual targeting clearly indicates that adenovirus receptor expression is necessary but not sufficient for vector transfer after systemic injection. The apparently very important role of anatomical barriers, in particular the endothelium, requires close attention when developing non-traumatic, organ-specific gene therapy protocols.

Highly sensitive and species-specific assay for quantification of human transgene expression levels

During the past few years great efforts have been made to construct and to test human factor VIII (hFVIII) and IX (hFIX) vectors suitable for haemophilia gene therapy in vivo. However, little is known about the molecular mechanisms of persistence and shut-off of transgene expression in the target organs after gene transfer using recombinant adenoviral vectors. To evaluate low transgene mRNA levels in different tissues, especially at long times after the gene transfer, the common northern blot method is often not sensitive enough. For this reason we developed a new, highly sensitive and species-specific method for hFIX mRNA quantification and employed it in mice treated with an adenoviral vector (Ad5CMVFIX) expressing human FIX. In addition to its very high sensitivity (lowest detection level=1 fg RNA), the method was shown to be strictly species-specific, since hFIX mRNA signals were never detected in untreated mice. In a long-term study of 18 vector-treated mice we compared the human FIX:Ag levels in the mouse plasma, the human FIX mRNA levels and human FIX vector DNA concentrations in the mouse liver. We found that a slow but continuous decrease of hFIX:Ag levels in mouse plasma was associated with a corresponding decrease of hFIX mRNA levels in the liver. However, the Ad5CMVFIX vector DNA levels did not decrease to a comparable degree, suggesting that the decrease of human FIX:Ag levels in mouse plasma is, to a significant extent, also caused by CMV promotor shut-off and only to a minor degree by loss of vector DNA.

'Autoreplication' of the vector genome in recombinant adenoviral vectors with different E1 region deletions and transgenes

High transgene stabilities of 1 year and more have been reported in immunodeficient hosts after adenovirus-mediated gene transfer. Transgene persistence of this duration could be due to inherently high stability of the episomal viral vector DNA. An alternative explanation would be limited 'autoreplication' of transgenic vector DNA, just sufficient to counteract slow but continuous degradation within the host cells. Autoreplication could occur in the absence of any production of infectious virus particles, based on residual activity of the adenoviral DNA replication system only. To test this hypothesis, a series of DNA metabolic labeling studies in non-permissive cells cultures transfected with different vectors was conducted. Due to extensive E1 region deletions none of the vectors was able to produce viral progeny in non-permissive cells. Vectors fell into two categories, however, with respect to their autoreplication potential. Neosynthesis of vector DNA in non-permissive vector-transfected cells was readily detectable in 'type A', but not in 'type B' vectors. In addition to their different transgene expression cassettes, vector DNA sequencing showed a less extensive E1 deletion in type A (nucleotides 453-3333 of wild-type virus) as compared to type B vectors (nucleotides 325-3523). Autoreplication was also associated with high transcriptional activity of several viral genes (E1B-14k, adenoviral DNA polymerase, single-strand DNA-binding protein, E4-25k), in contrast to type B vectors. In addition to these 'wild-type' transcripts, 'irregular' recombinant transcripts were detected in autoreplication vectors which contained the transgenic cDNA in conjunction with adenoviral vector sequences. Exogenous or cryptic promotors may (under certain conditions) enhance the transcriptional activity of a vector in such a way that autoreplication occurs. Conditions determining the level of transcriptional enhancement (extent of E1 deletion, type of promoter and transgene, etc) need to be further defined before rational design of adenovectors with high autoreplication capacity becomes possible. In summary, we have shown autoreplication to be a novel feature of certain E1-deleted adenovectors with likely relevance for their stability in vivo, but also with possibly adverse consequences for target cell function or vector immunogenicity. Full characterization of adenoviral vector systems should therefore include a description of their autoreplication capacity.

Dilated cardiomyopathy is associated with significant changes in collagen type I/III ratio

BACKGROUND

It is controversial whether myocardial fibrosis in end-stage dilated cardiomyopathy (DCM) is associated with altered collagen type I/type III (Col I/Col III) ratio.

METHODS AND RESULTS

Patients with DCM (ejection fraction [EF] <50%, n=12) and with mild global left ventricular dysfunction (EF >50%, n=18) were examined. Col I, Col III, and transforming growth factors-beta1 (TGF-beta1) and -beta2 (TGF-beta2) gene expression in endomyocardial biopsies was evaluated by quantitative competitive reverse transcriptase-polymerase chain reaction (qRT-PCR). Collagen content was quantified after picrosirius red and immunohistological staining and by hydroxyproline assay. In patients with EF <50%, there was a pronounced 2- to 6-fold increase of myocardial Col I mRNA abundance (P<0.01), with a corresponding 1.6-fold increase at the protein level versus that found in patients with EF >50%. The Col III mRNA abundance showed a 2.0-fold increase (P<0.04). There was a relevant shift in the Col I/Col III mRNA ratio for DCM patients (Col I/Col III, 8.2) compared with patients with an EF >50% (Col I/Col III, 6. 4). In addition, total collagen content was increased in patients with EF <50% (n=3) (4.3+/-0.1%) compared with patients with EF >50% (n=8) (2.7+/-0.9%) (P<0.004). The biochemically determined ratio of hydroxyproline/total protein (n=12) was correlated to the Col I mRNA abundance (P<0.05, r=0.77). TGF-beta1 and TGF-beta2 showed elevated myocardial mRNA abundances (1- to 7-fold and 4- to 5-fold, respectively) in DCM patients.

CONCLUSIONS

Differential increase of Col I and Col III leads to an increased Col I/Col III ratio in DCM myocardium. Because Col I provides substantial tensile strength and stiffness, this may contribute to systolic and in particular diastolic dysfunction in DCM.

Molecular characterisation of the defective alpha 1-antitrypsin alleles PI Mwurzburg (Pro369Ser), Mheerlen (Pro369Leu), and Q0lisbon (Thr68Ile)

Deficiency of the serine proteinase inhibitor (serpin) alpha 1-antitrypsin (alpha 1AT) is the most common autosomal recessive genetic disorder in Northern Europe. alpha 1AT is the physiological regulator of the proteolytic enzyme neutrophil elastase and severe deficiency states are associated with an increased risk of developing chronic obstructive pulmonary disease (COPD) as a consequence of chronic proteolytic damage to the lungs. Among the known mutations of the alpha 1AT gene causing severe alpha 1AT deficiency and COPD a few alleles are also associated with liver disease. When expressed in cell cultures, all these particular alleles cause intracellular alpha 1AT accumulation which appears to be a prerequisite for the development of hepatic injury. Liver disease is seen in only a small fraction of all patients carrying such alleles, however. The reason for this is not completely clear, but there is evidence that PI ZZ individuals 'susceptible' to liver disease carry an additional defect affecting protein degradation in the endoplasmic reticulum (ER). We characterise a newly identified defective alpha 1AT allele PI Mwürzburg (Pro369 [CCC] to Ser [TCC]) associated with a complete intracellular transport block in cell cultures in vitro. The allele PI Mheerlen, a previously described different amino acid substitution in the same position as PI Mwürzburg (Pro369 [CCC] to Leu [CTC]) is shown to cause complete retention of the mutant alpha 1AT in the ER, too, whereas in the recently described mutant allele PI Q0lisbon (Thr68 [ACC] to Ile [ATC]) a significantly reduced alpha 1AT secretion from the cells was observed. Adenovirus-mediated recombinant expression of mutant Mwürzburg and Mheerlen, and of wild-type alpha 1AT in mouse liver in vivo showed that the mutant human proteins were not secreted into the mouse plasma, in contrast with human wild-type alpha 1AT which circulated at high concentrations over several weeks. In summary, all transportation deficient alpha 1ATs analysed have the potential to cause lung disease in the homozygous state or in heterozygous carriers of another deficiency allele, and they may also cause liver disease in certain patients. The mutant PI Mwürzburg and Mheerlen alpha 1ATs are completely retained within synthesising cells, and the molecular defect of transportation in these two alleles may be similar to that in the common PI Z allele. The molecular defect in the PI Q0lisbon allele (Thr68Ile) shows similarity with the immediately neighbouring Mmineral springs mutation (Gly67Glu).

Analysis of expression kinetics and activity of a new B-domain truncated and full-length FVIII protein in three different cell lines

Transient expression of full-length wild-type (wt) and a new B-domain truncated (deltaB) FVIII has been investigated in three eukaryotic cell lines (HEK-293, COS, CHO). When expressed in CHO cells, both FVIII proteins reached the same peak antigen levels, whereas in HEK-293 and COS cells those of FVIII/deltaB were up to sixfold those of FVIII/wt. Investigation of specific activity of the recombinant FVIII proteins using a chromogenic and a one-stage assay in addition to the FVIII-antigen ELISA revealed large variations: In HEK-293 cells specific activity of FVIII/deltaB measured with both assays was higher than that of FVIII/wt. In COS cells specific activity of both FVIII proteins was higher measured in the one-stage assay than in the chromogenic assay. In CHO cells both FVIII proteins had similar specific activity in each assay. In summary, expression kinetics and specific activity of conditioned medium vary depending on cell type used.

Enteroviral RNA replication in the myocardium of patients with left ventricular dysfunction and clinically suspected myocarditis

BACKGROUND

Previous studies dealing with the detection of enteroviral RNA in human endomyocardial biopsies have not differentiated between latent persistence of the enteroviral genome and active viral replication. Enteroviruses that are considered important factors for the development of myocarditis have a single-strand RNA genome of positive polarity that is transcribed by a virus-encoded RNA polymerase into a minus-strand mRNA during active viral replication. The synthesis of multiple copies of minus-strand enteroviral RNA therefore occurs only at sites of active viral replication but not in tissues with mere persistence of the viral genome.

METHODS AND RESULTS

We investigated enteroviral RNA replication versus enteroviral RNA persistence in endomyocardial biopsies of 45 patients with left ventricular dysfunction and clinically suspected myocarditis. Using reverse-transcriptase polymerase chain reaction in conjunction with Southern blot hybridization, we established a highly sensitive assay to specifically detect plus-strand versus minus-strand enteroviral RNA in the biopsies. Plus-strand enteroviral RNA was detected in endomyocardial biopsies of 18 (40%) of 45 patients, whereas minus-strand RNA as an indication of active enteroviral RNA replication was detected in only 10 (56%) of these 18 plus-strand-positive patients. Enteroviral RNA was not found in biopsies of the control group (n=26).

CONCLUSIONS

These data demonstrate that a significant fraction of patients with left ventricular dysfunction and clinically suspected myocarditis had active enteroviral RNA replication in their myocardium (22%). Differentiation between patients with active viral replication and latent viral persistence should be particularly important in future studies evaluating different therapeutic strategies. In addition, molecular genetic detection of enteroviral genome and differentiation between replicating versus persistent viruses is possible in a single endomyocardial biopsy.